JPS638712B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a high frequency switching inverter.

Conventional inverters switch at high frequencies, but as shown in the waveform in Figure 2 i, basically
Since the waves are composed of switching frequencies including the 50Hz or 60Hz frequency and their harmonics, the coupling transformer is a transformer that takes into account the 50Hz or 60Hz frequency, making it large and heavy. Furthermore, the cutoff frequency of the filter in the DC/AC conversion circuit is low, making the filter itself large and heavy. Therefore, the inverter has disadvantages such as a large size and a large weight.

In order to eliminate the above-mentioned drawbacks, the present invention modulates the reference wave at a high frequency, performs large current switching,
Demodulate the output and return it to the same waveform as the reference wave,
By using an AC output system, the main transformer and filter circuit can be made smaller and lighter, thereby making the inverter smaller and lighter.

To achieve the above object, the present invention uses a signal generated by an oscillation circuit as a clock signal, divides the frequency of the clock signal, and generates a reference wave using the signal. The reference wave undergoes amplitude modulation by a signal from the AC output voltage in an amplitude modulation circuit to adjust the AC output voltage. The amplitude-modulated reference wave is combined with a signal from a triangular or sawtooth wave generation circuit to create a phase-modulated wave, and this signal drives a switching circuit. By switching, the frequency of the reference wave is several tens of times higher. It is a signal whose pulse width changes according to the amplitude of the reference wave. This inverter uses a demodulation circuit to synchronously rectify this signal using a signal synchronized with the reference wave, and then passes it through a filter to return it to the same waveform as the reference wave.

Next, as an embodiment of the present invention, a case of a positive arc wave output will be described.

In FIG. 1, 1 is a DC power supply, 2 and 3 are switching transistors of a switching circuit that switches DC from the DC power supply 1 and converts it into AC, 4 is a transistor drive circuit that drives the switching transistors 2 and 3, and 5 10 is a transformer that converts the output voltage from the switching circuit into a predetermined voltage; 6, 7, 8, and 9 are demodulation transistors that perform synchronous rectification and convert it into a sine wave alternating current voltage using a synchronous signal from the frequency dividing circuit; A transistor drive circuit drives the demodulating transistors 6, 7, 8, and 9, 11 is a filter, 12 is a sine wave AC output, 13 is an isolation transformer for detecting the voltage of the AC output 12, and 14 is a clock signal. 15 is a frequency dividing circuit that divides the clock signal generated by the oscillation circuit 14 to the frequency of the AC output 12; 16 is a sine wave generating circuit that generates a sine wave having a reference frequency; 18 is an amplitude modulation circuit that changes the amplitude of the sine wave using the deviation signal from the voltage adjustment circuit; 18 is a phase inversion circuit that inverts the phase of the sine wave from the amplitude modulation circuit 17;
20 is a triangular wave or sawtooth wave generating circuit that generates a triangular wave or sawtooth wave based on a clock signal; 20 is a triangular wave or sawtooth wave from the triangular wave or sawtooth wave generating circuit 19; and a sine wave to phase modulated wave from the amplitude modulation circuit 17. a comparator to take out the
21 is a triangular wave or sawtooth wave and phase inversion circuit 18
A comparator 22 is a voltage adjustment circuit that extracts and amplifies the deviation between the voltage of the AC output 12 and the set voltage. Note that A is the switching transistor 2,
3, and B is a demodulation circuit composed of demodulation transistors 6, 7, 8, and 9.

