JP2024041423A - short circuit protection device - Google Patents

Abstract

[Problem] To provide a short-circuit protection device that can immediately stop the flow of current in a line where a short circuit has occurred when a short circuit occurs. [Solution] A short-circuit protection device 7 is provided to protect a load driving device 1, which drives a load 2 based on a control signal Sa output from a control device 3, from a short circuit. A switch circuit 9 switches the driving of the load 2 on and off by controlling the switching state based on the result of a logical operation by a logic circuit 8. This switch circuit 9 outputs a voltage signal Sv generated between the load 2 and the switch circuit 9 as feedback to the logic circuit 8. The logic circuit 8 uses the control signal Sa and the voltage signal Sv as inputs for logical operation, and controls the switch circuit 9 based on the result of the logical operation of these signals. [Selected Figure] Figure 1

Description

The present invention relates to a short circuit protection device that protects a load drive device from short circuits.

As disclosed in Patent Document 1, a short-circuit protection circuit that protects a relay drive output circuit that outputs a drive current to a relay from short circuits is well known. In this short-circuit protection circuit, when a short-circuit detection circuit detects the presence or absence of a short circuit occurring on the output side of the relay drive output circuit, the output operation of the relay drive output circuit is stopped. Then, after a predetermined time has elapsed since the occurrence of the short circuit, a recovery signal is sent to the relay drive output circuit to restore the output operation of the relay drive output circuit.

Japanese Patent Application Publication No. 2009-254185

In the case of Patent Document 1, a CPU (microcomputer) executes the process of detecting a short circuit and stopping the output operation of the relay drive output circuit. Therefore, the operation of detecting a short circuit and stopping the circuit operation depends on the performance of the CPU. Therefore, depending on the performance of the CPU, it may take some time from detecting a short circuit to stopping the circuit operation, so a countermeasure has been required.

A short-circuit protection device that solves the above problem has a configuration that protects a load drive device that drives a load based on a control signal output from a control device from short circuits, and includes at least a logic that uses the control signal as an input for a logical operation. circuit, and a switch circuit that switches on/off driving of the load by controlling a switching state based on the result of a logical operation of the logic circuit, and the switch circuit A voltage signal is fed back to the logic circuit, and the logic circuit uses the control signal and the voltage signal as inputs for a logical operation, and controls the switch circuit based on the result of the logical operation of these signals.

When a short circuit occurs, the present invention can immediately stop the flow of current in the line where the short circuit occurs.

FIG. 1 is a configuration diagram of a short-circuit protection device according to a first embodiment. FIG. 3 is a configuration diagram of a high-side switch. This is a table summarizing how the short circuit protection device operates. This is a concrete diagram of a ground fault. It is a block diagram of the short circuit protection device of 2nd Embodiment. FIG. 3 is a configuration diagram of a low-side switch. This is a table summarizing how the short circuit protection device operates. This is a concrete diagram of a heavenly connection.

(First embodiment)
A first embodiment of the present disclosure will be described below.
(Load drive device 1)
As shown in FIG. 1, the load driving device 1 includes a control device 3 that controls the operation of the load 2. As shown in FIG. The control device 3 is, for example, an MCU (Micro Controller Unit). For example, one end of the load 2 is connected to the terminal 4 of the load driving device 1, and the other end is connected to GND. The load 2 is, for example, a heater, motor, relay, solenoid, lamp, capacitor, transformer, or the like. It is preferable that the load driving device 1 is composed of, for example, one integrated circuit.

(Short circuit protection device 7, logic circuit 8, and switch circuit 9)
1, the load driver 1 includes a short-circuit protection device 7 that protects the load driver 1 from a short circuit. In this example, the short circuit is a ground fault in which the load 2 comes into contact with the ground and a current flows to the ground. The short-circuit protection device 7 includes a logic circuit 8 that processes digital signals and performs logical operations, and a switch circuit 9 that switches the drive of the load 2 on and off. The control device 3, the logic circuit 8, and the switch circuit 9 are preferably configured in a single integrated circuit.

