The LED driver chip is actually a PWM control chip. After the component circuit works normally, the voltage obtained by detecting the current of the LED on the current detecting resistor is fed back to the chip, and the internal PWM duty cycle is controlled to adapt to the change of the LED characteristic. The current and voltage fluctuations caused by the LED keep the current obtained by the LED constant.
Led drive principle and function
An LED driver is a power conditioning electronics that drives LED illumination or LED module components to function properly. Due to the on-characteristics of the LED PN junction, the range of voltage and current variations that can be accommodated is very narrow. A slight deviation may not illuminate the LED or cause a significant decrease in luminous efficiency, or shorten the service life or even burn the chip. Current commercial power supplies and common battery power supplies are not suitable for direct supply to LEDs. LED drivers are electronic components that drive LEDs to operate at optimum voltage or current.
1. Since the LED is a characteristic sensitive semiconductor device and has a negative temperature characteristic, the LED driving power supply (also called a driver) is a stable working state protection during the application process.
2, LED devices on the drive power requirements are almost harsh, LED is not like ordinary incandescent bulbs, can be directly connected to 220V AC mains. LEDs are low-voltage drivers, and complex conversion circuits must be designed. LED lamps for different purposes must be equipped with different power adapters. Designing a good power supply must consider the factors of efficiency conversion, effective power, constant current accuracy, power supply life, and electromagnetic compatibility, because the power supply plays a role in the entire luminaire as important as a human heart.
LED driver price
Depending on the power level, it is generally between 10 and 100 yuan. Of course, the current cost has been continuously decreasing.
Analysis of several common classic LED driver chips
For IC design companies to understand what kind of ICs the market needs, what price should be suitable. Prices can only be changed at any time. Quality and price are the factors that determine whether or not to use, and it is important to meet the product design quality parameters! The price is more important!
Now more and more IC design manufacturers have joined the LED design team, designed a number of models, here from the performance price ratio in detail, how to choose their own suitable IC, which IC is most suitable for their own products.
1. LED driver IC-AMC7150 with mixed market
At that time, AMC7150 was still good. I thought about it or not. It has a very important factor, that is, the price. There is a market price of less than 2 yuan, which is the reason why you use it. The AMC7150 currently has dozens of IC models that can be directly replaced, and the price war will be unavoidable.
It can be selected in low-voltage 4-25V products with low design parameters, and the basic drive capability is designed below 3W. For example, 1W string 3 or 3W 1 LED design is stable.
2, Hangzhou Silan Microelectronics - SB42511
At present, Silan Semiconductor has introduced a new IC, which is mainly aimed at driving a battery with 24V to drive 6 LEDs. The price is higher than the AMC7153 discount in the European and American market IC, suitable for designing 1-6 LEDs, input 6-25V input voltage, SOP8 package form, mainly for the current low-end spotlight market.
3, the United States CATALYST company - CAT4201
This IC drives 1-7 1W LEDs. Efficiency up to 92%, 6-28V voltage input range buck drive application design. The biggest advantage of the previous two ICs is the size of the package SOT23, the introduction of the line, in line with the current design requirements for most small-sized lamp cups.
Large resistance range current regulation, can adjust the brightness of the potentiometer wide resistance range, such as the design of table lamps and other products need this.
4, Europe Zetex company - ZXLD1350
This IC is currently responding well in the market. It is also a SOT23 small-volume package. It has a 7-7V voltage step-down constant current drive 1-7psc LED, and the circuit is simple and practical. When designing, Rs should be close to the IC to avoid the power supply voltage being largely unmoved, which will affect the constant current effect.
The overall electronic material cost is slightly higher than the previous IC.
5. National Semiconductor LM3402
LM3402 market reflects good, the input voltage range covers the entire automotive application, built-in MOS tube can be up to 15 LEDs, 1-3 LEDs are a bit expensive, more than 5 when the price is very good. At present, the customer engineers who come into contact with it are highly rated, and the acceptance field is relatively simple and practical. It is the middle of many LED driver ICs in the country.
6, National Semiconductor LM3404
The LM3404 and LM3402 have the same line, the difference is that the current can reach 1A, and the 1-15pcs LED is cost-effective.
The IC specifications listed above are built-in MOS tubes. The built-in MOS tube simplifies the circuit design, reduces the size, reduces the overall design cost, and reduces the failure rate. An LED driver IC that is larger than 1A or more due to its current IC process fabrication, cost, etc. requires an external MOS transistor. In our daily product design, we often encounter high current design, such as 5W, 10W and other higher power design requirements, which can only choose the external MOS tube IC. Next, we will recommend several ICs for comprehensive cost, which is convenient for the selection of engineers.
