Patent ID: 6690586
Filing Date: 2004-02-10
Classification: H02M

Abstract:
A self-excited oscillation type switching power source device, comprising:an input power source; a transformer including a primary winding and a secondary winding; a first switching element including a control terminal and a switching terminal; a rectification-smoothing circuit connected to the secondary winding; the input power sources, the primary winding of the transformer, and the first switching element being connected in series with each other; the transformer having a first drive winding for developing a voltage which is substantially proportional to a primary winding voltage and which causes the first switching element to turn on, whereby the on-off operation of the first switching element is controlled, and thereby, the switching power source device is self-excitedly oscillated; and a start-stop circuit including: a switch connected between the control terminal and the switching terminal of the first switching element; and a control circuit which detects a voltage of the input power source across the input power source, compares the voltage to a predetermined voltage, causes the switch to turn off when it detects that the input power source voltage exceeds the predetermined voltage, whereby the first switching element is turned on, so that the oscillation is started, and causes the switch to turn on when the control circuit detects that the input power source voltage is equal to or less than the predetermined voltage, whereby the first switching element is turned off, so that the oscillation is stopped.