JPH1174057A - Power supply for silent discharge - Google Patents

Abstract

PROBLEM TO BE SOLVED: To lower a switching loss when voltage rises, by providing a switching element controlling power supply to the primary side of a transformer and a gate pulse control means supplying a pulse to a gate of the switching element in synchronization with oscillation voltage of the secondary side of the transformer. SOLUTION: If a gate pulse generating circuit is constituted so that it generates a pulse only when a zero-cross signal arrives, an additional tuning circuit is not necessary, because the gate pulse generating circuit itself has a synchronization function. Thus, the current flowing in a switching element 13 becomes a sine wave after the gate pulse is impressed, by adding the gate pulse in synchronization with the rise of oscillation voltage. Consequently, the current at the voltage rise of the switching element 13 is zero, then, a switching element loss, that is, a power loss in the switching element is lowered.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply for silent discharge used for an ozone generator having a silent discharge electrode.

[0002]

2. Description of the Related Art Conventionally, in this type of power supply for silent discharge, there is a type in which a high voltage of about 100 KHz and a high frequency discharge are performed by a switching element composed of a MOS-FET. In this discharging operation, a voltage VQ '(both shown by a solid line) across the switching element and a current I flowing through the switching element
Q ′ (shown by a broken line) is as shown in FIG. 8, for example.

[0003]

In such a conventional example, the change of the current IQ 'is not a sinusoidal waveform but a sawtooth waveform which rises slowly, and a large switching loss occurs in a hatched portion in FIG. A problem has been to reduce power loss in this switching element. SUMMARY OF THE INVENTION It is a first object of the present invention to provide a silent discharge power supply device having a small switching loss particularly at the time of rising of a voltage VQ '. A second object of the present invention is to provide a silent discharge power supply device in which discharge energy can be easily controlled.

[0004]

According to a first aspect of the present invention, there is provided a power supply for supplying a direct current, a silent discharge load, and the silent discharge load connected to a secondary side. A transformer that forms a series resonance circuit with a load and a secondary leakage inductance; a switching element that controls supply of the power supply power to a primary side of the transformer; and a pulse synchronized with a secondary-side oscillation voltage of the transformer. And a gate pulse control means for supplying a gate pulse to the gate of the switching element. The invention according to claim 2 is characterized in that the second object is achieved in addition to the first object. 1 wherein the gate pulse control means supplies a pulse in synchronism with every N (N is a positive integer) cycle of the secondary oscillation voltage, and the power supply apparatus for silent discharge makes N adjustable.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention is embodied as a power supply circuit for silent discharge in an ozone generator or the like. The silent discharge power supply circuit includes a power supply for supplying a direct current, a silent discharge load, a transformer that connects the silent discharge load to a secondary side, and forms a series resonance circuit with the silent discharge load and a secondary leakage inductance. A switching element for controlling the supply of the power to the primary side of the transformer; and a gate pulse control means for supplying a pulse to the gate of the switching element in synchronization with a secondary side oscillation voltage of the transformer. It is a thing. This embodiment will be described in detail below.

A silent discharge is a discharge that is generated between a pair of electrodes and does not emit a sound such as a spark discharge, and is also called a creeping discharge. Usually, an insulator is interposed between the electrodes. An electrode that performs such a silent discharge is used as a silent discharge load. The silent discharge load has a capacity (capacitor) component, is connected to the secondary coil of the step-up transformer, and has a capacitance C of the silent discharge load and a capacitance of the transformer.
A series resonance circuit is constituted by the next leakage inductance L. A power supply is connected to one end of the primary coil of the transformer, and a switching element for controlling power supply is connected to the other end. The power supplied to the primary side of the transformer is
A full-wave or half-wave rectified AC voltage and then smoothed, or a DC voltage power supply is used. As this power supply, a variable DC voltage power supply having a variable DC voltage can be used. When a pulse is supplied to the gate of the switching element and the switching element is turned on (conducted) in a state where the power is on, the series resonance circuit on the secondary side of the transformer starts oscillating. The oscillation frequency f is f ≒ 1 / 2π
(LC) Oscillates at a high frequency of ^1/2 . This frequency is between 20 KHz and 200 KHz. A MOS-FET is used as the switching element.

