Buck Converter Ripple Injection Feedback Network
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Solution Overview
Problem
Conventional buck switching regulators experience voltage offset and reduced accuracy due to output ripple, which degrades load regulation and PSRR performance, especially when using low ESR capacitors that do not generate sufficient ripple for feedback control.
Innovation Solution
The implementation of an accuracy enhanced feedback network with a ripple generation circuit and a balanced feedback network that injects ripple signals into both feedback circuits to correct for voltage offsets and improve stability, allowing for the use of low ESR capacitors and enhancing output voltage accuracy and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If low ESR capacitors are used in the output filter circuit, then power loss is reduced and efficiency is improved, but output ripple voltage becomes insufficient for feedback control and voltage accuracy deteriorates
Solution Approach 1:
A ripple injection circuit is introduced as an intermediary component that generates artificial ripple voltage and injects it into the feedback control loop. This mediator provides the necessary ripple signal for accurate feedback control without requiring high ESR output capacitors, thus resolving the contradiction between using low ESR capacitors for efficiency and maintaining sufficient ripple for voltage accuracy.
Solution Approach 2:
The invention changes the source of ripple voltage from the output capacitor's ESR to an active ripple injection circuit. By controlling the ripple injection circuit's parameters (such as switching frequency and amplitude), the system can maintain accurate feedback control while using low ESR capacitors, thereby improving efficiency without sacrificing voltage accuracy.
2Reliability
If output ripple is present in the feedback signal, then feedback control function is maintained, but voltage offset increases and measurement accuracy deteriorates
Solution Approach 1:
The feedback control function is segmented into two independent parts: the main feedback loop that provides voltage regulation, and a separate ripple injection circuit that provides controlled ripple without affecting the DC voltage level. This segmentation allows the system to maintain feedback control reliability while eliminating the harmful voltage offset that would otherwise accompany the ripple signal.
Solution Approach 2:
The ripple injection circuit acts as an intermediary that introduces ripple into the feedback path in a controlled manner. By injecting ripple at a specific point in the feedback loop rather than relying on the output capacitor's ESR, the system maintains feedback control functionality while preventing the ripple from causing voltage offset in the main feedback signal.
3Device complexity
If conventional feedback control is used with low ESR capacitors, then device complexity is reduced, but output voltage stability and load regulation performance deteriorate
Solution Approach 1:
The ripple injection circuit is designed to perform multiple functions simultaneously: it generates the necessary ripple signal for feedback control, improves output voltage stability, enhances load regulation performance, and enables the use of low ESR capacitors. This multi-functionality achieves performance improvements without significantly increasing device complexity.
Data Source
AI summary
A buck switching regulator includes a feedback control circuit including a feedback network including first and second gain circuits configured to generate first and second feedback signals, respectively, indicative of the regulated output voltage; a ripple generation circuit configured to inject a ripple signal to the first gain circuit; an operational transconductance amplifier (OTA) configured to receive the second feedback signal and a reference signal and to generate an output signal being coupled to the first gain circuit to adjust the first feedback signal; and a comparator configured to receive the first feedback signal and the reference signal and to generate a comparator output signal. The output signal of the OTA is applied to the first feedback signal to cancel a voltage offset in the regulated output voltage due to the injected ripple signal to the first gain circuit.