JP2002189041A - Device for monitoring voltage - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a voltage monitoring device which can monitor both overvoltage detection and discharge detection using simple circuit with accuracy. SOLUTION: When the output voltage of a high-voltage battery E1 is monitored with a power switch SW1 on the voltage obtained, by dividing the output voltage of the high-voltage battery E1 and an offset voltage are applied to an isolation amplifier 4, a high-precision voltage value can be detected at a high voltage level of about 400 to 500 V. When the voltage accumulated in a smoothing capacitor C1, with the power switch SW1 is set to off, since the offset voltage is not applied to the insulating amplifier 4, a high-precision voltage value can be detected at a low voltage level of about 20 to 30 V.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a voltage monitor for monitoring the output voltage of a high-voltage battery.

[0002]

2. Description of the Related Art Generally, an EV (electric vehicle) or HEV (hybrid electric vehicle) is equipped with a high-voltage battery of about 300 to 400 V DC in order to supply electric power for running the vehicle. In addition, a voltage monitoring device is installed to monitor whether the output voltage of the high-voltage battery is appropriate (this is called overvoltage detection).

Further, this voltage monitoring device has a function of detecting whether or not the voltage stored in the system using the high-voltage battery is sufficiently discharged when the system is stopped. (This is called discharge detection).

FIG. 3 is a circuit diagram showing a configuration of a conventional voltage monitoring device. As shown in FIG. 3, the voltage monitoring device 101 includes a smoothing capacitor C101 for smoothing an output voltage of a high-voltage battery E101. The smoothed output voltage is divided by the resistors R101 and R102 and input to the insulation amplifier 102.

[0005] The voltage signal amplified by the insulating amplifier 102 is further amplified by the amplifier circuit 103, and
04 is input to the A / D port. And microcomputer 1
By the control of 04, overvoltage detection and discharge detection are performed.

That is, the above-described conventional voltage monitor 1
01, the microcomputer 104 uses the high voltage battery E1
Since it has a configuration for monitoring the voltage value of “01”, the output voltage of the high-voltage battery is divided using the resistors R101 and R102, and the voltage is reduced to a low voltage that can be input to the microcomputer 104.

At this time, since the inputtable voltage of the microcomputer 104 is about 0 to 5 V, the output voltage of the amplifier circuit 103 is required to fluctuate in the range of 0 to 5 V. Possible voltage is usually 300m
Therefore, when monitoring the power supply voltage in the range of 0 to 500 V, the voltage output from the high-voltage battery E101 must be divided to about 1/1000.

Here, in the above-mentioned overvoltage detection, 400 to
It is required to detect a voltage of about 500 V, while
In discharge detection, it is required to detect a voltage of about 20 to 30 V. Therefore, in a low-voltage region required for discharge detection, the input offset voltage of the insulating amplifier 102 appears to be relatively large, and the accuracy of discharge detection is reduced.

Further, if the voltage division ratio is increased in order to improve the accuracy, it becomes impossible to read the voltage required for overvoltage detection. That is, FIG. 4 is a characteristic diagram showing the relationship between the output voltage Vcc of the high-voltage battery E101 and the voltage Vo input to the microcomputer 104. As shown in the characteristic curve S101 of FIG. If an attempt is made to detect a voltage exceeding the discharge detection level Vd
In the vicinity of, the detection accuracy is reduced. To avoid this, as shown in the characteristic curve S102, when the inclination is increased,
Although highly accurate measurement can be performed near the discharge detection level Vd, a voltage exceeding the overvoltage detection level Vov cannot be detected.

In order to solve the above-mentioned problem, it is conceivable to provide both a circuit for detecting discharge and a circuit for detecting overcurrent having different voltage division ratios. In addition to the cost increase,
04 causes an increase in the load on the A / D port.

[0011]

As described above, in the conventional voltage monitoring apparatus 101, the high-voltage battery E
It has not been easy to improve the accuracy of both the overvoltage detection and the discharge detection for the output voltage of 101.

The present invention has been made to solve such a conventional problem, and an object of the present invention is to improve the accuracy of both overvoltage detection and discharge detection with a simple circuit. It is to provide a voltage monitoring device which can be used.

[0013]

According to a first aspect of the present invention, there is provided a voltage monitor for detecting an output voltage when a high-voltage DC power supply is on and a charging voltage when off. A voltage dividing means for dividing the output voltage when the high voltage DC power supply is turned on or the charging voltage when the high voltage DC power is turned off to obtain a low level voltage, and a difference between the low level voltage obtained by the voltage dividing means and a predetermined offset voltage. An insulation amplifier for amplifying a voltage, main control means for detecting an output voltage when the high-voltage DC power supply is on or a charging voltage when off based on an output signal of the insulation amplifier; In addition, a clamp circuit that suppresses the output voltage of the insulated amplifier so that it does not exceed a predetermined level, a low level voltage obtained from the voltage dividing means, and a predetermined reference voltage,
And a discharge detection control unit that sets the offset voltage to substantially zero and outputs a drive signal to the clamp circuit when the reference voltage is higher.

