CHAPTER 4: Half Wave Rectifiers AC - DC Conversion
AC to DC CONVERSION (RECTIFIER) 1. Single-phase, half wave rectifier a) Uncontrolled : R load, R-L load b) Controlled : R load, R-L load c) Free wheeling diode 2. Single-phase, full wave rectifier a) Uncontrolled: R load, R-L load b) Controlled : R load, R-L load c) Continuous & discontinuous current mode
RECTIFIERS : INTRODUCTION A rectifier converts AC to DC signal. DEFINITION: Converting AC (from mains or other AC source) to DC power by using power diodes or by controlling the firing angles of thyristors / controllable switches. The purpose of a rectifier may be: • to produce an output that is purely dc • to produce a voltage/current waveform that has a specified dc component. half wave rectifier normally used in low applications only.
Uncontrolled Half - Wave Rectifier Circuit with R-LOAD
ncontrolled Half-Wave Rectifier with Resistive Load + v d - i s D1 • During the positive half-cycle of input voltage, D1 conducts and the input voltage appears across the load. • During the negative half - cycle of the input voltage, D1 is in a blocking condition and the output voltage is zero • The current produces a voltage across the load, which has the same shape as the positive half-cycle the input voltage. • Positive half cycle ⇒ diode is on • Negative half-cycle ⇒ diode is of
v (t ) = V V i ( t ) = p p sin( ωt ) sin( ωt ) R V I in D , ak I ( t ) Dak I out I V D , ak I ( t ) Dak I out in V ( t ) R V V ( t ) R V in out in out t= 0 ⇒ π t= π⇒ 2 π
controlled Half-Wave Rectifier with Resistive Load …cont. The average value of the output (load) voltage, V dc or V o or V avg is determined by finding the area under the curve over a full cycle. (4.0) (4.1)
controlled Half-Wave Rectifier with Resistive Load …cont. e dc component of the current for the purely resistive load is (4.2) The root-mean-square (rms) value of the output voltage, V rms (4.3) The rms value of the output current, I rms verage power absorbed by the resistor can be computed from ? ? ?? = ? ? 2 ?
Uncontrolled Half - Wave Rectifier Circuit with RL-LOAD
RESISTIVE-INDUCTIVE LOAD As the source voltage is positive in the circuit, the diode will be forward biased. After the diode turns off (reverse biased), the current continue to flow because of the energy storage into the inductor, which force the diode to turn on again and continue to be on until the current becomes zero. The Kirchhoff voltage law equation that describes the current in the circuit in this case is
The solution can be obtained by expressing the current as the sum of the forced response and the natural response. The forced response for this circuit is the current that exists after the natural response has decayed to zero.
Where τ is time constant L/R and A is a constant that is determined from the initial condition (A is the current value at t=0).
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- Fall '18
- Rashid Baloch