Multi Channel LED Driver Based On Charge Discharge Balance Of Switched Capacitor

High Brightness Light Emitting Diode(HB-LED)has the advantages of high luminous efficiency,long service life,low loss,fast response,etc.,and is widely used in lighting,display screens,LCD light sources,traffic signals and other fields.With continuous development,LED began to develop into general lighting and other fields in an all-round way.The power of single-bead light-emitting diodes is generally only(0.5-3W).In the application process,the LED lamp beads are generally connected in series and parallel in a mixed manner for use.In order to solve the current sharing problem of LED lamp beads in series and parallel,this thesis proposes a new topology circuit,adding a resonant circuit(Quasi-resonant Circuit,QRC)to the circuit structure.Due to the high efficiency of the resonant circuit,long running time and investment of low cost,It also solve the shortcomings of existing drives,the main research content is as follows:The parallel connection of multi-channel LEDs may cause current imbalance.In order to solve the problem of uneven output current of multi-channel LEDs in series and parallel,a new type of resonant current sharing topology circuit is proposed.The proposed new resonant topology circuit can realize the balanced output of any LED path.The control circuit part of the circuit adopts closed-loop control.In order to achieve the purpose of constant current output,the operation of the circuit has nothing to do with the connected load.Combined with the LLC resonant network,It can ensure zero voltage switching,thereby improving the working efficiency of the circuit,and the circuit structure is simple and reliable.This new topology circuit can also realize PWM precise dimming.In order to achieve multi-channel current sharing and constant current LED scene lighting applications,an efficient and high-precision current sharing method is provided.The series and parallel connection of multi-channel LEDs will cause the current imbalance of each branch.The current sharing method based on capacitive impedance matching is easy to control and expand,so it is widely used.As the path of the LED light string increases,the current sharing effect decreases sharply,and the loss in reactive power increases.Combining the above problems,a fixed-frequency current-sharing LED drive circuit is proposed,which mainly uses the superposition of the upper and lower half bridges to reduce the current imbalance caused by the mismatch of the capacitive reactance of the capacitors,and reduce the corresponding loss.Switched-Controlled Capacitor(SCC)in the resonant unit,this module is a wide-range dimming under constant frequency control.At the same time,the switching circuit part of the circuit adopts the method of pulse width modulation PWM,which can not only improve the current sharing effect,but also realize soft switching.In addition,the main application in lighting is also considered.LEDs achieve independent control of different brightness.In addition,the main application in lighting is also considered.LEDs achieve independent control of different brightness.In this regard,this thesis proposes a new multi-channel LED driver based on switched capacitors.In the resonant circuit part,the fixed current-sharing capacitor is replaced by a switched capacitor,so that the SCC capacitor can be adjusted at a fixed switching frequency to achieve the purpose of independent dimming of the LED string.Therefore,this method not only solves the complex and diverse problems of the control circuit structure,but also improves the current sharing of the multi-channel output.Combined with the multi-channel LED current sharing circuit,the complicated circuit structure will cause the setting of the control circuit to be very difficult.In the fifth chapter of this article,a multi-output LED drive circuit based on improved independent switched capacitors is proposed.Compared with the traditional current-sharing circuit,this improved drive circuit is composed of only semiconductor switches and magnetic elements,and this new drive circuit can also realize the output of the LED load with both odd and even paths.Therefore,the drive circuit has the advantages of small size,low cost and high performance.In addition,the driving circuit can realize the current balance of each LED path by controlling only one current,and the control circuit and logic circuit and the multi-channel LED current sharing technology are relatively simpler.The thesis analyzes the principles and related parameters of the current sharing topology of all structures,and at the same time builds an experimental platform to verify the proposed circuit,which verifies the correctness of the proposed circuit.