NXP Semiconductors SSL21083 User manual

UM10501
SSL21083 reference board user manual
Rev. 2 — 16 November 2011 User manual
Document information
Info Content
Keywords SSL21083, buck converter, reference board, LED driver, LED retrofit
lamp, low power
Abstract This document describes the performance, technical data and the
connection of the SSL21083 reference board. The SSL2108 series is an
NXP Semiconductors driver IC intended to provide a low cost, small form
factor LED driver. This board is intended to operate at 230 V (AC), using
an output voltage of 30 V or more.

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User manual Rev. 2 — 16 November 2011 2 of 18
Contact information
For more information, please visit: http://www.nxp.com
For sales office addresses, please send an email to: [email protected]
NXP Semiconductors UM10501
SSL21083 reference board user manual
Revision history
Rev Date Description
v.2 20111116 second issue
Modifications: •Section 9 “Active bypass” on page 11: minor text changes
•Section 10 “Known issues” on page 12: section added.
v.1 20110908 first issue

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User manual Rev. 2 — 16 November 2011 3 of 18
NXP Semiconductors UM10501
SSL21083 reference board user manual
1. Introduction
The SSL21083 is a highly integrated switching mode LED driver which enables constant
current driving from the mains input. It is a solution for small LED retrofit lamp application,
especially for low-power factor design.
The SSL21083 is a buck converter controller suitable for non-isolated, non-dimmable LED
retrofit lamps. It can drive long LED strings with, typically 70 V forward voltage. The
SSL2108 series is intended to operate with higher output voltages, as present in modern
LED modules.
Remark: Unless otherwise stated all voltages are in V (AC).
2. Safety warning
This demo board is connected to a high AC voltage. Avoid touching the reference board
during operation. An isolated housing is mandatory when used in uncontrolled,
non-laboratory environments. Galvanic isolation of the mains phase using a fixed or
variable transformer (Variac) is always recommended. These devices are recognized by
the symbols shown in Figure 1.
WARNING
Lethal voltage and fire ignition hazard
The non-insulated high voltages that are present when operating this product, constitute a
risk of electric shock, personal injury, death and/or ignition of fire.
This product is intended for evaluation purposes only. It shall be operated in a designated test
area by personnel qualified according to local requirements and labor laws to work with
non-insulated mains voltages and high-voltage circuits. This product shall never be operated
unattended.
a. Isolated b. Not isolated
Fig 1. Variac isolation symbols
019aab173
019aab174

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NXP Semiconductors UM10501
SSL21083 reference board user manual
3. Connecting to the board
The board is optimized for a 230 V (AC, 50 Hz) mains supply. In addition to the mains
voltage optimization, the board is designed to work with multiple LEDs or an LED module
with a high forward voltage.
Mains connection of this reference board is different from other general evaluation/demo
boards. Connect the mains to the screw connector J6.
Remark: The maximum rated voltage of the board is 280 V (limited by the value of
electrolytic capacitor C1) or 400 V (DC).
The anode of the LED load is connected to positive positions 1 to 3 of connector J5. The
cathode is connected to negative 4 to 6 of connector J5.
Use an LED string with a VFgreater than 20 volt on this board. Under the expected
conditions, the output current is 96 mA. If the rated current of the LED does not meet this
specification, the current can be adjusted. See Section 6 for instructions.
(1) J6: connect the L of the AC mains supply.
(2) J6: connect the N of the AC mains supply.
(3) J5 (1 to 3): Positive anode positions.
(4) J5 (4 to 6): Negative cathode positions.
Fig 2. Board connection diagram
aaa-000495
J5 (1 to 3)
J5 (4 to 6)
J6

