NFC programming for LEDs using a PWM output to control analog LED-drivers: Page 3 of 5

September 04, 2019 //By Dr. Qi Zhu
NFC programming
In the LED market, more and more LED power suppliers to offer two novel functions: near-field communication (NFC) programming and constant lumen output (CLO). The NFC programming function is designed to replace the labor-intensive “plug-in resistor” current setting method to improve the flexibility across the value chain.

The NFC-microcontroller concept

The existing implementation concept consists of a microcontroller and an NFC dynamic tag. Although this solution has its potential, it is expensive for the following reasons:


Figure 2: The NFC-microcontroller concept.

  • The microcontroller itself and the additionally required passive components increase the overall component count

  • A multi-layer PCB is needed (if the LED driver is using a single-layer or two-layer PCB, a separated daughter card is needed).

  • In addition, to enable the microcontroller to operate, the user has to write firmware. It can be challenging for some manufacturers who lack the experience and knowledge in software writing or microcontroller firmware.

So, is there a more compact solution that reduces component count, thus costs and still effective? This is where Infineon comes into place with its new NFC-PWM concept.

 

A new concept: the NFC-PWM series

This solution enables both NFC programming and CLO functions in analog systems using a featured NFC IC with PWM output to control the analog driver IC directly. Thus, the need for a microcontroller is eliminated. The system in a general setup consists of four parts: the antenna, the NFC IC, the RC filter, and the LED-driver IC.

How does this work? The working principle is simple. The configuration of the PWM parameters happens via a wireless NFC interface. While being powered, the chip generates a PWM output. Then the PWM signal is converted (via the RC filter) to DC voltage to control the output current. And finally, by adjusting the duty cycle of the PWM signal, it regulates the DC control voltage.


Figure 3: Infineon’s NFC-PWM concept.

Being compatible with existing analog LED-driver designs and the NFC programming specification from the Module-Driver Interface Special Interest Group (MD-SIG), makes this new NFC-PWM concept a perfect fit for cost-sensitive segments. The NFC-PWM method relies on dual-mode NFC configuration ICs (NLM0010 and NLM0011) with PWM output primarily designed for LED applications.


Figure 4: Application diagram.

In addition to the NFC programming advanced features like CLO, operating-time counting, and on/off counting are also integrated into the chips - without the need for any additional microcontroller or firmware development efforts.

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