STEVAL-ISA011V1 STMicroelectronics, STEVAL-ISA011V1 Datasheet - Page 10

• 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

STEVAL-ISA011V1 Board Design
1.2.2
10/33
Transformer Turns Ratio and D
Equation 13
Equation 14
Equation 15
Equation 16
The turns ratio that is selected for the transformer depends on the output voltage, the
chosen reflected voltage, and the average voltage drop across the output diode.
Keeping in mind the voltage drop across its dynamic resistance, V
expressed as:
Where,
V
V
r
I
Using the calculated V
Where,
N
N
V
V
Using the calculated turns ratio, I
Where,
I
I
Note: The worst case (maximum power dissipation) will be in full load condition.
The D
Where,
D
L
f
O
PKS
PKP
SW
dD
P
O
DROP(avg)
dD
R
P
S
s_cond
= diode output current, and
= primary inductance, and
= reflected voltage, and
= Primary Turns,
= Secondary Turns,
= output voltage.
= dynamic resistance,
= switching frequency.
= drop voltage (when the diode is forward-biased),
= peak current at secondary winding, and
= peak power current
11
= Secondary Diode conduction duty cycle,
conduction duty cycle is expressed as:
= average voltage drop (across the output diode)
DROP(avg)
V
D
DROP avg
N
-------
N
s co nd
P
S
–
I
value, the turns ratio is expressed as:
Rev. 1
PKS
=
PKS
11
--------------------------------------------- -
V
O
is then expressed as:
=
Peak Current
=
+
I
-------------------------------------------- -
=
N
------ - I
N
PKP
V
V
P
S
DRO P avg
V
dD
R
V
L
PKP
+
R
P
r
dD
f
SW
I
O
AN2272 - Application Note
DROP(avg)
is