Patent ID: 8120343
Filing Date: 2012-02-21
Classification: H02M,Y02B

Abstract:
1. A switching power supply comprising: a switching element connected between an input-side main terminal and a ground potential for turning a first DC voltage on or off; a converter circuit connected between an output-side main terminal of the switching element and the ground potential for converting a current intermittently outputted from the output-side main terminal in response to an on/off operation of the switching element to a second DC voltage smaller in absolute value than the first DC voltage and outputting the second DC voltage; a first control circuit block connected between the input-side main terminal and the output-side main terminal of the switching element for controlling the on/off operation of the switching element from a control terminal of the switching element; a first capacitor connected between the first control circuit block and the output-side main terminal of the switching element for generating a power supply voltage of the first control circuit block; an output voltage detection circuit for detecting the second DC voltage; a second control circuit block connected among the input-side main terminal of the switching element, the second DC voltage, and the ground potential, for receiving an output voltage signal of the output voltage detection circuit, and outputting a feedback signal to the first control circuit block in response to a change of the output voltage signal to allow the first control circuit block to perform feedback control on the on/off operation of the switching element; and a second capacitor connected between the second control circuit block and the ground potential for generating a power supply voltage of the second control circuit block, wherein the first control circuit block and the second control circuit block are connected such that the first control circuit block has a reference potential on a higher voltage side than a reference potential of the second control circuit block, and the first control circuit block for starting on/off operation of the switching element after the power supply voltage of the first control circuit block and the power supply voltage of the second control circuit block reach starting voltages and a feedback signal is inputted from the second control circuit block.