JP3142780B2 - Power meter LSI internal test circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a watt-hour meter internal test circuit for testing the measurement accuracy of an electronic watt-hour meter LSI (large-scale integrated circuit) for calculating a power amount by multiplying a voltage and a current. is there.

[0002]

2. Description of the Related Art Conventionally, as an internal test circuit of such a watt-hour LSI, for example, there is a test circuit having a configuration shown in FIG. In this LSI internal test circuit, a high resolution 2
The two-phase AC voltage output from the phase AC signal generator 1 is controlled by the calculator 4 in accordance with the standard of the watt-hour meter, and it is tested whether the electronic watt-hour meter LSI 5 has the performance satisfying the standard. You.

That is, the AC signal generator 1 generates a first phase voltage V1 corresponding to a voltage to be measured and a second phase voltage V2 corresponding to a current to be measured. The output of the AC signal generator 1 is measured by an AC voltmeter 2. If the measurement result is not within a predetermined accuracy, the output of the AC signal generator 1 is controlled by the calculator 4 via the control line 3. Self-adjusted. That is, the accuracy of the AC signal generator 1 is compensated by the AC voltmeter 2. Watt hour meter L
The SI5 performs pulse width modulation on the first phase voltage V1 corresponding to the voltage to be measured, and multiplies this modulated output by the second phase voltage V2 corresponding to the current to be measured to calculate the electric energy. The watt-hour meter LSI 5 integrates the converted voltage, performs power / frequency (W / F) conversion, and outputs a pulse signal having a frequency proportional to the power amount to the counter 6 as a measured power pulse.

Further, each output voltage V of the AC signal generator 1 is
1 and V2 are also supplied to a W / V converter 7 provided outside the LSI, and the W / V converter 7
The power amount is multiplied by 1 and V2 to calculate the power amount with high accuracy similarly to the LSI 5, and outputs a voltage proportional to the power amount. The V / F converter 8 generates a pulse signal having a frequency proportional to the output voltage of the W / V converter 7 with high precision, similarly to the LSI 5, and outputs the pulse signal to the counter 6 as a reference (master) power pulse.
The counter 6 counts a predetermined number of the measured power pulses output from the watt hour meter LSI 5 and a certain number of master power pulses output from the V / F converter 8, and outputs the counting result to the calculator 4. The calculator 4 is constituted by a personal computer (PC) or the like, compares the received number of power pulses to be measured with the number of master power pulses, and outputs a power meter LSI 5
Find the measurement error of.

[0005]

However, in order to evaluate the performance and accuracy of a wide range of current measurement required for a watt-hour meter by the above-described conventional watt-hour meter LSI internal test circuit, the AC signal generator 1 must High resolution is required. That is, the AC signal generator 1 needs to generate a two-phase AC signal corresponding to a small current to a large current in a wide range with extremely fine and high accuracy, and the AC signal generator 1 is expensive. In addition, in order to generate the master power pulse, which is the reference for error measurement, with high accuracy,
It is necessary to prepare special devices such as the W / V converter 7 and the V / F converter 8. Therefore, the power meter LSI 5 cannot be easily tested by the above-described conventional LSI internal test circuit.

Further, the inside of the power meter LSI 5 and the V /
When the W / V-converted voltage is frequency-converted in the F converter 8, one power pulse is output when the integrated value of the W / V-converted voltage reaches a reference value. However, since the watt-hour meter LSI 5 and the V / F converter 8 of the above-described conventional circuit are supplied with an AC signal that constantly varies at the commercial frequency, the voltage subjected to W / V conversion also varies. In addition, during integration of this voltage, for example, while integration is performed with a positive value, if the voltage to be W / V converted fluctuates and a negative value is input to the integration circuit, the integration value becomes the reference value. It takes time to reach. Therefore, in order to measure the AC power with high accuracy using the watt hour meter LSI 5 and the V / F converter 8 in the above-described conventional test circuit, it is necessary to measure and average the voltage and current to be measured for a long time. is there. For this reason, conventionally, this accuracy measurement for one power meter LSI
As a result, a long time exceeding 0 seconds is required. As a result, the test is costly, hindering the cost reduction of the watt hour meter LSI, and an obstacle to rapid production.

