JP2000245146A - Power supply for vehicle and onboard device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power supply for vehicles, wherein an overvoltage protective circuit does not malfunction even when the supply of direct-current input voltage to input ends ceases. SOLUTION: A DC-to-DC converter 10 converts a direct-current input voltage Vin supplied to input terminals 6 and 7 into a direct-current voltage V0, having a different voltage value and supplies it to output terminals 8 and 9. A control circuit 11 controls the DC-to-DC converter 10. An overvoltage protective circuit 12 detects the direct-current output voltage V0 supplied from the DC-to-DC converter 10 to the output terminals 8 and 9 and generates a voltage detection signal V1. In addition, the overvoltage protective circuit 12 generates a reference voltage signal Vr1 from the direct-current output voltage V0 and compares the voltage detection signal V1 with the reference voltage signal Vr1. Then the overvoltage protective circuit generates an overvoltage detection signal V2 and supplies the overvoltage detection signal V2 to the control circuit 11.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a vehicle-mounted power supply and a vehicle-mounted device including the vehicle-mounted power supply.

[0002]

2. Description of the Related Art An electric vehicle and a hybrid vehicle are provided with a vehicle-mounted power supply for driving a vehicle-mounted device (hereinafter referred to as an auxiliary machine) in addition to a motor for driving wheels and a motor drive circuit. The auxiliary equipment includes various devices such as various lamps, air conditioners, radios, and the like. These accessories operate by receiving power supply from a DC power source for accessories, which is a rechargeable battery. The in-vehicle power supply device is mainly used for charging the above-described accessory DC power supply and supplying power to the accessory together with the accessory DC power supply. The on-vehicle power supply device includes a DC-DC converter, switches DC power supplied from a main power supply (main battery) for a wheel drive motor via a main power supply switch, and has a DC voltage having a different voltage value. And supplies it to the auxiliary equipment and the DC power supply for the auxiliary equipment.

[0003] The terminal voltage of the DC power supply for auxiliary equipment and the DC output voltage of the vehicle-mounted power supply are usually maintained at voltage values suitable for the auxiliary equipment. However, an overvoltage state may occur due to a failure of the DC-DC converter or the like. If the overvoltage state occurs, the DC power supply for auxiliary equipment and the auxiliary equipment may be damaged. Therefore, an overvoltage protection circuit is usually provided in the vehicle-mounted power supply device.

Various circuit configurations have been proposed as overvoltage protection circuits. Basically, a DC output voltage of a vehicle-mounted power supply device is detected by a resistance voltage dividing circuit, and a detected voltage signal is output. It is supplied to one of the inputs of the comparator (usually a non-inverting input). The other input terminal (usually an inverting input terminal) of the comparator is supplied with a reference voltage signal supplied from the main battery. When the voltage detection signal becomes higher than the reference voltage signal, the output of the comparator is output. And outputs an overvoltage detection signal. Then, this overvoltage detection signal is
The operation is supplied to the control circuit, and the operation of the DC-DC converter is stopped by the control circuit.

As described above, the on-board power supply is used for charging the auxiliary equipment DC power supply and supplying power to the auxiliary equipment together with the auxiliary equipment DC power supply. On the DC output side of the on-vehicle power supply device, an auxiliary machine DC power supply for the auxiliary machine is always connected.
Therefore, a voltage signal obtained by dividing the terminal voltage of the auxiliary DC power supply is supplied to the non-inverting input terminal of the comparator.

In this circuit configuration, when the main power supply switch of the vehicle is pulled out and the supply of the DC input voltage to the vehicle-mounted power supply is stopped, the supply of the DC input voltage to the inverting input terminal in the comparator constituting the overvoltage protection circuit is performed. The reference voltage signal drops sharply, whereas the voltage signal supplied to the non-inverting input terminal of the comparator is a voltage signal obtained by dividing the terminal voltage of the DC power supply for auxiliary equipment. do not do. Therefore, the relationship between the voltage values seen at the non-inverting input terminal and the inverting input terminal of the comparator is the same as in the case of the overvoltage detection operation. In this state, if the main power supply switch is inserted and a DC voltage is supplied from the main battery to the vehicle-mounted power supply device, the overvoltage protection circuit starts operating from a state where the overvoltage is detected. At the same time when the power is turned on by the turning-on switch, the operation stop control is applied to the DC-DC converter constituting the power supply unit for vehicle.

