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Texas Instruments Isolated 70-W streetlight LED driver using UCC28810 Application notes
Application Report
SLUA752 – August 2015
Isolated 70-W Streetlight LED Driver Using UCC28810
Bharat Agrawal, Sanjay Dixit .................................................................................... Power Management
ABSTRACT
LED lighting is being used for residential, commercial and industrial applications. It offers various
advantages over incandescent bulbs, such as lower energy consumption, longer life, attainment of full
brightness without need for a warmup time, and so forth. With the advent of these lights in large numbers,
regulations in a few countries require LED drivers with high power factor (greater than 0.9) and low current
THD (less than 10 per cent), to have minimum effect on the grid.
Conventionally, UCC28810 operates in critical conduction mode, resulting in a high value of current THD.
This application report describes use of UCC28810 in a single-stage 70-W streetlight LED driver in AC/DC
Flyback topology with fixed-frequency and constant on-time switching, to achieve power factor greater
than 0.9 and current THD less than 10 percent. CD74HCT14 Schmitt-triggered inverter is used to
implement external oscillator, feedback sawtooth generator and short-circuit protection circuit. Output
current regulation and output open-circuit protection are implemented with both secondary-side and
primary-side regulation circuits. Implementation with single stage helps to reduce number of components,
system size and cost.
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3
4
5
6
7
8
Contents
Design Specifications ....................................................................................................... 2
Application Schematic ....................................................................................................... 3
2.1
Secondary-Side Output Current Regulation ..................................................................... 3
2.2
Primary-Side Output Current Regulation ........................................................................ 5
Principle of Operation ....................................................................................................... 7
3.1
Active Startup Circuit ............................................................................................... 8
3.2
Switching Oscillator ................................................................................................. 8
3.3
Soft-Start Circuit .................................................................................................... 9
3.4
Output Current Regulation ......................................................................................... 9
3.5
Output Short-Circuit Protection .................................................................................. 12
3.6
Output Open-Circuit Protection .................................................................................. 12
Performance Data and Typical Characteristic Curves................................................................. 14
4.1
Output Current Variation with Respect to Input Voltage ..................................................... 14
4.2
Power Factor Variation With Respect to Input Voltage ...................................................... 14
4.3
Variation of Current THD with Input Voltage................................................................... 15
4.4
External Oscillator and Feedback Ramp ...................................................................... 15
4.5
Primary-Side FET Gate Drive, Drain, and Current-Sense Waveforms ..................................... 16
4.6
MOSFET Drain and Primary-Side Current Sense Voltage Envelope ...................................... 16
4.7
Gate Drive, Auxiliary Winding, and Flip-Flop Toff Detector Waveforms ..................................... 17
Bill of Materials ............................................................................................................. 18
5.1
Secondary-Side Output Current Regulation ................................................................... 18
5.2
Primary-Side Output Current Regulation ....................................................................... 20
Test Results ................................................................................................................. 22
6.1
Secondary-Side Output Current Regulation ................................................................... 22
6.2
Primary-Side Output Current Regulation ....................................................................... 22
Conclusion .................................................................................................................. 23
References .................................................................................................................. 23
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Isolated 70-W Streetlight LED Driver Using UCC28810
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Design Specifications
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List of Figures
1
Schematic for 70-W Streetlight LED Driver With Secondary-Side Regulation (Part 1) ............................. 3
2
Schematic for 70-W Streetlight LED Driver with Secondary-Side Regulation (Part 2) ............................. 4
3
Schematic for 70-W Streetlight LED Driver with Primary-Side Regulation (Part 1) ................................. 5
4
Schematic for 70-W Streetlight LED Driver with Primary-Side Regulation (Part 2) ................................. 6
5
Active Startup Circuit ........................................................................................................ 8
6
Switching Oscillator .......................................................................................................... 8
7
Soft-Start Circuit
8
Alternate Implementation for Primary-Side Output Current Regulation
9
10
11
12
13
14
15
16
17
18
19
............................................................................................................. 9
............................................ 10
Primary-Side Output Current Regulation Logic......................................................................... 11
Flip-Flop Circuit to Extract Toff ............................................................................................ 11
Output Short-Circuit Protection ........................................................................................... 12
Output Open-Circuit Protection in Primary-Side Regulated System................................................. 13
Output Current Variation with Respect to Input Voltage .............................................................. 14
Power Factor Variation With Respect to Input Voltage ............................................................... 14
Variation of Current THD with Input Voltage............................................................................ 15
External Oscillator and Feedback Ramp ............................................................................... 15
Primary-Side FET Gate Drive, Drain, and Current-Sense Waveforms .............................................. 16
Primary-Side FET Drain and Current Sense Voltage Envelope ..................................................... 16
Primary-Side FET Gate Drive, Auxiliary Winding, and Flip-Flop Toff Detector .................................... 17
List of Tables
1
UCC28810-based 70-W Streetlight LED Driver Design Specifications ............................................... 2
2
Bill of Materials for Circuit with Secondary Side Regulation .......................................................... 18
3
Bill of Materials for Circuit with Primary Side Regulation ............................................................. 20
4
Performance Characteristics of 70-W LED Driver Design With Secondary-Side Output Current Regulation
5
1
.
Performance Characteristics of 70-W LED Driver Design with Primary-Side Output Current Regulation ......
22
22
Design Specifications
Table 1 lists the UCC28810-based 70-W streetlight LED driver design specifications.
Table 1. UCC28810-based 70-W Streetlight LED Driver Design Specifications
Design Specifications
Input voltage range (VIN)
2
Universal, 90 V–265 V AC RMS
Output voltage (VOUT)
106 V
Load current (IOUT)
600 mA
Power factor
Greater than 0.9 in VIN range
Current total harmonic distortion (ITHD)
Less than 10%
Output short-circuit protection
Yes
Output open-circuit protection
Yes
Isolated 70-W Streetlight LED Driver Using UCC28810
Copyright © 2015, Texas Instruments Incorporated
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J1
•
•
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•
C11
4.7 µF
•
•
•
UCC28810
ISENSE
TZE
GND
6
5
TZE
4.7E
ISENSE
U3
56 K
R20
Copyright © 2015, Texas Instruments Incorporated
•
VOUT
•
R35
1K
•
•
R40
47 K U4 TL431
FB
•
33 K
R28
•
FB
D11
12 V
12 V
•
TL431
•
470 nF
C20
R26
4.7 K
R27
150 K
C21
R6
22 K
R29
0.82E
•
U5
PC817
R24
0.2E
•
2.2 M
IRAMP
VINS
•
R7
22 K
•
•
3
Q3
STP8N80K5
•
4
•
•
R23
R25
•
••
C14
10 µF
7
2.7 K
C8
DNP
R31
DNP
1
J4
Secondary-Side Output Current Regulation
EAOUT GDRV
•
2
.1 µF
18 V
C7
1
J3
2.1
C2
220 nF
•
C13 100 nF
•
VDD
33 µF
C19
D1
US1 M
AUX_IN
C6
180 uF 180 uF
VOUT
Application Schematic
R10
•
VSENS
8
R38A
C18
1 nF
R4
STTH1008DTI
D4
•
1
U2
•
•
•
VSENSE
C3
220 K
T1
2
BAT85
•
BC557
Q1
SS
EAOUT
•
R8 22 K
VDD
220nF
C28
•
•
R18
1M
R21
82 K
C20A
C19A
•
VCC
1M
R21A
100 µH
L3
•
VCC
•
VCC
•
D4A
1N5399
•
•
2.2 M
D3A
1N5399
1M
R20A
10 mH
•
D9A
1N4007
C6A
•
•
D6
•
MOV1
•
100 nF
ACREC
•
C2A
100 µH
1M
L2
•
100 nF
D2A
1N5399
•
3
L1
D1A
1N5399
1 nF
•
2
•
C1
R10A
•
2.2 M
•
1
F1
R21B
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Application Schematic
Figure 1 and Figure 2 illustrate the secondary-side output current regulation schematics.
•
•
•
47 µF 25 V
•
•
••
Figure 1. Schematic for 70-W Streetlight LED Driver With Secondary-Side Regulation (Part 1)
Isolated 70-W Streetlight LED Driver Using UCC28810
3
Application Schematic
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C16
D8
VCC
R12
•
5.6 K
R9
ISENSE
12 K
R15
•
8.2 K
•
R19
•
1M
2.2 nF
IN4148
U1-B
R16
8.2 K
•
•
•
•
4 U7
Q2
BC547
R11
12 K
47 pF
C10
CD74HCT14
U1-A
•
U1-C
•
SS
•
•
D9
VSENSE
CD74HCT14
CD74HCT14
BAT54
D7
R22
VCC
4.7 K
IN4148
C22
U1-D 1 µF
•
C4
9
U1-E
C5
8
•
Q7
•
•
IRAMP
•
C15
10 nF
1 nF
CD74HCT14
100 pF
ACREC
• •
R34
1K
U1-F
BSS123
VCC
R13
5.6 K
TZE
R32 240 K
R33 CD74HCT14
1K
CD74HCT14
•
Q4
BC547
R5A
100 K
VDD
Q6
R17
0E
•
BC547
0.1 µF
C24
R37
•
150 K
D2
R38
•
R36
10 K
R5
100 K
D3
•
•
33 K
C26
R1
330 K
R2
•
150E
VCC
C27
47 µF 10 V
•
BC547
47 K
R3
Q8
FJP5027OTU
C23
0.1 µF
•
AUX_IN
R39
US1 M
D14
18 V
•
Q5
•
•
•
150 E
C12 US1 M
4.7 µF
•
•
R41
•
100 E
VDD
Figure 2. Schematic for 70-W Streetlight LED Driver with Secondary-Side Regulation (Part 2)
4
Isolated 70-W Streetlight LED Driver Using UCC28810
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Application Schematic
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2.2
Primary-Side Output Current Regulation
VOUT
1
J4
J3
1
Figure 3 and Figure 4 illustrate the primary-side output current regulation schematics.
C8
•
•
•
ISENSE
TZE
3
UCC28810
4
VINS
ISENSE
GND
TZE
5
6
EAOUT GDRV
IRAMP
C13 100 nF
R20
•
56 K
SS
C2
220 nF
R8 22 K
R18
1M
•
•
•
•
2.2 M
R20A
R24
0.2E
Q3
STP8N80K5
R23
.1 µF
33 µF
8
2
1
VSENSE
R21
82 K
VCC
1M
100 µH
VCC
•
EAOUT
C11
4.7 µF
BC557
Q1
R7
22 K
2.2 M
R10
BAT85
•
D6
MOV1
•
••
J1
VCC
3
C1
•
100 nF
•
2
•
•
•
1
R21A
D3A
1N5399
10 mH
L1
•
F1
•
C2A
100 nF
•
•
D4A
1N5399
L3
100 µH
1M
L2
R21B
R10A
•
2.2 M
D1A
1N5399
•
D2A
1N5399
•
7
VDD
VSENS
•
U2
•
4.7E
18 V
•
C20A
•
•
C19A
1M
D9A
1N4007
R38A
•
•
•
C19
•
•
•
C18
VDD
•
•
C14
10 µF
D1
C3
1 nF
•
•
•
220nF
C6A
ACREC
•
•
US1 M
AUX_IN
R4
220 K
C28
1 nF
T1
D4
STTH1008DTI
•
C7
•
C6
•
180 uF 180 uF DNP
•
Figure 3. Schematic for 70-W Streetlight LED Driver with Primary-Side Regulation (Part 1)
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6
Isolated 70-W Streetlight LED Driver Using UCC28810
Copyright © 2015, Texas Instruments Incorporated
D14
18 V
•
•
C23
0.1 µF
BC547
R41
100 E
C24
0.1 µF
R36
10 K
•
VDD
US1 M
D3
150E
R39
150 E
VDD
C26
•
•
BC547
Q5
R1
33 K
•
•
47 K
R3
330 K
R2
•
•
•
C27
47 µF 10 V
VCC
•
•
•
•
Q12
GDRV
1 µF
C31
22 nF
C32
•
GDRV
•
R48
10 K
Q13
•
R51
C12 US1 M
4.7 µF
•
AUX_IN
VDD
100 E
R45
100 pF
C37
•
•
4.7K
R53
•
C35
150 K
•
R38
12 V
BC547
BAT85
D15
Q10
100 K
R55
22 K
R49
FF
• • •
C34
1 µF
4.7 K
R54
•
1 nF
Q8
FJP5027OTU
R17
0E
•
D2
D16
Q4
R44
•
R37
C30
330 K
168 pF
•
FF
•
•
100 E
Q6
C29
1nF
•
R30
33 K
•
4.7 µF
47 K
C33
R50
100E
R5
100 K
R5A
100 K
IRAMP
VIN
•
Q9
BC547
•
C36
•
•
•
C15
10 nF
VSENSE
R14
120 K
R43
CD74HCT14
Q7
• •
BAT54
D9
SS
D5
12 V
165 K
R33 CD74HCT14
1K
•
R34
1K
R13
5.6 K
VCC
CD74HCT14
•
4 U7
VC12
VDD
R57
1 nF
•
U1-F
TZE
4.7 K
R22
•
U1-C
•
EAOUT
1N4148
CD74HCT14
•
U1-E
IN4148
D7
CD74HCT14
U1-A
CD74HCT14
U1-B
1M
R19
1 nF
8
Q2
BC547
•
D18
ACREC
9
C5
R11
12 K
•
R16
8.2 K
2.2 nF
C16
D19
100 pF
•
C22
•
•
IN4148
•
•
•
•
100 K
R56
•
C38
100pF
1N4148
U1-D 1 µF
•
•
8.2 K
•
D8
10 K
VCC
R32 240 K
47 pF
C10
12 K
R9
•
R15
10 K
C4
ISENSE
5.6 K
R12
VSENSE
AUX_IN
Q11
R58
BSS123
VCC
Application Schematic
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R52
D17
BAT85
R47
4.7 K
22 K
R46
Figure 4. Schematic for 70-W Streetlight LED Driver with Primary-Side Regulation (Part 2)
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Principle of Operation
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3
Principle of Operation
The UCC28810 is an off-line AC/DC controller specifically designed to drive high power LEDs for lighting
applications requiring power factor correction and EMC compliance. It is designed for controlling a
Flyback, single-ended primary-inductance converter (SEPIC), or Boost converter operating in critical
conduction mode. The UCC28810 features a transconductance amplifier for feedback error processing, a
simple current reference generator for generating a current command proportional to the input voltage, a
current-sense (PWM) comparator, PWM logic, and a totem-pole driver for driving an external FET. To
overcome the issue of high ITHD, these subsystems internal to low-cost UCC28810 are used here to
operate at fixed switching frequency with constant on-time, and achieve high power factor and low ITHD,
less than 10 percent.
Figure 1 depicts a reference schematic describing key components in the Flyback stage. Input AC voltage
is rectified using full bridge rectifier (D1A–D4A) to obtain a unidirectional AC bus. It may be noted that the
input capacitor is so small (220 nF) that the input voltage is close to a rectified sinusoid, as also required
to obtain high power factor. This rectified VIN is connected through transformer primary winding to the
drain of switching FET Q3, whose source is connected to ground return through the current-sensing
resistor R24.
The transformer primary inductance, Lp is related to the switching frequency fsw, converter output power
Pout, system efficiency η, maximum on-time, ton-max at minimum input line voltage Vin_rms(min) according to the
equation:
Lp =
2
h ´ Vin2 _ rms(min) ´ t on
-max
2 Pout ´
1
ƒ sw
2
(0.9) ´ (90)2 ´ (7.5 ms )
Þ Lp = 186.4 mH
Lp =
1
2 ´ 66 ´
(60,000)
(1)
Primary inductance, Lp is chosen as 200 µH for this design. Maximum on-time at minimum input voltage is
chosen as 7.5 µsec, considering maximum duty cycle of 45% at 60 kHz switching frequency.
For Lp=200 µH, peak input voltage at minimum AC input Vin_min(pk) and maximum on-time at minimum
Vin, ton-max, peak current in primary winding, Ip,pk is calculated as:
Vin _ min(pk) ´ t on-max
Ip,pk =
Lp
Ip,pk =
(90 2 )´ (7.5 ms) = 4.77 A
200 mH
(2)
Due to large output voltage (106 V), and limitations of FET maximum drain-source voltage rating (800 V),
turns ratio is selected as 1 (that is, N = 1). Hence, secondary peak current Is,pk is equal to 4.77 A, and
minimum secondary rectifier diode reverse voltage rating is 585 V. Thus, STTH1008 (800 V, 10-A rating)
is selected as secondary rectifier for this design.
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Principle of Operation
3.1
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Active Startup Circuit
Figure 5 illustrates the active startup circuit.
ACREC
•
Q4
BC547
R5A
100 K
VDD
Q6
•
R17
0E
BC547
R37
•
0.1 µF
C24
150 K
D2
R38
•
R5
100 K
D3
•
33 K
330 K
R2
•
R1
C26
150E
BC547
VCC
C27
47 µF 10 V
47 K
R3
Q8
FJP5027OTU
C23
0.1 µF
•
•
Q5
•
•
D14
18 V
•
R39
US1 M
•
•
AUX_IN
150 E
C12 US1 M
4.7 µF
R36
10 K
•
•
R41
•
100 E
VDD
Figure 5. Active Startup Circuit
It is not possible to supply bias voltage while meeting IC current requirements for both UCC28810 and
CD74HCT14 together using the resistive startup technique. In Figure 5, transistor Q8 as emitter-follower
sources 17.4 V VDD startup bias for UCC28810 at its emitter, which is converted to 5 V for CD74HCT14
supply using discrete, low-IQ linear regulator. Once switching begins and output voltage ramps-up, bias
voltage for these ICs is sourced from primary-side auxiliary winding, which is also used to disable activestartup circuit with Q6. Once in steady state, it is required to disable active-startup circuit in order to
minimize efficiency loss due to large voltage drop across Q8 and IC supply current flowing through it.
3.2
Switching Oscillator
Figure 6 shows the switching oscillator circuit.
VCC
C22
U1-D 1 µF
•
C4
9
U1-E
C5
8
CD74HCT14
100 pF
• •
R34
1K
U1-F
•
•
•
Q7
•
BSS123
VCC
R13
5.6 K
TZE
R32 240 K
IRAMP
C15
10 nF
1 nF
R33 CD74HCT14
1K
CD74HCT14
Figure 6. Switching Oscillator
The flyback stage is operating at a constant 60-kHz switching frequency, generated using CD74HCT14,
Schmitt-triggered inverter, as shown in Figure 6. Equation 3 is used to calculate oscillator frequency of a
Schmitt inverter-based oscillator. For C4 = 100 pF, feedback resistance R32 is obtained as 248 kΩ:
1
1
1
ƒ sw =
ÞR=
=
= 248 kW
0.67 RC
(0.67 )ƒsw ´ C (0.67)(60,000)(0.1 nf )
(3)
8
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Principle of Operation
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This 60-kHz square-pulse output of U1D is given to an RC high-pass filter, inverted, and fed as input to
UCC28810 TZE pin to initiate the next switching cycle (ton). A transition is detected when TZE input goes
low, which sets the gate drive to HIGH. This pulse also discharges RC ramp generator capacitor C15 at the
start of ton, using Q7. Gate drive turn-on edge is triggered with 60-kHz square-pulse input to the TZE pin
from the above oscillator, while gate DRV turn-off edge is determined by the output current regulation
circuit (when IRAMP voltage exceeds internal multiplier output voltage). In Figure 16, frequency of
waveform 2 governs fsw, while the on-time of this waveform (determined by values of C5 and R33) is the
time-period for which FET Q7 discharges capacitor C15.
3.3
Soft-Start Circuit
At startup, the 60-kHz switching begins as soon as bias on UCC28810 exceeds its VDD turn-on threshold
(15.8 V). Due to the use of the 470-nF capacitor C20 to slow down loop response, it is required to have
soft-start operation, such that the duty cycle increases gradually from its minimum value at startup. The
circuit in Figure 7 shows this implementation. As VCC bias voltage (5 V) is formed during startup, RC lowpass filter (R10 = 2.2 M, C11 = 4.7 µF) charges slowly to input peak value, resulting in Q1 pulling down error
amplifier output (EAOUT) low, initially, and allowing it to reach its final value after approximately a 1second delay. Diode D6 helps to discharge C11 for next soft-start initiation on VDD / system reset.
EAOUT
SS
D6
•
VCC
•
•
BAT85
BC557
Q1
•
C2
100 nF
R10
2.2 M
C11
4.7 µF
R7
22 K
Figure 7. Soft-Start Circuit
Additionally, duty cycle limiting at nearly 45% is incorporated to mitigate stability issues, by providing DC
voltage on the VINS pin as UCC28810 internal multiplier output clamp. For 60-kHz switching frequency,
the feedback ramp on C15 reaches a level of 0.53 V at 45% duty cycle. Since UCC28810’s internal
multiplier has a fixed gain of 2, an input of 0.26 V DC on the VINS pin helps clamp the duty cycle at
maximum 45%.
