Self-Driven Active Clamp Circuit for SMPS Leakage Energy Recovery
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Solution Overview
Problem
Conventional switch-mode power supplies (SMPS) face inefficiencies due to leakage inductance phenomena, which require costly and power lossy resistor-capacitor-diode (RCD) snubber circuits for voltage control, and existing active clamping solutions require complex control signals, making them unsuitable for cost-sensitive and power-efficient applications.
Innovation Solution
A self-driven active clamp circuit that replaces the RCD snubber circuit, comprising an active clamp switch, capacitor, delay circuit, and controller, which enables voltage clamping without additional control signals, allowing for energy recycling and reduced power losses by controlling the active clamp switch based on voltage amplitude and delay signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If RCD snubber circuits are used to control voltage, then voltage control is achieved, but power loss increases and cost increases
Solution Approach 1:
The active clamp circuit uses the leakage inductance energy that would normally be dissipated as waste. The circuit automatically captures this energy during the switch-off transient and recycles it back to the primary side, making the system self-sufficient in managing voltage spikes without external power lossy components
Solution Approach 2:
Instead of discarding the leakage inductance energy through resistive dissipation in RCD snubbers, the invention recovers this energy by directing it through the active clamp switch and capacitor back to the input, transforming a waste product into a useful resource
2Reliability
If RCD snubber circuits are used to control voltage, then voltage control is achieved, but cost increases
Solution Approach 1:
The active clamp circuit performs multiple functions simultaneously: it limits voltage spikes, recycles energy, and can be integrated with the existing power switch and transformer. This multi-functionality eliminates the need for separate RCD snubber components, reducing overall bill of materials cost
Solution Approach 2:
The invention merges the voltage clamping function with the existing power conversion circuitry by using the transformer leakage inductance and a single active switch. This consolidation eliminates standalone RCD snubber components and their associated cost
3Reliability
If conventional active clamping solutions are used, then voltage control is improved, but device complexity increases
Solution Approach 1:
The active clamp circuit is self-activating through voltage-driven operation. When the drain-source voltage exceeds the clamp threshold, the clamp switch automatically turns on without requiring external control signals, and turns off automatically when voltage is clamped, eliminating complex control logic
Solution Approach 2:
Instead of using control signals to activate the clamp switch, the invention inverts the approach by allowing the voltage condition itself to drive the switch operation. The high voltage condition directly enables the clamp, reversing the conventional control signal activation method
Data Source
AI summary
An active clamp circuit includes an active clamp switch having a drain node and a source node, an active clamp capacitor coupled in a series combination with the active clamp switch, a delay circuit, and an active clamp controller circuit coupled to the active clamp switch and to the delay circuit. The active clamp controller circuit is configured to i) receive an active clamp switch voltage based on a voltage developed across the drain node and the source node of the active clamp switch, ii) enable the active clamp switch based on a voltage amplitude of the active clamp switch voltage, and iii) disable the active clamp switch based on a delay signal generated by the delay circuit.