JPH0522948A - Resonance-type inverter - Google Patents

Abstract

PURPOSE:To suppress the low-order higher harmonic components of AC voltage and to reduce device size by changing the modulation period of a pulse width modulation signal in accordance with the amplitude of a reference sine wave, and making it into a modulation-period-variable pulse width signal having pulse width proportional to the amplitude of the reference sine wave. CONSTITUTION:High-frequency resonance output voltage (e1) synchronized with a reference oscillator 5 is generated by a resonance voltage generating circuit 1 and put into a polarity changing circuit 2. On the other hand, in a modulation-period-variable pulse width signal generating circuit 15, the output signal CP of the reference oscillator 5 and the output signal of the reference sine wave V1 of a sine wave generator 16 synchronized with the reference oscillator 5 are put into an arithmetic circuit 17 for a modulation-period-variable pulse width signal. In the arithmetic circuit 17, a pulse width modulation period and pulse width during its duration are determined. If the modulation-period- variable pulse width signal Vg is 'L', a polarity changing switch is operated as mode A for output-side current to flow back. And if the modulationperiod- variable pulse width signal Vg is 'H', a control switch is operated as mode B.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resonance type inverter for modulating a high frequency resonance voltage output from a resonance voltage generating circuit to obtain a low frequency AC voltage.

[0002]

2. Description of the Related Art In recent years, a resonance type inverter for converting a high frequency resonance voltage output from a resonance voltage generating circuit into a low frequency AC voltage for the purpose of reducing noise, improving efficiency and downsizing an AC power supply device. Is being studied.

A block diagram of a conventional resonant inverter is shown in FIG. This resonance type inverter A is composed of a resonance voltage generating circuit 1, a polarity switching circuit 2, a control circuit 3 and a low pass filter 4, and the control circuit 3 has a reference oscillator 5 and
It is composed of a pulse width modulation signal generation circuit 6, a synchronous pulse width modulation signal generation circuit 7, a switch decision logic circuit 8, a positive / negative signal generation circuit 9, and drive circuits 10 and 11. Also,
The pulse width modulation signal generation circuit 6 is, for example, the sine wave generator 1
2, a triangular wave generator 13 and a comparator 14.

The operation waveform of this circuit is shown in FIG. The high frequency resonance output voltage e1 synchronized with the reference oscillator 5 [FIG.
(A)] is generated by the resonance voltage generating circuit 1 and input to the polarity switching circuit 2. On the other hand, in the pulse width modulation signal generation circuit 6, the reference sine wave V1 output from the sine wave generator 12 synchronized with the reference oscillator 5 and the output signal V2 of the carrier triangular wave generator 13 [FIG. Compared with
A pulse width modulation signal V3 [FIG. 7 (c)] having a pulse width proportional to the amplitude of the sine wave V1 is generated, and the pulse width modulation signal V3 is generated by the synchronous pulse width modulation signal generation circuit 7 by the resonance voltage generation circuit 1 Is converted into a synchronous pulse width modulation signal Vc [FIG. 7 (d)] which is synchronized with the output voltage e1.

This synchronous pulse width modulation signal Vc is the signal of the output voltage e1 at the first time point (1T, 2T, 3T, ...) Of one generation cycle T of the output voltage e1 of the resonance voltage generating circuit 1 and its end. Holds up. That is, the signal does not change in the middle of one generation period T. The synchronous pulse width modulation signal Vc is input to the switch decision logic circuit 8, and if the synchronous pulse width modulation signal Vc is "L", the high frequency resonance output voltage e1 is not passed and the output side current is switched to the polarity switching circuit 2. In the mode A in which the electric current is returned through the switch, the control switch of the polarity switching circuit 2 is operated via the drive circuit 11.

Further, the synchronous pulse width modulation signal Vc is "H".
Then, the positive / negative direction signal V4 from the positive / negative signal generation circuit 9
If [FIG. 7 (e)] is “H”, that is, in the positive direction,
As a mode B in which the polarity switching circuit 2 is allowed to pass without switching the polarity of the high-frequency resonance output voltage e1 and the resonance output voltage e2 having a positive polarity is output, the control switch of the polarity switching circuit 2 is set to the drive circuit 11. To work through.