3.4
Output Current Regulation
We need to regulate constant 600-mA output current though the LEDs. This is achieved using both
secondary-side and primary-side regulation circuits. With secondary-side output current regulation,
current through the LEDs is measured as a voltage on very small current sense resistors (R29 and R31),
and regulated with TL431’s 2.495 V feedback reference. This circuit is shown in Figure 1. VDD voltage for
the optocoupler and TL431s is generated with a 12-V zener biased from the 106-V output voltage. During
the process of locking of loop to reach regulation, when the voltage on U4 REF pin exceeds 2.495 V, the
cathode of U4 pulls down optocoupler U3 cathode to 2.495 V, which reduces voltage on the EAOUT pin of
UCC28810. Since EAOUT pin of UCC28810 is output of internal error amplifier, this pulldown with
optocoupler helps to maintain duty cycle optimum for output current regulation point. Further, power loss
on sense resistors is proportional to voltage across them and the current flowing through them:
Ploss = Vsense × ILED
(4)
The U4 feedback reference of 2.495 V results in a power loss of 1.497 W for 600-mA current through
sense resistors. To minimize this loss and make the system more efficient, a 2-V DC offset is added to the
U4 feedback (using resistors R27 and R28) from the 12-V zener voltage, such that sense resistor drops only
0.5 V due to the current flowing through it.
Alternatively, primary-side output current regulation within ±2.5 percent of intended output current has
been achieved with the circuit in Figure 8:
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Principle of Operation
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VDD
•
•
R55
R56
100 K
100 K
R53
R43
165 K
4.7K
C37
C36
C38
100pF
•
100 E
C30
R52
BAT85
GDRV
100E
R45
•
•
R51
D16
12 V
D15
100 E
R44
330 K
C29
1nF
1 nF
•
•
4.7 K
C35
1 nF
100 pF
Q11
R54
• • •
•
•
1N4148
D19
D18
VIN
•
•
1N4148
Q10
R58
•
•
FF
10 K
R57
10 K
C34
1 µF
AUX_IN
GDRV
168 pF
•
•
VDD
C31
1 µF
FF
•
D17
BAT85
Q13
Q12
•
R49
R48
R46
22 K
•
•
22 nF
10 K
R50
•
22 K
R47
4.7 K
•
C32
VSENSE
47 K
C33
4.7 µF
(Circuit used in only-primary-side output current regulation scheme.)
Figure 8. Alternate Implementation for Primary-Side Output Current Regulation
For transformer T1 primary winding,
dIp
Vin(inst) ´ t on
Vin(inst) = Lp ´
Þ Ip,pk =
dt
Lp
(5)
Where:
Vin(inst) = instantaneous input voltage
Lp = Transformer primary inductance
ton = On-time during time period T
Further, output current in flyback converter is given by:
Is,pk t off
NIp,pk t off
N ´ Vin(inst) ´ t on t off
t
Iout =
´
Þ Iout =
´
Þ Iout =
´
Þ Iout aIp,pk ´ off
2
T
2
T
2 Lp
T
T
(6)
Where:
Iout = Current through LEDs
Is,pk = Secondary-side peak current
toff = Off-time during time period T
N = transformer turns ratio
Ip,pk = primary-side peak current
10
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Toff Chopped Primary/
(Secondary N = 1) Area
Primary Current
Equivalent Voltage
2
Primary Peak
Current Envelope
Secondary Current
Equivalent Voltage
3
¸2
1
(b)
(a)
(c)
Figure 9. Primary-Side Output Current Regulation Logic
From Equation 5 and Equation 6, since primary-side peak current is sinusoidal in nature, varying in
proportion to instantaneous Vin and Ton, if we generate a voltage proportional to Vin and ton, and calculate
the average for time period toff (over total time T), we get a DC voltage which is proportional to output LED
current.
Here, a ramp voltage (proportional to instantaneous Vin amplitude and ton) is generated using R43, R44, and
C30 during on-time, and discharged with the gate drive signal using D15 during toff. Consecutively, this ramp
is peak detected using emitter-follower transistor Q12. This envelope varying in proportion to Vin is again
buffered to obtain low output impedance using emitter-follower transistor Q13, and chopped during timeinterval toff (to obtain a time-average over toff) using flip-flop circuit as shown in Figure 10.
VDD
R58
C34
1 µF
R55
R56
100 K
100 K
FF
•
R53
•
4.7K
D19
•
4.7 K
C36
1 nF
C35
1 nF
C38
100pF
•
R52
100 E
•
R51
Q11
R54
• • •
C37
100 pF
•
100E
D18
1N4148
1N4148
•
Q10
10 K
•
10 K
R57
•
GDRV
AUX_IN
(Circuit used in only-primary-side output current regulation scheme.)
Figure 10. Flip-Flop Circuit to Extract Toff
This flip-flop used for Toff chopping is implemented using transistors Q10 and Q11, with Toff waveform edges
triggered by negative going transitions of FET gate drive (GDRV) and primary-side auxiliary winding
(AUX_IN) waveforms, thus generating square pulse of duration Toff, as also depicted in Figure 19.
This resulting waveform chopped for Toff is averaged using RC (R49 = 22 kΩ, C33 = 4.7 µF) averaging
circuit. Since the control loop needs to have a narrow bandwidth, for output current to be less sensitive to
the twice mains frequency ripple, cut-off frequency for this RC low-pass filter is selected much less than
100 Hz. It may be noted that this average is two-times of that obtained from Equation 6, and this doubling
factor needs to be accounted for by scaling resistor values. UCC28810 has an internal 2.5 V referenced
error amplifier with VSENSE inverting input. This error amplifier is used for primary-side output current
regulation. Since voltage from the primary-side current regulation circuit (output of RC averaging circuit) is
less than 2.5 V (1.85 V), superposition of a DC offset from 5-V supply and RC averaging circuit output is
undertaken to regulate at 2.5 V.
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Principle of Operation
3.5
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Output Short-Circuit Protection
At the instant of output LEDs being short-circuited, U4 immediately detects a voltage feedback greater
than 2.5 V, and engages U3 to reduce duty cycle to minimum value. The 12-V bias of optocoupler and U4
(and U5) reduces to zero during this period and secondary loop loses control. Voltage on current sense
resistor R24 is continuously monitored to detect short-circuit at output.
C16
D8
VCC
R12
5.6 K
R9
ISENSE
12 K
•
R15
8.2 K
•
•
IN4148
R19
•
1M
2.2 nF
U1-B
R16
8.2 K
•
•
•
•
4 U7
R11
12 K
47 pF
C10
Q2
BC547
CD74HCT14
U1-A
•
U1-C
•
SS
•
•
D9
VSENSE
CD74HCT14
CD74HCT14
BAT54
D7
R22
4.7 K
IN4148
Figure 11. Output Short-Circuit Protection
For 64-W output power, primary peak current reaches a maximum of nearly 1 V (see Figure 17). Shortcircuit detection threshold is thus set with sufficient margin (to avoid false triggering) at 1.4 V. This subsystem is shown in Figure 11. As the voltage on R24 reaches 1.4 V or greater, a latch including Q2 and U1A
is enabled. The 5-V output of this latch is inverted using U1C to form logic LOW level at output which then
pulls down voltage on capacitors C13 and C11 attached to the VSENS and EAOUT pins of UCC28810,
respectively. This short-circuit protection is auto-retry type, with Schmitt inverter oscillator (U1B) generating
a reset pulse every 3 seconds. This auto-retry interval may be modified by adjusting R19.
3.6
Output Open-Circuit Protection
In case of absence of LEDs at output (Output Open-Circuit), this design reduces power being delivered to
the secondary, to prevent voltage on output capacitors from exceeding their ratings. This feature is
implemented in different ways for the case of Primary-Side and Secondary-Side Output current regulation
schemes.
For a secondary-side regulated system, output voltage is divided using resistors R35 and R40, and fed to
the REF pin of TL431 (U5), as shown in Figure 1. These resistors are selected such that in case of an
open-circuit, output voltage reaches a maximum of 110% of its nominal value. For Vout = 106 V, Vout(open)
≈120 V.
