CN102905416A - Light source driving circuit and driving method - Google Patents
Light source driving circuit and driving method Download PDFInfo
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- CN102905416A CN102905416A CN201210156029XA CN201210156029A CN102905416A CN 102905416 A CN102905416 A CN 102905416A CN 201210156029X A CN201210156029X A CN 201210156029XA CN 201210156029 A CN201210156029 A CN 201210156029A CN 102905416 A CN102905416 A CN 102905416A
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- storage component
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Abstract
The invention discloses a light source driving circuit and a driving method. The driving circuit comprises a converter circuit which provides a first output voltage on a first power line to the light source for power supply, and provides a second output voltage on a second power line, and the second output voltage is smaller than the first output voltage; an energy storage component which modulates the current of the light source through charging and discharging the energy storage component; and a switch component which is coupled to the converter circuit and the energy storage component, and when the switch component is working at a first state, then the energy storage component is in charging, and when the switch component is working at a second state, the energy storage component is in discharging. The converter circuit provides the second output voltage, so that the working voltage at both ends of the switch component is maintained to be smaller than the first output voltage during the first state and the second state. As a result, a switch component with relatively low nominal voltage can be adopted so as to reduce power consumption and cost of the driving circuit.
Description
Technical field
The present invention relates to a kind of drive circuit and driving method, relate in particular to a kind of drive circuit and driving method of light source.
Background technology
In display system, drive circuit drives one or more light sources and illuminates display screen.Such as, in using light-emitting diode (Light Emitting Diode, LED) liquid crystal display (Liquid Crystal Display, LCD) system backlight, led array is used for illuminating LCDs.Led array generally includes one or more LED strings, and each LED string comprises one group of LED of mutual series connection.
Figure 1 shows that the schematic diagram of drive circuit 100 of the prior art.Drive circuit 100 driving LED strings 106, it comprises converter circuit 102, on-off controller 104 and switching regulaor 108.Converter circuit 102 receives input voltage V
IN, and provide output voltage V at power line 141
OUT, with driving LED string 106.Switching regulaor 108 comprises and LED string 106 inductance L of connecting 1.Switching regulaor 108 also comprises switch S 1 and diode D1, is used for controlling the inductive current of inductance L 1 of flowing through.More particularly, on-off controller 104 provides pulse-width modulation (Pulse Width Modulation, PWM) signal 130, in order to closed and disconnected switch S 1.When switch S 1 is closed, diode D1 reverse bias, inductive current flow through successively power line 141, LED string 106, inductance L 1, switch S 1 and resistance R
SENOutput voltage V
OUTBe 106 power supplies of LED string, and be inductance L 1 charging.When switch S 1 disconnects, diode D1 forward bias, inductive current flow through successively inductance L 1, diode D1, power line 141 and LED string 106.Inductance L 1 discharge, thus be 106 power supplies of LED string.Therefore, recently regulate the mean value of inductive current by the duty of adjusting pulsewidth modulation signal 130, thereby regulate the electric current of the LED string 106 of flowing through.
Yet when switch S 1 disconnected, the anode voltage of diode D1 was (such as V
ANODE) rise to greater than V
OUTThereby, forward bias diode D1.So the voltage at switch S 1 two ends is (such as V
ANODE-V
R) be substantially equal to V
OUTWhen switch S 1 closure, the voltage at diode D1 two ends is substantially equal to V
OUTTherefore, the rated voltage of switch block (for example, switch S 1 and diode D1) must be greater than V
OUTOtherwise, when the operating voltage of switch block is substantially equal to V
OUTThe time, switch block can be damaged.If increase the LED number in the LED string 106 in order to realize higher brightness, then output voltage V
OUTIncrease.In this case, the switch block that has a relatively high rated voltage has increased power consumption and the cost of drive circuit 100.
Summary of the invention
The technical problem to be solved in the present invention is to provide a kind of light source driving circuit and driving method, in order to reducing the rated voltage of switch block, thereby reduces power consumption and the cost of drive circuit.
