JP2016134960A - Power supply circuit and on-vehicle controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power supply circuit and on-vehicle controller capable of taking a prompt step to address an abnormality in an output element with a simple configuration.SOLUTION: A signal processor stops a switching operation of T1 of a switching regulator by outputting a T1OFF signal when VOM output from a series regulator continues to be an overvoltage until FT3 elapses, thereby suppressing a time for which an overvoltage is output to a microcomputer to FT3.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a power supply circuit configured by combining a switching regulator and a series regulator, and an in-vehicle control device including the power supply circuit.

  For example, in an in-vehicle control device, power is supplied after the battery voltage (for example, 12V) is stepped down to a predetermined internal voltage (for example, 5V) by a power circuit. In this case, in the configuration in which the battery voltage is stepped down to the internal voltage using only the switching regulator, the voltage accuracy of the internal voltage is low although the conversion efficiency is high. On the other hand, in the configuration where the battery voltage is stepped down to the internal voltage using only the series regulator, the conversion efficiency is low although the voltage accuracy of the internal voltage is high. For this reason, switching regulators and series regulators are connected in series, and the power supply voltage is stepped down to the intermediate voltage by the switching regulator and then the intermediate voltage is stepped down to the predetermined internal voltage by the series regulator. (See Patent Document 1).

JP 2004-147391 A

By the way, the power supply circuit employed in the in-vehicle control device is equipped with an overcurrent prevention function to prevent the overcurrent from continuously flowing through the microcomputer mounted in the in-vehicle control device due to, for example, the output element being short-circuited. . Patent Document 1 includes an output current detection circuit that detects an output current from a series regulator. When the output current detection circuit detects an overcurrent, the series regulator is stopped or the switching regulator is stopped. Propose that.
However, the output current detection circuit needs to be configured by combining a current-voltage conversion circuit, a voltage comparison circuit, a control circuit, and the like. The configuration is complicated and at the time when the output current detection circuit detects an overcurrent. There is a possibility that the abnormality of the power supply target is progressing.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a power supply circuit and an in-vehicle control device that can quickly cope with an abnormality of an output element with a simple configuration.

  According to the first aspect of the present invention, when the second output element of the series regulator is short-circuited for some reason, for example, the second voltage from the series regulator becomes an overvoltage. If it is detected that the second voltage is an overvoltage, it is determined to be abnormal. Then, since the 1st stop means stops outputting the 1st voltage from the 1st output element of a switching regulator, it can control that overvoltage is outputted to the candidate for electric power feeding. In this case, there is a high possibility that overcurrent will be output to the power supply target due to damage to the power supply target due to continuous output of the overvoltage to the power supply target. This can be prevented beforehand.

The block diagram which shows the electric constitution of the power supply circuit in one Embodiment Block diagram showing electrical configuration of in-vehicle controller The figure which shows the waveform of each signal at the time of T1 short The figure which shows the waveform of each signal at the time of T2 short

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
As shown in FIG. 2, the in-vehicle controller 1 includes an input circuit 2 for inputting detection signals and the like from various sensors, a drive circuit 3 for driving and controlling various objects to be controlled, and various arithmetic processes based on the detection signals. A microcomputer (hereinafter referred to as microcomputer) 4 (power supply target) and a power supply circuit 5 that control the drive circuit 3 by being executed are provided. The power supply circuit 5 is supplied with, for example, a 12V battery voltage (hereinafter referred to as VS) from a vehicle battery when an ignition switch (hereinafter referred to as IG switch; main power switch) (not shown) is in an ON state. Although not shown in FIG. 2, when the microcomputer 4 is activated in response to the power supply of the VS, the microcomputer 4 self-holds the power supply state of the VS by turning on the relay, and the IG switch is turned off. The VS power supply state is maintained until the relay is turned off after the shutdown process is completed. In addition, the vehicle is supplied with power when the main power switch is ON rather than a vehicle in which an IG switch is not provided, such as a hybrid vehicle or an electric vehicle.

As shown in FIG. 1, the power supply circuit 5 includes a switching regulator 6, a series regulator 7, a simple 5V power supply 8, and a signal processing unit 9 (first stopping means).
The switching regulator 6 includes a switching signal generation circuit 10, an N-channel type MOS FET (hereinafter referred to as T1, first output element), a smoothing circuit 11, a VO6 overvoltage detector 12 (second abnormality determination means) including an operational amplifier, 1 filter 13 (second stopping means) and an output stopping MOS type FET 14.