The gate pulse control means for supplying a gate pulse to the gate comprises a first embodiment for supplying a pulse in synchronism with every rise of the oscillation voltage of the series resonance circuit, and N (wherein (N is a positive integer) A second embodiment in which a pulse is supplied in synchronization with each cycle and N can be adjusted can be adopted. In the first embodiment,
A zero-crossing detecting circuit for detecting a rising of the oscillation voltage, that is, a zero-crossing of the same voltage, and a gate pulse generating circuit for generating a pulse in synchronization with the zero-crossing detected by the zero-crossing detecting circuit. If this gate pulse generating circuit is configured to output pulses continuously and autonomously, the following tuning circuit is required. That is, since the oscillation frequency changes when the capacitance and resistance of the series resonance circuit change, a tuning circuit that tunes the oscillation cycle of the gate pulse generation circuit and the oscillation cycle of the oscillation voltage. Is provided. However, when the gate pulse generation circuit is configured to generate a pulse only when a zero-cross signal arrives, the gate pulse generation circuit itself has a tuning function,
No separate tuning circuit is required. As described above, by applying the gate pulse in synchronization with the rise of the oscillation voltage, the current flowing through the switching element becomes a sine wave after the gate pulse is applied. As a result, the current when the voltage of the switching element rises becomes zero, and the switching element loss, that is, the power loss in the switching element is reduced.

In a second embodiment, the zero-cross detecting circuit, a variable-period pulse generating circuit for outputting a reference pulse at a cycle of N cycles of the oscillation voltage, and a first zero-crossing of the reference pulse are provided. And a gate pulse generation circuit that outputs a gate pulse in synchronization with only the gate pulse.
The gate pulse generation circuit has a function of generating a gate pulse in synchronization with a zero cross and a function of limiting synchronization with the zero cross to once every N cycles of the oscillation voltage.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, specific embodiments of the present invention will be described in detail with reference to the drawings. The specific examples described here are:
This is a power supply device for silent discharge using a silent discharge load as a discharge electrode of an ozone generator. First, a first example corresponding to the first embodiment will be described with reference to FIGS. FIG.
2 is an electric circuit diagram of a power supply device for silent discharge, and FIG. 2 is an electric block diagram of a main part of FIG. 1 is an AC power supply terminal, 2,
Reference numeral 3 denotes a current breaker, and 4 an SS having a function of controlling turning on / off of a power supply and adjusting supply power by phase control.
R is a switching element. Reference numeral 5 denotes a full-wave rectifier in which four rectifier diodes are connected to a bridge. Reference numeral 6 denotes a first reactor (inductance element), 7 denotes a first capacitor, 8 denotes a second reactor, and 9 denotes a second capacitor. The first reactor 6 and the first capacitor 7 constitute a smoothing circuit. The second reactor 8 is provided to eliminate the effect of high frequency on the DC power supply. Second capacitor 9
Is for supplying a high-frequency current to a load circuit (transformer-side circuit described later). The circuit between the switching element 4 and the second capacitor 9 constitutes a DC power supply whose supply voltage is adjustable. A primary coil 11, a first diode 12, and a MOS-FET (hereinafter, referred to as a switching element) 13 of a discharging transformer 10 are connected in series to an output terminal of the DC power supply, that is, an output terminal of the smoothing circuit. . The first diode 12 is provided to limit the current flowing through the switching element 13 in one direction. This diode 12 is unnecessary when the switching element 13 itself has a one-way limiting function. In this embodiment, since the switching element 13 does not have this function, the diode 12 is provided.

[0010] Silent discharge electrodes 15 and 16 of the ozone generator are connected to the secondary first coil 14 of the transformer 10. A series resonance circuit is formed by the silent discharge electrodes 15 and 16 and the leakage inductance of the transformer 10. Be composed. In this embodiment, the capacitance C of the discharge electrodes 15 and 16 is
Is, for example, about 1000 pF, and the leakage inductance L of the transformer 10 is, for example, about 1 mH, so that the oscillation frequency of the oscillation voltage is about 160 KHz. The secondary-side second coil 17 of the transformer 10 is provided for detecting the oscillation voltage V1 by lowering it. The detection voltage V2
Is input to the gate pulse control circuit 18. Reference numeral 19 denotes a gate of the switching element 13, to which an output signal V7 of the gate pulse control circuit 18 is applied.

Reference numeral 20 denotes a first surge absorber which includes a first resistor 21 for voltage division, a second diode 22 for rectification, and a second resistor 22 for voltage division.
A second surge absorber 24 is connected in series with the resistor 23, and is connected in parallel with the first resistor 21, the second diode 22, and the second resistor 23. Second diode 22 and second resistor 2
The three ends serve as terminals for detecting a voltage V9 obtained by dividing the voltage V8 between both ends of the first diode 12 and the switching element 13. This detection voltage V9 is input to the gate pulse control circuit 18. 25 is a switching element 1
0, a third resistor 26 is connected to the coil, and both ends thereof are connected to a current I flowing through the switching element 13.
Q detection terminal.

