When a single rectifier unit is placed in series with an ac supply,as illustrated in fig,it converts alternating voltage into unidirectional pulsing voltage,using one half cycles of the applied voltage,the other half cycles being suppressed because it conducts only in one direction.Unless there is an inductance or battery in the circuit,the current will be zero,therefore,for half the time. This is called half-wave rectification.
Diode is an electronic device consisting of two elements known as cathode and anode.since in a diode electrons can flow in one direction only i.e., from cathode to anode so the diode provides the unilateral conduction necessary for rectification.This is true for diodes of all types-vacuum,gas--filled,crystal,semiconductor or metallic(copper oxide and selenium types) diodes. semiconductor diodes,because of their inherent advantages are usually used as a rectifying device.However, for very high voltage, vacuum diode may be employed.
circuit: The half wave rectifier circuit using a semiconductor diode with a load resistance RL but no smoothing filter is given in fig. The diode is connected in series with the secondary of the transformer and the load resistance RL, the primary of the transformer is being connected to the ac supply mains.
Working : The ac voltage across the secondary winding changes polarity every half cycle. During the positive half cycles of the input ac voltage i.e., when upper end of the secondary winding is positive w.r.t its lower end,the diode is forward biased and, therefore,conducts current.if the forward resistance of the diode is assumed to be zero (in practice,however,a small resistance exist) the input voltage during the positive half cycles is directly applied to the load resistance RL, marking its upper end positive w.r.t its lower end. The wave forms of the output current and output voltage are of the same shape as that of the input ac voltage.
During the negative half cycles of the input ac voltage i.e., when the lower end of the secondary winding is positive w.r.t. its upper end, the diode is reverse biased and so does not conduct.Thus during the negative half cycles of the input ac voltage the current through and voltage across the load remains zero if the reverse current, being very small in magnitude,is neglected.Thus for the negative half cycle no power is delivered to the load.
Thus the output voltage developed across load resistance RL(VL) is a series of positive half cycles of alternating voltage,with intervening very small constant negative voltage levels, as shown in fig.It is obvious from the figure that the output is not a steady dc, but only a pulsating dc wave.since only half cycle of the input wave are used,it is called a half wave rectifier.
Diode is an electronic device consisting of two elements known as cathode and anode.since in a diode electrons can flow in one direction only i.e., from cathode to anode so the diode provides the unilateral conduction necessary for rectification.This is true for diodes of all types-vacuum,gas--filled,crystal,semiconductor or metallic(copper oxide and selenium types) diodes. semiconductor diodes,because of their inherent advantages are usually used as a rectifying device.However, for very high voltage, vacuum diode may be employed.
circuit: The half wave rectifier circuit using a semiconductor diode with a load resistance RL but no smoothing filter is given in fig. The diode is connected in series with the secondary of the transformer and the load resistance RL, the primary of the transformer is being connected to the ac supply mains.
Working : The ac voltage across the secondary winding changes polarity every half cycle. During the positive half cycles of the input ac voltage i.e., when upper end of the secondary winding is positive w.r.t its lower end,the diode is forward biased and, therefore,conducts current.if the forward resistance of the diode is assumed to be zero (in practice,however,a small resistance exist) the input voltage during the positive half cycles is directly applied to the load resistance RL, marking its upper end positive w.r.t its lower end. The wave forms of the output current and output voltage are of the same shape as that of the input ac voltage.
During the negative half cycles of the input ac voltage i.e., when the lower end of the secondary winding is positive w.r.t. its upper end, the diode is reverse biased and so does not conduct.Thus during the negative half cycles of the input ac voltage the current through and voltage across the load remains zero if the reverse current, being very small in magnitude,is neglected.Thus for the negative half cycle no power is delivered to the load.
Thus the output voltage developed across load resistance RL(VL) is a series of positive half cycles of alternating voltage,with intervening very small constant negative voltage levels, as shown in fig.It is obvious from the figure that the output is not a steady dc, but only a pulsating dc wave.since only half cycle of the input wave are used,it is called a half wave rectifier.
No comments:
Post a Comment