JP4123441B2 - Inrush current limiting power switch circuit for vehicles - Google Patents

Description

The present invention relates to a vehicle inrush current limiting type power switch circuit for intermittently supplying power from a battery to an on-vehicle electric load including a large-capacitance capacitor.

  In recent years, the electric system for vehicles has become increasingly larger, and in the electric system for vehicles such as hybrid cars, secondary battery cars, and fuel cell cars, the DC power source of secondary batteries, fuel cells, etc. is extremely high, such as several tens of kW or more. Powers large in-vehicle electrical loads. Among the in-vehicle electric loads, the one having the largest capacity is a motor circuit including an AC motor and an inverter circuit that supplies power to the AC motor as shown in Patent Document 1 below. The inverter circuit converts DC power supplied from a DC power source into AC power having a necessary frequency and supplies the AC power to the AC motor. Since the inverter circuit is switched at high speed by a PWM control method or the like for motor control, it is usual to connect the smoothing capacitor 6 in parallel with the inverter circuit 70 for driving the AC motor M as shown in FIG. . The smoothing capacitor 6 absorbs a high frequency component of current change caused by switching of the inverter circuit 70. The switching current of the inverter circuit 70 superimposes the switching noise voltage on the power supply voltage through the wiring inductance and generates electromagnetic noise, so that the positive and negative terminals of the smoothing capacitor 6 are connected close to the positive and negative DC power supply terminals of the inverter circuit 70. It is usually done. Such a smoothing capacitor is similarly employed in a DC-DC converter circuit in addition to an inverter circuit for driving a motor.

  Further, for safety inspection and repair / replacement of the battery 1 and the inverter circuit 70, etc., as shown in FIG. 10, a main power switch 2 or 5 is provided between the battery (DC power supply) 1 and the electric load 7. However, the system (see FIG. 10) in which the main power switches 2 and 5 are individually arranged on both sides of the battery 1 is excellent in safety.

  Further, when a large capacity smoothing capacitor 6 is connected in parallel with the electric load 7, a large inrush current flows from the battery 1 to the smoothing capacitor 6 at the moment when the main power switches 2 and 5 are turned on. An inrush current limiting circuit comprising a limiting resistor 4 and a sub power switch 8 connected in series with the inrush current limiting resistor 4 is preferably connected in parallel with the main power switch 2 or 5 (see FIG. 10). .

The operation of this inrush current limiting circuit will be described with reference to FIG. 10. When power supply is started from the battery 1 to the motor circuit 7 which is an electric load and the smoothing capacitor 6 connected in parallel thereto, first, the main power switch 5 and the sub power switch 5 are connected. The power switch 8 is turned on. As a result, the smoothing capacitor 6 is slowly charged through the inrush current limiting resistor 4, and the main power switch 2 is turned on when the terminal voltage of the smoothing capacitor 6 sufficiently rises to supply power from the battery 1 to the inverter circuit 70. To do. The sub power switch 8 may be a relay or the like.
Japanese Patent No. 2995940

  However, although the semiconductor switch 8 shown in FIG. 10 has a lower failure probability than a relay or the like, there is still a possibility that a faulty failure will occur in rare cases during operation. Even if an interruption failure occurs in the semiconductor switch 8, the current interruption function can be ensured as long as the main power switch 5 is turned off. However, since the failure probability of the main power switch 5 is naturally not zero, there is a probability that the semiconductor switch 8 and the main power switch 5 will fail at the same time, and it is desired to take measures for that.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a vehicle inrush current limiting type power switch circuit capable of predicting the performance degradation of the sub power switch while suppressing the complexity of the circuit configuration. Yes.

  The present invention comprises a main power switch that connects an electric load having a large input capacitance and a DC power source, and an inrush current limiting circuit that is connected in parallel with the main power switch, the inrush current limiting circuit comprising: Since it has a sub power switch that is conducted prior to the main power switch when supplying current from a DC power source to the electrical load, and an inrush current limiting resistor connected in series with the sub power switch, Power supply to the electric load can be realized without flowing a large inrush current to the electric load.

  In the present invention, it is further determined whether or not the voltage drop of the inrush current limiting resistor exceeds a predetermined threshold when the main power switch is turned off and the sub power switch is turned off. It is determined that the sub power switch is defective.

