JP2009294883A - Series regulator and electronic equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a series regulator protecting a boost transistor, and supplying desired currents to equipment using the output voltage of the series regulator even when a power supply voltage is reduced, and to provide electronic equipment equipped with the same. <P>SOLUTION: The series regulator is provided with a control part 7. The control part 7 controls a boost transistor 4 by switching between first overcurrent restriction characteristics wherein when an input voltage is higher than a predetermined first voltage, and the voltage of an output part 3 is higher than a predetermined second voltage, output currents from the output part 3 are held at predetermined currents, and when the input voltage is higher than a predetermined first voltage, and the voltage of the output part 3 becomes lower than a predetermined second voltage, output currents from the output part 3 are decreased; and a second overcurrent restriction characteristics wherein when the input voltage is within a predetermined range which is lower than the predetermined first voltage, and the voltage of the output part 3 is lower than the predetermined second voltage, output currents larger than the output currents in the first overcurrent restriction characteristics can be output from the output part 3. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a series regulator and an electronic apparatus including the same.

  For example, a power source such as a battery of a vehicle has a very large voltage fluctuation, so that an internal circuit of an electronic device connected to the power source is protected or a stable input from a sensor connected to the electronic device is secured. For this purpose, the voltage is stepped down by a series regulator or a switching regulator.

  In the series regulator, an overcurrent protection circuit is used to prevent the boost transistor from burning out when the output terminal of the power source exceeds a ground fault or allowable current. The over-current protection method for series regulators includes the “droop characteristic” method with a fixed limit current, the “A-shaped characteristic” method that varies the limiting current depending on the output voltage, and the “F-character characteristic”. There is a method. For example, in a system with a load current of 200 mA or more, the “A-shaped characteristic” method or the “F-shaped characteristic” method is used to reduce the loss between the base and collector of the transistor in the event of a ground fault.

  In addition, as a conventional technology, the overcurrent detection characteristics are switched after a certain period of time from power startup, the overcurrent detection level at power startup is increased, and the fail-safe function for quickly charging the output stabilization capacity has been improved. There is a low-voltage power supply circuit (see, for example, Patent Document 1).

JP 2006-155099 A

  FIG. 1 is a graph showing the output voltage of a series regulator having an overcurrent protection circuit (hereinafter referred to as “A-shaped method”) employing the “A-shaped characteristic” method. In FIG. 1, the horizontal axis indicates the output current, and the vertical axis indicates the output voltage. The A-shaped method has a problem that the operation of the internal circuit of the electronic device using the output voltage of the series regulator is sacrificed when the power supply is at a low voltage. In the A-shaped method, the output voltage of the series regulator is monitored, and when the output voltage of the series regulator is lower than the predetermined voltage Va, the output voltage cannot be obtained, so that the limit current is switched from Ia to Ib. In other words, in the conventional method, it cannot be distinguished whether the output voltage of the series regulator has dropped due to overload or whether the output voltage has fallen due to constant voltage operation of the series regulator.

  For example, in the case of in-vehicle products, especially when the temperature is low or when an aging battery is used, the battery voltage decreases greatly during cranking when the starter is turned on to start the engine. In order to complete, the internal circuit of the electronic device must perform minimum processing operations such as injection and ignition even when the battery voltage is low. However, when the battery voltage decreases, the output voltage of the series regulator also decreases at the same time. Therefore, there is a problem that the overcurrent protection circuit acts and the operation that the internal circuit of the original electronic device should perform is limited. For example, an IC (Integrated Circuit) that operates on a load line indicated by a virtual line in FIG. 1 requires a large input current when the input voltage is low, but when the power supply voltage decreases, a current necessary for the operation of the IC is input to the IC Instead, the operation is limited. The conventional technique described in Patent Document 1 also has the same problem.

  Accordingly, an object of the present invention is not only to protect the booth transistor but also to provide a series regulator that can supply a desired current to a device that uses the output voltage even when the power supply voltage drops, and an electronic device including the series regulator Is to provide.

The present invention (1) includes an input unit, an output unit, and a boost transistor provided between the input unit and the output unit. By controlling the boost transistor, an input voltage applied to the input unit is set to a predetermined voltage. Series regulator that can convert to
A detection unit for detecting the input voltage;
When the input voltage is higher than a predetermined first voltage and the voltage of the output unit is higher than a predetermined second voltage, an output current from the output unit is held at a predetermined current, and the input voltage Is higher than a predetermined first voltage, and when the voltage of the output unit is lower than a predetermined second voltage, a first overcurrent limiting characteristic for reducing an output current from the output unit, and the input When the voltage is in a predetermined range lower than the predetermined first voltage and the voltage of the output unit is lower than the predetermined second voltage, the output current in the first overcurrent limiting characteristic is more than And a control unit that controls the boost transistor by switching to a second overcurrent limiting characteristic capable of outputting a large output current from the output unit.

