VIPER15LDTR STMicroelectronics, VIPER15LDTR Datasheet - Page 16

• Manufacturer Part Number: VIPER15LDTR
• Description: IC OFFLINE CONV PWM OVP 16SOIC
• Manufacturer: STMicroelectronics
• Series: VIPer™ plusr

Specifications of VIPER15LDTR

• Output Isolation: Isolated
• Frequency Range: 122 ~ 150kHz
• Voltage - Input: 8.5 ~ 23.5 V
• Voltage - Output: 800V
• Power (watts): 12W
• Operating Temperature: -40°C ~ 150°C
• Package / Case: 16-SOIC (0.154", 3.90mm Width)
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: 497-10063-2

Operation description
7.3
16/40
Power-up description
If the input voltage rises up till the device start level, V
grow due to the I
start-up circuit. If the V
power MOSFET starts switching and the HV current generator is turned OFF, see
on page
The IC is powered by the energy stored in the capacitor on the VDD pin, C
the self-supply circuit (typically an auxiliary winding of the transformer and a steering diode)
develops a voltage high enough to sustain the operation.
C
value higher than V
switching operation before the controller receives any energy from the auxiliary winding.
The following formula can be used for the V
Equation 1
The t
estimated by applicator according to the output stage configurations (transformer, output
capacitances, etc.).
During normal operation, the power MOSFET is switched ON immediately after transformer
demagnetization, detected by the VIPER15, through the voltage V
pin. At power up the initial output voltage is zero and then the voltage V
enough to correctly arm the internal ZCD circuit. In this case, the power MOSFET is turned
ON with a fixed frequency determined by the internal oscillator. This fixed switching
frequency is F
to arm the ZCD circuit (i.e. its positive value exceeds V
MOSFET is driven by this circuit and is no more related to the internal oscillator (except for
the frequency fold-back function).
The start-up phase is managed by a dedicated internal logic and is activated every time the
device exits from UVLO because the V
timing (t
During the first part of the start-up phase soft start takes place: the drain peak current is
increased cycle-by-cycle from zero as far as the maximum value, I
Figure 25 on page
During soft-start and until the output voltage reaches its regulated value, the feedback loop
is open. To prevent an improper activation of the OLP function (see the
page
is clamped at V
In this way, the feedback voltage can exceed V
threshold, V
the end of the start-up phase (t > t
VDD
SSaux
28) during soft-start and until the start-up phase is over (t = t
capacitor must be sized enough to avoid fast discharge and keep the needed voltage
SU
17.
, see
is the time needed for the steady state of the auxiliary voltage. This time is
FBolp
STARTER
FBlin.
Table 8 on page
DDch
(see
18). The duration of soft-start is t
DDoff
(see
current (see
Figure 25 on page
DD
(see
threshold. In fact, a too low capacitance value could terminate the
Figure 24 on page
voltage reaches the V
Table 8 on page
Doc ID 15455 Rev 5
8) defines the end of the start-up phase.
SU
Table 7 on page
C
VDD
) if the output voltage is still below the regulated value.
DD
=
18), which would activate the OLP
voltage exceeds the threshold V
V
DD
I
DDch
DDon
18).
8). As soon as the voltage on ZCD pin is able
FBlin
capacitor calculation:
DDon
⋅
−
t
SSaux
V
7) coming from the internal high voltage
and ramp up as far as the overload
SS
DDoff
DRAIN_START
threshold (See
, (t
ZCDAth
SS
< t
), the turn-on of the power
SU
, the V
, see
SU
ZCD
Dlim
Table 7 on page
), the feedback voltage
, (see
sensed on the ZCD
Table 8 on page
DD
ZCD
Section 7.13 on
voltage begins to
DDon
VDD
function,
is not high
Figure 24
, until when
. An internal
Figure 23
VIPER15
only at
7) the
or
8),