Resonant Converter Power-Up Using Controlled Switch Paths
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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, leading to 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
1Speed
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 inrush currents and slow response times
Solution Approach 1:
The patent applies preliminary action by pre-charging the resonant capacitor through a dedicated switch path before the main power conversion begins. The controller activates a first switch path that connects the input voltage to the resonant capacitor through a switch and diode, allowing the capacitor to charge to a predetermined voltage level before normal operation starts. This preliminary charging action prevents inrush currents when the resonant converter begins operation and eliminates slow response times associated with unbalanced initial conditions.
2Reliability
If resonant converters operate without controlled switch paths, then the circuit is simpler, but components experience overcurrent and overvoltage stress during power-up
Solution Approach 1:
The patent applies segmentation by dividing the power-up control into separate, independent switch paths. The circuit is segmented into: (1) a first switch path with a first switch and first diode for resonant capacitor charging, (2) a second switch path with a second switch and second diode for high-side capacitor charging, and (3) a third switch path with a third switch and third diode for low-side capacitor charging. Each path is independently controlled by the controller, allowing precise management of current flow to different capacitors during power-up. This segmentation protects components from overcurrent and overvoltage stress while maintaining manageable circuit complexity through modular organization.
3Power
If the resonant capacitor charges without control during power-up, then the charging process is simpler, but the high-side driver cannot achieve adequate voltage for zero-voltage switching
Solution Approach 1:
The patent applies the intermediary principle by introducing a dedicated first switch path that acts as an intermediary charging circuit between the input voltage source and the resonant capacitor. This intermediary path includes a first switch and first diode that are controlled by the controller to regulate the charging process. The intermediary circuit ensures the resonant capacitor charges to an appropriate voltage level without directly connecting the input voltage to the capacitor, thereby enabling the high-side driver to achieve adequate voltage for zero-voltage switching while maintaining controlled and manageable charging complexity.
Data Source
AI summary
A half-bridge circuit of a power converter includes a high-side device and a low-side device coupled together at a half-bridge node, which is in turn coupled to a network including an inductor and/or a capacitor. In some examples, the network is a resonant network. The half-bridge circuit further includes a first switch and a second switch. The first switch is coupled between the half-bridge node and a ground reference, in parallel with the low-side device. The second switch is coupled between an input node of the power converter and the half-bridge node, in series with a high-side capacitor that powers a driver of the high-side device. During power-up, the second switch turns on to provide a charging current to the high-side capacitor, while the first switch turns on to augment the charging current by pulling down a voltage at the half-bridge node, thereby diverting a shunt current away from the network.