CN203896559U - Constant current driving circuit of light-emitting device - Google Patents
Constant current driving circuit of light-emitting device Download PDFInfo
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- CN203896559U CN203896559U CN201420284271.XU CN201420284271U CN203896559U CN 203896559 U CN203896559 U CN 203896559U CN 201420284271 U CN201420284271 U CN 201420284271U CN 203896559 U CN203896559 U CN 203896559U
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Abstract
The utility model provides a constant current driving circuit of a light-emitting device. The constant current driving circuit comprises a transformer, a switch device, a current sampling circuit, a driving control circuit, and a compensating circuit, the transformer comprises a primary winding and a secondary winding, the primary winding of the transformer and the light-emitting device are connected in series between a voltage input terminal and a first terminal of the switch device, a first terminal of the current sampling circuit is connected with a second terminal of the switch device, a second terminal of the current sampling circuit is connected with a second terminal of the secondary winding of the transformer, a first terminal of the driving control circuit is connected with a first terminal of the secondary winding of the transformer, a second terminal of the driving control circuit is connected with a second terminal of the secondary winding of the transformer, a third terminal of the driving control circuit is connected with a control terminal of the switch device and is configured to control the switch-on and switch-off of the switch device, a first terminal of the compensating circuit is connected with the first terminal of the secondary winding of the transformer, and a second terminal of the compensating circuit is connected with the first terminal of the current sampling circuit.
Description
Technical field
The utility model relates to luminescent device constant-current drive technology field, and relates more specifically to a kind of constant-current drive circuit.
Background technology
At present, in the drive circuit of luminescent device, due to the turn-off delay characteristic of switching device, after described drive circuit provides the control signal of control switch device shutoff, switching device could turn-off after substantially fixing turn-off delay time.Because such turn-off delay time is uncontrollable, in the time that input voltage increases, can cause the electric current that flows through luminescent device to increase, thereby the luminosity of luminescent device is increased; Otherwise, in the time that input voltage reduces, can cause the current reduction that flows through luminescent device, thereby the luminosity of luminescent device is also reduced.Therefore the problem that, exists the luminosity of luminescent device to fluctuate with the fluctuation of input voltage.
Utility model content
Consider the problems referred to above and proposed the utility model.The utility model provides a kind of constant-current drive circuit of luminescent device, the time that it turn-offs by compensating circuit regulation control switch device, thus make the mean value of the electric current that flows through described switching device not be subject to the impact of input voltage fluctuation.
According to the utility model embodiment, a kind of constant-current drive circuit of luminescent device is provided, comprising: transformer, it comprises former limit winding and time limit winding; Switching device, the former limit winding of described transformer and described luminescent device are connected in series between voltage input end and the first end of switching device; Current sampling circuit, its first end is connected with the second end of described switching device, and its second end is connected with the second end of the inferior limit winding of described transformer; Drive and Control Circuit, its first end connects the first end of the inferior limit winding of described transformer, its second end connects the second end of the inferior limit winding of described transformer, with and the 3rd end connect the control end of described switching device, and be configured to control the turn-on and turn-off of described switching device; And compensating circuit, its first end connects the first end of the inferior limit winding of described transformer, and its second end connects the first end of described current sampling circuit.
According to the utility model embodiment, in the time of described switching device conducting, described compensating circuit, by utilizing the voltage of inferior limit winding of described transformer to the described current sampling circuit electric current that affords redress, compensates the current fluctuation of the described luminescent device being caused by the input voltage fluctuation of described voltage input end.
According to the constant-current drive circuit of the utility model embodiment, in the time of described switching device conducting, compensating circuit utilizes the voltage of inferior limit winding of described transformer to the described current sampling circuit electric current that affords redress, thereby regulate the voltage of described current sampling circuit, then the time that regulation control switch device turn-offs, thus make the mean value of the electric current that flows through described switching device not be subject to the impact of input voltage fluctuation.
Brief description of the drawings
In conjunction with the drawings embodiment of the present utility model is described in detail, above-mentioned and other object, feature, advantage of the present utility model will become apparent, wherein:
Fig. 1 shows according to the schematic diagram of the constant-current drive circuit of the current mode luminescent device of the utility model embodiment;
Fig. 2 shows according to the schematic circuit of the constant-current drive circuit of the current mode luminescent device of the utility model embodiment;
Fig. 3 shows the equivalent circuit diagram in the first working hour according to the constant-current drive circuit of the current mode luminescent device of the utility model embodiment;
Fig. 4 shows the equivalent circuit diagram in the second working hour according to the constant-current drive circuit of the current mode luminescent device of the utility model embodiment;
Fig. 5 shows the equivalent circuit diagram in the 3rd working hour according to the constant-current drive circuit of the current mode luminescent device of the utility model embodiment;
Fig. 6 shows according to the exemplary waveform diagrams of signal in the constant-current drive circuit of the current mode luminescent device of the utility model embodiment.
