dm00097308

AN4376
Application note
10 W wide range non-isolated high power factor LED driver using
HVLED815PF
Federico Levati
Introduction
This application note describes the performances of a non-isolated 10 W, wide range,
regulated LED driver using the HVLED815PF device, with a high power factor and
a constant output current regulation. The maximum power and form factor have been
designed for the lighting market, facilitating the replacement of the incandescent lamps.
In fact the architecture is based on a single-stage buck-boost topology and it has been used
the STMicroelectronics® HVLED815PF device with a primary side control to achieve an
LED current regulation within ± 5% and a high power factor.
The patented primary side regulation, the internal high-voltage primary switcher operating
directly from the rectified mains and the high-voltage start-up generator contained in the
HVLED815PF device allow a very cost-effective solution for an LED driving.
Figure 1. EVLHVLED815W10A demonstration board
January 2014
DocID025380 Rev 1
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www.st.com
Contents
AN4376
Contents
1
Theory of operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
2
EVLHVLED815W10A - main characteristics and circuit description . . 8
2.1
LED current definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
2.2
LED current ripple definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
2.3
DMG pin and OVP setting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
2.4
External compensation network of the voltage loop . . . . . . . . . . . . . . . . . 10
2.5
Power factor corrector function and ILED pin modulation with the input
mains voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
2.6
High-voltage start-up generator and VCC capacitor . . . . . . . . . . . . . . . . .11
3
Electrical diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
4
Bill of material . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
5
Component layout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
6
Measurement results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
2/37
6.1
LED driver performance at nominal load 70 VDC - 140 mA . . . . . . . . . . . 16
6.2
Line regulation at nominal load . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
6.3
Power factor at nominal load . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
6.4
Total harmonic distortion (THD) at nominal load . . . . . . . . . . . . . . . . . . . 17
6.5
Driver efficiency at nominal load . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
6.6
LED driver performance varying the number of LEDs . . . . . . . . . . . . . . . 18
6.7
Line regulation at different LED load number . . . . . . . . . . . . . . . . . . . . . . 19
6.8
Power factor at different LED load number . . . . . . . . . . . . . . . . . . . . . . . 20
6.9
Total harmonic distortion (THD) at different LED load number . . . . . . . . . 21
6.10
LED driver efficiency at different LED load number . . . . . . . . . . . . . . . . . 22
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AN4376
7
Contents
PFC waveforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
7.1
Input and output LED driver waveforms . . . . . . . . . . . . . . . . . . . . . . . . . . 23
7.2
Transition mode operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
7.3
ILED pin modulation with the line voltage . . . . . . . . . . . . . . . . . . . . . . . . 25
7.4
Controller startup and light-ON . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
7.5
OVP protection and no load behavior . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
7.6
Short-circuit and output current limitation . . . . . . . . . . . . . . . . . . . . . . . . . 28
7.7
Thermal measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
7.8
Harmonic content at nominal mains voltage . . . . . . . . . . . . . . . . . . . . . . 34
7.9
Conducted emission pre-compliance test . . . . . . . . . . . . . . . . . . . . . . . . 35
8
Supporting material . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
9
Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
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List of figures
AN4376
List of figures
Figure 1.
Figure 2.
Figure 3.
Figure 4.
Figure 5.
Figure 6.
Figure 7.
Figure 8.
Figure 9.
Figure 10.
Figure 11.
Figure 12.
Figure 13.
Figure 14.
Figure 15.
Figure 16.
Figure 17.
Figure 18.
Figure 19.
Figure 20.
Figure 21.
Figure 22.
Figure 23.
Figure 24.
Figure 25.
Figure 26.
Figure 27.
Figure 28.
Figure 29.
Figure 30.
Figure 31.
Figure 32.
Figure 33.
Figure 34.
Figure 35.
Figure 36.
Figure 37.
Figure 38.
Figure 39.
Figure 40.
Figure 41.
Figure 42.
Figure 43.
Figure 44.
Figure 45.
Figure 46.
Figure 47.
Figure 48.
4/37
EVLHVLED815W10A demonstration board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Flyback (FL) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Buck-boost topology (BB) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
TM (transition mode) flyback currents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
TM (transition mode) buck-boost currents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
TM (transition mode) flyback waveforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
TM (transition mode) buck-boost waveforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
ILED pin modulation with the input mains voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
EVLHVLED815W10A demonstration board schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Top side . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Bottom side . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
LED current vs. AC line voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Power factor vs. AC line voltage at nominal load . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Total harmonic distortion vs. AC line voltage at nominal load . . . . . . . . . . . . . . . . . . . . . . 17
Efficiency vs. AC line voltage at nominal load . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Line regulation at different LED load . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Power factor versus AC line voltage at different LED load . . . . . . . . . . . . . . . . . . . . . . . . . 20
