JP2006222044A - Discharge lamp lighting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent the liquid leakage of an electrolytic capacitor constituting an identification potential circuit when a diode constituting a constant voltage circuit of a discharge lamp lighting device is short-circuited. <P>SOLUTION: AC voltage is generated from a primary coil n1 of a transformer TR constituting a first DC/DC conversion circuit 13 outputting an output converting voltages of DC power supply 11 into desired DC and AC voltages, respectively, and the AC voltage is converted into a direct current voltage of the constant voltage circuit 18. This DC voltage is applied to a control circuit 20 for generating the AC voltage of the first DC-DC conversion circuit 13 and a DC-AC conversion driving circuit 19 driving a DC-AC conversion circuit 17 converting the DC voltage into the AC voltage for lighting a discharge lamp as a power supply. The constant voltage circuit 18 comprises a diode D3 carrying out conversion into dc, a capacitor 2 and a transistor Q1 generating a constant voltage C2 , a resistor R2 and a Zener diode ZD. An inductance L1 is connected between the diode D3 and the transistor Q1. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a discharge lamp lighting device that converts a DC power source into a desired voltage to light a discharge lamp.

A conventional discharge lamp lighting device forms a constant voltage circuit via a diode to supply a constant voltage to a switching element drive circuit and a control circuit from a connection point between a transformer and a switching element of a DC / DC conversion circuit. (For example, Patent Document 1)
JP 2000-48991 A

  Since the technique of Patent Document 1 described above supplies voltage from the primary winding of the transformer of the DC / DC conversion circuit, which is a voltage source, to the constant voltage circuit, the DC / DC conversion circuit is several tens of kilometers or It operates at a high frequency of over 100 km. Since the ripple current of the switching frequency flows to the capacitor in the input stage of the constant voltage circuit, it was necessary to select a capacitor that can carry a high ripple current. In addition, when the diode is short-circuited, a ripple current that is not rectified flows to the capacitor, so the explosion-proof valve of the capacitor is activated and the electrolyte leaks to the outside instantly. is there.

  An object of the present invention is to provide a discharge lamp lighting device that prevents liquid leakage of an electrolytic capacitor constituting the same constant voltage circuit even when a rectifying diode constituting the constant voltage circuit is short-circuited.

  In order to solve the above-described problems, a discharge lamp lighting device according to the present invention includes a DC power supply, a first DC / DC conversion circuit that converts a voltage of the DC power supply into desired first DC voltage and AC voltage, and A second DC / DC conversion circuit for converting the voltage of the DC power source into a desired second DC voltage, and a desired high voltage based on the second DC voltage of the first DC / DC conversion circuit at the start. , An electric discharge lamp supplied with electric power required for lighting based on the output of the igniter, a direct current voltage output from the first DC / DC conversion circuit is converted into an alternating current voltage, and the electric discharge lamp A DC / AC conversion circuit for lighting an arc from glow, a drive circuit for generating an alternating voltage in the first DC / DC conversion circuit, and the first DC / DC conversion for driving the DC / AC conversion circuit Circuit A constant voltage circuit that converts a current voltage into a DC voltage and obtains a constant voltage, and a means for converting the DC voltage that constitutes the constant voltage circuit into a constant voltage. An impedance element is connected in series to the above.

  According to the present invention, even when the diode constituting the constant voltage circuit for lighting the discharge lamp is short-circuited, the ripple current flowing in the electrolytic capacitor constituting the constant voltage circuit is reduced, thereby reducing the electrolytic capacitor. Liquid leakage can be prevented.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a conceptual diagram for explaining an embodiment of the present invention. Reference numeral 11 denotes a DC power source having a constant voltage of 12 V, for example, and supplies the power of the DC power source 11 to the first DC / DC conversion circuit 13 via the power switch 12. The DC power supply 11 also supplies the second DC / DC conversion circuit 14 to generate a DC voltage Vd1 boosted to 1 kV and supply it to the igniter 15. The igniter 15 generates a high-voltage pulse voltage of, for example, about 25 kV based on the supplied 1 kV DC voltage and supplies it to the discharge lamp 16 to cause the discharge lamp 16 to glow discharge.

  In the first DC / DC conversion circuit 13, for example, a high DC voltage Vd <b> 2 of 400 V is generated and supplied to the DC / AC conversion circuit 17, and an AC voltage Va <b> 1 is generated and supplied to the constant voltage circuit 18. The constant voltage circuit 18 generates a constant DC voltage Vd3 that has been stepped down based on the AC voltage Va1 and supplies it as power sources for the DC / AC conversion drive circuit 19 and the control circuit 20, respectively. In the DC / AC conversion drive circuit 19, a drive AC voltage Va2 is generated and supplied to the DC / AC conversion circuit 17, and the DC voltage Vd2 supplied from the first DC / DC conversion circuit 13 is converted into an AC voltage Va3. Output. The control circuit 20 generates control signals for generating the AC voltage Va1 and the DC voltage Vd2 from the first DC / DC conversion circuit 13, respectively.

