VIPER53SP STMicroelectronics, VIPER53SP Datasheet - Page 13

• Manufacturer Part Number: VIPER53SP
• Description: IC OFFLINE SWIT PWM CM POWERSO10
• Manufacturer: STMicroelectronics
• Series: VIPER™r

Specifications of VIPER53SP

• Output Isolation: Isolated
• Frequency Range: 93 ~ 300kHz
• Voltage - Input: 8.4 ~ 19 V
• Voltage - Output: 620V
• Power (watts): 40W
• Operating Temperature: 25°C ~ 125°C
• Package / Case: PowerSO-10 Exposed Bottom Pad
• For Use With: 497-8435 - BOARD EVAL FOR VIPER53 28W497-6458 - BOARD EVAL BASED ON VIPER53-E497-6262 - BOARD REF SGL VIPER53 90-264VAC497-5866 - EVAL BOARD 24W NEG OUT VIPER53E497-4933 - BOARD PWR SUPPLY 24W OUTPUT VIPE
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: 497-3289-5

Figure 15: Off Line Power Supply With Optocoupler Feedback
SECONDARY FEEDBACK CONFIGURATION
EXAMPLE
When a more accurate output voltage is needed,
the definitive way is to monitor it directly on
secondary side, and to drive the PWM controller
through an optocoupler as shown on figure 15.
The optocoupler is connected in parallel with the
compensation network on the COMP pin. The
design of the auxiliary winding will be made in such
a way that the V
internal 15 V 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 0.6 mA to the
optotransistor. This current doesn’t depend on the
compensation voltage, and so it doesn’t depend on
the output load either. 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
AC IN
DD
R1
F1
C1
voltage is always lower than the
C4
R3
C5
OSC
T1
VIPer73
U1
15V
TOVL
VDD
R9
1k
C6
D1
10nF
C11
COMP
R4
SOURCE
R5
C7
C2
DRAIN
C3
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.
Since the dynamic characteristics of the converter
are set on the secondary side through components
associated to U3, the compensation network has
only a role of gain stabilization for the optocoupler,
and its value can be freely chosen. R5 can be set
to a fixed value of 1 k , offering the possibility of
using C7 as a soft start capacitor: When starting up
the converter, the VIPer53 device delivers a
constant current of 0.6 mA on the COMP pin,
creating a constant voltage of 0.6 V in R5 and a
rising slope across C7. This voltage shape
together with the operating range of 0.5 V to 4.5 V
D2
D3
R2
T2
D4
U2
U3
C10
C8
R8
VIPer53DIP / VIPer53SP
L1
C12
R7
R6
C9
DC OUT
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