JP2007066596A - Discharge lamp lighting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To achieve the lighting of a discharge lamp capable of suppressing influence of output power by fluctuation of ambient temperature. <P>SOLUTION: In order to improve decrease or increase of power for lighting the discharge lamp 15, a thermosensor R6 is used for power regulating resistance to reduce power variation by temperature. The thermosensor R6 has resistance having a positive characteristic, and a resistor R5 and the the thermosensor R6 are connected to the input side of a control circuit 19 for controlling power and to the ground side used for resistively dividing the thermosensor R6, respectively. When temperature rises, the resistance value of the thermosensor R6 is increased and the voltage supplied to the control circuit 19 is increased. When the voltage is increased, the output of the control circuit 19 acts in a direction for extending a period for turning on a transistor Q1 and increasing the output thereof. When the temperature lowers, the resistance value of the thermosensor R6 is decreased and the voltage supplied to the control circuit 19 is dropped. When the voltage is dropped, the output of the control circuit 19 reduces the on-time of the transistor Q1 to drop the output thereof, and controls the value of a D.C. voltage Vd2 output from a first DC/DC conversion circuit 12 to equalize the brightness of the discharge lamp 15. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a discharge lamp lighting device for lighting a high pressure discharge lamp used as a vehicle headlamp, a high pressure discharge lamp used as a light source of a liquid crystal projector, and the like.

A conventional discharge lamp lighting device is equipped with a temperature sensing element in the vicinity of the high pressure discharge lamp in order to control the rise of the luminous flux at the start of the high pressure discharge lamp according to the ambient temperature, and an inverter based on the temperature sensing result of the temperature sensing element. The supply amount of electric power supplied to the high pressure discharge lamp is adjusted. (For example, Patent Document 1)
Japanese Patent Application Laid-Open No. 6-132087

  The technique of the above-mentioned Patent Document 1 keeps the brightness constant by controlling the lamp power to be constant, but even if the load is adjusted to the desired power at the rated voltage and normal temperature. When the component temperature changes due to the ambient temperature and energization, there is a problem that the electric power deviates from the adjusted electric power.

  An object of the present invention is to provide a discharge lamp lighting device that suppresses the influence of changes in output power due to ambient temperature and changes in output power over time after power-on.

  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 a desired first DC voltage, and the DC power supply. A second DC / DC conversion circuit for converting the voltage of the power source into a desired second DC voltage; an igniter for generating a desired high voltage based on the second DC voltage at start-up; and an output of the igniter A discharge lamp to which power necessary for lighting is supplied, a DC / AC conversion circuit for converting the second DC voltage into an AC voltage and causing the discharge lamp to shift from glow to arc lighting, and the control signal based on the first signal. A control circuit for generating an AC voltage in one DC / DC conversion circuit, and driving the DC / AC conversion circuit to convert the AC voltage of the first DC / DC conversion circuit into a DC voltage and a constant voltage Constant power to get Consists of a circuit, the control signal of the control circuit generated based on the second DC voltage, characterized in that it is intended to be generated in response to changes in ambient temperature.

  According to the present invention, it is possible to suppress the influence of the change in the output power due to the ambient temperature and the change in the output power due to the passage of time after the power is turned on.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a configuration 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 DC voltage of the DC power source 11 to the first DC / DC conversion circuit 12. The DC power supply 11 also supplies the second DC / DC conversion circuit 13 via the first DC / DC conversion circuit 12, generates a DC voltage Vd1 boosted to 1 kV, and supplies it to the igniter 14. To do. The igniter 14 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 15 to cause the discharge lamp 15 to glow discharge.