The clock signal (second clock signal) generated by the transmitting circuit 14
Figure a) is applied to the frequency dividing circuit 15 and the triangular wave or sawtooth wave generating circuit 19. The clock signal applied to the frequency dividing circuit 15 is divided into a predetermined frequency, one of which is applied to the transistor drive circuit 10 as a synchronizing signal (FIG. 2b), and the other is applied to the sine wave generation circuit 16 to generate a reference sine wave. generate. This reference sine wave undergoes amplitude modulation in the amplitude modulation circuit 17 based on the deviation signal between the AC output 12 of the voltage adjustment circuit 22 and the voltage setting value (FIG. 2c);
and the other is supplied to the comparator 21 through the phase inversion circuit 18 (FIG. 2d). The comparators 20 and 21 take out phase-modulated waveforms such as f from c and e and g from d and e in FIG. , is added to the transistor drive circuit 4. Transistor drive circuit 4
Now, the waveforms f and g in FIG. 2, which are the signals from comparators 20 and 21, are synthesized and
A waveform of the following is applied to switching transistors 2 and 3 of switching circuit A. Since the waveform is converted to positive or negative for each pulse of the switching waveform, there is no need to consider the 50Hz or 60Hz frequency contained in this pulse train. Switching circuit A
The output from the transformer 5 is converted to a predetermined voltage. This voltage is applied to the demodulating transistor 6 of the demodulating circuit B, taking into account the polarity of the 50Hz or 60Hz waveform.
7, 8 and 9 perform rectification and polarity switching using the synchronization signal (FIG. 2b) from the transistor drive circuit 10, thereby obtaining a waveform as shown in FIG. 2i. This waveform is passed through a filter 11 to form a sine wave as shown in FIG.

As mentioned above, the present invention not only performs phase modulation using a triangular wave etc., but also takes into consideration that the polarity is changed for each pulse of the phase modulated pulse, and converts the pulse width modulated wave into a 50Hz or 60Hz modulated wave. Pulse trains are synchronized and aligned under certain conditions, and a transformer or filter that takes only the high-frequency switching frequency into account can be used. Therefore, by increasing the switching frequency from several kHz to several hundred kHz, transformer and filter circuits can be used. Compared to conventional inverters, it is possible to be significantly smaller and lighter, and the industrial value is extremely large, as the entire inverter device can be made smaller and lighter.

[Brief explanation of the drawing]

FIG. 1 is a block diaphragm showing an embodiment of the high frequency switching inverter of the present invention, and FIG. 2 is an operational waveform diagram of each part of the embodiment of the present invention. A is a switching circuit, B is a demodulation circuit, 14 is an oscillation circuit, 15 is a frequency division circuit, 16 is a sine wave generation circuit, 17 is an amplitude modulation circuit, 18 is a phase inversion circuit,
19 is a triangular wave or sawtooth wave generating circuit; 20, 2
1 is a comparator.

Claims (1)

[Claims] 1. A switching circuit that switches direct current and converts it into pulse width modulated high frequency alternating current, and a switching circuit that converts pulse width modulated high frequency alternating current into low frequency alternating current voltage through synchronous rectification using a predetermined synchronizing signal from a frequency dividing circuit. A demodulation circuit and an associated oscillation circuit that generates a clock signal, a frequency divider circuit that divides the clock signal to the frequency of a low-frequency AC output, a reference wave generation circuit that generates a low frequency with a reference frequency, and a reference low Amplitude modulation circuit that changes the amplitude of the frequency, a phase inversion circuit that inverts the phase of the amplitude modulated wave, a triangular or sawtooth wave from a triangular or sawtooth wave generation circuit, and a signal from the amplitude modulation circuit and phase inversion circuit are compared and processed. It includes a control circuit consisting of a comparator circuit that generates a phase modulated signal to generate a pulse width modulated wave, and the phase is determined by the reference wave generated by the reference wave generating circuit and the triangular or sawtooth wave from the triangular or sawtooth generating circuit. The signal is modulated, the switching circuit is driven by the signal, and each pulse is converted into a high-frequency signal whose polarity is converted.The high-frequency signal is then demodulated by synchronous rectification using the synchronous signal from the frequency dividing circuit as a reference in the demodulation circuit. A high frequency switching inverter characterized by converting a reference wave into the same waveform as a reference wave by doing the following.