JP2009199861A - Discharge lamp lighting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce power variation of a discharge lamp by temperature dependency of a component caused by the change of ambient temperature. <P>SOLUTION: An output DC voltage obtained by stepping up a DC voltage of a DC power source 11 by a first converter 13 is stepped up by a second converter 14, and a discharge lamp 16 is initiated by using an igniter 15 generating high-voltage pulses only for a predetermined period in startup. After starting the discharge lamp, power required for lighting the discharge lamp 16 is generated by an inverter 17 by converting the output DC voltage of the first converter into an AC. Lamp voltage and current are detected from the output DC voltage of the converter 13, and the result thereof is supplied to a control circuit 20 to control output power of the converter 13. The lamp voltage detection is carried out by comparing the lamp voltage with a reference voltage Vr, the lamp current detection is carried out by comparing a voltage generated from the lamp current with the reference voltage Vr, and the reference voltage compared with the voltage generated from the lamp current is obtained by dividing the reference voltage Vr by resistors R4 and R8. A temperature-sensitive resistive element RT is connected in parallel to the resistor R4. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a discharge lamp lighting device for a high-pressure discharge lamp used as a light source for a high-pressure discharge lamp, a liquid crystal projector, a liquid crystal television, or the like used as an in-vehicle headlamp.

A conventional discharge lamp lighting device for a high-pressure discharge lamp has a temperature-sensitive resistance element arranged in the vicinity of the high-pressure discharge lamp, and controls the resonance characteristics of the inverter to increase the amount of power supply at low temperatures, so that Correction of the luminous flux rise characteristic is performed. (For example, Patent Document 1)
Japanese Patent Laid-Open No. 6-132877 (3rd page [0010], FIG. 1)

  In the technique of the above-mentioned Patent Document 1, the resonance characteristic of the inverter changes with the change of the impedance characteristic due to the change of the high pressure discharge lamp with time, or the load characteristic of the lighting device changes with the change of the power supply voltage. There is a problem that the impedance characteristic is added and the power of the high-pressure discharge lamp is shifted by several watts.

  An object of the present invention is to provide a discharge lamp lighting device capable of reducing the change in power of a discharge lamp due to the influence of temperature by correcting the change in output power with respect to the temperature dependence of components due to a change in ambient temperature.

  In order to solve the above-described problems, a discharge lamp lighting device according to the present invention includes a first converter that converts a DC power supply voltage into a desired DC voltage, and a DC voltage obtained by adding the DC voltage output from the first converter. A second converter for converting to a igniter for generating a high-pressure pulse based on the output voltage of the second converter for a predetermined time at the start-up, and starting the high-pressure discharge lamp, and after the start of the discharge lamp, An inverter that converts the DC voltage output from the first converter into AC and supplies power necessary for lighting the discharge lamp, and detects the lamp voltage and lamp current based on the DC voltage output from the first converter. A control circuit for controlling the electric power output from the first converter based on the detected result, and detecting the lamp voltage supplied to the control circuit Comparing based on a lamp voltage and a reference voltage, the lamp current detection supplied to the control circuit is a comparison between a voltage generated from the lamp current and a reference voltage, and a voltage generated from the lamp current. The reference voltage to be compared is obtained by dividing the reference voltage by resistance, and a temperature-sensitive resistance element is connected in parallel to one of the divided resistors.

  According to the present invention, it is possible to reduce the change in the power of the discharge lamp due to the influence of the temperature by correcting the change in the lamp power that changes depending on the temperature dependence of the component due to the ambient temperature.

Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings.
1 and 2 are diagrams for explaining an embodiment of the discharge lamp lighting device according to the present invention. FIG. 1 is a circuit configuration diagram, and FIG. 2 is a more detailed circuit diagram of a partial configuration of FIG.

  In FIG. 1, reference numeral 11 denotes a DC power source having a constant voltage of 12 V, for example, and supplies the DC voltage of the power source 11 to the first converter 13 via the switch 12. Further, the voltage of the second converter 14 obtained by adding the output voltage of the first comparator 13 generates a DC voltage Vd1 boosted to 1 kV, for example, and supplies it to the igniter 15. The igniter 15 generates a high voltage pulse voltage of, for example, 25 kV based on the supplied DC voltage of 1 kV and supplies the high voltage pulse voltage to the discharge lamp 16, and the discharge lamp 16 is destroyed by discharge to cause glow discharge.

