Summary of the invention
The present invention is intended to solve the technical problem of the upper stroboscopic in dark space and time in the space that in prior art, the LED drive unit brings, and a kind of LED drive unit is provided, and solves dark space, space and time domain stroboscopic problem in LED light fixture, especially LED fluorescent tube.
Embodiments of the invention provide a kind of LED drive unit that dynamically changes series parallel structure with input voltage, this LED drive unit is used for the driving LED matrix, described LED drive unit comprises an input voltage sensing module, a circuit series parallel structure control module, switch combination and the constant-current source that can change the total current size that can change the series parallel structure of LED in the LED matrix;
Described input voltage sensing module compares the critical value of input voltage from the different voltage ranges of presetting, and arrives described circuit series parallel structure control module according to input voltage status signal of comparative result output;
Described circuit series parallel structure control module, the control signal corresponding according to input voltage status signal output is to described switch combination and the constant-current source that can change the total current size;
Described switch combination is connected to described constant-current source and the driven LED matrix that changes the total current size, change the series parallel structure of switch combination according to described different control signal, the described constant-current source that changes the total current size is diverted in driven LED matrix according to the series parallel structure of switch combination;
The described constant-current source that changes the total current size, the total current size that changes this constant-current source according to described different control signal coordinate described switch combination to make the electric current on unitary series of operations LED path remain on a continuous current scope.
Further, when described input voltage sensing module detected input voltage and is positioned at the minimum voltage scope, described circuit series parallel structure control module control switch matrix system drove LED all in driven LED matrix in the mode of multichannel parallel connection;
When described input voltage sensing module detected input voltage and is positioned at the ceiling voltage scope, described circuit series parallel structure control module control switch combination drove the mode of LED all in driven LED matrix multichannel series connection in parallel and with minimum road;
Wherein, under the control of described circuit series parallel structure control module, in described driven LED matrix, the number in parallel of LED reduces with the rising of input voltage.
Further, the total current size of the described constant-current source that changes the total current size variation that is directly proportional to the number in parallel of LED in driven LED matrix when changing.
Further, the described switch combination of described circuit series parallel structure control module control makes all conducting or the shutoffs together of LED in described driven LED matrix under different LED series parallel structures, when conducting, the total current that the described constant-current source that changes the total current size provides is diverted in LED all in described driven LED matrix path in parallel via described switch combination.
Further, described switch combination has two kinds of series parallel structures, and described predeterminated voltage scope is a low pressure range and a high pressure range;
When the input voltage sensing module detected input voltage and is positioned at low pressure range, described circuit series parallel structure control module control switch was combined in the first series parallel structure;
When the input voltage sensing module detected input voltage and is positioned at high pressure range, described circuit series parallel structure control module control switch was combined in the second series parallel structure;
Wherein, in described the first series parallel structure, the number in parallel of driven LED is the twice of the number in parallel of driven LED in described the second series parallel structure.
In order to make LED drive unit of the present invention that higher power-efficient be arranged, further, described switch matrix has three kinds of series parallel structures, and described predeterminated voltage scope is pressure scope and high pressure range in a low pressure range;
When the input voltage sensing module detected input voltage and is positioned at low pressure range, described circuit series parallel structure control module control switch was combined in the first series parallel structure;
When the input voltage sensing module detected input voltage and is arranged in the pressure scope, described circuit series parallel structure control module control switch was combined in the second series parallel structure;
When the input voltage sensing module detected input voltage and is positioned at high pressure range, described circuit series parallel structure control module control switch was combined in the third series parallel structure;
Wherein, in described the first series parallel structure, the number in parallel of driven LED is three times of number in parallel of driven LED in described the third series parallel structure, and in described the second series parallel structure, the number in parallel of driven LED is the twice of the number in parallel of driven LED in described the third series parallel structure.
Further, the LED in described LED matrix has three kinds of series parallel structures, and described predeterminated voltage scope is pressure scope and high pressure range in a low pressure range;
When the input voltage sensing module detected input voltage and is positioned at low pressure range, described circuit series parallel structure control module control switch was combined in the first series parallel structure;
When the input voltage sensing module detected input voltage and is arranged in the pressure scope, described circuit series parallel structure control module control switch was combined in the second series parallel structure;
When the input voltage sensing module detected input voltage and is positioned at high pressure range, described circuit series parallel structure control module control switch was combined in the third series parallel structure;
Wherein, the number in parallel of different from forenamed three kinds of structures is driven LED in described the first series parallel structure is three times of number in parallel of driven LED in described the third series parallel structure, and in described the first series parallel structure, the number in parallel of driven LED is the twice of the number in parallel of driven LED in described the second series parallel structure.
Further, described input voltage sensing module, switch combination, the constant-current source that can change the total current size and circuit series parallel structure control module all are integrated on same chip, and described driven LED arranged in matrix is in chip exterior; Described chip also is provided with to connect the interface of outer member, the size of current in LED matrix driven according to the capable setting parameter of described outer member on single LED series circuit, and the critical value of adjusting described different voltage ranges.
The present invention also provides a kind of above-mentioned method of work that changes the LED drive unit of series parallel structure with input voltage, comprises the following steps,
Step 1, collection power input voltage compare its critical value from the different voltage ranges of presetting, and according to control signal corresponding to comparative result output;
Step 2, according to LED all in different control signal driving LED matrixes with different series parallel structure conductings, when input voltage is positioned at the minimum voltage scope, control LED all in the LED matrix with the mode conducting of multichannel parallel connection; When input voltage is positioned at the ceiling voltage scope, control the mode conducting of LED all in LED matrix multichannel series connection in parallel and with minimum road; Wherein, the number in parallel of described LED reduces with the rising of input voltage.
Further, in described step 2, total current size and the way in parallel in the LED matrix of controlling driven LED matrix of flowing through are directly proportional, and the electric current on the unitary series of operations LED path of flowing through remains on a continuous current scope.
the above technical scheme, by the critical value of input voltage from the different voltage ranges of presetting compared, and the control signal corresponding according to comparative result output changes the series parallel structure of LED in driven LED matrix, and make the electric current on unitary series of operations LED path remain on a continuous current scope, realized that all LED are in the conducting or extinguish together in period of wave of each power supply string, efficiently solving LED in fluorescent tube has the phenomenon of dark space, clear zone in the space, also make the dark space on time shaft significantly shorten, further reduced the stroboscopic problem of conventional ADS driving LED light fixture when dc low-voltage.
Embodiment
In order to make technical problem solved by the invention, technical scheme and beneficial effect clearer, below in conjunction with drawings and Examples, the present invention is further elaborated.Should be appreciated that specific embodiment described herein only in order to explain the present invention, is not intended to limit the present invention.
According to shown in Figure 1, the invention provides a kind of LED drive unit that dynamically changes series parallel structure with input voltage, described LED drive unit is used for driving LED matrix 40, described LED drive unit comprises an input voltage sensing module 10, a circuit series parallel structure control module 20, capable of dynamic changes the constant-current source 30 of total current size, and capable of dynamic changes the switch combination 50 of the series parallel structure of LED in LED matrix 40;
Described LED matrix 40 has high-pressure side and low-pressure end, but the high-pressure side of LED matrix 40 and low-pressure end and between form the multiple branch road with different LED series parallel structure of conducting work, for example, all LED in described LED matrix 40 can mutually connect and form a single tandem paths, or the path that all LED in LED matrix 40 can all LED parallel forms of formation parallel with one another;
Described input voltage sensing module 10, the input voltage that is used for the monitoring power supply, and the critical value of input voltage from the different voltage ranges of presetting compared, and arrive described circuit series parallel structure control module 20 according to input voltage status signal of comparative result output.The critical value of default different voltage ranges described here can set in advance according to the input voltage of power supply, such as, be arranged to the high pressure range of low pressure range and the 110Vac ~ 220Vac of 0 ~ 110Vac; If will make light fixture for American market, the critical value of LED number and voltage range will be changed into the numerical value of the input voltage range of the 110Vac that can adapt to the U.S. so.
