| 摘要 |
PROBLEM TO BE SOLVED: To provide an auxiliary power supply circuit of a switching power supply where a stable voltage is accurately supplied to a control circuit in using electronic parts without margin in a breakdown voltage for the control circuit and power loss is reduced for improving efficiency. SOLUTION: A series circuit consisting of a first resistor R1, a voltage element 2, and a zener diode Zd; and a series circuit consisting of a second resistor R2, a first transistor Q1, a second transistor Q2, and a control circuit 3 of a switching element; are connected in parallel with a main power supply 1. The input terminal of the first transistor Q1 is connected to the connection point between the first resistor R1 and the voltage element 2, the input terminal of the second transistor Q2 is connected to the connection point between the voltage element 2 and the zener diode Zd, and an auxiliary power supply 41 for steadily operating the control circuit 3 is connected between the connection point between the first transistor Q1 and the second transistor Q2 and the reference terminal of the main power supply 1.
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