JP2006242610A - Single power source voltage measuring circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a single power source voltage measuring circuit which does not cause a dead zone in wide range in measuring a high voltage of a single polarity with an operational amplifier with a single power source. <P>SOLUTION: The single power source voltage measuring circuit is provided with a voltage divider dividing the voltage with a single polarity of the voltage measuring point, an operation amplifier of a single source converting the voltage divided with the voltage divider into impedance and outputting. A reference voltage generation means 22 maintaining the electric potential on a non-voltage measuring side in a series circuit of partial resistances R1, R2 constituting the voltage divider at a reference voltage value over an output voltage limit value and below an input voltage limit value of the single power source operation amplifier 20. For the reference voltage generation means, a variable shunt type stabilized power source circuit is used, for example. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a single power supply voltage measurement circuit that can measure a unipolar voltage over a wide voltage range using a single power supply operational amplifier.

Conventionally, in a vehicle drive system that requires a large driving force, a configuration as shown in FIG. 4 has been adopted in order to achieve high efficiency and energy saving.
In FIG. 4, reference numeral 100 denotes a direct current power supply, which uses a power supply from an overhead wire or a battery. The step-up / step-down converter 200 to which the voltage of the DC power supply 100 is supplied allows the voltage V _L (eg, 200 [V]) of the DC power supply 100 to be applied to the voltage V _H (eg, 1000) suitable for driving the three-phase motor 400 when the vehicle is driven. When the vehicle is braked, the voltage V _H of the three-phase motor 400 operating as a generator is stepped down to the voltage V _L and regenerated to the DC power source 100.

The inverter 300 connected to the step-up / down converter 200 controls the switching element on / off using the output voltage of the step-up / step-down inverter 200 as a power supply voltage during driving of the vehicle, and drives the motor 400 by flowing a current through each phase on the AC output side. The speed of the electric motor 400, that is, the vehicle speed changes depending on the switching frequency.
When the vehicle is braked, the switching element is turned on / off in synchronization with the voltage generated in each phase, so that a so-called rectification operation is performed, and the three-phase AC voltage output from the electric motor 400 is converted into a DC voltage to increase / decrease the voltage. It is regenerating on the converter 200 side.

Here, FIG. 5 is a diagram showing an internal configuration of the step-up / down converter 200.
In FIG. 5, switches SW1 and SW2 are semiconductor switching elements IGBT1 and IGBT2 connected in series between the DC input terminal of the inverter 300 and GND (ground), and free-wheeling diodes D1 and D2 connected in reverse parallel thereto, respectively. It is comprised by. CNT1 and CNT2 are control circuits for the switching elements IGBT1 and IGBT2.
A connection point between the switching elements IGBT1 and IGBT2 is connected to the positive electrode of the DC power supply 100 via a reactor L. The collector of the switching element IGBT2 is connected to the DC input terminal of the inverter 300, and a capacitor C is connected between the collector and GND.

The principle of the step-up / step-down in FIG. 5 will be described below. FIG. 6 shows a waveform of a current flowing through the reactor L (its inductance value is also L) during boosting.
- step-up operation (1) switching element IGBT1 is on (conducting) Then a current i flows through the reactor L, the energy of the ^Li 2/2 is accumulated.
The current change rate di / dt during this period is V _L / L as shown in FIG.
(2) When the switching element IGBT1 is turned off (non-conducting), a current flows through the diode D2 on the switching element IGBT2 side, and energy stored in the reactor L is sent to the capacitor C.
The current change rate di / dt during this period is (V _L −V _H ) / L as shown in FIG.
By repeating the above operation, the voltage of the capacitor C is boosted to a voltage higher than the voltage of the DC power supply 100.

• When the step-down operation (1) switching elements IGBT2 is turned on, a current i flows through the reactor L from the positive electrode side of the capacitor C, the energy of the ^Li 2/2 is accumulated.
(2) When the switching element IGBT2 is turned off, a current flows through the diode D1 on the switching element IGBT1 side, and the energy stored in the reactor L is regenerated in the DC power supply 100.
By repeating the above operation, the voltage of the capacitor C is gradually reduced.

