Constant current vs battery

214

02:22:31

 Is s battery  considered  a constant  current or constant  voltage  source?  Also  both  source  are   giving load components  107 miliamps but  for some  reason  the led with one source is drawing  20ma while  on the other source the led draws 20.1ma. What's going on?

published 5 years ago

Robert_Kidd

5 years ago

Neither! The battery voltage will reduce over time at a speed dependant on the load attached. As the battery voltage reduces the amount of current it is able to supply reduces accordingly.

Robert_Kidd

5 years ago

In a simulator the voltage source ( battery) is considered a perfect device and it’s voltage is constant. Likewise a simulator constant current source is perfect. Whatever load you connect it to it will deliver that precise current, indefinitely. Not in real life!

Robert_Kidd

5 years ago

Putting LED’s in parallel is not good practice as there are small differences in their operating voltages which, in real life, result in current ‘hogging’ whilst can cause components to fail. This doesn’t happen in a simulator where components are considered perfect. Try putting a 1 Ohm resistor in series with each LED. The problem goes away! However, I’m not sure how exactly to explain why the simulator gives the 20mA and 20.1mA figures. It’s possibly due to numerical rounding.

Robert_Kidd

5 years ago

Note, with the 1 Ohm resistors added you’ll need to increase the voltage supply to 2.02V to maintain LED currents of 20mA.

wyoelk

5 years ago

A website that explains parallel leds. http://lednique.com/parallel-leds/

j5892000

5 years ago

Ah ok. Are you speaking of thermal runaway

j5892000

5 years ago

Thsnk you wyoelk

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