When detecting a ground fault, the logic circuit 8 is, for example, an AND circuit 12 that calculates a logical product. The logic circuit 8 has two input terminals 13 (in this example, a first input terminal 13a and a second input terminal 13b) and one output terminal 14. The first input terminal 13a is connected to the output control terminal 15 of the control device 3. The logic circuit 8 receives the control signal Sa input from the output control terminal 15 of the control device 3 through the first input terminal 13a. In this way, the logic circuit 8 uses at least the control signal Sa as an input for logical operations. The control signal Sa is a binary signal of Hi level or Lo level. Output terminal 14 is connected to switch circuit 9 .

As shown in FIG. 2, when detecting a ground fault, the switch circuit 9 is, for example, a high-side switch 17 connected between the load 2 and the power source 16. In the case of the high-side switch 17, the load 2 is driven when the control device 3 outputs the "Hi" control signal Sa. The switch circuit 9 is, for example, a transistor (PNP type transistor). When the switch circuit 9 is a transistor, its emitter terminal is connected to the power supply 16 , its collector terminal is connected to the load 2 , and its base terminal is connected to the logic circuit 8 . Note that the switch circuit 9 may be, for example, a FET (Field Effect Transistor).

The switch circuit 9 controls the operation of the load 2 by applying the binary voltage signal Sv to the load 2. Specifically, when the switch circuit 9 applies a Hi-level voltage signal Sv to the load 2, the load 2 is driven. On the other hand, when the switch circuit 9 applies a Lo-level voltage signal Sv to the load 2, the load 2 is not driven.

(Voltage feedback of switch circuit 9)
As shown in FIG. 1, the switch circuit 9 feeds back the voltage signal Sv generated between the switch circuit 9 and the load 2 to the logic circuit 8. Specifically, a midpoint 19 between the load 2 and the switch circuit 9 is connected to the second input terminal 13b of the logic circuit 8 via a signal line 20. In this way, the signal line 20 is provided to feed back the voltage signal Sv from the switch circuit 9 to the logic circuit 8. When the switch circuit 9 is a transistor, the voltage fed back from the switch circuit 9 to the logic circuit 8 is, for example, the voltage generated at the collector terminal of the transistor.

The short circuit protection device 7 includes, for example, a voltage dividing resistor 21 that divides the voltage signal Sv and inputs the divided voltage signal to the logic circuit 8. The voltage dividing resistor 21 includes, for example, resistors R1 and R2, and is placed on the signal line 20. In the voltage dividing resistor 21, for example, a midpoint 22 of the resistors R1 and R2 is connected to the second input terminal 13b of the logic circuit 8. It is preferable that the midpoints 19 and 22, the signal line 20, and the voltage dividing resistor 21 are configured in one integrated circuit, for example.

(Initial drive circuit 25)
As shown in FIG. 1, the short circuit protection device 7 includes an initial drive circuit 25 that forcibly inverts the signal level of the voltage signal Sv in order to drive the load 2. The initial drive circuit 25 is connected to a signal line 20 that feeds back the voltage signal Sv from the switch circuit 9 to the logic circuit 8 . For the initial drive circuit 25, for example, a transistor or an FET is used. In the case of a transistor, the initial drive circuit 25 has a collector terminal connected to the power supply 26, an emitter terminal connected to the second input terminal 13b (midpoint 22) of the logic circuit 8, and a base terminal connected to the initial drive circuit 25 of the control device 3. It is connected to the drive control terminal 27.

Next, the operation of the short-circuit protection device 7 of this embodiment will be explained.
(When driving load 2)
As shown in the status number "4" in FIG. 3, when the control device 3 starts driving the load 2, it outputs a "Hi" control signal Sa as a drive request from the output control terminal 15, and also controls the initial drive. The initial drive signal Sb of "Hi" is output from the terminal 27. The initial drive signal Sb of "Hi" is outputted from the initial drive control terminal 27 to the logic circuit 8 by setting the second input terminal 13b to a Hi input, thereby setting both the two inputs of the logic circuit 8 to "Hi". It's for a reason.

