Pulse frequency modulation (PFM) primary side feedback controller and PFM primary side feedback converter using same

Abstract

The invention relates to a pulse frequency modulation (PFM) primary side feedback controller and a PFM primary side feedback converter using the same. The PFM primary side feedback controller comprises a current sampling (CS) comparator, a PFM control module, a feedback (FB) error amplifier, a constant voltage control module and a reference voltage generation module, wherein the reference voltage generation module generates peak current reference voltage and error reference voltage on the basis of primary side sampling voltage, first reference voltage and second reference voltage for the CS comparator and the FB error amplifier to use. By the controller and the converter using the same, the peak current reference voltage is related to the primary side sampling voltage, and is further related to output current, so that the peak current reference voltage under a light load and an idle load is effectively reduced, noise under the idle load is reduced and even eliminated, switching frequency under the idle load can be improved, and transient response characteristics are improved.

Description

technical field [0001] The present invention relates to the field of power converters, more specifically, to a pulse frequency modulation (Pulse Frequency Modulation, PFM) primary side feedback controller and a PFM primary side feedback converter using the PFM primary side feedback controller. Background technique [0002] With the vigorous development of various battery-powered handheld products (such as mobile phones), the market demand for low-cost and high-efficiency battery chargers has also increased dramatically, and the flyback power converter due to its own advantages (such as simple structure), become the preferred solution for this charger. In recent years, various PFM primary-side feedback converters have been applied to such flyback power converters. [0003] A typical PFM primary-side feedback converter such as Figure 1A As shown, it mainly includes a full-bridge rectifier 107, a transformer T1 (including three windings: a primary winding 101, a secondary win...

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Problems solved by technology

[0012] The technical problem to be solved by the present invention is that, for the PFM primary-side feedback converter of the prior art, when the load is small or even no-load, the switching frequency of the main switching tube will drop to about 1-2kHz, resulting in serious hearing loss. Noise problem, and the defect of very poor transient response characteristics from light load to heavy load, provide a primary side feedback controller and a PFM primary side feedback converter using the PFM primary side feedback controller, which can reduce or even eliminate voids Load noise, increase the switching frequency at no-load, and improve its transient response characteristics, while still ensuring sufficiently high light-load efficiency and simplicity of circuit implementation

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