THD versus AC line voltage at different LED load . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Efficiency versus AC line voltage at different LED load . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Input and output PFC waveforms at 100 VAC - 50 Hz - PF = 0.9889 . . . . . . . . . . . . . . . . 23
Input and output PFC waveforms at 230 VAC - 50 Hz - PF = 0.9211 . . . . . . . . . . . . . . . . 23
Transition mode operation at 100 VAC - 50 Hz . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
Transition mode operation at 100 VAC - 50 Hz -zoom of signals . . . . . . . . . . . . . . . . . . . . 24
Transition mode operation at 230 VAC - 50 Hz . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
Transition mode operation at 230 VAC - 50 Hz - zoom of signals . . . . . . . . . . . . . . . . . . . 24
ILED pin operation at 85 VAC. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
ILED pin operation at 100 VAC. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
ILED pin operation at 130 VAC. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
ILED pin operation at 175 VAC. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
ILED pin operation at 230 VAC. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
ILED pin operation at 265 VAC. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
Startup at 100 VAC - 50 Hz . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
Startup at 230 VAC - 50 Hz . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
Load disconnection at 100 VAC - 50 Hz . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
No load behavior at 100 VAC - 50 Hz. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
Load disconnection at 230 VAC - 50 Hz . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
No load behavior at 230 VAC - 50 Hz. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
Short-circuit of the output connector at 100 VAC - 50 Hz . . . . . . . . . . . . . . . . . . . . . . . . . . 28
Short-circuit removal at 100 VAC - 50 Hz . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
Short-circuit of the output connector at 230 VAC - 50 Hz . . . . . . . . . . . . . . . . . . . . . . . . . . 28
Short-circuit removal at 230 VAC - 50 Hz . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
Top side thermal map with 23 LED load . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
Bottom side thermal map with 23 LED load . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
Top side thermal map with 25 LED load - 10.5 W output . . . . . . . . . . . . . . . . . . . . . . . . . . 32
Bottom side thermal map with 25 LED load - 10.5 W output . . . . . . . . . . . . . . . . . . . . . . . 33
Measurement at 100 VAC, 50 Hz, PIN = 10.95 W, POUT = 9.5 W, PF = 0.9880 . . . . . . . . . 34
Measurement at 230 V, 50 Hz, PIN = 10.88 W, POUT = 9.48 W, PF = 0.9220 . . . . . . . . . . 34
100 VAC and 23 LED load - phase. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
DocID025380 Rev 1
AN4376
Figure 49.
Figure 50.
Figure 51.
List of figures
100 VAC and 23 LED load - neutral . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
230 VAC and 23 LED load - phase. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
230 VAC and 23 LED load - neutral . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
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37
Theory of operation
1
AN4376
Theory of operation
Most applications for an LED driver are designed using a common isolated flyback for
decoupling the secondary side and the load from the input mains, but sometimes the use of
transformers could be costly and is not always needed. In the bulb replacement market the
buck-boost topology without isolation and a transformer is often considered when isolation
is not requested by regulations.
Figure 2. Flyback (FL)
Figure 3. Buck-boost topology (BB)
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Figure 2 and Figure 3 show the differences, the flyback is derived from the basic buck-boost
topology and in fact it could be considered as a flyback with a unity primary to secondary
turn ratio. As a consequence the output of the buck-boost is floating and the negative side of
the output capacitor is not at GND but connected to the input mains.
Note then that the transformer of Figure 2 has been substituted by a simple inductor in
Figure 3.
Then in both situations, when the switch T is ON, the energy is stored in the inductor for the
BB or primary side for the FL, when the switch is OFF, the energy is transferred to the output
through the output diode. The primary current coming from the mains is in red and the
current flowing into the output is in blue.
Approaching the real LED driver, the LED load has been represented by the average LED
current in black.
Considering n as the transformer turn ratio, if n = 1, it is easy to represent the current and
waveforms for the buck-boost (Figure 5).
Figure 4. TM (transition mode) flyback currents
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Figure 5. TM (transition mode) buck-boost
currents
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6/37
DocID025380 Rev 1
'LRGHFXUUHQW
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AN4376
Theory of operation
Waveforms are represented in case of transition operating mode that is on the boundary
between continuous and discontinuous conduction mode, this is the most efficient and an
easy way to design EMI compliant low power single-stage LED drivers.
Figure 6. TM (transition mode) flyback
waveforms
Figure 7. TM (transition mode) buck-boost
waveforms
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Figure 6 and Figure 7 represent the split current.
To design a single-stage LED driver with a high power factor it is enough to modulate the
peak current of Figure 5 with a sinusoidal reference like in a common PFC in order to put
the input voltage with input current into phase.
DocID025380 Rev 1
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37
EVLHVLED815W10A - main characteristics and circuit description
2
AN4376
EVLHVLED815W10A - main characteristics and
circuit description
The main characteristics of this single-stage LED driver demonstration board are:

Line voltage range: 85 to 265 VAC

Line frequency (fL): 47-63 Hz

LED string voltage drop: 70 V nominal

LED nominal current: 140 mA ± 3%

LED current ripple: 100 mA

Rated output power: 10 W

Power factor > 0.9

Efficiency: 86 - 88% at full load

Maximum ambient temperature: 50 °C

Conducted EMI: in accordance with EN55022 Class-B

Protections against overvoltage, load disconnection and short-circuit
The LED driver provides a constant nominal current of 140 mA to an LED string with
a nominal voltage drop of 70 VDC in all the wide range input mains [85 - 265] VAC. Due to
the power factor correction, the input current of the driver is almost in phase with the mains
voltage and the power factor is close to the unity.
The power supply utilizes a typical non-isolated buck-boost converter topology with a simple
inductor to transfer energy to the LED load.
The inductor T1 (layer type, with standard ferrite size EF-20 and manufactured by
Magnetica) is charged by the internal Power MOSFET when it is turned on, and it
discharges into the three output parallel capacitors C11, C12, C16 (with 100 VDC rating see Figure 9 on page 12) and into the LED load when Power MOSFET turns off. In this
demonstration release the auxiliary winding is used to sense the inductor current
demagnetization, to sense the input line voltage for the voltage feed forward compensation,
to trigger the overvoltage protection and to self-supply the IC during normal operation. An
external high-voltage start-up circuitry is not needed because it is already embedded into
the IC. Also the buck-boost switch is embedded into the HVLED815PF in order to
maximizing the current sensing and the gate driving.
The board power cell has been designed using the procedure described in the AN1059
(See 2. in Section 8: Supporting material on page 36) used to design a standard high power
factor flyback; this document has been used as reference for calculating this demonstration
board, since the buck-boost topology can be considered as a simple flyback with a unity
transformer turn ratio and with the output voltage corresponding with the reflected voltage of
the flyback. Additional information has been reported in Section 2.1.
8/37
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AN4376
2.1
EVLHVLED815W10A - main characteristics and circuit description
LED current definition
The sense resistors R2 = 1.2  ± 1% and R3 = 1.8  ± 1% sense the current flowing into the
inductor primary side and fix the output LED current according to Equation 1:
1
02
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2 1 8 1 2
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.
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Equation 1
Where VCLED = [0.192 - 0.2 - 0.208] V is the equivalent internal voltage that includes Gi, Iref,
R parameters. and it is an internal parameters of the controller (see the HVLED815PF
device datasheet for more details [See 1. in Section 8: Supporting material on page 36] ).
2.2
LED current ripple definition
The output capacitor size and the LED current ripple definition have been calculated with
Equation 2:
Equation 2
For this demonstration board 3 parallel capacitor of 68 F-100 V have been selected to
have a current ripple of less than 100 mA pk-pk with 23 LEDs each with a dynamic
resistance of 0.8 .
2.3
DMG pin and OVP setting
Due to the topology the LED string load is connected to a floating output and the loop is
closed through a primary sensing regulation. From auxiliary winding, an accurate image of
the output voltage is fed to the DMG pin that is the inverting input of the internal, error
amplifier. Then R8 is connected to the auxiliary winding providing the inductor
demagnetization signal to the DMG pin and turning on the internal MOSFET at any
switching cycle. R8 value impacts on the voltage feed forward function and a 270 k
resistor has been selected for improving the line regulation (see the HVLED815PF
datasheet - section Voltage feed-forward block [1. in Section 8: Supporting material on
page 36]).
The divider composed by the R8 and R5 fixes the maximum output voltage VOVP at no load
(in case of LED -load disconnection) with Equation 3:
Equation 3
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2
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N = 3.8 ± 2% is turn-ratio between primary and auxiliary winding.
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37
EVLHVLED815W10A - main characteristics and circuit description
2.4
AN4376
External compensation network of the voltage loop
The compensation network composed by C6, C7 and R7 is placed between this pin and
GND to achieve stability and good dynamic performance of the voltage control loop.
Normally it is not working and operates only during an OVP.
2.5
Power factor corrector function and ILED pin modulation
with the input mains voltage
Once the signal at the current sense pin has reached the level programmed by reference
signal on the pin ILED, the internal MOSFET turns off.
The network composed by R15, R17, R21, R20 and R4, R22 and modulated by Q2, works
as a divider and it provides to the ILED pin of the HVLED815PF the information of the
instantaneous input voltage which is used to modulate the current flowing into the inductor.
Through this network the controller works as a power factor corrector.
The converter is connected after the mains rectifier and the capacitor filter, which in this
case is quite small to avoid damage to the shape of the input current maximizing the power
factor performances.
Referring to Figure 8 on page 11, a voltage Vx proportional to the input rectified mains is
summed on the average voltage present on the ILED pin trough the CLED capacitor
generating a voltage reference proportional to the input voltage (AC coupling).
Equation 4
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The ILED pin voltage is compared with the CS pin voltage, generating a primary current
proportional to the input voltage reaching the high power factor condition.
The average value of the ILED pin is not depending from the Vin input voltage (AC
coupling), as a consequence the desiderated output current can be programed trough the
current sense resistor Rsense according to Equation 1 (see the HVLED815PF device
datasheet for more details [1. in Section 8: Supporting material on page 36] ).
10/37
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AN4376
EVLHVLED815W10A - main characteristics and circuit description
Figure 8. ILED pin modulation with the input mains voltage
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In Section 7.3: ILED pin modulation with the line voltage on page 25 is showed the behavior
of the ILED pin depending on the action of the switch represented by the BJT Q2 (SW in
Figure 8, Q2 in Figure 9). At the low line the switch is Off (BJT base is low) and the pin is
modulated by the divider composed by RAC_H and RAC_L1. When, at the high line, the
BJT is ON the pin ILED is modulated by a different ratio of the divider (RAC_H and the
parallel of RAC_L1 with RAC_L2) in order to keep the same dynamic on the ILED pin.
2.6
High-voltage start-up generator and VCC capacitor
At a startup, a 5.5 mA internal current source of the HVLED815PF device [1. in Section 8:
Supporting material on page 36] charges the VCC capacitor (C8), until the voltage on the
pin Vcc reaches the start-up threshold, and then it is shut down. With a 22 f of the VCC
capacitor, the device turns-on typically in:
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 22 
.
︳
F
N
O
C
VCI

