JP2010119257A - Power supply device and vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To stably supply electric power to an electric load connected to each sub-power supply system in a power supply device for outputting voltages of a plurality of sub-power supply systems converted from the voltage from a single main power supply. <P>SOLUTION: The power supply device includes: a switching power supply circuit in which a DC voltage VH from a high voltage battery 10 is stepped down, and a voltage VL1 is output to a power supply line SPL1; an EPS 120 and a high voltage system auxiliary machine 130 which are connected to the power supply line SPL1 and driven by receiving the voltage VL1; a step up/down chopper circuit in which the voltage VL1 from the power supply line SPL1 is stepped down to a voltage VL2 and is output to a power supply line SPL2; an auxiliary battery 20 which is connected to the power supply line SPL2 and charged by receiving the voltage VL2; and a low-voltage system auxiliary apparatus 110 which is driven by receiving the voltage VL2. In the step up/down chopper circuit, the VL2 supplied from the auxiliary battery 20 to the power supply line SPL2 is stepped up and supplied to the power supply line SPL1 when a voltage reduction occurs in the voltage VL1. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a power supply apparatus and a vehicle for supplying electric power to an electric load, and more particularly to a power supply apparatus and a vehicle that output a plurality of sub power supply systems converted from a single main power supply voltage. The present invention relates to a configuration for stably supplying electric power to a connected electric load.

  Recently, attention has been focused on hybrid vehicles and electric vehicles that are driven by the driving force of an electric motor as environmentally friendly vehicles. These electric vehicles are equipped with a power supply device for supplying electric power to an electric motor as a drive source.

  For example, in Japanese Patent Application Laid-Open No. 9-200902 (Patent Document 1), in addition to a main power supply for supplying power to a drive motor, a plurality of power supplies converted to a voltage of the main power supply are supplied to supply electric loads having different rated voltages. An electric vehicle power supply device having a sub power supply system is disclosed. According to this, a high-voltage (about 100 V to about 300 V) battery is used as the main power supply, and the plurality of sub power supply systems convert the voltage of the main power supply into voltages corresponding to various rated voltages, respectively. It is comprised by the voltage converter which carries out.

  Japanese Patent Laid-Open No. 7-250470 (Patent Document 2) discloses a power supply circuit that outputs a plurality of secondary side output voltages with respect to a single primary side input voltage. According to this, the power supply circuit includes an AC-DC or DC-DC converter including a primary side input for inputting an AC or DC power source and a plurality of secondary side outputs for outputting a predetermined voltage.

In the power supply apparatus that outputs a plurality of sub power supply systems obtained by converting the voltage of a single main power supply as described above, a plurality of sub power supply systems are operated in order to stably operate an electric load connected to each sub power supply system. High output stability is desired. For example, according to Japanese Patent Laid-Open No. 4-255466 (Patent Document 3), a secondary main output circuit including a snubber circuit from a primary DC power supply via a transformer and a sub output circuit including a chopper circuit are provided. In a multi-output switching power supply configured to output, the output of the main output circuit on the secondary side is detected and fed back to the control circuit of the switching transistor on the primary side to stabilize the output of the main output circuit Separately from this, the sub-output circuit is controlled to output a stable voltage by a chopper method using a chopper circuit.
Japanese Patent Laid-Open No. 9-200902 JP-A-7-250470 JP-A-4-255466

  However, in the power supply device described in Patent Documents 1-3 described above, the plurality of sub power supply systems operate without being related to each other in other aspects, although timings such as activation and shut-off are interlocked. Yes. For this reason, in some sub power supply systems, there has been a problem that the output voltage decreases due to a rapid increase in power consumption of the connected electrical load. This drop in output voltage is particularly likely to occur in sub-power supply systems connected to power system electrical components (power steering, etc.) that consume relatively much power compared to lighting equipment and control devices. There is a possibility that a part of the operation traveling performance is impaired due to the voltage drop.

  Japanese Patent Laid-Open No. 4-255466 (Patent Document 3) discloses a configuration in which the primary side of the switching power supply has a rectifying and smoothing switching circuit. However, when a switching transistor in the switching circuit fails, Since the power supply from the primary side DC power supply is cut off, there is a problem that the operation of the electric load connected to each sub power supply system is stopped. In such a case, it is necessary to ensure fail-safe traveling for evacuating the vehicle to a safe place by guaranteeing the operation of a part of the electric load related to the traveling performance of the vehicle.

  However, the power supply device described in Patent Documents 1-3 has not been sufficiently disclosed as means for solving these problems.

  Therefore, the present invention has been made to solve such a problem, and an object of the present invention is to provide a power supply apparatus and a vehicle for outputting a plurality of sub power supply systems obtained by converting the voltage of a single main power supply. It is to stably supply power to an electric load connected to the power supply system.

  According to an aspect of the present invention, a power supply device includes a switching power supply circuit that steps down a power supply voltage from a power supply and outputs a first voltage to a first power supply line by a switching operation of a switching element, and a first power supply line And a voltage conversion circuit having a step-down function for stepping down the first voltage from the first power supply line to the second voltage and outputting the voltage to the second power supply line And a power storage unit connected to the second power supply line and charged by receiving the second voltage. The voltage conversion circuit further has a boosting function of boosting the second voltage supplied from the power storage unit to the second power supply line and supplying the boosted voltage to the first power supply line.

  Preferably, when the step-down function of the switching power supply circuit is impaired, the voltage conversion circuit boosts the second voltage from the power storage unit and supplies the second voltage to the first power supply line.

  More preferably, the power supply device detects that the step-down function of the switching power supply circuit is impaired when the period during which the voltage of the first power supply line is equal to or lower than a predetermined threshold voltage continues for a predetermined period or longer. And a control means for stopping the switching operation and outputting a boost command to the voltage conversion circuit when it is detected that the step-down function of the switching power supply circuit is impaired.

  Preferably, the voltage conversion circuit includes a first switching element connected between the first power supply line and the second power supply line, and a second switching element connected between the second power supply line and the ground line. And a reactor connected between the connection point of the first and second switching elements and the second power supply line. The control means maintains the first switching element in the OFF state and sets the duty ratio at which the voltage of the first power supply line becomes the first voltage to control the switching of the second switching element.

  More preferably, the chopper circuit further includes a diode connected in antiparallel to each of the first and second switching elements. When the boosting function of the voltage conversion circuit is impaired, the control means outputs a stop command for the boosting function to the voltage conversion circuit.

  According to another aspect of the present invention, a power supply apparatus includes a switching power supply circuit that steps down a power supply voltage from a power supply and outputs a first voltage to a first power supply line by a switching operation of a switching element, and a first power supply. An electric load connected to the line and driven by receiving the first voltage, a voltage conversion circuit for stepping down the first voltage from the first power supply line to the second voltage and outputting it to the second power supply line; When the power storage unit connected to the two power supply lines and charged by receiving the second voltage, the voltage drop detecting means for detecting the voltage drop of the first power supply line, and the voltage drop of the first power supply line are detected, And a control means for controlling the voltage conversion circuit so as to limit the output to the second power supply line.

  Preferably, the voltage conversion circuit includes a first switching element connected between the first power supply line and the second power supply line, and a second switching element connected between the second power supply line and the ground line. And a reactor connected between the connection point of the first and second switching elements and the second power supply line. When the voltage drop of the first power supply line is detected, the control means maintains the second switching element in the OFF state and sets a duty ratio at which the voltage of the second power supply line is lower than the second voltage. Switching control of one switching element is performed.

  According to another aspect of the present invention, a power supply apparatus includes a switching power supply circuit that steps down a power supply voltage from a power supply and outputs a first voltage to a first power supply line by a switching operation of a switching element, and a first power supply. An electric load connected to the line and driven by receiving the first voltage, a voltage conversion circuit for stepping down the first voltage from the first power supply line to the second voltage and outputting it to the second power supply line; When the power storage unit connected to the two power supply lines and charged by receiving the second voltage, the voltage drop detecting means for detecting the voltage drop of the first power supply line, and the voltage drop of the first power supply line are detected, Step-down control means for outputting a step-down command to the voltage conversion circuit so as to limit the output to the second power line, and a voltage step-up command to the voltage conversion circuit when a voltage drop of the first power line is detected during the output restriction. And a boost control means for outputting.

  Preferably, the voltage conversion circuit includes a first switching element connected between the first power supply line and the second power supply line, and a second switching element connected between the second power supply line and the ground line. And a reactor connected between the connection point of the first and second switching elements and the second power supply line. The step-down control means maintains the second switching element in the OFF state when a voltage drop of the first power supply line is detected, and sets a duty ratio at which the voltage of the second power supply line is lower than the second voltage. The first switching element is subjected to switching control. When the voltage drop of the first power supply line is detected, the boost control means maintains the first switching element in the off state and sets a duty ratio at which the voltage of the first power supply line becomes the first voltage. Switching control of the second switching element is performed.

