Switch Controller Zero-Cross Detection for Dimmer Synchronization

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Solution Overview

Problem

The synchronization between internal reference signals and input voltages is disrupted when AC input is passed through a triac dimmer, leading to unsynchronized control of switching operations in power switches.

Innovation Solution

A switch controller is developed that generates a reference signal synchronized with the input voltage by detecting zero cross-points and using a current source, digital sine wave generator, and digital-to-analog converter to produce a synchronized reference signal for controlling the switching operation of a power switch.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If a triac dimmer is used to control the amount of AC input supplied to a load, then the dimmer angle can be adjusted to control power delivery, but the synchronization between the internal reference signal and the input voltage is disrupted

Engineering Contradiction:

Improvedimmer angle controlVSAvoidsynchronization between reference signal and input voltage

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

A zero-cross detection circuit is introduced as an intermediary component to detect the zero-crossing point of the input voltage and generate a synchronized reference signal. This mediator ensures that the reference signal remains aligned with the actual input voltage phase, even when the triac dimmer modifies the AC input waveform by blocking certain portions during dimming operation.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Adaptability or versatility

If the internal reference signal is generated using full-wave rectified input voltage from a triac dimmer, then the circuit can operate with dimmed input, but the reference signal becomes unsynchronized with the input voltage

Engineering Contradiction:

Improveoperation with dimmed inputVSAvoidphase synchronization accuracy

Core Design Contradiction:

Adaptability or versatilityVSMeasurement precision

Solution Approach 1:

The invention extracts the zero-crossing information directly from the input voltage waveform before full-wave rectification using a dedicated zero-cross detection circuit. By separating the synchronization function from the power processing path, the reference signal can be generated with accurate phase information even when the main input voltage is modified by the triac dimmer for dimming control.

Inventive Principle:

Principle #2Taking out (Extraction)

Data Source

PatentUS9325255B2Switch controller, switch control method, and power supply device comprising the switch controller

Publication Date: 2016.04.26 SEMICON COMPONENTS IND LLC

AI summary

An exemplary embodiment of the present invention relates to a switch controller, a method for controlling a switch, and a power supply including the switch controller. According to the exemplary embodiment of the present invention, an AC input passed through a dimmer is rectified such that an input voltage is generated, and the input voltage is transmitted to the power switch. A charging current is generated using a voltage that depends on the input voltage, a zero cross-point at which the input voltage becomes zero voltage is detected using a detection voltage output from a current source, and a reference signal synchronized at the detected zero cross-point is generated.