Switching mode AC-DC converter and control circuit thereof

Abstract

The invention discloses a primary-side regulation switching mode AC-DC converter and a control circuit thereof. The switching mode AC-DC converter includes an input rectifier, an input capacitor, an output rectifier, an output capacitor, a controller, a controller energy storage capacitor and a controller power supply rectifier; and a transformer composed of a primary side winding, a secondary side winding and an auxiliary winding. The positive plate of the input capacitor, the negative plate of the output capacitor and the positive plate of the energy storage capacitor are coupled to one group of dotted terminals of the primary side winding, the secondary side winding and the auxiliary winding respectively. The negative plate of the input capacitor, the positive plate of the output capacitor and the negative plate of the energy storage capacitor are coupled to the other dotted terminals of the primary side winding, the secondary side winding and the auxiliary winding respectively. The controller includes a voltage opposition circuit, a constant voltage control circuit, a constant current control circuit and a drive circuit. When the secondary side winding performs charge for the output capacitor, the voltage opposition circuit of the controller negates the voltage of the auxiliary winding and outputs to the constant voltage control circuit so as to stabilize the output voltage.

Description

technical field [0001] The present invention relates to switch-mode AC-DC converter technology, in particular, the invention relates to a primary-side regulated switch-mode AC-DC converter and a corresponding control circuit. Background technique [0002] The switching mode AC-DC converter (switching power supply) has the advantages of small size and high conversion efficiency, and its application fields are expanding, including chargers, adapters, etc. For the charger, in the full load range (no load to heavy load), its output exhibits constant voltage and constant current characteristics. [0003] figure 1 Shown is a schematic diagram of a conventional primary side (or primary side) regulated switch mode charger system 100 . The switching power supply charger includes an AC input port (the AC voltage range is generally 85V AC to 265V AC ), bridge rectifier 1 (to convert the AC voltage V AC converted to DC voltage V IN ), input capacitor 2, transformer 3, controller 4...

AI Technical Summary

Problems solved by technology

And too large N A / N S It will cause the VCC voltage to become too high under the constant voltage output (5V), and at 85V AC The losses of driving a bipolar power switch become unacceptable

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