[0007]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problem, and a modulation circuit for pulse-width-modulating a voltage to be measured and a multiplication of the output of the modulation circuit and the current to be measured. The internal circuit of an electronic watt-hour meter LSI having an internal multiplication circuit for calculating the electric energy and a V / F conversion circuit for integrating the output of the internal multiplication circuit and outputting a pulse signal having a frequency proportional to the electric energy is provided. Watt hour meter LSI to be tested
The internal test circuit includes a first DC power supply circuit for generating a DC voltage corresponding to the voltage to be measured, a second DC power supply circuit for generating a DC voltage corresponding to the current to be measured, and a multiplication function by an internal multiplication circuit. An internal multiplier function stop circuit that stops and outputs a signal input from the outside of the watt-hour LSI to the internal multiplier circuit as it is to the V / F converter circuit, multiplies the output of the modulation circuit and the output of the second DC power supply circuit An external multiplier configured outside the watt hour meter LSI, a filter circuit for extracting a DC component from the output of the external multiplier and outputting the extracted DC component to the internal multiplier, and a pulse signal output from the V / F converter And a frequency measuring circuit for measuring the power pulse conversion frequency by the watt-hour meter LSI by using the reference clock to measure the pulse width of

In such a configuration, the DC voltage corresponding to the measured voltage output from the first DC power supply circuit is:
Pulse width modulation is performed by a modulation circuit inside the LSI. The external multiplying circuit multiplies the modulated output by a DC voltage corresponding to the current to be measured output from the second DC power supply circuit to calculate a power amount, and outputs this as a voltage. A direct current component is extracted from this voltage output by a filter circuit, and this direct current component is input to an internal multiplier circuit inside the LSI. At the time of testing inside the LSI, the multiplication function of the internal multiplication circuit is stopped by the internal multiplication circuit function stop circuit, and the DC component input to the internal multiplication circuit is directly output to the V / F conversion circuit inside the LSI. The V / F conversion circuit integrates this DC component, converts the frequency, and outputs a power pulse. The frequency of this power pulse is measured in a frequency measurement circuit using the reference clock as a master, and the measurement error of the watt hour meter LSI is evaluated.

In the present invention, since the DC component of the W / V converted voltage is applied to the V / F conversion circuit as described above, the voltage applied to the V / F conversion circuit is the same as that of the prior art. Does not fluctuate. Therefore, the conventional problem that the integral value decreases during integration during V / F conversion and it takes time to reach the reference value is solved, and the integral value quickly reaches the reference value, and the power pulse is reduced. Is output. In addition, watt hour meter L
Even when the measured voltage / current is given to the SI as a DC signal, the frequency of the power pulse output from the watt hour meter LSI is measured by the frequency measuring circuit using the reference clock. Therefore, the conversion frequency can be obtained from one power pulse, and the AC characteristics of the watt-hour meter LSI can be simulated using a DC signal.

Further, even if the voltage and current to be measured are supplied to the watt-hour meter LSI as a DC signal, the frequency of the power pulse can be measured. Therefore, it is not necessary to use a conventional high-resolution and expensive AC signal generator. Disappears. Therefore, the voltage corresponding to the measured voltage / current can be easily generated by the DC power supply circuit. Further, the multiplication function of the internal multiplication circuit is stopped by the internal multiplication function stop circuit at the time of testing the LSI, so that the V /
The F conversion circuit can be used for testing the LSI, and it is not necessary to provide a special V / F conversion circuit outside the LSI as in the related art.

[0011]

Next, a description will be given of a watt hour meter LSI internal test circuit according to an embodiment of the present invention.

