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Solid State Devices I

Solid State Devices I. Benchmark Companies Inc PO Box 473768 Aurora CO 80047. Transformers. Objectives: Definition of Transformer Uses of a Transformer Step-Up Step-Down Isolator. Back. Transformers. Back. Transformers. Symbol. Primary. :. Secondary. N P. :. N S.

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Solid State Devices I

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  1. Solid State Devices I Benchmark Companies Inc PO Box 473768 Aurora CO 80047

  2. Transformers • Objectives: • Definition of Transformer • Uses of a Transformer • Step-Up • Step-Down • Isolator Back

  3. Transformers Back

  4. Transformers Symbol Primary : Secondary NP : NS A transformer typically has two separate windings with a Varying number of turns (N). They are the primary winding And Secondary winding Back

  5. Transformers Symbol Primary : Secondary NP : NS The two lines in the center of the two coils indicate this Transformer has a core. (No lines indicates no core) Back

  6. Transformers Symbol Primary : Secondary NP : NS There is another type of transformer called a center-tap transformer (photo). It has many uses in today’s electronics Back

  7. Transformers Symbol Primary : Secondary NP : NS The benefit of center-tap transformers is the availability of several voltage levels on the secondary winding. Back

  8. Transformers Virtually every electronic devices which uses AC has to convert the power to a usable level. Back

  9. Transformers Symbol Primary : Secondary A transformer is a typically a pair of coils where ones magnetic field acts on the other Back

  10. Transformers Symbol Primary : Secondary The flow of current through the primary causes current to flow in the opposite direction in the secondary. Back

  11. Transformers Symbol Primary : Secondary The direction of current is designated by dots on either end of the windings. Back

  12. Transformers Symbol Primary : Secondary NP : NS RECALL current flows through the primary winding, a magnetic field is produced that causes a current to flow through the secondary winding. Back

  13. Transformers Symbol Primary : Secondary NP : NS The current flowing through the primary winding causes the current to flow in an opposite direction through the secondary. Back

  14. Transformers Symbol Primary : Secondary NP : NS The current direction is indicated by the dots on each coil. Having the dot on the same end tells us the output is in phase. Back

  15. Transformers Symbol Primary : Secondary NP : NS Output Voltage is directly proportional to the number of Turns in the secondary winding (Ns) with respect to the Primary windings(Np). This is called the Turns Ratio. Back

  16. Transformers Symbol Primary : Secondary NP : NS The relationship is defined as follows: Ep/Es = Np/Ns Back

  17. Transformers NP : NS Example: Primary winding has 20 turns and the Secondary Winding has 40 turns. The result is the input voltage is Increased by a factor of 2 . 10/V(out) = 20/40 >> 400/20 = V(out) = 20 volts. This is a Step-up Transformer Back

  18. Transformers NP : NS Likewise, if a Primary winding has 40 turns and the Secondary Winding has 20 turns. The result is the input voltage is decreased by ½. 10/V(out) = 40/20 >> 200/40 = V(out) = 5 volts. This is a Step-down Transformer Back

  19. Transformers NP : NS Sometimes, there is a need to isolate voltage source from the Circuit. This can be done by using a transformer with a 1:1 Turns ratio Back

  20. Transformers NP : NS You should understand that there is no net power loss In an ideal transformer. That means that: Power (primary) = Power (secondary) Ip*Ep = Is*Es Back

  21. Transformers Current (in) Current (out) Voltage (out) Voltage (in) NP : NS Moving Ip and Is to one side of the equal sign and Ep and Es to the other yields: Ip/Is = Es/Ep (Inversely Proportional) Back

  22. Transformers NP : NS Transformers and the secondary circuit have a loading Effect on the source voltage that is proportional to the Turns ratio Np/Ns x R1 = RL Back

  23. Transformers NP : NS Example: Primary winding has 20 turns and the Secondary Winding has 40 turns. If R1 = 10KOhms the Load Resistance (RL) = (20/40)x10k = 5kOhms. Note the difference in expected current needed to drive the circuit. Back

  24. Transformers Summary on Transformers Formulas: Vin/Vout = Np/Ns Iin/Iout = Ns/Np Pin = Pout Np/Ns x R1 = RL The Formulas above of are based on the assumption that The transformer is ideal and no power loss occurs in the Transformer. Back

  25. Transformer TransformersSummary Transformers take a waveform and scale the waveform according to the turns ratio of the primary coil with respect to the secondary coil. If the turns ratio is greater than 1 the waveform is increased, if the ratio is less than one, the waveform is decreased. Scaled Waveform Sine wave input Back

  26. End of Presentation Back

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