  The igniter 15 generates a pulse voltage with a high-voltage DC voltage generated based on the DC voltage supplied from the second DC / DC conversion circuit 14, and then glows the discharge lamp 16 from the DC / AC conversion circuit 17. For example, the supplied AC voltage Va3 of 400V is supplied. Thereby, the discharge lamp 16 is switched from glow discharge to arc discharge.

  Next, referring to the circuit configuration diagram of FIG. 2 and the waveform diagram of FIG. 3 showing the first DC / DC conversion circuit 13, the constant voltage circuit 18, and the DC / AC conversion circuit 17 in more detail in FIG. 1 will be described in more detail. In FIG. 2, the same parts as those in FIG.

  In FIG. 2, first, the configuration of the first DC / DC conversion circuit 13 will be described. The positive electrode of the DC power supply 11 is connected to one end of the primary coil n1 of the transformer TR. The other end of the primary side coil n1 is grounded via a switch circuit SW composed of CMOS transistors. The switch circuit SW is driven by the output of the control circuit 20. A series circuit of a diode D1 having a polarity shown and a capacitor C1 is connected in parallel to both ends of the primary coil n1, and a resistor R1 is connected in parallel to the capacitor C1. The diode D1, the capacitor C1, and the resistor R1 constitute a snubber circuit that absorbs the surge voltage generated by the transformer TR and prevents the surge voltage from being applied to the switch circuit SW.

  One end of the secondary coil n2 is connected to the second DC / DC conversion circuit 14 and grounded via the diode D2 and the capacitor C2. A connection point between the diode D2 and the capacitor C2 is connected to the DC / AC conversion circuit 17. The other end of the secondary coil n2 is connected to the other end of the primary coil n1.

  Next, the configuration of the constant voltage circuit 18 will be described. The anode of the diode D3 is connected to the connection point between the primary coil n1 of the transformer TR and the switch 12. The cathode of the diode D3 is grounded via, for example, a bead type inductor L1 and an electrolytic capacitor C2, which are impedance elements that suppress high frequency components. The connection point of the inductor L1 and the electrolytic capacitor C2 is connected to the emitter of the PNP transistor Q1 whose collector is grounded via the capacitor C3. A resistor R2 is connected between the emitter and base of the transistor Q1. The base of the transistor Q1 is grounded via a Zener diode ZD.

  Further, the DC / AC conversion circuit 17 comprises, for example, CMOS-type switching transistors switches Sa, Sb, Sc, and Sd to form a full bridge circuit, and the switches Sa and Sd, and the switches Sb and Sc are simultaneously turned on / off. These two groups of switches are alternately turned on and off.

  Next, the operation of the configuration shown in FIG. 2 will be described with reference to the waveform diagram of FIG. The AC voltage Va1 generated in the primary side coil n1 of the transformer TR by controlling the switch circuit SW on and off is a tertiary side (not shown) having a larger number of windings than the primary side coil n1 constituting the second DC / DC conversion circuit 14. A high AC voltage is generated in the coil, converted to a DC voltage Vd1 of, for example, 1 kV based on this AC voltage, and supplied to the igniter 15. The igniter 15 generates, for example, 25 kV shown in FIG. 3B based on the supplied 1 kV and supplies it to the discharge lamp 16 to cause the discharge lamp 16 to glow discharge.

  Further, the transformer TR increases the winding ratio of the secondary side coil n2 as compared with the primary side coil n1, and generates a high AC voltage corresponding thereto. This AC voltage is rectified to a DC voltage Vd2 of, for example, 400V shown in FIG. 3A using the diode D2 and the capacitor C2, and supplied to the DC / AC conversion circuit 17.

  The AC voltage Va1 generated on the primary side of the transformer TR is converted into a DC voltage as shown in FIG. 3C by the diode D3, the inductor L1, and the electrolytic capacitor C3. Since AC voltage Va1 includes a ripple current and a ripple voltage, high frequency components are removed by inductor L1 as shown in FIG. The converted DC voltage is generated from the collector of the transistor Q1 by making the DC voltage Vd3 constant by the voltage determined by the Zener voltage of the Zener diode ZD, and this DC voltage Vd3 is generated by the control circuit 20 and the DC / AC conversion drive circuit 19. These are supplied as a power source.

