A controlled full-wave rectifier is a type of rectifier circuit that converts AC power (alternative current) into DC power (direct current) by utilizing both halves of the AC waveform. It is called a "controlled" rectifier because it uses an external control signal to regulate the output DC voltage or current.
There are several types of controlled full-wave rectifiers, including phase-controlled rectifiers and pulse-width modulated rectifiers.
Phase-controlled rectifiers use the SCR thyristor as the control element, and the output DC voltage can be varied by adjusting the firing angle of the control element. The firing angle is the point in the AC waveform at which the control element begins to conduct, and it determines the amount of the AC waveform that is utilized.
Pulse-width modulated rectifiers use an electronic switch (such as a transistor or a MOSFET) as the control element, and the output DC voltage is varied by modulating the width of the pulses applied to the control element.
Controlled full-wave rectifiers have some advantages over uncontrolled rectifiers. They have the ability to regulate the output DC voltage or current, which can be useful in applications where a stable DC power supply is required.
As the uncontrolled full wave rectifier there are two main types of controlled full-wave rectifiers: center-tapped (use a transformer and two SCR switchs) and bridge rectifiers (uses four SCR switchs) as shown in Figure (1).
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Figure (1) Bridge and Center-Tapped Controlled FWR |
The circuit work as follow :
In the Bridge Rectifier shown in Figure (1) Switchs pair S1,2 conduct in the positive half cycle but after a trigger signal is applied to its gates at a firing angle 𝛼. and Switchs pair S3,4 conduct in the negative half cycle after a trigger signal is applied to its gates at a firing angle (𝜋+𝛼). so that the load current never changes its direction (up to down in the figure). (nor the load voltage polarity).
In the center tapped transformer circuit shown in Figure (1), diode S1 conducts in the positive half cycle but after a trigger signal is applied to its gates at a firing angle 𝛼 and S2 conducts in the negative half cycle after a trigger signal is applied to its gates at a firing angle (𝜋+𝛼). so that the load current never changes its direction (right to left in the figure). (nor the load voltage polarity).