Further, if the synchronous pulse width modulation signal Vc is "H" and the positive / negative direction signal V4 is "L", the polarity of the high frequency resonance output voltage e1 is changed to a resonance voltage having a negative direction polarity. The control switch of the polarity switching circuit 2 is operated via the drive circuit 11 as the mode C for outputting
These operation modes A to C are set to the synchronous pulse width modulation signal Vc.
And the positive / negative direction signal V4, the output waveform of the polarity switching circuit 2 becomes e2 [FIG. 7 (f)],
The voltage e2 passes through the low-pass filter 4 to become a low-frequency AC voltage e3 [FIG. 7 (g)].

Since the conventional resonance type inverter A switches the mode according to the synchronous pulse width modulation signal Vc, the mode is not switched in the middle of the output of the resonance voltage generating circuit 1, so that the polarity switching circuit 2 is also switched. The switching can be performed in the zero voltage state, and the switching loss and the switching surge can be reduced. Therefore, this conventional resonant inverter A has the advantages of high efficiency and low noise generation.

[0009]

On the other hand, however, according to this resonance type inverter A, the pulse width modulation signal V3
Since an error as shown in FIG. 7D occurs between the sync pulse width modulation signal Vc and the sync pulse width modulation signal Vc, a proportional relationship between the pulse width of the sync pulse width signal Vc and the amplitude of the reference sine wave V1 is lost. , The output voltage waveform e3 is distorted, leading to an increase in low-order harmonic components. In order to solve this, there are two methods, that is, the frequency of the resonance voltage generating circuit 1 is made sufficiently high, or the frequency of the carrier triangular wave output signal V2 is made sufficiently lower than the output voltage e1 of the resonance voltage generating circuit 1. Although considered, in the former method, the inductance of the resonance reactor and the capacitance of the resonance capacitor in the resonance voltage generation circuit 1 become smaller as the resonance frequency of the resonance voltage generation circuit 1 increases, so that the inductance component of wiring and It becomes easy to be influenced by the capacitance component and the design condition of the resonance voltage generating circuit 1 becomes strict.

In the latter method, the effect of suppressing the output harmonics by the pulse width modulation becomes small, and there arises a problem that the low-pass filter 4 becomes large and the output impedance increases to deteriorate the electrical characteristics. Here, in view of the above-mentioned drawbacks of the conventional resonant inverter, the present invention provides a resonant inverter that suppresses low-order harmonic components of an AC voltage and enables a high-frequency low-pass filter. is there.

[0011]

The solution of the above-mentioned problems can be achieved by adopting the novel characteristic constitutional means listed below in the present invention. That is, the first feature of the present invention is
A resonance voltage generation circuit that generates a high frequency resonance output voltage, a polarity switching circuit that switches the polarity of the high frequency resonance output voltage of the resonance voltage generation circuit, and an amplitude of an AC voltage of a desired frequency that is synchronized with the high frequency resonance output voltage. Resonant type having a control circuit for controlling switching of the polarity by a pulse width modulation signal, and a low-pass filter for passing an AC voltage of the desired frequency among the outputs of the polarity switching circuit to generate an output voltage In the inverter, the control circuit includes a modulation period variable pulse width signal generation circuit and a positive / negative signal generation circuit that share a reference oscillator, and the control circuit controls the modulation period of the pulse width modulation signal to the desired frequency. Is a resonance type inverter having a circuit configuration that can be changed according to the amplitude of the AC voltage.

According to a second aspect of the present invention, in the control circuit according to the first aspect, the modulation period variable pulse width signal generation circuit is synchronized with the high frequency resonance output voltage of the resonance voltage generation circuit, and The polarity switching circuit is controlled by outputting a modulation period variable pulse width signal such that the pulse width is proportional to the amplitude of the AC voltage of the desired frequency, and the circuit can freely suppress low-order harmonic components of the output voltage. It is a resonance type inverter configured.

[0013]

According to the present invention, since the above-mentioned means is taken, the modulation period of the pulse width modulation signal is changed according to the amplitude of the reference sine wave, and the reference voltage is synchronized with the output voltage of the resonance voltage generating circuit. Since the modulation period variable pulse width signal has a pulse width proportional to the amplitude of the sine wave, the low-order harmonic component of the AC voltage is suppressed.

