NCP1605FORWGEVB ON Semiconductor, NCP1605FORWGEVB Datasheet - Page 15

• Manufacturer Part Number: NCP1605FORWGEVB
• Description: EVAL BOARD FOR NCP1605FORWG
• Manufacturer: ON Semiconductor

Specifications of NCP1605FORWGEVB

• Design Resources: NCP1605FORWGEVB BOM NCP1605FORWGEVB Gerber Files NCP1605 EVB Schematic
• Main Purpose: AC/DC, Primary and Secondary Side with PFC
• Outputs And Type: 1, Isolated
• Voltage - Output: 19V
• Current - Output: 8A
• Voltage - Input: 90 ~ 265VAC
• Regulator Topology: Forward Converter
• Frequency - Switching: 133kHz
• Board Type: Fully Populated
• Utilized Ic / Part: NCP1217, NCP1605
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Power - Output: -
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant
• For Use With/related Products: NCP1605FORWG
• Other names: NCP1605FORWGEVBOS

internal parasitic SCR activation. One of them consists in
inserting a resistor in series with the high- -voltage pin to
keep the negative current to the lowest when the bulk
becomes negative (Figure 28). Please note that the negative
spike is clamped to (- -2*Vf) thanks to the diode bridge. Also,
the power dissipation of this resistor is extremely small since
it only heats up during the startup sequence.
Simple and inexpensive cures exist to prevent from
Figure 28. A simple resistor in series avoids any
Figure 27. A Negative Spike Takes Place on the Bulk Capacitor at the Switch- -Off Sequence
+
Cbulk
latch- -up in the controller . . .
1
2
3
4
Vcc 5 V/DIV
Vlatch 1 V/DIV
Time 10 ms/DIV
8
7
6
5
2
3
1
+
Rbulk
>4.7 k
CV
http://onsemi.com
CC
15
from V
VCC
the bulk capacitor gets deeply discharged. For security
reasons, two diodes can be connected in series.
Another option (Figure 29) consists in wiring a diode
Figure 29. . . . or one diode forces V
ON
CC
sooner and thus stops the switching activity before
to the bulk capacitor to force V
+
Cbulk
VCC
1
2
3
4
ON
sooner.
8
7
6
5
3
CC
to reach
CC
1
+
D3
1N4007
CV
to reach
CC