Therefore, the temperature output voltage V _H of the step-down converter 200 is adjustable by changing the on-duty (the ratio of the conduction period to the switching period of the switching element IGBT 1, IGBT 2), the on-duty is be represented by Equation 1 Can do.
[Formula 1]
V _L / V _H = on duty [%]
However, actually because there are fluctuations of the fluctuations and supply voltage of the load to monitor the output voltage V _H of the buck-boost converter 200, which feedback controls the on-duty of the switching element IGBT 1, IGBT 2 to match the command value is doing.

Figure 7 shows a block diagram of IPM (Intelligent Power Module) that the output voltage V _H of the buck-boost converter performs feedback control to match the buck-boost command value. When roughly classified, the upper arm switching unit 220, the lower arm switching unit 210, and the control unit 230 are configured. Since each unit needs to be electrically insulated, the photocouplers 241 to 243, a pulse transformer (not shown), etc. Is used to send and receive signals.

In FIG. 7, switching elements IGBT1A and IGBT2A connected in series correspond to the switching elements IGBT1 and IGBT2 in FIG. 5, but include an auxiliary emitter in the example of FIG.
The upper arm switching unit 220 includes an overcurrent detection element 221 and an overheat detection element 222 of the switching element IGBT2A, and the IGBT protection circuit 223 performs control for turning off the gate of the switching element IGBT2A by the detection output of each element 221 and 222. A signal can be output to the gate driving circuit 224.
Similarly, the lower arm switching unit 210 includes an overcurrent detection element 211, an overheat detection element 212, an IGBT protection circuit 213, and a gate drive circuit 214.

Further, the lower arm switching unit 210 is provided with a V _H detection circuit 215 that outputs a PWM signal having a pulse width corresponding to the magnitude of the output voltage V _H of the buck-boost converter.
The V _H detection circuit 215 includes a voltage dividing circuit 216 that divides the output voltage V _H , a level adjuster 217 that adjusts the level of the output voltage, a triangular wave generator 218, an output signal of the level adjuster 217, and a triangular wave And a comparator 219 for outputting a binarized PWM signal.

On the other hand, the control unit 230 controls the gate signals of the switching elements IGBT1A and IGBT2A. That is, the control unit 230 includes a low-pass filter 231 to which the output signal of the photocoupler 242 is input, a step-up / step-down command value (V _H command value), and an output signal of the low-pass filter 231 (corresponding to a V _H detection value). and _{V H} comparator 232 for comparing the switching element IGBT1A on the basis of the output signal, and a gate signal generator 233 for generating the gate signals for the IGBT 2a, the gate signal via a photocoupler 241, 243 The signals are input to the gate drive circuits 214 and 224, respectively.

FIG. 8 shows the configuration of the voltage dividing circuit 216 in FIG. 7, and high voltage dividing resistors R1 and R2 (the resistance value is also the same symbol R1) between the measurement point of the voltage V _H and the power supply GND. , R2) are connected in series. That is, the voltage across the resistor R2 (voltage at the voltage dividing point) V ₂ is V ₂ = V _H · {R2 / (R1 + R2)}.
The voltage V ₂ is input to the non-inverting input terminal of the bi-power operational amplifier 216Q as a buffer having a positive power 216P and the negative power source 216N, converted divided voltage V _OUT to a low impedance level controller of FIG. 7 It is output to 217.

Now, the amplitude of the triangular wave output from the triangular wave generator 218 in FIG. 7 is adjusted to change between 0 [V] and V _HMAX · {R2 / (R1 + R2)}.
The triangular wave and the divided voltage via the level adjuster 217 are compared by the comparator 219, and a binarized PWM signal having a duty of 0 to 100 [%] is output. A current is passed through the light emitting diode of the photocoupler 242 by this PWM signal, the photocurrent generated from the light receiving transistor is converted into a voltage by a load resistor, and then filtered by the low pass filter 231 to be converted into an analog signal. This signal is input to the V _H comparator 232 as a signal corresponding to the V _H detection value as described above.

