Different applications determine different driving methods for LED displays

Linear regulators for voltage conversion face power consumption issues, while switching methods have noise issues. The choice of conversion method for LED drivers depends on the application.
- Bill Rypka Bill Rypka Muzahid Huda Maxim HB LED driver product marketing manager

What kind of conversion method

Converting voltages using linear regulators faces power consumption issues, so this method is more suitable for conversion circuits that need to avoid noise (such as car audio) and therefore cannot use switching methods. The switching method is characterized by very high conversion efficiency, but it also has noise issues, so the choice of conversion method depends on the application.

Usually, the efficiency of the charge pump driving method will change with the input voltage. In applications with a large voltage range, its efficiency is relatively low. In applications with a small voltage range, its efficiency can only be maximized when the input and output voltages are integer multiples, but this is difficult to achieve in actual battery-powered applications. On the other hand, the conversion efficiency of the inductor is not much affected by voltage interference, and its application restrictions are less than those of the charge pump, so the current conversion circuit mostly uses the inductor method.

How to evaluate performance

Objectively speaking, the evaluation of HB LED driver IC performance should be based on different applications and cannot be generalized. For example, in decorative lighting applications, the control of RGB color changes is highly required, and this performance becomes the main indicator, while this is not required in monochrome applications. Another example is that applications in small spaces require heat dissipation capabilities; automotive lighting replacement applications require both smooth integration with the original circuit system and high reliability; in display applications such as NB, the control of the brightness balance of multiple strings of LEDs requires the driver IC to have precise control of the current on each branch, such as the control accuracy of Maxim's products can reach 3%; the application of projectors requires high-efficiency driver circuits, the ability to quickly adjust brightness, and thermal protection capabilities; in replacement applications, performance is more reflected in the entire solution rather than a single driver IC. In general, the integration of devices, the number of controls, response speed, fault diagnosis, heat resistance, etc. are all references for performance evaluation.

Generally, the purpose of high integration is to improve performance, but at high power, high integration will increase the chip area to meet the high current, which will increase the cost and also face the problem of heat dissipation. Therefore, how to balance the relationship between power and integration is a topic facing driver IC design. Driver ICs need to improve chip technology to meet the cost while improving packaging to solve the problem of heat dissipation.