LM338 Power Suply Current Regulator

[Fight]

In lm338 data sheet asking
Features:
Guaranteed 7A peak output current
Guaranteed 5A output current

But problem is that in Electrical Characteristics:
Vin-Vout = 30V Than max current 1A
what is meaning that
lets Vin = 38V  and Vout = 8V
38-8 = 30



and Vin-Vout = 10V or less than 5A can handle
mean
38-28 = 10
mean 8 to 28V 1A handle
and 28 to above 5A handle

Attatch Diagram



2.    in Application Hints diagram all diagram is designed that can handle 5A

Attatch Diagram

[hotwaterwizard]

Exactly what are you wanting to do here?

You Must Heatsink the components for 5 amps each if not they will only handle 1 amp each.
There is another way to make a high current power supply.

[hotwaterwizard]

http://www.national.com/ds/LM/LM138.pdf

http://www.national.com/mpf/LM/LM338.html#Overview

[Hero999]

Exactly what are you wanting to do here?

You Must Heatsink the components for 5 amps each if not they will only handle 1 amp each.
There is another way to make a high current power supply.

That circuit will have very poor regulation because the base-emitter saturation voltage of the 2N3055 will vary depending on the current drawn and the 0.47R resistors will have a significant voltage accross them.

Suppose the current draw is 0A and you set the voltage to 12V.

Then you increase the current to 5A.

@0A the V_BE of the transistors will be near 0.6V.

Each transistor will have 5/6 = 833mA through it, the same for the emitter resistor.

The voltage will drop by the 0.47R resistor will be 5/6

[Fight]

The LM338 will only be able to output 5A if the difference between the input and output voltage is under 10V and a good heat sink is used (1

[Hero999]

The LM338 will only be able to output 5A if the difference between the input and output voltage is under 10V and a good heat sink is used (1

[Fight]

Very Very Thanks Hero

[Fight]

Thats good answer

[Fight]

Attatch diagram
what is the role of emittr resistance 0.1 ohm
why using this resistor

[Hero999]

They help to ensure the current is shared equally between the transistors. The value isn't critical, I chose 0.1R because I originally designed it for high currents, for 5A you can use 1R which will be easier to get hold of.

[Fight]

if i change the value of 1R instead of 0.1R than what change in circuit current
the resistor wattage
the voltage across R = ?
the current across R = ?

[Hero999]

Changing the value will not change the current, the circuit does not provide current regulation, it's just that if the voltage drop across the resistors is very low, the current sharing won't be very good.

[Fight]

it's just that if the voltage drop across the resistors is very low, the current sharing won't be very good.

please explain it using examples
if 10R resistor use than

[Fight]

what is the efficiency of these circuit
if this method using with lm317 and lm338 than thses ic better current and voltage or not