Embodiment
Illustrate below with reference to the accompanying drawings according to the constant-current drive circuit of the current mode luminescent device of the utility model embodiment.
As shown in Figure 1, show according to the constant-current drive circuit 1 of the current mode luminescent device of the utility model embodiment, wherein, described constant-current drive circuit 1 comprises: transformer T1, switching device Q1, Drive and Control Circuit 10, compensating circuit 13 and current sampling circuit 14.
Described transformer T1 comprises former limit winding L A and time limit winding L B, and the first end B1 of the first end A1 of described former limit winding L A and described limit winding L B is Same Name of Ends.The turn ratio of described former limit winding L A and described limit winding L B is N.
The first end 101 of described Drive and Control Circuit 10 connects the first end B1 of the inferior limit winding L B of described transformer T1, its second end 102 connects the second end B2 of the inferior limit winding L B of described transformer T1, with and the 3rd end 103 connect the control end B of described switching device Q1, and described Drive and Control Circuit 10 is configured to control the turn-on and turn-off of described switching device Q1.
Described switching device Q1 can be current drive-type switching device, for example, can be pliotron, and its control end is base stage, and its first end is collector electrode, and its second end is emitter.
Described Drive and Control Circuit 10 is by controlling described switching device Q1 conducting at its 3rd end 103 output driving currents, and controls described switching device Q1 and turn-off by stop output driving current at its 3rd end 103.
Described Drive and Control Circuit 10 may further include: turn-on control circuit 11 and switch off control circuit 12.
The first input end 111 of described turn-on control circuit 11 connects the first end B1 of the inferior limit winding L B of described transformer T1, its second input 112 connects with reference to ground GND, and 12 the 3rd input 123 and the control end B of described switching device Q1 switch off control circuit described in its output 113 connects.
Described 12 the first input end 121 of switching off control circuit connects the first end B1 of the inferior limit winding L B of described transformer T1, its second input 122 connects the second end B2 (with reference to ground GND) of the inferior limit winding L B of described transformer T1, and the 3rd input 123 connects the output 113 of described turn-on control circuit 11 and the control end B of described switching device Q1.
The current potential of the first end B1 of the inferior limit winding L B that described turn-on control circuit 11 is configured at described transformer T1 output driving current during higher than the current potential of its second end B2 (with reference to ground GND earth potential), and at the current potential of the first end B1 of the inferior limit winding L B of described transformer T1 output driving current no longer during lower than the current potential of its second end B2.
Described switch off control circuit 12 be configured to not receive described drive current in the time that predetermined condition meets, and in the time that not meeting, predetermined condition receives described drive current, thereby make described drive current no longer flow to the control end B of described switching device Q1, turn-off to control described switching device Q1.
In other words, in the time that predetermined condition meets, the control end B of described switching device Q1 receives described drive current, thereby controls described switching device Q1 conducting; And in the time that predetermined condition does not meet, described in switch off control circuit 12 the 3rd input 123 receive described drive current, the control end B of described switching device Q1 no longer receives described drive current, turn-offs thereby control described switching device Q1.
The former limit winding L A of described transformer T1 and described luminescent device are connected in series between voltage input end and the first end of switching device Q1.
Described switching device Q1 is current mode switch device Q1, for example, can be pliotron.In the situation that switching device Q1 is pliotron, the base stage B that its control end is pliotron, the collector electrode C that its first end is pliotron, the emitter E that its second end is pliotron.
Particularly, as shown in Figure 1, the anode of described luminescent device is connected with described voltage input end, and the negative electrode of described luminescent device is connected with the first end A1 of the former limit winding L A of described transformer T1, and the second end A2 of described former limit winding L A is connected with the first end C of described switching device Q1.
But, be not limited to the connected mode described in Fig. 1, alternatively, the first end A1 of the former limit winding L A of described transformer T1 is connected with described voltage input end, the second end A2 of described former limit winding L A and the anodic bonding of described luminescent device, the negative electrode of described luminescent device is connected with the first end C of described switching device Q1.
The first end 131 of described compensating circuit 13 connects the first end B1 of the inferior limit winding L B of described transformer T1, and its second end 132 connects the first end 141 of described current sampling circuit 14.The first end 141 of described current sampling circuit 14 is connected with the second end E of described switching device Q1, and its second end 142 is connected with reference ground GND (being the second end B2 of the inferior limit winding L B of described transformer T1).
Described compensating circuit 13 is configured to: in the time of described switching device Q1 conducting, utilize the voltage of inferior limit winding L B of described transformer T1 to described current sampling circuit 14 electric current that affords redress, compensate the current fluctuation of the described luminescent device being caused by the input voltage fluctuation of described voltage input end.
In addition as shown in Figure 1, can also comprise according to the constant-current drive circuit 1 of the luminescent device of the utility model embodiment: filter circuit 15 and freewheeling circuit 16.
Filter circuit 15 is connected in parallel with described luminescent device.The first end of freewheeling circuit 16 connects the first end C of described switching device Q1, and its second end connects described voltage input end.
In the time of described switching device Q1 conducting, the current potential of the first end A1 of the former limit winding L A of described transformer T1 is higher than the current potential of the second end A2, now direction of current flow is: from voltage input end flow through described filter circuit 15 and described luminescent device, then flow to the second end A2 from the first end A1 of the former limit winding L A of transformer T1, then via the switching device Q1 current flowing sample circuit 14 of conducting, finally flow into reference to ground GND.
On the other hand, in the time that described switching device Q1 turn-offs, because the electric current of the former limit winding L A of described transformer T1 can not suddenly change, therefore now direction of current flow is: flow to the second end A2 from the first end A1 of the former limit winding L A of transformer T1, then via freewheeling circuit 16 afterflows and flow into described filter circuit 15 and described luminescent device.Now, the voltage reversal of the former limit winding L A of described transformer T1, the current potential of its first end A1 is lower than the current potential of described the second end A2.
As shown in Figure 2, show according to the schematic circuit of the constant-current drive circuit of the current mode luminescent device of the utility model embodiment.
Described compensating circuit 13 comprises the 3rd resistance R 3, and described current sampling circuit 14 comprises the first resistance R 1.
Described filter circuit 15 is the first capacitor C 1, and described freewheeling circuit 16 comprises the first diode D1, and the first end of freewheeling circuit 16 is the anode of described the first diode D1, and the second end of freewheeling circuit 16 is the negative electrode of described the first diode D1.
Described turn-on control circuit 11 comprises the second resistance R 2, the second capacitor C 2 and the second diode D2.
In described turn-on control circuit 11, described the second resistance R 2 and described the second capacitor C 2 are connected in series between the first input end 111 and output 113 of described turn-on control circuit 11, and the second input 112 of turn-on control circuit 11 and negative electrode connect the output 113 of described turn-on control circuit 11 described in the anodic bonding of described the second diode D2.
At the current potential of the first end B1 of the inferior limit winding L B of described transformer T1 during higher than the current potential of its second end B2 (with reference to ground GND earth potential), described the second capacitor C 2 is charged, and described turn-on control circuit 11 is from its output 113 output driving currents.
On the other hand, at the current potential of the first end B1 of the inferior limit winding L B of described transformer T1 during lower than the current potential of its second end B2 (with reference to ground GND earth potential), the electric current that flows through described the second capacitor C 2 is reverse, now direction of current flow is: from the anode of described the second diode D2 to negative electrode, flow through described the second capacitor C 2 and the second resistance R 2, flow into the first end B1 of the inferior limit winding L B of described transformer T1, and the no longer output driving current of output 113 of described turn-on control circuit 11 now.
Described switch off control circuit 12 comprise the 3rd diode D3, the 3rd capacitor C 3 and voltage-stabiliser tube ZD1.
Switch off control circuit in 12 described, the anodic bonding of the anode of described the 3rd diode D3, the first end of described the 3rd capacitor C 3 and described voltage-stabiliser tube ZD1,12 first input end 121 switches off control circuit described in the negative electrode of described the 3rd diode D3 connects, switch off control circuit described in the second end of described the 3rd capacitor C 3 connects the second input 122 of 12,12 the 3rd input 123 switches off control circuit described in the negative electrode of described voltage-stabiliser tube ZD1 connects.
The current potential of the described 12 control end B that are configured at described switching device Q1 that switch off control circuit is not enough so that the drive current that the output 113 that described voltage-stabiliser tube ZD1 does not extract described turn-on control circuit 11 from its 3rd input 123 while puncturing is exported, and the drive current that the output 113 that extracts described turn-on control circuit 11 from its 3rd input 123 in the time that the current potential of the control end B of described switching device Q1 is enough to described voltage-stabiliser tube ZD1 is punctured is exported, 12 the 3rd input 123 switches off control circuit described in the drive current that makes to export from the output 113 of described turn-on control circuit 11 flows into completely, and no longer flow into the control end B of described switching device Q1.