In the case of the AND circuit 12, when both inputs are "Hi", the logic circuit 8 outputs a "Hi" calculation value from the output terminal 14 to the switch circuit 9. When the switch circuit 9 receives a "Hi" calculation value from the logic circuit 8, it turns on. This causes the switch circuit 9 to apply a "Hi" voltage signal Sv to the load 2, which drives the load 2.

When the control device 3 detects the drive of the load 2 using a sensor (not shown) or the like, it switches the initial drive signal Sb from "Hi" to "Lo" and continues to output the "Hi" control signal Sa. At this time, the initial drive signal Sb is switched to "Lo", but the "Hi" voltage signal Sv fed back from the switch circuit 9 continues to input "Hi" to the second input terminal 13b. Therefore, the driving state of the load 2 is maintained.

(When stopping the drive of load 2)
As shown by the status number "2" in FIG. 3, when the control device 3 stops driving the load 2, it outputs a "Lo" control signal Sa as a stop request from the output control terminal 15. At this time, the logic circuit 8 which is the AND circuit 12 outputs the calculated value of "Lo" to the switch circuit 9 because one of the two inputs becomes "Lo". The switch circuit 9 is turned off when the calculated value of "Lo" is input from the logic circuit 8. As a result, the voltage signal Sv applied from the switch circuit 9 to the load 2 becomes "Lo", so that driving of the load 2 is stopped.

As shown by the status number "1" in FIG. 3, when the voltage signal Sv of the switch circuit 9 becomes "Lo", both of the two inputs of the logic circuit 8 become "Lo". Therefore, since the calculated value output from the logic circuit 8 to the switch circuit 9 is maintained at "Lo", the stoppage of the load 2 is maintained.

(If a ground fault occurs)
As shown in FIG. 4, when the load 2 is being driven, for example, if the wiring 29 of the load 2 comes into contact with the ground, a ground fault occurs in the load 2. When a ground fault occurs, the line connecting the power supply 16, the switch circuit 9, and the ground becomes the short circuit line 30, and current continues to flow through the short circuit line 30. At this time, if a large current flows through the switch circuit 9, it may cause an abnormality in the switch circuit 9, so it is necessary to immediately turn off the switch circuit 9. Note that the wiring 29 is, for example, a line that connects the terminal 4 of the load driving device 1 and the load 2.

As shown by status number "3" in FIG. 3, if a ground fault occurs while driving the load 2, the voltage signal Sv drops to "Lo". Therefore, a “Lo” signal is input to the second input terminal 13b of the logic circuit 8. Therefore, among the two inputs of the logic circuit 8, the input of the second input terminal 13b becomes "Lo", so that the logic circuit 8 outputs the calculation result of "Lo" to the switch circuit 9. As a result, the switch circuit 9 is turned off. Therefore, when a ground fault occurs, the switch circuit 9 is immediately turned off and the flow of current is stopped.

In the case of this example, when the logic circuit 8 receives a feedback input of the "Lo" signal as the voltage signal Sv from the switch circuit 9 when driving the load 2, the logic circuit 8 automatically outputs the "Lo" signal without receiving a command from the control device 3. The calculation result is output to the switch circuit 9 and the switch circuit 9 is turned off. Therefore, when a ground fault occurs while driving the load 2, it is possible to immediately switch the switch circuit 9 to the OFF state by utilizing the fact that the voltage signal Sv falls to "Lo". Therefore, it is possible to instantaneously stop the operation of the switch circuit 9 when a ground fault occurs.

