Load Regulation Equation

[mananshah93]

I am deriving load regulation for 7.5V 2Amp. linear power supply, but I am confused regarding the equation of percentage load regulation.

which of 3 is correct?

1....Load Reg = {(Vn - Vf) / Vf} x 100%
where Load Reg = load regulation;

Vn = no-load output voltage;

Vf = full-load output voltage

OR

2....Load Reg. = V full load -V Minimum Load
--------------------------
V nominal load

Where:

FullLoad is the load that draws the greatest current (is the lowest specified load resistance - never short circuit)
MinimumLoad is the load that draws the least current (is the highest specified load resistance - possibly open circuit for some types of linear supplies, usually limited by pass transistor minimum bias levels)
NominalLoad is the typical specified operating load

OR

3.....Load Reg = {(Vn - Vf) / Vn} x 100%

 

[Hero999]

#1 is correct.

What you are measuring is the % change in voltage from when the supply is unloaded to fully loaded, the smaller the figure the better.

 

[mananshah93]

Thanks, I have designed 7.5V 2 Amp. power supply using LM338, 230 to 12V 3Amp. Transformer, Bridge Rectifier having 1.1V Forward drop per bridge and filter capacitor around 20000MF.
I am having load regulation of around 1.06 percentage, but I read that linear power supply can give regulation of 0.01 %, how to achieve this?

 

[Hero999]

Sorry buy I think you've wasted your time because an audio amplifier doesn't need a regulated supply.

 

[mananshah93]

Sorry buy I think you've wasted your time because an audio amplifier doesn't need a regulated supply.

I am sorry, but i did not get this, why audio amplifier???
I need this to replace this...
**broken link removed**

 

[Hero999]

Sorry, I thought it was for an audio amplfier.

What do you need to power with this power supply?

It might not need a regulated supply, a 6V transformer with a bridge rectifier and 22,000µF capacitor might do.

The datasheet for the LM338 specifies a worst case of 0.6%, however it has a thermal stability of 1% meaning the output voltage can drift by 1% over the temperature range. Given the heating of the die, the regulation and the resistance of the wires, it woudln't surprise me if this could amount to 1.06%.

How thick are the wires?

How good is the heat sink?

https://www.electro-tech-online.com/custompdfs/2009/08/LM138PDF.pdf