1. Linear Power Supply

2. Outline Linear Power Supply Adjustable power supply Rectifier Circuit
Poor man’s cell phone charger
Small signal resistance
Adjustable power supply
Rectifier Circuit
Half-wave rectifier circuit
Full-wave rectifier circuit
Full-wave rectifier circuit as a Frequency mixer
Filter Circuit

3. Outline Large-Signal and Small-Signal Operation
Application of Diodes (Up to 3.5.1)

4. c03f19
How does a small increase in Vad affect Vout?

5. Drop in Output Voltage

6. c03f20
(Slope)

7. Small Signal Resistance
Small Signal Resistance: ID/VT

8. I-V Characteristic of a 1n4001 Diode

9. Export I-V Data to a Table

10. Export Table

11. Small Signal Resistance
VF (V)
IF (Computed)
0.748
67.57 mA
0.740
57.89 mA
Dynamic Resistance from the measurement:
( )/(67.57 mA mA)= Ohms
( )/(13.8 mA-5.74 mA)= 48 mV/8.06 mA =5.95 Ohms

12. c03f22
Using Small Signal Model in a Small Signal Calculation

13. c03f23

14. Small Signal Model of Adaptor
c03f25
Change in Vad

15. How should a load be modeled?
A laptop consumes an average power of 25 W with a supply
voltage of 3.3 V. Determine the average current drawn from
the batteries or the adaptor.
P=VI
I= 7.56 A
If the laptop is modeled by a resistor, then RL is Ohms.

16. You Can’t Power a Laptop with a Circuit Like this!

17. How should a Cellphone load be modeled?
A cellphone consumes an average power of 100 mW with a supply
voltage of 2.4 V. Determine the average current drawn from
the batteries or the adaptor.
P=VI
I= mA
If the cellphone is modeled by a resistor, then RL is 79 Ohms.

18. Use a 79 Ohm Resistor to Model a Cell Phone Load

19. Dual-Output Adjustable Linear Regulated Power Supply

20. Block Diagram

21. Simple Description
Transformer: “Downconvert” the AC line voltage to a smaller peak voltage Vm, usually about 2-3 Volts larger than the ultimately desired DC output.
Diode Rectifier Circuit: produce a waveform with large DC component.
Filter: smooth out the rectified sinusoid.
Regulator: eliminate residual ripple

22. c03f27
c03f27

23. c03f28 Half-Wave Rectifier Assume constant voltage model for diodes
Voltage offset
Diode is off for Vin < VD,on
Assume constant voltage model for diodes

24. c03f29
On for Vin less than –VD,on

25. c03f31
An AC-DC Converter Circuit
Ideal Diode Model

26. c03f30 An AC-DC Converter Circuit
Constant Voltage Diode Model
Issue: It remains to be seen whether it can provide a current to a load

27. How should a load be modeled?
A laptop consumes an average power of 25 W with a supply
voltage of 3.3 V. Determine the average current drawn from
the batteries or the adaptor.
P=VI
I= 7.56 A
If the laptop is modeled by a resistor, then RL is Ohms.

28. c03f32 Rectifier Driving a Resistive Load The diode is turned on again
ripples
Vin begins to fall after t1 because RL provides
a discharge path for C1.
C1 must be sufficient large so that the current
drawn by RL does not reduce Vout significantly.

29. c03f33
C1 is called smoothing capacitor

30. c03f34 Magnitude of the Ripple Tin (Vp-VD,on)/RL is the current
discharged through RL
(basic form of this equation:
Q=CV)

31. c03f35 The Maximum Forward Bias Current
Maximum Forward Current Occurs at the point when the diode turns on (t1)
C1dVout/dt is maximum
The current supplied to RL is (Vp-VD,on)/RL

32. Screen Shots

33. Smoothed Capacitor