  In the first converter 13, for example, a high DC voltage Vd <b> 2 of 380 V is generated from the input DC voltage of the 12 V power supply 11 and supplied to the inverter 17. An AC voltage Va1 of, for example, 380 V output from the inverter 17 is supplied to the discharge lamp 16 via a transformer winding constituting the igniter 15, and the discharge lamp 16 is shifted from glow discharge to arc discharge, so that arc discharge is normally turned on. Is supplied to the discharge lamp 16. In the arc discharge transition, the DC voltage Vd1 supplied from the second converter 14 to the igniter 15 decreases.

  FIG. 2 is a circuit diagram showing the configuration example of the first converter 13 of FIG. 1 in more detail. The first converter 13 includes a transformer TR, a MOS type switching element Q, a rectifying diode D, and a smoothing capacitor. C.

  In FIG. 2, when a control signal for turning on / off the switching element Q is supplied from the control circuit 20, the current flowing in the primary coil L1 of the transformer TR is controlled based on the on / off control of the switching element Q, and the secondary coil L2 is controlled. And the step-up according to the winding ratio is realized on the tertiary coil side on the second converter 14 side. The boosted AC voltage of the secondary coil L2 generates a DC voltage Vd2 (380 V) via the diode D and the capacitor C. The DC voltage Vd2 can be controlled to a value proportional to the on / off duty ratio of the control signal supplied from the control circuit 20.

  In FIG. 1 again, the output of the first converter 13 that generates the DC voltage Vd2 is connected to a reference potential point via resistors R1 and R2 connected in series. The ramp voltage VL detected from the connection point of the resistors R1 and R2 is supplied to the non-inverting input (+) of the operational amplifier OP1 through the resistor R3.

  The constant voltage circuit 18 generates, for example, a 12V DC voltage Vd3 and a 5V DC reference voltage Vr, which are converted to a constant voltage from the output. This DC voltage Vd3 is supplied from a drive circuit 19 for supplying a switching signal for switching a DC to AC power by alternately switching, for example, a full-bridge switching circuit from the inverter 17, and a control for supplying a driving signal to the driving circuit 19. The power is supplied to each of the circuits 20. The reference voltage Vr is a reference voltage of each of the operational amplifiers OP1 and OP2, and is directly connected to the inverting input (−) of the operational amplifier OP1 and connected to the resistance R4 connected in parallel to the inverting input (−) of the operational amplifier OP2. Each is supplied via the resistance element RT1.

  Further, a resistor R5 for detecting the lamp current IL is connected between the reference potential point to which the resistors R1 and R2 connected in series and the reference potential point of the inverter 17 are connected. The lamp current detected by the resistor R5 is supplied to the non-inverting input (+) of the operational amplifier OP2 via the resistor R6.

  The operational amplifier OP1 outputs to the control circuit 20 differential amplification between the reference voltage obtained by the resistor R7 connected between the reference voltage Vr and the reference potential point and the detected lamp voltage VL as lamp voltage information.

  The operational amplifier OP2 uses the differential amplification of the reference potential obtained by the resistor R8 connected between the reference voltage Vr and the reference potential point, the detected lamp current IL, and the voltage obtained by the resistor R6 as lamp current information as the control circuit 20. Output to.

  The control circuit 20 controls the switching element Q constituting the converter 13 with an on / off duty ratio obtained based on the lamp voltage VL and the lamp current IL, and controls the output DC voltage Vd1. Thereby, the lamp power of the discharge lamp 15 is made constant.

  The drive circuit 19 generates a drive AC voltage Va2 and supplies it to the inverter 17. The inverter 17 converts the DC voltage Vd1 supplied from the first converter 13 into an AC voltage Va1 and outputs it, and the discharge lamp 15 is normally output. Light up.

  Here, referring to FIG. 3 and FIG. 4, control is performed such that the lamp power is constant even when the temperature-sensitive resistance element RT1 connected between the reference potential Vr and the reference potential point changes due to a change in the ambient temperature. Explain what to do.

  As shown in FIG. 3, between the reference potential Vr generated by the constant voltage circuit 18 and the reference potential point, a resistor R8 is connected in series to the temperature-sensitive resistance element RT1 and resistor R4 connected in parallel. . The combined resistance RX of the temperature sensitive resistance element RT and the resistance R4 is (R4 · RT1) / (R4 + RT1). The output voltage Vo at the connection point of the combined resistor RX and the resistor R8 is (RX / (RX + R8)) · Vr. This output voltage Vo is supplied to the inverting input (−) of the operational amplifier OP2. The operational amplifier OP2 performs differential amplification with the voltage obtained by flowing the lamp current IL through the resistor R6 supplied to the non-inverting input (+), and supplies the output to the control circuit 20 as detection information of the lamp current IL. To do.

