Active Clamp Circuit for Power Converter Leakage Inductance Recovery
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Solution Overview
Problem
Existing power conversion topologies face inefficiencies due to energy storage in circuitry sections caused by leakage inductance, leading to reduced power handling, limited switching frequency, and electromagnetic interference, with current solutions either dissipating energy as heat or requiring complex active clamp devices.
Innovation Solution
A controlled reverse recovery charge device is implemented, which maintains a clamping switch in a conduction state to recover energy stored in a tank capacitor without a separate drive circuit, using a series resistor and R-C circuitry to manage the gate voltage of the clamping switch, allowing efficient energy recovery from leakage inductance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If dissipative clamping networks are used to handle leakage inductance energy, then voltage stress on switching devices is reduced, but overall converter efficiency deteriorates due to energy dissipation as heat
Solution Approach 1:
The patent converts the harmful leakage inductance energy that causes voltage stress into a beneficial resource by recycling it back to the input circuit. The clamping switch and tank capacitor temporarily store this energy, then the controlled power switch returns it to the input, transforming what was previously wasted heat into useful energy recovery.
2Reliability
If dissipative clamping networks are used, then switching devices are protected from high voltage stress, but operative switching frequency is limited and power handling capability deteriorates
Solution Approach 1:
By recycling the leakage inductance energy instead of dissipating it, the system can operate at higher switching frequencies without excessive power loss. The energy recovery mechanism allows the converter to maintain efficiency even at elevated switching frequencies, removing the limitation imposed by dissipative networks.
3Loss of energy
If controlled active clamp devices with separate drive circuits are used for energy recovery, then energy recovery efficiency is improved, but device complexity and circuit bulk increase due to additional sensing and control requirements
Solution Approach 1:
The patent merges the clamping function and energy recovery function into a single integrated circuit configuration. The clamping switch is part of the main power stage, and the tank capacitor serves dual purposes: voltage clamping during leakage inductance discharge and energy storage for recovery. This eliminates the need for separate current sensing, voltage sensing, and level-shifting circuits required by conventional active clamp devices.
Solution Approach 2:
The circuit uses itself to provide the necessary control functions. The voltage across the tank capacitor naturally indicates when energy recovery should occur, and the current through the clamping switch provides inherent feedback. No external sensing or complex control logic is needed - the circuit self-regulates based on its own operating states.
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 enhances energy recovery efficiency, reduces voltage stress on switching devices, and minimizes losses by maintaining the clamping switch in a conduction state for a defined time, improving overall converter performance and reducing electromagnetic noise.
Implementation Method 1
The R-C circuitry can provide a time constant to hold the gate voltage of the clamping switch positive for a precise time frame
Implementation Method 2
The clamping network includes a diode and a tank capacitor, which is charged with energy from the input circuit
Implementation Method 3
A controlled power switch is provided for recycling the energy stored in the capacitor towards the input circuit through an inductor
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
A power converter (10A) is disclosed, comprising: a transformer (5); an input circuit (3) connected to the transformer (5) and including at least one switching device (9), which connects a source voltage (7) across the transformer (5); an output circuit (4) coupled to the input circuit by said transformer (5); an active clamp circuit (15) including a tank capacitor (19) and a clamping switch (31) connecting the tank capacitor to the input circuit (3). The clamping switch (31 ) is controlled by a control circuit (33, 37, 39, 40) responsive to a voltage increase in the input circuit (3) following switching-off of the switching device (9). The control circuit maintains the clamping switch (31) in a conduction state for a time interval exceeding the tank capacitor-charging time, such as to allow a reverse current flow from said tank capacitor (19) to the input circuit through the clamping switch (31).