Ripple Regulator Control Circuit for Loop Stability and Offset Correction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Traditional constant on time (COT) ripple regulator systems face instability due to small output voltage ripples, particularly when using ceramic capacitors with low effective series resistance, making it difficult to maintain loop stability and output voltage regulation.
Innovation Solution
A control circuit and method that includes a ripple generation circuit to create a ripple signal in-phase with the inductor current, which is superposed to the feedback or reference voltage to enhance loop stability, and an offset cancellation circuit to extract ripple information and generate a signal that adjusts the error comparator, improving the output voltage offset.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If small output voltage ripples are used, then the system remains under specifications, but loop stability deteriorates
Solution Approach 1:
An artificial ripple signal is introduced as an intermediary element to mediate between the actual small output voltage ripple and the control circuit. This artificial ripple, generated by the ripple generation circuit and added to the feedback voltage, provides sufficient amplitude for reliable PWM triggering while the actual output voltage maintains small ripple magnitude to meet specifications.
2Stability of the object's composition
If large output voltage ripples are used, then loop stability is improved, but the system exceeds specifications
Solution Approach 1:
The ripple function is segmented into two separate components: an artificial ripple signal generated by the ripple generation circuit for control purposes, and the actual output voltage ripple determined by the power converter and output capacitor. This segmentation allows each component to be optimized independently for its specific function.
Solution Approach 2:
The artificial ripple signal serves as an intermediary that decouples the control function from the output voltage. By adding this artificial ripple to the feedback voltage, the control circuit receives sufficient ripple information for stable operation without requiring the actual output voltage to have large ripples.
3Stability of the object's composition
If an artificial ripple signal is added to improve loop stability, then loop stability is improved, but output voltage offset increases
Solution Approach 1:
The offset cancellation circuit uses feedback from the artificial ripple signal to dynamically adjust and eliminate the output voltage offset. By detecting the amplitude and phase of the artificial ripple and generating a compensating signal, the system maintains both loop stability and output voltage precision.
Solution Approach 2:
The offset cancellation circuit dynamically adjusts the error comparator reference voltage based on the artificial ripple signal characteristics. By changing the reference voltage parameter in response to the artificial ripple, the system compensates for the introduced offset and maintains accurate output voltage regulation.
Data Source
AI summary
A control circuit and method for a ripple regulator system generate a ripple signal in-phase and synchronous with an inductor current of the ripple regulator system, and extract a ripple information proportional to the amplitude of the ripple signal. The ripple signal is used for triggering control in PWM signal generation to make the ripple regulator system have small ripples and better loop stability simultaneously. The ripple information is used to improve the output offset of the ripple regulator system that is caused by the ripple signal.