ECE 131 Lecture 1.a.ppt_092045.pdf

ECE 131 Electronics 3 Antonio Angelo J, Limbaga WMSU College of Engineering Department of Electronics Engineering 1 LECTURE 1.A Power Electronics 2 What is Power Electronics is the application of...

ECE 131 Electronics 3 Antonio Angelo J, Limbaga WMSU College of Engineering Department of Electronics Engineering 1 LECTURE 1.A Power Electronics 2 What is Power Electronics is the application of electronicsis the application of electronics to the control and conversion of electric power. A study that utilizes electronic power devices from converting one form of electric power into another form of electric power with proper control Power Electronics is regarded as an important subfield of electrical and electronics engineering. 3 Concept of Power Electronics The branch of electrical engineering is sub-classified into three categories namely: Electronics Power Control Electronics generally revolves around semiconductor devices and circuits and thus the arrival of various technologies has made electronics a crucial branch of engineering. Power is associated with the generation, transmission, distribution, and utilization of various forms of electric power in static as well as rotating machinery. While control deals with the response characteristics of the systems incorporating feedback mechanisms for continuous or sampled 4 Operation of a power electronics-based system The pictorial representation 5 Relation of Power Electronics with other Disciplines 6 Block Diagram of Power Electronics 7 Power semiconductor devices ▪ A power semiconductor device is a semiconductor device used as a switch or rectifier in power electronics. ▪ Such a device is also called a power device. ▪ A power semiconductor device is usually used in "commutation mode" (i.e., it is either on or off), and therefore has a design optimized for such usage; it should usually not be used in linear operation.  Classification of Solid-state devices I. Two-terminal device A. Diode II. Three-terminal device A. Silicon-controlled rectifier (SCR) B. Thyristor C. Gate turn-off thyristor (GTO) D. Triac E. Bipolar junction transistor (BJT) F. Power MOSFET III. Four terminal device A. Insulated-gate bipolar transistor (IGBT) B. MOS-controlled thyristor (MCT) I. Integrated gate-commutated thyristor (IGCT) Power Semiconductor Devices 10 Silicon-controlled rectifier (SCR) - This semi-controlled device turns on when a gate pulse is present and the anode is positive compared to the cathode. When a gate pulse is present, the device operates like a standard diode. When the anode is negative compared to the cathode, the device turns off and blocks positive or negative voltages present. The gate voltage does not allow the device to turn off. Up to 3000 amperes, 5000 volts in a single silicon device. Silicon Controlled Rectifier is a four-layer solid-stat e current-controlling device. The name "silicon controlled rectifier" is General Electric's trade name for a type of thyristor 12 SCR 13 Current-Voltage characteristics IA(VAC) of the SCR thyristor for different values of the gate current IG. In the figure SCR’s threshold voltage VT and its holding current IH are also marked. 3 states of thyristors Thyristors operate in one of the following three states, depending on the requirements: Forward conducting Forward blocking Reverse blocking mode 15 1. Forward conducting This is a thyristor's primary operating mode. It is switched to conducting mode and stays that way until the current falls below a specific level, called the holding current. 2. Forward blocking The thyristor blocks the flow of current, despite voltage being applied in the direction that would signal a diode to conduct it. 3. Reverse blocking mode. Current attempts to pass through the thyristor in the opposite direction. However, a diode blocks it, and the thyristor is not activated. 16 SCR Conduction If an SCR’s gate is left floating (disconnected), it behaves exactly as a Shockley diode. It may be latched by breakover voltage or by exceeding the critical rate of voltage rise between anode and cathode, just as with the Shockley diode. Dropout is accomplished by reducing current until one or both internal transistors fall into cutoff mode, also like the Shockley diode. However, because the gate terminal connects directly to the base of the lower transistor, it may be used as an alternative means to latch the SCR. By applying a small voltage between gate and cathode, the lower transistor will be forced on by the resulting base current, which will cause the upper transistor to conduct, which then supplies the lower transistor’s base with current so that it no longer needs to be activated by a gate voltage. The necessary gate current to initiate latch-up, of course, will be much lower than the current through the SCR from cathode to anode, so the SCR does achieve a measure of amplification. 