JP7473435B2 - Discharge Circuit - Google Patents

Description

The present invention relates to a discharge circuit.

Patent document 1 describes a discharge circuit that discharges residual charge. In the discharge circuit described in patent document 1, a resistor and a MOS transistor form a series circuit, and this series circuit is connected between the output terminal of the power supply circuit and ground. In this discharge circuit, when the MOS transistor is turned on, the residual charge is discharged to ground via the resistor and the MOS transistor.

JP 2010-148234 A

MOS transistors may suffer from short-circuit failures. In the discharge circuit described in Patent Document 1, if a MOS transistor suffers a short-circuit failure, and the power supply circuit is outputting power, current constantly flows from the power supply circuit to ground via a resistor and the MOS transistor, resulting in constant wasteful power loss. Therefore, it is desirable to be able to detect short-circuit failures in MOS transistors.

The present invention aims to provide a discharge circuit that can detect short circuit faults.

The discharge circuit according to one aspect of the present invention comprises:
a first resistor, one end of which is electrically connected to the high potential terminal of the capacitor;
a first switching element having a first terminal electrically connected to the other end of the first resistor, a second terminal to which a control signal is input, the control signal being at a first level when discharging the charge of the capacitor and at a second level when not discharging the charge of the capacitor, and a third terminal electrically connected to a reference potential;
a comparator that receives a voltage corresponding to a voltage of the capacitor at a first input terminal, receives a threshold voltage at a second input terminal, and outputs a signal based on a comparison between the voltage corresponding to the capacitor and the threshold voltage;
a voltage setting circuit that sets a voltage of the first input terminal or the second input terminal of the comparator to a predetermined voltage based on a voltage of the first terminal of the first switching element;
Equipped with
It is characterized by:

In the discharge circuit,
The voltage setting circuit includes:
when the voltage of the first terminal of the first switching element is at a low level, the voltage of the second input terminal of the comparator is set to the predetermined voltage higher than the voltage of the first input terminal;
It is characterized by:

In the discharge circuit,
The voltage setting circuit includes:
a second resistor, one end of which is electrically connected to the power supply potential;
a third resistor, one end of which is electrically connected to the other end of the second resistor;
a first diode having an anode electrically connected to the other end of the third resistor and a cathode electrically connected to the first terminal of the first switching element;
a second switching element having a first terminal electrically connected to the power supply potential and a second terminal electrically connected to the other end of the first resistor and one end of the second resistor;
a fourth resistor, one end of which is electrically connected to the third terminal of the second switching element and the other end of which is electrically connected to the second terminal of the comparator;
Equipped with
It is characterized by:

In the discharge circuit,
The voltage setting circuit includes:
when the voltage of the first terminal of the first switching element is at a low level, the voltage of the first input terminal of the comparator is set to the predetermined voltage lower than the threshold voltage.
It is characterized by:

In the discharge circuit,
The voltage setting circuit includes:
a second diode having an anode electrically connected to the first terminal of the comparator and a cathode electrically connected to the first terminal of the first switching element;
It is characterized by:

The discharge circuit of one aspect of the present invention has the effect of being able to detect short circuit faults.

FIG. 1 is a diagram showing the overall configuration of a circuit using the first embodiment. FIG. 2 is a diagram showing a circuit configuration of a discharge circuit of a comparative example. FIG. 3 is a diagram showing a circuit configuration of the discharge circuit according to the first embodiment. FIG. 4 is a diagram showing a circuit configuration of a discharge circuit according to the second embodiment.

Below, an embodiment of the discharge circuit of the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to this embodiment.

<Overall composition>
1 is a diagram showing an overall configuration of a circuit using the first embodiment. The circuit 100 is illustrated as being mounted on a vehicle, but the present disclosure is not limited thereto. The circuit 100 includes a high-voltage battery 101, a DC-DC converter 102, and a circuit 103.

The high-voltage battery 101 outputs a high-potential side potential Vi+ from the high-potential side output terminal 101a, and outputs a low-potential side potential Vi- from the low-potential side output terminal 101b. The potential Vi- may be a reference potential (e.g., ground potential).

