In this type of Half wave rectifier , ofter a transformer is used to couple the ac input voltage from the source to the rectifier, as shown in the diagram. Transformer coupling provides two advantages. First, it allows the source voltage to be stepped up or stepped down as needed. Second, the ac source is electrically isolated from the rectifier, thus preventing a shock hazard in the secondry circuit.
Circuit Detail:↑Half Wave Rectifier with Transformer Coupled Input Voltage
As we know that the secondary voltage of a transformer equals the turns ratio, n, times the primary voltage, as expressed in Equation. We will be fine the turns ratio as the ratio of secondary turns, Nsec, to the primary turns, Npri
n= Nsec / Npri