Dioda 3

Dioda RectifierOleh:I Made WirawanPenggunaan DiodaDioda mempunyai karakteristik penggunaan yang berbeda-beda sesuai dengan daerah operasi beban kerja yang dimilikinya.Dioda Rectifier

Penggunaan DiodaDioda rectifier belum cukup untuk memperoleh tegangan DC yang memberi catu tegangan ke rangkaian elektronika

Half-wave RectifierRectifiers are circuits that convert ac to dc. Special diodes, called rectifier diodes, are designed to handle the higher current requirements in these circuits.The half-wave rectifier converts ac to pulsating dc by acting as a closed switch during the positive alteration.The diode acts as an open switch during the negative alteration.DDRLRL

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Tegangan Rerata keluaran penyearah setengah gelombang

Tegangan rerata diperkirakan sebesar 31,8% dari nilai Tegangan puncak pada penyerarah setengah gelombangContoh Berapa nilai tegangan rerata dari tegangan penyearah setengah gelombang dar gambar berikut:

Solusi:

Catatan: Tegangan rerata adalah 31,8% dari tegangan puncakPengaruh Tegangan Barrier pada keluaran penyearah setengah gelombang

Pengaruh tegangan barrier selama bias maju pada rangkaian penyearah setengah gelombang. Namun pengaruhtersebut akan diabaikan bila tegangan puncak dari catu tegangan sangat besar (>10 V)ContohGambarlah tegangan keluaran dari masing-masing dioda untuk tegangan masukkan seperti yang ditunjukkan di dalam gambar tersebut

Solusi:Rangkaian dengan catu tegangan 5 VRangkaian dengan catu tegangan 100 V

Pengaruh tegangan barrier diperhitungkan dalam rangkaian karena mempunyai tingkat kesalahan sebesar 14%Pengaruh tegangan barrier tidak diperhitungkan dalam rangkaian karena mempunyai tingkat kesalahan sebesar 0,7%Penyearah setengah gelombang dengan tegangan masukan trafo couple

dimana

Tegangan Puncak Inversi diperoleh sebesar

Soal

Tentukanlah nilai puncak tegangan keluaran dari rangkaian berikut. Jika rasio trafo couple sebesar 0,5Solusi:

Penyearah Gelombang Penuh

Tegangan rerata diperkirakan sebesar 63,7% dari tegangan puncak penyearah gelombang penuhFull-wave RectifierThe full-wave rectifier allows unidirectional current on both alterations of the input. The center-tapped full-wave rectifier uses two diodes and a center-tapped transformer.FD1D2RLVsec2Vsec2The ac on each side of the center-tap is of the total secondary voltage. Only one diode will be biased on at a time.

15Bridge RectifierThe bridge rectifier is a type of full-wave circuit that uses four diodes. The bridge rectifier does not require a center-tapped transformer. FD1D2RLAt any instant, two of the diodes are conducting and two are off. D3D4

16Peak inverse voltageDiodes must be able to withstand a reverse voltage when they are reverse biased. This is called the peak inverse voltage (PIV). The PIV depends on the type of rectifier circuit and the maximum secondary voltage.For example, in a full-wave circuit, if one diode is conducting (assuming 0 V drop), the other diode has the secondary voltage across it as you can see from applying KVL around the green path.

0 VVsecNotice that Vp(sec) = 2Vp(out) for the full-wave circuit because the output is referenced to the center tap. 17Peak inverse voltageFor the bridge rectifier, KVL can be applied to a loop that includes two of the diodes. Assume the top diode is conducting (ideally, 0 V) and the lower diode is off. The secondary voltage will appear across the non-conducting diode in the loop. 0 VNotice that Vp(sec) = Vp(out) for the bridge because the output is across the entire secondary.

Vsec18Soal

Tentukan nilai tegangan rerata dari tegangan keluaran penyearah gelombang penuh berikut:Solusi:

Tegangan rerata diperkirakan sebesar 63,7% dari tegangan puncak keluaran penyearah gelombang penuhPower suppliesBy adding a filter and regulator to the basic rectifier, a basic power supply is formed.

7805FD1D2C1D3D4C2Typically, a large electrolytic capacitor is used as a filter before the regulator, with a smaller one following the regulator to complete filtering action.1000 mF1 mFIC regulator21Special-purpose diodesSpecial purpose diodes include Zener diodes used for establishing a reference voltageVaractor diodes used as variable capacitors Light-emitting diodes used in displays Photodiodes used as light sensors

22Troubleshooting power suppliesBegin troubleshooting by analyzing the symptoms and how it failed. Try to focus on the most likely causes of failure.

7805FD1D2C1D3D4C21000 mF1 mFIC regulatorExample: A power supply has no output, but was working until a newly manufactured PC board was connected to it. (a) Analyze possible failures. (b) Form a plan for troubleshooting.23Troubleshooting power supplies

7805FD1D2C1D3D4C21000 mF1 mFIC regulator The supply had been working, so the problem is not likely to be an incorrect part or wiring problem. The failure was linked to the fact that a new PC board was connected to it, which points to a possible overloading problem. If the load was too much for the supply, it is likely a fuse would have blown, or a part would likely have overheated, accounting for the lack of output. Analysis:24Troubleshooting power supplies1. Disconnect power and check the fuse. If it is bad, replace it. Before reapplying power, remove the load, open the power supply case, and look for evidence of overheating (such as discolored parts or boards). If no evidence of overheating proceed.Planning:2. Check the new pc board (the load) for a short or overloading of the power supply that would cause the fuse to blow. Look for evidence of overheating.3. Verify operation of the supply with measurements (see next slide). Based on the analysis, a sample plan is as follows. (It can be modified as circumstances warrant.)25Troubleshooting power suppliesMeasurements:Reapply power to the supply but with no load. If the output is okay, put a resistive test load on the power supply and measure the output to verify it is operational. If the output is correct, the problem is probably with the new pc board. If not, you will need to further refine the analysis and plan, looking for an internal problem. The analysis showed that a likely cause of failure was due to an overload. For the measurement step, it may be as simple as replacing the fuse and confirming that the supply works. After replacing the fuse:26Penyearah gelombang penuh dengan trafo CT (Center-Tapped)

Soal

Gambarkan bentuk gelombang yang melewati beban RL ketika tegangan puncak gelombang sinus sebesar 100 V dikenakan pada bagian primer trafo?Berapa tegangan PIV yang dimiliki oleh dioda?Solusi 1:

Dimana diketahui nilai rasio trafo sebesar n = 0,5Solusi 2:

Setiap dioda memiliki PIV minimumOperasi Penyearah Setengah Gelombang dengan filter Kapasitor

Satu siklus penyearah setengah gelombang dengan filter kapasitor

Pada penggunaan filter kapasitor terdapat tegangan ripple akibat pengisiian dan pengosongan muatan pada kapasitorAkibat penggunaan filter kapasitor

Ripple FactorRipple factor merupakan indikasi keefektifan dari sebuah filter.Ripple factor dapat diperoleh dari persamaan berikut:

Dimana tegangan ripple dan tegangan DC diperoleh sebesar

soal

Tentukan riple factor untuk rangkaian penyearah gelombang dengan beban yang seperti pada gambar berikut: Solusi:

Regulator Tegangan

SoalRegulator 7805 memiliki tegangan keluaran tanpa beban sebesar 5,18 V dan tegangan keluaran dengan beban penuh sebesar 5,15 V. Berapa nilai load regulation dari regulator tersebut?Solusi:

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