1 MHz Power Transformer

West Coast Magnetics' 401 series high frequency transformers are intended for use in switch mode power supplies including push/pull, flyback, and forward converter circuits. Output power as high as 7 watts can be achieved in push/pull circuits. All sizes are based on low profile ER core geometry and all sizes are offered in surface mount packaging. West Coast Magnetics stocks core material which will accommodate a range of operating frequencies from 10 kHz to 3 MHz.

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Design Constants

Size Code	Al frequency > 500 kHz a.	Al frequency ≤500 kHz a.	Al single gap	Al double gap	Ae core area (mm²)	le magnetic path length (mm)	Ve core volume (mm³)	Wa bobbin winding area (mm^2⁾	WaAc core area x winding area (mm⁴)	Bobbin window width (mm)	Bobbin window height (mm)	Mean length per turn (mm)
ER 9.5	525	950	70	135	8.6	14.0	120	3.1	26.7	2.15	1.43	18
ER 11	725	1400	70	135	11.7	14.6	170	3.3	38.6	2.00	1.65	22
ER 14.5	---	1600	70	135	17.6	19.0	330	5.5	96.8	2.00	2.75	27

output frequency

Output Power vs Frequency of Operation (Watts)

Size Code	50kHz	100kHz	250kHz	500kHz	1000kHz	2000kHz	3000kHz
ER 9.5	0.9	1.3	2.0	2.3	3.5	2.8	2.3
ER 11	1.3	1.8	2.8	3.1	4.8	3.9	3.2
ER 14.5	2.8	3.9	6.1	6.9	---- not available ----

Power Curve Assumptions:

Push/Pull circuit topology
Bobbin Window area utilization = 40%
Flux density (B) chosen so that core losses at all frequencies are 100 mW/cm³.
a. Al measured for ungapped cores. nH/T² ± 25%

schematics

ER 9.5	ER 11 & ER 14.5
click image to enlarge	click image to enlarge

Size/Code	A	B	C	D	E	F	I	J	K	L
ER 9.5	.457/11.6	.319/8.1	.395/10.0	.028/0.7	.240/6.1	.004/0.1	.079/2.0	.079/2.0	.535/13.6	.051/1.3
ER 11	.480/12.2	.362/9.2	.460/11.7	028/0.7	.240/6.1	.004/0.1	.079/2.0	.079/2.0	.559/14.2	.051/1.3
ER 14.5	.630/16.0	.472/12.0	.600/15.2	028/0.7	.295/7.5	.004/0.1	.079/2.0	.098/2.5	.708/18.0	.051/1.3

Note: All materials of construction minimum Class B 130 degrees C rated.

Dimensions: Inches/mm

notes

Notes:

Reduce power rating in Table above by 50% for forward and flyback converter topologies.
Final sizing of the transformer will depend on a number of interrelated variables. The data in the above table should be considered a starting point only.
If safety agency is required, the final size may be significantly larger than the data in the table would indicate.
High frequency material (>500kHz) is available in ER 9.5 andER 11 sizes only.