| 摘要 |
PURPOSE:To reduce power consumption, simplify the circuit, and suppress the costs by forming each control switch circuit from specific switches, No.1 and No.2. CONSTITUTION:A control switch circuit is composed of No. 1 switch Q7, which is connected in series to a discharge lamp LP as the load, and No.2 switch Q4 connected in parallel with the same. A pulse width control signal is used first for control of the No.2 switch Q4, and No.1 switch Q7 operates in compliance with the motion of the No.2 switch Q4. That is, transistor Q4 is turned on when the pulse width control signal impressed between terminals T2 and T3 is at 'H' level, while transistor Q7 is turned off to cause extinction of the discharge lamp LP. Thereby wasteful shortcircuiting current when the discharge lamp LP is extinguished can be shut off to contribute to reduction of power consumption, and also the circuit configuration be simplified to lead to cost-down. |
