| 摘要 |
PROBLEM TO BE SOLVED: To reduce the number of parts used in a switching power source and the size of the power source by reducing the power loss of the power source by making a dummy resistor electrically nonconductive with a standby mode signal at light-load time, such as the standby time, etc., and constituting an operation switching circuit in a simple circuit configuration. SOLUTION: In a switching power source provided with a transformer T equipped with a primary main winding N1, a secondary output winding N2, and feedback windings NB1 and NB2, a switching element Q, a control circuit S and a switching frequency limiting circuit F which control the switching frequency and the conducting time of the element Q, an output voltage detecting circuit K, and a dummy resistor Rd, a signal circuit H which electrically disconnects the resistor Rd from the circuit K with a standby mode signal and a circuit which suppresses the switching frequency of the element Q are provided. |
