Active Overvoltage Limiting in Switch-Mode Converter
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Solution Overview
Problem
Switch-mode power supply circuits using transformers face inefficiencies due to reverse overvoltages generated during the switching off of static switches, which existing snubber circuits, such as those with passive elements, fail to adequately address, especially in high-power applications where they generate significant losses.
Innovation Solution
A switch-mode converter with an inductive transformer and a parallel active circuit comprising a transistor and a capacitive element, where the transistor is controlled by an amplifier monitoring the voltage across the capacitive element to limit overvoltages, providing adaptive protection against reverse overvoltages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a static switch is turned off in a switch-mode power supply, then the switching operation is completed, but reverse overvoltages are generated due to charge recovery phenomenon
Solution Approach 1:
A capacitive element is introduced as an intermediary component between the static switch and the load. This capacitor absorbs the reverse overvoltages generated during switch turn-off by providing a temporary energy storage path, thereby protecting the switch from voltage spikes while maintaining circuit operation.
Solution Approach 2:
An active control circuit continuously monitors the voltage across the capacitive element and dynamically adjusts the switching operation or activates protection mechanisms when overvoltage conditions are detected. This feedback mechanism enables real-time adaptation to prevent damage while optimizing performance.
2Reliability
If the static switch is designed to withstand higher reverse voltages, then protection against overvoltages is improved, but the forward voltage drop increases and efficiency decreases
Solution Approach 1:
The capacitive element serves as a mediator that absorbs voltage stress during reverse conditions, allowing the static switch to operate with lower voltage ratings. This separation of functions enables the switch to be optimized for low forward voltage drop while the capacitor handles the overvoltage protection.
Solution Approach 2:
The invention changes the operating parameters of the switch by limiting the maximum reverse voltage it must withstand through the capacitive element. This parameter modification allows selection of switches with lower on-resistance, thereby reducing conduction losses and improving overall efficiency.
3Object-affected harmful factors
If traditional snubber circuits with passive elements are used to filter overvoltages, then protection is provided, but significant power losses are generated in high-power applications
Solution Approach 1:
The active control circuit monitors voltage conditions and dynamically manages the capacitive element, enabling it to discharge stored energy back into the circuit or ground at optimal moments. This intelligent control minimizes energy dissipation compared to passive snubbers that continuously dissipate energy as heat.
Solution Approach 2:
Instead of continuously dissipating energy as heat like passive snubber circuits, the capacitive element recovers energy during switch turn-off by absorbing the voltage spike, then releases or redirects this energy during subsequent switching cycles, thereby reducing net power losses in high-power applications.
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 power losses and adapts to operational conditions, offering better filtering of overvoltages with lower dissipation compared to traditional snubber circuits, while being integrable and efficient in high-power applications.
Implementation Method 1
at least one first diode in series with a capacitive element; and in parallel with said capacitive element, an active circuit for limiting the voltage thereacross
Implementation Method 2
an inductive transformer having a secondary winding associated with at least one first switch
Data Source
AI summary
A switch-mode converter including an inductive transformer having a secondary winding associated with at least one first switch, including, in parallel with the first switch, at least one first diode in series with a capacitive element; and in parallel with the capacitive element, an active circuit for limiting the voltage thereacross.