Moreover, once the overvoltage protection circuit once detects the overvoltage, it usually has a self-holding operation for holding the state, and thus the latch-up state occurs. In order to cancel this, the main power supply switch is unplugged, and after a certain period of time, the main power supply switch is inserted again, so that there is no other place to start.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to provide a vehicle-mounted power supply device having an overvoltage protection function for protecting a DC power supply for auxiliary equipment and auxiliary equipment from overvoltage.

Another object of the present invention is to provide a vehicle-mounted power supply device in which an overvoltage protection circuit does not malfunction when a DC input voltage is applied.

[0010]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention discloses an on-vehicle power supply device according to two aspects and also discloses an on-vehicle device using them.
Next, a description will be given.

<In-vehicle power supply device according to first embodiment>
The vehicle-mounted power supply device according to the aspect includes at least one pair of input terminals, at least one pair of output terminals, a DC-DC converter, a control circuit, and an overvoltage protection circuit.

The DC-DC converter converts a DC input voltage supplied to the pair of input terminals into a different DC voltage and supplies the converted DC voltage to the pair of output terminals. The control circuit controls the DC-DC converter.

The overvoltage protection circuit detects a DC output voltage supplied from the DC-DC converter to the pair of output terminals to generate a voltage detection signal, and generates a reference voltage signal from the DC output voltage. Comparing the voltage detection signal with the reference voltage signal to generate an overvoltage detection signal, and supplying the overvoltage detection signal to the control circuit.

In the above-described power supply device for a vehicle according to the first aspect, the DC input voltage supplied to the pair of input terminals is:
The DC-DC converter converts the DC voltage into a DC voltage having a different voltage value and supplies the DC voltage to a pair of output terminals. The DC input voltage supplied to the pair of input terminals is supplied from a wheel drive motor and a main power supply (main battery) provided for a drive circuit thereof, as in the related art. A DC power supply for auxiliary equipment and auxiliary equipment are connected to the pair of output terminals according to a normal configuration. The DC-DC converter outputs a DC voltage having a voltage value suitable for the accessory DC power supply and the accessory. The accessory DC power supply is charged by a DC output voltage supplied from a DC-DC converter. The accessory mainly operates using a DC power supply for the accessory as a power supply.

The overvoltage protection circuit detects a DC output voltage supplied from the DC-DC converter to a pair of output terminals, and generates a voltage detection signal. When the DC output voltage becomes overvoltage due to a failure of the DC-DC converter or the like, the voltage detection signal rises. Then, when the voltage detection signal becomes higher than the reference voltage signal, an overvoltage detection signal is output. This overvoltage detection signal is supplied to the control circuit, and the operation of the DC-DC converter is stopped by the control circuit.

Here, in the overvoltage protection circuit according to the first aspect, the reference voltage signal is generated from the DC output voltage. That is, the reference voltage signal and the voltage detection signal input to the overvoltage protection circuit are obtained from the DC output voltage appearing at the output terminal. Therefore, when the main power-on switch of the car is pulled out and the supply of the DC input voltage to the on-vehicle power supply is stopped, the reference voltage signal and the voltage detection signal input to the overvoltage protection circuit are the same. Going down. Therefore, the relationship between the reference voltage signal and the voltage detection signal seen at the input terminal of the overvoltage protection circuit is not affected by the stop of the supply of the DC input voltage to the vehicle power supply.

Accordingly, when the main power supply switch is turned on again and a DC voltage is supplied from the main battery to the vehicle-mounted power supply, the vehicle-mounted power supply starts operating normally without causing latch-up. become.

<In-vehicle power supply device according to second embodiment>
The on-vehicle power supply device according to the first aspect includes at least one pair of input terminals, at least one pair of output terminals, a DC-DC converter, a control circuit, and an overvoltage protection circuit.
There is no difference from the vehicle-mounted power supply device according to the aspect. The vehicle power supply according to the second aspect is different from the vehicle power supply according to the first aspect in that an overvoltage protection circuit is operated using a DC voltage output from an auxiliary power supply circuit. And that the configuration of the overvoltage protection circuit is different. This will be described below.

First, the auxiliary power supply circuit generates a DC voltage from the DC input voltage. The overvoltage protection circuit,
An output voltage detection circuit includes a first comparator and a second comparator. The output voltage detection circuit detects a DC output voltage supplied from the DC-DC converter to the pair of output terminals and generates a voltage detection signal.

The first comparator has one input terminal supplied with the voltage detection signal, the other input terminal supplied with a reference voltage signal from the auxiliary power supply circuit, and a voltage value of the voltage detection signal. Performs an inversion operation and outputs an inversion signal when is higher than the voltage value of the reference voltage signal.