Particularly, in the time of output 113 output driving current of described turn-on control circuit 11, and in the time that the not enough so that described voltage-stabiliser tube ZD1 of the current potential of the control end B of described switching device Q1 punctures, described drive current all flows into the control end B of described switching device Q1; But, in the time that the current potential of the control end B of described switching device Q1 is enough to make described voltage-stabiliser tube ZD1 to puncture, described voltage-stabiliser tube ZD1 is breakdown extracts a large amount of electric currents from described 12 the 3rd input 123 of switching off control circuit, make described drive current all flow into described voltage-stabiliser tube ZD1, and no longer flow into the control end B of described switching device Q1.Thus, described in 12 drive currents of exporting by extracting described turn-on control circuit 11 that switch off control circuit, turn-off thereby control described switching device Q1.
Describe according to the concrete operations of the constant-current drive circuit of the current mode luminescent device of the utility model embodiment below with reference to Fig. 3-6.
First stage (, startup stage)
For example, in the time initially applying input voltage vin, now, in all electric capacity shown in Fig. 2, all not having does not all have electric current to flow through in storage voltage and described inductance.Switching device Q1 is in off-state, and because the first capacitor C 1 two ends pressure drop can not suddenly change, the electric current of the former limit winding L A of transformer T1 can not suddenly change, therefore input voltage vin is applied on switching device Q1 substantially completely.
In the time initially applying input voltage vin, utilize input voltage vin to provide small startup drive current by start-up circuit to the control end B of switching device Q1, make switching device Q1 work in linear conducting state.Described start-up circuit can be for example the resistance being connected between input voltage vin and the control end B of switching device Q1, and this resistance can have larger resistance value.In order not obscure technical solutions of the utility model, described start-up circuit is not shown in the accompanying drawings.In the utility model embodiment, the form to described start-up circuit is not done any restriction, it will be understood by a person skilled in the art that and can adopt any start-up circuit existing or that develop in the future.
At switching device Q1 when cut-off state becomes linear conducting state, the pressure drop V at switching device Q1 two ends
q1reduce, make the voltage V on the former limit winding L A of transformer T1
lAincrease, simultaneously the coupled voltages V on the inferior limit winding L B of transformer T1
lBalso increase, then make the charging current of the second capacitor C 2 increase, the drive current that flows to the control end B of switching device Q1 also increases, make switching device Q1 by linear conducting state to saturation conduction state-transition, and then make the pressure drop V at the two ends of switching device Q1
q1further reduce.As can be seen here, the former limit winding L A of switching device Q1, transformer T1 and inferior limit winding L B, the second resistance R 2, the second capacitor C 2 have formed positive feedback loop, make switching device Q1 saturation conduction rapidly.
In this process, along with the drive current of the control end B that flows into switching device Q1 increases gradually, switching device Q1 changes to operate in saturation district from linear work district.In the time that switching device Q1 works in operate in saturation district, according to the equivalent circuit diagram of the constant-current drive circuit of the current mode luminescent device of the utility model embodiment as shown in Figure 3.
In this stage, can set up following voltage equation:
Vin＝Vo+V
LA+V
Q1+V
R1 (1)
In formula (1), Vin represents input voltage, and Vo represents the voltage at the first capacitor C 1 two ends, V
lAthe voltage at the armature winding LA two ends of indication transformer T1, V
q1represent the voltage at switching device Q1 two ends, V
r1represent the voltage at the first resistance R 1 two ends.Figure 3 illustrates the positive direction of each voltage, in the utility model embodiment, the positive direction of each voltage shown in Fig. 3, respectively as the reference direction of each voltage, and will be adopted to such reference direction in the following description always.
After switching device Q1 is saturated, its two ends pressure drop V
q1be essentially 0, because the first resistance R 1 is very little resistance, its two ends pressure drop V
r1be only several volts.For example, the junction voltage that is 3.3V and switching device Q1 in the voltage stabilizing value of voltage-stabiliser tube ZD1 is 0.7V, and before voltage-stabiliser tube ZD1 punctures, the voltage at the first resistance R 1 two ends mostly is 2.6V most.Ignoring V
q1and V
r1afterwards, above voltage equation (1) is reduced to:
Vin＝Vo+V
LA (2)
In addition, according to the voltage-current relationship of inductance, can be by the voltage V of the former limit winding L A of transformer T1
lAcan pass through its current i
lAbe expressed as:
V
LA＝(Vin-Vo)＝LA*(d(i
LA)/dt) (3)
Current i on the former limit winding L A of transformer T1
lA(be the current i on switching device Q1
q1) while increasing to predetermined value, for example, while making the voltage of the control end B of switching device Q1 increase to the voltage stabilizing value of voltage-stabiliser tube ZD1, voltage-stabiliser tube ZD1 is breakdown and start to extract electric current, thereby the drive current IC2 that described turn-on control circuit 11 is exported no longer flows into the control end B of switching device Q1.
