Power Supply Based On Flyback Converter With Active Ripple Compensation For LED

With the development of productivity and constant enrichment of production,people pay more and more attention on energy conservation, environmental protection,and Low-Carbon life. Because of the advantages of LED, such as energy-efficiency,environmental protection and long-life, it is gradually favored by the people. Iftraditional lighting that has low efficiency, high-energy consumption can be replaced byLED, energy shortage problems would get some relief. Due to its Optical-Electricalcharacteristics of LED, special power is needed to drive it. Switching power supply thathas flexible structure, low losses, and high output efficiency becomes the first choice ofLED drive power. However, conventional switching power supply uses electrolyticcapacitor to filter. And the life of LED do not match with electrolytic capacitorextremely, so using linear circuit instead of electrolytic capacitor to filter becomes abetter way and the linear circuit combines perfectly with switching power supply whichhas a great significance for the promotion and development of LED.This paper uses Flyback converter with high practical value to be the main circuitof the LED power driver. It detailedly analyzes the operating principle and relatedcharacter of the converter, proposes a topological structure of the driving circuits ofActive Ripple Compensation Flyback LED aiming at the lifetime of filter capacitor,analyses the basic idea of driving power on the condition of removing electrolyticcapacitor and the circuit structure and function of drive power without electrolyticcapacitor. Then we design the inductor ripple current detection and compensation circuitand simulate to verify its excellent adaptability and make the linear circuits andswitching power supply cooperate perfectly.By comparing several switch loss buffer technologies, this paper designs a kind ofZCS-PWM. It adds an auxiliary circuit in the traditional Flyback circuit, realizing openand shutdown of the primary switch and auxiliary switch in the condition of zerocurrent. The other passive power devices also realize the soft open and shut off. Iteffectively suppresses voltage and current stress of power switch, reduces the switchinglosses, and improves the efficiency of the drive power supply.There are three kinds of driving way of synchronous rectifier transform circuit ofFlyback converter. By comparing their advantages and disadvantages, this paperchooses the simple circuit voltage type self-driven synchronous rectifier manner according to their own characteristics and uses the output voltage of the auxiliarywinding to drive synchronous rectifier tube. The circuit structure is simple and caneffectively drive synchronous rectifier to open and shut off.This paper proposes the output inductor current sampling way of hysteresis currentcontrol, mainly considering the function of battery power supply and the characteristicsof the LED current loads. This controlling way can well merge with ripplecompensation circuit and achieve the goal of outputting constant current. This paperanalyzes in detail the works of the hysteresis comparator and deduces hysteresis currentcontrol switching frequency formula and the relationship between the circuit outputcurrent and reference voltage, and completes the design of LED drive power supply.The design of power supply uses power electronic simulation software to simulateand furthermore, verifies circuit topology and control method. The results of simulationand experiment indicate that the hysteresis current control method has strong stabilityand good response and can control the change of the output inductor current in real-time.Active ripple compensation circuit can be very good to compensate the output inductorripple current and make the output constant current. Without the large electrolyticcapacitor, the new LED drive power supply is reliable and has a long lifespan. Thecircuit can realize miniaturization and integration.It is significant for the developmentof LED.