How to choose an LED driver. RGB LED driver chips Driver for RGB strip

RGB LED strips are convenient to use for decorative lighting of shop windows, car interiors, signs... They are easy to work with, unlike simple LEDs, because... The current limiters are already in place, you just need to supply the required voltage. The ability to cut into segments provides flexible installation options.

But what if you want more? what if you need to control each diode individually? You can install an MK, but not every microcontroller alone can handle many three-color diodes, you can try installing one for each one. For such purposes, there are special LED drivers, some of which are equipped with the ability to be controlled by one common, or sequentially passing through the drivers, bus. Somewhere they went further, and such a driver was built directly into an RGB LED, which requires a minimum of external wiring. Next, such diodes connected in series were placed on an LED strip - and in the end we got an addressable LED strip.

As you might guess, this article will focus on LED RGB driver e – WS2811, which are connected in series and controlled via a single-wire data line. And an addressable LED strip based on combined RGB diodes with such drivers.

As you can see in the photo, this LED strip consists of many RGB LEDs connected in series with built-in WS2811 drivers (small black dot in the middle). From the wiring, such a microcircuit, when powered by 5V, requires only one 0.1 µF capacitor at the power input; a 33 Ohm resistor on the data line is also recommended, which, apparently, the manufacturer missed.

All diodes sit in series on the same line. To change their displayed color and its intensity, you need to send the first diode a message containing an appeal to each of the diodes on the tape. The first driver receives the entire package and transmits it further, minus the last package, which he writes off to his account. The same thing happens with all the remaining LED-driver assemblies. The sending ends with a special RES command, which is highlighted by a long low signal level; upon receiving it, all diodes will apply their new states.

Each packet consists of 24 bits - 8 bits for each channel, resulting in 255 gradations of each color or 16 million colors. Each bit contains a positive and negative half-cycle; a zero or a one is encoded by the duration of the half-cycles.

To work with an addressable LED strip, a controller was assembled based on the PIC16F688 microcontroller and on a specially previously prepared universal board blank (), so I will not give the signet.

This LED strip is very power hungry; a meter with 60 LEDs consumes more than 2 amperes at maximum, so you need a good and powerful power source. You can give it a lower current, but then it will burn with a predominance of red shades.

The firmware was written in haste. The following operating algorithm was implemented: first, the entire package is downloaded from the computer to the microcontroller and only after that it displays it. Due to the small amount of RAM in the weak microcontroller, it was possible to implement a buffer for only 60 addressable LEDs with WS2811 drivers. Due to the average UART speed of 38400, the update speed of the entire tape is approximately 50 ms, i.e. The maximum allowable refresh rate was 20 frames/second. Which was enough for me to demonstrate the capabilities of the tape. Generates all effects special program on a PC, which was also written in haste.

Format of commands sent to the controller:
Sending is carried out via UART at a speed of 38400 8N1.

• The first byte is a space (32 ASCII int code)
• The second byte is the length of the transmitted package (number of LEDs), from 0 to 60 (transmitted by byte)
• Next, 3 bytes, in GRB order (green, red, blue), transmit PWM values ​​for each LED, starting from the opposite end of the strip.

The controller responds to the start of exchange via UART ASCII character ! , upon successful completion of sending the packet with an ASCII character b .

Based on similar LED strips You can implement small video screens and various installations.

Update dated September 1, 2015

For the convenience of checking the design, I am adding to the article firmware with autonomous smooth sequential pseudo-random transfusion (up to 60 LEDs). If this effect alone is enough, then you can simplify the circuit by removing cp2102 from it.

In small-sized equipment, including MP3 players and cell phones, three-color RGB LEDs are increasingly used, and so-called RGB clusters are used in various lighting equipment and decorative lamps. For optimal control of brightness and color, such devices use specialized drivers, many of which are controlled by an external controller. Some of them will be discussed in this article. The author examines a number of driver chips from ON Semiconductor, STMicroelectronics and National Semiconductor.

RGB LED driver with current stabilization CAT4109 (ON Semiconductor)

The CAT4109 chip is a driver for controlling three serial (R, G and B) LED chains with current stabilization, separate installation and PWM brightness control of these LED chains. The CAT4109 is manufactured in a miniaturized 11116-pin SOIC-16 package for surface mount. The assignment of the microcircuit pins is given in Table 1, the connection diagram is shown in Fig. 1, and the functional diagram is in Fig. 2.

Rice. 1. Connection diagram of the CAT4109 chip

Rice. 2. Functional diagram CAT4109 chips

Table 1. Pin assignments of the CAT4109 chip

A special feature of the CAT4109 microcircuit connection circuit is the absence of a choke and a minimum of wiring parts. The CAT4109 supply voltage is in the range of 3...5.5 V, and the supply voltage of the LED strings is 5...25 V.

Each of the three LED control channels consists of an adjustable current source and a maximum current setting circuit (see Figure 2). Common to all channels is a reference voltage source (VS) of 1.2 V.

The power supply voltage VIN determines the maximum number of LEDs in each string. The maximum current of each of the serial LED chains can reach 175 mA. The LED current creates a small voltage drop (0.4 V) on the open output switches of the microcircuit. The maximum current values ​​of the LED chains are set by external resistors R1, R2 and R3 (pins RSET1-RSET3 of the microcircuit). Table 2 shows the dependence of these values ​​on the resistances of the corresponding installation resistors R1-R3.

Table 2. Dependence of LED chain currents on the resistance of the corresponding installation resistor

External control of the CAT4109 microcircuit is carried out by the controller through inputs OE (pin 15), PWM1 (pin 5), PWM2 (4) and PWM3 (pin 3). Permission to turn on the LEDs is carried out by a high voltage level (≥1.2 V) at the OE input (15). Timing diagrams for the operation of the CAT4109 chip are shown in Fig. 3.

Rice. 3. Timing diagrams of the CAT4109 chip

The transition time of the microcircuit from the shutdown mode (Shutdown) to the on state (T PS) is 1.4 μs. The LEDs are turned off at the OE enable input by a low level (≤0.4 V) at this input with a delay T P2 =0.6 μs, and turned on again by a high level with a delay T P1 =0.3 μs. To transfer the IC to Shutdown mode, you must support the pin. 15 (OE) low potential for 4...8 µs (T PWRDWN). In this mode, the current consumption does not exceed 1 μA.

Inputs PWM1 (pin 5), PWM2 (pin 4) and PWM3 (pin 3) are used to separately adjust the brightness of LED chains using the PWM method at a high voltage level at the OE input (pin 15). To group adjust the brightness of all LEDs, you can apply a signal from the PWM controller to the OE input. In order not to be violated color balance, the frequency of this PWM signal must be an order of magnitude lower than the frequency of the PWM signal at the inputs PWM1-PWM3.

The CAT4109 chip has temperature protection with a response threshold of 150°C and a hysteresis of 20°C, as well as undervoltage protection with a response threshold of 1.8 V.

RGB LED driver with current stabilization CAT4103 (ON Semiconductor)

The CAT4103 chip is also designed to control three sequential RGB chains of current-stabilized LEDs, with separate installation and PWM brightness control. It is available in SOIC-16 package. The main feature of this chip is the ability to separately control each individual LED chain using a serial interface. Another feature of the CAT4103 is the ability to cascade multiple chips, which increases the number of controlled LEDs from one controller via a 4-wire interface. The assignment of the pins of this microcircuit is given in Table 3, the functional diagram is shown in Fig. 4, and the connection diagram is in Fig. 5.

The LED control channels of the CAT4103 chip are similar to the corresponding channels of the CAT4109, but the CAT4103 chip has one important feature, the essence of which is that PWM signals for controlling the brightness of the LEDs are generated in the chip itself from signals from the controller. To do this, a three-bit RAM is introduced into the microcircuit (see Fig. 4), which consists of three latched flip-flops (a 3-bit latch register) and a 3-bit shift register. The shift register itself converts the serial code of the input data signal into a parallel one, which is stored in the latch register.

Rice. 4. Functional diagram of the CAT4103 chip

Rice. 5. Connection diagram of the CAT4103 chip

Table 3. Pin assignments of the CAT4103 chip

In order to control the next chip when cascaded, four buffer amplifiers and a delay trigger (D-flip-flop) are used.

