Half-Bridge Power Converter ZVS Using Adaptive Dead-Time Control
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Solution Overview
Problem
Existing power converters face challenges in achieving zero-voltage switching (ZVS) for all transitions in half-bridge topologies due to limitations in existing hardware and control-based approaches, leading to inefficiencies and increased energy dissipation.
Innovation Solution
A system comprising a first half-bridge and a second auxiliary half-bridge with an auxiliary inductor, coupled with a controller that adjusts pulse width modulation (PWM) control signals and dead times to ensure ZVS for all transitions by measuring current and voltage values, allowing the auxiliary half-bridge to function as a current source and control the auxiliary inductor's current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If switching frequency is increased to achieve higher power density, then productivity improves, but turn-on losses in transistors increase causing efficiency to deteriorate
Solution Approach 1:
The patent applies preliminary action by driving the voltage of each transistor to zero before turning them on through ZVS technique. The controller monitors voltage across transistors and delays turn-on until voltage reaches zero, preventing immediate turn-on losses and enabling high-frequency operation with maintained efficiency
Solution Approach 2:
The patent changes the voltage parameter of transistors dynamically by implementing ZVS control. The controller adjusts switching timing based on real-time voltage measurements, ensuring voltage transitions to zero before each turn-on event, thereby reducing energy dissipation while maintaining high switching frequency
2Loss of energy
If ZVS is implemented using auxiliary resonance circuit to reduce turn-on losses, then energy loss decreases, but device complexity increases and switching frequency is limited
Solution Approach 1:
The patent extracts the essential ZVS function from complex auxiliary resonance circuits and implements it through a simplified controller-based approach. The controller monitors voltage across transistors and controls switching timing to achieve ZVS without requiring additional resonance components, thereby reducing device complexity while maintaining energy efficiency
Solution Approach 2:
The patent replaces the mechanical/hardware-based auxiliary resonance circuit with a control-based electronic system. The controller uses voltage sensing and PWM adjustment to achieve ZVS, substituting physical resonance components with electronic control logic, thereby simplifying the overall device structure
3Reliability
If critical conduction mode is used to enable ZVS for all transitions, then ZVS capability improves, but conduction loss increases and EMI filter design becomes more difficult
Solution Approach 1:
The patent implements feedback control by continuously monitoring voltage across transistors and adjusting PWM duty cycle accordingly. The controller uses voltage feedback to determine optimal turn-on timing, ensuring ZVS is achieved without requiring critical conduction mode, thereby avoiding increased conduction losses while maintaining full ZVS capability
Data Source
Figure 1A~1B
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AI summary
Disclosed is a system for zero voltage switching in a power converter (102, 302) comprising first half-bridge (106, 202) and second half-bridge (108, 204, 310, 312, 314). The first half-bridge comprises first set of transistors (202a, 202b, 304a, 304b, 306a, 306b, 308a, 308b) and output inductor (212). The second half-bridge comprises second set of transistors (204a and 204b) and auxiliary inductor (206). A current sensing means measures (110), at switching cycle scale, average and maximum current values of output inductor and average, minimum and maximum current values of auxiliary inductor. A voltage sensing means (112) measures input and output voltages of first and second half-bridge. A controller (114) is configured to compute dead times of pulse width modulation control signal of second half-bridge, generate pulse width modulation control signal of second half-bridge (108, 204, 310, 312, 314) and to adapt dead times of first half-bridge (106, 202).