Asymmetric Half-Bridge Control for Light-Load ZVS
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Solution Overview
Problem
Existing asymmetric half-bridge (AHB) power supplies face challenges in maintaining zero-voltage switching (ZVS) during medium or light load conditions, as increasing the switching cycle to reduce switching loss complicates achieving ZVS for both the high-side and low-side switches.
Innovation Solution
The AHB power supply incorporates a resonance circuit with an assisting switch and a transformer auxiliary winding, allowing for adaptive control of switching times and utilizing an assisting duration to ensure zero-voltage switching by providing energy to the transformer during the off-cycle of the high-side switch, thereby maintaining high conversion efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the switching cycle is increased to reduce switching loss, then switching loss decreases, but zero-voltage switching cannot be maintained
Solution Approach 1:
The resonance circuit performs charging and discharging operations in advance during the switching cycle to prepare the voltage conditions for zero-voltage switching before the actual switching event occurs. This preliminary action ensures that when switching happens, the voltage across the switch is already at zero, enabling lossless switching even at extended switching cycles.
Solution Approach 2:
The patent employs periodic resonance charging and discharging cycles through the LC resonance circuit. This periodic action creates predictable voltage waveforms that facilitate zero-voltage switching at specific intervals, allowing the system to maintain ZVS capability across varying switching frequencies and extended switching cycles.
2Loss of energy
If the switching frequency is reduced to reduce switching loss, then switching loss decreases, but zero-voltage switching cannot be maintained
Solution Approach 1:
The resonance circuit performs charging and discharging operations in advance during the switching cycle to prepare the voltage conditions for zero-voltage switching before the actual switching event occurs. This preliminary action ensures that when switching happens, the voltage across the switch is already at zero, enabling lossless switching even at extended switching cycles.
Solution Approach 2:
The patent employs periodic resonance charging and discharging cycles through the LC resonance circuit. This periodic action creates predictable voltage waveforms that facilitate zero-voltage switching at specific intervals, allowing the system to maintain ZVS capability across varying switching frequencies and extended switching cycles.
3Loss of energy
If asymmetric switching control is applied to reduce switching loss, then switching loss decreases, but control complexity increases
Solution Approach 1:
The control system monitors the voltage across the switches and the current through the resonance circuit, using this feedback information to dynamically adjust the switching timing and duration. This feedback mechanism enables the system to achieve optimal asymmetric switching patterns that minimize losses while maintaining simplicity through adaptive rather than pre-programmed control.
Solution Approach 2:
The patent implements dynamic switching control where the ON and OFF times of the high-side and low-side switches are continuously adjusted based on real-time operating conditions such as load current and input voltage. This dynamic approach allows the system to maintain optimal performance across varying conditions without requiring complex fixed timing circuits.
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
This approach ensures zero-voltage switching across varying load conditions, enhancing efficiency and reducing switching losses by optimizing the switching cycle through adaptive energy management.
Implementation Method 1
The transformer in the AHB power supply is also coupled to a resonance capacitor on the primary side to form a resonance circuit. During a heavy load condition, the AHB power supply switches the high-side switch and the low-side switch in a substantially complementary manner in a switching cycle. The resonance circuit performs charging, discharging and resonance for the high-side switch and the low-side switch to achieve zero voltage switching (ZVS) and low switching loss
Implementation Method 2
The primary winding and the assisting winding are inductively coupled to each other... turning on the assisting switch for an assisting duration after the discharge duration, so as to assist the first switch to achieve zero-voltage switching in a next switching cycle via the assisting winding
Data Source
AI summary
A control method is disclosed for an asymmetric half-bridge power supply having a resonant circuit, a first switch, a second switch, and an assisting switch. The resonant circuit includes a transformer and a resonance capacitor. The transformer has a primary winding connected to the resonance capacitor and an auxiliary winding connected to the assisting switch. Within a switching cycle, the first switch is turned on for a first ON time to increase an exciting current of the transformer. After the first ON time, the second switch is turned on for a second ON time to decrease the exciting current. Whether a discharge duration of the transformer ends is detected. The assisting switch is turned ON after the end of the discharge duration, making the exciting current negative, so as to assist the first switch achieving ZVS.