NSIC2050JB, NSIC2030JB: 120 Vac, Dimmable, 3-Stage Parallel-to-Series LED Lighting Circuit

DN05051/D
120 VAC, Dimmable, Linear
3‐stage, Parallel‐to‐Series
LED Lighting Circuit
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DESIGN NOTE
Table 1. DEVICE DETAILS
Device
Application
Topology
Efficiency
Input Power
Power Factor
THD
NSIC2030JB,
NSIC2050JB
AC LED
Lighting
Linear
82%
7.8 W
0.99
13.6%
Overview
an additional CCR to increase LED current at high voltages
to improve PF and THD.
This circuit uses inventive techniques to provide
a cost-efficient and effective AC LED lighting solution for
120 VAC mains power. Its primary features are its high
efficiency, dimmability, high light output, high power factor,
and low THD.
The circuit is designed for use with input voltages
between 110 VAC and 130 VAC.
The circuit uses a parallel-to-series topology that
dynamically adjusts LED forward voltage (Vf) to match the
bridge output voltage for high efficiency.
The circuit employs ON Semiconductor Constant Current
Regulators (CCRs) to regulate LED current and protect
LEDs from over-voltage conditions. The circuit also utilizes
F1
D1
D3
D2
D4
Key Circuit Features
• Functional with Wide Range of Standard Phase-Cut
•
•
•
•
•
•
TRIAC Dimmers
Low-Cost
PF = 0.99
Efficiency > 80% Over Voltage Range
THD < 15%
Adjustable for Different LED Voltages
Adjustable for Different Currents/Power Levels
Vin
MOV1
Q6
R6
CCR2
CCR1
R7
R9
LED1
Q4
C1
LED2
R4
Q9
D5
R11
R15
R12
LED3
Q2
D6
Q1
Q10
Q3
Q8
C2
R2
R14
R10
Q7
LED4
R5
Q11
D7
Q5
C3
R16
R8
R3
R13
R1
Figure 1. 3-stage Parallel-to-Series LED Lighting Circuit
© Semiconductor Components Industries, LLC, 2014
June, 2014 − Rev. 2
1
Publication Order Number:
DN05051/D
DN05051/D
Circuit Description
Using the values
VSWITCH(Q1) = 72 V.
The circuit consists of a full-wave bridge rectifier
(D1–D4), parallel-to-series switching circuitry (R1–R5,
R9–R16, C1–C3, Q1–Q5, Q7–Q11), CCR turn-on circuitry
(R6–R8, Q6), CCRs (CCR1–CCR2), LED routing diodes
(D5–D7), and LEDs (LED1–LED4).
R2 = 9.53 kW,
†† Similar
to the VSWITCH(Q1) relationship, Q11 is
triggered on by the R15/R16 resistor divider. Also an
ON Semiconductor MMBT3904L, the expected VBE(sat) of
Q11 is roughly 0.68 V, and by the following equation:
ǒ
Circuit Operation
Ǔ
V SWITCH(Q11) + V BE(sat) @ R15 ) R16
R16
The bridge rectifier outputs a half-wave sine peaking at
about 170 V (for 120 VAC). This bridge output is referenced
between the cathodes of D3 and D4 to the anodes of D1 and
D2.
The circuit dynamically adjusts the LED Vf to closely
resemble the rectified half-sine output of the full-wave
bridge. As seen in the “Representational Circuit Diagrams”
section, the LEDs change between three configurations with
varying bridge output.
The first configuration, when the bridge output is between
0 V and 72 V†, is a “parallel” stage, when all LEDs are in
parallel with each other. CCR2 is on, as well as all the Q3
through Q5 and Q7 through Q9 transistors. The D5, D6, and
D7 diodes are all reverse-biased. CCR current (when above
the LED Vf turn-on voltage of 36 V) is split down the four
strings of LEDs.
The second configuration, when the bridge output is
between 72 V and 145 V††, shifts the LEDs into two parallel
strings. Q1 initiates the transition into the second stage
switching on at 72 V due to the R1/R2 voltage divider. When
Q1 turns on, Q2’s VBE is shorted, eliminating base current
for transistors Q3, Q4, Q8, and Q9. As these turn off, the D5
and D7 diodes are forward biased, connecting LED1 to
LED2, and LED3 to LED4. D6 is still reverse-biased.
The third stage, when the bridge output is above 145 V,
puts all the LEDs in one series string. Q11 turns on by the
R15/R16 voltage divider and initiates this transition. Q11
turns off Q10, which then deprives Q5 and Q7 of base
current, turning them off as well. D6 becomes
forward-biased, and all the LEDs pass CCR2’s current.
After the LEDs are all in series, CCR1 is set to turn on to
provide additional current at high voltages. This matches the
total current waveform to the input voltage waveform,
achieving better power factor and THD performance. With
about an extra 7 V over the device, CCR1 is in full regulation
at about 152 V bridge output.
Using the values
VSWITCH(Q11) = 145 V.
