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High power constant current supply. Left part of the circuit is rectified ac voltage (USA voltage 120v rms, 170v rectified and smoothed dc).
Load is a series of commonly available high power LED's, rated at approximately 1 amps and 32 volts. (~50w LED COB)
The MOSFET is throttled to regulate the current through the load, the gate is supplied by a pull-up resistor and throttled down through bjt transistor, the bjt is in turn regulated by the three transistor network on the lower right of the circuit.
The 10 ohm resistor must handle carrying all the amps through the circuit. The pot and 9.1k resistor were picked to limit the current to between 90mA and 1A. This amperage range matches the rating of some high power LEDs. The fixed 9.1k resistor is what limits the power to approximately 1 amp, these pieces were chosen as they are relatively common values and therefore easy to source. As the pot and 9.1k only supply enough current to activate the bjt they don't need to be high power but the 10ohm resistor need to be rated to at least 10 watts (1 amp through 10 ohms gives a 10v drop which gives at least 10 watts power, anything higher should potentially work.
The smoothing capacitor by the rectifier should be chosen to give you the required maximum output ripple appropriate for your application. The 900 microfarad capacitor in the circuit gives about 15% ripple at 1 amps DC, with lower amperages allowing for a smaller smoothing capacitor.
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