Rectified DC Voltage Calculator

Calculator

Rectifier type

AC input voltage

Input voltage type

Line frequency, Hz

Diode forward drop, V

Conducting diodes in path

Load current

Current unit

Load resistance, ohms

Filter capacitance

Capacitance unit

Series resistance, ohms

Transformer regulation or sag, %

Decimal places

Example Data Table

Rectifier	AC input	Frequency	Diodes	Load	Capacitor	Expected use
Bridge	24 V RMS	50 Hz	2 at 0.7 V	1 A	2200 uF	Control supply
Half wave	12 V RMS	60 Hz	1 at 0.7 V	0.2 A	1000 uF	Simple relay
Three phase bridge	208 V RMS	60 Hz	2 at 1 V	5 A	4700 uF	DC bus estimate

Formula Used

Peak voltage: Vpeak = Vrms x sqrt(2). For peak to peak input, Vpeak = Vpp / 2.

Loaded peak: Vpeak loaded = Vpeak x (1 - regulation percent / 100).

Diode loss: Vdiode total = diode forward drop x conducting diodes.

Half wave average: Vdc = Vpeak / pi - diode loss - series loss.

Full wave or bridge average: Vdc = 2 x Vpeak / pi - diode loss - series loss.

Three phase half wave: Vdc = 1.17 x phase RMS voltage - losses.

Three phase bridge: Vdc = 1.35 x line RMS voltage - losses.

Capacitor ripple: Vripple = Iload / (ripple frequency x capacitance).

Filtered average: Vdc filtered = (Vmax + Vmin) / 2.

How to Use This Calculator

Select the rectifier circuit used in your supply.
Enter the AC input voltage and choose its type.
Add line frequency, diode drop, and conducting diode count.
Enter load current. Or enter load resistance and set current to zero.
Add filter capacitance if a smoothing capacitor is used.
Enter transformer sag and series resistance for a loaded estimate.
Press Calculate to view DC voltage, ripple, and power.
Use CSV or PDF buttons to save the result.

Why Rectified DC Voltage Matters

Rectified DC is the average output created when an AC waveform passes through diodes. It appears in chargers, supplies, motor drives, relays, amplifiers, and control panels. A good estimate helps you select parts before building a circuit. It also helps you judge transformer size, capacitor rating, diode heating, and load behavior. This calculator joins those checks in one place. It covers half wave, full wave, bridge, and three phase rectifier styles. It also compares unfiltered average voltage with filtered capacitor output. For advanced checks, record worst case values. Try low line input, high diode drop, and maximum current. The weakest result shows the needed design margin before purchase, assembly, installation, service, and final testing.

What Changes the Output

The first factor is the incoming AC value. RMS, peak, and peak to peak entries describe the same waveform in different ways. The calculator converts them to peak voltage. The next factor is the diode path. A bridge usually has two conducting diodes at one time. A center tapped full wave stage often has one. Each diode subtracts forward voltage. Load current then creates ripple when a capacitor is used. Higher current increases ripple. Larger capacitance reduces ripple. Higher ripple frequency also reduces ripple.

Using Results Safely

The estimated DC value is not always the exact bench value. Real transformers sag under load. Diodes heat up. Capacitors have tolerance, leakage, and equivalent series resistance. The mains voltage may rise or fall. Use margin when selecting voltage ratings. A capacitor should normally be rated above the highest no load peak. A diode should handle surge current and reverse voltage. A regulator also needs enough headroom after ripple. Use the minimum voltage line for that check.

Practical Design Notes

Unfiltered rectifiers suit heaters, lamps, simple relays, and some motor loads. Filtered outputs suit logic, audio, sensors, and control circuits. A larger capacitor makes voltage smoother, but it raises diode surge current. It can also stress a transformer. A smaller capacitor lowers stress, but it may allow hum or resets. Choose a balanced value. Then test the supply with the real load. Measure AC input, DC output, ripple, diode temperature, and transformer temperature. The calculator gives a strong starting point.

FAQs

What is rectified DC voltage?

It is the DC output produced after AC passes through rectifier diodes. The value depends on waveform type, peak voltage, diode drop, load current, and filtering.

Why is bridge output lower than peak voltage?

A bridge rectifier normally has two conducting diodes. Their forward drops reduce the capacitor charging peak and the usable DC output.

What does ripple voltage mean?

Ripple is the repeated rise and fall of filtered DC voltage. It happens because the capacitor discharges into the load between charging peaks.

How does capacitance affect output?

Higher capacitance reduces ripple and raises the minimum DC voltage. It can also increase diode surge current during startup and charging peaks.

Which diode count should I enter?

Use one for half wave and center tapped full wave circuits. Use two for most bridge rectifiers and three phase bridge conduction paths.

Can this calculator size a regulator input?

Yes, use the filtered minimum DC value. It should stay above the regulator dropout voltage plus the required regulated output.

Why include transformer regulation?

Transformer voltage drops under load. Regulation or sag gives a more realistic loaded peak voltage and avoids an optimistic DC estimate.

Is this result exact for every supply?

No. Real supplies include diode temperature, capacitor ESR, transformer impedance, wiring loss, and line variation. Use the result as a design estimate.