LED Driver TRIAC Dimmer Latching Current Control
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Solution Overview
Problem
Conventional LED driver systems using TRIAC dimmers face challenges in optimizing input current shaping under boundary conduction mode, either increasing power loss with large RC circuits or stressing power components with high peak currents, leading to increased circuit size and cost.
Innovation Solution
The LED driver design provides a high average inductor current at the initial stage of each AC voltage delivery cycle, ensuring sufficient latching current for the TRIAC dimmer without the need for large RC circuits, by utilizing a power stage with a main and freewheel power switch, an inductor, and a control circuit that adjusts the operation mode based on reference voltages and current sense signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a large RC circuit is added to supply latching current for the dimmer, then sufficient latching current is provided, but power loss increases
Solution Approach 1:
The patent applies preliminary action by pre-charging the input capacitor during the off-period before the TRIAC triggers. The control circuit monitors the voltage across the input capacitor and ensures it reaches a sufficient level before the TRIAC latching current is needed. This pre-preparation eliminates the need for large RC circuits while ensuring adequate latching current is available when required.
2Reliability
If the peak current of power device is increased to supply sufficient latching current, then latching current requirement is met, but stress on power components increases and circuit size and cost increase
Solution Approach 1:
The patent applies dynamics by implementing a dynamic control strategy that adjusts the switching timing of the power device based on real-time monitoring of the input capacitor voltage. Instead of using a fixed high peak current design, the control circuit dynamically determines the optimal switching moment when the capacitor voltage is sufficient, thereby reducing the required peak current and stress on power components while still meeting latching current requirements.
3Reliability
If the peak current of power device is increased to supply sufficient latching current, then latching current requirement is met, but circuit size and cost increase
Solution Approach 1:
The patent applies parameter changes by shifting the design parameter from fixed high peak current to dynamic voltage-based timing control. The control circuit monitors the voltage parameter of the input capacitor and uses this information to determine the optimal switching timing. This parameter change allows the system to meet latching current requirements with lower peak currents, thereby reducing circuit size and cost while maintaining reliability.
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
This approach ensures sufficient latching current for the TRIAC dimmer with reduced power loss and component stress, eliminating the need for large RC circuits and minimizing circuit size and cost.
Implementation Method 1
an inductor, coupled between the power stage and the output port, wherein the inductor gains energy from the input AC voltage and delivers the energy to the output port when the main power switch is ON and when the freewheel power switch is OFF
Data Source
AI summary
The present invention discloses a LED driver including a power stage, an inductor, an error amplifier, a set comparator, a first timer, a logical AND circuit, a reset comparator, a second timer a logical OR circuit, a RS flip flop and a driving circuit. The LED driver provides sufficient latching current for the TRIAC dimmer with no large RC circuit, so as to optimize the dimming and reduce system size.