FIG. 2 is a block diagram showing the internal circuit configuration of the electronic watt-hour meter LSI used in the watt-hour meter LSI internal test circuit according to the present embodiment.

A reference voltage source 31 is provided inside the watt hour meter LSI 22, and a reference voltage output from the voltage source 31 is supplied to a triangular wave generating circuit 32 and a V / F converter 33. The modulation circuit 34 receives the triangular wave output from the triangular wave generation circuit 32 and uses the triangular wave to generate a voltage at the voltage input terminal 3.
5 is subjected to pulse width modulation (PW).
M). The output of the modulation circuit 34 is output to a terminal 41 and is also applied to an internal multiplication circuit 36 via a switch (first switch) 42 described later. Internal multiplication circuit 36
Switches the current signal to be measured input to the current input terminal 37 with the voltage signal modulated to the time width output from the modulation circuit 34. This switch multiplies the output of the modulation circuit 34 by the measured current to calculate the electric energy. The internal multiplying circuit 36 W / V converts the calculated power amount into a voltage amount and outputs the voltage amount to the V / F conversion unit 33.

The V / F converter 33 includes the internal multiplication circuit 3
6 to output a power pulse signal having a frequency proportional to the amount of power.

The internal configuration of the V / F converter 33 is shown in the circuit diagram of FIG. 3, and a voltage corresponding to the amount of power output from the internal multiplier 36 is applied to a terminal 51. The voltage input to the terminal 51 is supplied to an integrator 53 via a resistor 52, and charges a capacitor 54. A switch 55 provided in parallel with the capacitor 54 is controlled by an output of an AND circuit 58 described later. At the time of integration by the integration circuit 53, the output of the AND circuit 58 is at a low level, and the switch 55 is opened by the low level signal output from the AND circuit 58. When the charge value of the capacitor 54 reaches the reference voltage of the comparator 56, the comparator 56 outputs a high-level signal to the S terminal of the RS flip-flop 57. This reference voltage of the comparator 56 is provided from the reference voltage source 31.

The RS flip-flop 57 is set when a high-level signal is input to the S terminal, and outputs a high-level signal from the Q terminal. This signal is applied to one input of a logical product (AND) circuit 58. The other input of the AND circuit 58 is supplied to a switch (third switch) 59, which will be described later, via a D.
Connected to the inverted Q terminal of the flip-flop 61,
In addition, a high-level signal is normally given to the other inputs.
Accordingly, the RS flip-flop 57 outputs the AND circuit 58
When a high-level signal is input to one input, the output of the AND circuit 58 is at a high level, and this high-level output is output to the terminal 62 as a power pulse. Also, AND
This high level output of circuit 58 closes switch 55, discharges the charge stored in capacitor 54, and resets integrator 53.

The high level output of the AND circuit 58 is also supplied to the D terminal of the D flip-flop 60. The high-level signal input to the D terminal is output to the Q terminal in synchronization with a clock (CLK) signal input to the C terminal, and one input of the exclusive OR (NOR) circuit 63 becomes high level. . The high-level output of the D flip-flop 60 is further provided to the D terminal of the D flip-flop 61,
A low-level output appears at the inverted Q terminal of the D flip-flop 61 in synchronization with the CLK signal input to the C terminal. This low level output is ANDed via switch 59
Since the signal is supplied to the circuit 58, the output of the AND circuit 58 changes from the high level to the low level with a predetermined time delay. A
When the output of the ND circuit 58 goes low, the switch 55
Opens, and the capacitor 54 is ready for the next charge. Then, the D terminal of the D flip-flop 60 becomes low level, and the input of the CLK signal also changes the Q terminal to low level. Accordingly, both inputs of the NOR circuit 63 are at low level, so that the output is at high level, and the RS flip-flop 57 is reset. Due to this delay time by the D flip-flops 60 and 61,
A predetermined discharge time of the capacitor 54 is secured.

