NCL30051LEDGEVB ON Semiconductor, NCL30051LEDGEVB Datasheet - Page 11

• Manufacturer Part Number: NCL30051LEDGEVB
• Description: Power Management IC Development Tools 90-265VAC 60W ISO CC EVB
• Manufacturer: ON Semiconductor
• Type: Power Factor Correctionr

Specifications of NCL30051LEDGEVB

• Rohs: yes
• Product: Evaluation Boards
• Tool Is For Evaluation Of: NCL30051
• Input Voltage: 90 VAC to 265 VAC
• Output Voltage: 35 V to 50 V
• Output Current: 1.5 A

Dimming Capabilities
circuit, the same DIM control card used in the NCL30001
LED driver circuit described in AND8470 has been used
here. Dimming can be accomplished using three methods:
pulse width modulation (PWM) of the output current;
analog current dimming where the current reference voltage
for U4B is modified via a 1 to 10 V control signal to linearly
control the output current to the LEDs; and bi−level
dimming in which a logic level signal will lower the LED
intensity level by reducing the LED output current. Without
this DIM card, a PWM input terminal (J3) is still provided
for an external 160 to 300 Hz PWM input signal to control
the output current. This is done by switching transistor Q6
on and off which in turn switches the sample and hold
transistor gate drive, and toggles optocoupler U2 which
switches U1’s Ct pin (2) via buffer transistor Q7. This pin,
when grounded, will terminate drive to the half−bridge
MOSFETs (Q2A, Q2B) thus rapidly stopping output current
flow. Due to the low value of output capacitors C18 and C19,
a rectangular wave signal in the frequency range of 160 to
300 Hz will adequately PWM the output current with good
rise and fall times (see Figure 6). C1 on the DIM card sets
this frequency. Higher dimming frequencies can but used
but the dynamic range of the dimming can be limited due to
waveform fall times. It should be noted that jumper J2 across
pins 2 and 3 of connector P1 is necessary if the DIM card is
of Figure 7), it is possible to get a slight beat between this
frequency and a harmonic of the line frequency. Depending
on the magnitude of the overall output ripple and the
selection of C4 / C5, there is the potential for LED current
To demonstrate the LED dimming capabilities of this
Depending on the selected PWM dimming frequency (C1
Figure 6. PWM Dimming Mode – Output Current Profile
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not installed. More details of the DIM card operation can be
found in AND8470. A table for configuring the three
different operating modes is shown below and the schematic
for the DIM card circuit is shown in Figure 7.
modulation at some pulse widths. It is best to select the
PWM dimming frequency to be in between the line
frequency harmonics. Thus, 160 or 220 Hz would be
recommended optimum PWM frequencies for a line
frequency of 60 Hz. (See section on Output Ripple below.)
Dimming Configuration
External PWM dimming
input
Internal PWM dimming
Bi−Level Dimming
Analog Dimming, Internal
Adjust
Analog Dimming, External
Adjust
Modifications; Jumper
Configurations
Omit DIM card; short pins 2 and
3 of P1.
Inject PWM signal into J3
Add DIM card with JMP1 added
to P1 on DIM card; Add JMP3 to
P2 on DIM card. Adjust pot R1 to
vary pulse width.
Add DIM card with JMP1 (P1)
removed; Add JMP3 to P2 on
card; Connect switch from TP1
and TP2. Closed switch gives
low dim level.
Add DIM card with JMP1 (P1)
removed: Add JMP2 to P2;
Adjust pot R9 for LED
brightness.
Add DIM card with JMP1 (P1)
removed. Add JMP2 to P2.
Remove pot R9 and wire in
external 100k potentiometer to
TPs 2, 3 and 4. TP3 is the pot
wiper. Adjust external pot for
LED brightness.