RDK-268 Power Integrations, RDK-268 Datasheet - Page 3

• Manufacturer Part Number: RDK-268
• Description: REFERENCE DESIGN LINKSWITCH-PL
• Manufacturer: Power Integrations
• Series: LinkSwitch®-PLr

Specifications of RDK-268

• Mfg Application Notes: LinkSwitch-PL Family AppNote
• Design Resources: RDR-268
• Current - Output / Channel: 366mA
• Outputs And Type: 1, Non-Isolated
• Voltage - Output: 2.5 V ~ 3.5 V
• Voltage - Input: 85 ~ 265VAC
• Utilized Ic / Part: LNK454DG
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Features: -
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant
• Other names: 596-1423

Functional Description
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.
In a direct LED current sensing configuration, the average
FEEDBACK pin voltage is a replica of the LED current, scaled
by the sense resistor (R
(R
FEEDBACK pin.
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 set 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.
If the FEEDBACK pin peak voltage exceeds 520 mV, cycle
skipping mode is triggered and the power processed by the
integrated power 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.
Figure 4.
www.powerint.com
F
and C
F
Typical Application Schematic.
in Figure 4) reduces high frequency noise at the
AC
IN
SENSE
in Figure 4). A small low-pass filter
D
S
CONTROL
LinkSwitch-PL
FB
C
BP
F
Auto-restart protection is triggered by a FEEDBACK pin voltage
in excess of 2 V. This feature can be used to provide output
overvoltage protection (via DZ
triggers the IC to enter auto-restart.
Figure 5.
FEEDBACK Pin Operational Voltage Thresholds.
Normal Operation
Cycle Skipping
D
R
Auto-Restart
ES
ES
R
SENSE
Mode
290 mV
R
LNK454/456-458/460
F
OV
PI-5837-060710
and R
R
DZ
OV
OV
OV
, in Figure 4), which
2 V
520 mV
PI-5838-091010
Rev. A 11/01/10
3