The second comparator has a time constant charging / discharging circuit connected to one of its input terminals, and outputs an output signal of the first comparator and the auxiliary signal through the time constant charging / discharging circuit. The DC voltage generated by the power supply circuit is supplied. The DC voltage generated by the auxiliary power supply circuit is supplied to the other input terminal of the second comparator. Then, the second comparator performs the inversion operation on condition that the voltage value seen at one of the input terminals is higher than the voltage value seen at the other of the input terminals.

In the above-described vehicle-mounted power supply device according to the second aspect, when the DC voltage supplied from the auxiliary power supply circuit is at a normal level, the following operation is performed.

First, the first comparator compares a voltage detection signal supplied from the voltage detection circuit to one of the input terminals with a reference voltage signal supplied from the auxiliary power supply circuit to the other of the input terminals. When the voltage value of the voltage detection signal is higher than the voltage value of the reference voltage signal, an inversion operation is performed and an inversion signal is output.

In the second comparator, when the DC voltage supplied from the auxiliary power supply circuit is at a normal level, a substantially constant charging voltage is applied to one of the input terminals.

In this state, when an inverted signal higher than the reference voltage signal supplied to the other input terminal is supplied to one of the input terminals, the second comparator is supplied from the first comparator. The inversion operation is performed by the inverted signal to generate an overvoltage detection signal. The overvoltage detection signal is supplied to the control circuit. The control circuit stops operation of the DC-DC converter when receiving the supply of the overvoltage detection signal.

When the DC output voltage is in the normal voltage range, the voltage value of the voltage detection signal in the first comparator becomes lower than the voltage value of the reference voltage signal. Therefore, the first comparator does not perform the inversion operation.

Next, a case where the DC voltage supplied from the auxiliary power supply circuit drops to a low level will be described. Such a state occurs when the main power supply switch of the vehicle is pulled out and the supply of the DC input voltage to the vehicle-mounted power supply is stopped.

First, in the first comparator, while the reference voltage signal supplied from the auxiliary power supply circuit sharply decreases, the voltage detection signal supplied from the voltage detection circuit is connected to the terminal of the auxiliary DC power supply. Since it is also a voltage, it does not decrease so much. For this reason, the relationship between the input signals seen at the two input terminals of the first comparator becomes the same state as in the case of the overvoltage detection operation, the first comparator performs the inversion operation, and the inverted signal is output. .

When viewed at one of the inputs of the second comparator,
The level of the DC voltage generated by the auxiliary power supply circuit drops sharply. Since the time constant charging / discharging circuit is connected to one of the input terminals, the voltage signal supplied to one of the input terminals attenuates with time due to the discharging action of the time constant charging / discharging circuit.

On the other hand, the level of the reference voltage signal supplied from the auxiliary power supply circuit to the other input terminal of the second comparator also decreases. However, since the voltage signal compared with the reference voltage signal in the second comparator also attenuates with time,
The level relationship between the voltage signal supplied to one of the input terminals and the reference voltage signal supplied to the other of the input terminals does not reverse. Therefore, when the DC voltage supplied from the auxiliary power supply circuit drops to a low level, the second comparator does not perform the inversion operation even if the inversion signal is supplied from the first comparator. Therefore, when the main power supply switch is turned on again and a DC voltage is supplied from the main battery to the vehicle-mounted power supply device, the vehicle-mounted power supply device starts operating normally without causing latch-up.

<In-Vehicle Device> The in-vehicle device according to the present invention includes a main power supply, a main power-on switch, a motor drive circuit, a motor, and a power supply device. The main power supply includes a battery. The motor drive circuit supplies a DC power supplied from the main power supply via the main power supply switch to the motor. The motor is used as a wheel drive source.

The power supply unit is one of the above-described two types of vehicle-mounted power supply units. In this power supply device, the DC input voltage is supplied from the main power supply via a main power-on switch.

Other objects, configurations and advantages of the present invention will be described in more detail with reference to the accompanying drawings. The accompanying drawings are merely illustrative.

[0034]

DESCRIPTION OF THE PREFERRED EMBODIMENTS <In-Vehicle Apparatus Using In-Vehicle Power Supply According to First Aspect> FIG. 1 is an electric circuit diagram of an in-vehicle apparatus using an in-vehicle power supply according to a first aspect. The illustrated in-vehicle device includes a main power supply 1, a main power supply switch 2,
It includes a motor drive circuit 3, a motor 4, and a power supply device 5 according to the first embodiment. Main power supply 1 includes a main battery. Main power-on switch 2 is generally called an ignition switch. The motor drive circuit 3 supplies the DC power supplied from the main power supply 1 via the main power supply switch 2 to the motor 4. The motor 4 is used as a wheel drive source.