Described circuit series parallel structure control module 20 is used for receiving described input voltage status signal, and the control signal corresponding according to described input voltage status signal output is to described switch combination 50 and the constant-current source 30 that can change the total current size;
Described switch combination 50, be connected to constant-current source 30 and driven LED matrix 40 that can change the total current size, switch combination 50 dynamically changes series parallel structure according to described different control signal, again that each tandem paths is in parallel after allowing part LED in driven LED matrix 40 first connect, concrete series connection number and number in parallel can set in advance according to country variant supply voltage standard the configuration of driven LED matrix and control signal, when being integrated into circuit in chip, can reserving and set the critical value that interface is adjusted voltage range.
the forward conducting voltage that electric current on the unitary series of operations path multiply by total LED number and LED is approximately just total wattage of LED matrix, neutralization keeps stable brightness in time in the space in order to make every LEDs, will keep the constant current state of fixing to the drive current of each LEDs, namely constant-current source 30 dynamically changes its total current size in company with switch combination 50 control signal corresponding according to different voltage ranges together, make the electric current on unitary series of operations LED path keep fixing, because driven LED first connects again each tandem paths to be carried out parallel connection after bunchiness, the variation that can be directly proportional to way in parallel of the described total current value that changes the constant-current source 30 of total current size, but the proportionate relationship that is difficult to when making hardware guarantee to change is with theoretical just the same, therefore as long as can allow the electric current on unitary series of operations LED path remain in a certain continuous current scope all right, the hot spot that cause the less bright dark space of this scope and the flicker in time domain are just less.
Further, when described input voltage sensing module 10 monitors input voltage and is positioned at lower predeterminated voltage scope, the described input voltage status signal of output drives LED all in driven LED matrix 40 for described circuit series parallel structure control module control switch combination 50 in the mode than the multichannel parallel connection, the work of namely switching on; When described input voltage sensing module 10 detects input voltage when being positioned at higher predeterminated voltage scope, the described input voltage status signal of output drives LED all in driven LED matrix for described circuit series parallel structure control module control switch combination 50 in the mode of less road parallel connection; When described input voltage sensing module detected input voltage and is positioned at the minimum voltage scope, described circuit series parallel structure control module control switch combination 50 drove LED all in driven LED matrix in the mode of multichannel parallel connection; When described input voltage sensing module detected input voltage and is positioned at the ceiling voltage scope, described circuit series parallel structure control module control switch combination 50 drove the mode of LED all in driven LED matrix 40 multichannel series connection in parallel and with minimum road; Wherein, under the control of described circuit series parallel structure control module, in described driven LED matrix 40, the number in parallel of LED reduces with the rising of input voltage.
In above technical scheme, for the electric current on single in LED matrix 40 series LED path is remained in a certain continuous current scope, the number in parallel of LED variations that the be directly proportional when series parallel structure of total current size all LED in LED matrix 40 of the described constant-current source that changes the total current size changes and in LED matrix 40, so the current value that makes electric current be diverted to by described switch combination 50 in the single LED tandem paths of each parallel connection can maintain in a fixing scope.The simultaneously described circuit series parallel structure control module 20 described switch combinations of control make all conducting or the shutoffs together of LED in described LED matrix 40 under different LED series parallel structures, when conducting, the total current that the described constant-current source that changes the total current size provides is diverted in LED all in described driven LED matrix 40 path in parallel via described switch combination.
A nearlyer step ground, described input voltage sensing module 10, switch combination 50, the constant-current source 30 that can change the total current size and circuit series parallel structure control module 20 can be integrated on same chip, and described driven LED matrix 40 is arranged on chip exterior; Described chip also is provided with to connect outer member and gets interface, according to the parameter of described outer member, can set size of current on single LED series circuit and the critical value of adjusting described different voltage ranges by described interface.
For instance, can utilize a non-essential resistance to adjust electric current on single LED tandem paths, adjust the critical value of different voltage ranges with other resistance.With Chinese supply voltage for example, if when being afraid of the abnormal step-down of supply voltage, the LED light fixture is excessively dark, not necessarily fully proportional the cutting apart of input supply voltage scope of standard, can reduce the LED number on tandem paths, and all voltage range critical values reduce together when adjusting critical value so; If but lie in very much the power-efficient of normal input supply voltage scope, do not mind the abnormal step-down of supply voltage, so just can increase the number of LED and heighten the critical value of each voltage range.
The below will be further detailed LED drive unit and the operation principle thereof with input voltage change series parallel structure of the present invention by embodiment.
