LNK403-409/413-419
Functional Description
A LinkSwitch-PH device monolithically integrates a controller and
high-voltage power FET into one package. The controller
implements both high power factor and a constant current
output in a single stage. The LinkSwitch-PH controller consists
of an oscillator, feedback (sense and logic) circuit, 5.9 V regulator,
hysteretic over-temperature protection, frequency jittering,
cycle-by-cycle current limit, auto-restart, inductance correction,
power factor and constant current control.
FEEDBACK Pin Current Control Characteristics
The figure shown below illustrates the operating boundaries of
the FEEDBACK pin current. Above I
FB(SKIP)
switching is disabled
and below I
FB(AR)
the device enters into auto-restart.
the line undervoltage and overvoltage thresholds of the
VOLTAGE MONITOR pin. For non-dimming or PWM dimming
applications with LNK413-419, the external resistor should be a
24.9 kW ±1%, for high-line and universal input voltage designs,
and 49.9 kW ±1% for low-line input voltage designs. For phase
angle AC dimming with LNK403-409, the external resistor
should be a 49.9 kW ±1%. One percent resistors are
recommended as the resistor tolerance directly affects the
output tolerance. Other resistor values should not be used.
BYPASS Pin Capacitor Power Gain Selection
LinkSwitch-PH devices have the capability to tailor the internal
gain to either full or a reduced output power setting. This allows
selection of a larger device to minimize dissipation for both
thermal and efficiency reasons. The power gain is selected with
the value of the BYPASS pin capacitor. The full power setting is
selected with a 100
mF
capacitor and the reduced power setting
(for higher efficiency) is selected with a 10
mF
capacitor. The
BYPASS pin capacitor sets both the internal power gain as well
as the over-current protection (OCP) threshold. Unlike the
larger devices, the LNK4x3 power gain is not programmable.
Use a 10
mF
capacitor for the LNK4x3.
Switching Frequency
The switching frequency is 66 kHz. To further reduce the EMI
level, the switching frequency is jittered (frequency modulated)
by approximately ±1 kHz.
Soft-Start
The controller includes a soft-start timing feature which inhibits
the auto-restart protection feature for the soft-start period (t
SOFT
)
to distinguish start-up into a fault (short-circuit) from a large
output capacitor. At start-up the LinkSwitch-PH clamps the
maximum duty cycle to reduce the output power. The total
soft-start period is t
SOFT
.
Remote ON/OFF and EcoSmart
The VOLTAGE MONITOR pin has a 1 V threshold comparator
connected at its input. This voltage threshold is used for
remote ON/OFF control. When a signal is received at the
VOLTAGE MONITOR pin to disable the output (VOLTAGE
MONITOR pin tied to ground through an optocoupler photo-
transistor) the LinkSwitch-PH will complete its current switching
cycle before the internal power FET is forced off.
The remote ON/OFF feature can also be used as an eco-mode
or power switch to turn off the LinkSwitch-PH and keep it in a
very low power consumption state for indefinite long periods.
When the LinkSwitch-PH is remotely turned on after entering
this mode, it will initiate a normal start-up sequence with
soft-start the next time the BYPASS pin reaches 5.9 V. In the
worst case, the delay from remote on to start-up can be equal
to the full discharge/charge cycle time of the BYPASS pin. This
reduced consumption remote off mode can eliminate expensive
and unreliable in-line mechanical switches.
I
FB(SKIP)
Skip-Cycle
I
FB
CC Control
Region
I
FB(DCMAXR)
Soft-Start and
CC Fold-Back
Region
I
FB(AR)
DC10
Auto-Restart
DC
MAX
PI-5433-060410
Maximum Duty Cycle
Figure 5.
FEEDBACK Pin Current Characteristic.
The FEEDBACK pin current is also used to clamp the maximum
duty cycle to limit the available output power for overload and
open-loop conditions. This duty cycle reduction characteristic
also promotes a monotonic output current start-up
characteristic to prevent over-shoot.
REFERENCE Pin
The REFERENCE pin is tied to ground (SOURCE) via an
external resistor. The value selected sets the internal
references, determining the operating mode for dimming
(LNK403-409) and non-dimming (LNK413-419) operation and
3
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Rev. D 08/11
POWERINT [ POWER INTEGRATIONS, INC. ]
