LED Ballast Bleeder Current Control for Dimmer Compatibility
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Solution Overview
Problem
Existing LED lighting systems face inefficiencies and electromagnetic interference issues due to the need for bleeder circuits that present a low ohmic load, which can result in unnecessary energy loss and inefficiency when connected to non-dimmable mains connections.
Innovation Solution
A method to dynamically control the bleeder current in LED ballasts based on the phase of the power supply, adjusting the current during different parts of the mains half-cycle to match the requirements of leading or trailing edge dimmers, thereby optimizing efficiency and reducing losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a bleeder circuit is provided to present a low ohmic load to dimmer circuits, then the dimmer circuit operates correctly, but energy loss increases by up to 10% and electromagnetic interference problems occur
Solution Approach 1:
The patent applies dynamics by making the bleeder circuit configurable and adaptable rather than fixed. The control circuit dynamically adjusts the bleeder's operation based on detected dimmer presence and type (leading-edge or trailing-edge), enabling the system to optimize between providing necessary load for dimmer operation and minimizing energy loss when dimmers are not present.
Solution Approach 2:
The patent changes the operational parameters of the bleeder circuit based on system conditions. By detecting whether a dimmer is present and its type, the control circuit modifies the bleeder's current draw characteristics, switching between different operational states to resolve the contradiction between maintaining dimmer compatibility and reducing energy consumption.
2Device complexity
If a fixed bleeder control circuit is used, then the circuit design is simple, but efficiency is reduced due to continuous current draw
Solution Approach 1:
The patent implements feedback by using a control circuit that detects system conditions (dimmer presence and type) and uses this information to adjust the bleeder circuit operation. This feedback mechanism enables the system to automatically optimize efficiency without requiring complex manual configuration, resolving the contradiction between simplicity and efficiency.
Solution Approach 2:
The system performs self-service by automatically detecting the presence and type of dimmer and configuring the bleeder circuit accordingly without external intervention. The control circuit autonomously makes decisions about bleeder operation based on real-time system conditions, improving efficiency while maintaining design simplicity.
Data Source
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AI summary
A method of controlling a ballast in a circuit for a lighting application and connected to a mains power supply is disclosed. The method comprises determining whether a dimmer is present in the circuit; in response to detecting that a dimmer is present, determining a zero-crossing of the power supply and setting a bleeder current through the ballast in dependence on the phase of the power supply within a mains half-cycle; and in response to determining that a dimmer is not present, disabling the bleeder current. A ballast which is controlled by such a method is also disclosed. Additionally, a controller, which may include a digital signal processor, for a ballast and operable according to the above method is disclosed.