CN207354677U - Led drive circuit - Google Patents
Led drive circuit Download PDFInfo
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- CN207354677U CN207354677U CN201721309944.2U CN201721309944U CN207354677U CN 207354677 U CN207354677 U CN 207354677U CN 201721309944 U CN201721309944 U CN 201721309944U CN 207354677 U CN207354677 U CN 207354677U
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Abstract
This application discloses LED drive circuit.The LED drive circuit is used to drive the first LED light and the second LED light, including：First linear constant current circuit, including be connected to the first end of feeder ear, be connected to the first LED light anode second end and be connected to the second LED light cathode the 3rd end；And second linear constant current circuit, first end including the cathode that is connected to the second LED light and the second end being connected to the ground, wherein, first linear constant current circuit selects one of the first current path and the 3rd current path, first current path is located between the first end and second end of the first linear constant current circuit, 3rd current path is located between the 3rd end and the second end of the first linear constant current circuit, second linear constant current circuit selectively turns on or disconnects the second current path, and the second current path is located between the first end and second end of the second linear constant current circuit.The LED drive circuit reduces the parameter request of input capacitance using the switching of the connection mode of LED load.
Description
Technical field
LED lighting technology is the utility model is related to, more particularly, to LED drive circuit.
Background technology
LED (light emitting diode) has the excellent of small, energy saving, long lifespan, high brightness and environmental protection relative to conventional light source
Point, therefore it is widely used for indoor and outdoors illumination.
The brightness of LED light is related to driving current, and corresponding drive scheme is Linear Driving scheme and switch drive scheme.
The mode of linear regulation transistor is respectively adopted in the two and the mode of switch controlling transistor adjusts driving current.
Fig. 1 shows the schematic circuit of LED drive circuit according to prior art.As shown in the figure, LED drive circuit
100 include ac current source 101, rectifier bridge 102, input capacitance Cin, current sampling resistor Rs, linear constant current circuit 110.It is whole
Bridge 102 is flowed to be used for AC rectification into direct current.Input capacitance Cin carries out smothing filtering.Two output terminals of rectifier bridge 102
Between input voltage vin is provided.LED light 103 is connected in series in rectifier bridge with linear constant current circuit 110 and current sampling resistor Rs
Between 102 two output terminals.
Linear constant current circuit 110 includes power tube M10 and amplifier 111.Amplifier 111 obtains current sampling resistor Rs
Current sampling signal compared with reference voltage Vref, drive signal, control power tube M10 are produced according to the difference of the two
In the driving current that flows through.After circuit stability, the value for the driving current that linear constant current circuit 100 controls is Vref/Rs.
In above-mentioned LED drive circuit, the signal of input is the signal for exchanging 50Hz/60Hz, it is necessary to there is big input
Capacitance Cin, causes the increase of circuit volume.Input capacitance short life is additionally, since, therefore shortens integral LED drive circuit
Service life.
Utility model content
In view of the above problems, the purpose of this utility model is to provide LED drive circuit, wherein, by switching LED load
Connection mode reduce the parameter request of input capacitance, so as to reduce circuit volume and improve reliability and service life.
One side according to the present utility model, there is provided a kind of LED drive circuit, for driving the first LED light and the 2nd LED
Lamp, including：First linear constant current circuit, including be connected to the first end of feeder ear, be connected to the first LED light anode second
Hold and be connected to the 3rd end of the cathode of the second LED light；And second linear constant current circuit, including it is connected to the second LED light
Cathode first end and the second end that is connected to the ground, wherein, first linear constant current circuit selects the first current path
One of with the 3rd current path, first current path be located at first linear constant current circuit first end and second end it
Between, the 3rd current path is located between the 3rd end and the second end of first linear constant current circuit, and described second is linear
Constant-current circuit selectively turns on or disconnects the second current path, and second current path is located at second linear constant current electricity
Between the first end and second end on road.
Preferably, first linear constant current circuit and second linear constant current circuit are respectively according to the feeder ear
Input voltage selects current path so that first LED light and second LED light are switched in parallel connect according to input voltage
One of connect and be connected in series.
Preferably, further include：Diode, its anode are connected to the cathode of second LED light, its cathode is connected to described
3rd end of the first linear constant current circuit.
Preferably, first linear constant current circuit includes：First linear constant flow module, it is linear permanent to be connected to described first
Between the first end and second end of current circuit, for providing the first current path；Third linear constant flow module, is connected to described
Between 3rd end of one linear constant current circuit and second end, for providing the 3rd current path；And the first path selecting module,
It is connected with the described first linear constant flow module and the 3rd constant-current control module, for selecting current path, wherein, in institute
When stating the input voltage of feeder ear and being less than or equal to predetermined value, the first path selecting module disconnects the 3rd current path,
And conducting first current path, when the input voltage of the feeder ear is more than predetermined value, the first path selection
Module disconnects first current path, and conducting the 3rd current path.
Preferably, second linear constant current circuit includes：Second linear constant current module, it is linear permanent to be connected to described second
Between the first end and second end of current circuit, for providing the second current path；Alternate path selecting module, with second line
Property constant flow module is connected, for selecting current path, wherein, it is less than or equal to predetermined value in the input voltage of the feeder ear
When, the alternate path selecting module turns on second current path, is more than predetermined value in the input voltage of the feeder ear
When, the alternate path selecting module disconnects second current path.
Preferably, the described first linear constant flow module, the second linear constant current module and the third linear constant current mould
Block includes respectively：Power tube, for controlling the current value of corresponding current path；And amplifier, for by reference voltage with
Current sampling signal compares to produce the drive signal of the power tube.
Preferably, first linear constant current circuit further includes：Current sampling resistor, positioned at first current path and
On the common path of 3rd current path, the first path selecting module is the current sampling resistor.
Preferably, the reference voltage of amplifier is less than the third linear constant flow module in the described first linear constant flow module
The reference voltage of middle amplifier.
Preferably, first linear constant current circuit further includes：First current sampling resistor, with first linear constant current
Mould power tube in the block is connected in series, and first node between provides the first current sampling signal；And the 3rd electric current
Power tube in sampling resistor, with the third linear constant flow module is connected in series, and the 3rd node between provides the
Three current sampling signals, wherein, the amplified signal of the 3rd current sampling signal is superimposed by the first path selecting module
On the current sampling signal or reference voltage of the described first linear constant flow module amplifier.
Preferably, the first path selecting module includes：It is connected in series in the first node and the 3rd node
Between the first feedback resistance and amplification module, wherein, the current sampling signal of the first linear constant flow module amplifier takes
Fourth node between first feedback resistance and the amplification module.
Preferably, when the 3rd current path turns on, the amplification module is by the 3rd current sampling signal
Amplified signal is applied in the fourth node as control signal, and the control signal is more than the described first linear constant flow module
The reference voltage of middle amplifier, so as to disconnect first current path.
Preferably, second linear constant current circuit further includes：Second current sampling resistor, with second linear constant current
Mould power tube in the block is connected in series, and section point between provides the second current sampling signal, wherein, described second
Path selecting module produces control signal according to the voltage sampling signal of the input voltage, and the control signal is superimposed
On the current sampling signal or reference voltage of the second linear constant current module amplifier.
Preferably, the alternate path selecting module includes：First divider resistance and the second divider resistance, are connected in series in
Between the first end and second end of second linear constant current circuit, and first divider resistance and second partial pressure electricity
The 5th node between resistance provides the voltage feedback signal for being used for characterizing the input voltage；It is connected in series section point and the 5th
Voltage comparator and the second feedback resistance between node, wherein, the electric current of amplifier is adopted in the second linear constant current module
Sample signal is derived from the 6th node between second feedback resistance and the voltage comparator, and the voltage comparator is by described in
Voltage feedback signal is compared with reference voltage to obtain control signal so that small in the voltage sampling signal of the input voltage
When the reference voltage, the alternate path selecting module turns on second current path, in the electricity of the input voltage
When pressure sampled signal is more than or equal to the reference voltage, the alternate path selecting module disconnects second current path.
Preferably, the alternate path selecting module includes：3rd divider resistance and the 4th divider resistance, are connected in series in
Between the second end of the cathode of the diode and second linear constant current circuit, wherein, the 3rd divider resistance and
The 7th node between four divider resistances provides the voltage feedback signal for the cathode voltage for being used to characterize the diode, as institute
State reference voltage.
Another aspect according to the present utility model, there is provided a kind of control method for LED drive circuit, for driving the
One LED light and the second LED light, including：When the input voltage of feeder ear is less than or equal to predetermined value, use the first current path for
First LED light provides the first electric current, and the second current path provides the second electric current for second LED light so that institute
State the first LED light and the second LED light parallel operation；And when the input voltage of feeder ear is more than predetermined value, using
Three current paths provide the 3rd electric current for first LED light and second LED light so that the first LED and described
Two LED light are connected in series.
Preferably, first is set respectively on the first to the 3rd current path to third linear constant flow module, to control respectively
Make the current value of the first to the 3rd electric current, wherein, first current path successively via the described first linear constant flow module and
First LED light, second current path is successively via second LED light and the second linear constant current module, institute
The 3rd current path is stated to pass through due to second LED light, the third linear constant flow module and first LED light successively.
Preferably, the described first to the 3rd constant-current control module respectively by the current sampling signal of the first to the 3rd electric current with
Reference voltage compares, to control the current value of the first to the 3rd electric current.
Preferably, it is respective to third linear flow control module according to described first according to the input voltage of the feeder ear
Conducting and off-state, so as to fulfill first LED light and second LED light be connected in series and be connected in parallel cut
Change.
Preferably, the described first linear constant flow module and the third linear constant flow module common current sampling resistor, and
And the reference voltage of amplifier is less than the ginseng of amplifier in the third linear constant flow module in the first linear constant flow module
Examine voltage so that when the 3rd current path turns on, first current path disconnects.
Preferably, the described first linear constant flow module and the third linear constant flow module obtain the first current sample respectively
Signal and the 3rd current sampling signal, the amplified signal of the 3rd current sampling signal are superimposed upon the first current sample letter
Number or reference voltage on.
Preferably, when the 3rd current path turns on, using the amplified signal of the 3rd current sampling signal as
Control signal is superimposed upon on first current sampling signal, and the control signal is more than the ginseng of the described first linear constant flow module
Examine voltage so that when the 3rd current path turns on, first current path disconnects.
Preferably, the second linear constant current module obtains the second current sampling signal, according to the electricity of the input voltage
Press sampled signal to produce control signal, and the control signal is superimposed upon the of the second linear constant current module amplifier
On two current sampling signals, when the voltage sampling signal of the input voltage is less than the reference voltage, conducting described second
Current path, when the voltage sampling signal of the input voltage is more than or equal to the reference voltage, disconnects second electric current
Path.
Preferably, further include：Diode, is connected between second LED light and the third linear constant flow module, and
And when the 3rd current path turns on, the diode current flow, wherein, the voltage sampling signal of the input voltage is derived from
The anode of the diode, the reference voltage are derived from the cathode of the diode.
According to the LED drive circuit and its control method of the utility model embodiment, the first current path is used as first
LED light provides the first electric current, uses the second current path to provide the second electric current for the 2nd LED, and use the 3rd current path
The 3rd electric current is provided for the first LED light and the second LED light, so as to fulfill first LED light and second LED light and alliance
Electric and described first LED light and the second LED light series-fed.Under parallel operation state, the first linear constant flow module
It is connected in turn with the first LED light on the first current path, the second LED light is connected to second in turn with the second linear constant current module
On current path.Under series-fed state, the second LED light, third linear constant flow module and the first LED light are connected in turn
On three current paths.This method can realize the spirit of the first LED light and the second LED light connection mode using simple circuit structure
Configuration living.
In a preferred embodiment, according to the input voltage of feeder ear automatic switchover first LED light and described second
The connection mode of LED light.When the input voltage of feeder ear is less than or equal to predetermined value, the first LED light and the 2nd LED are switched to
Parallel operation.When the input voltage of feeder ear is more than predetermined value, the first LED light and the 2nd LED are switched to series-fed.The
One LED light and the second LED light are automatically switched to according to input voltage and one of are connected in parallel and are connected in series as load, can be with
The parameter of input capacitance is reduced, so as to reduce circuit volume and improve reliability and service life, and improves lamp bead
Utilization rate, reduces complete machine cost, improves efficiency.
Brief description of the drawings
By the description to the utility model embodiment referring to the drawings, above-mentioned and other mesh of the utility model
, feature and advantage will be apparent from.
Fig. 1 shows the schematic circuit of LED drive circuit according to prior art；
Fig. 2 shows the schematic circuit of the LED drive circuit according to the utility model first embodiment；
Fig. 3 shows the schematic electricity of linear constant current circuit in the LED drive circuit according to the utility model second embodiment
Lu Tu；
Fig. 4 shows the schematic electricity of linear constant current circuit in the LED drive circuit according to the utility model 3rd embodiment
Lu Tu；
Fig. 5 shows the schematic electricity of linear constant current circuit in the LED drive circuit according to the utility model fourth embodiment
Lu Tu；And
Fig. 6 shows the schematic electricity of linear constant current circuit in the LED drive circuit according to the 5th embodiment of the utility model
Lu Tu.
Embodiment
Hereinafter reference will be made to the drawings is more fully described the various embodiments of the utility model.In various figures, it is identical
Element is represented using same or similar reference numeral.For the sake of clarity, the various pieces in attached drawing are not drawn to paint
System.
In this application, term " LED light " is, for example, the LED light string that multiple LED are connected in series to form.If multiple LED
LED light string is formed, then the cathode of previous LED is connected to the anode of next LED in LED light string.The anode of LED light refers to
The anode of first LED light in LED light string, the cathode of LED light refer to the cathode of last LED light in LED light string.
The utility model can be presented in a variety of manners, some of them example explained below.
Fig. 2 shows the schematic circuit of the LED drive circuit according to the utility model first embodiment.As shown in the figure,
LED drive circuit 200 includes ac current source 101, rectifier bridge 102, input capacitance Cin, diode D1, linear constant current circuit
210 and 220.Rectifier bridge 102 is used for AC rectification into direct current.Input is provided between two output terminals of rectifier bridge 102
Voltage Vin.Input capacitance Cin carries out smothing filtering to input voltage vin.
LED light 103 and linear constant current circuit 210 are connected in series between two output terminals of rectifier bridge 102.Linear constant current
The first end of circuit 210 is connected with the hot end of rectifier bridge 102, and second end is connected to the anode of LED light 103.LED light
103 minus earth.
LED light 104 and linear constant current circuit 220 are connected in series between two output terminals of rectifier bridge 102.LED light 104
Anode be connected with the hot end of rectifier bridge 102, the first end of the cathode of LED light 104 connection linear constant current circuit 220.
The second end ground connection of linear constant current circuit 220.
Different from the LED drive circuit of the prior art, linear constant current circuit 210 further includes the 3rd end, via diode D1
It is connected with the cathode of LED light 104.Linear constant current circuit 210 provides the first current path between first end and second end and the
The 3rd current path between three ends and second end.Linear constant current circuit 220 provides the second electricity between first end and second end
Flow path.The anode of diode D1 is connected to the cathode of LED light 104, and cathode is connected to the 3rd end of linear constant current circuit 210,
So as to ensure the one-way flow of the 3rd current path.Below in conjunction with Fig. 6 the embodiment described, the anode voltage of diode D1
V1 and cathode voltage V2 will lead on and off for path selecting module the 3rd current path of progress in linear constant current circuit 220
Open control.
When alternating voltage is relatively low, the input current difference two-way after rectification.The electric current that rectifier bridge 102 provides flows separately through
First current path and the second current path, the 3rd current path disconnect, 104 parallel operation of LED light 103 and LED light.First electricity
Stream is since the first output terminal of rectifier bridge 102, linear constant-current circuit 210, LED light 103, returns again to the of rectifier bridge 102
Two output terminals.Linear constant current circuit 210 controls the current value of the first electric current.First output terminal of second electric current from rectifier bridge 102
Start, through LED light 104, linear constant current circuit 220, return again to the second output terminal of rectifier bridge 102.Linear constant current circuit 220 is controlled
Make the current value of the second electric current.Diode disconnects at this time, does not have electric current to flow through in the 3rd current path.
When alternating voltage is higher, the input current after rectification is single channel.The electric current that rectifier bridge 102 provides flows through the 3rd electricity
Flow path, the first current path and the second current path disconnect, 104 tandem working of LED light 103 and LED light.3rd electric current is from whole
First output terminal of stream bridge 102 starts, and through LED light 104, linear constant current circuit 210, LED light 103, returns again to rectifier bridge 102
Second output terminal.Linear constant current circuit 210 controls the current value of the 3rd electric current.Diode current flow at this time, in the 3rd current path
Electric current flows through.
Linear constant current circuit 210 includes linear constant current module 110 and 120 and path selecting module 111.Linear constant current
Module 110 is located on the first current path, for controlling the current value of the first electric current.Linear constant current module 120 is positioned at the 3rd electricity
On flow path, for controlling the current value of the 3rd electric current.Linear constant current circuit 220 includes linear constant current module 130 and path
Selecting module 112.Linear constant current module 130 is located on the second current path, for controlling the current value of the second electric current.
Linear constant current module 110,120 and 130 is respectively used to realize the current constant control of the first to the 3rd current path.Path
Selecting module 111 and 112 is respectively used to enabled or disabled linear constant current module 120 and 130, so as to fulfill the first current path,
The selection of second current path and the 3rd current path, to change the connection mode of LED load.
Fig. 3 shows the schematic electricity of linear constant current circuit in the LED drive circuit according to the utility model second embodiment
Lu Tu.Linear constant current circuit 210 is used for the selectivity conducting for providing one of the first current path and the 3rd current path.First electricity
Flow path for linear constant current circuit 210 first end to the current path between second end, the 3rd current path is linear constant current
3rd end of circuit 210 is to the current path between second end.
Linear constant current circuit 210 includes power tube M1 and M3, amplifier 301 and 303 and current sampling resistor Rs1.Work(
Rate pipe M1 and current sampling resistor Rs1 are connected in series between the first end and a second end, and the first node of the two provides electric current and adopts
Sample signal.Power tube M3 is connected between the 3rd end and first node.Amplifier 301 is by current sampling signal and reference voltage
Vref1 is compared to produce drive signal, so that it is the first electric current I1 to control the electric current flowed through in power tube M1, for example, the
The constant current value of one electric current I1 is Vref1/Rs1.Amplifier 303 by current sampling signal compared with reference voltage Vref 3 with
Drive signal is produced, so that it is the 3rd electric current I3 to control the electric current flowed through in power tube M3, for example, the constant current value of the 3rd electric current I3
For Vref3/Rs1.
In this embodiment, the electric current that the first current path in linear constant current circuit 210 and the 3rd current path share
Sampling resistor Rs1 is also used as path selecting module, for controlling power tube M1 to turn off so that linear constant current circuit 210 is used to carry
Turned on for the selectivity of one of the first current path and the 3rd current path.
When alternating voltage is relatively low, diode D1 is disconnected, and power tube M3 does not have electric current to flow through.At this time, power tube M1 is flowed through
Current value be limited to Vref1/Rs1.Therefore, the first current path turns on, and the 3rd current path disconnects.
When alternating voltage gradually rises, diode D1 conductings, power tube M3 has electric current to flow through.The electric current that power tube M1 flows through
The electric current that power tube M3 flows through is subtracted for Vref1/Rs1.Power tube M3 electric currents gradually increase, it is constant after current value be Vref3/
Rs1.Power tube M1 electric currents are gradually reduced, it is constant after current value be Vref1/Rs1-Vref3/Rs1.As long as ensure herein
Vref3 is more than Vref1, it is possible to and to ensure when power tube M3 electric currents is Vref3/Rs1, the electric current that power tube M1 flows through is 0,
So as to fulfill automatically shutting down for power tube M1.Therefore, the first current path disconnects, the conducting of the 3rd current path.
Fig. 4 shows the schematic electricity of linear constant current circuit in the LED drive circuit according to the utility model 3rd embodiment
Lu Tu.Linear constant current circuit 310 is used for the selectivity conducting for providing one of the first current path and the 3rd current path.First electricity
Flow path for linear constant current circuit 310 first end to the current path between second end, the 3rd current path is linear constant current
3rd end of circuit 310 is to the current path between second end.
Linear constant current circuit 310 includes power tube M1 and M3, amplifier 301 and 303, feedback resistance R11, current sample electricity
Hinder Rs1 and Rs3 and amplification module 401.Power tube M1 and current sampling resistor Rs1 are connected in series in first end and second end
Between, the first node of the two provides the first current sampling signal.Power tube M3 and current sampling resistor Rs3 is connected in series in
Between three ends and second end, the 3rd node of the two provides the 3rd current sampling signal.
The inverting input of amplifier 301 receives control signal, and in-phase input end receives reference voltage Vref 1.Amplifier
301 by control signal compared with reference voltage Vref 1 to produce drive signal, so as to control the electricity flowed through in power tube M1
Flow for the first electric current I1, for example, the constant current value of the first electric current I1 is Vref1/Rs1.
The inverting input of amplifier 303 receives the 3rd current sampling signal, and in-phase input end receives reference voltage
Vref3.Amplifier 301 by the 3rd current sampling signal compared with reference voltage Vref 3 to produce drive signal, so as to control
The electric current flowed through in power tube M3 processed is the 3rd electric current I3, for example, the constant current value of the first electric current I3 is Vref3/Rs3.
The path selecting module of linear constant current circuit 310 includes amplification module 401 and feedback resistance R11.Feedback resistance R11
And amplification module 401 is connected in series between first node and the 3rd node.Between feedback resistance R11 and amplification module 401
Node provide control signal.The inverting input of amplifier 301 receives control signal.Therefore, amplification module 401 is electric by the 3rd
Sampled signal amplification is flowed, so as to obtain control signal K*Vref3/Rs3, wherein K is the amplification coefficient of amplification module 401.
When alternating voltage is relatively low, diode D1 is disconnected, and power tube M3 does not have electric current to flow through.At this time, power tube M1 is flowed through
Current value be limited to Vref1/Rs1.Therefore, the first current path turns on, and the 3rd current path disconnects.
When alternating voltage gradually rises, diode D1 conductings, power tube M3 has electric current to flow through.In this embodiment, amplify
The inverting input of device 301 receives control signal K*Vref3/Rs3, since control signal K*Vref3/Rs3 is not only greater than the
One current sampling signal, and it is more than reference voltage Vref 1, therefore the drive signal controlling transistor M1 that amplifier 301 produces
Disconnect.In alternate embodiments, control signal K*Vref3/Rs3 subtracts each other with reference voltage Vref 1, so as to reduce amplifier
The numerical value of the reference voltage of 301 in-phase input end, therefore the drive signal controlling transistor M1 that amplifier 301 produces is disconnected.
Fig. 5 shows the schematic electricity of linear constant current circuit in the LED drive circuit according to the utility model fourth embodiment
Lu Tu.Linear constant current circuit 220 is used for the selectivity conducting for providing the second current path.Second current path is linear constant current electricity
The first end on road 220 is to the second current path between second end.
Linear constant current circuit 220 include power tube M2, amplifier 302, voltage comparator 321, divider resistance R31 and R32,
Feedback resistance 322 and current sampling resistor Rs2.Power tube M2 and current sampling resistor Rs2 is connected in series in first end and
Between two ends, the section point of the two provides current sampling signal.Power tube M2 is connected between first end and section point.Put
Big device 302 by current sampling signal compared with reference voltage Vref 2 to produce drive signal, so as to control in power tube M2
The electric current flowed through is the second electric current I2, for example, the constant current value of the second electric current I2 is Vref2/Rs2.Amplifier 302 is by current sample
Signal compared with reference voltage Vref 2 to produce drive signal so that it is second to control the electric current that is flowed through in power tube M2
Electric current I2, for example, the constant current value of the second electric current I2 is Vref2/Rs2.
In this embodiment, the path selecting module in linear constant current circuit 220 includes voltage comparator 321, partial pressure electricity
Hinder R31 and R32, feedback resistance 322.Divider resistance R31 and R32 be connected in series in first end in linear constant current circuit 220 and
Between second end, the voltage (i.e. the drain terminal voltage of power tube M2) of the cathode for obtaining LED light 104.Due to transistor M2 works
Make in linear condition, the voltage of the cathode of LED light 104 is corresponding with input voltage vin, and what divider resistance R31 and R32 were obtained adopts
The voltage sampling signal of sample voltage, that is, input voltage vin.
The first input end of voltage comparator 321 is connected to the intermediate node of divider resistance R31 and R32, for being somebody's turn to do
Voltage sampling signal, the second input terminal receive reference voltage Vref 4.The output terminal of voltage comparator 321 is connected to amplifier 302
Inverting input.Feedback resistance 322 is connected between the inverting input of section point and amplifier 302.Voltage comparator
321 output voltage is superimposed to the inverting input of amplifier 302 as control signal.When input voltage vin is more than or equal to ginseng
When examining the scheduled voltage of voltage Vref4 characterizations, which reduces the electric current for flowing through power tube M2, until power tube M2 is closed
It is disconnected.When input voltage vin is less than the scheduled voltage that reference voltage Vref 4 characterizes, which is 0, amplifier 302
Inverting input receives the current feedback signal of the second electric current I2, realizes current constant control.
When alternating voltage is relatively low, power tube M2 electric currents flow through, and the current value for flowing through power tube M1 at this time is limited to
Vref2/Rs2。
When alternating voltage gradually rises, power tube M2 does not have electric current to flow through.Path selecting module realizes oneself of power tube M2
Dynamic shut-off.
Fig. 6 shows the schematic electricity of linear constant current circuit in the LED drive circuit according to the 5th embodiment of the utility model
Lu Tu.Linear constant current circuit 320 is used for the selectivity conducting for providing the second current path.Second current path is linear constant current electricity
The first end on road 320 is to the current path between second end.
Linear constant current circuit 320 include power tube M2, amplifier 302, voltage comparator 321, divider resistance R31 and R32,
Divider resistance R33 and R34, feedback resistance 322 and current sampling resistor Rs2.Power tube M2 and current sampling resistor Rs2 strings
Between the first end and a second end, the section point of the two provides current sampling signal for connection connection.Power tube M2 is connected to first
Between end and section point.Amplifier 302 believes current sampling signal compared with reference voltage Vref 2 to produce driving
Number, so that it is the second electric current I2 to control the electric current flowed through in power tube M2, for example, the constant current value of the second electric current I2 is Vref2/
Rs2.Amplifier 302 by current sampling signal compared with reference voltage Vref 2 to produce drive signal, so as to control power
The electric current flowed through in pipe M2 is the second electric current I2, for example, the constant current value of the second electric current I2 is Vref2/Rs2.
In this embodiment, the path selecting module in linear constant current circuit 320 includes voltage comparator 321, partial pressure electricity
Hinder R31 and R32, divider resistance R33 and R34, feedback resistance 322.The anode voltage V1 and cathode voltage V2 of diode D1 is used for
Path selecting module in linear constant current circuit 320 carries out the conducting of current path and disconnects control.Divider resistance R31 and R32
It is connected in series between the first end and second end in linear constant current circuit 320, for obtaining the anode voltage V1 of diode D1
(i.e. the drain terminal voltage of power tube M2).Divider resistance R33 and R34 are connected in series in the cathode and linear constant current circuit of diode D1
Between second end in 320, for obtaining reference voltage Vref 4.Since transistor works in linear condition, power tube M2 is being led
The drain terminal voltage of logical state is corresponding with input voltage vin, sampled voltage, that is, input voltage that divider resistance R31 and R32 are obtained
The voltage sampling signal of Vin.
The first input end of voltage comparator 321 is connected to the node of divider resistance R31 and R32, for obtaining the voltage
Sampled signal, the second input terminal receive reference voltage Vref 4.The output terminal of voltage comparator 321 is connected to the anti-of amplifier 302
Phase input terminal.Feedback resistance 322 is connected between the inverting input of section point and amplifier 302.When input voltage vin is big
When the scheduled voltage characterized equal to reference voltage Vref 4, the output voltage of voltage comparator 321 is superimposed to amplifier 302
Inverting input, so as to reduce the electric current for flowing through power tube M2, until power tube M2 is turned off.When input voltage vin is less than ginseng
When examining the scheduled voltage of voltage Vref4 characterizations, the output voltage of voltage comparator 321 is 0, the anti-phase input of amplifier 302
End receives the current feedback signal of the second electric current I2, realizes current constant control.
When alternating voltage is relatively low, power tube M2 electric currents flow through, and the current value for flowing through power tube M1 at this time is limited to
Vref2/Rs2。
When alternating voltage gradually rises, power tube M2 does not have electric current to flow through.Path selecting module realizes oneself of power tube M2
Dynamic shut-off.
In this embodiment, linear constant current circuit 320 is controlled according to the anode voltage V1 and cathode voltage V2 of diode D1
The conducting and disconnection of current path.Switch the conducting with diode D1 due to the current path of linear constant current circuit 210 and 320
State is related, it is thereby achieved that the synchronism switching of linear constant current circuit 210 and 320, further improves LED drive circuit
Job stability.
According to the LED drive circuit of the utility model embodiment, for driving the first LED light and the second LED light, including the
One linear constant current circuit and the second linear constant current circuit, wherein the first linear constant current circuit selects the first current path and the 3rd electricity
One of flow path, the second linear constant current circuit selectively turn on the second current path so that first LED light and described
Two LED light are switched to according to input voltage one of to be connected in parallel and is connected in series, so that the parameter of input capacitance is reduced, so as to subtract
Small circuit volume and raising reliability and service life.
Embodiment according to the utility model is for example above, these embodiments do not have all details of detailed descriptionthe, not yet
Limit the specific embodiment that the utility model is only.Obviously, as described above, can make many modifications and variations.This explanation
Book is chosen and specifically describes these embodiments, is the principle and practical application in order to preferably explain the utility model, so that
Skilled artisan can be used using the utility model and the modification on the basis of the utility model well.This
The protection domain of utility model should be subject to the scope that the utility model claims are defined.
Claims (14)
- A kind of 1. LED drive circuit, for driving the first LED light and the second LED light, it is characterised in that including：First linear constant current circuit, including be connected to the first end of feeder ear, be connected to the first LED light anode second end, And it is connected to the 3rd end of the cathode of the second LED light；AndSecond linear constant current circuit, including the first end of the cathode of the second LED light and the second end being connected to the ground are connected to,Wherein, the selection of the first linear constant current circuit one of first current path and the 3rd current path, first electric current Path is located between the first end and second end of first linear constant current circuit, and the 3rd current path is located at described first Between 3rd end of linear constant current circuit and second end,Second linear constant current circuit selectively turns on or disconnects the second current path, and second current path is located at institute Between the first end and second end for stating the second linear constant current circuit.
- 2. LED drive circuit according to claim 1, it is characterised in that first linear constant current circuit and described Bilinear constant-current circuit selects current path according to the input voltage of the feeder ear respectively so that first LED light and institute State the second LED light and be switched to according to input voltage and one of be connected in parallel and be connected in series.
- 3. LED drive circuit according to claim 1, it is characterised in that further include：Diode, its anode are connected to institute The cathode of the second LED light is stated, its cathode is connected to the 3rd end of first linear constant current circuit.
- 4. LED drive circuit according to claim 3, it is characterised in that first linear constant current circuit includes：First linear constant flow module, is connected between the first end and second end of first linear constant current circuit, for providing First current path；Third linear constant flow module, is connected between the 3rd end and the second end of first linear constant current circuit, for providing 3rd current path；AndFirst path selecting module, is connected with the described first linear constant flow module and the third linear constant flow module, is used for Select current path,Wherein, when the input voltage of the feeder ear is less than or equal to predetermined value, described in the first path selecting module disconnection 3rd current path, and conducting first current path,When the input voltage of the feeder ear is more than predetermined value, the first path selecting module disconnects the first electric current road Footpath, and conducting the 3rd current path.
- 5. LED drive circuit according to claim 4, it is characterised in that second linear constant current circuit includes：Second linear constant current module, is connected between the first end and second end of second linear constant current circuit, for providing Second current path；Alternate path selecting module, is connected with the second linear constant current module, for selecting current path,Wherein, when the input voltage of the feeder ear is less than or equal to predetermined value, described in the alternate path selecting module conducting Second current path,When the input voltage of the feeder ear is more than predetermined value, the alternate path selecting module disconnects the second electric current road Footpath.
- 6. LED drive circuit according to claim 5, it is characterised in that the first linear constant flow module, described second Linear constant current module and the third linear constant flow module include respectively：Power tube, for controlling the current value of corresponding current path；AndAmplifier, for being compared reference voltage with current sampling signal to produce the drive signal of the power tube.
- 7. LED drive circuit according to claim 6, it is characterised in that first linear constant current circuit further includes：Electricity Sampling resistor is flowed, on the common path of first current path and the 3rd current path, the first path choosing It is the current sampling resistor to select module.
- 8. LED drive circuit according to claim 7, it is characterised in that amplifier in the first linear constant flow module Reference voltage be less than the third linear constant flow module in amplifier reference voltage.
- 9. LED drive circuit according to claim 6, it is characterised in that first linear constant current circuit further includes：Power tube in first current sampling resistor, with the described first linear constant flow module is connected in series, and between One node provides the first current sampling signal；AndPower tube in 3rd current sampling resistor, with the third linear constant flow module is connected in series, and between Three nodes provide the 3rd current sampling signal,Wherein, the amplified signal of the 3rd current sampling signal is superimposed upon the First Line by the first path selecting module On the current sampling signal or reference voltage of property constant flow module amplifier.
- 10. LED drive circuit according to claim 9, it is characterised in that the first path selecting module includes：The first feedback resistance and amplification module being connected in series between the first node and the 3rd node,Wherein, the current sampling signal of the described first linear constant flow module amplifier is derived from first feedback resistance and described puts Fourth node between big module.
- 11. LED drive circuit according to claim 10, it is characterised in that when the 3rd current path turns on, institute State amplification module to be applied to the amplified signal of the 3rd current sampling signal in the fourth node as control signal, institute Reference voltage of the control signal more than amplifier in the described first linear constant flow module is stated, so as to disconnect the first electric current road Footpath.
- 12. LED drive circuit according to claim 6, it is characterised in that second linear constant current circuit further includes：Second current sampling resistor, is connected in series with the second linear constant current mould power tube in the block, and between Two nodes provide the second current sampling signal,Wherein, the alternate path selecting module produces control signal according to the voltage sampling signal of the input voltage, and The control signal is superimposed upon on the current sampling signal or reference voltage of the second linear constant current module amplifier.
- 13. LED drive circuit according to claim 12, it is characterised in that the alternate path selecting module includes：First divider resistance and the second divider resistance, are connected in series in the first end and second end of second linear constant current circuit Between, and the 5th node between first divider resistance and second divider resistance provides and is used to characterize the input The voltage feedback signal of voltage；The voltage comparator and the second feedback resistance being connected in series between section point and the 5th node,Wherein, the current sampling signal of amplifier is derived from second feedback resistance and described in the second linear constant current module The 6th node between voltage comparator,The voltage comparator compares the voltage feedback signal to obtain control signal with reference voltage so that described When the voltage sampling signal of input voltage is less than the reference voltage, the alternate path selecting module turns on second electric current Path, when the voltage sampling signal of the input voltage is more than or equal to the reference voltage, the alternate path selecting module Disconnect second current path.
- 14. LED drive circuit according to claim 13, it is characterised in that the alternate path selecting module includes：3rd divider resistance and the 4th divider resistance, are connected in series in the cathode and second linear constant current electricity of the diode Between the second end on road,Wherein, the 7th node between the 3rd divider resistance and the 4th divider resistance, which provides, is used to characterize the diode The voltage feedback signal of cathode voltage, as the reference voltage.
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| CN201721309944.2U CN207354677U (en) | 2017-10-11 | 2017-10-11 | Led drive circuit |
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| CN201721309944.2U CN207354677U (en) | 2017-10-11 | 2017-10-11 | Led drive circuit |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN107846745A (en) * | 2017-10-11 | 2018-03-27 | 杭州士兰微电子股份有限公司 | LED drive circuit and its control method |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN107846745A (en) * | 2017-10-11 | 2018-03-27 | 杭州士兰微电子股份有限公司 | LED drive circuit and its control method |
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