Three-Pin Integrated Synchronous Rectifier for Compact Power Supply

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Solution Overview

Problem

Traditional synchronous rectifier circuits require a minimum of four pins for packaging, excluding low-cost industry standards, and necessitate external components and linear regulators for voltage regulation, increasing costs and reducing power efficiency.

Innovation Solution

A three-pin integrated synchronous rectifier with a control pin for power bias and synchronous pulses, and two pins for the power transistor, reducing the number of external components and board area, while maintaining efficient power transmission.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a traditional synchronous rectifier circuit is implemented with separate control circuit and power transistor, then the circuit can achieve synchronous rectification function, but the number of connection pins increases to at least four pins and requires external components

Engineering Contradiction:

Improvesynchronous rectification functionVSAvoidnumber of connection pins

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent merges the control circuit and power transistor into a single integrated device package, combining multiple previously separate components (control circuit, power transistor, and necessary passive components) into one unified synchronous rectifier module. This integration reduces the number of external connection pins from at least four to exactly three pins, while maintaining the synchronous rectification function through internal circuit coordination between the control circuit and power transistor.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The control pin of the integrated synchronous rectifier serves multiple functions: it receives the synchronous pulse signal for timing control, provides power bias voltage to the internal control circuit, and enables the device to operate in synchronous rectification mode. This multi-functionality reduces the need for separate dedicated pins for control signals and power supply, contributing to the reduced pin count.

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Reliability

If an eight pin synchronous rectifying controller with discrete elements and external power transistor is used, then the synchronous rectification can be achieved, but the cost increases

Engineering Contradiction:

Improvesynchronous rectification functionVSAvoidcost

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent integrates the control circuit and power transistor into a single package, eliminating the need for multiple discrete components and external connections. This integration reduces assembly complexity, minimizes the bill of materials, and lowers overall manufacturing cost compared to using an eight-pin controller with separate discrete elements and external power transistor.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The patent adopts a cost-effective three-pin industry standard package structure that segments the device into essential functional components only, excluding unnecessary pins and external components. This streamlined segmentation reduces packaging cost and assembly cost while maintaining the core synchronous rectification functionality.

Inventive Principle:

Principle #1Segmentation

3Reliability

If more external components and larger package are used, then the synchronous rectifier can be implemented, but the board area increases

Engineering Contradiction:

Improvesynchronous rectification functionVSAvoidboard area

Core Design Contradiction:

ReliabilityVSArea of stationary object

Solution Approach 1:

By merging the control circuit and power transistor into a single integrated package with only three connection pins, the patent significantly reduces the footprint required on the printed circuit board compared to implementations using separate components, discrete elements, and multiple connection pins. The integrated structure minimizes the space required for component placement and interconnections.

Inventive Principle:

Principle #5Merging (Combining)

4Ease of operation

If linear regulator is used for voltage regulation, then the output voltage can be controlled, but the power efficiency decreases

Engineering Contradiction:

Improvevoltage regulationVSAvoidpower efficiency

Core Design Contradiction:

Ease of operationVSLoss of energy

Solution Approach 1:

The patent replaces the linear regulator (which dissipates excess voltage as heat) with a switching-based voltage regulation approach using the synchronous rectifier circuit. The synchronous rectifier uses active switching of the power transistor to achieve voltage regulation, significantly reducing power losses compared to linear regulation while maintaining the ability to control output voltage.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Data Source

PatentUS7889521B2Three-pin integrated synchronous rectifier and a flyback synchronous rectifying circuit

Publication Date: 2011.02.15 NIKO SEMICON

AI summary

A three-pin integrated synchronous rectifier is the synchronous rectifier chip where the quantity of connection pins is the smallest possible quantity. The three-pin integrated synchronous rectifier uses a control pin to receive a control signal used as a power bias voltage and a synchronous pulse to make the synchronous rectifier chip operate normally. The control signal is obtained from the output pin of an auxiliary winding via a diode. The other pins are respectively the drain pin and the source pin of an internal power transistor and are connected with the output winding and the voltage output terminal for transmitting the power of the transformer to supply current for the loading.