For solving the problems of the technologies described above, the invention provides a kind of light source driving circuit.This drive circuit comprises: converter circuit, and provide the first output voltage to think described light source power supply at the first power line, and provide the second output voltage at the second power line, wherein, described the second output voltage is less than described the first output voltage; Energy storage component is by regulating the electric current of described light source for described energy storage component charging and discharging; And switch block, be coupled to described converter circuit and described energy storage component, when described switch block works in the first state, described energy storage component charging; When described switch block works in the second state, described energy storage component discharge; Wherein, described converter circuit provides described the second output voltage, and with when described the first state and described the second state, the operating voltage at described switch block two ends all keeps less than described the first output voltage.
The present invention also provides a kind of light source driving circuit, and described light source is a plurality of.This drive circuit comprises: converter circuit, and be used for providing the first output voltage to think described a plurality of light source power supply at the first power line, and provide the second output voltage at the second power line, wherein, described the second output voltage is less than described the first output voltage; And a plurality of switching regulaors, with described converter circuit coupling, be respectively applied to regulate the electric current of described a plurality of light sources, each described switching regulaor comprises switch block and energy storage component, wherein, when described switch block works in the first state, described energy storage component charging; When described switch block works in the second state, described energy storage component discharge; Regulate the electric current of corresponding light source by the duration of regulating described energy storage component charging and discharging, wherein, described converter circuit provides described the second output voltage, with when described the first state and described the second state, the operating voltage at described switch block two ends all keeps less than described the first output voltage.
The present invention provides again a kind of light source driving method, comprising: provide the first output voltage at the first power line, be described light source power supply; Provide the second output voltage less than described the first output voltage at the second power line; Switch block works in the first state, so that the energy storage component charging; Described switch block works in the second state, so that the discharge of described energy storage component; And, be in duration of described the first state and described the second state by regulating described switch block, regulate the electric current of described light source; Wherein, described the second output voltage that provides is so that when described the first state and described the second state, the operating voltage at described switch block two ends all keeps less than described the first output voltage.
It is light source power supply that drive circuit of the present invention provides the first output voltage at the first power line, and provide the second output voltage less than the first output voltage at the second power line, therefore, when switch block was in the first state and the second state, the operating voltage at switch block two ends all kept less than the first output voltage.Therefore, can select the switch block that adopts rated voltage relatively low, to reduce power consumption and the cost of drive circuit.
Description of drawings
Below by to the description of some embodiments of the present invention in conjunction with its accompanying drawing, can further understand purpose of the present invention, specific structural features and advantage.
Figure 1 shows that the schematic diagram of drive circuit of the prior art;
Figure 2 shows that the schematic diagram according to the drive circuit that is used for the driving load of the embodiment of the invention;
Figure 3 shows that the circuit diagram according to the drive circuit that is used for the driving load of the embodiment of the invention;
Be respectively the circuit diagram according to the converter circuit of the embodiment of the invention shown in Fig. 4 A and Fig. 4 B;
Figure 5 shows that another circuit diagram according to the converter circuit of the embodiment of the invention;
Figure 6 shows that another circuit diagram according to the drive circuit that is used for the driving load of the embodiment of the invention;
Figure 7 shows that the another circuit diagram according to the drive circuit that is used for the driving load of the embodiment of the invention;
Figure 8 shows that the circuit diagram for the drive circuit that drives a plurality of loads according to the embodiment of the invention; And
Figure 9 shows that the flow chart according to embodiment of the invention light source driving method.
Embodiment
Below will provide detailed reference to embodiments of the invention.Although the present invention sets forth by these execution modes and illustrates, it should be noted that the present invention not merely is confined to these execution modes.On the contrary, all substitutes, variant and the equivalent in the defined invention spirit of appended claim and the invention scope contained in the present invention.
In addition, for better explanation the present invention, provided numerous details in the embodiment hereinafter.It will be understood by those skilled in the art that does not have these details, and the present invention can implement equally.In the other example, method, formality, parts and the circuit known for everybody are not described in detail, so that highlight purport of the present invention.