  Preferably, the power supply device further includes control means for controlling the switching of the switching element while fixing the duty ratio in the switching operation.

  If another situation of this invention is followed, a vehicle carries the power supply device as described in any one of said.

  Preferably, the vehicle includes a rotating electrical machine that receives electric power from a power source and drives the wheels. The electric load includes a vehicle driving control device.

  According to the present invention, in a power supply device that outputs a plurality of sub power supply systems obtained by converting the voltage of a single main power supply, it is possible to stably supply power to an electric load connected to each sub power supply system.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same reference numerals indicate the same or corresponding parts.

[Embodiment 1]
FIG. 1 is a schematic configuration diagram of an electric vehicle equipped with a power supply device according to Embodiment 1 of the present invention.

  Referring to FIG. 1, the vehicle according to the first embodiment of the present invention is typically a hybrid vehicle, which is equipped with an internal combustion engine (not shown) and motor M1, and has an optimum ratio of driving force from each. Drive under control. Further, the vehicle is equipped with a high voltage battery 10 for supplying electric power to the motor M1. The high voltage battery 10 is a main battery of the motor M1 for driving the vehicle, and is made of, for example, a nickel metal hydride or lithium ion battery. Note that the high-voltage battery 10 may be configured with a large-capacity capacitor for power storage such as an electric double layer capacitor instead of such a secondary battery.

  Boost converter 12 boosts voltage VH between power supply line PL1 and ground line SL1, and outputs the boosted voltage between power supply line PL2 and ground line SL. Inverter 14 receives a DC voltage between power supply line PL2 and ground line SL1 as a power supply voltage, and is subjected to switching control so as to generate a three-phase AC current. Then, the motor M1 is driven by the inverter 14, and a differential gear and wheels (not shown) are rotated by the motor M1.

(Auxiliary load)
The vehicle further includes an auxiliary battery 20, a plurality of auxiliary loads 110, 120, and 30 and a DC / DC converter 100 connected to power supply line PL1 and ground line SL1.

  DC / DC converter 100 steps down voltage VH between power supply line PL1 and ground line SL1 to a plurality of different voltages VL1 and VL2 and supplies them to a plurality of auxiliary loads and auxiliary battery 20 respectively. To do.

  Specifically, the DC / DC converter 100 steps down the voltage VH to the voltage VL1 and supplies it to the power supply line SPL1. An electric power steering device (EPS) 120 and a high-voltage auxiliary machine 130 are connected to the power supply line SPL1, and these auxiliary machines load is supplied with the voltage VL1 to operate. The high-voltage auxiliary machine 130 is a general term for auxiliary loads that operate at a higher voltage (for example, 48V) than the output voltage (for example, 14V) of the auxiliary battery 20, and as an example, a suspension device, a stabilizer. And control systems with high power consumption such as driving control devices such as devices and brake control devices.

  Furthermore, the DC / DC converter 100 steps down the voltage VH to a voltage VL2 lower than the voltage VL1 and supplies it to the power supply line SPL2. An auxiliary battery 20 and a low-voltage auxiliary machine 110 are connected to the power line SPL2.

  The auxiliary battery 20 constitutes the “power storage unit” in the present invention, and is composed of, for example, a lead storage battery. Auxiliary battery 20 is charged with DC power from power supply line SPL <b> 2 and supplies the stored power to low-voltage auxiliary machine 110. That is, the auxiliary battery 20 also functions as a power buffer for compensating for an imbalance between the output power of the DC / DC converter 100 and the demand power of the low-voltage auxiliary device 110.

  The low-voltage auxiliary machine 110 is a general term for auxiliary loads that operate at the same voltage as the output voltage of the auxiliary battery 20, and includes, for example, a car navigation system, a car audio, an interior lamp, and the like. Such a low-pressure auxiliary machine 110 is an auxiliary machine load for providing a comfortable indoor environment to a vehicle occupant.

  Control device 50 performs step-up control of step-up converter 12 and switching control of inverter 14 and step-down control of DC / DC converter 100. The control device 50 includes a plurality of ECUs such as an engine control ECU, a hybrid control ECU, a control unit in an IPM (intelligent power module) of the inverter 14 and the boost converter 12, and a battery control ECU. It may be realized by communication.

(Configuration of DC / DC converter)
FIG. 2 is a circuit diagram showing the configuration of the DC / DC converter 100 of FIG.

  Referring to FIG. 2, DC / DC converter 100 includes a switching power supply circuit 30 and a step-up / down chopper circuit 40.

  The switching power supply circuit 30 rectifies the AC current generated on the secondary side of the transformer Tr, the bridge circuit that receives the power from the high-voltage battery 10 and generates AC current, the primary side that receives power from the bridge circuit, and the like. A rectifier circuit.

  The bridge circuit includes a transistor Q1 having a collector connected to the high voltage battery 10, a transistor Q2 having a collector connected to the emitter of the transistor Q1, a transistor Q2 having an emitter connected to the ground line SL1, and a collector connected to the high voltage battery 10. Transistor Q3, and a transistor Q4 having a collector connected to the emitter of transistor Q3 and an emitter connected to ground line SL1. Each base of the transistors Q1 to Q4 constituting the “switching element” in the present invention is subjected to switching control when a control signal CNT instructing step-down operation is given by the control device 50 of FIG.

  The transformer Tr has a primary coil L2 having one end connected to the emitter of the transistor Q1 and the other end connected to the emitter of the transistor Q3, secondary coils L3 and L4 connected in series, and a primary coil L2. And an iron core that electromagnetically couples the secondary coils L3 and L4.

  The rectifier circuit includes diodes D5 and D6, a coil L5, and a smoothing capacitor C2. The cathodes of the diodes D5 and D6 are both connected to one end of the coil L5. The anode of the diode D5 is connected to one end of the secondary coil L3. The anode of the diode D6 is connected to one end of the secondary coil L4. Both the other end of secondary coil L3 and the other end of secondary coil L4 are connected to ground line SL2. The other end of coil L5 is connected to power supply line SPL1. Smoothing capacitor C2 is connected between power supply line SPL1 and ground line SL2.

  The switching power supply circuit 30 switches the DC input voltage VH from the high-voltage battery 10 by the switching operation of the transistors Q1 to Q4 connected to the primary coil L2 of the transformer Tr, and outputs the switching output to the secondary coil of the transformer Tr. Take out to L3 and L4. The voltage appearing in the secondary coil accompanying the switching operation of the transistor is rectified by the rectifier circuit, converted to the DC voltage VL1 by the smoothing capacitor C2, and output to the power supply line SPL1.

  The step-up / step-down chopper circuit 40 includes transistors Q7 and Q8 which are switching elements, diodes D7 and D8, coils L7 and L8, and smoothing capacitors C3 and C4.

  Transistors Q7 and Q8 are connected in series between power supply line SPL1 and ground line SL2. The collector of transistor Q7 is connected to power supply line SPL1, and the emitter of transistor Q8 is connected to ground line SL2. Further, diodes D7 and D8 for passing a current from the emitter side to the collector side are connected between the collector and emitter of the transistors Q7 and Q8, respectively.

  One end of coil L7 is connected to the collector of transistor Q7, and the other end is connected to power supply line SPL1. One end of coil L8 is connected to an intermediate point between transistors Q7 and Q8, that is, the emitter of transistor Q7 and the collector of transistor Q8, and the other end is connected to power supply line SPL2. The bases of the transistors Q7 and Q8 are subjected to switching control when a control signal DRV instructing a step-up operation or a step-down operation is given by the control device 50 of FIG.

  Smoothing capacitor C3 is connected between power supply line SPL1 and ground line SL2. Smoothing capacitor C4 is connected between power supply line SPL2 and ground line SL2.

  The step-up / step-down chopper circuit 40 steps down the DC voltage VL1 output from the switching power supply circuit 30 to the voltage VL2 in accordance with the control signal DRV from the control device 50, and supplies the voltage VL2 to the power supply line SPL2.

  More specifically, the step-up / step-down chopper circuit 40 turns on / off the transistor Q7 at a predetermined duty ratio and turns off the transistor Q8 based on the control signal DRV from the control device 50 during the step-down operation. To maintain. In the ON period of transistor Q7, a charging current flows from auxiliary power supply line SPL1 to auxiliary battery 20 through transistor Q7, coil L8, and electric power supply line SPL2. Subsequently, when the transistor Q7 transitions from the on state to the off state, a magnetic flux is generated so as to prevent a current change in the coil L8, so that the charging current continues to flow through the diode D8, the coil L8, and the power supply line SPL2 in order. On the other hand, in terms of electrical energy, DC power is supplied only through the power supply line SPL1 and the ground line SL2 only during the ON period of the transistor Q7. The average voltage of the DC power supplied from the pressure chopper circuit 40 to the auxiliary battery 20 is a value obtained by multiplying the DC voltage VL2 between the power supply line SPL1 and the ground line SL2 by the duty ratio.

