P6142
APPLICATION SCHEMATICS
In the flyback converter topology, the transformer operates as an energy storage element, and the ferrite
core of P6142 is gapped to avoid saturation. The variants P6142-1 and P6142-2 differ in their gap sizes to
suit particular applications and switching frequencies. P6142-2 is recommended for frequencies from
100kHz to 350kHz; P6142-1 is recommended for frequencies from 350kHz to 500kHz
Note that in the discontinuous conduction flyback mode, the output load current flows when the switch is
open. Observe winding polarities.
The auxiliary winding may be used to provide a power rail for switching and control circuits. In the
schematics below, switch drive circuitry and feedback components are omitted for simplicity.
24V operation (22–32V)
For 24V operation the transformer primaries are
connected in series, giving nominal primary
inductance of 4µH (P6142-1) and 5µH (P6142-2),
and primary DCR of 14mΩ.
Fig 2 shows a typical schematic with a 15V @ 1A
output. For a 5V output, use the output tap as
shown in fig 3.
24V Operation
Fig 2
3
2
1A
8
+
15V
+
22-32V
–
4
–
9
For 5V output see fig 3
7
SWIT
CH
12V operation (10–22V)
For 12V operation the transformer primaries are
connected in parallel, giving nominal primary
inductance of 1µH (P6142-1) and 1.26µH
(P6142-2), and primary DCR of 3.5mΩ.
Fig 3 shows a typical schematic with a 5V @ 3A
output. For a 15V output, use the output tap as
shown in fig 2.
12V Operation
Fig 3
3
3A
8
+
10
5V
+
10-22V
–
4
–
7
SWIT
CH
9
For 15V outp ut see fig 2
Multiple output
Following the examples given in figs 2 and 3, the
secondary taps can be utilized to provide multiple
output voltages. For example, fig 4 shows a 24V
input flyback converter with +10V and ±5V
outputs. Other combinations are possible.
Multiple output
Fig 4
3
2
+ 10V
8
1
10
0V
+ 5V
+
24V
–
4
0V
7
SWIT
CH
9
-5V
ETALDOC 857/2
Page 3 of 4
August 2004
ETAL [ ETAL Group ]
