JPH088773B2 - High frequency power output controller - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a high-frequency power supply output control device used for a power supply circuit when, for example, a plasma generator, an induction heating device, or a resonance circuit is used as a load. Therefore, the present invention relates to a high frequency power supply output control device capable of controlling its output from 0 to a set maximum.

(B) Conventional technology Conventionally, as a circuit device for obtaining a high-frequency power source, a semiconductor is connected to a full bridge and each arm is made to perform push-pull operation, and each arm is alternately turned OFF and ON to drive DC power at a high frequency. There is a semiconductor inverter device that converts electric power.

In this semiconductor inverter device, as a conventional method for controlling the output power, there is a method of changing the voltage or current of the power supply supplied to the inverter device by using a thyristor that cannot self-extinguish.

In the case of this method, there is a problem that the configuration becomes complicated and the power supply power factor becomes low because the commutation circuit is indispensable, and the response speed to the load fluctuation is slow, so due to overcurrent during load short circuit, Further, when the load is released, there is a concern that the elements may be destroyed due to overvoltage.

Another method of output control is a method of variably controlling the output frequency of the inverter device in the case of a load resonance circuit.

This method provides maximum output (series resonance) when the output frequency of the inverter device is equal to the resonance frequency of the load resonance circuit.
In this method, the output frequency of the inverter device is variably controlled to be higher or lower than the resonance frequency to control the output to be small.

However, if the variable control is performed to the lower side, there is a problem that the power supply is short-circuited during the recovery period of the flywheel diode forming the inverter device. Therefore, the variable control is generally performed to the higher side.

Therefore, the resonant frequency of the resonant circuit of the load is necessarily
Since it has to be lower than the maximum operating frequency of the inverter device, the resonant circuit of the load is limited by the inverter device.

Further, the output power variable characteristic of the resonance circuit of the load is strongly influenced by the resonance sharpness index Q of the resonance circuit, and when the Q is small, the output power does not become so small even if the frequency is increased,
On the other hand, when Q is large, the output power greatly changes due to a slight frequency change, and there is a problem that output control is difficult.

(C) Object of the Invention The present invention has a simple structure and is easy to control because of the unique structure that changes the phase difference between two arms of a full-bridge type inverter composed of a self-extinguishing semiconductor device. , A high-frequency power supply of about 500 KHz can be obtained, and even when the phase difference and load circuit constants change due to the PLL circuit, the point at which the arm self-extinguishing semiconductor device performs the switching operation matches the zero current point of the output current. By controlling the inverter frequency so that it does not become the current lead phase in all switching devices, it is possible to operate at high frequency without the occurrence of excessive recovery phenomenon of the diode. An object is to provide an output control device.

(D) Structure of the Invention According to the present invention, a self-arc-extinguishing semiconductor device is connected to a full bridge, each arm is made to perform push-pull operation, and each arm is alternately turned OFF and ON to convert DC power to high frequency power. A 90-degree locked PLL that controls the inverter frequency so that the semiconductor inverter and the one arm described above correspond to the one-arm self-extinguishing semiconductor device that constitutes the arm and the zero cross point of the output current coincides with the time when the switching operation occurs. A circuit and a signal corresponding to the other arm and having a phase difference from the operation phase of the self-arc-extinguishing semiconductor device forming the arm are set to 0. Degree Lock PL
A high frequency power supply output control device comprising an L circuit, a phase difference control means for controlling output power by changing a phase difference between these two PLL circuits, and a load circuit composed of a series resonance circuit. .

(E) Effect of the Invention According to the present invention, the commutation circuit is unnecessary and the configuration is simple compared to the conventional output control using a thyristor (semiconductor device that cannot self-extinguish), and the power supply is simple. The power factor is high, the response speed to the load fluctuation is fast, and it is possible to prevent the destruction of the element due to the load short circuit or the open circuit due to the load fluctuation.

Furthermore, compared with the output control by the resonance phenomenon with the load resonance circuit, the output can be controlled independently of the resonance frequency of the series resonance circuit as the load, so the control is easy and reliable. Since the circuit is not controlled to the maximum operating frequency of the semiconductor inverter, it is easy to obtain a high-frequency power supply of about 500 KHz.

Moreover, the operating frequency of the semiconductor inverter is
The circuit always sets the optimum value according to the phase and the constant of the load resonance circuit. That is, the 90-degree locked PLL
Even if the phase difference and the load circuit constant change depending on the circuit, the inverter frequency is adaptively controlled so that the time when the switching device of the arm (see A1 in Fig. 1) performs the switching operation and the zero cross point of the output current match. Therefore, the current lead phase does not occur in all switching devices, and therefore the diode recovery transient phenomenon does not occur. Therefore, there is an effect that it is possible to operate at a high frequency.

