SLVAFQ9 January   2024 TPS92201

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Introduction
    1. 1.1 Why Building Automation Need IR LED in Video Doorbell, Security Cam System
  5. 2Basic Dimming Knowledge – PWM and Analog Dimming
    1. 2.1 Analog Dimming
    2. 2.2 PWM Dimming
  6. 3Video Doorbell, Security Cam Industry Common Design for IR LED
    1. 3.1 External PWM Low Pass Filter
    2. 3.2 Industry Application Advantage and Disadvantage
  7. 4TPS92201 Design in Video Doorbell, Security Cam
  8. 5Summary
  9. 6References

5 Summary

IR LED design is very important depend on current range, accuracy requirement especially in low current and how much the current ripple can be accepted.

Some product spec are usually 350 mA as 100% current. Old design issue happened at current below 25 mA around 7% duty. Old design can go into Power saving mode. In the meantime, voltage ripple can go up to 100 m V which is unacceptable. Most customers can have 50 mv ripple which is acceptable for their system. Usually, use 70 to approximately 80% as an average max dimming current.

IR LED design also needs high dimming resolution. Some product spec dimming resolution is around 1% as a stage, customer mention normally in this industry 2% accuracy is hard to achieve. So TPS92201 can make analog dimming as 1% accuracy.