Applications and functions of ferrites

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1. APPLICATIONS AND FUNCTIONS OF FERRITES From History to Innovation

2. Introduction Magnetism is First natural force discovered by man. Frequency Range of application of magnetic materials is ranging from DC(Direct Current) to the highest frequency at which any electronic device can function. The emergence of many new technology has led to the large variety of magnetic materials. These are in supplied in many different shapes and sizes.

3. History Magnetite was earliest naturally occurring ferrite. However Magnetite has very poor magnetic properties. Prof. Takeshi Takei (Japan) and Prof. Kato discovered the first ferrites with promising properties. J.L.Snoek (Holland) was able to continue ferrite research and produce commercial soft ferrites. Permanent Magnet ferrites were produced by Philips in 1952. Commercially, the first large-scale applications for ferrites were in the television industry.

4. After that it was successively used in following applications: TV tube deflection yokes High voltage flyback transformers In development of radar, satellite communications, memory and computer applications Also useful in in radio, television, video tape recorders and the internet. Automotive industry and most recently in hybrid cars.

5. Gepgraphical changes in Ferrites Suppliers In 1970s , 60% of the soft ferrities were manufactured in Japan. In 1980's, Western Europe and Southeast Asia entered the market. Many mergers and ownership changes have occurred. These include; 1.Change from Siemens to Siemens-Matsushita a nd finally to EPCOS. 2. Sale of Philips ferrite (Ferroxcube) to Yageo 3. Sale of Thomson SCF to AVX

6. taken from M.J. Ruther's paper at ICF9 Shows the Estimated Annual Soft Ferrite Production in Metric Tons per Year restricted to electronic Applications and its Geographical Location in %.

7. GENERAL CATEGORIES OF FERRITEAPPLICATIONS Classification based on market Classification based on function and for our purposes Classification based on frequency

8. 1. Classification based on market 1. Consumer -entertainment 2. Electrical Appliances 3. Automotive 4. Telecommunications- circuit components, power supplies 5. Specialty and Custom- aircraft, microwave devices, recording heads

9. 2. Classification based on functions 1. Voltage and current multipliers-Transformers 2. Impedance Matching 3. Inductor in LC circuit 4. Filter to remove any unwanted frequencies- Wide band transformer ,channel filter, EMI suppression 5.Output choke- remove ac component from D.C

10. 2. Classification based on functions 6. Bistable element in a binary memory device- recording media 7. Magnetic head- Write or read data on tape or disk 8. Microwave devices 9. Delay lines

11. 3.Classification based on frequency 1. D.C.-Permanent magnets and D.C. motors, generators and other D.C. devices 2. Line frequencies-50-60 Hz 3. Aircraft frequencies-400 Hz 4. Audio Frequencies-to 20,000 Hz.

12. 3.Classification based on frequency 5 . High frequency power- 25000-100000 Hz. and climbing 6. High frequency telecommunications-100,000 Hz. To 100 MHz 7. Microwave and Radar-1 GHz. And beyond

13. Applications Now sequentially , we will talk about the applications of different types of ferrities. D.C. Ferrite permanent magnets Used in Loudspeakers, Microphones, TV Picture tube ion traps and in D.C. motors in portable electric motors etc POWER APPLICATIONS Ferrites have no use for a.c. power generation and transformation at line frequencies because of low saturation and cost.

14. DC Power Supply Applications There are two main types of devices for this purpose. Linear Power Supply 50-60 Hz. transformer, a rectifier to convert to DC and an output choke to reduce the residual AC ripple present. Switching Power Supply. 50-60 Hz. AC to a high frequency square wave through the use of a transistor or similar solid state switching device, transforms it to the desired voltage at high frequency. This lowered AC voltage is then rectified and the AC ripple removed.

15. Audio Frequency Applications transformers, microphones, speakers and other audio-processing equipment use these magnetic materials. Telecommunications Applications It includes the areas of telephony, radio and television.

16. Telephony Applications Some of the functions of magnetic materials in telephony can be characterized as 1. Channel filters The Inductor is used in an L-C Resonant tuned circuit. 2. Wide band transformers The high frequency transformers used in conjunction with these transmission lines must be capable of passing this wide band of frequencies while rejecting those outside the limits.

17. Telephony Applications 3. Loading Coils a special problem is encountered that the inductance remains the same, due to the insulation of the wire, the capacitance of the circuit increases with the length of the wire. Therefore, the inductance must increase correspondingly. These inductors are called load coils or Pupin coils. 4. Touch-tone generator Each of the digits in the dialing sequence is represented by a separate audio tone. The inductor is usually a wound ferrite with multiple windings so various combinations can produce different frequencies or ton.

18. ENTERTAINMENT APPLICATIONS 1. Television picture tube yokes 2. Flyback transformers 3. Power transformers 4. Interstage transformers 5. Pin Cushion transformers 6. Radio and television antennae 7. Tuning slugs

19. Television Picture Tube Yokes uses the highest tonnage of magnetic material for the entertainment segment of the business. The yokes are funnel-shaped rings placed on the neck of the television picture tube. The horizontal sweep is produced by a triangular waveform which steadily deflects the beam across the screen and then very rapidly returns (flies back) to the initial point on the next line. By this, the eye sees it as continuous motion (greater than 16 frames per second)

20. 2.Flyback Transformers T he large magnetic field stored in the deflection core is rapidly collapsed The voltage induced is transferred to a single turn primary winding of the flyback transformer. Contains thousands of turns producing a very high voltage (about 25,000 V.) Placed on the accelerator anodes of the electron gun. Stored up energy of the horizontal deflection system is recaptured.