Let us give a description of the CAT4103 MS pins, through which the control controller and the next microcircuit are connected to it when connected in cascade.

Pin 4 (SIN) - serial data input.

Pin 5 (CIN) - clock input with a frequency of up to 25 MHz. This dynamic input is triggered by the edge of the clock pulse (transition from logic "0" to logic "1"). In this case, the logic level from the SIN input is written to the shift register.

Pin 3 (LIN) - input of the data storage command. When the signal transitions from log. "0" to log. “1” at this input records the states of the shift register flip-flops into the “latch” register, where they are stored until the positive edge of the next pulse arrives at the LIN input.

Pins 13 (SOUT), 12 (COUT) and 14 (LOUT) are the outputs of the corresponding interface signals to the next CAT4103 chip when connected in cascade. In this case, the signal at the SOUT output is changed (clocked) by cutting off the clock pulse (signal transition from logic “1” to logic “0”).

Pin 2 (BIN) - the input is used to extinguish all LEDs, but does not affect the contents of the latch register. The LEDs are extinguished at a high level (log "1") at the BIN input.

Pin 15 (BOUT) - output of the blanking signal to the next CAT4103 chip when connected in cascade.

The dependences of the currents of the LED chains on the resistances of the resistors installed in the CAT4103 microcircuit are similar to the corresponding dependences discussed above for the CAT4109 IC. In addition, the CAT4103 chip has the same protections as the CAT4109.

24-channel RGB driver STP24DP05 (STMicroelectronics)

The STP24DP05 is one of the Power Logic (STP) driver ICs, designed specifically for driving discrete RGB LED color information displays.

The basis of the STP24DP05 MS, as well as all drivers of this family, is a shift register and a latch register, just like the CAT4109 chip discussed above. The STP24DP05 chip has three shift registers and three latch registers, one for each LED color (R, G and B).

In total, the STP24DP05 contains 24 LED control channels, which are divided into three interface ports (R, G, B) of 8 channels each. That is, the STP24DP05 chip is three conventional 8-channel monochrome drivers built into a small-sized TQFP48 package measuring 7x7 mm and supplemented with circuits for diagnosing open loads and shorting outputs with the case and power. Alarms about the detection of accidents are sent to the control controller in the form of special error codes via serial interface.

One STP24DP05 chip controls eight RGB LED triads or groups of triads of a color LED screen. The supply voltage of the microcircuit is within 3...5.5 V, and the supply voltage of the LED chains can be selected up to 20 V, depending on the number of LEDs in the chains. Output current (current of each LED chain) 5...80 mA.

The functional diagram of the STP24DP05 chip is shown in Fig. 6, cascade circuit for connecting N microcircuits of this type - in Fig. 7, and the assignment of the pins is given in Table 4.

Rice. 6. Functional diagram of the STP24DP05 chip

Rice. 7. Cascade circuit for connecting STP24DP05 microcircuits

Table 4. Pin assignments of the STP24DP05 chip

As noted above, the basis of the STP24DP05 chip for driving 8-channel RGB interfaces is an 8x3 RGB data shift register (8 bits of 3 bits), which converts the serial code of the SDI input signal into three 8-bit parallel codes. These codes are stored in a 24-bit (8x3) RGB data latch register. Each of the output stages of the microcircuit (24 in total - eight for each color) is a current stabilizer (source). In addition, for each color there is a resolution circuit and a detector for breaks and short circuits of the output lines. Common to all channels are control logic, temperature protection and undervoltage protection circuits. Buffer stages are installed at pins 2, 3, 4, 32, 33 and 34.

Let's look at some features of the STP24DP05 chip. The clock frequency of this chip can reach 25 MHz. The LED current is programmed separately for each color using three external resistors that are connected to the pin. 26, 27 and 28.

The dependence of the LED currents, as well as the response threshold of the detector for broken output lines (LED lines) on the resistance of the corresponding installation resistor is given in Table 5.

Table 5. Dependence of LED currents and the response threshold of the output line break detector on the resistance of the corresponding installation resistor

When LEDM is at the input (pin 3) high level The latch register captures the data that passes through the shift register. When this input is low, the latch register holds (stores) them.

