JPH0456552B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a power supply device, more specifically, an inverter circuit that converts a rectified voltage obtained by rectifying a low-frequency AC voltage into a high-frequency AC voltage, and an input terminal of the inverter circuit. A series circuit of a capacitor and a diode having a polarity opposite to the rectified voltage is connected, and the input voltage of the inverter circuit is the same as the rectified voltage when viewed from the inverter circuit side in an area where the input voltage of the inverter circuit is relatively high. The present invention relates to a power supply device including a charging circuit that charges polarity, and in which power is supplied from the capacitor to the inverter circuit in an area where the input voltage of the inverter circuit is relatively low.

As a conventional power supply device, for example, U.S. Pat.
No. 4017785 rectifies a part of the voltage taken out from the secondary winding of the output transformer of the inverter to charge the capacitor. Furthermore, in the device disclosed in Japanese Patent Application Laid-Open No. 125970/1983, a part of the voltage taken out from the primary winding of the output transformer is rectified to charge a capacitor. Further, Japanese Patent Application Laid-Open No. 56-50093 discloses a device in which a low frequency AC voltage is stepped down and then rectified to charge a capacitor.

This type of power supply device can improve the lighting characteristics by eliminating the no-current section of the discharge lamp, for example, and is therefore applied to high-quality discharge lamp lighting devices. A commercial power source is generally used as the low frequency AC power source. In the case of commercial power sources as well as in the case of privately generated power sources, surge voltages are generated due to various causes, and this surge voltage flows into discharge lamp lighting equipment, etc., and can destroy electronic components that are particularly sensitive to high voltages, such as semiconductor devices. may reach.

In order to absorb such surge voltage, for example, Japanese Patent Laid-Open No. 56-56180 discloses a device that is specially provided with a surge absorption circuit (or surge reduction circuit). However, providing such a special surge circuit increases the number of parts, making the device expensive and unavoidably large.

SUMMARY OF THE INVENTION An object of the present invention is to provide a power supply device having a power surge voltage absorbing means that can be constructed at a particularly low cost by skillfully utilizing the above-mentioned features of the circuit configuration so that parts can be used for multiple purposes.

To achieve this object, the present invention is characterized in that a switch element is connected in antiparallel to the diode, the switch element becoming conductive in response to a surge voltage contained in the rectified voltage and entering the rectified voltage. With this configuration, when a surge voltage arrives and the switch element becomes conductive, the capacitor and the switch element are inserted in series between the power supply lines, thereby absorbing the surge voltage of the capacitor.

Hereinafter, the present invention will be explained in more detail with reference to the drawings.

The figure shows an embodiment in which the present invention is applied to a discharge lamp lighting device. The basic main circuit of this device is to rectify the AC voltage obtained from a low frequency AC power source, for example, a commercial power source, using a rectifier 2 to rectify the resulting pulsating DC through a self-excited oscillation type inverter circuit 3. It consists of a circuit that converts the high-frequency AC voltage into a high-frequency AC voltage and supplies it to the discharge lamp 15. The inverter circuit 3 includes a transformer 4 having a primary winding 41 having a center tap connected to one output terminal of the rectifier 2, a secondary winding 42, and a self-oscillation control winding 43; 41, a reactor 6 connected in series to the other output terminal of the rectifier 2, and a reactor 6 connected in parallel to the other output terminal of the rectifier 2.
It includes transistors 7 and 8 connected between the other end and both winding ends of the primary winding 41. A base current is supplied to both transistors 7, 8 from one output terminal of the rectifier 2 via a common resistor 9 and diode 10, as well as individual resistors 11, 12 for each transistor. The transformer winding 4 is used for on/off control of the transistors 7 and 8, that is, for oscillation control.
3 is connected between the base terminals of both transistors 7 and 8 via a series reactor 13 and a shunt resistor 14. The above components 4 to 14 constitute the self-oscillation type inverter circuit 3.

The illustrated circuit supplies energy to the inverter circuit 3 in the section where the instantaneous value of the pulsating DC output of the rectifier 2 is small, in order to eliminate the lack of output of the inverter circuit 3, that is, the no-current section of the discharge lamp 15. The capacitor 16 is a diode 1 arranged with opposite polarity to the output DC of the rectifier 2.
7 in series and connected between both output terminals of the rectifier 2. A capacitor 16 is connected to a reactor 18 and diodes 19, 20 from the midpoint tap of the transformer 4 and auxiliary taps appropriately set on both sides of the transformer 4 in an area where the instantaneous output voltage value of the rectifier 2 is large.
is charged in the same polarity as the output voltage of the rectifier 2, and when the instantaneous value of the output voltage of the rectifier 2 decreases, it is discharged via the transformer primary winding 41, transistor 7 or 8, reactor 6, and diode 17. However, this discharge is prevented from causing the above-mentioned no-current section.

