Totem-Pole PFC Switching Control for Zero-Voltage Turn-On
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Solution Overview
Problem
Existing power conversion circuits, particularly totem-pole PFC circuits, lack effective solutions for implementing zero voltage switching (ZVS) control on switches S1 and S2, limiting efficiency improvements.
Innovation Solution
A power conversion circuit with a PFC circuit module and controller that performs PWM control based on load voltage, inductor current, and alternating current input voltage to achieve ZVS of switching transistors S1 and S2, utilizing voltage and current sampling units, turn-off and turn-on control units, and PWM control to determine optimal switching times.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional PWM control is used on switching transistors S1 and S2, then the circuit operation is simple, but zero voltage switching (ZVS) cannot be achieved and efficiency is limited
Solution Approach 1:
The control circuit performs preliminary actions by detecting voltage and current states before switching occurs, using voltage sampling units to detect whether the voltage across switches S1 and S2 has reached zero, and current sampling units to detect inductor current direction and magnitude, ensuring ZVS conditions are met before actuation
Solution Approach 2:
The control circuit implements feedback by continuously monitoring the voltage across switches S1 and S2 through voltage sampling units and the inductor current through current sampling units, using this feedback information to dynamically adjust switching timing and achieve comprehensive ZVS control
2Productivity
If switching timing is not precisely controlled, then the control circuit is simple, but switching losses increase and efficiency decreases
Solution Approach 1:
The patent replaces conventional mechanical or simple electronic timing mechanisms with a sophisticated control system that uses voltage and current sampling units to electronically detect and determine optimal switching moments based on real-time circuit states, achieving precise timing control for ZVS
3Loss of energy
If comprehensive ZVS control is implemented on both S1 and S2, then switching efficiency is improved, but the control algorithm and circuit complexity increase
Solution Approach 1:
The control circuit is segmented into functional modules including voltage sampling units, current sampling units, and a control unit, with each module performing a specific function (voltage detection, current detection, switching timing determination) to manage the complexity of comprehensive ZVS control on both switches S1 and S2
Data Source
Figure 1~2a
Figure 2b~2c
Figure 2d~3
AI summary
Embodiments of this application provide a power conversion circuit and a power conversion circuit control method. In the embodiments of this application, the power conversion circuit determines polarity of an alternating current voltage by using a PFC circuit controller, determines, based on a current of an inductor, a signal for controlling a secondary switch to be turned off, determines, based on a voltage at a midpoint of a series connection between a switching transistor S 1 and a switching transistor S2, a signal for controlling the secondary switch to be turned on again and a signal for controlling a primary switch to be turned off, and performs PWM control on the switching transistor S1 and the switching transistor S2. The power conversion circuit can control, based on the current of the inductor, the secondary switch to be turned off, and control, based on the voltage at the midpoint of the series connection between the switching transistor S 1 and the switching transistor S2, the secondary switch to be turned on again and the primary switch to be turned off, to implement ZVS of the switching transistors in a PFC circuit. In addition, the embodiments of this application further provide a power supply including the power conversion circuit.