17 Triggering/Firing This method of securing SCR conduction is called triggering or firing, and it is by far the most common way that SCRs are latched in actual practice. In fact, SCRs are usually chosen so that their breakover voltage is far beyond the greatest voltage expected to be experienced from the power source so that it can be turned on only by an intentional voltage pulse applied to the gate. 18 Reverse Triggering A variation of the SCR, called a Gate-Turn-Off thyristor, or GTO. But even with a GTO, the gate current required to turn it off may be as much as 20% of the anode (load) current! The schematic symbol for a GTO is shown in the following illustration: 19 SCRs vs GTOs SCRs and GTOs share the same equivalent schematics (two transistors connected in a positive-feedback fashion), the only differences being details of construction designed to grant the NPN transistor a greater β than the PNP. This allows a smaller gate current (forward or reverse) to exert a greater degree of control over conduction from cathode to anode, with the PNP transistor latched state being more dependent upon the NPN than vice versa. The Gate-Turn-Off thyristor is also known by the name of Gate-Controlled Switch, or GCS. 20 The Thyristor A thyristor is a solid-statea solid-state semiconductor devicea solid-state semiconductor device with four layers of alternating P-a solid-state semiconductor device with four layers of alternating P- and N-typea solid-state semiconductor device with four layers of alternating P- and N-type materials. It acts exclusively as a bistable switch, conducting when the gate receives a current trigger, and continuing to conduct until the voltage across the device is reversed biased, or until the voltage is removed (by some other means). A three-lead thyristor is designed to control the larger current of the Anode to Cathode path by controlling that current with the smaller current of its other lead, known as its Gate. In contrast, a two-lead thyristor is designed to switch on if the potential difference between its leads is sufficiently large (breakdown 3 states of thyristors Thyristors operate in one of the following three states, depending on the requirements: Forward conducting Forward blocking Reverse blocking mode 22 Types of Thyristors Silicon controlled Bidirectional phase thyristor or SCRs controlled thyristors or Gate turn off thyristors BCTs or GTOs Fast switching thyristors or SCRs Emitter turn off thyristors or ETOs Light activated silicon controlled rectifiers or Reverse conducting LASCRs thyristors or RCTs FET controlled thyristors Bidirectional Triode or FET-CTHs Thyristors or TRIACs Integrated gate MOS turn off thyristors commutated Thyristors or or MTOs IGCTs 23  AGT – Anode Gate Thyristor – A thyristor with gate on n-type layer near to the anode ASCR – Asymmetrical SCR BCT – Bidirectional Control Thyristor – A bidirectional switching device containing two thyristor structures with separate gate contacts BOD – Breakover Diode – A gateless thyristor triggered by avalanche current – DIAC – Bidirectional trigger device – Dynistor – Unidirectional switching device – Shockley diode – Unidirectional trigger and switching device – SIDAC – Bidirectional switching device – Trisil, SIDACtor – Bidirectional protection devices  BRT – Base Resistance Controlled Thyristor ETO – Emitter Turn-Off Thyristor GTO – Gate Turn-Off thyristor – DB-GTO – Distributed buffer gate turn-off thyristor – MA-GTO – Modified anode gate turn-off thyristor IGCT – Integrated gate-commutated thyristor Ignitor – Spark generators for fire-lighter ckts LASCR – Light-activated SCR, or LTT – light-triggered thyristor LASS – light-activated semiconducting switch MCTMCT – MOSFET Controlled Thyristor – It contains two additional FET structures for on/off control.  PUT or PUJT – Programmable Unijunction Transistor – A thyristor with gate on n-type layer near to the anode used as a functional replacement for unijunction transistor RCT – Reverse Conducting Thyristor SCS – Silicon Controlled Switch or Thyristor Tetrode – A thyristor with both cathode and anode gates SCR – Silicon Controlled Rectifier SIThSITh – Static Induction Thyristor, or FCTh – Field Controlled Thyristor – containing a gate structure that can shut down anode current flow. TRIAC – Triode for Alternating Current – A bidirectional switching device containing two thyristor structures with common gate contact QuadracQuadrac – special type of thyristor which combines a DIACQuadrac – special type of thyristor which combines a DIAC and a TRIAC into a single package. Power MOSFET A power MOSFET is a specific type of metal oxide semiconductor field-effect transistor (MOSFET) designed to handle significant power levels. Compared to the other power semiconductor devicesCompared to the other power semiconductor devices, for example an insulated-gate bipolar transistor (IGBTCompared to the other power semiconductor devices, for example an insulated-gate bipolar transistor (IGBT) or a thyristorCompared to the other power semiconductor devices, for example an insulated-gate bipolar transistor (IGBT) or a thyristor, its main advantages are high switching speed and good efficiency at low voltages. It shares with the IGBT an isolated  The design of power MOSFETs was made possible by the evolution of CMOSThe design of power MOSFETs was made possible by the evolution of CMOS technology, developed for manufacturing integrated circuits in the late 1970s. The power MOSFET shares its operating principle with its low-power counterpart, the lateral MOSFET. The power MOSFET is the most widely used low-voltage (that is, less than 200 V) switch. It can be found in most power suppliesThe power MOSFET is the most widely used low-voltage (that is, less than 200 V) switch. 