Figure 2 shows that according to an embodiment of the invention to be used for driving load, such as light source 206, the schematic diagram of drive circuit 200.Drive circuit 200 comprises converter circuit 202, on-off controller 204, switching regulaor 208 and current inductor 210.Converter circuit 202 receives input voltage V
IN, produce the first output voltage (output voltage V for example at the first power line (for example power line 241)
OUT_H), and produce less than the first output voltage V at the second power line (for example power line 242)
OUT_HThe second output voltage (output voltage V for example
OUT_L).The first output voltage V
OUT_HBe used for driving light source 206.The second output voltage V
OUT_LOperating voltage for reducing the one or more switch blocks in the switching regulaor 208 (for example switch block 222).
In one embodiment, light source 206 comprises one or more LED strings.Each LED string comprises one or more LED of mutual series connection.In one embodiment, switching regulaor 208 comprises energy storage component 220 and switch block 222.Energy storage component 220 and light source 206 couplings, the electric current I of the energy storage component 220 of flowing through
220The flow through current value of electric current of light source 206 of decision.
In one embodiment, switch block 222 is coupled to power line 241, power line 242 and has reference voltage V
REFReference node 244(for example, if reference node 244 is coupled to ground, reference voltage V then
REFEqual 0 volt).Controlled by 230 pairs of switch blocks 222 of switch controlling signal, so that switch block 222 is worked under a plurality of operating states.Under different operating states, switch block 222 optionally is coupled to power line 241, power line 242 and reference node 244 one or more ports of energy storage component 220, thus the electric current I of conducting energy storage component 220
220Different current paths.
More particularly, the operating state of switch block 222 comprises the first state (for example switch closed condition) and the second state (for example switch off state).Under switch closed condition, switch block 222 On current I
220The first current path so that electric current I
220Among power line 241, power line 242 and the reference node 244 two flow through.The operating voltage V of energy storage component 220
220Has the first magnitude of voltage, so that electric current I
220Increase, and energy storage component 220 chargings.Under switch off state, switch block 222 On current I
220The second current path so that electric current I
220Among power line 241, power line 242 and the reference node 244 other two flow through.The operating voltage V of energy storage component 220
220Has the second voltage value, so that electric current I
220Reduce, and energy storage component 220 discharges.
Therefore, the ratio between the duration by by-pass cock parts 222 switch closed condition and the duration of switch off state is regulated the electric current of the light source 206 of flowing through (such as electric current I
220Mean value).The operation of switching regulaor 208 will further describe in Fig. 3, Fig. 6 and Fig. 7.
Advantageously, as what in Fig. 3, Fig. 6 and Fig. 7, will further describe, because the output voltage V on the power line 242
OUT_L, so that the operating voltage at switch block 222 two ends all remains on less than V under switch closed condition and switch off state
OUT_HTherefore, compare with diode D1 with the switch S 1 in the drive circuit 100 of Fig. 1 in the prior art, switch block 222 can adopt the lower parts of rated voltage.Therefore, power consumption and the cost of drive circuit 200 have been reduced.
Figure 3 shows that the load that be used for to drive according to the embodiment of the invention, such as light source 206, the circuit diagram of drive circuit 300.Number identical parts with Fig. 2 among Fig. 3 and have similar function.Fig. 3 is described in connection with Fig. 2.
In the embodiment shown in fig. 3, light source 206 comprises the LED string, the LED that this LED string has a plurality of series coupled.Drive circuit 300 comprises converter circuit 202, on-off controller 204, switching regulaor 208 and current inductor 210.Current inductor 210 comprises resistance R 3, and for generation of induced signal 234, this induced signal 234 is indicated the electric current of the LED string 206 of flowing through.In one embodiment, induced signal 234 is the voltage at resistance R 3 two ends.On-off controller 204 produces switch controlling signal 230(such as pulse-width signal according to induced signal 234) and feedback signal 232.