Now, the electric current that flows into the control end B of switching device Q1 is 0, the current potential of the control end B of switching device Q1 can be represented as follows:
V
ZD1＝V
QBE+V
R1＝V
QBE+i
R1*R1 (4)
In formula (4), V
zD1represent the puncture voltage of voltage-stabiliser tube ZD1, i
r1represent the electric current of resistance R 1, V
qBEvoltage between control end B and the second end E of expression switching device Q1, i.e. the junction voltage of switching device Q1.Therefore, can now be flow through the current i of the first resistance R 1
r1with the current i that flows through switching device Q1
q1:
i
R1＝(V
ZD1-V
QBE)/R1 (5)
i
Q1＝i
R1-i
R3＝i
R1-((V
LB-i
R1*R1)/R3) (6)
In formula (6), V
lBfor the voltage of the inferior limit winding L B of transformer T1, i
r3be the electric current of the 3rd resistance R 3, it may be calculated:
V
LB＝V
LA/N＝(Vin-Vo)/N (7)
Can be obtained by above formula (5), (6) and (7):
i
Q1＝(V
ZD1-V
QBE)/R1-((Vin-Vo)/N-(V
ZD1-V
QBE))/R3) (8)
As shown in Figure 3, show the schematic equivalent circuit diagram according to the first stage of the utility model embodiment.
Second stage
Due to the retardance that current mode switch device Q1 turn-offs, flow into the control end B of switching device Q1 even without electric current, switching device Q1 also keeps conducting in time of delay in ts.Now, the voltage between the first end C of switching device Q1 and the second end E is still approximately zero, flows through the current i of switching device Q1
q1in fact continue to be decided by the charge condition of the former limit winding L A of transformer T1, determined by above formula (3), therefore, flow through transformer T1 former limit winding L A electric current and flow through the current i of switching device Q1
q1still rise, thereby in the time that this time of delay, ts finished, flow through the electric current and the current i that flows through switching device Q1 of the former limit winding L A of transformer T1
q1just reach its peak current.
In this time of delay ts, flow through the current i of switching device Q1
q1variation delta i
q1can be expressed as:
Δi
Q1＝((Vin-Vo)/LA)*ts (9)
Therefore the peak current that, flows through switching device Q1 can be expressed as:
i
peak Q1＝i
Q1+Δi
Q1 (10)
Therefore, comprehensive above formula (8), (9) and (10), the former limit winding L A that flows through transformer T1 can be expressed as with the peak current that flows through switching device Q1:
i
peak Q1＝(V
ZD1-V
QBE)/R1-((Vin-Vo)/N-(V
ZD1-V
QBE))/R3+((Vin-Vo)/LA)*ts＝(V
ZD1-V
QBE)*(1/R1+1/R3)+(Vin-Vo)*(ts/LA-1/(N*R3)) (11)
As shown in Figure 4, show the schematic equivalent circuit diagram according to the second stage of the utility model embodiment.
Phase III
Now, switching device Q1 turn-offs completely, and the former limit winding L A electric current of transformer T1 can not suddenly change, and therefore the electric current of the former limit winding L A of the transformer T1 first diode D1 that flows through carries out afterflow, the now voltage reversal on the former limit winding L A of transformer T1, as shown in Figure 5.Still taking the voltage direction shown in Fig. 3 as positive direction, V now
lA=-Vo, the former limit winding L A of transformer T1 starts electric discharge.Meanwhile, the coupled voltages of the inferior limit winding L B of transformer T1 is also reverse, as shown in Figure 5.Still taking the voltage direction shown in Fig. 3 as positive direction, V now
lB=-Vo/N.As shown in Figure 5, coupled voltages V
lBvia the 3rd diode D3, the 3rd capacitor C 3 is charged on the one hand, through the second diode D2, the second capacitor C 2 is discharged on the other hand.
Finally, on the one hand, the voltage V of the 3rd capacitor C 3
c3there is polarity as shown in Figure 5, and V
lB+ V
c3+ V
d2=0, ignore the voltage V of the second diode D2
d2, V
c3=Vo/N, it is taking the direction shown in Fig. 5 as positive direction.On the other hand, in the second capacitor C 2, the voltage of storage is discharged completely, and in this, the 3rd working stage also can be called as the recovery stage.
In the time that this phase III finishes, the current i of the former limit winding L A of transformer T1
lAbe reduced to gradually zero from its peak value.
As shown in Figure 5, show the schematic equivalent circuit diagram according to the phase III of the utility model embodiment.
