Adaptive Dead Time Control for LLC Power Supplies
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Solution Overview
Problem
Existing LLC power supply topologies face challenges in accurately controlling dead time to achieve zero-voltage switching, which is crucial for reducing switching losses and minimizing EMI, especially under varying load conditions.
Innovation Solution
An adaptive dead time control method using a voltage divider and comparators to dynamically adjust the dead time based on detection voltages and reference voltages, ensuring proper timing for zero-voltage switching by triggering high-side and low-side power switches accordingly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If fixed dead time is used in LLC power supply, then circuit simplicity is maintained, but zero-voltage switching cannot be achieved under varying load conditions
Solution Approach 1:
The patent implements dynamic dead time adjustment by detecting the voltage at the connection node and using a comparator to generate adaptive dead time signals. The dead time duration changes dynamically based on the detected voltage, enabling the system to adapt to varying load conditions while maintaining zero-voltage switching. This resolves the contradiction by transforming the fixed dead time into a dynamic parameter that automatically adjusts to system conditions.
Solution Approach 2:
The patent employs a feedback mechanism where the voltage at the connection node is continuously detected and fed back to the comparator. The comparator compares the detected voltage with a reference voltage and adjusts the dead time signal accordingly. This closed-loop feedback system enables automatic adaptation to load variations, achieving both adaptability and maintaining reasonable circuit complexity through intelligent control.
2Loss of energy
If dead time is not properly controlled, then switching speed is maintained, but switching losses increase and EMI is minimized
Solution Approach 1:
The patent implements a self-service mechanism where the system automatically determines the appropriate dead time based on its own operating state. The detection circuit monitors the connection node voltage, and the comparator automatically generates the corresponding dead time signal without external intervention. This self-adjusting capability reduces switching losses by ensuring proper dead time while keeping the control circuit relatively simple through autonomous operation.
3Reliability
If voltage detection is used for dead time control, then zero-voltage switching is achieved, but additional circuit components are required
Solution Approach 1:
The patent makes the connection node serve multiple functions: it is both the switching node for power conversion and the detection point for voltage sensing. By using the existing connection node for dual purposes, the patent avoids adding separate detection circuits, thereby achieving reliable zero-voltage switching while minimizing the increase in circuit components. This multi-functional approach resolves the contradiction between reliability and complexity.
Data Source
AI summary
A power controller has a high-side driver, a low-side driver, a voltage divider, and a comparator. The high-side driver drives a high-side power switch, powered by a boost power line and a connection node. The low-side driver drives a low-side power switch, powered by an operation power line and a ground power line. The voltage divider has a first resistor having a first node for providing a detection voltage and a second node coupled to the boost power line or the connection node. The voltage divider has a second resistor coupled between the first node of the first resistor and the ground power line. When the low-side power switch is turned off, the comparator compares the detection voltage with a reference voltage. When the detection voltage is higher than the reference voltage, the comparator renders to turn on the high-side power switch.