Furthermore, since the present invention has a resonance frequency tracking function,
If the load resistance value does not change, the output power does not change even if the load resonance frequency changes, and even if the load resistance value changes, the control characteristic of the output power with respect to the phase difference is always constant.

Further, since the phase change range is widened to 0 ° ± 360 ° by using the above-mentioned 0 ° locked PLL circuit, there is an effect that stable operation can be performed even if the phase difference is widened.

(F) Embodiment One embodiment of the present invention will be described in detail below with reference to the drawings.

The drawing shows an output control device of a high frequency power supply. In FIGS. 1 and 2, four transistors Q1, Q2, Q3, Q4 as self-extinguishing semiconductor devices are connected to a full bridge,
Flywheel diodes D1, D2, D3, D4 are connected in parallel to each.

The DC power source E is a transistor Q that constitutes each arm A1, A2.
1, Q2 and Q3, Q4 are connected to both ends, and each arm A1,
The primary side T1 of the output transformer T is connected between the intermediate points of A2, and the series resonant circuit LC including the capacitor C1 and the coil L1 is connected as a load to the secondary side T2 of the output transformer T.

The two transistors Q1 and Q2 that make up each arm A1 and A2
The Q3 and Q4 are push-pulled by the drive circuit B, and are alternately turned OFF and ON with a duty cycle of 50%.

That is, as shown in FIG. 2, transistors Q1 and Q4,
Alternatively, when the transistors Q2 and Q3 are alternately driven with the phase difference φ, a load current as shown in FIG. 2 flows in the series resonant circuit LC. That is, a current flows through the above circuit as shown in the table below.

Therefore, when transistors Q1 and Q3 are in phase, output 0
Then, when the transistors Q1 and Q4 are in phase, the output becomes maximum and the phase difference φ between the two arms A1 and A2 is varied, so that the output power can be variably controlled from 0 to the set maximum value. it can.

FIG. 3 shows an example in which the high-frequency power supply output control device according to the present invention is applied to an induction heating device. Since the components having the same reference numerals as those in FIG. 1 are the same as the components described in FIG. 1, the description thereof will be omitted. .

A work coil L2 forming an induction heating device is connected in series to the series resonance circuit LC of the load of the main circuit portion.

Also, the capacitor C2 in the main circuit is the output transformer T
The current transformer CT detects the current on the load side and inputs the detected current to the load short circuit detection circuit 10, the current detection circuit 11, and the current control circuit 12.

The first phase comparator 13, the first integrating circuit 14, the first voltage controlled oscillator 15, the first frequency dividing circuit 16, and the 90 degree phase delay circuit 17 are a 90 degree locked main phase locked loop (PLL).

A signal obtained by converting the output current into a square wave by the current detection circuit 11 and advancing the phase by 90 degrees is input to one input terminal of the first phase comparator 13 described above.

The signal output from the first voltage controlled oscillator 15 is halved by the first frequency dividing circuit 16 to the other input terminal via the first integrating circuit 14 which is a low pass filter, and the duty cycle 90% phase delay circuit 17
Input a signal whose phase is delayed by 90 degrees.

Then, in the main phase-locked loop described above, the output frequency on the high frequency power supply side is made to match the resonant frequency of the load series resonant circuit LC when the output is maximum.

The second phase comparator 18, the second integrator circuit 19, the second voltage controlled oscillator 20, and the second frequency divider circuit 21 are a phase locked loop (PLL) of 0 degree lock and generate a signal having a phase difference φ. .

One input terminal of the second phase comparator 18 is connected to the output of the main phase locked loop (PLL) 9
A signal whose phase is delayed by 0 degrees is input, and the signal output from the second voltage controlled oscillator 20 is input to the other input terminal via the second integrating circuit 19 which is a low pass filter. Divide by 1/2 to set the duty cycle to exactly 50
Input the signal in%.

The input of the above-mentioned second integrating circuit 19 is connected to the output of the two-phase comparator 18 and the output setting circuit 22 composed of a variable resistor.
And the current limiting circuit 12 are connected.

The current limiting circuit 12 reduces the output phase difference φ when the output current exceeds a certain value.

The outputs of the two phase-locked loops (PLL) described above are passed through the dead time adding circuits 23 and 24 and the output cutoff / recovery circuits 25 and 26, and then the drive circuit B corresponding to the respective arms A1 and A2.
Input to 1, B2.

