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ELEKTRONIKA DASAR

Bahan Kuliah Minggu ke 6. ELEKTRONIKA DASAR. Jurusan Teknik Elektro FT-UGM 2007. DIODA DAYA. Typical medium power diode. Diode symbol and ideal current–voltage characteristic. Bentuk gelombang output. beban. V max. I max. Tegangan dan arus beban. Tegangan dioda. THYRISTOR.

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ELEKTRONIKA DASAR

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  1. Bahan Kuliah Minggu ke 6 ELEKTRONIKA DASAR Jurusan Teknik Elektro FT-UGM 2007

  2. DIODA DAYA Typical medium power diode Diode symbol and ideal current–voltage characteristic.

  3. Bentuk gelombang output beban Vmax Imax Tegangan dan arus beban Tegangan dioda

  4. THYRISTOR Thyristor or silicon controlled rectifier (SCR) symbol. Thyristor current–voltage characteristics.

  5. STRUKTUR THYRISTOR

  6. Bentuk gelombang • Gelombang tegangan beban • Gelombang tegangan thyristor

  7. Bentuk gelombang • Gelombang tegangan beban • Gelombang tegangan dan arus thyristor

  8. Bentuk fisik thyristor Two flat-pack thyristors mounted on a liquid cooled heat sink Figure 9.14 Demonstration of thyristor operat

  9. Thyristor sbg saklar S1 S2

  10. FORCED COMMUTATION NO : Normally Open NO NC : Normally Closed NC NO NO Menghubung singkat thyristor Memutus arus

  11. SWITCHED OFF • Thyristor harus dipaksa OFF dgn capasitor

  12. SWITCHED OFF • Pemaksaan lewat thyristor 2

  13. PENGUJIAN THYRISTOR

  14. Thyristor di trigger lewat cahaya Light-fired thyristor used for HVDC transmission. Figure 9.14 Demonstration of thyristor operat

  15. Controllable rectifiers Single-phase thyristor-controlled bridge rectifier. Figure 9.14 Demonstration of thyristor operat

  16. Operation of the single-phase thyristor-controlled bridge rectifier • (b) Negative ac supply cycle (a) Positive ac supply cycle • Operation • Thyristor 1 & 2 fired in the positive cycle • Thyristor 3 & 4 fired in the negative cycle .

  17. Controllable rectifiers (a) AC voltage, current and thyristor voltage DC voltage is controlled by the delay of firing (b) DC voltage, current and gate pulse delay Voltage and current waveforms of the single-phase thyristor-controlled bridge rectifier Figure 9.14 Demonstration of thyristor operat

  18. Operation Concept Bridge Inverters Current flow when S1 and S2 are conducting Current flow when S3 and S4 are conducting Bridge operation generated voltage waveform. Purpose: Converts DC to AC

  19. RMS value of the output voltage and operation frequencyBridge Inverters

  20. GTO GTO (Gate Turn-Off thyristor) Vmax = 4,500 V, Imax = 3,000 A, Von = 2-3V Thyristor Vmax = 7,000 V, Imax = 4,000 A, Von = 1.5-3V

  21. GTO Gate turn-off thyristor (GTO) symbol. Gate turn-off thyristor (GTO) operation. Figure 9.14 Demonstration of thyristor operat

  22. Bidirectional Triode Thyristor ( TRIAC) • TRIAC dapat bersifat konduktif dalam dua arah. Dapat dianggap dua buah thyristor tersambung secara antiparalel dengan koneksi gerbang. Untuk pengendalian tegangan AC • Karena TRIAC merupakan devais bidirectional, terminalnya tidak disebut anode/katode tetapi terminal MT1 dan MT2. MT2 positif terhadap terminal MT1. • TRIAC dapat dimatikan dengan memberikan sinyal gerbang positip antara gerbang G dan MT1. Jika terminal MT2 negatif terhadap MT1, maka TRIAC akan dapat dihidupkan dengan memberikan sinyal pulsa negatif antara gerbang G dan terminal MT1. • Tidak perlu untuk memiliki kedua sinyal gerbang positif dan negatif sehingga TRIAC dapat dihidupkan baik oleh sinyal gerbang positif maupun negatif. • Simbol TRIAC

  23. Obviously a triac can also be triggered by exceeding the breakover voltage. This is not normally employed in triac operation. The breakover voltage is usually considered a design limitation. One other major limitation, as with the SCR, is dV/dt, which is the rate of rise of voltage with respect to time. A triac can be switched into conduction by a large dV/dt. Typical applications are in phase control, inverter design, AC switching, relay replacement, etc. • Major considerations when specifying a triac are:(a) Forward and reverse breakover voltage.(b)Maximum current(c) Minimum holding current(d) Gate voltage and gate current trigger requirements.(e) Switching speed(f) Maximum dV/dt

  24. Triode Alternating Current Switch TRIAC

  25. DIMMER

  26. komponen

  27. DIAC DIAC merupakan salah satu jenis dioda SCR, namun memiliki dua terminal (elektroda) saja,

  28. KARAKTERISTIK DIAC • The diac is a bidirectional trigger diode which is designed specifically to trigger a triac or SCR. • Basically the diac does not conduct (except for a small leakage current) until the breakover voltage is reached. • Typically about 5 volts, creating a breakover current sufficient to trigger a triac or SCR. Typical diacs have a power dissipations ranging from 1/2 to 1 watt.

