AHB Converter Valley Switching via Switch-Node On-Time Control
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Solution Overview
Problem
Existing power converters face challenges in achieving high efficiency and reduced size due to significant switching losses and electromagnetic interference (EMI) in asymmetric half-bridge (AHB) converters, particularly when the resonant amplitude of the switch node voltage is small.
Innovation Solution
A controller circuit is used to sense the voltage at the switch node of an AHB converter, comparing it to a predetermined threshold to adjust the on-time of the high-side switch, increasing it when the voltage is below the threshold and decreasing it when above, thereby implementing full ring valley switching to minimize switching losses and EMI.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional switching control is used in AHB converters, then the converter can operate with simple control circuitry, but switching losses and EMI remain significant
Solution Approach 1:
The controller circuit senses the switch node voltage and uses feedback control to dynamically adjust the high-side switch on-time based on the sensed voltage compared to a threshold, achieving valley switching that minimizes switching losses
Solution Approach 2:
The system transitions from fixed on-time control to dynamic on-time adjustment, where the high-side switch on-time varies cycle-to-cycle based on the resonant amplitude of the switch node voltage to achieve optimal switching timing
2Loss of energy
If the high-side switch on-time is increased to achieve full ring valley switching, then switching losses are reduced, but the risk of voltage threshold misalignment increases
Solution Approach 1:
The controller continuously senses the switch node voltage and compares it to a predetermined threshold, using this feedback to dynamically adjust the on-time and ensure accurate valley timing
Solution Approach 2:
The system changes the on-time parameter dynamically based on operating conditions, adjusting it to achieve full ring valley switching when beneficial while maintaining reliable operation under varying voltage conditions
3Temperature
If resonant amplitude of switch node voltage is small, then the converter can operate with lower voltage stress, but switching losses increase
Solution Approach 1:
The controller dynamically adjusts the high-side switch on-time based on the actual resonant amplitude of the switch node voltage, enabling full ring valley switching even when resonant amplitude varies, thereby maintaining low switching losses across different operating conditions
Data Source
AI summary
A circuit is disclosed. The circuit includes a transformer having a primary winding and a secondary winding, the primary winding extending from a first terminal to a second terminal, a first switch having a first source terminal and a first drain terminal, the first drain terminal connected to the first terminal, a second switch having a second source terminal and a second drain terminal, the second source terminal connected to the second terminal, and the second drain terminal connected to the first source terminal at a switch node, and a controller circuit connected to the switch node and arranged to sense a voltage at the switch node, compare the sensed voltage to a predetermined threshold, increase an on-time of the first switch when the sensed voltage is less than the predetermined threshold, and decrease the on-time of the first switch when the sensed voltage is greater than the predetermined threshold.