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CRM Buck PFC convertor with optimal frequency variation range

A technology of frequency change and converter, which is applied in the direction of output power conversion device, irreversible AC power input conversion to DC power output, high-efficiency power electronic conversion, etc., and can solve problems such as complex design of inductors and EMI filters

Inactive Publication Date: 2015-06-10
NANJING UNIV OF SCI & TECH
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  • Application Information

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Problems solved by technology

However, its switching frequency varies with input voltage and loa

Method used

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  • CRM Buck PFC convertor with optimal frequency variation range
  • CRM Buck PFC convertor with optimal frequency variation range
  • CRM Buck PFC convertor with optimal frequency variation range

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Embodiment Construction

[0021] Attached below picture and Specific embodiments further describe the present invention in detail.

[0022] 1 Working principle of CRM Buck PFC converter

[0023] figure 1 It is the main circuit of the Buck PFC converter.

[0024] For the convenience of analysis, the following assumptions are first made: 1. All devices are ideal components; 2. The output voltage ripple is very small compared with its DC value; 3. The switching frequency is much higher than the input voltage frequency.

[0025] figure 2 The inductor current waveform in one switching cycle when CRM is given. When Q b When turned on, D b cutoff, the boost inductor L b The voltage across it is v g -V o , its current i Lb Start with zero and start with (v g -V o ) / L b The slope increases linearly. When Q b When shutting down, i Lb by D b freewheeling, at this time L b The voltage across it is v o , i Lb with V o / L b the slope of the drop. Since the Buck converter works in CRM mode,...

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Abstract

The invention discloses a CRM Buck PFC convertor with optimal frequency variation range. The CRM Buck PFC convertor with optimal frequency variation range comprises a main power circuit, a CRM control and driving circuit, a voltage feed forward circuit, a first multiplying unit, a second multiplying unit and an output voltage feedback circuit; the output end of a first follower circuit is respectively connected to two input ends of the first multiplying unit and one input end of a first subtraction circuit; the output end of a second follower circuit is respectively connected to two input ends of the second multiplying unit and the other input end of the first subtraction circuit; the output ends of the first multiplying unit and the second multiplying unit are respectively connected with two input ends of the second subtraction circuit; the output ends of the first subtraction circuit and the second subtraction circuit are respectively connected with two input ends of a third subtraction circuit; the output end of the third subtraction circuit is connected with the input end of the CRM control and driving circuit. The turn-on time of the switch tube changes according to certain rule in a power frequency period due to that the voltage feed forward circuit is used, and the switching frequency variation range is optimized.

Description

technical field [0001] The invention relates to the field of AC-DC converters of power conversion devices, in particular to a CRM Buck PFC converter with an optimal frequency variation range. Background technique [0002] A power factor correction (Power Factor Correction, PFC) converter can reduce input current harmonics and improve input power factor, and has been widely used. PFC converters are divided into active and passive methods. Compared with passive methods, the active method has the advantages of high input power factor, small size, and low cost. [0003] Active PFC converters can adopt a variety of circuit extension and control methods, among which Buck PFC converter is one of several commonly used PFC converters. According to whether the inductor current is continuous or not, it can be divided into three operating modes, namely, inductor current Current continuous mode (Continuous Current Mode, CCM), inductor current critical continuous mode (Critical Continuou...

Claims

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Application Information

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IPC IPC(8): H02M7/12H02M1/42
CPCH02M1/4225H02M7/12Y02B70/10
Inventor 姚凯王小平周旭峰李辉王祎
Owner NANJING UNIV OF SCI & TECH
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