In one embodiment, converter circuit 202 comprises switching controller 302 and double conversion device 304.Switching controller 302 receiving feedback signals 232 also correspondingly produce control signal 310, and these feedback signal 232 indication LED strings 206 are for producing the required forward voltage of expectation current value.Double conversion device 304 receives input voltage V
IN, and produce the first output voltage (output voltage V for example according to control signal 310
OUT_H) and the second output voltage (output voltage V for example
OUT_L).For example, switching controller 302 is regulated control signal 310 according to feedback signal 232, to raise or to reduce output voltage V
OUT_HThereby, the electric current of LED string 206 is adjusted to the expectation current value.
In one embodiment, double conversion device 304 receives input voltage V
IN, and produce output voltage V
OUT_LAnd output voltage V
OUT_HShown in formula (1), output voltage V
OUT_HEqual output voltage V
OUT_LAdd voltage V
DIFF(V
DIFFThe expression output voltage V
OUT_HAnd output voltage V
OUT_LBetween difference).
V
OUT_H=V
OUT_L+V
DIFF (1)
As the formula (1), if V
DIFFFor on the occasion of, V then
OUT_LLess than V
OUT_HThe operation of double conversion device 304 will further describe in Fig. 4 A, Fig. 4 B and Fig. 5.
When switch controlling signal 230 was logic low potential, switch block 222 worked in switch off state.Under switch off state, switch S 3 disconnects, and diode D3 forward bias.TA end and power line 241 electric coupling of inductance L 3, TB end and power line 242 electric coupling.Therefore, then electric current I 2 flow through power line 241, LED string 206, inductance L 3, diode D3 and power line 242 flow to power line 241 from power line 242 through double conversion devices 304.The operating voltage of inductance L 3 has the second voltage value, and this second voltage value is by output voltage V
OUT_HAnd V
OUT_LDetermine.At this moment, inductance L 3 discharges, its electric current reduces.
Therefore, in one embodiment, when switch controlling signal 230 was logic high potential, inductive current increased; When switch controlling signal 230 was logic low potential, inductive current reduced.In the embodiment shown in fig. 3, the flow through electric current of led light source 206 is substantially equal to the average current of the inductance L 3 of flowing through.As a result, the duty ratio that on-off controller 204 can be by control switch control signal 230 is adjusted to the expectation current value with the electric current of the led light source 206 of flowing through.
Advantageously, when switch block 222 is in switch closed condition, the voltage V at diode D3 two ends
D3Less than V
OUT_H(such as V
D3Be substantially equal to V
OUT_L).When switch block 222 is in switch off state, the voltage V at switch S 3 two ends
S3Also less than V
OUT_HThat is to say, by adopting the output voltage V of double conversion device 304
OUT_L, no matter under switch closed condition or switch off state, the operating voltage at switch S 3 and diode D3 two ends all keeps less than V respectively
OUT_HTherefore, can adopt the relatively low switch block of rated voltage, to reduce power consumption and the cost of drive circuit 300.
Fig. 4 A and 4B are depicted as the circuit diagram according to the converter circuit 202 of the embodiment of the invention.Number identical parts with Fig. 2 and Fig. 3 among Fig. 4 A and Fig. 4 B and have similar function.Fig. 4 A and Fig. 4 B are described in connection with Fig. 2 and Fig. 3.
In the embodiment shown in Fig. 4 A and Fig. 4 B, double conversion device 304 comprises resistance 402, switch 416, transformer T1, diode 410 and diode 412 and electric capacity 408 and electric capacity 414.Transformer T1 comprises primary coil 404, magnetic core 405 and secondary coil 406, and wherein, primary coil 404 receives input voltage V
IN, the first port 470 of secondary coil 406 provides described the first output voltage (output voltage V for example
OUT_H), the second port 472 of secondary coil 406 provides described the second output voltage (output voltage V for example
OUT_L).Double conversion device 304 produces output voltage V
OUT_LWith voltage V
DIFFMore particularly, shown in Fig. 4 A, the primary coil 404 of transformer T1, diode 412, electric capacity 414 and switch 416 have consisted of the boost converter 452 of switching mode.Switching controller 302 produces driving signal 460 and comes control switch 416.In one embodiment, driving signal 460 is that duty ratio is D
DUTYPulse-width signal, be used for being alternately closed and cut-off switch 416.Therefore, the boost converter 452 of switching mode is with input voltage V
INConvert output voltage V to
OUT_LIf the resistance of negligible resistance 402, the output voltage V on the power line 242
OUT_LCan be represented by formula (2):
V
OUT_L=V
IN/(1-D
DUTY) (2)
In addition, shown in Fig. 4 B, transformer T1(T1 comprises primary coil 404, magnetic core 405 and secondary coil 406), diode 410, electric capacity 408 and switch 416 consisted of inverse-excitation type (flyback) transducer 454 of switching mode.Drive signal 460 and be alternately closed and cut-off switch 416, thus, flyback converter 454 is with input voltage V
INConvert voltage V to
DIFFVoltage V
DIFFCan be represented by formula (3):
V
DIFF=V
IN*(N
406/N
404)*D
DUTY/(1-D
DUTY) (3)
Wherein, N
406/ N
404The turn ratio of expression secondary coil 406 and primary coil 404.
