Research On LED Drive Power Supply Without Electrolytic Capacitors

Light emitting diode(LED) is a solid semiconductor device that can converts electrical energy into visible light. It has the advantages of safety, long service life,low power consumption and so on. LED as the fourth generation of light source,which triggers a new revolution in lighting and has a very broad application prospects and development prospects. Due to its own unique characteristics of the LED, that is determined that the power supply can not be directly connected to the power supply,which needs drive power to drive the LED. In general, the filter of the driving power supply mostly uses the electrolytic capacitor. On the one hand, the electrolytic capacitor can only play a ripple effect that can not completely eliminate. The remained ripple will affect the luminous efficiency of LED. On the other hand, the lifetime of the electrolytic capacitor and the LED light source are seriously unbalanced. It will directly affect its service life and reliability. Therefore, How to solve the lifetime problem of electrolytic capacitors and improve the reliability of power supply has become an important issue in the current development of LED.Aiming at the above problems, this paper designs the main circuit topology of improved Buck converter as the LED driver with the advantages of continuous input current, strong buck capability. On the basis of the improved Buck converter, the ripple compensation circuit is used to suppress the output ripple of the circuit. so that the electrolytic capacitor can be removed and ensure that the current flowing through the LED is constant current. The control method of I2 U is designed, which can improve the dynamic response speed of the circuit and which can accurately control the current flowing through the LED. The new driving power supply has no electrolytic capacitor and the output ripple is small, which greatly improves the service life and working reliability of the driving power supply. The specific research contents of this paper are as follows:(1) Aiming at the ability to reduce voltage of traditional Buck circuit is not strong, discontinuous input current will cause electromagnetic interference etc.Improved Buck converter with continuous input current and strong buck ability is designed as the main circuit topology. Then, the effect of output filter capacitor on the stability of the system and the lifetime of the electrolytic capacitor is also analyzed,then points out the importance of removing the electrolytic capacitor to improve the service life of the driving power.(2) The structure of an improved LED Buck drive circuit without electrolytic capacitor is proposed. On the basis of the improved Buck converter, the ripple compensation circuit is used to suppress the output ripple of the circuit. Thus it can replace the the filter electrolytic capacitor, So that the current flowing through the LED is constant current.(3) Introducing the I2 U control method. Compared with the traditional peak current control, which can accurately control the current through the LED and keep it constant, meanwhile it has a better dynamic response speed and apply it to the improved LED Buck drive circuit without electrolytic capacitor.