The power pulse obtained at the terminal 62 after the V / F conversion is output to the averaging circuit 38 at the subsequent stage of the V / F converter 33 shown in FIG. The averaging circuit 38 includes a low-pass filter, and outputs a power amount obtained by subtracting a reactive power amount from an active power amount to a switch (second switch) 39. This switch 39, which will be described later, is in the state shown in FIG.
8 is transmitted to the terminal 40.

FIG. 1 is a block diagram showing a configuration of a watt-hour meter LSI internal test circuit according to the present embodiment for testing the measurement accuracy of such a watt-hour LSI 22.

The first DC power supply circuit 21 generates a DC voltage corresponding to the voltage to be measured, and outputs the DC voltage to the watt-hour meter LSI 22 and the voltmeter 23. The second DC power supply circuit 24 generates a DC voltage corresponding to the current to be measured, and outputs this to the external multiplier 25 and the voltmeter 23. The accuracy of the voltage output from each of the DC power supply circuits 21 and 24 is compensated by a voltmeter 23. That is, the output of the voltmeter 23 is given to the control device 27 via the control line 26,
The control device 27 monitors the output voltage of each of the DC power supply circuits 21 and 24. When the measured value of the voltmeter 23 deviates from the predetermined accuracy range, the control device 27 informs the DC power supply circuits 21 and 24 via the control line 26 that the output voltage has deviated from the predetermined range, and The power supply circuits 21 and 24 make the output voltage self-adjust.

The control device 27 forms an internal multiplication circuit function stop circuit, and outputs a signal to the terminal 43 of the watt-hour meter LSI 22 via the control line 26 when the watt-hour meter LSI 22 is tested. The connection states of 39 and 42 are inverted. The control device 27 further outputs a high-level signal to the terminal 44 of the watt hour meter LSI 22 via the control line 26. The voltage level applied to the terminal 44 is given to the internal multiplying circuit 36 because the switch 42 is tilted to the opposite side as shown. When the voltage level becomes high, the internal multiplying circuit 36 stops the multiplying function and outputs the signal input from the current input terminal 37 to the V / F converter 33 as it is.

The external multiplier 25 provided outside the watt-hour LSI 22 has the same performance as the internal multiplier 36 formed inside the LSI. The external multiplier 25 is connected to the terminal 41 of the power meter LSI 22 and
4 is input. External multiplier 2
5 multiplies the modulation signal by the DC voltage output from the second DC power supply circuit 24. Watt hour meter L during LSI testing
The first DC power supply circuit 2 is connected to the voltage input terminal 35 of the SI 22.
Since the voltage to be measured output from 1 is input, the modulation signal output from the modulation circuit 34 corresponds to the voltage to be measured. Therefore, in the external multiplier 25, the power meter LSI 22
The measured current is switched by the measured voltage signal modulated to the time width by the above, and the electric energy is calculated. This power amount is converted into a voltage amount and output to the DC filter 28.

The output of the external multiplier 25 has a rectangular waveform in which the current to be measured is switched by a modulation signal, and is smoothed by extracting a DC component in the DC filter 28. The DC component extracted by the DC filter 28 is output to the current input terminal 37 of the watt hour meter LSI 22. When the watt hour meter LSI 22 is tested, the signal input to the internal multiplication circuit 36 passes through and is output to the V / F conversion unit 33.
The output of the DC filter 28 is provided to a V / F converter 33.

The switch 59 is connected to the control device 27.
Is switched in advance through the control line 26 to the side opposite to the illustrated side, and the switch 55 is closed, that is, the integrator 53 is reset. Then, at the time of testing the watt-hour meter LSI 22, a conversion start signal is input from the control device 27 to the terminal 45 of the watt-hour meter LSI 22 via the control line. This conversion start signal is a low level signal, and is transmitted to the terminal 64 of the V / F converter 33 shown in FIG. Therefore, A in the V / F conversion unit 33
A low level signal is given to one input of the ND circuit 58,
The output of the AND circuit 58 becomes low level. Therefore, the switch 55 connected in parallel with the capacitor 54 opens,
The integrator 53 is set.