  Smoothing capacitor C4 smoothes the DC voltage output to power supply line SPL2, and supplies the smoothed DC voltage VL2 to auxiliary battery 20 and low-voltage auxiliary 110 (FIG. 1).

  Further, the step-up / step-down chopper circuit 40 receives the DC voltage VL2 supplied from the auxiliary battery 20 in accordance with the control signal DRV from the control device 50 when the step-down function of the preceding switching power supply circuit 30 is impaired. The voltage is increased to the voltage VL1 using the coil L8 and supplied to the power supply line SPL1.

  More specifically, the step-up / step-down chopper circuit 40 maintains the transistor Q7 in the off state and turns on / off the transistor Q8 at a predetermined duty ratio based on the control signal DRV from the control device 50 during the boosting operation. Let In the on period of transistor Q8, discharge current flows from power supply battery 20 to power supply line SPL1 through power supply line SPL2, coil L8, and diode D7 in this order. At the same time, pump current flows from auxiliary battery 20 through power supply line SPL2, coil L8, transistor Q8, and ground line SL2 in this order. The coil L8 accumulates electromagnetic energy by this pump current. Subsequently, when the transistor Q8 transitions from the on state to the off state, the coil L8 superimposes the accumulated electromagnetic energy on the discharge current. As a result, the average voltage of the DC power supplied from the step-up / step-down chopper circuit 40 to the power supply line SPL1 and the ground line SL2 is boosted by a voltage corresponding to the electromagnetic energy accumulated in the coil L8 according to the duty ratio.

  As described above, the step-up / step-down chopper circuit 40 according to the present embodiment has a step-up function for stepping up DC power from the auxiliary battery 20 in addition to a step-down function for stepping down DC power received from the switching power supply circuit 30. Is. That is, it has a step-up / step-down function, which is different from the sub power supply system in the conventional power supply apparatus that only reduces the DC voltage from the main power supply. As a result, as described below, according to DC / DC converter 100 according to the present embodiment, high output stability is ensured, so that power can be stably supplied to each auxiliary load. It becomes possible.

  FIG. 3 is a diagram for explaining a voltage conversion operation executed by the DC / DC converter 100 of FIG.

  Referring to FIG. 3, in a normal time when a short circuit failure or the like does not occur in switching power supply circuit 30, the DC power supplied from high-voltage battery 10 is supplied from switching power supply circuit 30 as shown by line LN1 in the figure. Is stepped down to the voltage VL1 and supplied to the power supply line SPL1. Then, the DC power after step-down is further stepped down to voltage VL2 and supplied to power supply line SPL2 and auxiliary battery 20 in step-up / step-down chopper circuit 40 as shown by line LN2 in the drawing.

  As described above, the DC / DC converter 100 is configured to have a two-step voltage step-down function so that two DC / DC converters connected in parallel to the power supply line PL1 and the ground line SL1 are integrated. Can do. As a result, the power supply device can be reduced in size.

  In addition, since the high-voltage auxiliary machine and the low-voltage auxiliary machine are connected to the separate power supply lines SPL1 and SPL2, the power supply line SPL2 having a relatively small amount of current compared to the power supply line SPL1 can be thinned. Cost can be reduced.

  On the other hand, when the step-down function of the switching power supply circuit 30 is impaired due to a short circuit failure of the transistors Q1 to Q4, the power supply to the power supply line SPL1 is cut off, so the EPS 120 and the high-voltage auxiliary machine 130 May not operate normally, and may hinder the running performance of the vehicle.

  Therefore, in the present embodiment, when it is determined that the step-down function of the switching power supply circuit 30 has been impaired, the step-up / step-down chopper circuit 40 performs a boost operation as shown by the line LN3 in the drawing. The DC power from the machine battery 20 is boosted and supplied to the power line SPL1. According to this, even after the abnormality of the switching power supply circuit 30 is detected, it is possible to stably supply power to the EPS 120 and the high-voltage auxiliary machine 130 by suppressing the voltage VL1 of the power supply line SPL1 from decreasing. . As a result, stable operation of the EPS 120 and the high-voltage auxiliary machine 130 is guaranteed, so that the running performance of the vehicle can be improved.

  In the present specification, a control mode in which a voltage conversion operation is performed so that electric power is supplied from the switching power supply circuit 30 to the power supply line SPL1 is referred to as a “normal mode”. On the other hand, a control mode in which the switching operation of the switching power supply circuit 30 is stopped and the voltage conversion operation is performed to supply power from the auxiliary battery 20 to the power supply line SPL1 instead of the switching power supply circuit 30 is referred to as “backup mode” Is also referred to.

  Further, when the boosting function of the step-up / step-down chopper circuit 40 is impaired due to a short circuit failure of the transistor Q7 or Q8 during the execution of the backup mode, as shown by the line LN4 in the figure, the auxiliary battery 20 DC power is supplied to the power supply line SPL1 via the diode D7 connected in antiparallel to the transistor Q7. According to this, although the power supplied to the EPS 120 and the high-voltage auxiliary machine 130 is reduced, it is possible to avoid that the power supply to these auxiliary machine loads is immediately interrupted when an abnormality is detected. As a result, it is possible to improve the traveling performance in the vehicle retreating that is executed in accordance with the abnormality detection, and therefore, a fail-safe function for ensuring the safety of the vehicle when the abnormality is detected is ensured. In the present specification, the control mode in which the voltage conversion operation is stopped so that power is directly supplied from the auxiliary battery 20 to the power supply line SPL1 is also referred to as “fail-safe mode”.

  During the execution of the backup mode and the fail safe mode, the electric power stored in the auxiliary battery 20 is supplied to the EPS 120, the high-voltage auxiliary machine 130, and the low-voltage auxiliary machine 110. When the voltage decreases, there may occur a problem that an ECU (Electronic Control Unit) including the control device 50 becomes inoperable.

  Therefore, during the backup mode, the power consumption of the EPS 120 and the high-voltage auxiliary device 130 is reduced based on the fact that the duty ratio (that is, the boost ratio) of the transistor Q7 of the step-up / step-down chopper circuit 40 is equal to or less than a predetermined threshold. It is determined that the battery has been reduced, and the backup mode is terminated and the normal mode is restored.

  In the fail-safe mode, a preset period of time is set so that the power supply voltage of the auxiliary battery 20 does not fall below the limit value of the operating voltage at which normal operation of the ECU is guaranteed (hereinafter also referred to as the operating voltage lower limit value). It is set as the structure which performs restricting to.

(Control structure of DC / DC converter)
Next, referring to FIG. 4, a control structure for realizing a voltage conversion operation in DC / DC converter 100 according to the present embodiment will be described.

  FIG. 4 is a block diagram showing a control structure in control device 50 according to the first embodiment of the present invention. Each function block shown in FIG. 4 is typically realized by the control device 50 executing a program stored in advance, but part or all of the function may be implemented as dedicated hardware.

  Referring to FIG. 4, control device 50 includes a switching control circuit 502, an output drive control circuit 504, a voltage drop detection circuit 506, a backup mode determination circuit 508, and a voltage sensor 42.

  Voltage sensor 42 is arranged between power supply line SPL1 and ground line SL2, and detects voltage VL1 of power supply line SPL1 and outputs it to voltage drop detection circuit 506.

  When voltage drop detection circuit 506 receives voltage VL1 from voltage sensor 42, voltage drop detection circuit 506 detects a voltage drop in voltage VL1. Specifically, the voltage drop detection circuit 506 determines whether or not the voltage VL1 is equal to or lower than a predetermined threshold voltage Vth (for example, 20V) set in advance. At this time, when the voltage VL1 is equal to or lower than the threshold voltage Vth, the time when the voltage VL1 is equal to or lower than the threshold voltage Vth is measured using a timer (not shown). When the period during which the voltage VL1 is equal to or lower than the threshold voltage Vth continues for a predetermined time Tth or more that is set in advance, the voltage drop detection circuit 506 detects that the voltage VL1 has dropped and detects H (logic high). ) A level detection signal DET is generated, and the generated detection signal DET is output to the backup mode determination circuit 508. On the other hand, when the time during which the voltage VL1 is equal to or lower than the threshold voltage Vth is shorter than the predetermined period Tth, the voltage drop detection circuit 506 generates an L (logic low) level detection signal DET and sends it to the backup mode determination circuit 508. Output.