In one embodiment, since the non-polar end of secondary coil 406 and power line 242 couplings, output voltage V
OUT_HEqual output voltage V
OUT_LAdd voltage V
DIFF, as shown in formula (1).Therefore, derive formula (4) by formula (1), (2) and (3):
V
OUT_H=V
OUT_L*(1+D
DUTY*(N
406/N
404)) (4)
As shown in formula (4), as long as duty ratio D
DUTYGreater than 0, output voltage V then
OUT_HGreater than output voltage V
OUT_L, and output voltage V
OUT_HAccording to output voltage V
OUT_LAnd change.In addition, according to formula (2) and (4), by regulating the duty ratio D that drives signal 460
DUTY, V
OUT_HAnd V
OUT_LAll regulated accordingly.
Advantageously, the flyback converter 454 shown in the boost converter 452 shown in Fig. 4 A and Fig. 4 B has common elements, and for example primary coil 404 and switch 416 have reduced component count like this.Therefore, reduce the size of converter circuit 202, and reduced the cost of drive circuit 200.
Figure 5 shows that another circuit diagram according to the converter circuit 202 of the embodiment of the invention.Numbering identical parts with Fig. 2 to Fig. 4 among Fig. 5 and have similar function. Fig. 5 is described in connection with Fig. 2 and Fig. 3.
In the embodiment shown in fig. 5, double conversion device 304 comprises transformer T2, diode 510 and diode 512, electric capacity 514 and electric capacity 516, switch 518 and resistance 402.Transformer T2 comprises primary coil 504, magnetic core 505, secondary coil 506 and ancillary coil 508, and wherein secondary coil 506 and ancillary coil 508 are coupled to common node 572, and primary coil 504 receives input voltage V
IN, the first port 570 of secondary coil 506 provides described the first output voltage, and described ancillary coil provides described the second output voltage at described common node 572 places.Switching controller 302 produces and drives signal 460(such as pulse-width signal), be used for being alternately closed and cut-off switch 518.Primary coil 504, magnetic core 505, secondary coil 506, switch 518, diode 510 and electric capacity 514 have consisted of the first inverse-excitation type (flyback) transducer.The first flyback converter is with input voltage V
INConvert voltage V to
DIFF'.Voltage V
DIFF' can be represented by formula (5):
V
DIFF'=V
IN*(N
506/N
504)*D
DUTY/(1-D
DUTY) (5)
N wherein
506/ N
504The turn ratio of expression secondary coil 506 and primary coil 504.
Similarly, primary coil 504, magnetic core 505, ancillary coil 508, switch 518, diode 512 and electric capacity 516 have consisted of the second flyback converter.The second flyback converter is with input voltage V
INConvert output voltage V to
OUT_LOutput voltage V
OUT_LCan be represented by formula (6):
V
OUT_L=V
IN*(N
508/N
504)*D
DUTY/(1-D
DUTY) (6)
N wherein
508/ N
504The turn ratio of expression ancillary coil 508 and primary coil 504.
