LLC Converter Burst Pulse Control for Light-Load Voltage Stability
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Solution Overview
Problem
LLC converters operating at light load tend to experience uncontrollable output voltage increases due to their inability to manage transitions between continuous and burst modes effectively.
Innovation Solution
A controller is configured to generate specific switching patterns, including initial, full, and final pulses, to manage transitions between continuous and burst modes in LLC converters, minimizing transient components and optimizing operation at light loads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If LLC converter operates in continuous mode at light load, then output voltage becomes uncontrollable and increases, but switching to burst mode causes transient components stress and output ripple
Solution Approach 1:
The controller prepares for mode transition by generating an initial first pulse with duration roughly half of a full second pulse before switching to burst mode, and generates a final first pulse with similar duration when exiting burst mode. This preliminary action ensures that the resonant tank is properly charged/discharged before and after burst mode, preventing transient components stress and output ripple that would otherwise occur during mode transitions.
Solution Approach 2:
The controller dynamically adjusts the duration of first pulses (initial and final) relative to second pulses during mode transitions. By making the first pulse duration roughly half of the full second pulse duration at transition points, the system adaptively manages the resonant tank energy, enabling seamless switching between continuous and burst modes without causing harmful transients or output ripple.
2Productivity
If LLC converter switches between continuous and burst modes, then light load operation is optimized, but switching transitions cause output ripple and transient stress
Solution Approach 1:
Before entering burst mode, the controller generates an initial first pulse with duration roughly half of a full second pulse to properly charge the resonant tank. When exiting burst mode, it generates a final first pulse with similar duration. This preliminary action ensures smooth energy transition in the resonant tank, enabling efficient light load operation while minimizing output ripple during mode transitions.
3Reliability
If LLC converter uses standard burst mode switching, then output voltage control is improved, but component stress increases during transitions
Solution Approach 1:
The controller generates an initial first pulse with duration roughly half of a full second pulse before burst mode and a final first pulse with similar duration after burst mode. This preliminary action properly charges and discharges the resonant tank, reducing stress on switching components during transitions while maintaining reliable output voltage control through effective burst mode operation.
Data Source
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AI summary
A controller is presented. The controller may be configured to control operation of an inductor-inductor-capacitor LLC converter comprising a bridge circuit with a first switching element and a second switching element. The controller may be configured to generate first pulses for turning on the first switching element and second pulses for turning on the second switching element. The controller may be configured to, in a burst operation mode, generate an initial first pulse, a full second pulse, and a final first pulse, wherein a duration of the initial first pulse is roughly half of a duration of the full second pulse, and wherein a duration of the final first pulse is roughly half of the duration of the full second pulse.