Parts List:

R1,R6,R11 = 10K                  C1 = 1000uF, 64V
    R2,R9 = 1K8                  C2 = 10nF, polyester
       R3 = 100 ohm              C3 = 100uF, 64V
    R4,R8 = 1K                   C4 = 22nF
       R5 = 22K                  C5 = 47uF, 35V
       R7 = 1M
     *R10 = 0.003 ohm         D1,D2 = 1N4004
      R12 = 3K9                  U1 = LM7810, volt regulator
      R13 = 100K                 U2 = LM324, Op-amp
      R14 = 10 ohm/1 Watt        Q1 = IRFP064, IRFZ44, etc.  MOSFet
       P1 = 20K (Frequency)
       P2 = 10K (Duty C.)
       P3 = 1K (Current L.)
			
*see text

Notes:
Resistor R10 is there more for safety purposes than anything else and can be 
omitted if you wish.  It protects Q1 in case of a short circuit.