PWM Compensator Switching for Duty-Cycle-Insensitive Loop Gain
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Solution Overview
Problem
Unity gain bandwidth (UGB) of switching power converters varies with duty cycle, leading to larger output voltage undershoot and overshoot during sudden load current changes due to its dependence on input and output voltages, resulting in suboptimal performance across different applications.
Innovation Solution
Incorporating a compensator with a duty-cycled resistor or capacitor within the power converter's control loop, where the resistor or capacitor is selectively enabled/disabled based on the duty cycle, effectively making the loop gain insensitive to duty cycle variations, thereby stabilizing the output voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the duty cycle is adjusted based on input voltage variations, then the converter adapts to different input voltage conditions, but the unity gain bandwidth varies causing larger output voltage undershoot and overshoot
Solution Approach 1:
The compensator uses dynamic component values that change with duty cycle. Specifically, the first compensator component has a first value at a first duty cycle and a second value at a second duty cycle, allowing the compensator to adapt its characteristics to maintain stable loop gain across varying input voltage conditions and duty cycles
Solution Approach 2:
The invention changes the parameters of the compensator components based on duty cycle. The compensator is configured to have different component values at different duty cycles, which directly addresses the variation in unity gain bandwidth and maintains consistent output voltage stability across different operating conditions
2Device complexity
If a fixed compensator is used, then the circuit is simple, but the loop gain is sensitive to duty cycle variations causing performance degradation
Solution Approach 1:
Rather than using a fixed compensator, the invention employs a dynamic compensator where component values change with duty cycle. This dynamic adjustment stabilizes the loop gain across varying operating conditions while maintaining practical circuit implementation
Solution Approach 2:
The compensator parameters are changed based on duty cycle variations. By configuring the compensator to have different component values at different duty cycles, the invention maintains stable loop gain without requiring overly complex circuit topologies
Data Source
AI summary
A power converter includes a power stage circuit having a control input and an output. A pulse width modulation (PWM) controller has a control output coupled to the control input of the power stage. A compensator includes a passive component and a switch coupled to the passive component. The switch has a switch control input coupled to the control output of the PWM controller.