  In the first DC / DC conversion circuit 12, for example, a high DC voltage Vd 2 of 400 V is generated from the output terminal Vo and supplied to the DC / AC conversion circuit 16, and an AC voltage Va 1 is generated and supplied to the constant voltage circuit 17. To do. The constant voltage circuit 17 generates a constant DC voltage Vd3 that is stepped down based on the AC voltage Va1, and supplies the DC voltage Vd3 as a power source for the DC / AC conversion drive circuit 18 and the control circuit 19, respectively. The DC / AC conversion drive circuit 18 generates a drive AC voltage Va2, converts it to the DC / AC conversion circuit 16, and outputs it. The control circuit 19 generates control signals for generating the AC voltage Va1 and the DC voltage Vd2 from the first DC / DC conversion circuit 12, respectively.

  The igniter 14 generates a pulse voltage with a high-voltage DC voltage generated based on the DC voltage supplied from the second DC / DC conversion circuit 13 and supplies the pulse lamp 15 to the glow discharge discharge lamp 15 from the DC / AC conversion circuit 16. For example, the supplied AC voltage Va3 of 400V is supplied. Thereby, the discharge lamp 15 is switched from glow discharge to arc discharge.

  Here, the first DC / DC conversion circuit 12, the constant voltage circuit 17, and the DC / AC conversion circuit 16 of FIG. 1 will be described in more detail.

  First, the configuration of the first DC / DC conversion circuit 12 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 coil n1 is connected to the drain of the switching CMOS transistor Q1. A parallel circuit of a resistor R1 and a capacitor C0 connected in series and a capacitor and a parallel circuit of a diode D1 shown in the drawing are connected to both ends of the primary coil n1. The diode D1, the capacitors C0 and 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 transistor Q1.

  The source of the transistor Q1 is connected to the reference potential point via the resistor R2. The gate of the transistor Q1 is connected to the reference potential point via the resistor R3. A drive signal from the control circuit 19 that generates a signal for driving the transistor Q1 is supplied to the gate of the FET Q1 via the resistor R4.

  One end of the secondary coil n2 is connected to the second DC / DC conversion circuit 13, and is connected to a reference potential point via a diode D2 and a capacitor C2. The other end of the secondary coil n2 is connected to the other end of the primary coil n1. A connection point between the diode D2 and the capacitor C2 supplies a DC voltage Vd2 from the output terminal Vo as a power source for the DC / AC conversion circuit 16.

  Between the output terminal Vo and the reference potential point, a resistor R5 connected in series and a temperature sensitive element R6 which is a resistor having a positive characteristic are connected. The resistor R5 and the temperature sensitive element R6 constitute a voltage detection circuit 20 for detecting a change in the DC voltage Vd2. The connection point between the resistor R5 and the temperature sensing element R6 is connected to the reference potential point via the resistors Ra and Rb. The DC voltage Vw generated at the connection point between the resistor R5 and the temperature sensing element R6 supplies the control circuit 19 with the voltage Vw 'divided by the resistors Ra and Rb. Further, the voltage is supplied from the reference potential point to the control circuit 19 via the resistor R7 and also supplied to the DC / AC conversion circuit 16.

  Next, the configuration of the constant voltage circuit 17 will be described. The anode of the diode D3 is connected to the primary coil n1 of the transformer TR. The cathode of the diode D3 is connected to a reference potential point via, for example, a bead type inductor L1 and an electrolytic capacitor C3, which are impedance elements that suppress high-frequency components. The connection point of the inductor L1 and the electrolytic capacitor C3 is connected to the emitter of the PNP transistor Q2 whose collector is connected to the reference potential point via the capacitor C4. A resistor R8 is connected between the emitter and base of the transistor Q2. The base of the transistor Q2 is connected to the reference potential point via the Zener diode ZD.

  The DC / AC conversion circuit 16 is a so-called full-bridge circuit composed of, for example, CMOS-type switching transistors switches Sa, Sb, Sc, and Sd. The switches Sa and Sd, and the switches Sb and Sc are simultaneously turned on and off. These two groups of switches are alternately turned on and off.

