Do you need 10000000000000000 Watts?
Just kidding
How much is the max current you need?
How many volts do you need?
Try LM317 adjustable linear regulator for 1.5 A
aiks..... I forget to mention already
The max voltage output around 25 Volt is enough and the max current is around 3 Amps.....
I found some circuit diagram on internet but the output current will decrease when we increase the voltage.
I would like to make one DC power supply for which both of it can be variate
The output current depends on your load, i.e. how much do you need for your circuit. You can't change that, but you can only limit the max current can be supplied by the power supply.
For example, connect a 1 k resistor to the 5 V supply, there is 5 mA current flowing. How can you increase or reduce the current? That's depending on the load, or change the supply voltage.
Check here also: https://www.electro-tech-online.com/threads/power-supply-help.32803/
But its performance doesn't meet its spec's (at 3A its output is full of ripple and the max voltage is only 25V) and some of its parts burn up when its output voltage is low and its current is high. Its opamps operate with a supply voltage higher than their max allowed voltage.
Look in the forum there for a discussion about fixing it.
Here is its schematic: