DF04M View Datasheet(PDF) - STMicroelectronics
Part Name
Description
Manufacturer
DF04M Datasheet PDF : 42 Pages
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AN1262 APPLICATION NOTE
The optimum value will be found empirically once the transformer construction has been frozen. Also the divider
RH, RL that sets the VCC voltage (and as a consequence, the output voltage) is likely to need adjustment after
bench verification. Some improvement in terms of load regulation can be achieved by using an inductor (typi-
cally, between 1 and 10µH) instead of a resistor. Any inexpensive axial inductor able to carry few mA will serve
the purpose.
Figure 17. Leading Edge Blanking (LEB) circuit for leakage inductance spikes filtering
Vout [V]
BC327 1N4148
100 pF
22 µF
10 kΩ
Vcc
L6590
L6590D
L6590A
18
Rs
17
16
15
14
LEB
13
12
11
GND
0.01
0.1
1
Iout [A]
However, the most effective way to improve regulation is to use the circuit shown in figure 17, which blanks the
spike appearing at the leading edges of the voltage generated by the self-supply winding. This spike, due to the
transformer's leakage inductance, is the major responsible for the poor load regulation.
18 LAYOUT RECOMMENDATIONS
A proper printed circuit board (PCB) layout is essential for correct operation of any switch-mode converter and
this is true for the devices of the L6590 family as well. Careful component placing, correct traces routing, appro-
priate traces widths and compliance with isolation distances are the major issues.
Figure 18. Suggested ground routing for converters with secondary feedback.
Vin
Vout
L6590A and
L6590D only
Vac
DRAIN
BOK
L6590
Vcc
L6590D
L6590A
VFB
COMP GND
Secondary Power GND
Secondary Signal GND
C
Y1
L6590 and
L6590D only
Primary Signal GND
Primary Power GND
One-point GND
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