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Teilenummer | ECO7213 |
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Beschreibung | Design of HF Wideband Power Transformers | |
Hersteller | Philips | |
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Gesamt 10 Seiten APPLICATION NOTE
Design of H.F. Wideband Power
Transformers; Part II
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Philips Semiconductors
Design of H.F. Wideband Power Transformers; Part II
ECO7213
At the secondary side the correction components become:
C2 = n2 × C1 and L2 = Ln----12-
In general L2 is so small that the tracks on the p.c. board can perform this function.
6 A PRACTICAL EXAMPLE
For a low voltage S.S.B. amplifier a transformer was required with the following specification:
Frequency range: 1.6 − 28 MHz
Power handling: 52 W
Load impedance: 100 Ω
Input impedance: 4.6 Ω
The most suitable Ferroxcube material for this frequency range is 4C6. From the power handling point of view a toroid
core will be chosen with the dimensions: 23 × 14 × 7 mm3, catalog nr. 4322 020 91070. The parallel reactance at
1.6 MHz measured at the secondary side must be +j400 Ω (see Ref. 1), corresponding with an inductance of 40 µH. The
required number of turns is then:
nsec = -µ---o----×-L----µ-×---r--l-×-----A--
in which A--l- = 0.5525 mm for this core and µr = 120 for 4C6 material, so:
nsec = 21.9
A logical choice would be nsec = 22. The voltage transformation ratio is
turns must be: 4---2-.--62---6-- = 4.7
We choose: npr = 5.
1-4---0-.-6-0-- = 4.66 , by which the primary number of
The required transformation ratio can be approached better if the secondary number of turns is modified from 22 to 23.
Now the secondary parallel inductance becomes 44 µH and the impedance transformation ratio
2--5--3--
2
=
21.1
by which
the input impedance will be 4.74 Ω being appr. 3% higher than the required value.
L.F. compensation of the parallel inductance can be carried out by means of a single capacitor in series with the
secondary (see Ref. 1):
CL = L-R---p--s2-s-e-e--cc- = 4----4---1--×-0---0-1---20---–---6- = 4400 pF
A standard value of 4700 pF has been chosen.
The maximum voltage across the secondary winding is: Vsec = 2Rsec × P = 2 × 100 × 52 = 102 V
Now the maximum flux density can be calculated:
1998 Mar 23
6
6 Page | ||
Seiten | Gesamt 10 Seiten | |
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Teilenummer | Beschreibung | Hersteller |
ECO7213 | Design of HF Wideband Power Transformers | Philips |
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