  29. Light bulb a b + Van – + Van – + Van – + 0V – + 0V – + Van – Light bulb a b n Before firing, the triac is an open switch, so that practically no voltage is applied across the light bulb. The small current through the 3.3kΩ resistor is ignored in this diagram. After firing, the triac is a closed switch, so that practically all of Van is applied across the light bulb. n Triac Light Dimmer Light bulb a b • Ingenious • Simple • Efficient • Inexpensive Triac (front view) 3.3kΩ MT2 + Van (from Variac) – c Triac 250kΩ linear pot G MT1 Bilateral trigger diode (diac) 0.1µF MT1 MT2 G n

  30. Triac Closed When the voltage across the diac reaches about ±35V, it self-fires and its voltage collapses to about ± 5V Light bulb Light bulb 3.3kΩ 3.3kΩ + Van (from Variac) – + Van (from Variac) – 250kΩ linear pot 250kΩ linear pot Bilateral trigger diode (diac) Bilateral trigger diode (diac) 0.1µF 0.1µF • Light bulb resistance is a few ohms when cold, and about 100-200Ω when bright (use to get R) Triac Open Capacitor discharges into triac gate • The light bulb resistance is small compared to the 3.3kΩ and potentiometer combination and can be ignored when analyzing the RC electronic circuit • The circuit resets and the process repeats every half-cycle of 60Hz

  31. Variac Isolation transformer Light dimmer Hookup

  32. Variac voltage Capacitor voltage No-Firing Condition – Actual • When potentiometer resistance is large, there is no firing because the capacitor voltage never exceeds (positive or negative) the diac breakover voltage • Capacitor voltage lags variac voltage almost 90º for large potentiometer resistance

  33. Firing Condition – Actual • Capacitor voltage Vcn does not go into steady state AC right away as Van crosses the zero axis. There is a time delay due to the RC time constant. • The RC time constant delay plus phase shift of the AC solution for Vcn determines the point at which the diac breakover is achieved

  34. TERMISTOR

  35. Light-dependent resistors • The simplest of the photoconductive devices is the light-dependent resistor or LDR. • It is typically used in a voltage divider circuit. • LDRs are cheap and simple to use, but are slow to respond to changes in light intensity and are often not suitable for high-speed computer applications. • Due to its relatively large size and power requirements, the LDR tends not to be used for data signal production, but it has a use in applications such as simple alarm circuits and detectors on production lines.

  36. LDR

  37. UNTAI LDR

  38. LDR consists of a slab of bulk semiconducting material • cadmium sulphide (CdS) or cadmium selenide (CdSe) • a pair of electrical contacts across its ends • Incident light creates electron-hole pairs • minimum photon energy needed to excite electrons • will only respond to light below a maximum value • Long wavelength cut-off • c = hc/Wmin • The increased number of electrons & holes available for conduction provide an increase in the conductivity of material • a decrease in the resistivity of the material • a voltage in series with a load resistor is applied across semiconductor to pull electrons and holes to respective terminals • Response times of LDR's depend purely on the drift of the photon-generated carriers to their respective electrodes •  relatively long with 50 ms being fairly typical

  39. Calculate the cut-off wavelengths of intrinsic CdS, CdSe and PbS LDR's, for respective excitation energies of 2.4, 1.7 and 0.4 eV. • Solution • For CdS, the excitation energy in Joules is, • Wmin = 2.4 eV x 160x10-21 J eV-1 • = 384 x 10-21 J • The cut-off wavelength is • max = hc/Wmin • = (663x10-36 Js x 300x106 m s-1)/ 384x10-21 J • = 520 nm • Detector will respond only to light in blue-green part of the spectrum. • Similarly for CdSe, max is 720 nm and will respond to all visible wavelengths • PbS, with a cut-off at 3 m, is sensitive out to the infra-red.

  40. Photoconductive • such devices do not produce electricity, but simply change their resistance • photodiode (as described earlier) can be used in this way to produce a linear device • phototransistors act like photodiodes but with greater sensitivity • light-dependent resistors (LDRs) are slow, but respond like the human eye

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