JP2000307400A - Power supply controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect an over-current without the need for replacement of a resistor by automatically changing a detected value for discrimination of the over-current even when a load is changed. SOLUTION: A power supply controller is provided with a reference circuit consisting of overheat self-interruption type semiconductor switches QA, QB controlling the current flowing to motors M1, M2 in response to a control signal and a series circuit comprising the switch QB and a reference resistor 5, of a comparator circuit CMP1 that compares a prescribed over-current discrimination value C with a difference (A-B) between the source voltage A of the switch QA and the source voltage B of the switch QB so as to discriminate whether an over-current takes place and outputs a detection signal in response to the discrimination result, and a drive circuit 2 that turns on/off the switch QA depending on a control signal in response to the detection signal. The power supply controller that controls on/off of the switch QA depending on the quantity relation between the over-current discrimination value C and the difference (A-B) is provided with a sensor 7 which detects a change in a load VB and outputs a corresponding signal, and changes the current flowing in the reference resistor 5 in response to the output of the sensor 7.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention comprises an overheat self-interrupting semiconductor switch for controlling a current flowing in a power supply line between a power supply and a load in accordance with a control signal, and determining whether the current is an overcurrent. The present invention relates to a power supply control device that turns on and off a semiconductor switch by overheating and self-interruption type by detecting the above.

[0002]

2. Description of the Related Art Conventionally, as a power supply control device of this type, for example, a fuse provided on a power supply line between a power supply and a load such as a motor, and a semiconductor switch provided between the load and the ground have been proposed. An overcurrent detection sensor that detects whether the current flowing in the power supply line is an overcurrent based on a fixed reference value generated by a fixed resistor and outputs a signal corresponding to the detection result; and A control unit for turning on and off a semiconductor switch provided on the power supply line according to the output, so that the semiconductor switch provided on the power supply line is turned off by a control signal output from the control unit when overcurrent is detected. Structured ones are known.

[0003]

However, in such prior art, the overcurrent detection sensor detects the overcurrent based on a fixed reference value made by a fixed resistor. Therefore, when changing the load connected to the power supply line, it is necessary to change the reference value for overcurrent determination according to the value of this change. For this reason, the fixed resistor, which is a reference resistor for detecting overcurrent, must be replaced with a resistor having a different resistance value, and an operation for that is necessary.
That is, for example, when the load is increased, it is necessary to replace the fixed resistor with a resistor having a resistance value such that the reference value of the overcurrent determination increases in accordance with the change of the load.

[0004] It is an object of the present invention to automatically change the detection value of the overcurrent discrimination according to the change in load even if the load is changed, without performing the work of exchanging the resistance accompanying the change in load. The purpose is to be able to cope with accurate overcurrent detection.

[0005]

The invention according to claim 1 is
A first overheating self-interrupting semiconductor switch for controlling a current flowing through a power supply line between a power supply and a load in accordance with a control signal; and a second overheating self-interrupting semiconductor switch having the same voltage characteristics as the first overheating self-interrupting semiconductor switch. A first reference circuit composed of a series circuit composed of an overheated self-interrupting semiconductor switch and a first reference resistor connected in parallel to the power supply line, and a drain-source voltage of the first overheating self-interrupting semiconductor switch; By comparing a difference (A−B) between A and the drain-source voltage B of the second overheat self-interruption type semiconductor switch with a predetermined overcurrent determination value C, the current flowing through the power supply line is overcurrent. And a comparison circuit that outputs a detection signal according to the result of the determination, and a control circuit that turns on and off the first overheat self-interrupting semiconductor switch with a control signal corresponding to the detection signal. A first reference resistor, the same voltage as the drain-source voltage of the first overheating self-interrupting semiconductor switch when a predetermined load current flows through the first overheating self-interrupting semiconductor switch. Is set to a value that causes the second overheat self-interruption type semiconductor switch, and the predetermined overcurrent determination value C is set to the difference (A−
B), and when the value of the difference (A−B) is greater than the overcurrent determination value C, it is determined that an overcurrent has occurred, and the first overheat self-interrupting semiconductor switch is turned off. The overheating self-interruption type semiconductor switch is once turned off, and thereafter, the on / off control of the first overheating self-interruption type semiconductor switch is repeated,
A power supply device configured to turn on the first overheat self-interrupting semiconductor switch when the current is determined to be a normal current during the on / off control, detects a change in load, and responds to the change. And a sensor that outputs a detected signal, and the current flowing through the first reference resistor is changed according to the output of the sensor. With this configuration, even if the load is changed, the sensor detects the change in the load, outputs a signal corresponding to the change in the load, and automatically changes the current flowing through the reference resistor according to the output. Therefore, the overcurrent judgment value, which is the detection value of the overcurrent judgment, is automatically changed according to the change in the load, and it is necessary to cope with the accurate overcurrent detection without performing the work of replacing the resistor accompanying the load change. Can be.

According to a second aspect of the present invention, the first reference resistor is connected to a fixed resistor connected to the source of the second overheat self-interruption type semiconductor switch, and the fixed resistor is connected between the fixed resistor and the ground. And current changing means for changing the current flowing through the fixed resistor according to the signal,
There is provided control means for outputting a current control signal corresponding to the output of the sensor to the current changing means. With this configuration, even if the load is changed, the sensor detects the change in the load, outputs a signal corresponding to the change in the load, and automatically changes the current flowing through the reference resistor according to the output. Therefore, the overcurrent judgment value, which is the detection value of the overcurrent judgment, is automatically changed according to the change in the load, and it is necessary to cope with the accurate overcurrent detection without performing the work of replacing the resistor accompanying the load change. Can be.

According to a third aspect of the present invention, there is provided a third overheated self-cutoff semiconductor switch having the same voltage characteristics as the first overheated self-cutoff semiconductor switch and having a smaller number of transistors than the first overheated self-cutoff semiconductor switch. Cut-off semiconductor switch and second
A second reference circuit connected in parallel to a power supply line, a drain-source voltage A of a first overheat self-interruption type semiconductor switch, and a second overheat self-interruption type semiconductor switch. Is compared with a predetermined undercurrent determination value D to determine whether or not the current flowing through the power supply line is an undercurrent. A second comparison circuit that outputs a corresponding detection signal, and a sensor that detects a change in load and outputs a signal in accordance with the change, and flows through the second reference resistor in accordance with the output of the sensor. The current is changed. According to such a configuration, even when the load is changed, the sensor detects the change in the load and outputs a signal corresponding to the change in the load,
Since the current flowing through the reference resistor is automatically changed according to this output, not only the overcurrent judgment value, which is the detection value of overcurrent judgment, but also the undercurrent judgment value, which is the detection value of undercurrent judgment, changes in the load. , And it is possible to cope with accurate detection of overcurrent / undercurrent without performing the work of exchanging the resistance accompanying the change of the load.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below. FIG. 1 is a schematic configuration diagram showing a power supply control device according to an example of an embodiment of the present invention. FIG. 2 is a detailed circuit diagram of a first overheat self-interruption type semiconductor switch QA shown in FIG. FIG. 3 is a detailed circuit diagram of the second overheated self-interruption type semiconductor switch QB shown in FIG. 1, and FIG. 4 is a third overheated self-interruption type semiconductor switch QC shown in FIG.
5 is a detailed circuit diagram of FIG. 5, FIG. 5 is a configuration diagram showing an example of a reference resistor used in the power supply control device shown in FIG.
FIG. 6 is a configuration diagram showing another example of the reference resistor used in the power supply control device shown in FIG.

