| 摘要 |
PURPOSE:To improve the universality of a switching control circuit by controlling voltage drops generated at resistors connected between a power source, a booster and a negative power source and separately inputting to a differential amplifier and controlling the drive pulse of a switching circuit by the output obtained from the amplifier. CONSTITUTION:5V of a power source 1 is supplied through a resistor R1 to a booster 4 controlled by a pulse from the terminal 7 of a switching control circuit 2 to generate a high voltage 12V. A voltage drop generated at the resistor R1 is applied to the positive polarity terminal of a comparator 20, and compared with a reference voltage of a negative polarity terminal. A comparator 15 feeds a pulse of a repetition period to a AND gate 18 in response to an error voltage by a triangular wave signal from a triangular wave generator 16, a soft starting signal made of a resistor R5 and a capacitor 5 and the output of an error amplifier 11. When the comparator 20 detects a voltage drop of the prescribed value of higher due to an overload, the output becomes L, the AND gate 18 is turned OFF to stop switching of TRQ1, Q2, and to rise the voltage of a terminal 19. A negative power source 5 similarly operates. Thus, the universality is improved. |
