Compare SCR and Asymmetrical SCR ( ASCR )

SCR 

• It has thousand of volts reverse blocking capacity. 
• However it may not requires in some applications particular in the inverter. 
• The flywheel diode is connected in anti parallel with load in order to conduct inductive load. 
• The peak repetitive voltage rating of the SCR is higher than the ASCR.
• The on state voltage drop and turn off time of the SCR is higher than the ASCR.

Asymmetrical SCR

• The reverse blocking capacity of the ASCR is very low. 
• It is in the order of 20  to 30 V. 
• The ASCR is useful where very low reverse blocking capacity requires.
• The forward blocking capacity of the ASCR is very high typically 400 to 2000 V. 
• The forward and reverse blocking capacity of the ASCR are not equal.
• There is additional N₂⁺ layer added in the ASCR therefore N₂ ^–  become narrow. 
• The N₂⁺ layer is acts as Electrical field stopper. The P₂N₂⁺ junction avalanches at very low voltage therefore the ASCR does any usable peak repetitive voltage rating ( V_RRM ).  
• The ASCR has faster turn off time and reduction in ON state voltage is achieved by sacrificing reverse voltage blocking capacity.
• If the gold doping is same as that of conventional SCR, the on state voltage drop is reduced but turn off time is unaltered. 
• It should be noted that the on state voltage drop and turn off time of the ASCR is adjusted by suitable doping level of N₂ ^–.

You may also like :

Compare Power Transformer and Distribution Transformer

Compare Squirrel cage IM and Slip Ring IM

Compare Transistor and MOSFET

Compare Voltage Amplifier and Power Amplifier

Compare Transistor and SCR