Further, the present invention (3) includes an input unit, an output unit, and a boost transistor provided between the input unit and the output unit. By controlling the boost transistor, an input voltage applied to the input unit is set to a predetermined value. A series regulator that can convert to voltage and output from the output section,
A detection unit for detecting a potential difference between the input voltage and the voltage of the output unit;
When the potential difference is larger than a predetermined potential difference and the voltage of the output unit is higher than a predetermined voltage, the output current from the output unit is held at a predetermined current, and the input voltage is larger than the predetermined potential difference. A first overcurrent limiting characteristic that reduces the output current from the output unit when the voltage of the output unit is lower than a predetermined voltage, and a predetermined range in which the input voltage is smaller than the predetermined potential difference And a second overcurrent limit capable of outputting an output current larger than the output current in the first overcurrent limit characteristic when the voltage of the output section is lower than a predetermined voltage. And a control unit that controls the boost transistor by switching characteristics.

  The present invention (5) is an electronic apparatus comprising the series regulator.

  According to the present invention (1), the input voltage is detected by the detection unit, and the control unit switches the first and second overcurrent limiting characteristics in accordance with the input voltage to control the boost transistor. The first overcurrent limiting characteristic is that when the input voltage is higher than the predetermined first voltage and the voltage of the output unit is higher than the predetermined second voltage, the output current from the output unit is set to the predetermined current. When the input voltage is higher than the predetermined first voltage and the voltage of the output unit is lower than the predetermined second voltage, the output current from the output unit is reduced. The second overcurrent limiting characteristic is the first overcurrent when the input voltage is a voltage in a predetermined range lower than the predetermined first voltage and the voltage of the output unit is lower than the predetermined second voltage. This is a characteristic that can output an output current larger than the output current in the current limiting characteristic from the output unit.

  As a result, when the input voltage is higher than the predetermined first voltage, the output current is limited when the output voltage is lower than the predetermined second voltage. Burnout can be suppressed, and when the input voltage is lower than the predetermined first voltage, the output current from the output unit is changed to the first voltage when the output voltage is lower than the predetermined second voltage. Since the boost transistor is controlled by the control unit so as to increase compared to the case of the overcurrent limiting characteristic, a desired current can be supplied to a device using the output voltage even when the input voltage is lowered. . Therefore, both high fail-safety and operation at low voltage can be achieved.

  According to the present invention (3), the potential difference between the input voltage and the voltage of the output unit is detected by the detection unit, and the control unit switches between the first and second overcurrent limiting characteristics according to the potential difference, and the boost transistor To control. In the first overcurrent limiting characteristic, when the potential difference is larger than a predetermined potential difference and the voltage of the output unit is higher than a predetermined voltage, the output current from the output unit is held at a predetermined current, and the potential difference is When the voltage difference is larger than the predetermined potential difference and the voltage of the output unit becomes lower than the predetermined voltage, the output current from the output unit is reduced. The second overcurrent limiting characteristic is an output current in the first overcurrent limiting characteristic when the potential difference is a potential difference in a predetermined range smaller than the predetermined potential difference and the voltage of the output unit is lower than the predetermined voltage. It is a characteristic that a larger output current can be output from the output unit.

  As a result, when the potential difference is larger than the predetermined potential difference, the output current is limited when the output voltage drops below the predetermined voltage, so that the loss between the base and collector of the transistor can be reduced during a ground fault. In addition, when the potential difference is smaller than a predetermined voltage, when the output voltage drops from a predetermined voltage, the output current from the output unit is increased as compared with the case of the first overcurrent limiting characteristic. Since the boost transistor is controlled by the control unit, a desired current can be supplied to a device using the output voltage even when the input voltage is lowered. Therefore, both high fail-safety and operation at low voltage can be achieved.

  According to the present invention (5), by providing the switching regulator, the burnout destruction of the boost transistor is suppressed, and the current output from the switching regulator is reduced when the input voltage input to the switching regulator is reduced. Since the decrease is suppressed, it is possible to suppress the operation of a circuit that operates by being supplied with a current from the switching regulator, and an electronic device with improved reliability can be provided.

