Datasheet

CCRACGEVB
http://onsemi.com
3
Conduction Time (T
ON
)
The conduction time (on time) of the LED string is based
on the V
F−Total
LEDs. The rectified voltage needs to rise
above the forward voltage of the LEDs before they begin to
conduct and the CCR regulates the current through them.
The T
ON
conduction time (%) calculation for the typical
120 VAC is the following:
T
ON
(%) + 100
ƪ
1*
ǒ
2 sin
*1
1
p
V
F*Total
LEDs
ACVin
TYPPeak
Ǔ
ƫ
(eq. 3)
When using 5 x Cree XLamp MX-6S in series providing
a V
F−Total
LEDs = 100 V, conduction time equals:
T
ON
(%) + 100
ƪ
1*
ǒ
2 sin
*1
1
p
100 V
120 V 1.414
Ǔ
ƫ
+ 62.3
%
Design Trade−off
• The lower the V
F−Total
LEDs:
♦ Higher %T
ON
conduction time , more light output
♦ Lower efficiency due to higher power lost across
CCR
• The higher the V
F−Total
LEDs:
♦ Higher efficiency due to less power lost across CCR
♦ Lower %T
ON
conduction time, less light output
Straight LED Driver, Non−dimming, with Output
Capacitor (120 VAC Example):
This circuit will have a higher efficiency compared to the
straight LED driver.
To set up the CCRACGEVB for the Straight LED driver
non-dimming topology with output Capacitor, place
jumpers according to Table 2. Figure 3 depicts the schematic
with the evaluation board reference designators.
Table 2. JUMPERS PLACED ONTO THE EVB
Jumpers in Place Reference Data
J1, J10, J13, J18, J19, J20,
J22, J26
Appendix B
The AC input is rectified using an AC bridge (D1 – D4)
and charges the capacitor (C7 & C8 in series). The voltage
on the capacitor will be equal to or a little below the peak
rectified voltage. A CCR (CCR3, 4, 5 or 6) controls the
current through the LED string. The charge on the capacitor
allows the CCR to continue providing current to the LED
string when the rectified AC voltage is below the
V
F−Total
LEDs. The Inrush current limiter (T1, R2 & C6) can
be employed to limit the inrush current or current spike from
a power surge. As the capacitor C6 charges, T1 will turn on
and provide a low impedance bypass.
Figure 3. Straight Non−dimmable LED Driver with Output Capacitor (120 VAC example)
Straight LED Driver, with Triac Dimming (120 VAC
Example):
This circuit incorporates an additional circuit to provide
a minimum load for the Triac dimmer.
To set up the CCRACGEVB for the Straight LED driver
dimming topology, place jumpers according to Table 3.
Figure 4 depicts the schematic with the evaluation board
reference designators.
Table 3. JUMPERS PLACED ONTO THE EVB
Jumpers in Place Reference Data
J1, J7, J13, J15, J16, J18, J20,
J22, J26
Appendix C
This circuit comprises R3 – R7, R17, CCR1, M1, Q1 and
D8. The selection of R3/4 and the value of R7 are based on
the Triac dimmer. The selection of R3 & R4 in parallel
(5.0 KW) and R7 & R17 in series (50 W) have produced good
results.