c
c

CV

p
u
t
r
a
t
TS
Equation 5
The T1 auxiliary winding (pins 4 - 5) and a diode D2 and a limiting resistor R9 generate
a constant VCC voltage that powers externally the HVLED815PF device during normal TM
(transition mode) operation. See the real behavior in Section 7.4: Controller startup and
light-ON on page 26.
DocID025380 Rev 1
11/37
37
12/37
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Electrical diagram
AN4376
Electrical diagram
Figure 9. EVLHVLED815W10A demonstration board schematic
&203
AN4376
4
Bill of material
Bill of material
Table 1. Bill of material
Ref.
Value
Description
Manufacturer
PCB
-
HVLED8XX HPF NI WR BULB EB rev. 2.0
TECNOMETAL
BD1
HD06-T
Bridge diode HD06-T 600 V 0.8 A Minidip
Diodes
C1
100 nF
CAP X2 305 V MKP P. 10
EPCOS
C2
220 nF
CAP X2 305 V MKP P. 15
EPCOS
C4
100 nF
Cap. ± 10% X7R 50 V 0805
KEMET
C5
2.2 F
Cap. ±1 0% X5R 25 V 0805
KEMET
C6
470 nF
Cap. ±1 0% X7R 25 V 0805
KEMET
C7, C17
2.2 nF
Cap. ± 5% C0G 50 V 0805
MURATA
C8
22 F
Cap. ± 20% EL. 50 V 105 °C rad. D5 P 2.5 mm
Panasonic
C10
2.2 nF
CAP X1 Y1 250 V CERAMIC P.10
Murata
C11, C12,
C16
68 F
Cap. ± 20% EL. 100 V 105 °C LL LOW ESR rad. D10 P 5 mm
Nichicon
C13, C14,
C15, C20
N.M.
-
-
C19
4.7 F
Cap. ± 10% X5R 50 V 1206
TAIYO YUDEN
D2
BAV20W
Diode rect. 150 V 200 mA SOD123
Diodes
D3
STTH2L06U
Diode rect. UFAST STTH2L06U 600 V 2 A SMB
STMicroelectronics
R13
120 k
Res.1/4 W 1% 100 ppm 1206 SMD
VISHAY
D7
BZV55-C18
Zener 18 V ± 5% 500 mW MINIMELF
NXP
F1
1 A - 250 V - fast
Fuse 1 A 250 V fast radial 8.4 mm x 7.7 mm P 5 mm
MULTICOM
2
J1
+Vout
Cable color red 0.5 mm L.50 mm, stripped and tinned 5 mm
-
J2
CON1
Cable color brown 0.5 mm2 L.50 mm, stripped and tinned 5 mm
-
J3
-Vout
Cable color black 0.5
mm2
L.50 mm, stripped and tinned 5 mm
-
2
J4
CON1
Cable color brown 0.5 mm L.50 mm, stripped and tinned 5 mm
-
L1 L2
2.2 mH
Choke RF 2.2 mH 250 mA axial D 6.5 L 12 mm
EPCOS
Q2
BC847C
NPN SML SIG G.P. AMP SOT23
NXP
R2
1.2 
Res.1/4 W 1% 100 ppm 1206 SMD
Panasonic
R3
1.8 
Res.1/4 W 1% 100 ppm 1206 SMD
Panasonic
R4
120 k
Res.1/8 W 1% 100 ppm 0805 SMD
VISHAY
R5
33 k
Res.1/8 W 1% 100 ppm 0805 SMD
VISHAY
R7
10 k
Res.1/8 W 1% 100 ppm 0805 SMD
VISHAY
R8
270 k
Res.1/4 W 1% 100 ppm 1206 SMD
VISHAY
R9
180 
Res.1/8 W 1% 100 ppm 0805 SMD
VISHAY
DocID025380 Rev 1
13/37
37
Bill of material
AN4376
Table 1. Bill of material (continued)
Ref.
Value
Description
Manufacturer
R10
62 k
Res.1/8 W 1% 100 ppm 0805 SMD
VISHAY
R12, R21
51 k
Res.1/8 W 1% 100 ppm 0805 SMD
VISHAY
R11, R19
N.M.
-
-
R15, R17
180 k
Res.1/4 W 1% 100 ppm 1206 SMD
WELWYN
R16
0
Res. 0  0603 SMD
VISHAY
R20
20 k
Res.1/8 W 1% 100 ppm 0805 SMD
VISHAY
R22
6.2 k
Res.1/8 W 1% 100 ppm 0805 SMD
VISHAY
R23, R24
4.7 k
Res.1/8 W 1% 100 ppm 0805 SMD
VISHAY
R25, R26
3.9 
Res.1/4 W 1% 100 ppm 1206 SMD
VISHAY
T1
2267.0001
Inductor L = 1.1 mH 0.6 A core EF20
Magnetica
U1
HVLED815PF
Offline LED driver HVLED815PF SO16
STMicroelectronics
14/37
DocID025380 Rev 1
AN4376
5
Component layout
Component layout
Figure 10. Top side
Figure 11. Bottom side
$0
DocID025380 Rev 1
$0
15/37
37
Measurement results
6
AN4376
Measurement results
The EVLHVLED815W10A non-isolated LED driver demonstration board has been tested
using the following instrumentations/load:
6.1

