JP4809046B2 - Motor drive circuit and cooling device using the same - Google Patents

Description

  The present invention relates to a motor driving technique.

  With recent increases in the speed of personal computers and workstations, the operation speed of arithmetic processing LSIs (Large Scale Integrated Circuits) such as CPUs (Central Processor Units) and DSPs (Digital Signal Processors) continues to increase.

  In such an LSI, the amount of heat generation increases as the operation speed, that is, the clock frequency increases. There is a problem that heat generated from the LSI leads to the thermal runaway of the LSI itself or affects surrounding circuits. Therefore, appropriate thermal cooling of LSI is an extremely important technology.

  As an example of a technique for cooling an LSI, there is an air cooling method using a cooling fan. In this method, for example, a cooling fan is installed facing the surface of the LSI, and cold air is blown onto the LSI surface by the cooling fan. When the LSI is cooled by such a cooling fan, the temperature in the vicinity of the LSI is monitored, and the degree of cooling is adjusted by changing the rotation of the fan according to the temperature (Patent Documents 1 and 2). ). Patent Document 3 discloses a technique for limiting the duty ratio of a signal subjected to pulse width modulation so that the fan motor rotates at a predetermined minimum number of rotations or more.

JP-A-7-31190 JP 2001-284868 A JP 2004-153955 A JP-A-6-98574

  When the rotating motor is stopped, a regenerative current flows through the coil, and this regenerative current flows toward the power source. The back electromotive voltage generated at this time may be assumed to exceed the breakdown voltage of the transistor element or the like. Such a problem occurs not only when driving the fan motor but also when driving other motors.

  Patent Document 4 discloses a technique in which a thyristor is provided in parallel with a motor to be driven to perform regenerative control. However, the technique described in Patent Document 4 is used when a bridge circuit is configured by a plurality of transistors and is driven when the plurality of transistors are alternately turned on and off (for example, the H bridge circuit of Patent Document 3). I can't.

  In a motor drive circuit using an H-bridge circuit or the like, a capacitor or a Zener diode is provided between the power supply voltage terminal and the ground in order to protect the circuit from a counter electromotive voltage generated when the motor is stopped. And a method of clamping the counter electromotive voltage. However, the addition of a capacitor or a Zener diode has a problem of increasing the circuit area and cost.

  The present invention has been made in view of such problems, and an object thereof is to suppress generation of a counter electromotive voltage when the motor is stopped in a motor driving circuit that drives the motor by a bridge configuration.

  According to an aspect of the present invention, a drive signal is supplied to an output stage including at least two transistor pairs including a high-side transistor and a low-side transistor connected in series between a power supply voltage terminal and a ground terminal. The present invention relates to a motor driving circuit for supplying a switching voltage to the coil of the motor. This motor drive circuit outputs a drive signal based on a drive signal generation circuit that generates a drive signal for controlling on / off of an output stage transistor according to a target value of the motor torque, and a drive signal output from the drive signal generation circuit. And a driver circuit for alternately turning on and off the high-side transistor and the low-side transistor of the stage. When the driver circuit is instructed to stop the motor, the driver circuit immediately turns off either the high-side transistor or the low-side transistor of the transistor pair and turns off the other of the high-side transistor or the low-side transistor of the transistor pair by a predetermined delay. Turns off after time.

  According to this aspect, during the delay time, the regenerative current can flow through the loop composed of the high-side transistor or the loop composed of the low-side transistor, so that the occurrence of the back electromotive voltage can be suppressed.

The driver circuit may control either the high-side transistor or the low-side transistor based on the drive signal during the delay time.
In this case, during the delay time, the regenerative current flows through a body diode of a MOSFET (Metal Oxide Semiconductor Field Effect Transistor) or a separately provided flywheel diode.

The driver circuit may forcibly turn on either the high-side transistor or the low-side transistor during the delay time.
In this case, since the high-side transistor or the low-side transistor is turned on during the delay time, the regenerative current flows through a channel having a low resistance value of the transistor, so that power consumption of the circuit can be reduced.