According to a second aspect of the present invention, an amplifier circuit is provided on the output side of the isolation amplifier.

According to a third aspect of the present invention, the discharge detection control means compares the low level voltage with the reference voltage, and outputs an ON signal when the reference voltage is determined to be higher. Means, when an on signal is output from the comparing means, an offset voltage canceling means for making the offset voltage substantially zero, and when an on signal is output from the comparing means, a drive signal is supplied to the clamp circuit. And a clamp driving means for outputting.

According to a fourth aspect of the present invention, the offset voltage canceling means includes an offset voltage input terminal of the insulating amplifier when an ON signal is output from the comparing means.
It is characterized by comprising a non-contact switch that operates to short-circuit with the ground.

According to a fifth aspect of the present invention, the clamp driving means has a photocoupler, and when an ON signal is output from the comparison means,
A driving signal is supplied to the clamp circuit.

[0018]

According to the first aspect of the invention, when measuring the output voltage when the high-voltage DC power supply is turned on, the low-level voltage obtained by the voltage dividing means is larger than the reference voltage. Therefore, an offset voltage is applied to one input terminal of the isolation amplifier. Therefore, a high voltage (400 to 500
(About volts).
Also, when measuring the charging voltage when the high-voltage DC power supply is turned off, the low-level voltage obtained by the voltage dividing means becomes smaller than the reference voltage, and the application of the offset voltage to the isolation amplifier becomes difficult. It is released. Thus, highly accurate voltage measurement can be performed in a low voltage range (about 20 to 30 volts).

According to the second aspect of the present invention, since the amplifier circuit is provided on the output side of the isolation amplifier, the voltage signal output from the isolation amplifier is converted into a voltage having a level matching the input voltage of the main control means. Can be.

According to the third aspect of the invention, the low level voltage obtained by the voltage dividing means is compared with the reference voltage by the comparing means,
If the reference voltage is higher, the offset voltage canceling means operates to cancel the supply of the offset voltage to the insulating amplifier. This enables highly accurate voltage measurement in a low voltage range. Further, since the driving signal is output to the clamp circuit by the clamp driving means, the level of the voltage supplied to the main control means can be limited.

According to the fourth aspect of the present invention, since the offset voltage canceling means is constituted by a non-contact switch, the life can be extended.

According to the fifth aspect of the present invention, since the photocoupler is used for the clamp driving means, it is possible to reliably insulate the high-current ground and the low-current ground.

[0023]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a circuit diagram showing a configuration of a voltage monitoring device according to one embodiment of the present invention. As shown in FIG. 1, the voltage monitoring device 1 monitors a DC voltage output from a high-voltage battery (high-voltage DC power supply) E1 to detect occurrence of an overvoltage and also detects a charging voltage when the power supply is stopped. A power switch SW1, a smoothing capacitor C1, a voltage dividing circuit 2,
An offset voltage generation circuit 3, an insulation amplifier 4, an amplification circuit 5, a discharge detection control circuit (discharge detection control means) 6,
It comprises a clamp circuit 7 and a microcomputer (main control means) 8.

The discharge detection control circuit 6 has a comparator (comparing means) 11, a photocoupler PC1, switching transistors Q1 and Q2, and the like. The amplifier circuit 5 includes an operational amplifier OP1 and resistors R8, R9, R
10, R11.

The plus terminal of the high voltage battery E1 is connected to the plus terminal of the smoothing capacitor C1 via the power switch SW1, and the minus terminal of the high voltage battery E1 is
It is connected to the minus terminal of the smoothing capacitor C1.
The voltage dividing circuit 3 is configured as a series connection circuit of a resistor R1 and a resistor R2, and both ends of the series connection circuit are connected to both ends of a smoothing capacitor C1. The resistance R
A connection point P1 between the resistor 1 and the resistor R2 is connected to a non-inverting input terminal (plus side) of the insulating amplifier 4. On the other hand, a voltage Voff output from the offset voltage generation circuit 3, that is, a voltage Voff obtained by dividing the voltage Vdd by the resistors R3 and R4 is provided to an inverting input terminal (minus side) of the insulating amplifier 4.
Is supplied.