7, the United States US letter integrated products company MAX16819/MAX16820
The MAX16819/MAX16820 operate from a 4.5V to 28V input voltage range and have a 5V/10mA on-chip voltage regulator. The output current is regulated by a high-side current sense resistor, and a dedicated PWM input (DIM) enables a wide range of pulsed brightness adjustments.
The MAX16819/MAX16820 are ideal for applications that require a wide input voltage range. High-side current sensing and built-in current setting circuitry minimizes the number of external components and provides ±5% accuracy of LED current. The hysteresis control algorithm guarantees excellent input supply rejection and fast response during load switching and PWM dimming. The MAX16819 has an inductor ripple current of 30%, while the MAX16820 has a ripple current of 10%. These devices operate at switching frequencies up to 2MHz, allowing the use of small components.
The MAX16819/MAX16820 operate over the -40°C to +125°C automotive temperature range and are available in a 3mm x 3mm x 0. 8mm, 6-pin TDFN package.
Personal recommendation 200-500Hz PWM gray frequency adjustment, 1-6pcs LED serial connection maximum 25W product design, recommended about price of about 0. 5 US dollars.
8, National Semiconductor LM3401
The LM3401 is an external MOS high-power LED driver introduced by the National Semiconductor. It can design a driving current of less than 3A. The input voltage is up to 35V, and more than 10 LEDs can be connected in series.
9, the United States US letter integrated products company MAX16802
The MAX16802A/B is a high-brightness (HB) LED driver control IC that contains all the circuitry needed to design a wide input range LED driver for general lighting and display applications. Suitable for low input voltage (10. 8V DC to 24V DC) LED drivers. When it is necessary to fine-tune the LED current, an on-chip error amplifier and a reference with an accuracy of 1% can be used. A wide range of brightness adjustments can be achieved with low frequency PWM brightness adjustment.
The MAX16802 features an input undervoltage lockout (UVLO) feature that sets the input startup voltage and ensures proper operation when the power supply is dropped. The MAX16802 has an internal bootstrap undervoltage lockout circuit with a high hysteresis voltage.
This simplifies the design of off-line LED drivers. The MAX16802 does not have this bootstrap circuit internally and can be biased directly from +12V. The internally trimmed 262kHz fixed switching frequency allows optimized selection of magnetic and filter components for a compact, cost-effective LED driver.
The MAX16802A has a maximum duty cycle of 50% and the MAX16802B has a maximum duty cycle of 75%. These devices are available in an 8-pin μMAX® package and are fully specified over the -40°C to +85°C temperature range.
Personally recommend 200-500Hz PWM gray frequency adjustment, 1-6pcs LED serial connection maximum 50W product design, about 1. 4 US dollars.
10, the United States US letter integrated products company MAX16818
The MAX16818 Pulse Width Modulation (PWM) LED driver controller is available in a compact package that provides large output current with minimal external components. The MAX16818 is ideal for both synchronous and non-synchronous buck topologies, as well as boost, buck-boost, SEPIC, and buck LED driver architectures. Fast LED transient currents up to 20A/μs and brightness adjustment frequencies of 30kHz can be achieved.
The device uses average current mode control to optimize the use of MOSFETs with optimum charge and on-resistance characteristics, minimizing the need for external heat sinks even at output LED currents up to 30A. True differential detection technology precisely controls the LED current. A wide range of brightness adjustments can be easily achieved with an external PWM signal. An internal voltage regulator with a simple external biasing device allows the device to operate over a wide 4.75V to 5.5V or 7V to 28V input voltage range. The wide switching frequency range, up to 1.5MHz, allows the use of small inductors and capacitors.
The MAX16818 has a delayed 180° phase clock output that can be used to control another out-of-phase LED driver to reduce input and output filter capacitor size and reduce ripple current. The MAX16818 also offers programmable hiccup overcurrent, overvoltage, and thermal protection. The MAX16818ETE+ is rated for operation over the extended temperature range (-40°C to +85°C), while the MAX16818ATE+ operates over the automotive temperature range (-40°C to +125°C). The LED driver controller is available in a lead-free, 0.8mm thick, 5mm x 5mm 28-pin TQFN package with exposed pad.
High-current LED driver controller IC with output current up to 30A, it is recommended to design 50-300W ultra-high power portable LED projector, LCD TV and display backlight, front panel projector / rear projection TV, car, bus / truck exterior light, car emergency Lighting and symbol lights, and more.
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