Dc chhopers

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Dc chhopers

  1. 1. A PRESENTATION ONCHOPPERS Submitted By
  2. 2. CONTENTSIntroductionStep down chopperStep up chopperClassification of choppersApplicationsReferences
  3. 3. Introduction The conversion of fixed DC voltage to an adjustable DC output voltage, through the use of semiconductor devices is called chopping. A chopper is a static device that converts fixed dc input voltage to a variable dc output voltage directly. It is a high speed on/off semiconductor switch . Chopper systems offer smooth control, high efficiency, fast response and regeneration
  4. 4. DEFINATION:Converting the unregulated DC input to a controlledDC output with a desired voltage level.• It is also known as dc-to-dc converter or DC Chopper
  5. 5. DC supply(from rectifier- DC output LOAD filter, battery, fuel cell etc.) Vcontrol (derived from feedback circuit)
  6. 6. Choppers are of Two Types :1. Step-down choppers. (buck converter)2. Step-up choppers. (boost converter ) In step down chopper output voltage is less than input voltage. In step up chopper output voltage is more than input voltage.
  7. 7. Principle Of Step-down Chopper : Chopper i0 + V R V0 A step-down chopper with resistive load.
  8. 8. • The thyristor in the circuit acts as a switch.• When thyristor is ON, supply voltage appears across the load• When thyristor is OFF, the voltage across the load will be zero.
  9. 9. The average output voltage can be found by :Average Output Voltage tON Vdc V tON tOFF tON Vdc V V .d T tONbut d duty cycle t
  10. 10. Principle Of Step-up Chopper : Chopper i0 + R V V0 D L E A step-up chopper with R-L Load
  11. 11. • When chopper is ON, supply is connected across load.• Current flows from supply to load.• When chopper is OFF, load current continues to flow in the same direction through Diode due to energy stored in inductor ‘L’.
  12. 12. Therefore voltage across load is given by : dIVO V L i.e., VO V dt We clearly see that the output voltage is greater than the input voltage.
  13. 13. Classification Of Choppers• Choppers are classified as : • Class A Chopper • Class B Chopper • Class C Chopper • Class D Chopper • Class E Chopper
  14. 14. Widely used in DC motor . For Speed Controller In Switched mode power supply (SMPS)Battery chargersAlso used in regenerative braking. Class D Electronic amplifiers Switched capacitor filters Variable Frequency Drive
  15. 15. References• Google• Wikipedia• encon.fke.utm.my/notes/MSc-Chopper.pdf• www.scribd.com/doc/24544535/DC-Choppers

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