Analysis - what criteria are used to select a reasonable LED driver

Linear regulators are subject to power dissipation problems when switching voltages, and noise problems in switching modes. Which conversion method LED driver chooses depends on which application.

What kind of conversion method

Switching voltages through a linear regulator can be a power hazard problem, which is more suitable for use in converter circuits that need to avoid noise (such as car audio) and therefore cannot be switched. The switching method is characterized by very high conversion efficiency, but it also has noise problems, so the choice of which conversion method depends on which application.

Generally, the efficiency of the charge pump drive mode varies with the input voltage. In applications with large voltage variations, the efficiency is relatively low. In applications where the voltage variation range is small, only the input and output voltages are used. When the relationship is an integral multiple, its efficiency can be maximized, but this is difficult to achieve in battery-powered applications. In contrast, the conversion efficiency of the inductor is not subject to voltage interference, and the application limit is less than that of the charge pump. Therefore, the current conversion circuit is mostly inductive.

How to evaluate performance

Objectively speaking, evaluation of hb led driver ic performance depends on different applications, can not be generalized. For example, in decorative lighting applications, the control requirements for rgb color changes are high, and this performance becomes the main indicator, which is not required in monochrome applications. For example, the application of narrow space requires heat dissipation capability; in automotive lighting replacement applications, it requires both smooth integration of the original circuit system and high reliability; in display applications such as nb, multi-string LED The brightness equalization control requires that the drive ic have precise control of the current on each branch. For example, maxim's product control accuracy can reach 3%; the projector application requires high efficiency drive circuit, fast brightness adjustment and thermal protection. Capabilities; in alternative applications, performance is more manifested throughout the solution than on a single driver ic. In general, device integration, control quantity, response speed, fault diagnosis, heat resistance, etc. are all performance evaluation references.

Generally, the purpose of high integration is to improve performance, but at high power, high integration will increase the chip area in order to meet large currents, and also face heat dissipation problems while increasing costs. Therefore, how to balance power and integration The relationship is the subject of driving ic design. The driver ic should improve the package to solve the problem of heat dissipation while improving the chip process to meet the cost.