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DC-DC Converters (choppers)

DC-DC Converters (choppers). The objective is to convert a fixed DC voltage to a variable DC voltage It is possible to step up and step down voltage. Voltage step down (buck converter). First, suppose L=0, E=0. The diode is not needed. V a =(t on /T)V s . k=t on /T is the duty cycle.

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DC-DC Converters (choppers)

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  1. DC-DC Converters (choppers) • The objective is to convert a fixed DC voltage to a variable DC voltage • It is possible to step up and step down voltage.

  2. Voltage step down (buck converter) First, suppose L=0, E=0. The diode is not needed. Va=(ton/T)Vs k=ton/T is the duty cycle VRMS=k1/2Vs Pout=(kVs2)/R

  3. Step down converter with RL load

  4. Pspice schematics Step down dc-dc converter

  5. Voltage step up (boost) converter “On” mode: VL=L(di/dt) “Off” mode: Assume current decreases at a constant rate. Then Vo=Vs+VL To ensure continuous current flow, a capacitor is included.

  6. Performance of a step up converter with resistive load (C=0).

  7. DC-DC Converter classification • First quadrant converter • Second quadrant converter • 1st and 2nd quadrant converter • 3rd and 4th quadrant converter • Four quadrant converter

  8. Second Quadrant Converter

  9. 1-2 and 3-4 quadrant converters 1st quad: S1, D4 2nd quad: S4, D1 3rd quad: S3, D2 4th quad: S2, D3 Polarity of the load EMF is reversed.

  10. Four quadrant converter

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