LYT4212E Power Integrations, LYT4212E Datasheet - Page 6

• Manufacturer Part Number: LYT4212E
• Description: LED Lighting Drivers HighPower LED Driver 15 W (85-132 VAC)
• Manufacturer: Power Integrations

Specifications of LYT4212E

• Rohs: yes
• Input Voltage: 85 V to 132 V
• Operating Frequency: 124 kHz to 140 kHz
• Maximum Supply Current: 1.2 mA
• Output Current: 1.17 A
• Maximum Operating Temperature: + 150 C
• Mounting Style: Through Hole
• Package / Case: eSIP-7C
• Minimum Operating Temperature: - 40 C

Application Example
25 W TRIAC Dimmable High Power Factor LED Driver
Design Example (DER-350)
The circuit schematic in Figure 8 shows a TRIAC dimmable high
power factor LED driver based on LYT4317E from the LYTSwitch
family of devices. The design is configurable for non-dimmable
only applications by simple component value changes. It was
optimized to drive an LED string at a voltage of 36 V with a
constant current of 0.7 A ideal for Lumens PAR lamp retro-fit
applications. The design operates over an input voltage range
of 90 VAC to 132 VAC.
The key goals of this design were compatibility with standard
leading edge TRIAC AC dimmers, very wide dimming range
(1000:1, 700 mA:0.7 mA), high efficiency (>85%) and high power
factor (>0.9). The design is fully protected from faults such as
no-load (open load), overvoltage and output short-circuit or
overload conditions and over temperature.
Circuit Description
The LYTSwitch device (U1- LYT4317E) integrates the power FET,
controller and start-up functions into a single package reducing
the component count versus typical implementations. Configured
as part of an isolated continuous conduction mode flyback
converter, U1 provides high power factor via its internal control
algorithm together with the small input capacitance of the
design. Continuous conduction mode operation results in
reduced primary peak and RMS current. This both reduces
EMI noise, allowing simpler, smaller EMI filtering components
and improves efficiency. Output current regulation is maintained
without the need for secondary-side sensing which eliminates
current sense resistors and improves efficiency.
Input Stage
Fuse F1 provides protection from component failures while RV1
provides a clamp during differential line surges, keeping the
Figure 8.
Rev. B 02/13
47 kΩ
1/8 W
R25
LYT4211-4218/4311-4318
6
5 A
F1
L
1 mH
L1
1/2 W
DER-350 Schematic of an Isolated, TRIAC Dimmable, High Power Factor, 90-132 VAC, 25 W / 36 V / 700 mA LED Driver.
510
R1
140 VAC
90 - 132
47 kΩ
1/8 W
RV1
VAC
R2
220 nF
250 V
C1
MB6S
600 V
BR1
N
1 mH
L2
470 nF
50 V
100 nF
250 V
C3
C2
X0202MA2BL2
100 Ω
1 W
360 kΩ
R8
R6
Q1
47 kΩ
1/8 W
5 mH
R24
L3
DFLU1400-7
D9
100 nF
250 V
C4
510 kΩ
1/8 W
2.2 µF
250 V
R9
C6
LYTSwitch
LYT4317E
2 MΩ
R10
1%
DFLU1400
U1
D2
peak drain voltage of U1 below the 725 V rating of the internal
power FET. Bridge rectifier BR1 rectifies the AC line voltage.
EMI filtering is provided by L1-L3, C1, C4, R2, R24 and R25
together with the safety rated Y class capacitor (CY1) that bridges
the safety isolation barrier between primary and secondary.
Resistor R2, R24 and R25 act to damp any resonances formed
between L1, L2, L3, C1 and the AC line impedance. A small
bulk capacitor (C4) is required to provide a low impedance
source for the primary switching current. The maximum value
of C2 and C4 is limited in order to maintain a power factor of
greater than 0.9.
LYTSwitch Primary
To provide peak line voltage information to U1 the incoming
rectified AC peak charges C6 via D2. This is then fed into the
VOLTAGE MONITOR pin of U1 as a current via R10. This
sensed current is also used by the device to set the line input
overvoltage protection threshold. Resistor R9 provides a
discharge path for C6 with a time constant much longer than
that of the rectified AC to prevent generation of line frequency
ripple.
The VOLTAGE MONITOR pin current and the FEEDBACK pin
current are used internally to control the average output LED
current. For TRIAC phase-dimming applications a 49.9 kW
resistor (R14) is used on the REFERENCE pin and 2 MW (R10)
on the VOLTAGE MONITOR pin to provide a linear relationship
between input voltage and the output current and maximizing
the dimming range.
Diode D3, R15 and C7 clamp the drain voltage to a safe level
due to the effects of leakage inductance. Diode D4 is
necessary to prevent reverse current from flowing through U1
for the period of the rectified AC input voltage that the voltage
across C4 falls to below the reflected output voltage (V
D
S
200 kΩ
US1J
US1D
R15
CONTROL
D3
D4
R
49.9 kΩ
V
1/16 W
R14
1%
FB
BAV16
1/10 W
3 kΩ
2.2 nF
R17
BP
630 V
D5
47 µF
16 V
C7
C8
165 kΩ
1/16 W
10 nF
MMBT3904
C14
50 V
R18
1%
Q2
12
1
1/10 W
RM8
10 Ω
T1
R27
FL1
FL2
10
11
1/10 W
BAV21
1/8 W
1 kΩ
R22
39 Ω
R20
D8
BAV21
100 nF
BYW29-200
100 nF
30 Ω
R26
D6
50 V
50 V
C15
C5
D7
100 pF
200 V
C13
20 kΩ
1/8 W
R19
250 VAC
56 µF
50 V
470 pF
C9
CY1
330 µF
www.powerint.com
C11
63 V
330 µF
63 V
C12
PI-6875-101812
20 kΩ
OR
R23
).
700 mA
36 V,
RTN