Fourth stage
In the current i of the former limit winding L A of transformer T1
lAbe reduced to gradually at 1 o'clock from its peak value, due to the existence of the first diode D1, the current i of former limit winding L A
lAcan be not reverse.
In the time that this fourth stage starts, the first capacitor C 1 both end voltage is Vo, and the voltage at the 3rd capacitor C 3 two ends is Vo/N.
Similar with the first stage, switching device Q1 arrives operate in saturation district from starting conducting via linear work district.In the time that fourth stage finishes, the voltage of the control end B of switching device Q1 is about to rise to V
zD1-V
c3, voltage-stabiliser tube ZD1 is punctured.
Five-stage
Now, the voltage of the control end B of switching device Q1 rises to V
zD1-V
c3, voltage-stabiliser tube ZD1 is punctured, the electric current that flows into the control end B of switching device Q1 is 0, referring to Fig. 4, the current potential of the control end B of switching device Q1 can be represented as follows:
V
ZD1＝V
QBE+V
R1+V
C3＝V
QBE+i
R1*R1+Vo/N (12)
Therefore, can now be flow through the electric current and the electric current that flows through switching device Q1 of the first resistance R 1:
i
R1＝(V
ZD1-V
QBE-Vo/N)/R1 (13)
i
Q1＝i
R1-i
R3＝i
R1-((V
LB-i
R1*R1)/R3)＝i
R1-(((Vin-Vo)/N-i
R1*R1)/R3) (14)
Due to the retardance that current mode switch device Q1 turn-offs, flow into the control end B of switching device Q1 even without electric current, switching device Q1 also keeps conducting in time of delay in ts.Now, the voltage between the first end C of switching device Q1 and the second end E is still approximately zero, flows through the current i of switching device Q1
q1in fact continue to be decided by the charge condition of the former limit winding L A of transformer T1, determined by above formula (3), therefore, flow through transformer T1 former limit winding L A electric current and flow through the current i of switching device Q1
q1still rise, thereby in the time that this time of delay, ts finished, flow through the electric current and the current i that flows through switching device Q1 of the former limit winding L A of transformer T1
q1just reach its peak current.
In this time of delay ts, flow through the current i of switching device Q1
q1variation delta i
q1can be expressed as:
Δi
Q1＝((Vin-Vo)/LA)*ts (15)
Now, the peak current that flows through switching device Q1 can be expressed as:
i
peak Q1＝i
Q1+Δi
Q1 (16)
Therefore, comprehensive above formula (15) and (16), the former limit winding L A that flows through transformer T1 can be expressed as with the peak current that flows through switching device Q1:
i
peak Q1＝(V
ZD1-V
QBE-Vo/N)/R1-((Vin-Vo)/N-(V
ZD1-V
QBE))/R3+((Vin-Vo)/LA)*ts＝(V
ZD1-V
QBE-Vo/N)*(1/R1+1/R3)+(Vin-Vo)*(ts/LA-1/(N*R3)) (17)
The 6th stage
The 6th stage is identical with the phase III, does not repeat them here.
After this, repeat successively fourth stage, five-stage and the 6th stage.In fourth stage, inductive current rises gradually; In five-stage, rise and reach peak current in the internal inductance electric current continuation time of delay of switching device Q1; In the 6th stage, inductive current declines to be reduced to 0 gradually.Therefore,, according to the utility model embodiment, the former limit winding L A of transformer T1 works in electric current critical conduction mode.
As mentioned above, in the time that five-stage finishes, the electric current of former limit winding L A that flows through transformer T1 is identical with the electric current that flows through switching device Q1, and all reaches peak current, that is:
i
peak Q1＝i
peak LA＝(V
ZD1-V
QBE-Vo/N)/R1-((Vin-Vo)/N-(V
ZD1-V
QBE))/R3+((Vin-Vo)/LA)*ts＝(V
ZD1-V
QBE-Vo/N)*(1/R1+1/R3)+(Vin-Vo)*(ts/LA-1/(N*R3)) (18)
In the time reaching stable state according to the constant-current drive circuit of the current mode luminescent device of the utility model embodiment, the current average that flows through the former limit winding L A of transformer T1 equals to flow into the current average of luminescent device.