  FIG. 2 is a circuit diagram showing a series regulator 1 according to an embodiment of the present invention. A series regulator (hereinafter referred to as a regulator) 1 includes an input unit 2, an output unit 3, and a boost transistor (hereinafter referred to as an output transistor) 4 provided between the input unit 2 and the output unit 3. By controlling the above, the input voltage applied to the input unit 2 can be converted into a predetermined voltage and output from the output unit 3. A battery (BATT) 5 as a power source is connected to the input unit 2, and a power supply voltage is applied from the battery 5. Therefore, in the present embodiment, the input voltage applied to regulator 1 is equal to the power supply voltage (battery voltage). The boost transistor 4 is a PNP-type bipolar transistor (hereinafter referred to as “PNP transistor”), an emitter is electrically connected to the input unit 2 via a resistance element 10 described later, and a collector is electrically connected to the output unit 3. It is connected. The boost transistor 4 converts the voltage applied to the emitter into a predetermined voltage according to the signal applied to the base, and outputs the voltage from the collector.

  The regulator 1 is configured to include a power supply voltage monitor unit 6 and a control unit 7. The power supply voltage monitor unit 6 is a detection unit that detects an input voltage. The power supply voltage monitoring unit 6 compares the input voltage with a predetermined first voltage Vth1, and gives the result to the switching unit 16 described later. The power supply voltage monitoring unit 6 outputs a high level signal when the input voltage is equal to or higher than a predetermined first voltage Vth1, for example, and outputs a low level signal when the input voltage is lower than the predetermined first voltage Vth1. Output.

  FIG. 3 is a diagram illustrating an example of a circuit configuration of the power supply voltage monitor unit 6. The power supply voltage monitor unit 6 includes two resistance elements 7 a and 7 b that are resisted in series, a comparator 8, and a first reference voltage source 9. One terminal of the resistance elements 7a and 7b connected in series is electrically connected to the input unit 2, and the other is electrically connected to the ground. The non-inverting input terminal of the comparator 8 is connected to the connection portion 7c of the resistance elements 7a and 7b, and the inverting input terminal is connected to the first reference voltage source 9. The output terminal of the comparator 8 is electrically connected to a switching control terminal 16d of the switching unit 16 described later. The voltage of the first reference voltage source 9 is a predetermined first voltage Vth1.

  The control unit 7 includes a resistance element 10, first and second transistors 11 and 12, a regulator control circuit 13, a capacitor 14, a switching unit 16, and a first for realizing a plurality of overcurrent limiting characteristics. An overcurrent control circuit 21 and a second overcurrent control circuit 22 are provided. The first overcurrent control circuit 21 and the second overcurrent control circuit 22 are protection circuits for protecting the boot transistor 4 from overcurrent.

  The resistance element 10 has one terminal connected to the input unit 2 and the other terminal electrically connected to the emitter of the boost transistor 4. The first transistor 11 is an NPN-type bipolar transistor (hereinafter referred to as “NPN transistor”), the emitter is connected to the ground, the collector is connected to the base of the boost transistor 4, and the base is connected to the regulator control circuit 13. Has been.

  The second transistor 12 is an NPN transistor, the emitter is connected to the ground, the collector is connected to the base of the first transistor 11, and the base is connected to the switching circuit 17. The regulator control circuit 13 detects the output voltage output from the collector of the boost transistor 4, changes the current supplied to the base of the first transistor 11, and controls the base current of the boost transistor 4. The output voltage is controlled to be a predetermined voltage.

  The capacitor 14 has one terminal connected to the collector of the boost transistor 4 and the other terminal connected to the regulator control circuit 13. By providing the capacitor 14, the output voltage output from the collector of the boost transistor 4 can be stably detected in the regulator control circuit 13 by suppressing rapid fluctuations in the output voltage output from the collector of the boost transistor 4. Can do.

  The switching unit 16 includes a three-terminal switch having two input terminals 16a and 16b, one output terminal 16c, and a switching control terminal 16d. The switching unit 16 selectively connects one of the two input terminals 16a and 16b and the output terminal 16c in accordance with a signal given from the power supply voltage monitoring unit 6 to the switching control terminal 16d. Here, the input terminal 16a and the output terminal 16c are connected when the signal supplied from the power supply voltage monitoring unit 6 is high level, and the input terminal 16b and the output are output when the signal supplied from the power supply voltage monitoring unit 6 is low level. The terminal 16c is connected.