(Effects of the embodiment)
According to the short circuit protection device 7 of the above embodiment, the following effects can be obtained.
(1-1) The short-circuit protection device 7 is provided to protect the load driving device 1, which drives the load 2 based on the control signal Sa output from the control device 3, from a short circuit. The short-circuit protection device 7 includes a logic circuit 8 and a switch circuit 9. The logic circuit 8 takes at least the control signal Sa as an input for logical operation. The switch circuit 9 switches the drive of the load 2 on and off by controlling the switching state based on the result of the logical operation of the logic circuit 8. The switch circuit 9 outputs a voltage signal Sv generated between the load 2 and the logic circuit 8 as a feedback to the logic circuit 8. The logic circuit 8 takes the control signal Sa and the voltage signal Sv as inputs for logical operation, and controls the switch circuit 9 based on the result of the logical operation of these signals.

According to this configuration, for example, when a short circuit occurs in the load drive device 1, the voltage signal Sv, which is an inverted rectangular wave, is fed back and output from the switch circuit 9 to the logic circuit 8. Then, in response to the input of this voltage signal Sv, the logic circuit 8 outputs to the switch circuit 9 the result of a logical operation that turns the switch circuit 9 into an off state. In this way, when a short circuit occurs, it is possible to turn off the switch circuit 9 only by the operation of the logic circuit 8 without involving the MCU or CPU. Therefore, when a short circuit occurs, the flow of current in the short circuit generating line 30 can be immediately stopped.

(1-2) The short circuit protection device 7 includes an initial drive circuit 25 connected to a signal line 20 that feeds back a voltage signal Sv from the switch circuit 9 to the logic circuit 8. The initial drive circuit 25 forcibly inverts the signal level of the voltage signal Sv input to the logic circuit 8 in order to drive the load 2 . According to this configuration, when the voltage signal Sv between the load 2 and the switch circuit 9 is fed back to the logic circuit 8 and is input to the logic circuit 8, at the time of initial driving, the voltage signal Sv from the logic circuit 8 to the switch circuit 9, the result of a logical operation for turning on the switch circuit 9 can be output.

(1-3) The short circuit protection device 7 includes a voltage dividing resistor 21 that divides the voltage signal Sv and inputs it to the logic circuit 8. According to this configuration, when feeding back the voltage signal Sv between the load 2 and the switch circuit 9 to the logic circuit 8, the voltage signal Sv having a value suitable for the logic circuit 8 can be input to the logic circuit 8. .

(1-4) The logic circuit 8 is an AND circuit 12 that calculates logical product. The switch circuit 9 is a high-side switch 17 connected between the load 2 and the power supply 16. According to this configuration, a ground fault in the load drive device 1 can be detected.

(1-5) When a ground fault occurs, it is also possible to take measures to prevent current from flowing through the short circuit line 30, for example, by controlling polarity reversal. However, in this configuration, output lines of the same system are required, and a circuit for polarity reversal control is also required, so there is a concern that the circuit scale will increase. On the other hand, in the case of the configuration of this example, since it is sufficient to simply add a configuration for feeding back the voltage signal Sv, which is the output of the switch circuit, to the logic circuit 8, the circuit scale does not become large.

(Second embodiment)
Next, a second embodiment will be described. Note that the second embodiment is an example in which the ground fault in the first embodiment is changed to a power fault. Therefore, the same parts as those in the first embodiment are denoted by the same reference numerals, and the explanation thereof will be omitted, and only the different parts will be described in detail.

(Short circuit protection device 7)
As shown in FIG. 5, the short circuit protection device 7 detects a ground fault as a short circuit in the load 2. In this way, the short-circuit protection device 7 of this example protects the load 2 from short-circuits to power supply. Short-to-power is a phenomenon in which the load 2 is short-circuited to the power supply 16. When detecting a power short, the logic circuit 8 is, for example, a NOR circuit 35 that calculates a negative logical sum. NOR circuit 35 also has two input terminals 36 and one output terminal 37. Specifically, the first input terminal 36a is connected to the output control terminal 15, the second input terminal 36b is connected to the midpoint 22 (initial drive circuit 25), and the output terminal 37 is connected to the switch circuit 9. .

