Power Supply Calculator
The numbers behind a linear DC supply: transformer turns ratio, rectifier output voltage, filter-capacitor sizing for a target ripple, percent regulation, and efficiency. Pairs with the Rectifier Lab visualizer in the Circuits Lab. For the theory behind each formula, see the Study guide.
Transformer Turns Ratio
The turns ratio sets how the transformer steps voltage up or down. Current steps the opposite way.
Rectifier Output Voltage
From the transformer's secondary RMS voltage, this finds the peak, the resulting DC and the diode peak inverse voltage (PIV). Choose the rectifier type; diode drops are included (0.7 V silicon). For a center-tapped transformer enter the voltage of each half of the secondary: a "24 V CT" transformer is 12 V per half.
Filter Capacitor Sizing
A reservoir capacitor smooths rectified DC. Bigger cap and higher ripple frequency mean less ripple. Full-wave/bridge ripple is at twice the line frequency.
Ripple From a Given Capacitor
The reverse: if you already have a capacitor value, how much ripple will you get at a given load?
Percent Voltage Regulation
How much the output sags from no-load to full-load. Lower is better — a stiff (well-regulated) supply has a low percentage.
Power Supply Efficiency
The fraction of input power delivered to the load. Linear supplies are typically 40–60%; switching supplies 80–95%.