  The predetermined threshold voltage Vth is set to a voltage higher than the operating voltage lower limit value of the EPS 120 and the high-voltage auxiliary machine 130. The predetermined time Tth is set to a period sufficiently longer than the control period of the voltage conversion operation so that a voltage drop is not erroneously detected when the voltage VL1 temporarily falls below the threshold voltage Vth.

  When receiving the detection signal DET from the voltage drop detection circuit 506, the backup mode determination circuit 508 generates control commands for the switching control circuit 502 and the output drive control circuit 504 based on the logic level of the detection signal DET.

  Specifically, the backup mode determination circuit 508 first determines the control mode of the DC / DC converter 100 based on the detection signal DET. At this time, the backup mode determination circuit 508 selects an optimum control mode from the plurality of control modes (the normal mode, the backup mode, and the fail-safe mode) according to the detection signal DET by the method described below to perform DC / The control mode of the DC converter 100 is determined.

  FIG. 5 is a diagram for explaining a control mode determined based on the detection signal DET and a control command generated based on the determined control mode.

  Specifically, the backup mode determination circuit 508 determines that the step-down function of the switching power supply circuit 30 is normal when the detection signal DET is at L level, that is, when the voltage drop of the voltage VL1 is not detected. The normal mode is determined as the control mode of the DC / DC converter 100.

  On the other hand, when the detection signal DET is at the H level, that is, when the voltage drop of the voltage VL1 is detected, the backup mode determination circuit 508 further determines the backup mode and the failure based on the temporal change of the detection signal DET. Either one of the safe modes is determined as the control mode.

  Specifically, the backup mode determination circuit 508 determines that the step-down function of the switching power supply circuit 30 is impaired in response to the detection signal DET rising from the L level to the H level. In this case, the backup mode determination circuit 508 determines the backup mode as the control mode.

  Further, the backup mode determination circuit 508 determines that the boosting function of the step-up / step-down chopper circuit 40 has been impaired in response to the detection signal DET being held at the H level even after the execution of the backup mode is started. In this case, the backup mode determination circuit 508 determines the fail safe mode as the control mode.

  Next, backup mode determination circuit 508 generates a control command based on the determined control mode, and outputs the generated control command to switching control circuit 502 and output drive control circuit 504, respectively.

  Specifically, referring to FIG. 5, when the control mode of DC / DC converter 100 is the normal mode, backup mode determination circuit 508 generates H-level step-down commands DWN1, DWN2 and a switching control circuit. 502 and output drive control circuit 504, respectively. When switching control circuit 502 receives step-down command DWN1, switching control circuit 502 outputs a control signal CNT for switching control of transistors Q1-Q4 to switching power supply circuit 30 when stepping down DC voltage VH from high-voltage battery 10. To do. In response to step-down command DWN2, output drive control circuit 504 generates control signal DRV that steps down DC voltage VL1 from switching power supply circuit 30 and outputs the control signal DRV to the gates of transistors Q7 and Q8 of step-up / down chopper circuit 40. .

  On the other hand, when the control mode of the DC / DC converter 100 is the backup mode, the backup mode determination circuit 508 generates an H level stop command STP1 and outputs it to the switching control circuit 502. Is generated and output to the output drive control circuit 504. When switching control circuit 502 receives stop command STP1, switching control circuit 502 outputs to switching power supply circuit 30 a control signal CNT for switching control of transistors Q1 to Q4 so as to stop the step-down operation. On the other hand, the output drive control circuit 504 generates a control signal DRV that boosts the DC voltage VL2 from the auxiliary battery 20, and outputs the control signal DRV to the transistors Q7 and Q8 of the step-up / down chopper circuit 40.

  Further, when the control mode of DC / DC converter 100 is the fail-safe mode, backup mode determination circuit 508 generates H-level stop commands STP1 and STP2 to switching control circuit 502 and output drive control circuit 504, respectively. Output. When switching control circuit 502 receives stop command STP1, switching control circuit 502 outputs to switching power supply circuit 30 a control signal CNT for switching control of transistors Q1 to Q4 so as to stop the step-down operation. Further, the output drive control circuit 504 generates a control signal DRV for stopping the boosting operation and outputs it to the transistors Q7 and Q8 of the step-up / step-down chopper circuit 40.

  Note that the backup mode determination circuit 508 previously has a relationship between the control mode and the control command shown in FIG. 5 as a map, and when receiving the detection signal DET from the voltage drop detection circuit 506, refer to the map of FIG. The control command is generated and output to the switching control circuit 502 and the output drive control circuit 504.

  FIG. 6 is a flowchart for realizing voltage conversion control in the control device 50. 6 is realized by the control device 50 (FIG. 1) functioning as each control block shown in FIG.

  Referring to FIG. 6, when voltage drop detection circuit 506 obtains voltage VL1 of power supply line SPL1 from voltage sensor 42 (FIG. 4) (step S01), voltage drop detection circuit 506 detects a voltage drop of voltage VL1. Specifically, the voltage drop detection circuit 506 determines whether or not the period during which the voltage VL1 is equal to or lower than the predetermined threshold voltage Vth continues for the predetermined time Vth (step S02).

  When the period in which voltage VL1 is equal to or lower than predetermined threshold voltage Vth does not continue for a predetermined time Tth or longer (NO in step S02), voltage drop detection circuit 506 determines L level detection signal DET as a backup mode. Output to the circuit 508. When the backup mode determination circuit 508 receives the L level detection signal DET, the backup mode determination circuit 508 determines that the step-down function of the switching power supply circuit 30 is normal, and determines the control mode of the DC / DC converter 100 to the normal mode (step S07). ). Then, the backup mode determination circuit 508 generates control commands (step-down commands DWN1, DWN2) with reference to the map of FIG. 5 and outputs them to the switching control circuit 502 and the output drive control circuit 504. As a result, the DC power from the high voltage battery 10 is stepped down to the voltage VL1 and supplied to the power line SPL1, and the DC power is further stepped down to the voltage VL2 and supplied to the power line SPL2.

  On the other hand, when the period during which voltage VL1 is equal to or lower than predetermined threshold voltage Vth continues for a predetermined time Tth or longer (in the case of YES in step S02), voltage drop detection circuit 506 causes voltage VL1 to drop. In response to this, an H level detection signal DET is output to the backup mode determination circuit 508. When receiving the H level detection signal DET, the backup mode determination circuit 508 determines that the step-down function of the switching power supply circuit 30 has been impaired, and determines the control mode of the DC / DC converter 100 as the backup mode (step S03). . Then, backup mode determination circuit 508 generates control commands (stop command STP1 and boost command UP2) with reference to the map of FIG. 5 and outputs them to switching control circuit 502 and output drive control circuit 504. Thereby, for power supply line SPL1, power supply from high voltage battery 10 is interrupted because switching power supply circuit 30 stops the step-down operation, while step-up / step-down chopper circuit 40 performs the step-up operation. The DC power from the auxiliary battery 20 is boosted and supplied.

  Even during the execution of the backup mode, the voltage drop detection circuit 506 detects a voltage drop of the voltage VL1 by the same procedure as in step S02 (step S04). When the period during which the voltage VL1 is equal to or lower than the predetermined threshold voltage Vth does not continue for the predetermined time Tth (NO in step S04), the voltage drop detection circuit 506 backs up the L level detection signal DET. The data is output to the mode determination circuit 508. When the backup mode determination circuit 508 receives the L level detection signal DET, based on the control signal DRV output from the output drive control circuit 504, the duty ratio (that is, the boost ratio) of the transistor Q8 of the step-up / down chopper circuit 40 Is less than or equal to a predetermined threshold value (step S05).

  When the duty ratio of transistor Q8 of step-up / step-down chopper circuit 40 exceeds a predetermined threshold (NO in step S05), backup mode determination circuit 508 determines that the power consumption of EPS 120 and high-voltage auxiliary machine 130 is large. By returning the process to step S03, the power supply from the auxiliary battery 20 is continued.

  When the duty ratio of transistor Q8 of step-up / step-down chopper circuit 40 is equal to or smaller than a predetermined threshold (YES in step S05), backup mode determination circuit 508 uses power consumption of EPS 120 and high-voltage auxiliary machine 130. And the normal mode is restored (step S06).

  On the other hand, when the period during which voltage VL1 is equal to or lower than predetermined threshold voltage Vth continues for a predetermined time Tth or longer (in the case of YES in step S04), voltage drop detection circuit 506 causes voltage VL1 to drop. In response to this, an H level detection signal DET is output to the backup mode determination circuit 508. When the backup mode determination circuit 508 receives the H level detection signal DET, the backup mode determination circuit 508 determines that the boosting function of the step-up / step-down chopper circuit 40 is impaired, and changes the control mode of the DC / DC converter 100 from the backup mode to the fail-safe mode. (Step S08). Then, the backup mode determination circuit 508 generates control commands (stop commands STP1, STP2) with reference to the map of FIG. 5 and outputs them to the switching control circuit 502 and the output drive control circuit 504. As a result, DC power from the auxiliary battery 20 is supplied to the power supply line SPL1 via the diode D7 so that the step-up / step-down chopper circuit 40 stops the boosting operation. Then, the backup mode determination circuit 508 returns to the normal mode in response to the elapse of a predetermined period after the start of the execution of the fail safe mode (YES in step S09) (step S06).

