JPH10304672A - Power supply unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power supply unit which can reduce the deterioration of a device in a high-frequency power supply circuit at low cost by improving detection accuracy with simpler circuitry, and following and matching an impedance between matching circuit input and output for a change in the impedance of a load circuit. SOLUTION: This unit, which involves a DC voltage source, a high-frequency power supply circuit E having FETs(field effect transistors) 2, 3 which convert the DC voltage output VDD of the DC voltage source into high-frequency power and supplies it to a load circuit G, and a matching circuit F which performs impedance matching of both the high-frequency power supply circuit E and the load circuit G, is provided with a control means which detects regenerative current flowing though the FET3 with a current transformer CT31 and controls a drive circuit 1, so that the detected value is almost zero.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply.

[0002]

2. Description of the Related Art An example of a conventional example according to the present invention in which a load is an electrodeless discharge lamp is disclosed in Japanese Patent Application Laid-Open No. 6-1111967, and its circuit diagram is shown in FIG.

[0003] 1 is a field effect transistor (hereinafter referred to as FET).
Call. ) A drive circuit for switching between 2 and 3;
Reference numerals 2 and 3 denote FETs that increase the high-frequency current, 4 denotes a current transformer (hereinafter referred to as CT) that detects the high-frequency current 10, and 5 denotes an electrodeless discharge of energy by electromagnetic coupling with the inside of the electrodeless discharge lamp 6. An excitation coil to be supplied into the electric lamp 6, an electrodeless discharge lamp 6 in which a rare gas or the like is sealed, a low pass filter (hereinafter referred to as an LPF) 7 for smoothing a detection current, and a smoothing voltage 8 for detection. 9 is an amplifier for amplifying the detection current, 10 is an amplifier for increasing the detection voltage, and 11 is a phase difference between the detection current and the detection voltage. A phase detection circuit that compares the phase detection voltage and outputs a phase detection voltage corresponding to the difference, 12 is a low-pass filter (hereinafter, referred to as an LPF) that smoothes the phase detection voltage, and 13 is a filter having a frequency corresponding to the control voltage. Oscillation signal A voltage controlled oscillator (hereinafter, referred to as a VCO) oscillating 60, a crystal oscillator oscillating an oscillation signal 50 having a constant frequency, a NAND circuit 15, 17, an inverter 16, an inverter 18 from the electrodeless discharge lamp 6 A glass fiber for transmitting the generated light, 19 is a phototransistor for detecting the illuminance of the light transmitted through the glass fiber 18, and 20 is an LPF1 for the reference voltage VF.
An adder 61 adds the phase detection voltage input from 2 to a control voltage, 61 is a gas probe for ionizing the gas in the electrodeless discharge lamp 6, C1 and C2 are capacitors for voltage division, C3 and C4. Is a capacitor for impedance matching. The control voltage of the VCO 13 is equal to the reference voltage V.
When it becomes F, it is assumed that the reference voltage VF is selected so that the oscillation frequency is the same as the oscillation frequency of the crystal oscillator 14.

Next, the operation will be described. At the time t1 when the electrodeless discharge lamp 6 starts lighting, the control signal 100 is at a low level as shown in FIG. 5, whereby the oscillation signal 50 output from the crystal oscillator 14 is transmitted through the NAND circuit 17 to the drive circuit 1. Is input to On the other hand, at this time, since the NAND circuit 15 is closed, the oscillation signal 60 output from the VCO 13 is not input to the drive circuit 1. Here, the drive circuit 1 receives the input oscillation signal 50.
Is applied to the gates of the FETs 2 and 3. Thereby, FE
T2 and T3 are switched to increase the current of the oscillating signal, which is output from output terminals a and b to the excitation coil 5 side. As a result, the high-frequency current becomes CT4 and the capacitor C3
To a state where it can be supplied to the excitation coil 5 via.

In this state, a high voltage is applied to the gas probe 61 close to the electrodeless discharge lamp 6 by a high voltage generating circuit (not shown). Thereby, the gas probe 61
The corona discharge generated therein penetrates into the electrodeless discharge lamp 6 to generate a corona discharge in the electrodeless discharge lamp 6. At time t2, the control signal 100 is switched to high level by timer control or the like, and the NAND circuit 15 is opened and the NAND circuit 17 is closed. Therefore, the oscillation signal 60 output from the VCO 13 is input to the drive circuit 1 instead of the oscillation signal 50 output from the crystal oscillator 14. The oscillation signal input to the drive circuit 1 is the oscillation signal 6
Since the operation of the FETs 2 and 3 is the same even when the frequency is replaced with 0, a high-frequency current having the same frequency as the oscillation signal 60 is supplied to the excitation coil 5 side. When corona discharge occurs in the electrodeless discharge lamp 6, current flows into the lamp, the current channel increases, and the current flowing through the excitation coil 5 also increases. In such a state, the current flowing through the excitation coil 5 is detected by the CT 4 and the detected current is
And smoothed. The high-frequency voltage applied to the load circuit including the excitation coil 5 includes capacitors C1 and C
2 to become a detection voltage, and this detection voltage is L
It is input to PF8 and smoothed.