21. 3.Interstage and Pincushion Transformers U sed to couple different stages with regard to isolation and impedance matching in both audio and television circuits. Pincushion transformer of the video circuit is used to correct the spherical aberration. This Results from the use of a radial or circular sweep on a planar television picture tube.

22. 4.Antennae for Radio and Television To match wavelengths associated with radio and television, these wavelengths the antennae would be quite large. Magnetic materials have the ability to concentrate the received signal. Thus , antennae made of magnetic material can be quite small.

23. 5.Tuning Slugs C hannel in television can be fine-tuned to the proper frequency by adjusting the inductance of a wound coil into which a threaded slug of magnetic material is inserted.

24. HIGH FREQUENCY POWER SUPPLIES In the past twenty years, a new type of power supply has been developed using transistor switching to produce a high frequency square wave. Transformation is done at the high frequency. These power supplies, known as switchedmode power supplies (SMPS) Used extensively for providing the DC needed for the bias voltage of semiconductors (transistor and IC) in computers, microprocessors as well as in recording devices.

25. Pulse Transformers These usually are small toroidal (or ring) magnetic cores with the ability to perform the rapid voltage rise with controllable voltage waveforms.

26. 2. SMPS Power Transformers The power transformers that transform the high frequency input voltage to the usable voltage is at the heart of the SMPS system. These transformers are able to reduce the size of the large linear 60-Hz. Thus size of Transformer to a very much smaller one.

27. 3. Switching Regulators The output of the switching power supply must have very controllable voltage limits or a good degree of regulation. Thus, Switching Regulators are used. It involves : sampling of the output voltage comparing it with a known voltage detecting the difference feeding back to change the on-off time of the transistor and correct the voltage.

28. 4. Output Chokes The output DC of the inverter power supply contains a certain degree of unwanted ripple or residual ac. output choke is used to remove this ripple. This device is similar to the output choke for mains or linear power supplies.

29. 5. EMI Applications EMI ( electromagnetic interference) is a disturbance generated by an external source that affects an electrical circuit by electromagnetic induction, electrostatic coupling, or conduction. This legislation would require both: The manufacturers of devices producing the EMI Those devices sensitive to the EMI to provide appropriate means of minimizing the EMI effect. The input must be protected against sudden spikes or interference. To eliminate these input spikes, the power supply is often protected by input or noise filters.

30. 5. EMI Applications There are two types of such devices. Common Mode Filter both of the input or mains wires are encircled by a magnetic core. the currents are 180 degrees out of phase to each other and pass through unaffected. However, when a sharp spike appears in one wire, the sudden current surge produces a strong magnetic field than is dissipated slowly in the magnetic core. Thus, the core acts as an input protective choke.

31. 5. EMI Applications 2. In-line Filter There is a magnetic core surrounding each of the input wires. Because each line carries the entire amount of Current ,the type of component and the magnetic material used is expected to be different. Although the input frequency for the noise filter is line or mains (50-60 Hz.), the frequency or rise time of the spike is consistent with the high frequency range.

32. MICROWAVE APPLICATIONS At very high frequencies (above 1 GHz.) electrical energy is radiated by means of electromagnetic waves similar to light. New devices called Faraday rotators, circulators and phase shifters can interact with microwave radiation and perform useful functions. used in radar, aircraft and satellite guidance and in space communication systems.

33. MAGNETIC RECORDING APPLICATIONS T his application is the highest dollar volume segment. 1. Magnetic memory cores 2. Magnetic audio tape 3. Floppy disks 4. Hard disks 5. Video cassette tape 6. Magnetic ink for credit cards 7. Magnetic media 8. Magnetic recording heads 9. Rotary transformers 10. Copier powders 11. Bubble memories 12.Magneto-optic memory disks

34. Magnetic Memory Cores The earliest mass memory banks were composed of matrices of small ferrite memory cores with each core representing a logical memory bit. The cores were addressed by selectively sending current pulses through two orthogonal systems of wires threading the cores. This put certain cores into logical "1" conditions while others remained in the "0" state. The cores could be read by sending a reverse pulse through the wires and noting those which experienced a flux change or voltage

35. 2. Magnetic Recording Media-Tapes, Disks, Drums Most modern magnetic memories are based on small regions or islands of magnetic media that can be magnetized into digital bits for writing and then returned to their initial state for reading the stored bits. This technology provides more compact memories at low cost and easy access. used for audio, video or digital computer applications

36. 3. Magnetic Recording Heads used to write or read magnetic information stored in the media. construction of both types of heads is similar with only the associated electronics varying. Heads can be metallic, ceramic or thin film.

37. 4. Rotary Transformers To read the large amount of data on a video tape, a rotating magnetic head is used. To transfer the data from the head to the ensuing electronic system, a rotary transformer is used. In this case, the part of the core receiving the data moves and the secondary part of the transformer is stationary

38. 5. Copier Powders U sed to store hard copies of the output of computers. This is a case where the only attribute to the carrier powder in xerographic copiers is that it be magnetic. 6. Bubble Memories Developed using thin ceramic magnetic films on which small regions of reverse single domains could be generated, stored and later read by noting their presence or absence in a designated area.

39. MISCELLANEOUS APPLICATIONS These applications includes: 1 . Magnetic transducers-magnetostrictive 2. Delay lines 3. Reed Switches 4. Electrodes 5. Sensors 6. Ferrofluids 7. Anechoic Chamber Tiles

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