Multi-phase DC-DC Converter PWM Control for Ripple Reduction
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Solution Overview
Problem
Conventional multi-phase DC-DC power converters with constant on time (COT) regulators face issues with output ripple and reduced power conversion efficiency due to high equivalent series resistance (ESR) in output capacitors, and noise interference affects phase separation between channels.
Innovation Solution
A multi-phase DC-DC power converter design incorporating a PWM controller with a ramp generator, feedback circuit, phase channel current sensor, and phase channel selector, which generates a PWM signal with constant on time and adjusts duty cycles based on error current signals, using an output capacitor with low ESR to minimize ripple and noise interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a high ESR output capacitor is used in the COT regulator, then the regulated output voltage is provided, but the output ripple increases and power conversion efficiency decreases
Solution Approach 1:
The patent implements a feedback circuit that detects the output voltage and compares it with a reference voltage to generate an error signal. This error signal is then used to adjust the duty cycle of the PWM signal, enabling closed-loop voltage regulation. The feedback mechanism allows the system to maintain stable output voltage without relying on high ESR capacitors, thereby reducing output ripple while preserving voltage regulation capability.
Solution Approach 2:
The patent transitions from a COT (constant on-time) control mode to a PWM (pulse width modulation) control mode with adjustable duty cycle. By changing the control parameter from fixed on-time to variable duty cycle based on feedback, the system achieves better voltage regulation with low ESR capacitors, eliminating the need for high ESR capacitors that cause excessive output ripple.
2Ease of operation
If a triangular wave signal is transmitted to all current mode regulators for phase separation, then phase separation is implemented, but noise interference from switching operations aggravates the signal and limits actual phase separation
Solution Approach 1:
The patent divides the multi-phase control into separate independent control channels, each with its own PWM controller. Instead of sharing a common triangular wave signal that is susceptible to noise, each phase has dedicated control circuitry that generates its own PWM signals. This segmentation isolates the control signals from cross-phase noise interference while maintaining proper phase separation for current sharing.
Solution Approach 2:
The patent introduces a current sensing mechanism that acts as an intermediary to detect actual current flow in each phase. The sensed current information is fed back to adjust the PWM duty cycle, creating a current-mode control loop. This intermediary current feedback mechanism enables accurate phase separation and current balancing without relying on noisy shared triangular wave signals.
Data Source
AI summary
A multi-phase DC-DC power converter including a pulse width modulation (PWM) controller and a plurality of output stage circuits is provided. The output stage circuits convert an input voltage into an output voltage. The PWM controller includes a PWM generation module, a ramp generator and a feedback circuit. The feedback circuit generates a trigger signal according to the output voltage and a ramp signal. The PWM generation module generates a PWM signal with a constant on time, and adjusts a duty cycle of the PWM signal according to the trigger signal, the input and output voltages, so as to control phase channels of the multi-phase DC-DC power converter in order.