NSIC2020JB, NSIC2030JB: 230 Vac, Low-Cost, Dimmable, Three-Stage, Linear LED Lamp Circuit

DN05047/D
Design Note – DN05047/D
230 Vac, Low-Cost, Dimmable,
Three-Stage LED Driver
Device
Application
NSIC2020JB,
NSIC2030JB
LED Lighting
Topology Efficiency THD Power Factor Input Power
Linear
78%
17%
0.99
15 W
Schematic
Figure 1: Three-Stage 230 Vac CCR lighting circuit
Overview
This circuit uses an innovative linear topology
to meet and exceed the design requirements for LED
lamps that operate on 230 Vac mains power. Its
primary features are its low cost, phase-cut
dimmability, compactness, high light output,
efficiency, high power factor, and low THD. The
circuit uses ON Semiconductor Constant Current
Regulators (CCRs) to control the current through the
LEDs and protect against overvoltage. The circuit is
capable of operating at 50 or 60 Hz and at voltages
from 80 to 255 Vac.
May 2014, Rev. 3
Circuit Description
The circuit consists of a full-wave bridge
rectifier (D1-D4), threshold detection and switching
circuitry (R1-R22, Q1-Q11, and D5-D7), four LED
strings (LED1-LED3, LED4-LED6, LED7-LED9, and
LED10-LED12), and three ON Semiconductor
Constant Current Regulators (CCR1-CCR3).
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DN05047/D
Circuit Operation
The bridge rectifies the 230 Vac input
providing a waveform with a peak voltage of 322 V.
The bridge output is referenced from the cathodes of
D3 and D4 to the anodes of D1 and D2.
Referring to Figures 2-6, it can be seen that
the arrangement of the LED strings is adjusted
through three distinct stages. The four strings of
LEDs automatically adjust their configuration with
each other depending on the bridge output voltage.
If the bridge output voltage is from 0 to 110 V,
the circuit is in Stage 1 and the four strings are
configured in parallel. Between 110 and 230 V, the
circuit is in Stage 2 and the four strings are
configured in a 2 x 2 parallel and series array. Stage
3 is when the bridge output voltage is greater than
230 V. In the third stage, all of the LEDs are in
series.
The circuit uses voltage dividers in
conjunction with the bridge output voltage to switch
between the three stages. Q1 initiates the switching
process between Stage 1 and Stage 2, and Q3
initiates the switching process between Stage 2 and
Stage 3.
This circuit is configured to function with the
LEDs having a forward voltage of about 56 V with 70
mA through them. This topology should be applied
with LED strings with forward voltages between 55
and 60 V. The switching points between stages
should be set so that the voltage across CCR2 and
CCR3 is between 5 and 15 V when transitioning
between stages. An example of this is the second
waveform in Figure 9. Setting the switching points
properly allows for high efficiency and prevents
adverse effects such as flickering while dimming.
R3 and R10 may be adjusted to move the
switching points. For example, the switching point
for Q1, denoted VSWITCH(Q1) depends on R1, R2, R3
and the VBE(Sat) of Q1. This relationship is
expressed by the following equation:
𝑉𝑆𝑊𝐼𝑇𝐶𝐻(𝑄1)
𝑅1 + 𝑅2 + 𝑅3
= VBE(Sat) �
�
𝑅3
May 2014, Rev. 3
Circuit Data
220 Vac
230 Vac
240 Vac
50
50
50
Power (W)
13.9
14.6
15.4
Input Current (mArms)
64.0
64.3
64.7
Power Factor
0.985
0.986
0.987
Efficiency (%)
79.4
77.7
75.4
THD (%, Input Irms)
17.1
16.5
16.0
Input Frequency (Hz)
Table 1: Electrical Characteristics
Key Circuit Features
Q1 is an ON Semiconductor MMBT3904L. A
typical VBE(Sat) value of Q1 at 25 °C is 0.68 V. With
R1 = 560 kΩ, R2 = 442 kΩ, and R3 = 6.2 kΩ, VSWITCH
is at about 110 V.
A similar equation may be used for adjusting
the switching point between Stage 2 and Stage 3:
𝑅8 + 𝑅9 + 𝑅10
�
𝑉𝑆𝑊𝐼𝑇𝐶𝐻(𝑄3) = VBE(Sat) �
𝑅10
Q3 is also an ON Semiconductor
MMBT3904L. With R8 = 560 kΩ, R9 = 442 kΩ, and
R10 = 2.94 kΩ, VSWITCH is at about 230 V.
To achieve high power factor and low THD
characteristics, it is important to match the input
current waveform to the input voltage sine wave.
The circuit in this design note does this by allowing
more current to pass through the load in Stage 3. As
the input voltage rises, Q5 turns on. When Q5 is on,
CCR1 is in parallel with CCR2 and CCR3.
CCR1 and CCR2 are 20 mA CCRs and
CCR3 is a 30 mA CCR. Therefore, the total current
to the LEDs is about 50 mA in Stage 1 and Stage 2,
and about 70 mA in Stage 3.
Testing has shown that THD may be
minimized to 6.9% at 230 Vac by eliminating CCR2
and substituting an NSIC2050B (50 mA CCR) for
CCR1. This more closely matches the input current
waveform to the input voltage waveform. The only
disadvantage to this configuration is that the linearity
of the dimming may be adversely affected.
Input power and current may be raised or
lowered by using different CCRs. ON Semiconductor
NSIC2020B (20 mA), NSIC2030B (30 mA), and
NSIC2050B (50 mA) are suitable for this application.
Higher levels of current may require adjustments to
resistors to provide higher base currents for the
BJTs.
