View DI-67_1232669.PDF datasheet online --- IC-ON-LINE

Datasheet File OCR Text:

Design Idea DI-67 (R) TOPSwitch-GX Isolated, Power
Factor Corrected (PFC), 17 W LED Driver
Application LED Arrays Device TOP246F Power Output 17.6 W max Input Voltage 108-132 VAC 60 Hz Output Current 700 mA (16-24 V) Topology Flyback
Design Highlights
* * * * * * 700 mA of output current regulated to within 5% Power factor: > 0.98, THD: 9.6% No output current overshoot at power-on Temperature range: -40 C to +80 C Harmonics comply with IEC61000-3-2, Edition 2.1 Conducted EMI complies with CISPR-22 B
The DC input capacitor (C3, 100 nF) was sized so that its voltage approaches zero at the AC input zero crossings (see the middle waveform of Figure 2). A 220 F capacitor (C6) was chosen for the bias supply to minimize the 120 Hz ripple current into the current source (Q1), which provides control current to U1. The output rectifier (D9) must be rated for an average of 3.5 A. Capacitor C7's value (680 F) sets the magnitude of the output ripple current to 600 mA peak to peak, at 120 Hz. Resistors R7, R8, R9 and U2's LED set the 700 mA average current limit. The U2 phototransistor drives the current source (Q1) and the PFC-loop filter capacitor (C8, 100 F). Capacitor C8 was sized to provide the low loop bandwidth necessary for high power-factor. R4 is the power-off discharge path for C6 and C8. The CONTROL pin bypass capacitor (C5, 1 F) is just large enough to allow smooth start-up of the output load current, and yet small enough to prevent output current overshoot. A larger value of C5 would increase start-up delay time.
700 mA 16-24 V
Operation
This low-cost, TOP246F based PFC LED Driver takes advantage of built-in TOPSwitch-GX features. This supply is current (not voltage) regulated, except in the case of no-load. Without a load, the output voltage is limited to about 30 V (max), by R6 and VR2. Configured as a flyback converter, this circuit operates in the discontinuous conduction mode. It can deliver an average of 700 mA (1 A at the peak of output ripple) over a 16 V to 24 V range, which makes it ideal for driving high current LED arrays, such as the Luxeon 12 UP LED Ring.
C4 2.2 nF Y CAP D1-D4 IN4004 VR1 P6KE200A T1 D9 BYV28-200
+
C7 680 uF 35 V R6 100 5%
L2 150 uH
8
1 C3 100 nF C2 100 nF X2 CAP 5 2 D5 UF4005
7 6 4 D8 UF4002 C6 220 uF 25 V R4 10 k 5% R2 499 1% R3 1.00 k 1% Q1 PN2907A TOPSwitch-GX U1 CONTROL TOP246F
L C
2 L1 1
3
3
27 mH 4 C1 100 nF X2 CAP RV1 150 V D6 UF4005
D
VR2 1N5254B
D7 1N4148
R5 3.01 k 1%
F1 T1A 250 V 108-132 VAC 60 Hz L
PI-3746-110303
R7 100 1% R8 1.50 , 1%
S
X
F
R1 10.0 k 1% N
C5 1.0 uF
C8 100 uF 25 V U2 PC81711NSZ
RETURN R9 10.0 , 1%
Figure 1. Isolated Constant Current PFC LED Driver.
DI-67
www.powerint.com
October 2003
DI-67 Key Design Points
* To have high power factor, a constant duty factor must be maintained over the 8.33 ms half cycle period. Therefore, the bias supply voltage and the U1 CONTROL pin current must remain extremely constant. The values of C6 and C8 must be chosen accordingly. * Decreasing the value of C8 will reduce the turn-on delay time, but will also degrade the power factor. * Because low-cost is the goal of this low-loop-gain design, the tolerance of the output current depends on the CTR of the opto-coupler and the (unregulated) value of the bias voltage. The restricted AC input voltage range allows using the forward (not flyback) configuration for the bias winding. If the AC input voltage range is extended, voltage regulation of the bias supply circuit will be required. TRANSFORMER PARAMETERS
Core Bobbin EF-20 or Equivalent ALG of 1570 nH/T2 Miles-Platts EF0700 EF20 8 Pin Horizontal Primary: 70T, 2 layers, 29 AWG Secondary: 13T, 2 x 32 AWG Triple Insulated Wire Bias: 9T, 2 x 23 AWG Primary: 2-5, tape Secondary: 8-7, tape Primary: 5-1, tape Bias: 3-4, tape 3 layers 350 H 10% 2.0 MHz (Min) 10 H (Max)
Winding Details
Winding Order (pin numbers) Primary Inductance Primary Resonant Frequency Leakage Inductance
PI-3747-110403
0.5 A/Div. 0A
Table 1. Transformer Construction Information.
Voltage (V)
0V 100 V/Div.
Average Output Current (mA)
+5% Upper Specification Limit
720
700
0.5 A/Div. 0A 0 25 50
680
LED Current must be maintained within manufacturer's specified temperature range. -5% Lower Specification Limit
Time (ms) Figure 2. PFC LED Driver Waveforms. Top: Input Current at 120 VAC 60 Hz. Middle: C3 Capacitor Voltage. Bottom: Output Current (with 20 V LED Load).
660 -40
-20
0
20
40
60
80
Ambient Temperature (C)
Figure 3. PFC Driver Current vs. Temperature.
For the latest updates, visit www.powerint.com Power Integrations reserves the right to make changes to its products at any time to improve reliability or manufacturability. Power Integrations does not assume any liability arising from the use of any device or circuit described herein, nor does it convey any license under its patent rights or the rights of others. The products and applications illustrated herein may be covered by one or more U.S. and foreign patents or potentially by pending U.S. and foreign patent applications assigned to Power Integrations. A complete list of Power Integrations' patents may be found at www.powerint.com. The PI logo, TOPSwitch, TinySwitch, LinkSwitch and EcoSmart are registered trademarks of Power Integrations. PI Expert and DPA-Switch are trademarks of Power Integrations. Copyright 2003, Power Integrations
Power Integrations
MAIN PHONE NUMBER +1 408-414-9200
A 10/03
5245 Hellyer Avenue
APPLICATIONS FAX +1 408-414-9760
San Jose, California 95138
For a complete listing of worldwide sales offices, please visit www.powerint.com
APPLICATIONS HOTLINE +1 408-414-9660
www.powerint.com
PI-3748-110303
740

▲Up To Search▲

Price & Availability of DI-67

	To Download DI-67 Datasheet File
If you can't view the Datasheet, Please click here to try to view without PDF Reader .