Understanding Peak Supply Voltage
Peak voltage is the highest point of an AC waveform. Power supply designers use it to choose rectifiers, capacitors, regulators, and safe test limits. A transformer label usually gives RMS voltage. A sine wave peak is higher than that value. The common multiplier is square root of two. Other waveforms use different crest factors.
Why Rectifier Loss Matters
A rectifier does not pass the full peak. Silicon diodes drop voltage while conducting. A bridge rectifier usually has two conducting diodes. A center tapped supply usually has one conducting diode. Schottky parts drop less voltage. High current rectifiers may drop more. This calculator lets you enter the actual drop, so the estimate matches your selected parts.
Ripple and Filter Capacitors
A reservoir capacitor charges near the waveform peak. The load then discharges it between charging pulses. The ripple estimate uses load current, capacitance, and ripple frequency. Full wave rectifiers charge twice each mains cycle. Half wave rectifiers charge once per cycle. More capacitance lowers ripple. More load current raises ripple. The tool estimates peak, average DC, and minimum capacitor voltage.
Line Tolerance and Regulation
Real supplies rarely run at the exact label value. Utility voltage can be high or low. Small transformers also rise at light load. The regulation field adds a no load rise. This is useful when checking capacitor voltage rating. Always size capacitors above the highest expected peak. Add a margin for heat, aging, and meter error.
Practical Design Notes
Use measured values for final work. Transformer ratings change with load. Diode drops change with current and temperature. Ripple formulas are simplified. They are still helpful for planning. They show whether a design is near a safe range. For sensitive circuits, follow the calculator with bench measurements. Check regulator input limits before connecting a board. Also check diode peak inverse voltage. A low PIV rating can fail during reverse stress.
Safe Use
Discharge capacitors before touching a circuit. Use insulated probes. Work with one hand where possible. High peak voltage can remain after power is removed. Treat every supply as charged until verified. Record the result, date, parts, and assumptions for later service notes. Repeat the check carefully after any transformer or load change.