The switching signal generation circuit 10 includes a triangular wave generator 15, an error amplifier (EOP) 16 composed of an operational amplifier, a comparator (COM) 17 composed of an operational amplifier, and resistors 18 and 19 connected in series between the source of T1 and the ground. It is configured. The comparator 17 compares the triangular wave output from the triangular wave generator 15 with the comparison level output from the error amplifier 16, and becomes high when the triangular wave level is higher than the comparison level, and low when the triangular wave level is low. Outputs a level switching signal. The error amplifier 16 compares the voltage obtained by dividing the target step-down voltage 6V (hereinafter referred to as VO6, first voltage) of the switching regulator 6 with the resistors 18 and 19 with the reference voltage, and determines the difference (error) between them. Accordingly, the comparison level output to the comparator 17 is adjusted. In this case, the reference voltage is set so that VO6 is 6V. The drain of T1 is supplied with VS via a diode 20 when an IG switch (not shown) is turned on, and a switching signal from the comparator 17 is input to the gate. Thus, T1 performs a switching operation in accordance with the switching signal supplied from the comparator 17, and adjusts the duty ratio of the switching operation in accordance with the level of VO6, thereby adjusting VO6 to 6V.
The source of T1 is connected to the smoothing circuit 11. The smoothing circuit 11 includes a coil 21 that constitutes a low-pass filter, a capacitor 22, and a flywheel diode 23 that allows a return current to flow when T1 is turned off.

  The VO6 overvoltage detector 12 compares VO6 with a preset reference voltage, and notifies the first filter 13 when it detects that VO6 exceeds the reference voltage. In this case, hysteresis is set for the reference voltage, and an overvoltage is detected when VO6> threshold OVH, and it is detected that the overvoltage has been released when VO6 <threshold OVL (see FIG. 3). .

  The first filter 13 outputs a high-level stop signal when the overvoltage is continuously input from the VO6 overvoltage detector 12 until the FT1 time elapses, and the overvoltage is eliminated from the VO6 overvoltage detector 12. When the input is continued until FT2 time elapses, the output of the stop signal is stopped. FT1 and FT2 are times for setting a filter function determined based on a margin with respect to an overshoot time expected to occur in VO6, a breakdown voltage breakdown margin of the transistor, and a thermal breakdown margin of the transistor.

The drain of the FET 14 is connected to the gate of T1, the source thereof is connected to the ground, and the gate of T1 is connected to the ground line when the FET 14 is in the ON state.
On the other hand, the series regulator 7 includes a linear signal generation circuit 24, a PNP type transistor (hereinafter referred to as T2, second output element), a VOM overvoltage detector 25 (first abnormality determination means) including an operational amplifier, and a second filter 26 (first output). 1 stop means), a temperature sensor 27 (temperature detection means) comprising a diode, a superheat degree detector 28 (superheat degree detection means) comprising an operational amplifier, and a transistor 29 for stopping output.

  The linear signal generation circuit 24 includes resistors 30 and 31 connected between T2 and the ground, an amplifier (OP) 32 including an operational amplifier, and a transistor 33. The amplifier 32 compares a voltage obtained by dividing the voltage output from T2 (hereinafter referred to as VOM, second voltage) with the resistors 30 and 31 with a preset reference voltage, and a current corresponding to the voltage difference therebetween. Is output to the base of the transistor 33. The collector of the transistor 33 is connected to the base of T2.

  The emitter of T2 is connected to the smoothing circuit 11 of the switching regulator 6, and the collector is connected to the ground line via a capacitor. Thereby, T2 performs a linear operation according to the current supplied from the amplifier 32. In this case, the reference voltage applied to the amplifier 32 is set so that VOM is 5V, and the VOM is adjusted to 5V by controlling the linear operation of T2 according to the level of VOM. The VOM overvoltage detector 25 compares the voltage obtained by dividing the VOM with the resistors 30 and 31 with the reference voltage, and notifies the second filter 26 that the VOM is overvoltage when it is detected that the VOM is overvoltage. The base of the transistor 33 is connected to the collector of the transistor 29. When the transistor 29 is on, the base of the transistor 33 is connected to the ground line.

