Parallel Switch Circuit Reverse Current Protection

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Solution Overview

Problem

Conventional power supplies face challenges in accurately preventing reverse current flow due to high conducting voltage drop in diodes and increased manufacturing costs when using power transistors, which affects power efficiency and component safety.

Innovation Solution

A power supply system with a control unit that manages parallel-connected switch circuits to adjust impedance dynamically, turning on or off switch circuits based on current magnitude to prevent reverse current flow effectively and reduce manufacturing costs.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If diodes are used in the output protection circuit to limit reverse current, then reverse current protection is provided, but conducting voltage drop is high causing significant power loss

Engineering Contradiction:

Improvereverse current protectionVSAvoidconduction loss

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The patent changes the electrical parameters of the protection circuit by using power transistors instead of diodes. Power transistors have much lower on-state voltage drop compared to diode forward voltage drop, thereby reducing conduction loss while maintaining reverse current protection capability through controlled switching.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent replaces the passive diode-based protection mechanism with an active transistor-based control system. This substitution allows for intelligent control of the protection circuit, enabling it to switch between protective and conductive states based on operating conditions, thus optimizing both protection and efficiency.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Loss of energy

If power transistors are used to replace diodes in the output protection circuit, then conducting impedance is reduced and power efficiency is improved, but control circuit complexity increases due to need for simultaneous switching control

Engineering Contradiction:

Improvepower lossVSAvoidcontrol circuit complexity

Core Design Contradiction:

Loss of energyVSDevice complexity

Solution Approach 1:

The patent merges the control of multiple power transistors into a unified control scheme where all transistors in the output protection circuit are controlled to switch on or off simultaneously. This integration simplifies the control logic by treating the transistor array as a single controlled unit, reducing the complexity of coordinating individual transistor switching.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The control circuit uses periodic switching signals to control the power transistors, enabling them to switch between on and off states in unison. This periodic control approach simplifies the timing coordination required for multiple transistors, as they all respond to the same periodic control signal.

Inventive Principle:

Principle #19Periodic action

3Reliability

If conventional control circuits are used to control power transistors, then reverse current can be blocked, but manufacturing cost increases due to requirement for comparators with low input offset voltage

Engineering Contradiction:

Improvereverse current blockingVSAvoidmanufacturing cost

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent employs a control circuit design that uses readily available, low-cost comparator components with standard input offset voltage specifications. By designing the control logic to work effectively with these conventional, inexpensive components rather than requiring precision low-offset-voltage comparators, the overall manufacturing cost is significantly reduced while maintaining adequate reverse current blocking functionality.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

Data Source

PatentUS8649128B2Power supply and power supply system incorporating a plurality of power supplies

Publication Date: 2014.02.11 DELTA ELECTRONICS INC(CN)

AI summary

Disclosed is a power supply for receiving an input voltage and generating an output voltage and an output current, which includes a power converter for receiving the input voltage and generating an intermediate output voltage, an output protection circuit connected to an output terminal of the power converter and including a plurality of switch circuits connected in parallel with each other. The output protection circuit is configured to limit the flowing direction of the output current by the switching operations of the switch circuits. The power supply further includes a control unit connected to the output protection circuit for issuing a plurality of control signals to the switch circuits, in which at least two of the control signals are set to allow at least two of the switch circuits to be turned off with different timings.