Solid-State Lighting AC-DC Converter Without Rectifier

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Solution Overview

Problem

Existing LED bulbs face challenges due to high manufacturing costs, inefficiencies in power conversion, and inability to be controlled by conventional dimmer switches, leading to issues like low power factor, reliability problems, and flickering or premature shutdown when dimming.

Innovation Solution

A solid-state lighting system that directly converts AC power to DC power without a bridge rectifier or step-down transformer, using an AC-DC converter and phase-offset dimmer control signals to control LED dimming, allowing for autonomous and individually powered LEDs, and integration of power conversion components into IC chips for reduced parts count and increased efficiency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If a bridge rectifier and smoothing capacitor are used to convert AC to DC, then DC power can be provided to LEDs, but the input current becomes non-sinusoidal with low power factor

Engineering Contradiction:

Improvepower conversion efficiencyVSAvoidpower factor

Core Design Contradiction:

Use of energy by moving objectVSObject-generated harmful factors

Solution Approach 1:

The patent extracts and removes the bridge rectifier and smoothing capacitor from the power conversion circuit. Instead of using conventional AC-to-DC conversion components, the invention directly converts AC power to DC power at the LED level, eliminating the source of harmonic distortion and low power factor issues.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent segments the power conversion function by providing each LED with its own AC-to-DC converter and separate power supply, rather than using a centralized power conversion stage. This segmentation allows each LED to process AC power independently, avoiding the nonlinear load issues of centralized rectification.

Inventive Principle:

Principle #1Segmentation

2Object-generated harmful factors

If a PFC pre-regulator is added to improve power factor, then power factor increases, but energy efficiency decreases and parts count increases

Engineering Contradiction:

Improvepower factorVSAvoidenergy efficiency

Core Design Contradiction:

Object-generated harmful factorsVSLoss of energy

Solution Approach 1:

The patent removes the PFC pre-regulator from the circuit by eliminating the need for separate power factor correction stages. The direct AC-to-DC conversion at each LED eliminates the source of power factor issues, making additional PFC circuitry unnecessary and thereby preserving energy efficiency.

Inventive Principle:

Principle #2Taking out (Extraction)

3Ease of operation

If conventional dimmer switches are used with LED bulbs, then dimming control is attempted, but flickering or premature shutdown occurs

Engineering Contradiction:

Improvedimming controlVSAvoidoperational stability

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

The patent segments the power supply so that each LED has its own AC-to-DC converter and operates autonomously. This segmentation allows each LED to respond independently to dimmer control signals, preventing the collective failure mode that causes flickering or premature shutdown in conventional LED bulbs.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent changes the operational parameters of each LED by providing individual AC-to-DC conversion and independent power supply. This allows each LED to maintain stable operation across a wide dimming range, with the ability to sense and adapt to the presence of dimmer switches, thereby improving reliability during dimming operations.

Inventive Principle:

Principle #35Parameter changes

4Object-generated harmful factors

If high voltages are generated by boost converter in PFC circuit, then power factor correction is achieved, but LED parts are stressed and safety concerns arise

Engineering Contradiction:

Improvepower factorVSAvoidparts stress and safety

Core Design Contradiction:

Object-generated harmful factorsVSObject-affected harmful factors

Solution Approach 1:

The patent removes the boost converter and high voltage generation stages from the power conversion circuit. By implementing direct AC-to-DC conversion at each LED without intermediate high voltage stages, the invention eliminates the source of electrical stress on LED parts and removes safety concerns associated with high voltage operation.

Inventive Principle:

Principle #2Taking out (Extraction)

Data Source

PatentUS8760078B2Power conversion and control systems and methods for solid-state lighting

Publication Date: 2014.06.24 MCCUNE EARL W

AI summary

A solid-state lighting system comprises a plurality of light-emitting devices (e.g., light-emitting diodes) and an alternating current to direct current (AC-DC) converter that converts AC power to DC power for powering the plurality of light-emitting devices. The AC-DC converter is configured to perform AC-DC conversion directly, without the need for or use of a bridge rectifier or step-down transformer. According to one aspect of the invention, the light-emitting devices of the solid-state lighting system are autonomous and individually powered by a plurality of DC power supplies generated from the DC power produced by the AC-DC converter. According to another aspect, a plurality of phase-offset dimmer control signals are generated based on waveform distortions in a dimming signal produced by a conventional dimmer switch. The phase-offset dimmer control signals are used to individually control the dimming of the light-emitting devices.