  The second filter 26 outputs a high-level stop signal when it is continuously notified from the VOM overvoltage detector 25 that an overvoltage has elapsed until FT3 time elapses. This stop signal is output to a signal processing unit 9 described later. FT3 is a time for setting a filter function determined based on a margin with respect to an overshoot time assumed to occur in the VOM, a breakdown voltage breakdown margin of the transistor, and a thermal breakdown margin of the transistor.

The superheat detector 28 detects the superheat degree of T2, and notifies the respective filters 13, 26 of the difference voltage between the voltage detected by the temperature sensor 27 and the reference voltage as the superheat degree.
Here, FT1 to FT3 set in each of the filters 13 and 26 are set so as to become shorter as the degree of superheat detected by the degree of superheat detector 28 increases. This is because the margin of operation of T2 decreases as T2 overheats.

  The simple 5V power supply 8 is supplied with VS. The simple 5V power supply 8 includes a resistor 35 connected in series between the VS line and the ground, a series circuit of a backflow prevention diode 36 and a Zener diode 37, and a transistor 38. VS is supplied to the collector of the transistor 38, and the Zener voltage of the Zener 37 is input to the base.

The signal processing unit 9 includes a state holding circuit 39 and an activation circuit 40, and 5V is supplied from a simple 5V power source 8 to each circuit.
The state holding circuit 39 is formed of a flip-flop, and a high level (5 V) is input to the data input terminal of the power supply state of the simple 5 V power supply 8, and an overvoltage is detected from the second filter 26 to the clock input terminal (rising edge active). Is generated as a signal change from the low level to the high level and the state is maintained in the high level input state from the data output terminal to the data input terminal, a high level stop signal is applied to the base of the FET 14 Output. The starting circuit 40 is composed of an AND circuit 41 and a delay circuit 42. A high level (5 V) is input to one input terminal of the AND circuit 41 in a power supply state of the simple 5 V power supply 8, and a high level (5 V) is input to the other input terminal via the delay circuit 42. The delay circuit 42 outputs a high level to the AND circuit 41 with a predetermined time delay from the power supply timing of 5V. The AND circuit 41 outputs a high level VS activation signal to the reset terminal (low active) of the state holding circuit 39 when both input terminals become high level.

Next, the operation of the above configuration will be described.
When the user turns on the IG switch of the vehicle, VS is supplied to the power supply circuit 5. Then, T1 of the switching regulator 6 performs a switching operation so that VS is stepped down so that VO6 becomes 6V, and T2 of the series regulator 7 performs a linear operation so that VO6 is stepped down and VOM becomes 5V. As a result, the VOM is supplied from the power supply circuit 5 to the microcomputer 4, so that the microcomputer 4 starts to operate and the control target can be controlled.

  In a state where the vehicle is driven by the user, VS varies or the load to be controlled (output load) varies, so VO6 and VOM may temporarily overshoot from the target voltage. When VO6 temporarily overshoots, the switching operation of T1 is temporarily stopped, so that the overshoot of VO6 is immediately eliminated. Similarly, when the VOM temporarily overshoots, T2 is temporarily turned off, so that the VOM overshoot is immediately eliminated.

  When T1 of the switching regulator 6 is short-circuited for some reason, VO6 from the switching regulator 6 exceeds the threshold value OVH as shown in FIG. 3, so that overvoltage (≈VS) is applied to the transistor of the series regulator 7. It will be in the state where it is output. In such a case, since the overvoltage is stepped down to VOM by the series regulator 7, it is possible to prevent the overvoltage from being output to the microcomputer 4, but the input voltage of the series regulator 7 is higher than the rating. This is a high state, and the series regulator 7 is in a high load state. At this time, the VO6 overvoltage detector 12 detects the overvoltage and notifies the first filter 13. The first filter 13 measures the time during which the overvoltage is notified from the VO6 overvoltage detector 12, and when the time reaches FT1, it determines that T1 may be short-circuited, and the series regulator 7 A high level T2OFF signal is output to the transistor 29. As a result, the transistor 29 is turned on, and the transistor 33 and thus T2 is turned off, and the linear operation of T2 is stopped. Therefore, the high load state of the series regulator 7 can be suppressed to FT1.

