JP5524729B2 - Voltage detection circuit and power supply device - Google Patents

Description

  The present invention relates to a voltage detection circuit and a power supply device, and more particularly to a voltage detection circuit and a power supply device using an A / D conversion circuit such as a microcomputer.

Conventionally, in order to input a voltage higher than the withstand voltage of an A / D arithmetic unit such as a microcomputer or an amplifier (hereinafter referred to as an IC), the voltage is divided using a resistor and a voltage level-shifted below the withstand voltage of the IC is applied. To do.
In this case, if the voltage dividing resistor does not function properly, the original voltage may be input to the IC and cause voltage breakdown. Sometimes it is done.

The voltage dividing calculation method is as follows. When the voltage dividing circuit is configured as a resistor RH (high potential side) and RL (low potential side),
Input voltage / (RH + RL) × RL = detection circuit output Here, detection circuit output ≦ IC power supply voltage.
In order to improve the detection accuracy, for example, as disclosed in Patent Document 1, a plurality of voltage dividing resistors are measured while switching with a switch, each potential difference is smoothed with a capacitor, and the value is converted to an A / D conversion circuit. Use the input method.

JP 2005-207826 A

However, in the method described in Patent Document 1, since the circuit is disconnected every time measurement is switched, noise is generated and the measurement is adversely affected. In addition, since the sum of the individual measurement values is used as the measurement result, the measurement result value is not continuous and is not suitable for a device in which the detection target voltage changes.
Further, when the A / D conversion circuit (A / D converter) performs conversion, a quantization error and an A / D reference voltage error exist, and these are included in the detection circuit value as errors.
Furthermore, there are impedance errors, temperature characteristics for voltage dividing resistors, resistance value errors, leakage currents for protection diodes, and offset voltages for buffers (amplifiers), which are excluded to achieve high accuracy. This is very important.

Here, problems in the conventional voltage detection circuit will be described.
FIG. 7 is a schematic circuit configuration diagram of a conventional power supply device for a hybrid vehicle.
The conventional power supply device 10P can be broadly divided into a generator (G) 61 driven by an engine (not shown), a high-voltage battery (BAT) 162 charged by the power generation output of the generator 61, and a battery 62. A motor (M) 63 that drives a drive wheel (not shown) using at least one of the discharge output and the power generation output of the generator 61, and the supply voltage from the battery 62 to the motor 63 or the supply voltage from the generator 61 to the battery 62 are set. The voltage detection circuit 50 to detect and the power control circuit 65 which controls the whole electric power supply apparatus 10P are provided.

The power control circuit 65 drives the motor 63 via the conversion circuit 71 that functions as a booster circuit by the power supplied from the battery 62 and also converts the power when the motor 63 is regeneratively operated to function as a step-down circuit. The first inverter 72 supplied to the battery 62 via the power source and the power generated by the generator 61 to the battery 62 via the conversion circuit 71 functioning as a step-down circuit, or the motor 63 using the power generated by the power generator 61 The second inverter 73 that drives the ECU, the ECU 74 configured as a microcomputer that centrally controls the entire power control circuit 65, and the drive control of the conversion circuit 71, the first inverter 72, and the second inverter 73 under the control of the ECU 74 A gate driver 75.
The voltage detection circuit 50 buffers and outputs a voltage dividing circuit including a resistor R51 and a resistor R52 that divides a detection target voltage (high potential side voltage) of the inverter, and a detection target voltage divided by the voltage dividing circuit. And a clamp diode D51 that is connected to the preceding stage of the buffer circuit BF51 and clamps the input voltage of the buffer circuit BF51 to the power supply voltage of the voltage detection circuit 50 when an overvoltage is applied through the voltage dividing circuit. And.

Here, if the reference potential of the inverter that is the detection target circuit and the reference potential of the voltage detection circuit 50 are the same potential, the high potential side voltage of the inverter is Vpn, and the current that flows from the resistor R51 to the resistor R52 is I. In this case, the voltage V51 obtained by dividing the high potential side voltage Vpn is
V51 = Vpn / (R51 + R52) × R52
= I × R52
It becomes.

Further, since the buffer circuit BF51 outputs the voltage V51 as it is when the amplification factor is 1, the output voltage V52 of the buffer circuit BF51 is:
V52 = V51
It becomes.
Accordingly, since the voltage input to the A / D conversion circuit AD51 of the ECU 74 has the same value as the voltages V51 and V52, the voltage data DV also has the same value as the voltages V51 and V52.
Therefore, the high potential side voltage Vpn to be detected detected by the ECU 74 is:
Vpn = I × R52
It becomes.