  The driver circuit receives a stop signal instructing to stop the motor, and outputs a first timing signal and a second timing signal at different timings shifted by a delay time, and a driving signal generating circuit Is provided on the path of the high-side drive signal supplied to the high-side transistor, and the high-side drive signal is logically synthesized with the first timing signal, and the high-side transistor is forcibly set while the first timing signal is at a predetermined level. A first synthesis circuit that is turned off, and a low-side drive signal that is supplied from the drive signal generation circuit to the low-side transistor are provided on a path, and the low-side drive signal is logically synthesized with the second timing signal. A second synthesis circuit for forcibly turning off the low-side transistor for a period; It may also include a.

  The timing signal generation circuit sets the first timing signal to a predetermined level and then sets the second timing signal to a predetermined level after the delay time has elapsed, and the second synthesis circuit drives the low-side transistor based on the low-side drive signal during the delay time. May be.

  The timing signal generation circuit sets the second timing signal to a predetermined level and then sets the first timing signal to a predetermined level after the delay time has elapsed, and the first synthesis circuit sets the high side transistor to the high side drive signal during the delay time. You may drive based on it.

  The timing signal generation circuit sets the first timing signal to a predetermined level and then sets the second timing signal to a predetermined level after the delay time has elapsed, and the second synthesis circuit forcibly turns on the low-side transistor during the delay time. Also good.

  The timing signal generation circuit sets the second timing signal to a predetermined level and then sets the first timing signal to a predetermined level after the delay time has elapsed, and the first synthesis circuit forcibly turns on the high-side transistor during the delay time. May be.

  There may be further provided a stop signal generation circuit that monitors the state of the motor and generates a stop signal that reaches a predetermined level when a predetermined condition is satisfied and instructs the motor to stop.

  The stop signal generation circuit may monitor the temperature of the motor and set the stop signal to a predetermined level when the motor deviates from a predetermined temperature range. The stop signal generation circuit may monitor the rotation state of the motor and set the stop signal to a predetermined level when rotation is impossible. The stop signal generation circuit may detect a current flowing through the motor coil and set the stop signal to a predetermined level when the detected current exceeds a predetermined value.

  The motor drive circuit may be integrated on a single semiconductor substrate. “Integrated integration” includes the case where all of the circuit components are formed on a semiconductor substrate and the case where the main components of the circuit are integrated. A resistor, a capacitor, or the like may be provided outside the semiconductor substrate. By integrating the motor drive circuit as one LSI, the circuit area can be reduced.

  Another aspect of the present invention is a cooling device. The cooling device includes a fan motor and the above-described motor drive circuit that drives the fan motor.

  Yet another embodiment of the present invention is an electronic device. This electronic apparatus includes the above-described cooling device. According to this aspect, the object to be cooled inside the electronic device can be suitably cooled according to the temperature.

  According to still another aspect of the present invention, a drive signal is supplied to an output stage including at least two transistor pairs including a high-side transistor and a low-side transistor connected in series between a power supply voltage terminal and a ground terminal. This is a motor driving method for supplying a switching voltage to the motor coil. This motor driving method includes a step of generating a drive signal for controlling on / off of the output stage transistor according to a target value of the torque of the motor, and a high side transistor and a low side transistor of the output stage based on the generated drive signal. The step of alternately turning on and off, the step of generating a stop signal that instructs to stop the motor, and the instruction to stop the motor, immediately turn off either the high-side transistor or the low-side transistor of the transistor pair, and the transistor Turning off the other of the pair of high-side transistors or low-side transistors after a predetermined delay time has elapsed.

  Note that any combination of the above-described constituent elements and the constituent elements and expressions of the present invention replaced with each other among methods, apparatuses, systems, etc. are also effective as an aspect of the present invention.

  ADVANTAGE OF THE INVENTION According to this invention, generation | occurrence | production of the back electromotive voltage at the time of a motor stop can be suppressed in the motor drive circuit which drives a motor by bridge | bridging structure.

(First embodiment)
The embodiments of the present invention relate to a motor drive circuit used in a cooling device for cooling an electronic computer such as a desktop computer or a notebook personal computer or a workstation, or an electronic device such as a refrigerator.

  FIG. 1 is a circuit diagram showing a configuration of a cooling device 200 according to the first embodiment of the present invention. The cooling device 200 includes a motor drive circuit 100, an H bridge circuit 110, and a fan motor 120.

  The fan motor 120 is a single-phase full-wave motor in the present embodiment, and is disposed to face a cooling object (not shown). The fan motor 120 is controlled in rotation by controlling the coil current, that is, the energized state by the switching signals Vsw1 and Vsw2 generated by the motor driving circuit 100 and the H bridge circuit 110.

  The H bridge circuit 110 includes a first high side transistor MH1, a second high side transistor MH2, a first low side transistor ML1, a second low side transistor ML2, and a current detection resistor Rdet. The H bridge circuit 110 is an output stage for driving the fan motor 120. The first high-side transistor MH1 and the first low-side transistor ML1 are connected in series between the power supply voltage terminal 112 and the ground terminal GND, and constitute a transistor pair (hereinafter referred to as a first transistor pair). Similarly, the second high side transistor MH2 and the second low side transistor ML2 also constitute a transistor pair (hereinafter referred to as a second transistor pair). In the present embodiment, the first high-side transistor MH1 and the second high-side transistor MH2 are P-channel MOSFETs. The first low side transistor ML1 and the second low side transistor ML2 are N-channel MOSFETs.

  The first high side transistor MH1 and the second high side transistor MH2 constituting the first transistor pair are alternately turned on and off alternately. On / off of the first high-side transistor MH1 and the first low-side transistor ML1 is controlled by a first high-side drive signal SDH1 and a first low-side drive signal SDL1 that are applied to the gates of the transistors.

  The voltage at the connection point of the first high-side transistor MH1 and the first low-side transistor ML1 is applied to one end of the coil of the fan motor 120 as the first switching signal Vsw1. When the first high-side transistor MH1 is on, the first switching signal Vsw1 becomes the power supply voltage Vdd, and when the first low-side transistor ML1 is on, the first switching signal Vsw1 becomes the ground potential (0V).

  On / off of the second high-side transistor MH2 and the second low-side transistor ML2 constituting the second transistor pair is controlled by a second high-side drive signal SDH2 and a second low-side drive signal SDL2 applied to the gates of the transistors. The voltage at the connection point of the two transistors is applied to the other end of the coil of the fan motor 120 as the second switching signal Vsw2. The second switching signal Vsw2 is controlled to have a phase opposite to that of the first switching signal Vsw1.

  A current detection resistor Rdet is provided between the sources of the first low-side transistor ML1 and the second low-side transistor ML2 connected in common and the ground terminal GND. The current detection resistor Rdet converts the current flowing through the coil of the fan motor 120 into a voltage (referred to as a detection voltage Vdet). The detection voltage Vdet is fed back to the motor drive circuit 100.

  Note that the four transistors constituting the H-bridge circuit 110 may be integrated in the motor drive circuit 100. Further, a diode for preventing reverse connection may be provided in the sources of the first high-side transistor MH1 and the second high-side transistor MH2 and the power source (not shown) that outputs the power supply voltage Vdd.

  The motor drive circuit 100 supplies drive signals SDH1, SHL1, SDH2, and SDL2 to the H bridge circuit 110 that is an output stage. As a driving method of the H-bridge circuit 110, there are a linear driving method and a pulse driving method. However, this embodiment can be applied to any method.

  The motor drive circuit 100 includes a drive signal generation circuit 10, a driver circuit 20, and a stop signal generation circuit 30, and is a functional IC integrated on a single semiconductor substrate.

