NFC wireless flexible configuration LED driver power supply
NFC is a mature short-range wireless communication technology, which has been widely used in transportation cards, bank cards, ID cards and smart door locks for many years.
In NFC applications, there are a transmitter and a receiver, both with built-in antennas, and the receiver can be powered without additional power. When working, the transmitter transmits a signal with a frequency of 13.56MHz. The receiver receives this signal at a relatively short distance, and converts it into electrical energy to supply power to the receiver. At the same time, it decodes to obtain information, modifies information, and performs reverse transmission, and finally realizes the information exchange.
It can be imagined that as shown in Figure 1, if a receiver IC is designed on the LED power supply, the information to be configured can be sent and written to the LED power supply non-contact using a mobile phone or a transmitting device, and the LED power supply can output according to this information. Different currents, and even light attenuation compensation according to the working time.
If there is enough space inside this IC, it can be used to store more information. The required data (such as brand, serial number, etc.) can be written in or read out through the reading and writing equipment, which is convenient for maintenance and management.
Based on the above concepts, Infineon has developed NFC control chips NLM0010 and NLM0011 dedicated to LED drive power. The package is a very compact SOT-23, 5-pin package, with a wealth of built-in functions. It can be set before leaving the factory or according to different light sources before installation by the end customer, which greatly simplifies the design and use.
As shown in Figure 2, the NFC IC directly controls the primary main control IC. When the LED power supply is not connected to the AC power supply, the parameter information that needs to be configured is transmitted through the reading and writing device, and the NFC control chip receives power through the antenna to maintain its own work. , receive and store the target information in it in internal memory. The information of the NFC control chip can also be transmitted to the read-write device in the reverse direction to obtain the configured parameter information. When the LED driving power supply is powered on, it will supply power to the NFC control chip, which is converted into a PWM signal by calculation and output to the LED driving controller according to the information already stored in the register, and controls the output current to change the brightness of the LED.
As shown in Figure 3, the NFC controller chip can directly control the secondary main control IC. The ILD8150(E) is a DC/DC LED driver controller. The PWM output of the NFC controller chip is directly connected to the DIM pin of the ILD8150(E), for simpler output current control.
The NFC control chip provides richer functions:
The current setting is fine and flexible, while the traditional DIP switch setting is limited by the resistance of the resistor, generally only a few current gears can be set.
Using an internal clock of 27MHz, even with a PWM frequency of 10kHz, the resolution can still be 1/2700, which means that 2700 different outputs can be set.
The built-in 2.8V output precision voltage regulator is also beneficial to suppress additional errors caused by fluctuations in the VCC power supply.
Because of the flexible digital control, the actual output current can be closer to the target output current through the output current calibration in the production process, and a voltage stabilizer circuit with a relatively large error can be used to reduce costs, and the chip can record the switching times of the drive power supply and its working time can be obtained through the NFC reading and writing device to facilitate product maintenance and optimization.
Among them, the NLM0011 has a built-in CLO (constant lumen output), which can dynamically adjust the driving current according to the light decay characteristics of the LED light source to achieve the purpose of constant lumen output, that is light decay compensation.