JPS604676B2 - power supply - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a power supply device used, for example, in a discharge lamp lighting device.

Conventionally, this type of power supply device connects a rectifier circuit to an AC power source, connects a smoothing capacitor between the output terminals of this rectifier circuit, connects a load via a high frequency generator, for example a high frequency inverter, and connects the rectifier circuit to the rectifier circuit. There is a system that generates a high-frequency output by rectifying the DC current using a capacitor and applying it to a high-frequency inverter with no rest period.

However, with this configuration, since the smoothing capacitor is charged and discharged at the peak portion of the rectified waveform, the capacitor needs to have a large capacity in order to reduce the ripple current rate.

This is not only economically disadvantageous but also unfavorable in terms of reliability, and has the disadvantage of significantly lowering the circuit power factor. Therefore, conventionally, in order to eliminate the above-mentioned disadvantages, a capacitor was connected to the output end of the rectifier circuit, and a feedback winding was specially provided on the secondary side of the output transformer of the high frequency inverter, and the output of this winding was fed back to connect the above capacitor. It has been considered that the capacitor is charged and the capacitor is discharged when the output voltage of the rectifier circuit becomes equal to or lower than a certain voltage in each cycle, thereby generating an output without any rest period on the load side.

However, in this case, since the total winding of the output transformer increases, the transformer's bobbin and core become larger, resulting in increased copper loss and iron loss.

Also, providing a feedback winding on the secondary side of the output transformer is the same as connecting another load to the secondary side of this transformer, so the induced voltage in the feedback winding may vary depending on the actual load situation. This has the drawback that fluctuations tend to occur, making it impossible to obtain a stable feedback output, resulting in unstable high-frequency output on the load side. Furthermore, the high frequency component of the induced voltage in the feedback winding may affect the load side, causing an increase in radio noise.
This invention was made to eliminate the above-mentioned drawbacks, and by using the primary winding of the output transformer of the high frequency generator as a feedback winding, the output transformer can be downsized and a stable feedback output can be obtained. It is an object of the present invention to provide a power supply device that can generate a good high-frequency output without a rest section on the side.

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows an example in which the present invention is applied to a discharge lamp lighting device. In the figure, 11 is an AC power supply, and this AC power supply 1
1 is connected to a rectifier circuit, for example, a full-wave rectifier circuit 12.
This rectifier circuit 12 has a series circuit of a capacitor 13 and an isolation diode 14 connected between its output terminals, and is also connected to a high frequency generator such as a high frequency inverter 16 via a constant current inductor 15. This inverter 6 uses a push-pull type inverter, and includes a pair of transistors 17 and 18, bias resistors 19 and 20,
It consists of a resonant capacitor 21 and an output transformer 22. In this case, the inverter 6 connects the midpoint a of the primary winding 221 of the output transformer 22 to the positive terminal of the rectifier circuit 12, and also connects the base of the transistor 17 via the bias resistor 19 and the base of the transistor 17 via the bias resistor 20. The bases of the transistors 18 are connected to each other, and the emitters of the transistors 7 and 18 are also connected to the negative terminal of the rectifier circuit 12 via the inductor 15, respectively, and the collectors of the transistors 17 and 18 are connected to the output transformer 22, respectively. A resonant capacitor 21 is connected between the primary winding 221 and the tertiary winding 223 of the output transformer 22 is connected to the bases of the transistors 17 and 18. There is. On the other hand, intermediate taps b and c are provided between the intermediate point a and both ends of the primary winding 221 of the output transformer 22, respectively.

A high frequency rectifier circuit, for example a full wave rectifier circuit consisting of diodes 23 and 24, is connected to these taps b and c, and this rectifier circuit is connected to the connection point between the capacitor 3 and the diode 14 via an inductor 25 to form a feedback circuit. It consists of Here, the inductor 25 suppresses the peak current to the capacitor 3 and enables full-wave rectification by the diodes 23 and 24, and has a constant current function.

Then, a load such as a discharge lamp 26 is connected to the secondary winding 222 of the output transformer 22.

Next, the operation of the apparatus configured as above will be described.

When the AC power supply 11 is now turned on, a full-wave rectified output is generated from the full-wave rectifier circuit 12, and this is applied to the inverter 16. From this, in the inverter 16, the rectified output is passed through the bias resistors 19, 20 to the transistors 17, 1.
8 as the base current. Then, one of the transistors 17 and 18 turns on first due to a slight imbalance, but if transistor 7 turns on first, current flows through the primary winding 221' of the output transformer 22. Therefore, in this state, an oscillating voltage is generated by the inductance of the primary winding 221 and the resonant capacitor 21, and this
An electromotive force is generated in the next winding 223, which in turn turns on the transistor 8. Therefore, in the following, transistors 7 and 1 will be referred to as the same machine.
8 will be turned on and off alternately. In this case, a rectified output is generated by the induced output of the primary winding 221 of the output transformer 22 via a rectifier circuit consisting of diodes 23 and 24, and this output is applied to the capacitor 13 as a feedback output.