From Equation 7, R35 and R40 is obtained as 1 kΩ and 47 kΩ to get 2.495 V level at the U5 REF pin.
Vout(open)
VREF(U5) =
´ R35
R35 + R 40
(7)
Where:
VREF(U5) = TL431 reference pin 2.495-V regulation voltage
Vout(open) = maximum voltage at output when open-circuited
In case of an output open-circuit, U5 enables the optocoupler, pulling the EAOUT pin of UCC28810 low,
limiting duty cycle to its minimum value, and preventing voltage on output capacitors from exceeding their
ratings or reaching dangerously high values.
12
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Open-circuit protection with primary-side output current regulation is shown in Figure 12. Voltage (VC12)
formed on C12 from primary auxiliary winding is used to detect open-circuit at output. This voltage on C12
(VC12) is stepped down using a zener and resistance divider (R39, R30), enabling transistor Q11 in case of
open-circuit. Transistor Q11, when active, pulls down the EAOUT pin of UCC28810 (which is the error
amplifier output), and reduces duty cycle to its minimum value.
EAOUT
VC12
12 V
120 K
Q9
BC547
•
R39
R30
33 K
(Circuit used in only-primary-side output current regulation scheme.)
Figure 12. Output Open-Circuit Protection in Primary-Side Regulated System
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Performance Data and Typical Characteristic Curves
4
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Performance Data and Typical Characteristic Curves
Figure 13 through Figure 19 present some typical performance curves for the UCC28810-based 70-W
LED driver design.
4.1
Output Current Variation with Respect to Input Voltage
587.4
587.2
Output Current (mA)
587
586.8
586.6
586.4
586.2
586
585.8
585.6
585.4
90
115
140
165
190
215
RMS Input Voltage (V)
240
265
D001
Figure 13. Output Current Variation with Respect to Input Voltage
4.2
Power Factor Variation With Respect to Input Voltage
0.9995
0.999
0.9985
Power Factor
0.998
0.9975
0.997
0.9965
0.996
0.9955
0.995
0.9945
90
115
140
165
190
215
RMS Input Voltage (V)
240
265
D002
Figure 14. Power Factor Variation With Respect to Input Voltage
14
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4.3
Variation of Current THD with Input Voltage
5
4.5
Current THD (%)
4
3.5
3
2.5
2
1.5
1
0.5
0
90
115
140
165
190
215
RMS Input Voltage (V)
240
265
D003
Figure 15. Variation of Current THD with Input Voltage
4.4
External Oscillator and Feedback Ramp
Ch1: CD74HCT14 Inverting Schmitt 60kHz Oscillator, Ch2: 60kHz Square Pulses input to UCC28810 TZE pin,
Ch3: Regulation Feedback Ramp
Figure 16. External Oscillator and Feedback Ramp
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Performance Data and Typical Characteristic Curves
4.5
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Primary-Side FET Gate Drive, Drain, and Current-Sense Waveforms
Ch1: Primary-Side FET Gate Drive, Ch2: Primary-Side FET Drain Waveform,
Ch3: Primary-Side Current Sense Waveform
Figure 17. Primary-Side FET Gate Drive, Drain, and Current-Sense Waveforms
4.6
MOSFET Drain and Primary-Side Current Sense Voltage Envelope
Ch2: Primary-Side FET Drain, Ch3: Primary-Side Current Sense Waveform
Figure 18. Primary-Side FET Drain and Current Sense Voltage Envelope
16
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4.7
Gate Drive, Auxiliary Winding, and Flip-Flop Toff Detector Waveforms
Ch1: Primary-Side FET Gate Drive, Ch2: Transformer Auxiliary Winding, Ch3: Flip-Flop based Toff Detector
Figure 19. Primary-Side FET Gate Drive, Auxiliary Winding, and Flip-Flop Toff Detector
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Bill of Materials
5
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Bill of Materials
Table 2 lists the bill of materials (BOM) for the secondary-side output current regulation circuit.
5.1
Secondary-Side Output Current Regulation
Table 2. Bill of Materials for Circuit with Secondary Side Regulation
Count
RefDes
Value
Description
Size
Part Number
MFR.
1
C1
100nF
Capacitor, Film, 100nF, 300VAC
Radial
B32023A3104M
Epcos
1
C2
220nF
Capacitor, ceramic, 220nF, 10V
805
Std
Std
2
C3,C28
1nF
Capacitor, ceramic, 1nF, 2kV
Radial
DEBE33D102ZB2B
Murata
1
C4
100pF
Capacitor, ceramic, 100pF, 10V
805
Std
Std
2
C5,C22
1nF
Capacitor, ceramic, 1nF, 10V
805
Std
Std
2
C6,C7
220µF
Capacitor, electrolytic, 220µF, 160V
Radial
UVR2C221MHA
Nichicon
1
C6A
220nF
Capacitor, Film, 220nF, 305VAC
Radial
B32922C3224M189
Epcos
DNP
C8
220µF
Capacitor, electrolytic, 220µF, 160V
Radial
UVR2C221MHA
Nichicon
1
C10
47pF
Capacitor, ceramic, 47pF, 6.3V
805
Std
Std
1
C11
4.7µF
Capacitor, electrolytic, 4.7µF, 25V
Radial
UVR1E4R7MDA
Nichicon
2
C12,C17
4.7µF
Capacitor, ceramic, 4.7µF, 25V
805
Std
Std
2
C13,C24
100nF
Capacitor, ceramic, 100nF, 6.3V
805
Std
Std
1
C14
10µF
Capacitor, ceramic, 10µF, 6.3V
805
Std
Std
1
C15
10nF
Capacitor, ceramic, 10nF, 10V
805
Std
Std
1
C16
2.2nF
Capacitor, ceramic, 2.2nF, 10V
805
Std
Std
1
C18
33µF
Capacitor, electrolytic, 33µF, 25V
Radial
UVR1E330MDA
Nichicon
2
C19,C23
100nF
Capacitor, ceramic, 100nF, 35V
805
Std
Std
2
C19A,C20A
10µF
Capacitor, electrolytic, 10µF, 315V
Radial
UVR2F100MPA
Nichicon
1
C20
470nF
Capacitor, ceramic, 470nF, 25V
Radial
Std
Std
1
C21
47µF
Capacitor, electrolytic, 47µF, 25V
Radial
UVR1E470MDA
Nichicon
DNP
C25
47µF
Capacitor, electrolytic, 47µF, 25V
Radial
UVR1E470MDA
Nichicon
1
C26
10µF
Capacitor, electrolytic, 10µF, 25V
Radial
UVR1E100MDA
Nichicon
1
C27
47µF 10V
Capacitor, electrolytic, 47µF, 10V
Radial
UVR1A470MDA
Nichicon
DNP
C2A
100nF
Capacitor, Film, 100nF, 300VAC
Radial
B32023A3104M
Epcos
3
D1, D2, D3
US1M
Diode, rectifier, 1000V, 1A
DIODE0.4
US1M
Diodes Inc.
4
D1A, D2A,
D3A, D4A
1N5399
Diode, rectifier, 1000V, 1.5A
DIODE0.6
1N5399-E3/54
Vishay
1
D4
STTH1008DTI
Diode, hyperfast, 800V, 10A
TO220AC
STTH1008DTI
STMicro
1
D11
12V
Diode, Zener, 12V, 1W
DIODE0.4
1N4742A-TP
MCC
1
D6
BAT85
Diode, Schottky, 30V, 200mA
DO-34
BAT85,113
NXP
2
D7,D8
IN4148
Diode, rectifier, 75V, 150mA
SOD523
1N4148X-TP
MCC
1
D9
BAT54
Diode, Schottky 30V, 200mA
SOT-23
BAT54S-TP
MCC
1
D9A
1N4007
Diode, rectifier, 1000V, 1A
DIODE0.4
1N4007-TP
MCC
1
D10
18V
Diode, Zener, 18V, 1W
SMA
SMAZ18-13-F
Diodes Inc.
DNP
D12
68V
Diode, Zener, 68V, 1/2W
SOD123
MMSZ5266BT1G
On Semi
DNP
D13
56V
Diode, Zener, 56V, 1/2W
SOD123
MMSZ5263BT1G
On Semi
1
D14
18V
Diode, Zener, 18V, 1W
DIODE0.4
1N4746A-TP
MCC
1
F1
39213150000
Fuse, 3.15A, 250V
Radial, Box
39213150000
Littelfuse
1
J1
TC03236200J0G
Terminal Block, 15A, 5.1mm
200-3
TC03236200J0G
FCI
1
J3
5010
Test point, red, thru hole
0.125 × 0.125 in
5010
Keystone
1
J4
5011
Test point, black, thru hole
0.125 × 0.125 in
5011
Keystone
1
L1
10mH
Inductor, Common-Mode, 10mH, 3A, TH
UU10.5
Custom
Custom
2
L2,L3
100uH
Inductor, Differential, 100µH, 3A, TH
TH
Custom
Custom
1
MOV1
B72207S271K321
MOV, 387V, 1.2kA
Disc 7mm
B72207S271K321
Epcos
1
Q1
BC857
Transistor, PNP, 45V, 100mA
SOT-23
BC857BLT3G
On Semi
3
Q2,Q4,Q5
BC847
Transistor, NPN, 45V, 100mA
SOT-23
BC847CLT3G
On Semi
18
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Bill of Materials
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Table 2. Bill of Materials for Circuit with Secondary Side Regulation (continued)
Count
RefDes
Value
Description
Size
Part Number
MFR.
1
Q3
STP8N80K5
Transistor, N-ch FET, 800V, 6A
TO-220-3
STP8N80K5
STMicro
1
Q6
BC547
Transistor, NPN, 45V, 100mA
TO-92
BC547CZL1G
On Semi
1
Q7
BSS123
Transistor, N-ch FET, 100V, 170mA
SOT-23
BSS123LT1G
On Semi
1
Q8
FJP5027OTU
Transistor, NPN, 800V, 3A
TO-220-3
FJP5027OTU
Fairchild
2
R1,R28
33K
Resistor, chip, 1/4W, 1%
1206
Std
Std
1
R2
330K
Resistor, chip, 1/4W, 1%
1206
Std
Std
2
R3,R40
47kΩ
Resistor, chip, 1/4W, 1%
1206
Std
Std
1
R4
220kΩ
Resistor, axial,1/4W, 1%
AXIAL0.4
Std
Std
R4A
220kΩ
Resistor, axial,1/4W, 1%
AXIAL0.4
Std
Std
1
R5
100K
Resistor, axial,1/4W, 1%
AXIAL0.4
Std
Std
1
R5A
100K
Resistor, chip, 1/4W, 1%
1206
Std
Std
1
R6
22kΩ
Resistor, axial,1/4W, 1%
AXIAL0.4
Std
Std
2
R7,R8
22kΩ
Resistor, chip, 1/4W, 1%
1206
Std
Std
1
R9
12kΩ
Resistor, axial,1/4W, 1%
AXIAL0.4
Std
Std
1
R10
2.2MΩ
Resistor, chip, 1/4W, 1%
1206
Std
Std
R10A,R20A
2.2MΩ
Resistor, chip, 1/4W, 1%
1206
Std
Std
1
R11
12kΩ
Resistor, chip, 1/4W, 1%
1206
Std
Std
2
R12,R13
5.6kΩ
Resistor, chip, 1/4W, 1%
1206
Std
Std
1
R15
8.2kΩ
Resistor, axial,1/4W, 1%
AXIAL0.4
Std
Std
1
R16
8.2kΩ
Resistor, chip, 1/4W, 1%
1206
Std
Std
1
R17
0E
Resistor, axial,1/4W, 1%
AXIAL0.4
Std
Std
2
R18,R19
1MΩ
Resistor, chip, 1/4W, 1%
1206
Std
Std
1
R20
56kΩ
Resistor, chip, 1/4W, 1%
1206
Std
Std
1
R21
82kΩ
Resistor, chip, 1/4W, 1%
1206
Std
Std
R21A,R21B
1MΩ
Resistor, chip, 1/4W, 1%
1206
Std
Std
2
R22,R26
4.7kΩ
Resistor, chip, 1/4W, 1%
1206
Std
Std
1
R23
4.7E
Resistor, axial,1/4W, 1%
AXIAL0.4
Std
Std
1
R24
0.2Ω
Resistor, chip, 1/2W, 1%
1206
Std
Std
1
R25
2.7kΩ
Resistor, chip, 1/4W, 1%
1206
Std
Std
2
R27,R37
150kΩ
Resistor, chip, 1/4W, 1%
1206
Std
Std
1
R29
0.82Ω
Resistor, axial,1W, 1%
AXIAL0.4
Std
Std
DNP
R31
1Ω
Resistor, axial,1W, 1%
AXIAL0.4
Std
Std
1
R32
240kΩ
Resistor, chip, 1/4W, 1%
1206
Std
Std
3
R33, R34,
R35
1kΩ
Resistor, chip, 1/4W, 1%
1206
Std
Std
1
R36
10kΩ
Resistor, chip, 1/4W, 1%
1206
Std
Std
1
R38
150Ω
Resistor, axial,1/4W, 1%
AXIAL0.4
Std
Std
1
R38A
1MΩ
Resistor, axial,1/4W, 1%
AXIAL0.4
Std
Std
1
R39
150Ω
Resistor, chip, 1/4W, 1%
1206
Std
Std
1
R41
100E
Resistor, chip, 1/4W, 1%
1206
Std
Std
DNP
R42
0.5Ω
Resistor, chip, 1/4W, 1%
1206
Std
Std
T1
200µH
Transformer, Custom
PQ3230
Std
Std
DNP
T1A
200µH
Transformer, Custom
PQ2625
Std
Std
1
U1
CD74HCT14M
IC, High Speed CMOS Logic Hex SchmittTriggered Inverters
SOIC-14
CD74HCT14M
TI
1
U2
UCC28810
IC, LED Lighting Power Controller
SOIC-8
UCC28810DR
TI
1
U3
PC817B
IC, Optocoupler
DIP4
PC817B
Sharp
2
U4,U5
TL431
Adjustable Precision Shunt Regulator
TO-92
TL431CLPM
TI
DNP
DNP
DNP
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Bill of Materials
5.2
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Primary-Side Output Current Regulation
Table 3 lists the BOM for the primary-side output current regulation circuit.