The power supply 5 is a vehicle-mounted power supply according to the first aspect. The power supply 5 is supplied with a DC input voltage Vin from the main power supply 1 via the main power supply switch 2. The power supply device 5 has at least a pair of input terminals 6, 7,
It includes at least a pair of output terminals 8 and 9, a DC-DC converter 10, a control circuit 11, and an overvoltage protection circuit 12. Further, in the embodiment, the accessory DC power supply 13 and the accessory 14 are illustrated. The auxiliary power supply 13 is a rechargeable secondary battery.

The DC-DC converter 10 has an input terminal 6,
The DC input voltage Vin supplied to 7 is converted into a DC voltage V0 having a different voltage value and supplied to output terminals 8 and 9.
The control circuit 11 controls the DC-DC converter 10.

The overvoltage protection circuit 12 is provided with a DC output voltage V supplied from the DC-DC converter 10 to the output terminals 8 and 9.
0 to generate a voltage detection signal V1, generate a reference voltage signal Vr1 from the DC output voltage V0, and compare the voltage detection signal V1 with the reference voltage signal Vr1 to generate an overvoltage detection signal V2. The signal V2 is sent to the control circuit 1
Feed to 1.

In the vehicle-mounted power supply device 5 according to the first embodiment, the overvoltage protection circuit 12 can include a comparator 121. The comparator 121 has a voltage detection signal V at an input terminal (+).
1 is supplied, and the reference voltage signal Vr1 is supplied to the input terminal (-). When the voltage value of the voltage detection signal V1 is higher than the voltage value of the reference voltage signal Vr1, that is, V1> V
At r1, an overvoltage detection signal V2 indicating an overvoltage is generated. A diode 124 is connected between the output terminal of the comparator 121 and the input terminal (+). This diode 124 is added for the self-holding operation of the comparator 121.

In the embodiment, the DC output voltage V0 is divided by the resistors 122 and 123, and the divided voltage is supplied to the input terminal (+) as the voltage detection signal V1. Also, a high-potential-side output line 7 that outputs the DC output voltage V0
1 and the low-potential output line 72, a reference voltage generation circuit 125 is connected, and the DC output voltage V0 to the reference voltage signal V
r1 is generated.

In the on-vehicle power supply device 5 according to the first aspect described above, the DC input voltage V supplied to the input terminals 6 and 7 is
in is converted into a DC voltage V0 having a different voltage value by the DC-DC converter 10 and supplied to the output terminals 8 and 9. DC input voltage Vin supplied to input terminals 6 and 7
Is supplied from a main power supply (main battery) 1 provided for the wheel driving motor 4 and the motor drive circuit 3 as in the conventional case. The output terminals 8 and 9 are connected to an auxiliary machine DC power supply 13 and an auxiliary machine 14 according to a normal configuration. The DC-DC converter 10 outputs a DC voltage V0 having a voltage value suitable for the accessory DC power supply 13 and the accessory 14. The accessory DC power supply 13 outputs a DC output voltage V0 supplied from the DC-DC converter 10. Will be charged by. The accessory 14 mainly operates using the accessory DC power supply 13 as a power supply. The auxiliary device 14 includes various devices such as various lamps, a cooling / heating device, and a radio.

Next, the operation when the main power switch 2 of the vehicle is closed will be described with reference to the time chart shown in FIG. The overvoltage protection circuit 12 is DC-DC
The DC output voltage V0 supplied from the converter 10 to the output terminals 8 and 9 is detected to generate a voltage detection signal V1. When the DC output voltage V0 is at a normal value, the voltage detection signal V1
Is lower than the reference voltage signal Vr1.
The output of 21 is at a low level (logic 0). This state corresponds to no overvoltage occurring.

Due to the failure of the DC-DC converter 10 or the like, the DC output voltage V0 becomes, for example, at t1 (see FIG. 2A).
, The voltage detection signal V1 rises.
Then, when the voltage detection signal V1 becomes higher than the reference voltage signal Vr1, the comparator 121 performs an inverting operation and outputs an overvoltage detection signal V2 of logical value 1. This overvoltage detection signal V2 is supplied to the control circuit 11, and the control circuit 11 stops the operation of the DC-DC converter 10. Since the diode 124 is connected between the output terminal and the input terminal (+) of the comparator 121, when an overvoltage detection signal V2 having a logical value 1 is generated at the output terminal, the overvoltage detection signal having the logical value 1 is detected. The signal V2 is supplied to the input terminal (+) through the diode 124. Therefore, after the overvoltage detection signal V2 is output once, even if the voltage detection signal V1 degenerates to the logical value 0, the overvoltage detection signal V2 output from the comparator 121 maintains the logical value 1 (see FIG. b)).