  The temperature sensitive resistance element RT1 is an element having a temperature characteristic as shown in FIG. 4 with respect to the ambient temperature. That is, when the resistance value of the temperature-sensitive resistance element RT1 at 25 ° C. is set to 0%, the resistance value changes as the temperature rises, and the resistance value decreases as the temperature falls. It has changing temperature characteristics.

  Here, when the ambient temperature rises, the combined resistance RX of the temperature sensitive resistance element RT1 and the resistance R4 increases from the relationship of (R4 · RT1) / (R4 + RT1). The output voltage Vo obtained by dividing the combined resistance RX and resistance R8 by the reference potential Vr is increased, and the output voltage of the operational amplifier OP2 is decreased.

  When the lamp current IL increases, the operational amplifier OP2 performs an operation of narrowing the on-duty for controlling the switch element Q of the first converter 13 from the control circuit 20 in order to keep the lamp power constant. From the temperature characteristics of the temperature sensitive resistor RT1, the output voltage Vo obtained by resistance-dividing the reference voltage Vr when the ambient temperature rises increases in voltage as shown in FIG. 5 and decreases the output voltage of the operational amplifier OP2. Become. The on-duty signal output from the control circuit 20 is narrowed, the DC voltage Vd2 of the first converter 13 is reduced, and control is performed to keep the lamp power supplied to the discharge lamp 16 constant.

  In the above description, the case where the ambient temperature rises has been described. However, when the ambient temperature falls, the reverse control is performed. That is, it is possible to realize control that reduces the lamp power when the ambient temperature is low and increases the lamp power when the ambient temperature is high.

  In this embodiment, it is possible to reduce the lamp power change of the discharge lamp due to the influence of the ambient temperature by performing the control for correcting the change of the lamp power that changes due to the temperature dependency of the component due to the ambient temperature. This also means that the change in the power of the discharge lamp due to the change in the ambient temperature of the part over time after the power is turned on can be reduced.

  6 and 7 are explanatory views corresponding to FIG. 3, and FIG. 7 is an explanatory view corresponding to FIG. 5, for explaining a modification of the embodiment relating to the discharge lamp lighting device of the present invention. . That is, in this embodiment, a temperature-sensitive resistance element RT2 is connected in parallel to a resistor R8 from a state where the temperature-sensitive resistance element RT1 is connected in parallel to the resistance R4. For example, similar temperature characteristics of the temperature sensitive resistance elements RT1 and RT2 are used.

  In this embodiment, the combined resistance RX of the temperature sensitive resistance element RT2 and the resistance R8 is (R8 · RT2) / (R8 + RT2). The output voltage Vo at the connection point of the combined resistor RX and resistor R4 is (RX / (RX + R4)) · Vr.

  Therefore, when the ambient temperature rises, the output voltage Vo obtained by resistance-dividing the reference voltage Vr decreases and the output voltage of the operational amplifier OP2 increases. The lamp power will decrease as shown in FIG. Also in this case, it is possible to correct a change in lamp power that changes depending on the temperature dependence of the component due to the ambient temperature.

  FIG. 8 is a circuit configuration diagram for explaining another embodiment relating to the discharge lamp lighting device of the present invention. In addition, the same code | symbol is attached | subjected to the same component as above-described embodiment, and a different part is demonstrated here.

  This embodiment is different from the configuration of FIG. 1 in that the temperature-sensitive resistance element RT1 is connected in parallel to the resistor R4 and the temperature-sensitive resistance element RT3 is also connected in parallel to the resistor R7. That is, the temperature sensitive resistance elements are respectively connected to the inverting inputs (−) of the operational amplifiers OP1 and OP2 for detecting the lamp current and the lamp voltage. The temperature sensitive resistance element RT3 may have the same temperature characteristics as the temperature sensitive resistance element RT1.

  Here, a case where the ambient temperature rises is considered. When the ambient temperature rises, the resistance value increases due to the temperature characteristics of the voltage detection resistors R1 and R2 and the current detection resistor R5, and the voltage input to the control circuit 20 increases.

