Active Clamping in Transformer Power Supplies to Suppress Ringing
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Solution Overview
Problem
Power supply circuits experience inefficiencies due to ringing in transformer windings, leading to energy losses and voltage fluctuations across switches, which existing technologies fail to adequately mitigate.
Innovation Solution
A power supply system with an active clamping circuit that includes a clamping switch activated during the dead-time between input switch activations, using a switching controller to generate switching signals for input and output switches, and a transformer to rectify secondary current, facilitating zero-volt switching (ZVS) and reducing ringing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a transformer is used to deliver output voltage from square-wave input voltage, then power conversion is achieved, but ringing occurs in transformer windings causing voltage fluctuations and energy losses
Solution Approach 1:
The clamping switch is activated during the dead-time period before the main switches turn on, preemptively clamping the transformer winding voltage to prevent ringing oscillations from developing. This preliminary action eliminates the harmful voltage fluctuations before they can cause energy loss.
Solution Approach 2:
The clamping switch acts as an intermediary element between the transformer windings and the rest of the circuit. It provides a controlled path for circulating current during switching transitions, mediating the energy transfer and preventing harmful ringing while maintaining efficient power conversion.
2Ease of operation
If switching operations are performed to convert input voltage, then power supply function is achieved, but ringing causes voltage fluctuations across switches
Solution Approach 1:
The clamping switch provides beforehand cushioning by clamping the voltage across transformer windings during the dead-time period. This prevents harmful voltage fluctuations from developing across the main switches, protecting them from stress and ensuring smooth operation.
3Reliability
If dead-time is introduced between input switch activations, then switching conflicts are avoided, but energy inefficiencies persist due to ringing
Solution Approach 1:
The invention converts the harmful ringing energy that would normally be lost during dead-time into a beneficial effect. By activating the clamping switch during dead-time, the circulating current that would otherwise cause losses is instead used to maintain magnetic flux in the transformer, preparing it for the next switching cycle and reducing overall energy loss.
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 active clamping circuit mitigates ringing and energy inefficiencies, enabling more efficient operation by achieving ZVS, thereby improving the overall energy efficiency of the power supply system across various load conditions.
Implementation Method 1
A transformer generates a secondary current responsive to the primary current
Data Source
AI summary
A power supply system includes an input stage comprising first and second input switches to provide a primary current responsive first and second input switching signals. A transformer generates a secondary current responsive to the primary current. An output stage comprises an output, a first output switch, a second output switch and a clamping switch. The output stage can be configured to generate an output voltage at the output by rectifying the secondary current responsive to respective first and second output switching signals. The clamping switch can be configured to close responsive to a clamp switching signal during an activation dead-time between closing the first input switch and the second input switch. The system further includes a switching controller configured to generate the first and second input switching signals and the first and second output switching signals based on the output voltage, and to generate the clamp switching signal.