The insulating amplifier 4 has two output terminals. One output terminal is connected to the inverting input terminal (negative side) of the operational amplifier OP1 via the resistor R8 of the amplifier circuit 5, and the other output terminal is connected to the output terminal. The end is connected to an operational amplifier OP via a resistor R9.
1 non-inverting input terminal (plus side). The non-inverting input terminal is connected to ground via a resistor R10, and the inverting input terminal is connected to the output terminal of the operational amplifier OP1 via a resistor R11. The output terminal of the operational amplifier OP1 is connected to the A / D port of the microcomputer 8.

On the other hand, a connection point P1 between the resistors R1 and R2
Is also connected to the inverting input terminal of the comparator 11, and the non-inverting input terminal of the comparator 11
Is divided by resistors R6 and R7 to supply a reference voltage Vref. Further, the output terminal of the comparator 11 is branched into two systems, of which the first branch line is connected to the base of the transistor Q1. The collector and the emitter of the transistor Q1 are connected to both ends of the resistor R4.

The second branch line is a transistor Q
The emitter of the transistor Q2 is connected to the ground, and the collector is connected to the power supply Vdd via the light emitting diode D1 and the resistor R12. The phototransistor PT1 paired with the light emitting diode D1 is connected to a clamp circuit 7 having a function of suppressing the output voltage of the amplifier circuit 5 to a certain level when the output voltage rises.

Next, the operation of the present embodiment configured as described above will be described. When the power switch SW1 is turned on, a voltage (300 to 4) from the high-voltage battery E1 is supplied to a subsequent driving device (not shown) via the high-voltage line L1.
(A voltage of about 00 V) is output. This voltage is
The low level voltage (voltage generated at the point P1) Vin obtained by voltage division by the resistors R1 and R2 is supplied to the non-inverting input terminal of the insulating amplifier 4.

Further, the voltage Vin is supplied to the comparator 11
In this case, since the voltage Vin generated at the point P1 is higher than the reference voltage Vref, the output signal of the comparator 11 is at "L" level. Therefore, the transistor Q1 does not operate, and the offset voltage Voff obtained by dividing the voltage Vdd by the resistors R3 and R4 is supplied to the inverting input terminal of the insulating amplifier 4.

The insulation amplifier 4 detects the voltage V generated at the point P1.
A voltage signal obtained by amplifying the voltage of the difference between in and the offset voltage Voff is output to the amplifier circuit 5, and the amplifier circuit 5 amplifies the voltage signal. Then, this voltage signal is supplied to the A / D port of the microcomputer 8. Therefore,
The microcomputer 8 can monitor the output voltage of the high-voltage battery E1, and can detect the occurrence of overvoltage.

FIG. 2 shows the voltage (output voltage Vcc of the high voltage battery E1 or the voltage stored in the smoothing capacitor C1) Vp2 generated at the point P2 shown in FIG.
Is a characteristic diagram showing a relationship with a voltage Vo supplied to the voltage dividing circuit 2. As shown in an area x1 shown in FIG. The voltage Vo supplied to the microcomputer 8 with respect to the voltage
Is represented by a characteristic curve S1-1, and the high-voltage battery E1
Can be reliably detected when the output voltage has reached the overcurrent detection level Vov.

On the other hand, when the voltage stored in the smoothing capacitor C1 is not discharged when the power switch SW1 is turned off, for example, the voltage (about 20 to 30 V) is applied to the resistors R1 and R2. The voltage Vin at the point P1 is supplied to the non-inverting input terminal of the insulating amplifier 4. At the same time, this voltage Vin is supplied to the inverting input terminal of the comparator 11.

In this case, the voltage Vin has a smaller voltage value than when the voltage of the high-voltage battery E1 is applied. Therefore, since the voltage Vin becomes lower than the reference voltage Vref, the output of the comparator 11 switches to the “H” level. As a result, the H-level voltage is applied to the base of the transistor Q1, and the transistor Q1 is turned on. Accordingly, both ends of the resistor R4 are short-circuited, so that the offset voltage Voff supplied to the non-inverting input terminal of the insulating amplifier 4 becomes substantially zero volt.

The insulating amplifier 4 amplifies the difference voltage between the voltage Vin and the offset voltage Voff (substantially zero volt), and the difference voltage is amplified by the amplifier circuit 5 to a voltage level suitable for the input voltage of the microcomputer 8. Is done. And
The microcomputer 8 monitors the voltage accumulated when the power is turned off by the same processing as described above, and can detect the voltage when the voltage is equal to or higher than a predetermined level. At this time, since the offset voltage Voff supplied to the inverting input terminal of the insulating amplifier 4 is substantially zero volt, even if the voltage Vin generated at the point P1 is a small value, it can be accurately detected.