Next, a gate pulse control circuit 1 according to FIG.
8 will be described. Reference numeral 31 denotes a zero-cross detection circuit which receives a detection voltage V2, detects a timing at which the same voltage V2 crosses (crosses) a zero-voltage line, and rises and falls in synchronization with this timing (FIG. 6 (c)). See). Reference numeral 32 denotes a variable-period pulse generation circuit which outputs a pulse serving as a source of a gate pulse and a gate source pulse V5 (FIG. 6 (g)) having an immediate duty ratio of 50%. The pulse output period is based on the oscillation frequency. An oscillation cycle is set, and at the same time, the reference oscillation cycle is configured to be adjustable by an external DC voltage input. A tuning circuit 33 has a function of outputting a signal V4 for tuning the phase of the output pulse of the variable-period pulse generation circuit 32 to the phase of the output pulse of the zero-cross detection circuit 31. As the tuning circuit 33, a well-known PLL (PHASE-LOC
KED LOOP) circuit is used. This tuning circuit 3
3 compares the phases of two input pulses, for example, as shown in FIG.
a phase comparator (not shown) that outputs a signal as shown in (d),
A low-pass filter (not shown) for converting the output of the phase comparator into a signal containing a large amount of DC components is included. The variable period pulse generation circuit 32 receives the signal of the tuning circuit 33, changes the pulse generation period, and outputs a pulse signal V5 tuned to the phase of the output pulse of the zero cross pulse generation circuit 31.

Reference numeral 34 denotes a reset pulse generation circuit which detects a reverse voltage VG generated at both ends of the switching element 13 which becomes conductive when the application of the gate pulse is continued,
This reverse voltage causes the gate pulse reset signal V10
(FIG. 6 (f)). Reference numeral 35 denotes a gate pulse cut circuit which receives the signal V10 of the reset pulse generation circuit 34 and cuts a portion after the rising timing of the reset pulse V10 in one pulse period of the output pulse V5 of the gate pulse generation circuit 32, and FIG. (A) has a function of outputting a signal V6 having the same waveform as the gate pulse signal V7. 36 is a gate pulse cut circuit 35
Amplifier that amplifies the output signal from the
Is applied to the gate 19 as a gate pulse.

The operation of the first embodiment in the above configuration will be described below. To the gate 19 of the switching element 13, a rectangular gate pulse V7 is applied from the gate pulse control circuit 18. Thereby, the switching element 10
Are conducted for a short time, and a current IQ flows as shown in FIG.
As a result, a current flows through the primary coil 11 of the transformer 10, thereby starting oscillation on the secondary side of the transformer 10. The oscillation voltage V1 has a sinusoidal waveform as shown in FIG. As shown in FIG. 6, the rise of the oscillation voltage V1 (zero cross) and the rise of the pulse V7 applied to the gate 19 are synchronized, and as shown by the dashed line in FIG. The rise of the current IQ is also synchronized. When the oscillation cycle of the oscillation voltage V1 is shifted, the timing of applying the gate pulse V7 to the switching element 13 is synchronized with the zero cross of the oscillation voltage V1 by the tuning function of the tuning circuit 33 and the variable cycle pulse generating circuit 32 described above. Is controlled.
Further, the pulse V5 is cut by the gate pulse cut circuit 35 using the reverse voltage VQ generated when the switching element 13 is turned off. The gate pulse cut circuit 35 has a function of preventing the switching element 13 from conducting twice during one cycle. Thus, the voltage VQ across the switching element 13 and the flowing current IQ are
The waveform is as shown in FIG.

According to the first embodiment constructed as described above, as is apparent from FIG. 8 which is an enlarged view of a part of FIG. 4 and which is schematically shown in FIG. Thirteen currents IQ become substantially zero. Therefore, the switching element loss proportional to the product of the current IQ and the voltage VQ can be made substantially zero when the switching element is off. Further, since the switching loss is small, the number of switching elements used can be reduced in the device of the embodiment. Further, it is possible to reduce the size of the heat radiation part for cooling the switching element 13.

Next, a second embodiment corresponding to the second embodiment will be described with reference to FIGS. 9 differs from FIG. 1 in that a switch 41 for simple ON-OFF control is used instead of the switching element 4 for power control, and the configuration of the gate pulse control circuit 18 is the same as that in FIG. The point is that the gate pulse control circuit 42 is used. The other parts are the same as those in FIG.

First, the configuration and function of the gate pulse control circuit 42 will be described. Reference numeral 43 denotes a zero-crossing detection circuit having the same configuration and function as the zero-crossing detection circuit 31 of FIG. 1, and outputs the signal V3 of FIG. 11B (same as FIG. 6C). 44 is a voltage adjusting circuit capable of manually adjusting the output voltage, 45 is a variable period pulse generating circuit for changing the generation period (frequency) of the output pulse according to the change of the input voltage, and N (where N Is a positive integer) cycle of the reference pulse signal V12 including the cycle ((a) of FIG. 11).
). 46 is a reset pulse generation circuit having the same configuration and function as the reset pulse generation circuit 34 of FIG.
A signal V10 shown in FIG. 11D (same as FIG. 6F) is output. Reference numeral 47 denotes a gate pulse generation circuit having a function of outputting a gate pulse only in synchronization with the first zero-cross during the one-pulse period of the reference pulse and a function of cutting a gate pulse, and includes a logic element such as a flip-flop or a NOT circuit. Is done. The output signal V13 is amplified by the amplifier circuit 48 and formed as a gate pulse V14.