28 It can be found in most power supplies, DC to Power MOSFET Cont…… Insulated-gate bipolar transistor (IGBT) An insulated-gate bipolar transistor (IGBT) is a three-terminal power semiconductor device) is a three-terminal power semiconductor device primarily used as an electronic switch which, as it was developed, came to combine high efficiency and fast switching. It consists of four alternating layers (P-N-P-N) that are controlled by a metal-oxide-semiconductor (MOS) gate structure without regenerative action. Although the structure of the IGBT is topologically the same as a thyristor) is a three-terminal power semiconductor device primarily used as an electronic switch which, as it was developed, came to combine high efficiency and fast switching. It consists of four alternating layers (P-N-P-N) that are controlled by a metal-oxide-semiconductor (MOS) gate structure without regenerative action. Although the structure of the IGBT is topologically the same as a thyristor with a MOS gate (MOS gate thyristor), the thyristor action is completely suppressed and only the transistor) is a three-terminal power semiconductor device primarily used as an electronic switch which, as it was developed, came to combine high efficiency and fast switching. It consists of four alternating layers (P-N-P-N) that are controlled by a metal-oxide-semiconductor (MOS) gate structure without regenerative action. Although the structure of the IGBT is topologically the same as a thyristor with a MOS gate (MOS gate thyristor), the thyristor action is completely suppressed and only the transistor action is permitted in the IGBT Cont…… IGBT Cont……  MOS-controlled thyristor (MCT) An MOS-controlled thyristor (MCT) is a voltage-controlled fully controllable thyristor. It was invented by V.A.K. Temple.MCTs are similar in operation to GTO thyristorsMCTs are similar in operation to GTO thyristors, but have voltage controlled insulated gates. They have two MOSFETsMCTs are similar in operation to GTO thyristors, but have voltage controlled insulated gates. They have two MOSFETs of opposite conductivity types in their equivalent circuits. One is responsible for turn-on and the other for turn-off. A thyristor with only one MOSFET in its equivalent circuit, which can only be turned on (like normal SCRs), is called an MOS-gated thyristor Positive voltage on the gate terminal with respect to the cathode turns the thyristor to the on state. Negative voltage on the gate terminal with respect to the anode, which is close to cathode voltage during the on state, turns the thyristor to the off state. These devices proved unwanted current crowding when fabricated, consequently small SOA (safe operating area), so Fairchild withdrew them after brief commercialization. MOS-controlled thyristor (MCT) Cont…… IX. Integrated gate-commutated thyristor (IGCT) The integrated gate-commutated thyristor (IGCT) is a power semiconductor electronic device, used for switching electric current in industrial equipment. It is related to the gate turn-off (GTO) thyristor. It was jointly developed by Mitsubishi and ABB. Like the GTO thyristor, the IGCT is a fully controllable power switch, meaning that it can be turned both on and off by its control terminal (the gate). Gate drive electronics are integrated with the thyristor device. Integrated gate-commutated thyristor (IGCT) Top view of a typical 91mm wafer Gate Commutated Thyristor with cathode segments arranged in 10 concentric rings and the gate contact placed between Ring 5 and Ring 6 Advantages of Power Electronics Converters The advantages are as follows: ❑ Highly reliable ❑ Less loss of power ❑ Efficient ❑ Fast response ❑ Long life ❑ Small size and less in weight 37 Disadvantages of Power Electronics Converters The disadvantages are listed below: ❑ Low overload capacity ❑ Harmonics are generated ❑ Expensive 38 Applications of Power Electronics Industries Home appliances Commercial Medical Automotive and Security Systems Aerospace Transportation Telecommunications Power Systems 39 Applications for thyristors Thyristors support high voltages and possess a simplified approach to switching on and off states. As a result, they are used for the following applications: speed controls; light dimmers; camera flashes; and various types of circuits, such as inverter, logic and timer circuits. 40 Emergency Lamp Circuit 41 SCR DC Motor Switch 42 Crowbar Over Voltage Circuit 43 Thank You! 44