JP3446611B2 - DC high voltage measuring device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a DC high voltage measuring device having a simple structure.

[0002]

2. Description of the Related Art As a direct current high voltage measuring device, a conventional one has
There is provided a structure as shown in. Connect the isolation amplifier 2 to the resistor divider circuit 1 consisting of four resistors,
The measured voltage is changed to a maximum of 5V and output to the arithmetic unit 4.
The isolation amplifier 2 operates by being supplied with power from the isolation power supply 3 and functions as a buffer, and electrically isolates the output voltage from the high voltage to be measured. The arithmetic unit 44 calculates and measures the voltage to be measured by the input voltage and the voltage division ratio of the resistance voltage dividing circuit.

[0003]

However, in the above configuration, the measurement accuracy is related to the voltage division accuracy of the resistance voltage dividing circuit 1, and is influenced by the input impedance of the insulation type amplifier 2. Therefore, it is necessary to set the input impedance high. However, if the input impedance is high, noise is apt to occur and influences the measurement, so there is a limit to improvement of the measurement accuracy. Also, by setting the resistance value of the resistance voltage divider circuit low, it is possible to contribute to the improvement of measurement accuracy.
In this case, there is a problem that a large current flows and the resistance becomes large. The present invention has been made in view of the above problems, and an object of the present invention is to provide a DC high-voltage measuring device that is not easily affected by noise and has a simple configuration.

[0004]

Therefore, the invention according to claim 1 is to provide a signal output circuit for outputting a charging pulse signal of a predetermined width, a capacitor for accumulating a voltage to be measured, and a capacitor connected in parallel with the capacitor. A current discharge circuit, a discharge signal output circuit that outputs a discharge pulse signal by changing the voltage only while the constant current discharge circuit operates, and a charge that connects the measured voltage to the capacitor in response to the charge pulse signal. A circuit and an arithmetic circuit that calculates the voltage to be measured by the charge pulse signal and the discharge pulse signal are provided.

When the charging pulse signal is output, the charging circuit responds and operates. As a result, the capacitor is connected to the voltage to be measured and charged. The voltage to be measured is accumulated and held in the capacitor by charging. During that time, current flows through the constant current discharge circuit and the discharge pulse signal is output.

When the charge pulse signal ends, the capacitor then discharges to the constant current circuit. However, since the discharge current is a constant current, the discharge time is proportional to the measured voltage. The discharge pulse width is thus the charge pulse width plus the discharge time of the capacitor. The arithmetic circuit can subtract, for example, the charge pulse width and the discharge pulse width to obtain a portion proportional to the measured voltage, and the measured voltage can be calculated by the proportional relationship.

A constant current diode can be used in the constant current circuit. Since the arithmetic circuit is provided with the low-pass filter, the discharge pulse width is displayed instead of the potential here. The voltage to be measured can be calculated in a predetermined proportional relationship by subtracting only the amount corresponding to the charging pulse. Since the arithmetic circuit has an AND circuit that inverts the discharge pulse and the charge pulse to the polarities and performs an AND operation, the measured voltage calculation can obtain the measured voltage only by proportionally calculating the output of the AND circuit.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Next, embodiments of the present invention will be described with reference to Examples. FIG. 1 is a diagram showing the configuration of the first embodiment. The charging circuit 5 includes a transistor 51 whose base is connected to the A terminal of the arithmetic unit 4, a photocoupler 58, and a transistor 54. The light emitting diode 53 of the photocoupler 58 is connected to the collector of the NPN transistor 51 by the resistor 55 in the forward direction.

The phototransistor 52 of the photocoupler 58 is an NPN type, the emitter of which is connected to the negative terminal of the voltage to be measured, and the collector of which is connected to the base of the PNP type transistor 54 through the resistor 56. The emitter of the transistor 54 is connected to the positive terminal of the voltage to be measured, and the collector is connected to the capacitor 61. A resistor 57 is connected between the emitter and the base. The constant current discharge circuit 6 is connected to both ends of the capacitor 61. The constant current discharge circuit 6 is configured by connecting a light emitting diode 63 and a constant current diode 62 in the forward direction.

The discharge signal output circuit 7 is composed of an NPN type phototransistor 71, from the emitter to the B of the arithmetic unit 4.
Connected to the terminal. The emitter is connected to ground via resistor 72. Capacitor 61, emitter of transistor 51, emitter of phototransistor 52 to ground,
The earth of the arithmetic unit 4 is connected to each.

