JPS62207174A - High frequency generator - Google Patents

Abstract

PURPOSE:To improve a power factor, and to reduce noises by forming a high-frequency generator so as to have a capacitor having predetermined capacitance at the time of the view of the DC power supply side from an inverter. CONSTITUTION:Load 4 such as an electric-discharge lamp is supplied with high-frequency power through an inverter 3 by a DC power supply 2 including a full wave rectification circuit 21, etc. from an AC power supply 1. The inverter 3 is constituted of a parallel resonance circuit consisting of a capacitor 7 and a coil 5, a transistor 8 conducting switching operation, etc. The DC power supply 2 is combined with auxiliary DC power units 22-26 generating output voltage lower than the peak value of the full wave rectification circuit 21, and a capacitor 27 is connected between output terminals. When the capacitance of the capacitor 27 is represented by C and the synthetic capacitance of the capacitors 22-23 by C0 at that time, a capacitance ratio K=C/C0 at that time is set within a range of 0.05<=K<=0.35. Accordingly, a power factor at the time of view from the AC power supply 1 side can be kept at a high value.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a high-frequency generator that supplies high-frequency power to a load such as a discharge lamp.

[Conventional technology]

Various devices have been proposed that use inverters to supply high-frequency power to loads such as discharge lamps. Among these, a single-stone inverter having a resonant circuit is used as a lighting device for a compact fluorescent lamp. This type of inverter is disclosed in Japanese Patent Application Laid-Open No. 60-30094 or Japanese Patent Application Laid-open No. 60-118067.

Figure 4 shows the basic configuration of the conventional inverter in this building. In Figure 4, 1 is an AC power supply, 2 is a DC power supply including a full-wave fluorescent circuit and a smoothing capacitor, etc.
3 is an inverter, a parallel resonant circuit consisting of a capacitor 7 and a coil 5, a choke coil 6 serving as a parast of the discharge lamp 4, and a transistor 8 for performing a switching operation.

In the inverter constructed as described above, a voltage as shown in FIG. 5(a) is applied to the transistor 8, and a current as shown in FIG. 5(b) flows, supplying high-frequency power to the load. do.

However, when a smoothing capacitor is used as a DC power supply to obtain a DC voltage with little ripple, the power factor as seen from the AC power supply 1 side becomes low due to the capacitor.

As shown in Fig. 6, it is known that as a DC power supply device to reduce the power factor, it is used in combination with an auxiliary DC power supply that generates an output voltage lower than the peak value of the full-wave rectifier circuit 21. There is. The capacitors 22 and 23 and the diodes 24 to 26 generate a DC voltage that is approximately 1/2 of the peak output voltage of the full-wave rectifier circuit 21, and the inverter 3 has a fixed voltage of 1 in Figure 7. Since a DC voltage having a peak voltage vp is supplied, the power factor of the device can be reduced to 11i.

[Problem that the invention seeks to solve]

Since the current waveform of the transistor in the inverter 3 is as shown in Figure 5, a device using such a DC power source has a large noise voltage. There is a problem in that this noise cannot be sufficiently suppressed with a capacitance comparable to that of a commonly used noise prevention capacitor.

The present invention was made to solve these problems, and an object of the present invention is to obtain a high frequency generator that can increase the power factor and reduce noise.

[Means for solving problems]

The high frequency generator according to the present invention is provided with an auxiliary DC power source that handles an output voltage lower than the output voltage peak value of the full-wave rectifier circuit, and when looking at the DC power source side from the inverter, a predetermined This is a capacitor with a small capacity.

[For production]

In this invention, by using an auxiliary power supply that handles a low output voltage and including a capacitor of a predetermined capacity, the power factor seen from the AC power supply side is maintained high and noise is reduced. .

〔Example〕

Embodiments of the high frequency generator of the present invention will be described below with reference to the drawings. FIG. 1 is a circuit diagram of one embodiment of the present invention, and the same parts as in FIGS. 4 and 6 are designated by the same reference numerals.

In this Figure 1, 1 is an AC power supply, 2 is a DC power supply, a device similar to that explained in Figure 6 is used as an auxiliary DC power supply, and a capacitor 27 is connected between the output terminals of this DC power supply 2. has been done.

3 shows an example of an inverter suitable for the high frequency generator of the present invention. A series circuit including a resistor 12, a diode 13, and a resistor 14 is connected between the output terminals of the DC power supply 2.

The connection point between the resistor 12 and the diode 13 is the transistor 8.
Between the base and emitter of this transistor 8, both ends of a series circuit of a feedback transformer 90, a secondary winding 92, and a capacitor 11 are connected.

Feedback transformer 9 feeds back the load current, and transistor 8t
- Generates a signal for automatic oscillation. One end of the primary winding 91 of this feedback transformer 9 is connected to the collector of the transistor 8, and the other end is connected to the polarization 42 of the discharge lamp 4.

The discharge lamp 4 has electrodes 41, 42 on its shoulders, and a capacitor 10 is connected between the electrodes 41 and 42. That is, the capacitor 10 is placed in parallel with the discharge lamp 4. This capacitor 10 preheats the electrodes 41.42tl and generates a resonant voltage.