Therefore, D input to the V / F converter 33
The output of the C filter 28 is integrated by the integrator 53. When the charge value of the capacitor 54 reaches the reference voltage of the comparator 56, a high-level signal is output from the comparator 56 as described above, and the RS flip-flop 57
Is set. By the setting of the RS flip-flop 57, a high-level signal is applied to two inputs of the AND circuit 58, and a high-level signal is output from the AND circuit 58. This high level signal is output as a power pulse from the terminal 62, and the switch 55 is closed to reset the integrator 53.

At the time of the LSI test, the switch 39 shown in FIG. 2 is switched to the state opposite to the state shown in FIG. 2 so that the power pulse output from the terminal 62 of the V / F converter 33 is averaged. The signal is transmitted to the terminal 40 bypassing the circuit 38. The power pulse transmitted to the terminal 40 is input to the counter 29 shown in FIG. 1, and the counter 29 measures the frequency of the input power pulse. That is, the counter 29
And the control device 27 constitute a frequency measurement circuit,
The counter 29 measures the pulse width of the power pulse signal output from the V / F converter 33 using a reference clock.
That is, the counter 29 measures the time between the level change points from the falling edge to the rising edge of the power pulse using the built-in reference clock. The measurement time is input to the control device 27 via the control line 26, and the control device 27 calculates the conversion frequency of the power pulse based on the measurement time.

As described above, at the time of testing the watt hour meter LSI 22, the DC voltage corresponding to the measured voltage output from the first DC power supply circuit 21 is pulse width modulated by the modulation circuit 34 inside the LSI. The external multiplier 25 calculates the amount of power by multiplying the modulated output by a DC voltage corresponding to the current to be measured output from the second DC power supply circuit 24, and outputs this as a voltage. This voltage output is applied to the DC filter 2
8, a DC component is extracted, and the DC component is input to an internal multiplication circuit 36 in the LSI. The multiplication function of the internal multiplication circuit 36 is stopped by the control device 27, and the DC component input to the internal multiplication circuit 36 is the V / F within the LSI.
The data is output to the conversion unit 33 as it is. The V / F converter 33 integrates the DC component, converts the frequency, and outputs a power pulse. The pulse width of the power pulse is measured by the counter 29 using the reference clock as a master,
Is used to calculate the frequency.

Such frequency measurement is performed for each test in the procedure shown in FIG. That is, a rated frequency test (Step 101), a current characteristic test (Step 102), a voltage characteristic test (Step 103), a starting current test (Step 104), a latent test (Step 105), a power fluctuation test and others (Step 106). In each test, the frequency of the power pulse described above is measured. In the current characteristic test, the current to be measured is changed from twice to 1/100 times the rated current, and it is tested whether or not the power pulse output from the watt-hour meter LSI 22 changes linearly with respect to this current change. You. In the voltage characteristic test, the voltage to be measured is changed from 0.8 times to 1.2 times the rated voltage, and the watt hour meter L
It is tested whether or not the power pulse output from the SI 22 changes linearly with this voltage change. Through such a series of tests, it is tested whether or not the watt hour meter LSI 22 has a performance satisfying a predetermined standard. At the time of each of these tests, the output of each of the DC power supply circuits 21 and 24 is controlled by the control device 27 in accordance with the specifications of the watt hour meter.

In the watt-hour meter LSI internal test circuit according to the present embodiment, the DC component of the voltage W / V converted by the DC filter 28 is given to the V / F converter 33 as described above. Even if the voltage waveform output from the external multiplier 25 is a rectangular wave, the voltage applied to the V / F converter 33 does not fluctuate as in the related art. Therefore, V /
The conventional problem that the integration value decreases during integration during F-conversion and the time required to reach the reference value fluctuates is solved, and the integration value quickly reaches the reference value and a power pulse is output. .