The gate pulse control circuit 42 outputs a signal as shown in FIG. 11 in each component. As a result, the gate pulse V14 is formed in synchronization with the rising edge of the zero-cross pulse that occurs first from the rising point of each reference pulse. The gate pulse has been cut after the rise of the signal by the gate pulse reset signal V10.

The operation of the second embodiment will be described. FIG.
At the gate 19 of the switching element 13, the gate pulse control circuit 42 supplies a rectangular gate pulse V 1
4 is applied. As a result, the switching element 13 conducts for a short time, and the current IQ flows. As a result, a current flows through the primary coil 11 of the transformer 10, thereby starting oscillation on the secondary side of the transformer 10. This gate pulse is supplied in synchronization with the rise of the oscillation voltage as in the first embodiment, but unlike the first embodiment, it is supplied not every cycle of the oscillation voltage but every N cycles. Therefore, as shown in FIGS. 12 and 13, the amplitude of the oscillating voltage attenuates as time elapses after the application of the gate pulse, and when the gate pulse is applied again, the amplitude increases and attenuates again as time elapses. . FIG. 14 is an enlarged view of a main part of FIG. The supply period T of the gate pulse is adjusted by operating the voltage adjustment circuit 44 in FIG. The example shown in FIG. 12 is an example in which the cycle T is short, and the example shown in FIG. 13 is an example in which the cycle T is long. The energy supplied to the silent discharge load in the former example, that is, the discharge energy is larger than that in the latter example. FIG. 12 and FIG.
The upper waveform in FIG. 3 shows the oscillation voltage V1, and the lower waveform shows the switching element 13 current IQ. As described above, in the second embodiment, the switching loss can be reduced as in the first embodiment, and the gate pulse can be reduced without the need for the capacitance control means such as the switching element 4 of the first embodiment. By controlling the supply cycle, it is possible to easily control the discharge energy.

[0020]

As described above, according to the present invention, the switching loss can be reduced, and according to the second aspect of the present invention, it is possible to easily control the discharge energy. A large power supply circuit for silent discharge can be provided.

[Brief description of the drawings]

FIG. 1 is a circuit configuration diagram of a power supply circuit for silent discharge according to a first embodiment of the present invention;

FIG. 2 is an electrical block diagram of a main part of the embodiment.

FIG. 3 is a signal waveform diagram showing a switching element current IQ and a voltage of a main part of the embodiment.

FIG. 4 is a signal waveform diagram showing a switching element current IQ and a switching element voltage VQ of the embodiment.

FIG. 5 is a signal waveform diagram showing a switching element current IQ and an oscillation voltage V1 of the embodiment.

FIG. 6 is a signal waveform diagram for explaining an operation of a main part of the embodiment.

FIG. 7 is an explanatory diagram in which a part of FIG. 4 is enlarged and schematic.

FIG. 8 is a conventional explanatory diagram corresponding to FIG. 7;

FIG. 9 is a circuit diagram of a power supply circuit for silent discharge according to a second embodiment of the present invention;

FIG. 10 is an electrical block diagram of a main part of the embodiment.

FIG. 11 is a signal waveform diagram showing voltages of main parts of the embodiment.

FIG. 12 is an explanatory diagram for explaining, by a photograph, a signal waveform of a switching element current IQ and an oscillation voltage V1 when a gate pulse is supplied in a short cycle in the embodiment.

FIG. 13 is an explanatory diagram for explaining, with photographs, the signal waveforms of the switching element current IQ and the oscillation voltage V1 when a gate pulse is supplied in a long cycle in the embodiment.

14 is an enlarged signal waveform diagram of a main part of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Transformer 13 Switching element 15 Silent discharge load 18 Gate pulse control circuit 19 Gate 42 Gate pulse control circuit

Continued on the front page (51) Int.Cl. ⁶ Identification code FI H02M 7/48 H02M 7/48 A

Claims (2)

[Claims] 1. A power supply for supplying a direct current, a silent discharge load, a transformer connecting the silent discharge load to a secondary side, and forming a series resonance circuit by the silent discharge load and a secondary leakage inductance. And a gate pulse control means for supplying a pulse to the gate of the switching element in synchronization with a secondary oscillation voltage of the transformer. Characteristic power supply for silent discharge. 2. The method according to claim 1, wherein said gate pulse control means supplies a pulse in synchronization with every N (N is a positive integer) cycle of said secondary oscillation voltage and adjusts said N. Item 2. A power supply device for silent discharge according to item 1.