Table 3. Bill of Materials for Circuit with Primary Side Regulation
Count
20
RefDes
Value
Description
Size
Part Number
MFR
1
C1
100nF
Capacitor, Film, 100nF, 300VAC
Radial
B32023A3104M
Epcos
1
C2
220nF
Capacitor, ceramic, 220nF, 10V
805
Std
Std
2
C3,C28
1nF
Capacitor, ceramic, 1nF, 2kV
Radial
DEBE33D102ZB2B
Murata
1
C4
100pF
Capacitor, ceramic, 100pF, 10V
805
Std
Std
2
C5,C22
1nF
Capacitor, ceramic, 1nF, 10V
805
Std
Std
2
C6,C7
220µF
Capacitor, electrolytic, 220µF, 160V
Radial
UVR2C221MHA
Nichicon
1
C6A
220nF
Capacitor, Film, 220nF, 305VAC
Radial
B32922C3224M189
Epcos
DNP
C8
220µF
Capacitor, electrolytic, 220µF, 160V
Radial
UVR2C221MHA
Nichicon
1
C10
47pF
Capacitor, ceramic, 47pF, 6.3V
805
Std
Std
1
C11
4.7µF
Capacitor, electrolytic, 4.7µF, 25V
Radial
UVR1E4R7MDA
Nichicon
2
C12,C17
4.7µF
Capacitor, ceramic, 4.7µF, 25V
805
Std
Std
2
C13,C24
100nF
Capacitor, ceramic, 100nF, 6.3V
805
Std
Std
1
C14
10µF
Capacitor, ceramic, 10µF, 6.3V
805
Std
Std
1
C15
10nF
Capacitor, ceramic, 10nF, 10V
805
Std
Std
1
C16
2.2nF
Capacitor, ceramic, 2.2nF, 10V
805
Std
Std
1
C18
33µF
Capacitor, electrolytic, 33µF, 25V
Radial
UVR1E330MDA
Nichicon
2
C19,C23
100nF
Capacitor, ceramic, 100nF, 35V
805
Std
Std
2
C19A,C20A
10µF
Capacitor, electrolytic, 10µF, 315V
Radial
UVR2F100MPA
Nichicon
DNP
C25
47µF
Capacitor, electrolytic, 47µF, 25V
Radial
UVR1E470MDA
Nichicon
1
C26
10µF
Capacitor, electrolytic, 10µF, 25V
Radial
UVR1E100MDA
Nichicon
1
C27
47µF 10V
Capacitor, electrolytic, 47µF, 10V
Radial
UVR1A470MDA
Nichicon
DNP
C2A
100nF
Capacitor, Film, 100nF, 300VAC
Radial
B32023A3104M
Epcos
1
C29
1nF
Capacitor, ceramic, 1nF, 2kV
Radial
DEBE33D102ZB2B
Murata
1
C30
168pF
Capacitor, ceramic, 168pF, 25V
805
Std
Std
1
C31
1µF
Capacitor, electrolytic, 1µF, 25V
Radial
Std
Std
1
C32
22nF
Capacitor, ceramic, 22nF, 25V
805
Std
Std
1
C33
4.7µF
Capacitor, ceramic, 4.7µF, 6.3V
805
Std
Std
1
C34
1µF
Capacitor, electrolytic, 1µF, 25V
Radial
Std
Std
2
C35,C36
1nF
Capacitor, ceramic, 1nF, 35V
805
Std
Std
2
C37,C38
100pF
Capacitor, ceramic, 100pF, 35V
805
Std
Std
3
D1, D2, D3
US1M
Diode, rectifier, 1000V, 1A
DIODE0.4
US1M
Diodes Inc.
4
D1A, D2A,
D3A, D4A
1N5399
Diode, rectifier, 1000V, 1.5A
DIODE0.6
1N5399-E3/54
Vishay
1
D4
STTH1008DTI
Diode, hyperfast, 800V, 10A
TO220AC
STTH1008DTI
STMicro
1
D5
12V
Diode, Zener, 12V, 1W
DIODE0.4
1N4742A-TP
MCC
1
D6
BAT85
Diode, schottky, 30V, 200mA
DO-34
BAT85,113
NXP
2
D7,D8
IN4148
Diode, rectifier, 75V, 150mA
SOD523
1N4148X-TP
MCC
1
D9
BAT54
Diode, Schottky 30V, 200mA
SOT-23
BAT54S-TP
MCC
1
D9A
1N4007
Diode, rectifier, 1000V, 1A
DIODE0.4
1N4007-TP
MCC
1
D10
18V
Diode, Zener, 18V, 1W
SMA
SMAZ18-13-F
Diodes Inc.
1
D14
18V
Diode, Zener, 18V, 1W
DIODE0.4
1N4746A-TP
MCC
2
D15,D17
BAT85
Diode, schottky, 30V, 200mA
DO-34
BAT85,113
NXP
1
D16
12V
Diode, Zener, 12V, 1W
DIODE0.4
1N4742A-TP
MCC
2
D18,D19
IN4148
Diode, rectifier, 75V, 150mA
SOD523
1N4148X-TP
MCC
1
F1
39213150000
Fuse, 3.15A, 250V
Radial, Box
39213150000
Littelfuse
1
J1
TC03236200J0G
Terminal Block, 15A, 5.1mm
200-3
TC03236200J0G
FCI
1
J3
5010
Test point, red, thru hole
0.125 × 0.125 in
5010
Keystone
1
J4
5011
Test point, black, thru hole
0.125 × 0.125 in
5011
Keystone
1
L1
10mH
Inductor, Common-Mode, 10mH, 3A, TH
UU10.5
Custom
Custom
Isolated 70-W Streetlight LED Driver Using UCC28810
Copyright © 2015, Texas Instruments Incorporated
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Bill of Materials
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Table 3. Bill of Materials for Circuit with Primary Side Regulation (continued)
Count
RefDes
Value
Description
Size
Part Number
MFR
2
L2,L3
100uH
Inductor, Differential, 100uH, 3A, TH
TH
Custom
Custom
1
MOV1
B72207S271K321
MOV, 387V, 1.2kA
Disc 7mm
B72207S271K321
Epcos
1
Q1
BC857
Transistor, PNP, 45V, 100mA
SOT-23
BC857BLT3G
On Semi
3
Q2,Q4,Q5
BC847
Transistor, NPN, 45V, 100mA
SOT-23
BC847CLT3G
On Semi
1
Q3
STP8N80K5
Transistor, N-ch FET, 800V, 6A
TO-220-3
STP8N80K5
STMicro
2
Q6,Q9
BC547
Transistor, NPN, 45V, 100mA
TO-92
BC547CZL1G
On Semi
1
Q7
BSS123
Transistor, N-ch FET, 100V, 170mA
SOT-23
BSS123LT1G
On Semi
1
Q8
FJP5027OTU
Transistor, NPN, 800V, 3A
TO-220-3
FJP5027OTU
Fairchild
4
Q10, Q11,
Q12, Q13
BC847
Transistor, NPN, 45V, 100mA
SOT-23
BC847CLT3G
On Semi
2
R1,R30
33K
Resistor, chip, 1/4W, 1%
1206
Std
Std
1
R2
330K
Resistor, chip, 1/4W, 1%
1206
Std
Std
1
R3
47kΩ
Resistor, chip, 1/4W, 1%
1206
Std
Std
1
R4
220kΩ
Resistor, axial,1/4W, 1%
AXIAL0.4
Std
Std
R4A
220kΩ
Resistor, axial,1/4W, 1%
AXIAL0.4
Std
Std
1
R5
100K
Resistor, axial,1/4W, 1%
AXIAL0.4
Std
Std
1
R5A
100K
Resistor, chip, 1/4W, 1%
1206
Std
Std
1
R7
22kΩ
Resistor, chip, 1/4W, 1%
1206
Std
Std
1
R8
82kΩ
Resistor, chip, 1/4W, 1%
1206
Std
Std
1
R9
12kΩ
Resistor, axial,1/4W, 1%
AXIAL0.4
Std
Std
1
R10
2.2MΩ
Resistor, chip, 1/4W, 1%
1206
Std
Std
R10A,R20A
2.2MΩ
Resistor, chip, 1/4W, 1%
1206
Std
Std
1
R11
12kΩ
Resistor, chip, 1/4W, 1%
1206
Std
Std
2
R12,R13
5.6kΩ