Here, the voltage per 1 LSB of the A / D conversion circuit AD1 is as follows when the reference power supply voltage V is ref and the resolution of the A / D conversion circuit AD1 is Bit.
1LSB = Vref / Bit
It becomes.
Here, an arithmetic expression for applying 1LSB to the detected voltage value VDET is:
VDET = 1LSB / (1 / (R51 + R52) × R52)
It becomes.
However, the above operation is ideal in an ideal state, and in an actual circuit, errors in each part of the circuit are integrated.

That is, when the reference potential of the inverter that is the detection target circuit and the reference potential of the voltage detection circuit are the same potential, the voltage V51 is divided into the clamp diode D51 (overvoltage protection diode) when the high potential side voltage Vpn to be detected is divided. ) Leaks current IL51 into resistor R52.
V51 = (Ia + IL51) × R52
It becomes.
The buffer circuit BF51 outputs the voltage V51 with the same value when the amplification factor is 1, but V52 = V51 + Voffset from the potential difference generated at the input of the buffer circuit BF51.
It becomes.

Further, the value input to the A / D conversion circuit AD1 is the same value as the voltage V52, but since there is a quantization error (AD error), the voltage corresponding to the voltage data DV is
V52 + AD error.
Therefore, Vpn = (Ia + leakage current) × R52 + Voffset + AD error, which is different from the ideal value Vpn = I × R2.

FIG. 8 is an explanatory diagram of errors occurring in each part in the conventional power supply apparatus.
As shown in FIG. 8, the error ER caused by the voltage dividing circuit composed of the resistors R51 and R52 and the error EREF caused by the change in the reference voltage are constant over the entire range regardless of the change in the input voltage. On the other hand, the error ED caused by the leakage current of the clamp diode D51, the error EB caused by the offset voltage of the buffer circuit BF51, the error EO caused by the output impedance, and the quantization error EAD in the AD conversion unit AD1 are input to the voltage detection circuit. It shows a tendency to increase when the voltage is low, and it can be seen that there is a problem that voltage detection with high accuracy cannot be expected when the input voltage is low.

In addition, when the scale to be detected is enlarged, the effective resolution becomes coarse, so there is a problem that there is a limit to increase the accuracy in the low input voltage region, which is easily affected by errors. It was.
Accordingly, an object of the present invention is to provide a voltage detection circuit and a power supply device that can improve the detection accuracy by removing the influence of the detection error without impairing the continuity of the detection voltage value.

According to a first aspect of the present invention, in the voltage detection circuit that sets a reference ground potential of a power conversion circuit and detects a detection target voltage and a reference voltage with respect to the reference ground potential, the detection target voltage is set based on the reference ground potential. It has a voltage dividing circuit in which at least three or more resistors are connected in series, and each of the two voltage dividing points of the voltage dividing circuit is manufactured by the same process and has a characteristic that can be regarded as the same characteristic. The clamp diode and the buffer circuit are connected, and a difference voltage between the detection target voltage and the reference voltage is obtained based on an output voltage of each buffer circuit.
According to the above configuration, each of the divided detection target voltage and reference voltage generated is input to the buffer circuit via the clamp diode, and the detection target voltage and the reference voltage are calculated based on the output voltage of the buffer circuit. Since the difference voltage is obtained, the continuity of the detected voltage value can be ensured, and the error due to the leakage current flowing from the clamp diode and the error due to the offset voltage of the buffer circuit are cancelled.

The second aspect of the present invention, Oite the first aspect, wherein the input is the output voltage of the buffer circuit, an A / D conversion circuit which outputs as digital data by performing analog / digital conversion, the A / D converter Difference voltage data corresponding to a difference voltage between the detection target voltage and the reference voltage is obtained based on circuit output data.
According to the above configuration, the detection target voltage and the reference voltage are subjected to analog / digital conversion and output as digital data, and difference voltage data is obtained based on these.
At this time, the continuity of the detected voltage value can be ensured, and the error due to the leakage current flowing from the clamp diode, the error due to the offset voltage of the buffer circuit, and the quantization error of the A / D conversion circuit should be obtained as the difference voltage data. And cancel each other.

According to a third aspect of the present invention, in the voltage detection circuit according to the first aspect or the second aspect, the power conversion circuit is mounted on a vehicle and driven by an engine based on a differential voltage detected by the voltage detection circuit. The present invention is characterized in that the drive power is supplied to the in-vehicle motor by converting the power supplied from the in-vehicle generator or the in-vehicle battery.
Therefore, continuity of the detected voltage value can be ensured, and the voltage detection circuit detects the difference voltage with a small error, so that the power conversion circuit can be controlled accurately.

According to a fourth aspect of the present invention, the voltage detection circuit according to any one of the first to third aspects and power conversion of power supplied from an in-vehicle generator or an in-vehicle battery mounted on a vehicle and driven by an engine. And a control circuit that controls the power conversion of the power conversion circuit based on the output of the voltage detection circuit.
According to the above configuration, the voltage detection circuit obtains a difference voltage between the detection target voltage of the power conversion circuit and the reference voltage, and the control circuit performs the power conversion of the power conversion circuit based on the output of the pressure detection circuit. Control.
As a result, the continuity of the detected voltage value can be ensured, and the power conversion circuit performs power conversion control based on the difference voltage with a small error, and can perform an efficient power conversion operation, thereby driving the vehicle efficiently. It becomes possible.

  According to the present invention, the detection accuracy can be improved by removing the influence of the detection error without impairing the continuity of the detection voltage value.

It is a circuit block diagram of the electric power supply apparatus for hybrid vehicles as an electric power supply apparatus of 1st Embodiment. It is explanatory drawing of the effect of 1st Embodiment. It is a general | schematic circuit block diagram of the electric power supply apparatus of 2nd Embodiment. It is explanatory drawing of the effect of 2nd Embodiment. It is a general | schematic circuit block diagram of the electric power supply apparatus of 3rd Embodiment. It is explanatory drawing of the effect of 3rd Embodiment. It is a general | schematic circuit block diagram of the conventional electric power supply apparatus for hybrid vehicles. It is explanatory drawing of the error which generate | occur | produces in each part in the conventional electric power supply apparatus.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
Therefore, in each of the following embodiments, in order to cancel the leakage current from the clamp diode, the offset voltage Voffset of the buffer circuit, or the quantization error (AD error) of the A / D conversion circuit, these errors are almost equal to each other. A circuit for generating the same value is added, and the difference between them is obtained.

[1] First Embodiment FIG. 1 is a circuit configuration diagram of a power supply device for a hybrid vehicle as a power supply device of a first embodiment.
The power supply device 10 drives a driving wheel by a discharge output of a battery 12 described later, or a motor (M) 11 that is driven by an engine (not shown) and functions as a generator, and the motor 11 functions as a generator. A motor that drives a drive wheel (not shown) using at least one of a high-voltage battery (BAT) 12 that is charged by the power generation output and a discharge output of the battery 12 or a power generation output of the motor 11 that functions as a generator. (M) 13, a voltage detection circuit 14 that detects a supply voltage from the battery 12 to the motor 13 or a supply voltage from the motor 11 to the battery 12, and a power control circuit 15 that controls the entire power supply device 10. I have.

The power control circuit 15 drives the motor 13 with the power supplied from the battery 12 via the conversion circuit 21 that functions as a booster circuit, and converts the power when the motor 13 is regeneratively operated to function as a step-down circuit 21. The first power conversion circuit 22 that supplies the battery 12 via the power supply circuit, and the conversion circuit 21 that functions as a step-down circuit for the power generated by the motor 11 that functions as a generator or the power generated when the motor 12 is regenerated. A second power conversion circuit 23 for driving the motor 13 with electric power supplied to the battery 12 or generated by the motor 11 functioning as a generator; an ECU 24 configured as a microcomputer for centrally controlling the entire power control circuit 15; The conversion circuit 21, the first power conversion circuit 22, and the second power conversion circuit 23 are controlled under the control of the ECU 24. Includes a gate driver 25 for controlling the drive, the.
Here, the first power conversion circuit 22 functions as an inverter circuit (DC-AC conversion circuit) when the motor 13 is driven by the power of the battery 12 and performs a regenerative operation using the motor 13 as a generator. Functions as a converter circuit (AC-DC conversion circuit).
The second power conversion circuit 23 functions as an inverter circuit (DC-AC conversion circuit) when the motor 11 is driven by the power of the battery 12, and when the motor 11 performs a regenerative operation using the motor 11 as a generator. , Functioning as a converter circuit (AC-DC conversion circuit).

The conversion circuit 21 includes a reactor 21 a and a chopper circuit 21 b having two transistors 29 </ b> H and 29 </ b> L, and is a voltage conversion device provided on the input side of the first power conversion circuit 22. Further, the conversion circuit 21 includes a secondary smoothing capacitor 21c on the downstream side of the chopper circuit 21b and a primary smoothing capacitor 21d on the upstream side of the reactor 21a. The conversion circuit 21 is connected by a gate driver 25 operating under the control of the ECU 24. The voltage of the battery 12 is boosted and output to the motor 11 or the motor 13, and the output voltage of the motor 11 or motor 13 is stepped down and output to the battery 12.
More specifically, the chopper circuit 21b includes a pair of a high potential side transistor 29H and a low potential side transistor 29L connected in series.

  Furthermore, a diode 30H is connected as a freewheel diode between the collector and emitter of the high potential side transistor 29H so as to be forward from the emitter to the collector, and between the collector and emitter of the low potential side transistor 29L. A diode 30L is connected as a free wheel diode so that the forward direction is from the emitter to the collector.

One end of the reactor 21a is connected to the positive terminal of the battery 12, and the other end of the reactor 21a is connected to the collector of the high potential side transistor 29H and the emitter of the low potential side transistor 29. The emitter of the high potential side transistor 29H is connected to the negative terminal of the battery 12 and the negative terminal Nt of the conversion circuit 21. The collector of the low-potential side transistor 29L is connected to the positive terminal Pt of the conversion circuit 21.
In the above description, in the chopper circuit 21b, the two IGBTs 29H and 29L are used as a pair. However, when further current capacity is required, the IGBTs of the same high potential side transistor and low potential side transistor are used. A pair or a plurality of pairs may be arranged in parallel with the two IGBTs 29H and 29L. In this case, as in the above-described embodiment, the forward direction is from the emitter to the collector between the collector and emitter of the high-potential side transistor and the low-potential side transistor connected in series. Connect a diode as a freewheeling diode.
Note that switching elements such as IGBTs (Insulated Gate Bipolar Transistors), MOSFETs, and bipolar transistors can be used as the transistors constituting the chopper circuit 21b.

The first power conversion circuit 22 is a pulse width modulation (PWM) PWM inverter having a bridge circuit 22a in which six IGBTs are bridge-connected and a smoothing capacitor 22b. The first power conversion circuit 22 includes a motor. 13 and the conversion circuit 21 are connected.
More specifically, the bridge circuit 22a of the first power conversion circuit 22 includes a high potential side U phase transistor 31UH, a low potential side U phase transistor 31UL, a high potential side V phase transistor 31VH, and a low potential paired for each phase. The side V phase transistor 31VL, the high potential side W phase transistor 31WH, and the low potential side W phase transistor 31WL are bridge-connected.

Here, the high-potential side U-phase transistor 31UH, the high-potential side V-phase transistor 31VH, and the high-potential side W-phase transistor 31WH are connected to the positive terminal Pt of the conversion circuit 21 to form a high-side arm, and the low-potential side The U-phase transistor 31UL, the low-potential side V-phase transistor 31VL, and the low-potential side W-phase transistor 31WL are connected to the negative-side terminal Nt of the conversion circuit 21 to form a low-side arm.
Further, the high potential side U-phase transistor 31UH, the low potential side U phase transistor 31UL, the high potential side V phase transistor 31VH, the low potential side V phase transistor 31VL, the high potential side W phase transistor 31WH, and the low potential side W phase transistor 31WL Between the collector and the emitter, diodes 32UH, 32UL, 32VH, 32VL, 32WH, and 32WL are connected so as to be in the forward direction from the emitter to the collector.

Between the conversion circuit 21 and the first power conversion circuit 22, a second power conversion circuit 23 having a configuration similar to that of the first power conversion circuit 22 is connected to the positive terminal Pt and the negative terminal Nt. 2 The motor 11 is connected to the power conversion circuit 23.
Similarly to the first power conversion circuit 22, the second power conversion circuit 23 includes a bridge circuit 23 a formed by bridge connection using a plurality of transistor switching elements and a smoothing capacitor 23 b and a PWM inverter by pulse width modulation (PWM). It is. The second power conversion circuit 23 steps down the output voltage of the motor 11 by the conversion circuit 21 to charge the battery 12 or drives the motor 13 via the first power conversion circuit 22.

The second power conversion circuit 23 is a PWM inverter based on pulse width modulation (PWM), which includes a bridge circuit 23a in which six IGBTs are bridge-connected and a smoothing capacitor 23b.
More specifically, the bridge circuit 23a of the second power conversion circuit 23 includes a high potential side U phase transistor 33UH, a low potential side U phase transistor 33UL, a high potential side V phase transistor 33VH, and a low potential paired for each phase. The side V-phase transistor 33VL, the high potential side W phase transistor 33WH, and the low potential side W phase transistor 33WL are bridge-connected.