As previously mentioned, in the utility model embodiment, the former limit winding L A of transformer T1 is operated in electric current critical conduction mode, and the current average that therefore flows through the former limit winding L A of transformer T1 is the half of the peak current of the former limit winding L A of transformer T1.In other words, the current average of current flowing type luminescent device is the half of the peak current of the former limit winding L A of transformer T1.Therefore, the average current I of current mode luminescent device
lEDcan be expressed as:
I
LED＝i
peak LA/2＝((V
ZD1-V
QBE-Vo/N)*(1/R1+1/R3)+(Vin-Vo)*(ts/LA-1/(N*R3)))/2 (19)
In above formula (19), have (Vin-Vo) * (ts/LA-1/ (N*R3)), in the time that the value of R3 is LA/ (ts*N), above formula (19) can be reduced to:
I
LED＝((V
ZD1-V
QBE-Vo/N)*(1/R1+1/R3) (20)
In formula (20), the current average I of current mode luminescent device
lEDirrelevant with input voltage vin, therefore, even if input voltage vin increases or reduces the current average I of current mode luminescent device
lEDall keep constant, correspondingly the luminosity of current mode luminescent device also keeps constant.
As shown in Figure 6, show according to the constant-current drive circuit of the current mode luminescent device of the utility model embodiment and reach while stablizing the wherein voltage V of the former limit winding L A of transformer T1
lAand current i
lA, and the current i of the control end B of switching device Q1
b.Should be appreciated that, in Fig. 6, do not illustrate that the first stage is to the phase III.
From t0 to t1, be fourth stage, wherein the current i LA of the former limit winding L A of transformer T1 starts from scratch and constantly rises, until the voltage of the control end B of switching device Q1 makes voltage-stabiliser tube ZD1 puncture in the t1 moment.
In the t1 moment, the current i B of the control end B of switching device Q1 is reduced to rapidly zero.
From t1 to t2, be five-stage, wherein due to the delay turn-off characteristic of switching device Q1, the current i of the former limit winding L A of transformer T1
lAcontinue to rise, the difference between t2 and t1 equals ts time of delay of switching device Q1.
In the t2 moment, the current i of the former limit winding L A of transformer T1
lAreach peak value.
From t2 to t3, be the 6th stage, the wherein voltage reversal of the former limit winding L A of transformer T1, by the first diode D1 afterflow.
In the t3 moment, the current i of the former limit winding L A of transformer T1
lAdrop to zero.
Then, enter the next one from fourth stage to the circulation in six stages.
In Fig. 6, in order to illustrate to have exaggerated amplitude and the proportionate relationship of signal, the utility model embodiment is not limited to the signal amplitude shown in Fig. 6 and proportionate relationship, as long as meet the trend that the each signal shown in Fig. 6 changes according to each time point.
According to the constant-current drive circuit of the current mode luminescent device of the utility model embodiment, by according to the former limit winding inductance LA of the former limit winding L A of delay turn-off time ts, the transformer T1 of switching device Q1 and inferior limit winding L B turn ratio N and transformer T1, mean value and the input voltage vin of the electric current of current flowing type luminescent device are had nothing to do, thereby the brightness constancy that ensures current mode luminescent device, does not fluctuate along with the fluctuation of input voltage.
Although in the utility model embodiment, luminescent device is expressed as to LED, but the utility model is not limited to this, luminescent device can comprise current mode luminescent device.In addition, although in the utility model embodiment, switching device is expressed as to pliotron, but the utility model is not limited to this, and switching device can comprise current mode switch device.
Although example embodiment has been described with reference to the drawings here, it is only exemplary should understanding above-mentioned example embodiment, and is not intended to scope of the present utility model to be limited to this.Those of ordinary skill in the art can make various changes and modifications therein, and do not depart from scope and spirit of the present utility model.Within all such changes and modifications are intended to be included in the desired scope of the present utility model of claims.
Claims (10)
1. a constant-current drive circuit for luminescent device, comprising:
Transformer, it comprises former limit winding and time limit winding;
Switching device, the former limit winding of described transformer and described luminescent device are connected in series between voltage input end and the first end of switching device;
Current sampling circuit, its first end is connected with the second end of described switching device, and its second end is connected with the second end of the inferior limit winding of described transformer;
Drive and Control Circuit, its first end connects the first end of the inferior limit winding of described transformer, its second end connects the second end of the inferior limit winding of described transformer, with and the 3rd end connect the control end of described switching device, and be configured to control the turn-on and turn-off of described switching device; And
Compensating circuit, its first end connects the first end of the inferior limit winding of described transformer, and its second end connects the first end of described current sampling circuit.
2. constant-current drive circuit as claimed in claim 1, also comprises:
Filter circuit, itself and described luminescent device are connected in parallel; And
Freewheeling circuit, its first end connects the first end of described switching device, and its second end connects described voltage input end.
3. constant-current drive circuit as claimed in claim 2, wherein, described switching device is current drive-type switching device, and its control end is base stage, and its first end is collector electrode, and its second end is emitter;
Described Drive and Control Circuit is by controlling described switching device conducting at its 3rd end output driving current; And
Described Drive and Control Circuit is controlled described switching device shutoff by stop output driving current at its 3rd end.
