JP2003092889A - Method and device of detecting voltage - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve problems in the prior art that it was only possible to recognize that main voltage was higher or lower than compared voltage (detected voltage) without a correct main circuit voltage value being obtained, and that a switching circuit, an analog isolation, and an A/D converter are needed, thus making a circuit complex and expensive. SOLUTION: This method of detecting voltage, which isolates and detects high voltage, converts digital data into a PWM signal with a PWM converter circuit 1, isolates and smoothens the PWM signal, so as to be taken as a comparative reference value of analog voltage, compares with high voltage with the comparative reference value, isolates and feeds back the compared result to the PWM converter circuit, and compensates for the conversion of the PWM converter circuit based on the feedback value, so that the digital data is the detected voltage of the high voltage.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for use in a control device for an electric motor, for example, for detecting a digital value by insulating a high voltage such as a main circuit voltage of an inverter or an AC servo drive device. .

[0002]

2. Description of the Related Art Conventionally, in order to obtain the voltage of a circuit requiring isolation, a comparator 4 is used as shown in FIG.
The necessary voltage (main circuit voltage) is compared with the detection voltage (reference voltage), and the comparison result is isolated by the photo isolator 5 to obtain the result in the microcomputer 6. Alternatively, a signal obtained by switching the main voltage (main circuit voltage) as shown in FIG.
Isolate and use it for A / D converter 7
Then, it was converted into a digital value, and the microcomputer 6 obtained the value.

[0003]

However, in the conventional technique as shown in FIG. 5, it is possible to obtain an accurate main circuit voltage value by knowing whether the main voltage is higher or lower than the compared voltage (detected reference voltage). There was a problem of not having. In the example of FIG. 5, a switching circuit, analog isolation, and an A / D converter are required, and there is a problem that the circuit becomes large and expensive. Therefore, an object of the present invention is to obtain a strong voltage, such as a main circuit voltage, which requires isolation with a simple circuit.

[0004]

In order to solve the above-mentioned problems, the invention of claim 1 is a voltage detection method for detecting a high voltage by insulating it, wherein digital data is converted into a PWM signal by a PWM conversion circuit, This PWM signal is insulated and then smoothed to be a comparison reference value of the analog voltage, the strong voltage is compared with this comparison reference value, the comparison result is insulated and fed back to the PWM conversion circuit, and this feedback value is used. Performs conversion correction of the PWM conversion circuit,
3. The voltage detecting method, wherein the digital data is set to the detection voltage of the strong voltage.
Of the present invention, in a voltage detection method for detecting a high voltage by insulating it, digital data is transferred to a P
It is converted into a WM signal, the PWM signal is insulated, and then smoothed to obtain a comparison reference value of an analog voltage, the strong voltage is compared with the comparison reference value, and the comparison result is insulated and fed back to the microcomputer. 4. The voltage detection method according to claim 3, wherein the comparison reference value is changed by the microcomputer, and the digital data is used as the detection voltage of the strong voltage. PW for converting digital data into a PWM signal in a voltage detection device that insulates and detects
An M conversion circuit, a first photo isolator for insulating the PWM signal, a filter for converting the output of the first photo isolator into an analog voltage, and a comparator for comparing the output of the filter with the strong voltage, A voltage detecting device comprising: a second photo isolator for insulating the output of the comparator; and a microcomputer for adjusting the PWM signal according to the output of the second photo isolator.

[0005]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A concrete embodiment of the present invention will be described below with reference to FIG. In FIG. 1, 1 is a PWM conversion circuit, 2 is a photo isolator, 3 is a filter 4, a comparator, and 5 is a photo isolator. The operation of the circuit configured as described above will be described. First P
The details of the WM conversion circuit 1 are composed of an up / down counter 10 and a counter 11 for making timing as shown in FIG. When the counter 11 (timing circuit) counts a clock by the period setting counter 11 and overflows, the cycle is generated by loading the cycle and repeating the count. Up-down counter 1
0 (PWM generation circuit) counts data and PWM
Generate a signal. PW generated from PWM conversion circuit 1
The M signal is isolated by the photo isolator 2 and enters the filter 3. The filter 3 filters the PWM signal and outputs an analog signal. The comparator 4 compares this signal with, for example, a signal obtained by dividing the voltage of the main circuit (main voltage), drives the photoisolator 5 with the output of the comparator 4, and transmits it to the PWM conversion circuit 1 (up / down of FIG. 2). Input to the counter 10). The PWM conversion circuit 1 performs up / down of the up / down counter of the PWM generation circuit based on the comparison result. By repeating this, the data in the equilibrium state can be obtained and used as the data of the main circuit. For example, when the main voltage is a constant voltage, the data may be averaged and used as the voltage data of the main circuit. In this embodiment, the data of the main circuit is used, but the data is not limited to this.
It means data obtained by isolation. FIG. 3 shows another embodiment of the present invention. As shown in the embodiment of FIG. 1, the output of the comparator 4 drives the photo isolator 5 instead of correcting the PWM generation circuit based on the comparison result of the comparator 4. Then, the output of the photo isolator 5 is input to the microcomputer 6, and the microcomputer 6 performs PWM conversion for driving. The operation of the photo isolator 5, filter 3, and comparator 4 is shown in FIG.
Since the operation is the same as the above, the comparison value (detection value or voltage to be compared) of the comparator 4 can be freely changed by the microcomputer 6. This makes it possible to obtain a comparison between rough data and some data. For example, when used as a variable voltage detection, a microcomputer is used when it is necessary to detect a high voltage when the main voltage is higher than a certain abnormal voltage (detection voltage) and a low voltage when it is lower than a certain abnormal voltage (detection voltage). An abnormal voltage is set as the comparison voltage of the comparator 4 by 6 and the comparison result is obtained from the comparator 4. When the main voltage is obtained as a digital voltage as another method of use, it can be obtained by repeating the comparison and setting at certain intervals as in the flow of FIG. First, in step S1 of FIG. 4, the comparison voltage of the comparator 4 is set as the detection voltage (output of the filter 3 of FIG. 3), and when the main voltage is lower than the comparison result, the setting value of the PWM conversion circuit 1 is set to the following formula in step S2. For example, half of the detection unit is added. If it is higher than the comparison result of the comparator 4 in step 1, PWM is executed in step S3.
For example, the set value of the conversion circuit 1 is subtracted by half the detection unit as in the following equation. In this way, the detected voltage is calculated as follows. If it is lower than the comparison result: Detection voltage = set value + Detection unit / 2 If it is higher than the comparison result: Detection voltage = set value-Detection unit / 2 The detection unit may be the resolution of the PWM conversion circuit 1. In this case, the set value in the above formula On the other hand, the detection voltage may be added or subtracted, and when the voltage changes quickly, the detection unit needs to be larger than the resolution. Also, for a constant voltage with no voltage change, the data of the main voltage value goes back and forth within the width of the detection unit.
In that case, a more accurate voltage can be obtained by averaging the data in the microcomputer 6 to obtain a detection voltage. For averaging, whether the voltage changes fast or slow,
Depending on the case and usage, whether the detection cycle is long or short, etc.
It may be an average of several times or a weighted average.

[0006]

As described above, according to the present invention, P
There is an effect that an isolated voltage can be obtained by a simple circuit such as a WM conversion circuit, a comparator and photo isolation. Further, since the circuit is simple and can be composed of inexpensive parts, there is an effect that the cost is low and space is not required.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a specific embodiment of the present invention.

FIG. 2 is a detailed diagram of a PWM conversion circuit of the present invention.

FIG. 3 is a configuration diagram of another embodiment of the present invention.

FIG. 4 is a detection flow of another embodiment of the present invention.

FIG. 5 is a configuration diagram of a conventional example.

FIG. 6 is a configuration diagram of another conventional example.

[Explanation of symbols]

1 PWM conversion circuit 2, 5 photo isolator 3 filters 4 comparator 6 microcomputer 7 A / D converter 8 analog isolators 9 Switching circuit 10 up-down counter 11 counter

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 2G035 AA12 AB06 AC16 AD20 AD23                       AD28 AD29 AD39 AD43 AD55                 5H007 CA01 CB02 CC03 DA06 DB07                       DC05 EA02                 5J092 AA01 AA27 CA87 CA92 FA17                       HA02 HA25 HA29 HA35 HA45                       KA00 KA17 KA33 KA35 KA41                       MA11 TA01 TA07 UM01 VM01                       VM02 VM06 VM07 VM09 VM18                 5J500 AA01 AA27 AC87 AC92 AF17                       AH02 AH25 AH29 AH35 AH45                       AK00 AK17 AK33 AK35 AK41                       AM11 AT01 AT07 MU01 MV01                       MV02 MV06 MV07 MV09 MV18

Claims (3)

[Claims] 1. A voltage detecting method for detecting a high voltage by insulating it, wherein digital data is PWed by a PWM conversion circuit.
The PWM signal is converted into an M signal, and the PWM signal is insulated and then smoothed to obtain a comparison reference value of an analog voltage. The strong voltage is compared with the comparison reference value.
The voltage detection method is characterized in that the M conversion circuit is fed back, the conversion value of the PWM conversion circuit is corrected by this feedback value, and the digital data is used as the detection voltage of the strong voltage. 2. A voltage detecting method for detecting a strong voltage by insulation, wherein digital data is converted into a PWM signal by a microcomputer, and the PWM signal is insulated and smoothed to obtain a comparison reference value of an analog voltage. A strong voltage is compared with this comparison reference value, the comparison result is insulated and fed back to the microcomputer, the microcomputer changes the comparison reference value, and the digital data is used as the detection voltage of the strong voltage. A voltage detection method characterized in that 3. A voltage detecting device for detecting a high voltage by insulating it, and a PW for converting digital data into a PWM signal.
An M conversion circuit, a first photoisolator for insulating the PWM signal, a filter for converting the output of the first photoisolator into an analog voltage, and a comparator for comparing the output of the filter with the strong voltage, A voltage detecting device comprising: a second photo isolator that insulates the output of the comparator; and a microcomputer that adjusts the PWM signal according to the output of the second photo isolator.