Self-adaptive Current-mode Control Circuit for Switching Regulators
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Solution Overview
Problem
Current-mode controlled switching regulators experience sub-harmonic oscillations at duty ratios greater than 50%, compromising stability and requiring complex noise filtering, which adds to their complexity and inefficiency.
Innovation Solution
A current-mode-control circuit for switching regulators that includes a slope compensation generation circuit and an inductor current sensing circuit, generating a slope compensation current to stabilize the control loop by ensuring the compensation slope is at least half of the inductor current falling slope, thereby suppressing sub-harmonic oscillations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If current-mode control is used for switching regulators, then efficiency and size are improved, but sub-harmonic oscillations occur at duty ratios greater than 50% compromising stability
Solution Approach 1:
The patent applies preliminary anti-action by introducing a slope compensation signal that preemptively counteracts the sub-harmonic oscillations before they can develop. The compensation signal is added to the current control voltage in advance, creating a stabilizing effect that prevents oscillations at duty ratios greater than 50% without requiring complex filtering circuits.
2Volume of moving object
If switching regulators operate at high frequency, then size and weight are reduced, but high-amplitude energy and ripple voltage noises are generated
Solution Approach 1:
The patent implements feedback by continuously monitoring the current through the switch and inductor, and using this information to adjust the control voltage. The current-mode control architecture provides inherent feedback that allows the regulator to operate at high frequencies while maintaining stability and reducing noise, eliminating the need for complex additional filtering circuits.
3Object-generated harmful factors
If complex filtering circuits are added to reduce noise, then ripple voltage is reduced, but device complexity increases
Solution Approach 1:
The patent replaces complex mechanical filtering circuits with an electronic control solution. By using current-mode control with slope compensation and feedback mechanisms, the system achieves noise reduction through electronic regulation rather than physical filtering, thereby reducing circuit complexity while maintaining low ripple voltage.
Data Source
AI summary
A current-mode-control circuit for a switching regulator is provided. The circuit includes a first transistor coupled to a power supply voltage, a second transistor, and an inductor. The circuit further includes a slope compensation generation circuit coupled to the output of the current control circuit through a feedback loop, the slope compensation generation circuit generating a slope compensation current related to the output voltage, an inductor current sensing circuit coupled to the first transistor and the second transistor, and configured to calculate a current through the inductor and output a inductor sense current, and a pulse-width modulation control circuit coupled to the slope generation circuit and the inductor current sense circuit, the pulse-width modulation control circuit receiving the output of the current control circuit, the slope compensation current and the inductor sense current as inputs.