Presentation on theme: "Power Design Engineer for Lighting"— Presentation transcript:
1 Power Design Engineer for Lighting Bringing light to lifeNajmi KamalPower Design Engineer for LightingMarch 2012
2 TI Solid State Lighting (SSL) Core Competencies ApplicationsGeneral IlluminationRetrofitCommercialProfessionalBack LightingPortableMonitorDigital TVAutomotiveExterior LightingFull System SolutionsPower ManagementMulti-StringSingle-StringMulti-StageSingle-StageMonitoringCommunicationHigh Performance SolutionExpertiseAC/DCAnalogDigitalDC/DCLinearWireless & PLCLight MeasurementResourcesEVMsCook BookRef. designsSample softwareApplication reportsLocal design servicesLighting training supportLighting Know-How
3 High Power Wide Area LM340x Market Segment FocusDownlighting LM3464,LM3466High Power Wide Area LM340xStreet LightsParking LightsExt. BuildingEnergy Savingintelligent LightsPublic BuildingsCommercialEnergy SavingLED Lamp LM3445,TPS92310Cost drivenHigh Light qualityCost drivenFast growthAutomotive LM342x, LM3409
4 TI Lighting System Solution NSC + TI = strong system level know-how
5 Lighting SummaryLighting Portfolio LED driver Architecture Dimming techniques LED driver MR16 LED bulb design Controller, Ref design High brightness LEDs driver Off line LED Bulb/T8 Ref design Multi Channel LED driver System solutions ( Triac, DALI, 0 to 10V) WEBENCH Architect
6 Texas Instrument’s Current LED Driver Solutions Quick Selection guide
7 DC/DC Buck Converters for LED Lighting 2A1.5A1A0.5A0.35A102030405060708090TPS92510 (RTM:10/2011)LM3406LM3406HVLM3414LM3414HVMAX LED CurrentLM3404LM3404HVLM3405ALM3402LM3402HVTPS92501 (RTM:12/2011)LM3407Input Voltage (V)
8 With current (high end system) How to drive LEDs?With current (high end system)Light output is proportional to forward currentBrightness AND color can change with currentWith power(low end system)Bulb
10 Duty Cycle Limits Max VO in Bucks High Side N-MOSFETs (internal or external FETs)Must turn off for ~200 ns each cycle to recharge CBOOTThe max number of LEDs is then:This section of a block diagram is from the LM3404, but it applies to the LM3402 and LM3406 as well.Do you have an idea why we didn’t use in the past P mosfet but N mosfte driver?The lower the switching frequency, fSW, the closer VO-MAX is to VIN
11 PFET Bucks Can Provide 100% Duty Cycle Gate is driven below source to turn the PFET ONGate can drive to VCC indefinitelyPFET can stay on indefinitelyTrue 100% duty cycle capabilityBuck is better than buck-boostBetter efficiencyLess partsFaster dimmingHigh Side P-MOSFETsThe LM3401 and LM3409/09HV are all PFET bucks
13 Various dimming techniques 4/14/2017Various dimming techniquesDimming using PWM signalWhite LEDs change Colour over Current!Solution:Maintain Current and Change ON-Time = PWM
14 Two different PWM dimming methods 4/14/2017Two different PWM dimming methodsFirst method: Dim 1: Continuous inductor current (Good EMC, extra Mosfet )Second method: Dim 2: more efficient (2khz dim max)
16 Buck (step-down) DCM or CCM Vo Limited by VINCout not neededContinuous output current, low EMIEasy to stabilize, if neededInherent protections against failureLIoΔI+LΔIVCF+-VINCO+DVo-Do we need an output cap for driving LEDs ?Since we need a current source and not voltage source.In CCM mode you can leave without cap but big inductor and EMI PBIn DCM mode small inductor and big cap.The best is in between.+RFBVFB-
17 BUCK - To Cap or Not to Cap No Output CapacitorNo output cap provides high output impedanceSaves a componentLeads to higher LED ripple currentMay generate more electromagnetic interference (EMI)With Output CapacitorAdding an output cap reduces ripple currentSmall cap + small inductor is smaller than one large inductorSlows pulse-width modulation (PWM) dimmingMust be rated to VIN in case of output open circuit
18 BUCK - To Cap or Not to Cap No Output CapWith Output CapNote inductor height as well4.5mm1.4mm
19 Three Pieces of the Puzzle Optical – Just as critical, must be integrated into the mechanical design of the lampThermal – Critical. Good designs integrate heat sinking into the design of the lampLED Driver – Critical.Must be good designs.(Efficient, small size,EMI/Safety proved)
21 LM3409/09HV: High-Side PFET Buck Controller VIN 6V to 42V (LM3409)VIN 6V to 75V (LM3409HV)External power PFET100% Duty Cycle CapableOutput Currents up to 4ADifferential, high-side current senseSimplifies system wiringPWM dimming and analog dimming at 1000:1Thermally enhanced eMSOP-10 packageNo control-loop compensationThe LM3409 and LM3409HV are buck PFET controllers that extend the input voltage range of the LM3401 and provide several new features at the same time. These controllers use a constant off-time control scheme which naturally combines the safety current limit with peak current control. Like the LM3401 the LM3409 is capable of a true 100% duty cycle, but it adds two important features.First, the current sensing is done on the high side. Within National, “high-side” current sensing means that the current sense resistor is placed before the anode of the first LED. The principal advantage of this is the simplification of the wiring. LED current returns through system ground, and this eases the design of systems with wiring harnesses, especially those where the LEDs are placed on a separate PCB or are physically distant from the drive electronics.The second addition to the LM3409 is the IADJ pin, which is designed for linear adjustment of the LED current. A 5 μA current source flows from IADJ, allowing the user to set the current sense voltage by placing a resistor from IADJ to ground. The user can also apply a control voltage to IADJ, which then directly sets the current sense voltage. Both methods allow the user to make the tradeoff between power dissipation in the current sense resistor and the accuracy of the LED current. Linear dimming also opens the door to simple temperature or ambient light feedback loops.
22 LM3401 Hysteretic PFET controller HB LED Driver Key FeaturesVIN Range: 4.5V – 35VOutput range: 0.2V (Vfb) to VIN, adjusts to deliver constant current to up to 9 HB LEDs in series with scalable LED current > 2ANo output cap, no compensation componentsLogic level dimming 1% to 100%, 70nS delayControlled start up allows PWM at Vin for dimmingPFET driver 100% duty cycle capableAdjustable Dual Side HysteresisAdjustable ripple currentFlexible inductor selectionFine tuning of switching frequency up to 1.5MHzMSOP-8 packageVIN can also be used for PWM dimming when a logic signal is not available. In this mode of operation DIM should be connected to VIN through a 10 kΩ resistor. There is typically 10 us of startup delay time when using VIN for dimming.Depending on the application, this de-lay limits the maximum dimming frequency to typically several hundred Hz.When 100% duty, Vo=Vin, I_LED is fixed to I_LED_MAX (L is a short).HYST control Vo goes between Vref – HYS and Vref + HYSRsns ADJUST THE OUTPUT CURRENTHyst adjust the hysterisysCS detect the max peak current and switch off the mosfetI lim adjust the peak currentApplications:Automotive Lighting, General Illumination, MR16 replacement, Industrial Lighting, Gaming, High-end LCD Backlighting
23 Hysteretic Control (LM3401) 4/14/2017Fast load Transient / no compensation requiredFsw changes with VIN and VOUTILED Ripple constant23
24 Ref design: LM3401 - 20 Cent-Sized PCB Runs from 6V to 35VDrives one white LED in at 800 mAHigh-side PFET topology can do 100% duty cycle
25 LM3402/4/6 and LM3402HV/4HV/6HV 0.5A/1.0A/1.5A HB LED Driver Key Features: COTVIN Range:LM340X: 6V – 42V, BuckLM340XHV: 6V – 75V, BuckTrue average current controlTwo PWM LED dimming options:Fast logic pin PWM dimmingLM3406: 2-wire dimming by VIN pin-70%Feedback Voltage = 200mVInternal NFET for reduced parts countSwitching Frequency up to 1MHzExposed pad eTSSOP-14 packageDrives 1W, 3W, and higher powered LEDsFast PWM Dim2-Wire DimLM COT: in CCM, fsw costant enough with the Vin - ton inv. Proportionally to Vin - 1WLM COT: in CCM, fsw costant enough with the Vin - ton inv. Proportionally to Vin WLM COT: in CCM, fsw costant enough with the Vin - ton inv. Proportionally to Vin -5WAdding an external input diode and using the internal VINS comparator allows the LM3406/06HV to sense and respondto dimming that is done by PWM of the input voltage.If the VINS pin voltage falls 70% below the VIN pin voltage, the LM3406/06HV disables the internal power FET and shuts off the current to the LED array. The support circuitry (driver, bandgap, VCC) remains active in order to minimize the time needed to the turn the LED back on when the VINS pin voltage rises and exceeds 70% of VIN. This minimizes the response time needed to turn the LeD array back on.he LM3402, 04 and 06 all feature internal power MOSFETs, giving them the advantage of reduced component count, smaller solution footprint, and built in safety features such as current limit and thermal shutdown. Because power LED currents have coalesced around several discrete points, each member of the LM340x family specifies a minimum current limit over the full temperature range that takes into account both the average current and gives headroom for a wide LED ripple current. These minimum current limit thresholds have been set to allow the ripple currents to be 30% or more peak to peak. All the members of the LM340x family operate over National´s industrial temperature range of minus 40 to plus 125 degrees celsius, which means that the lighting designer can count on getting the full drive current plus ripple even in harsh thermal conditions.This is a constant on time ARCHITECTURE ,which means that Ton TIME IS FIXED BY rON, ton time is inversly prportional to vin and vout.Comp pin make the systeme stable for high dimming. High transientApplications:Automotive Lighting, General Illumination, Industrial Lighting, Arcitectual
26 Fsw is constant with VIN COT Control (LM3402/4/6)4/14/2017Fast load Transient / no compensation requiredTon is inversely proportional to VINFsw is constant with VINILED Ripple is variableTON26
27 COT Control Revised: LM3406 4/14/2017The LM3406 has the switching frequency constant not only with respect to the input voltage but also to the output voltageInstead of having a fixed reference, this timer references VOUT so that frequency is truly fixed.27
28 LM3405A 1A LED Driver Key Features SOT23-6 eMSOP-8 VIN Range from 3V to 22VLow 205mV Feedback VoltageSelf-Adjusting Output to deliver Constant 1A CurrentPWM Dim PinLow Side Current Sense With External ResistorLow 30nA Shutdown CurrentInternal NFET for reduced parts count1.6 MHz Switching FrequencyTiny 6 Lead TSOT packageCurrent Mode Control with internal compensationSOT23-6Existing SOT-23 pkg (LM3405AXMK) can drive ~ 600mA for an MR16 applicationeMSOP8 version of the LM3405A can drive ~ 1A in an MR16 applicationeMSOP-8
29 LM3414/14HV Low Side Converter for High Power LED Drives 4/14/2017Support LED power up to 60W*: 18x 3W HBLEDsPatented True Average Current Control Provides ±3% Accuracy to Average LED CurrentRequires NO external current sensing resistorUp to 96% efficiency ,1 active componentHigh contrast ratio(Minimum dimming current pulse width <10 µS)Adjustable Constant LED current from 350mA to 1000mA±3% LED current accuracySupport PWM /analog dimming and thermal fold-backWide input voltage range:4.5V to 42V (LM3414)4.5V to 65V (LM3414HV)Constant Switching Frequencyadjustable from 250 kHz to 1000 kHzThermal shutdown protectionePSOP-8 or LLP-8 packageInternal mosfetThe mosfet is a N MOSF,we do not need a Boost cap.No Rseens resitor.Few external componentrs
30 TPS92550 (LML416504) LED Driver Module Wide Input Voltage Range : 4.5V - 65VCan drive up to 18 LEDs in series with 65V inputLED current accurately trimmed to +/-3%450mA LED current + fine tuning by external resistor (= analog dimming!)Integrated shielded inductor and power componentsEfficiency up to 95%Input Under-Voltage Lock-Out (UVLO)Stable with ceramic and low ESR capacitorsLow radiated and conducted emissionsLED open and short circuit protectionThermal ShutdownOnly 3 external passive components neededSimple PCB layout and high Power DensityRoHS CompliantActual LML Module
31 An Evolution of Simple 350mA LED Buck Driver Solution (TO-MOD-7 Module) 10.16mm8.64mm14.35mmLED+IADJGNDLED-DIM4th Gen LED Buck DC-DC Driver SMT Module+1Cs3rd Gen LED Buck DC-DC Driver (Higher Integration) IC+L+D+2Rs+2CsNational 3.0 Conference[insert presenter’s name(s)]
33 LED MR16 Replacement Solutions AC Transformer for MR16 Reference DesignsLED MR16 Replacement SolutionsIssue:Resistive load = PFDoesn’t switch off at 0v inputSmall form factormr16 HALOGENE are driven by two kind of transformer.electronic and 50hz transformerTo make an LED bulb working with 50 hz is easy bridge cap and driver , to make it run with ELECTRONIC TRANSFORMER is more complexe that why you will find in the market MR16 WORKING ONLY WITH 50HZ transformer and some with 50 hz and not all electronic transformer.If you go to shop and buY led MR16 you should know what you have in your selling.A good MR16 design has the following criteria:Cost effectiveFits into a standard MR16 enclosureNo electrolyticOperates well (no flicker) with most of the common electronic transformers (non-dimming)Good efficiency (system > 80%)Mitigation of high input current spikes to reduce failure of electronic transformer or MR16 diode bridge
34 Automotive Lighting, General Illumination, Industrial Lighting LM A HB LED DriverKey Features: floating buckVIN Range: 4.5V to 30VLess than ±10% load current variationAdjustable switching frequency from 150 kHz to 1 MHzInternal low side NFET for reduced parts countFeedback Voltage = 200mVFast PWM dimming enabledExposed pad eMSOP-8 packageDrives 1W LEDsOne of our solution for low current.Standard LED Driver with pulse width modulationNo loop compensationInternal mosfetFs:FHZISNS: I SENSE PINANODE OF LED TO PLUS VINApplications:Automotive Lighting, General Illumination, Industrial Lighting
36 LM MR-16 RetrofitRuns from low voltage: 11VAC to 20VAC or 14V to 30VDCMagnetic transformers onlyNominal 12VAC or 24VDC inputsDrive three white LEDs in series at 350 mA ±10%1 MHz switching frequency for minimum inductor sizeLow-side buck topology uses small, efficient N-MOSFETComplete solution including a diode bridge and holdup capacitor fits in standard MR-16 bulb housing
37 Halogen MR16 vs. SSL MR16 waveforms Issue #1 - The two scope captures above illustrate the SSL MR16 technical challenges. Figure one shows typical Halogen MR16 waveforms, and figure two is common MR16 replacement bulbs waveforms. The SSL replacement bulb looks capacitive to the ELVT; therefore large current spikes charge the energy storage device within the SSL MR16 bulb. The switching converter within the bulb then processes the input power from the energy storage element to the LED load. At this time the minimum load requirement of the ELVT is not satisfied, and the ELVT turns off. Once the energy is depleted within the MR16 converter, the ELVT will start up, and the process cycles. The turning off/on of the ELVT will manifest itself as visible flicker.Issue #2 – The maximum input current to the Halogen bulb is approximately 4.25A. The maximum input current to the SSL bulb is approximately 12A. The large magnitude spike associated with charging the SSL MR16 input capacitor can cause premature failures within the SSL bulb, or even the ELVT.
48 Why Not More Internal FET Boosts? Boost and Buck-boostThe buck is the only switching converter where average output current (LED current) is equal to average inductor current. In every other converter the average inductor current is different from LED current. Any time the circuit is boosting, be it the boost topology or one of the buck-boost topologies, the inductor current will be higher than the output current. How much higher depends upon the topology and upon both input and output voltage. Internal FET regulators are very limiting because their current limits are almost always fixed. Even within the very few internal FET boosts or buck-boosts that have adjustable current limits, power dissipation and self heating limit the true maximum current. To make matters worse, current limits detect peak current, not average current. This means that output current, input and output voltage, and also inductance must all be taken into account when designing a circuit.Exemple 10v out 1a outVin 5v 2A average on the coil.SEPIC and Flyback
49 LM3410 Boost and SEPIC LED Driver Key FeaturesInput voltage range of 2.75 to 5.5VOutput voltage range of 3 to 24VSwitch current up to 2.1A guaranteed over temperatureLow, 190mV feedback voltageOption of 520 or 1600 kHz switching frequencyPWM Dim pin160mΩ switch resistanceCurrent Mode control with internal compensationApplications:Portable Illumination/Flashlight, Personal Navigation Device, Portable Measurement Equipment, Automotive Control/Entertainment Console, Portable DVD PlayerLLP-6eMSOP-8SOT23-5
50 TPS61500 3A, Boost High Brightness LED Driver FeaturesBenefitsOperating Voltage Ranges:VIN: VVOUT: VIN to 38VSuitable for Use in Battery,12V, or 15V Systems3A Peak Switch CurrentCan be Used to Drive High Current LEDsAdjustable Switching Frequency: 200k-2.2MHz with up to 93% EfficiencyAllows Designed to be Optimized for Efficiency or SizeDimming: PWM or PWM-to-AnalogUse PWM for No LED Color Shift. Use Analog to Eliminate Audible Noise from Pulsed Currents.UVLO, Over-Voltage, Current Limit and Thermal ShutdownProtects Against Abnormal and Fault ConditionsApplicationsLED General IlluminationLED FlashlightsLED BacklightingTPS61500EVM-369TOOLS
51 TPS40211 4.5V to 52V Current Mode N-Ch Controller FeaturesBenefitsSupports Boost, Flyback and SEPIC TopologiesSuitable for a Wide Variety of LED Lighting Applications4.5 to 52V Input Voltage RangeCan Drive Up To 14 Series HB LEDsProgrammable Switching Frequency (35kHz to 1MHz)Flexible Filter DesignFrequency Synchronization (with External Components)Can Operate with an External Clock260mV Internal Voltage ReferenceReduces Power Dissipation in Sense ResistorIntegrated Low-Side DriverReduces Component CountProgrammable Over-Current Limit and Internal UVLOProtects Against Fault and Abnormal Operating ConditionsApplicationsHigh Current LED Drivers (Street Lighting, High Bay)LED Based MR-16 Light Bulb ReplacementLED BacklightingTPS40211EVM-352TOOLS
52 LM3429: Low Side N-MOSFET Controller for Constant Current LED Drivers High side current sense.A “low side” controller is a switching power regulator that uses an external power MOSFET whose source is connected to system ground. The LM3421, 3423 and 3429 are a family of low side N-MOSFET controllers designed specifically to drive LEDs with a constant current. While the boost regulator is the most common circuit built with low side controllers, they are also capable of SEPIC converters and transformer-based flyback converters.Like the LM3409 buck controller, the LM342X family feature integrated, differential, high-side current sensing. In addition to simplifying the system wiring, this differential current sense allows them to be used in two more topologies. These are the Vin-referenced buck and the Vin-referenced buck-boost. As the names imply, these are converter topologies that perform step-down and step up-and-down functions, respectively. The difference is that the output current flows back to the input voltage as opposed to ground. In the case of a current source driving LEDs, a load that connects between output voltage and input voltage is perfectly OK in many applications.
53 LM342x Controls the Floating Buck-Boost VO controlled with respect to VINAdjustable, precision threshold protection for LEDs that fail open-circuitLinear IF controlThe circuit shown in this slide is possible thanks to differential current sensing. Other names for this topology are “floating buck-boost”, “negative buck-boost” and “Vin referenced flyback”. Current flows from the input, through the inductor and through the external power FET while the FET is on. When the FET turns off, the current commutates through the Schottky diode, through the LEDs, and back to the input. At first glance it appears that this circuit should have a continuous input current, since the inductor is connected to Vin. This is not the case, however. Like the classic buck-boost and the flyback, this circuit has a discontinuous input current and a discontinuous output current. One principal advantage of this topology is the power efficiency. While not as good as the buck or boost, it is higher than the SEPIC or the flyback.The voltage designated “Vo” on this slide is equal to the input voltage plus the voltage across the LED string, so the user must be aware that the 75V limit for the IS, HSP and HSN pins is reached more easily. This can be alleviated by moving the current sense resistor to between Vin and the cathode of the last LED in the chain, and by using an external peak current sense resistor between ground and the source of the power FET Q1.
54 LM3423: Adds Fault Flag, Powergood Flag, and Input Disconnect FLT pin is for error signaling or for input disconnect via PFETTIMR sets the delay between when LED current is out of spec and when FLT flag goes logic HIGHDPOL selects the polarity of the nDIM pin when PWM dimmingLRDY is a powergood pin for signaling a system microprocessor
55 LM3429: Features VIN range: 4.5V to 75V: runs from 12V, 24V, 48V rails Adjustable current sense voltage: 50 mV to 1.24VAllows linear (analog) dimming without changing the current sense resistorUser can make tradeoff between average current accuracy and power dissipation in RSNSHigh-side current sense: LED current returns through system GNDInput for PWM (digital) dimmingPrecision output over-voltage protectionDisables the regulator if an LED fails open circuit or the LED array is disconnectedInput under-voltage lockoutSwitching frequency as high as 2 MHzThermally enhanced TSSOP-14 EP packageRuns at high frequency and drives N-FETs with large gate chargeA “low side” controller is a switching power regulator that uses an external power MOSFET whose source is connected to system ground. The LM3421, 3423 and 3429 are a family of low side N-MOSFET controllers designed specifically to drive LEDs with a constant current. While the boost regulator is the most common circuit built with low side controllers, they are also capable of SEPIC converters and transformer-based flyback converters.Like the LM3409 buck controller, the LM342X family feature integrated, differential, high-side current sensing. In addition to simplifying the system wiring, this differential current sense allows them to be used in two more topologies. These are the Vin-referenced buck and the Vin-referenced buck-boost. As the names imply, these are converter topologies that perform step-down and step up-and-down functions, respectively. The difference is that the output current flows back to the input voltage as opposed to ground. In the case of a current source driving LEDs, a load that connects between output voltage and input voltage is perfectly OK in many applications.
56 Ref design: LM3429 PAR-38 Spotlight DC Input Voltage 12V to 30VSEPIC circuit bucks or boosts as neededILED up to 1.5A6 White and one yellow LED for CCT adjustmentAll LEDs in seriesYellow LED has separate shunt NFET dimming250Hz PWM dimmingLM26675 supplies 5V for Nuventix SynJet active cooling1500 lumens at 50 lm/WThis is a tunable white with high CRI .(Excelent colour rending.)
58 Ref Design:LM3429 MR-16 retrofit with active cooling DC Input Voltage 9V to 36VBuck-boost circuit runs from 12VDC or 24VDC railsILED up to 1APowers 1 to 12 LEDs in seriesAccepts standard 0-10V linear dimming signals and adjusts LED current down to zeroLM2842 supplies 5V for Nuventix SynJet active coolingDimmable using buck boost topology
60 - Automotive Backlight LM Channel Constant Current LED Driver with Integrated Boost ControllerProduct Overview:The LM3492 is a 2-channel linear current controller combined with a boost switching controller ideal for driving LED backlight panels.Key Features:VIN Range: 4.5V to 65VDrive two individual PWM dimmable LED strings up to 65V total 15W (around 230mA)2 individually dimmable output channelNo Loop compensation required> 15000:1 contrast ratio for 200Hz dimming frequencyNear constant adjustable switching frequency up to 1 MHzLED driver Over-Power protection for short to supply scenarioDynamic Headroom ControlPrecision Enable pinVersatile COMM I/O pin for FAULT reporting (LED rail Power- Good, Short-FAULT, Open-FAULT and Over-Temperature Alert) and Digital Tune for switching frequencyIndividual LED string voltage diagnosis modeeTSSOP-28 packageApplications:- Automotive Backlight- 6.5”-10” LCD display backlight applications up to 36 LEDs which requires ultra-high contrast ratio
61 LM3433 HB LED Driver LM3434 Common Anode Capable real High Brightness LED drivers
62 LM3433 Common Anode Capable HB LED Driver Key Features:COTOperating Input voltage Range: -9V to -14V w.r.t. LED AnodeControl inputs are referenced to the LED anodeOutput current > 6AGreater than 30 kHz PWM Dimming frequencyNo output capacitor requiredProgrammable up to 1 MHz switching frequencyLow IQ, 1 mA typicalSoft start“Intelligent” constant ON time allows for constant ripple currentLLP-24 packageOutput configuration allows the anode of the LED to be tied directly to the ground reference chassis for maximum heat sink efficiencyApplications:LCD Backlighting, Projection Systems, Solid State Lighting, Automotive Lighting
63 Synchronous Buck HB LED Driver with Common Anode Capability Negative Buck Approachoffers Negative output voltage capabilityallows common anode LED modulesLED mounted directly to chassis for Maximum heat sink efficiency!!Directly mounted onprojector chassisHere shows the application circuits of LM3433 Buck LED driver, which is designed for driving common anode LED modules in projector application.If you compared the conventional Buck LED driver shown in previous slides p.9, there are two main differences of LM3433 from conventional Buck LED driver.First, the LM3433 application circuits, as shown in here, configures as negative buck approach. This offers Negative output voltage capability which allows common anode LED modules to be tied directly to chassis without any insulation layer for maximizing heat sink efficacy!!As you can see in this block diagram, the reference ground of LED driver is at the same electrical potential as the LED anode. Therefore, this point can be connected to the chassis (earth) without any safety issue.
64 LED Offline productsRetrofit E27T8 tube non retrofitHigh power bay (multi string)