The high-potential input terminal 102a of the DCDC converter 102 is electrically connected to the output terminal 101a of the high-voltage battery 101 via a switch SW1. The low-potential input terminal 102b of the DCDC converter 102 is electrically connected to the output terminal 101b of the high-voltage battery 101 via a switch SW2.

The DC-DC converter 102 includes a capacitor C1, a power conversion circuit 110, and a discharge circuit 1.

Capacitor C1 stabilizes the voltage Vi input to input terminal 102a and input terminal 102b. The power conversion circuit 110 converts the voltage Vi into different DC voltages and outputs them from the high-potential output terminal 102c and the low-potential output terminal 102d.

The high-potential input terminal 103a of the circuit 103 is electrically connected to the output terminal 101a of the high-voltage battery 101 via a switch SW1. The low-potential input terminal 103b of the circuit 103 is electrically connected to the output terminal 101b of the high-voltage battery 101 via a switch SW2. The circuit 103 includes a capacitor C2. The capacitor C2 stabilizes the voltage Vi input to the input terminals 103a and 103b. An inverter is exemplified as the circuit 103, but the present disclosure is not limited thereto.

The DC-DC converter 102 and the circuit 103 are connected in parallel. Therefore, the capacitors C1 and C2 are connected in parallel.

Discharge circuit 1 discharges the charge stored in capacitors C1 and C2 based on a control signal input from an external control circuit. Examples of the external control circuit include a DSP (Digital Signal Processor) and a CPU (Central Processing Unit), but the present disclosure is not limited thereto.

First embodiment and comparative example
The first embodiment will be described below, but in order to facilitate understanding of the first embodiment, a comparative example will be described first.

Comparative Example
Fig. 2 is a diagram showing a circuit configuration of a discharge circuit of a comparative example, in which the parallel-connected capacitors C1 and C2 are shown as one capacitor.

When the voltage Vi is equal to or higher than a predetermined voltage, the discharge circuit 120 does not cause the light-emitting diode PCa that constitutes the photocoupler to emit light. When the voltage Vi is lower than the predetermined voltage, the discharge circuit 120 causes the light-emitting diode PCa to emit light. In other words, the discharge circuit 120 has a low-voltage detection function, and the light of the light-emitting diode PCa serves as a low-voltage detection signal.

When the control signal S input from an external control circuit is at a low level, the discharge circuit 120 does not discharge the charge stored in the capacitors C1 and C2. When the control signal S is at a high level, the discharge circuit 120 discharges the charge stored in the capacitors C1 and C2.

The control signal S may be input to the discharge circuit 120 via a photocoupler.

The discharge circuit 120 includes resistors R1 to R7, a comparator CMP, and a transistor Q1.

The resistors R1 and R2 are connected in series between the potential Vi+ and the potential Vi-. The connection point between the resistors R1 and R2 is electrically connected to the non-inverting input terminal of the comparator CMP. In other words, the voltage Vi divided by the resistors R1 and R2 is input to the non-inverting input terminal of the comparator CMP.

Resistors R3 and R4 are connected in series between the power supply potential Vcc and potential Vi-. The connection point between resistors R3 and R4 is electrically connected to the inverting input terminal of comparator CMP. In other words, the voltage between the power supply potential Vcc and potential Vi- is divided by resistors R3 and R4 and input to the inverting input terminal of comparator CMP.

The voltage input to the inverting input terminal of the comparator CMP is constant because the power supply potential Vcc is constant. On the other hand, the voltage input to the non-inverting input terminal of the comparator CMP fluctuates because the voltage Vi fluctuates.

The resistance values of resistors R1 to R4 are set so that when voltage Vi is equal to or greater than a predetermined voltage, the voltage input to the non-inverting input terminal of comparator CMP is higher than the voltage input to the inverting input terminal, and when voltage Vi is lower than the predetermined voltage, the voltage input to the non-inverting input terminal is lower than the voltage input to the inverting input terminal.

