Burst-Mode Control Circuit for SMPS Light Load Efficiency
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Solution Overview
Problem
Switch mode power supplies (SMPS) face efficiency and noise issues under light load conditions due to high switching frequencies, which can lead to significant losses and audible noise when frequencies drop below 20KHz.
Innovation Solution
Implementing a burst-mode function that modulates the switch based on high frequency signals for a portion of the time and keeps it off for another portion, with the periods automatically adjusted according to load power, using a control circuit that detects switch current and feedback signals to manage the burst-mode operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the switch frequency is decreased below 20KHz to reduce switching losses under light load conditions, then switching loss is reduced, but audible noise is generated
Solution Approach 1:
The patent applies periodic action by implementing burst-mode operation where the switch operates in periodic bursts rather than continuous switching. The control circuit generates periodic drive signals that turn the switch on for a predetermined period and then keep it off for a predetermined period, creating a periodic pattern that reduces average switching frequency and losses while maintaining output voltage regulation.
Solution Approach 2:
The patent applies dynamics by making the switch operating state changeable between different modes. The control circuit dynamically adjusts the switch operation based on load conditions, transitioning between continuous switching mode and burst-mode operation. This dynamic adjustment allows the system to optimize between switching losses and noise based on actual operating conditions.
2Loss of energy
If burst-mode operation is implemented with automatically adjusted periods according to load power, then switching loss is reduced, but the periods become uncertain causing noise issues
Solution Approach 1:
The patent applies parameter changes by fixing the burst-mode period parameters to predetermined values rather than allowing them to vary dynamically with load conditions. The control circuit uses a fixed predetermined on-period and a fixed predetermined off-period for the burst-mode operation. This parameter fixation ensures that the switching frequency remains stable and predictable, preventing audible noise while maintaining reduced switching losses.
3Loss of energy
If the switch is kept off for extended periods in burst-mode to reduce losses, then switching loss decreases, but output voltage stability becomes challenging to maintain
Solution Approach 1:
The patent applies feedback by implementing a feedback circuit that continuously monitors the output voltage and provides feedback signals to the control circuit. The control circuit compares the feedback signal with a reference voltage and adjusts the burst-mode drive signal accordingly to maintain the output voltage at a predetermined level. This feedback mechanism ensures output voltage stability even when the switch is kept off for extended periods during burst-mode operation.
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 reduces switching losses and noise by adjusting the burst-mode periods to maintain efficiency and prevent audible noise, ensuring stable DC voltage output even under light load conditions.
Implementation Method 1
The control circuit senses load current demand by monitoring the output current of the converter
Implementation Method 2
The high frequency signal is coupled by a transformer and a steady DC voltage is preferably output
Data Source
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AI summary
Switching mode power supplies (SMPS) that can operate in a control mode for a normal load condition and operate with a burst-mode controller for a light load condition are disclosed herein. In one embodiment, a method for controlling the switching mode power supply includes when the load is in a light load condition, the switching mode power supply is controlled by a burst-mode controller.