  Next, the operation of the configuration shown in FIG. 1 will be described with reference to the waveform diagram of FIG. The transistor Q1 is controlled to be turned on / off based on a control signal from the control circuit 19, thereby generating an AC voltage Va1 in the primary coil n1 of the transformer TR. The AC voltage Va1 generates a high AC voltage in a tertiary coil (not shown) having a larger number of windings than the primary coil n1 constituting the second DC / DC conversion circuit 14, and a DC of, for example, 1 kV based on this AC voltage. The voltage Vd1 is converted and supplied to the igniter 14. The igniter 14 generates, for example, 25 kV shown in FIG. 2B based on the supplied 1 kV and supplies it to the discharge lamp 15 to cause the discharge lamp 15 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, 400 V shown in FIG. 2A using the diode D2 and the capacitor C2, and supplied to the DC / AC conversion circuit 16.

  The AC voltage Va1 generated on the primary side of the transformer TR is converted into a DC voltage as shown in FIG. 2C by the diode D3, the inductor L1, and the electrolytic capacitor C3. Since AC voltage Va1 includes a ripple current and a ripple voltage, the high frequency component is removed by inductor L1 as shown in FIG. 2 (d). The converted DC voltage is generated from the collector of the transistor Q2 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 19 and the DC / AC conversion driving circuit 18. These are supplied as a power source.

  The control circuit 19 generates a switching signal, turns on / off the transistor Q1, and generates a DC voltage of the DC power supply 11 as an AC voltage Va1. The DC / AC conversion circuit 16 having a full bridge configuration is a drive signal output from the DC / AC conversion drive circuit 18 and turns on the switch Sa and the switch Sd, turns off the switch Sb and the switch 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 15 has been glow-discharged with the high DC voltage generated by the igniter 14 based on the DC voltage Vd1 so far, the discharge lamp 15 shifts to arc discharge based on the AC voltage Va3. Maintain until supplied.

  By the way, the discharge lamp 15 is turned on via the control circuit 19 and the first DC / DC conversion circuit 12 with power set by the DC voltage Vd2 and the output current Ir7 flowing through the resistor R7. Part characteristics change. Therefore, when the set power changes with temperature, the voltage Vw at the connection point of the resistor R6 and the temperature sensing element R7 changes, and the DC voltage Vd2 output from the first DC / DC conversion circuit 12 is the ambient temperature change or the like. The voltage value also changes. For this reason, a voltage change of the DC voltage Vd2 is detected, and control is performed so that the DC voltage Vd2 becomes constant regardless of the ambient temperature based on the detection result.

  Specifically, the resistance change rate with respect to the temperature of the temperature sensing element R7 of the temperature detection circuit 20 is as shown in FIG. 3, for example. In the temperature sensing element R7, as shown in FIG. 3A, the resistance change rate at an ambient temperature of 25 ° C. changes linearly around 0%, and the resistance change rate increases as the temperature increases. The low-efficiency change rate also decreases as the temperature decreases.

  The control based on the temperature change of the temperature sensing element R7 will be described with reference to FIG. First, when the ambient temperature is 25 ° C., as shown in FIG. 3, there is no change in resistance of the temperature sensitive element R7 due to the temperature. Therefore, the DC voltage Vw generated based on the resistance values of the resistor R5 and the temperature sensing element R7 becomes a voltage Vw ′ divided by the resistors Ra and Rb and is supplied to the comparator 191 of the control circuit 19. In this case, the output of the comparator 191 is that the gate of the transistor Q1 from the control circuit 19 is turned off during the ON period of the gate-source voltage Vgs shown in FIG. During the off period of the voltage Vgs, a control signal for turning on the drain-source voltage Vds is output.

  Next, when the ambient temperature rises to about 85 ° C., the output of the control circuit 19 acts to increase the output by extending the time to turn on the transistor Q1, as shown in FIG. 4B. When the ambient temperature becomes as low as about −40 ° C., the resistance value of the temperature sensing element R7 decreases and the voltage at the input terminal of the control circuit 19 decreases. When the ambient voltage decreases, the output of the control circuit 19 acts in the direction of decreasing the on-time of the transistor Q1 as shown in FIG. 4C.