The constant voltage input to the inverting input terminal of the comparator CMP corresponds to an example of a "threshold voltage" in this disclosure. The non-inverting input terminal of the comparator CMP corresponds to an example of a "first terminal" in this disclosure. The inverting input terminal of the comparator CMP corresponds to an example of a "second terminal" in this disclosure.

The comparator CMP outputs a high-level voltage when the voltage input to the non-inverting input terminal is equal to or greater than the threshold voltage input to the inverting input terminal. The comparator CMP outputs a low-level voltage when the voltage input to the non-inverting input terminal is lower than the threshold voltage input to the inverting input terminal.

One end of resistor R5 is electrically connected to the power supply potential Vcc. One end of resistor R6 is electrically connected to the other end of resistor R5. The other end of resistor R6 is electrically connected to the output terminal of comparator CMP. The anode of light-emitting diode PCa is electrically connected to one end of resistor R6. The cathode of light-emitting diode PCa is electrically connected to the other end of resistor R6. In other words, a voltage obtained by dividing the voltage between the power supply potential Vcc and the output potential of comparator CMP by resistors R5 and R6 is input to light-emitting diode PCa.

When the output potential of the comparator CMP is at a high level (when the voltage Vi is equal to or higher than a predetermined voltage), no voltage is applied to the light-emitting diode PCa, and the light-emitting diode PCa does not emit light. On the other hand, when the output potential of the comparator CMP is at a low level (when the voltage Vi is lower than a predetermined voltage), a voltage is applied to the light-emitting diode PCa, and the light-emitting diode PCa emits light.

One end of resistor R7, which is a discharge resistor, is electrically connected to the high potential terminals of capacitors C1 and C2. The drain of transistor Q1 is electrically connected to the other end of resistor R7. The source of transistor Q1 is electrically connected to potential Vi-.

In this disclosure, the transistor Q1 is a MOSFET (Metal Oxide Semiconductor Field Effect Transistor), but the disclosure is not limited to this. The transistor Q1 may be a bipolar transistor.

Resistor R7 corresponds to an example of a "first resistor" in this disclosure. Transistor Q1 corresponds to an example of a "first switching element" in this disclosure. The drain or collector of transistor Q1 corresponds to an example of a "first terminal" in this disclosure. The gate or base of transistor Q1 corresponds to an example of a "second terminal" in this disclosure. The source or emitter of transistor Q1 corresponds to an example of a "third terminal" in this disclosure.

When the control signal S is at a low level, the transistor Q1 is turned off, and the charge stored in the capacitors C1 and C2 is not discharged. When the control signal S is at a high level, the transistor Q1 is turned on, and the charge stored in the capacitors C1 and C2 is discharged via the resistor R7 and the transistor Q1. When the charge stored in the capacitors C1 and C2 is discharged, the switches SW1 and SW2 are controlled to be turned off.

In the discharge circuit 120, if the transistor Q1 short-circuits and the high-voltage battery 101 is outputting the voltage Vi, current constantly flows from the high-voltage battery 101 through the resistor R7 and the transistor Q1, resulting in constant wasteful power loss. Therefore, it is desirable to be able to detect the short-circuit failure of the transistor Q1.

(First embodiment)
FIG. 3 is a diagram showing a circuit configuration of the discharge circuit according to the first embodiment.

The components of the discharge circuit 1 of the first embodiment that are the same as those of the discharge circuit 120 of the comparative example are given the same reference numerals and will not be described.

Discharge circuit 1 differs from discharge circuit 120 of the comparative example in that it further includes a voltage setting circuit 2.

The voltage setting circuit 2 includes resistors R11 to R13, a diode D1, and a transistor Q2.

One end of resistor R11 is electrically connected to the power supply potential Vcc. One end of resistor R12 is electrically connected to the other end of resistor R11. The anode of diode D1 is electrically connected to the other end of resistor R12. The cathode of diode D1 is electrically connected to the drain of transistor Q1. The emitter of transistor Q2 is electrically connected to the power supply potential Vcc. The base of transistor Q2 is electrically connected to the connection point between resistor R11 and resistor R12. One end of resistor R13 is electrically connected to the collector of transistor Q2. The other end of resistor R13 is electrically connected to the inverting input terminal of comparator CMP.