Further, the collector of the transistor 8 is connected to the positive output end of the DC power supply 2 via a parallel resonant circuit of the coil 5 and the capacitor 7. This positive output end is connected to the polarization 41 of the discharge lamp 4 via the choke coil 6.

Next, the operation of the high frequency generator of the present invention constructed as described above will be explained with reference to FIGS. 2 and 3. When the current power supply 1 is turned on, the inverter 3 has the seventh
A DC voltage as shown in the figure is applied, the inverter 3 starts an oscillation operation, and the discharge lamp 4 is turned on.

At this time, a voltage as shown in FIG. 5(a) VC is applied to the transistor 8 of the inverter 3, and a voltage as shown in FIG. 5(b) is applied to the transistor 8 of the inverter 3.
A current as shown by Ic flows. Therefore, the change N, the power supply l
However, the capacitor 27 can reduce the noise.

At this time, the electrostatic capacitance of the capacitor 27 is set to ifl:k C, and the auxiliary DC'+ from the capacitors 22, 23 and the diodes 24 to 26 is connected in series with the capacitor 22.
The 23 synthetic companies are referred to as Co.

Figure 2 shows this capacitance ratio K = C/c. FIG. 3 shows the power factor as seen from the current power supply side, and FIG. 3 shows the value measured using the above-mentioned value of K as a parameter and the noise generated on the current power supply 1 side as the noise terminal voltage.

In this experiment, approximately 20 W of high-frequency power was supplied to the load discharge lamp at approximately 40 KHz, and AC power source 1 was supplied with ACl 00 V.
, set the capacitance of capacitor 22.23 to 22 μF (therefore, C
0=11 μF). The capacity of the CG may be appropriately set depending on the high frequency power supplied to the load.

As shown in Figure 2, the power factor can be made high (approximately 0.8 to 0.85 or more) when viewed from the AC'4 source 1 side if the capacity ratio is ≦
It is 0.35. Regarding the noise terminal' voltage, the results were as shown in FIG. From this, it has been found that if the capacitance of the capacitor 27 is increased to a certain extent, even if it is increased further, the noise reduction effect is small. From this Figure 3, the effect was found in dogs when the volume ratio was ≧0.05.

From the above results, it is clear that by setting 0.05≦0.35, the power factor can be maintained well and noise can be reduced.

In the above explanation, a device that generates a voltage approximately 7 times higher than the output voltage peak value vp of the full-wave rectifier circuit 21 was used as the auxiliary DC' power supply. Other configurations may be used as long as the circuit has a high power factor.

The capacitor 27 may be provided on the current transformer input side near the AC power supply 1, as shown by the phantom line in FIG. All you have to do is take I]k.

Even if the inverter 3 is other than the embodiment, if the voltage and current of at least the parallel resonant circuit kWL and the switching transistor are similar to those shown in FIG. 5, that is, the voltage has a half-wave shape of a sine wave.

As long as the current is a sawtooth wave, it does not matter if it is self-excited or separately excited.

Further, the present invention can also be applied to loads other than discharge lamps.

〔Effect of the invention〕

As explained above, in this invention, an auxiliary DC power supply having an output voltage tl - which is lower than the output voltage peak value of a full-wave rectifier circuit is provided in the DC 'i section source, and when looking at this DC power supply side from the inverter. Since it has a capacitor with a predetermined capacity, it also has the advantage of maintaining a high power factor as seen from the power supply side and reducing noise.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram showing an embodiment of the high frequency generator of the present invention, and Fig. 2 is an auxiliary DC' in the same high frequency generator.
A diagram showing the relationship between the power factor of the four sources and the capacitance ratio of the capacitors connected in parallel to these four auxiliary DC sources, and Figure 3 shows the relationship between the frequency and the noise terminal voltage of the same high frequency generator as above. Figure 4 is a circuit diagram showing the basic configuration of a conventional inverter, Figure 5 (a) is a waveform diagram of the heavy pressure applied to the transistor in the inverter of Figure 4, and Figure 5 (b) is a diagram of the pressure waveform applied to the transistor in the same as above. A current waveform diagram, FIG. 6 is a circuit diagram showing another example of a conventional inverter, and FIG. 7 is a voltage waveform diagram applied to the inverter of FIG. 6. 1... AC power supply, 2... DC power supply, 3... Inverter, 4... Discharge lamp, 8... Transistor, 9...
・Feedback transformer, 22.23.27...capacitor,
24-26...Diode. Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (2)

[Claims] (1) A DC power supply including an auxiliary DC power supply that generates a DC voltage lower than the output voltage peak value of the rectifier circuit that rectifies the AC power supply, and a load that has a parallel resonant circuit and converts the DC power of the above DC power supply into high-frequency power. An inverter is connected so as to have a predetermined capacitance when looking at the DC power supply side from the input terminal of this inverter, and the capacitance is C, and the capacitance of the capacitor provided in the auxiliary DC power supply is C_0. When the ratio of capacitance is K=C/C_0, 0.05≦
A high frequency generator equipped with a capacitor satisfying K≦0.35. (2) The high frequency power supply according to claim 1, wherein the auxiliary DC power supply has two capacitors connected in series and generates an output voltage that is approximately 1/2 of the rectifier circuit output voltage peak value. Generator.