The first embodiment:
in conjunction with shown in Figure 2, described LED matrix 40 is provided with two LED strings between its high-pressure side and low-pressure end, suppose that this is the circuit of doing for city's electrical specification of China, the forward conducting voltage of the white light LEDs of industry is that 3.0V is to the 3.6V left and right at present, so LED string 53 and 57 each the 39 LEDs series connection naturally of LED string, it is series connection 78 LEDs altogether that two string LED add up, so forward conducting voltage arrives the 302Vdc left and right at 234Vdc, 220Vac is through the nearly 310Vdc of heap that passes a bridge, can directly promote this 78 LEDs, and there is enough voltage to stablize the constant-current source electric current, if worry that AC supply voltage is unstable, during AC supply voltage peak value step-down, LED is bright not, the unitary series of operations number can be reduced to 36 ~ 38 by 39 series connection so, the brightness meeting becomes stable, but the pressure drop meeting of electric current on constant-current source increases, this pressure drop is not luminous on LED, but generate heat on constant-current source, therefore reduced power-efficient.Two LED string of giving an example in Fig. 2 is serially connected with respectively 39 LEDs, during general supply voltage peak reduction the brightness meeting slightly dimmed, but can't extinguish fully.
simultaneously, suppose that described predeterminated voltage scope is a low pressure range and a high pressure range, when power input voltage drops on low pressure range, the input voltage status signal of described input voltage sensing module 10 outputs controls LED all in described LED matrix 40 with more way conducting in parallel for described circuit series parallel structure control module 20, be in Fig. 2, LED in described circuit series parallel structure control module 20 control LED matrixes 40 drives in the mode of two-way parallel connection, gate-controlled switch 55 is off-state, gate-controlled switch 52, 54, 56 and 58 is closure state, first LED branch current in the two-way parallel connection is with single-point line expression, by the high-pressure side gate-controlled switch 52 of flowing through, LED string 53 and gate-controlled switch 54 are to low-pressure end, second LED branch current in the two-way parallel connection is also with single-point line expression, by the high-pressure side gate-controlled switch 56 of flowing through, LED string 57 and gate-controlled switch 58 are to low-pressure end.
when power input voltage drops on high pressure range, the input voltage status signal of described input voltage sensing module 10 outputs controls LED all in described LED matrix 40 with less way conducting in parallel for described circuit series parallel structure control module 20, be in Fig. 2, LED in described circuit series parallel structure control module 20 control LED matrixes 40 drives in the mode of one tunnel parallel connection, at this moment, gate-controlled switch 55 becomes closure state, gate-controlled switch 54 and 56 becomes open-circuit condition, electric current in this LED branch road is represented by dotted lines, by the high-pressure side gate-controlled switch 52 of flowing through, LED string 53, gate-controlled switch 55, LED string 57 and gate-controlled switch 58 are to low-pressure end, wherein gate-controlled switch 52 and gate-controlled switch 58 are the state of conducting always, configuration shares if this drive circuit does not need can change with other multi-segment voltage scope frameworks, switch 52 and switch 58 do not need to make gate-controlled switch so, directly make guiding path all right, although therefore indicated numeral in Fig. 2, but directly be drawn as the guiding path of closure state, can save cost.
in the above control procedure, no matter form what kind of LED branch road path between the high-pressure side of LED matrix 40 and low-pressure end, the operating current that current source 30 offers each LED string is identical, in other words, the variation that is directly proportional with the way in parallel that LED goes here and there of the size of the total current of described current source output, therefore total output current of current source is the twice of total output current during in 53 and 57 series connection of LED string when LED string 53 and LED string 57 are parallel connection, when producing light fixture, will LED go here and there 53 and LED string 57 match, allow both forward conducting voltage is consistent as far as possible, this operation can make current source when two LED connection in series-parallel work, shunting is consistent to the electric current of each LED branch road, current balance type when adding series resistance to strengthen parallel connection in LED string 53 and 57, but this series resistance will reduce power-efficient, if constant-current source is splitted into two parts, respectively put a constant-current source in LED string 53 and 57, still meet above-mentioned patent working method, but can increase cost, and can reduce power-efficient when causing constant-current source is not of uniform size when series connection.
