How to Calculate Bridge Rectifier Voltage

By Alexander Rudinski

A bridge rectifier is a one-way device made from diodes that effectively converts AC voltage to DC voltage. Because no electronic design is ideal, the voltage across the circuit changes during this transformation process and depends on the design of the rectifier and the variables related to the AC power source connected to it. In many designs, you will need a bridge rectifier to output a certain voltage level in order to properly power the circuit. Determining this voltage requires isolating a few variables and performing a simple calculation.

Determine the total resistance of the circuit. This resistance is measured before the resistive load that the circuit powers. It is called a resistive load because it can be modeled as a resistor, having a resistor-like impact on voltage levels and current measurements.

Determine the total current of the circuit. The current can be measured at the output of the secondary transformer coil and is usually available on the data sheet for the transformer. This value is measured in amperes, or amps.

Multiply the current value, I, by the resistance value, R.

Multiply the resulting number by 150%. This figure accounts for aging of the rectifier stacks.

Use the resulting number as the output voltage of your full-wave bridge rectifier circuit.