Here, the high-potential side U-phase transistor 33UH, the high-potential side V-phase transistor 33VH, and the high-potential side W-phase transistor 33WH are connected to the positive terminal Pt of the conversion circuit 21 to form a high-side arm, and the low-potential side The U-phase transistor 33UL, the low-potential side V-phase transistor 33VL, and the low-potential side W-phase transistor 33WL are connected to the negative-side terminal Nt of the conversion circuit 21 to constitute a low-side arm.
Further, the high potential side U-phase transistor 33UH, the low potential side U phase transistor 33UL, the high potential side V phase transistor 33VH, the low potential side V phase transistor 33VL, the high potential side W phase transistor 33WH, and the low potential side W phase transistor 31WL Between the collector and the emitter, diodes 34UH, 34UL, 34VH, 34VL, 34WH, and 34WL are connected so as to be in the forward direction from the emitter to the collector.

Also, three buses LU1, LV1, and LW1 are connected from the first power conversion circuit 22 to the U-phase, V-phase, and W-phase coils of the motor 13, and the second power conversion circuit 23 to the U of the motor 11 are connected. Three buses LU2, LV2, and LW2 are connected to the coils of the phase, V phase, and W phase.
Further, the signal lines from the gate driver 25 are connected to the gates of the transistors constituting the conversion circuit 21, the first power conversion circuit 22, and the second power conversion circuit 23, respectively.

Next, the configuration of the voltage detection circuit will be described.
The voltage detection circuit 14 includes a resistor R11 having one end connected to the positive electrode side terminal Pt of the conversion circuit 21, and a resistor R12 connected in series to the other end of the resistor R11. The resistor R11 and the resistor R12 include the first resistor R11 and the resistor R12. A voltage dividing circuit is configured.
The voltage dividing point of the resistor R11 and the resistor R12 is connected to the anode terminal of the first clamp diode D1 whose cathode terminal is connected to the power supply VCC of the voltage detection circuit 14, and the anode terminal of the first clamp diode D1 is connected to the ground. Is connected to a ceramic capacitor C1 for noise removal. The first buffer circuit BF1 is connected to the subsequent stage of the first clamp diode D1.

The voltage detection circuit 14 includes a resistor R21 having one end connected to the negative terminal Nt of the conversion circuit 21, and a resistor R22 connected in series to the other end of the resistor R21. The resistor R21 and the resistor R22 are: A second voltage dividing circuit is configured.
The voltage dividing point of the resistor R21 and the resistor R22 is connected to the anode terminal of the second clamp diode D2 whose cathode terminal is connected to the power supply VCC of the voltage detection circuit 14, and the anode terminal of the second clamp diode D2 is connected to the ground. Is connected to a ceramic capacitor C2 for noise removal. The second buffer circuit BF2 is connected to the subsequent stage of the second clamp diode D2.
Further, the output terminal of the first buffer circuit BF1 is connected to the non-inverting input terminal of the differential amplifier DA, and the output terminal of the second buffer circuit BF2 is connected to the inverting input terminal of the differential amplifier DA. The output terminal of the differential amplifier DA is connected to the A / D conversion circuit AD1 via the A / D conversion port of the ECU 24.

In the above configuration, the first clamp diode D1 and the second clamp diode D2 are manufactured by the same process and have characteristics that can be regarded as substantially the same characteristics.
Similarly, the first buffer circuit BF1 and the second buffer circuit BF2 are manufactured by the same process and have characteristics that can be regarded as substantially the same characteristics.

Next, the operation of the voltage detection circuit 14 will be described.
Here, if the current flowing out of the resistor R11 is Ia, the current flowing into the resistor R12 is Ib, and the leakage current of the first clamp diode D1 is IL1,
Ib = Ia + IL1
The voltage V1 is
V1 = Ib × R12
= (Ia + IL1) × R12
It becomes.

Further, the output voltage V2 of the first buffer circuit BF1 is given by assuming that the offset voltage of the first buffer circuit BF1 is Voffset.
V2 = V1 + Voffset
It becomes.
Further, if the current flowing out of the resistor R21 is Ic, the current flowing into the resistor R22 is Id, and the leakage current of the second clamp diode D2 is IL2,
Id = Ic + IL2
The voltage V3 is
V3 = Id × R22
= (Ic + IL2) × R22
It becomes.

Further, the output voltage V4 of the second buffer circuit BF2 is set so that the first buffer circuit BF1 and the second buffer circuit BF2 are manufactured by the same process, so that the offset voltage of the second buffer circuit BF2 is set to the offset of the first buffer circuit BF1. If Voffset is equal to the voltage,
V4 = V3 + Voffset
It becomes.