Next, a case where the main power supply switch 2 of the vehicle is pulled out and the supply of the DC input voltage Vin to the vehicle power supply 5 is stopped will be described with reference to FIG. When the main power-on switch 2 of the car is pulled out at t2, the DC input voltage Vin to the on-vehicle power supply 5
(See FIG. 3A) Here, in the overvoltage protection circuit 12, the reference voltage signal Vr1 is generated from the DC output voltage V0.
The reference voltage signal Vr input to the overvoltage protection circuit 12
1 and the voltage detection signal V1 are obtained from the DC output voltage V0 appearing at the output terminals 8 and 9. Therefore, when the main power supply switch 2 of the car is pulled out at the time t2 (see FIG. 3A) and the supply of the DC input voltage Vin to the vehicle-mounted power supply device 5 is stopped, it is inputted to the overvoltage protection circuit 12. Reference voltage signal Vr1 and voltage detection signal V1
Decrease in the same manner (see FIG. 3B). Therefore, the two input terminals (+) and (−) of the comparator 121 are
The relationship between the reference voltage signal Vr1 and the voltage detection signal V1 is not affected by the stoppage of the supply of the DC input voltage Vin to the vehicle-mounted power supply 5, and Vr1> V1
Is maintained, the comparator 121 continues to output the signal of the logical value 0 without performing the inversion operation.

Therefore, for example, when the main power supply switch 2 is turned on again at time t3 (see FIG. 3B) and a DC voltage is supplied from the main power supply 1 to the vehicle power supply device 5, the vehicle power supply device 5 Starts the operation from the state of Vr1> V1, so that no latch-up occurs. The same applies to the case of initial startup.

<In-Vehicle Device Using In-Vehicle Power Supply 5 According to Second Aspect> FIG. 4 is an electric circuit diagram of an in-vehicle device using the in-vehicle power supply 5 according to the second aspect. In the figure,
The same components as those shown in FIG. 1 are denoted by the same reference numerals. The on-vehicle power supply device 5 according to the second embodiment is different from the first embodiment in that it includes input terminals 6 and 7, output terminals 8 and 9, a DC-DC converter 10, a control circuit 11, and an overvoltage protection circuit 12. There is no difference from the vehicle-mounted power supply device 5 according to the first embodiment. The second mode differs from the first mode in that the reference voltage of the comparator is supplied from the auxiliary power supply circuit 15 and the configuration of the overvoltage protection circuit 12 is different. This will be described below.

First, the auxiliary power supply circuit 15 generates DC voltages Vr1, Vc1, and Vc2 from the DC input voltage Vin. The overvoltage protection circuit 12 includes an output voltage detection circuit including voltage dividing resistors 122 and 123 and a first comparator 121.
And a second comparator 19. The voltage dividing resistors 122 and 123 constituting the output voltage detecting circuit are connected to the DC output voltage V0 supplied from the DC-DC converter 10 to the output terminals 8 and 9.
Is divided to generate a voltage detection signal V1.

The first comparator 121 has an input terminal (+) supplied with the voltage detection signal V1 and an input terminal (-) supplied with the first reference voltage signal Vr1 from the auxiliary power supply circuit 15.
In a normal state without an overvoltage state, there is a relationship of Vr1> V1, and at this time, the output of the first comparator 121 is at a low level (the logical value is 0). When an overvoltage occurs, the voltage value of the voltage detection signal V1 becomes higher than the voltage value of the first reference voltage signal Vr1. That is, V1> Vr1. At this time, the first comparator 121 performs an inverting operation and outputs a high-level (logical value 1) inverted signal.

The second comparator 19 has an input terminal (+) connected to a time constant charging / discharging circuit, and outputs the output signal V2 of the first comparator 121 and the time signal through the time constant charging / discharging circuit.
The DC voltage Vc1 generated by the auxiliary power supply circuit 15 is supplied. The time constant charge / discharge circuit uses the DC voltage Vc1
The circuit includes a circuit for charging the capacitor 23 through the resistors 20 and 21, and a discharging circuit for discharging the electric charge accumulated in the capacitor 23 through the resistor 22. The DC voltage Vc1 generated by the auxiliary power supply circuit 15 is also supplied to the control circuit 11 and the like.