 Fully functional with standard phase-cut dimmers
 Extremely low cost
 Power factor = 0.99
 Input current THD = 17% (tunable to 6.9%)
 Efficiency = 78%
 Functional from 80 to 255 Vac
 Constant current and protection for LEDs
 Compact form factor
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DN05047/D
Bill of Materials
Designator
Manufacturer Part Number
Qty
Description
Value
Tolerance
C1
Any
-
1
Capacitor
2.2 nF, 500 V
-
C2-C4
Any
-
1
Capacitor
1.0 nF, 10 V
-
CCR1, CCR2
ON Semi
NSIC2020JB
2
Constant Current Regulator
120 V, 20 mA
±15%
CCR3
ON Semi
NSIC2030JB
1
Constant Current Regulator
120 V, 30 mA
±15%
D1-D4
ON Semi
MRA4007
4
Diode
1000 V, 1 A
-
D5, D7
ON Semi
BAS16H
2
Diode
75 V, 200 mA
-
D6
ON Semi
MRA4004
1
Diode
400 V, 1.0 A
-
F1
Any
-
1
Fuse
350 Vac, 1 A
-
LED1-LED12
Any
-
12
LED
20 V, 175 mA
-
MOV1
Any
-
1
Varistor
300 Vac
-
Q1, Q3
ON Semi
MMBT3904L
2
NPN Transistor
40 V, 200 mA
-
Q2, Q4, Q6, Q8
ON Semi
MMBT6517L
4
NPN Transistor
350 V, 100 mA
-
Q5
ON Semi
MMBT5401L
1
PNP Transistor
150 V, 500 mA
-
Q7, Q9, Q11
ON Semi
MMBT6520L
3
PNP Transistor
350 V, 500 mA
-
Q10
ON Semi
MMBT5550L
1
NPN Transistor
140 V, 600 mA
-
R1, R8
Any
-
2
Resistor
560 kΩ, 1/8 W
±1%
R2, R9
Any
-
2
Resistor
442 kΩ, 1/8 W
±1%
R3
Any
-
1
Resistor
6.2 kΩ, 1/8 W
±1%
R4, R5, R11, R12
Any
-
4
Resistor
150 kΩ, 1/8 W
±5%
R6
Any
-
1
Resistor
30 kΩ, 1/8 W
±5%
R7, R14, R19, R21, R22
Any
-
5
Resistor
2.2 kΩ, 1/8 W
±5%
R10
Any
-
1
Resistor
2.94 kΩ, 1/8 W
±1%
R13, R18, R20
Any
-
3
Resistor
10 kΩ, 1/8 W
±5%
R15
Any
-
1
Resistor
1.4 kΩ, 1/8 W
±1%
Any
-
2
Resistor
200 kΩ, 1/8 W
±1%
R16, R17
Table 2: Bill of Materials for the circuit shown in Figure 1.
Dimmers Tested
Dimmer
Clipsal 32V500
Clipsal KB31RD400
Legrand 99314
Legrand 99958
MK SX8501
Relco RTS65R
SCT Y-25082A
Table 3: The circuit was fully functional with each dimmer tested.
May 2014, Rev. 3
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DN05047/D
Representational Circuit Operation and Waveforms
Figure 2: The LED strings alternate between three different configurations.
Figure 3: The circuit is in Stage 1 when the bridge output voltage is less than about 110 V. All four of the LED
strings are in parallel in Stage 1.
May 2014, Rev. 3
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DN05047/D
Figure 4: Stage 2 occurs when the bridge output voltage is between about 110 V and 230 V. In this stage, the
LED strings are in a 2 x 2 array. In total, there are two parallel strings each consisting of six 20 V LEDs.
Figure 5: In Stage 3, all of the LEDs are in series. The circuit is in Stage 3 if the bridge output voltage is greater
than approximately 230 V.
May 2014, Rev. 3
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DN05047/D
Figure 6: The total input current waveform is nearly sinusoidal, which provides excellent power factor and THD
characteristics.
Figure 7: The LED current through each of the four strings is identical.
May 2014, Rev. 3
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DN05047/D
Figure 8: Each LED string receives the same voltage.
Figure 9: CCR1 conducts when the circuit is in Stage 3. CCR2 and CCR3 are on in all three stages.
May 2014, Rev. 3
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DN05047/D
Evaluation Board
The evaluation kit CCR230PS3GEVK implements this circuit on metal-clad board, and
includes both driver and LED boards, pictured in Figure 10. The driver board (top board) may
be obtained singularly via the CCR230PS3AGEVB evaluation board.
Figure 10: Contents of evaluation kit CCR230PS3GEVK.
If the user desires to use their own LEDs with the evaluation board, it should be noted that the off-board
connections (in keeping with the design note’s designators) are as follows:
Figure 11: Connections to map to off-board LEDs. The circuit will not function in all three stages if one or more
strings are connected incorrectly or missing.
Further References
For a similar CCR LED lighting solution at 120VAC, please refer to this design note:
•
Design Note – DN05051/D: 120 VAC, Dimmable, Linear, 3-Stage, Parallel-to-Series
LED Lighting Circuit
http://www.onsemi.com/pub_link/Collateral/DN05051-D.PDF
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© 2014 ON Semiconductor.
Disclaimer: ON Semiconductor is providing this design note “AS IS” and does not assume any liability arising from its use; nor
does ON Semiconductor convey any license to its or any third party’s intellectual property rights. This document is provided only to
assist customers in evaluation of the referenced circuit implementation and the recipient assumes all liability and risk associated
with its use, including, but not limited to, compliance with all regulatory standards. ON Semiconductor may change any of its
products at any time, without notice.
Design note created by Andrew Niles, e-mail: [email protected]
May 2014, Rev. 3
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