  That is, in the present invention, since the resistor for limiting the inrush current described above is used as a leakage current detection element for the sub power switch, the existing inrush current limiting resistor is set when the main power switch and the sub power switch are turned off. With the simple circuit configuration of monitoring the voltage drop of the device, it is possible to accurately determine the abnormality of the sub power switch.

Further , in the present invention, since the sub power switch is composed of a semiconductor switching element, it is possible to realize downsizing and power consumption reduction. However, there is a probability that the semiconductor switching element will cause an interruption failure. However, a failure in which the semiconductor switch is normally interrupted (failure failure) has a stage in which the leakage current of the semiconductor switch in the off state increases with time prior to the failure.

  Therefore, in this aspect, if an increase in the voltage drop of the inrush current limiting resistor is detected in a state where the main power switch and the sub power switch (semiconductor switch) are in the off state, the increase in the leakage current is allowed to be allowed. It is possible to determine whether or not it has been exceeded, and it is possible to predict in advance and deal with the occurrence of a faulty semiconductor switch failure in the near future.

  In addition, there is a rare but unsatisfactory pattern of a semiconductor switch whose leakage current suddenly increases. Even in this case, if the voltage drop of the inrush current limiting resistor is abnormally large in the state where the semiconductor switch is turned off and the main power switch is turned off, it is determined that the semiconductor switch, that is, the sub power switch is defective. It is possible.

In the present invention, the connection point between the sub power switch 8 and the inrush current limiting resistor 4 is X, the connection point between the sub power switch 8 and the main power switch 2 or 5 is Y, and the main power switch. When the connection point of the inrush current limiting resistor 4 is Z, the determination circuit inputs the potential of the connection point X to the negative input terminal through the input resistance element 26, and the potential of the connection point Z is + The inverted voltage amplifier circuit 25 having the operational amplifier 28 input to the input terminal, and the output voltage of the inverted voltage amplifier circuit 25 and the predetermined threshold voltage Vth are compared to determine the leakage current failure of the sub power switch 8. The negative terminal of the comparator 29 is connected to the negative power supply terminal of the inverted voltage amplification circuit 25 and the comparator 29, and the positive terminal is connected to the positive power supply terminal of the reverse voltage amplification circuit 25 and the comparator 29. And a control power source 24 is. In this way, the configuration of the control power source that drives the circuit elements that constitute the determination circuit can be simplified. The specific configuration and function of the determination circuit of this aspect will be described in the embodiment.

Further, according to the present invention, the potential of the non-inverting input terminal (+ input terminal) of the inverting voltage amplifier circuit 25 including the operational amplifier 28 whose output voltage accuracy is reduced near the input voltage of 0 V is set higher than the potential of the connection point Z. Offset circuits 32 and 33 for offsetting in the + direction by the offset potential Voffset. However, the offset is performed in the output voltage range of the control power supply 24 from the potential of the connection point Z. In this way, the lower limit value or the upper limit value of the output voltage range of the operational amplifier 28 is shifted by a predetermined potential by the amount that the potential of the non-inverting input terminal (+ input terminal) of the operational amplifier 28 is offset by the offset potential Voffset. Therefore, the output voltage accuracy can be improved as compared with the case where the potential of the positive input terminal is set near the input potential to the power supply terminal of the operational amplifier 28.

In a preferred embodiment, one main electrode terminal of the N-channel MOS transistor forming the sub power switch 8 is connected to a connection point between one of a pair of electrode terminals of the DC power source and one end of the main power switch, Another main electrode terminal of the N-channel MOS transistor is connected to the other end of the main power switch through the inrush current limiting resistor 4. In this way, the sub power switch 8 can be driven easily and favorably, and the sub power switch 8 can be downsized.
In a preferred embodiment, the auxiliary power switch 8 and the inrush current limiting resistor 4 are connected in series, and the determination circuit includes the inrush current limiting resistor 4 and the constant voltage dropping element. A total of 50 voltage drops is read to determine the magnitude of the voltage drop of the inrush current limiting resistor. In this way, the level of the signal voltage Vx input to the determination circuit when a leakage current is generated in the sub power switch 8 can be level shifted substantially by the voltage drop of the constant voltage drop element 50. The potential of the signal voltage Vx input to the determination circuit can be set within a suitable range for high-precision signal processing of the determination circuit, for example, voltage amplification processing. It can be carried out.

