ON Semiconductor
NCL30186SMRTGEVB
8 W Smart LED Driver
Evaluation Board User Manual
Rev 00 3/27/17
1
ON Semiconductor
Overview
This manual covers the specification, theory of operation, testing and construction of the
NCL30186SMRTGEVB demonstration board. The NCL30186 board demonstrates an 8 W high PF
SEPIC LED driver with a 3.3V ‘always on’ auxiliary voltage rail to power a MCU/wireless
transceiver plus other accessories. A simple dimming and ON/OFF control is also provided
that demonstrates dimming control of the NCL30186 as well as dim to off operation.
Specifications
Input voltage (Class 2 Input, no ground)
Line Frequency
Power Factor (100 % Load)
IEC61000-3-2 Class C
LED Output Voltage Range
LED Output Current
Aux. Voltage (Available in all modes)
Aux. Current (user adjustable)
Efficiency
Standby Power
230 V 50 Hz
120 V 60 Hz
Analog Dimming Voltage
100 % Output
0 % Output
PWM Dimming Voltage
PWM Range (Freq > 200 Hz)
Start Up Time
Rev 00 3/27/17
100 – 265 V ac
50 Hz/60 Hz
0.9
Yes
40 – 80 V dc
100 mA dc
3.3 – 3.5 V
20 mA
84 %
Max
Typ.
Typ
Min
400 mW Universal Mains or
170mW 230 V Optimized
Typ.
Typ.
170 mW
Vdim > 2.5 V
Vdim < 0.1 V
0 – 3.3 V
0 – 100 %
< 500 ms
Typ.
2
ON Semiconductor
EMI (conducted)
Class B
FCC/CISPR
As illustrated, the key features of this demo board include:
Wide Mains
IEC61000-3-2 Class C Compliance over line and load
High Power Factor across wide line and load
Integrated Auto recovery Fault Protection (can be latched by choice of options)
o
Over Temperature on board (a PCB mounted NTC)
o
Over Current
o
Output and Vcc Over Voltage
3.3 V Aux Voltage
o
Available in all modes
“Dim to Zero Output”
On / Off Control
Theory of Operation
Power Stage
The power stage for the demo board is a non-isolated coupled SEPIC converter. The controller has a
built in control algorithm that is specific to the flyback transfer function and applies to flyback, buck-
boost, and SEPIC converters. Specifically:
Vout
Vin
=
Duty
(1−Duty)
Rev 00 3/27/17
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ON Semiconductor
The control is very similar to the control of the NCL30080-83 with the addition of a power factor
correction control loop. The controller has a built in hardware algorithm that relates the output
current to a reference on the primary side.
Vref × Nps
2 × Rsense
Npri
Nsec
Iout =
Nps =
Where Npri = Primary Turns and Nsec = Secondary Turns
We can now find Rsense for a given output current.
Vref × Nps
2 × Iout
Rsense =
Line Feedforward
The controller is designed to precisely regulate output current and can be compensated to
address variation due to line voltage variation. R14 sets the line feedforward and compensates
for power stage delay times by reducing the current threshold as the line voltage increases.
R14 is also used for the shorted CS (current sense) pin detection. At start up, the controller
puts out a current to check for a shorted pin. If R14 was not present, the measured voltage
would be too low due to the low value of the current sense resistor and the controller will not
start because it will detect a shorted pin. So R14 is required for proper operation and should be
greater than 250 Ω.
Voltage Sense
The voltage sense pin has several functions:
1. Basis for the reference of the PFC control loop
2. Line range detection
Rev 00 3/27/17
4
ON Semiconductor
The reference scaling is automatically controller inside the controller. The shape of the voltage
waveform on Vs is critical for the PFC loop control. The amplitude of Vs is important for the range
detection. Generally, the voltage on Vs should be 3.5 V peak at the highest input voltage of interest.
Voltage on Vs must
not
be greater than 4 V under any operating condition. The voltage on Vs
determines which valley the power stage will operate in. At low line and maximum load, the power
stage operates in the first valley (standard CrM operation). At the higher line range, the power stage
moves to the second valley to lower the switching frequency while retaining the advantage of quasi-
resonant soft switching.
Auxiliary Winding
The auxiliary winding has 3 functions:
1. CrM timing
2. Vcc Power
3. Output Voltage Sense
CrM Timing
In the off time, the voltage on the transformer/inductor forward biases Dout and D9. When the
current in the magnetic has reached zero, the voltage collapses to zero. This voltage collapse triggers a
comparator on the ZCD pin to start a new switching cycle. The ZCD pin also counts rings on the
auxiliary winding for higher order valley operation. A failure of the ZCD pin to reach a certain threshold
also indicates a shorted output condition.
Vcc Power
The auxiliary winding forward biases D9 to provide power for the controller. This arrangement is called
a “bootstrap”. Initially Cvcc, is charged through R4 and R13. When the voltage on Cvcc reaches the
startup threshold, the controller starts switching and providing power to the output circuit and the
Rev 00 3/27/17
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