A low level at the inputs OE-RDM (pin 34), OE-G (pin 33) and OE-B (pin 32) allows the passage of data from the latch register to the output stages of the microcircuit, and a high level locks the output stages.

As is known, the greatest current consumption from the power source in any switching circuit occurs during transient processes at the moment of switching. To facilitate the current and thermal conditions of the microcircuit when all LEDs are turned on simultaneously, as well as to reduce the level of ripple, a channel-by-channel delay (Gradual delay) is provided for turning on the LEDs, which is not noticeable to the eye. It is carried out by applying a log level to the DG input (pin 9). "0". The delay time for turning on the output stages is given in Table 6.

Table 6. LED switching delay based on log differences. 0 - log. 1 at the enable inputs depending on the logical level at the Gradual delay input

The data signal of the STP24DP05 chip (input and output on pins 2 and 35) contains a stream of RGB signals alternating with clock frequency, the sequence of which is set by the logical levels at the inputs DF0 and DF1 (see table 7).

Table 7. Setting the sequence of R, G and B signals in the input and output signal code

Switching from the operating mode to the error detection mode is carried out by applying a low potential to the DM input (pin 5) or more than 1 μs to the OE-RDM input (pin 34). After which, within 24 clock cycles, an error code is sent to the output data bus.

The interface of the STP24DP05 chip has two flags: TF (pin 29) - overtemperature flag and EF (pin 8) - error flag. Both of these outputs are open drain, so a 10k ohm pull-up resistor is connected between each of these outputs and the power supply. When an emergency occurs, the internal key of the microcircuit closes the corresponding pin (29 or 8) to ground. The level obtained in this way is log. "0" signals the external controller about a failure. If, instead of pull-up resistors, LEDs are connected to the outputs (via limiting resistors), then a visual indication of an emergency situation is realized.

LP55281 I2C Quad RGB LED Driver (National Semiconductor)

The LP55281 chip is a specialized RGB backlight driver for small-sized liquid crystal displays. It provides separate adjustment of the brightness and color tone for each of the four RGB LEDs from an external controller via a standard I 2 C or SPI serial interface. The main applications of the LP55281 chip are cell phones, communicators and MP3 players.

The LP55281 contains four PWM channels for controlling the brightness and color of RGB LEDs, an audio synchronization channel for the background LED, as well as a built-in boost converter, I 2 C and SPI interfaces. In addition, the LP55281 provides LED open circuit testing via the serial interface. The main parameters of the microcircuit are given in Table 8.

T Table 8. Main parameters of the LP55281 chip

The microcircuit is manufactured in miniature MicroSMD packages measuring 3x3x0.6 mm and Micro SMDxt (3x3x0.65 mm) with 36 ball pins with a pitch of 0.5 mm. The pinout location of the LP55281 chip is shown in Fig. 8, and the assignment of the pins is summarized in Table 9.

Rice. 8. Pinout of the LP55281 chip

Table 9. Pin assignments of the LP55281 chip

The functional diagram and connection diagram of the LP55281 microcircuit is shown in Fig. 9.

Rice. 9. Functional diagram and connection diagram of the LP55281 chip

The microcircuit contains a boost converter with a built-in output switch based on a MOSFET transistor, which can operate at a conversion frequency of up to 2 MHz. The external LBOOST inductor for this conversion frequency should have an inductance of 4.7 µH, and for a conversion frequency of 1 MHz - twice as much (approximately 10 µH). An external diode D1 with a low forward voltage drop should be used as a pulse rectifier (Schottky diodes with a peak current of at least 1 A are suitable). The output voltage of the converter is set by default to 5 V, but it can be programmatically changed via the control bus from 4 to 5.3 V in steps of 0.15 V.

The microcircuit, and therefore the LEDs, are controlled by an external controller. It is not at all necessary that this control be carried out along all seven conductors, as shown in Fig. 9. For example, the IF_SEL interface selection input (pin 2B) can be connected directly to ground or to the plus of the power supply. In the first case, the I 2 C bus interface is turned on, and in the second - SPI. In any embodiment, the LP55281 chip is used as a slave device. As you know, the I 2 C bus interface is two-wire (clock line SCL and data line SDA), and the SPI bus interface is four-wire (SS - slave chip selection input, SCK - clock input, SI - data input and SO - data output).

