Dual Compensation Ramp Current Control for Higher SMPS Bandwidth
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Solution Overview
Problem
Existing current control schemes in switched mode power supplies, such as asymmetrical average current control, are limited by bandwidth restrictions due to constraints on inductance current slopes, which hinder dynamic capability and require parallel converters to achieve higher bandwidth.
Innovation Solution
A symmetrical peak current control scheme is developed, utilizing both an upper and a lower compensation ramp signal to control the peak and valley of the controlled current, respectively, allowing for slopes greater than the sawtooth slope and enabling control of both current peaks and valleys.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If asymmetrical average current control is used, then the control scheme is stable, but the bandwidth is restricted due to constraints on inductance current slopes
Solution Approach 1:
The patent divides the single compensation ramp into two separate ramps: an upper compensation ramp for controlling peak current and a lower compensation ramp for controlling valley current. This segmentation allows independent optimization of each ramp's slope characteristics, enabling the system to achieve higher bandwidth while maintaining stability through dual-ramp control
2Speed
If the sawtooth slope is increased to improve dynamic capability, then the bandwidth increases, but the inductance current slopes must be constrained to maintain control stability
Solution Approach 1:
The patent applies different slope characteristics to different parts of the control signal: the upper compensation ramp has a slope optimized for peak current control while the lower compensation ramp has a slope optimized for valley current control. This local differentiation allows each ramp to operate independently with optimal slope values, increasing dynamic capability without requiring global slope constraints
3Speed
If parallel converters are used to achieve higher bandwidth, then the bandwidth requirement is met, but the device complexity increases
Solution Approach 1:
The patent combines peak current control and valley current control into a single converter using dual compensation ramps. By merging both control functions into one system with coordinated upper and lower ramps, the patent achieves the bandwidth performance of parallel converters while maintaining simpler device architecture and avoiding the complexity of multiple parallel converter configurations
Data Source
AI summary
A method for controlling peak and valley of a controlled current in a switched mode power supply comprising a current mode control loop and being connected to an electrical power source. The method comprises providing an upper compensation ramp signal for controlling a peak of the controlled current, the upper compensation ramp signal being a sawtooth signal with a negative, falling, substantially linear slope (−Se,Upper), starting periodically in time. The method further comprising providing a lower compensation ramp signal for controlling a valley of the controlled current, the lower compensation ramp signal being a sawtooth signal with a positive, raising, substantially linear slope (Se,Lower), starting periodically in time. The method additionally comprising providing a reference voltage signal (Vref), to the control loop, and obtaining a signal indicative of the controlled current (I). Finally, the method comprises comparing alternatingly the signal indicative of the controlled current referenced to the reference voltage signal to the lower compensation ramp and the upper compensation ramp, respectively, to switch on or off the electrical power from the electrical power source into the control loop, and switching the electrical power with modulation at a fixed frequency (fs).