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Flyback Transformer Power Supply Design Calculator

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Flyback Transformer Power Supply Design Calculator
Main Switching Parameters
kHz
V
V
%
V
µH
V
Output Winding 1
V
A
Optional Secondary Windings
V
A
V
A
V
A
Please enter valid values. Frequency, efficiency, AL, input voltage and output 1 values must be greater than zero.
RESULTS
Switching Period T
Output Power P1
Output Power P2
Output Power P3
Output Power P4
Input Power Pin
Primary to Secondary 1 Ratio
Charge Period Tch
Discharge Period Tdis
Dead Time Tdt
Primary Inductance
Primary Turns Np
Secondary Turns Ns1
Secondary Turns Ns2
Secondary Turns Ns3
Secondary Turns Ns4
Peak Primary Current
Primary RMS Current
Primary Wire Diameter
Primary Wire Gauge

Input Parameters Specification

Frequency and PeriodSwitching frequency in kHz is converted to Hz, then period is calculated in microseconds.
Voltage ParametersInput voltage, diode drop, transistor drop and maximum VDS define turns ratio and flyback stress margin.
Core AL ValueAL in µH per turns squared is used to estimate required primary turns from primary inductance.
Output WindingsUp to four output voltage and current pairs can be included for total flyback output power.

Practical Operational Examples

Single Output Flyback

Use Vo1 and Io1 for one isolated output. Leave optional outputs as 0 if unused.

Multi Output Supply

Add Vo2 to Vo4 and Io2 to Io4 when designing auxiliary or multiple isolated secondary windings.

Diagrams & Theory

A flyback converter stores energy in the transformer primary during switch on-time, then transfers energy to the secondary side through the diode when the switch turns off.

Vs Np SW Ns D C Vo

Formulas & Mathematical Logic

Output power: Po = (Vo + Vd) × Io
Input power: Pin = total output power / efficiency
Original turns ratio: Nps1 = (Vdsmax × 0.8 - Vin) / (Vo2 + Vd)
Dead time: Tdt = T × 0.2
Charge time: Tch = (Vo1 + Vd) × Nps1 × (T - Tdt) / ((Vin - Vtran) + (Vo1 + Vd) × Nps1)
Primary inductance: L = ((Vin × Tch) × (Vin × Tch)) / (2.5 × T × Pin)
Primary turns: Np = sqrt(L / AL)
Primary current: Ip = Vin × Tch / L

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About this tool

Flyback Transformer Power Supply Design Calculator is a free online calculator tool. Use it to get instant, accurate results for your electronics calculations.