Constant current supply vs Direct power supply

434

06:32:43

LED needs stable current to correctly work. This circuit will demonstrate the differents between Constant current supply and Direct power supply. 

The yellow led is connected directly to battery. The cyan one is powered through 2 npn transistors system.

The battery is a oscillator to demonstrate how led's current react to fluctuating voltage. As the result, the yellow led's current is more fluctuating than the cyan one's. 

As you see, the transistors work like a smart current controller. They are so intelligent! :)

published 8 years ago

BillyT

8 years ago

Good information.

tonyinselby

8 years ago

I like it! 👍

Ajinkya_Mahajan

8 years ago

Why is yellow LED not turning off in -ve half cycle of sine wave ?

FernandoCPF

8 years ago

you put 3.7vDC and it does not work with 0vDC / 3.7vAC

FernandoCPF

8 years ago

if I want in AC and not in an oscillating source like I would have to do?

wowueh

8 years ago

This circuit works with DC only. You can use it in One LED driver application. The oscillator is just simulated fluctuations of voltage when you run a LED. This circuit doesn't work with AC.

FernandoCPF

8 years ago

@wowueh entonces para AC no tengo otra opción que usar un puente de diodos y capacitor de filtrado?o ay otra opción?

eekee

8 years ago

I changed the voltage source to a pulse type & configured it to sawtooth wave. It made the effect easier to see. It was interesting with a low voltage of 3V and high of 6V. It was also cool to see the circuit take a high voltage of 200V! The left transistor and the resistor above it drew just under 200mA, which is less than I expected. It also seems immune to changes in transistor gain. It's a really cool little circuit!

wowueh

8 years ago

Thks for response eecee

wowueh

8 years ago

Thks eekee

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