Why are LED power supplies called Drivers and not Ballasts?

Froyn , 6 months ago

Boosted this post based only on your name and pic

FuglyDuck , 6 months ago (edited 6 months ago)

So, it’s kind of doing different things. Ballasts are reducing current to protect things. From the wikipedia article:

An electrical ballast is a device that limits the current through an electrical load. These are most often used when a load (such as an arc discharge) has its terminal voltage decline when current through the load increases. If such a device were connected to a constant-voltage power supply, it would draw an increasing amount of current until it is destroyed or causes the power supply to fail. To prevent this, a ballast provides a positive resistance or reactance that limits the current. The ballast provides for the proper operation of the negative-resistance device by limiting current.

A constant-voltage power supply used for a single-LED (such as these loose LEDs) is simply dropping the voltage to match the needs of the LED, but there’s no need to to add more than a resistor…and depending on the power supply and your particular circuit’s layout, there might not actually be any need for that resistor at all.

an LED driver, is typically some form of microcontroller. RBG and RBGW led’s are increasingly receiving digital control signals rather than being controlled by modifying it’s power supply. for example, NeoPixels which have to be driven by some type of microcontroller to get their full capability out. (for example a purpose built controller, or something like a feather or pi pico or arduino) for neopixels and similar sets, you’re controlling the individual brightness of the r, b and g LEDs (and the w,), as well as the over-all brightness of each pixel, all of them largely independently. (it’s as complicated and not complicated as you want. honest.)

Eideen , 6 months ago

LED power supply are more like power supply, the in the simple form create a direct current.

Ballast have the ability to create a boost, and only make a square wave.

ie.rs-online.com/web/generalDisplay.html?id=ideas…

sound-au.com/lamps/fluoro-lamps.html

Bishma , 6 months ago

The way that it was explained to me it that “driver” is shorthand for “constant voltage driver” and ballasts provide an initial startup voltage that is different from the constant one they go on to provide.

EatYouWell , 6 months ago

Sounds kinda like how your car will draw a few hundred amps to start but it’s fairly low after that.

towerful , 6 months ago

Yeh, except the battery will provide 12v throughout. So that’s essentially just an inrush current.

A ballast is actually the opposite. It limits the current.
From wiki:

A familiar and widely used example is the inductive ballast used in fluorescent lamps to limit the current through the tube, which would otherwise rise to a destructive level due to the negative differential resistance of the tube’s voltage-current characteristic.

And later…

In operation, an increase in current through the fluorescent tube causes a drop in voltage across it. If the tube were connected directly to the power line, the falling tube voltage would cause more and more current to flow, until it destroyed itself. To prevent this, fluorescent tubes are connected to the power line through a ballast. The ballast adds positive impedance (AC resistance) to the circuit to counteract the negative resistance of the tube, limiting the current.

wikipedia.org/wiki/Electrical_ballast