NO-LOAD PROTECTION CIRCUIT OF MAGNETIC STABILIZER FOR HIGH-VOLTAGE DISCHARGE LAMP

摘要

PURPOSE: A no-load protection circuit of a magnetic stabilizer for high-voltage discharge lamp is provided to prevent an electric shock and reduce the power consumption by interrupting the supply voltage in a state of no-load of a lamp. CONSTITUTION: A no-load protection circuit of a magnetic stabilizer for high-voltage discharge lamp includes an igniter(23), a no-load sense/time delay unit(25) and an input control unit(26). The igniter(23) is used for applying a pulse voltage to a lamp(24). The no-load sense/time delay unit(25) detects a state of no-load to interrupt the input power and performs a time delay operation during a predetermined period of time according to a hot state of a lamp. The input control unit(26) interrupts the input power according to an output signal of the no-load sense/time delay unit when the no-load sense/time delay unit detects the state of no-load. An SCR element(Q3) of the igniter is turned off when the lamp(24) is turned on whereas the SCR element(Q3) is turned on when the lamp is turned off. The no-load sense/time delay unit is formed with a capacitor(C5), a transistor(Q2) for forming a turn-on circuit, a resistor(R4), and a zener diode(ZD2).