  The drive signal generation circuit 10 includes drive signals SDH1, SDH2, SDL1, and the like, which control on / off of the transistors MH1, MH2, ML1, and ML2 of the H bridge circuit 110 in accordance with the target torque value of the fan motor 120 and the phase transition of the rotor. SDL2 is generated. For example, the drive signal generation circuit 10 may generate a drive signal (hereinafter, collectively referred to as SD as necessary) based on a Hall signal output from a Hall element (not shown). Furthermore, the drive signal SD may be generated by generating a pulse width modulation signal in which a duty ratio is set according to the target value of torque, and synthesizing this pulse width modulation signal and the Hall signal.

  Based on the drive signal SD output from the drive signal generation circuit 10, the driver circuit 20 turns on and off the high-side transistors MH1 and MH2 and the low-side transistors ML1 and ML2 of the H bridge circuit 110 alternately and complementarily.

  When instructed to stop the motor, the driver circuit 20 immediately turns off either the high-side transistor or the low-side transistor of the transistor pair. In the present embodiment, the driver circuit 20 immediately turns off the first high-side transistor MH1 and the second high-side transistor MH2 of each of the first and second transistor pairs.

  Further, the driver circuit 20 turns off either the high-side transistor or the low-side transistor of the transistor pair after a predetermined delay time τd has elapsed. In the present embodiment, the driver circuit 20 turns off the first low-side transistor ML1 and the second low-side transistor ML2 of each of the first and second transistor pairs after the delay time τd has elapsed.

  Next, a configuration example of the driver circuit 20 will be described based on the block diagram of FIG. In the present embodiment, the driver circuit 20 includes a timing signal generation circuit 22, a first synthesis circuit 24, a second synthesis circuit 26, and a pre-driver 28.

  The timing signal generation circuit 22 receives the stop signal Sstop instructing to stop the fan motor 120, and outputs the first timing signal ST1 and the second timing signal ST2 that become high level at different timings shifted by the delay time τd. In the present embodiment, the timing signal generation circuit 22 sets the first timing signal ST1 to the high level and then sets the second timing signal ST2 to the high level after the delay time τd has elapsed.

  The first synthesis circuit 24 is supplied from the drive signal generation circuit 10 to the first high-side transistor MH1 and the second high-side transistor MH2 on the path of the first high-side drive signal SDH1 and the second high-side drive signal SDH2. Provided. The first synthesis circuit 24 logically synthesizes the high side drive signals SDH1 and SDH2 with the first timing signal ST1, and forcibly turns off the high side transistors MH1 and MH2 while the first timing signal ST1 is at a high level. The first synthesis circuit 24 fixes the signal levels of the high side drive signals SDH1 and SDH2 to a logical value at which the high side transistors MH1 and MH2 are turned off while the first timing signal ST1 is at a high level. The first synthesis circuit 24 can be easily configured using an AND gate or an OR gate.

  The second synthesis circuit 26 is provided on the path of the first low side drive signal SDL1 and the second low side drive signal SDL2 supplied from the drive signal generation circuit 10 to the first low side transistor ML1 and the second low side transistor ML2. The second synthesis circuit 26 logically synthesizes the low side drive signals SDL1 and SDL2 with the second timing signal ST2, and forcibly turns off the low side transistors ML1 and ML2 while the second timing signal ST2 is at a high level. The second synthesis circuit 26 fixes the signal levels of the low-side drive signals SDL1 and SDL2 to a logical value at which the low-side transistors ML1 and ML2 are turned off while the second timing signal ST2 is at a high level.

  In the present embodiment, the second synthesis circuit 26 sets on / off of the low side transistors ML1 and ML2 based on the low side drive signals SDL1 and SDL2 during the delay time τd.

  The high side drive signals SDH1 'and SDH2' and the low side drive signals SDL1 'and SDL2' output from the first synthesis circuit 24 and the second synthesis circuit 26 are input to the pre-driver 28. The pre-driver 28 has a driving capability sufficient to drive the transistors constituting the H bridge circuit 110. The pre-driver 28 switches on and off the transistors MH1, MH2, ML1, and MH2 based on the drive signals SDH1 ', SDH2', SDL1 ', and SDL2'.

