STEVAL-ISA029V1 STMicroelectronics, STEVAL-ISA029V1 Datasheet - Page 17

• Manufacturer Part Number: STEVAL-ISA029V1
• Description: BOARD EVAL BASED ON VIPER53-E
• Manufacturer: STMicroelectronics
• Series: VIPER™r
• Type: MOSFET & Power Driverr

Specifications of STEVAL-ISA029V1

• Design Resources: STEVAL-ISA029V1 Gerber Files STEVAL-ISA029V1 Schematic STEVAL-ISA029V1 Bill of Material
• Main Purpose: AC/DC, Primary Side
• Outputs And Type: 3, Isolated
• Power - Output: 13W
• Voltage - Output: 12V, 3.3V, -24V
• Current - Output: 1A, 100mA, 40mA
• Voltage - Input: 85 ~ 300VAC
• Regulator Topology: Flyback
• Frequency - Switching: 60kHz
• Board Type: Fully Populated
• Utilized Ic / Part: VIPer53
• Input Voltage: 85 V to 300 V
• Output Voltage: 12 V
• Product: Power Management Modules
• Silicon Manufacturer: ST Micro
• Silicon Core Number: VIPer53-E
• Kit Application Type: Power Management
• Application Sub Type: Power Supply
• Kit Contents: Board
• Rohs Compliant: No
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• For Use With/related Products: VIPer53-E
• Other names: 497-6458; STEVAL-ISA029V1

VIPer53 - E
6
Secondary feedback configuration example
When a more accurate output voltage is needed, the way is to monitor it directly secondary
side, and drive the PWM controller through an optocoupler as shown on
The optocoupler is connected in parallel with the compensation network on the COMP pin.
The design of the auxiliary winding that the VDD voltage is always lower than the internal
15V reference. The internal error amplifier will therefore be saturated in the high state, and
because of its transconductance nature, will deliver a constant biasing current of 0.6mA to
the optotransistor. This current does not depend on the compensation voltage, and so it
does not depend on the output load either. Consequently, the gain of the optocoupler
ensures consequently a constant biasing of the TL431 device (U3) which is in charge of
secondary regulation. If the optocoupler gain is sufficiently low, no additional components
are required to ensure a minimum current biasing of U3. Also, the low biasing current value
avoid any ageing of the optocoupler.
The constant current biasing can be used to simplify the secondary circuit: Instead of a
TL431, a simple zener and resistance network in series with the optocoupler diode can
insure a good secondary regulation. As the current flowing in this branch remains constant
for the same reason as above, typical load regulation of 1% can be achieved from zero to full
output current with this simple configuration.
Figure 19. Off line power supply with optocoupler feedback
AC IN
F1
R1
C1
C4
R3
C5
OSC
T1
VIPer73
U1
15V
TOVL
VDD
R9
1k
C6
D1
10nF
C11
COMP
R4
SOURCE
R5
C7
C2
DRAIN
Secondary feedback configuration example
C3
D2
D3
R2
T2
D4
U2
U3
C10
C8
R8
Figure 17.
L1
C12
R7
R6
C9
17/36
DC OUT