SELF-EXCITED OSCILLATION TYPE SWITCHING POWER SOURCE

摘要

PURPOSE:To enable to set the overcurrent drooping characteristic of an output characteristic by dividing the voltage between the collector and the emitter of a switching transistor by a resistor and a Zener diode into constant voltages, and applying it to the charging voltage of a capacitor. CONSTITUTION:The voltage waveform clipped to a Zener voltage VZD by a resistor 4 and a Zener diode ZD1 from the voltage VCE between the collector and the emitter of a switching transistor Q1 is applied through a diode D2 to a capacitor C1. Therefore, even if an output voltage VOUT is decreased by an overcurrent, the charging voltage VOFF of the capacitor C1 becomes constant by the voltage VZD, and the ON period becomes constant irrespective of the output voltage VOUT. Thus, the overcurrent drooping characteristic exhibits substantially vertical droop.