John Popelish said:
For the two doubler capacitors, I would use something like 5,000 to
10,000 microfarads per amp of output load and rated for at least 16 volts
DC. Your diodes and transformer will allow about 300 to 400 mA load
current. If your load current is at or below 400 mA, that implies
something around 2,200 to 4,700 uF 16 or 25 volt capacitors for the
doubler.
Of course, if you use the full 30 volt winding, you can get pretty close
to 45 volts output with a bridge rectifier made with 4 of your diodes and
a single capacitor, say, 2,200 to 4,700 uF, rated for 50 volts. This
will give you a voltage around 40 to 45 volts, depending on load current
that can be up to about 0.7 amps.
You need to use capacitors rated at least as high as the maximum peak to
peak unloaded output voltage of the transformer, so for 24 VAC that would
be about 75 volts. Here is an LTspice ASCII showing a 24 VAC source boosted
to 68 VDC with two diodes and two capacitors. The first capacitor can be
rated at half the voltage of the second one. This circuit has poor
regulation, but is inherently current limiting, so you can just add a zener
(as shown) to the output for regulation. You need to adjust the value of C1
for the wattage of the zeners and load current. This is set for 45 VDC and
about 50 mA max.
Paul
=================================================================
Version 4
SHEET 1 880 680
WIRE 64 144 -48 144
WIRE 240 144 128 144
WIRE 288 144 240 144
WIRE 416 144 352 144
WIRE 512 144 416 144
WIRE 528 144 512 144
WIRE 640 144 528 144
WIRE 240 192 240 144
WIRE 416 192 416 144
WIRE -48 224 -48 144
WIRE 528 224 528 144
WIRE 640 224 640 208
WIRE 640 304 640 288
WIRE -48 384 -48 304
WIRE 240 384 240 256
WIRE 240 384 -48 384
WIRE 416 384 416 256
WIRE 416 384 240 384
WIRE 528 384 528 304
WIRE 528 384 416 384
WIRE 640 384 640 368
WIRE 640 384 528 384
WIRE 640 432 640 384
FLAG 640 432 0
FLAG 512 144 V+
SYMBOL diode 288 160 R270
WINDOW 0 32 32 VTop 0
WINDOW 3 0 32 VBottom 0
SYMATTR InstName D2
SYMATTR Value MUR460
SYMBOL polcap 400 192 R0
SYMATTR InstName C2
SYMATTR Value 1000µ
SYMATTR Description Capacitor
SYMATTR Type cap
SYMATTR SpiceLine V=63 Irms=2.51 Rser=0.025 MTBF=5000 Lser=0 ppPkg=1
SYMBOL voltage -48 208 R0
WINDOW 3 -14 227 Left 0
WINDOW 123 0 0 Left 0
WINDOW 39 24 44 Left 0
SYMATTR Value SINE(0 35 60 0 0 0 120)
SYMATTR SpiceLine Rser=.1
SYMATTR InstName V1
SYMBOL res 512 208 R0
SYMATTR InstName R1
SYMATTR Value 2000
SYMBOL polcap 128 128 R90
WINDOW 0 0 32 VBottom 0
WINDOW 3 32 32 VTop 0
SYMATTR InstName C1
SYMATTR Value 47µ
SYMATTR Description Capacitor
SYMATTR Type cap
SYMATTR SpiceLine V=63 Irms=2.51 Rser=0.025 MTBF=5000 Lser=0 ppPkg=1
SYMBOL diode 224 256 M180
WINDOW 0 24 72 Left 0
WINDOW 3 24 0 Left 0
SYMATTR InstName D1
SYMATTR Value MUR460
SYMBOL zener 656 288 R180
WINDOW 0 40 32 Left 0
WINDOW 3 -137 34 Left 0
SYMATTR InstName D4
SYMATTR Value BZX84C15L
SYMATTR Description Diode
SYMATTR Type diode
SYMBOL zener 656 208 R180
WINDOW 0 41 31 Left 0
WINDOW 3 -138 34 Left 0
SYMATTR InstName D3
SYMATTR Value BZX84C15L
SYMATTR Description Diode
SYMATTR Type diode
SYMBOL zener 656 368 R180
WINDOW 0 41 47 Left 0
WINDOW 3 -144 33 Left 0
SYMATTR InstName D5
SYMATTR Value BZX84C15L
SYMATTR Description Diode
SYMATTR Type diode
TEXT 184 528 Left 0 !.tran 2