Synchronous Rectifier Driving Circuit with Slope Sensing for Voltage Spike Absorption

Solution Overview

Problem

Conventional RC snubber circuits are neither economic nor efficient in absorbing large overshoot voltage spikes induced in synchronous rectifier devices during the operation of isolated converters, which can lead to severe damage to circuit elements.

Innovation Solution

A driving circuit with a controllable charging circuit and a slope sensing circuit that senses abrupt voltage drops and provides a charging current during a predetermined duration to absorb the overshoot voltage spikes, using a capacitive energy storage device and a logic control circuit to manage the synchronous rectifier device.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional RC snubber circuit is used to absorb overshoot voltage spike, then voltage spike protection is provided, but cost and device complexity increase

Engineering Contradiction:

Improvevoltage spike protectionVSAvoidcircuit structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent utilizes the synchronous rectifier device itself to absorb and utilize the overshoot voltage spike through its inherent capacitance, eliminating the need for external RC snubber circuits. The control circuit triggers the synchronous rectifier to operate in a specific mode during voltage spikes, converting the harmful spike into useful energy for the circuit.

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The patent converts the harmful overshoot voltage spike into beneficial energy by controlling the synchronous rectifier to charge its internal capacitance during the spike event. This stored energy is then utilized to power the control circuit, transforming what was previously a destructive phenomenon into a useful energy source.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

2Reliability

If RC snubber circuit is used to absorb overshoot voltage spike, then voltage spike protection is provided, but power consumption increases

Engineering Contradiction:

Improvevoltage spike protectionVSAvoidpower consumption

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

The patent converts the harmful overshoot voltage spike into beneficial energy by controlling the synchronous rectifier to charge its internal capacitance during the spike event. This stored energy is then utilized to power the control circuit, transforming what was previously a destructive phenomenon into a useful energy source.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

The patent recovers energy that would otherwise be dissipated as heat in RC snubber circuits. By capturing the overshoot voltage spike energy in the synchronous rectifier's capacitance and utilizing it to power the control circuit, the system recovers what would have been wasted energy.

Inventive Principle:

Principle #34Discarding and recovering

3Reliability

If conventional RC snubber circuit is used, then voltage spike absorption is achieved, but cost increases

Engineering Contradiction:

Improvevoltage spike absorptionVSAvoidcost

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent utilizes the synchronous rectifier device itself to absorb and utilize the overshoot voltage spike through its inherent capacitance, eliminating the need for external RC snubber circuits. The control circuit triggers the synchronous rectifier to operate in a specific mode during voltage spikes, converting the harmful spike into useful energy for the circuit.

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The patent recovers energy that would otherwise be dissipated as heat in RC snubber circuits. By capturing the overshoot voltage spike energy in the synchronous rectifier's capacitance and utilizing it to power the control circuit, the system recovers what would have been wasted energy.

Inventive Principle:

Principle #34Discarding and recovering

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

Effectively reduces power consumption and cost while improving system power efficiency by absorbing and utilizing the overshoot voltage spikes, reducing the need for additional RC snubber circuits.

Implementation Method 1

a capacitive energy storage device coupled between the reference ground terminal and a supply terminal of the driving circuit

Methodology Applied

Scientific EffectCapacitance: Capacitance

Data Source

PatentUS11381151B2Circuit with slope sensing for driving synchronous rectifier device

Publication Date: 2022.07.05 CHENGDU MONOLITHIC POWER SYST

AI summary

A driving circuit for driving a synchronous rectifier device. The driving circuit may include a controllable charging circuit and a slope sensing circuit. The slope sensing circuit may sense whether an abrupt rising change in a voltage drop from a sensing terminal to a reference ground terminal of the driving circuit is occurring, and provide a slope sensing signal in response to a rising edge of the abrupt rising change in the voltage drop. The controllable charging circuit may receive the slope sensing signal and provide a charging current to a supply terminal of the driving circuit in response to each rising edge of the abrupt rising change in the voltage drop.