The smoothed detection current and detection voltage are input to the phase detection circuit 11 via amplifiers 9 and 10,
After calculating the phase difference between the current and the voltage (same as the phase angle), the phase difference is compared with a predetermined phase difference, and the phase detection voltage corresponding to the difference between the two is determined by the LPF 12.
Output to The LPF 12 smoothes the phase detection voltage and outputs this to the adder 20. Since the reference voltage VF is applied to the adder 20, a control voltage obtained by adding the phase detection voltage to the reference voltage VF is input to the VCO 13. The VCO 13 changes the frequency of the oscillation signal 60 to a frequency corresponding to the control voltage, and supplies the oscillation signal 60 to the drive circuit 1. Here, the VCO 13 is LP
The oscillation frequency is changed so that the phase detection voltage output from F12 becomes zero. FET2, 3 are the drive circuits 1
Amplifies the oscillation signal 60 input through the oscillating signal 60 and supplies a high-frequency current having the same frequency as the oscillation signal 60 to the load circuit on the excitation coil 5 side. The frequency of the high-frequency current changes so that the phase difference from the high-frequency voltage applied to the load circuit maintains a predetermined phase difference.

When the current flowing through the excitation coil 5 increases,
An electric field is formed in the circumferential direction in the electrodeless discharge lamp 6 by the magnetic field generated by the excitation coil 5, and the electric field grows a ring-shaped discharge path. Thus, when the excitation coil 5 and the ring-shaped discharge path are deeply magnetically coupled to each other and a high-frequency current rises, the discharge of the electrodeless discharge lamp 6 changes from a glow discharge to an arc discharge, and the electrodeless discharge lamp 6 6 will shine at the rated brightness. A glow discharge is formed in the electrodeless discharge lamp 6 as described above, and then grows in a ring-shaped discharge path,
Further, during the period before the glow arc transition occurs, the capacitance of the load circuit including the excitation coil increases, and the impedance of the load circuit changes every moment. However, in this example, by changing the frequency of the high-frequency current supplied from the FETs 2 and 3 with respect to the above change every moment,
Feedback control is performed such that the phase difference between the high-frequency current supplied to the load circuit and the high-frequency voltage applied to the load circuit is always constant. When the electrodeless discharge lamp 6 performs glow arc transition as described above and shines at a rated value, the impedance of the load circuit is settled to a predetermined state. As shown in FIG. 5, the control signal 100 is used as a low level
The oscillation signal 50 output from the crystal oscillator 14 is input to the input terminal. Thereafter, the frequency of the high-frequency current output from the FETs 2 and 3 to the load circuit becomes a predetermined frequency.

According to this conventional example, during a transient state period during the lighting transition of the electrodeless discharge lamp, the phase difference between the high-frequency current flowing through the load circuit and the high-frequency voltage applied to the load circuit becomes a predetermined phase difference. In order to change the frequency of the high-frequency current so as to always hold, even if the impedance of the load circuit changes in the transition period, the impedance of the high-frequency current output circuit side is made to follow by changing the frequency, The impedance matching of the two circuits can be matched moment by moment. Thereby, it is possible to prevent the occurrence of a high voltage or a large current due to a sudden change in the phase difference between the high-frequency voltage output and the high-frequency current output. Can be prevented from being destroyed, and the electrodeless discharge lamp 6 can be stably lit without loss.

[0009]

However, in the above-mentioned conventional example, a high-frequency current flowing through a load circuit and a high-frequency voltage applied to the load circuit are respectively detected, and a phase difference between them is determined. The first problem is that the operating frequency of the high-frequency current output side circuit (hereinafter, referred to as a high-frequency power supply) must be changed as compared with the phase difference, and the circuit configuration becomes very complicated. Will happen.

Further, since the high-frequency current flowing through the load circuit and the high-frequency voltage applied to the load circuit are detected, in order to change the operating frequency of the high-frequency power supply, the wiring (circuit pattern) becomes long and malfunctions. This causes a second problem that the operation becomes easier.

SUMMARY OF THE INVENTION The present invention has been made in view of all of the above problems, and has as its object to improve detection accuracy with a simpler circuit configuration and to reliably prevent a change in the impedance of a load circuit. It is an object of the present invention to provide a low-cost power supply device capable of reducing the performance deterioration of a high-frequency power supply device by following and matching the impedance between the input and output of a matching circuit.