  The control circuit 20 generates a switching signal, and controls the switch circuit SW to be turned on / off to generate a DC voltage of the DC power supply 11 as an AC voltage. The DC / AC conversion circuit 17 having a full bridge configuration is a drive signal output from the DC / AC conversion drive circuit 19 and turns on the switches Sa and Sd, turns off the switches Sb and Sc, and then turns on the switch Sa. Control for turning off the switch Sd and turning on the switch Sb and the switch Sc are alternately performed, and an AC voltage Va3 in which the AC voltage Va2 is superimposed on the DC voltage Vd2 is obtained from the output. From the state in which the discharge lamp 16 has been glow-discharged with the high DC voltage generated by the igniter 15 based on the DC voltage Vd1 until now, the discharge lamp 16 shifts to arc discharge based on the AC voltage Va3. Maintain until supplied.

  By the way, when the diode D3 fails, the inductor L1 is opened so that the output of the constant voltage circuit 18 is turned off, and the ballast operation is stopped without the electrolytic capacitor C2 failing. As a result, the explosion-proof valve of the electrolytic capacitor C2 is activated, and the electrolyte leaks to the outside, and it is possible to prevent the generation of smoke and off-flavor due to evaporation of the electrolyte. Further, since the ripple current flowing through the electrolytic capacitor C2 of the constant voltage circuit 18 is small, a capacitor with a small ripple current rating can be used, and the shape can be reduced.

  FIG. 4 is a circuit configuration diagram corresponding to FIG. 2 for explaining another embodiment of the present invention. In this embodiment, the AC voltage Va11 is extracted from the intermediate tap of the primary coil n1 of the transformer TR from the state where the AC voltage Va1 is supplied to the constant voltage circuit 18 from the connection point between one end of the switch 12 and the transformer TR. Is different from the above-described embodiment. The same components as those in FIG. 2 are denoted by the same reference numerals and different configurations will be described here.

  Since the intermediate tap with few windings is taken out, the generated AC voltage Va11 is lower than the AC voltage Va1 generated in FIG. For this reason, the generated ripple current component also flows into the constant voltage circuit 18 with its level being low.

  In this embodiment, since the ripple current flowing through the wiring pattern from the primary coil n1 of the transformer TR to the constant voltage circuit 18 becomes smaller, the high-frequency ripple voltage becomes smaller, so that noise can be reduced. Similarly to the above-described embodiment, when the diode D3 fails, the inductor L1 is opened so that the output of the constant voltage circuit 18 is turned off, and the ballast operation is stopped without causing the electrolytic capacitor C2 to fail. As a result, the explosion-proof valve of the electrolytic capacitor C2 is activated, and the electrolyte leaks to the outside, and it is possible to prevent the generation of smoke and off-flavor due to evaporation of the electrolyte. Further, since the ripple current flowing through the electrolytic capacitor C2 of the constant voltage circuit 18 is small, a capacitor with a small ripple current rating can be used, and the shape can be reduced.

The circuit block diagram for demonstrating one Embodiment of this invention. Explanatory drawing for demonstrating the operation | movement of FIG. The circuit block diagram for demonstrating other embodiment of this invention. Explanatory drawing for demonstrating the operation | movement of FIG.

Explanation of symbols

11 DC power supply 12 Power switch 13 First DC / DC conversion circuit 14 Second DC / DC conversion circuit 15 Igniter 16 Discharge lamp 17 DC / AC conversion circuit 18 Constant voltage circuit 19 DC / AC conversion drive circuit 20 Control circuit TR Transformer D3 Diode L1 Inductor C2 Electrolytic capacitor Q1 Transistor ZD Zener diode

Claims (2)

DC power supply,
A first DC / DC conversion circuit for converting the voltage of the DC power source into desired first DC voltage and AC voltage;
A second DC / DC conversion circuit for converting the voltage of the DC power source into a desired second DC voltage;
An igniter that generates a desired high voltage based on the second DC voltage of the second DC / DC conversion circuit at the time of starting;
A discharge lamp to which power necessary for lighting is supplied based on the output of the igniter;
A DC / AC conversion circuit that converts a DC voltage output from the first DC / DC conversion circuit into an AC voltage, and the discharge lamp shifts from glow to arc lighting;
A control circuit for generating an AC voltage in the first DC / DC conversion circuit and an AC voltage of the first DC / DC conversion circuit for driving the DC / AC conversion circuit are converted into a DC voltage and a constant voltage And a constant voltage circuit
A discharge lamp lighting device, wherein an impedance element is connected in series between a means for converting to direct current constituting the constant voltage circuit and a means for converting the voltage converted into direct current by the means into a constant voltage. The first DC / DC conversion circuit includes a transformer having a coil whose secondary side has a larger number of turns than the primary side, and means for converting an AC voltage generated on the secondary side of the transformer into a DC voltage,
2. The discharge lamp lighting according to claim 1, wherein the AC voltage supplied to the constant voltage circuit is one end or the middle of the primary side of the transformer that generates the AC voltage of the first DC / DC conversion circuit. apparatus.

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