JPS60208097A - Device for firing discharge lamp - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a discharge lamp lighting device that detects half-wave discharge of a discharge lamp and completely or intermittently stops an inverter.

(Prior art) Conventionally, when a half-wave discharge occurs in a discharge lamp lighting device using a single-speed inverter, the voltage across the discharge lamp is detected and output to the control circuit, and the inverter is completely switched off, but the output voltage of the single-speed inverter is Since the positive and negative values are asymmetrical, there is a difference in the detected voltage depending on the direction of the half-wave discharge, which may cause the w control circuit to malfunction.

The output voltage of a discharge lamp lighting device using such a one-wheel inverter is asymmetrical in positive and negative as shown in the solid line waveform shown in Figure 4, and when the switching transistor of the inverter is on, the waveform is a, and when it is off, the output voltage is asymmetrical. has the waveform b and the output voltage is different. For this reason, the lamp voltage is a when the transistor is on, as shown in the dotted line waveform during normal lighting.
', when off, the waveform is b', but when a half-wave discharge occurs, the lamp voltage during the half-wave period when the lamp is not turned on has a waveform of a solid line instead of a dotted line, and the polarity is asymmetrical. For example, the lamp voltage waveform when the lamp is lit during the on period and not lit during the off period is the dotted line a--
The waveform will be as shown by the solid line, and if it is not lit during the on period but is lit during the off period, the waveform will be as shown by the solid line a and dotted line b'.
In the case of the real 1i1 waveform of b, the detected voltage has a larger voltage value than that on the a side.

Conventionally, as mentioned above, different voltage values were detected depending on the direction of half-wave discharge, and this was output to the safety control circuit to stop the inverter, so when a low voltage value was detected, even if half-wave discharge was occurring, When the safety circuit did not operate and a high voltage value was detected, there was a risk that the safety circuit would malfunction and cause the lamp to turn off or blink even if half-wave discharge was not occurring.

In order to prevent such malfunctions, conventionally, the detection winding provided on the secondary side of the inverter transformer is made of Na, Na, Na, or Na, with different numbers of windings corresponding to the direction of the half-wave discharge, as shown in Figure 5.
It was configured with a Nb winding, which made the different detection voltages into almost the same voltages and output them to the safety circuit, but the winding was complicated and the number of taps was large (which led to an increase in cost).

(Object of the Invention) The present invention provides a discharge lamp lighting device that completely protects equipment by setting the output voltage of a detection device to a voltage that is unrelated to the direction of half-wave discharge.

(Structure of the Invention) Figures 1 to 3 all show one embodiment of the present invention. In Figure 1, Ql is a switching transistor of a single-stone inverter, ■ is a transformer of the inverter, and N1 is a switching transistor of a single-stone inverter. The primary @ wire, N2 is an output winding connected to the discharge lamp 1a as a load, and N3 is a self-help base winding of the switching transistor. DI and C4 are diodes and capacitors for rectifying and smoothing the power supply, and C5 and R7 are the diodes and capacitors for rectifying and smoothing the power supply.
Resistor and capacitor in parallel to next winding N1, C6 to -N4
is a detection winding serving as a detection device for the voltage across the discharge lamp La, and the detection voltage is detected by the diodes D2, C3,
Applied to a safety control path consisting of resistors R1-R6, capacitors C1, C2, C3, and 888.8CR.

Resistor R+, R2 and capacitor of the control circuit, CI
, C2 are impedances corresponding to positive and negative asymmetric voltages as described above and shown in the fourth diagram, and when the output voltage of the detection winding N4 is a half wave of one degree, I! anti-R1
, is applied to capacitor 01, and when the other half wave is applied, it is applied to resistor R2 and capacitor C2. For example, resistor R1
, the impedance of capacitor C1 is small, resistor R2,
The impedance of the capacitor C2 is made large, and the detection voltage of the larger voltage of the positive and negative asymmetric voltages shown in Figure 4 charges the capacitor C1 of the smaller capacity, and the detection voltage of the smaller voltage charges the capacitor of the larger capacity. Charge C2. As a result, even if the voltages are asymmetrical in positive and negative, the discharge voltages of both containers I'C1 and C2 are made equal, and the capacitor C3 is charged by this discharge voltage.

