Half-Bridge Converter Timing for Zero-Voltage MOSFET Switching
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Solution Overview
Problem
Existing resonant power converters face challenges in accurately controlling non-overlap times between switching elements at high frequencies, leading to hard-switching and reduced efficiency and lifespan of MOSFETs due to turn-on delays and varying operational conditions.
Innovation Solution
A controller is configured to adjust non-overlap times by sending command signals to MOSFETs based on regulated times relative to the rising and falling voltages at the half-bridge node, accounting for turn-on delays and other delays, ensuring zero voltage switching across varying frequencies and conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If fixed non-overlap times are used in resonant power converters, then device simplicity is maintained, but switching accuracy deteriorates leading to hard-switching and reduced MOSFET lifespan
Solution Approach 1:
The controller measures the actual HB voltage rising time and uses this feedback to dynamically adjust the non-overlap time parameter. This closed-loop feedback mechanism ensures accurate zero-voltage switching timing while adapting to variations in operating conditions, thereby extending MOSFET lifespan without requiring overly complex open-loop control circuits
Solution Approach 2:
The controller pre-calculates and sets the non-overlap time based on measured HB voltage characteristics before the next switching cycle begins. By preparing the optimal timing parameter in advance based on previous cycle measurements, the system achieves accurate switching control without requiring complex real-time calculations during critical switching moments
2Productivity
If operating frequency is increased to reduce converter size, then productivity improves, but switching control accuracy deteriorates due to reduced non-overlap time margins
Solution Approach 1:
The non-overlap time is made dynamic rather than fixed, automatically adjusting based on the measured HB voltage rising time at each operating condition. This dynamic adaptation allows the system to maintain precise switching timing even at high frequencies where fixed timing would fail, enabling reduced converter size without sacrificing control accuracy
Solution Approach 2:
The controller changes the non-overlap time parameter based on measured HB voltage characteristics and operating conditions. By adapting this critical timing parameter to match actual circuit behavior at different frequencies and loads, the system maintains switching precision across the full operating range, enabling high-frequency operation with accurate control
3Reliability
If non-overlap time is extended to ensure proper switching sequence, then switching reliability improves, but energy loss increases due to extended dead time
Solution Approach 1:
The controller dynamically changes the non-overlap time parameter based on measured HB voltage rising time and operating conditions. By optimizing this parameter to be as short as possible while still ensuring reliable zero-voltage switching, the system minimizes dead time energy losses while maintaining switching sequence accuracy across varying loads and frequencies
Data Source
AI summary
One example discloses a converter circuit, including: an input configured to receive either a voltage or a current; an output configured to transmit either a voltage or a current; a voltage reference; a half-bridge (HB) node; a high-side (HS) switch coupled between the input and the HB node; a low-side (LS) switch coupled between the voltage reference and the HB node; and a controller coupled to the HB node, the HS switch, and the LS switch; wherein the controller is configured to send a first command signal after a first regulated time to turn on the HS switch after an HB voltage on the HB node begins rising in response to the LS switch having been turned off.