JPS5854595A - 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 dimming device that provides stable discharge even during deep dimming.

Conventionally, a discharge lamp lighting device of a so-called high-frequency superposition type that lights a discharge lamp by applying a low-frequency voltage and a high-frequency voltage in a superimposed manner, and a phase control circuit inserted in series with the low-frequency power supply of this lighting device, have been used. 2. Description of the Related Art A discharge lamp light control device is known that controls light by applying a phase-controlled voltage as a voltage on the low frequency side. However, such a dimming device has a drawback that when the dimming is deepened, the lamp current of the discharge lamp decreases, the filament temperature decreases, and lighting becomes unstable.

In view of the above-mentioned problems with the conventional type, an object of the present invention is to provide a discharge lamp lighting device which performs dimming by controlling the phase of the low frequency power supply voltage of a discharge lamp lighting device of the high frequency superimposition type. On the side of each filament that is directly connected to the power supply (power supply side) and the opposite side (non-power supply side), there is an impedance (
Based on the concept of connecting a series circuit of a high-frequency impedance (hereinafter referred to as high-frequency impedance) and a semiconductor switch and controlling the opening and closing of this semiconductor switch, stable dimming is achieved by ensuring preheating of the discharge lamp.

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 a filament)11.
2 is a low-frequency power source, for example, a commercial power source with a voltage similar to the tube voltage of the discharge lamp 1; 3 is a phase control circuit including a phase control element such as a SEA or a TRIAC connected in antiparallel; 4; is a high frequency power source whose combined voltage with the voltage of the low frequency power source 2 is higher than the starting voltage or restriking voltage of the discharge lamp 1, for example, the low frequency power source 2 or the phase control circuit 3.
A high-frequency inverter 5 inputs the output of the high-frequency power source 4 to the low-frequency power source 2, and prevents interference from the high-frequency power source 4 to the low-frequency power source 2. This is a low-frequency current-limiting element that limits the supplied lamp current, such as a choke "i!" or filter, 6
7 is a high frequency current limiting element, such as a capacitor or filter, for preventing interference from the low frequency power source 2 to the high frequency power source 4 and limiting the lamp current flowing from the high frequency power source 4 into the discharge lamp 1; 7 is the frequency of the high frequency power source 4; An impedance (hereinafter referred to as high frequency impedance) that has a high impedance for
is a semiconductor switch such as a thyristor, triac,
GTO or transistor 9 is a control circuit that controls opening and closing of the semiconductor switch. The phase control circuit 3 is connected to the low frequency power supply 2 and outputs a phase-controlled voltage. In the discharge lamp I IC, a phase control circuit 6 and a high frequency power source 4 are connected in parallel via a low frequency current limiting element 5 and a high frequency current limiting element 6, respectively. Filament of discharge lamp 1) 11.12
A series circuit of a high frequency impedance 7 and a semiconductor switch 8 is connected between the non-power supply side of the . The control circuit 9 controls the conduction start phase β or the conduction period of the semiconductor switch 5 in synchronization with the low frequency power supply 2. 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 within the range of 0 to β. Also,
The input of the control circuit 9 is connected to the low frequency power supply 2 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 dimming is more severe, the conduction start phase β is controlled in relation to the control phase α. In this case, the input of the control circuit 9 is connected to a desired location inside the phase control circuit 2 to directly detect the control phase α,
Alternatively, it is connected to the output of the phase control circuit 2 to detect α from the phase control output voltage or its differential value.

In addition, when using a high frequency inverter as a high frequency power supply, the input may be taken from either before or after phase control.

Further, in this discharge lamp dimming device, the phase control circuit and the lighting device may be configured separately, or a system configuration may be adopted in which a large number of lighting devices are connected to one phase control circuit.

Next, the operation of this discharge lamp dimmer device will be explained with reference to voltage and current waveforms at various parts in FIG.

When the phase control circuit 3 becomes conductive at the control phase α (Fig. 2b)
, a lamp current It in which a low-frequency electric current and a high-frequency current are superimposed from the phase control circuit 3 and the high-frequency power supply 4 to the discharge lamp 1 via the low-frequency current-limiting element 5 and the high-frequency current-limiting element 6, (Fig. 2C) flows. Then, at the conduction start phase β, the control circuit 9
When the semiconductor switch 8 is closed by a control signal from
The non-power side of the filament (11, 12) of the discharge lamp 1 short-circuits the low frequency current through the high frequency impedance 7, and the lamp current (2) is reduced to only the high frequency current and dimmed. on the other hand,
The low frequency current flows through the path of the filament 11, the high frequency impedance 7, the semiconductor switch 8, and the filament 12 as the filament If (FIG. 2d), and the discharge lamp 1 is preheated.

As described above, according to the present invention, constant preheating is achieved by keeping the conduction start phase β of the semiconductor constant, or by linking the conduction start phase β with the control phase α, such as advancing the conduction start phase β as the dimming becomes deeper. Since sufficient preheating can be achieved by controlling the discharge lamp, in combination with the fact that a high-frequency current is continuously passed through the discharge lamp, lighting is stable even when the lamp is dimmed deeply.

[Brief explanation of the drawing]

FIG. 1 is a circuit/configuration diagram of a discharge lamp dimmer according to an embodiment of the present invention, and FIGS. 2 a to 2 d are voltage and current waveform diagrams of each discharge lamp dimmer of FIG. A is a power supply voltage, b is a phase control circuit output voltage, C is a lamp current, and d is a filament current waveform diagram. DESCRIPTION OF SYMBOLS 1... Preheating discharge lamp, 2... Low frequency power supply, 6... Phase control circuit, 4... High frequency power supply, 5... Low frequency current limiting element, 6... High frequency current limiting element, 7... - High frequency impedance, 8... semiconductor switch, 9... control circuit. Patent applicant: Toshiba Electric Materials Corporation Representative patent attorney: Tatsuo Ito 〃 Tetsuya Ito

Claims (1)

[Claims] 1. A low frequency power source, a phase control circuit connected to the low frequency power source and outputting a phase-controlled voltage, a low frequency current limiting element, a high frequency power source, a high frequency current limiting element, the phase control circuit and the high frequency current limiting element. - a preheating discharge lamp in which a frequency power source is connected in parallel via a low frequency current limiting element and a high frequency current limiting element, a high frequency impedance having a high impedance with respect to the frequency of the high frequency power source, and a semiconductor switch; , a control circuit that controls opening and closing of the semiconductor switch in synchronization with the low frequency power source, and a series circuit of the high frequency impedance and the semiconductor switch is connected between the non-power side of each filament of the discharge lamp. A discharge lamp dimmer device characterized by: