High voltage LED applications DownloadLink 3921

Application note MLX10803
High voltage solutions.
1 Scope
The following document describes how to create high voltage circuit designs, using the MLX10803.
The target is domestic and industrial use, or any application requiring high light levels from light emitting diodes.
The applications described in this document are applications for driving high power LED diodes. The described
circuits can be applied on other applications with similar circumstances as well, in case they fall within the
specifications of the MLX10803. This is a conceptual description and in some case no component values are given.
The applications described in this document have in most cases been implemented. Demonstration systems and
components are available at Melexis. Please contact our closest sales office or representative to learn more
2 General
It is not a trivial task to design for high voltage, great care must to be taken in respect for the high voltages involved.
The examples given in this document have to be carefully designed and fabricated. Slight errors can have
devastating results. These examples are not recommended for the inexperienced or untrained lay people, it is
intended for electrical and electronic engineers with relevant training and experience designing and building high
voltage circuits. The circuit board has to be design according to high voltage rules. Depending on the users
specific implementation these examples can have lethal voltages present.
The circuits described in this document have a very good efficiency, converting efficiencies up to 98-99% is
to be expected! This makes the circuit design fairly simple in respect of thermal handling. Please remember that if
you design lamps with up to 100 watt and more, even 1% loss generates 1 watt, and more of heat.
Every kind of active current regulation generates ripple on the regulated output, this ripple can generate
electromagnetic radiation (EMR), resulting in electromagnetic coupling to the surrounding electronic (EMC). The
MLX10803 and the applications described in this document are designed to minimize EMR. Additional care has to
be taken when designing the circuit board and the physical application. Melexis makes no claims about the
suitability of any of these circuits for EMI/EMC and EMR compliance against international regulations. Compliance
testing is recommended and it will fall to the user to conduct such testing prior to sale in specific countries and
markets.
390111080311Rev.003
Author: RAH
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Application note MLX10803
High voltage solutions.
3 Design tools
High volt design is more demanding than making low voltage applications using MLX10803. We strongly
recommend using the following presented tools when making high volt applications. Use these tools for your own
safety, before you connect your LED application to the 110/220 V net.
3.1
Coil calculation program
This Micorsoft Excel calculation sheet is a necessity when designing with high energies
.
Find this program on the Melexis web site at, http://www.melexis.com/prodmain.asp_Q_family_E_MLX10803 .
Download the coil_calc_(x).zip file and use the Microsoft Excel spreadsheet included.
The spreadsheet is self instructive. Play with it and get a feeling about the relation ship between coils, currents and
sense values. The real mathematics behind the MLX10803 function is complicated, this sheet is a simplification.
The tool gives only rough values, but it gives an impression what component sizes and settings are needed.
This tool will help you to find a rough value for:
•
•
•
The coil
The programmable sense voltage and the sense resistor
The mono flop time. The time to partly discharging the coil. This times is a derivate from the oscillator
frequency in MLX10803
After finding out coil, reference resistors and sense resistor value, as well as mono flop time, oscillator resistor value
and sense voltage settings with this tool, it is time to apply the component values to the MLX10803 LED driver
circuit and try out the values in an application.
3.2
Evaluation board EVB10803
You should make try and tests with the evaluation board. This will save you time and money understanding the
function of the MLX10803 chip.
You should not design any high volt application without an understanding of the function of the MLX10803 circuit.
Warning:
The evaluation board EVB10803 is specified to function up to 32V, or 80V for half a second. It is not
intended to be used at 220V.
The LED supply can be separated from the circuit supply (VS/PWM) by removing the jumper for that on the
EVB10803. See the manual for EVB10803 for instructions. When the supply to the LED is separated from the
VS/PWM then the supply voltage to the LED is limited by the switching N-FET transistor parameters and the fly
back diode. Please use this option with great care, and check carefully what type of transistor and fly back diode
your EVB10803 is equipped with before applying any higher voltage than 32V.
390111080311Rev.003
Author: RAH
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Application note MLX10803
High voltage solutions.
4 Applications
4.1
Simplest solution
LEDs
Vsupply typical 100 – 240V DC < X% ripple
N
D1
R5
L1
MLX10803
1
2
D3
3
4
VREF
VS/PWM
ROSC DRVGATE
IREF1
IREF2
GND
RSENSE
8
D2
T1
7
6
5
R1
R4
R3
R2
Above circuit schematic describes the simplest possible high volt solution. The coil and the Rsense resistor have to
be adapted to the type of diodes used and the number in series. Also the desired operational range has to be taken
into calculation for the right size of this coil and resistor. The circuit is a down regulation, so at a given minimum
operational voltage there are a maximum number of diodes possible to connect in series. This number of diodes
depends on the forward voltage of that type of diode. The sum of the diode voltages must in all cases be lower than
the input voltage.
Example: Typical white diodes have a forward voltage of 3.5V. 25 diodes in series results in 87.5V in total forward
voltage, which will give a margin on a 110V supply. This is the recommended maximum number of diodes for 110V
in this case. The forward voltage varies with many factors and one among these is temperature. The difference
between 87.5V and 100V is needed for this variations of forward voltage as well as variations of the supply voltage.
Note that this design will also work for much higher applied supply voltage and gives you a universal voltage lamp if
so is desired.
390111080311Rev.003
Author: RAH
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Application note MLX10803
High voltage solutions.
4.1.1 Component selection
LEDs
Vsupply typical 100 – 240V DC < X% ripple
N
D1
R5
L1
MLX10803
D3
1
C1
2
3
4
C2
R4
C3
R3
C4
VREF
VS/PWM
ROSC DRVGATE
IREF1
GND
IREF2
RSENSE
8
D2
T1
7
6
5
R1
R2
Values range of components, please use coil_calc to estimate.
Values for 300mA application 20 LED in series 100-250V
R1
R2
R3
R4
R5
0.05Ω – 10Ω
NTC: 1kΩ – 2MΩ
100kΩ (MLX10803A); 20k (MLX10803)
39kΩ - 440 kΩ
150kΩ / 0.5 watt
R1
R2
C1
C2
C3
C4
0 - 10uF / 16V
0 - 1nF / 16V
0 - 1nF / 16V
0 - 1nF / 16V
D1
D2
D3
ES2G ( check max current and voltage )
1N4148
ZENER 12V / 2mA
L1
T1
0.1mH - 10mH / 4A – 10mA
SPN04N60S5 (Infineon) ( check max current and voltage)
390111080311Rev.003
Author: RAH
Ceramic
Ceramic
Ceramic
Ceramic
R3
R4
R5
0.4Ω => 0.5A peak => about 300mA average
NTC: aprox. 100kΩ @ 125 ºC TN05- 4W205 (MLX10803A)
NTC: aprox. 20kΩ @ 125 ºC TN05- 4W474 (MLX10803)
100kΩ (MLX10803A); 20kΩ (MLX10803)
39kΩ
150kΩ / 0.5 watt
C1
C2
C3
C4
10uF / 16V
Ceramic
1nF / 16V Ceramic
1nF / 16V Ceramic
1nF / 16V Ceramic
D1
D2
D3
ES2G
1N4148
ZENER 12V
L1
T1
2.2 mH / 500mA (MLX10803A); 1mH / 500mA (MLX10803)
SPN04N60S5 (Infineon)
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Application note MLX10803
High voltage solutions.
4.2
More efficient solution
Above circuit schematic describes an efficient possible high volt solution. The coil and the Rsense resistor have to
be adapted to the type of diodes used and the number in series. Also the desired operational range has to be taken
into calculation for the right size of this coil and resistor. The circuit is a down regulation, so at a given minimum
operational voltage there are a maximum number of diodes possible to connect in series. This number of diodes
depends on the forward voltage of that type of diode. The sum of the diode voltages must in all cases be lower than
the input voltage.
Example: Typical white diodes have a forward voltage of 3.5V. 25 diodes in series results in 87.5V in total forward
voltage, which will give a margin on a 110V supply. This is the recommended maximum number of diodes for 110V
in this case. The forward voltage varies with many factors and one among these is temperature. The difference
between 87.5V and 100V is needed for this variations of forward voltage as well as variations of the supply voltage.
Note that this design will also work for much higher applied supply voltage and gives you a universal voltage lamp if
so is desired.
390111080311Rev.003
Author: RAH
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02/Dec/05
Application note MLX10803
High voltage solutions.
4.2.1 Component selection
LEDs
Vsupply typical 10 – 240V DC < X% ripple
N
D1
R5
T2
L1
MLX10803
D3
1
C1
2
3
4
C2
R4
C3
R3
C4
VREF
VS/PWM
ROSC DRVGATE
IREF1
GND
IREF2
RSENSE
8
D2
T1
7
6
5
R1
R2
Values range of components, please use coil_calc to estimate.
Values for 30mA application 22 LED in series 100-240V
R1
R2
R3
R4
R5
0.05Ω – 1Ω
NTC: 1kΩ – 2MΩ
100kΩ (MLX10803A); 20k (MLX10803)
39kΩ - 440 kΩ
1MΩ
R1
R2
C1
C2
C3
C4
0 - 10uF / 16V
0 - 1nF / 16V
0 - 1nF / 16V
0 - 1nF / 16V
D1
D2
D3
ES2G ( check max current and voltage )
1N4148
ZENER 12V / 2mA
L1
T1
T2
0.1mH - 10mH / 4A – 10mA
SPN04N60S5 (Infineon) ( check max current and voltage)
Highvolt NPN, hfe> 100
390111080311Rev.003
Author: RAH
Ceramic
Ceramic
Ceramic
Ceramic
R3
R4
R5
5Ω => 50mA peak => about 30mA average
NTC: aprox. 100kΩ @ 125 ºC TN05- 4W205 (MLX10803A)
NTC: aprox. 20kΩ @ 125 ºC TN05- 4W474 (MLX10803)
91kΩ (MLX10803A); 18kΩ (MLX10803)
39kΩ
1MΩ
C1
C2
C3
C4
10uF / 16V
Ceramic
1nF / 16V Ceramic
1nF / 16V Ceramic
1nF / 16V Ceramic
D1
D2
D3
ES2G
1N4148
ZENER 12V
L1
T1
T2
2.2 mH / 500mA (MLX10803A); 1mH / 500mA (MLX10803)
SPN04N60S5 (Infineon)
Highvolt NPN, hfe> 100
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Application note MLX10803
High voltage solutions.
4.3
LED lamp with dimming function
390111080311Rev.003
Author: RAH
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Application note MLX10803
High voltage solutions.
5 Disclaimer
Be aware that these circuit applications works directly with 220V or 110V supply. There are national and
international safety regulations for this type of electrical circuits. This document does not cover any safety issues for
electric circuit designs.
The circuit applications in this document have been thoroughly tested by Melexis when not otherwise mentioned;
and have worked satisfactorily in described applications. However, Melexis does not assume any legal
responsibility or will not be held legally liable in the use of these circuit applications, under any circumstances.
For the latest version of this document, go to our website at:
www.melexis.com
Or for additional information contact Melexis Direct:
Europe and Japan:
Phone: +32 13 61 16 31
E-mail: [email protected]
All other locations:
Phone: +1 603 223 2362
E-mail: [email protected]
QS9000, VDA6.1 and ISO14001 Certified
390111080311Rev.003
Author: RAH
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