As a result, when the output voltage V5 of the differential amplifier DA is R11 = resistor R21, R12 = resistor R22, and the offset voltage of the differential amplifier DA is Voffset equal to the offset voltage of the first buffer circuit BF1,
V5 = V2-V4
= (Ia-Ic) × resistance R12 + Voffset
Here, VDV corresponding to the voltage detection data DV output from the A / D conversion circuit AD1 of the ECU 24 is represented by VAD as a conversion error by the A / D conversion circuit AD1.
VDV = (Ia−Ic) × resistance R12 + Voffset + VAD
It becomes.

FIG. 2 is an explanatory diagram of the effect of the first embodiment.
In FIG. 2, LP is an error characteristic of the voltage detection circuit shown in FIG.
According to the first embodiment, as shown in FIG. 2, the influence of the leakage current values of the first clamp diode and the second clamp diode, the first buffer circuit BF1, and the first buffer circuit BF1, without impairing the continuity of the detection values. It is possible to obtain a more accurate detection value by removing the influence of the offset voltage of the two-buffer circuit BF2.

[2] Second Embodiment FIG. 3 is a schematic circuit configuration diagram of a power supply device according to a second embodiment.
3, the same parts as those in the first embodiment in FIG. 1 are denoted by the same reference numerals, and detailed description thereof is omitted.
First, the configuration of the voltage detection circuit will be described.
The voltage detection circuit 14A of the power supply device 10A of the second embodiment includes a resistor R21 having one end connected to the positive terminal Pt of the conversion circuit 21, and resistors R22, R23 sequentially connected in series to the other end of the resistor R21. R24 is provided, and the resistors R21 to R24 constitute a voltage dividing circuit.

  The voltage dividing point of the resistor R22 and the resistor R23 is connected to the anode terminal of the first clamp diode D111 whose cathode terminal is connected to the power supply VCC of the voltage detection circuit 14A. The anode terminal of the first clamp diode D11 and the ground Is connected to a ceramic capacitor C11 for noise removal. The first buffer circuit BF111 is connected to the subsequent stage of the first clamp diode D11.

The voltage dividing point of the resistor R23 and the resistor R24 is connected to the anode terminal of the second clamp diode D12 whose cathode terminal is connected to the power supply VCC of the voltage detection circuit 14A, and the anode terminal of the second clamp diode D12. A ceramic capacitor C12 for removing noise is connected between the ground and the ground. The second buffer circuit BF12 is connected to the subsequent stage of the second clamp diode D12.
Further, the output terminal of the first buffer circuit BF11 is connected to the first A / D conversion circuit AD11 via the A / D conversion port of the ECU 24A, and the output terminal of the second buffer circuit BF12 is connected to the A / D conversion port of the ECU 24A. To the second A / D conversion circuit AD12.

In the above configuration, the first clamp diode D11 and the second clamp diode D12 are manufactured by the same process and have characteristics that can be regarded as substantially the same characteristics.
Similarly, the first buffer circuit BF11 and the second buffer circuit BF12 are also manufactured by the same process and have characteristics that can be regarded as substantially the same characteristics.
Furthermore, the first A / D conversion circuit AD11 and the second A / D conversion circuit AD12 of the ECU 24A are also manufactured by the same process and have characteristics that can be regarded as substantially the same characteristics.

Next, the operation of the voltage detection circuit 14A will be described.
Here, if the current flowing out of the resistor R22 is Ia, the current flowing into the resistor R23 is Ib, and the leakage current of the first clamp diode D11 is IL11,
Ib = Ia + IL11
The voltage V11 is
V11 = Ib × R24
= (Ia + IL11) × (R23 + R24)
It becomes.

Further, the output voltage V2 of the first buffer circuit BF 11, when the offset voltage of the first buffer circuit BF 11 and Voffset,
V2 = V1 + Voffset
It becomes.
Here, VDV1 corresponding to the voltage detection data DV1 output by the A / D converter AD11 of the ECU24, when the VAD1 conversion errors due to the A / D conversion circuit AD 11,
VDV1 = V11 + VAD1
= (Ia + IL11) × (R23 + R24) + Voffset + VAD1
It becomes.

Similarly, if the current flowing out of the resistor R23 is Ic, the current flowing into the resistor R24 is Id, and the leakage current of the second clamp diode D12 is IL11,
Ic = Ib
= Ia + IL11
When the leakage current of the second clamp diode D12 is IL11, the voltage V13 is
V13 = (Ic + IL11) × R24
It becomes.
Further, the output voltage V14 of the second buffer circuit BF 12, when the offset voltage of the second buffer circuit BF 12 and Voffset,
V14 = V13 + Voffset
It becomes.