Agilent Technologies 6813B
AC source

®
watt meter
YOGOGAWA WT210
®

Tektronix DP07054 500 MHz
digital oscilloscope

Tektronix TCP0030
current probe

TELEDYNE LECROY PPE4kV 100:1 400 MHz
high-voltage probe

KEITHLEY 2000
digital multimeter

Avio TVS-200 P
thermal video system

CHROMA TECHNOLOGY CORP® 6314
DC electronic load

SEOUL SEMICONDUCTOR Z-Power LED P4
LED series
LED driver performance at nominal load 70 VDC - 140 mA
First measurement set has been collected using a nominal load with an LED voltage drop of
70 VDC. Following Equation 1 the current flowing into the LED is set by: R2 = 1.2  ± 1%
and R3 = 1.8  ± 1% at 140 mA.
6.2
Line regulation at nominal load
Figure 12 shows the measured average output current versus line voltage at the nominal
load:
Figure 12. LED current vs. AC line voltage
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The output current is 140 mA ± 1% over all the input voltage range [85 - 265] VAC.
16/37
DocID025380 Rev 1
AN4376
6.3
Measurement results
Power factor at nominal load
The “Power Factor” (PF) at the nominal load remains above 0.9 for every input mains
voltage.
Figure 13. Power factor vs. AC line voltage at nominal load
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Total harmonic distortion (THD) at nominal load
Figure 14 shows the total harmonic distortion versus line voltage:
Figure 14. Total harmonic distortion vs. AC line voltage at nominal load
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6.4
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The THD curve presents two minimum valley point corresponding to the Japanese and
European nominal voltage.
DocID025380 Rev 1
17/37
37
Measurement results
6.5
AN4376
Driver efficiency at nominal load
The LED driver efficiency is up to 89%.
Figure 15. Efficiency vs. AC line voltage at nominal load
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Efficiency at Japanese range is around 87% and increases to 88% at European voltage.
6.6
LED driver performance varying the number of LEDs
The performance of the LED driver has been collected varying the LED number and as
consequence the string voltage drops after a thermal warm-up (T = 1 h). In Table 2 are
shown the descriptions of the loads applied and corresponding to a total voltage drop after
a warm-up:
Table 2. LED string voltage specification
18/37
LED number
String voltage drop
Variation respect to nominal
voltage
23 LEDs
68.3 VDC
- 2.4%
25 LEDs
74.0 VDC
+ 5.7%
21 LEDs
62.3 VDC
- 11%
18 LEDs
53.2 VDC
- 24%
DocID025380 Rev 1
AN4376
Line regulation at different LED load number
Figure 16 shows the measured average output current versus line voltage at different
numbers of LEDs applied:
Figure 16. Line regulation at different LED load
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6.7
Measurement results
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When the LED string voltage drop is passing from 75 VDC to 50 VDC the controller is able
to maintain the current practically stable in all the input mains range.
DocID025380 Rev 1
19/37
37
Measurement results
6.8
AN4376
Power factor at different LED load number
Following relation of the AN1059, the power factor performance is directly related to the
output voltage of the buck-boost. For this reason when the load is composed only by 18
LEDs corresponding to a load 30% lower the nominal specification, the power factor
remains above 0.9 only at low mains till 200 VAC.
A good power factor performance for the light market can be reached decreasing the load
from 23 LEDs to a minimum level of 21 LEDs.
Figure 17 shows the measured power factor (PF) at different LED load.
Figure 17. Power factor versus AC line voltage at different LED load
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20/37
DocID025380 Rev 1
AN4376
Total harmonic distortion (THD) at different LED load number
Figure 18 shows the total harmonic distortion (THD) versus the line.
Figure 18. THD versus AC line voltage at different LED load
7+'>@
6.9
Measurement results
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THD at nominal input voltage (Japanese - European) is lower than 20% applying different
loads. Also the distortion of the PFC current is increasing, decreasing the number of LED.
DocID025380 Rev 1
21/37
37
Measurement results
6.10
AN4376
LED driver efficiency at different LED load number
