| 摘要 |
PROBLEM TO BE SOLVED: To provide a lamp current detecting circuit which uses a shunt resistor where floating capacitance is not generated in its circuit applying high voltage to lamps. SOLUTION: In a lamp lighting device, on-off control of semiconductor switching devices Q1 to Q4 is carried out, a high frequency signal is generated and it is supplied to primary sides of output transformers T71 to T74, lighting apparatuses L1 to L16 which are connected to the secondary sides of the output transformers are lighted, lamp current flowing the lighting apparatuses L1 to L16 is detected, PWM (pulse width modulation) control of the semiconductor switching devices Q1 to Q4 is carried out, based on the detected lamp current, and output of secondary sides of the output transformers T71 to T74 is controlled. In the lamp current detecting circuit, the shunt resistor 16 is connected, in series with the circuit applying the voltage to the lighting apparatuses L1 to L16, which are connected to the secondary sides of the output transformers T71 to T74, an input side of a photocoupler 20 is connected between both ends of the shunt resistor 16 in parallel, and a lamp current signal is outputted from the output side of the photocoupler 20. COPYRIGHT: (C)2007,JPO&INPIT |