As shown in FIGS. 1 to 4, the power supply control device controls a current supplied from a battery to each load such as a headlight in a vehicle such as an automobile, and is configured as a single chip. I have. Reference numeral 1 denotes a power supply device, and the power supply device 1 is configured as one semiconductor chip. In this power supply device 1, a connection terminal for connecting an external element is indicated by a circle.

A battery VB is connected to the input terminal A of the power supply device 1, and two motors M1 and M2 are connected in parallel to the output terminal B as loads. A semiconductor switch SW2 that turns on and off the motors M1 and M2 according to a control signal from the control unit 8 is provided between the motors M1 and M2.
Is provided. This semiconductor switch SW2 is an FET
It is composed of

On the other hand, a switch SW1 having one end grounded and the other end connected to the battery VB via a resistor R4 is connected to the switching terminal C. The input side terminal A is connected to the drain side terminal DA of the first overheating self-interruption type semiconductor switch QA, and the source side terminal SA of the first overheating self-interruption type semiconductor switch QA is connected to the output side. Terminal B is connected. Further, the first overheated self-interruption type semiconductor switch QA is provided with a gate terminal GA. The first overheated self-interruption type semiconductor switch QA is connected to a battery VB and a load (motors M1, M2).
2) are connected in series.

The first overheated self-interruption type semiconductor switch QA has a configuration as shown in FIG. That is,
The drain of the main FET Q1 is connected to the drain terminal DA, and the source terminal SA is connected to the source of the main FET Q1. The gate of the main FET Q1 is connected to a gate terminal GA via an internal resistor RA (for example, 10 kΩ). A temperature detecting circuit 30 is provided between the gate terminal GA and the source terminal SA.
Is connected. This temperature detection circuit 30 is connected to the main F
This is for detecting the temperature of the ETQ 1, and a latch circuit 31 is connected to the temperature detection circuit 30. When the temperature of the main FET Q1 reaches a predetermined temperature (abnormal temperature), the temperature detection circuit 30
To output an ON signal. The latch circuit 31 has a function of receiving a signal from the temperature detection circuit 30 and continuously outputting an ON signal. The output terminal of the latch circuit 31 is connected to the gate of an overheat cutoff FET Q2. When the temperature detection circuit 30 detects that the main FET Q1 is overheated, an ON signal output via the latch circuit 31 outputs the signal. The overheat cut-off FET Q2 turns on and the main FET Q
The main FET Q1 is cut off by dropping the gate voltage of No. 1.

On the other hand, loads (motors M1 and M2) are connected to a source terminal SA of the first overheat self-interruption type semiconductor switch QA via an output terminal B. The power supply to the loads (motors M1 and M2) is performed by the main FET Q1 of the first overheated self-interrupting semiconductor switch QA. In this way, the first overheated self-interruption type semiconductor switch QA is overheated when an overcurrent flows between the drain and source of the main FET Q1 due to a short circuit of the load (motor M1, M2) or the like. In order to prevent the main FET Q1 from being destroyed, an overheating self-interruption function is provided which forcibly turns off (interrupts) by its own action when the temperature of the main FET Q1 rises above a specified value. The main FET Q1 that constitutes the power supply overheat self-interruption type semiconductor switch QA is composed of an NMOSFET having a DMOS structure.

First overheated self-interruption type semiconductor switch QA
The drain-side terminal DA of the second overheat self-interruption type semiconductor switch QB and the drain-side terminal DC of the third overheat self-interruption type semiconductor switch QC are connected to the drain-side terminal DA. An output terminal E is connected to a source terminal SB of the second overheated self-interruption type semiconductor switch QB, and an output terminal F is connected to a source side terminal SC of the third overheated self-interruption type semiconductor switch QC. It is connected. Also,
The second overheated self-interruption type semiconductor switch QB has a gate-side terminal GB connected to the third overheated self-interruption type semiconductor switch QB.
C is provided with a gate-side terminal GC.

The second overheated self-interruption type semiconductor switch QB has a configuration as shown in FIG. 3, and the second overheated self-interruption type semiconductor switch QB is configured as shown in FIG. It has the same configuration as the self-interrupting semiconductor switch QA. That is, the drain of the main FET Q3 is connected to the drain-side terminal DB,
The source 3 is connected to the source side terminal SB.
The gate of the main FET Q3 is connected to the gate terminal GB via an internal resistor RB (for example, 10 kΩ). The temperature detection circuit 40 is connected between the gate side terminal GB and the source side terminal SB. The temperature detecting circuit 40 is for detecting the temperature of the main FET Q3.
Is connected. And this temperature detection circuit 40
It has a function of outputting an ON signal to the latch circuit 41 when the temperature of the main FET Q3 becomes equal to or higher than a predetermined temperature (abnormal temperature) due to a current larger than a predetermined current flowing through the main FET Q3. Then, the latch circuit 41
Has an operation of receiving a signal from the temperature detection circuit 40 and continuously outputting an ON signal. Further, the output terminal of the latch circuit 41 is connected to the gate of the overheat cutoff FET Q4.
When detecting that TQ3 is overheated, the latch circuit 4
FE for overheating cut-off by ON signal output through
TQ4 is turned on, the gate voltage of the main FET Q3 is dropped, and the main FET Q3 is cut off.

On the other hand, a first reference resistor 5 is connected to a source-side terminal SB of the second overheat self-interruption type semiconductor switch QB via an output-side terminal E.
The ETQ 3 and the first reference resistor 5 constitute a first reference circuit. This first reference circuit comprises a first overheated self-interruption type semiconductor switch Q
A is connected in parallel to a series circuit of a main FET Q1 and loads (motors M1, M2). This first reference circuit includes a first overheated self-interruption type semiconductor switch QA.
Turn on the main FET Q1 of the load (motor M1, M
2) When a current flows through the load (motors M1 and M2), the current is generated at the source (source side terminal SA) of the main FET Q1 of the first overheated self-interruption type semiconductor switch QA when the current is flowing normally. This has the function of constantly generating the same voltage (reference voltage) at the source (source-side terminal SB) of the main FET Q3 of the second overheat self-interruption type semiconductor switch QB. That is, the load (motor M1) connected to the source-side terminal SA of the first overheated self-interruption type semiconductor switch QA is connected to the source (source side terminal SB) of the main FET Q3 of the second overheated self-interruption type semiconductor switch QB. , M2), a constant source voltage is always generated regardless of the change in the state.

