Resonant Converter Switch Paths for Controlled Power-Up
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Solution Overview
Problem
Resonant converters face challenges in successfully powering up to steady state without overstressing components, particularly due to unbalanced initial conditions and capacitance ratios, which can lead to damaging inrush currents and slow response times during power-up.
Innovation Solution
The use of switch paths to control current flow during power-up, where a first switch path sinks current from the resonant capacitor while a second switch path sources current to the high-side capacitor, and a third switch path controls current to the low-side capacitor, ensuring predictable charging and reducing stress on drivers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional power-up methods are used in resonant converters, then the converter can be powered on, but unbalanced initial conditions and capacitance ratios cause damaging inrush currents and slow response times
Solution Approach 1:
The patent applies preliminary action by controlling the switching state of power stage switches before the resonant converter reaches steady state. Specifically, during power-up, the controller maintains certain switches in specific states to pre-condition the circuit, ensuring that when power is applied, the resonant capacitor charges through controlled paths rather than direct inrush current paths. This preliminary control of switch states prevents the harmful inrush current while enabling reliable power-up.
Solution Approach 2:
The patent uses the power stage switches as intermediary elements to control and mediate the power-up process. These switches act as controllable intermediaries between the power source and the resonant circuit, allowing the controller to direct current flow through safe paths during initialization. The switches mediate the charging process of the resonant capacitor, preventing direct connection that would cause inrush current, while still enabling the capacitor to charge to the required voltage level for steady-state operation.
2Reliability
If conventional power-up methods are used in resonant converters, then the converter can be powered on, but the response time to reach steady state is slow
Solution Approach 1:
The controller pre-positions the power stage switches in optimal states during the power-up sequence, creating favorable initial conditions that accelerate the transition to steady state. By controlling which switches are on or off during initialization, the circuit is pre-configured to enable faster charging of the resonant capacitor and quicker establishment of zero-voltage switching conditions, reducing the time loss during power-up.
3Reliability
If switch paths are controlled during power-up, then inrush current is reduced and steady state is achieved quickly, but device complexity increases
Solution Approach 1:
The controller uses the existing power stage switches, which are already part of the resonant converter's normal operation, to also perform the power-up control function. Rather than adding dedicated power-up control switches or circuits, the system makes the operational switches serve dual purposes: controlling the power-up sequence and enabling steady-state operation. This self-service approach reduces the need for additional components and minimizes the increase in device complexity.
Data Source
AI summary
Control of a resonant power converter using switch paths during power-up is described herein. During power-up, a first switch path sinks current away from a resonant capacitor while a second switch path sources current to a high-side capacitor. In this way the high-side capacitor may predictably charge to sufficient bootstrap voltage for steady state operation. Additionally, a third switch path may control current to a low-side capacitor.