R15 = 1 MW,
R16 = 4.7 kW,
Design Modifications
Special modifications for this circuit might include LED
string forward voltage (Vf) and CCR1 current value. For
optimal performance, it is recommended that LED strings of
Vf between 15 V and 40 V are used. Generally, the higher
the LED Vf, the greater the efficiency, though the benefits of
PF/THD-improving CCR1 are reduced. The lower the Vf,
the lower the efficiency and the earlier the LEDs will turn on.
Note that changing LED Vf will require R2 and R16 to be
changed to adjust switching points.
If a higher CCR1 value is desired, a darlington-connected
PNP pair or PFET is recommended in place of Q6 to reduce
base current and increase gain. Multiple CCRs may be used
in parallel with CCR2 to no adverse effect, only ensure that
R4, R11, and R12 allow sufficient base current.
Circuit Performance Data
Table 2. ELECTRICAL CHARACTERISTICS FOR THE
CIRCUIT SHOWN IN FIGURE 1
110 VAC
120 VAC
130 VAC
IRMS(IN) (mA)
64.39
65.49
66.06
PF
0.9886
0.9907
0.9921
THD (IRMS, %)
14.86
13.56
12.35
PIN (W)
6.93
7.75
8.44
Efficiency (%)
80.4
82.2
81.0
Product parametric performance is indicated in the Electrical
Characteristics for the listed test conditions, unless otherwise noted.
Product performance may not be indicated by the Electrical
Characteristics if operated under different conditions.
Dimmers Tested
† This switching voltage is determined by the R1/R2
resistor divider and the VBE(sat) of the transistor used − in
this case, an ON Semiconductor MMBT3904L NPN BJT.
A typical value for VBE(sat) at 25°C is roughly 0.68 V. The
switching voltage may be found using the following
equation:
ǒ
R1 = 1 MW,
Table 3. THE CIRCUIT WAS FULLY FUNCTIONAL
WITH EACH DIMMER TESTED
Ǔ
V SWITCH(Q1) + V BE(sat) @ R1 ) R2
R2
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Manufacturer
Serial Number
Leviton
600W−1D4102
Leviton
600W−1B4105
Lutron
Skylark CTCL−153PDH
Lutron
TG−600P−AC
DN05051/D
Representational Circuit Diagrams
LED1
Q4
D5
Q7
Q9
LED2
LED1
LED2
LED3
LED4
D6
LED3
Q3
Q5
D7
Q8
LED4
Figure 2. Stage 1/Parallel configuration of LEDs, showing behavior of switching circuitry. D5−D7 are open
circuits, whereas all the transistors Q3–Q5 and Q7–Q9 are on. The LEDs are then in parallel below the CCR.
The driver is in this state at bridge voltages below 72 V
LED1
Q4
D5
Q7
Q9
LED2
LED1
LED3
LED2
LED4
D6
LED3
Q3
Q5
D7
Q8
LED4
Figure 3. Stage 2/Parallel-Series configuration of LEDs. Transistors Q3–Q4 and Q8–Q9 are open, and current
flows through the routing diodes D5 and D7. Simplified schematic containing only the LEDs is shown to the right.
The driver is in this state between 72 V and 145 V
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DN05051/D
LED1
Q4
D5
Q7
LED1
Q9
LED2
LED2
D6
LED3
LED3
Q3
Q5
LED4
D7
Q8
LED4
Figure 4. Stage 3/Series configuration of the LEDs and switching circuitry shown. All transistors Q3–Q5
and Q7–Q9 are off at high bridge voltages, and current passes through the routing diodes D5–D7.
The driver is in this stage at bridge voltages above 145 V
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DN05051/D
Waveforms
Figure 5. The total input current follows the voltage waveform very closely, yielding high power factor
and outstanding THD performance
Figure 6. LED current through each of the LEDs. Note the current waveforms are nearly identical,
as well as the three distinct levels of current, coinciding with the three LED configurations
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DN05051/D
Figure 7. The LED forward voltage is identical for all LEDs. When the LED voltage is not 0 V, the LEDs are on.
Given an LED Vf of 32 V, the LEDs are on about 92% of the time
Figure 8. The CCR2 Vak demonstrates the different stages of the LED configurations. Q3 blocks CCR1 from
conducting only until the highest bridge voltages. Q3 and CCR1 are in parallel with CCR2
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DN05051/D
Figure 9. The circuit receives no input current when the TRIAC is off, and the current is normal
when the TRIAC is on
Figure 10. LED1’s voltage and current waveforms, unaffected by TRIAC dimming. The voltage on the LEDs
is due to the non-zero voltage out of the dimmer during the “off” state
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DN05051/D
Evaluation Board
The evaluation board CCR230PS3AGEVB (driver
circuitry, pictured below) may be altered from its original
design for 230 VAC to replicate the performance of this
circuit at 120 VAC.
Figure 11. CCR230PS3AGEVB Evaluation Board with Changes Marked for DN05051/D
A list of modifications appears below, along with data
taken using the metal-clad board. Overall circuit
performance is greatly improved when using metal-clad
boards.