[0014]

Embodiments of the present invention will be described with reference to the drawings. Figure 1
Is a block configuration diagram of the resonant inverter circuit of the present embodiment,
2 is an operation waveform in the present embodiment of FIG. 1, FIG. 3 is a flowchart of calculation in the modulation period variable pulse width signal arithmetic circuit in FIG. 1, and FIG. 4 is a harmonic component of the output voltage of the polarity switching circuit of the present embodiment. 5 is an analysis graph of the harmonic component of the polarity switching circuit of the resonant inverter A of the conventional example of FIG. In the figure, B is the resonant inverter of this embodiment,
Reference numeral 15 is a modulation period variable pulse width signal generation circuit, 16 is a sine wave generator, and 17 is a modulation period variable pulse width signal calculation circuit. In the figure, the same elements as those of the conventional example of FIG. 6 are designated by the same reference numerals.

The specifications of the resonance type inverter B of this embodiment are as follows.
The operation will be described below by presenting such a concrete embodiment. A high frequency resonance output voltage e1 synchronized with the reference oscillator 5 is generated by the resonance voltage generating circuit 1 and input to the polarity switching circuit 2. On the other hand, the modulation period variable pulse width signal generation circuit 1
5, the output signal CP of the reference oscillator 5 and the reference sine wave V1 output signal of the sine wave generator 6 synchronized with the reference oscillator 5 are input to the modulation cycle variable pulse width signal calculation circuit 17, and the modulation cycle variable pulse width signal is output. The arithmetic circuit 17 determines the pulse width modulation period and the pulse width within that period according to the flow chart including steps I to VII from the start (START) to the end (END) shown in FIG.

Specifically, as an initial procedure, the number of resonance voltages in the pulse width modulation period is n = 1, and the number of resonance voltages output in the positive or negative direction corresponding to the pulse width is k =.
Start setting from 0 (see step I), then period i
In order to determine the modulation period and pulse width of the reference sine wave V1, the ratio of the average value bi (see step II) of the reference sine wave V1 that varies with the pulse width modulation period to the maximum amplitude a of the reference sine wave V1 bi / a is compared with the ratio k / n of the number n and the number k, and the difference | bi / a−k / n | is less than a small allowable value D (see step III). Is obtained (see steps IV to VI), the pulse width modulation period niT is synchronized with the output voltage e1 of the resonance voltage generating circuit 1 and has a pulse width proportional to the amplitude of the reference sine wave V1.
And a pulse width kiT are given, and the variable modulation period pulse width signal Vg as shown in FIG. 2C is obtained by repeatedly calculating for each period (see steps II and III) (see step VII). .

Obtained modulation period variable pulse width signal Vg
Is inputted to the switch decision logic circuit 8, and if the modulation variable pulse width signal Vg is "L", the high frequency resonance output voltage e
The polarity switching circuit 2 is set as a mode A in which the current on the output side is returned through the switch of the polarity switching circuit 2 without passing through 1.
The control switch is operated via the drive circuit 11. Further, when the modulation cycle variable pulse width signal Vg is “H” and the positive / negative direction signal V4 [FIG. 2 (d)] is “H”, that is, in the positive direction, the polarity of the high frequency resonance output voltage e1 is switched. The control switch of the polarity switching circuit 2 is operated via the drive circuit 11 as a mode B in which the resonance voltage having the positive polarity is output without passing through the polarity conversion circuit 2.

If the modulation cycle variable pulse width signal Vg is "H" and the positive / negative direction signal V4 is "L", the polarity of the high-frequency resonance output voltage e1 is changed and the resonance having the negative direction polarity is generated. In mode C for outputting a voltage, the control switch of the polarity switching circuit 2 is operated via the drive circuit 11.
By repeating these operation modes A to C according to the modulation cycle variable pulse width signal Vg and the positive / negative direction signal V4, the waveform of the output voltage e2 of the polarity switching circuit 2 becomes as shown in FIG.
(E)], and the output voltage e2 is passed through the low-pass filter 4 to obtain a sinusoidal AC voltage e3 [Fig.
(F)] is acquired. A high-speed microprocessor is used for the modulation period variable pulse width signal calculation circuit 17, and a method of instantaneously calculating the waveform is used.

(Comparative Example) FIGS. 4 and 5 are graphs in which the harmonic components of the output voltage e2 of the polarity switching circuit 2 when the resonant inverters B and A of this embodiment and the conventional example are used.
Shown in. FIG. 4 is a graph in which the harmonic components of the output voltage [FIG. 2 (e)] of the polarity switching circuit 2 when the resonant inverter B of this embodiment is used are analyzed.
0 V, generation cycle of high frequency resonance output voltage e1 100 kHz
z, the allowable value D in FIG. 3 is 0.005.

