JPH06102298A - Electronic watthour meter - Google Patents

Abstract

PURPOSE:To reduce cost while enhancing reliability by providing a creeping circuit for comparing the count of an internal counter with a reference value upon interruption of a power pulse from an electric energy frequency converting circuit. CONSTITUTION:An anticreeping circuit comprises a microcomputor and an AND gate. The microcomputor compares the count of an internal counter with a predetermined reference value upon interruption of power pulse from an electric energy frequency converting circuit. A predetermined value is set upon rising of the internal counter which subsequently performs down counting until next rising time. If the count is higher than a reference value, a 'High level' creeping output is delivered to the AND gate and the power pulse is counted thus accumulating the electric energy. If the count is lower than the reference value, a 'Low level' creeping output is delivered to the AND gate and no power pulse is counted thus preventing the creeping.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic watt-hour meter having a one-chip micro computer, and more particularly to a latent-state prevention circuit for the electronic watt-hour meter.

[0002]

2. Description of the Related Art The configuration of a conventional example will be described with reference to FIG. FIG. 3 is a block diagram showing a conventional electronic watt hour meter. In the figure, a conventional electronic watt-hour meter includes a load voltage terminal 1, a load current terminal 2, an electric power frequency conversion circuit 3 including an operational amplifier connected to the load voltage terminal 1 and the load current terminal 2, Electric energy frequency conversion circuit 3
A frequency discriminating circuit 4, an AND gate 5 connected to the electric energy frequency converting circuit 3 and the frequency discriminating circuit 4, and a one-chip micro computer 6 having an electric energy count input terminal connected to the AND gate 5. , Display circuit 7 connected to this one-chip micro computer 6
It consists of and.

Next, the operation of the above conventional example will be described. In the electronic watt-hour meter, when the voltage alone is applied, the electric energy should not be integrated, but the electric energy frequency conversion circuit 3
A very small amount of pulse (long cycle) is output due to an error caused by the operational amplifier offset. Therefore, the frequency discriminating circuit 4 is used so as not to count pulses having a certain period or longer. The power amount frequency conversion circuit 3 multiplies the voltage and the current to obtain the power amount and converts it into a corresponding DC voltage, which is further converted into a frequency and output as a power pulse. The frequency discriminating circuit 4 discriminates a power pulse of, for example, 1.5 Hz or more as a threshold value. In this way, the one-chip micro computer 6 counts the power pulses of 1.5 Hz or more, integrates the power amount, and displays it on the display circuit 7.

[0004]

As described above, in the conventional electronic watt-hour meter, since the frequency discriminating circuit 4 is provided, the number of parts increases, the cost becomes high, and the reliability is low. There was a problem. The present invention has been made to solve the above problems, and an object thereof is to obtain an electronic watt-hour meter that can improve reliability at low cost.

[0005]

The electronic watt-hour meter according to the present invention is provided with the following means. (1) Obtain the electric energy based on the load voltage and load current,
A power amount frequency conversion circuit that converts this power amount into a frequency and outputs a power pulse. (2) The count value of the internal counter is compared with the reference value based on the interruption of the power pulse, and if the count value is larger than the reference value, the electric energy is integrated, and the count value is the reference value. A latent motion prevention circuit that does not integrate the electric energy if it is smaller than a value and sets a predetermined value in the internal counter for each interrupt.

[0006]

In the present invention, the amount of electric power is obtained in the electric power amount frequency conversion circuit on the basis of the load voltage and the load current, and the amount of electric power is converted into the frequency to output the electric power pulse. Further, the anti-latent circuit compares the count value of the internal counter with a reference value based on the interruption of the power pulse, and if the count value is larger than the reference value, the electric energy is integrated, If the count value is smaller than the reference value, the above electric energy is not integrated,
In addition, a predetermined value is set in the internal counter for each interrupt.

[0007]

【Example】

Example 1. The configuration of the embodiment of the present invention will be described with reference to FIG. FIG. 1 is a block diagram showing an embodiment of the present invention, in which a load voltage terminal 1, a load current terminal 2, an electric energy frequency conversion circuit 3, and a display circuit 7 are exactly the same as those of the conventional instrument. In FIG. 1, an embodiment of the present invention is exactly the same as that of the above-mentioned conventional instrument, a one-chip micro computer 6A whose interrupt input terminal is connected to the electric energy frequency conversion circuit 3, and one input terminal. Is connected to the electric energy frequency conversion circuit 3, the other input terminal is connected to the latent output terminal of the one-chip micro computer 6A, and the output terminal is connected to the one-chip micro computer 6A.
AND gate 8 connected to A's energy count input terminal
It consists of and. The one-chip micro computer 6A has an internal counter. By the way, the latent motion prevention circuit of the present invention is composed of the one-chip micro computer 6A and the AND gate 8 in the embodiment of the present invention.

Next, the operation of the above embodiment will be described with reference to the waveform diagram (FIG. 2) showing the operation. As shown in FIG. 2 (b), the one-chip micro computer 6A sets a count value read from the internal counter and a predetermined reference value every time there is an interrupt by the power pulse from the power amount frequency conversion circuit 3. To compare. The internal counter is set to a certain set value at the rising edge of the power pulse and starts counting down until the next rising edge. If the count value is larger than the reference value as shown in FIG. 2 (a), the latent output “high level” is output to the AND gate 8 as shown in FIG. The number of pulses is counted and the electric energy is integrated. In addition, in FIG.
If the count value is smaller than the reference value as shown in (a), the latent output “low level” is output to the AND gate 8 and the power pulse is counted, as shown in (c) of FIG. do not do. In this way, latent movement can be prevented. Since one embodiment of the present invention uses the counter and the interrupt input terminal in the general-purpose one-chip micro computer 6A as described above, it is possible to improve the reliability at a low cost. .

Example 2. In the above embodiment, if the count value of the internal counter is smaller than the reference value, the latent output "low level" is output to the AND gate 8 so that the power pulse is not counted. However, the AND gate 8 is removed. The same operation can be expected even if the power amount is integrated by directly counting the power pulses, and if the count value of the internal counter is smaller than the reference value, the power pulses are not simply counted.

Embodiment 3. Although the power pulse is counted in the above embodiment, it is needless to say that the intended purpose can be achieved by counting the number of interrupts and integrating the electric energy.

[0011]

As described above, the present invention provides a power amount frequency conversion circuit for obtaining a power amount based on a load voltage and a load current, converting this power amount into a frequency and outputting a power pulse, and The count value of the internal counter is compared with the reference value based on the interruption of the power pulse, and if the count value is larger than the reference value, the electric energy is integrated, and if the count value is smaller than the reference value. Since the latent-state prevention circuit for setting a predetermined value in the internal counter is provided without integrating the amount of electric power, there is an effect that the reliability can be improved at a low price.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a waveform diagram showing the operation of the embodiment of the present invention.

FIG. 3 is a block diagram showing a conventional electronic watt-hour meter.

[Explanation of symbols]

 1 load voltage terminal 2 load current terminal 3 voltage frequency conversion circuit 6A one-chip micro computer 7 display circuit 6 AND gate

Claims (1)

[Claims] 1. A power amount frequency conversion circuit for obtaining a power amount based on a load voltage and a load current, converting the power amount into a frequency and outputting a power pulse, and an internal counter based on the interruption of the power pulse. Comparing the count value and the reference value, if the count value is larger than the reference value, integrate the power amount, if the count value is smaller than the reference value, do not integrate the power amount, An electronic watt hour meter, further comprising: a latent motion prevention circuit that sets a predetermined value in the internal counter for each interrupt.