CN104519617B - LED driving circuit - Google Patents
LED driving circuit Download PDFInfo
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- CN104519617B CN104519617B CN201310460468.4A CN201310460468A CN104519617B CN 104519617 B CN104519617 B CN 104519617B CN 201310460468 A CN201310460468 A CN 201310460468A CN 104519617 B CN104519617 B CN 104519617B
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Abstract
The invention discloses an LED driving circuit which comprises a direct-current conversion unit, a control driving unit and a signal processing unit. The direct-current conversion unit is controlled by the control driving unit, the signal processing unit is connected with the control driving unit, LED loads can be driven by currents outputted by the direct-current conversion unit, the direct-current conversion unit is provided with an inductor, the signal processing unit comprises a first signal sampling unit, a second signal sampling unit, a third signal sampling unit, a logic operation unit and a comparator, reference signals can be formed after first signals, second signals and third signals are subjected to logic operation by the aid of the logic operation unit, the reference signals and inductive currents of the direct-current conversion unit are compared to one another by the aid of the comparator so that control signals can be outputted, and the product of each first signal and the corresponding third signals is divided by the square of the corresponding second signal to obtain a value of the corresponding reference signal.
Description
【Technical field】
The present invention relates to a kind of LED drive circuit, a kind of especially LED drive circuit of constant current.
【Background technology】
LED light source needs constant-current driving, to guarantee in different input voltages and output voltage（Be equivalent to different loads）Feelings
The concordance of light output under condition, also can ensure that LED light source will drive lead to overheated so that light output is declined because of overcurrent simultaneously
Subtract, shorten lamp life.In prior art, the topology of constant-current drive circuit has isolated topology structure and non-isolated topology knot
Structure.Not in isolated topology, such as reduction voltage circuit and step-up/step-down circuit, because LED load and switch drive be not altogether so that defeated
Go out current sample extremely difficult；Although LED load and switch drive are common ground structures in booster circuit, can conveniently carry out
The current feedback of LED load, however, the sampling of LED load electric current needs in constant-current drive circuit output loop series connection sampling electricity
Resistance, increasing sampling resistor can increase the loss of circuit, it is also desirable to increase electric current outer shroud control, including a reference source and computing
Amplifier, to set peak point current with outputting inductance current peak reference signal so that constant-current drive circuit control is extremely complex.
And in isolated topology, sampled output current needs to increase secondary current sampling A/D chip and respective chip power supply circuits, output electricity
Stream signal arrives primary-side-control chip by opto-coupled feedback, and circuit structure is also extremely complex and high cost, is unfavorable for reducing driving electric
Volume source.A general signal processing circuit is not had can be suitable for different topological realization output constant current controls in prior art yet
System.
On the other hand, power factor specification is also more and more important in the performance of LED drive circuit, many international standard pins
Requirement to LED light source and all clear and definite power factor of LED lamp.Therefore, also usually add power factor school in LED drive circuit
Positive function.For critical current control mode, traditional PFC is to force inductive current peak to follow input electricity
Pressure sinusoidal variations, this can realize input current sinusoidal variations in booster circuit really, but to reduction voltage circuit and buck
Circuit, inductive current peak sinusoidal variations are but not equal to input current sinusoidal variations, and in fact input current is not sine
Ripple, but have certain distortion so that input current total harmonic distortion higher it is impossible to accomplish real PFC.
Therefore, in order to overcome drawbacks described above it is necessary to provide a kind of improved LED drive circuit.
【Content of the invention】
It is an object of the invention to provide a kind of LED drive circuit.
To achieve these goals, the present invention adopts the following technical scheme that：A kind of LED drive circuit, including DC converting
Unit, the control driver element controlling described DC converting unit and the signal processing list connecting described control driver element
Unit, described DC converting unit output current drives LED load, and described DC converting unit has inductance, described signal processing
Unit includes the first signal sampling unit, secondary signal sampling unit, the 3rd signal sampling unit, ALU and ratio
Compared with device, the signal that described first signal sampling unit sampling arrives is the first signal, and described secondary signal sampling unit samples
Signal is secondary signal, and the signal that described 3rd signal sampling unit sampling arrives is the 3rd signal, described first signal, the second letter
Number and the 3rd signal form reference signal after ALU, the inductance of described reference signal and DC converting unit
Electric current passes through the comparison output control signal of comparator, and the value of described reference signal is that the first signal is removed with the product of the 3rd signal
With square obtaining of secondary signal.
Preferably, described secondary signal is DC Variable.
Preferably, described secondary signal sampling unit includes filter circuit.
Preferably, described secondary signal sampling unit and LED drive circuit described in the 3rd signal sampling unit sampling
Input voltage signal.
Preferably, described DC converting unit includes reduction voltage circuit, described first signal sampling unit, secondary signal sampling
Unit and the 3rd signal sampling unit are all sampled the input voltage signal of described LED drive circuit.
Preferably, described first signal sampling unit is identical with the 3rd signal sampling unit, the first signal and the 3rd signal
For identical signal.
Preferably, described DC converting unit includes booster circuit, and described first signal sampling unit gathers described LED and drives
The output voltage signal on galvanic electricity road, described first signal is output voltage signal.
Preferably, described DC converting unit includes step-up/step-down circuit, and described first signal sampling unit gathers described LED
The input and output voltage sum of drive circuit, described first signal is input and output voltage and signal.
Preferably, described signal processing unit also includes two dividers and a multiplicative operator, and described
One signal sampling unit and secondary signal sampling unit connect described first divider respectively so that described first signal with
Secondary signal input the first divider, described secondary signal sampling unit and the 3rd signal sampling unit connect described respectively
Second divider is so that described secondary signal and the 3rd signal input the second divider, described first division arithmetic
Device is connected the input of multiplicative operator respectively with the outfan of the second divider, and the outfan of described multiplicative operator is even
Connect the first input end of described comparator.
Preferably, described signal processing unit also includes two amplitude limiter circuits, and described amplitude limiter circuit is located at described removing respectively
Between method arithmetical unit and described multiplicative operator.
Preferably, described signal processing unit also includes soft starting circuit, and described soft starting circuit is located at described multiplication fortune
Calculate between device and described comparator.
Preferably, described signal processing unit also includes square reciprocal arithmetic unit and multiplicative operator, described second letter
Number sampling unit connects the input of described square reciprocal arithmetic unit, and described secondary signal is after described square of reciprocal arithmetic unit
The inverse of output secondary signal square, the outfan described multiplicative operator of connection of described square of reciprocal arithmetic unit, described first
Signal sampling unit and the 3rd signal sampling unit connect the input of described multiplicative operator respectively, the falling of secondary signal square
Number, the first signal and the 3rd signal are multiplied by multiplicative operator, and the outfan of described multiplicative operator connects described comparison
The first input end of device.
Preferably, described signal processing unit also includes two amplitude limiter circuits, and described amplitude limiter circuit is located at described removing respectively
Between method arithmetical unit and described multiplicative operator.
Preferably, described signal processing unit also includes soft starting circuit, and described soft starting circuit is located at described multiplication fortune
Calculate between device and described comparator.
Preferably, described LED drive circuit also includes connecting the switch element of described DC converting unit, at described signal
Reason unit output cut-off signals, described cut-off signals control the shutoff of described switch element.
Compared to prior art, LED drive circuit of the present invention has the advantage that：Output be can achieve by simple circuit
Constant current and PFC, circuit control part can be with general different topology structure, and due to without sampled output current, energy
Enough reduce the loss of circuit.
【Brief description】
Fig. 1 is the schematic diagram of LED drive circuit of the present invention.
Fig. 2 is the circuit diagram of the first preferred embodiment of LED drive circuit of the present invention.
Fig. 3 is the schematic diagram of another embodiment of ALU of LED drive circuit of the present invention.
Fig. 4 is the circuit diagram of the second preferred embodiment of LED drive circuit of the present invention.
Fig. 5 is the circuit diagram of the 3rd preferred embodiment of LED drive circuit of the present invention.
Fig. 6 is the schematic diagram of the ALU with amplitude limiter circuit of LED drive circuit of the present invention.
Fig. 7 is showing of the ALU of another embodiment with amplitude limiter circuit of LED drive circuit of the present invention
It is intended to.
Fig. 8 is the signal of the ALU with amplitude limiter circuit and soft starting circuit of LED drive circuit of the present invention
Figure.
【Specific embodiment】
Refer to shown in Fig. 1, a kind of LED drive circuit of the present invention, including DC converting unit, control DC converting unit
Control driver element and connect control driver element signal processing unit, DC converting unit output current drive LED
Load, DC converting unit has inductance, signal processing unit include the first signal sampling unit, secondary signal sampling unit,
3rd signal sampling unit, ALU and comparator, the signal that the first signal sampling unit sampling arrives is the first letter
Number, the signal that secondary signal sampling unit samples is secondary signal, and the signal that the 3rd signal sampling unit sampling arrives is the 3rd
Signal, the first signal, secondary signal and the 3rd signal form reference signal after ALU, reference signal with straight
The inductive current of stream converter unit passes through the comparison output control signal of comparator, and the value of reference signal is the first signal and the 3rd
The product of signal square obtains divided by secondary signal.The present invention patrols to the first signal, secondary signal and the 3rd signal
Volume computing, obtains the product of the first signal and secondary signal divided by secondary signal square as reference signal.This reference signal
Reference value as inductive current peak is connected to comparator.Another input of comparator is then inductive current peak sampling,
The comparator upset when inductive current peak exceedes reference value, thus outputing control signals to control driver element, straight to control
The shutoff of stream converter unit.The signal processing unit of the present invention to the mode of signal processing so that the first signal, secondary signal with
And the 3rd the sample circuit of signal can be simpler, and control can also be to input while LED drive circuit constant current output
Electric current carry out PFC.
Specifically, when DC converting unit is reduction voltage circuit, the first signal, secondary signal, the 3rd signal are all sampling
The LED drive circuit input voltage signal arriving.When DC converting unit is booster circuit, voltage raising and reducing circuit etc. circuit,
Secondary signal sampling unit, the 3rd signal sampling unit are all sampled the input voltage signal of LED drive circuit, the first signal sampling
Unit is according to the different signal of different topology samplings.Meanwhile, no matter for which kind of topology, secondary signal is all direct current signal.
In the present invention, using secondary signal sampling unit add filter circuit by the way of by secondary signal sampling unit sample defeated
Entering photovoltaic conversion is direct current signal, in other embodiment, it would however also be possible to employ additive method obtains the secondary signal of direct current.
Refer to shown in Fig. 2, the LED drive circuit 1 of first embodiment of the invention includes DC converting unit 10, controls directly
The control driver element of stream converter unit 10（Non- label）And connecting the signal processing unit 11 controlling driver element, direct current becomes
Change unit 10 output current and drive LED load, DC converting unit 10 has inductance L.DC converting unit 10 includes diode
D, inductance L and output capacitance C.Signal processing unit 11 includes the first signal sampling unit（Non- label）, secondary signal sampling
Unit（Non- label）, the 3rd signal sampling unit（Non- label）, ALU 110 and comparator 112.First signal is adopted
The signal that sample unit sampling arrives is the first signal A, and the signal that secondary signal sampling unit samples is secondary signal B, the 3rd letter
Number signal that sampling unit samples is the 3rd signal C.First signal A, secondary signal B and the 3rd signal C transport through logic
Form reference signal after calculating unit 110.Reference signal be by the first signal A and the 3rd signal C product again divided by secondary signal B
Square obtain.Reference signal exports control with the inductor current signal of DC converting unit 10 by the comparison of comparator 112
Signal processed.Control signal input controls driver element, controls the shutoff of DC converting unit 10, thus controlling DC converting unit
10 constant current outputs and the power factor adjusting DC converting unit 10.In the present embodiment, ALU 110 includes two
1101,1102 and multiplicative operator 1103 of divider.First signal sampling unit and secondary signal sampling unit
Connect the first divider 1101 respectively so that the first signal A inputs the first divider 1101 with secondary signal B.The
Binary signal sampling unit and the 3rd signal sampling unit connects the second divider 1102 respectively so that secondary signal B and
Three signal C input the second divider 1102.First divider 1101 and the outfan of the second divider 1102
Connect the input of multiplicative operator 1103 respectively.The outfan of multiplicative operator 1103 connects the first input of comparator 112
End（Non- label）.In other embodiment, the process realizing the first signal A, secondary signal B and the 3rd signal C can also adopt
Other logical-arithmetic units.For example, referring to shown in Fig. 3, signal processing unit 410 includes square reciprocal arithmetic unit 4101 and multiplication fortune
Calculate device 4102.Wherein secondary signal sampling unit connects the input of square reciprocal arithmetic unit 4101, square reciprocal arithmetic unit
4101 outfan connects multiplicative operator 4102, and the first signal sampling unit and the 3rd signal sampling unit connect multiplication respectively
Arithmetical unit 4102, square being taken advantage of by multiplicative operator 4102 of the inverse of the first signal A, the 3rd signal C and secondary signal B
Method computing, thus obtain the signal obtaining that square is divided by of the product of the first signal A and the 3rd signal C and secondary signal B.
In first embodiment, DC converting unit 10 includes reduction voltage circuit, the first signal sampling unit, secondary signal sampling
Unit and the 3rd signal sampling unit all connect the input of LED drive circuit 1, with the input electricity of LED drive circuit 1 of sampling
Pressure Vin.First signal A, secondary signal B, the 3rd signal C are all LED drive circuit 1 input voltage signal sampling.Wherein,
First signal sampling unit is identical with the 3rd signal sampling unit, and sampling identical signal obtains the first signal A and the 3rd signal
C, then inputs the first divider 1101 and the second divider 1102 respectively.Secondary signal sampling unit and first,
Between 3rd signal sampling unit, there is divider resistance R2.First signal sampling unit and the 3rd signal sampling unit have partial pressure
Resistance R3, secondary signal sampling unit includes divider resistance R1, R2 and the R3 being connected in series and filter circuit 113.Filtered electrical
Road 113 includes resistance R4 and filter capacitor C1.Divider resistance R3 one end is grounded.Secondary signal sampling unit one end connects LED and drives
The input on galvanic electricity road 1, the other end connects the second letter of the first divider 1101 and the second divider 1102 respectively
Number input（Non- label）.First divider 1101 also has the first signal input part（Non- label）, the second division arithmetic
Device 1102 also has the 3rd signal input part（Non- label）, the first signal input part and secondary signal input are both connected to partial pressure
Between resistance R2 and divider resistance R3.First divider 1101 and the second divider 1102 are also respectively provided with the second letter
Number input（Non- label）, the secondary signal input of the first divider 1101 and the second divider 1102 is by filter
After wave circuit 113, it is connected between divider resistance R2 and divider resistance R3.In other embodiment, secondary signal sampling unit
Can not have divider resistance R1, R2, the setting of divider resistance R1, R2, R3 can change as needed.So, sampling
One signal A is the input voltage signal of LED drive circuit 2, and secondary signal B is that the input voltage signal of LED drive circuit 2 passes through
The direct current signal that filter circuit 113 obtains, the 3rd signal C is the input voltage signal of LED drive circuit 1.
LED drive circuit 1 also includes the switch element Q controlling DC converting unit 10 to switch off and on, signal processing list
Unit 11 also includes sampling resistor Rs, in the present embodiment, sampling resistor Rs one end connecting valve element Q, and the other end is grounded.Comparator
112 first input end（Non- label）Connect reference signal, the second input（Non- label）It is connected to sampling resistor Rs and switch
So that inductor current signal inputs the second input, thus controlling the inductive current peak of DC converting unit 10 between element Q
Value.In the present embodiment, the first input end of comparator 112 is the negative pole of comparator 112, and the second input is comparator 112
Positive pole.It is also possible to the first input end of comparator 112 is set to positive pole in other embodiment, the second input is set to bear
Pole, i.e. the positive pole of reference signal input comparator 112, the negative pole of inductor current signal input comparator 112.
In the present embodiment, input voltage vin carries out partial pressure, wherein resistance R2 and resistance through divider resistance R1, R2 and R3
Voltage Feedback between R3 is the first signal A and the 3rd signal C.Because input voltage vin is the signal of sinusoidal variations, therefore
One signal A and the 3rd signal C is also corresponding sinusoidal variations.Voltage between resistance R1 and resistance R2 is through resistance R4 and electric capacity C1
It is filtered, be secondary signal B average back.The principle of resistance R4 and the selection of electric capacity C1 parameter is neither to affect resistance
The partial pressure of R1, R2 and R3, filtering bandwidth is very little simultaneously, such as 20Hz, only direct current signal is fed back to secondary signal B.The
Binary signal B is DC Variable.The ratio of the first signal A and secondary signal B and the ratio warp of the 3rd signal C and secondary signal B
The reference signal of inductive current peak is obtained, its expression formula is after crossing multiplicative operator 1103：
Wherein K1 is design parameter, and the expression formula of design parameter K1 is：
It can be seen that reference signal is with square change sinusoidal with input voltage vin same phase, the amplitude of change is one and consolidates
Definite value, unrelated with input voltage vin and output voltage Vo.The expression formula of input current Iin is：
Wherein Vinpk is crest voltage.It can be seen that input current Iin and input voltage vin are synchronous sinusoidal variables, this
Mean that input current Iin and input voltage vin are homophase sinusoidal variations, input impedance characteristic is close to pure resistance.Therefore logical
The control signal crossing the signal processing unit generation of the present invention can be good at controlling LED drive circuit 1 constant current output, again simultaneously
PFC can be carried out, make input current Iin and input voltage vin homophase sinusoidal variations.
Refer to shown in Fig. 4, the LED drive circuit 2 of second embodiment of the invention includes DC converting unit 20, controls directly
The control driver element of stream converter unit 20（Non- label）And connecting the signal processing unit 21 controlling driver element, direct current becomes
Change unit 20 output current and drive LED load, DC converting unit 20 has inductance L.DC converting unit 20 includes diode
D, inductance L and output capacitance C.Signal processing unit 21 includes the first signal sampling unit（Non- label）, secondary signal sampling
Unit（Non- label）, the 3rd signal sampling unit（Non- label）, ALU 210 and comparator 212.First signal is adopted
The signal that sample unit sampling arrives is the first signal A, and the signal that secondary signal sampling unit samples is secondary signal B, the 3rd letter
Number signal that sampling unit samples is the 3rd signal C.First signal A, secondary signal B and the 3rd signal C transport through logic
Form reference signal after calculating unit 210.Reference signal be by the first signal A and the 3rd signal C product again divided by secondary signal B
Square obtain.Reference signal exports control with the inductor current signal of DC converting unit 20 by the comparison of comparator 212
Signal processed.Control signal input controls driver element, controls the shutoff of DC converting unit 20, thus controlling DC converting unit
20 constant current outputs and the power factor adjusting DC converting unit 20.In the present embodiment, ALU 210 includes two
2101,2102 and multiplicative operator 2103 of divider.First signal sampling unit and secondary signal sampling unit
Connect the first divider 2101 respectively so that the first signal A inputs the first divider 2101 with secondary signal B.The
Binary signal sampling unit and the 3rd signal sampling unit connects the second divider 2102 respectively so that secondary signal B and
Three signal C input the second divider 2102.First divider 2101 and the outfan of the second divider 2102
Connect the input of multiplicative operator 2103 respectively.The outfan of multiplicative operator 2103 connects the first input of comparator 212
End（Non- label）.In other embodiment, the process realizing the first signal A, secondary signal B and the 3rd signal C can also adopt
Other logical-arithmetic units, for example, referring to shown in Fig. 3, using square reciprocal arithmetic unit and multiplicative operator, wherein secondary signal is adopted
Sample unit connects the input of square reciprocal arithmetic unit, and the outfan of square reciprocal arithmetic unit connects multiplicative operator, the first letter
Number sampling unit and the 3rd signal sampling unit connect multiplicative operator respectively, the first signal A, the 3rd signal C and the second letter
The inverse of number B square multiplying is done by multiplicative operator, thus obtain the product of the first signal A and the 3rd signal C with
The signal obtaining that square is divided by of secondary signal B.
DC converting unit 20 is booster circuit, and the first signal sampling unit gathers the output voltage letter of LED drive circuit 2
Number.Secondary signal sampling unit and the input voltage signal of the 3rd signal sampling unit collection LED drive circuit 2.First signal
One end of sampling unit is in parallel with output capacitance C, and the other end connects the first signal input part of the first divider 2101（Not
Label）.In the present embodiment, the first signal sampling unit includes divider resistance R5 and divider resistance R6, partial pressure in other embodiment
The determining using as needed of resistance.Secondary signal sampling unit includes divider resistance R1, R2, R3 and filter circuit 213.
3rd signal sampling unit includes divider resistance R3.Between secondary signal sampling unit and the 3rd signal sampling unit, there is partial pressure
Resistance R2.Secondary signal sampling unit one end connects the input of LED drive circuit 2 with sampled input voltage Vin, and the other end divides
Do not connect the first divider 2101 and the secondary signal input of the second divider 2102（Non- label）.3rd signal
Sampling unit connects the 3rd signal input part of the second divider 2102（Non- label）.The of second divider 2102
Three signal input parts are connected between divider resistance R3 and divider resistance R2.I.e. the first signal A is the defeated of DC converting unit 20
Go out voltage signal, secondary signal B is that the input voltage signal of LED drive circuit 2 is believed by the direct current that filter circuit 213 obtains
Number, the 3rd signal C is the input voltage signal of LED drive circuit 2.
LED drive circuit 2 also includes the switch element Q controlling DC converting unit 20 to switch off and on, signal processing list
Unit 21 also includes sampling resistor Rs, in the present embodiment, sampling resistor Rs one end connecting valve element Q, and the other end is grounded.Comparator
212 first input end（Non- label）Connect reference signal, the second input（Non- label）It is connected to sampling resistor Rs and switch
So that inductor current signal inputs the second input, thus controlling the inductive current peak of DC converting unit 20 between element Q
Value.In the present embodiment, the first input end of comparator 212 is the negative pole of comparator 212, and the second input is comparator 212
Positive pole.It is also possible to the first input end of comparator 212 is set to positive pole in other embodiment, the second input is set to bear
Pole, i.e. the positive pole of reference signal input comparator 212, the negative pole of inductor current signal input comparator 212.
In the present embodiment, input voltage vin carries out partial pressure through resistance R1, R2 and R3, between resistance R2 and resistance R3
Voltage Feedback forms the 3rd signal C, and this is the voltage signal of a sinuous pulsation.Voltage between resistance R1 and resistance R2 passes through
After resistance R4 and filter capacitor C1 becomes low ripple direct current, feedback forms secondary signal B.Output voltage Vo is through resistance R5 and electricity
Resistance R6 carries out partial pressure feedback and forms the first signal A.The ratio of the first signal A and secondary signal B and the 3rd signal C and second letter
The ratio of number B obtains the reference signal of current peak after multiplier.Reference signal expresses formula:
Wherein K2 is design parameter, and the expression formula of K2 is：
.
Reference signal is the sinusoidal quantity of and the change of input voltage vin same phase, and amplitude and output voltage Vo are directly proportional,
It is inversely proportional to input voltage vin peak value.The expression formula of input current Iin is：
Input current Iin is sinusoidal variations, and amplitude size and input voltage vin peak value are inversely proportional to, and become with output voltage Vo
Direct ratio, there is not input current Vin dead band in booster circuit, therefore can realize extraordinary power factor, make input impedance yet
Assume pure resistance characteristic.Output current Io expression formula is：
Output current Io assumes Sine-squared change, and amplitude is only relevant with design parameter K2 and sampling resistor Rs, is not subject to
Input voltage vin and the impact of output voltage Vo change.Meansigma methodss in power frequency period for output current Io can be equivalent to flow through
The flip-flop of LED load, its expression formula is：
It can be seen that the LED drive circuit 2 in the present embodiment makes sample circuit very to the processing mode of sampled signal
And the control signal after signal processing unit processes can be good at realizing the defeated of LED drive circuit 2 simply, conveniently,
Go out constant current and PFC.
Refer to shown in Fig. 5, the LED drive circuit 3 of third embodiment of the invention includes DC converting unit 30, controls directly
The control driver element of stream converter unit 30（Non- label）And connecting the signal processing unit 31 controlling driver element, direct current becomes
Change unit 30 output current and drive LED load, DC converting unit 30 has inductance L.DC converting unit 30 includes diode
D, inductance L and output capacitance C.Signal processing unit 31 includes the first signal sampling unit（Non- label）, secondary signal sampling
Unit（Non- label）, the 3rd signal sampling unit（Non- label）, ALU 310 and comparator 312.First signal is adopted
The signal that sample unit sampling arrives is the first signal A, and the signal that secondary signal sampling unit samples is secondary signal B, the 3rd letter
Number signal that sampling unit samples is the 3rd signal C.First signal A, secondary signal B and the 3rd signal C transport through logic
Form reference signal after calculating unit 310.Reference signal be by the first signal A and the 3rd signal C product again divided by secondary signal B
Square obtain.Reference signal exports control with the inductor current signal of DC converting unit 30 by the comparison of comparator 312
Signal processed.Control signal input controls driver element, controls the shutoff of DC converting unit 30, thus controlling DC converting unit
30 constant current outputs and the power factor adjusting DC converting unit 30.In the present embodiment, ALU 310 includes two
3101,3102 and multiplicative operator 3103 of divider.First signal sampling unit and secondary signal sampling unit
Connect the first divider 3101 respectively so that the first signal A inputs the first divider 3101 with secondary signal B.The
Binary signal sampling unit and the 3rd signal sampling unit connects the second divider 3102 respectively so that secondary signal B and
Three signal C input the second divider 3102.First divider 3101 and the outfan of the second divider 3102
Connect the input of multiplicative operator 3103 respectively.The outfan of multiplicative operator 3103 connects the first input of comparator 312
End（Non- label）.In other embodiment, the process realizing the first signal A, secondary signal B and the 3rd signal C can also adopt
Other logical-arithmetic units, for example, referring to shown in Fig. 3, using square reciprocal arithmetic unit and multiplicative operator, wherein secondary signal is adopted
Sample unit connects the input of square reciprocal arithmetic unit, and the outfan of square reciprocal arithmetic unit connects multiplicative operator, the first letter
Number sampling unit and the 3rd signal sampling unit connect multiplicative operator respectively, the first signal A, the 3rd signal C and the second letter
The inverse of number B square multiplying is done by multiplicative operator, thus obtain the product of the first signal A and the 3rd signal C with
The signal obtaining that square is divided by of secondary signal B.
DC converting unit 30 is voltage raising and reducing circuit, and the first signal sampling unit gathers the input electricity of LED drive circuit 3
Pressure Vin and output voltage Vo sum.Secondary signal sampling unit and the 3rd signal sampling unit gather the defeated of LED drive circuit 3
Enter voltage signal.One end of first signal sampling unit is connected to the near end of output capacitance C, and the other end connects the first division fortune
Calculate the first signal input part of device 3101（Non- label）.In the present embodiment, the first signal sampling unit include divider resistance R5 and
Divider resistance R6, in other embodiment, divider resistance determines using as needed.Secondary signal sampling unit includes partial pressure
Resistance R1, R2, R3 and filter circuit 313.3rd signal sampling unit includes divider resistance R3.Secondary signal sampling unit and
Between 3rd signal sampling unit, there is divider resistance R2.Secondary signal sampling unit one end connects the input of LED drive circuit 3
With sampled input voltage Vin, the other end connects the of the first divider 3101 and the second divider 3102 respectively at end
Binary signal input（Non- label）.3rd signal sampling unit connects the 3rd signal input part of the second divider 3102
（Non- label）.3rd signal input part of the second divider 3102 is connected between divider resistance R3 and divider resistance R2.
I.e. the first signal A is the output voltage signal of DC converting unit 30, and secondary signal B is the input voltage letter of LED drive circuit 3
Number direct current signal being obtained by filter circuit 313, the 3rd signal C is the input voltage signal of LED drive circuit 3.
LED drive circuit 3 also includes the switch element Q controlling DC converting unit 30 to switch off and on, signal processing list
Unit 31 also includes sampling resistor Rs, in the present embodiment, sampling resistor Rs one end connecting valve element Q, and the other end is grounded.Comparator
312 first input end（Non- label）Connect reference signal, the second input（Non- label）It is connected to sampling resistor Rs and switch
So that inductor current signal inputs the second input, thus controlling the inductive current peak of DC converting unit 30 between element Q
Value.In the present embodiment, the first input end of comparator 312 is the negative pole of comparator 312, and the second input is comparator 312
Positive pole.It is also possible to the first input end of comparator 312 is set to positive pole in other embodiment, the second input is set to bear
Pole, i.e. the positive pole of reference signal input comparator 312, the negative pole of inductor current signal input comparator 312.
In the present embodiment, input voltage vin carries out partial pressure by resistance R1 and R2, and secondary signal B and the 3rd signal C pass through
Resistance R1, R2 and R3 carry out partial pressure input voltage vin, and the 3rd signal C is the sinusoidal variations magnitude of voltage between resistance R2 and R3,
And the DC Variable that secondary signal B is then obtained after resistance R4 and filter capacitor C1 filtering.The input of the first signal A is derived from
The positive pole of output capacitance C, the first signal A is input and output voltage sum, that is,（Vinpk*sinα+Vo）.Input voltage vin with
Output voltage this voltage signal of Vo sum carries out partial pressure feedback by resistance R5 and R6 and forms the first signal A.First signal A and
The ratio of the ratio of secondary signal B and the 3rd signal C and secondary signal B obtains inductive current peak after multiplicative operator
Reference signal.The expression formula of reference signal is：
Wherein K2 is design parameter, and the expression formula of K2 is：
.
It can be seen that reference signal is not simple sinusoidal variations, it is not a fixed value, and and input
Voltage Vin and output voltage Vo is relevant.The expression formula of input current Iin is：
The input current of input current Iin expression formula and reduction voltage circuit is closely similar, and simply design parameter is different, input
Electric current Iin is also sinusoidal variations, and amplitude size and input voltage vin peak value are inversely proportional to, and output voltage Vo is directly proportional, and rises pressure drop
There is not input current Iin dead band in volt circuit, therefore can realize extraordinary power factor, makes input impedance assume pure resistance special
Property.Output current Io expression formula is：
Output current Io assumes Sine-squared change, and amplitude is only relevant with design parameter K2 and sampling resistor Rs, is not subject to
Input voltage vin and the impact of output voltage Vo change.Meansigma methodss in power frequency period for output current Io can be equivalent to flow through
The flip-flop of LED load, its expression formula is：
It can be seen that the LED drive circuit 3 in the present embodiment makes sample circuit very to the processing mode of sampled signal
And the control signal after signal processing unit processes can be good at realizing the defeated of LED drive circuit 3 simply, conveniently,
Go out constant current and PFC.
Further, all introduce division arithmetic in the signal processing unit in three embodiments.In division arithmetic, when point
When female smaller, division can obtain a very big value it is possible to computing circuit saturation or work can be led to abnormal,
Therefore, for making LED drive circuit more stable, amplitude restriction can be carried out to division arithmetic, it is to avoid the feelings of height output occurred
Condition.On the other hand, LED drive circuit is it is also desirable that be capable of soft start, it is to avoid the ginseng of inductive current peak in upper electricity
Examine signal and be constantly in too high level, lead to output current overshoot, or even power device can be damaged, solution can add
Enter soft open circuit so that inductive current peak reference signal upper electricity certain time in gradually rise, such inductive current peak
Also can slowly become big therewith, be conducive to circuit start.Refer to shown in Fig. 6, as needed, signal processing unit can also include
Two amplitude limiter circuits.Amplitude limiter circuit is located between divider and multiplicative operator respectively.In other embodiment, refer to figure
Shown in 7, when ALU employing square reciprocal arithmetic unit, amplitude limiter circuit is located at square reciprocal arithmetic unit and multiplying
Between device.Refer to shown in Fig. 8, as needed, signal processing unit can also include soft starting circuit.Soft starting circuit is located at
Between multiplicative operator and comparator.Add soft starting circuit can avoid excessive in startup snap switch electric current, thus ensureing
Output current will not overshoot, even damage power device.
Claims (14)
1. a kind of LED drive circuit, including DC converting unit, control described DC converting unit control driver element and
Connect the described signal processing unit controlling driver element, described DC converting unit output current drives LED load, described straight
Stream converter unit has inductance it is characterised in that described signal processing unit includes the first signal sampling unit, secondary signal is adopted
Sample unit, the 3rd signal sampling unit, ALU and comparator, described secondary signal sampling unit and the 3rd letter
Number sampling unit is sampled the input voltage signal of described LED drive circuit, and LED described in described first signal sampling unit sampling drives
The input voltage signal on galvanic electricity road or the output voltage signal or the collection described LED drive that gather described LED drive circuit
The input and output voltage sum on galvanic electricity road, the signal that described first signal sampling unit sampling arrives is the first signal, described second
The signal that signal sampling unit sampling arrives is secondary signal, and the signal that described 3rd signal sampling unit sampling arrives is the 3rd letter
Number, described first signal, secondary signal and the 3rd signal form reference signal after ALU, described reference letter
Number pass through the comparison output control signal of comparator with the inductive current of DC converting unit, the value of described reference signal is first
The product of signal and the 3rd signal square obtains divided by secondary signal.
2. LED drive circuit as claimed in claim 1 is it is characterised in that described secondary signal is DC Variable.
3. LED drive circuit as claimed in claim 2 is it is characterised in that described secondary signal sampling unit includes filter circuit.
4. LED drive circuit as claimed in claim 1 is it is characterised in that described DC converting unit includes reduction voltage circuit, institute
State the first signal sampling unit, secondary signal sampling unit and the 3rd signal sampling unit all to sample described LED drive circuit
Input voltage signal.
5. LED drive circuit as claimed in claim 4 is it is characterised in that described first signal sampling unit and the 3rd signal
Sampling unit is identical, and the first signal and the 3rd signal are identical signal.
6. LED drive circuit as claimed in claim 1 is it is characterised in that described DC converting unit includes booster circuit, institute
State the output voltage signal that the first signal sampling unit gathers described LED drive circuit, described first signal is believed for output voltage
Number.
7. LED drive circuit as claimed in claim 1 is it is characterised in that described DC converting unit includes step-up/step-down circuit,
Described first signal sampling unit gathers the input and output voltage sum of described LED drive circuit, and described first signal is input
Output voltage and signal.
8. LED drive circuit as claimed in claim 1 is it is characterised in that described signal processing unit also includes first, second
Divider and a multiplicative operator, described first signal sampling unit and secondary signal sampling unit connect institute respectively
State the first divider so that described first signal and secondary signal input the first divider obtain the first signal divided by
Secondary signal, described secondary signal sampling unit and the 3rd signal sampling unit connect described second divider respectively, make
Obtain described secondary signal and obtain the 3rd signal divided by secondary signal with the 3rd signal input the second divider, described first removes
Method arithmetical unit and the outfan of the second divider are connected the input of multiplicative operator respectively, described multiplicative operator defeated
Go out the first input end that end connects described comparator.
9. LED drive circuit as claimed in claim 8 is it is characterised in that described signal processing unit also includes two amplitude limits
Circuit, described amplitude limiter circuit is located between described divider and described multiplicative operator respectively.
10. LED drive circuit as claimed in claim 9 is it is characterised in that described signal processing unit also includes soft start electricity
Road, described soft starting circuit is located between described multiplicative operator and described comparator.
11. LED drive circuits as claimed in claim 1 are it is characterised in that described signal processing unit also includes a square inverse
Arithmetical unit and multiplicative operator, described secondary signal sampling unit connects the input of described square reciprocal arithmetic unit, described
Secondary signal exports the inverse of secondary signal square after described square of reciprocal arithmetic unit, described square of reciprocal arithmetic unit defeated
Go out end and connect described multiplicative operator, described first signal sampling unit and the 3rd signal sampling unit connect described multiplication respectively
The input of arithmetical unit, the inverse of secondary signal square, the first signal and the 3rd signal are multiplied by multiplicative operator, described
The outfan of multiplicative operator connects the first input end of described comparator.
12. LED drive circuits as claimed in claim 11 are it is characterised in that described signal processing unit also includes a limit
Width circuit, described amplitude limiter circuit is located between described square of reciprocal arithmetic unit and described multiplicative operator.
13. LED drive circuits as claimed in claim 12 are it is characterised in that described signal processing unit also includes soft start
Circuit, described soft starting circuit is located between described multiplicative operator and described comparator.
14. LED drive circuits as claimed in claim 1 are it is characterised in that described LED drive circuit is also included described in connection
The switch element of DC converting unit, described signal processing unit exports cut-off signals, and described cut-off signals control described switch
The shutoff of element.
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Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2011120374A (en) * | 2009-12-03 | 2011-06-16 | Shindengen Electric Mfg Co Ltd | Constant current power supply device |
| CN102938953A (en) * | 2012-10-18 | 2013-02-20 | 上海晶丰明源半导体有限公司 | Average linear LED (Light Emitting Diode) drive circuit |
| CN103327675A (en) * | 2012-03-23 | 2013-09-25 | 国钰电子(北海)有限公司 | LED driving system and method |
| CN203554743U (en) * | 2013-09-29 | 2014-04-16 | 欧普照明股份有限公司 | LED drive circuit |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| KR101337349B1 (en) * | 2012-03-21 | 2013-12-06 | 주식회사 동운아나텍 | Light Driving Apparatus and Method thereof |
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Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2011120374A (en) * | 2009-12-03 | 2011-06-16 | Shindengen Electric Mfg Co Ltd | Constant current power supply device |
| CN103327675A (en) * | 2012-03-23 | 2013-09-25 | 国钰电子(北海)有限公司 | LED driving system and method |
| CN102938953A (en) * | 2012-10-18 | 2013-02-20 | 上海晶丰明源半导体有限公司 | Average linear LED (Light Emitting Diode) drive circuit |
| CN203554743U (en) * | 2013-09-29 | 2014-04-16 | 欧普照明股份有限公司 | LED drive circuit |
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