The collector of the phototransistor 71 is connected to the power supply terminal of the arithmetic unit 4 together with the positive terminal of the light emitting diode 53, and 5 V is supplied from the outside. The phototransistor 71 and the light emitting diode 63 form a photocoupler 64. The arithmetic unit is composed of an arithmetic unit centering on a CPU, and includes a signal output circuit for outputting a charge pulse signal and a discharge pulse signal input circuit. The charge pulse signal is output from the A terminal and the discharge pulse signal is input from the B terminal.

Next, the operation will be described with reference to the time chart of FIG. A charging pulse signal having a predetermined width as shown in (a) is output from the A terminal of the arithmetic unit 4. When this signal is applied to the base of the transistor 51, the collector and the emitter are brought into conduction, and a positive current flows through the light emitting diode 53 to turn on the light. As a result, the phototransistor 52 becomes conductive and a voltage drop occurs in the resistor 57. The amount of voltage drop is determined by the resistance ratio of the resistors 57 and 56, and is set so that the transistor 54 becomes conductive. As a result, the measured voltage is connected to the capacitor 61. By charging, the capacitor 61 holds a voltage having the same height as the measured voltage.

While the voltage to be measured and the capacitor 61 are connected, a current flows through the constant current discharge circuit 6 and the light emitting diode 63 is turned on. When the phototransistor 71 becomes conductive, the discharge pulse signal having the same width as the charge pulse signal is output to the B terminal of the arithmetic unit 4.

When the discharge pulse signal disappears, the capacitor 61 then discharges through the light emitting diode 63. Since the discharge current is a constant current, the discharge has a time proportional to the measured voltage. The change in the output voltage of the capacitor 61 is shown in FIG. That is, while the charge pulse signal is output, the capacitor 61 holds the same voltage V as the measured voltage, and when the charge pulse signal disappears, the voltage drops according to the proportional constant k. The proportional constant k is the discharge current and the capacitance of the capacitor. Can be decided As a result, a signal corresponding to the discharge of the capacitor 61 is input to the B terminal of the arithmetic unit 4 in addition to the signal having the same width as the charging pulse signal. Therefore, the discharge pulse signal applied to the B terminal of the arithmetic unit 4 is the charge pulse signal plus the discharge time t of the capacitor 61 as shown in (c). The discharge time of the capacitor 61 is obtained by multiplying the proportional constant k by the measured voltage v.

The arithmetic unit 4 subtracts the charge pulse signal width from the discharge pulse signal width, extracts the discharge time t of the capacitor 61, and calculates the measured voltage v by using the proportional constant k. The arithmetic unit 4 constitutes the arithmetic circuit of the present invention. The present embodiment is configured as described above, and the measured voltage is converted into time by holding the measured voltage in the capacitor and discharging it in the constant current discharge circuit. The measured voltage is calculated and detected by measuring the time. In this way, the entire structure is simplified and the impedance does not influence the measurement result. It is highly accurate and can be used even in a noisy environment.

FIG. 3 is a diagram showing a modification of this embodiment.
In the above embodiment, the photocoupler 58 is used to output the charging pulse signal to electrically isolate it from the high voltage side. However, in this modification, the photocoupler 58 is omitted and a transistor 52 ′ is used instead. Has become. Others are the same as in the embodiment. This eliminates the electrical isolation between the measured voltage and the arithmetic unit 4, but the configuration is simpler.

Next, a second embodiment will be described. This embodiment corresponds to the discharge signal output circuit 7 of the first embodiment.
A low-pass filter circuit 8 is connected between the above and the arithmetic unit 4. Here, the arithmetic unit 41 is used instead of the arithmetic unit 4. The other points are similar to those of the first embodiment. The low-pass filter circuit 8 uses a circuit having a high damping property in which two low-pass filter circuits each including a resistor R and a capacitor C are stacked. The low-pass filter circuit 8 attenuates high-frequency noise, integrates and outputs a low-frequency discharge pulse signal.

The discharge pulse signal from the discharge signal output circuit 7 is converted into an analog signal by integration in the low pass filter circuit 8. The arithmetic unit 41 measures the output voltage of the low-pass filter circuit 8, subtracts the charging pulse amount, and calculates the measured voltage by proportional calculation. The arithmetic unit 41 and the low-pass filter circuit 8 form the arithmetic circuit of the present invention.

Also in this embodiment, the same effect as that of the first embodiment can be obtained, and the effect of isolating high frequency noise can be obtained by using the low-pass filter circuit. Further, since the measurement signal is analog, the arithmetic unit can be configured in analog.