Resistor, chip, 1/4W, 1%
1206
Std
Std
1
R14
120kΩ
Resistor, chip, 1/4W, 1%
1206
Std
Std
1
R15
8.2kΩ
Resistor, axial,1/4W, 1%
AXIAL0.4
Std
Std
1
R16
8.2kΩ
Resistor, chip, 1/4W, 1%
1206
Std
Std
1
R17
0E
Resistor, axial,1/4W, 1%
AXIAL0.4
Std
Std
2
R18,R19
1MΩ
Resistor, chip, 1/4W, 1%
1206
Std
Std
1
R20
56kΩ
Resistor, chip, 1/4W, 1%
1206
Std
Std
1
R21
68kΩ
Resistor, chip, 1/4W, 1%
1206
Std
Std
R21A,R21B
1MΩ
Resistor, chip, 1/4W, 1%
1206
Std
Std
1
R22
4.7kΩ
Resistor, chip, 1/4W, 1%
1206
Std
Std
1
R23
4.7E
Resistor, axial,1/4W, 1%
AXIAL0.4
Std
Std
1
R24
0.2Ω
Resistor, chip, 1/2W, 1%
1206
Std
Std
1
R37
150kΩ
Resistor, chip, 1/4W, 1%
1206
Std
Std
1
R32
240kΩ
Resistor, chip, 1/4W, 1%
1206
Std
Std
2
R33,R34
1kΩ
Resistor, chip, 1/4W, 1%
1206
Std
Std
1
R36
10kΩ
Resistor, chip, 1/4W, 1%
1206
Std
Std
1
R38
150Ω
Resistor, axial,1/4W, 1%
AXIAL0.4
Std
Std
1
R38A
1MΩ
Resistor, axial,1/4W, 1%
AXIAL0.4
Std
Std
1
R39
150Ω
Resistor, chip, 1/4W, 1%
1206
Std
Std
1
R41
100E
Resistor, chip, 1/4W, 1%
1206
Std
Std
DNP
R42
0.5Ω
Resistor, chip, 1/4W, 1%
1206
Std
Std
1
R43
165kΩ
Resistor, chip, 1/4W, 1%
1206
Std
Std
1
R44
330kΩ
Resistor, chip, 1/4W, 1%
1206
Std
Std
3
R45, R51,
R52
100Ω
Resistor, chip, 1/4W, 1%
1206
Std
Std
2
R46 ,R49
22kΩ
Resistor, chip, 1/4W, 1%
1206
Std
Std
3
R47, R53,
R54
4.7kΩ
Resistor, chip, 1/4W, 1%
1206
Std
Std
3
R48, R57,
R58
10kΩ
Resistor, chip, 1/4W, 1%
1206
Std
Std
DNP
DNP
DNP
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Isolated 70-W Streetlight LED Driver Using UCC28810
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21
Test Results
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Table 3. Bill of Materials for Circuit with Primary Side Regulation (continued)
Count
RefDes
Value
Description
Size
Part Number
MFR
1
R50
47kΩ
Resistor, chip, 1/4W, 1%
1206
Std
Std
2
R55, R56
100kΩ
Resistor, chip, 1/4W, 1%
1206
Std
Std
2
R57, R58
10kΩ
Resistor, chip, 1/4W, 1%
1206
Std
Std
1
T1
200µH
Transformer, Custom
PQ3230
Std
Std
DNP
T1A
200µH
Transformer, Custom
PQ2625
Std
Std
1
U1
CD74HCT14M
IC, High Speed CMOS Logic Hex SchmittTriggered Inverters
SOIC-14
CD74HCT14M
TI
1
U2
UCC28810
IC, LED Lighting Power Controller
SOIC-8
UCC28810DR
TI
6
Test Results
6.1
Secondary-Side Output Current Regulation
Table 4 lists the performance characteristics of a 70-W LED driver design with secondary-side output
current regulation.
Table 4. Performance Characteristics of 70-W LED Driver Design With
Secondary-Side Output Current Regulation
6.2
Input RMS
Voltage
(V)
Input Power
(W)
Output Voltage
(V)
Output Current
(mA)
Output Power
(W)
Efficiency
(%)
Power Factor
Current THD
(%)
90
71.35
105.8
586
61.99
86.89
0.996
4.67
120
69.55
106
587
62.22
89.46
0.997
3.25
150
68.85
106.1
586
62.17
90.30
0.998
2.67
180
68.68
106.1
586
62.17
90.52
0.998
2.56
220
67.91
106.1
586
62.17
91.55
0.998
2.54
250
68.12
106.2
586
62.23
91.35
0.999
2.55
265
68.17
106.2
586
62.23
91.29
0.998
2.97
Primary-Side Output Current Regulation
Table 5 lists the performance characteristics of a 70-W LED driver design with primary-side output current
regulation.
Table 5. Performance Characteristics of 70-W LED Driver Design with
Primary-Side Output Current Regulation
22
Input RMS
Voltage
(V)
Input Power
(W)
Output Voltage
(V)
Output Current
(mA)
Output Power
(W)
Efficiency
(%)
Power Factor
Current THD
(%)
90
79.41
112.6
621
69.92
88.05
0.999
3.88
120
78.25
112.3
622
69.85
89.26
0.999
3.58
150
75.3
111.0
611
67.82
90.06
0.999
2.12
180
73.57
109.9
605
66.48
90.37
0.999
1.92
220
69.37
107.5
595
63.96
92.20
0.998
2.80
250
70.69
108.3
599
64.87
91.77
0.998
2.26
265
70.93
108.4
598
64.82
91.39
0.997
2.25
Isolated 70-W Streetlight LED Driver Using UCC28810
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Conclusion
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7
Conclusion
This application report describes design details and test results for a fixed-frequency, single-stage 70-W
AC/DC flyback LED driver for streetlight applications, both with primary-side and secondary-side output
current regulation circuits. Due to constant on-time and fixed switching-frequency operation, power factor
greater than 0.9, and current THD less than 10 percent, is easily achieved. This design meets all the
necessary performance specifications, including output open-circuit and short-circuit protections.
8
References
1. UCC28810 LED lighting power controller: http://www.ti.com/product/ucc28810.
2. CD74HCT14M High Speed CMOS Logic Hex Schmitt-Triggered Inverter:
http://www.ti.com/product/cd74hct14.
3. TL431 Adjustable Precision Shunt Regulator: http://www.ti.com/product/tl431.
4. TPS92314 Off-Line Primary Side Sensing Controller with PFC: http://www.ti.com/product/tps92314
SLUA752 – August 2015
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Isolated 70-W Streetlight LED Driver Using UCC28810
Copyright © 2015, Texas Instruments Incorporated
23
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