LLC Resonant Converter Dead Time Control via Voltage Detection
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Solution Overview
Problem
Existing LLC resonant converters face challenges in accurately adjusting dead time for zero-voltage switching (ZVS), leading to inefficiencies, and the use of PFC circuits with specialized control ICs limits flexibility in controller options.
Innovation Solution
A power control device that includes a controller to detect switching voltage variations and generate signals for turning on switching elements, allowing for adjustable dead time and compatibility with a wide range of control ICs by incorporating a current feeder and burst detection mechanisms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If dead time is calculated according to a formula based on excitation current and parasitic capacitance, then ZVS can be achieved, but the accuracy of ZVS timing is reduced due to deviation from actual voltage zero-crossing
Solution Approach 1:
The patent replaces the calculation-based dead time control method with a detection-based method using voltage detection circuits. Instead of calculating dead time from excitation current and parasitic capacitance formulas, the system directly detects the actual voltage across switching elements and generates turn-on signals when voltage reaches zero, eliminating the deviation between calculated and actual ZVS timing.
Solution Approach 2:
The patent implements feedback control by continuously monitoring the voltage across switching elements through detection circuits and adjusting the turn-on timing based on real-time voltage status. The control circuit generates turn-on signals for Q1 and Q2 only when the detected voltage reaches zero, creating a closed-loop system that ensures accurate ZVS timing rather than relying on open-loop calculations.
2Loss of energy
If a PFC circuit uses a specialized control IC with AC-COMP synthesizing circuit for burst operation, then efficiency is improved, but the degree of freedom in controller selection is reduced
Solution Approach 1:
The patent designs a universal control interface that can work with various types of control ICs. The voltage detection circuit and control logic are configured to provide standardized signals that can drive different switching elements, allowing the PFC circuit to perform burst operation with multiple controller options rather than requiring a specialized AC-COMP synthesizing circuit.
Solution Approach 2:
The patent introduces an intermediary voltage detection and control circuit that acts as a bridge between the control IC and the switching elements. This intermediary layer translates various control IC outputs into the required switching signals, enabling different control IC types to work with the PFC circuit without requiring specialized circuits within each controller.
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
Improves the accuracy of ZVS, enhances efficiency, and increases flexibility in using control ICs for PFC circuits, enabling burst operation and efficient power control.
Implementation Method 1
the dead time is secured for the period required to charge and discharge the electric charges of a parasitic capacitance of the switching element with the excitation current of a transformer, and thereby ZVS (zero-voltage switching) during turning on is achieved
Data Source
AI summary
A power control device for controlling driving of an LLC resonant converter including a first switching element to one end of which an input voltage is applied, a second switching element of which one end is connected to the other end of the first switching element, and a primary winding and a resonant capacitor connected in series between a first connection node at which the first and second switching elements are connected together and the other end of the second switching element includes an on-timing controller that detects variation of a switching voltage detection signal based on a switching voltage appearing at the first connection node rising up to the input voltage and falling down to 0 V and that, based on the result of the detection, generates a high-side on-signal for turning on the first switching element and a low-side on-signal for turning on the second switching element.