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Formulas used to calculate electrical characteristics
Connecting windings in series:
- Inductance = Inductancetable × (number of windings)2
- DCR = DCRtable × number of windings
- Isat = (Isattable × 6) ÷ number of windings connected in series
- Irms = Irmstable
Connecting windings in parallel:
- Inductance = Inductancetable
- DCR = 1 ÷ [number of windings × (1 ÷ DCRtable)]
- Isat = (Isattable × 6) ÷ number of windings connected in series
- Irms = Irmstable × number of windings
Create a 13 Watt 2:1:1 flyback transformer with a bias winding
Choose HPH3-0138L
Vin = 36 – 57 Vdc; Vout = 12 V, 1.1 A
| Part number |
Inductance (µH) |
Percent Tolerance |
DCR max (Ω) |
Volt-time product (V-µs) |
Peak energy storage (µJ) |
Isat (A) |
Irms (A) |
| HPH3-0138L |
23.6 |
20 |
0.125 |
43.9 |
1.457 |
0.42 |
1.13 |
Connecting primary windings in series:
When primary windings (W
pri) are connected in series, inductance increases, energy storage and Irms remain the same, but DCR increases and Isat decreases.
Example: For HPH3-0138L, connect two primary windings in series:
- Inductance = Inductancetable × Wpri2 = 23.6 × 22 = 94.4 μH
- DCR = DCRtable × Wpri = 0.125 × 2 = 0.25 Ohms
- Isat = (Isattable × 6) ÷ Wpri = (0.42 × 6) ÷ 2 = 1.26 A
- Irms = Irmstable) = 1.13
Connecting secondary windings in parallel:
When secondary windings (W
sec) are connected in parallel, DCR decreases and Irms increases.
Example: For HPH3-0083L, connect two secondary windings in parallel:
- DCR = 1 ÷ [Wsec × (1 ÷ DCRtable)] = 1 ÷ [(2 × (1 ÷ 0.125)] = 0.0625 Ohms
- Irms = Irmstable × Wsec = 1.13 × 2 = 2.26 A