  The operation of the temperature-sensitive resistance element RT corresponding to the temperature characteristics of the current detection resistor R5 is as described in the above embodiment.

  The ramp voltage detected by the resistors R1 and R2 is supplied to the non-inverting input (+) of the operational amplifier OP1, and differentially amplified with the reference voltage of the other inverting input (−) to control the output voltage of the operational amplifier OP1. I do.

  When the temperature is high, the resistance values of the resistors R1 and R2 increase, the voltage supplied to the operational amplifier OP1 increases, and the operation of the operational amplifier OP1 operates to decrease the output voltage. The control circuit 20 outputs a signal for narrowing the on-duty of the signal for controlling the switching element Q of the first converter 13, and the first converter 13 outputs a DC voltage Vd2 for reducing the lamp power.

  Conversely, when the temperature is low, the input voltage is low and the operation of the operational amplifier OP1 increases the output voltage. However, the temperature change of the resistance value due to the temperature can be compensated by connecting the temperature sensitive resistor RT3. The on-duty for the switch element Q of the first converter 13 is changed according to the temperature.

  As described above, since the output power varies depending on the temperature, the temperature-sensitive resistance elements RT1 and RT3 are connected in parallel with the resistance connected to the inverting input (−) on the side to be compared with the current and voltage detection results, respectively. Thus, the power characteristics depending on the temperature are made constant power by matching the characteristics with the temperature characteristics of the lighting device.

  In this embodiment, when the temperature is low, the on-duty is narrowed, and when the temperature is high, the on-duty is widened and the operation of canceling the influence of the temperature is performed. This combination makes it possible to make the output power constant by compensating the temperature characteristics of the control circuit, the voltage detection resistors R1 and R2, and the current detection resistor R5.

  The present invention is not limited to the above-described embodiment. For example, in another embodiment of the present invention described with reference to FIG. 8, the temperature sensing resistor RT1 is used as the temperature sensing resistor RT2 in parallel with the resistor R8 as shown in FIG. Is configured to rise to the right, and to the left on the current detection side, so that the temperature characteristics of the resistance on the voltage detection side and the temperature characteristics of the resistance on the current detection side cancel each other, further suppressing the influence on the temperature characteristics. Can do.

The circuit block diagram for demonstrating one Embodiment regarding the discharge lamp lighting device of this invention. Explanatory drawing for demonstrating the specific circuit example of the 1st converter of FIG. Explanatory drawing for demonstrating the principal part of FIG. Explanatory drawing for demonstrating the temperature characteristic example of the temperature sensitive resistance element used for FIG. Explanatory drawing for demonstrating the effect of FIG. Explanatory drawing equivalent to FIG. 3 for demonstrating the modification of one Embodiment regarding the discharge lamp lighting device of this invention. Explanatory drawing equivalent to FIG. The circuit block diagram for demonstrating other embodiment regarding the discharge lamp lighting device of this invention.

Explanation of symbols

11 DC power supply 13 1st converter 14 2nd converter 15 igniter 16 discharge lamp 17 inverter 18 constant voltage circuit 19 drive circuit 20 control circuit Q switching element RT1 to RT3 temperature sensitive resistance element R1 to R8 resistance OP1, OP2 operational amplifier

Claims (2)

A first converter for converting a DC power supply voltage into a desired DC voltage;
A second converter that converts the DC voltage output by the first converter into a DC voltage obtained by adding the DC voltage;
An igniter that generates a high-pressure pulse to start a high-pressure discharge lamp based on the output voltage of the second converter for a predetermined time at the start;
After starting the discharge lamp, an inverter that converts the DC voltage output from the first converter into AC and supplies power necessary for lighting the discharge lamp;
A control circuit that detects a lamp voltage and a lamp current based on the DC voltage output from the first converter, and controls the power output from the first converter based on the detection result;
The lamp voltage detection supplied to the control circuit is a comparison based on the lamp voltage and a reference voltage, and the lamp current detection supplied to the control circuit is a comparison between a voltage generated from the lamp current and a reference voltage. Is,
The reference voltage to be compared with the voltage generated from the lamp current is obtained by dividing the resistance into a reference voltage, and a temperature-sensitive resistance element is connected in parallel to one of the divided resistors. Electric light lighting device.   The reference voltage to be compared with the lamp voltage is generated by a resistor connected between the reference voltage and a reference potential point, and a temperature sensitive resistance element is connected in parallel to the resistor. Discharge lamp lighting device.

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