  The stop signal generation circuit 30 monitors the state of the fan motor 12 and generates a stop signal Sstop that is high when a predetermined condition is satisfied and instructs the fan motor 120 to stop. In the present embodiment, detection signal Vdet corresponding to the current flowing through the coil of fan motor 120 is input to stop signal generation circuit 30. The stop signal generating circuit 30 instructs the stop of the fan motor 120 by setting the stop signal Sstop to a high level when the detection voltage Vdet exceeds a predetermined threshold voltage, that is, when the coil current exceeds a predetermined value. To do.

  The stop signal generation circuit 30 may monitor the temperature of the fan motor 120 in addition to the coil current of the fan motor 120, and may set the stop signal Sstop to a high level when the temperature deviates from a predetermined temperature range. Further, the stop signal generation circuit 30 may monitor the rotation state of the fan motor 120, and may set the stop signal Sstop to a high level when the fan motor 120 cannot be rotated due to foreign matter or the like. The stop signal generation circuit 30 may monitor a plurality of pieces of information and analyze them in combination to generate a stop signal Sstop. The stop signal generation circuit 30 may be understood as a circuit that detects a circuit abnormality. Further, the stop signal Sstop input to the timing signal generation circuit 22 may be given from the outside of the motor drive circuit 100.

  The operation of the motor drive circuit 100 configured as described above will be described. 2A to 2E are time charts showing operation states of the motor drive circuit 100 according to the present embodiment when the motor is stopped. 2A shows the stop signal Sstop, FIG. 2B shows the first timing signal ST1, FIG. 2C shows the second timing signal ST2, and FIG. 2D shows the first synthesis. The high-side drive signal SDH ′ output from the circuit 24 and the low-side drive signal SDL ′ output from the second synthesis circuit 26 are shown in FIG.

  During the period from time t0 to t1, the motor driving circuit 100 rotates the fan motor 120 at a predetermined rotational speed. If a circuit abnormality is detected by the stop signal generation circuit 30 at time t1, the stop signal Sstop becomes high level. When the stop signal Sstop becomes high level, the timing signal generation circuit 22 immediately sets the first timing signal ST1 to high level.

  When the first timing signal ST1 becomes high level at time t1, the first synthesis circuit 24 fixes the logical value of the high side drive signal SDH and turns off the first high side transistor MH1 and the second high side transistor MH2. .

  At time t2 after the elapse of delay time τd from time t1, the timing signal generation circuit 22 sets the second timing signal ST2 to the high level. When the second timing signal ST2 becomes high level, the second synthesis circuit 26 fixes the logic value of the low-side drive signal SDL and turns off the first low-side transistor ML1 and the second low-side transistor ML2.

  During the delay time τd from time t1 to time t2, the first low-side transistor ML1 and the second low-side transistor ML2 are controlled to be turned on / off by the drive signals SDL1 and SDL2 generated by the drive signal generation circuit 10. As described above, since the first low-side drive signal SDL1 and the second low-side drive signal SDL2 are exclusively controlled to be turned on / off, one of them depends on the position of the rotor of the fan motor 120 at times t1 to t2. On, the other is off.

  FIGS. 3A to 3C are diagrams showing the state of the H-bridge circuit 110 when the motor is stopped. FIG. 3A shows the state immediately before time t1 when the stop signal Sstop transited to a high level, and FIG. 3B shows the state of the delay time τd from time t1 to t2. Indicates a state after time t2. In FIGS. 3A to 3C, the transistors constituting the H-bridge circuit 110 are shown as switches.

  As shown in FIG. 3A, it is assumed that the first high-side transistor MH1 and the second low-side transistor ML2 are on immediately before time t1 when the stop signal Sstop becomes high level. At this time, the coil current Icoil flows through the coil L of the fan motor 120 through the path from the power supply voltage terminal 112 to the first high-side transistor MH1, the coil L, and the second low-side transistor ML2.

