SMPS Control Circuit Reducing Voltage Undershoot
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Switching mode power supplies (SMPS) face challenges in reducing output voltage drops during load transients due to reduced switching frequency in light load or no load conditions, leading to inefficiencies and performance limitations.
Innovation Solution
The implementation of a transformer with a primary, secondary, and auxiliary winding, where electrical signals are applied to the secondary winding to communicate system output changes to the primary side controller during discontinuous conduction mode, allowing the controller to adjust the power switch and reduce output voltage undershoot during dynamic load changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If switching frequency is reduced in light load or no load conditions, then power conversion efficiency is improved and standby power is reduced, but output voltage drops during load transients worsen
Solution Approach 1:
The patent applies preliminary action by detecting output voltage status in advance during discontinuous conduction mode and proactively transferring energy from primary to secondary side before the load transient fully develops. The control circuit monitors the secondary winding voltage and initiates energy transfer when voltage drops are detected, preventing severe undershoot rather than reacting after it occurs. This allows the SMPS to maintain low switching frequency for efficiency while still responding quickly to load changes.
Solution Approach 2:
The patent implements feedback by continuously monitoring the output voltage through the secondary winding and auxiliary circuitry, and using this information to control the power switch timing. The system detects when output voltage drops below a threshold during discontinuous conduction mode and adjusts the primary side switching accordingly. This closed-loop feedback enables the system to maintain voltage stability during transients while operating at optimized low frequencies for efficiency.
2Loss of energy
If switching frequency is reduced in light load conditions, then switching loss of power transistor is reduced, but response time to load changes worsens
Solution Approach 1:
The system performs preliminary detection of output voltage status during the discontinuous conduction mode intervals. By monitoring the secondary winding voltage and detecting drops in advance, the control circuit can initiate energy transfer before the load transient fully impacts the output. This proactive approach compensates for the slower response inherent in low-frequency operation, maintaining both efficiency and responsiveness.
Solution Approach 2:
The patent applies dynamics by enabling the system to operate in two distinct modes: normal low-frequency operation for efficiency during steady-state light load, and accelerated energy transfer mode when transients are detected. The control circuit dynamically switches between these behaviors based on real-time voltage conditions, allowing the system to adapt its response characteristics to match operational requirements without sacrificing overall efficiency.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach effectively reduces output voltage drops during load transients by enabling timely energy transfer from the primary to the secondary side, enhancing the dynamic performance and efficiency of SMPS, particularly in light load conditions.
Implementation Method 1
the primary winding stores energy during the turn-on period of the power switch and releases the energy to the secondary winding when the power switch is turned off
Implementation Method 2
electrical signals are communicated to a primary side controller through an auxiliary winding
Data Source
AI summary
A switching mode power supply (SMPS) includes a transformer having a primary winding, a secondary winding for providing an output voltage, and an auxiliary winding. The SMPS also includes a power switch coupled to the primary winding. A first control circuit is coupled to the secondary winding, and is configured to provide a first electrical signal to the secondary winding when the output voltage of the SMPS is less than a reference voltage during a discontinuous time, whereupon a second electrical signal is induced in the auxiliary winding. A second control circuit is coupled to the auxiliary winding and the power switch. The second control circuit is configured to regulate the output of the SMPS by controlling the power switch in response to a feedback voltage signal from the auxiliary winding, and is further configured to turn on the power switch in response to the second electrical signal.