Thereby, the capacitor 13 is charged in a predetermined direction.
Further, this capacitor 13 is discharged when the rectified output of the rectifier circuit 12 becomes lower than a predetermined voltage every half cycle, that is, the charging voltage of the capacitor 3 in this embodiment, and provides this discharge output to the inverter 16. Here capacitor 13
The current waveform of is shown in FIG. 2a. As a result, a small pulsating flow envelope curve is drawn on the secondary winding 222 side of the output transformer 22 of the inverter 16, as shown in FIG.
Moreover, since a high-frequency output without a pause period is generated, the discharge lamp 23 is lit with good luminous efficiency using this high-frequency output.

Incidentally, with such high frequency output, the luminous efficiency of the discharge lamp 23 could be increased by about 10%. Therefore, with this configuration, a feedback signal is obtained from the primary winding side of the output transformer of the high frequency inverter, so the output transformer can be made into a 4-shape, and copper loss and iron loss can be reduced.

Also, compared to conventional ones, which tend to cause fluctuations in the electromotive force in the feedback winding depending on the load condition, the output transformer
Since a stable feedback output can be obtained from the next winding, it is possible to generate a good high-frequency output without any rest periods on the load side, and it is possible to generate a high-frequency output with no rest period on the load side. It is also possible to eliminate the cause of the components affecting the load side and increasing radio noise. Of course, in this case, the capacitor is charged by the feedback output from the primary winding of the output transformer, and when the power supply rectified output drops below a predetermined voltage every half cycle, the capacitor is discharged, thereby generating a high frequency signal with no rest period. Since the output can be obtained, the capacitance of the capacitor can be significantly reduced compared to the conventional method in which the capacitor is charged and discharged at the peak portion of the power supply rectification waveform, which is not only economically advantageous but also preferable in terms of reliability. The power factor can also be improved. Next, FIG. 3 shows another embodiment of this invention.
The same parts as in FIG. 1 are given the same reference numerals.

In this case, the diodes 23 and 24 are connected to one of the output transformers 22.
These are connected to both ends of the next winding 221, respectively. Even with this arrangement, the same effects as described above can be expected.
It should be noted that the present invention is not limited to the above-mentioned embodiments, but can be implemented with appropriate modifications within the scope without changing the gist.

For example, in the embodiment described above, two high-frequency rectifier circuits are used.
Although a full-wave rectifier circuit including two diodes 23 and 24 is used, a half-wave rectifier circuit with one diode may be used as long as the biased magnetization of the output transformer 22 is not considered. Furthermore, although the above description has been given of an example in which the discharge lamp lighting device is applied, it is of course possible to apply the present invention to other loads. As described above, according to the present invention, by using the primary winding of the output transformer of the high frequency generator as the feedback winding, the output transformer can be downsized, stable feedback output can be obtained, and there is a rest section on the load side. It is possible to provide a power source that can generate good high frequency output without any interference.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram showing an embodiment of the present invention, Fig. 2a,
b is a waveform diagram for explaining the same embodiment, and FIG. 3 is a circuit diagram showing another embodiment of the present invention. 11... AC power supply, 12... Full wave rectifier circuit, 13... Capacitor, 14... Diode, 15
... Constant current inductor, 16 ... High frequency inverter, 17, 18 ... Transistor, 19, 20
...Bias resistor, 21...Resonance capacitor,
22 cores...Output transformer, 23, 24...Diode, 25...Inductor, 26...Discharge lamp. Figure 1 Figure 2 Figure 3

Claims (1)

[Scope of Claims] 1. A high-frequency generator that includes an AC power source, a first rectifier circuit that generates a rectified output from the AC power source, and an output transformer, and that generates a high-frequency output from the rectified output via the output transformer. and a second rectifier circuit that generates a rectified output from the induced output of the primary winding of the output transformer;
A power supply device comprising a capacitor that is charged by the rectified output of the second rectifier circuit, discharges while the output voltage of the first rectifier circuit is lower than a predetermined voltage, and supplies the capacitor to the high frequency generator. . 2. The power supply device according to claim 1, wherein the second rectifier circuit is a full-wave rectifier circuit. 3. The power supply device according to claim 1, wherein the second rectifier circuit is a half-wave rectifier circuit. 4. The power supply device according to claim 1, characterized in that a constant current inductor is connected to the second rectifier circuit.