The Use of Transistor Technology in Manufacturing

Transcription

1 NAIT 2000 The Use of Transistor Technology in Manufacturing Thomas E. Scott, Ph.D. Ohio University For your own personal copy of this presentation

2 Solid State Switching January 3, 2000 EXTRA!!! EXTRA!! EMR is DEAD As the 21st century commences, we bid fond adieu to one of the mainstays of industrial electronics, the electro-magnetic relay. Surviving are numerous antiquated installations where EMRs continue to..

3 Industrial Electronics Typical Applications Rectification Motor Control Amplification Regulation Process Control

4 Transistor Capable of performing Amplifying Switching Most common types Bipolar junction (BJT) Field effect (FET)

5 Transistor A three terminal device that controls current through the device depending on the amount of voltage applied to the base PNP or NPN emitter, base, collector bipolar device - both holes and electrons are used as internal carriers for maintaining current flow

6 Transistor

7 Biasing a Transistor Base/emitter junction must be forward biased emitter more negative than the base base/collector junction must be reverse biased base is more negative that the collector

8 Biasing a Transistor

9 Transistor Current Flow Forward bias of base/emitter causes emitter to inject electrons into the depletion region between the emiitter and the base Biasing process is the turn on action

10 Transistor Current Flow

11 Transistor Applications Developed to replace mechanical switches No moving parts High resistance when transistor not turned on Low resistance when transistor turned on

12 Transistor Applications

13 Transistor Applications May be used as amplifiers Transistors gradually shut off By carefully controlling the base/emitter junction bias, possible to control varying degrees the through put of the emitter/collector current Acts as an amplifier

14 Transistors as amplifiers Darlington amplifier Two transistors used together Gain is multiplicative

15 Field Effect Transistor Like Bipolar Junction transistor except BJT is current controlled FET is voltage controlled Two types JFETs Junction FETs MOSFETs Metal Oxide Semiconductor FETs Power MOSFETS have high power capability

16 Insulated Gate Bipolar Has attractive features of both MOSFET and BJT Very fast on/off times (1 micro second) Extensively used in Inverters High frequency welding systems

17 IGBT Application

18 Special Types of Transistors THYRISTOR SCR DIAC TRIAC UJT

19 THYRISTOR Thyra (Greek) - door, inferring either open or closed Thyristor - generic name for a type of semiconductor switch Two stable states - ON and OFF No intermediate state Like a mechanical toggle switch Made up of alternating layers of semiconductor material

20 THYRISTOR Applications Used in lamp-dimming circuits, motor speed control, ignition systems, charging circuits Control the transfer of power to various AC loads SCRs, TRIACs, DIACs, and UJTs

21 Silicon Controlled Rectifier (SCR) Major element of motor control equipment Ratings as high as 2500 Volts and 2500 Amps Reverse blocking triode thyristor

22 SCR - Continued Three terminals anode - P-layer cathode - N-layer (opposite end) gate - P-layer near the cathode Three junctions - four layers Connect power such that the anode is positive with respect to the cathode - no current will flow NOTE: Blocked by the reverse bias of junction 2

23 SCR - Continued Positive potential applied to the gate Current will flow - TURNED-ON Once turned on, gate potential can be removed and the SCR still conducts CALLED LATCHING Holding current maintains latch

24 Silicon Controlled Rectifier

25 SCR - Continued Phase controller produces a trigger pulse to permit on a portion of the positive half cycle to get through Average power delivered is thereby controlled

26 Silicon Controlled Rectifier

27 Silicon Controlled Rectifier

28 SCR Application Gate Turn Off switch (GTO) Electronic (pointless) automotive ignition

29 TRIAC Bidirectional triode thyristor Equivalent of two SCRs connected Allows gate control of current flow in either direction

30 TRIAC Operation

31 DIAC Bi-directional device without a gate Conducts in both directions but waits for a breakover voltage Therefore, always the same and not controllable Acts like two zener diodes in series, but conducts in both directions Excellent for controlling TRIAC

32 DIAC - Application Brightness of a lamp

33 DIAC - Application Brightness of a lamp beginning half cycle, TRIAC off capacitor charges based on RC time constant eventually DIAC is activated TRIAC is activated and conducts Process repeated for each half cycle of the AC sine wave Adjust the brightness by changing the variable resistance which effects charging time

34 Unijunction Transistor (UJT) Simple two layer transistor Operates using the principle of avalanche breakdown producing a saw tooth output Used to trigger an SCR or TRIAC Also used within pulse circuitry Output from photocells, thermistors, and other transducers can be used to trigger

35 Unijunction Transistor (UJT)

36 UJT as a trigger for an SCR

37 Industrial Blending Process Computer sends bit (5 VDC) to UJT UJT sends trigger signal to SCR SCR activates and provides power to device

38 Application with UJT and SCR

39 Application with UJT and SCR

40 Inverter AC Motor Control

41 Solid State Switching Advantages No moving parts Controllable in the time domain Disadvantages Low resistance - but substantial heat

42 Solid State Switching Advice for the future If you own stock in a company who s main product line is EMRs SELL!