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Here is an interesting challenge, I'm looking or ideas.
I've been asked to design a very low cost lighting device that uses voltage reversal to select which set of LED lights are illuminated when they are wired in two parallel chains of alternately reversed parallel LEDs. The chains will be driven with a 2KHz square wave with a short dead time at transitions and each chain will have about 500 LEDs, 250 wired one way and the other 250 wired in opposite polarity across the two wires. The maximum voltage allowed is +4V or -4V +/- 5% on one wire relative to the other. The chains might be shorter or longer depending on the end users chosen configuration but the current required has to be fixed at 300mA (600mA for both chains) from source. So essentially it is a voltage limited constant current but reversing polarity generator.
My first thought is a single constant current source supplying a H-Bridge with the four switches driven by an MCU. Given the low voltage it can be done without bootstrap supply. I wonder if any readers have alternative ideas. Cost is paramount. A single 12V unregulated supply is available.
Brian.
I've been asked to design a very low cost lighting device that uses voltage reversal to select which set of LED lights are illuminated when they are wired in two parallel chains of alternately reversed parallel LEDs. The chains will be driven with a 2KHz square wave with a short dead time at transitions and each chain will have about 500 LEDs, 250 wired one way and the other 250 wired in opposite polarity across the two wires. The maximum voltage allowed is +4V or -4V +/- 5% on one wire relative to the other. The chains might be shorter or longer depending on the end users chosen configuration but the current required has to be fixed at 300mA (600mA for both chains) from source. So essentially it is a voltage limited constant current but reversing polarity generator.
My first thought is a single constant current source supplying a H-Bridge with the four switches driven by an MCU. Given the low voltage it can be done without bootstrap supply. I wonder if any readers have alternative ideas. Cost is paramount. A single 12V unregulated supply is available.
Brian.
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