SEPIC Voltage Clamp Circuit for Leakage Inductance Spike Management

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Solution Overview

Problem

Isolated single-ended primary inductor converters (SEPIC) in harsh environments, such as aerospace, face issues with large voltage spikes and electromagnetic interference due to leakage inductances in transformers, which reduce reliability and efficiency.

Innovation Solution

The proposed SEPIC circuit incorporates a voltage clamp diode and a controller to manage the voltage across the controllable switch, preventing voltage spikes by clamping the peak voltage to the sum of input and output voltages, and utilizing a MOSFET switch for efficient operation in both continuous and discontinuous conduction modes.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If isolation transformer windings are close-coupled to meet insulation voltage requirements, then reliability is improved, but leakage inductance decreases and voltage spikes are reduced

Engineering Contradiction:

Improvecircuit reliabilityVSAvoidvoltage spikes

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

A clamp circuit is introduced as an intermediary component to manage the voltage spikes generated by transformer leakage inductance. The clamp circuit includes a clamp switch connected in parallel with the primary winding, which activates during switching transitions to clamp the voltage and prevent harmful voltage spikes while allowing the transformer to maintain close coupling for reliability.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The invention changes the operating parameters of the transformer by introducing controlled voltage clamping. The clamp circuit modifies the voltage waveform across the primary winding during switching transitions, effectively changing the voltage stress parameters to prevent harmful spikes while maintaining the close-coupled configuration for reliability.

Inventive Principle:

Principle #35Parameter changes

2Object-affected harmful factors

If isolation transformer windings are close-coupled, then electromagnetic interference is reduced, but leakage inductance decreases causing larger voltage spikes

Engineering Contradiction:

Improveelectromagnetic interferenceVSAvoidcircuit reliability

Core Design Contradiction:

Object-affected harmful factorsVSReliability

Solution Approach 1:

The clamp circuit serves as an intermediary that decouples the relationship between transformer coupling and voltage spike generation. It allows close coupling (reducing EMI) while independently managing voltage spikes through the clamp switch activation during switching transitions.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Reliability

If voltage clamp circuit is added to reduce voltage spikes, then reliability is improved, but device complexity increases

Engineering Contradiction:

Improvecircuit reliabilityVSAvoidcircuit complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The clamp switch is merged with the existing switching circuitry of the SEPIC converter. The clamp switch shares the same gate drive circuitry and is integrated into the existing power switch node, reducing the overall complexity increase compared to a completely separate clamp circuit implementation.

Inventive Principle:

Principle #5Merging (Combining)

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 solution effectively reduces voltage spikes, enhances circuit reliability, and minimizes electromagnetic interference, allowing for lower voltage-rated switches with reduced conduction and switching losses, thereby improving efficiency and reducing undesirable electromagnetic interference.

Implementation Method 1

a voltage clamp diode and a controller to manage the voltage across the controllable switch, preventing voltage spikes by clamping the peak voltage to the sum of input and output voltages

Methodology Applied

Scientific EffectVoltage clamping:

Implementation Method 2

an isolation transformer 106. The isolation transformer 106 includes a primary 124 and a secondary 126

Methodology Applied

Scientific EffectElectromagnetic induction: Electromagnetic Induction

Implementation Method 3

utilizing a MOSFET switch for efficient operation in both continuous and discontinuous conduction modes

Methodology Applied

Scientific EffectMOSFET conduction:

Data Source

PatentEP3324707B1Isolated single-ended primary inductor converter with voltage clamp circuit

Publication Date: 2019.10.16 HONEYWELL INTERNATIONAL INC

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AI summary

A single-ended primary-inductor converter (SEPIC) circuit has at least a circuit input node and a circuit common node, and includes an inductor, a first coupling capacitor, an isolation transformer, a controllable switch, a second coupling capacitor, and a clamp diode. The inductor is electrically connected in series between the circuit input node and the first coupling capacitor. The first coupling capacitor is connected in series between the inductor and the first primary input terminal. The controllable switch is electrically connected in series between an internal circuit node and the circuit common node, and the internal circuit node is located between the inductor and the first coupling capacitor. The second coupling capacitor is electrically connected in series between the second primary input terminal and the circuit common node. The clamp diode is electrically connected in series between the internal circuit node and the second primary input terminal.