Power Converter Active Clamp Circuit Reduces Switching Losses
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Solution Overview
Problem
Existing power converters face significant switching losses and voltage transients due to leakage inductance, leading to higher energy losses and the need for higher voltage-rated semiconductors and lossy snubbers.
Innovation Solution
The power converter incorporates an Active Clamp Circuit (ACC) with a secondary side configuration featuring two capacitors and a diode, which alters the current waveform to reduce turn-off losses and eliminates voltage spikes, achieving Zero Voltage Switching (ZVS) and Zero Current Switching (ZCS) for primary and secondary switches.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If traditional switching power converter topology is used, then power conversion function is achieved, but significant switching losses occur due to trapezoidal current waveform with higher current at turn-off
Solution Approach 1:
The patent inverts the conventional current waveform characteristics by using a resonant circuit to achieve a sinusoidal current waveform where the current is higher at turn-on and lower at turn-off. This inversion of the traditional trapezoidal waveform reduces switching losses significantly, as turn-off losses are normally dominant due to higher current at that moment.
Solution Approach 2:
The patent employs resonant oscillation at a specific frequency to shape the current waveform. By tuning the resonant circuit to operate at the switching frequency, the current naturally follows a sinusoidal pattern that minimizes switching losses, effectively using vibrational/resonant principles to optimize power conversion efficiency.
2Loss of energy
If leakage inductance is present in the transformer, then power conversion is enabled, but voltage transients and spikes are generated over secondary side rectifiers
Solution Approach 1:
The patent converts the harmful effect of leakage inductance, which normally causes voltage spikes, into a beneficial resonant element. By incorporating the leakage inductance into a resonant circuit with a capacitor, the voltage transients are transformed into controlled resonant oscillations that actually help reduce switching losses and improve overall efficiency.
Solution Approach 2:
The patent introduces a capacitor as an intermediary element that works with the leakage inductance to form a resonant circuit. This intermediary component mediates between the harmful voltage spikes and the power conversion process, converting the problematic inductive effects into useful resonant behavior.
3Reliability
If higher voltage rating semiconductors are used to handle voltage transients, then reliability is improved, but device complexity and cost increase
Solution Approach 1:
The patent converts the harmful voltage transients into beneficial resonant oscillations, which eliminates the need for higher voltage-rated semiconductors. By transforming the problem rather than merely protecting against it, the system achieves the same reliability with standard voltage-rated components.
4Object-affected harmful factors
If lossy snubbers are added to reduce voltage ringing, then voltage transients are suppressed, but additional energy losses occur
Solution Approach 1:
The patent converts the harmful voltage ringing into a useful resonant oscillation that actually reduces switching losses. Instead of suppressing the oscillations with lossy snubbers, the patent harnesses the oscillatory energy to improve overall efficiency, eliminating the need for additional loss-generating components.
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 configuration reduces dominant turn-off losses, achieves efficiency greater than 96%, and allows for lower voltage rating of secondary rectifiers, thereby enhancing overall power conversion efficiency.
Implementation Method 1
a transformer TX1 having a primary winding on the primary side and a secondary winding on the secondary side
Implementation Method 2
the leakage inductance of the transformer TX1 limits the derivate of the current, i.e. di/dt, making the turn-on losses smaller in this case
Implementation Method 3
The at least one ACC comprises: a first capacitor C1 connected in series with a parallel combination of a switch S1 and a diode D1, and a second capacitor C2 connected in parallel with the series combination of the first capacitor C1 and the parallel combination of the switch S1 and the diode D1
Data Source
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AI summary
A power converter for DC/DC or AC/DC conversion includes a primary side and a secondary side separated by a transformer (TX1). The primary side is connected to a primary winding of the transformer (TX1) and is the input circuit of the power converter. The secondary side is connected to a secondary winding of the transformer (TX1) and is an output circuit of the power converter. The power converter further includes at least one active clamp circuit (ACC) connected to the secondary side. The at least one ACC includes a first capacitor (C1) connected in series with a parallel combination of a switch (S1) and a diode (D1), and a second capacitor (C2) connected in parallel with the series combination of the first capacitor (C1) and the parallel combination of the switch (S1) and the diode (D1).