When the short state of T1 is eliminated, VO6 becomes lower than the threshold value VOL as shown in FIG. 3, so the VO6 overvoltage detector 12 notifies the first filter 13 that the overvoltage has been eliminated. The first filter 13 measures the time when the overvoltage has been notified from the VO6 overvoltage detector 12, and when the measured time reaches FT2, it is determined that the short state of T1 has been resolved. The output of the T2OFF signal is stopped. As a result, the transistor 29 is turned off, and the transistor 33 operates accordingly, and T2 resumes the linear operation, so that the power supply state from the series regulator 7 to the microcomputer 4 is restored.
In addition, when the short state of T1 is not eliminated, the abnormality of the power supply circuit 5 is notified to the user as will be described later.

  On the other hand, when the transistor of the series regulator 7 is short-circuited for some reason, as shown in FIG. 4, the VOM from the series regulator 7 exceeds the threshold value OVH, so an overvoltage (≈VO6) is output to the microcomputer 4. It will be in a state. If an overvoltage higher than the rated voltage of the microcomputer 4 continues to be output to the microcomputer 4 in this way, the microcomputer 4 will eventually be damaged by the overvoltage and an overcurrent will be generated. It is necessary to stop the overvoltage output state immediately.

  Therefore, when the VOM overvoltage detector 25 detects that it is an overvoltage and notifies the second filter 26, the second filter 26 counts the time that the VOM overvoltage detector 25 is notified of the overvoltage, When the measured time reaches FT3, a high-level stop signal is output to the signal processing unit 9. When the stop signal is input, the state holding circuit 39 of the signal processing unit 9 holds the high level signal input to the data input terminal. Therefore, the high level T1OFF signal is output from the output terminal of the state holding circuit 39 to the switching regulator 6. Output to the gate of the FET 14. In this case, the state holding circuit 39 holds the state of the T1OFF signal. As a result, the FET 14 is turned on and the switching operation is stopped due to the T1 being turned off, so that the voltage of VO6 and consequently VOM is lowered. As shown in FIG. Is output to the microcomputer 4 in FT3 time.

  Here, since the signal processing unit 9 is supplied with power from the simple 5V power supply 8, even if the voltage of the VOM decreases as described above, the signal processing unit 9 holds the output state of the T1OFF signal by the state holding circuit 39. Can do. Then, when the VOM drops below the operable voltage of the microcomputer 4, the operation of the microcomputer 4 and consequently the in-vehicle control device 1 is stopped.

  When the in-vehicle control device 1 is stopped as described above, for example, an abnormality is notified to the user by a warning lamp or the like installed on the instrument panel. In this case, even if the in-vehicle control device 1 stops, the limp home mode functions by the fail-safe function, and the functions of the in-vehicle control device 1 are limited to the minimum. If you are concerned, you can get to your home or maintenance shop at low speed. When the IG switch is turned off, the state holding function by the state holding circuit 39 is lost because the VS is not supplied with power as shown in FIG.

  When the IG switch is turned on after the abnormality of the power supply circuit 5 naturally recovers or the failure is repaired, VS is repowered to the power supply circuit 5. When VS is repowered to the power supply circuit 5, the start circuit 40 outputs a high level signal to the state holding circuit 39 as shown in FIG. 4, but the start circuit 40 outputs the high level signal for a predetermined time. Since the delay is delayed, a high level signal is input to the reset terminal (low active) of the state holding circuit 39 in a state where power is normally supplied to the state holding circuit 39, and normalization is performed. As a result, since a high-level T1OFF signal is not output from the output terminal of the state holding circuit 39 as an initial state, T1 of the switching regulator 6 can perform a switching operation.

  On the other hand, the 1st filter 13 sets FT1 and FT2 short in steps, so that the superheat degree of T2 which temperature sensor 27 detected becomes large. Similarly, the 2nd filter 26 sets FT3 short in steps, so that the superheat degree of T2 becomes large. Thereby, even if the degree of superheat of T2 increases, the T1OFF signal and the T2OFF signal can be stably output.

According to such an embodiment, the following effects can be produced.
The signal processing unit 9 stops the switching operation of T1 of the switching regulator 6 when the VOM output from the series regulator 7 is continuously overvoltage until FT3 elapses, so that the overvoltage is output to the microcomputer 4 FT3 can be suppressed to the time.

  The signal processing unit 9 is supplied with 5V from the simple 5V power source 8 and maintains the T1 operation stop state of the switching regulator 6 until the IG switch is turned off and the power supply from the simple 5V power source 8 is stopped. Can be reliably prevented from being output to the microcomputer 4 again.

