Switch Control Circuit Input Current Integration

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Solution Overview

Problem

Existing power supply systems face challenges in precisely controlling input current, leading to distortion at zero crossing points of input voltage and requiring appropriate setting of external elements like capacitors and resistors, which complicates current limit management.

Innovation Solution

An input current control method that generates an input sense voltage by integrating a sense voltage indicating the switch current over a switching period, compares it with a predetermined reference voltage, and controls the switching operation of the power switch to maintain constant and precise input current, using a switch control circuit with capacitors and transistors to charge and discharge currents accordingly.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If the current limit is changed to constantly control the input current, then the input current control is improved, but distortion occurs at zero crossing points and external elements require complex setting

Engineering Contradiction:

Improveinput current control precisionVSAvoidexternal element setting complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent implements feedback control by continuously monitoring the switch current through a sense resistor, integrating the sense voltage over the switching period, and comparing it with a reference voltage. The controller adjusts the current limit based on this feedback to maintain constant input current control while eliminating distortion at zero crossing points.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent replaces complex external element settings (capacitors and resistors) with an integrated control circuit that performs current limit adjustment electronically. The controller internally generates the appropriate current limit waveform without requiring external passive components, simplifying the overall system design.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Measurement precision

If the current limit is changed to constantly control the input current, then the input current control is improved, but distortion occurs at zero crossing points

Engineering Contradiction:

Improveinput current control precisionVSAvoidinput current distortion

Core Design Contradiction:

Measurement precisionVSObject-generated harmful factors

Solution Approach 1:

The feedback mechanism continuously monitors the integrated sense voltage and compares it with the reference voltage, enabling the controller to dynamically adjust the current limit. This ensures accurate input current control while preventing distortion at zero crossing points through real-time correction.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent integrates the sense voltage over the switching period before comparison, preparing the control signal in advance. This preliminary integration smooths out variations and prevents distortion at zero crossing points by ensuring the current limit adjustment is based on accumulated switching cycle data rather than instantaneous values.

Inventive Principle:

Principle #10Preliminary action

3Ease of manufacture

If external elements are appropriately set to control the current limit, then the current limit setting is improved, but the device complexity and manufacturing difficulty increase

Engineering Contradiction:

Improvecurrent limit setting easeVSAvoidexternal element configuration

Core Design Contradiction:

Ease of manufactureVSDevice complexity

Solution Approach 1:

The controller performs self-configuration by internally generating the current limit waveform and adjustment signals. The system automatically adapts to different operating conditions without requiring external components to be manually set or configured, making the device easier to manufacture and deploy.

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The patent extracts the current limit setting function from external passive components and integrates it into the control circuit. This eliminates the need for external capacitors and resistors that would require precise setting, simplifying both manufacturing and application.

Inventive Principle:

Principle #2Taking out (Extraction)

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 method allows for precise and constant control of input current, reducing distortion and eliminating the need for complex external element settings, thereby enhancing the reliability and efficiency of power supply systems.

Implementation Method 1

generating an input sense voltage by integrating a sense voltage that indicates a switch current flowing to the power switch for a switching period of the power switch

Methodology Applied

Scientific EffectCapacitance: Capacitance

Data Source

PatentUS9467137B2Input current control method, switch control circuit and power supply including the switch control circuit

Publication Date: 2016.10.11 SEMICON COMPONENTS IND LLC

AI summary

A switch control circuit that controls a switching operation of a power switch includes: an input current calculator generating an input sense voltage by integrating a sense voltage that indicates a switching current flowing to the power switch for a switching period unit of the power switch; and an input current comparator generating a gate-off signal according to a result of comparison between the input sense voltage and a predetermined input reference voltage, wherein the power switch is turned off according to the gate-off signal.