LNK454/456-458/460
DES
DZOV
ROV
RES
AC
IN
LinkSwitch-PL
D
S
CONTROL
BP
FB
CF
RF
RSENSE
PI-5837-060710
Figure 4. Typical Application Schematic.
Functional Description
Latching shutdown protection is triggered by a FEEDBACK pin
voltage in excess of 2 V. This feature can be used to provide
output overvoltage protection (via DZOV and ROV, in Figure 4),
which triggers the IC to latch off. This condition is reset when
the BYPASS pin voltage drops below 4.9 V, after removal of the
AC input.
The LinkSwitch-PL combines a high-voltage power MOSFET
switch with a power supply controller in one device. The IC
provides a single stage power factor correction plus LED
current control. The LinkSwitch-PL controller consists of an
oscillator, feedback (sense and logic) circuit, 5.85 V regulator,
hysteretic over-temperature protection, frequency jittering,
cycle-by-cycle current limit, loop compensation circuitry, auto-
restart, switching on-time extension, power factor and constant
current control.
Latch Off
In a direct LED current sensing configuration, the average
FEEDBACK pin voltage is a replica of the LED current, scaled
by the sense resistor (RSENSE in Figure 4). A small low-pass filter
(RF and CF in Figure 4) reduces high frequency noise at the
FEEDBACK pin.
2 V
Figure 5 illustrates the operating regions of the FEEDBACK pin
voltage. The LinkSwitch-PL sets its operating point such that
the average FEEDBACK pin voltage in steady-state operation is
290 mV. This threshold is low to minimize the sensing resistor
dissipation. The internal MOSFET switching frequency and
on-time are updated once every input AC half-cycle to regulate
the output current and maintain high power factor.
Cycle Skipping
Mode
520 mV
If the FEEDBACK pin peak voltage exceeds 520 mV, cycle
skipping mode is triggered and the power processed by the
integrated MOSFET is clamped on a cycle-by-cycle basis.
Switching frequency may vary during an input voltage half-cycle
to reduce thermal stress on the output LEDs.
Normal Operation
290 mV
PI-5838-041910
Figure 5. FEEDBACK Pin Operation Voltage Thresholds.
3
PRELIMINARY
This document contains information on a new product. Specifications and information herein
are subject to change without notice.
www.powerint.com
Rev. A 06/10
POWERINT [ Power Integrations ]
