| 摘要 |
PURPOSE:To reduce a temperature drift by detecting charging currents, operating either of two error amplifiers and changing over the output voltage of a switching power supply. CONSTITUTION:When recovery charging is completed and load currents are reduced, a transistor Q2 is turned ON because the detecting voltage of a current detecting resistor R5 is made lower than reference voltage E3 on the positive side of an error amplifier IC3 and the output side of the error amplifier IC3 is at High, an error amplifier IC1 for detecting voltage is brought to the state of operation, and the error amplifier IC1 detects detecting resistance R2+R3. Consequently, the error amplifier IC1 works in the direction that output voltage is made lower than a case when the error amplifier IC1 detects the detecting resistance R3, an ON period is shortened in the switching signal of a control circuit CONT, and output voltage is lowered. The output voltage of an error amplifier IC2 is at High and is reverse-biassed by a diode D3 at that time, thus preventing an adverse effect on constant-voltage control of the output voltage of the IC2. |
