CN103108432A - Light-emitting diode (LED) driver and LED illuminating device with the same - Google Patents

Abstract

The invention relates to a light-emitting diode (LED) driver which is used for driving a load subcircuit. The load subcircuit comprises a first load group (S1) and at least one second load group (S2) which are connected with each other in series. The LED driver comprises a power factor correction (PFC)-alternating current/direct current (AC/DC) switching circuit (1), a switching control unit (3) and at least one switching unit (2). The PFC- AC/DC switching circuit (1) provides expected working voltage (Vb) for the first load group (S1) and the second load groups (S2). The switching units (2) are connected with the second load groups (S2) in parallel. The switching control unit (3) outputs first control signals (Ctrl_1) to the switching units (2) according to first sampling voltage (Vs_1) of load current (I_s) flowing through the load subcircuit so as to adjust a conducting state of the switching units (2). Consequently, current (I_s2) flowing through the second load groups (S2) is changed. In addition, the invention further relates to an LED illuminating device provided with the LED driver.

Description

LED driver and the LED lighting device with this LED driver

Technical field

The present invention relates to a kind of LED driver.In addition, the invention still further relates to a kind of LED lighting device with this LED driver.

Background technology

LED light source has as cold light source that photochromic pure, light beam is concentrated, color rendering index is high, good temp characteristic, and has the advantages such as electric quantity consumption is low, stable performance, the life-span is long, pollution-free, use is simple.For LED light source is driven, a large amount of dissimilar AC-DC LED drivers has appearred on market, comprising the PFC driver of single-stage, the pwm driver of two-stage, traditional Linear actuator and be used for switch element of LED chain etc.But they have respectively different pluses and minuses.For example, single-stage PFC activation configuration is simple, with low cost, good power factor can be provided, but it has larger ripple current.The two-stage pwm driver can provide high power factor and low ripple current, but its complex structure, cost are high, and electromagnetic interference source has two high frequencies, and antijamming capability is relatively poor.Traditional Linear actuator simple in structure, with low cost, but its efficient is lower and power factor is also lower.And the structure of switch element that is used for the LED chain is the simplest, cost is minimum, good power factor can be provided, and have good efficient in high-tension application scheme, and antijamming capability is very strong, but it produces very high ripple current.

Summary of the invention

For solving the problems of the technologies described above, the present invention proposes a kind of LED driver, this LED driver set all advantages of driver of the prior art, it is simple in structure, with low cost, have high power factor and efficient, antijamming capability is stronger, and it produces less ripple current.The invention still further relates in addition a kind of LED lighting device with LED driver of the above-mentioned type.

First purpose of the present invention realizes thus by a kind of LED driver, namely this LED driver be used for to drive the first load group and at least one second load group that is one another in series, and this LED driver comprises: the PFC-AC/DC change-over circuit that the operating voltage of expection is provided for the first load group and the second load group; Switch control unit; And at least one switch element, wherein, switch element is in parallel with the second load group separately, switch control unit flows through first sampled voltage of load current of load branch to switch element output the first control signal according to sign, with adjustment switch element conducting state, thereby change the electric current that flows through the second load group.LED driver according to the present invention has adopted the compound mode of PFC-AC/DC change-over circuit and switch element, the output voltage that can obtain to have high power factor by the PFC-AC/DC change-over circuit.In design according to the present invention, the PFC-AC/DC change-over circuit can be the pfc circuit of any type.BUCK PFC for example.The PFC-AC/DC change-over circuit can be controlled by traditional PFC control IC or MCU.In this way, can obtain high power factor.The output voltage of PFC-AC/DC change-over circuit is direct current.The average voltage of controlling by pfc circuit has very high precision.Yet, inevitably have AC portion and exist in this DC source, according to the V-I characteristic of LED light source, di/dv is very high, and for little dv, the variation of electric current is very violent, and this will cause high ripple current.Can adjust the electric current that flows through the second load group according to the conducting state of the switch element in LED driver of the present invention by controlling, thereby change the electric current that flows through load group, to reach the purpose of eliminating ripple current.

Propose according to design of the present invention, the PFC-AC/DC change-over circuit comprises power factor correction part and the feedback control unit of exporting described operating voltage, feedback control unit produces the second control signal according to the second sampled voltage of the operating voltage acquisition of the second reference voltage that utilizes the first sampled voltage to obtain and the current output of power factor correction part, and the power factor correction part is according to the operating voltage of described the second control signal output expection.The pfc circuit that PFC-AC/DC change-over circuit according to the present invention can be any type, but some control models can not be controlled pfc circuit well, for example, some DCM pfc circuits have only been fixed the duty ratio in each work period, and each linear period is adjusted PFC output average voltage one time.Its structure is very simple, but the PFC average voltage of output is not very accurate.The larger tolerance of PFC output voltage will affect the LED electric current.Therefore the operating voltage of PFC-AC/DC change-over circuit output is a very crucial parameter.Can well the operating voltage of exporting be controlled in an acceptable zone of reasonableness by the PFC-AC/DC change-over circuit in LED driver according to the present invention, thereby make the elimination ripple current become possibility.

A preferred design according to the present invention proposes, switch control unit comprises the first operational amplifier, the first default reference voltage of its in-phase input end access, inverting input access the first sampled voltage, output is connected to switch element, the conducting state of the control voltage control switch unit of conduct the first control signal that calculates according to the first sampled voltage and the first default reference voltage.Can adjust the electric current that flows through the second load group by the conducting state that changes switch element, thus the voltage on the change load group, and then change the electric current that flows through load group, to reach the purpose of eliminating ripple current.

Preferably, switch control unit also comprises second, third resistance, wherein, described the second resistance and the 3rd resistance are connected in series between supply power voltage and ground, and the in-phase input end of described the first operational amplifier is connected to the node between the second resistance and the 3rd resistance.In design of the present invention, this supply power voltage can be taken from IC or the MCU that PFC AC/DC change-over circuit is controlled, and can certainly be supply power voltage independently.Determine the value of reference voltage by the resistance size of adjusting the second resistance and the 3rd resistance.

Further preferably, switch control unit also comprises the 4th resistance and the first electric capacity, it is connected between the inverting input and output of the first operational amplifier with being one another in series, is used for consisting of a feedback loop between the inverting input of the first operational amplifier and output.

Advantageously, switch control unit also comprises the 5th resistance, and an end of the 5th resistance is connected to the inverting input of the first operational amplifier and the node between the first electric capacity, and the other end of the 5th resistance is connected to the output of load branch.The 5th resistance and the second resistance mate, to improve the antijamming capability of control unit.

Propose according to the present invention, LED driver also comprises the 6th resistance, and the 6th resistance is connected between node and ground between the output of the other end of the 5th resistance and the second load group.Can determine the size of the first sampled voltage of calculating according to the load current that flows through load branch by the resistance size of selecting the 6th resistance.

Preferably, switch element comprises a MOSFET pipe, wherein, the drain electrode of the one MOSFET pipe is connected to the positive pole as the LED light-emitting diode of the second load group, source electrode is connected to the negative pole of described LED light-emitting diode, and grid is connected to the output of the first operational amplifier and the node between the 4th resistance.By adjusting the conducting state of a MOSFET pipe as the control voltage of the first control signal, thereby adjust the size of current that flows through a MOSFET pipe.Because the LED light-emitting diode is in parallel with a MOSFET pipe, therefore the electric current that flows through the LED light-emitting diode also changes, thereby cause the voltage of LED light-emitting diode also to change, and then guarantee that the AC portion in operating voltage consumes by the second load group, to guarantee the first load group with direct voltage work, reach the purpose of eliminating ripple current in the first load group.

Further preferably, switch element also comprises the first diode, and the positive pole of the first diode is connected to the output of the first operational amplifier and the node between the 4th resistance, and negative pole is connected to the grid of a MOSFET pipe.This first diode is used for preventing that electric current is back to the first operational amplifier from a MOSFET pipe.

In addition, the present invention also proposes, switch element also comprises the first resistance, and an end of this first resistance is connected to the node between the negative pole of the grid of a MOSFET pipe and the first diode, and the other end is connected to the node between the negative pole of the source electrode of a MOSFET pipe and LED light-emitting diode.This has produced a discharge loop between the grid of a MOSFET pipe and source electrode, thereby plays the effect of protection the one MOSFET pipe.

a preferred design according to the present invention proposes, power factor correction partly comprises the 2nd MOSFET pipe, inductance, the second electric capacity, the second diode, wherein, the drain electrode of the 2nd MOSFET pipe is connected to the live wire of AC power, source electrode is connected to an end of described inductance, grid is connected to feedback control unit, the other end of inductance is connected to the output of PFC-AC/DC change-over circuit, one end of the second electric capacity is connected to the other end of inductance and the node between power factor correction output partly, other end ground connection, the negative pole of the second diode is connected to the node between an end of the source electrode of the 2nd MOSFET pipe and inductance, positive pole is connected to the other end of the second electric capacity and the node between ground.By adjusting the duty ratio of the control signal that the 2nd MOSFET pipe is controlled, can make power factor correction partly export the operating voltage of expection.

Preferably, feedback control unit comprises the second operational amplifier, PFC control circuit and reference voltage generating circuit, the in-phase input end of the second operational amplifier is connected to the output of reference voltage generating circuit, the input of reference voltage generating circuit is connected to the output of the second load group, inverting input is connected to the output of power factor correction part, the output of the second operational amplifier is connected to the input of PFC control circuit, and the grid of the 2nd MOSFET pipe is connected to the output of PFC control circuit.Reference voltage generating circuit receives the first sampled voltage, and this first sampled voltage and the threshold value of presetting are compared, when the first sampled voltage output second reference voltage during greater than default threshold value, the second operational amplifier calculates according to the second reference voltage with from the second sampled voltage that the operating voltage of the current output of PFC-AC/DC change-over circuit obtains and obtains second and control voltage.The PFC control circuit controls according to second the second control signal that Voltage-output has been adjusted duty ratio, and this control signal is controlled the 2nd MOSFET pipe, thereby makes power factor correction partly export the operating voltage of expection.

Further preferably, the quantity N of the LED light-emitting diode in the first load group can obtain by following formula, i.e. N=Vdc/Vf, and wherein Vdc is the direct voltage of PFC-AC/DC change-over circuit output, Vf is the forward voltage of LED light-emitting diode.The quantity M of the LED light-emitting diode in the second load group can obtain by following formula, i.e. M=Vacp-p/Vf, and wherein Vacp-p is the AC portion in the operating voltage of PFC-AC/DC change-over circuit output, Vf is the forward voltage of LED light-emitting diode.

Another object of the present invention realizes thus by a kind of LED lighting device, and namely this LED lighting device has the LED driver of the above-mentioned type.More stable according to the output of LED lighting device of the present invention, simultaneously simple in structure, with low cost.

Description of drawings

Accompanying drawing consists of the part of this specification, is used for helping further to understand the present invention.These accompanying drawings illustrate embodiments of the invention, and are used for illustrating principle of the present invention together with specification.Identical parts represent with identical label in the accompanying drawings.Shown in figure:

Fig. 1 is the oscillogram according to the operating voltage of the PFC AC/DC change-over circuit output of LED driver of the present invention;

Fig. 2 is the theory diagram according to LED driver of the present invention;

Fig. 3 is the circuit diagram according to LED driver of the present invention.

Embodiment

Fig. 1 shows the oscillogram of operating voltage of the PFC AC/DC change-over circuit output of LED driver of the present invention.As seen from the figure, the operating voltage Vb of PFCAC/DC change-over circuit output is also not exclusively direct voltage, and this operating voltage Vb is made of direct current component Vdc and AC portion Vacp-p.Wherein the operating voltage minimum value is Vbmin=Vdc (1); Maximum is Vbmax=Vdc+Vacp-p (2).So as shown in Figure 1, time dependent operating voltage Vb (t)=Vdc+Vac (t) (3).Purpose of the present invention just is to eliminate ripple voltage to the impact of the first load group.

Fig. 2 is the theory diagram according to LED driver of the present invention.as seen from the figure, drive the first load group S1 and at least one the second load group S2 that is one another in series according to LED driver of the present invention, in the present embodiment, load group S1 and S2 are made of at least one LED light-emitting diode, wherein can determine according to following formula the quantity N of the LED light-emitting diode in the first load group S1, be N=Vdc/Vf, wherein Vdc is the direct voltage of PFC-AC/DC change-overcircuit 1 output, Vf is the forward voltage of LED light-emitting diode, and can determine that the quantity M of the LED light-emitting diode in the second load group S2 can obtain by following formula according to following formula, be M=Vacp-p/Vf, wherein Vacp-p is the AC portion in the operating voltage of PFC-AC/DC change-overcircuit 1 output, Vf is the forward voltage of LED light-emitting diode.In the present embodiment, for convenience, each second load group S2 only comprises a LED light-emitting diode DL11; ...; DLm1, certain the second load group S2 also can comprise respectively the LED light-emitting diode of varying number as required.

Further as can be seen from Fig. 2, LED driver is included as the PFC-AC/DC change-overcircuit 1 that the first load group S1 and the second load group S2 provide the operating voltage Vb of expection;Switch control unit 3; And at least oneswitch element 2, wherein,switch element 2 is in parallel with the second load group S2 separately,switch control unit 3 flows through the load current I_s of load branch according to sign the first sampled voltage Vs_1 exports the first control signal Ctrl_1 to switchelement 2, withadjustment switch element 2 conducting states, thereby change the electric current I _ s2 that flows through the second load group S2.In the present embodiment, the quantity ofswitch element 2 equates with the quantity of the second load group S2.In addition, as can be seen from Fig. 2, PFC-AC/DC change-overcircuit 1 comprises powerfactor correction part 5 and the feedback control unit 4 of output services voltage Vb, 4 couples of the first sampled voltage Vs_1 of this feedback control unit compare, when the first sampled voltage Vs_1 surpasses default threshold value, export the second reference voltage Vref _ 2.Feedback control unit 4 produces the second control signal Ctrl_2 according to these the second reference voltage Vref _ 2 with from the second sampled voltage Vs_2 that the operating voltage Vb_1 of powerfactor correction part 5 current outputs obtains, and powerfactor correction part 5 is according to the operating voltage Vb of the second control signal Ctrl_2 output expection.

Fig. 3 is the circuit diagram according to LED driver of the present invention.as seen from the figure,switch control unit 3 comprises the first operational amplifier X1, the first reference voltage Vref that the in-phase input end access of the first operational amplifier X1 ispreset _ 1, inverting input access the first sampled voltage Vs_1, output X1_out is connected to switchelement 2, control according to the Vg_1 first of the first sampled voltage Vs_1 and the first reference voltage Vref ofpresetting _ 1 conduct that calculates the first control signal Ctrl_1 the conducting state that voltage Vg_1 adjustsswitch element 2, wherein,switch control unit 3 also comprises thesecond resistance R 2 and the3rd resistance R 3, wherein, thesecond resistance R 2 and the3rd resistance R 3 are connected in series between supply power voltage Vcc and ground, the in-phase input end of the first operational amplifier X1 is connected to the node between thesecond resistance R 2 and the 3rd resistance R 3.Further as seen,switch control unit 3 comprises that also the 4th resistance R 4 and thefirst capacitor C 1, the four resistance R 4 and thefirst capacitor C 1 are connected between the inverting input and output X1_out of the first operational amplifier X1 with being one another in series from figure.In addition,switch control unit 3 comprises that also an end of the5th resistance R 5, the fiveresistance R 5 is connected to the inverting input of the first operational amplifier X1 and the node between thefirst capacitor C 1, and the other end of the5th resistance R 5 is connected to the output of load branch.

In addition, comprise also that in driver according to the present invention the 6th resistance R 6, the six resistance R 6 are connected between node and ground between the output of the other end of the5th resistance R 5 and the second load group S2.

Further as can be seen from Fig. 3,switch element 2 comprises a MOSFET pipe Q11; ...; Q1m, wherein, a MOSFET pipe Q11; ...; The drain electrode of Q1m is connected to the LED light-emitting diode DL11 as the second load group S2; ...; The positive pole of DLm1, source electrode are connected to LED light-emitting diode DL11; ...; The negative pole of DLm1, grid are connected to the output X1_out of the first operational amplifier X1 and the node between the 4th resistance R 4, andswitch element 2 also comprises the first diode D11; ...; D1m, the first diode D11; ...; The positive pole of D1m is connected to the output X1_out of the first operational amplifier X1 and the node between the 4th resistance R 4, and negative pole is connected to a MOSFET pipe Q11; ...; The grid of Q1m.In addition,switch element 2 also comprises the first resistance R 11; ...; R1m, the first resistance R 11; ...; The end of R1m is connected to a MOSFET pipe Q11; ...; The grid of Q1m and the first diode D11; ...; Node between the negative pole of D1m, and the other end is connected to a MOSFET pipe Q11; ...; The source electrode of Q1m and LED light-emitting diode DL11; ...; Node between the negative pole of DLm1.

show the circuit diagram of PFC-AC/DC change-overcircuit 1 in the left side of the circuit diagram shown in Fig. 3, this PFC-AC/DC change-overcircuit 1 comprises conventional powerfactor correction part 5 and feedback control unit 4, wherein powerfactor correction part 5 comprises the 2nd MOSFET pipe Qp,inductance L 1, thesecond capacitor C 2, the second diode D2, wherein, the drain electrode of the 2nd MOSFET pipe Qp is connected to the live wire of AC power, source electrode is connected to an end ofinductance L 1, grid is connected to feedback control unit 4, the other end ofinductance L 1 is connected to the output Out_pfc of PFC-AC/DC change-overcircuit 1, one end of described thesecond capacitor C 2 is connected to the node between the output of the other end ofinductance L 1 and powerfactor correction part 5, other end ground connection, the negative pole of the second diode D2 is connected to the node between an end of the source electrode of the 2nd MOSFET pipe Qp andinductance L 1, positive pole is connected to the other end of thesecond capacitor C 2 and the node between ground.

In design of the present invention, feedback control unit 4 can be conventional A/D converter, it will export to controller after the first sampled voltage conversion, the duty ratio of the signal that this controller adjustment is controlled the 2nd MOSFET pipe, thus reach the purpose of the operating voltage that makes the 1 output expection of PFC AC/DC change-over circuit.in a specific embodiment of the present invention, feedback control unit 4 comprises the second operational amplifier X2, PFC control circuit 6 and reference voltage generating circuit 7, the in-phase input end of the second operational amplifier X2 is connected to the output of reference voltage generating circuit 7, the input of reference voltage generating circuit 7 is connected to the output of the second load group S2, inverting input is connected to the output of powerfactor correction part 5, the output X2_out of the second operational amplifier X2 is connected to the input of PFC control circuit 6, and the grid of the 2nd MOSFET pipe Qp is connected to the output of PFC control circuit 6.Reference voltage generating circuit 7 receives the first sampled voltage Vs_1, and this first sampled voltage Vs_1 is compared with the threshold value of presetting, when the first sampled voltage Vs_1 during greater than default threshold value output the second reference voltage Vref _ 2, the second operational amplifier X2 calculate according to the second reference voltage Vref _ 2 with from the second sampled voltage Vs_2 that the operating voltage Vb_1 of PFC-AC/DC change-overcircuit 1 current output obtains and obtain the second control voltage Vg_2.PFC control circuit 6 controls according to second the second control signal Ctrl_2 that duty ratio has been adjusted in voltage Vg_2 output, and this second control signal Ctrl_2 controls the 2nd MOSFET pipe Qp, thereby makes the operating voltage Vb of powerfactor correction part 5 output expections.

In the actual motion according to LED driver of the present invention, export the output voltage V b with high power factor by PFC-AC/DC change-overcircuit 1, the direct driving LED of this output voltage V b, V-I characteristic according to LED, di/dv is very high, for little dv, the variation of electric current is very dramatic, and this will cause high ripple current.In order to process this ripple voltage, some LED electric currents and voltage are controlled.According to relational expression (3), Vb (t)=Vdc+Vac (t).Voltage in the first load group S1 is approximately Vdc, its Chang Liang.Electric current and the voltage of the second load group S2 are controlled.In design of the present invention, the 2nd MOSFET pipe is connected in parallel with the second load group S2, connects the LED electric current with bypass.

In the work of reality, when Vb=Vdc, only the LED in the first load group S1 lights.LED light-emitting diode D11 in the first load group S1 ..., the forward voltage of D1n is Vf, the electric current of LED light-emitting diode is restricted to requirement.Supply power voltage Vcc provides the DC signal of energy for operational amplifier X2.The first reference voltage Vref can be the compound of DC signal or DC signal and AC signal.This depends on requirement.When the LED electric current is restricted to when requiring, the first reference voltage Vref and the 6th resistance R 6 can be designed to make the first sampled voltage Vs_1 of the 6th resistance R 6 lower than the first reference voltage Vref, it is high that voltage Vg_1 is controlled in the output first of the first operational amplifier X1, and so all MOSFET pipe Q1-Qn connect.

When Vdc＜Vb＜Vdc+Vf, the first and second load group S1, the voltage of S2 rises, and this causes higher electric current.The first sampled voltage Vs_1 also rises.Poor according to Vref and Vs, first of the first operational amplifier X1 output is controlled voltage Vg_1 and will be descended.The electric current of the one MOSFET pipe Q1 descends, and remaining electric current will flow through the LED light-emitting diode DL11 in the second load group S2.The voltage of the first load group S1 remains on Vdc and other voltage will add to LED light-emitting diode DL11 in the second load group S2.When Vb=Vdc+Vf, the electric current of a MOSFET pipe Q1 disconnection and LED light-emitting diode DL11 is identical with the electric current in the first load group S1.

When Vdc+Vf＜Vb＜Vdc+2*Vf, the voltage of the first load group S1 and LED light-emitting diode DL11 is higher than Vdc+Vf, Current rise.The first sampled voltage Vs_1 also rises.Poor according to Vref and Vs, first of the first operational amplifier X1 output is controlled voltage Vg_1 and will be descended.The electric current of the one MOSFET pipe Q1 descends, and remaining electric current will flow through the LED light-emitting diode DL21 in the second other load group S2.The voltage of the first load group S1 and LED light-emitting diode DL11 remains on Vdc+Vf and other voltage will add to LED light-emitting diode DL21 in the second other load group S2.When Vb=Vdc+2*Vf, a MOSFET pipe Q2 in addition disconnect and the electric current of the electric current of the electric current of LED light-emitting diode DL21 and the first load group S1 and LED light-emitting diode DL11 identical.

When Vb continue to rise, a MOSFET pipe will disconnect one by one, and the LED electric current will sequentially flow through DL31, DL41......DLml, thus guarantee that the electric current in the first load group S1 remains unchanged.

The pfc circuit that PFC-AC/DC change-overcircuit 1 according to the present invention can be any type.BUCK PFC for example.PFC-AC/DC change-overcircuit 1 can be controlled by traditional IC or MCU.But some control models can not be controlled pfc circuit well, and for example, some DCMPFC circuit have only been fixed the duty ratio in each work period, and adjust the PFC output average voltage of a time of each linear period.Its structure is very simple, but the PFC average voltage of output is not very accurate.The larger tolerance of PFC output voltage will affect the LED electric current.Therefore the operating voltage of PFC-AC/DC change-over circuit output is a very crucial parameter.In design of the present invention, when the first sampled voltage Vs_1 that characterizes the load current I_s flow through load branch being detected and surpass default threshold value, will produce the second reference voltage Vref _ 2 to feedback control unit 4.In the present embodiment, the second operational amplifier X2 of feedback control unit 4 calculates according to the second reference voltage Vref _ 2 with from the second sampled voltage Vs_2 that the operating voltage of the current output of PFC-AC/DC change-over circuit obtains and obtains second and control voltage Vg_2, and control according to second the second control signal Ctrl_2 that duty ratio is adjusted in voltage Vg_2 output, this control signal Ctrl_2 controls the 2nd MOSFET pipe Qp, thereby makes the operating voltage Vb of powerfactor correction part 5 output expections.

These are only the preferred embodiments of the present invention, be not limited to the present invention, for a person skilled in the art, the present invention can have various modifications and variations.All any modifications of doing within the spirit and principles in the present invention, be equal to replacement, improvement etc., within protection scope of the present invention all should be included in.

Reference number

1 PFC-AC/DC change-over circuit

2 switch elements

3 switch control units

4 feedback control units

5 power factor correction parts

6. PFC control circuit

7 reference voltage generating circuits

X1 the first operational amplifier

X2 the second operational amplifier

R11; ...; R1m the first resistance

R2 the second resistance

R3 the 3rd resistance

R4 the 4th resistance

R5 the 5th resistance

R6 the 6th resistance

C1 the first electric capacity

C2 the second electric capacity

D11; ...; D1m the first diode

D2 the second diode

Q11; ...; Q1m the one MOSFET pipe

Qp the 2nd MOSFET pipe

The L1 inductance

S1 the first load group

S2 the second load group

D11 ..., the LED light-emitting diode in D1n the first load group S1

DL11; ...; The LED light-emitting diode of DLm1 the second load group S2

The Vcc supply power voltage

The operating voltage of Vb expection

The operating voltage of the current output of Vb_1

Vs_1 the first sampled voltage

Vs_2 the second sampled voltage

Vg_1 first controls voltage

Vg_2 second controls voltage

The forward voltage of Vf LED light-emitting diode

The direct voltage of Vdc PFC-AC/DC change-over circuit output

AC portion in the operating voltage of Vacp-p PFC-AC/DC change-over circuit output

The first reference voltage that Vref_1 is default

Vref_2 the second reference voltage

I_s flows through the load current of load branch

I_s2 flows through the electric current of the second load group S2

Ctrl_1 the first control signal

Ctrl_2 the second control signal

The output of X1_out the first operational amplifier X1

The output of X2_out the second operational amplifier X2

The output of Out_pfc PFC-AC/DC change-over circuit

Claims (15)

1. LED driver, be used for to drive and to comprise the first load group (S1) of being one another in series and the load branch of at least one the second load group (S2), it is characterized in that, described LED driver comprises: the PFC-AC/DC change-over circuit (1) that the operating voltage (Vb) of expection is provided for described the first load group (S1) and the second load group (S2); Switch control unit (3); And at least one switch element (2), wherein, described switch element (2) is in parallel with described the second load group (S2) separately, described switch control unit (3) flows through first sampled voltage (Vs_1) of load current (I_s) of described load branch to described switch element (2) output the first control signal (Ctrl_1) according to sign, adjusting described switch element (2) conducting state, thereby change the electric current (I_s2) that flows through described the second load group (S2).

2. LED driver according to claim 1, it is characterized in that, described PFC-AC/DC change-over circuit (1) comprises power factor correction part (5) and the feedback control unit (4) of the operating voltage (Vb) of exporting described expection, described feedback control unit (4) produces the second control signal (Ctrl_2) according to the second reference voltage (Vref_2) that utilizes described the first sampled voltage (Vs_1) to obtain with from the second sampled voltage (Vs_2) that the operating voltage (Vb_1) of described power factor correction part (5) current output obtains, described power factor correction part (5) is according to the operating voltage (Vb) of the described expection of described the second control signal (Ctrl_2) output.

3. LED driver according to claim 1, it is characterized in that, described switch control unit (3) comprises the first operational amplifier (X1), default first reference voltage (Vref_1) of in-phase input end access of described the first operational amplifier (X1), inverting input access described the first sampled voltage (Vs_1), output (X1_out) is connected to described switch element (2), first of described the first control signal of conduct (Ctrl_1) that calculates according to described the first sampled voltage (Vs_1) and default the first reference voltage (Vref_1) is controlled the conducting state that voltage (Vg_1) is adjusted described switch element (2).

4. LED driver according to claim 3, it is characterized in that, described switch control unit (3) also comprises the second resistance (R2) and the 3rd resistance (R3), wherein, described the second resistance (R2) and the 3rd resistance (R3) are connected in series between supply power voltage (Vcc) and ground, and the in-phase input end of described the first operational amplifier (X1) is connected to the node between described the second resistance (R2) and the 3rd resistance (R3).

5. LED driver according to claim 4, it is characterized in that, described switch control unit (3) also comprises the 4th resistance (R4) and the first electric capacity (C1), and described the 4th resistance (R4) and described the first electric capacity (C1) are connected between the inverting input and output (X1_out) of described the first operational amplifier (X1) with being one another in series.