  In addition, in order to facilitate understanding of the invention, reference numerals are attached to the claims, but it goes without saying that the numbers do not limit the claims.

Preferred embodiments of the present invention will be specifically described by the following examples.
(Reference example)

(Circuit explanation)
The inrush current limiting type power switch circuit according to the first embodiment will be described with reference to FIG.

  1 is a battery (DC power supply), 2 is a first main power switch (main power switch referred to in the present invention), 4 is an inrush current limiting resistor, 5 is a second main power switch, and 8 is a sub-transistor composed of a MOS transistor. A power switch, 100 is a determination circuit, and 300 is a load side circuit (electric load referred to in the present invention). The load side circuit 300 includes the smoothing capacitor 6.

  The positive terminal of the battery 1 is connected to the load side circuit 300 through the main power switch 2, and the negative terminal of the battery 1 is connected to the load side circuit 300 through the main power switch 5. The sub power switch 8 and the inrush current limiting resistor 4 are connected in series to form the inrush current limiting circuit referred to in the present invention, and this inrush current limiting circuit is connected in parallel with the main power switch 2. The voltage drop ΔV of the inrush current limiting resistor 4 is input to the determination circuit 100, and the determination circuit 100 makes a determination based on the input voltage drop of the inrush current limiting resistor 4. Details of the determination will be described later.

  To supply power to the load side circuit 300, first, the main power switch 5 and the sub power switch 8 are turned on, the smoothing capacitor 6 is charged to a predetermined level through the inrush current limiting resistor 4, and then the main power switch 2 is turned on. To do. This can prevent a large inrush current from flowing through the circuit.

In FIG. 1, the auxiliary power switch 8 and the inrush current limiting resistor 4 are disposed on the positive terminal side of the battery 1, but may be disposed on the negative terminal side of the battery 1. Further, the sub power switch 8 may be an IGBT, a bipolar transistor, or an electromagnetic relay in addition to the MOS transistor shown in FIG. Further, as will be described later, the determination circuit 100 can be configured by an analog circuit using an operational amplifier, or can be processed by a digital circuit, a microcomputer circuit, or the like.
(Description of judgment operation)
The determination operation of the determination circuit 100 will be described below.

Whether the voltage drop ΔV of the inrush current limiting resistor 4 is larger than a predetermined threshold voltage Vth in a state where the main power switch 5 is turned on, the main power switch 2 is turned off, and the sub power switch 8 is turned off. If it is larger, it is determined that the leakage current of the sub power switch 8 is abnormally large. This abnormal increase in the leakage current of the sub power switch 8 often leads to a failure in shutting down the sub power switch 8, so that it is possible to take measures such as displaying a replacement request for the sub power switch 8 based on the determination result.
(Specific configuration example and operation of determination circuit 100)
A specific example of the determination circuit 100 will be described with reference to FIG. However, the inrush current limiting circuit described above is configured by connecting the auxiliary power switch 8 and the inrush current limiting resistor 4 in series. In FIG. 2, X is a connection point between the sub power switch 8 and the inrush current limiting resistor 4, Y is a connection point between the sub power switch 8, the battery 1, and the main power switch 2, and Z is an inrush current limiting resistor 4. This is a connection point with the main power switch 2.

  The determination circuit 100 includes an inverting voltage amplifier circuit 25 and a comparator 29. The inverting voltage amplifier circuit 25 includes an operational amplifier type inverted voltage amplifier circuit including an input resistor 26, a feedback resistor 27, and an operational amplifier 28.

  The potential (signal potential) Vx of the connection point X between the sub power switch 8 and the inrush current limiting resistor 4 is input to the negative input terminal of the operational amplifier 28 through the input resistor 26, and the positive input terminal of the operational amplifier 28 is connected to the connection point Z. Has been. The signal voltage Vs output from the operational amplifier 28 is input to the negative input terminal of the comparator 29, and the threshold voltage Vth is input to the positive input terminal of the comparator 29. The voltage amplification factor of the inverting voltage amplifier circuit 25 is defined by the resistance ratio between the input resistor 26 and the feedback resistor 27.

  A determination operation of the determination circuit 100 shown in FIG. 2 will be described. Hereinafter, for the sake of simplicity, it is assumed that the potential at the connection point Z is 0V. With the main power switch 2 turned on and the main power switch 5 and the sub power switch 8 turned off, the potential Vx at the connection point X is read into the negative input terminal of the operational amplifier 28 through the input resistor 26. Since the potential at the connection point Z is assumed to be 0V, the potential at the connection point X is relatively negative, and the signal voltage Vs of the operational amplifier 28 is +.

  The comparator 29 compares the signal voltage Vs with the threshold voltage Vth, and when the signal voltage Vs is larger than the threshold voltage Vth, a low level potential (for example, 0 V) indicating that the leakage current of the sub power switch 8 is abnormally large. ) Is output, otherwise a high level potential (positive potential) is output. In FIG. 2, the threshold voltage Vth is configured by dividing the voltage of the control power supply 24 by a voltage dividing circuit including resistors 30 and 31.

  It should be noted in the circuit of FIG. 2 that the potential Vx at the connection point X is first a negative potential relative to the potential at the connection point Z, that is, the potential of the non-inverting amplification input terminal (+ input terminal) of the operational amplifier 28. That is, it deviates from the power supply voltage range of the inverting voltage amplifier circuit 25 and the comparator 29 to the negative side. However, in this embodiment, since the inverting voltage amplification circuit 25 using the operational amplifier 28 is used, the potential Vx at the connection point X which is a negative potential can be amplified without any problem as described above. That is, although the signal potential Vx of the determination circuit 100 is a negative potential (when the connection point Z is set to 0 V), the potential at the negative input terminal of the operational amplifier 28 can be regarded as being virtually grounded, and Since the output voltage Vs of the inverted voltage amplifier circuit 25 swings to the positive side, a power supply voltage in the range of 0 to a predetermined positive potential Vd may be applied from the control power supply 24 to the inverted voltage amplifier circuit 25 and the comparator 29. That is, the negative output terminal of the single control power supply 24 is connected to the connection point Z, and the positive output terminal is connected to the positive power supply terminals 280 and 282 of the inverting voltage amplification circuit 25 and the comparator 29 to supply the power supply voltage. A simple control power supply configuration in which Vd is applied can be employed.

  More specifically, since the control power supply 24 applies a predetermined + potential to the positive power supply terminal 280 of the operational amplifier 28 and 0 V to the negative power supply terminal 281 of the operational amplifier 28, the operational amplifier 28 has a special circuit. Unless a configuration is adopted, only a positive signal voltage can be output. Similarly, since a predetermined + potential is applied to the positive power supply terminal 282 of the comparator 29 and 0 V is applied to the negative power supply terminal 283 of the comparator 29, only the signal voltage having a positive potential is applied to the input terminal of the comparator 29. Cannot input. Therefore, in this embodiment, the operational amplifier 28 is used as an inverted voltage amplification circuit, so that the output level of the operational amplifier 28 is maintained at a positive potential (when the connection point Z is 0 V), whereby the signal voltage Vs is inverted voltage amplified. The operable output voltage range of the circuit 25 and the operable input voltage range of the comparator 29 are maintained. As a result, it is possible to amplify and compare the signal potential Vx that is more negative than the output voltage range of the control power supply 24 without any problem, even though the single control power supply 24 is used.

  Furthermore, in the circuit of FIG. 2, the control power supply 24 constitutes a power supply for the determination circuit 100 and also constitutes a power supply for the overvoltage determination circuit 200. The overvoltage determination circuit 200 is a circuit that determines whether or not the DC power supply voltage applied to the transformer step-down DC-DC converter circuit 9 (which may be an inverter circuit for driving a motor) exceeds a predetermined maximum allowable voltage value. The voltage dividing circuit is composed of resistors 18 and 19, the voltage dividing circuit is composed of resistors 21 and 22, and the comparator 23.

  The voltage of the battery 1 is divided by a voltage dividing circuit including resistors 18 and 19 and input to the + input terminal of the comparator 23. The output voltage of the control power supply 24 is divided by a voltage dividing circuit including resistors 21 and 22 and input to the negative input terminal of the comparator 23. The comparator 23 is at a high level so as to command the inverter to stop when the voltage of the battery 1 exceeds a predetermined threshold voltage. This converter stop signal is a command signal for instructing the DC-DC converter circuit 9 to stop when the DC voltage applied to the DC-DC converter circuit 9 (electric load referred to in the present invention) is an overvoltage exceeding a predetermined level. is there.