When the source voltage of the main FET Q3 of the second self-heating semiconductor switch QB excessively flows through the main FET Q1 of the first self-heating semiconductor switch QA, the source (source) of the main FET Q1 This is a reference voltage for detecting that an overcurrent has flowed through the loads (motors M1 and M2) as compared with the source voltage generated at the side terminal SA).

As described above, the second overheated self-interrupting semiconductor switch QB is connected to the main FET Q3 of the second overheating self-interrupting semiconductor switch QB by the short circuit of the first reference resistor 5 connected to the source of the main FET Q3. When an overcurrent flows between the drain and source, this main F
In order to prevent the ETQ3 from being overheated and destroyed, the ETQ3 has an overheating self-interruption function that forcibly turns off (interrupts) by its own action when the temperature of the main FET Q3 rises above a specified value. The main FET Q3 constituting the second overheat self-interruption type semiconductor switch QB is constituted by an NMOSFET having a DMOS structure.

The third overheat-self-interruption type semiconductor switch QC has a configuration as shown in FIG.
Has the same configuration as the first overheated self-interruption type semiconductor switch QA shown in FIG. That is, the drain of the main FET Q5 is connected to the drain side terminal DC,
A source terminal SC is connected to the source of Q5. The gate of the main FET Q5 is connected to an internal resistor RC.
(For example, 10 kΩ) via a gate terminal GC. The gate side terminal GC and the source side terminal SC
Is connected to the temperature detection circuit 50. The temperature detection circuit 50 is for detecting the temperature of the main FET Q5, and a latch circuit 51 is connected to the temperature detection circuit 50. And this temperature detection circuit 5
0 has a function of outputting an ON signal to the latch circuit 51 when the temperature of the main FET Q5 becomes equal to or higher than a predetermined temperature (abnormal temperature) due to a current larger than a predetermined current flowing through the main FET Q5. The latch circuit 51 has a function of outputting an ON signal to the latch circuit 51 when the temperature of the main FET Q5 becomes equal to or higher than a predetermined temperature (abnormal temperature) due to a current larger than a predetermined current flowing through the main FET Q5. are doing. The latch circuit 51 has a function of receiving a signal from the temperature detection circuit 50 and continuously outputting an ON signal. Further, the output terminal of the latch circuit 51 is connected to the gate of the overheat cutoff FET Q6. When the temperature detection circuit 50 detects that the main FET Q5 is overheated, the output is output via the latch circuit 51. The overheat cutoff FET Q6 is turned on by the ON signal, and the gate voltage of the main FET Q5 is dropped to cut off the main FET Q5.

On the other hand, a second reference resistor 6 is connected to a source terminal SC of the third overheat self-interruption type semiconductor switch QC via an output terminal F. This main FET Q5 and the second reference resistor The resistor 6 constitutes a second reference circuit. The second reference circuit includes a main FET Q1 and a load (motors M1, M2) of the first overheated self-interruption type semiconductor switch QA.
Are connected in parallel to a series circuit. This second reference circuit turns on the main FET Q1 of the first overheated self-interruption type semiconductor switch QA to load (the motor M1,
M2), and a current is generated at the source (source terminal SA) of the main FET Q1 of the first overheat self-interruption type semiconductor switch QA when the current (motor M1, M2) is flowing normally. This has the function of constantly generating the same voltage (reference voltage) at the source (source side terminal SC) of the main FET Q5 of the third overheat self-interruption type semiconductor switch QC. That is, the source (source terminal SC) of the main FET Q5 of the second reference overheating self-interruption type semiconductor switch QC is connected to the load connected to the source side terminal SA of the power supply overheating self-interruption type semiconductor switch QA. A constant source voltage is always generated regardless of a change in the state.

The source voltage of the main FET Q5 of the third overheated self-interruption type semiconductor switch QC is changed by the load (motor M1, M2) despite the fact that the main FET Q1 of the first overheated self-interruption type semiconductor switch QA is on. When no current flows or an excessively small current flows in M2) (in the case of disconnection of the load (motors M1, M2), poor connection, etc.), the current flowing in the main FET Q1 of the first overheated self-interrupting semiconductor switch QA. When the amount flows below the second predetermined value, the reference voltage is a reference voltage for detecting that the current has flown to the loads (motors M1, M2) by comparing with the source voltage of the main FET Q1. .

As described above, the third overheat self-interruption type semiconductor switch QC is connected to the main FET Q5 of the third overheat self-interruption type semiconductor switch QC by short-circuiting the second reference resistor 6 connected to the source of the main FET Q5. When an overcurrent flows between the drain and source, this main F
In order to prevent the ETQ 5 from being overheated and destroyed, the ETQ 5 is provided with an overheat self-interruption function of forcibly turning off (interrupting) by its own action when the temperature of the main FET Q5 rises above a specified value. The main FET Q5 constituting the third overheat self-interruption type semiconductor switch QC is constituted by an NMOSFET having a DMOS structure.

The main FET Q1 of the first semiconductor switch QA, the main FET Q3 of the second semiconductor switch QB, and the main FET Q5 of the third semiconductor switch QC are: This main FET is composed of multiple transistors.
The ratio of the number of transistors constituting the main FET Q1, the main FET Q3, and the main FET Q5 is: main FET Q1> main FET Q3 main FET Q1> main FET Q5. Specifically, for example, the main FET Q1 of the first overheating self-interruption type semiconductor switch QA and the main FET Q3 of the second overheating self-interruption type semiconductor switch QB,
And a main FET Q1 of the first overheated self-interruption type semiconductor switch QA and a third overheated self-interruption type semiconductor switch QA.
The ratio of the number of transistors of the main FET Q5 of C is 100
0: 1 is set.

For example, when a load current (drain current) of 5 A flows through the main FET Q1 of the first overheated self-interruption type semiconductor switch QA, the first overtemperature self-interruption type semiconductor switch is turned on. A drain current of 5 mA flows through the main FET Q3 of the QB, and a drain-source voltage equal to the drain-source voltage Vds of the main FET Q1 of the first overheated self-interrupting semiconductor switch QA is applied to the second overheating self-interrupting semiconductor switch QB. Main FE
The value is set so as to be generated between the drain and source of TQ3. Also, the second reference resistor 6
For example, when a load current of 5 A flows through the main FET Q1 of the first overheating self-interruption type semiconductor switch QA, a drain current of 5 mA flows through the main FET Q5 of the third overheating self-interruption type semiconductor switch QC, A value such that the same drain-source voltage as the drain-source voltage Vds of the main FET Q1 of the cut-off semiconductor switch QA is generated between the drain-source of the main FET Q5 of the third overheat self-cutoff semiconductor switch QC. It has been set.

Therefore, the gate-source voltage of the main FET Q1 of the first overheated self-interruption type semiconductor switch QA and the gate-source voltage of the main FET Q3 of the second overheated self-interruption type semiconductor switch QB are equal to the first voltage. As long as the loads (motors M1 and M2) connected to the main FET Q1 of the overheat self-interruption type semiconductor switch QA are normal, the values become the same. Similarly, the gate-source voltage of the main FET Q1 of the first overheated self-interruption type semiconductor switch QA and the gate-source voltage of the main FET Q5 of the third overheated self-interruption type semiconductor switch QC are equal to the first superheated self-interruption type semiconductor switch QC. As long as the loads (motors M1 and M2) connected to the main FET Q1 of the cutoff type semiconductor switch QA are normal, the values will be the same.

First overheating self-interruption type semiconductor switch QA
Of the main FET Q1, the gate of the main FET Q3 of the second overheat self-interruption type semiconductor switch QB, and the main FET of the third overheat self-interruption type semiconductor switch QC
The gate of Q5 is connected to the drive circuit 2 via a series circuit of a resistor R7 and a resistor R8, and the gate signal output from the drive circuit 2 causes the main FET Q1 of the first overheat self-interrupting semiconductor switch QA to be connected. A main FET Q3 of the second overheated self-interruption type semiconductor switch QB and a main FET of the third overheated self-interruption type semiconductor switch QC
Q5 is turned on and off at the same time.

The drain DA of the first overheated self-interruption type semiconductor switch QA, the drain DB of the second overheated self-interruption type semiconductor switch QB, and the drain DC of the third overheated self-interruption type semiconductor switch QC are shared. By sharing the gate GA of the first overheated self-interruption type semiconductor switch QA, the gate GB of the second overheated self-interruption type semiconductor switch QB, and the gate GC of the third overheated self-interruption type semiconductor switch QC, the same chip can be used. Integration can be facilitated. Further, the first overheated self-interruption type semiconductor switch QA, the second overheated self-interruption type semiconductor switch QB, and the third overheated self-interruption type semiconductor switch QC are formed on the same chip by the same process. In other words, the effects of temperature drift and lot-to-lot variation are eliminated.

The anode of the Zener diode ZD1 is connected to the source of the main FET Q1 of the first overheat self-interruption type semiconductor switch QA. The resistor R7 and the resistor R8 are connected to the cathode of the Zener diode ZD1.
Connection points are connected. This zener diode Z
D1 is a power supply voltage (12) between the gate and source of the main FET Q1 of the first overheat self-interruption type semiconductor switch QA.
When the overvoltage is applied to the gate while maintaining V), the overvoltage is bypassed.

The source of the main FET Q1 of the first overheat self-interruption type semiconductor switch QA is constituted by a (+) side input terminal of a comparator CMP1 constituted by a comparator via a resistor R5 and a comparator. The (−) side input terminals of the comparison circuit CMP2 are connected to each other. The comparison circuit CMP1 compares the voltage induced at the source of the main FET Q1 of the first overheated self-interruption type semiconductor switch QA with the voltage induced at the source of the main FET Q3 of the second overheated self-interruption type semiconductor switch QB. And the main F of the first overheat self-interruption type semiconductor switch QA.
This is for detecting that an excessive current flows to loads (motors M1 and M2) connected to the ETQ1. That is, the output of the comparison circuit CMP1 is based on the source voltage of the main FET Q1 (potential on the source SA side) of the first overheated self-interruption type semiconductor switch QA and the source voltage of the main FET Q3 of the second overheated self-interruption type semiconductor switch QB ( The potential of the source of the main FET Q1 of the first overheating self-interruption type semiconductor switch QA is compared with the second overheating self-interruption type semiconductor switch while the difference is equal to or less than the overcurrent determination value. Hi is output while the potential of the source of the main FET Q3 of the QB is higher than or equal to the potential of the source of the main FET Q1 of the first overheated self-interruption type semiconductor switch QA. FET Q3 of the overheat self-interruption type semiconductor switch QB
(When the potential becomes lower than the source potential), the output is inverted and Low is output, and it is determined that an excessive current has flowed.

Further, the comparison circuit CMP2 is induced at the voltage induced at the source of the main FET Q1 of the first overheated self-interruption type semiconductor switch QA and at the source of the main FET Q5 of the third overheated self-interruption type semiconductor switch QC. The first overheated self-interruption type semiconductor switch QA
To detect whether a predetermined amount of current is flowing through the main FET Q1 (whether the current is not too small).
That is, the output of the comparison circuit CMP2 is based on the source voltage (potential on the source SA side) of the main FET Q1 of the first overheating self-interruption type semiconductor switch QA and the source voltage of the main FET Q5 of the third overheating self-interruption type semiconductor switch QC ( The source voltage of the main FET Q1 of the first overheated self-interruption type semiconductor switch QA is compared with the third overheated self-interruption type semiconductor switch QC while the difference is equal to or smaller than the undercurrent determination value. Is output during the period when the source voltage of the main FET Q5 is lower than the source voltage of the main FET Q5, and when the difference is larger than the undercurrent determination value (the source voltage of the main FET Q1 of the first overheated self-interruption type semiconductor switch QA becomes the third). (When the voltage becomes higher than the source voltage of the main FET Q5 of the overheat self-interruption type semiconductor switch QC)
It is determined that w has been output and the current has become too small. Also, the second
FET of the overheated self-interruption type semiconductor switch QB
The source of No. 3 is connected to the (-) side input terminal of the comparison circuit CMP1 via the resistor R6. Furthermore, the (+) side input terminal of the comparison circuit CMP2 is connected to the source of the main FET Q5 of the third overheat self-interruption type semiconductor switch QC.

On the other hand, the input terminal A of the power supply device 1 is connected to the emitter of a PNP transistor Tr1, and the collector of the PNP transistor Tr1 is
A series circuit of a resistor R1, a resistor R3 and a resistor R2 is connected, and the other end of the resistor R2 is grounded. The (+) side input terminal of the comparison circuit CMP1 is connected to the resistor R1 and the resistor R1.
3 is connected via a diode D1 to a connection point,
The (−) input terminal of the comparison circuit CMP1 is connected to a connection point between the resistors R3 and R2 via a diode D2. Therefore, the power supply voltage supplied from the battery VB is supplied to the (+) side input terminal of the comparison circuit CMP1 by the resistor R
1 and the voltage divided by the combined resistance of the resistors R3 and R2, and the voltage divided by the combined resistance of the resistors R1 and R3 and the voltage R2 are applied to the (−) side input terminal of the comparison circuit CMP1. It is configured to be applied. The PNP transistor Tr1, the resistors R1, R3 and R2, and the diodes D1 and D2
A return circuit for returning the main FET Q1 of the first overheated self-interrupting semiconductor switch QA to ON after the main FET Q1 of the first overheated self-interrupting semiconductor switch QA is turned off from on due to an abnormality such as a short circuit. Is composed. That is, the return circuit includes a PNP circuit whose emitter is connected to the output terminal on the battery VB side and whose base is connected to the input terminal on the switch SW1 side via the resistor R10.
The transistor Tr1 and the PNP transistor Tr1
A resistor R1 connected in series between the collector of
A resistor R3, a resistor R2, and a diode D1 for passing a current flowing through the resistor R1 to the (+) terminal side of the comparison circuit CMP1.
And the current flowing through the resistors R1 and R3 are compared with a comparison circuit CMP.
1 and a diode D2 passing through the (−) terminal side.