When using the I 2 C bus in the device, the SO output (pin 4B) will remain unconnected.

In this case, the SI/A0 input (pin 4C) can be connected to ground, thereby selecting the chip address 4Ch, or it can be connected to the plus of the power supply, which ensures the choice of address 4Dh.

Output stages, which are PWM-controlled current stabilizers (sources or generators), to the outputs of which, in addition to LEDs, a multiplexer is connected. When the output stages are locked, it provides alternate, periodic switching of signal levels from the outputs of the microcircuit to the ADC input.

At normal operation these levels are high, and if one of the LEDs breaks or the output stage breaks down, the voltage at the output of the multiplexer will drop, which will indicate a malfunction. The voltage from the multiplexer output is digitized into the ADC and sent to an external controller via the control bus (I 2 C or SPI).

The LP55281 chip has a built-in channel called the audio sync channel. It is used in cell phones, MP3 players, etc. as a “color music” channel, providing LEDs blinking in time with the ringtone or melody being played. This channel has two inputs (2D and 4D pins), which are fed with signals or a stereo signal with a swing of up to 1.6 V. They are mixed, and then the total signal is digitized, passed through an AGC circuit and a digital peak detector. After this, the digital signal is converted back to analog. Received analog signal controls the output stage (current source), and therefore the brightness of the background LED.

Literature and Internet sources

1. www.MonolithicPower.com - website of Monolithic Power Systems.

2. STMicroelectronics. STP24DP05. 24-bit constant current LED sink driver with output error detection. First release. 2008.

3. www.st.com - website of STMicroelectronics.

4. National Semiconductor. LP55281. Quad RGB Driver. General Description. June 2007.

5. www.national.com - website of the National Semiconductor Corporation.

However, I used more powerful components and a different chip.

The datasheet can be downloaded. The LED current is set through a current-sensing control resistor. The output current I is equal to 0.1/Rs. I needed about 300 mA of current for each channel, so I chose a 0.33 ohm resistor. For a current of 350 mA, select a 0.27 ohm resistor.

Each channel is controlled using a PWM signal, for example from an Arduino microcontroller (you will need to solder male/female headers to the board).

You can use input voltage up to 30V and drive 3W/10W/20W LEDs.

Required components:

• Tantalum capacitorsC1, C2, C3 : capacitance 22uF
• D1, D2, D3 ; Schottky diode 2A in SMA package
• L1, L2, L3 : Powerful chokes 68 µH, 0.7A
• R1, R2, R3 : Resistors with a nominal value of 0.33 Ohm, housing 0805.
• 4 x screw clamp, 3.5 mm(available from Tayda Electronics)
• 3x PT4115 drivers.
• 1x 4-pin + 1x 2-pin male connector "dad" or "mom".

The photo above shows the fully assembled driver.

List of radioelements

The most optimal way to connect to 220V, 12V is to use a current stabilizer or LED driver. In the language of the intended enemy it is written “led driver”. By adding the desired power to this request, you can easily find a suitable product on Aliexpress or Ebay.

• 1. Features of Chinese
• 2. Service life
• 3. LED driver 220V
• 4. RGB driver 220V
• 5. Module for assembly
• 6. Driver for LED lamps
• 7. Power supply for LED strip
• 8. DIY LED driver
• 9. Low voltage
• 10. Brightness adjustment

Features of Chinese

Many people like to buy from the largest Chinese bazaar, Aliexpress. The prices and assortment are pleasing. LED driver is most often chosen due to its low cost and good characteristics.

But with the rise in the dollar exchange rate, it became unprofitable to buy from the Chinese, the cost became equal to the Russian one, and there was no guarantee or possibility of exchange. For cheap electronics, the characteristics are always overestimated. For example, if the power specified is 50 watts, at best this is the maximum short-term power, not constant. The nominal will be 35W - 40W.