As shown in FIG. 6, when detecting a short-to-power supply, the switch circuit 9 is, for example, a low-side switch 38 connected between the load 2 connected to the power supply 16 and the ground. In the case of the low-side switch 38, the load 2 is driven when the "Lo" control signal Sa is output from the control device 3. The switch circuit 9 is, for example, a transistor (NPN transistor). If the switch circuit 9 is a transistor, the collector terminal is connected to the load 2, the emitter terminal is connected to GND, and the base terminal is connected to the logic circuit 8. Note that the switch circuit 9 may be, for example, a FET (Field Effect Transistor).

As shown in FIG. 5, the initial drive circuit 25 is a switch section 39 for forcibly lowering the signal level of the second input terminal 36b to "Lo" when driving the load 2. For the switch section 39, for example, an FET is used.

Next, the operation of the short-circuit protection device 7 of this embodiment will be explained.
(When driving load 2)
As shown by the status number "1" in FIG. 7, when the control device 3 starts driving the load 2, it outputs a "Lo" control signal Sa as a drive request from the output control terminal 15. At this time, the control device 3 forcibly sets the second input terminal 36b of the logic circuit 8 to “Lo” through the switch section 39 using the initial drive signal Sb output from the initial drive control terminal 27. In this way, both of the two inputs of the logic circuit 8 are set to "Lo".

In the case of the NOR circuit 35, when both inputs are "Lo", the logic circuit 8 outputs a calculation value of "Hi" from the output terminal 37 to the switch circuit 9. When the logic circuit 8 inputs a calculation value of "Hi", the switch circuit 9 goes into an on state. This causes the circuit of the load 2 to become a closed loop, so that the load 2 is driven.

When the control device 3 detects the drive of the load 2 using a sensor (not shown) or the like, it stops driving the switch section 39 using the initial drive signal Sb and continues to output "Lo" of the control signal Sa. At this time, the switch section 39 does not force the potential drop to "Lo", but the "Lo" voltage signal Sv fed back from the switch circuit 9 causes the input of "Lo" at the second input terminal 36b. will continue. Therefore, the driving state of the load 2 is maintained.

(When stopping the drive of load 2)
As shown in status number "3" in FIG. 7, when the control device 3 stops driving the load 2, it outputs a "Hi" control signal Sa as a stop request from the output control terminal 15. At this time, the logic circuit 8, which is the NOR circuit 35, outputs a calculated value of "Lo" to the switch circuit 9 because one of its two inputs becomes "Hi". The switch circuit 9 is turned off when the calculated value of "Lo" is input from the logic circuit 8. As a result, the voltage signal Sv applied from the switch circuit 9 to the load 2 becomes "Hi", so that driving of the load 2 is stopped.

As shown in status number "4" in FIG. 7, when the voltage signal Sv of the switch circuit 9 becomes "Hi", both of the two inputs of the logic circuit 8 become "Hi". Therefore, since the calculated value output from the logic circuit 8 to the switch circuit 9 is maintained at "Lo", the stoppage of the load 2 is maintained.

(If a short circuit occurs)
As shown in FIG. 8, when the load 2 is being driven, for example, if the wiring 29 of the load 2 is short-circuited to the power supply 16, a power short occurs in the load 2. When a short-circuit occurs, the line connecting the load 2 and the power supply 16 becomes the short-circuit line 30, and voltage continues to be applied to the short-circuit line 30. At this time, since the load 2 continues to be driven, it is necessary to immediately turn off the switch circuit 9.