The resistor R1 which is a component of the return circuit
Is turned on when the switch SW1 is turned on.
When the NP transistor Tr1 is turned on, the resistors R1, R
3 is about 60-80% of the battery, and the voltage at the source terminal SA of the first overheat-self-interruption type semiconductor switch QA is reduced by the voltage V3 (diode) at the resistor R5. D1 (cathode side potential of D1).

Further, an anode of a diode D3 is connected to the (+) side input terminal of the comparison circuit CMP1 via a resistor R9, and a gate signal output terminal of the drive circuit 2 is connected to a cathode of the diode D3. Have been. The output terminal of the comparison circuit CMP1 is connected to the drive circuit 2, and the result of the determination by the comparison circuit CMP1 is input to the drive circuit 2. The drive circuit 2 supplies a voltage VP (for example, VP =
VB + 5V) is applied, and the driving circuit 2 receives the Hi signal output from the comparison circuit CMP1 and the ON signal input from the switch side by turning on the switch SW1 to input the driving signal to the driving circuit 2. The source-side transistor 2a is turned on, the sink-side transistor 2b is turned off, and a drive signal of the voltage VP is output to the gate of the main FET Q1 of the first overheat self-interruption type semiconductor switch QA via the resistors R8 and R7. Thereby, the main FET Q1 of the first overheat self-interruption type semiconductor switch QA is turned on. The drive circuit 2 outputs an ON signal to the gate of the main FET Q1 of the first overheat self-interruption type semiconductor switch QA while the Hi signal is being input from the comparison circuit CMP1 (unless a Low signal is output). to continue. The driving circuit 2 includes a comparison circuit CMP1
Are inverted and the Low signal is input from the comparison circuit CMP1, the source transistor 2a of the drive circuit 2 is turned off, the sink transistor 2b is turned on, and the output from the drive circuit 2 becomes Low, causing the first overheating. An off signal is output to the gate of the main FET Q1 of the self-cutoff semiconductor switch QA to turn off the main FET Q1 of the first overheated self-cutoff semiconductor switch QA. The output terminal of the comparison circuit CMP2 is connected to the output terminal F to the outside, and the result determined by the comparison circuit CMP2 is used by the circuit connected to the output terminal F.

At start-up, when the switch SW1 is turned on, P
The NP transistor Tr1 is turned on, and a voltage value (for example, 60% to 80% of the power supply voltage) obtained by dividing VB (12V) by the resistor R1 and (the resistor R3 + the resistor R2) is on the (+) side of the comparison circuit CMP1. It is applied to the terminal. The (−) side terminal of the comparison circuit CMP1 has a resistor R1
A voltage value (for example, 20% to 40% of the power supply voltage) divided by the + resistor R3) and the resistor R2 is applied. The resistor R3 has a small resistance value, and the difference between the resistance value of the resistor R1 and the resistance value of (resistance R3 + resistance R2) is a slight difference.

When the switch SW1 is turned on and the PNP transistor Tr1 is turned on, VB (12 V) is changed to the resistance R1.
And (R3 + R2) are applied to the (+) input terminal of the comparison circuit CMP1 and the (−) input terminal of the comparison circuit CMP1, and are applied to the (+) input terminal of the comparison circuit CMP1. The applied voltage is the comparison circuit CMP1
Is higher than the voltage applied to the (−) side input terminal, the output of the comparison circuit CMP1 becomes Hi, and the driving circuit 2
, And the drive circuit 2 outputs a gate drive signal Hi. The gate drive signal Hi is applied to the gate of the main FET Q1 of the first overheated self-interruption type semiconductor switch QA to turn on the main FET Q1. This gate drive signal simultaneously turns on the main FET Q3 of the second overheated self-interruption type semiconductor switch QB and the main FET Q5 of the third overheated self-interruption type semiconductor switch QC.

The output of the comparison circuit CMP1 is used to determine that an overcurrent has flowed through the main FET Q1 of the first overheated self-interruption type semiconductor switch QA. Now, load (motor M1, M2) or load (motor M
If a dead short circuit such as a short circuit occurs in the power supply line on the load side of the main FET Q1 to which the (1, M2) is connected,
The current that should flow into the loads (motors M1, M2) flows to ground. When a dead short occurs in this way, no current flows through the loads (motors M1 and M2).
Main FE of first overheat self-interruption type semiconductor switch QA
Since there is no load (only the line load) in which no load is connected to TQ1, an excessive current (overcurrent) flows through the main FET Q1 of the first overheat self-interruption type semiconductor switch QA. This overcurrent flows between the drain and source of the main FET Q1 of the first overheated self-interruption type semiconductor switch QA, and the first overheated self-interruption type semiconductor switch QA
The drain-source voltage Vds of the main FET Q1 increases (the first overheated self-interruption type semiconductor switch QA).
As long as the main FET Q1 is ON, the voltage between the drain and the source increases, and the first overheated self-interruption type semiconductor switch QA is stabilized at the ON resistance of the main FET Q1 and the short-circuit current.

On the other hand, if the source voltage of the main FET Q3 of the second overheated self-interruption type semiconductor switch QB is normal in the continuously turned on state, the main FET Q3 of the second overheated self-interruption type semiconductor switch QB is normal. Since the first reference resistor 5 is set so that the source voltage of the main FET Q1 of the first overheated self-interrupting semiconductor switch QA is higher than the source voltage of the first overheating self-interrupting semiconductor switch QA. The source voltage of the main FET Q1 of the QA decreases. The source voltage of the main FET Q3 of the second overheat self-interruption type semiconductor switch QB is
When the switch is normally on, the source voltage Vds of the main FET Q1 of the first overheat self-interruption type semiconductor switch QA
(Approximately 0.5 V), the source voltage of the main FET Q1 of the first overheated self-interruption type semiconductor switch QA and the second overheated self-interruption type semiconductor switch are higher than the divided voltage by the resistors R1, R3, and R2. QB main FET Q3
Source voltage is high (approaching the power supply voltage).
The voltage divided by the resistors R1, R3, and R2 is
It is cut by the diodes D1 and D2, and the (+) side input terminal of the comparison circuit CMP1 and the comparison circuit C
It becomes irrelevant to the (−) side input terminal of MP1. That is, the value of the source voltage of the main FET Q1 of the first overheating self-interruption type semiconductor switch QA and the value of the source voltage of the main FET Q3 of the second overheating self-interruption type semiconductor switch QB are directly input to the (+) side input terminal of the comparison circuit CMP1. ,
This is input to the (−) side input terminal of the comparison circuit CMP1.