In addition, they save a lot on the filling to reduce the price. In some places there are not enough elements that provide stable work. The cheapest components are used, with a short service life and low quality, so the defect rate is relatively high. As a rule, components operate at the limit of their parameters, without any reserve.

If the manufacturer is not listed, then he does not have to be responsible for the quality and no review will be written about his product. And the same product is produced by several factories in different configurations. For good products, the brand must be indicated, which means that he is not afraid to be responsible for the quality of his products.

One of the best is the MeanWell brand, which values ​​the quality of its products and does not produce junk.

Life time

Like anyone electronic device The LED driver has a service life that depends on operating conditions. Branded modern LEDs already work up to 50-100 thousand hours, so the power fails earlier.

Classification:

1. consumer goods up to 20,000 hours;
2. average quality up to 50,000 hours;
3. up to 70,000h. power supply using high-quality Japanese components.

This indicator is important when calculating long-term payback. There is enough consumer goods for household use. Although the miser pays twice, and this works great in LED spotlights and lamps.

LED driver 220V

Modern LED drivers are designed using a PWM controller, which can stabilize the current very well.

Main parameters:

1. rated power;
2. operating current;
3. number of connected LEDs;
4. degree of protection against moisture and dust
5. Power factor;
6. Stabilizer efficiency.

Housings for outdoor use are made of metal or impact-resistant plastic. When the case is made of aluminum, it can act as a cooling system for electronic components. This is especially true when filling the body with compound.

The markings often indicate how many LEDs can be connected and what power. This value can be not only fixed, but also in the form of a range. For example, 4 to 7 pieces of 1W are possible. It depends on the design electrical diagram LED driver.

RGB driver 220V

Three-color RGB LEDs differ from single-color LEDs in that they contain crystals of different colors (red, blue, and green) in one housing. To control them, each color must be lit separately. For diode strips, an RGB controller and power supply are used for this.

If a power of 50W is indicated for an RGB LED, then this is the total for all 3 colors. To find out the approximate load on each channel, divide 50W by 3, we get about 17W.

In addition to powerful led drivers, there are also 1W, 3W, 5W, 10W.

Remotes remote control(DU) there are 2 types. With infrared control, like a TV. With radio control, the remote control does not need to be pointed at the signal receiver.

Assembly module

If you are interested in an LED driver for assembling an LED spotlight or lamp with your own hands, then you can use an LED driver without a housing.

Before making a 50W led driver with your own hands, it’s worth searching a little, for example, every diode lamp contains it. If you have a faulty light bulb whose diodes are faulty, then you can use the driver from it.

Low voltage

We will analyze in detail the types of low-voltage ice drivers operating from voltages up to 40 volts. Our Chinese brothers-in-mind offer many options. Voltage stabilizers and current stabilizers are produced on the basis of PWM controllers. The main difference is that the module with the ability to stabilize the current has 2-3 blue regulators on the board, in the form of variable resistors.

As technical characteristics of the entire module indicate the PWM parameters of the microcircuit on which it is assembled. For example, the outdated but popular LM2596 according to its specifications holds up to 3 Amperes. But without a radiator it will only handle 1 Ampere.

A more modern option with improved efficiency is the XL4015 PWM controller designed for 5A. With a miniature cooling system it can operate up to 2.5A.

If you have very powerful, super-bright LEDs, then you need an LED driver for LED lamps. Two radiators cool the Schottky diode and the XL4015 chip. In this configuration, it is capable of operating up to 5A with voltage up to 35V. It is advisable that it does not operate in extreme conditions, this will significantly increase its reliability and service life.

If you have a small lamp or pocket spotlight, then a miniature voltage stabilizer with a current of up to 1.5A is suitable for you. Input voltage from 5 to 23V, output up to 17V.

Brightness adjustment

To regulate the brightness of the LED, you can use compact LED dimmers that have appeared recently. If its power is not enough, then you can install a larger dimmer. They usually operate in two ranges: 12V and 24V.

You can control it using an infrared or radio remote control (RC). They cost from 100 rubles for a simple model and from 200 rubles for a model with a remote control. Basically, such remote controls are used for 12V diode strips. But it can easily be connected to a low-voltage driver.

Dimming can be analog in the form of a rotary knob or digital in the form of buttons.