[0012]

According to the first aspect of the present invention, there is provided a DC power supply having at least one switching element and converting an output voltage of the DC power supply into a high-frequency voltage. A high-frequency power supply for supplying the load to the load, and control means for making the regenerative current flowing through the switching element substantially zero.

According to the second aspect of the present invention, the control means makes the difference between the positive current flowing through the switching element and the regenerative current substantially constant.

According to a third aspect of the present invention, the control means controls the operating frequency of the high frequency power supply.

According to a fourth aspect of the present invention, the control means controls the output voltage of the DC power supply.

According to the fifth aspect of the present invention, a matching circuit for matching impedance of both the high-frequency power supply and the load is provided, and the control means controls the impedance of the matching circuit. .

According to a sixth aspect of the present invention, the load includes a discharge lamp, and the control means operates only when the discharge lamp is started.

According to the invention described in claim 7, the regenerative current flowing through the switching element has a substantially constant value after the discharge lamp is turned on.

According to the eighth aspect of the present invention, the difference between the positive current flowing through the switching element and the regenerative current has a substantially constant value after the discharge lamp is turned on, which is different from when the discharge lamp is started. I do.

According to a ninth aspect of the present invention, the discharge lamp is an electrodeless discharge lamp.

According to the tenth aspect of the present invention, the current flowing through the switching element of the high-frequency power supply is a lag current.

According to the eleventh aspect of the present invention, the operating frequency of the high frequency power supply is several MHz to several hundred MHz.

According to a twelfth aspect of the present invention, the high frequency power supply is a class D amplifier circuit.

According to the thirteenth aspect, the high frequency power supply is a class E amplifier circuit.

[0025]

Embodiment

(Embodiment 1) FIG. 1 shows a main part circuit diagram of a first embodiment according to the present invention.

The difference from the conventional example shown in FIG. 4 is that, in the conventional example, the high-frequency current and the high-frequency voltage flowing through the load circuit G are detected, and the drive circuit 1 is controlled so that the phase difference between them is substantially constant. Instead of this configuration, in the present embodiment, the regenerative current flowing through the FET 3 forming the high-frequency power source E is detected, and the drive circuit 1 is controlled so that the value becomes substantially zero. The same reference numerals are given to the same components as those of the other conventional examples, and the description is omitted.

Hereinafter, a brief description will be given. A current transformer CT31 is provided between the source terminal of the FET3 and the ground to detect a current flowing through the FET3, and the detection voltage (X
) Is input to the half-wave rectifier circuit 21 and only a negative voltage is taken out as a positive voltage. The output voltage from the half-wave rectifier circuit 21 is smoothed via the amplifier 9 and the low-pass filter 12 and input to the adder 20. And LPF1
The control voltage obtained by adding the reference voltage VF to the output voltage from the control signal 2 is input to the VCO 13, and the VCO 13 supplies the drive circuit 1 with an oscillation signal 60 changed to a frequency corresponding to the control voltage. The drive circuit 1 is controlled by changing the frequency according to the oscillation signal 60 so that the regenerative current flowing through the FET 3 becomes substantially zero.

(Embodiment 2) FIG. 2 shows a circuit diagram of a second embodiment according to the present invention.

The difference from the conventional example shown in FIG. 4 is that, in the conventional example, a high-frequency current and a high-frequency voltage flowing through the load circuit G are detected in the conventional example, and the drive circuit is controlled so that the phase difference between them is substantially constant. 1 in this embodiment, a DC power supply connected to the input terminal of the high-frequency power supply E as a power supply so that the difference between the positive current flowing through the FET 3 and the regenerative current becomes constant. The configuration is such that the output voltage of the power supply H is variably controlled, and the description of the same components as those of the other conventional examples will be omitted by retaining the same reference numerals. In the present embodiment, a so-called step-up chopper circuit including an inductor L100, a diode D100, a power MOSFET Q100, a smoothing capacitor C100, and a control circuit 34 for turning on and off the power MOSFET Q100 is used as the DC power supply H. . The commercial power supply AC is connected to the input terminal of the DC power supply H via the filter circuit f and the diode bridge DB.

Hereinafter, a brief description will be given. A current transformer CT33 is provided between the source terminal of the FET3 and the ground to detect the current flowing through the FET3,
Then, only the positive voltage is taken out of the detected voltage (point Z) and inputted to the differential amplifier circuit 22 through the low-pass filter 23. Further, a current flowing through the FET 3 is detected, and only a negative voltage is taken out of the detected voltage (point Y) by the half-wave rectifier circuit 26 and input to the differential amplifier circuit 22 via the low-pass filter 24. In the differential amplifier circuit 22, these two
Amplify by taking the difference between the two input voltages. Then, the output voltage of the differential amplifier circuit 22 is input to the comparator 27, and the comparator 27 varies the DC output voltage of the DC power supply H so that the difference between the output voltage and the reference voltage VF2 becomes substantially constant. Control.