A Zener diode 25 is connected to the input terminal (−) of the second comparator 19. The Zener diode 25 is connected to the DC voltage Vc supplied through the resistor 24.
1 to generate a second reference voltage signal Vr2.
Is supplied to the input terminal (−) of the second comparator 19.

In the second comparator 19, when the DC voltage Vc 1 supplied from the auxiliary power supply circuit 15 is at a normal level, the first comparator 121 supplies the signal V 2 of logical value 1. When the voltage signal V3 supplied to the input terminal (+) becomes higher than the second reference voltage signal Vr2 supplied to the input terminal (-), that is, when V3> Vr2, the inverting operation is performed. To generate an overvoltage detection signal V4, and supply the overvoltage detection signal V4 to the control circuit 11. In the second comparator 19, when the DC voltage Vc1 supplied from the auxiliary power supply circuit 15 drops to a low level, both the second reference voltage signal Vr2 and the voltage signal V3 drop, and the first comparator 121 No inverting operation occurs even if an inverting signal is supplied from.

Next, the operation of the on-vehicle device shown in FIG. 4, particularly the on-vehicle power supply device 5, will be described with reference to the time charts of FIGS. FIG. 5 is a time chart showing the operation when the DC voltage Vc1 supplied from the auxiliary power supply circuit 15 is at the normal level.

First, the first comparator 121 receives the voltage detection signal V1 supplied from the voltage detection circuit to the input terminal (+),
A comparison is made with the first reference voltage signal Vr1 supplied from the auxiliary power supply circuit 15 to the input terminal (-). When the voltage value of the voltage detection signal V1 is lower than the voltage value of the first reference voltage signal Vr1, that is, when Vr1> V1, the first comparator 121
Outputs a low-level (logical value 0) signal V2. In the time chart of FIG. 5, a state before t1 corresponds to this state. At this time, the input terminal (+) of the second comparator 19
The voltage V3 is 0V because the signal V2 is 0V. The input terminal (−) of the second comparator 19 has a second reference voltage signal Vr2 by the Zener diode 25.
(> V3).

Next, as shown in FIG. 5A, when an overvoltage occurs at t1, the voltage value of the voltage detection signal V1 becomes the first voltage.
Is higher than the voltage value of the reference voltage signal Vr1. That is,
V1> Vr1. At this time, the first comparator 121
Performs an inversion operation and outputs a high-level (logical value 1) signal V2 (see FIG. 5B).

The signal V2 of the logical value 1 generated in the first comparator 121 converts the voltage signal V3 supplied to the input terminal (+) of the second comparator 19 into the voltage signal V3 of the second comparator 19. The voltage is increased to a voltage value higher than the second reference voltage signal Vr2 supplied to (−). Input terminal (−) of the second comparator 19
When the inverted signal V3 higher than the second reference voltage signal Vr2 supplied to the input terminal (+) is supplied to the input terminal (+), the second comparator 19 performs an inverting operation, and FIG. , An overvoltage detection signal V4 having a logical value of 1 is generated.

The overvoltage detection signal V 4 having the logical value 1 is supplied to the control circuit 11. When the control circuit 11 receives the supply of the overvoltage detection signal V4 of the logical value 1, the control circuit 11 stops the operation of the DC-DC converter 10.

When the DC output voltage V0 is within the normal voltage range, the first comparator 121 outputs the voltage detection signal V1.
Becomes lower than the voltage value of the first reference voltage signal Vr1. Therefore, the first comparator 121 does not perform the inversion operation.

Next, referring to FIG.
Voltage (first reference voltage signal) Vr1 supplied from
Will be described below. In such a state, the main power-on switch 2 of the car is pulled out, and the supply of the DC input voltage Vin to the on-vehicle power supply 5 is
For example, it occurs when the operation is stopped at t2 (see FIG. 6A).

First, in the first comparator 121, the first reference voltage signal Vr1 supplied from the auxiliary power supply circuit 15
Decreases sharply, whereas the voltage detection signal V1 divided by the voltage dividing resistors 122 and 123 is a terminal voltage signal of the auxiliary DC power supply 13, and therefore hardly decreases.
Therefore, two input terminals (+) of the first comparator 121,
The relationship between the input signals V1 and Vr1 as seen from (−) is V1> V
r1 (see FIG. 6B). The first comparator 121 performs the inversion operation at t3, and outputs the signal V2 of the logical value 1 (see FIG. 6C). At this timing, since the DC voltage Vc1 output from the auxiliary power supply circuit 15 is also decreasing, the level of the signal V2 also decreases (see FIG. 6C).