  As described above, the lamp power is controlled by changing the ON / OFF ratio of the DC / AC conversion circuit 16 by changing the ON / OFF ratio of the transistor Q1 according to the change in the ambient temperature, and the power applied to the discharge lamp 15 becomes constant. To control. Thereby, it is possible to prevent a change in brightness of the discharge lamp 15 due to a change in the characteristics of the components used due to the ambient temperature or heat generation of the electronic components.

  FIG. 5 is a circuit configuration diagram for explaining another embodiment of the present invention. The same components as those in FIG. 1 are denoted by the same reference numerals, and different portions will be described.

  In FIG. 1, the DC voltage Vd2 generated at the output terminal Vo is about 400V at the start and about 45V at the rated time. For this reason, in order to suppress the power consumption at the time of starting, it is necessary to make resistance value of resistance R5 small compared with resistance value of temperature sensing element R6. For example, R5 is 400 kΩ and R6 is 2 kΩ. For this reason, when the resistance value of the temperature sensing element R6 is low, it is conceivable that even a slight resistance change makes the power change small and difficult to make fine adjustments.

  Therefore, in this embodiment, the temperature sensing element R6 of FIG. 1 is changed to a normal resistor R8, and the resistor Rb among the resistors Ra and Rb for dividing the voltage input to the comparator 191 is replaced with a resistor having a positive characteristic. The temperature sensitive element Rc is changed.

  The resistance values of the resistor Ra and the temperature sensing element Rc can be set to the same value, for example, about 1 kΩ. For this reason, even if the change amount of the temperature sensing element Rc whose resistance value changes with temperature is very small, the change amount of the voltage Vw ′ obtained at the connection point between the resistance Ra and the temperature sensing element Rc is large. For this reason, it is possible to obtain a reliable control signal from the control circuit 19 even for a subtle temperature change.

  In this embodiment, fine adjustment control can be performed to keep the voltage related to the discharge lamp constant even with a slight temperature change.

The circuit block diagram for demonstrating one Embodiment of this invention. Explanatory drawing for demonstrating the operation | movement of FIG. Explanatory drawing for demonstrating the example of the positive characteristic of a temperature sensing element. 1A is an explanatory diagram for explaining the operation of the main part of FIG. 1 at room temperature, FIG. 1B at 85 ° C., and FIG. The circuit block diagram for demonstrating other embodiment of this invention.

Explanation of symbols

11 DC power supply 12 1st DC / DC conversion circuit 13 2nd DC / DC conversion circuit 14 igniter 15 discharge lamp 16 DC / AC conversion circuit 17 constant voltage circuit 18 DC / AC conversion drive circuit 19 control circuit 20 voltage detection circuit R6, Rc Temperature sensing element

Claims (4)

DC power supply,
A first DC / DC conversion circuit for converting the voltage of the DC power source into a desired first DC 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 at start-up;
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 the second DC voltage into an AC voltage and shifts the discharge lamp from glow to arc lighting;
A control circuit for generating an alternating voltage in the first DC / DC conversion circuit based on a control signal;
The DC / AC converter circuit is driven, and the AC voltage of the first DC / DC converter circuit is converted into a DC voltage and a constant voltage circuit for obtaining a constant voltage,
The discharge lamp lighting device according to claim 1, wherein the control signal of the control circuit generated based on the second DC voltage is generated according to a change in ambient temperature.   2. The discharge lamp according to claim 1, wherein the control signal of the control circuit controls the second DC voltage value in association with an element having a resistance value that linearly changes with a temperature change. Lighting device.   The element having a resistance value that changes linearly with a temperature change is a resistance element on a reference potential point side that obtains a divided voltage set at an output of the first DC / DC conversion circuit. 2. The discharge lamp device according to 2.   3. The element according to claim 2, wherein the element having a resistance value that linearly changes with a temperature change is any one of the resistance elements that further divide the voltage obtained by dividing the second DC voltage. Electric light device.

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