  In Patent Document 1 below, in a motor control device that is capable of regenerative operation including a secondary battery and an inverter, a voltage that depends on the current flowing through the motor is input to an operational amplifier of a single power source, and the output voltage is A motor control device is described in which the operating state of the motor is monitored depending on whether or not it is within a predetermined range centered on a value of ½ of the power supply voltage.

JP-A-9-131083 ([0040] to [0051], FIGS. 1 to 3 etc.)

The operational amplifier 216Q shown in FIG. 8 uses a positive and negative dual power supply, and as the output of the operational amplifier 216Q, it is possible to output a _divided voltage of V _H in the entire range of measured voltage (0 to V _HMAX ). it can.
On the other hand, the IPM as shown in FIG. 7 has been conventionally required to be reduced in cost and reduced in size, and if the operational amplifier in the voltage dividing circuit 216 can be made a single power supply, the above request can be met.

However, a single supply of the operational amplifier of the power supply voltage is +5 [V] (e.g., NEC "μPC842" Co., Ltd.) Output voltage range _{(V OUTL ~V OUTH)} is approximately 0.7 [V] to 3 .5 [V].
Therefore, when the operational amplifier 216Q in FIG. 8 is replaced with the above-described single power supply operational amplifier (μPC842), as shown in the input / output characteristics of FIG. 9 (scales on the vertical and horizontal axes are different), for example, When V _HMAX = 1000 [V], which is the maximum value of the voltage to be measured, if the voltage division ratio (= (R1 + R2) / R2) is 286, the output voltage of the operational amplifier is 3.5 [V], which is the upper limit value. However, since the lower limit is about 0.7 [V], the output voltage of the operational amplifier is fixed at about 0.7 [V] in the range of V _H = 0 to about 200 [V] by proportional distribution. As a result, there is a problem that V _H cannot be accurately detected and a dead zone in the voltage measurement range is generated.
Further, Patent Document 1 described above does not particularly disclose specific means for eliminating the above-described dead band in the voltage measurement range.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a single power supply voltage measurement circuit that prevents a dead band from being generated over a wide voltage range when measuring a unipolar high voltage with a single power supply operational amplifier.

In order to solve the above-mentioned problem, the invention described in claim 1 is a voltage dividing unit that divides a unipolar voltage at a voltage measuring point, and a single unit that impedance-converts and outputs the voltage divided by the voltage dividing unit. In a single power supply voltage measurement circuit comprising a power supply operational amplifier,
Reference voltage generating means for holding the potential on the non-voltage measurement point side of the voltage dividing means at a reference voltage value that is greater than or equal to the output voltage lower limit value of the operational amplifier and less than or equal to the input voltage upper limit value is provided.
Accordingly, in the present invention, it is possible to measure a wide range of voltages that are equal to or higher than the reference voltage and reach the measured voltage upper limit value (determined by the output voltage upper limit value of the operational amplifier).

  According to a second aspect of the present invention, in the first aspect, the measured voltage is compared with the triangular wave whose amplitude changes corresponding to 0 to 100% of the measured voltage value and the output signal of the operational amplifier. Means are provided for converting the value into a pulse of a predetermined duty.

According to a third aspect of the present invention, in the second aspect of the present invention, the apparatus further includes a transmission unit that insulates and transmits the pulse.
This transmission means may be configured by a photocoupler as described in claim 4.

  Further, as the reference voltage generation means, for example, a variable shunt type stabilized power supply circuit can be used as the reference voltage generating means.

  According to the present invention, a low voltage to be measured can be measured without causing a dead band while using an operational amplifier of a single power supply, and can be applied to a wide range of unipolar voltage measurements.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. First, FIG. 1 is a circuit configuration diagram of an embodiment of the present invention.
In FIG. 1, reference numeral 20 denotes a single power supply operational amplifier such as “μPC842” manufactured by NEC Corporation described above, which converts an input voltage into a low impedance and outputs it. A DC power supply (positive power supply) 21 is connected to the positive power supply terminal of the operational amplifier 20, and the negative power supply terminal is grounded. The non-inverting input terminal is connected to the interconnection point (voltage dividing point) of the voltage dividing resistors R1 and R2, and the inverting input terminal is connected to the output terminal of the operational amplifier 20.