Further, the measured voltage and
Even if the current is given as a DC signal, the frequency of the power pulse output from the watt-hour meter LSI 22 is measured by the counter 29 and the control device 27 using the reference clock incorporated in the counter 29 as a master.
Can be simulated by DC. In the present embodiment, the watt hour meter LSI 22 outputs a power pulse at a conversion frequency of 1000 Hz when a power amount of 1 kW is measured, and outputs one power pulse at a cycle of 1 msec. In the LSI internal test circuit according to the present embodiment, the conversion frequency can be measured even with one power pulse by the frequency measurement circuit, so that the power meter LSI can be measured in 1 msec.
22 power pulse conversion frequencies. However, in the frequency measurement of one power pulse, the reliability of the measured value is low. Therefore, in the present embodiment, the frequency is measured for five power pulses, and the average value of five measurements is used as the conversion frequency. This number of measurements can be set arbitrarily in the control device 27.

As a result, according to the LSI internal measurement circuit of the present embodiment, the voltage and current to be measured
There is no need to measure and average for a long time exceeding 0 seconds, and the measurement time for one power meter LSI is 5 m.
sec. That is, the measurement time of the power pulse conversion frequency is greatly reduced to 1/200 of the conventional one. Therefore, the price of the power meter LSI and the LSI internal test circuit can be reduced,
In addition, production can be speeded up.

Further, even if the voltage / current to be measured is supplied as a DC signal to the power meter LSI 22 as described above, the frequency of the power pulse can be measured. There is no need to use. Therefore, the voltage corresponding to the voltage / current to be measured can be easily generated by the DC power supply circuits 21 and 24. Further, the multiplication function of the internal multiplication circuit 36 is stopped by the control device 27 during the test of the LSI.
The V / F converter 33 configured inside the SI can be used for testing the LSI. Therefore, L
There is no need to provide a special V / F conversion circuit outside the SI. Therefore, the test of the watt-hour meter LSI 22 can be easily performed using a relatively easily available general-purpose product,
Moreover, the size of the test circuit can be reduced.

A control device 27 for controlling each unit via the control line 26 is a device capable of controlling the timing of frequency conversion start by the V / F conversion unit 33, controlling the number of times of measurement of the conversion frequency, and calculating the conversion frequency. Is fine. Such a control device 27 can be constituted by a personal computer, but since no special control is required,
In particular, it is possible to use a microcomputer (microcomputer) chip for simple configuration without being particular about upper system control.

That is, the voltage supplied to the watt-hour meter LSI 22 is converted to DC, and the control function of V / F conversion is performed by the watt-hour meter LS
The I22 provides a high-speed test, and can test all the performances of the watt-hour meter LSI 22 except for the internal multiplication circuit 36. Further, a peripheral device prepared at the time of the test is a general-purpose product which is relatively easy to obtain. You can do it.

[0035]

As described above, according to the present invention, V
Since the DC component of the W / V converted voltage is supplied to the / F conversion circuit, the voltage supplied to the V / F conversion circuit does not fluctuate as in the conventional case using a commercial frequency AC power supply. Therefore, the integral value quickly reaches the reference value, and a power pulse is output. Further, even when the voltage and current to be measured are given to the watt-hour meter LSI as a DC signal, the frequency of the power pulse output from the watt-hour LSI is measured by the frequency measurement circuit using the reference clock. Therefore, the conversion frequency can be obtained from one power pulse. Therefore, unlike the related art, it is not necessary to measure and average the voltage and current to be measured for a long time, and the measurement time for one power meter LSI is greatly reduced. Therefore, the watt hour meter LS
It is possible to reduce the cost of the I and LSI internal test circuits and speed up the production.

