lnk403 Power Integrations, Inc., lnk403 Datasheet - Page 4

• Manufacturer Part Number: lnk403
• Description: Led Driver Ic With Triac Dimming, Single-stage Pfc And Primary-side Constant Current Control
• Manufacturer: Power Integrations, Inc.

Figure 5.
5.9 V Regulator/Shunt Voltage Clamp
The internal 5.9 V regulator charges the bypass capacitor
connected to the BYPASS pin to 5.9 V by drawing a current
from the voltage on the DRAIN pin whenever the power
MOSFET is off. The BYPASS pin is the internal supply voltage
node. When the power MOSFET is on, the device operates
from the energy stored in the bypass capacitor. Extremely low
power consumption of the internal circuitry allows LinkSwitch-PH
to operate continuously from current it takes from the DRAIN
pin. A bypass capacitor value of 10 or 100 mF is sufficient for
both high frequency decoupling and energy storage. In
addition, there is a 6.4 V shunt regulator clamping the BYPASS
pin at 6.4 V when current is provided to the BYPASS pin
through an external resistor. This facilitates powering of
LinkSwitch-PH externally through a bias winding to increase
operating efficiency. It is recommended that the BYPASS pin is
supplied current from the bias winding for normal operation.
Auto-Restart
In the event of an open-loop fault (open FEEDBACK pin resistor
or broken path to feedback winding), output short-circuits or an
overload condition the controller enters into the auto-restart
mode. The controller annunciates both short-circuit and
open-loop conditions once the FEEDBACK pin current falls
below the I
minimize the power dissipation under this fault condition the
shutdown/auto-restart circuit turns the power supply on (same
as the soft-start period) and off at an auto-restart duty cycle of
typically DC
fault is removed during the auto-restart off-time, the power
supply will remain in auto-restart until the full off-time count is
completed. Special consideration must be made to appropriately
size the output capacitor to ensure that after the soft-start
period (t
threshold to ensure successful power-supply start-up.
After the soft-start time period, auto-restart is activated only
Rev. A 080610
4
SOFT
Remote ON/OFF VOLTAGE MONITOR pin Control
LNK403-409EG
FB(AR)
) the FEEDBACK pin current is above the I
AR
for as long as the fault condition persists. If the
threshold after the soft-start period. To
D
S
CONTROL
R
V
FB
BP
PI-5435-052510
FB(AR)
when the FEEDBACK pin current falls below I
have been triggered.
Over-Current Protection
The current limit circuit senses the current in the power
MOSFET. When this current exceeds the internal threshold
(I
cycle. A leading edge blanking circuit inhibits the current limit
comparator for a short time (t
turned on. This leading edge blanking time has been set so
that current spikes caused by capacitance and rectifier reverse
recovery will not cause premature termination of the power
MOSFET conduction.
Line Under/Overvoltage Protection
This device includes both line under- and overvoltage detection
to limit the minimum start-up and maximum operating voltage
detected through the VOLTAGE MONITOR pin. An external peak
detector consisting of a diode and capacitor are required to
provide input line peak voltage to the VOLTAGE MONITOR pin
through a resistor. At power up, I
off until the input line voltage reaches the undervoltage threshold.
At power down, I
goes out of regulation.
The same resistor used for UV also sets line overvoltage (OV)
shutdown threshold which, once exceeded, forces the
LinkSwitch-PH to stop switching (after completion of the current
switching cycle). Once the line voltage returns to normal, the
device resumes normal operation after the auto-restart off-time
has completed. A small amount of hysteresis is provided on the
OV threshold to prevent noise triggering. When the power
MOSFET is off, the rectified DC high voltage surge capability is
increased to the voltage rating of the power MOSFET (725 V),
due to the absence of the reflected voltage and leakage spikes
on the drain.
Hysteretic Thermal Shutdown
The thermal shutdown circuitry senses the controller die
temperature. The threshold is set at 142 °C typical with a 75 °C
hysteresis. When the die temperature rises above this threshold
(142 °C) the power MOSFET is disabled and remains disabled
until the die temperature falls by 75 °C, at which point the power
MOSFET is re-enabled.
Safe Operating Area (SOA) Protection
The device also features a safe operating area (SOA) protection
mode which disables MOSFET switching in the event there are
consecutive cycles having an on-time less than t
protection mode protects the device under short-circuited LED
conditions and at start-up during the soft-start period when
auto-restart protection is inhibited. The SOA protection mode
remains active in normal operation.
LIMIT
), the power MOSFET is turned off for the remainder of that
UV-
prevents restart attempts after the output
LEB
) after the power MOSFET is
UV+
keeps the LinkSwitch-PH
FB(AR)
www.powerint.com
ON(SOA)
, or I
. This
UV-
and I
OV