  Reference numeral 23 denotes a voltage measurement point to which the voltage to be measured is applied, specifically, an output terminal of the buck-boost converter 200 in FIG. 5 and an output terminal of the upper arm switching unit 220 in FIG. A series circuit of the voltage dividing resistors R1 and R2 and the reference voltage generating means 22 are connected in series between the voltmeter side point 23 and GND. Further, the reference voltage generating means 22 is supplied with power from the DC power source 21 via a resistor R3.

Here, as the reference voltage generating means 22, a variable shunt-type stabilized power supply circuit capable of stably outputting a voltage equal to or higher than the output voltage lower limit value of the single power supply operational amplifier 20 is used.
As an example of this stabilized power supply circuit, for example, “μPC1944T” manufactured by NEC Corporation can be used, and the output voltage lower limit value V _outL of the single power supply operational amplifier 20 is 0.7 [V] or higher. 1.26 [V] can be output as the reference voltage V _shunt . The reference voltage V _shunt is applied to one end of the voltage _dividing resistor R2 on the non-voltage measurement point side. The specific configuration of the reference voltage generating means 22 is not particularly limited as long as it can output the predetermined DC voltage with high accuracy and stability.
Since the output voltage (reference voltage) of the variable shunt-type stabilized power supply circuit described above is variable by an external resistor, a desired reference voltage can be output according to the single power supply operational amplifier 20 or the voltage to be measured.

The resistance values of the voltage _dividing resistors R1 and R2 are 3.5 [V, which is the upper limit value of the output voltage _VOUT of the single power supply operational amplifier 20 when the maximum value V _{HMAX of the} measured voltage is 1000 [V]. ] Not to exceed.
For example, when V _HMAX is 1000 [V] and V _shunt is 1.26 [V], the voltage across the series circuit of the voltage dividing resistors R1 and R2 is 998.74 [V]. If the current flowing through the series circuit of the voltage dividing resistors R1 and R2 is 0.5 [mA], the combined resistance of the series circuit is 1997.48 [kΩ], and the voltage dividing ratio (= (R1 + R2) / R2) is the same as the conventional one. 286, R1 = 1990.05≈1990 [kΩ], and R2≈6.99≈7 [kΩ].
Therefore, if the voltage dividing resistors R1 and R2 are set to these values, the output voltage _VOUT of the operational amplifier 20 does not exceed the upper limit value.

In this case, the voltage _{V 2} of the voltage dividing point of the voltage dividing resistors R1, R2 is represented by Equation 2. Needless to say, this voltage is less than or equal to the input voltage upper limit value of the operational amplifier 20.
[Formula 2]
V ₂ = (V _H −V _shunt ) / R _r + V _shunt
R _r : partial pressure ratio (= (R1 + R2) / R2)
V _shunt : Output voltage (reference voltage) of the reference voltage generating means 22
V _H : Voltage at voltage measurement point 23

FIG. 2 shows input / output characteristics of the single power supply operational amplifier 20 shown in FIG. In FIG. 2, the scales of the vertical axis and the horizontal axis are different, and the reference voltage V _shunt on the horizontal axis is exaggerated in magnitude.
As is apparent from FIG. 2, according to this embodiment, even when the voltage V _{H at the} voltage measurement point 23 is 0 [V], the reference voltage V _shunt (= 1.26 [V ]) Appears as an offset, but in the range from the voltage V _{H at the} voltage measurement point 23 exceeding the reference voltage V _shunt to the maximum value V _HMAX , a _divided voltage corresponding to V _H is output from the operational amplifier 20. Will be.
That is, in this embodiment, the dead band of the voltage measurement range is 0 to 1.26 [V] (= V _shunt ), which corresponds to about 0.13 [%] with respect to the full scale (1000 [V]). 8 can be significantly narrower than 0 to 200.2 [V] (about 20 [%] with respect to full scale) in the prior art.

