Asymmetric Half-Bridge Control for ZVS Under Light Load
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Solution Overview
Problem
Maintaining zero voltage switching (ZVS) for high-side and low-side switches in asymmetric half-bridge power supplies becomes challenging when the load is medium or light, leading to increased switching losses.
Innovation Solution
A control method and controller for an asymmetric half-bridge power supply that adjusts the turn-on time of the second arm switch based on whether the first arm switch has performed ZVS, ensuring ZVS at the start of the next switching cycle.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the switching cycle of the AHB power supply is increased to reduce switch frequency and switch loss, then switching loss is reduced, but maintaining ZVS for the high-side and low-side switches becomes difficult
Solution Approach 1:
The patent implements a feedback mechanism where the controller detects whether ZVS is achieved for each switch and uses this information to adjust the turn-on time of subsequent switches. Specifically, when ZVS is detected for the low-side switch, the controller extends the turn-on time of the high-side switch in the next cycle to ensure the low-side switch can achieve ZVS again, creating a closed-loop control system that maintains ZVS under varying load conditions.
Solution Approach 2:
The patent makes the switching parameters dynamic by continuously adjusting the turn-on time of switches based on real-time ZVS detection results. Instead of using fixed switching parameters, the system adapts the switching timing dynamically to maintain optimal performance across different operating conditions, particularly when switching frequency is reduced.
2Use of energy by moving object
If the switching frequency is reduced to improve efficiency under medium or light load, then energy efficiency is improved, but the ability to maintain ZVS deteriorates
Solution Approach 1:
The controller continuously monitors ZVS achievement and adjusts switching parameters accordingly. When operating at reduced switching frequencies for improved efficiency, the feedback mechanism ensures that turn-on times are extended when necessary to maintain ZVS, preventing the system from sacrificing reliability for efficiency.
Solution Approach 2:
The patent changes the switching parameters (turn-on time duration) based on operating conditions and ZVS detection results. By dynamically adjusting these parameters, the system can operate at lower switching frequencies for improved efficiency while still maintaining ZVS through appropriate parameter modification.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution effectively reduces switching losses and improves conversion efficiency by ensuring ZVS in each switching cycle, even under varying load conditions.
Implementation Method 1
The transformer in the AHB power supply is also connected to an oscillating capacitor on the primary side to form a resonance circuit. When the load powered by the AHB power supply is heavy, the high-side switch and the low-side switch are roughly complementary in one switching cycle. The resonance circuit can undergo charging and discharging and resonate, which can make the high-side and low-side switches perform zero voltage switching (ZVS) with low switching loss
Data Source
AI summary
A controller and a control method for an asymmetric half-bridge power supply are disclosed. The asymmetric half-bridge power supply includes a first arm switch and a second arm switch forming a half-bridge, and a resonant circuit connected to the half-bridge. The method includes providing a duration parameter reflecting a second turn-on time of the second arm switch in a earlier switching cycle; providing a control signal to turn on the first arm switch for a first turn-on time in a later switching cycle; detecting whether the first arm switch has performed ZVS in response to a signal edge of the control signal to adjust the duration parameter accordingly; determining the second turn-on time of the second arm switch in the later switching cycle based on the duration parameter; and turning on the second arm switch for the second turn-on time after the first turn-on time in the later switching cycle.