Surge Current Protection Circuit Using Silicon Symmetrical Switch

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Solution Overview

Problem

Conventional surge current protection circuits for motors, such as those using NTC thermistors and mechanical relay contacts, suffer from high power consumption, reduced reliability, and increased production costs due to continuous operation and short lifetimes.

Innovation Solution

A surge current protection circuit comprising a control unit, a photoelectric coupling and driving circuit, and a silicon symmetrical switch with a current-limiting resistor, which are parallel and serially connected to the load and AC input, allowing the silicon symmetrical switch to control current flow and reduce energy loss, eliminating mechanical contacts, and enhancing reliability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If an NTC thermistor is used for surge current protection, then surge current can be limited, but power consumption increases and reliability decreases due to continuous operation and high temperature generation

Engineering Contradiction:

ImprovereliabilityVSAvoidpower consumption

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

The patent uses a silicon symmetrical switch controlled by a timer to periodically connect and disconnect the current-limiting resistor, rather than continuous connection. The timer controls the switch to operate only during specific time periods when surge protection is needed, reducing continuous power consumption while maintaining protection functionality.

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The patent replaces the mechanical relay contact system with a silicon symmetrical switch controlled by photoelectric coupling and driving circuits. This electronic substitution eliminates mechanical wear, extends service life, and reduces power consumption compared to mechanical relay-based surge protection circuits.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Reliability

If an NTC thermistor is used for surge current protection, then surge current can be limited, but temperature increases and reliability reduces

Engineering Contradiction:

ImprovereliabilityVSAvoidtemperature

Core Design Contradiction:

ReliabilityVSTemperature

Solution Approach 1:

The current-limiting resistor is connected periodically through the silicon symmetrical switch rather than continuously, allowing the circuit to cool down during disconnection periods. This reduces cumulative heat generation and operating temperature while maintaining surge protection capability when needed.

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The silicon symmetrical switch provides solid-state switching without mechanical contact wear, generating less heat compared to mechanical relay contacts. The photoelectric coupling isolation also prevents heat transfer between control and power circuits, improving overall thermal management and reliability.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Reliability

If a mechanical relay contact is used for surge current protection, then surge current can be limited, but service life decreases and production cost increases

Engineering Contradiction:

Improveservice lifeVSAvoidproduction cost

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent replaces mechanical relay contacts with a silicon symmetrical switch controlled by photoelectric coupling circuits. This eliminates mechanical wear, extends service life indefinitely, and reduces maintenance costs. The solid-state components are also more suitable for automated production, lowering manufacturing costs despite higher component complexity.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The photoelectric coupling acts as an intermediary between the control unit and the silicon symmetrical switch, providing electrical isolation while transmitting control signals. This isolation protects the control circuit from high voltage and current surges, improving reliability and reducing the need for expensive protective measures in the control section.

Inventive Principle:

Principle #24Intermediary (Mediator)

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 configuration reduces power consumption, extends the lifespan of the protection circuit, lowers production costs, and effectively suppresses surge currents, improving the safety and reliability of both AC and DC motors.

Implementation Method 1

a photoelectric coupling and driving circuit... the control end of the silicon symmetrical switch is connected to the output end of the control unit via the photoelectric coupling and driving circuit

Methodology Applied

Scientific EffectPhotoelectric conversion: Photoelectric Effect

Data Source

PatentUS8598820B2Surge current protection circuit and motor using the same

Publication Date: 2013.12.03 ZHONGSHAN BROAD OCEAN

AI summary

A surge current protection circuit, has a control unit having an output end, a photoelectric coupling and driving circuit, a silicon symmetrical switch having a control end, and a current-limiting resistor. The current-limiting resistor and the silicon symmetrical switch are parallel connected altogether and then serially connected to a load and an AC input, and the control end of the silicon symmetrical switch is connected to the output end of the control unit via the photoelectric coupling and driving circuit. The invention features low production cost, high reliability and improved power efficiency, and is capable of effectively suppressing surge current.