The level of the voltage signal V3 applied to the input terminal (+) of the second comparator 19 becomes higher at the time t3 when the level of the signal V2 becomes the level corresponding to the logical value 1 (FIG. 6D).
) Is the DC voltage Vc generated by the auxiliary power supply circuit 15.
Since the level of 1 rapidly decreases, the voltage signal V3 also decreases accordingly. Since the time constant charge / discharge circuit is connected to the input terminal (+), the voltage signal V3 attenuates with time due to the discharge action of the time constant charge / discharge circuit (see FIG. 6D).

However, the second reference voltage signal Vr2 supplied to the input terminal (-) of the second comparator 19 is also generated based on the DC voltage Vc1 supplied from the auxiliary power supply circuit 15. Also, the level of the reference voltage signal Vr2 decreases rapidly with the level of the DC voltage Vc1 supplied from the auxiliary power supply circuit 15. Therefore, the voltage signal V3 supplied to the input terminal (+) and the second reference voltage signal Vr2 supplied to the input terminal (-) are: Vr2> V3
Is maintained, and this relationship does not reverse (see FIG. 6D).

Therefore, when the level of DC voltage Vc1 supplied from auxiliary power supply circuit 15 decreases, second comparator 19 performs an inversion operation even if an inversion signal is supplied from first comparator 121. Does not occur (see FIG. 6E).

Next, the case where the main power switch 2 is turned on again will be described with reference to FIG. When the main power switch 2 is turned on again at t0, the DC input voltage V
Since in increases (see FIG. 7A), the DC voltages 1Vc1 and Vr1 output from the auxiliary power supply circuit 15 also become t.
It starts rising at t01, which is a little later than 0 (see FIG. 7)
(See (b) and (c)).

In the first comparator 121, immediately after the main power-on switch 2 is turned on again, the voltage detection signal V1 supplied to the input terminal (+) is at a constant terminal voltage of the DC power supply 13 for auxiliary equipment. On the other hand, since the reference voltage signal Vr1 supplied to the input terminal (-) is in a rising process, the input signal Vr seen at the two input terminals (+) and (-) of the first comparator 121 is detected.
The relationship between Vr1 and Vr1 is V1> Vr1 (FIG. 7C).
reference). Therefore, immediately after the main power-on switch 2 is turned on again, the first comparator 121 performs the inversion operation at t01, and outputs the signal V2 of the logical value 1 (see FIG. 7D). The signal V2 of the logical value 1 continues until t02 when V1 <Vr1.

Next, in the second comparator 19, of the input signals V3 and Vr2 viewed at the two input terminals (+) and (-), the input signal V3 is connected to the input terminal (+). The time constant gradually increases in accordance with the charging time constant of the charge / discharge circuit.
The rising curve of the input signal V3 is gentler than the rising characteristic of the input signal (second reference voltage signal) Vr2 supplied to the input terminal (-). Therefore, the first comparator 121
Performs an inverting operation at t3 and outputs a signal V2 having a logical value of 1, the two input terminals (+) of the second comparator 19,
Regarding the input signals V3 and Vr2 viewed in (-), Vr2>
The relationship of V3 is maintained (see FIG. 7E). Therefore, when the main power supply switch 2 is turned on again, the second comparator 19 does not perform an inversion operation (see FIG. 7F). Therefore, the vehicle-mounted power supply device 5 starts operating normally without causing latch-up.

Another advantage of the onboard power supply 5 shown in FIG. 4 is that when the main power switch 2 is turned off,
That is, when the vehicle is stopped, the DC power supply 1
3 is reduced to only the power consumed by the series circuit of the voltage dividing resistors 122 and 123. Conventionally,
When the vehicle stops, the current flowing out of the auxiliary machine DC power supply 13 is:
The limit was to reduce the current to about 5 mA. However, according to the vehicle-mounted power supply device shown in FIG.
It can be reduced to a degree or less.

[0066]

As described above, according to the present invention, the following effects can be obtained. (A) It is possible to provide a vehicle-mounted power supply device having an overvoltage protection function of protecting an auxiliary device DC power supply and auxiliary devices from overvoltage. (B) It is possible to provide a vehicle-mounted power supply device in which the overvoltage protection circuit does not malfunction when a DC input voltage is applied.

[Brief description of the drawings]

FIG. 1 is an electric circuit diagram of a vehicle-mounted device using a vehicle-mounted power supply device according to a first embodiment.

