Hybrid Flyback Circuit Control for Quasi-ZVS Current Tuning
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Solution Overview
Problem
The existing control methods for hybrid flyback circuits in USB PD 3.1 systems face inefficiencies due to excessive negative excitation current, leading to increased conduction and transformer core losses, which hinder precise control of zero voltage switching (ZVS) and overall efficiency.
Innovation Solution
A circuit control method that adjusts the negative excitation current in hybrid flyback circuits by determining an acquisition time point and using a feedback compensation network to adjust the turn-on duration of the second MOS switch, ensuring zero voltage switching while optimizing efficiency and stability under dynamic loads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the negative excitation current is increased to ensure zero voltage switching of the primary-side switch tube, then the ZVS condition is achieved, but additional conduction loss and transformer core loss are caused, resulting in decreased efficiency
Solution Approach 1:
The patent implements a feedback control mechanism that detects whether zero voltage switching is achieved by the primary-side switch tube and adjusts the turned-on duration of the secondary-side switch tube accordingly. When ZVS is not achieved, the control unit increases the turned-on duration in subsequent cycles to increase negative excitation current until ZVS is achieved. When ZVS is achieved, the control unit decreases the turned-on duration to reduce negative excitation current to near the optimization point, thereby resolving the contradiction between ensuring ZVS and minimizing energy losses.
Solution Approach 2:
The patent dynamically adjusts the turned-on duration of the secondary-side switch tube based on real-time detection of ZVS achievement status. This dynamic adjustment allows the system to adapt the negative excitation current level to the actual operating conditions, ensuring ZVS when needed while minimizing excessive current and associated losses, thus optimizing the balance between reliability and energy efficiency.
2Measurement precision
If the turned-on duration of the secondary-side switch tube is continuously adjusted to control negative excitation current, then the negative excitation current can be controlled to the vicinity of an optimization point, but the control process becomes complex and time-consuming
Solution Approach 1:
The patent uses a feedback control loop where the control unit continuously monitors whether the primary-side switch tube achieves zero voltage switching and adjusts the secondary-side switch tube's turned-on duration accordingly. This feedback mechanism enables precise control of negative excitation current to near the optimization point while maintaining a relatively simple control structure that does not require complex algorithms or additional hardware.
Solution Approach 2:
The control system automatically adjusts the turned-on duration of the secondary-side switch tube based on the detected ZVS status without requiring external intervention or complex control algorithms. The system self-regulates the negative excitation current level, achieving precise control while minimizing control complexity through an autonomous feedback-adjustment mechanism.
Data Source
AI summary
The present disclosure provides a circuit control method and a circuit control apparatus, which are applied to a hybrid flyback circuit. The method includes: determining an acquisition time point according to a turn-on alternating duration of a first MOS switch and a second MOS switch on a main side of the hybrid flyback circuit and a preset time coefficient; acquiring a midpoint voltage between the first MOS switch and the second MOS switch according to the acquisition time point to obtain a first voltage signal; and adjusting negative excitation current in the hybrid flyback circuit according to a comparison result of the first voltage signal and a preset voltage value, so that the negative excitation current meets zero voltage switching of a primary-side switch of the hybrid flyback circuit.