Figure 19 shows the efficiency versus the line.
Figure 19. Efficiency versus AC line voltage at different LED load
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Varying the number of the LEDs , the efficiency remains comparable with the nominal load,
of course increasing the load to 25 LEDs means increasing the converter output power till
11.5 W. Section 7.7: Thermal measurements on page 29 shows that the HVLED815PF
device is not overeating and is able to support this load properly.
Note:
22/37
Important: In this design a sort of short-circuit protection has been previewed, the R25 and
R26 in series with the diode have been added to sense the short-circuit of the output
connectors. If this function is not needed, the two parallel resistors could be removed and
the converter efficiency will increase of 1.5%.
DocID025380 Rev 1
AN4376
PFC waveforms
7
PFC waveforms
7.1
Input and output LED driver waveforms
The waveforms of the input current and drain voltage at the nominal input voltage mains and
nominal LED load are illustrated in this section. Drain voltage is modulated by the sinusoidal
shape of the input mains voltage and the peak increase with the line.
The input current is in phase with the input voltage and a high power factor is achieved
(PF > 0.9).
Figure 20. Input and output PFC waveforms
at 100 VAC - 50 Hz - PF = 0.9889
CH1: DRAIN
CH2: INPUT PFC CURRENT
CH3: VOUT
CH4: LED CURRENT
Figure 21. Input and output PFC waveforms
at 230 VAC - 50 Hz - PF = 0.9211
CH1: DRAIN
CH2: INPUT PFC CURRENT
CH3: VOUT
CH4: LED CURRENT
Also the LED current and output voltage have been checked.
Note that the regulated LED current remains constant all over the input mains voltage. The
LED pk-pk ripple is the ± 27% of the average current. Increasing the value of the output
capacitor it is possible to decrease the LED current ripple following (Equation 2 on page 9).
For this demonstration board 3 parallel capacitors of 68 F have been selected to have
a current ripple of less than 100 mA pk-pk with 23 LEDs each with a dynamic resistance
of 0.8 .
DocID025380 Rev 1
23/37
37
PFC waveforms
7.2
AN4376
Transition mode operation
During ON-time, the peak drain current is modulated by a signal proportional to the ILED
pin. This reference sets the turn-off of the MOSFET.
The MOSFET turn-on depends on the DMG signal that senses the demagnetization of the
drain current realizing a transition mode operation.
Figure 22. Transition mode operation
at 100 VAC - 50 Hz
CH1: DRAIN
CH2: CS
CH3: ILED
CH4: DMG
CH1: DRAIN
CH2: CS
CH3: ILED
CH4: DMG
Figure 24. Transition mode operation
at 230 VAC - 50 Hz
CH1: DRAIN
CH2: CS
CH3: ILED
CH4: DMG
Figure 23. Transition mode operation
at 100 VAC - 50 Hz -zoom of signals
Figure 25. Transition mode operation
at 230 VAC - 50 Hz - zoom of signals
CH1: DRAIN
CH2: CS
CH3: ILED
CH4: DMG
A primary inductance of 1.1 mH has been selected in order to obtain the converter switching
frequency into the interval [35 - 70] kHz (Magnetica PN-2267.0001).
24/37
DocID025380 Rev 1
AN4376
7.3
PFC waveforms
ILED pin modulation with the line voltage
From Figure 26 to Figure 31, the effect off the ILED pin modulation through a divider
connected to the mains is represented. The effect is a very sinusoidal shape at nominal
mains voltage 100 VAC and 230 VAC with high performance in terms of PF and THD.
Figure 26. ILED pin operation at 85 VAC
CH1: VIN
CH2: BJT-base
CH3: ILED pin
CH4: C5 capacitor
CH1: VIN
CH2: BJT-base
CH3: ILED pin
CH4: C5 capacitor
Figure 28. ILED pin operation at 130 VAC
CH1: VIN
CH2: BJT-base
CH3: ILED pin
CH4: C5 capacitor
Figure 27. ILED pin operation at 100 VAC
Figure 29. ILED pin operation at 175 VAC
CH1: VIN
CH2: BJT-base
CH3: ILED pin
CH4: C5 capacitor
DocID025380 Rev 1
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37
PFC waveforms
AN4376
Figure 30. ILED pin operation at 230 VAC
CH1: VIN
CH2: BJT-base
CH3: ILED pin
CH4: C5 capacitor
7.4
Figure 31. ILED pin operation at 265 VAC
CH1: VIN
CH2: BJT-base
CH3: ILED pin
CH4: C5 capacitor
Controller startup and light-ON
With a VCC capacitor of 22 F (see Figure 9: EVLHVLED815W10A demonstration board
schematic on page 12), the HVLED815PF turns-on in 50 ms. A light appears hundreds
milliseconds later (see CH1-LED current).
A capacitor C5 (2.2 µF) on the ILED pin is charging during the start-up phase and it is
responsible of the LED current soft-start time.