On the other hand, a series circuit of a resistor R9 and a diode D3 is connected to the (+) side input terminal of the comparison circuit CMP1, and the cathode of the diode D3 of this series circuit is connected to the gate signal output terminal. This diode D3
When the power supply line for supplying power to the loads (motors M1 and M2) is normal, the main FET Q1 of the first overheat self-interruption type semiconductor switch QA is turned on by the gate signal. The cathode has a considerably high voltage when the main FET Q1 is on. Therefore, the diode D3 is cut off, and no current flows through the series circuit of the resistor R9 and the diode D3. Therefore, no current flows through the resistors R5 and R6, and the first overheated self-interruption type semiconductor switch Q
A source voltage of the main FET Q1 (source terminal SA)
Is input to the (+) side input terminal of the direct comparison circuit CMP1, and the source voltage (the voltage of the source side terminal SB) of the main FET Q3 of the second self-heating semiconductor switch QB is directly applied to the (−) side of the direct comparison circuit CMP1. Are input to the side input terminals. At this time, if the power supply line for supplying power to the loads (motors M1 and M2) is normal (no dead short circuit), the second overheat self-interruption type semiconductor switch QA is compared with the source voltage of the main FET Q1 by the second. FET Q3 of the overheat self-interruption type semiconductor switch QB
Since the resistance value of the first reference resistor 5 is set so that the source voltage of the first reference resistor 5 becomes low, the output of the comparison circuit CMP1 is Hi.

In this state, if a short circuit occurs on the downstream side of the source of the main FET Q1 of the first overheat self-interrupting semiconductor switch QA which is a power supply line for supplying power to the loads (motors M1 and M2), the first A large current flows on the main FET Q1 side of the overheated self-interruption type semiconductor switch QA, and a large current is applied to the on-resistance of the main FET Q1 of the first overheated self-interruption type semiconductor switch QA.
The potential difference between the sources increases. However, the potential difference between the drain and the source of the main FET Q3 of the second overheat self-interrupting semiconductor switch QB is fixed by the first reference resistor 5 and is constant. Therefore, the second
FET of the overheated self-interruption type semiconductor switch QB
The source voltage of the main FET Q1 of the first overheated self-interruption type semiconductor switch QA is lower than the source voltage of the third.

First overheating self-interruption type semiconductor switch QA
When the source voltage of the main FET Q1 drops below the source voltage of the main FET Q3 of the second overheat self-interruption type semiconductor switch QB and becomes equal to or less than the overcurrent determination value, the output of the comparison circuit CMP1 changes from Hi to Low. And a Low signal is output to the drive circuit 2. Drive circuit 2
When the Low signal is input from the comparison circuit CMP1, the source-side transistor 2a of the drive circuit 2 is turned off, the sink-side transistor 2b is turned on, and the output from the drive circuit 2 is changed from Hi to Low, causing the first overheating. An off signal is output to the gate of the main FET Q1 of the self-interruption type semiconductor switch QA to try to shut off the main FET Q1 of the first overheat self-interruption type semiconductor switch QA. In response to the Low signal from the drive circuit 2, an off signal is also input to the gate of the main FET Q3 of the second overheated self-interruption type semiconductor switch QB and the gate of the main FET Q5 of the third overheated self-interruption type semiconductor switch QC. Attempts to shut off the gate of the main FET Q3 of the semiconductor switch QB and the main FET Q5 of the third semiconductor switch QC.

When trying to cut off the main FET Q1 of the first overheating self-cutoff type semiconductor switch QA, the transistor 2a on the source side of the drive circuit 2 is turned off and the transistor 2b on the sink side is turned on. Therefore, the resistance R
Since the cathode side of the diode D3 of the series circuit of the diode 9 and the diode D3 is grounded, a current flows through the series circuit of the resistor R9 and the diode D3. This current flows from the source of the main FET Q1 of the first overheated self-interrupting semiconductor switch QA, through the resistor R5, through the resistor R9, and through the diode D3 to the ground. Then, a current flows through the resistor R5, causing a voltage drop by the resistor R5. Because of this voltage drop, the comparison circuit CM
The (+) side input terminal of P1 has a resistance R higher than the source of the main FET Q1 of the first overheat self-interruption type semiconductor switch QA.
5 drops. This is hysteresis.

Second overheating self-interruption type semiconductor switch QB
Once the source of the main FET Q1 of the first overheat self-interrupting semiconductor switch QA is once lower than the source of the main FET Q3, the comparison circuit CMP1 is inverted and the Low signal of the drive circuit 2 is input and the drive circuit 2 Try to turn off. When the driving circuit 2 is temporarily stopped, the transistor 2a on the source side of the driving circuit 2 is turned off and the transistor 2b on the sink side is turned on, so that a current flows through the series circuit of the resistor R9 and the diode D3, and the comparison circuit CMP1
The (+) side input terminal has a voltage lower than that of the source of the main FET Q1 of the actual first overheat self-interruption type semiconductor switch QA. Therefore, even if the source of the main FET Q1 of the first overheated self-interruption type semiconductor switch QA rises slightly and fluctuates, the comparison circuit CMP1 is stably turned off. That is, the resistor R9 and the diode D3 form a hysteresis circuit.

In this state, since the drive circuit 2 is turned off, the main FET Q1 of the first overheated self-interruption type semiconductor switch QA and the second overheated self-interruption type semiconductor switch Q
The B main FET Q3 shifts to the off direction. First,
The voltage between the drain and the source gradually increases in both cases. As the drain-source voltage increases, the capacitance of the CGD in the gate is charged by being pulled by it, and is pulled while being charged, and the main FET Q1 of the first overheat self-interruption type semiconductor switch QA, The voltage between the true gate and source of the main FET Q3 of the overheated self-interruption type semiconductor switch QB2 increases, and the current temporarily increases. However, since the source voltages of the main FET Q1 and the main FET Q3 do not increase infinitely, the power supply voltage (1
2V), it saturates when it is slightly over, and no longer has the pulling effect.
FET Q of overheating self-interruption type semiconductor switch QA
(1) The gate charge of the main FET Q3 of the second overheated self-interruption type semiconductor switch QB is gradually removed, and the gate voltage is reduced with respect to the source voltage. Therefore, the main FET Q1 of the first overheated self-interruption type semiconductor switch QA, the second overheated self-interruption type semiconductor switch QB
As the current of the main FET Q3 decreases, the first
FET Q of overheating self-interruption type semiconductor switch QA
The voltage between the drain and the source of both the main FET Q3 of the first and second overheat self-interruption type semiconductor switches QB increases steadily.

As described above, since the current flowing through the main FET Q1 of the first overheated self-interruption type semiconductor switch QA decreases, the potential of the source side terminal SA of the main FET Q1 of the first overheated self-interruption type semiconductor switch QA becomes It approaches the ground potential. Then, the source terminal SA of the main FET Q1 of the first overheat self-interruption type semiconductor switch QA,
Main FE of second overheat self-interruption type semiconductor switch QB
The source terminal SB of TQ3 connects the power supply voltage VB to the resistor R1,
It becomes lower than the voltage divided by the resistors R3 and R2. As a result, the source terminal SB of the main FET Q3 of the second overheating self-interruption type semiconductor switch QB and the source terminal SA of the main FET Q1 of the first overheating self-interruption type semiconductor switch QA are the (-) side input terminal of the comparison circuit CMP1, A signal cannot be sent to the (+) input terminal of the comparison circuit CMP1.