The second embodiment:
Fig. 3 is the current distributing path under arrange schematic diagram and the different series parallel structure of the LED matrix of the second embodiment of the present invention and gate-controlled switch; In conjunction with shown in Figure 3, Fig. 3 is the example that can form three kinds of LED connection in series-parallel combinations in a LED matrix 40, the predeterminated voltage scope is divided into three sections voltage ranges, respectively low pressure range, middle pressure scope and high pressure range, embodiment compares with the first, the present embodiment can reduce power loss that the voltage on the constant-current source 30 causes to improve the overall efficiency of circuit, can also shorten temporal dark space at lower input supply voltage shorting advance LED.in described LED matrix 40, series-parallel switch combination and six LED strings are arranged between high-pressure side and low-pressure end, we are still to give an example in implementation of China, suppose that each LED string is serially connected with respectively 13 LEDs, a LED string is 13 LEDs, two LED strings are 26 LEDs, three LED go here and there 39, by that analogy, the longest LED string is when the situation of six string LED strings in the series connection of single road, LED series connection sum is 78, if worry that supply voltage is unstable, during AC supply voltage peak value step-down, LED is bright not, the LED series connection number of each LED string can be reduced to 12 by 13 series connection so, the brightness meeting is more relatively stable.
when the input supply voltage that detects when input voltage sensing module 10 is positioned at low pressure range, the output-input voltage status signal gives described circuit series parallel structure control module 20 control switch combinations 50 with the mode conducting of LED all in described LED matrix 40 with three tunnel parallel connections, i.e. gate-controlled switch 640 in Fig. 3, 650, 654 and 660 is off-state, gate-controlled switch 610, 612, 620, 652, 622, 630 and 632 is closure state, first LED branch current in three road parallel connection LEDs is represented by dotted lines, by the high-pressure side gate-controlled switch 610 of flowing through, two LED strings are connected in series 26 LEDs that form and arrive low-pressure end through gate-controlled switch 612 again, second LED branch current in three tunnel parallel connections also is represented by dotted lines, by high-pressure side through gate-controlled switch 620 13 LEDs that LED string forms of flowing through, again through gate-controlled switch 652, then 13 LEDs that form through another LED string, then through gate-controlled switch 622 to low-pressure end, the 3rd LED branch current in three tunnel parallel connections also is represented by dotted lines, by high-pressure side 26 LEDs that gate-controlled switch 630, two LED string serial connection form of flowing through, then through gate-controlled switch 632 to low-pressure end.
when the input supply voltage that detects when input voltage sensing module 10 is arranged in the pressure scope, the output-input voltage status signal gives described circuit series parallel structure control module 20 control switch combinations 50 with the mode conducting of LED all in described LED matrix 40 with the two-way parallel connection, it is controlled switch 612, 620, 622, 630 and 652 is off-state, gate-controlled switch 610, 650, 660, 640, 654 and 632 is closure state, first LED branch current in the two-way parallel connection is with single-point line expression, by high-pressure side flow through gate-controlled switch 610 then through 26 LEDs again through gate-controlled switch 650, again through 13 LEDs, arrive low-pressure end finally by gate-controlled switch 660, second LED branch current in the two-way parallel connection be also with single-point line expression, by high-pressure side flow through gate-controlled switch 640 then through 13 LEDs again through gate-controlled switch 654, then through 26 LEDs, finally by gate-controlled switch 632 to low-pressure end.
when the input supply voltage that detects when input voltage sensing module 10 is positioned at high pressure range, the output-input voltage status signal gives described circuit series parallel structure control module 20 control switch combinations 50 with the mode conducting of LED all in described LED matrix 40 with one tunnel parallel connection, gate-controlled switch 612, 620, 640, 630, 660 and 622 is off-state, gate-controlled switch 610, 650, 652, 654 and 632 is closure state, the electric current of all LED of single channel conducting represents with double dot dash line, by high-pressure side flow through gate-controlled switch 610 then through 26 LEDs again through gate-controlled switch 650, again through 13 LEDs, again through gate-controlled switch 652 then through 13 LEDs again through gate-controlled switch 654, again through 26 LEDs, arrive low voltage rail finally by gate-controlled switch 632.
in above-described three kinds of series parallel structure modes, no matter which kind of series parallel structure mode, described circuit series parallel structure control module 20 is all controlled constant-current source 30 operating current of same size is provided to the single LED string in described LED matrix 40, therefore, in the present embodiment, the variation that also is directly proportional to the way in parallel of LED string of the total current size of constant-current source 30 output, when the total current of the constant-current source 30 when in parallel in three paths of LEDs string paths is a paths of LEDs connection in series-parallel three times, the total current of the constant-current source 30 when in parallel in two paths of LED string path is paths of LEDs string path twices when in parallel, so no matter be that several roads are in parallel, electric current in single LED string is all to maintain an identical definite value.