  When VO6 continues to be overvoltage until FT1 elapses, T2 of the series regulator 7 stops linear operation, and when VO6 continues to elapse until FT2 elapses, it is detected that the overvoltage has been eliminated. Since the operation stop state is released, it is possible to prevent the power supply circuit 5 from being unnecessarily stopped when T2 is temporarily short-circuited.

  Since the time of FT1 to FT3 of each filter 13 and 26 is changed stepwise according to the detected temperature of T2, the margin for detecting the overvoltage can be appropriately set according to the detected temperature of T2. .

(Other embodiments)
The present invention is not limited to the above-described embodiment, but may be modified or expanded as follows, each modified example may be combined with the above-described embodiment, or each modified example may be combined.
The temperature of T1 of the switching regulator 6 may be detected by a temperature sensor, and FT1 to FT3 of each filter may be changed stepwise according to the detected temperature.
The switching operation of T1 may be stopped by setting the duty ratio to 0, or a means for blocking the output of VO6 from T1 may be provided.
The configuration of the switching regulator and the series regulator is not limited to the above embodiment, and any configuration can be adopted.

  In the drawings, 1 is an in-vehicle control device, 5 is a power supply circuit, 6 is a switching regulator, 7 is a series regulator, 9 is a signal processing unit (first stopping means), 12 is a VO6 overvoltage detector (second abnormality determining means), 13 is a first filter (second stopping means), 25 is a VOM overvoltage detector (first abnormality determining means), 26 is a second filter (first stopping means), 27 is a temperature sensor (temperature detecting means), and 28 is A superheat degree detector (superheat degree detection means), 39 is a state holding circuit, 40 is a starting circuit, T1 is a FET (first output element), and T2 is a transistor (second output element).

Claims (8)

A switching regulator (6) for stepping down a feeding voltage fed from an external power source to a first voltage by a switching operation of the first output element (T1);
A series regulator (7) for stepping down the first voltage to a second voltage by a linear operation of the second output element (T2) and feeding power to a power supply target;
First abnormality determining means (25) for determining that the second voltage is abnormal when it is detected that the second voltage is an overvoltage;
First stopping means (9, 26) for stopping the output of the first voltage from the first output element when the first abnormality determining means determines that there is an abnormality;
A power supply circuit comprising:   2. The power supply circuit according to claim 1, wherein the first stop unit performs a holding operation for holding an output stop state of the first voltage.   3. The power supply circuit according to claim 2, wherein the first stop unit is provided so as to be supplied with power from the external power source, and performs the holding operation until power supply from the external power source is stopped. The first stop means includes
A state holding circuit (39) for stopping the output of the first voltage from the first output element and holding the operation stopped state when the first abnormality determining means determines that the abnormality is present;
A startup circuit (40) that starts after resetting the state holding circuit when power is re-supplied after stopping power feeding from the external power source;
The power supply circuit according to claim 3, comprising: Second abnormality determining means (12) for determining that the first voltage is abnormal when it is detected that the first voltage is an overvoltage, and for canceling the abnormality determination when detecting that the first voltage is a non-overvoltage; ,
When the second abnormality determining means determines that there is an abnormality, the output of the second voltage from the second output element is stopped, and when the second abnormality determining means cancels the abnormality determination, the second output element is stopped. A second stop means (13) for releasing the stop state for the two output elements;
The power supply circuit according to any one of claims 1 to 4, further comprising: Temperature detecting means (27) for detecting the temperature of the second output element;
Superheat degree detection means (28) for detecting the superheat degree of the second output element based on the temperature detected by the temperature detection means,
The first abnormality determining means determines that the second voltage is abnormal when the second voltage is detected to be overvoltage for the first time, and determines the first time according to the degree of superheat by the overheat detecting means. The power supply circuit according to claim 1, wherein the power supply circuit is changed.   The second abnormality determination means determines that an abnormality is detected when the first voltage is detected to be overvoltage for a second time, and the first voltage continues for a third time to eliminate the overvoltage. 7. The power supply circuit according to claim 6, wherein when the detection is detected, the abnormality determination is canceled, and the second time and the third time are changed according to the degree of superheat by the overheat detection means. The power supply circuit according to any one of claims 1 to 7,
A microcomputer (4),
The external power supply is a vehicle battery that supplies power to the power supply circuit when the main power switch is on.
The vehicle-mounted control device, wherein the power supply target is the microcomputer.

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