1. Electronic Power and Control Electronic Power and Control
Semiconductors
Semiconductors

2. The Elements Silicon Germanium Good Conductors Semiconductors Poor
Simpler Table of Elements
Silicon
Good
Conductors
Semiconductors
Poor
Conductors
Inert Gases
Germanium

3. A SEMICONDUCTOR has FOUR electrons in its outermost shell or orbit.
Semiconductors
A SEMICONDUCTOR has FOUR electrons in its outermost shell or orbit.
Adjacent atoms SHARE Electron Pair Bonds; the crystal structure behaves like an INSULATOR
Outermost Electrons
form PAIR BONDS

4. Semiconductors
If the semiconductor has a few per million atoms with THREE outermost (valence) electrons ....
The “Hole” is an absence of an electron, and is thus POSITIVELY charged.
... THREE valence atoms leave a “HOLE” in the crystal structure.
This is Called “P-TYPE”

5. Semiconductors
If the semiconductor has a few per million atoms with FIVE outermost (valence) electrons ....
The “extra” electron is NEGATIVELY charged.
... FIVE valence atoms have an “extra” electron in the crystal structure.
This is Called “N-TYPE”

6. Junction Diode If external voltage is applied:
NEGATIVE to ANODE; POSITIVE to Cathode
The Depletion (Barrier) Zone is increased, BLOCKING CONDUCTION

7. .... and also during discharge.
Rectifier Filters
The parallel load also draws current from supply during the charging period .....
.... and also during discharge.
.... the resulting Ripple depends on the load resistance AND capacitor size.

8. Rectifier Filters No Load (load open circuit) ....
Capacitor charges and holds peak value.

9. Rectifier Filters Moderate Load ....
Capacitor charges to Peak value as voltage rises, but discharges when voltage drops away.

10. Rectifier Filters Heavy Load ....
Capacitor charges to Peak value as voltage rises, but discharges greatly when voltage drops away.

11. Rectifier Filters Series Choke Filter
A PARALLEL CAPACITOR opposes change in VOLTAGE
However, being SERIES, there will be some voltage drop across the resistance of the choke
A SERIES INDUCTIVE CHOKE opposes change in CURRENT

12. Rectifier Filters Choke Input L/C Filter
The Choke filters changes of current;
the Capacitor gives higher load voltage
A Capacitor and Choke are often used together.

13. Single-Phase Full-Wave Bridge Rectifier
Diode – voltage, current and PIV ratings to suit application
AC Supply - often from a transformer
(example: 12V 50Hz)
DC Load to be supplied by Rectifier

14. Single-Phase Full-Wave Bridge Rectifier
Conduction During
Positive ½ Cycle

15. Single-Phase Full-Wave Bridge Rectifier
Conduction During
Negative ½ Cycle
Back

16. Three-Phase Waveforms
3-phase AC Features
2400
1200
Phase Voltages are 1200 out-of-phase

17. Three-Phase Half-Wave Rectifier
3-phase STAR connected transformer secondary
Diode in each “Active”
VAC (RMS)
AC Voltage is PHASE Voltage (Active-Neutral)
Return to transformer “Star Point” (Neutral)

18. Three-Phase Half-Wave Rectifier
(Animated)

19. Three-Phase Half-Wave Rectifier
VRipple = VPeak – (VPeak x 0.5) = VPeak x 0.5
Maximum value = VPeak
Minimum value = VPeakx0.5

20. Three-Phase Full-Wave Rectifier
VRipple = VPeak – (VPeak x 0.866) = VPeak x 0.134
Maximum value = VPeak
Minimum value = VPeakx0.866

21. The Zener Diode voltage appears across the load.
Voltage Regulator
ZENER SHUNT REGULATOR
Assume the filtered rectifier output is 12 volts DC and the Zener Diode is rated at 8.2 volts, 1 watt
The Zener Diode voltage appears across the load.
Excess voltage (12 – 8.2 = 3.8V) is dropped across the SERIES RESISTANCE (RS)
8.2V
3.8V
8.2V 1W
12VDC

22. Voltage Regulator ZENER SHUNT REGULATOR
Assume the load has a resistance of 200 ohms
Load current = 8.2 volts ÷ 200 ohms = amps = 41mA
Power rating of RS = 3.8 volts x amps = 0.37 watts MINIMUM
Zener Current = IRS – ILoad = 97mA – 41mA = 56mA
97mA
8.2V
3.8V
41mA
8.2V 1W
12VDC

23. THREE-TERMINAL REGULATOR
Voltage Regulator
THREE-TERMINAL REGULATOR
(7xxx Series)
The 3-Terminal Regular is an integrated circuit chip with INPUT, OUTPUT and GROUND or COMMON terminals
Output
Input
Ground

24. THREE-TERMINAL REGULATOR
Voltage Regulator
THREE-TERMINAL REGULATOR
(7xxx Series)
Positive Output
7812
7812
Input
Output
Ground
Regulated Voltage (12V)

25. THREE-TERMINAL REGULATOR
Voltage Regulator
THREE-TERMINAL REGULATOR
(7xxx Series)
Negative Output
7912
7912
Ground
Regulated Voltage (12V)
Input
Output

26. THREE-TERMINAL REGULATOR (Typical Connections)
Voltage Regulator
THREE-TERMINAL REGULATOR
(Typical Connections)
In operation, a small QUIESCENT CURRENT (IQ) flows between INPUT and GROUND
IQ = 2mA to 5mA

27. Electronic Control Devices (Thyristors)
Thyristors are solid-state devices used to control power to a load
Silicon Controlled Rectifier (SCR)
The SCR conducts when the Anode is POSITIVE relative to the Cathode, PLUS ....
The DIODE conducts when the Anode is POSITIVE relative to the Cathode.
..... the GATE must be POSITIVE
relative to the Cathode

28. Electronic Control Devices (Thyristors)
Silicon Controlled Rectifier (SCR)
Once the SCR is conducting,
the GATE loses ALL CONTROL
The SCR can only be turned OFF by removing the Anode-Cathode voltage

29. Electronic Control Devices (Thyristors)
Silicon Controlled Rectifier (SCR)
Varying R1 varies the voltage available at the Gate at any instant.
This varies the Trigger Point, controlling the average load current
Trigger Point can be delayed ONLY to 900
Animated

30. Electronic Control Devices (Thyristors)
Silicon Controlled Rectifier (SCR)
Varying R1 varies charging rate of the Capacitor.
This varies the Trigger Point, controlling the average load current
Trigger Point can be delayed up to nearly 1800
Animated

31. Electronic Control Devices (Thyristors)
Silicon Controlled Rectifier (SCR)
Waveform across Load
Waveform across SCR

32. Electronic Control Devices (Thyristors)
TRIAC
Like the SCR, The TRIAC is used to control loads, but with current in EITHER direction
MT2
To provide a short trigger pulse, a DIAC is often used with an R/C network
A DIAC is like a TRIAC without a Gate. It conducts in EITHER direction when a voltage across it reaches a required threshold value
MT1
Gate
DIAC

33. Electronic Control Devices (Thyristors)
TRIAC
Varying R1 varies charging rate of the Capacitor.
This varies the Trigger Point, controlling the average load current
Animated

34. Electronic Control Devices (Thyristors)
TRIAC
Waveform across Load
Waveform across TRIAC