Table 4. LIST OF MODIFICATIONS
CCR230PS3AGEVB
Reference
Recommended Modification
Alternative Modification
R3
Replace with 9.53 kW
Desired Rset1 Value
R2
R10
Replace with 4.7 kW
Desired Rset2 Value
R16
R15
Replace with 255 W
Parallel with 309 W
R6
R16
Replace with 24.9 kW
Parallel with 28 kW
R7
R17
Replace with 24.9 kW
Parallel with 28.7kW
R8
CCR1
Replace with NSIC2030JBT3G
−
−
Circuit Data
for switching resistors R2 and R16 is also given, as
a function of LED string voltage.
Of course, optimizing the system may require some
experimentation, but the plot is provided as a ballpark design
tool. With this design, four strings between 15 Vf and 40 Vf
are recommended, for a total of 60 to 160 Vf total of LEDs.
Table 5. USING REFITTED EVALUATION BOARD
110 VAC
120 VAC
130 VAC
IRMS(IN) (mA)
61.05
65.03
67.86
PF
0.9864
0.9890
0.9907
THD (IRMS, %)
16.5
14.42
13.02
PIN (W)
6.64
7.75
8.76
Efficiency (%)
84.1
83.3
80.1
DN05051/D Designator
Design Modifications
If the user wishes to connect their own LEDs to the
evaluation board, it should be noted that the off-board
connections (in keeping with the design note’s designators)
will be as shown in Figure 12.
It should also be noted that different LED voltages will
require you to adjust switchpoints for best performance.
A reference plot (Figure 13) showing recommended values
Figure 12. Off-board Connections, from Driver
Board to LEDs
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DN05051/D
Switching Resistor (R2) Value vs. LED String Vf
For Parallel-to-Series Applications
given R1 = 1 MW, and MMBT3904L (0.68 V VBEon)
Rswitch Resistor Value (kW)
20
18
Rswitch, Stage1-to-2
16
Rswitch, Stage2-to-3
14
12
10
8
6
4
2
0
15
20
25
30
35
40
LED String Voltage (V)
Figure 13. Plot showing recommended values for the Rswitch resistor values to determine the driver’s
switchpoints. The second-to-third stage trigger resistor is roughly half the value of the first-to-second stage
trigger resistor
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DN05051/D
Bill of Materials
Table 6. BILL OF MATERIALS FOR CIRCUIT SHOWN IN FIGURE 1
Designator
Qty
Description
Value
Tolerance
Manufacturer
Part Number
CCR1
1
Constant Current Regulator
120 V, 30 mA
±15%
ON Semiconductor
NSIC2030JB
CCR2
1
Constant Current Regulator
120 V, 50 mA
±15%
ON Semiconductor
NSIC2050JB
F1
1
Fuse
250 V, 1 A
−
Any
−
MOV1
1
Varistor
150 VAC
−
Any
−
D1−D4
4
Diode
400 V, 1 A
−
ON Semiconductor
MRA4004
D5, D7
2
Diode
75 V, 200 mA
−
ON Semiconductor
BAS16H
D6
1
Diode
250 V, 200 mA
−
ON Semiconductor
BAS21L
C1
1
Capacitor
2.2 nF, 500 V
−
Any
−
C2−C3
2
Capacitor
1 nF, 10 V
−
Any
−
Q1, Q11
2
NPN Transistor
40 V, 200 mA
−
ON Semiconductor
MMBT3904L
Q2, Q10
2
NPN Transistor
350 V, 100 mA
−
ON Semiconductor
MMBT6517L
Q3, Q5, Q8
3
NPN Transistor
140 V, 600 mA
−
ON Semiconductor
MMBT5550L
Q4, Q6, Q7, Q9
4
PNP Transistor
150 V, 500 mA
−
ON Semiconductor
MMBT5401L
R1, R15
2
Resistor
1 MW, 1/8 W
±1%
Any
−
R2
1
Resistor
9.53 kW, 1/8 W
±1%
Any
−
R3, R14
2
Resistor
300 kW, 1/8 W
±1%
Any
−
R4
1
Resistor
30 kW, 1/8 W
±1%
Any
−
R5, R9
2
Resistor
1 kW, 1/8 W
±1%
Any
−
R6
1
Resistor
255 W, 1/8 W
±1%
Any
−
R7−R8
2
Resistor
24.9 kW, 1/8 W
±1%
Any
−
R10, R13
2
Resistor
2.2 kW, 1/8 W
±1%
Any
−
R11−R12
2
Resistor
15 kW, 1/8 W
±1%
Any
−
R16
1
Resistor
4.7 kW, 1/8 W
±1%
Any
−
LED1−LED4
4
LEDs
36 V, 480 mA
−
Any
−
Further Reference
• Design Note – DN05047/D: 230 VAC, Low-Cost,
For a similar design (3-stage, Parallel-to-Series) adapted
to 230 VAC, please refer to design note DN05047.
Dimmable, 3-stage, LED Lamp Circuit
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