SMPS Controller Slope Compensation for CCM-DCM Load Jumps
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Solution Overview
Problem
Conventional switched-mode power supplies experience additional DC offset and output voltage overshooting during load jumps due to conventional slope compensation approaches, which deteriorate performance.
Innovation Solution
A controller with a sampling and feedback circuit, a slope compensation circuit that adjusts peak voltage by a compensating DC offset when switching from continuous to discontinuous conduction mode, and subtracts it when switching back, to maintain a constant valley of the sampled feedback voltage and reduce overshooting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional slope compensation is applied by clamping the compensation slope when switching from CCM to DCM, then the frequency jitter problem is mitigated, but an additional DC offset is introduced causing output voltage overshooting
Solution Approach 1:
The patent applies dynamics by making the compensation slope adaptive rather than static. The compensation slope is dynamically adjusted based on the operating mode (CCM or DCM) and load conditions. Specifically, the compensation slope is enabled when operating in DCM and disabled when operating in CCM, creating a dynamic control mechanism that adapts to changing operating conditions to prevent both frequency jitter and output voltage overshooting
Solution Approach 2:
The patent changes the parameter of the compensation slope (its amplitude and presence) based on operating conditions. By detecting the conduction mode (CCM or DCM) and adjusting the compensation slope parameter accordingly - adding it in DCM and removing it in CCM - the system achieves both frequency stability and accurate output voltage control without the DC offset problem caused by conventional clamping approaches
2Reliability
If the compensation slope is increased to enhance noise rejection capability, then frequency jitter is reduced, but output ripple increases proportionally
Solution Approach 1:
The patent applies local quality by applying compensation only where and when needed - specifically in DCM operation where frequency jitter occurs - rather than uniformly across all operating conditions. The compensation slope is selectively added only during DCM operation and removed during CCM operation, providing noise rejection exactly where required without unnecessarily increasing output ripple in other operating modes
3Manufacturing precision
If a DC loop is added to eliminate DC differences caused by compensation slope margin, then steady-state accuracy is improved, but response speed decreases
Solution Approach 1:
The patent applies preliminary action by proactively preventing the DC offset from occurring in the first place through mode-based compensation control. Instead of using a DC loop to reactively eliminate DC differences after they occur, the system preemptively adjusts the compensation slope based on detected operating mode (CCM or DCM), preventing the condition that would generate DC offset and eliminate the need for slow DC correction loops
Data Source
AI summary
The present invention provides a controller, a switched-mode power supply and a method for controlling a switched-mode power supply. In response to a change of the switched-mode power supply from a continuous conduction mode to a discontinuous conduction mode, slope compensation is carried out with an output peak voltage raised by a compensating DC offset. Moreover, in response to a change of the switched-mode power supply from the discontinuous conduction mode to the continuous conduction mode, the compensating DC offset is subtracted from the peak voltage. In this way, an additional DC offset that would be introduced by a conventional slope compensation approach can be eliminated, maintaining a valley of a sampled feedback voltage constant both under steady load conditions and during load jumps.