FIG. 2 is a time chart illustrating an operation of the in-vehicle apparatus illustrated in FIG. 1 when a main power-on switch of the vehicle is closed.

FIG. 3 is a time chart for explaining an operation of the vehicle-mounted apparatus shown in FIG. 1 when a main power-on switch of the car is turned off.

FIG. 4 is an electric circuit diagram of a vehicle-mounted device using the vehicle-mounted power supply device according to the second embodiment.

FIG. 5 is a time chart illustrating an operation of the in-vehicle device illustrated in FIG. 4 when a main power supply switch of the vehicle is closed.

FIG. 6 is a time chart illustrating an operation of the on-vehicle apparatus illustrated in FIG. 4 when a main power supply switch of the vehicle is turned off.

FIG. 7 is a time chart for explaining the operation when the main power switch of the vehicle is turned on again in the on-vehicle apparatus shown in FIG. 4;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Main power supply (main battery) 2 Main power supply switch 3 Motor drive circuit 4 Motor 5 In-vehicle power supply 6, 7 Input terminal 8, 9 Output terminal 10 DC-DC converter 11 Control circuit 12 Overvoltage protection circuit 13 DC for auxiliary equipment Power supply 14 Auxiliary equipment 15 Auxiliary power supply circuit 18 First comparator 19 Second comparator

Claims (5)

[Claims] 1. An on-vehicle power supply device including at least one pair of input terminals, at least one pair of output terminals, a DC-DC converter, a control circuit, and an overvoltage protection circuit, wherein the DC-DC converter comprises: Converting the DC input voltage supplied to the pair of input terminals into DC voltages having different voltage values and supplying the DC voltage to the pair of output terminals; the control circuit controlling the DC-DC converter; The protection circuit detects a DC output voltage supplied from the DC-DC converter to the pair of output terminals to generate a voltage detection signal, generates a reference voltage signal from the DC output voltage, and generates the voltage detection signal. And a reference voltage signal to generate an overvoltage detection signal and supply the overvoltage detection signal to the control circuit. 2. The on-vehicle power supply device according to claim 1, wherein the overvoltage protection circuit includes a comparator, wherein the comparator has one of its input terminals to which the voltage detection signal is supplied, The reference voltage signal is supplied to the other of the input terminals,
An in-vehicle power supply device that generates the overvoltage detection signal indicating an overvoltage when the voltage value of the voltage detection signal is higher than the voltage value of the reference voltage signal. 3. An on-vehicle power supply device including at least one pair of input terminals, at least one pair of output terminals, a DC-DC converter, a control circuit, an auxiliary power supply circuit, and an overvoltage protection circuit, The DC-DC converter converts the DC input voltage supplied to the pair of input terminals into DC voltages having different voltage values and supplies the DC voltage to the pair of output terminals, and the control circuit controls the DC-DC converter Controlling, the auxiliary power supply circuit generates a DC voltage from the DC input voltage, the overvoltage protection circuit includes an output voltage detection circuit, a first comparator, and a second comparator, the output A voltage detection circuit configured to detect a DC output voltage supplied from the DC-DC converter to the pair of output terminals to generate a voltage detection signal; the first comparator includes a voltage detection signal provided to one of input terminals; Signal A reference voltage signal is supplied to the other of the input terminals from the auxiliary power supply circuit, and when the voltage value of the voltage detection signal is higher than the voltage value of the reference voltage signal, an inversion operation is performed and an inversion signal is output. The second comparator has a time constant charge / discharge circuit connected to one of the input terminals,
An output signal of the first comparator and a DC voltage generated by the auxiliary power supply circuit are supplied through the time constant charge / discharge circuit, and the DC voltage generated by the auxiliary power supply circuit is supplied to the other input terminal. And the inverting operation is performed on condition that a voltage value seen at one of the input terminals is higher than a voltage value seen at the other of the input terminals. 4. The vehicle-mounted power supply device according to claim 1, wherein the pair of output terminals are provided for connecting a vehicle-mounted load, and the vehicle-mounted load is chargeable. An in-vehicle power supply including a DC power supply for auxiliary equipment and auxiliary equipment. 5. An in-vehicle device including a main power supply, a main power supply switch, a motor drive circuit, a motor, and a power supply device, wherein the main power supply includes a main battery, and the motor drive circuit includes: DC power supplied from the main power supply via the main power-on switch to the motor, wherein the motor is used as a wheel drive source, and the power supply device is any one of claims 1 to 4. An on-vehicle device, comprising the on-vehicle power supply device described above, wherein the DC input voltage is supplied from the main power source via the main power-on switch.