A pulse-skipping mode psm control method suitable for primary-side feedback flyback converter

Abstract

The invention discloses a pulse hopping mode PSM control method suitable for a primary side feed-back fly-back converter. The method comprises the following steps: indirectly sampling output voltage through an auxiliary winding; outputting the value of the output voltage through a comparison module; selecting a proper duration hopping mode from a duration hopping control module by adding the judgment of a peak current module and a duration hopping calculation module; finally, outputting a proper duty cycle through a DPWM module to drive a switch MOS transistor and control the voltage-stabilized output of digital power. Through the adoption of the method, on one hand, the light load efficiency can be high by switching off a part of circuit modules of a system in a part of switch duration; on the other hand, compared with the conventional PFM control method, the pulse hopping mode PSM control method has the advantages that PSM control is simpler, filtering can be easier due to a controllable frequency range, and the EMI can be reduced effectively.

Description

technical field [0001] The invention belongs to the field of digital switching power supplies, and in particular relates to a pulse-skipping mode PSM control method suitable for a primary-side feedback flyback converter. The method can improve the light-load efficiency of the primary-side feedback flyback converter. Background technique [0002] With the increasing development and wide application of portable electronic products, the isolated AC-DC flyback switching power converter has a simple circuit structure, can efficiently provide multiple DC outputs, and realizes complete isolation from input to output, and is also No need for output filter inductors, small size, high power density, and low manufacturing cost, thus occupying a large market in power adapters. [0003] Traditional flyback AC-DC switching converters use secondary side feedback, that is, optocouplers are used to achieve output voltage feedback and electrical isolation. However, the current transfer ratio...

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Problems solved by technology

[0005] Secondary-side feedback AC-DC switching power converters usually use PSM or BURST control mode to improve light-load efficiency by turning off a part of the switching cycle at light load. This method has a simple circuit structure, but it cannot be applied in traditional control schemes. In the feedback structure of the primary side, because the voltage on the secondary winding will decay and oscillate once a switching cycle is turned off, so that it is no longer possible to detect the correct V knee Feedback digital signal

However, the primary-side feedback AC-DC switching power converter can only use the pulse frequency modulation mode (PFM) at light loads. The efficiency of this method is lower than that of PSM or BURST mode at light loads, and there is a wide range of frequency variations Conducive to post-stage filtering, complex circuit structure, and poor EMI performance

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