If you want to a LM338 variable dc voltage power supply circuit during 1.2V to 30Vdc and can provide a current maximum to 5A.
The LM138/LM238/LM338 are adjustable 3-terminal positive voltage regulators capable of supplying in excess of 5A over a 1.2V to 32V output range. They are exceptionally easy to use and require only 2 resistors to set the output voltage. Careful circuit design has resulted in outstanding load and line regulation comparable to many commercial power supplies. The LM138 family is supplied in a standard 3-lead transistor package.
7A Maximum output current
5A output current
Adjustable output 1.2V to 37V
Line regulation typically 0.005% /V
Line regulation typically 0.1%
Current limit constant with temperature
PINS of LM338K To-03 and LM338T TO-220
1.2-30V, 5A Variable power supply using LM338
We may be have the many ways such as: to be modified the LM317 Variable Regulator 0-30V 1A by add the power transistor MJ2955 in circuit following Adjustable Voltage and current regulator IC power supply or will build the Variable dc regulator 0-30V 5A circuit to be well as well, But these methods. Rather cumbersome and wasting too money.
However we can build this circuit easily and cheap, By using the packages IC No. LM338 only one, Similar to the LM317 IC number, but it can supply up to 5A, as the circuit shown in Fig.
How this circuit works
The transformer T1 converts the AC 220V to 24 Vac, so be rectified the current by the bridge diode rectifier BD1 – 10A 400V. Until DCV has come out that the filter capacitor C1 is equal to 35 volt.
The IC1 is the heart of the operation of this circuit. By the voltage output value obtained from the IC depends on the voltage value at the Adj pin of IC1, or can be varied by adjusting the VR1.
However output voltage will be approximately equal to 1.25+1.25VR1/R1
The output voltage at the output pin of the IC1 is a more powerful filter with the capacitor C3.
You must to place all devices in the PCB to completely, for the IC LM338K should install with a large heat sink. and all device has the poles. Caution connected the correct, especially electrolytic capacitor.
Figure 2 The PCB layout and components layout
Because IC number is high price.You may use the LM317 and transistor, to expand the current demand.
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Adjustable Voltage and current regulator IC power supply
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