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Synchronous rectification Buck converter all-soft switching circuit and control method thereof

A technology of synchronous rectification and control method, which is applied in the direction of converting DC power input to DC power output, control/regulation systems, instruments, etc. Issues such as turn-on or turn-off

Active Publication Date: 2020-04-24
CENT SOUTH UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0004] However, these soft switching circuits increase the current stress or voltage stress of the main switch, resulting in additional main circuit conduction losses
In addition, since the auxiliary circuit cannot achieve soft turn-on or turn-off, the voltage stress or current stress of the auxiliary switch is also high, causing a large loss in the auxiliary circuit, and the improvement of system efficiency is not obvious, but the volume, weight and cost increase

Method used

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  • Synchronous rectification Buck converter all-soft switching circuit and control method thereof
  • Synchronous rectification Buck converter all-soft switching circuit and control method thereof
  • Synchronous rectification Buck converter all-soft switching circuit and control method thereof

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Embodiment 1

[0064] Such as figure 1 As shown, the present invention proposes a fully soft switching circuit for a synchronous rectification Buck converter, including a DC voltage source U DC , main inductance L, auxiliary inductance L r , Output storage capacitor C o , Auxiliary clamp capacitor C r , Power MOSFET main switch Q 1 , Power MOSFET synchronous rectification switch Q 2 , power MOSFET auxiliary switch Q r , auxiliary diode D r and the protection diode D P ; Wherein, the DC voltage source U DC with power MOSFET main switch Q 1 A branch circuit is formed in series, and the branch circuit one and the power MOSFET synchronous rectification switch Q 2 , Auxiliary clamp capacitor C r Parallel to form branch two, the power MOSFET auxiliary switch Q r with auxiliary inductance L r , auxiliary diode D r The branch circuit three is formed in series, the branch circuit three is connected in parallel with the main inductance L to form the branch circuit four, the branch circuit...

Embodiment 2

[0067] For the fully soft switching circuit of the synchronous rectification Buck converter, a soft switching modulation strategy is proposed that can eliminate the reverse recovery loss of the synchronous rectification switch and realize zero-voltage turn-on and near-zero-voltage turn-off of the main switch and the synchronous rectifier switch:

[0068] t 0 ~t 1 stage: t 0 moment, C r voltage is equal to the input voltage UDC . Main switch Q 1 controlled shutdown due to C r The clamping action, Q 1 Drain-source (DS) voltage rises less during turn-off, Q 1 Approximate zero-voltage turn-off, the equivalent circuit such as figure 2 . Because the main inductance relative to C r Larger, the resonance period is much larger than t 0 ~t 1 time period, it is considered that the current of the main inductor L remains unchanged and reaches the maximum value i during this process L,max , then C r The voltage drop time is:

[0069]

[0070] t 1 ~t 2 stage: t 1 moment,...

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Abstract

The invention discloses a high-efficiency all-soft switching circuit applied to a non-isolated Buck DC-DC converter and a modulation method of the high-efficiency all-soft switching circuit. The circuit comprises a synchronous rectification switch tube Q2 used for replacing a common freewheel diode and reducing freewheel loss, an auxiliary capacitor Cr used for voltage clamping at the moment whenthe switch tube is turned off, a series branch composed of an auxiliary switch tube Qr, a diode Dr and an inductor Lr and used for eliminating reverse recovery loss of the diode and realizing zero-voltage switching of a main switch, and a protection diode DP used for protecting the auxiliary switch tube when the load fluctuates violently. For the proposed soft switching circuit, in order to realize soft switching in a wide load range, a feasible modulation method is proposed. Zero-voltage turn-on and approximate-zero-voltage turn-off of all main switches and synchronous rectification switchesare realized, and zero-current turn-on and turn-off of auxiliary switches are realized.

Description

technical field [0001] The invention is applied to the field of high-efficiency, low-cost, step-down switching power supply, and especially proposes a fully soft switching circuit and a control method for improving conversion efficiency for a synchronous rectification Buck circuit. Background technique [0002] With the development of power electronics and power supply technology, it is necessary to have a higher efficiency power supply. In low-voltage and high-current applications, non-isolated Buck converters are widely used because of their wide step-down range. Ordinary Buck converters have large switching losses due to hard switching, low conversion efficiency, and serious heat generation, which leads to a decrease in system stability. The use of wide bandgap semiconductor SiC power devices can significantly reduce switching loss, but it is expensive, not suitable for low-cost applications and industrialization, and still operates in a hard switching mode, and switchin...

Claims

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Application Information

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IPC IPC(8): H02M3/158H02M1/38
CPCH02M1/38H02M3/1588H02M1/0058Y02B70/10
Inventor 刘芳万江湖刘玲李勇
Owner CENT SOUTH UNIV
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