  When the output voltage is higher than the predetermined second voltage Vth2, the first overcurrent control circuit 21 holds the output current from the output unit 3 at the predetermined current, and the output voltage is the predetermined second voltage Vth2 If it becomes lower than that, a command signal is output so as to reduce the output current from the output unit 3. The first overcurrent control circuit 21 includes three input terminals 21a, 21b, 21c and one output terminal 21d. The input terminal 21 a is electrically connected to one end of the resistance element 10, the input terminal 21 b is electrically connected to the other end of the resistance element 10, and the input terminal 21 c is electrically connected to the collector of the boost transistor 4. Yes. The output terminal 21 d is electrically connected to the input terminal 16 a of the switching unit 16.

  FIG. 4 is a diagram illustrating an example of the first overcurrent control circuit 21. The first overcurrent control circuit 21 includes resistance elements 31a, 31b, and 31c, comparators 32a and 32b, current sources 33a and 33b, a second reference voltage source 34, and a control switch 35. One terminal of the resistance element 31a is electrically connected to the input terminal 21a, and the other terminal is connected to the non-inverting input terminal of the comparator 32a. The inverting input terminal of the comparator 32a is connected to the input terminal 21b. The output terminal of the comparator 32a is connected to the output terminal 21d. The voltage of the second reference voltage source 34 is a predetermined third voltage Vth3 that is lower than the predetermined second voltage Vth2. The predetermined first voltage Vth1 is set to satisfy Vth2 <Vth1 <Vth3.

  The resistance elements 31b and 32c are connected in series, one terminal of the resistance elements 31b and 32c connected in series is connected to the input terminal 21c, and the other terminal is connected to the ground. The non-inverting input terminal of the comparator 32 b is connected to the connection portion of the resistance elements 31 b and 32 c, and the inverting input terminal is connected to the second reference voltage source 34. The current source 33a and one terminal of the control switch 35 are connected to the inverting input terminal of the comparator 32a and the other terminal of the resistance element 31a. A current source 33 b is connected to the other terminal of the control switch 35. The control terminal of the control switch 35 is connected to the output terminal of the comparator 32b.

  In the first overcurrent control circuit 21, the control switch 35 is connected between one connection terminal and the other connection terminal according to the voltage applied between the input terminals 21a and 21b and the voltage applied to the input terminal 21c. By switching between conduction and non-conduction, a signal is output from the output terminal 21d so that the voltage and current characteristics output from the regulator 1 become a so-called “A-shaped characteristic”.

  FIG. 5 is a graph showing the voltage and current characteristics output from the regulator 1 when the input terminal 16a and the output terminal 16c of the switching unit 16 are connected. In FIG. 5, the horizontal axis represents the output current, and the vertical axis represents the output voltage. In FIG. 5, it is assumed that an input voltage Vin larger than a predetermined first voltage Vth is input. Further, the regulator 1 adjusts the output voltage so that the output voltage becomes the predetermined third voltage Vth when the input voltage Vin is larger than the predetermined first voltage Vth. As shown in FIG. 5, the regulator 1 sets the output voltage to Vout. When Vth3 ≧ Vout ≧ Vth2, the output current is held constant at Ia to suppress overcurrent. When Vth3> Vout, the output unit 3 Since there is a possibility that a short circuit has occurred, the circuit connected to the output unit 3 is protected by keeping the output current constant with Ib smaller than Ia. Vin is, for example, about 14V, Vth2 is, for example, about 3V, and Vth3 is, for example, about 5V. Ib is set to about 1/2 or less of Ia.

  Referring again to FIG. 2, the second overcurrent control circuit 22 is configured to be more than the output current in the first overcurrent control circuit 21 when the output voltage is in a predetermined range lower than the predetermined voltage Vth2. A command signal for outputting a large output current from the output unit 3 is output. The second overcurrent control circuit 22 includes two input terminals 22a and 22b and one output terminal 22d. The input terminal 22 a is electrically connected to one end of the resistance element 10, and the input terminal 22 b is electrically connected to the other end of the resistance element 10. The output terminal 22 d is connected to the input terminal 16 b of the switching unit 16.

