Switching power supply driving chip and switching power supply driving circuit

Abstract

The invention belongs to the field of switching power supply driving circuits, and provides a switching power supply driving chip and a switching power supply driving circuit, wherein the chip is controlled by quasi-resonance and the valley bottom under the quasi-resonance state is detected by a valley bottom detecting circuit after the transformer is demagnetized, a power supply circuit judges whether to supply power to a power supply pin through a power tube drain electrode of the chip according to the detected valley bottom and the current voltage value of the power supply pin of the chip, and at the same time, a pulse frequency modulation control circuit adjusts the switching frequency of a power tube in the chip according to the value of a feedback pin and a current detection pin of the chip to achieve the constant voltage or constant current output of the switching power supply drive circuit. The switching power supply drive circuit of the chip is adopted, and an auxiliary winding is not required, so that the number of the peripheral circuit devices of the switching power supply drive chip decreases, the cost of the switching power supply drive circuit is lowered, the integration is improved, the board area is reduced, the system operation reliability is improved, and the electricity taking dynamic adjustment is achieved.

Description

technical field [0001] The invention belongs to the field of switching power supply driving circuit design, in particular to a switching power supply driving chip and a switching power supply driving circuit. Background technique [0002] In the primary side feedback flyback switching power supply drive circuit, the feedback signal of the primary side winding of the transformer is used to realize the control of the output. Such as figure 1 A typical structure of a primary-side feedback flyback switching power supply drive circuit provided by the prior art is shown. [0003] Among them, the diode D1, the diode D2, the diode D3 and the diode D4 form a rectifier bridge, and the rectifier bridge and the capacitor C1 together form an input circuit for rectifying and filtering the AC input voltage Vin and outputting it to the primary winding of the transformer T1 ; Wherein, the diode D5, the capacitor C2 and the resistor R2 form an output circuit, which is used to rectify and fi...

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