FIG. 5 shows the configuration of the third embodiment. This embodiment is configured by adding an AND operation circuit 9 between the discharge signal output circuit 7 and the operation device 4 to the first embodiment. The other points are similar to those of the first embodiment. Here, the arithmetic unit 42 is used instead of the arithmetic unit 4. The AND operation circuit 9 is composed of an AND circuit 91 and an inverting circuit 92. The inverting circuit 92 inverts the polarity of the discharge pulse signal from the A terminal of the arithmetic unit 42 and outputs it to the AND circuit 91. AN
The D circuit 91 takes the logical sum of the inverted charge pulse signal and the discharge pulse signal from the discharge signal output circuit 7 and outputs it to the arithmetic unit 41. By taking the logical sum, only the discharge time of the capacitor 61 remains as a signal in the output signal,
In the arithmetic unit 42, the calculation for obtaining it is eliminated, and the measured voltage can be calculated only by measuring the discharge time t of the capacitor 61. Arithmetic unit 42 and AND arithmetic circuit 9
Constitutes the arithmetic circuit of the present invention. According to this embodiment, the same effect as the first embodiment can be obtained, and
Since the signal input to the arithmetic unit is only the time t which is proportional to the measured voltage, the arithmetic burden on the arithmetic unit is reduced.

[0021]

According to the present invention, a signal output circuit for outputting a charging pulse signal of a predetermined width, a capacitor for accumulating a measured voltage, a constant current discharging circuit connected in parallel with the capacitor, and a constant current discharging circuit. The charge pulse has a discharge signal output circuit that changes the voltage only while the circuit is operating and outputs a discharge pulse signal, and a charge circuit and an arithmetic circuit that connect the measured voltage to the capacitor in response to the charge pulse signal. While the signal is output, the measured voltage charges the capacitor and the voltage is held. When the charging pulse signal ends,
The capacitor discharges into the constant current discharge circuit, causing the discharge signal output circuit to form a discharge pulse.

Since the discharge pulse width is proportional to the voltage to be measured, the arithmetic circuit can obtain the voltage to be measured by a predetermined proportional calculation by measuring it. Noise is unlikely to be included in the value calculated in this way, the voltage can be measured with high accuracy, and the configuration is simplified.

By providing a low pass filter,
High frequency noise is dropped. Since the AND operation circuit extracts the capacitor discharge time, the operation for that time is omitted.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of an example.

FIG. 2 is a time chart in the example.

FIG. 3 is a diagram showing a modification of the embodiment.

FIG. 4 is a diagram showing a configuration of a second exemplary embodiment.

FIG. 5 is a diagram showing a configuration of a third exemplary embodiment.

FIG. 6 is a diagram showing a conventional example.

[Explanation of symbols]

1 resistance voltage divider circuit 2 isolated amplifier 3 isolated power supply 4, 41, 42, 44 arithmetic unit 5 charging circuit 6 constant current discharge circuit 7 Discharge pulse output circuit 8 low pass filter 9 AND operation circuit 51, 54 transistors 52, 64 Phototransistor 53, 63 Light emitting diode 55, 56, 57, 72 Resistance 58,71 Photo coupler 61 Capacitor 62 constant current diode 91 AND circuit 92 Inversion circuit R resistance C capacitor

Continuation of the front page (56) Reference JP-A-52-35670 (JP, A) JP-A-52-35851 (JP, A) JP-A-54-160285 (JP, A) JP-A-6-95806 (JP , A) JP-A-6-242159 (JP, A) JP-A-8-66642 (JP, A) Actually opened 63-19275 (JP, U) Actually opened 63-193368 (JP, U) Actually opened 7-41473 (JP, U) Actually opened Sho 64-51879 (JP, U) Actually opened 3-68019 (JP, U) Actually opened 63-188572 (JP, U) Actually opened 5-30774 (JP, U) Japanese Patent Publication No. 48-26796 (JP, B1) (58) Fields investigated (Int.Cl. ⁷ , DB name) G01R 19 / 00-19 / 32

Claims (4)

(57) [Claims] 1. A signal output circuit for outputting a charge pulse signal of a predetermined width, a capacitor for accumulating a voltage to be measured, a constant current discharge circuit connected in parallel with the capacitor, and a period during which the constant current discharge circuit operates. A discharge signal output circuit that changes the voltage only to output a discharge pulse signal, a charging circuit that connects the measured voltage to the capacitor in response to the charging pulse signal, and the charging pulse signal and the discharging pulse signal. A DC high-voltage measuring device having a calculation circuit for calculating the measured voltage. 2. The DC high voltage measuring device according to claim 1, wherein a constant current diode is used in the constant current discharge circuit. 3. The DC high voltage measuring device according to claim 1, wherein the arithmetic circuit includes a low-pass filter connected to the discharge signal output circuit. 4. The arithmetic circuit includes an AND circuit, and the discharge signal output circuit and the signal output circuit are connected to the AND circuit with their output polarities inverted from each other. DC high voltage measuring device.