Power Supply - Stage 1

1
Power Supply - Stage 1

• Mains voltage has to be reduced

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-
-
30 VAC
120 VAC
1 - Transformation
2
Power Supply - Stage 2

• Alternating voltage has to be converted to DC

30 VAC
9.6 VDC
Load
Half wave rectification
2 - Rectification
3
Power Supply - Stage 2

• Alternating voltage has to be converted to DC

30 VAC
-9.6 VDC
Load
Half wave rectification
2 - Rectification
4
Power Supply - Stage 2

• Alternating voltage has to be converted to DC

19.1 VDC
30 VAC
Full wave rectification
RL
2 - Rectification
5
Power Supply - Stage 3

• Fluctuating voltage has to be smoothed

RL
RL 5.1 k? C 33 ?F Vout 40VDC with 1V ripple
3 - Filtered
6
Power Supply - Stage 3 (Filtering)
When first turned on capacitor acts as a short.
The surge current can damage diodes. This can be
reduced by adding a surge resistor.
RL
RS
7
Power Supply - Stage 3 (Filtering)
A more effective (although more costly) way is to
use an inductor to oppose the changes in current.
The capacitors in the LC ? filter oppose changes
in voltage.
RL
8
Power Supply - Stage 4

• Voltage has to be smoothed further

RL
Zener diode gives constant base voltage. Thus
base current is constant and so will be the
collector and emitter currents.
4 - Regulation
9
Graymark 808 Power Supply

• Power supply was built from a kit.
• Has two 0 - 15V and one 5V
• Also has three protoboards
• Ideal for doing analogue and digital lab projects

10
Graymark Power Supply
Circuit Board
Bottom plate
Transformer

• Bottom plate shows transformer and circuit board

11
Graymark Power Supply
Filter capacitor
IC regulator
Rectifier diodes

• Circuit board