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User manual Rev. 2 — 16 November 2011 5 of 18
NXP Semiconductors UM10501
SSL21083 reference board user manual
4. Specification
5. Performance data
Table 1. Specifications for the reference board
Parameter Value Comment
AC line input voltage 170 V (AC) to 260 V (AC) the board is optimized for
230 V (AC), 50 Hz
output voltage 20 V (DC) to 130 V (DC) -
output current 96 mA at VO= 92 V (DC) 4%V
O= 60 V (DC) to
120 V (DC)
Maximum power in to LED load
(PO(load))12.5 W -
efficiency > 94 % 96 mA
power factor 0.6 at 10 W; 70 V; 96 mA output
0.5 at 3 W; 70 V; 96 mA output
board dimensions 17.5 mm 53.5 mm 17.5 mm length width height
(internal)
40 mm 83 mm length width (external)
operating temperature 40 Cto+100C-
NTC threshold temperature
(Tth(NTC))60 C onboard NTC activates above
60 C
IEC61000-3-2 compliant yes Po> 8.5 W
IEC55015 compliant yes see Figure 7 and Figure 8
Fig 3. Load regulation: output current as a function of output voltage
98
102
94
106
110
l
o
(mA)
90
V
out
(V (DC))
30 13011070 9050
aaa-000496

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User manual Rev. 2 — 16 November 2011 6 of 18
NXP Semiconductors UM10501
SSL21083 reference board user manual
Fig 4. Line regulation: output current as a function of input voltage
Fig 5. Line regulation: efficiency as a function of input voltage
(1) Efficiency
(2) Power factor
Fig 6. Load regulation: efficiency and power factor as a function of output voltage
aaa-000497
97
l
o
(mA)
90
96
95
94
93
92
91
V
i
(V)
170 270250210 230190
94
96
92
98
100
η
(%)
90
V
i
(V)
170 270250210 230190
aaa-000498
60
80
100
η
(%)
40
0.6
0.8
1
PF
0.4
V
OUT
(V (DC))
30 13011070 9050
aaa-000499
(1)
(2)

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SSL21083 reference board user manual
Fig 7. SSL21083 EMC measurement L-phase according to EN55015 norm
Fig 8. SSL21083 EMC measurement N-phase according to EN55015 norm
aaa-000500
NXP Semiconductors
1 P
K
M
AXH
2 A
V
CLRWR
SGL
6DB
TDF
dBµVdBµV
9 kHz 30 MHz
MT 15 ms
RBW 9 kHz
PREAMP OFFAtt 10 dB
15.Jun 11 15:30
100 kHz 1 MHz 10 MHz
0
10
20
30
40
50
60
70
80
90
100
1
Marker 1 [T2 ]
50.97 dBµV
9.000000000 kHz
EN55015A
EN55015Q
aaa-000501
NXP Semiconductors
1 P
K
M
AXH
2 A
V
CLRW
R
SGL
6DB
TDF
dBµVdBµV
9 kHz 30 MHz
MT 15 ms15.Jun 11 15:34
RBW 9 kHz
PREAMP OFFAtt 10 dB
100 kHz 1 MHz 10 MHz
0
10
20
30
40
50
60
70
80
90
100
1
Marker 1 [T2 ]
49.86 dBµV
9.000000000 kHz
EN55015A
EN55015Q

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User manual Rev. 2 — 16 November 2011 8 of 18
NXP Semiconductors UM10501
SSL21083 reference board user manual
6. Changing the output current
The SSL21083 monitors the charging current in the inductor using the sense resistors R5
and R6. It controls a MOSFET to retain a constant peak current. In addition, the IC
supports valley switching.
These features enable a driver to operate in Boundary Conduction Mode (BCM) with
valley switching where the average current in the inductor is the output current.
The SSL21083 turns off the MOSFET when the voltage on pin SOURCE reaches 500 mV.
If the value of R5 in parallel with R6 is 2 , the peak current is limited to 250 mA.
(1)
When the MOSFET is turned off, inductor L2 is discharged and the current flowing
through the inductor decreases. When the current in the inductor reaches 0 mA, the
voltage on the DRAIN pin starts to oscillate because of the stray capacitance (ringing).
SSL21083 waits for a valley of this oscillation.
The charge time of the inductor is calculated using Equation 2:
(2)
The discharge time of the inductor is calculated using Equation 3:
(3)
When the inductor is charging/discharging, a current flows through it. However, there is
also an effective current when ringing. Consider the oscillation frequency when adjusting
the output current. It is calculated using Equation 4:
(4)
The time from the start of oscillation to the first valley is calculated using Equation 5:
(5)
The output current is calculated using Equation 6. The resulting output current is:
(6)
Therefore by changing Ipeak we can change ILED.
Ipeak 0.5 R5 R6+
R5 R6
---------------------------------------
=
tch L2 2I
LED

