Snubber Circuit Buffer Device Reverse Recovery Time Extension

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Solution Overview

Problem

Conventional snubber circuits in high-speed switching applications experience power losses due to short reverse recovery times of diodes, leading to inefficiencies in power conversion and increased power losses when using bleeder resistors to manage voltage spikes.

Innovation Solution

A snubber circuit with a buffer device that operates in two conduction modes, allowing a charge current to flow and then generating a discharge current over a specific period, extending the reverse recovery time and reducing voltage spikes without the need for bleeder resistors.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If a diode with short reverse recovery time is used in the snubber circuit, then the switching speed is improved, but the capacitor cannot be fully discharged and power losses increase

Engineering Contradiction:

Improveswitching speedVSAvoidpower losses

Core Design Contradiction:

SpeedVSLoss of energy

Solution Approach 1:

The patent changes the reverse recovery time parameter of the buffering device from short (conventional diode) to long (buffering device), fundamentally altering the discharge characteristic to enable complete capacitor discharge while maintaining fast switching operation

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent replaces the conventional diode with a buffering device that has long reverse recovery time, eliminating the need for expensive high-power bleeder resistors while maintaining circuit functionality

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

2Reliability

If a bleeder resistor is added to discharge the capacitor, then the voltage spike is reduced, but power conversion efficiency decreases

Engineering Contradiction:

Improvevoltage spike reductionVSAvoidpower conversion efficiency

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The patent extracts and eliminates the bleeder resistor from the circuit by using a buffering device with long reverse recovery time that naturally discharges the capacitor, removing the source of continuous power loss

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The buffering device performs dual function: it limits ring current during switching and automatically discharges the capacitor without external assistance, making the circuit self-sufficient and eliminating the need for separate discharge path

Inventive Principle:

Principle #25Self-service

3Productivity

If fast switching mode is used, then the productivity is improved, but the reverse recovery time becomes insufficient and power losses increase

Engineering Contradiction:

Improveswitching frequencyVSAvoidreverse recovery time

Core Design Contradiction:

ProductivityVSDuration of action of moving object

Solution Approach 1:

The patent fundamentally changes the reverse recovery time parameter from short to long in the buffering device, enabling the circuit to maintain effective capacitor discharge even at high switching frequencies where conventional diodes fail

Inventive Principle:

Principle #35Parameter changes

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

The proposed snubber circuit effectively limits ring currents and reduces power losses in high-speed switching applications by extending the reverse recovery time, improving power conversion efficiency and eliminating the need for bleeder resistors.

Implementation Method 1

When the buffer device switches from the first conduction mode to a second conduction mode, the buffer device generates a discharge current which flows from the first terminal to the second terminal through the buffer device over a specific period of time, such that after the buffer device enters the second conduction mode, a relative maximum voltage level appearing first at the second terminal is lower than a voltage level at the first terminal

Methodology Applied

Scientific EffectReverse recovery time extension:

Implementation Method 2

Methodology Applied

Scientific EffectPower loss reduction:

Data Source

PatentUS9455635B2Snubber circuit and buffering method for snubber circuit

Publication Date: 2016.09.27 SPI ELECTRONICS

AI summary

A snubber circuit includes a capacitor and a buffer device. The buffer device has a first terminal and a second terminal. The first terminal is electrically connected to the capacitor. When the buffer device operates in a first conduction mode, a charge current flows from the second terminal to the first terminal through the buffer device. When the buffer device switches from the first conduction mode to a second conduction mode, the buffer device generates a discharge current which flows from the first terminal to the second terminal through the buffer device over a specific period of time, such that after the buffer device enters the second conduction mode, a relative maximum voltage level appearing first at the second terminal is lower than a voltage level at the first terminal.