FIG. 3 shows a V _H detection circuit (FIG. 3) in the lower arm switching unit when the single power supply voltage measurement circuit according to this embodiment is applied to an IPM that controls the output voltage V _H of the buck-boost converter as in FIG. 7 is equivalent to reference numeral 215 in FIG. 7), and a circuit diagram showing a configuration of a control unit (also equivalent to reference numeral 230). Since the single power supply voltage measuring circuit of this embodiment has a function corresponding to the voltage dividing circuit 216 in FIG. 7, when configuring an IPM, the voltage dividing circuit 216 in FIG. Replace with a measurement circuit.

In FIG. 3, the voltage output from the single power supply operational amplifier 20 via the level adjuster 217, and the triangular wave having an amplitude in the range of 1.26 to 3.5 [V] output from the triangular wave generator 218, Are compared by a single power source comparator 219, and a binarized PWM signal having a duty of 0 to 100% is output. Current is passed through the light emitting diode of the photocoupler 242 by this binarized PWM signal, and the photocurrent generated from the light receiving transistor is converted into a voltage by a load resistor, and filtered by the low pass filter 231 to be converted into an analog value. ,Output.
Then, the _{V H} comparator 232 of FIG. 7, the analog output voltage of the low-pass filter 231 as compared to the buck-boost command value, the upper arm and the lower arm switching element IGBT 2a, is to create a gate signal for the IGBT 1a.

As described above, according to the present embodiment, it is possible to realize a voltage measurement circuit with a very small dead band in the voltage measurement range even when the operational amplifier for impedance conversion in the voltage dividing circuit is used with a single power source.
For example, Japanese Patent Laid-Open No. 5-181991 describes a technique for level-shifting a plurality of AC input voltages with a reference voltage in an adding circuit that adds a plurality of AC input voltages using a single power supply operational amplifier. Yes. However, this known technique has a purpose, a configuration, and an action in that it does not measure a unipolar voltage as in the present invention, and creates two reference voltages from a single power source unlike the present invention. It is different.

It is a circuit block diagram of embodiment of this invention. FIG. 2 is an input / output characteristic diagram of the single power supply operational amplifier in FIG. 1. It is a circuit block diagram of the principal part of IPM which has embodiment of this invention. It is a block diagram which shows the conventional vehicle drive system. It is a figure which shows the internal structure of the buck-boost converter in FIG. It is a figure which shows the electric current waveform which flows into a reactor at the time of pressure | voltage rise operation. It is a block diagram of IPM for buck-boost converters. It is a block diagram of the voltage dividing circuit in FIG. FIG. 8 is an input / output characteristic diagram when a single power supply operational amplifier is applied to the voltage dividing circuit of FIG. 7.

Explanation of symbols

20: Single power supply operational amplifier 21: DC power supply 22: Reference voltage generating means 23: Voltage measuring point 217: Level adjuster 218: Triangular wave generator 219: Comparator 231: Low pass filter 242: Photocoupler R1, R2: Voltage dividing resistor R3: Resistance

Claims (5)

In a single power supply voltage measurement circuit comprising: voltage dividing means for dividing a unipolar voltage at a voltage measurement point; and a single power supply operational amplifier for impedance-converting and outputting the voltage divided by the voltage dividing means.
Reference voltage generating means for holding the voltage value on the non-voltage measurement point side of the voltage dividing means at a reference voltage value that is not less than the output voltage lower limit value of the operational amplifier and not more than the input voltage upper limit value is provided. Single power supply voltage measurement circuit. In the single power supply voltage measuring circuit according to claim 1,
Comparing a triangular wave whose amplitude changes corresponding to 0 to 100% of the measured voltage value with an output signal of the operational amplifier, the means for converting the measured voltage value into a pulse of a predetermined duty is provided. Single power supply voltage measurement circuit. In the single power supply voltage measuring circuit according to claim 2,
A single power supply voltage measuring circuit, comprising a transmission means for insulating and transmitting the pulse. In the single power supply voltage measuring circuit according to claim 3,
A single power supply voltage measuring circuit, wherein the transmission means is a photocoupler. In the single power supply voltage measuring circuit according to any one of claims 1 to 4,
A single power supply voltage measuring circuit, wherein the reference voltage generating means is a variable shunt type stabilized power supply circuit.

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