Since the capacitors C1 and C2 and the diodes D2 and C3 constitute a voltage doubler rectifier circuit, the capacitor C3 is charged with the double voltage. When the discharge lamp La performs a half-wave discharge, the detection voltage of the detection winding N4 differs depending on the direction of the half-wave discharge as described above, but as mentioned above, both capacitors C1 and C2 have different impedances to equalize the voltage. Since the capacitor C3 is charged to a double voltage by each of these voltages, if a half-wave discharge occurs, the voltage of the capacitor C3, which is charged to a double voltage, changes regardless of the direction of the half-wave discharge. Due to this change in the voltage of capacitor C3, S
The BS turns on and triggers the SCR, said SCR being connected to the base of the switching transistor Q1.
When turned on, the switching transistor Q1 is turned off, thereby completely or intermittently stopping the lighting of the discharge lamp undergoing half-wave discharge. Note that R4 is a resistor for preventing malfunction.

FIG. 2 shows the resistors R1, R2, and S of the embodiment shown in the first diagram.
This is a modification that does not use BS, SCR, etc., and the same reference numerals as in FIG. 1 indicate the same elements. In this embodiment, when the voltage of the capacitor C3 exceeds the Zener voltage of the voltage regulator diode ZD, the capacitor C7 is charged, and when this capacitor C7 reaches a predetermined voltage, the transistor Q2 is turned on, thereby turning on the main switching transistor Q1.
Turn off the lamp to stop lighting the discharge lamp that is discharging half-wave.

Note that the resistor RIO after the constant voltage diode ZD is omitted.
A fluorescent lamp may be used as the discharge lamp La.

Figures A and 8 in Figure 3 are modified examples of the circuit within the dotted line of the embodiment shown in the second figure, where the same reference numerals as in Figures 1 and 2 indicate the same elements, and Figure A is more detailed. Balancer resistors R1 and R2 are added for precise setting.

Note that since the illustrated embodiment is of a one-cage type with an inverter transformer, an example is shown in which a detection winding N4 for detecting the secondary side voltage C is used as a device for detecting the voltage across the discharge lamp.
In an apparatus in which the transformer is not of the leakage type, the voltage across the discharge lamp is directly detected via an impedance element in the circuit of the discharge lamp, and is output to the voltage doubler rectifier circuit.

(Effects of the Invention) As described above, the present invention configures a voltage doubler rectifier circuit by making the impedances of the capacitors C1 and C2 in series different, and inserts this into the output side of the device for detecting the voltage across the lamp. Therefore, when the discharge lamp la makes a half-wave discharge, regardless of the direction of the half-wave discharge, the voltage across the discharge lamp can be detected without error and applied to the τ control circuit, and therefore the Ill can be safely protected. can do. In addition, the reliability of the lighting device is improved, and not only is it possible to accurately notify the end of the lamp life, but the design margin is wider than when there is a difference in detection voltage, making it easier to make adjustments. It is possible.

[Brief explanation of drawings]

Fig. 1 shows one embodiment of the present invention, Figs. 2 and 3 A and B each show other embodiments, 4vA shows a voltage waveform diagram, and Fig. 5 shows a conventional example. It is a drawing. N4: Detection device. La: discharge lamp. C1, C2: Capacitor. Patent Applicant Toshiba W10 Corporation Agent Patent Attorney Oka 1) Kikuji Figure 1 4 Figure 3 □ Figure 4 Figure 5

Claims (1)

[Claims] Discharge lamp lighting comprising: a single-stone inverter that energizes a discharge lamp; a detection device that detects voltage across the discharge lamp; and a control circuit that stops the inverter based on the detection output of the detection device during half-wave discharge. In the device, a discharge lamp characterized in that a voltage doubler rectifier i circuit is provided on the output side of the detection device, and the voltage doubler rectifier circuit has series capacitors having different impedances, and the output of the voltage doubler rectifier circuit is applied to the control circuit. lighting device.