Abstract: A power supply includes a rectifying circuit, a power converting circuit, and a snubber circuit. The rectifying circuit is configured to convert an ac input voltage to a first dc voltage. The power converting circuit is electrically coupled to the rectifying circuit at a node. The power converting circuit includes a switching element and is configured to convert the first dc voltage to a second dc voltage by selectively turning on or off the switching element. The snubber circuit is electrically coupled to the rectifying circuit and the power converting circuit at the node. When the first dc voltage is higher than a limiting level, the snubber circuit is configured to absorb the electricity power to prevent the voltage across the switching element from exceeding a safety upper limit.

Abstract: A power conversion device includes a transformer having a primary winding and a secondary winding, a switch coupled between the primary winding and a primary ground, a control circuit configured to output a control signal to turn on or off the switch selectively, a secondary circuit coupled to the secondary winding and configured to output an output voltage, a voltage regulating feedback circuit coupled to the secondary circuit, and an isolation circuit coupled between the voltage regulating feedback circuit and the control circuit. On the condition that the output voltage is greater than an upper limit, the voltage regulating feedback circuit is configured to output a feedback signal via the isolation circuit to the control circuit such that the control circuit turns off the switch.

Abstract: A power supply includes a rectifying circuit, a power converting circuit, and a snubber circuit. The rectifying circuit is configured to convert an ac input voltage to a first dc voltage. The power converting circuit is electrically coupled to the rectifying circuit at a node. The power converting circuit includes a switching element and is configured to convert the first dc voltage to a second dc voltage by selectively turning on or off the switching element. The snubber circuit is electrically coupled to the rectifying circuit and the power converting circuit at the node. When the first dc voltage is higher than a limiting level, the snubber circuit is configured to absorb the electricity power to prevent the voltage across the switching element from exceeding a safety upper limit.