An article about a new LED controller from Linear Technologies was the inspiration for this post. I decided upon seeing this article that it could be a good way to talk about a theoretical LED lighting scheme in your theoretical DC powered home.
One key I’ve learned to engineering is not trying to re-invent the wheel every time you start a project. In that spirit, I thought I would show case a new Linear Tech part that would fit well into an all DC powered home.
The basic idea of this circuit is to create a buck-boost converter, in order to pump more voltage into an array of power hungry (yet hopefully efficient) LEDs. Also there are other options on the chip to allow it to be even more versatile and act as a buck, boost, flyback or SEPIC, depending on setup and peripherals. Even though the listed applications are more for driving headlights and industrial applications (powering detection LEDs on an assembly line and then using a photo detector to determine changes), I believe this could work in a house wired with DC power in the walls. I believe a
Looking at the schematic on the EDN site, also directly linked here, you can see that there are some external components that are required for this part, but are mostly in the realm of resistors for detecting shutdown currents or providing feedback to the circuit. A look at page 8 of the schematic shows just how complicated this circuit is and that you are probably saving yourself a good deal of trouble by using this instead of the individual components.
An added bonus for this new part is the dimmer control, with analog ratios of up to 10:1. That means that in our theoretical DC powered home of tomorrow (eat your heart out, Disney World!), we could wire in a simple dimmer with minimal cost, using an oscillator, a PWM generator, and a potentiometer built into a wall switch (and peripherals). The dimmer control would also allow us to bring down the output current (via PWM_OUT) of the chip in order to save power.
The efficiency of this part can reach 94% in an inductive boost mode. Assuming there are no restrictions on some EMI emmitance issues and size of the parts, this could be a very good option for an LED lighting fixture in a home (with even simpler implementations also possible). Maybe one day we’ll see some wall fixtures with similar parts in them.
rolling your own is not "that" complicated, switchers are beautifully simple… most of them work as "two stroke" engines : breathe in and compress, explode and exhale :-). Efficiency is high, but even with "turn-key" circuits most is dependent on the external components (the inductor, the diode and the capacitor).