  FIG. 6 is a diagram illustrating an example of the second overcurrent control circuit 22. The second overcurrent control circuit 22 includes a resistance element 50, a comparator 49, and a current source 53. One terminal of the resistor element 50 is electrically connected to the input terminal 22 a, and the other terminal is connected to the non-inverting input terminal of the comparator 49. The inverting input terminal of the comparator 49 is connected to the input terminal 22b. The output terminal of the comparator 49 is connected to the output terminal 22d. A current source 53 is connected to the inverting input terminal of the comparator 49 and the other terminal of the resistance element 50.

  In the second overcurrent control circuit 22, the voltage and current characteristics output from the regulator 1 are so-called “droop characteristics” according to the voltage applied between the input terminals 22a and 22b. Output a signal.

  FIG. 7 is a graph showing the voltage and current characteristics output from the regulator 1 when the input terminal 16b and the output terminal 16c of the switching unit 16 are connected. In FIG. 7, the horizontal axis indicates the output current, and the vertical axis indicates the output voltage. In FIG. 5, it is assumed that an input voltage Vin larger than a predetermined first voltage Vth is input. When the input voltage Vin smaller than the predetermined first voltage Vth is input, the regulator 1 adjusts the output voltage so that the output voltage becomes the predetermined second voltage Vth2. As shown in FIG. 7, the regulator 1 sets the output voltage to Vout. When Vth2 ≧ Vout, the regulator 1 keeps the output current constant at Ia and suppresses overcurrent.

  As described above, in the regulator 1, the first overcurrent control circuit 21 and the second overcurrent control circuit 22 are selectively set to the first overcurrent control circuit 21 when the input voltage is larger or smaller than the predetermined first voltage Vth1. The two transistors 12 are electrically connected, and the output voltage and current characteristics as shown in FIGS. 5 and 7 are switched to control the output voltage and the output current. As a result, when the input voltage is higher than the predetermined first voltage Vth1, the output current is limited when the output voltage drops from the predetermined second voltage Vth2, so that the base of the boost transistor 4 and the Burnout between the collectors can be suppressed, and when the input voltage is lower than the predetermined voltage, the output current from the output unit is changed to the first when the output voltage is lower than the predetermined second voltage Vth2. Since the boost transistor 4 is controlled by the control unit 7 so as to be increased as compared with the case of the overcurrent limiting characteristic, even when the input voltage decreases, a desired current is supplied to the device using the output voltage. be able to. Therefore, both high fail-safety and operation at low voltage can be achieved.

  In the present embodiment, the first overcurrent control circuit 21 is a U-shaped protection circuit, but the first overcurrent control circuit 21 may be a U-shaped protection circuit. When a protection circuit with a U-shaped characteristic is used, the output current can be changed linearly when the output voltage drops. Even with such a combination, it is possible to achieve the same effect as that of the above-described embodiment.

  FIG. 8 is a circuit diagram showing a regulator 41 according to another embodiment of the present invention. The regulator 41 of the present embodiment is similar to the regulator 1 shown in FIG. 2, and basically has a configuration in which a third overcurrent control circuit 23 is added to the configuration of the regulator 1 shown in FIG. Therefore, the same reference numerals are given to the same components, and the duplicate description is omitted. The power supply voltage monitor unit 6 compares the input voltage with a predetermined first voltage Vth1, and further compares the input voltage with a predetermined fourth voltage Vth4 lower than the predetermined first voltage Vth1. The result is given to the switching unit 16 described later. The power supply voltage monitor unit 6 includes, for example, two output terminals. For example, when the input voltage is equal to or higher than a predetermined first voltage Vth1, a high level signal is output from one output terminal, and the input voltage is determined in advance. When the voltage is less than one voltage Vth1, a low level signal is output from one output terminal. For example, when the input voltage is equal to or higher than a predetermined fourth voltage Vth4, a high level signal is output from the other output terminal. When the input voltage is lower than the predetermined fourth voltage Vth4, a low level signal is output from the other output terminal.

  In the present embodiment, the switching unit 16 is configured by a switch having one input terminal 16e in addition to the two input terminals 16a and 16b, the one output terminal 16c, and the switching control terminal 16d. Yes. The switching unit 16 selectively connects any one of the three input terminals 16a, 16b, and 16e to the output terminal 16c in accordance with a signal given from the power supply voltage monitoring unit 6 to the switching control terminal 16d. . Here, when the signal given from one output terminal of the power supply voltage monitor unit 6 is at a high level and the signal level given from the other output terminal is at a high level, the input terminal 16a and the output terminal 16c are connected, When the signal supplied from one output terminal is at a low level and the signal level supplied from the other output terminal is at a high level, the input terminal 16e and the output terminal 16c are connected, and the signal supplied from one output terminal is at a low level. When the signal level applied from the other output terminal is low, the input terminal 16b and the output terminal 16c are connected.

