JPS5854596A - Device for dimming 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 dimmer, and more particularly to a discharge lamp dimmer that provides sufficient preheating and stable lighting even when deeply dimmed.

Conventionally, a discharge lamp dimmer has been known in which a phase control circuit is inserted between an AC power supply and a discharge lamp lighting device, and the discharge lamp is lit and dimmed by the phase-controlled output voltage from the phase control circuit. There is. By the way, in such a light control device,
When the control phase of the phase control circuit is increased to achieve deep dimming, the filament current of the discharge lamp decreases, the filament temperature decreases, and the period during which the lamp current is stopped becomes longer, causing ions to disappear. There was a drawback that the lighting was unstable, such as turning off and flickering.

The purpose of the present invention is to solve the above-mentioned problems in the conventional type.
The side directly connected to the power supply (power supply side) and the opposite side (non-power supply side) of each filament of the discharge lamp are connected via a semiconductor switch, and this semiconductor switch is opened and closed in synchronization with the AC power supply. The idea is to maintain a constant level of preheating even when dimming deeply, or to increase preheating the deeper the dimming is done, to maintain stable discharge even when dimming deeply.

The present invention will be described in detail below using the drawings.

FIG. 1 is a circuit diagram of a discharge lamp dimming device according to an embodiment of the present invention. In the figure, 1 is an AC power source such as a commercial power supply, 2 is a phase control circuit including phase control elements such as SCRs and triacs connected in antiparallel, and 3 is a discharge lamp lighting device.
4 is a preheated discharge lamp having a filament of 41°42; 5
6 is a semiconductor switch such as SCR, TRIAC, GTO, transistor, etc., and 6 is a control device for controlling opening/closing of the semiconductor switch. The phase control circuit 2 is connected to an AC power supply,
Outputs phase controlled voltage. The discharge lamp lighting device 3 is
The discharge lamp 4 is turned on by this phase-controlled voltage. The semiconductor switch 5 connects the filaments 41 and 4 of the discharge lamp 4.
Connected between the non-power side of 2.

The control circuit 6 controls the conduction start phase β or the conduction period of the semiconductor switch 5 in synchronization with the AC power supply 1.

The conduction start phase β is kept constant or controlled in relation to the control phase α of the phase control circuit 2. In order to obtain constant preheating, the conduction start phase β is kept constant. In this case, the control phase α
is controlled in the range of 0 to β.

Further, the input of the control circuit B is connected to the AC power supply 1 or the output of the phase control circuit. For example, when the conduction start phase β is advanced to increase preheating as the control phase α is larger, that is, the deeper the dimming is, the conduction start phase β is controlled in relation to the control phase α. In this case, the input of the control circuit B can be connected to a desired point inside the phase control circuit 2 to directly detect the control phase α, or the input of the control circuit B can be connected to the output of the phase control circuit 2 or the output of the lighting device B to α is detected from the effective value, average value, differential value, etc. of the control output voltage or current.

Next, we will explain the operation of the discharge lamp dimmer and the voltages at each part in Figure 2. will be explained with reference to current waveforms.

When the phase control circuit 2 becomes conductive at the control phase α (Fig. 2b)
A lamp current IL (FIG. 2C) flows through the discharge lamp 4 through the lighting device 3, and the discharge lamp 4 is lit. Next, when the control circuit 6 sends out a control signal at the conduction start phase β, the semiconductor switch 5 becomes conductive, the non-power supply sides of the filaments 41 and 4-2 of the discharge lamp 1 are short-circuited, and the voltage across the discharge lamp 1 becomes zero. So discharge lamp 1
is extinguished and the lamp current becomes zero, and a filament current If (FIG. 2C) flows from the lighting device 3 via the filament 41, the semiconductor switch 5, and the filament 42, and the discharge lamp 1 is preheated. That is, the discharge lamp 4 is ignited between the control phase α and the conduction start phase β, and is preheated in the range after the conduction start phase within the range of the conduction section of the phase control circuit 2.

As described above, according to the present invention, constant preheating is achieved by keeping the conduction start phase β of the semiconductor switch constant, and the conduction start phase β is related to the control phase α, so that, for example, the deeper the dimming, the more conduction starts. By advancing the phase β and increasing preheating, stable discharge can be maintained even when dimming is deep.

[Brief explanation of the drawing]

FIG. 1 is a circuit configuration diagram of a discharge lamp dimmer according to the first embodiment to example of the present invention, and FIG. 2 is a diagram showing each voltage and current waveform of the discharge lamp dimmer of FIG. 3 is a power supply voltage, b is a phase control circuit output voltage, C is a lamp 1 current, and d is a waveform diagram of a filament current. DESCRIPTION OF SYMBOLS 1. AC power supply, 2.. Phase control circuit, 6.. Discharge lamp lighting device, 4.. Preheating discharge lamp, 5.. Semiconductor switch, 6.. Control circuit. Patent applicant: Toshiba Electric Materials Corporation Representative patent attorney: Tatsuo Ito 〃 Tetsuya Ito

Claims (1)

[Claims] 1. An AC power source, a phase control circuit connected to the AC power source and outputting a phase-controlled voltage, and a preheating discharge lamp;
a lighting device that lights the discharge lamp using the phase-controlled voltage; a semiconductor switch connected between the non-power side of each filament of the discharge lamp; and a semiconductor switch that opens and closes in synchronization with the AC power source. A discharge lamp dimmer comprising a control circuit for controlling the discharge lamp. 2. The discharge lamp dimmer according to claim 1, wherein the conduction start phase of the semiconductor switch is constant, and the control phase of the phase control circuit is controlled in a range from zero to the conduction start phase. 3. The discharge lamp dimmer according to claim 1, wherein the conduction start phase of the semiconductor switch is controlled in relation to the control phase of the phase control circuit.