(Embodiment 3) FIG. 3 shows a main part circuit diagram of a third embodiment according to the present invention.

The difference from the first embodiment shown in FIG. 1 is that an oscillation signal 60 is supplied to a matching circuit F composed of a capacitor C3 and a variable capacitor C5,
3 is configured to vary the impedance of the matching circuit F so that the regenerative current flowing through 3 becomes substantially zero.
The description of the same components as those of the other first embodiment will be omitted by retaining the same reference numerals.

In all of the above embodiments, the load circuit G includes the electrodeless discharge lamp 6, but may have any other configuration. For example, the electrodeless discharge lamp 6 may have another discharge lamp. A light may be used. The high-frequency power source E has two FEs.
Although T2 and T3 are included, any other configuration may be used. For example, a so-called class E amplifier circuit including one FET or a so-called class D amplifier circuit may be used. Further, when the load circuit G is configured to include the electrodeless discharge lamp 6, the operating frequency of the high-frequency power source E is preferably several MHz to several hundred MHz. This allows stable lighting. Furthermore, it is desirable that the current flowing through the FET 3 is a slow-phase current. Further, although the boost chopper circuit is used as the DC power supply H, any other configuration may be used.

Further, in the third embodiment, the configuration for varying the impedance of the matching circuit F may not only control the variable capacitor C5 but may be another configuration.

[0035]

According to the first to fifth aspects of the present invention, the detection accuracy is improved with a simpler circuit configuration, and
By matching the impedance between the input and output of the matching circuit by following the change in the impedance of the load circuit, it is possible to provide a low-cost power supply device capable of reducing the performance deterioration of the high-frequency power supply device.

According to the inventions described in claims 6 to 8, in addition to the effects of the inventions described in claims 1 to 5, it is possible to provide a power supply device capable of always stably lighting the discharge lamp.

According to the ninth to thirteenth aspects, in addition to the effects of the first to eighth aspects, it is possible to provide a power supply device capable of stably lighting the electrodeless discharge lamp at all times. .

[Brief description of the drawings]

FIG. 1 shows a main part circuit diagram of a first embodiment according to the present invention.

FIG. 2 shows a circuit diagram of a second embodiment according to the present invention.

FIG. 3 is a main part circuit diagram of a third embodiment according to the present invention.

FIG. 4 shows a circuit diagram of a conventional example according to the present invention.

FIG. 5 shows a waveform diagram of a control signal 100 according to the conventional example.

[Explanation of symbols]

 E High frequency power supply F Matching circuit G Load H DC power supply 2, 3 Switching element 6 Electrodeless lamp

Claims (13)

[Claims] 1. A power supply device comprising: a DC power supply; and a high-frequency power supply having at least one switching element and converting an output voltage of the DC power supply into a high-frequency voltage and supplying the high-frequency voltage to a load, wherein a regenerative current flowing through the switching element A power supply device provided with control means for setting the value to approximately zero. 2. The power supply device according to claim 1, wherein said control means makes a difference between a positive current flowing through said switching element and a regenerative current substantially constant. 3. The apparatus according to claim 1, wherein said control means controls an operating frequency of said high frequency power supply.
Or the power supply device according to claim 2. 4. The power supply device according to claim 1, wherein the control means controls an output voltage of the DC power supply. 5. The apparatus according to claim 1, further comprising a matching circuit for matching impedance of both said high frequency power supply and said load, and wherein said control means controls the impedance of said matching circuit. The power supply device according to claim 2. 6. The load comprises a discharge lamp, and
The power supply device according to any one of claims 1 to 5, wherein the control means operates only when the discharge lamp is started. 7. The power supply device according to claim 6, wherein a regenerative current flowing through the switching element has a substantially constant value after the discharge lamp is turned on. 8. The method according to claim 6, wherein a difference between a positive current flowing through the switching element and a regenerative current has a substantially constant value after the discharge lamp is turned on, which is different from when the discharge lamp is started. The power supply device according to claim 7. 9. The power supply device according to claim 6, wherein the discharge lamp is an electrodeless discharge lamp. 10. The current flowing through a switching element of the high frequency power supply is a lag current.
The power supply device according to claim 9. 11. The operating frequency of the high-frequency power source is several M
The power supply device according to any one of claims 1 to 10, wherein the power supply frequency is from Hz to several hundred MHz. 12. The power supply device according to claim 1, wherein the high-frequency power supply is a class D amplifier circuit. 13. The power supply device according to claim 1, wherein the high-frequency power supply is a class E amplifier circuit.