Voltage Droop Control for Paralleled SMPS Current Sharing
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Solution Overview
Problem
In power supply systems with paralleled switched mode power supplies, current sharing accuracy is poor during start-up, particularly when switching frequencies are not synchronized, leading to voltage differences and current imbalances.
Innovation Solution
A controller that regulates output voltage using a first droop function during the ramp-up phase and a different second droop function after the ramp is complete, allowing for improved current sharing without synchronizing switching frequencies or using a current-sharing bus.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single droop function is used for voltage-regulated SMPS, then current sharing is improved during normal operation, but current sharing accuracy deteriorates during start-up ramp phase
Solution Approach 1:
The patent applies dynamics by making the droop function adjustable based on the operational phase. The controller dynamically switches between a first droop function during the voltage ramp phase and a second droop function during normal operation, allowing the system to adapt its characteristics to different operating conditions and resolve the contradiction between start-up performance and steady-state current sharing accuracy
Solution Approach 2:
The patent changes the droop parameter (droop coefficient) based on the operational phase. During the voltage ramp phase, a first droop coefficient is used, and during normal operation, a second droop coefficient is used. This parameter change allows optimization of current sharing accuracy for each specific phase, resolving the contradiction between the requirements of different operational states
2Stability of the object's composition
If voltage regulation is maintained during start-up ramp, then output voltage stability is improved, but current sharing balance deteriorates among paralleled SMPS
Solution Approach 1:
The patent applies preliminary action by implementing a specific droop function during the start-up ramp phase that anticipates and prepares for the current sharing requirements. The first droop function is designed to accommodate voltage differences during ramp-up while maintaining current sharing balance, preventing future instability rather than reacting to it
Solution Approach 2:
The patent makes the droop characteristic dynamic by using different droop functions for different phases. During the ramp phase, the first droop function allows greater voltage variation to maintain current balance, while during normal operation, the second droop function provides tighter voltage regulation. This dynamic adjustment resolves the contradiction between voltage stability and current sharing balance
Data Source
AI summary
A controller for a switched mode power supply (SMPS) including a reference voltage signal generator to generate a variable reference voltage signal for regulating an output voltage of the SMPS, and a voltage droop control signal generator to receive a current indicator signal indicative of an output current of the SMPS, and generate an output voltage droop control signal in response to a first function and a second function of the current indicator signal. The first function is employed when the reference voltage signal generator ramps the variable reference voltage signal, and the second function is employed thereafter. The controller includes a switching control signal generator to receive a voltage indicator signal, and to generate a control signal to regulate the output voltage of the SMPS based on the voltage indicator signal, the variable reference voltage signal, and the output voltage droop control signal.