Difference between Active and Passive rectification

Active rectification and passive rectification are two methods of converting alternating current (AC) into direct current (DC).
Passive rectification uses diodes to convert AC to DC. In a simple rectifier circuit, a diode is placed in series with the load, allowing current to flow in only one direction. This causes the negative half-cycle of the AC wave to be blocked, resulting in a pulsating DC waveform. While this method is simple and inexpensive, it is less efficient as it wastes half of the AC power.

Active rectification, on the other hand, uses active devices such as transistors or thyristors to rectify AC to DC. Active rectification can be implemented in two ways: synchronous rectification and active clamp rectification.
Synchronous rectification uses a pair of MOSFETs or other active devices to switch the current flow direction. By using a control signal to synchronize the switching of the devices with the AC waveform, the negative half-cycle of the AC wave can be utilized, resulting in a higher efficiency compared to passive rectification.
Active clamp rectification uses an additional active device to clamp the voltage across the main rectifier to a fixed level. This allows the main rectifier to operate more efficiently as it is no longer required to withstand high-voltage transients.
Overall, active rectification is more efficient than passive rectification but is more complex and costly to implement.