On the other hand, when the output signal of the comparator 11 becomes H level, an H level voltage is applied to the base of the transistor Q2, so that the transistor Q2 is turned on and the resistor R12 and the light emitting diode D
Current flows through 1. Therefore, the phototransistor PT1 is turned on, and the clamp circuit 7
Works. Therefore, when the voltage output from the amplifier circuit 5 becomes higher than the clamp voltage Vcl set by the clamp circuit 7, the voltage is controlled so as not to become higher than the clamp voltage Vcl.

Therefore, the characteristic curve S shown in the area x2 of FIG.
As shown in 1-2, as the voltage Vp2 generated at the point P2 (the connection point between the resistor R1 and the power switch SW1 shown in FIG. 1) increases, the input voltage Vo of the microcomputer 8 increases linearly from zero volts. When the voltage reaches the clamp voltage Vcl, the voltage Vcl changes to be suppressed to this voltage value Vcl. As a result, a voltage near the discharge detection level Vd shown in FIG. 2 can be accurately detected.

As described above, in the voltage monitoring device 1 according to the present embodiment, when the output voltage Vcc of the high-voltage battery E1 exceeds the overvoltage detection level Vov, this can be reliably detected, and In addition, the discharge detection level Vd when the power switch SW1 is turned off can be accurately detected.

Therefore, a voltage dividing circuit for an overvoltage detection level,
In addition, both can be accurately detected by an extremely simple method without installing a voltage dividing circuit for the discharge detection level.

Since the discharge detection control circuit 6 is configured to output a drive signal to the clamp circuit 7 via the photocoupler PC1, the ground of the high-voltage system (high-voltage battery E1) and the low-voltage system (high-voltage battery E1). Microcomputer 8 and amplifier circuit 5)
Can be reliably insulated from the ground.

The voltage monitoring apparatus according to the present invention has been described based on the illustrated embodiment. However, the present invention is not limited to this, and the configuration of each unit may be any configuration having the same function. Can be replaced by

For example, when mounted on the discharge detection control circuit 6,
The transistors Q1 and Q2 can be replaced with semiconductor elements such as MOS-FETs.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a configuration of a voltage monitoring device according to an embodiment of the present invention.

FIG. 2 is a characteristic diagram showing a relationship between a voltage Vp2 generated at a point P2 and a voltage Vo input to a microcomputer.

FIG. 3 is a circuit diagram showing a configuration of a conventional voltage monitoring device.

FIG. 4 is a characteristic diagram showing a relationship between a voltage generated at both ends of a voltage dividing circuit and a voltage input to a microcomputer in a conventional example.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 voltage monitor 2 voltage divider 3 offset voltage generator 4 insulating amplifier 5 amplifier 6 discharge detection control circuit (discharge detection control means) 7 clamp circuit 8 microcomputer (main control means) 11 comparator (comparison means) E1 high voltage battery (High voltage DC power supply) PC1 Photocoupler D1 Light emitting diode PT1 Phototransistor Q1 Transistor (offset voltage release means) Q2 Transistor OP1 Operational amplifier SW1 Power switch C1 Smoothing capacitor

Claims (5)

[Claims] 1. A voltage monitoring device for detecting an output voltage when a high-voltage DC power supply is turned on and a charging voltage when the high-voltage DC power supply is turned off. Voltage dividing means for obtaining a low level voltage; an insulating amplifier for amplifying a difference voltage between the low level voltage obtained by the voltage dividing means and a predetermined offset voltage; and the high voltage based on an output signal of the insulating amplifier. A main control means for detecting an output voltage when the DC power supply is turned on or a charging voltage when the DC power supply is turned off; and a clamp circuit for suppressing an output voltage of the insulating amplifier from being higher than a predetermined level when a drive signal is given. The low-level voltage obtained from the voltage dividing means is compared with a predetermined reference voltage, and when it is determined that the reference voltage is higher,
A discharge detection control unit that sets the offset voltage to substantially zero and outputs a drive signal to the clamp circuit. 2. The voltage monitoring device according to claim 1, further comprising an amplifier circuit on an output side of the insulation amplifier. 3. The discharge detection control means compares the low level voltage with the reference voltage, and outputs an ON signal when the reference voltage is determined to be higher. When an ON signal is output, an offset voltage canceling unit that makes the offset voltage substantially zero; When an ON signal is output from the comparing unit, a clamp driving unit that outputs a driving signal to the clamp circuit; The voltage monitoring device according to claim 1, further comprising: 4. The offset voltage release means is a non-contact switch that operates to short-circuit the offset voltage input terminal of the insulation amplifier and ground when an ON signal is output from the comparison means. The voltage monitoring device according to claim 3, wherein the voltage monitoring device is configured. 5. The clamp driving unit includes a photocoupler, and supplies a driving signal to the clamp circuit via the photocoupler when an ON signal is output from the comparison unit. The voltage monitoring device according to claim 3 or 4, wherein