The dead time adding circuits 23 and 24 described above slightly delay the mutual outputs in order to prevent the output transistors Q1 to Q4 from being simultaneously turned on, and the output cutoff / recovery circuits 25 and 26 are the same as those of the current limiting circuit 12 described above. If the response is not in time, the short circuit detection circuit 10 detects overcurrent such as load short circuit and shuts off the output.
The output is restored when the overcurrent is avoided.

Since the high frequency power supply output control device in the induction heating device configured as described above can change the phase difference φ from 0 degree to 180 degrees by controlling the direct current of the output setting circuit 22, this phase difference φ The output can be variably controlled from 0 to the set maximum value, and the output of the work coil L2 can be satisfactorily controlled.

Moreover, semiconductor inverter (See each element Q1 to Q4, B)
The operating frequency of is always set to an optimum value by the above-mentioned PLL circuit according to the phase and the constant of the load series resonant circuit (LC). That is, even if the phase difference and the load circuit constant are changed by the 90-degree locked PLL circuit, the switching device (see Q1 and Q2) of the arm (see A1 in Fig. 1) performs the switching operation and the zero crossing of the output current. Since the inverter frequency is adaptively controlled so that the points coincide with each other (see FIG. 2), the current advance phase does not occur in all switching devices, and therefore the diode recovery transient phenomenon does not occur. Therefore, there is an effect that it is possible to operate at a high frequency.

Furthermore, since the present invention has a resonance frequency tracking function,
If the load resistance value does not change, the output power does not change even if the load resonance frequency changes, and even if the load resistance value changes, the control characteristic of the output power with respect to the phase difference is always constant.

In addition, since the phase change range is widened to 0 ° ± 360 ° by using the 0 ° locked PLL circuit, stable operation can be performed even if the phase difference is widened.

In the correspondence between the configuration of the present invention and the above-described embodiment, the semiconductor inverter of the present invention includes transistors Q1 to Q4 (self-extinguishing semiconductor devices) of the embodiment and drive circuits B, B1, B2 for driving them. Correspondingly, similarly, the two PLL circuits are the first phase comparator 13 and the first integrator circuit 1 which form the main phase-locked loop (PLL) of 90-degree lock
4, a first voltage controlled oscillator 15, a first frequency divider circuit 16, a 90-degree phase delay circuit 17, a second phase comparator 18, which constitutes a 0-degree locked phase locked loop (PLL), a second integration circuit 19, The second voltage controlled oscillator 20 and the second frequency divider circuit 21 correspond, and the phase difference control means corresponds to the output setting circuit 22, but the present invention is not limited to the configuration of the above-described embodiment.

[Brief description of drawings]

The drawings show one embodiment of the present invention. Fig. 1 is a basic configuration diagram of a high-frequency power supply output control device, Fig. 2 is a time chart of its main part, and Fig. 3 is a high-frequency power supply when applied to a series resonance load. It is a circuit block diagram of an output control device. Q1 to Q4 …… Transistors (self-extinguishing devices) A1, A2 …… Arm φ …… Phase difference B, B1, B2 …… Drive circuit 13,18 …… Phase comparator 14,19 …… Integrator circuit 15,20 ...... Voltage controlled oscillator 16,21 …… Dividing circuit 17 …… 90 degree phase delay circuit 22 …… Output setting circuit (phase difference control means)

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Satoshi Nagai 1-10-10 Daito-cho, Miyakojima-ku, Osaka City, Osaka Prefecture Kyoeidenso Co., Ltd. (56) Reference JP-A-61-237644 (JP, A)

Claims (1)

[Claims] 1. A semiconductor inverter in which a self-extinguishing semiconductor device is connected to a full bridge, each arm is made to perform push-pull operation, and each arm is alternately turned OFF and ON to convert DC power into high frequency power. A 90-degree-locked PLL circuit that controls the inverter frequency so as to correspond to the one arm and the time when the self-extinguishing semiconductor device that constitutes the arm performs the switching operation and the zero cross point of the output current, and the other one. 0-degree-locked PLL that corresponds to the arm of the first arm and combines the operation phase of the self-extinguishing semiconductor device that constitutes the arm with the operation phase of the self-extinguishing semiconductor device of one arm to obtain a signal having a phase difference. Circuit, a phase difference control means for controlling the output power by changing the phase difference between these two PLL circuits, and a load circuit consisting of a series resonance circuit. High frequency power supply output control device.