The third embodiment:
Fig. 4 is the current distributing path under arrange schematic diagram and the different series parallel structure of the LED matrix of the third embodiment of the present invention and gate-controlled switch, in conjunction with shown in Figure 4, Fig. 4 is the example that can form three kinds of LED series parallel structure combinations in another kind of LED matrix 40, in Fig. 3, the series LED number of three of the second embodiment kinds of structures is respectively 26, 39 and 78, corresponding conducting voltage ratio is 2:3:6, therefore the low pressure conducting is interval, middle pressure conducting is interval, the voltage range ratio in high pressure conducting interval is roughly 2:(3-2): (6-3)=2:1:3, although so design is more excellent than the first embodiment, but make constant-current source 30 at the different height of efficient meeting of different voltage ranges, for further optimization efficiency, take new series connection number ratio, the number of three kinds of series connection is respectively 26, 52 and 78, so, the ratio of three sections voltage ranges has been exactly 1:1:1, constant-current source 30 is equally high in the efficient of each voltage range, can promote whole power-efficient.
Series-parallel switch combination and six LED strings are arranged between the high-pressure side of LED matrix 40 and low-pressure end in Fig. 4, we suppose that each LED string is serially connected with respectively 26 LEDs, a string have 26, and two strings have 52, and three strings just have 78, and previous embodiments, if it is unstable that supply voltage is worried in puzzlement, LED is bright not when the maximum mains voltage step-down, and the number of single-string LED can being connected so reduces to 25 or 24 series connection by 26 series connection, the brightness meeting is stable, but can lose efficient.
Predeterminated voltage scope in Fig. 4 embodiment also is divided into three sections voltage ranges, is respectively low pressure range, middle pressure scope and high pressure range.when the input supply voltage that detects when input voltage sensing module 10 is positioned at low pressure range, the output-input voltage status signal controls LED all in described LED matrix 40 with the mode conducting of six tunnel parallel connections for described circuit series parallel structure control module 20, controlling corresponding gate-controlled switch makes the electric current in LED matrix 40 mobile by the direction of dotted line, first LED branch current first gone here and there and 712 flow to low-pressure end through a gate-controlled switch again after in parallel by high-pressure side 700 LED that flows through with second LED branch current through a gate-controlled switch again by the high-pressure side 700 LED string 710 of flowing through, in like manner the 3rd LED branch current first gone here and there and 722 flow to low-pressure end through a gate-controlled switch again after in parallel by high-pressure side 700 LED that flows through with the 4th LED branch current through a gate-controlled switch again by the high-pressure side 700 LED string 720 of flowing through, in like manner the 5th LED branch current first gone here and there and 732 flow to low-pressure end through a gate-controlled switch again after in parallel by high-pressure side 700 LED that flows through with the 6th LED branch current through a gate-controlled switch again by the high-pressure side 700 LED string 730 of flowing through, due to identical in the control principle of gate-controlled switch and previous embodiment, just gate-controlled switch is closed different from the combination that disconnects, therefore in the present embodiment, the control details to gate-controlled switch is not described in detail.
when the input supply voltage that detects when input voltage sensing module 10 is arranged in the pressure scope, the output-input voltage status signal controls LED all in described LED matrix 40 with the mode conducting of three tunnel parallel connections for described circuit series parallel structure control module 20, under this kind control mode, circuit series parallel structure control module 20 is controlled corresponding gate-controlled switch makes the electric current in LED matrix 40 flow by single dashdotted direction, first LED branch current by high-pressure side flow through LED string 710 with LED string 720 tandem pathss that form to low-pressure end, second LED branch current by high-pressure side flow through LED string 712 with LED string 730 tandem pathss that form to low-pressure end, the 3rd LED branch current by high-pressure side flow through LED string 722 with LED string 732 tandem pathss that form to low-pressure end.