4. constant-current drive circuit as claimed in claim 3, wherein, described compensating circuit comprises the 3rd resistance, described current sampling circuit comprises the first resistance.
5. constant-current drive circuit as claimed in claim 4, wherein, described Drive and Control Circuit comprises:
Turn-on control circuit, its first input end connects the first end of the inferior limit winding of described transformer, and its second input connects the second end of the inferior limit winding of described transformer, and its output connects the control end of described switching device; And
Switch off control circuit, its first end connects the first end of the inferior limit winding of described transformer, and its second end connects the second end of the inferior limit winding of described transformer, with and the 3rd end connect the control end of described switching device;
Wherein, the output output driving current of described turn-on control circuit; In the time that predetermined condition meets, the control end of described switching device receives described drive current, thereby controls described switching device conducting; And in the time that predetermined condition does not meet, described in the 3rd termination that switches off control circuit receive described drive current, the control end of described switching device no longer receives described drive current, turn-offs thereby control described switching device.
6. constant-current drive circuit as claimed in claim 5, wherein, described in switch off control circuit and comprise the 3rd diode, the 3rd electric capacity and voltage-stabiliser tube,
Wherein, the anode of described the 3rd diode, described the 3rd first end of electric capacity and the anodic bonding of described voltage-stabiliser tube, the first input end switching off control circuit described in the negative electrode of described the 3rd diode connects, the second input switching off control circuit described in the second end of described the 3rd electric capacity connects, the 3rd input switching off control circuit described in the negative electrode of described voltage-stabiliser tube connects
Wherein, described predetermined condition is that described voltage-stabiliser tube is not breakdown.
7. constant-current drive circuit as claimed in claim 6, wherein, described turn-on control circuit comprises the second resistance, the second electric capacity and transistor seconds,
Wherein, described the second resistance and described the second capacitances in series are connected between the first input end and output of described turn-on control circuit, and the second input of turn-on control circuit and negative electrode connect the output of described turn-on control circuit described in the anodic bonding of described transistor seconds.
8. constant-current drive circuit as claimed in claim 7, wherein, described filter circuit comprises the first electric capacity, described freewheeling circuit comprises the first diode.
9. constant-current drive circuit as claimed in claim 8, wherein,
The anode of described luminescent device is connected with described voltage input end, the negative electrode of described luminescent device is connected with the first end of the former limit winding of described transformer, the second end of described former limit winding and the first end of described switching device and the anodic bonding of described the first diode, the negative electrode of described the first diode is connected with described voltage input end.
10. constant-current drive circuit as claimed in claim 8, wherein,
The first end of the former limit winding of described transformer is connected with described voltage input end, the second end of described former limit winding and the anodic bonding of described luminescent device, the anodic bonding of the negative electrode of described luminescent device and the first end of described switching device and described the first diode, the negative electrode of described the first diode is connected with described voltage input end.
Priority Applications (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201420284271.XU CN203896559U (en) | 2014-05-30 | 2014-05-30 | Constant current driving circuit of light-emitting device |
| PCT/CN2015/080148 WO2015180675A1 (en) | 2014-05-30 | 2015-05-29 | Constant-current drive circuit for light-emitting device and drive method therefor |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201420284271.XU CN203896559U (en) | 2014-05-30 | 2014-05-30 | Constant current driving circuit of light-emitting device |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN203896559U true CN203896559U (en) | 2014-10-22 |
Family
ID=51722907
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201420284271.XU Expired - Fee Related CN203896559U (en) | 2014-05-30 | 2014-05-30 | Constant current driving circuit of light-emitting device |
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| Country | Link |
|---|---|
| CN (1) | CN203896559U (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2015180675A1 (en) * | 2014-05-30 | 2015-12-03 | 欧普照明股份有限公司 | Constant-current drive circuit for light-emitting device and drive method therefor |
| CN105228288A (en) * | 2014-05-30 | 2016-01-06 | 欧普照明股份有限公司 | The constant-current drive circuit of luminescent device and driving method |
-
2014
- 2014-05-30 CN CN201420284271.XU patent/CN203896559U/en not_active Expired - Fee Related
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2015180675A1 (en) * | 2014-05-30 | 2015-12-03 | 欧普照明股份有限公司 | Constant-current drive circuit for light-emitting device and drive method therefor |
| CN105228288A (en) * | 2014-05-30 | 2016-01-06 | 欧普照明股份有限公司 | The constant-current drive circuit of luminescent device and driving method |
| CN105228288B (en) * | 2014-05-30 | 2018-03-06 | 欧普照明股份有限公司 | The constant-current drive circuit and driving method of luminescent device |
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