Here, VDV2 corresponding to the voltage detection data DV2 output by the A / D converter circuit AD 12 of ECU24, when the VAD2 conversion errors due to the A / D conversion circuit AD 12,
VDV2 = V11 + VAD1
= (Ia + IL11 × 2) × R24 + Voffset + VAD2
It becomes.
Therefore, the difference voltage between the voltage V12 and the voltage V14 calculated in the ECU 24, that is, the voltage difference VR23 across the resistor R23 is:
VR23 = VDV1-VDV2
It becomes.

Therefore,
VPN = VR23 / {[R23 + R24] -R24}
/ (R21 + R22 + R23 + R24)
= (Ia + Ic + IL11) / R24
It becomes. Here, since Ic << Ia,
VPN≈ (Ia + IL11) / R24
It becomes.

FIG. 4 is an explanatory diagram of the effect of the second embodiment.
In FIG. 4, LP is an error characteristic of the voltage detection circuit shown in FIG.
According to the second embodiment, as shown in FIG. 4, the influence of the leakage current values of the first clamp diode and the second clamp diode and the first buffer circuit BF 11 and and influence of the offset voltage of the second buffer circuit BF 12, to remove the influence of the quantization error of the 1A / D converter AD11 and the 2A / D converter AD12, in a wider voltage detection circuit input voltage range, and more It is possible to obtain a detection value that is accurate and has few errors.

[3] Third Embodiment FIG. 5 is a schematic circuit configuration diagram of a power supply device according to a third embodiment.
In FIG. 5, the same parts as those of the first embodiment of FIG. 1 are denoted by the same reference numerals, and detailed description thereof is omitted.
First, the configuration of the voltage detection circuit will be described.
The voltage detection circuit 14B of the power supply device 10B of the third embodiment includes a resistor R31 having one end connected to the positive terminal Pt of the conversion circuit 21, and a resistor R32 connected in series to the other end of the resistor R31. The resistor R31 and the resistor R32 constitute a first voltage dividing circuit.

  The voltage dividing point of the resistor R31 and the resistor R32 is connected to the anode terminal of the first clamp diode D21 whose cathode terminal is connected to the power supply VCC of the voltage detection circuit 14, and the anode terminal of the first clamp diode D21 is connected to the ground. Is connected to a ceramic capacitor C21 for noise removal. The first buffer circuit BF21 is connected to the subsequent stage of the first clamp diode D21.

The voltage detection circuit 14B includes a resistor R41 having one end connected to the negative terminal Nt of the conversion circuit 21, and a resistor R42 connected in series to the other end of the resistor R41. The resistor R41 and the resistor R42 are: A second voltage dividing circuit is configured.
The voltage dividing point of the resistor R41 and the resistor R42 is connected to the anode terminal of the second clamp diode D22 whose cathode terminal is connected to the power supply VCC of the voltage detection circuit 14B. The anode terminal of the second clamp diode D22 is connected to the ground. Is connected to a ceramic capacitor C22 for noise removal. The second buffer circuit BF2 is connected to the subsequent stage of the second clamp diode D22.
Further, the output terminal of the first buffer circuit BF21 is connected to the first A / D conversion circuit AD21 via the A / D conversion port of the ECU 24B, and the output terminal of the second buffer circuit BF22 is connected to the A / D conversion port of the ECU 24A. To the second A / D conversion circuit A22.

In the above configuration, the first clamp diode D21 and the second clamp diode D22 are manufactured by the same process and have characteristics that can be regarded as substantially the same characteristics.
Similarly, the first buffer circuit BF21 and the second buffer circuit BF22 are manufactured by the same process and have characteristics that can be regarded as substantially the same characteristics.
Further, the first A / D conversion circuit AD21 and the second A / D conversion circuit AD22 of the ECU 24B are also manufactured by the same process and have characteristics that can be regarded as substantially the same characteristics.

Next, the operation of the voltage detection circuit 14B will be described.
Here, if the current flowing out of the resistor R31 is Ia, the current flowing into the resistor R32 is Ib, and the leakage current of the first clamp diode D21 is IL21,
Ib = Ia + IL21
The voltage V21 is
V21 = Ib × R32
= (Ia + IL21) × R32
It becomes.