Note that the transformer step-down DC-DC converter circuit 9 in FIG. 2 shows only a single-phase inverter circuit provided on the primary side of the transformer, and a rectifier circuit, a smoothing circuit provided on the secondary side of the transformer, and this single-phase circuit. The illustration of the PWM control circuit that outputs the PWM control voltage to the switching element of the inverter circuit is omitted. Of course, the transformer step-down DC-DC converter circuit 9 may be replaced with a three-phase inverter circuit for driving the motor.
(Modification 1)
A modification of the circuit shown in FIG. 2 will be described with reference to FIG. This circuit shows a determination circuit 100 and an overvoltage determination circuit 200 in the case where an inrush current limiting circuit including a sub power switch 8 and an inrush current limiting resistor 4 is arranged on the main power switch 2 side. The determination circuit 100 and the overvoltage determination circuit 200 shown in FIG. 3 are essentially the same as those shown in FIG. 2 and have the same effects.

However, in the circuit configuration shown in FIG. 3, since the sub power switch 8 that is an N-channel MOS transistor performs a source follower operation, the sub power switch 8 capable of source grounding operation shown in FIG. 2 is superior in performance.
(Modification 2)
A modification of the circuit shown in FIG. 3 will be described with reference to FIG.

The circuit shown in FIG. 4 is configured such that the power supply voltage is supplied from the dedicated constant voltage power supply 20 instead of the control power supply 24 to the voltage dividing circuit for generating the threshold voltage Vth of the comparators 29 and 23 in the circuit shown in FIG. It is characterized by that. 3 and 4, the resistors 30 and 21 may be changed to constant voltage diodes.
(Modification 3)
A modification of the circuit shown in FIG. 2 will be described with reference to FIG. The circuit shown in FIG. 5 is configured such that the power supply voltage is supplied from the dedicated constant voltage power supply 20 instead of the control power supply 24 to the voltage dividing circuit for generating the threshold voltage Vth of the comparators 29 and 23 in the circuit shown in FIG. It is characterized by that. 2 and 5, the resistors 31 and 22 may be changed to constant voltage diodes.
(Modification 4)
In each of the above drawings, the sub power switch 8 is constituted by a MOS transistor, but it is naturally not limited thereto.
(Modification 5)
A modification of the circuit shown in FIG. 4 will be described with reference to FIG.

The circuit shown in FIG. 6 includes a pair of power supply voltage terminals (positive power supply terminal 280 and negative power supply terminal 281 in FIG. 2) of the operational amplifier 28 of the inverting voltage amplification circuit 25 in FIG. Diodes 10 and 11 are respectively connected between the two. Thereby, it is possible to prevent the voltage input to the negative input terminal from being abnormally high or abnormally low due to some factor. In FIG. 6, only the single-phase inverter circuit 9 a is illustrated in the transformer step-down DC-DC converter circuit 9 illustrated in FIG. 2, and other circuit portions of the transformer-type step-down DC-DC converter circuit 9 are not illustrated. ing.
(Deformation mode 6)
A modification of the circuit shown in FIG. 5 will be described with reference to FIG.

The circuit shown in FIG. 7 includes a pair of power supply voltage terminals (a positive power supply terminal 280 and a negative power supply terminal 281 in FIG. 2) and a − input terminal of the operational amplifier 28 of the inverting voltage amplification circuit 25 in the circuit shown in FIG. Diodes 10 and 11 are respectively connected between the two. Thereby, it is possible to prevent the voltage input to the negative input terminal from being abnormally high or abnormally low due to some factor. In FIG. 7, only the single-phase inverter circuit 9 a is illustrated in the transformer step-down DC-DC converter circuit 9 illustrated in FIG. 2, and other circuit portions of the transformer-type step-down DC-DC converter circuit 9 are not illustrated. ing.
( Example )
An embodiment of the present invention will be described with reference to FIG. 8 showing a modified circuit of the circuit shown in FIG.

  In the circuit shown in FIG. 8, the potential of the non-inverting input terminal (+ input terminal) out of the pair of input terminals of the operational amplifier 28 of the inverting voltage amplifier circuit 25 in the circuit shown in FIG. It is offset in the + direction by Voffset.

