Presentation on theme: "Electronic Power and Control Electronic Power and Control"— Presentation transcript:
1Electronic Power and Control Electronic Power and Control SemiconductorsSemiconductors
2The Elements Silicon Germanium Good Conductors Semiconductors Poor Simpler Table of ElementsSiliconGoodConductorsSemiconductorsPoorConductorsInert GasesGermanium
3A SEMICONDUCTOR has FOUR electrons in its outermost shell or orbit. SemiconductorsA SEMICONDUCTOR has FOUR electrons in its outermost shell or orbit.Adjacent atoms SHARE Electron Pair Bonds; the crystal structure behaves like an INSULATOROutermost Electronsform PAIR BONDS
4SemiconductorsIf 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”
5SemiconductorsIf 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”
6Junction Diode If external voltage is applied: NEGATIVE to ANODE; POSITIVE to CathodeThe Depletion (Barrier) Zone is increased, BLOCKING CONDUCTION
7.... and also during discharge. Rectifier FiltersThe 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.
8Rectifier Filters No Load (load open circuit) .... Capacitor charges and holds peak value.
9Rectifier Filters Moderate Load .... Capacitor charges to Peak value as voltage rises, but discharges when voltage drops away.
10Rectifier Filters Heavy Load .... Capacitor charges to Peak value as voltage rises, but discharges greatly when voltage drops away.
11Rectifier Filters Series Choke Filter A PARALLEL CAPACITOR opposes change in VOLTAGEHowever, being SERIES, there will be some voltage drop across the resistance of the chokeA SERIES INDUCTIVE CHOKE opposes change in CURRENT
12Rectifier Filters Choke Input L/C Filter The Choke filters changes of current;the Capacitor gives higher load voltageA Capacitor and Choke are often used together.
13Single-Phase Full-Wave Bridge Rectifier Diode – voltage, current and PIV ratings to suit applicationAC Supply - often from a transformer(example: 12V 50Hz)DC Load to be supplied by Rectifier
14Single-Phase Full-Wave Bridge Rectifier Conduction DuringPositive ½ Cycle
15Single-Phase Full-Wave Bridge Rectifier Conduction DuringNegative ½ CycleBack
16Three-Phase Waveforms 3-phase AC Features24001200Phase Voltages are 1200 out-of-phase
17Three-Phase Half-Wave Rectifier 3-phase STAR connected transformer secondaryDiode in each “Active”VAC (RMS)AC Voltage is PHASE Voltage (Active-Neutral)Return to transformer “Star Point” (Neutral)
19Three-Phase Half-Wave Rectifier VRipple = VPeak – (VPeak x 0.5) = VPeak x 0.5Maximum value = VPeakMinimum value = VPeakx0.5
20Three-Phase Full-Wave Rectifier VRipple = VPeak – (VPeak x 0.866) = VPeak x 0.134Maximum value = VPeakMinimum value = VPeakx0.866
21The Zener Diode voltage appears across the load. Voltage RegulatorZENER SHUNT REGULATORAssume the filtered rectifier output is 12 volts DC and the Zener Diode is rated at 8.2 volts, 1 wattThe Zener Diode voltage appears across the load.Excess voltage (12 – 8.2 = 3.8V) is dropped across the SERIES RESISTANCE (RS)8.2V3.8V8.2V 1W12VDC
22Voltage Regulator ZENER SHUNT REGULATOR Assume the load has a resistance of 200 ohmsLoad current = 8.2 volts ÷ 200 ohms = amps = 41mAPower rating of RS = 3.8 volts x amps = 0.37 watts MINIMUMZener Current = IRS – ILoad = 97mA – 41mA = 56mA97mA8.2V3.8V41mA8.2V 1W12VDC
23THREE-TERMINAL REGULATOR Voltage RegulatorTHREE-TERMINAL REGULATOR(7xxx Series)The 3-Terminal Regular is an integrated circuit chip with INPUT, OUTPUT and GROUND or COMMON terminalsOutputInputGround
24THREE-TERMINAL REGULATOR Voltage RegulatorTHREE-TERMINAL REGULATOR(7xxx Series)Positive Output78127812InputOutputGroundRegulated Voltage (12V)
25THREE-TERMINAL REGULATOR Voltage RegulatorTHREE-TERMINAL REGULATOR(7xxx Series)Negative Output79127912GroundRegulated Voltage (12V)InputOutput
26THREE-TERMINAL REGULATOR (Typical Connections) Voltage RegulatorTHREE-TERMINAL REGULATOR(Typical Connections)In operation, a small QUIESCENT CURRENT (IQ) flows between INPUT and GROUNDIQ = 2mA to 5mA
27Electronic Control Devices (Thyristors) Thyristors are solid-state devices used to control power to a loadSilicon 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 POSITIVErelative to the Cathode
28Electronic Control Devices (Thyristors) Silicon Controlled Rectifier (SCR)Once the SCR is conducting,the GATE loses ALL CONTROLThe SCR can only be turned OFF by removing the Anode-Cathode voltage
29Electronic 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 currentTrigger Point can be delayed ONLY to 900Animated
30Electronic Control Devices (Thyristors) Silicon Controlled Rectifier (SCR)Varying R1 varies charging rate of the Capacitor.This varies the Trigger Point, controlling the average load currentTrigger Point can be delayed up to nearly 1800Animated
31Electronic Control Devices (Thyristors) Silicon Controlled Rectifier (SCR)Waveform across LoadWaveform across SCR
32Electronic Control Devices (Thyristors) TRIACLike the SCR, The TRIAC is used to control loads, but with current in EITHER directionMT2To provide a short trigger pulse, a DIAC is often used with an R/C networkA DIAC is like a TRIAC without a Gate. It conducts in EITHER direction when a voltage across it reaches a required threshold valueMT1GateDIAC
33Electronic Control Devices (Thyristors) TRIACVarying R1 varies charging rate of the Capacitor.This varies the Trigger Point, controlling the average load currentAnimated
34Electronic Control Devices (Thyristors) TRIACWaveform across LoadWaveform across TRIAC