In such a state, the voltage obtained by dividing the power supply voltage by the resistors R1, R3, and R2 is applied to the (+) input terminal of the comparison circuit CMP1 and the comparison circuit CMP1.
(-) Side input terminal. Then
The voltage divided by the resistors R1, R3, and R2 applied to the (+) input terminal of the comparison circuit CMP1 is equal to the resistances R1, R3, and R2 applied to the (−) input terminal of the comparison circuit CMP1. Is higher by the voltage drop of the resistor R3 than the divided voltage by the comparator circuit CMP1.
Is inverted and surely becomes Hi. This comparison circuit CM
When the output of P1 becomes Hi, the drive circuit 2 is turned on again, and a gate signal is sent to the gate of the main FET Q1 of the first overheated self-interruption type semiconductor switch QA, and the main FET Q1 of the first overheated self-interruption type semiconductor switch QA is turned on. Turn on.
As a result, a current flows through the loads (motors M1 and M2). Such repetition is performed.

The ON / OFF counting circuit 4 is in a state where the gate of the main FET Q1 of the first overheat self-interruption type semiconductor switch QA is off and the driving circuit 2 is off, that is, the sink transistor 2b of the driving circuit 2 is on. In some cases, the voltage of the source side terminal SA of the main FET Q1 of the first overheat self-interruption type semiconductor switch QA is higher than the ground voltage (5 V), and the operation is performed in such a state. Is what you do. Specifically, a CR integrating circuit is used, and the capacitor C1 is a capacitor of the CR integrating circuit.

As described above, in the power supply device 1, while the current supplied to the power supply line is detected to be a normal current, the first overheating self-interruption type semiconductor switch QA
The first control for maintaining the main FET Q1 in the continuous ON state and turning off the main FET Q1 of the first overheat self-interruption type semiconductor switch QA when an overcurrent is detected in the current supplied to the power supply line in this state. After the main FET Q1 of the first overheating self-interruption type semiconductor switch QA is once turned off, the on / off control of the main FET Q1 of the first overheating self-interruption type semiconductor switch QA is repeated to repeat this first overheating self-interruption type semiconductor switch QA. Main FET of semiconductor switch QA
In order to prevent overheating of Q1, when it is detected that the current supplied to the power supply line is a normal current during the on / off control, the main FET Q1 of the first overheating self-interruption type semiconductor switch QA is turned on. The second control for shifting to the first control is performed.

The source terminal SB of the main FET Q3 of the second overheat self-interruption type semiconductor switch QB of the power supply device 1 is connected to a first reference resistor via an output terminal E as shown in FIG. The second reference resistor 6 is connected to the source terminal SC of the main FET Q5 of the third overheat self-interruption type semiconductor switch QC of the power supply device 1 via the output terminal F. I have. The first reference resistor 5 has a configuration as shown in FIG. That is, the first reference resistor 5 has a fixed resistor 5a having one end connected to the source-side terminal SB of the main FET Q3 of the second overheat self-interruption type semiconductor switch QB, and the other end of the fixed resistor 5a. Is connected to the collector of an NPN transistor 5b, which is a current changing means whose emitter is grounded. As described above, the first reference resistor 5 includes the fixed resistor 5a and the NPN
And a transistor 5b. This first
Of the reference resistor 5 can be changed by the base current of the NPN transistor 5b connected to the fixed resistor 5a. Also, the reference resistor 6
Has the same configuration as the first reference resistor 5 shown in FIG.

When the object to be driven changes depending on the load and the load (motors M1 and M2) needs to be changed, the drive load is changed. A sensor 7 for detecting whether or not the control is required is provided on the control target. This sensor 7
For example, in the case of a power seat that electrically drives an automobile seat, for example, a pressure sensor detects the weight on the power seat, and a change in the driving load is instructed by a change in the weight on the power seat. Become. The detection by the sensor 7 is an output of a signal corresponding to the change (for example, whether to drive only by the motor M1 or to drive by both the motor M1 and the motor M2 according to a change in weight on the power sheet).

The output of this sensor (for example, a pressure sensor) 7 controls the resistance values of the first reference resistor 5 and the second reference resistor 6 and the base current of the NPN transistor 5b connected to the fixed resistor 5a. Will be. That is, the control unit 8 is connected to the bases of the NPN transistors 5b of the first reference resistor 5 and the second reference resistor 6. The control unit 8 has a function of controlling the turning on and off of the switch SW2 in accordance with the output of the sensor 7, and the output from the sensor 7 drives the control unit 8 to change the driving load. In the case, the control unit 8
The drive load is changed by turning on and off the switch SW2 according to the output signal from the switch. When the switch SW2 is turned on by the output signal from the control unit 8,
The motor M2 is disconnected from the power supply line.

With such a configuration, the sensor (for example,
A change in the output of the pressure sensor 7 (for example, a change in the weight on the power seat) changes the drive load (motor M1, M2), and the sensor 7 outputs a signal corresponding to the detected value to the control unit. 8 is output. The control unit 8 that has received a signal corresponding to the detection value output from the sensor 7 outputs a current control signal corresponding to the output of the sensor 7 to the first reference resistor 5.
Of the first reference resistor 5 and the fixed resistance of the second reference resistor 6 are automatically output by the output signal from the control unit 8. Will change. At the same time, the control unit 8 controls on / off of the switch SW2 according to the output of the sensor 7.
Specifically, when the output of the sensor 7 is smaller than a predetermined threshold value, the control unit 8 takes a small load (motors M1 and M2) (an example of a power seat that electrically drives an automobile seat). And the weight on the sheet is small), the switch SW2 is turned off to drive only the motor M1, and the current flowing through each of the first reference resistor 5 and the second reference resistor 6 is fixed. A current control signal that reduces the
The base of the transistor 5b and the base of the NPN transistor of the second reference resistor 6 are output. By the base current supplied from the control unit 8,
First reference resistor 5, second reference resistor 6
, The overcurrent determination value generated by the first reference resistor 5 and the undercurrent determination value generated by the second reference resistor 6 are both the load (motor M1,
It automatically decreases in accordance with the decrease in M2).

On the other hand, when the output of the sensor 7 is larger than a predetermined threshold, the load (motors M1 and M2) is large. Switch S
W2 is turned on to drive both the motor M1 and the motor M2, and a current control signal for increasing the current flowing through each fixed resistor of the first reference resistor 5 and the second reference resistor 6 is output. The first reference resistor 5 outputs the base of the NPN transistor 5b and the second reference resistor 6 outputs the base of the NPN transistor 5b. The resistance values of the first reference resistor 5 and the second reference resistor 6 change according to the base current supplied from the control unit 8, and the overcurrent determination value generated by the first reference resistor 5 and the second reference resistor The undercurrent determination value generated by the resistor 6 is automatically increased in accordance with an increase in the load (motor M1, M2).

As described above, the power supply control device is constituted by the power supply device 1, the first reference resistor 5, the second reference resistor 6, the sensor 7, the control section 8, and the switch SW2. .

According to the power supply control device according to the present embodiment, when the load (motor M1, M2) is changed or the load (motor M1, M2) is changed, the sensor 7 causes the load (motor M1, M2) to change. ) Is detected, a signal corresponding to the change is output, and the current flowing through the first reference resistor 5 and the second reference resistor 6 is automatically changed in accordance with the output. Both the undercurrent determination values are automatically changed according to the change in the load (motor M1, M2), and the first value accompanying the change in the load (motor M1, M2).
It is not necessary to replace the fixed resistors constituting the reference resistor 5 and the second reference resistor 6.

The first reference resistor 5 and the second reference resistor 6 can be configured as shown in FIG. Since the first reference resistor 5 and the second reference resistor 6 have the same configuration, only the first reference resistor 5 is shown. The first reference resistor 5 shown in FIG. 6 is connected to the source side terminal SB of the main FET Q3 of the second overheat self-interruption type semiconductor switch QB.
Has a fixed resistor 5c connected to one end thereof, and the other end of the fixed resistor 5c is grounded via a fixed resistor 5d. The fixed resistor 5d is connected to both ends of the fixed resistor 5d.
And a semiconductor switch 5e as a current changing means is connected. This semiconductor switch 5e is, for example, F
ET is configured to be turned on and off by applying a control signal (switching signal) from the control unit 8 to the gate of the semiconductor switch 5e. Therefore, when the semiconductor switch 5e is turned on by a control signal from the control unit 8, the fixed resistor 5d is short-circuited by the semiconductor switch 5e, and the resistance of the first reference resistor 5 becomes the fixed resistor 5c. The resistance value of the reference resistor 5 becomes small. Also,
When the control signal is not output from the control unit 8 and the semiconductor switch 5e is turned off, the current flows through the fixed resistor 5c and the fixed resistor 5c.
As a result, the resistance value of the first reference resistance 5 becomes a series combined resistance of the fixed resistance 5c and the fixed resistance 5d, and becomes large.

When the first reference resistor 5 shown in FIG. 6 is used, when the load (motor M1, M2) becomes small, the semiconductor switch 5e is turned on and the fixed resistor 5d is disconnected from the fixed resistor 5c. , The resistance value of the first reference resistor 5 becomes smaller, and both the overcurrent determination value and the undercurrent determination value become the load (motor M1, M2).
Automatically lowers in response to a drop in On the other hand, when the load (motors M1 and M2) increases, the semiconductor switch 5e is turned off and the fixed resistor 5d is connected in series with the fixed resistor 5c, so that the resistance value of the first reference resistor 5 increases. Therefore, both the overcurrent determination value and the undercurrent determination value automatically decrease in response to the decrease in the load (motors M1, M2).

The sensor 7 includes, in addition to the pressure sensor,
Other sensors such as a temperature sensor and a strain sensor may be used to detect a change in various loads (motors M1 and M2), for example, a change in temperature.

[0058]

As described above, according to the present invention,
The detection value of the overcurrent determination is automatically changed according to the change of the load (motor M1, M2), and the load (motor M1, M2) is changed.
It is possible to eliminate the necessity for the work of replacing the resistor accompanying the change of the resistance.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing a power supply device according to an example according to an embodiment of the present invention.

FIG. 2 is a detailed circuit diagram of a first overheat self-interruption type semiconductor switch QA shown in FIG. 1;

FIG. 3 is a detailed circuit diagram of a second overheat self-interruption type semiconductor switch QB shown in FIG. 1;

FIG. 4 is a detailed circuit diagram of a third overheat self-interruption type semiconductor switch QC shown in FIG. 1;

FIG. 5 is a configuration diagram illustrating an example of a reference resistor illustrated in FIG. 1;

FIG. 6 is a configuration diagram showing another example of the reference resistor shown in FIG. 1;

[Explanation of symbols]

1 Power supply device 2 Driving circuit 5 Reference resistance 6 Reference resistance 7 Reference resistance 7 ………………………………… Sensor 8 ………………………………………………………………………………………………………. 1. Overheated self-interruption type semiconductor switch QB: Second overheated self-interception type semiconductor switch QC: Third overheated self-interruption type semiconductor switch VB: ……… DC power supply

Claims (3)

[Claims] A first overheating self-interrupting semiconductor switch for controlling a current flowing through a power supply line between a power supply and a load in accordance with a control signal; and a voltage characteristic identical to that of the first overheating self-interrupting semiconductor switch. Second self-interrupting semiconductor switch having overheat and first
A first reference circuit which is constituted by a series circuit comprising reference resistors and is connected in parallel to the power supply line; a drain-source voltage A of the first overheat self-interruption type semiconductor switch; The difference (A−B) between the drain-source voltage B of the cut-off type semiconductor switch and a predetermined overcurrent determination value C is compared to determine whether or not the current is an overcurrent. A comparison circuit for outputting a corresponding detection signal, and a first control signal corresponding to the detection signal.
And a drive circuit for turning on and off the overheated self-interruption type semiconductor switch. The first overheating is performed when a predetermined load current flows through the first overheating self-interruption type semiconductor switch. The same voltage as the drain-source voltage of the self-interruption type semiconductor switch is set to a value that is generated in the second overheat self-interruption type semiconductor switch, and the predetermined overcurrent determination value C is set to the difference (A). −B)
When the value of the difference (AB) is greater than the overcurrent determination value C, it is determined that an overcurrent has occurred, and the first overheat self-interrupting semiconductor switch is turned off. Is turned off, and then the first overheating self-interrupting type semiconductor switch is repeatedly turned on and off. When the current is determined to be a normal current during the on / off control, the first overheating self-interruption type semiconductor switch is turned off. A power supply device configured to turn on a cut-off semiconductor switch, comprising: a sensor that detects a change in the load and outputs a signal in accordance with the change, and the first reference according to an output of the sensor. A power supply control device characterized by changing a current flowing through a resistor. 2. The semiconductor device according to claim 1, wherein the first reference resistor is connected to a fixed resistor connected to a source side of the second overheat-self-interruption type semiconductor switch, and is connected between the fixed resistor and a ground. 2. The control device according to claim 1, further comprising a current changing unit configured to change a current flowing through the fixed resistor, and a control unit configured to output a current control signal corresponding to an output of the sensor to the current changing unit. Power supply control device. 3. A third overheated self-interrupting semiconductor switch having the same voltage characteristics as the first overheated self-interrupting semiconductor switch and having a smaller number of transistors than the first overheated self-interrupting semiconductor switch. A second reference circuit connected in parallel to the power supply line and comparing the difference (A−B) with a predetermined undercurrent determination value D and connecting the second reference circuit to the power supply line. A second comparing circuit for judging whether the flowing current is an undercurrent, and outputting a detection signal corresponding to the judgment result, and detecting a change in the load and outputting a signal corresponding to the change; 3. The power supply control device according to claim 1, further comprising a sensor configured to change a current flowing through the second reference resistor in accordance with an output of the sensor.