Resistor R11 corresponds to an example of a "second resistor" in the present disclosure. Resistor R12 corresponds to an example of a "third resistor" in the present disclosure. Resistor R13 corresponds to an example of a "fourth resistor" in the present disclosure. Diode D1 corresponds to an example of a "first diode" in the present disclosure. Transistor Q2 corresponds to an example of a "second switching element" in the present disclosure.

In the first embodiment, the transistor Q2 is a bipolar transistor, but the present disclosure is not limited to this. The transistor Q2 may be a MOSFET. The emitter or source of the transistor Q2 corresponds to an example of a "first terminal" in the present disclosure. The base or gate of the transistor Q2 corresponds to an example of a "second terminal" in the present disclosure. The collector or drain of the transistor Q2 corresponds to an example of a "third terminal" in the present disclosure.

When the control signal S is at a low level (when the charge stored in the capacitors C1 and C2 is not discharged) and when the transistor Q1 is not short-circuited, the drain potential of the transistor Q1 becomes the potential Vi+, and the diode D1 becomes non-conductive. As a result, the base potential of the transistor Q2 becomes the power supply potential Vcc, and the transistor Q2 becomes off. Therefore, the voltage of the inverting input terminal of the comparator CMP remains at the threshold voltage.

When the control signal S is at a low level (when the charge stored in the capacitors C1 and C2 is not discharged) and when the transistor Q1 is short-circuited, the drain potential of the transistor Q1 becomes the potential Vi-, and the diode D1 becomes conductive. As a result, the base potential of the transistor Q2 becomes the potential obtained by dividing the voltage between the power supply potential Vcc and the potential Vi- by the resistors R11 and R12, and the transistor Q2 becomes ON. As a result, the voltage of the inverting input terminal of the comparator CMP is pulled up to the power supply potential Vcc via the resistor R13. Therefore, the comparator CMP outputs a low-level voltage regardless of the voltage input to the non-inverting input terminal. As a result, the light-emitting diode PCa emits light.

In other words, when the drain potential of transistor Q1 is at a low level, voltage setting circuit 2 sets the voltage of the inverting input terminal of comparator CMP to a voltage higher than the voltage of the non-inverting input terminal.

The external control circuit can determine that transistor Q1 has a short-circuit fault because light-emitting diode PCa emits light (low voltage detection) even though voltage Vi is being supplied. For example, the external control circuit can notify the vehicle that transistor Q1 has a short-circuit fault.

As described above, the discharge circuit 1 can cause the light-emitting diode PCa to emit light when the transistor Q1 has a short-circuit failure. This allows the discharge circuit 1 to detect the short-circuit failure of the transistor Q1.

In addition, the discharge circuit 1 can share the comparator CMP for both low voltage detection and short circuit fault detection, which reduces the number of circuit elements and wiring.

Second Embodiment
FIG. 4 is a diagram showing a circuit configuration of a discharge circuit according to the second embodiment.

The components of the discharge circuit 1A of the second embodiment that are the same as those of the discharge circuit 120 of the comparative example or the discharge circuit 1 of the first embodiment are given the same reference numerals and will not be described.

Discharge circuit 1A differs from discharge circuit 120 of the comparative example in that it further includes a voltage setting circuit 3.

The voltage setting circuit 3 includes a diode D2.

The anode of diode D2 is electrically connected to the non-inverting input terminal of comparator CMP. The cathode of diode D2 is electrically connected to the drain of transistor Q1.

Diode D2 corresponds to an example of the "second diode" of this disclosure.

When the control signal S is at a low level (when the charge stored in the capacitors C1 and C2 is not discharged) and the transistor Q1 is not short-circuited, the drain potential of the transistor Q1 becomes the potential Vi+, and the diode D2 becomes non-conductive. Therefore, the voltage of the non-inverting input terminal of the comparator CMP remains at the voltage obtained by resistively dividing the voltage Vi by the resistors R1 and R2.