  In the present embodiment, the switching power supply circuit 30 corresponds to a “switching power supply circuit”, the step-up / step-down chopper circuit 40 corresponds to a “voltage conversion device”, and the auxiliary battery 20 corresponds to a “power storage unit”. And the control apparatus 50 implement | achieves a "voltage drop detection means" and a "control means."

  As described above, according to the first embodiment of the present invention, when the step-down function of the switching power supply circuit 30 is impaired, the auxiliary battery is switched by switching the step-up / step-down chopper circuit 40 from the step-down operation to the step-up operation. 20 can be used to prevent a voltage drop of the power supply line SPL1. As a result, stable operation of the EPS 120 and the high-voltage auxiliary machine 130 is guaranteed, so that the running performance of the vehicle can be improved.

[Embodiment 2]
In the first embodiment, when the step-down function of the switching power supply circuit 30 is impaired, the step-up / step-down chopper circuit 40 is switched from the step-down operation to the step-up operation, whereby the DC power from the auxiliary battery 20 is supplied to the power supply line. The configuration for supplying to SPL1 has been described.

  However, as shown in FIG. 7, even when the step-down function of the switching power supply circuit 30 is normal, the power consumption of the EPS 120 and the high-voltage auxiliary machine 130 increases suddenly to the voltage VL1 of the power supply line SPL1. There is a case where a typical voltage drop occurs.

  FIG. 7 is a diagram for explaining the relationship between power supplied from power supply line SPL1 to EPS 120 and high-voltage auxiliary machine 130 and power supplied from power supply line SPL2 to auxiliary battery 20 and low-voltage auxiliary machine 110.

  FIG. 7 shows a timing chart of voltage VL1 of power supply line SPL1 and supply current IL1 from power supply line SPL1, and a timing chart of voltage VL2 of power supply line SPL2 and supply current IL2 from power supply line SPL2. Yes.

  Referring to FIG. 7, voltage VL1 of power supply line SPL1 and voltage VL2 of power supply line SPL2 are monitored by control device 50 (FIG. 1), and feedback control of the step-down operation is performed so that each voltage matches the target voltage. It is done.

  However, the EPS 120 generally consumes a large amount of power and may require a large supply current IL1 depending on the turning operation of the steering wheel. Therefore, when supply current IL1 increases rapidly at time t1 in the figure, a voltage drop occurs in voltage VL1 as a result. Then, the steering force of the EPS 120 may suddenly disappear due to this voltage drop, and the steering feeling may change suddenly.

  Thus, in the present embodiment, when voltage drop occurs in voltage VL1, DC / DC converter 100 is configured to limit output to power supply line SPL2. In this configuration, the low-voltage auxiliary machine 110 connected to the power supply line SPL2 is supplied with power from the auxiliary battery 20 serving as an output buffer. It is based on the fact that normal operation is guaranteed.

  FIG. 8 illustrates a relationship between power supplied from power supply line SPL1 to EPS 120 and high-voltage auxiliary machine 130 and power supplied from power supply line SPL2 to auxiliary battery 20 and low-voltage auxiliary machine 110 according to the present embodiment. FIG.

  Referring to FIG. 8, it is assumed that voltage VL1 decreases with a rapid increase in supply current IL1 at time t1. At this time, the feedback control circuit for the voltage VL2 monitors the voltage VL1 together with the voltage VL2, and in response to detecting the voltage drop of the voltage VL1, the duty ratio (that is, the step-down voltage) of the transistor Q8 of the step-up / down chopper circuit 40 is detected. Ratio). As a result, voltage VL2 and supply current IL2 decrease after time t1. On the other hand, the voltage VL1 is held at a predetermined reference voltage Vstd. The predetermined reference voltage Vstd is set in advance to a voltage that exceeds the operating voltage lower limit value of the EPS 120 and the high-voltage auxiliary machine 130. Therefore, the EPS 120 can obtain a necessary steering force by receiving power supply from the power supply line SPL1.

  FIG. 9 is a block diagram showing a control structure in control device 50 according to the second embodiment of the present invention. Each functional block shown in FIG. 9 is typically realized by the control device 50 executing a program stored in advance, but a part or all of the function may be implemented as dedicated hardware.

  Referring to FIG. 9, control device 50 includes an output drive control circuit 504, a step-down feedback control circuit 510, voltage sensors 42 and 44, and a switching control circuit (not shown).

  Voltage sensor 42 is arranged between power supply line SPL1 and ground line SL2, and detects voltage VL1 of power supply line SPL1 and outputs it to step-down feedback control circuit 510. Voltage sensor 44 is arranged between power supply line SPL2 and ground line SL2, detects voltage VL2 of power supply line SPL2, and outputs it to step-down feedback control circuit 510.

  The step-down feedback control circuit 510 monitors the voltage VL2 of the power supply line SPL2, and feedback-controls the step-up / step-down chopper circuit 40 so that the voltage VL2 matches the target voltage. Further, the step-down feedback control circuit 510 monitors the voltage VL1 of the power supply line SPL1, and performs feedback control of the step-up / step-down chopper circuit 40 so as to keep the voltage VL1 at or above the reference voltage Vstd.

  Specifically, step-down feedback control circuit 510 includes error amplifiers EA1 and EA2, a triangular wave generator 514, and a comparator COM1.

  The error amplifier EA1 amplifies an error voltage between the voltage VL2 of the power supply line SPL2 from the voltage sensor 44 and the reference voltage Vref, and outputs the amplified error signal to the comparator COM1. At this time, the error signal is controlled to increase when the voltage VL2 is lower than the reference voltage Vref, and is controlled to decrease when the voltage VL2 is higher than the reference voltage Vref.

  The error amplifier EA2 amplifies an error voltage between the voltage VL1 of the power supply line SPL1 from the voltage sensor 42 and the reference voltage Vstd and outputs the amplified error signal to the comparator COM1. At this time, the error signal is controlled to decrease when the voltage VL1 is lower than the reference voltage Vstd, and is controlled to increase when the voltage VL1 is higher than the reference voltage Vstd.

  The triangular wave generator 514 generates a triangular wave and outputs it to the comparator COM1. A sawtooth wave may be generated instead of the triangular wave.

  The comparator COM1 compares the error signal from the error amplifier EA1 and the error signal from the error amplifier EA2 with a triangular wave, and outputs a PWM (Pulse Width Modulation) pulse to the output drive control circuit 504. The output drive control circuit 504 generates a control signal DRV for turning on / off the transistors Q7 and Q8 in accordance with the duty ratio of the PWM pulse and outputs it to the step-up / down chopper circuit 40.

  With such a configuration, the step-down feedback control circuit 510 includes the power supply line in addition to the original function of performing feedback control of the step-up / step-down chopper circuit 40 so that the voltage VL2 of the power supply line SPL2 matches the reference voltage Vref. A function for feedback control of the step-up / step-down chopper circuit 40 is added so that the voltage VL1 of SPL1 matches the reference voltage Vstd. As a result, when a voltage drop occurs in the voltage VL1, the voltage VL1 can be held at the reference voltage Vstd by limiting the step-down operation by reducing the duty ratio of the PWM pulse.

  FIG. 10 is a flowchart for realizing voltage conversion control in the control device 50. In addition, the process of each step shown in FIG. 10 is implement | achieved when the control apparatus 50 (FIG. 1) functions as each control block shown in FIG.

  Referring to FIG. 10, when a series of control is started, step-down feedback control circuit 510 obtains voltage VL1 of power supply line SPL1 from voltage sensor 42 and obtains voltage VL2 of power supply line SPL2 from voltage sensor 44. (Step S11). The step-down feedback control circuit 510 compares the output signals (error signals) of the error amplifiers EA1 and EA2 with the triangular wave by the method described above, and outputs a PWM pulse with a duty ratio corresponding to the comparison result.

  At this time, the step-down feedback control circuit 510 determines whether or not the voltage VL1 is lower than a predetermined reference voltage Vstd (step S12). When voltage VL1 is lower than predetermined reference voltage Vstd (YES in step S12), step-down feedback control circuit 510 controls step-up / step-down chopper circuit 40 so as to limit the output power to power supply line SPL2. . As a result, the voltage VL2 and the supply current IL2 of the power supply line SPL2 are reduced, while the voltage VL1 of the power supply line SPL1 is held at the reference voltage Vstd.

  In contrast, when voltage VL1 is equal to or higher than a predetermined reference voltage Vstd (NO in step S12), step-down feedback control circuit 510 sets the error voltage between voltage VL2 of power supply line SPL2 and reference voltage Vref. Based on this, the step-up / step-down chopper circuit 40 is controlled (step S14). As a result, the voltage VL2 of the power supply line SPL2 is held at a voltage that matches the reference voltage Vref.

  In the present embodiment, the switching power supply circuit 30 corresponds to a “switching power supply circuit”, the step-up / step-down chopper circuit 40 corresponds to a “voltage conversion device”, and the auxiliary battery 20 corresponds to a “power storage unit”. And the control apparatus 50 implement | achieves a "voltage drop detection means" and a "control means."

  As described above, according to the second embodiment of the present invention, of the power supply lines SPL1 and SPL2 connected in parallel to the DC / DC converter 100, the power supply line is increased by a sudden increase in the supply current to the auxiliary load. When a voltage drop occurs in SPL1, the voltage drop of power supply line SPL1 can be prevented by limiting the output to the remaining power supply line SPL2. As a result, stable operation of the EPS 120 and the high-voltage auxiliary machine 130 is guaranteed, so that the running performance of the vehicle can be improved.

[Embodiment 3]
As described in the second embodiment, when the voltage VL1 of the power supply line SPL1 is reduced, the DC / DC converter 100 limits the output to the power supply line SPL2, thereby reducing the voltage VL1 to the reference voltage. Vstd can be held.

  However, when the power consumption of EPS 120 and high-voltage auxiliary machine 130 further increases, as shown in FIG. 11, it is possible to completely avoid the voltage drop of voltage VL1 even by limiting the output to power supply line SPL2. Sex is left.

  FIG. 11 is a diagram for explaining the relationship between the power supplied from power supply line SPL1 to EPS 120 and high-voltage auxiliary machine 130 and the power supplied from power supply line SPL2 to auxiliary battery 20 and low-voltage auxiliary machine 110.

  FIG. 11 shows a timing chart of voltage VL1 of power supply line SPL1 and supply current IL1 from power supply line SPL1, and a timing chart of voltage VL2 of power supply line SPL2 and supply current IL2 from power supply line SPL2. Yes.

  Referring to FIG. 11, voltage VL1 of power supply line SPL1 and voltage VL2 of power supply line SPL2 are monitored by control device 50 (FIG. 1), and feedback control of the step-down operation is performed so that each voltage matches the target voltage. It is done. Then, when voltage VL1 decreases as supply current IL1 suddenly increases at time t1 in the figure, output restriction on power supply line SPL2 is performed in response to voltage VL1 becoming equal to or lower than reference voltage Vstd. At this time, the larger the supply current IL1, the smaller the supply current IL2.

  However, when the power consumption of EPS 120 and high-voltage auxiliary machine 130 is remarkably large, the supply power of power supply line SPL1 is also reduced by setting supply current IL2 to zero, that is, by cutting off the power supply to power supply line SPL2. Moreover, it becomes difficult to satisfy the power consumption of the high-voltage auxiliary machine 130. Therefore, the voltage VL1 becomes lower than the reference voltage Vstd after time t5, and there arises a problem that the driving control in the EPS 120 and the high-voltage auxiliary machine 130 becomes unstable.

  Therefore, in the present embodiment, if the voltage drop of voltage VL1 is not eliminated even by limiting the output to power supply line SPL2, auxiliary battery 20 is switched by switching step-up / step-down chopper circuit 40 from the step-down operation to the step-up operation. To supply power to the power line SPL1. This configuration is realized by shifting the control mode of the DC / DC converter 100 from the normal mode to the backup mode as described in the first embodiment. Note that the backup mode according to the present embodiment supplies power from both high voltage battery 10 and auxiliary battery 20 to power supply line SPL1 by continuing the switching operation of switching power supply circuit 30. This is different from the backup mode according to the first embodiment in which the switching operation of the switching power supply circuit 30 is stopped.

  FIG. 12 illustrates the relationship between power supplied from power supply line SPL1 to EPS 120 and high-voltage auxiliary machine 130 and power supplied from power supply line SPL2 to auxiliary battery 20 and low-voltage auxiliary machine 110 according to the present embodiment. FIG.

  Referring to FIG. 12, it is assumed that voltage VL1 decreases with a rapid increase in supply current IL1 at time t1. At this time, the feedback control circuit for the voltage VL2 monitors the voltage VL1 together with the voltage VL2, and in response to detecting the voltage drop of the voltage VL1, the duty ratio (that is, the step-down voltage) of the transistor Q8 of the step-up / down chopper circuit 40 is detected. Ratio). As a result, voltage VL2 and supply current IL2 decrease after time t1.

  If the voltage drop of the voltage VL1 is detected due to the further increase of the supply current IL1 despite the output restriction on the power supply line SPL2, the feedback control circuit for the voltage VL2 is raised or lowered. The pressure chopper circuit 40 is switched from the step-down operation to the step-up operation. As a result, the boosting operation is executed in the period from time t5 to time t2. As a result, voltage VL1 is held at a predetermined reference voltage Vstd or higher during a period from time t1 to time t2 when supply current IL1 increases. As a result, the EPS 120 and the high-voltage auxiliary machine 130 can stably perform the driving control by receiving power supply from the power supply line SPL1.

  FIG. 13 is a block diagram showing a control structure in control device 50 according to the third embodiment of the present invention. Each function block shown in FIG. 13 is typically realized by the control device 50 executing a program stored in advance, but part or all of the function may be implemented as dedicated hardware.

  Referring to FIG. 13, control device 50 includes output drive control circuit 504, step-down feedback control circuit 510, step-up feedback control circuit 520, mode determination unit 530, voltage sensors 42 and 44, and switching control (not shown). Circuit.

  Voltage sensor 42 is arranged between power supply line SPL1 and ground line SL2, detects voltage VL1 of power supply line SPL1, and outputs it to step-down feedback control circuit 510 and step-up feedback control circuit 520. Voltage sensor 44 is arranged between power supply line SPL2 and ground line SL2, detects voltage VL2 of power supply line SPL2, and outputs it to step-down feedback control circuit 510.

  When step-down feedback control circuit 510 receives signal MDN instructing to control DC / DC converter 100 in the normal mode from mode determination unit 530, voltage VL2 of power supply line SPL2 is monitored, and voltage VL2 matches the target voltage. Thus, the step-up / step-down chopper circuit 40 is feedback-controlled.

  Specifically, step-down feedback control circuit 510 includes error amplifiers EA1 and EA2, a triangular wave generator 514, a comparator COM1, and a voltage drop detection circuit 512.

  The error amplifier EA1 amplifies an error voltage between the voltage VL2 of the power supply line SPL2 from the voltage sensor 44 and the reference voltage Vref, and outputs the amplified error signal to the comparator COM1. At this time, the error signal is controlled to increase when the voltage VL2 is lower than the reference voltage Vref, and is controlled to decrease when the voltage VL2 is higher than the reference voltage Vref.

  The error amplifier EA2 amplifies an error voltage between the voltage VL1 of the power supply line SPL1 from the voltage sensor 42 and the reference voltage Vstd, and outputs the amplified error signal to the comparator COM1 and the voltage drop detection circuit 512. At this time, the error signal is controlled to decrease when the voltage VL1 is lower than the reference voltage Vstd, and is controlled to increase when the voltage VL1 is higher than the reference voltage Vstd.

  The triangular wave generator 514 generates a triangular wave and outputs it to the comparator COM1. A sawtooth wave may be generated instead of the triangular wave.

  The comparator COM1 compares the error signal from the error amplifier EA1 and the error signal from the error amplifier EA2 with a triangular wave, and outputs a PWM pulse to the output drive control circuit 504. The output drive control circuit 504 generates a control signal DRV for turning on / off the transistors Q7 and Q8 in accordance with the duty ratio of the PWM pulse and outputs it to the step-up / down chopper circuit 40.

  The voltage drop detection circuit 512 detects a voltage drop of the voltage VL1 based on the error signal from the error amplifier EA2. Specifically, the voltage drop detection circuit 512 determines whether or not the voltage VL1 is lower than the reference voltage Vstd. At this time, when the voltage VL1 is lower than the reference voltage Vstd, it detects that the voltage VL1 has dropped, generates an H level detection signal DET1, and outputs the generated detection signal DET1 to the mode determination unit 530. . On the other hand, when the voltage VL1 is equal to or higher than the reference voltage Vstd, the voltage drop detection circuit 512 generates an L level detection signal DET1 and outputs the detection signal DET1 to the mode determination unit 530.

  Thus, in step-down feedback control circuit 510, when a voltage drop of voltage VL1 is detected, output restriction on power supply line SPL2 is performed. When a voltage drop of the voltage VL1 is detected regardless of the output limitation, the H level detection signal DET1 is output.

  When mode determination unit 530 receives H level detection signal DET1 from step-down feedback control circuit 510, mode determination unit 530 switches the control mode of DC / DC converter 100 from the normal mode to the backup mode. Then, signal MDB instructing to control DC / DC converter 100 in the backup mode is generated and output to boost feedback control circuit 520.

  When the boost feedback control circuit 520 receives the signal MDB from the mode determination unit 530, the boost feedback control circuit 520 monitors the voltage VL1 of the power supply line SPL1, and feedback-controls the step-up / step-down chopper circuit 40 so that the voltage VL1 matches the target voltage.

  Specifically, the boost feedback control circuit 520 includes an error amplifier EA3, a triangular wave generator 524, a comparator COM2, and a voltage drop detection circuit 522.

  The error amplifier EA3 amplifies the error voltage between the voltage VL1 of the power supply line SPL1 from the voltage sensor 42 and the reference voltage Vstd, and outputs the amplified error signal to the comparator COM2 and the voltage drop detection circuit 522. At this time, the error signal is controlled to increase when the voltage VL1 is lower than the reference voltage Vstd, and is controlled to decrease when the voltage VL1 is higher than the reference voltage Vstd.

  The triangular wave generator 524 generates a triangular wave and outputs it to the comparator COM2. A sawtooth wave may be generated instead of the triangular wave.

  The comparator COM2 compares the error signal from the error amplifier EA3 with a triangular wave and outputs a PWM pulse to the output drive control circuit 504. The output drive control circuit 504 generates a control signal DRV for turning on / off the transistors Q7 and Q8 in accordance with the duty ratio of the PWM pulse and outputs it to the step-up / down chopper circuit 40.

  The voltage drop detection circuit 522 detects a voltage drop of the voltage VL1 based on the error signal from the error amplifier EA3. At this time, similarly to the voltage drop detection circuit 512, the voltage drop detection circuit 522 detects that the voltage VL1 has dropped when the voltage VL1 is lower than the reference voltage Vstd, and outputs the H level detection signal DET2. Generate and output to mode determination unit 530. On the other hand, when the voltage VL1 is equal to or higher than the reference voltage Vstd, the voltage drop detection circuit 522 generates an L level detection signal DET2 and outputs the detection signal DET2 to the mode determination unit 530.

  In this way, boost feedback control circuit 520 boosts the DC power from auxiliary battery 20 and supplies it to power supply line SPL1. When the voltage drop of the voltage VL1 is eliminated by the power supply from the auxiliary battery 20, the L level detection signal DET2 is output from the voltage drop detection circuit 522.

  When the mode determination unit 530 receives the L level detection signal DET2, the duty ratio (that is, the step-up ratio) of the transistor Q8 of the step-up / step-down chopper circuit 40 is based on the control signal DRV output from the output drive control circuit 504. It is determined whether it is below a predetermined threshold. When the duty ratio of transistor Q8 exceeds a predetermined threshold value, mode determination unit 530 determines that the power consumption of EPS 120 and high-voltage auxiliary machine 130 is large and maintains the backup mode, so that the power from auxiliary battery 20 Continue supplying.

  When the duty ratio of transistor Q8 becomes equal to or less than a predetermined threshold, mode determination unit 530 determines that the power consumption of EPS 120 and high-voltage auxiliary machine 130 has decreased, ends the backup mode, and returns to the normal mode. To do.

  FIG. 14 is a flowchart for realizing voltage conversion control in the control device 50. The processing of each step shown in FIG. 14 is realized by the control device 50 (FIG. 1) functioning as each control block shown in FIG.

  Referring to FIG. 14, when a series of control is started, step-down feedback control circuit 510 acquires voltage VL1 of power supply line SPL1 from voltage sensor 42 and acquires voltage VL2 of power supply line SPL2 from voltage sensor 44. (Step S21). The step-down feedback control circuit 510 compares the output signals (error signals) of the error amplifiers EA1 and EA2 with the triangular wave by the method described above, and outputs a PWM pulse with a duty ratio corresponding to the comparison result.

  At this time, the step-down feedback control circuit 510 determines whether or not the voltage VL1 is lower than a predetermined reference voltage Vstd (step S22). When voltage VL1 is equal to or higher than a predetermined reference voltage Vstd (NO in step S22), step-down feedback control circuit 510 performs step-up / step-down chopper based on an error voltage between voltage VL2 of power supply line SPL2 and reference voltage Vref. The circuit 40 is controlled (step S29). As a result, the voltage VL2 of the power supply line SPL2 is held at a voltage that matches the reference voltage Vref.

  On the other hand, when voltage VL1 is lower than predetermined reference voltage Vstd (YES in step S22), step-down feedback control circuit 510 performs step-up / step-down chopper so as to limit the output power to power supply line SPL2. The circuit 40 is controlled (step S23). As a result, the voltage VL2 and the supply current IL2 of the power supply line SPL2 are reduced, while the voltage VL1 of the power supply line SPL1 is held at the reference voltage Vstd.

  At this time, in the step-down feedback control circuit 510, the voltage drop detection circuit 512 detects a voltage drop of the voltage VL1. Specifically, the voltage drop detection circuit 512 determines whether or not the voltage VL1 is lower than a predetermined reference voltage Vstd (step S24).

  When voltage VL1 is equal to or higher than predetermined reference voltage Vstd (NO in step S24), voltage drop detection circuit 512 outputs L level detection signal DET1 to mode determination unit 530. Upon receiving L level detection signal DET1, mode determination unit 530 maintains the control mode of DC / DC converter 100 in the normal mode. Then, the step-down feedback control circuit 510 returns to the first process.

  On the other hand, when voltage VL1 is lower than predetermined reference voltage Vth (YES in step S24), voltage drop detection circuit 512 detects that voltage VL1 has dropped and detects an H level detection signal. DET1 is output to the mode determination unit 530. Upon receiving H level detection signal DET1, mode determination unit 530 determines the control mode of DC / DC converter 100 to be the backup mode (step S25). When the voltage feedback control circuit 520 obtains the voltage VL1 of the power supply line SPL1 from the voltage sensor 42, the booster feedback control circuit 520 compares the output signal (error signal) of the error amplifier EA3 with the triangular wave by the method described above, and the duty ratio according to the comparison result. The PWM pulse is output. Thereby, DC power from auxiliary battery 20 is boosted and supplied to power supply line SPL1 by boosting / lowering chopper circuit 40 performing a boosting operation.

  During execution of this backup mode, the voltage drop detection circuit 522 in the boost feedback control circuit 520 detects the voltage drop of the voltage VL1 by the same procedure as the above step S24 (step S26).

  When voltage VL1 is lower than predetermined reference voltage Vstd (YES in step S26), voltage drop detection circuit 522 detects that voltage VL1 has dropped, and uses H level detection signal DET2 as a mode determination unit. Output to 530. When mode determination unit 530 receives H level detection signal DET2, mode control unit 530 maintains the control mode of DC / DC converter 100 in the backup mode. Then, the boost feedback control circuit 520 returns the process to step S25.

  On the other hand, when voltage VL1 is equal to or higher than predetermined reference voltage Vstd (NO in step S26), voltage drop detection circuit 522 outputs L level detection signal DET2 to mode determination unit 530. When the mode determination unit 530 receives the L level detection signal DET2, the duty ratio (that is, the step-up ratio) of the transistor Q8 of the step-up / step-down chopper circuit 40 is based on the control signal DRV output from the output drive control circuit 504. It is determined whether or not it is below a predetermined threshold (step S27).

  When the duty ratio of transistor Q8 of step-up / step-down chopper circuit 40 exceeds a predetermined threshold (NO in step S27), mode determination unit 530 determines that the power consumption of EPS 120 and high-voltage auxiliary machine 130 is large. By returning the process to step S25, the power supply from the auxiliary battery 20 is continued.

  When the duty ratio of transistor Q8 of step-up / step-down chopper circuit 40 is equal to or smaller than a predetermined threshold (YES in step S27), mode determination unit 530 determines that the power consumption of EPS 120 and high-voltage auxiliary machine 130 is low. It is determined that the voltage has decreased, and the normal mode is restored (step S28).

  In the present embodiment, the switching power supply circuit 30 corresponds to a “switching power supply circuit”, the step-up / step-down chopper circuit 40 corresponds to a “voltage conversion device”, and the auxiliary battery 20 corresponds to a “power storage unit”. The control device 50 implements “voltage drop detection means”, “step-down control means”, and “step-up control means”.

  As described above, according to the third embodiment of the present invention, when the voltage drop of power supply line SPL1 cannot be eliminated even by the output restriction on power supply line SPL2, step-up / step-down chopper circuit 40 is switched from the step-down operation to the step-up operation. Thus, by supplying power from the auxiliary battery 20 connected to the power supply line SPL2 to the power supply line SPL1, it is possible to prevent a voltage drop in the power supply line SPL1. As a result, since the stable operation of the EPS 120 and the high-voltage auxiliary machine 130 is reliably ensured, the running performance of the vehicle can be further improved.

(Example of change)
2, the duty ratio in the switching operation of the transistors Q1 to Q4 connected to the primary coil L2 of the transformer Tr is monitored by monitoring the voltage VL1 of the power supply line SPL1. Although it is configured to be variably set by feedback, it may be configured to be fixed to a duty ratio (50%) that minimizes power loss during switching operation.

  With such a configuration, it is possible to reduce power loss in the DC / DC converter 100 and increase voltage conversion efficiency. The voltage VL1 of the power supply line SPL1 varies in proportion to the variation of the input DC voltage VH, but is stable for the high-voltage auxiliary machine 130 in which the variation of the supply voltage has a small influence on the operation performance. The operation can be kept.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  The present invention can be used for a power supply apparatus that steps down DC power from a power storage unit to a plurality of different voltages and supplies them to a plurality of auxiliary loads, and an electric vehicle equipped with the power supply apparatus.

It is a schematic block diagram of the electric vehicle carrying the power supply device which concerns on Embodiment 1 of this invention. FIG. 2 is a circuit diagram illustrating a configuration of the DC / DC converter of FIG. 1. It is a figure for demonstrating the voltage conversion operation | movement performed with the DC / DC converter of FIG. It is a block diagram which shows the control structure in the control apparatus according to Embodiment 1 of this invention. It is a figure for demonstrating the control mode determined based on a detection signal, and the control command produced | generated based on the determined control mode. It is a flowchart for implement | achieving voltage conversion control in a control apparatus. It is a figure for demonstrating the relationship between the power supplied from a power supply line to EPS and a high voltage system auxiliary machine, and the power supplied from a power supply line to an auxiliary machine battery and a low voltage system auxiliary machine. It is a figure for demonstrating the relationship between the power supplied from the power supply line to EPS and a high voltage system auxiliary machine according to Embodiment 2 of this invention, and the power supplied from a power supply line to an auxiliary battery and a low voltage system auxiliary machine. It is a block diagram which shows the control structure in the control apparatus according to Embodiment 2 of this invention. It is a flowchart for implement | achieving voltage conversion control in a control apparatus. It is a figure for demonstrating the relationship between the power supplied from a power supply line to EPS and a high voltage system auxiliary machine, and the power supplied from a power supply line to an auxiliary machine battery and a low voltage system auxiliary machine. It is a figure for demonstrating the relationship between the power supplied from the power supply line to EPS and a high voltage system auxiliary machine according to Embodiment 3 of this invention, and the power supplied from a power supply line to an auxiliary battery and a low voltage system auxiliary machine. It is a block diagram which shows the control structure in the control apparatus according to Embodiment 3 of this invention. It is a flowchart for implement | achieving voltage conversion control in a control apparatus.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 High voltage battery, 12 Boost converter, 14 Inverter, 20 Auxiliary battery, 30 Switching power supply circuit, 40 Buck-boost chopper circuit, 42,44 Voltage sensor, 50 Control apparatus, 100 DC / DC converter, 110 Low voltage system auxiliary machine, 120 EPS, 130 High-voltage auxiliary machine, 502 Switching control circuit, 504 Output drive control circuit, 506, 512, 522 Voltage drop detection circuit, 508 Backup mode determination circuit, 510 Step-down feedback control circuit, 514, 524 Triangular wave generator, 520 Boost feedback control circuit, 530 mode determination unit, C1-C4 smoothing capacitor, COM1, COM2 comparator, D1-D8 diode, EA1, EA2, EA3 error amplifier, L1-L8 coil, M1 motor, PL1, PL2, SPL1, SPL2 Power line, Q1-Q8 transistors, SL1, SL2 ground line, Tr transformer.

Claims (12)

A switching power supply circuit for stepping down the power supply voltage from the power supply and outputting the first voltage to the first power supply line by the switching operation of the switching element;
An electrical load connected to the first power supply line and driven by receiving the first voltage;
A voltage conversion circuit having a step-down function of stepping down the first voltage from the first power supply line to a second voltage and outputting it to a second power supply line;
A power storage unit connected to the second power supply line and charged by receiving the second voltage;
The voltage conversion circuit further has a boosting function of boosting the second voltage supplied from the power storage unit to the second power supply line and supplying the second voltage to the first power supply line.   2. The power supply device according to claim 1, wherein when the step-down function of the switching power supply circuit is impaired, the voltage conversion circuit boosts the second voltage from the power storage unit and supplies the second voltage to the first power supply line. . Voltage drop detection means for detecting that the step-down function of the switching power supply circuit is impaired when a period in which the voltage of the first power supply line is equal to or lower than a predetermined threshold voltage continues for a predetermined period or more;
The power supply according to claim 2, further comprising a control unit that stops the switching operation and outputs a boost command to the voltage conversion circuit when it is detected that the step-down function of the switching power supply circuit is impaired. apparatus. The voltage conversion circuit includes a first switching element connected between the first power supply line and the second power supply line, and a second switching connected between the second power supply line and the ground line. A chopper circuit including at least an element, and a reactor connected between a connection point of the first and second switching elements and the second power supply line,
The control means maintains the first switching element in an off state and sets a duty ratio at which the voltage of the first power supply line becomes the first voltage to control the switching of the second switching element. The power supply device according to claim 3. The chopper circuit further includes a diode connected in antiparallel to each of the first and second switching elements,
The power supply device according to claim 3, wherein the control means outputs a stop command for the boosting function to the voltage conversion circuit when the boosting function of the voltage conversion circuit is impaired. A switching power supply circuit for stepping down the power supply voltage from the power supply and outputting the first voltage to the first power supply line by the switching operation of the switching element;
An electrical load connected to the first power supply line and driven by receiving the first voltage;
A voltage conversion circuit for stepping down the first voltage from the first power supply line to a second voltage and outputting it to a second power supply line;
A power storage unit connected to the second power supply line and charged by receiving the second voltage;
Voltage drop detection means for detecting a voltage drop in the first power supply line;
A power supply apparatus comprising: control means for controlling the voltage conversion circuit so as to perform output restriction on the second power supply line when a voltage drop of the first power supply line is detected. The voltage conversion circuit includes a first switching element connected between the first power supply line and the second power supply line, and a second switching connected between the second power supply line and the ground line. A chopper circuit including at least an element, and a reactor connected between a connection point of the first and second switching elements and the second power supply line,
When the voltage drop of the first power supply line is detected, the control means maintains the second switching element in an off state, and a duty ratio in which the voltage of the second power supply line is lower than the second voltage. The power supply device according to claim 6, wherein the first switching element is subjected to switching control by setting the value. A switching power supply circuit for stepping down the power supply voltage from the power supply and outputting the first voltage to the first power supply line by the switching operation of the switching element;
An electrical load connected to the first power supply line and driven by receiving the first voltage;
A voltage conversion circuit for stepping down the first voltage from the first power supply line to a second voltage and outputting it to a second power supply line;
A power storage unit connected to the second power supply line and charged by receiving the second voltage;
Voltage drop detection means for detecting a voltage drop in the first power supply line;
A step-down control means for outputting a step-down command to the voltage conversion circuit so as to limit the output to the second power line when a voltage drop of the first power line is detected;
A power supply apparatus comprising boost control means for outputting a boost command to the voltage conversion circuit when a voltage drop of the first power supply line is detected during execution of the output restriction. The voltage conversion circuit includes a first switching element connected between the first power supply line and the second power supply line, and a second switching connected between the second power supply line and the ground line. A chopper circuit including at least an element, and a reactor connected between a connection point of the first and second switching elements and the second power supply line,
When the voltage drop of the first power supply line is detected, the step-down control means maintains the second switching element in an OFF state, and the duty of the voltage of the second power supply line being lower than the second voltage Setting the ratio to control the switching of the first switching element;
When the voltage drop of the first power supply line is detected, the boost control means maintains the first switching element in an off state, and a duty at which the voltage of the first power supply line becomes the first voltage. The power supply device according to claim 8, wherein a ratio is set to control switching of the second switching element.   The power supply device according to claim 1, further comprising: a control unit that performs switching control of the switching element while fixing a duty ratio in the switching operation.   A vehicle equipped with the power supply device according to any one of claims 1 to 10. The vehicle includes a rotating electrical machine that receives power from the power source and drives wheels,
The vehicle according to claim 11, wherein the electric load includes a driving control device for the vehicle.

Images