NCP1351LEDGEVB ON Semiconductor, NCP1351LEDGEVB Datasheet - Page 5

• Manufacturer Part Number: NCP1351LEDGEVB
• Description: EVAL BOARD FOR NCP1351LEDG
• Manufacturer: ON Semiconductor

Specifications of NCP1351LEDGEVB

• Design Resources: NCP1351 EVB BOM NCP1351LEDGEVB Gerber Files NCP1351LED EVB Schematic
• Current - Output / Channel: 700mA
• Outputs And Type: 1, Isolated
• Voltage - Output: 33V
• Features: Short-Circuit Protection
• Voltage - Input: 85 ~ 265 V
• Utilized Ic / Part: NCP1351
• Core Chip: NCP1351
• Topology: Flyback
• No. Of Outputs: 1
• Output Current: 700mA
• Output Voltage: 33V
• Development Tool Type: Hardware - Eval/Demo Board
• Leaded Process Compatible: Yes
• Rohs Compliant: Yes
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• For Use With/related Products: NCP1351LEDG
• Other names: NCP1351LEDGEVBOS

Rectifier snubber
rectifier as there was a large amount of ringing present
after the rectifier turns off.
series, and knowing the junction capacitance and ringing
frequency we can determine the necessary values:
allows us to calculate the necessary snubber resistor.
...............................................................................(Eq.22)
September 2008, Rev. 2
Testing demonstrated the need for snubbing on the
The snubber consists of a resistor and capacitor in
Knowing that:
We can determine L, the stray inductance which then
C
R =
L
f
s
s
=
=
=
f = 14.5 MHz (measured on oscilloscope)
C
=
. 1
4
2
j
C
π
= 80 pF (datasheet figure for MUR840 at 62 V)
2
51
C
π
L
j
1
( )
1
j
μ
π
R
LC
H
f
.......................................................(Eq.19)
LC
s
2
j
j
=
................................................(Eq.21)
..............................................(Eq.20)
4
×
80
×
10
−
12
×
1
(
π
×
14
5 .
×
10
6
)
2
DN06040/D
www.onsemi.com
inserting these into the circuit eliminated the ringing due to
the rectifier.
Auxiliary winding
would be in the form of a flyback winding, i.e. in phase
with the output winding, and thus provide a semi-regulated
voltage to supply the controller. As this ballast is current
controlled and the output voltage can vary over a
considerable range depending on the number of LED’s
connected, a forward phased winding is used. The
auxiliary will therefore vary with line rather than output
voltage. Since neither option could supply sufficient volts
at low input/output voltage whilst still staying below the
maximum V
formed by Q1 and D6. Below ~20 V the regulator does
nothing other than act as a small volt drop, however as the
voltage rises it clamps the voltage to around 20.7 V, since
the current is very low into the V
loss.
.............................................................................. (Eq.24)
The nearest standard values are 470 pF and 140 Ω,
Normally in a flyback converter the auxiliary winding
C
R
s
s
=
=
2
. 1
×
80
CC
π
51
×
figure of 28 V, a voltage regulator is used
×
×
10
10
. 1
−
12
−
51
6
×
=
137
10
137
−
6
Ω
×
80
......................... (Eq.23)
CC
×
pin there is very little
10
−
12
=
504
pF
5