Further, even if the voltage / current to be measured is given as a DC signal to the watt-hour meter LSI, the frequency of the power pulse can be measured. Therefore, it is not necessary to use a conventional high-resolution and expensive AC signal generator. Disappears. Therefore, the voltage corresponding to the measured voltage / current can be easily generated by the DC power supply circuit. Further, the multiplication function of the internal multiplication circuit is stopped by the internal multiplication function stop circuit at the time of testing the LSI, so that the V /
The F conversion circuit can be used for testing the LSI, and it is not necessary to provide a special V / F conversion circuit outside the LSI as in the related art. For this reason, the test of the watt hour meter LSI can be easily performed by using a relatively easily available general-purpose product, and the test circuit can be reduced in size.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a watt hour meter LSI internal test circuit according to an embodiment of the present invention.

FIG. 2 is a block diagram showing an internal configuration of the watt hour meter LSI used in the watt hour meter LSI internal test circuit according to the embodiment;

FIG. 3 is a circuit diagram showing an internal configuration of a V / F converter constituting the watt hour meter LSI shown in FIG. 2;

FIG. 4 is a flowchart illustrating a test procedure of a watt hour meter LSI.

FIG. 5 is a block diagram showing a configuration of a conventional watt-hour meter LSI internal test circuit.

[Explanation of symbols]

 21, 24 ... DC power supply circuit 22 ... Electronic watt-hour meter LSI 23 ... Voltmeter 25 ... External multiplier 26 ... Control line 27 ... Control device 28 ... DC filter 29 ... Counter 33 ... V / F converter 34 ... Modulation circuit 35 voltage input terminal 36 internal multiplier circuit 37 current input terminal 53 integrator 54 capacitor

Claims (4)

(57) [Claims] 1. A modulation circuit for pulse width modulating a voltage under test, an internal multiplication circuit for multiplying an output of the modulation circuit and a current to be measured to calculate a power amount, and an electric power obtained by integrating an output of the internal multiplication circuit. Electronic watt-hour meter L having a voltage / frequency conversion circuit for outputting a pulse signal having a frequency proportional to the amount
A watt hour meter LSI internal test circuit for testing an internal circuit of an SI, wherein a first DC power supply circuit for generating a DC voltage corresponding to the measured voltage, and a second DC power supply circuit for generating a DC voltage corresponding to the measured current The DC power supply circuit and the internal multiplying circuit that stops the multiplying function of the internal multiplying circuit and directly outputs a signal input from the outside of the watt-hour meter to the internal multiplying circuit to the voltage / frequency conversion circuit. A circuit, an external multiplier configured outside the watt-hour meter LSI for multiplying an output of the modulation circuit and an output of the second DC power supply circuit, and extracting a DC component from an output of the external multiplier. A filter circuit for outputting to the internal multiplying circuit and a pulse width of a pulse signal output from the voltage / frequency conversion circuit are measured using a reference clock, and the power meter L is measured. A frequency meter LSI internal test circuit comprising: a frequency measuring circuit for measuring a power pulse conversion frequency by an SI. 2. The power meter LSI according to claim 1, wherein the internal multiplication circuit function stop circuit inputs a voltage level signal for stopping the multiplication function of the internal multiplication circuit or an output of the modulation circuit to the internal multiplication circuit. 2. The power supply device according to claim 1, further comprising a first switch formed therein, wherein the first switch is controlled to be switched by a control device external to the watt-hour meter LSI.
A power meter LSI internal test circuit as described. 3. The power meter LSI according to claim 1, wherein an output of an averaging circuit for subtracting a reactive power from an output of the voltage / frequency converter or an output of the voltage / frequency converter is output to the power meter LSI. 3. The internal test of the watt-hour meter LSI according to claim 2, further comprising a second switch for outputting to the outside, wherein the second switch is controlled to be switched together with the first switch by the control device. circuit. 4. The voltage / frequency conversion circuit includes an integrator that integrates an output of the internal multiplication circuit, and a third switch that takes in a conversion start signal from the control device during a test and sets the integrator to a set state. 4. The power meter LSI internal test circuit according to claim 3, comprising: