Capacitance clamping type current-equalizing circuit with multi-string load branches
A clamping and branching technology, applied in the field of power electronic converters, can solve the problems of large linear voltage drop, high cost of drive circuit, and large loss
Inactive Publication Date: 2013-11-06
NANJING UNIV OF AERONAUTICS & ASTRONAUTICS
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Problems solved by technology
[0004] (1) Each string of LEDs uses a separate DC-DC converter to adjust its terminal voltage or output current. The circuit block diagram is as follows figure 2 As shown; however, the disadvantage of this structure is: when more than 2 strings of LEDs are required to be connected in parallel, more than 2 DC-DC converters are required, which makes the cost higher;
[0005] (2) Each string of LEDs is connected in series with a triode or MOSFET, and the triode or MOSFET bears the voltage difference between the power supply and the LED string to complete the current regulation of the LED string, as shown in Figure 3(a) and Figure 3(b) ; However, due to the large linear voltage drop on the triode or MOSFET, the loss is large;
[0006] (3) Bernd Clauberg and Robert A.Erhardt proposed to use high-frequency AC power supply, and through parameter design to make the high-frequency AC impedance of each LED string approximately equal to achieve a good current sharing effect, see the case of US Patent No. US6853150; However, the disadvantages of this solution are: because the high-frequency half-sine wave passes through the LED string, and the peak-to-average ratio of the current is 2, the reliability of the circuit is low, and the cost of the driving circuit is high.
[0007] From the above analysis, it can be seen that although there are many current sharing methods for multi-string LED parallel circuits, the effects are not satisfactory and need to be improved.
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[0044] The circuit structure and beneficial effects of the present invention will be described in detail below in conjunction with the accompanying drawings and specific embodiments.
[0045] first as figure 1 Shown is a typical structure of a capacitive clamp type multi-string load branch current sharing circuit provided by the present invention, which may have multiple variants, which will be introduced separately below.
[0046] Such as Figure 6 As shown, it is a preferred embodiment of the capacitive clamp type multi-string load branch current equalizing circuit provided by the present invention, wherein the load branch adopts LED string branch, and the described current equalizing circuit includes a constant current source, n (n is a natural number greater than 1) LED string branches connected in parallel and h clamping capacitors, where the components and connection structure of each LED string branch are the same, LED string branch E_i (i=1 , 2, 3,..., n) also inclu...
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The invention discloses a capacitance clamping type current-equalizing circuit with multi-string load branches, which comprises a constant current source and at least two load branches in parallel connection, wherein each load branch comprises a load unit and a one-way conducted controllable switch which are serially connected; the number of the load is one or two; one end of each load branch is connected to the anode of the constant current source while the other end is connected to the cathode of the constant current source; the anode of the controllable switch is directly or indirectly connected to the anode of the constant current source while the cathode is directly or indirectly connected to the cathode of the constant current source; the load branch further comprises at least one clamping capacitor; the number of the clamping capacitor is one less than the number of the load branch at least; one end of the clamping capacitor is connected to any point except the two end points of any load branch while the other end is connected to any point except the two end points of any one of the other load branches; and any load branch is at least connected to one clamping capacitor. The current-equalizing circuit structure is convenient to integrate, is low in cost and is high in transformation efficiency.
Description
technical field [0001] The invention relates to a power electronic converter, in particular to a current equalizing circuit of a plurality of light-emitting diode strings and a control method thereof. Background technique [0002] High-brightness light-emitting diode (Light Emitting Diode, referred to as LED) is a new generation of lighting source, which has the advantages of long life, high efficiency, good optical performance, and no pollution. LED driver refers to a power conversion device that provides power supply voltage or current, mostly power electronic conversion devices, and is one of the core components of LED lighting sources. [0003] LED is a semiconductor device, and its volt-ampere characteristics are similar to ordinary Zener diodes. Due to the production process and other reasons, at a specific current operating point, even for the same batch of LED products, the voltage drop at both ends has a large dispersion, and the temperature coefficient of their vo...
Claims
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IPC IPC(8): H05B37/02
Inventor张方华俞忆洁刘硕
OwnerNANJING UNIV OF AERONAUTICS & ASTRONAUTICS