Secondary-Side Controller for Pseudo-Digital LED Dimming
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Solution Overview
Problem
Conventional digital LED dimming schemes suffer from visible light flicker and electromagnetic interference (EMI) issues, while analog schemes offer alternatives but are less efficient and lack fine control, especially in high-current applications.
Innovation Solution
A pseudo-digital LED dimming scheme using a secondary-side controller across a pulse transformer in a flyback converter, employing a constant current (CC) loop for precise dimming with programmable analog reference steps, allowing for both LED current measurement and control without additional components, thus reducing EMI and flicker.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If digital PWM-based dimming is used, then dimming resolution is improved, but visible light flicker and electromagnetic interference occur
Solution Approach 1:
The patent replaces digital PWM switching control with analog dimming control, substituting the mechanical/electronic switching mechanism with a continuous analog voltage control mechanism. This eliminates the high-frequency switching that causes EMI and flicker while maintaining precise dimming resolution through programmable analog reference steps.
Solution Approach 2:
The patent changes the control parameter from digital pulse width modulation to analog voltage levels. By using a digital-to-analog converter and programmable analog reference voltage with fine resolution steps, the system achieves precise dimming control without the harmful effects of high-frequency switching.
2Object-generated harmful factors
If analog dimming is used, then electromagnetic interference and flicker are reduced, but dimming resolution and control precision deteriorate
Solution Approach 1:
The patent combines the advantages of both digital and analog systems by using a hybrid approach: digital processing for generating programmable reference voltage steps and analog output for precise continuous control. This multi-functional system achieves both high resolution and low EMI/flicker.
Solution Approach 2:
The patent enhances traditional analog dimming by incorporating a digital-to-analog converter with programmable reference voltage, substituting simple analog control with a sophisticated hybrid system that provides fine resolution steps while maintaining analog smoothness.
3Measurement precision
If additional components are added for LED current measurement and control, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent makes the secondary-side controller multi-functional by integrating both LED current measurement and dimming control capabilities into a single device. This eliminates the need for separate measurement components while achieving precise current control through the programmable analog reference voltage.
Solution Approach 2:
The patent merges the current measurement function and dimming control function into a unified secondary-side controller, combining multiple functions into a single integrated component to reduce overall system complexity.
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
The pseudo-digital LED dimming scheme achieves high-frequency switching harmonics, simplifying system design for electromagnetic compatibility and significantly reducing perceivable light flicker, while maintaining high dimming resolution and efficiency.
Implementation Method 1
communicating a control signal with a primary-side controller via a galvanic isolation barrier of a pulse transformer
Implementation Method 2
A pseudo-digital LED dimming scheme using a secondary-side controller across a pulse transformer in a flyback converter
Data Source
AI summary
Pseudo-digital light-emitting diode (LED) with secondary-side flyback control is described. In one embodiment, a Digital Addressable Lighting Interface (DALI) compatible driver includes a secondary-side controller coupled to a secondary winding of a transformer and coupled to a light-emitting element. The secondary-side controller includes a DALI-compatible interface to receive information. The secondary-side controller communicates a control signal with a primary-side controller via a galvanically-isolated link. The primary-side controller is coupled to a primary winding of the transformer. The DALI-compatible driver modifies a light output of the light-emitting element in response to the information.