6. LED driver according to claim 4, it is characterized in that, described switch control unit (3) also comprises the 5th resistance (R5), one end of described the 5th resistance (R5) is connected to the inverting input of described the first operational amplifier (X1) and the node between described the first electric capacity (C1), and the other end of described the 5th resistance (R5) is connected to the output of described load branch.

7. LED driver according to claim 6, it is characterized in that, described LED driver also comprises the 6th resistance (R6), and described the 6th resistance (R6) is connected between node and ground between the output of the other end of described the 5th resistance (R5) and described the second load group (S2).

8. LED driver according to claim 6, is characterized in that, described switch element (2) comprises a MOSFET pipe (Q11; ...; Q1m), wherein, a described MOSFET pipe (Q11; ...; Q1m) drain electrode is connected to the LED light-emitting diode (DL11 as described the second load group (S2); ...; DLm1) positive pole, source electrode are connected to described LED light-emitting diode (DL11; ...; DLm1) negative pole, grid are connected to the output (X1_out) of described the first operational amplifier (X1) and the node between described the 4th resistance (R4).

9. LED driver according to claim 8, is characterized in that, described switch element (2) also comprises the first diode (D11; ...; D1m), described the first diode (D11; ...; D1m) positive pole is connected to the output (X1_out) of described the first operational amplifier (X1) and the node between described the 4th resistance (R4), and negative pole is connected to a described MOSFET pipe (Q11; ...; Q1m) grid.

10. LED driver according to claim 9, is characterized in that, described switch element (2) also comprises the first resistance (R11; ...; R1m), described the first resistance (R11; ...; R1m) a end is connected to a described MOSFET pipe (Q11; ...; Q1m) grid and described the first diode (D11; ...; D1m) node between negative pole, and the other end is connected to a described MOSFET pipe (Q11; ...; Q1m) source electrode and described LED light-emitting diode (DL11; ...; DLm1) node between negative pole.

11. the described LED driver of any one according to claim 1 to 10, it is characterized in that, described power factor correction part (5) comprises the 2nd MOSFET pipe (Qp), inductance (L1), the second electric capacity (C2), the second diode (D2), wherein, the drain electrode of described the 2nd MOSFET pipe (Qp) is connected to the live wire of AC power, source electrode is connected to an end of described inductance (L1), grid is connected to described feedback control unit (4), the other end of described inductance (L1) is connected to the output (Out_pfc) of described PFC-AC/DC change-over circuit (1), one end of described the second electric capacity (C2) is connected to the node between the output of the other end of described inductance (L1) and described power factor correction part (5), other end ground connection, the negative pole of described the second diode (D2) is connected to the node between an end of the source electrode of described the 2nd MOSFET pipe (Qp) and described inductance (L1), positive pole is connected to the other end of described the second electric capacity (C2) and the node between ground.

12. LED driver according to claim 10, it is characterized in that, described feedback control unit (4) comprises the second operational amplifier (X2), PFC control circuit (6) and reference voltage generating circuit (7), the in-phase input end of described the second operational amplifier (X2) is connected to the output of described reference voltage generating circuit (7), described reference voltage generating circuit

(7) input is connected to the output of described the second load group (S2), inverting input is connected to the output of described power factor correction part (5), the output (X2_out) of described the second operational amplifier (X2) is connected to the input of described PFC control circuit (6), and the grid of described the 2nd MOSFET pipe (Qp) is connected to the output of described PFC control circuit (6).

13. the described LED driver of any one according to claim 1 to 10, it is characterized in that, the quantity N of the LED light-emitting diode in described the first load group (S1) can obtain by following formula, be N=Vdc/Vf, wherein Vdc is the direct voltage of described PFC-AC/DC change-over circuit (1) output, and Vf is the forward voltage of described LED light-emitting diode.

14. the described LED driver of any one according to claim 1 to 10, it is characterized in that, the quantity M of the LED light-emitting diode in described the second load group (S2) can obtain by following formula, be M=Vacp-p/Vf, wherein Vacp-p is the AC portion in the operating voltage of described PFC-AC/DC change-over circuit (1) output, and Vf is the forward voltage of described LED light-emitting diode.

15. a LED lighting device is characterized in that, described LED lighting device has the described LED driver of any one according to claim 1 to 14.

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