JPS5875797A - 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 phase control device that requires a peak value.

The conventional control system is shown in Figure 1, and the waveforms of each part are shown in Figure 2.

This method is synchronized with the power supply, and after a certain time ta, a one-firing pulse 9 shown in FIG. to dim the discharge lamp. However, when the firing angle exceeds 90°', the voltage applied to the ballast decreases by Δ■ as shown in the waveform after 10 tb. Generally, discharge lamps require a high lamp restriking voltage, so when the voltage peak tN decreases, stable discharge cannot be maintained, flickering occurs, and the lamp goes out.

When the firing angle is 90° or less, the time from when the lamp current becomes zero until the voltage is applied is short, so the restriking voltage is relatively low due to the residual thermoelectrons in the discharge μ. Therefore, stable discharge is maintained for hours.

An object of the present invention is to perform stable dimming of a discharge lamp.

In the present invention, even if the effective value of the voltage applied to the ballast that performs dimming is low, a peak voltage is always added to the discharge lamp to perform stable control.

An example of the present invention is shown in FIG. 185, and waveforms of various parts are shown in FIG.

This control circuit performs phase control using a gate turn-off thyristor 14 that is passed through a full-wave rectifier 13 between an AC power supply 12 and a ballast 16.

The characteristics of the gate turn-off thyristor 14, which is the main control element, are that when a forward pulse is applied to the gate, it becomes conductive;
When a reverse bias pulse is applied to the gate, the conduction current is cut off and the gate becomes non-conducting. Gate signal generation circuit has 1 phase angle 9
A forward pulse is applied at a phase angle before 0°, and a reverse pulse is applied at a phase angle after 90°.

In circuit operation, when the forward pulse 21 is applied after t from the zero potential of the AC power supply 20, the Guthton-off thyristor 14 becomes conductive, and a voltage is applied to the ballast 16 through the full-wave rectifier 13. After conduction, when the phase angle 901 has passed and a reverse direction gate pulse is applied after t(1), the gate turn-off thyristor 14 remains non-conductive, and the voltage of waveform 22 is applied to the ballast 16IC.

To dim the light by lowering the ballast 160 input voltage.

The ignition phase is longer than tc (tf), and the cutoff phase is also shorter than td to tg. Therefore, the maximum voltage vp of the AC power supply 12 with a phase angle of 90° is always applied, and the discharge lamp 19 maintains stable discharge.

Therefore, there is an effect of stabilizing the dimming of the discharge lamp.

[Brief explanation of the drawing]

FIG. 4 is a diagram of the gate pulse waveform. 13...Full wave rectifier, 14...Gate turn-off thyristor, 15...Gate signal generation circuit, 16...Stable i, 17...Capacitor, 19 River filament coil, 19...Discharge lamp .Representative Patent Attorney Susuki 1) Tori Yukio 1 size Z size Kano 3 size

Claims (1)

[Claims] An AC power supply, a discharge lamp and a ballast connected to this power supply, and a phase control circuit are provided between the ballast and the power supply, and a gate turn-off thyristor is used as the main control element of the phase control circuit, and its gate signal The generating circuit generates a firing pulse between 0 and 9000 with a phase angle of 900 as the center to conduct.
A discharge lamp dimmer characterized in that the conduction angle is controlled by applying a turn-off gate bus V bus between ° and 180 ° to make it non-conductive.