Led drive circuit based on current transformer
Technical field
The invention belongs to the switch power technology field, relate to a kind of led drive circuit.Specifically realize the drive circuit of LED multi-path load current equilibrium by current transformer.
Background technology
LED needs constant current to drive, the application scenario of some high-power illuminations, and LED needs serial or parallel connection to use usually.Every road all needed constant current control when the LED parallel connection was used, and had increased circuit cost.Therefore, for LED, directly Chuan Lian mode is the simplest, if but LED series connection number is too much, driver output voltage is higher on the one hand, increased the line component cost, if it is not one of them LED inefficacy can cause whole string LED lamp to lose efficacy on the other hand, therefore high from the system perspective reliability.A kind of technology is to adopt the former limit series connection of a plurality of high frequency transformers, secondary is with the LED load after rectification, the principle of utilizing the former secondary current of ideal transformer and the transformer turn ratio to be inversely proportional to is guaranteeing under the identical condition of a plurality of transformer turn ratioes, realize the LED electric current current-sharing of secondary, as shown in Figure 1.Though feasible on this technology principle, there are some shortcomings in actual applications, have influence on its practical application, as: the discreteness of (1) static exciter inductance can make the equal mobility of multichannel output current be affected.(2) when the load short circuits of a certain road, because capacitor filtering only, so the transformer of this road correspondence is equivalent to short circuit, cause total magnetizing inductance amount of former limit series connection to change, thereby influence the steady-state gain of current transformer, increased the control difficulty, therefore can seriously reduce the reliability of current transformer.
Summary of the invention
The present invention is directed to the deficiencies in the prior art, propose a kind of LED multi-path flow equalizing circuit of realizing based on current transformer (CT), have advantages such as simple in structure, that cost is low and the current-sharing performance is good.
The technical scheme that technical solution problem of the present invention is taked is:
The present invention includes high-frequency ac current source, a N current transformer module; Each current transformer module comprises a current transformer, an output rectifier and an output capacitance, and wherein N is natural number.
The former limit of current transformer winding one end in output termination first current transformer module in high-frequency ac current source, the former limit of all current transformers winding is connected in series in turn, up to the input of another input termination current transformer module of current transformer module N-1 N, another output of another termination source of high frequency current of the former limit of the current transformer in N current transformer module winding.The positive input terminal of the LED load of the positive output termination correspondence of each current transformer module, the negative input end of the LED load of the negative output termination correspondence of current transformer module.
Described high-frequency ac current source is the high-frequency inverter circuit with ac current source characteristic, comprises direct voltage source, high-frequency ac voltage source generating circuit and impedance network.Direct voltage source can be DC source such as storage battery or be obtained after rectification by civil power; Described high-frequency ac voltage source generating circuit is one of some kinds of isolated forms or non-isolation type switch topology, is used for producing the high-frequency ac pulse voltage signal; Described impedance network is the impedance inverting network of inductance or inductance and electric capacity formation, and the high-frequency ac pulse voltage signal is converted to the high-frequency ac current signal.
In the described current transformer module, the secondary winding of current transformer is received the input of output rectifier, and the output of output rectifier is received the two ends of output capacitance, and the LED load is in parallel with output capacitance.
In the described current transformer module, the secondary of current transformer can be the simplex winding structure, also can be many windings rectifier structure, as centre tapped winding construction.
In the described current transformer module, output rectifier can be half-wave rectifying circuit, also can be full bridge rectifier, perhaps center-tap rectifier circuit, and perhaps voltage doubling rectifing circuit, and other is applicable to the rectification circuit of output capacitance filtering.
Specifically, core concept of the present invention is: at first construct a high-frequency ac current source, utilize current transformer to induce electric current then and come the driving LED load; As long as guarantee current transformer turn ratio unanimity, can realize each paths of LEDs load current equilibrium automatically.
The main distinction of the present invention and the former limit of a plurality of high frequency transformers of employing series connection method shown in Figure 1 is: the high frequency pulse AC power supply output impedance among Fig. 1 is lower, equivalence is voltage source, the former limit of high frequency transformer magnetizing inductance amount is required to be high impedance to bear this voltage source, when the main circuit parameter of the former limit of design, need the former limit of high frequency transformer magnetizing inductance amount is taken into account; High frequency pulse AC power supply of the present invention is current source, and output impedance is bigger, and the current transformer magnetizing inductance is Low ESR, and the current transformer magnetizing inductance is not considered when former limit main circuit parameter designs.
Beneficial effect of the present invention is:
(1) the former limit of current transformer winding seals in main circuit, and the primary current of responding to is passed to secondary, and former limit winding does not bear voltage substantially, and the current transformer magnetizing inductance is to the not influence of current-sharing effect;
(2) during the induced current of the former limit of current transformer, the conducting of secondary rectifier, the current transformer magnetizing inductance has been equivalent to by the short circuit of secondary output capacitance, also can not have any impact to circuit performance when therefore the load short circuits situation occurring;
(3) current-sharing effect is subjected to the load voltage deviation effects less;
(4) current transformer module can standardization, realizes modularization production easily, reduces production costs.
Description of drawings
Fig. 1: existing a plurality of high frequency transformer series connection realize secondary current-sharing structure chart;
Fig. 2: be structured flowchart of the present invention;
Fig. 3: first specific embodiment of the present invention
Fig. 4: the concrete optional topological structure of high frequency voltage source generating circuit;
Fig. 5: the concrete optional structure of impedance network;
Fig. 6: the concrete optional structure of output rectifier;
Fig. 7: second specific embodiment of the present invention.
Embodiment
Below in conjunction with specific embodiment and accompanying drawing content of the present invention is elaborated.
As shown in Figure 2, the present invention includes a high-frequency ac current source, a N current transformer module; An input of an output termination current transformer module 1 in high-frequency ac current source, an input of another input termination current transformer module 2 of current transformer module 1, all current transformer module inputs all join end to end, up to the input of another input termination current transformer module of current transformer module N-1 N, another output in another input termination high-frequency ac current source of current transformer module N; The positive input terminal of the LED load of the positive output termination correspondence of each current transformer module, the negative input end of the LED load of the negative output termination correspondence of current transformer module; In the current transformer module, the secondary winding of current transformer is received the input of output rectifier, and the output of output rectifier is received the two ends of output capacitance.
Figure 3 shows that first specific embodiment of the present invention, comprise a direct voltage source Vin, high-frequency ac voltage source generating circuit, impedance network and N two winding current instrument transformer modules; Wherein, the high-frequency ac current source shown in direct voltage source Vin, high-frequency ac voltage source generating circuit and the impedance network pie graph 2; The positive input terminal of the positive output termination high-frequency ac voltage source generating circuit of direct voltage source Vin, the negative input end of the negative output termination high-frequency ac voltage source generating circuit of direct voltage source Vin, two outputs of high-frequency ac voltage source generating circuit link to each other with two inputs of impedance network respectively, and two outputs of impedance network are as two outputs in described high-frequency ac current source; Each current transformer module comprises the current transformer of two windings, an output rectifier and an output capacitance; An output output of impedance network connects the former limit of current transformer CT1 winding end of the same name, the end of the same name of the different name termination current transformer CT2 of current transformer CT1, the former limit of all current transformers winding is connected in series in turn, up to the end of the same name of the former limit of different name termination current transformer CTN of the former limit of current transformer CTN-1 winding winding, another output of the different name termination impedance network of the former limit of current transformer CTN winding; Among any one current transformer module n, the positive input terminal of the termination output rectifier of the same name of the secondary winding of current transformer CTn, the negative input end of the different name termination output rectifier of the secondary winding of current transformer CTn; The anode of the positive output termination output capacitance Con of output rectifier, the negative terminal of the negative output termination output capacitance Con of output rectifier, LED load n is in parallel with output capacitance Con.
Wherein, direct voltage source Vin can be DC source such as storage battery or be obtained after rectification by civil power.
Wherein, the high-frequency ac voltage source generating circuit is isolated form or non-isolation type switch topology, in 10 kinds of topological structures as shown in Figure 4 any one.