When the control signal S is at a low level (when the charge stored in the capacitors C1 and C2 is not discharged) and when the transistor Q1 has a short-circuit fault, the drain potential of the transistor Q1 becomes potential Vi-, and the diode D2 becomes conductive. This causes the voltage of the non-inverting input terminal of the comparator CMP to be pulled down to the reference potential. Therefore, the comparator CMP outputs a low-level voltage regardless of the threshold voltage input to the non-inverting input terminal. This causes the light-emitting diode PCa to emit light.

In other words, when the drain potential of transistor Q1 is at a low level, the voltage setting circuit 3 sets the voltage of the non-inverting input terminal of comparator CMP to a voltage lower than the voltage of the inverting input terminal.

The external control circuit can determine that transistor Q1 has a short-circuit fault because light-emitting diode PCa emits light (low voltage detection) even though voltage Vi is being supplied. For example, the external control circuit can notify the vehicle that transistor Q1 has a short-circuit fault.

As described above, the discharge circuit 1A can cause the light-emitting diode PCa to emit light when the transistor Q1 has a short-circuit failure. This allows the discharge circuit 1A to detect the short-circuit failure of the transistor Q1.

In addition, the discharge circuit 1A can share the comparator CMP for both low voltage detection and short circuit fault detection, which reduces the number of circuit elements and wiring.

Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the gist of the invention. These embodiments and their modifications are within the scope of the invention and its equivalents as set forth in the claims, as well as the scope and gist of the invention.

1, 1A, 120 Discharge circuit 2, 3 Voltage setting circuit 101 High voltage battery 102 DCDC converter SW1, SW2 Switch R1, R2, R3, R4, R5, R6, R7, R11, R12, R13 Resistor D1, D2 Diode CMP Comparator C1, C2 Capacitor PCa Light emitting diode Q1, Q2 Transistor

Claims (5)

a first resistor, one end of which is electrically connected to the high potential terminal of the capacitor;
a first switching element having a first terminal electrically connected to the other end of the first resistor, a second terminal to which a control signal is input, the control signal being at a first level when discharging the charge of the capacitor and at a second level when not discharging the charge of the capacitor, and a third terminal electrically connected to a reference potential;
a comparator that receives a voltage corresponding to a voltage of the capacitor at a first input terminal, receives a threshold voltage at a second input terminal, and outputs a signal based on a comparison between the voltage corresponding to the capacitor voltage and the threshold voltage;
a voltage setting circuit that sets a voltage of the first input terminal or the second input terminal of the comparator to a predetermined voltage based on a voltage of the first terminal of the first switching element;
Equipped with
A discharge circuit comprising: The voltage setting circuit includes:
when the voltage of the first terminal of the first switching element is at a low level, the voltage of the second input terminal of the comparator is set to the predetermined voltage higher than the voltage of the first input terminal;
2. The discharge circuit according to claim 1 . The voltage setting circuit includes:
a second resistor, one end of which is electrically connected to the power supply potential;
a third resistor, one end of which is electrically connected to the other end of the second resistor;
a first diode having an anode electrically connected to the other end of the third resistor and a cathode electrically connected to the first terminal of the first switching element;
a second switching element having a first terminal electrically connected to the power supply potential and a second terminal electrically connected to the other end of the first resistor and one end of the second resistor;
a fourth resistor, one end of which is electrically connected to the third terminal of the second switching element and the other end of which is electrically connected to the second terminal of the comparator;
Equipped with
3. The discharge circuit according to claim 2 . The voltage setting circuit includes:
when the voltage of the first terminal of the first switching element is at a low level, the voltage of the first input terminal of the comparator is set to the predetermined voltage which is lower than the threshold voltage;
2. The discharge circuit according to claim 1 . The voltage setting circuit includes:
a second diode having an anode electrically connected to the first terminal of the comparator and a cathode electrically connected to the first terminal of the first switching element;
5. The discharge circuit according to claim 4, wherein the discharge circuit comprises:

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