Switching Regulator Virtual Ripple Stabilization
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Solution Overview
Problem
Existing switching regulators face system instability due to the small equivalent series resistance (ESR) of output capacitors, leading to phase differences in feedback voltage, which affects power efficiency and response time.
Innovation Solution
A switching regulator design that incorporates a first virtual ripple generator to produce a modulated reference voltage, which is used in conjunction with a comparator and constant-time trigger to control the on and off times of switches, thereby stabilizing the system by improving the discrimination of feedback voltage variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If a switching regulator uses a constant-time trigger to control switch timing, then response time is improved, but system stability deteriorates due to phase differences caused by small ESR output capacitors
Solution Approach 1:
The patent introduces a virtual ripple signal as an intermediary element that mediates between the constant-time trigger and the switch control. This virtual ripple signal, generated by a dedicated circuit, serves as a reference that compensates for the phase differences caused by small ESR output capacitors, allowing the constant-time trigger to maintain both fast response and system stability
Solution Approach 2:
The patent changes the reference parameter from a fixed voltage level to a dynamic virtual ripple signal that mimics the actual ripple voltage across the output capacitor. By using a modulated reference voltage that varies in sync with the switching cycle, the system adapts to the small ESR conditions while maintaining stability
2Loss of energy
If the output capacitor has small equivalent series resistance (ESR), then power efficiency is improved, but feedback voltage discrimination deteriorates causing system instability
Solution Approach 1:
The patent creates a copy of the desired ripple waveform through the virtual ripple generator circuit. This copied signal serves as a reference that replaces the need for actual high-ESR capacitor ripple, allowing the system to maintain proper feedback discrimination while using low-ESR capacitors for improved efficiency
Solution Approach 2:
The virtual ripple signal acts as an intermediary that bridges the gap between the low-ESR capacitor output and the feedback comparison circuit. It provides the necessary ripple characteristics for accurate feedback voltage discrimination without requiring high ESR from the output capacitor
Data Source
AI summary
A switching regulator includes a power stage, an output capacitor, a first reference voltage generator, a first virtual ripple generator, a comparator, and a constant-time trigger. The power stage includes a first switch, a second switch coupled to the first switch, and an output inductor coupled to the first switch and the second switch. The output capacitor coupled to the output inductor with an output voltage across the capacitor. The first virtual ripple generator is coupled to the first reference voltage generator for generating a first modulated reference voltage which reverses the output voltage according to the first reference voltage. The comparator includes a first input end coupled to the output inductor and the output capacitor and a second input end coupled to the first virtual ripple generator. The constant-time trigger is coupled between an output end of the comparator and a control end of the power stage.