  When the first high-side transistor MH1 and the second high-side transistor MH2 were forcibly turned off at time t1, the back electromotive force was generated by the energy stored in the coil L and was flowing in FIG. The coil current Icoil is kept flowing. As a result, the coil current Icoil is supplied through the body diode D1 existing between the back gate and the drain of the first low-side transistor ML1.

  When the state shown in FIG. 3B is held for the delay time τd, the energy stored in the coil L is dissipated and the coil current Icoil becomes zero. In other words, the delay time τd is desirably set longer than the time required for energy to be dissipated by regeneration. This time is a value to be determined by the inductance of the coil and the like. For a motor used for a fan motor or the like, it is desirable to set the time in a range from sub ms to several tens of ms, for example.

  When the second timing signal ST2 becomes high level at time t2, as shown in FIG. 3C, all transistors (switches) are turned off.

  As described above, according to the motor drive circuit 100 according to the present embodiment, a regeneration path is provided by a loop including two low-side transistors by delaying the low-side transistor after turning off the motor. And regenerative current can be dissipated. As a result, since the regenerative current flowing through the coil L does not flow into the power supply connected to the outside via the power supply voltage terminal 112, the potential of the power supply voltage terminal 112 is prevented from instantaneously jumping up due to the counter electromotive voltage. be able to.

  Further, according to this aspect, since current does not flow into the power supply, it is not necessary to provide a Zener diode or a capacitor between the power supply voltage terminal 112 and the ground terminal, thereby simplifying the circuit and reducing the cost. You can also plan.

  Next, a modification of the first embodiment will be described. In the above-described embodiment, the high-side transistor is turned off after the stop signal Sstop becomes high level, and then the low-side transistor is turned off for a period until the delay time τd elapses. In a modified example, the low side transistor may be immediately turned off in response to the transition of the stop signal Sstop, and then the high side transistor may be turned off after the delay time has elapsed.

  Such a modification can be easily realized by, for example, switching the level transition timings of the first timing signal ST1 and the second timing signal ST2 in the timing signal generation circuit 22.

  4A to 4C are diagrams showing the state of the H-bridge circuit 110 when the motor is stopped in this modification. 4A and 4C are the same as FIGS. 3A and 3C. In this modification, the regenerative current flows in a loop formed by the body diodes of the first high-side transistor MH1 and the second high-side transistor MH2 during the delay time τd from time t1 to time t2. As a result, the regenerative current does not flow into the power supply (not shown) via the power supply voltage terminal 112, and the potential of the power supply voltage terminal 112 can be prevented from jumping up instantaneously.

(Second Embodiment)
In the first embodiment, the drive signal generating circuit 10 turns on / off the low-side transistor (in the modified example, the high-side transistor) until the delay time τd elapses after the stop signal Sstop becomes high level. It was set based on the drive signal output from. On the other hand, in the second embodiment, the two low-side transistors are forcibly turned on during the period from when the stop signal Sstop becomes high level until the delay time τd elapses.

  The motor drive circuit 100 according to the second embodiment may be basically configured similarly to FIG. For example, by inputting the first timing signal ST1 in addition to the second timing signal ST2 to the second synthesis circuit 26 and performing a logical operation on the two timing signals, a period in which only the first timing signal ST1 is at a high level is detected. To do. The second synthesis circuit 26 includes the first low-side drive signal SDL1 ′ and the second low-side so that both the first low-side transistor ML1 and the second low-side transistor ML2 are turned on while only the first timing signal ST1 is high. The logical value of the drive signal SDL2 ′ is controlled.

  FIGS. 5A to 5E are time charts showing operation states of the motor drive circuit 100 according to the second embodiment when the motor is stopped. FIGS. 6A to 6C are diagrams showing the state of the H-bridge circuit 110 when the motor is stopped according to the present embodiment.