Wherein, impedance network can be the LC network, the structure one shown in Fig. 5 (a); In order to reduce the requirement of withstand voltage to back level current transformer, with 5(a) shown in structure one in capacitor C r split into two capacitor C r1 and Cr2, become the structure two shown in Fig. 5 (b), utilize electric capacity to realize the electrical isolation of circuit; Above-mentioned two kinds of structures be applicable to 10 kinds of topological structure kinds shown in Figure 4 any one; The third impedance network directly is made up of inductance, as 5(c) shown in, Fig. 4 (b), Fig. 4 (d), Fig. 4 (e), Fig. 4 (f), Fig. 4 (g), Fig. 4 (h), Fig. 4 (i) and Fig. 4 eight kinds of topologys such as (j) be applicable to.
Wherein, output rectifier can be three kinds of rectification circuit kinds shown in Figure 6 any one, the rectifying tube in the output rectifier can be diode or synchronous rectification MOSFET.
Fig. 7 is second specific embodiment of the present invention, comprise a direct voltage source Vin, the high-frequency ac voltage source generating circuit, impedance network and N three winding current instrument transformer modules, wherein, direct voltage source Vin, the high-frequency ac voltage source generating circuit, the impedance network specific implementation is all identical with first specific embodiment shown in Figure 3 with connected mode, and difference is the current transformer module implementation: the current transformer module of present embodiment is with centre tapped three winding current instrument transformer CT by one, two output rectifier and output capacitance compositions that rectifier diode is formed.The anode output of impedance network connects the former limit of current transformer CT1 winding end of the same name, the end of the same name of the different name termination current transformer CT2 of current transformer CT1, the former limit of all current transformers winding all joins end to end, up to the end of the same name of the former limit of different name termination current transformer CTN of the former limit of current transformer CTN-1 winding winding, the output of the negative terminal of the different name termination impedance network of the former limit of current transformer CTN winding; Among any one current transformer module n, the anode of the terminating diode Ds1n of the same name of the first secondary winding of current transformer CTn, the end of the same name of the different name end of the first secondary winding and the second secondary winding links to each other and receives the negative terminal of output capacitance Con and the negative electrode of corresponding LED load n, the anode of the different name terminating diode Ds2n of the second secondary winding is received the anode of output capacitance Con and the anode of corresponding LED load n after the negative electrode of the negative electrode of diode Ds1n and diode Ds2n links to each other.
No matter above how detailed explanation is, and those skilled in the art can have many modes to implement the present invention under the prerequisite of its spirit, and described in the specification is some specific embodiment of the present invention.All spirit essence is done according to the present invention equivalent transformation or modification all should be encompassed within protection scope of the present invention.The above-mentioned detailed description of the embodiment of the invention be not exhaustive or be used for limiting the present invention to above-mentioned clear and definite in form.Above-mentioned with schematic purpose specific embodiment of the present invention and example are described in, those skilled in the art will recognize that and can carry out various equivalent modifications within the scope of the invention.
The present invention's enlightenment provided here is not must be applied in the said system, can also be applied in other system.Can combine to provide more embodiment with element and the effect of above-mentioned various embodiment.Can make amendment to the present invention according to above-mentioned detailed description, at above-mentioned declarative description specific embodiment of the present invention and having described in the anticipated optimal set pattern, no matter how detailed explanation appearred hereinbefore, also can be implemented in numerous ways the present invention.The details of foregoing circuit structure and control mode thereof is carried out in the details at it can carry out considerable variation, yet it still is included among the present invention disclosed herein.
Should be noted that as above-mentioned employed specific term should not redefine this term here with restriction of the present invention some certain features, feature or the scheme relevant with this term for being illustrated in when explanation some feature of the present invention or scheme.In a word, should be with the terminological interpretation in the claims of enclosing, used for not limiting the invention to disclosed specific embodiment in the specification, unless above-mentioned detailed description part defines these terms clearly.Therefore, actual range of the present invention not only comprises the disclosed embodiments, also is included in to implement or carry out all equivalents of the present invention under claims.