Further, the output voltage V22 of the first buffer circuit BF21 is given by assuming that the offset voltage of the first buffer circuit BF21 is Voffset.
V22 = V21 + Voffset
It becomes.
Here, the VDV11 corresponding to the voltage detection data DV11 output by the A / D conversion circuit AD21 of the ECU 24 is assumed that the conversion error by the A / D conversion circuit AD21 is VAD21.
VDV11 = V21 + VAD21
= (Ia + IL21) × R32 + Voffset + VAD21
It becomes.

Similarly, if the current flowing out of the resistor R41 is Ic, the current flowing into the resistor R42 is Id, and the leakage current of the second clamp diode D12 is IL21,
Ic = Ib
= Ia + IL21
When the leakage current of the second clamp diode D12 is IL21, the voltage V23 is
V23 = (Ic + IL21) × R42
It becomes.

Further, the output voltage V14 of the second buffer circuit BF 22, when the offset voltage of the second buffer circuit BF 22 and Voffset,
V24 = V23 + Voffset
It becomes.
Here, VDV12 corresponding to the voltage detection data DV12 output by A / D converter circuit AD 22 of ECU24, when the VAD22 conversion errors due to the A / D conversion circuit AD22,
VDV12 = V11 + VAD1
= (Ic + IL21) × R42 + Voffset + VAD22
It becomes.

Therefore, if R32 = R42,
VPN = VDV11−VDV12
= (Ia + Ic) / R32
It becomes. Here, since Ic << Ia,
VPN ≒ Ia / R32
It becomes.

FIG. 6 is an explanatory diagram of the effect of the third embodiment.
In FIG. 6, LP is an error characteristic of the voltage detection circuit shown in FIG.
According to the third embodiment, as shown in FIG. 6, the influence of the leakage current values of the first clamp diode D21 and the second clamp diode D22 and the first buffer circuit BF21 without impairing the continuity of the detection values. In addition, the influence of the offset voltage of the second buffer circuit BF22 and the influence of the quantization error of the first A / D conversion circuit AD21 and the second A / D conversion circuit AD22 are removed, and the input voltage range is wider. It is possible to obtain a detection value that is accurate and has few errors.

  In the description of FIG. 1, FIG. 3, and FIG. 5, the capacitor 21c, the capacitor 22b, and the capacitor 23b are provided separately. However, if a compact layout is possible and the wiring inductance component is small, one capacitor is provided. It is also possible to replace with.

10, 10A, 10B Power supply device 11 Motor 12 Battery 13 Motor 14, 14A, 14B Voltage detection circuit 22 First power conversion circuit (inverter circuit, converter circuit)
23 Second power conversion circuit (converter circuit)
24, 24A, 24B ECU
AD1 A / D conversion circuit AD11, AD21 First A / D conversion circuit AD12, AD22 First A / D conversion circuit BF1, BF11, BF21 First buffer circuit BF2, BF12, BF22 Second buffer circuit D1, D11, D21 First clamp Diodes D2, D12, D22 Second clamp diode Nt Negative side terminal Pt Positive side terminal R11, R12, R21-R24 Resistance (voltage dividing circuit)
R31, R32, R41, R42 Resistance (voltage divider circuit)

Claims (4)

In a voltage detection circuit that sets a reference ground potential of a power conversion circuit and detects a detection target voltage and a reference voltage with respect to the reference ground potential,
A voltage dividing circuit in which at least three or more resistors are connected in series to divide the voltage to be detected based on the reference ground potential;
A clamp diode and a buffer circuit, which are manufactured in the same process and have the same characteristics as each other , are connected to two different voltage dividing points of the voltage dividing circuit, and based on the output voltage of each buffer circuit. To obtain a difference voltage between the detection target voltage and the reference voltage,
A voltage detection circuit. The voltage detection circuit according to claim 1, wherein
An A / D conversion circuit that receives the output voltage of the buffer circuit, performs analog / digital conversion, and outputs the digital data;
Obtaining difference voltage data corresponding to a difference voltage between the detection target voltage and the reference voltage based on output data of the A / D conversion circuit;
A voltage detection circuit. The voltage detection circuit according to claim 1 or 2,
The power conversion circuit is mounted on a vehicle and performs power conversion of power supplied from an in-vehicle generator or in-vehicle battery driven by an engine to supply driving power to the in-vehicle motor.
A voltage detection circuit. A voltage detection circuit according to any one of claims 1 to 3,
A power conversion circuit that is mounted on a vehicle and that converts power supplied from an in-vehicle generator or in-vehicle battery driven by an engine to supply driving power to the in-vehicle motor;
A control circuit for controlling the power conversion of the power conversion circuit based on the output of the voltage detection circuit;
A power supply device comprising:

Images