FIG. 5 shows the output voltage e2 of the polarity switching circuit 2 when the conventional resonance type inverter A is used [FIG.
(F)] is a graph in which the harmonic components are analyzed. The measurement conditions are as follows: input voltage 100 V, high frequency resonance output voltage e1 generation period 100 kHz, carrier triangular wave V2 frequency 10
kHz. This condition is an example in which the resonance-type inverter A using the conventional technique has the least low-order harmonic components.

Comparing FIG. 4 and FIG. 5, the low-order harmonics of the resonance type inverter B in this embodiment are smaller than those of the resonance type inverter A using the prior art.
It can be seen that the following components are suppressed to about 1/2 to 1/5. In the present embodiment, the effect of suppressing the low-order harmonic component changes depending on the allowable value D shown in FIG. 3, and therefore, depending on the generation period of the high frequency resonance output voltage e1 and the frequency of the AC voltage of the inverter output, It is necessary to select the optimum allowable value D.

[0022]

As described above, according to the present invention,
The modulation cycle of the pulse width modulation signal is changed according to the amplitude of the reference sine wave, synchronized with the output voltage of the resonance voltage generation circuit,
Moreover, by using a modulation period variable pulse width signal having a pulse width proportional to the amplitude of the reference sine wave, it becomes possible to suppress the low-order harmonic components of the AC voltage, and the low-pass filter of the device is used. The cutoff frequency can be increased, and the low-pass filter can be reduced in size and weight. Therefore, the resonance type inverter device as a whole can be reduced in size and weight, thus exhibiting excellent utility and usefulness.

[Brief description of drawings]

FIG. 1 is a block configuration diagram of a resonance type inverter circuit showing an embodiment of the present invention.

FIG. 2 is an operation waveform of the above.

FIG. 3 is a flowchart of calculation in a modulation period variable pulse width signal calculation circuit provided therein.

FIG. 4 is an analysis graph of a harmonic component of the output voltage of the polarity switching circuit provided in the same.

FIG. 5 is an analysis graph of harmonic components of a polarity switching circuit of a conventional resonance type inverter.

FIG. 6 is a block diagram of a conventional resonant inverter circuit.

FIG. 7 is an operation waveform of the above.

[Explanation of symbols]

A: Conventional resonance type inverter B ... Resonant inverter of this embodiment 1 ... Resonance voltage generation circuit 2 ... Polarity switching circuit 3 ... Control circuit 4 ... Low pass filter 5 ... Reference oscillator 6 ... Pulse width modulation signal generation circuit 7. Synchronous pulse width modulation signal circuit 8 ... Switch decision logic circuit 9 ... Positive / negative signal generation circuit 10, 11 ... Driving circuit 12, 16 ... Sine wave generator 13 ... Triangle wave generator 14 ... Comparator 15. Modulation cycle variable pulse width signal generation circuit 17 ... Modulation cycle variable pulse width signal arithmetic circuit

Claims (2)

[Claims] 1. A resonance voltage generation circuit for generating a high frequency resonance output voltage, a polarity switching circuit for switching the polarity of the high frequency resonance output voltage of the resonance voltage generation circuit, and an alternating current of a desired frequency synchronized with the high frequency resonance output voltage. A control circuit that controls the switching of the polarity of the polarity switching circuit by a pulse width modulation signal corresponding to the amplitude of the voltage, and an AC voltage of the desired frequency among the outputs of the polarity switching circuit is passed to generate an output voltage. In a resonance type inverter having a low-pass filter, the control circuit includes a modulation period variable pulse width signal generation circuit and a positive / negative signal generation circuit that share a reference oscillator, and the control circuit is pulse width modulated. A resonance type inverter characterized in that the circuit is configured so that the modulation period of the signal can be changed corresponding to the amplitude of the AC voltage of the desired frequency. 2. In the control circuit, the modulation period variable pulse width signal generation circuit is synchronized with the high frequency resonance output voltage of the resonance voltage generation circuit and has a pulse width proportional to the amplitude of the AC voltage of the desired frequency. 2. The resonant inverter according to claim 1, wherein the polarity switching circuit is controlled by outputting a variable modulation period variable pulse width signal, and the low-order harmonic component of the output voltage can be suppressed.