  The motor drive circuit 100 according to the second embodiment and the motor drive circuit 100 according to the first embodiment are different in operation only during the delay time τd between times t1 and t2. As shown in FIG. 5E, during the period from time t1 to time t2, the drive signal SDL ′ output from the second synthesis circuit 26 is a logic in which both the first low-side transistor ML1 and the second low-side transistor ML2 are turned on. Set to a value.

  FIG. 6A shows the state immediately before time t1 when the stop signal Sstop transited to the high level, and FIG. 6B shows the state of the delay time τd from time t1 to t2. Indicates a state after time t2.

  As shown in FIG. 6B, in the present embodiment, the first low-side transistor ML1 and the second low-side transistor ML2 are turned on during the delay time τd. As a result, in the first embodiment, the regenerative current flowing through the body diode of the first low-side transistor ML1 flows in the channel of the first low-side transistor ML1, and the first low-side transistor ML1 and the first low-side transistor ML1 A loop is formed by the channel of the two low-side transistors ML2, and the energy stored in the coil is dissipated.

  As in the first embodiment, when a current flows through the body diode of the transistor, a voltage drop corresponding to the forward voltage Vf occurs. On the other hand, in the present embodiment, since the regenerative current flows through the channel of the first low-side transistor ML1, the voltage drop becomes the drain-source voltage Vds. Since the drain-source voltage Vds is smaller than the forward voltage Vf, power consumption can be suppressed.

  A modification similar to that of the first embodiment can be considered for this embodiment. That is, in the modification, the low side transistor may be immediately turned off in response to the transition of the stop signal Sstop, and then the two high side transistors may be turned on for the delay time, and then the high side transistor may be turned off.

  Those skilled in the art will understand that the above-described embodiment is an exemplification, and that various modifications can be made to combinations of the respective constituent elements and processing processes, and such modifications are also within the scope of the present invention. is there.

  In the embodiment, the case where the motor drive circuit 100 is integrally integrated in one LSI has been described. However, the present invention is not limited to this, and some components are provided as discrete elements or chip components outside the LSI. Alternatively, it may be composed of a plurality of LSIs. For example, the H bridge circuit 36 may be configured using a discrete power transistor, or may be built in the motor drive circuit 100.

  In addition, the transistor used in the embodiment may be configured by replacing the bipolar transistor and the FET with each other or by replacing the P-channel and N-channel transistors.

  In the embodiment, the case of driving a single-phase motor has been described, but the present invention is not limited to this. That is, even in a motor drive circuit that drives a three-phase motor, etc., when the motor is stopped, the regenerative current is shifted by shifting the timing for turning off the high side and the timing for turning off the low side transistor by the delay time. Can be prevented from flowing toward the power source.

  In the embodiment, the motor drive circuit 100 has been described with respect to driving a fan motor. However, the motor to be driven by the motor drive circuit according to the present invention is not limited to the fan motor, and other single motors. It can be widely applied to phase and multiphase motors.

  In the circuit described in the embodiment, the setting of the high level and low level logic values of the signal is an example, and can be freely changed by appropriately inverting it with an inverter or the like.

It is a circuit diagram which shows the structure of the cooling device which concerns on 1st Embodiment. It is a time chart which shows the operation state at the time of the motor stop of the motor drive circuit which concerns on 1st Embodiment. It is a figure which shows the state at the time of the motor stop of the H bridge circuit in 1st Embodiment. It is a figure which shows the state at the time of the motor stop of the H bridge circuit in the modification of 1st Embodiment. It is a time chart which shows the operation state at the time of the motor stop of the motor drive circuit which concerns on 2nd Embodiment. It is a figure which shows the state at the time of the motor stop of the H bridge circuit in 2nd Embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 100 Motor drive circuit, 110 H bridge circuit, 112 Power supply voltage terminal, 120 Fan motor, 200 Cooling device, 10 Drive signal generation circuit, 20 Driver circuit, 22 Timing signal generation circuit, 24 1st synthetic circuit, 26 2nd synthetic circuit , 28 pre-driver, 30 stop signal generation circuit, ST1 first timing signal, ST2 second timing signal, SDH1 first high side drive signal, SDH2 second high side drive signal, SDL1 first low side drive signal, SDL2 second low side Drive signal, MH1 first high side transistor, ML1 first low side transistor, MH2 second high side transistor, ML2 second low side transistor, Vsw1 first switching signal, Vsw2 second switch Switching signal.

Claims (11)

A drive signal is supplied to an output stage including at least two transistor pairs including a high-side transistor and a low-side transistor connected in series between a power supply voltage terminal and a ground terminal, and a switching voltage is applied to a coil of a motor to be driven. A motor drive circuit to supply,
A drive signal generation circuit that generates a drive signal for controlling on / off of the transistor of the output stage according to a target value of the torque of the motor;
A driver circuit that alternately turns on and off the high-side transistor and the low-side transistor of the output stage based on the drive signal output from the drive signal generation circuit;
With
When the driver circuit is instructed to stop the motor, the driver circuit immediately turns off either the high-side transistor or the low-side transistor of the transistor pair and turns off the other of the high-side transistor or the low-side transistor of the transistor pair. And turn off after a predetermined delay time, and the driver circuit
A timing signal generating circuit which receives a stop signal instructing to stop the motor and outputs a first timing signal and a second timing signal which are at predetermined levels at different timings shifted by the delay time;
Provided on a path of a high-side drive signal supplied from the drive signal generation circuit to the high-side transistor, and logically synthesizes the high-side drive signal with the first timing signal, and the first timing signal has a predetermined level. A first synthesis circuit for forcibly turning off the high-side transistor for a period of time;
Provided on a path of a low-side drive signal supplied from the drive signal generation circuit to the low-side transistor, logically synthesizing the low-side drive signal with the second timing signal, and the second timing signal being in a predetermined level, A second synthesis circuit for forcibly turning off the low-side transistor;
A motor drive circuit comprising: The timing signal generation circuit sets the first timing signal to a predetermined level and then sets the second timing signal to a predetermined level after the delay time has elapsed.
2. The motor drive circuit according to claim 1 , wherein the second synthesis circuit sets ON / OFF of the low-side transistor based on the low-side drive signal during the delay time. The timing signal generation circuit sets the second timing signal to a predetermined level and then sets the first timing signal to a predetermined level after the delay time has elapsed.
2. The motor drive circuit according to claim 1 , wherein the first synthesis circuit sets ON / OFF of the high-side transistor based on the high-side drive signal during the delay time. The timing signal generation circuit sets the first timing signal to a predetermined level and then sets the second timing signal to a predetermined level after the delay time has elapsed.
The motor drive circuit according to claim 1 , wherein the second synthesis circuit forcibly turns on the low-side transistor during the delay time. The timing signal generation circuit sets the second timing signal to a predetermined level and then sets the first timing signal to a predetermined level after the delay time has elapsed.
The motor drive circuit according to claim 1 , wherein the first synthesis circuit forcibly turns on the high-side transistor during the delay time. Monitoring the state of the motor becomes a predetermined level when a predetermined condition is satisfied, any one of claims 1 to 5, characterized by further comprising a stop signal generating circuit for generating a stop signal for instructing the stop of the motor The motor drive circuit described in 1. The motor drive circuit according to claim 6 , wherein the stop signal generation circuit monitors the temperature of the motor and sets the stop signal to a predetermined level when deviating from a predetermined temperature range. The motor drive circuit according to claim 6 , wherein the stop signal generation circuit monitors a rotation state of the motor and sets the stop signal to a predetermined level when the motor cannot rotate. The motor according to claim 6 , wherein the stop signal generation circuit detects a current flowing through a coil of the motor, and sets the stop signal to a predetermined level when the detected current exceeds a predetermined value. Driving circuit. The motor drive circuit according to any one of claims 1-9, characterized in that it is integrated on a single semiconductor substrate. A fan motor,
The motor drive circuit according to any one of claims 1 to 10 , which drives the fan motor;
A cooling device comprising:

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