Figure 32. Startup at 100 VAC - 50 Hz
CH1: LED current
CH2: CS
CH3: VOUT
CH4: VCC
Figure 33. Startup at 230 VAC - 50 Hz
CH1: LED current
CH2: CS
CH3: VOUT
CH4: VCC
Acting on this C5 capacitor, it is possible to modify the soft-start time. In detail, to speed up
the loop it is enough to reduce the C5 capacitor reducing the soft-start time.
26/37
DocID025380 Rev 1
AN4376
PFC waveforms
7.5
OVP protection and no load behavior
During a load disconnection the HVLED815PF device senses the output voltage through the
DMG pin and controls the voltage loop in order to regulate the output capacitor voltage to
a level below its maximum rating (100 V) (see the HVLED815PF datasheet [1. in Section 8:
Supporting material on page 36]).
Figure 34. Load disconnection
at 100 VAC - 50 Hz
CH1: DRAIN
CH2: IOUT
CH3: VOUT
CH4: DMG
Figure 35. No load behavior
at 100 VAC - 50 Hz
CH1: DRAIN
CH2: IOUT
CH3: VOUT
CH4: DMG
Figure 36. Load disconnection
at 230 VAC - 50 Hz
CH1: DRAIN
CH2: IOUT
CH3: VOUT
CH4: DMG
Figure 37. No load behavior
at 230 VAC - 50 Hz
CH1: DRAIN
CH2: IOUT
CH3: VOUT
CH4: DMG
As shown in Figure 35 and Figure 37 the converter works in a burst mode during no load
condition. No current is flowing into the LED load.
DocID025380 Rev 1
27/37
37
PFC waveforms
7.6
AN4376
Short-circuit and output current limitation
During a short-circuit of the output connector, all the energy stored in the output electrolytic
capacitor is discharged into the output side loop, so that no current will flow to the external
LED, thus preventing their failure.
Figure 38. Short-circuit of the output connector
at 100 VAC - 50 Hz
CH1: output LED driver current
CH2: DMG
CH3: VOUT
CH4: VCC
CH1: output LED driver current
CH2: DMG
CH3:V OUT
CH4:V CC
Figure 40. Short-circuit of the output connector
at 230 VAC - 50 Hz
CH1: output LED driver current
CH2: DMG
CH3: VOUT
CH4: VCC
Figure 39. Short-circuit removal
at 100 VAC - 50 Hz
Figure 41. Short-circuit removal
at 230 VAC - 50 Hz
CH1: output LED driver current
CH2: DMG
CH3: VOUT
CH4: VCC
When the output capacitor is shorted, the HVLED815PF device works with the internal selfsupply function because no charging current came from the auxiliary winding. The controller
doesn't stop switching but reduces the on-time to its minimum level. The selection of the
R24 and R24 allows limiting the output diode current at a level of about 260 mA. Increasing
28/37
DocID025380 Rev 1
AN4376
PFC waveforms
the two resistor value allows to regulate the output current at a lower level. Here
a compromise between the output current limitation level and efficiency losses has been
selected.
7.7
Thermal measurements
To check the reliability of the design, the thermal maps have been checked with an IR
camera.
The LED driver has been stressed not only at a nominal load with 23 LEDs (Pout = 10 W)
but also at 25 LEDs, here the requested output power is increased at 10.5 W across the
input mains voltage range. Only minimum voltage range (85 VAC), maximum voltage range
(265 VAC) and the two nominal mains voltages 100/50 Hz and 230/50 Hz have been
reported.
DocID025380 Rev 1
29/37
37
PFC waveforms
AN4376
Figure 42. Top side thermal map with 23 LED load
Vin = 85 VAC- 23 LEDs
Point
Temperature
Description
A
B
C
D
E
F
58.2 °C
56.1 °C
58.7 °C
48.2 °C
49.3 °C
47.9 °C
L1
L2
Drain
T1 - magnetic
T1 - winding
T1 - magnetic
Vin = 100 VAC - 23 LEDs
Point
Temperature
Description
A
B
C
D
E
F
52.6 °C
50.6 °C
55.5 °C
46.5 °C
49.0 °C
46.5 °C
L1
L2
Drain
T1 - magnetic
T1 - winding
T1 - magnetic
Vin = 230 VAC - 23 LEDs
Point
Temperature
Description
A
B
C
D
E
F
50.4 °C
46.7 °C
55.0 °C
47.0 °C
49.8 °C
47.9 °C
L1
L2
Drain
T1 - magnetic
T1 - winding
T1 - magnetic
Vin = 265 VAC - 23 LEDs
30/37
Point
Temperature
Description
A
B
C
D
E
F
53.1 °C
49.0 °C
58.2 °C
49.0 °C
50.9 °C
48.7 °C
L1
L2
Drain
T1 - magnetic
T1 - winding
T1 - magnetic
DocID025380 Rev 1
AN4376
PFC waveforms
Figure 43. Bottom side thermal map with 23 LED load
Vin = 230 VAC - 23 LEDs
Point
Temperature
Description
A
B
C
D
E
F
G
H
52.1 °C
52.9 °C
53.2 °C
52.6 °C
67.4 °C
56.7 °C
56.7 °C
48.5 °C
D4 - 1206 resistor
R13
R17
R15
HVLED815PF
R25
R26
D3
Vin = 230 VAC - 23 LEDs
Point
Temperature
Description
A
B
C
D
E
F
G
H
50.7 °C
50.4 °C
50.7 °C
50.2 °C
61.6 °C
54.5 °C
54.5 °C
47.9 °C
D4 - 1206 resistor
R13
R17
R15
HVLED815PF
R25
R26
D3
Vin = 230 VAC - 23 LEDs
Point
Temperature
Description
A
B
C
D
E
F
G
H
