Burst Mode PFC Controller for SMPS Standby Voltage Stability
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Solution Overview
Problem
Switched mode power supplies face increased costs and requirements for higher specifications during transitional periods when load is reconnected after standby mode, due to lower input voltage, leading to potential voltage drops and the need for enhanced components like larger transformers or higher current-rated switches.
Innovation Solution
A power supply with a controller that switches the power factor correction stage between normal and standby modes, operating in a burst mode to maintain output voltage within specific levels below the normal range, allowing the SMPS to handle full load without voltage dips or enhanced capacity requirements, using a bistable device and comparators to manage voltage levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the PFC stage is switched off in standby mode to minimize power draw, then power consumption is reduced, but the output voltage drops to rectified mains voltage level which causes voltage drops when load is reconnected
Solution Approach 1:
The PFC stage operates in burst mode during standby, switching on periodically to maintain the output voltage within a specific range (between high and low burst levels) rather than remaining continuously on. This periodic operation minimizes power consumption while ensuring the voltage is sufficient when load is reconnected, avoiding the need for uprated SMPS components.
2Reliability
If the SMPS is designed with higher specification components to handle full load from rectified mains voltage, then voltage drop is avoided during transitional period, but cost increases
Solution Approach 1:
The PFC stage is maintained in a ready state during standby by operating in burst mode to keep the output voltage within an acceptable range (between high and low burst levels). This preliminary action ensures that when full load is reconnected, the SMPS can immediately handle it with standard components rather than requiring uprated components designed for worst-case scenarios.
3Reliability
If the PFC stage operates continuously in normal mode to maintain high output voltage, then voltage stability is improved, but power consumption increases during standby
Solution Approach 1:
The PFC stage dynamically switches between off mode and burst mode operation based on standby conditions. The controller monitors the output voltage and activates burst mode when voltage falls below the high burst level, creating a dynamic system that adapts to maintain voltage stability while minimizing power consumption during standby periods.
Data Source
AI summary
A power supply includes a PFC stage 6 and an SMPS stage 8. The power supply can operate in a normal mode in which the PFC stage supplies a voltage to the SMPS stage. In a standby mode, the PFC stage is operated in bursts to supply a lower voltage to the SMPS stage that is high enough that the SMPS stage can rapidly respond when it needs to supply a load.