  More specifically, the voltage output from the constant voltage power supply 20 is divided by a resistance voltage dividing circuit including resistors 32 and 33, and the offset potential Voffset is applied to the non-inverting input terminal (+ input terminal) of the operational amplifier 28. Apply.

  In this way, the lower limit value of the output voltage range of the operational amplifier 28 can be raised from 0 V by a predetermined potential by the amount that the potential of the non-inverting input terminal (+ input terminal) of the operational amplifier 28 is raised by the offset potential Voffset. As a result, accuracy can be ensured even when a general-purpose operational amplifier whose output voltage accuracy decreases near 0 V is adopted.

Similarly to this modification, the offset potential Voffset can be applied to the + input terminal of the operational amplifier 28 by the resistance voltage dividing circuit constituted by the resistors 32 and 33 in the circuit of FIG. Of course.
( Modification of Example )

  The circuit shown in FIG. 9 is obtained by connecting a diode 50 in series with the leakage current detecting resistor 4 in the circuit shown in FIG. In this way, when a leakage current is generated in the sub power switch 8, the signal voltage Vx can be offset in the negative direction by the forward voltage drop (about 0.6 to 0.7 V) of the diode 50. As a result, by using the resistor 4 whose resistance value r4 is set to be relatively small in order to secure the current flowing through the sub power switch 8 and the resistor 4 by turning on the sub power switch 8, the leakage current of the sub power switch 8 Even when the voltage drop of the resistor 4 is small, the general-purpose operational amplifier 28 can detect it with high accuracy.

  That is, when the leakage current Ix flows through the sub power switch 8 and the forward voltage drop ΔVf occurs in the diode 50, the signal voltage Vx becomes the voltage drop r4 · Ix + ΔVf of the resistor 4, which is negative by ΔVf than in the case of FIG. It becomes. This substantially corresponds to an increase in the leakage current by ΔVf / r4, and the output voltage Vs of the operational amplifier is positively increased accordingly. Therefore, due to variations in offset current and offset voltage, it is possible to detect the leakage current of the sub power switch 8 with high accuracy even when using a general-purpose operational amplifier that is difficult to detect a small leakage current. On the other hand, in a situation where the leakage current can be regarded as substantially zero, the forward voltage drop of the diode 50 can be regarded as substantially 0 V, and the output voltage Vs of the operational amplifier 28 is as small as in FIG. Become. That is, the diode 50 has an effect of nonlinearly amplifying the signal voltage Vx due to the leakage current in a small current region of the leakage current.

  The diode 50 may further increase the amount of voltage drop when a plurality of diodes are connected in series and a leakage current flows. As the diode 50, a parasitic diode, a Zener diode, or a Schottky diode of a MOS transistor may be employed. . Further, the resistor 4 and the diode 50 may be connected in reverse to the case shown in FIG. Further, the diode 50 may be provided in series with the resistor 4 in the circuit of FIG. 3, and in this case, the direction of the diode 50 is opposite.

(Example effect)
Note that the leakage current detection of the secondary power supply switch 8 in the above-described Rei及beauty variants of like turns on the main power switch 2 is turned on the state or the main power switch 5 turns off the main power switch 5 the main power switch 2 This is performed in an off state, that is, in a state where the main power switch on the sub power switch 8 side is turned off and the other main power switch is turned on. At this time, the leakage current of the sub power switch 8 flows in the order of the power source 1, the main power switch 2, the resistors 18 and 19, the resistor 4 (including the diode 50 when the diode 50 is used), the sub power switch 8 and the power source 1. Alternatively, the power source 1, the sub power switch 8, the resistor 4 (including the diode 50 when the diode 50 is used), the resistors 18 and 19, the main power switch 5, and the power source 1 flow in this order. That is, the resistors 18 and 19 of the voltage dividing circuit for dividing the DC power supply voltage of the overvoltage determination circuit 200 for detecting the overvoltage also serve as a part of the leakage current conducting circuit when the leakage current of the sub power switch 8 is detected. Therefore, the circuit configuration can be simplified correspondingly.