60.3 °C
59.0 °C
59.8 °C
57.9 °C
57.2 °C
52.3 °C
51.0 °C
47.4 °C
D4 - 1206 resistor
R13
R17
R15
HVLED815PF
R25
R26
D3
Vin = 230 VAC - 23 LEDs
Point
Temperature
Description
A
B
C
D
E
F
G
H
68.8 °C
65.8 °C
66.1 °C
64.8 °C
61.3 °C
54.7 °C
54.5 °C
47.9 °C
D4 - 1206 resistor
R13
R17
R15
HVLED815PF
R25
R26
D3
DocID025380 Rev 1
31/37
37
PFC waveforms
AN4376
Figure 44. Top side thermal map with 25 LED load - 10.5 W output
Vin = 85 VAC- 25 LEDs
Point
Temperature
Description
A
B
C
D
E
F
63.0 °C
62.3 °C
66.0 °C
50.6 °C
51.7 °C
50.6 °C
L1
L2
Drain
T1 - magnetic
T1 - winding
T1 - magnetic
Vin = 100 VAC - 25 LEDs
Point
Temperature
Description
A
B
C
D
E
F
55.5 °C
54.7 °C
60.2 °C
48.7 °C
50.9 °C
49.2 °C
L1
L2
Drain
T1 - magnetic
T1 - winding
T1 - magnetic
Vin = 230 VAC - 25 LEDs
Point
Temperature
Description
A
B
C
D
E
F
50.1 °C
47.6 °C
56.0 °C
48.7 °C
51.5 °C
48.4 °C
L1
L2
Drain
T1 - magnetic
T1 - winding
T1 - magnetic
Vin = 265 VAC - 25 LEDs
32/37
Point
Temperature
Description
A
B
C
D
E
F
49.5 °C
53.1 °C
58.7 °C
48.7 °C
52.0 °C
49.2 °C
L1
L2
Drain
T1 - magnetic
T1 - winding
T1 - magnetic
DocID025380 Rev 1
AN4376
PFC waveforms
Figure 45. Bottom side thermal map with 25 LED load - 10.5 W output
Vin = 230 VAC - 25 LEDs
Point
Temperature
Description
A
B
C
D
E
F
G
H
52.1 °C
52.9 °C
53.2 °C
52.6 °C
67.4 °C
56.7 °C
56.7 °C
48.5 °C
D4 - 1206 resistor
R13
R17
R15
HVLED815PF
R25
R26
D3
Vin = 230 VAC - 25 LEDs
Point
Temperature
Description
A
B
C
D
E
F
G
H
50.7 °C
50.4 °C
50.7 °C
50.2 °C
61.6 °C
54.5 °C
54.5 °C
47.9 °C
D4 - 1206 resistor
R13
R17
R15
HVLED815PF
R25
R26
D3
Vin = 230 VAC - 25 LEDs
Point
Temperature
Description
A
B
C
D
E
F
G
H
60.3 °C
59.0 °C
59.8 °C
57.9 °C
57.2 °C
52.3 °C
51.0 °C
47.4 °C
D4 - 1206 resistor
R13
R17
R15
HVLED815PF
R25
R26
D3
Vin = 230 VAC - 25 LEDs
Point
Temperature
Description
A
B
C
D
E
F
G
H
68.8 °C
65.8 °C
66.1 °C
64.8 °C
61.3 °C
54.7 °C
54.5 °C
47.9 °C
D4 - 1206 resistor
R13
R17
R15
HVLED815PF
R25
R26
D3
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PFC waveforms
7.8
AN4376
Harmonic content at nominal mains voltage
One of the main purposes of this converter is the correction of input current distortion,
decreasing the harmonic contents below the limits of the actual regulation. Therefore, the
board has been tested according to the Japanese JEIDA-MITI Class-C standard and
European EN61000-3-2 Class-C standard, at a full load and both nominal input voltage
mains.
Figure 46. Measurement at 100 VAC, 50 Hz, PIN = 10.95 W, POUT = 9.5 W, PF = 0.9880
0HDVXU HGYDOXH
-(,7$0,7,&ODVV&OLPLWV
+DUPRQLF FXUUHQW>$@
+DUPRQLF RUGHU >Q @
$0
Figure 47. Measurement at 230 V, 50 Hz, PIN = 10.88 W, POUT = 9.48 W, PF = 0.9220
0HDVXU HGYDOX H
(1&ODVV&OL PLWV
+DUPRQLFFXUUHQW>$ @
+DUPRQLFRUGHU>Q@
$0
Figure 46 and Figure 47 show as the harmonics respect the limits for the Class-C
equipment.
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AN4376
7.9
PFC waveforms
Conducted emission pre-compliance test
From Figure 48 to Figure 51 are the average measurements of the conducted noise with 23
LED load and nominal mains voltages. The limits shown on the diagrams are those of the
EN55022 Class-B, which is the most popular standard for domestic equipment. As visible in
the diagrams, good margins with respect to the limits are present in all test conditions.
Increasing the CX capacitor value of the EMI filter will improve the safe margin but affecting
the PF. A compromise has been fixed in this design.
Figure 48. 100 VAC and 23 LED load - phase
Figure 49. 100 VAC and 23 LED load - neutral
Figure 50. 230 VAC and 23 LED load - phase
Figure 51. 230 VAC and 23 LED load - neutral
Note that a CY capacitor between the negative output pin of the converter and ground has
been placed to filter common mode noise flowing into the demonstration board.
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Supporting material
8
9
AN4376
Supporting material
1.
HVLED815PF datasheet: “Offline LED driver with primary-sensing and high power
factor up to 15 W”.
2.
AN1059: “Design equations of high-power factor flyback converters based on the
L6561”.
3.
AN4314: “25 W wide-range high power factor buck-boost converter demonstration
board using the L6564H”.
Revision history
Table 3. Document revision history
36/37
Date
Revision
09-Jan-2014
1
Changes
Initial release.
DocID025380 Rev 1
AN4376
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