As shown in the status number "2" in FIG. 7, if a power short occurs when the load 2 is driven, the voltage signal Sv switches to "Hi". Therefore, a “Hi” signal is input to the second input terminal 36b of the logic circuit 8. Therefore, among the two inputs of the logic circuit 8, the input of the second input terminal 36b becomes "Hi", so that the logic circuit 8 outputs the calculation result of "Lo" to the switch circuit 9. As a result, the switch circuit 9 is turned off. Therefore, when a short circuit occurs, the switch circuit 9 is immediately turned off and the flow of current is stopped.

(Effects of embodiment)
According to the short circuit protection device 7 of the above embodiment, the following effects can be obtained.
(2-1) The logic circuit 8 is a NOR circuit 35 that calculates a negative OR. The switch circuit 9 is a low-side switch 38 connected between the load 2 connected to the power supply 16 and ground. According to this configuration, a short-circuit to power supply of the load drive device 1 can be detected.

(Other embodiments)
Note that this embodiment can be implemented with the following modifications. This embodiment and the following modified examples can be implemented in combination with each other within a technically consistent range.

- In each embodiment, the logic circuit 8 may use a logic circuit other than the AND circuit 12 or the NOR circuit 35.
- In each embodiment, the switch circuit 9 may be a circuit other than the high-side switch 17 or the low-side switch 38.

- In each embodiment, the control device 3, the logic circuit 8, and the switch circuit 9 may be configured from independent integrated circuits, or may be configured from an integrated circuit including two of them.

- In each embodiment, the power supplies 16 and 26 may be the same power supply or may be different.
- In each embodiment, the initial drive circuit 25 can use various switching elements and switches.

- In the second embodiment, the initial drive circuit 25 may be omitted from the short circuit protection device 7. That is, the initial drive circuit 25 may be omitted in the short-circuit protection device 7 that protects the load 2 from short-circuit to power supply.

- In each embodiment, the control device 3 may be, for example, an MPU (Micro Processor Unit) or a CPU (Central Processing Unit).
- In each embodiment, the short circuit protection device 7 is not limited to use in a vehicle, and can be used in other devices and systems.

- Although the present disclosure has been described based on examples in each embodiment, it is understood that the present disclosure is not limited to the examples or structures. The present disclosure also includes various modifications and equivalent modifications. In addition, various combinations and configurations, as well as other combinations and configurations that include only one, more, or fewer elements, are within the scope and scope of the present disclosure.

DESCRIPTION OF SYMBOLS 1...Load drive device, 2...Load, 3...Control device, 7...Short circuit protection device, 8...Logic circuit, 9...Switch circuit, 12...AND circuit, 16...Power supply, 17...High side switch, 20...Signal line , 21... Voltage dividing resistor, 25... Initial drive circuit, 35... NOR circuit, 38... Low side switch, Sa... Control signal, Sv... Voltage signal.

Claims (5)

A short circuit protection device that protects a load drive device that drives a load based on a control signal output from a control device from short circuits,
a logic circuit that uses at least the control signal as an input for logical operations;
a switch circuit that switches on/off driving of the load by controlling a switching state based on a result of a logical operation of the logic circuit;
The switch circuit feeds back a voltage signal generated between the switch circuit and the load to the logic circuit, and
The logic circuit is a short-circuit protection device, wherein the logic circuit uses the control signal and the voltage signal as inputs for a logical operation, and controls the switch circuit based on the result of the logical operation of these signals. an initial drive circuit connected to a signal line that feeds back the voltage signal from the switch circuit to the logic circuit, and forcibly inverts the signal level of the voltage signal input to the logic circuit in order to drive the load; The short circuit protection device according to claim 1, comprising: The short-circuit protection device according to claim 1 , further comprising a voltage dividing resistor that divides the voltage signal and inputs the divided voltage signal to the logic circuit. The logic circuit is an AND circuit that calculates logical product,
The short-circuit protection device according to claim 1, wherein the switch circuit is a high-side switch connected between the load and a power source. The logic circuit is a NOR circuit that calculates a negative logical sum,
The short-circuit protection device according to claim 1, wherein the switch circuit is a low-side switch connected between the load connected to a power source and ground.

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