ViVLED
–
------------------------
=
tdch L2 2I
LED

VLED
--------------------
=
fring 1
2 L2 CFET C5
--------------------------------------------------------------------
=
tring 1
2f
ring

-------------------
=
ILED 1
2
---Ipeak tch tdch
+
tch tdch tring
++
--------------------------------------
=

UM10501 All information provided in this document is subject to legal disclaimers. © NXP B.V. 2011. All rights reserved.
User manual Rev. 2 — 16 November 2011 9 of 18
NXP Semiconductors UM10501
SSL21083 reference board user manual
7. External OverTemperature Protection (OTP)
The SSL21083 supports external OTP by adding an external Negative Temperature
Coefficient (NTC) resistor. This feature is delivered by detecting a voltage on pin NTC. Pin
NTC has an integrated current source. The Resistance of the NTC resistor is decreased
as the temperature is raised. When the NTC temperature rises and the voltage on pin
NTC falls below 0.5 V, the SSL21083 lowers the threshold level for detecting peak current
in the inductor. Decreasing the peak current in the inductor causes the power current to
decrease. The output current is regulated to the point where a balance between
temperature and output current can be retained (the so called thermal management).
If the temperature on NTC increases continuously and the voltage on the pin drops below
0.3 V, the SSL21083 starts the NTC time-out timer. If the voltage on pin NTC pin does not
drop below 0.2 V within the time-out, the SSL21083 detects an abnormal condition and
stops switching. If the voltage reaches 0.2 V within the time-out period, a PWM signal is
assumed.
An NTC resistor can be directly connected to pin NTC. It is also possible to tune the
protection temperature by adding a resistor in parallel or in series with the NTC. One NTC
and one resistor are installed on the reference board. The values of these components
can be changed depending on the protection temperature requirement and component
availability.
The NTC should be mounted in thermal contact with the LED string.

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SSL21083 reference board user manual
8. Power factor adjustment
The SSL21083 IC and SSL21083 reference designs are designed for standard operation
with a power factor of 0.6 at 230 V (AC). This choice offers highest efficiency. It is possible
to tune the power factor to higher values using two methods.
Increasing the value of R1 raises the power factor above 0.7 with additional losses. (see
Table 2).
A resistor value of 270 for R1 also results in operation with most available phase cut
dimmers without damaging the lamp or dimmer. This change is not intended to reach
stable operation without flicker or a good dimming range.
Dimension the power rating of R1 to handle peak powers that occur using leading-edge
dimmers. These powers range between 2 W to 4 W. Alternatively, make a thermal link
between the onboard NTC and R1, causing the board to turn off at overtemperature of R1.
The second option is to increase power factor is using a valley fill circuit. The basic
schematic for this circuit is shown in Figure 9. Table 3 shows the results when using a
4.7 F capacitor for C2X and C2Y.
The valley fill circuit can only be employed, if the output voltage is below half the peak
input voltage. At 230 V (AC) input, it operates up to 85 V (DC) output voltage, otherwise
no power is delivered to the LEDs during the valley duration.
Table 2. Power factor adjustment - increasing the value of resistor R1
VIN (V (AC)) Vo(Vavr) Io(mA) R1 ()Efficiency (%) Power factor THD (%)
230 101.5 94 10 95.2 0.59 109.2
230 102.9 127 10 94.7 0.6 94
230 98 46 22 91.6 0.52 150
230 100.6 94 22 94.4 0.6 107
230 100.8 94 270 85.2 0.71 84
Table 3. Power factor adjustment - valley fill circuit
VIN (V (AC)) Vo(Vavr) Io(mA) R1 ()Efficiency (%) Power factor THD (%)
230 85 97 22 95.1 0.78 66
230 61 100 270 89.3 0.8 58
Fig 9. Valley fill circuit
aaa-000502
R1
C2X
C2Y