when the input supply voltage that detects when input voltage sensing module 10 is positioned at high pressure range, the output-input voltage status signal controls LED all in described LED matrix 40 with the mode conducting of two-way parallel connection for described circuit series parallel structure control module 20, under this kind control mode, the circuit series parallel structure is controlled the mould 20 corresponding gate-controlled switches of control makes the electric current in LED matrix 40 mobile by the direction of double dot dash line, first LED branch current is by the high-pressure side LED string 710 of flowing through, LED string 720, flow to low-pressure end behind the path that 730 series connection of LED string form, second LED branch current is by the high-pressure side LED string 712 of flowing through, LED string 722, flow to low-pressure end behind the path that 732 series connection of LED string form.
in above-described three kinds of control modes, no matter which kind of control mode, described control module 20 is all controlled current source 30 and is provided same operating current to the string of the LED in described LED matrix 40, therefore, in the present embodiment, the variation that also is directly proportional to the way in parallel of LED string of the total current size of current source 30 output, when therefore the total current of current source is the two paths of LED connection in series-parallel when six paths of LEDs connection in series-parallel three times, twice when the current source total current when six paths of LEDs connection in series-parallel is three paths of LEDs connection in series-parallel, so no matter be that several roads are in parallel, electric current in single LED string is all to maintain definite value, and voltage range is all take 26 LEDs as a scope, therefore obtain best balanced constant-current source efficient, and then obtain better whole power-efficient, but the number of gate-controlled switch has been Duoed some than the second embodiment, some costs have been increased.
above-described the second embodiment and the third embodiment, embodiment compares with the first, is divided into three sections voltage ranges and can improves power-efficient and power factor, and increasing number of switches can improve hardware cost, when the mode of voltage range two-part can't reach the power-efficient of customer demand and power factor, it is the mode of 3:2:1 that the meeting of intuition develops top the first number in parallel, the roughly direct ratio of number but the upper limit of each supply voltage scope is connected with LED in this scope, be 2:3:6, first paragraph scope namely: second segment scope: the 3rd segment limit=2:(3-2): (6-3)=2:1:3, the distribution of this supply voltage scope is also inhomogeneous, therefore be ready to spend more slightly again under the prerequisite of some costs, just can adopt the mode that in three scopes of the second, number ratio in parallel is 6:3:2, the series connection number ratio of its correspondence is 2:4:6, first paragraph scope namely: second segment scope: the 3rd segment limit=2:(4-2): (6-4)=2:2:2, distributing very evenly of this supply voltage scope.
The switch cost of paying above-mentioned increase obtains uniform voltage range, can reduce maximum pressure drop and total heating above constant-current source, and provide higher merit because of and higher power-efficient.
The present invention also provides a kind of above-mentioned method of work that changes the LED drive unit of series parallel structure with input voltage, comprises the following steps,
Step 1, collection power input voltage compare its critical value from the different voltage ranges of presetting, and according to control signal corresponding to comparative result output;
Step 2, according to LED all in different control signal driving LED matrixes 40 with different series parallel structure conductings, when input voltage is positioned at the minimum voltage scope, control LED all in LED matrix 40 with the mode conducting of multichannel parallel connection; When input voltage is positioned at the ceiling voltage scope, control the mode conducting of LED all in LED matrix multichannel series connection in parallel and with minimum road; Wherein, the number in parallel of described LED reduces with the rising of input voltage.
Further, in described step 2, total current size and the way in parallel in the LED matrix of controlling driven LED matrix of flowing through are directly proportional, and the electric current on the unitary series of operations LED path of flowing through remains on a continuous current scope.
the LED drive circuit that above embodiment of the present invention provides, can be at certain more than specific wattage (for example 5 watts) realize that large merit is because of the usefulness of (for example merit because of greater than 0.8), the efficient of this LED driving power effectively improves simultaneously, and all LED are in the conducting or extinguish together together in period of wave of each power supply string, do not have the difference of dark space, clear zone in fluorescent tube, solve high merit because of, the problem of high efficiency LED drive circuit, and because when the low pressure all LED are conductings together, make the dark space on time shaft significantly shorten, further reduced conventional ADS driving causes the LED light fixture when dc low-voltage stroboscopic problem.
The above is only preferred embodiment of the present invention, not in order to limiting the present invention, all any modifications of doing within the spirit and principles in the present invention, is equal to and replaces and improvement etc., within all should being included in protection scope of the present invention.