Two-Wire Dimmer Circuit for Compact Fluorescent Lamps

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Solution Overview

Problem

Conventional dimmer circuits fail to provide smooth dimming for screw-in compact fluorescent lamps, leading to issues like flicker, audible noise, and excessive stress due to multiple firings of the semiconductor switch, which limits energy savings and commercial success.

Innovation Solution

A two-wire dimmer control circuit with a controllably conductive switching device, phase-cut AC drive circuit, and high-end intensity regulation, limiting the conduction interval to less than 75% of each half-cycle to prevent multiple firings and ensure smooth dimming.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Illumination intensity

If conventional dimmer circuits use forward phase control to maximize conduction interval for high-end intensity setting, then maximum light output is achieved, but multiple firings of the semiconductor switch occur causing flicker, audible noise, and excessive stress

Engineering Contradiction:

Improvemaximum light outputVSAvoidsmooth dimming operation

Core Design Contradiction:

Illumination intensityVSReliability

Solution Approach 1:

The patent changes the conduction interval parameter from the conventional maximum (nearly 100% of half-cycle) to a limited value (less than 75% of half-cycle). This parameter change prevents multiple firings of the semiconductor switch while still providing adequate light output, resolving the contradiction between maximum illumination and reliable operation

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent applies partial action by intentionally not using the full available conduction interval. By limiting the conduction interval to less than 75% of each half-cycle, the circuit achieves sufficient light output without the harmful effects of multiple firings, trading a small portion of potential maximum output for operational reliability

Inventive Principle:

Principle #16Partial or excessive action

2Power

If the conduction interval is extended to maximize power delivery to the lamp, then high-end intensity setting is improved, but multiple firings cause flicker and audible noise

Engineering Contradiction:

Improvepower delivery to lampVSAvoidflicker and audible noise

Core Design Contradiction:

PowerVSObject-generated harmful factors

Solution Approach 1:

The patent modifies the conduction interval parameter from conventional values that maximize power delivery to a limited value (less than 75% of half-cycle). This parameter change reduces power delivery slightly but eliminates multiple firings, thereby removing flicker and audible noise while maintaining acceptable high-end intensity

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent converts what would normally be considered excessive power delivery (which causes multiple firings) into a beneficial limitation. By intentionally restricting the conduction interval, the circuit avoids the harmful effects of multiple firings while still providing sufficient power for adequate light output

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

3Illumination intensity

If the semiconductor switch is fired multiple times to achieve high-end intensity setting, then maximum light output is obtained, but excessive stress is placed on components

Engineering Contradiction:

Improvehigh-end intensity settingVSAvoidcomponent durability

Core Design Contradiction:

Illumination intensityVSStrength

Solution Approach 1:

The patent changes the conduction interval parameter from conventional maximum values to a limited value (less than 75% of half-cycle). This parameter change eliminates multiple firings of the semiconductor switch, thereby removing excessive stress on components while maintaining adequate high-end intensity output

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent applies beforehand cushioning by pre-limiting the conduction interval to prevent multiple firings before they can occur. By establishing the conduction interval limit (less than 75% of half-cycle) in advance, the circuit avoids subjecting components to the stress of multiple firings, thereby protecting component durability

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

Data Source

PatentUS8704459B2Two-wire dimmer circuit for a screw-in compact fluorescent lamp

Publication Date: 2014.04.22 LUTRON TECHNOLOGY COMPANY LLC

AI summary

A dimmer switch for controlling the intensity of a dimmable screw-in compact fluorescent lamp provides smooth dimming of the fluorescent lamp and prevents flickering of the lamp due to multiple re-strikes. The dimmer switch prevents multiple re-strikes by avoiding multiple firings of a controllably conductive switching device of the dimmer circuit by limiting the high-end light intensity of the fluorescent lamp. Specifically, the dimmer switch limits the length of a conduction interval of the controllably conductive switching device to less than approximately 75% of each half-cycle. The dimmer switch may include a user-accessible adjustment actuator for changing the dimmer switch between an incandescent operating mode and a screw-in compact fluorescent mode. The dimmer switch may also be operable to automatically change the dimmer switch between the incandescent operating mode and the screw-in compact fluorescent mode by detecting the occurrence of the multiple firings of the controllably conductive switching device.