  The first and second overcurrent control circuits 21 and 22 are the same as those in the above-described embodiment, and the third overcurrent control circuit 23 includes three input terminals 23a, 23b, and 23c and one output terminal. 23d, and outputs a signal from the output terminal 23d so that the voltage and current characteristics output from the regulator 1 are so-called “f-shaped characteristics”. That is, in the regulator 41, as the input voltage decreases, the output voltage / current characteristic of the regulator 41 changes from the A-characteristic to the F-characteristic, and further changes to the drooping characteristic. As described above, by changing the characteristics in a plurality of stages according to the input voltage, the current used in the addition connected to the output unit 3 can be finely adjusted. Therefore, the output voltage and the output current can be suitably changed according to the load circuit, and the operation process in the load circuit can be performed smoothly.

  FIG. 9 is a circuit diagram showing a regulator 51 according to still another embodiment of the present invention. The regulator 51 of the present embodiment is similar to the regulator 1 shown in FIG. 2 described above. Basically, in the configuration of the regulator 1 shown in FIG. 2 described above, the power supply voltage monitor unit 6 is replaced with the differential voltage monitor unit 52. Since other configurations are the same as those of the regulator 1, the same configurations are denoted by the same reference numerals, and redundant description is omitted.

  The differential voltage monitor unit 52 detects a potential difference between the input voltage applied to the input unit 2 and the output voltage of the output unit 3, and provides a control signal to the switching control terminal 16d according to the potential difference. If the potential difference detected by the difference voltage monitor unit 52 is equal to or greater than a predetermined potential difference, the differential voltage monitor unit 52 connects the input terminal 16a and the output terminal 16c of the switching unit 16 so that the potential difference is less than the predetermined potential difference. If so, the differential voltage monitor unit 52 connects the input terminal 16b and the output terminal 16c of the switching unit 16 to each other.

  In the regulator 51 as described above, the same effect as that of the regulator 1 described above can be achieved. Further, since the output voltage current characteristic is switched based on the potential difference between the input voltage and the output voltage, the circuit can be configured without using the first reference voltage source 9 that is necessary in the power supply voltage monitor unit 6. The circuit configuration can be simplified.

  FIG. 10 is a circuit diagram showing a regulator 61 according to still another embodiment of the present invention. The regulator 61 of the present embodiment is similar to the regulator 1 shown in FIG. 2 described above. Basically, in the configuration of the regulator 1 shown in FIG. 2, the first and second overcurrent control circuits 21, 22 and the switching unit 16 are replaced with the letter A protection circuit 62, and the same reference numerals are given to the same components, and the description thereof is omitted.

  The A-shaped protection circuit 62 includes three input terminals 21a, 21b, and 21c and one output terminal 21d, and the output terminal so that the voltage and current characteristics output from the regulator 61 become the A-shaped characteristics. A signal is output from 21d.

  FIG. 11 is a graph showing the voltage and current characteristics output from the regulator 61. When the input voltage Vin is equal to or higher than the predetermined voltage VT, the regulator 61 sets the voltage level for switching the current in the A-shaped characteristic to V1, and when the input voltage Vin is lower than the predetermined voltage VT, the current in the A-shaped characteristic Is set to Vth4 lower than Vth2. Therefore, in the regulator 61, the first overcurrent limiting characteristic in which the voltage level is V1 by the A-shaped characteristic and the second overcurrent limiting characteristic in which the voltage level is V2 by the A-shaped characteristic are switched. Therefore, the second overcurrent limiting characteristic is a characteristic in which a predetermined voltage VT, which is a reference for reducing the output current from the output unit 3 in the first overcurrent limiting characteristic, is reduced, that is, the voltage of the output unit is set in advance. When a predetermined second voltage Vth2 or less and a predetermined threshold voltage Vth4 are exceeded, the output current from the output unit 3 is held at a predetermined current, and the voltage of the output unit 3 becomes less than the predetermined threshold voltage Vth4 The output current from the output unit 3 is reduced.

