SMPS Burst Mode Controller for Switching Loss Reduction
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Solution Overview
Problem
Conventional quasi-resonant switching mode power supplies face challenges in reducing switching loss and noise in the audible frequency range, particularly at low loads, where switching frequency restrictions lead to non-optimal operation and increased switching loss, and burst mode switching can generate audible noise.
Innovation Solution
A switch mode power supply (SMPS) with a switch controller that determines burst mode operation based on feedback signals, maintains a longer switching operation off period, and counts switching operations to control the on/off periods, preventing switching during the off period to reduce switching loss and noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the switching frequency is increased under light load condition, then the output power response is improved, but the switching loss increases
Solution Approach 1:
The patent implements burst mode switching operation where the SMPS performs repeated switching operations for a predetermined period, then stops switching for a predetermined time. This periodic action allows the system to maintain adequate power delivery under light load conditions while significantly reducing switching losses during the off periods, thereby resolving the contradiction between output power response and switching loss.
2Loss of energy
If the switching frequency is restricted to a predetermined value, then the switching loss is reduced, but the operation at low switching voltages becomes non-optimal
Solution Approach 1:
The patent dynamically adjusts the switching frequency based on load conditions. Under light load, the burst mode operation allows the switching frequency to be effectively reduced (longer off periods), while under heavier loads, the switching frequency increases (shorter off periods or continuous operation). This dynamic adaptation optimizes both switching loss reduction and switching operation efficiency across different operating conditions.
3Loss of energy
If the burst mode switching operation is used, then the switching loss is reduced, but the audible noise in the 2-3 kHz frequency range increases
Solution Approach 1:
The patent carefully controls the burst mode parameters, specifically setting the reference frequency and the duration of switching operation off periods to ensure the fundamental switching frequency and its harmonics remain below the 2-3 kHz audible range. By adjusting these parameters, the system maintains low switching loss while avoiding the generation of audible noise.
4Loss of energy
If the switching operation off period is extended, then the switching loss is reduced, but the output power delivery capability decreases
Solution Approach 1:
The patent employs feedback control where the switch controller receives feedback signals corresponding to the output voltage and adjusts the burst mode parameters accordingly. When the output power demand increases, the controller reduces the off period duration or increases the switching operation frequency, thereby maintaining adequate power delivery capability while still benefiting from reduced switching losses compared to continuous high-frequency 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
The solution effectively reduces switching loss and noise in the audible frequency range by maintaining a lower reference frequency below 2-3 kHz, preventing audible noise and enhancing efficiency during burst mode operations.
Implementation Method 1
a power supply including a transformer having a primary coil connected to the main switch, and supplying power to a secondary coil of the transformer according to the operation of the main switch
Data Source
AI summary
The present invention relates to a switch mode power supply and a driving method for reducing switching loss and audible noise in the burst mode. The switch mode power supply includes a main switch, a power supply, an output unit, and a switch controller. The power supply includes a transformer having a primary coil connected to the main switch, and supplies power to a secondary coil of the transformer according to the operation of the main switch. The output unit is connected to the secondary coil of the transformer and outputs power supplied to the secondary coil of the transformer. The switch controller receives a feedback signal corresponding to the output voltage of the output unit, a sense signal corresponding to the current flowing to the main switch, and a sync signal corresponding to the voltage difference at the main switch, controls the on/off of the main switch, and determines whether to start the burst mode by using the feedback signal, and maintains the switching operation forcibly off period in the burst mode so that the reference frequency of burst switching may be less than a predetermined value.