LIGHTING CIRCUIT FOR DISCHARGE LAMP FOR CAR

Japanese Patent JP3136451

B2

PURPOSE: To suppress increase in the consumed current when the supply voltage drops by performing a current limiting control according to the condition of a discharge lamp in a lighting circuit for discharge lamp of a car.
CONSTITUTION: In a lighting circuit 1 for a discharge lamp of a car, the battery voltage is turned into AC through a DC-AC converter circuit 7 with turning-on of a lighting switch 5 after voltage boost made by a DC voltage booster circuit 6 and impressed on a metal halide lamp 10. A control circuit 11 has a V-I control part 14 and a PWM control part 15. A current compensation part 16 limits so that over-current does not flow in an FET in a DC booster circuit in the initial period of lamp lighting-up or when the battery voltage drops. The current compensation part 16 monitors the lamp operating condition, produces a saw-tooth signal according to the present condition, superposes it on a current sensing signal ISW from the FET, and controls the mean current and the peak value of the current flowing in the FET by the slope compensating function which the PWM control part 15 has. This permits achieving such a control as increasing the degree of current limitation when the lamp current is large.

Masayasu Yamashita
Satoru Oda
Masaru Sasaki

JP18744692A

February 19, 2001

June 23, 1992

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Koito Manufacturing Co., Ltd.

B60Q1/04; B60Q11/00; H05B41/16; H05B41/282; H05B41/285; H05B41/288; H05B41/292; H05B41/38; (IPC1-7): H05B41/282; H05B41/16

JP62150697A
JP62259391A
JP5184152A
JP4212294A
JP4274197A
JP554990A
JP5266982A

Yuji Komatsu

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