  FIG. 12 is a circuit diagram showing an example of the letter A protection circuit 62. In addition to the configuration of the first overcurrent control circuit 21 shown in FIG. 4, a resistor element 64 and a switch element 65 are provided. The resistance element 64 is interposed between the resistance element 31c and the ground, and the switch element 65 is connected in parallel with the resistance element 31c. One terminal of the switch element 65 is connected to a connection portion between the resistance element 31c and the resistance element 64, and the other terminal is connected to the ground. The switch element 65 opens and closes in response to a control signal from the power supply voltage monitor unit 6. When a high level signal is given from the power supply voltage monitor unit 6, the switch element 65 is closed, and the power supply voltage monitor unit 6 outputs a high level signal. When the signal is given, the switch is opened. The voltage input to the non-inverting input terminal of the comparator 32b changes according to the opening / closing of the switch element 65. As a result, the voltage level at which the current in the letter A characteristic is switched can be changed from V1 to V2.

  The resistance elements 31b, 31c, 64, the comparator 32b, the current sources 33a, 33b, the second reference voltage source 34, the control switch 35, and the switch element 65 are provided, and an overcurrent detection level switching circuit unit is provided. 63 is configured. In the regulator 61 as described above, the same effect as that of the regulator 1 described above can be achieved.

  FIG. 13 is a circuit diagram showing a regulator 71 according to still another embodiment of the present invention. The regulator 71 of the present embodiment is similar to the regulator 1 shown in FIG. 2 and FIG. 10 described above. Basically, in the configuration of the regulator 1 shown in FIG. Therefore, the same reference numerals are given to the same components, and the description thereof is omitted.

  In the embodiment shown in FIG. 10, the second overcurrent limiting characteristic is a characteristic in which a predetermined voltage VT that is a reference for reducing the output current from the output unit 3 in the first overcurrent limiting characteristic is reduced. However, in the present embodiment, the second overcurrent limiting characteristic is the output current output from the output unit 3 when the input voltage is lower than the predetermined voltage VT in the first overcurrent limiting characteristic. Increased characteristics.

  FIG. 14 is a graph showing the voltage and current characteristics output from the regulator 71. When the input voltage Vin is equal to or higher than the predetermined voltage VT, the regulator 71 sets the current limit level (Ib) in the A-shaped characteristics as the first limit level Ib1, and when the input voltage Vin is lower than the predetermined voltage VT. In addition, the current limit level in the letter A characteristic is set to a second limit level Ib2 that is larger than Ib1. Therefore, in the regulator 71, the first overcurrent limiting characteristic in which the voltage level is V1 by the letter A characteristic and the second overcurrent limiting characteristic in which the voltage level is V2 by the letter A characteristic are switched. Therefore, the second overcurrent limiting characteristic increases the output current output from the output unit 3 when the output voltage becomes lower than the predetermined second voltage Vth2 in the first overcurrent limiting characteristic. Characteristic, that is, when the voltage of the output unit 3 is equal to or higher than the predetermined second voltage Vth2, the output current from the output unit 3 is held at the predetermined current, and the voltage of the output unit 3 is the predetermined second voltage. When the voltage is lower than Vth2, the output current from the output unit 3 is maintained at a current larger than a predetermined current. In the regulator 51 as described above, the same effect as that of the regulator 1 described above can be achieved.

  In still another embodiment of the present invention, a regulator may be configured by combining the circuits shown in FIGS. 12 and 13 described above. By providing the voltage level for switching the current in the A-shaped characteristic and the current limit level in the A-shaped characteristic, it becomes possible to output a further optimal current from the output unit 3 to the connected load.

  Further, in the above-described character-shaped protection circuit 62 shown in FIG. 12, the chattering at the time of switching may be suppressed by providing the comparator 32b with a hysteresis characteristic or inserting a filter in the output of the comparator 32b. As a result, the output voltage current characteristic is prevented from changing due to chattering, and the reliability of the regulator can be improved.

  In each of the above-described embodiments, the regulator input unit 2 is connected to the battery 5. However, the input unit 2 is connected to the regulator output unit 3 of each of the embodiments of the present invention, and the regulator May be connected in multiple stages.

  In addition, in an electronic device including any of the regulators of the above-described embodiments, by providing the regulator, burnout destruction of the boost transistor is suppressed and the input voltage input to the switching regulator is reduced. Since the decrease in the current output from the regulator is suppressed, it is possible to suppress the operation of the circuit that operates by being supplied with the current from the regulator. Therefore, an electronic device with improved reliability can be provided.

FIG. 1 is a graph showing the output voltage of a series regulator having an overcurrent protection circuit employing the “A-shaped characteristic” method. 1 is a circuit diagram showing a series regulator 1 according to an embodiment of the present invention. 3 is a diagram illustrating an example of a circuit configuration of a power supply voltage monitor unit 6. FIG. 2 is a diagram illustrating an example of a first overcurrent control circuit 21. FIG. 6 is a graph showing voltage and current characteristics output from the regulator 1 when an input terminal 16a and an output terminal 16c of a switching unit 16 are connected. 3 is a diagram illustrating an example of a second overcurrent control circuit 22. FIG. 4 is a graph showing voltage and current characteristics output from the regulator 1 when an input terminal 16b and an output terminal 16c of a switching unit 16 are connected. It is a circuit diagram which shows the regulator 41 of other embodiment of this invention. It is a circuit diagram which shows the regulator 51 of other embodiment of this invention. It is a circuit diagram which shows the regulator 61 of other form of implementation of this invention. It is a graph which shows the voltage and current characteristic output from the regulator 61. FIG. 6 is a circuit diagram showing an example of a letter-shaped protection circuit 62. FIG. It is a circuit diagram which shows the regulator 71 of further another form of implementation of this invention. 7 is a graph showing voltage and current characteristics output from a regulator 71.

Explanation of symbols

1, 41, 51, 61, 71 Series regulator 2 Input unit 3 Output unit 4 Boost transistor 6 Power supply voltage monitor unit 7 Control unit 21 First overcurrent control circuit 22 Second overcurrent control circuit 23 Third overcurrent Control circuit 52 Differential voltage monitor 62, 72 A-shaped protection circuit

Claims (5)

An input unit, an output unit, and a boost transistor provided between the input unit and the output unit are provided, and by controlling the boost transistor, an input voltage applied to the input unit is converted into a predetermined voltage to be output from the output unit. A series regulator capable of output,
A detection unit for detecting the input voltage;
When the input voltage is higher than a predetermined first voltage and the voltage of the output unit is higher than a predetermined second voltage, an output current from the output unit is held at a predetermined current, and the input voltage Is higher than a predetermined first voltage, and when the voltage of the output unit is lower than a predetermined second voltage, a first overcurrent limiting characteristic for reducing an output current from the output unit, and the input When the voltage is in a predetermined range lower than the predetermined first voltage and the voltage of the output unit is lower than the predetermined second voltage, the output current in the first overcurrent limiting characteristic is more than And a control unit that controls the boost transistor by switching to a second overcurrent limiting characteristic capable of outputting a larger output current from the output unit.   In addition to the first and second current limiting characteristics, the control unit has a predetermined second range voltage in which the input voltage is lower than the predetermined first voltage, and the voltage of the output unit is When the voltage is lower than the predetermined second voltage, the boost is switched to a third overcurrent limiting characteristic capable of outputting from the output unit an output current larger than the output current in the first overcurrent limiting characteristic. The series regulator according to claim 1, wherein the transistor is controlled. An input unit, an output unit, and a boost transistor provided between the input unit and the output unit are provided, and by controlling the boost transistor, an input voltage applied to the input unit is converted into a predetermined voltage to be output from the output unit. A series regulator capable of output,
A detection unit for detecting a potential difference between the input voltage and the voltage of the output unit;
When the potential difference is larger than a predetermined potential difference and the voltage of the output unit is higher than a predetermined voltage, the output current from the output unit is held at a predetermined current, and the input voltage is larger than the predetermined potential difference. A first overcurrent limiting characteristic that reduces the output current from the output unit when the voltage of the output unit is lower than a predetermined voltage, and a predetermined range in which the input voltage is smaller than the predetermined potential difference And a second overcurrent limit capable of outputting an output current larger than the output current in the first overcurrent limit characteristic when the voltage of the output section is lower than a predetermined voltage. And a control unit that controls the boost transistor by switching characteristics.   The second overcurrent limiting characteristic is that when the voltage of the output unit is lower than the predetermined second voltage and higher than the predetermined third voltage, the output current from the output unit is set to a predetermined current. Holding, when the voltage of the output unit becomes lower than a predetermined threshold voltage, the characteristic of reducing the output current from the output unit, and when the voltage of the output unit is higher than a predetermined second voltage, The output current from the output unit is held at a predetermined current, and the output current from the output unit is held at a current larger than the predetermined current when the voltage of the output unit is lower than the predetermined second voltage. The series regulator according to claim 1, wherein the series regulator has at least one of the following characteristics.   An electronic apparatus comprising the series regulator according to claim 1.

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