Sequential LED Driver Circuit Reduces Power Dissipation
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Solution Overview
Problem
Existing circuits driving series-connected LEDs struggle to efficiently manage the variation in forward voltage drop across different strings, leading to excessive power consumption as they must supply the highest voltage drop plus overhead voltage to all strings, resulting in inefficient energy use.
Innovation Solution
A circuit with comparators, an amplifier, a PWM circuit, and output switch sequencer is used to control FET switches connected to each string of LEDs, allowing tailored voltage delivery to each string by sequentially activating switches, ensuring each string receives only the necessary voltage, reducing power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a common switching regulator supplies voltage to all LED strings in parallel, then all strings can be driven simultaneously, but the voltage must be high enough for the string with the greatest voltage drop plus overhead voltage, resulting in excessive power consumption
Solution Approach 1:
The patent divides the parallel LED string configuration into multiple separate current sink circuits, each dedicated to a specific LED string. This segmentation allows each current sink to operate independently with its own switching regulator, eliminating the need for one regulator to supply excessive voltage to all strings simultaneously. Each regulator only needs to supply voltage for its assigned string, dramatically reducing overall power consumption.
Solution Approach 2:
The patent implements dynamic voltage supply by enabling each current sink circuit to be independently controlled and activated only when needed. The switching regulators can be dynamically enabled or disabled based on which LED strings require operation, allowing the system to adapt voltage supply to actual operational requirements rather than continuously supplying maximum voltage to all strings.
2Reliability
If the switching regulator supplies the highest voltage drop plus overhead voltage to all strings, then all strings can operate, but power dissipation increases significantly
Solution Approach 1:
The patent applies local quality by providing customized voltage supply to each LED string based on its specific requirements. Each current sink circuit is tailored to its associated LED string's forward voltage characteristics, allowing optimal voltage matching for each string rather than forcing all strings to operate at the highest voltage requirement. This localized optimization reduces unnecessary power dissipation in strings with lower voltage requirements.
Solution Approach 2:
The patent changes the voltage parameter dynamically for each LED string through independent current sink circuits. Instead of maintaining a fixed high voltage for all strings, the system adjusts the voltage supplied to each string according to its specific forward voltage drop characteristics, thereby optimizing power efficiency while ensuring reliable operation of all strings.
Data Source
AI summary
In one aspect, a circuit includes a plurality of comparators. Each comparator is configured to receive a first input from a corresponding load of a plurality of loads and to receive a second input as a regulation voltage. The circuit also includes an amplifier configured to receive signals provided by the plurality of comparators, a pulse-width modulation (PWM) circuit configured to receive a control signal from the amplifier and to provide a signal to a primary switch to control voltage provided to the loads and an output switch sequencer coupled to each of the comparators and configured to provide control signals to control switches coupled to the primary switch enabling one control switch to be active at a time. Each control switch provides a voltage increase to a respective load of the plurality of loads if enabled.