STEVAL-ISA011V1 STMicroelectronics, STEVAL-ISA011V1 Datasheet - Page 7

• Manufacturer Part Number: STEVAL-ISA011V1
• Description: BOARD EVAL VIPER12A LP AC/DC
• Manufacturer: STMicroelectronics
• Series: VIPER™r
• Type: AC/DC Switching Convertersr

Specifications of STEVAL-ISA011V1

• Design Resources: STEVAL-ISA011V1 Gerber Files STEVAL-ISA011V1 Schematic STEVAL-ISA011V1 Bill of Materials
• Main Purpose: AC/DC, Primary Side
• Outputs And Type: 1, Isolated
• Power - Output: 4.1W
• Voltage - Output: 4.5V
• Current - Output: 900mA
• Voltage - Input: 88 ~ 265VAC
• Regulator Topology: Flyback
• Frequency - Switching: 60kHz
• Board Type: Fully Populated
• Utilized Ic / Part: VIPer12A
• Input Voltage: 88 V to 265 V
• Output Voltage: 4.5 V
• Product: Power Management Modules
• Silicon Manufacturer: ST Micro
• Silicon Core Number: VIPER12ADIP-E
• Kit Application Type: Power Management - Voltage Regulator
• Application Sub Type: AC / DC Adapter
• Kit Contents: Board
• Rohs Compliant: No
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• For Use With/related Products: VIPer12A
• Other names: 497-6413; STEVAL-ISA011V1

AN2272 - Application Note
The D
Equation 5
The transformer selected for this application provides an L
than the maximum inductance (L
that the system is not working at boundary and will always function in DCM.
Using the transformer’s L
Equation 6
Equation 7
Equation 8
Peak Primary Current, expressed as,
Where,
I
P
f
L
actual Maximum Duty Cycle (D
and
the primary side Root Mean Square (RMS) current value (I
current that flows through the main switch and primary winding. It is expressed as:
Where,
I
PEAK
SW
PRMS(max)
MAX
P
IN
= primary inductance.
= input power,
= switching frequency, and
at the boundary between CCM and DCM is expressed as:
= peak primary current,
= Primary Current root mean square,
I
PRM S max
P
D
, the designer can calculate the:
D
I
M AX
PEAK
MAX
=
=
MAX
=
=
I
PEAK
--------------------------------------------- -
V
2 P
------------------------------------------------- -
MAX
) calculated in the first equation (3.5mH). This ensures
DC m in
Rev. 1
------------------------ -
f
2 P
SW
f
), expressed as,
IN
SW
V
R
IN
L
D
------------------ -
f
SW
P
L
MAX
+
3
⇒
P
V
R
I
L
PEAK
⇒
P
⇒
⇒
I
D
PRMS max
D
M AX
=
MAX
STEVAL-ISA011V1 Board Design
258mA
P
=
of 3mH, which is a little less
=
0.47
0.42
PRMS(max)
=
97mA
), which is the
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