Power Supply Transformer Commutation Noise Reduction
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Solution Overview
Problem
Transformer commutation noise, particularly ringing, voltage spikes, and common mode current, are exacerbated by large load currents in transformer-based power supplies, as the energy stored in leakage inductance can cause rapid commutation and distortion, which existing methods struggle to mitigate effectively.
Innovation Solution
The power supply reduces load-dependent distortion by temporarily reducing the primary-side voltage of the transformer using a transition capacitor or other methods, such as resistors or additional windings, to absorb the leakage inductance energy, thereby slowing down the commutation process and minimizing noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If additional capacitors are added to increase commutation capacitance to slow down commutation, then common mode current is reduced, but leakage inductance energy increases commutation rate when load current is large
Solution Approach 1:
The patent introduces an intermediary component (resistor or inductor) between the primary side and the transformer to mediate the commutation process. This intermediary absorbs or dissipates leakage inductance energy, preventing it from directly affecting the commutation capacitance and causing excessive commutation rates. The intermediary acts as a buffer that decouples the harmful effects of leakage energy from the commutation process.
Solution Approach 2:
The patent extracts or removes the leakage inductance energy from the commutation path by using external resistors or inductors to absorb it. This separates the harmful leakage energy from the useful commutation function, allowing the commutation capacitance to perform its intended function of slowing down voltage changes without being overwhelmed by leakage energy.
2Object-generated harmful factors
If switch transition is slowed down to dissipate more leakage energy as heat, then commutation noise is reduced, but switch temperature increases
Solution Approach 1:
The patent extracts the leakage energy dissipation function from the power switches by introducing external resistors or inductors. These external components are specifically designed to absorb and dissipate leakage energy, thereby removing the burden of heat generation from the power switches. This allows the switches to operate at normal temperatures while still achieving slow commutation and reduced noise.
Solution Approach 2:
The patent introduces intermediary components (resistors or inductors) that act as mediators between the leakage inductance and the power switches. These intermediaries absorb the leakage energy and provide a controlled path for energy dissipation, preventing direct heat generation in the switches while still achieving the desired slow commutation effect.
3Productivity
If commutation occurs quickly to maintain productivity, then power supply efficiency is improved, but voltage spikes and ringing increase
Solution Approach 1:
The patent applies preliminary action by pre-charging or pre-conditioning the commutation capacitance before the actual commutation event. This preliminary preparation ensures that the capacitance is ready to absorb the voltage change smoothly, preventing sudden voltage spikes and ringing. The intermediary components are also pre-configured to be in position to absorb leakage energy at the moment of commutation.
Solution Approach 2:
The patent uses intermediary components to mediate the energy transfer during commutation, providing a controlled and gradual transition rather than a abrupt change. This intermediary action smooths out voltage variations and prevents harmful spikes while maintaining efficient power transfer.
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 effectively reduces undesirable effects like ringing, voltage spikes, and common mode current, even at high load currents, by transferring leakage energy away from the primary capacitance, thereby stabilizing the commutation process.
Implementation Method 1
the energy stored in the transformer's leakage inductance (Lleakage)
Implementation Method 2
current on the primary side of the transformer is directed through Ct, increasing the voltage on Ct and reducing voltage across the transformer
Data Source
AI summary
Embodiments of the present invention provide improved techniques and devices for reducing transformer commutation distortion caused by large load currents. Traditional power supplies which have two or more phases typically commutate a transformer during the end of each phase. When the load current is large, energy stored in the transformer's leakage inductance can cause undesirable effects during commutation. Embodiments of the present invention reduce these effects by lowering the voltage across the primary side of the transformer prior to commutation. In one embodiment, a capacitor is added to the primary side of the transformer. A switch directs current through the capacitor prior to commutation, allowing the capacitor to absorb the transformer's leakage inductance energy and lower the primary side voltage. Other suitable components, such as resistors, diodes, transistors, or additional transformer windings, may also be used to reduce the primary-side voltage prior to commutation.