CRM buck-flyback PFC converter with fixed frequency control

A converter and filter technology, used in control/regulation systems, output power conversion devices, DC power input conversion to DC power output, etc., can solve the problem of large switching frequency conversion range, complex EMI design, low power factor, etc. problem, to achieve the effect of improving PF, improving efficiency, and reducing output voltage ripple

Active Publication Date: 2019-11-29
NANJING UNIV OF SCI & TECH
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

The advantages are simple control, high power factor in the high-voltage range, and no reverse recovery problem of the diode; the disadvantage is that the switching frequency of the switching tube within half a power cycle can be changed in a large range, the power factor in the low-voltage range is very low, the EMI design is complicated, and the efficiency is low.

Method used

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  • CRM buck-flyback PFC converter with fixed frequency control
  • CRM buck-flyback PFC converter with fixed frequency control
  • CRM buck-flyback PFC converter with fixed frequency control

Examples

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Embodiment Construction

[0025] figure 1 It is the main circuit of Buck-FlybackPFC converter.

[0026] The following assumptions are made: (1) All devices are ideal; (2) The output voltage ripple is small compared to its DC value; (3) The switching frequency is much higher than the input voltage frequency.

[0027] figure 2 The waveforms of the switching tube current and the inductor current in one switching cycle when the inductor current is critically continuous are given, where figure 2 (a) Waveform diagram when Buck topology works, figure 2 (b) Waveform diagram when working for the Flyback topology. When the input voltage v g less than the output voltage V o When the Flyback topology works, Q b off, Q f When turned on, D o cutoff, the inductance L p The voltage across it is v g , its current i Lp start with zero and start with v g / L p The slope rises linearly, the output filter capacitor C o supply power to the load; when Q f When turned off, according to the conservation of amp...

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Abstract

The invention provides a CRM buck-flyback PFC converter with fixed frequency control. The CRM buck-flyback PFC converter comprises a main power circuit, an input voltage digital feedforward circuit, an output voltage differential circuit, a feedback circuit, a state determination circuit, a driving signal generation circuit, a comparison circuit and a multiplication circuit. According to the invention, the input voltage digital feedforward circuit, an input voltage comparison circuit and a gating circuit are introduced to achieve a double-fixed-frequency control mode, so that the switching frequencies of the switching tubes of the converter at the Buck stage and the Flyback stage are respectively kept at different constant values.

Description

technical field [0001] The invention relates to an AC / DC converter technology, in particular to a constant frequency controlled CRM step-down-flyback PFC converter. Background technique [0002] Due to problems such as input current dead zone and switching tube floating ground, it is difficult for the traditional BuckPFC converter to meet the design technical requirements in many applications. In order to solve these problems, someone proposed a buck-flyback PFC converter, which combines the Buck topology with the Flyback topology. When the input voltage is greater than the output voltage, the Buck topology works. When the input voltage is lower than the output voltage, the Flyback Topology works. However, the traditional CRM buck-flyback PFC converter adopts constant on-time control. When the two topologies of the converter work, the on-time is equal, so that the switching frequency of the switching tube in the second half of the power frequency cycle of this control mode ...

Claims

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Application Information

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IPC IPC(8): H02M7/219H02M1/42H02M3/335H02M1/15
CPCH02M1/15H02M1/42H02M3/33592H02M7/219H02M1/0058Y02B70/10
Inventor 马春伟姚凯张震邬程健管婵波李凌格陈杰楠
Owner NANJING UNIV OF SCI & TECH
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