Advantages and disadvantages of linear and switching LED driver solutions

Lighting power supply and drive solutions:

There are generally two types of drive schemes: linear drive and switching drive.

Linear drive application is the simplest and most direct drive application method. In lighting-level white light LED applications, although there are problems such as low efficiency and poor regulation, it can meet more specific applications due to its simple circuit and small size.

Switching drive can obtain good current control accuracy and high overall efficiency. Its application methods are mainly divided into two categories: buck and boost. Buck switching drive is used when the power supply voltage is higher than the terminal voltage of the LED or when multiple LEDs are driven in parallel. Boost switching drive is used when the power supply voltage is lower than the terminal voltage of the LED or when multiple LEDs are driven in series.

It is generally believed that isolated drivers are safe but less efficient, while non-isolated drivers are more efficient and should be selected according to actual use requirements. At present, the design of general basic LED driver lighting applications is relatively simple, but if other functions such as phase control dimming and power factor correction (PFC) are required, the design becomes complicated. Non-dimming LED drivers without power factor correction function usually include an offline switching power supply for adjusting the output at a constant current.

The back-end architecture of an LED driver includes a current regulation circuit with short-circuit protection. This can be achieved using a linear regulation circuit, however this approach is inherently inefficient and therefore suitable for low output currents and is not typically applied to multi-stage architectures. An alternative approach is to use a simple buck regulator circuit with current feedback to limit the output current to exceed the desired LED drive current. This offsets the variation of the total LED forward voltage with temperature and device tolerances, and also limits the current in the event of a short circuit or other fault condition, thereby protecting the driver from damage.