| 摘要 |
<p>A self-excited switching power supply circuit is provided which is quick to respond to an increase in a primary winding current, is easy to perform constant voltage control, and makes an intermittent oscillation operation for suppressed power loss when no load or a light load is connected. A switching diode is connected between a shunt resistor for the primary winding current to flow through and a control terminal of a driver element so as to be in parallel with a discharge resistor, with its forward direction from the shunt resistor to the control terminal. In an ON operation period of an oscillating field-effect transistor, the driver element quickly controls off the oscillating field-effect transistor in response to an increase in the primary winding current. When no load or a light load is connected, the discharge resistor of high resistance is used to slow down the discharge rate of the controlling capacitor in connection with the control terminal of the driver, thereby extending an OFF operation period.</p> |