  Moreover, it is preferable that each switching element of the inverter circuit 9a is turned off when the leakage current is detected. Accordingly, it should be noted that in this state, the potential at the connection point Z that is actually regarded as 0 V is actually a positive potential when viewed from the negative terminal of the DC power supply 1.

It is a circuit diagram which shows the inrush current limiting type | mold power switch circuit of a reference example . FIG. 2 is a circuit diagram illustrating a specific configuration of a determination circuit in FIG. 1. It is a circuit diagram which shows the modification of FIG. It is a circuit diagram which shows the deformation | transformation aspect of FIG. It is a circuit diagram which shows the modification of FIG. It is a circuit diagram which shows the modification of FIG. FIG. 6 is a circuit diagram showing a modification of FIG. 5. It is a circuit diagram which shows an Example . It is a circuit diagram which shows the modification of FIG. It is a circuit diagram which shows an example of the conventional inrush current limiting type | mold power switch circuit.

Explanation of symbols

1 Battery (DC power supply)
2 First main power switch (Main power switch)
4 Inrush current limiting resistor 5 Second main power switch (Main power switch)
6 Smoothing Capacitor 8 Sub Power Switch 9 Converter Circuit 18 Resistor 20 Constant Voltage Power Supply 21 Resistor 23 Comparator 24 Control Power Supply 25 Inverting Voltage Amplifier Circuit 26 Input Resistor 27 Feedback Resistor 28 Op Amp 29 Comparator 30 Resistor 31 Resistor 100 Determination Circuit 200 Overvoltage Determination Circuit 280 Positive power supply terminal 281 Negative power supply terminal 282 Positive power supply terminal 283 Negative power supply terminal 300 Load side circuit (electric load)

Claims (3)

A main power switch that connects an electric load having a large input capacitance and a DC power source; and an inrush current limiting circuit that is connected in parallel with the main power switch; and the inrush current limiting circuit is connected to the DC power source from the DC power source. A sub-power switch composed of a semiconductor switching element that is conducted prior to the main power switch when supplying current to the electric load; an inrush current limiting resistor connected in series with the sub-power switch; and the main power switch. It is determined whether or not the voltage drop of the inrush current limiting resistor when the sub power switch is off exceeds a predetermined threshold value, and if it exceeds, the determination that the sub power switch is defective the vehicle inrush current limiting type power switching circuit having a circuit,
Before SL connection point X of the secondary power supply switch 8 and the inrush current limiting resistor 4, the connection points of the auxiliary power switch 8 and the main power supply switch 2 or 5 Y, wherein inrush current limiting and the main power switch When the connection point with the resistor 4 is Z,
The determination circuit includes:
An inverting voltage amplification circuit 25 having an operational amplifier 28 in which the potential of the connection point X is input to the negative input terminal through the input resistance element 26 and the potential of the connection point Z is input to the positive input terminal;
A comparator 29 that compares the output voltage of the inverting voltage amplifier circuit 25 with a predetermined threshold voltage Vth to determine a leakage current failure of the sub power switch 8;
A control power supply 24 having a negative end connected to the negative power supply terminal of the inversion voltage amplification circuit 25 and the comparator 29 and a positive end connected to the positive power supply terminal of the inversion voltage amplification circuit 25 and the comparator 29 ;
Is offset to a predetermined offset potential Voffset only + direction from the non-inverting input voltage of the connection point Z the potential of the terminal before Symbol inverting voltage amplifying circuit 25 comprising the operational amplifier 28 the output voltage accuracy decreases in the input voltage 0V vicinity Offset circuits 32 and 33 ;
Vehicle inrush current limiting type power switch circuit, characterized in that it has a.   In the vehicle inrush current limiting type power switch circuit according to claim 1,
  One main electrode terminal of the N-channel MOS transistor forming the sub power switch 8 is connected to a connection point between one of the pair of electrode terminals of the DC power supply and one end of the main power switch, and Another one of the main electrode terminals is connected to the other end of the main power switch through the inrush current limiting resistor 4. In the vehicle inrush current limiting type power switch circuit according to claim 1 ,
A constant voltage drop element 50 connected in series with the auxiliary power switch 8 and the inrush current limiting resistor 4;
The determination circuit reads the sum of the voltage drops of the inrush current limiting resistor 4 and the constant voltage drop element 50 to determine the magnitude of the voltage drop of the inrush current limiting resistor. Limited power switch circuit.

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