The configuration up to this point has already been proposed, and both transistors 7 and 8 are turned on based on the base current supplied via the resistor 9, the diode 10, and the resistors 11 and 12 by the output voltage of the rectifier 2. is alternately subjected to negative bias and positive bias by the induced voltage in the winding 43, and on the other hand, due to the resonance between the primary winding 41 and the capacitor 5, the transformer 4 is excited at high frequency, and the secondary winding 42 is The discharge lamp 15 is turned on by inducing a high frequency voltage. Note that when the power is first turned on, one of the transistors 7 and 8 is turned on first due to a slight difference in characteristics between the transistors 7 and 8.
The function of the capacitor 16 is as already described.

A feature of the present invention is that a switch element, such as a thyristor 21, is connected in antiparallel to the diode 17, and the thyristor 21 is made conductive by a surge voltage entering from the power supply side. For conduction control, resistors 22 and 23 are connected in series between the output terminals of the rectifier 2, and a Zener diode is connected between the connection point of both resistors and the gate of the thyristor 21.

When a surge voltage enters from the power supply side, the voltage shared by the resistor 23 also increases, so that the thyristor 21 becomes conductive via the Zener diode 24. Due to the conduction of the thyristor 21, the surge voltage that enters from the power supply side is absorbed by the capacitor 16, thereby preventing dielectric breakdown of electronic components such as transistors included in the device. By using the capacitor 16, it is possible to absorb high-energy surge voltages that cannot be absorbed by voltage non-linear resistance elements, and it is also possible to absorb surge voltages with a wide range of, for example, 1ms (milliseconds). can also be absorbed effectively.

The illustrated device also includes a voltage non-linear element 25 in parallel with the capacitor 16. By doing this, narrow steep waves can be mainly absorbed by the capacitor 16, wide power surges can be mainly absorbed by the voltage non-linear element 25, and both wide and narrow surge voltages can be absorbed well. This makes it even more effective.

In the embodiments described above, it has been explained that power is supplied from the self-oscillation type inverter circuit 3 to the discharge lamp 15, but the present invention is not limited thereto. The inverter circuit can be replaced with other known ones as appropriate, and the present invention is also well applicable to loads other than discharge lamps in which the supply voltage and current do not have any rest periods. be able to.

Furthermore, although the charging energy of the capacitor 16 is taken from the transformer winding included in the inverter circuit 3 in the embodiment described above, it is not necessarily necessary, and for example, the charging energy of the capacitor 16 is taken from the input power supply of the rectifier 2. It may also be taken via impedance.

As described above, according to the present invention, the capacitor installed so as not to create a no-current section in a load such as a discharge lamp can also be used as a surge voltage absorber, so a dedicated surge voltage absorber can be used. The number of parts can be reduced compared to the case where the power supply device is specially provided, and the power supply device can be constructed at a lower cost and in a smaller size.

[Brief explanation of the drawing]

The figure is a circuit connection diagram showing an embodiment of the power supply device according to the present invention. 2... Rectifier, 3... Inverter circuit, 16...
... Capacitor, 17, 19, 20 ... Diode, 21 ... Thyristor, 22, 23 ... Resistor,
24... Zener diode, 25... Voltage nonlinear element.

Claims (1)

[Claims] 1. An inverter circuit that converts a rectified voltage obtained by rectifying a low-frequency AC voltage into a high-frequency AC voltage;
Connected between the input terminals of this inverter circuit,
A series circuit of a capacitor and a diode having a polarity opposite to the rectified voltage, and charging the capacitor to the same polarity as the rectified voltage when viewed from the inverter circuit side in an area where the input voltage of the inverter circuit is relatively high. in a power supply device comprising a charging circuit and configured to supply power to the inverter circuit from the capacitor in an area where the input voltage of the inverter circuit is relatively low, antiparallel to the diode,
A power supply device characterized in that a switch element is connected which conducts in response to a surge voltage included in the rectified voltage and enters the rectified voltage. 2. The power supply device according to claim 1, characterized in that a voltage non-linear element is connected in parallel to the capacitor.