Since the non-polar end of secondary coil 506 and power line 242 couplings, as shown in formula (1), output voltage V
OUT_HEqual output voltage V
OUT_LAdd voltage V
DIFFTherefore, according to formula (1), (5) and (6), output voltage V
OUT_HCan be represented by formula (7):
V
OUT_H=V
OUT_L*(1+N
506/N
508) (7)
As shown in formula (7), output voltage V
OUT_HGreater than output voltage V
OUT_L, and output voltage V
OUT_HAccording to output voltage V
OUT_LAnd change.Shown in (6) and formula (7), by regulating the duty ratio D that drives signal 460
DUTY, V
OUT_HAnd V
OUT_LAll regulated accordingly.
Advantageously, the first flyback converter and the second flyback converter are shared some common elements, have reduced like this size of converter circuit 202, and have reduced the cost of drive circuit 200.
Such as the description of Fig. 3, when switch block 222 is in switch closed condition (such as switch S 3 closures), electric current I 1 flow to power line 241 from ground through double conversion device 304.(disconnect such as switch S 3) when switch block 222 is in switch off state, electric current I 2 flow to power line 241 from power line 242 through double conversion device 304.If adopt the double conversion device 304 shown in Fig. 4 A and Fig. 4 B, when switch block 222 is in switch closed condition, electric current I 1 flow through from ground electric capacity 414 and secondary coil 406 and flow to power line 241.When switch block 222 was in switch off state, electric current I 2 was from flow through secondary coil 406 and flow to power line 241 of power line 242.If adopt double conversion device 304 as shown in Figure 5, when switch block 222 is in switch closed condition, electric current I 1 flow through from ground electric capacity 516 and secondary coil 506 and flow to power line 241.When switch block 222 was in switch off state, electric current I 2 was from flow through secondary coil 506 and flow to power line 241 of power line 242.Double conversion device 304 can have other structures, and is not limited to the embodiment among Fig. 4 A, Fig. 4 B and Fig. 5.
Figure 6 shows that the load that be used for to drive according to the embodiment of the invention, such as LED string 206, another circuit diagram of drive circuit 600.Number identical parts with Fig. 2, Fig. 3 among Fig. 6 and have similar function.Fig. 6 is described in connection with Fig. 2 to Fig. 5.
In the embodiment shown in fig. 6, current inductor 210 comprises resistance R 6 and error amplifier 602.Error amplifier 602 receives the voltage at resistance R 6 two ends, and correspondingly produces induced signal 234, and this induced signal 234 is indicated the electric current of the LED string 206 of flowing through.In one embodiment, the switching regulaor 208 that is coupling between current inductor 210 and the LED string 206 is step-down controllers.Switching regulaor 208 comprises switch block 222 and energy storage component 220.In one embodiment, energy storage component 220 comprises the inductance L 6 that is coupled with LED string 206.Switch block 222 comprises switch S 6 and diode D6.In one embodiment, switch S 6 can be the P-type mos transistor.The anode of diode D6 and power line 242 couplings.The drain electrode of the negative electrode of diode D6 and switch S 6 is coupled to common node together, and this common node for example is coupled to reference node 244(, ground by inductance L 6 and LED string 206).The source electrode of switch S 6 is coupled to power line 241 by current inductor 210.
In addition, when switch controlling signal 230 was logic high potential, switch block 222 worked in switch off state.Under switch off state, switch S 6 disconnects, and diode D6 forward bias.Therefore, the TA of inductance L 6 end and power line 242 electric coupling, TB end and ground electric coupling.Then electric current I 2' flow through power line 242, diode D6, inductance L 6, LED string 206 and ground flow to power line 242 from ground through double conversion device 304.Inductance L 6 discharges, thus be 206 power supplies of LED string, and the inductive current (such as I2') that flow to the TB end from the TA end reduces gradually.The duty ratio similar to drive circuit 300 shown in Figure 3, that on-off controller 204 can be by control switch control signal 230 is adjusted to the expectation current value with the electric current of led light source 206.
Advantageously, when switch block 222 is in switch closed condition, the voltage V at diode D6 two ends
D6Less than V
OUT_HWith V
OUT_LDifference.When switch block 222 is in switch off state, the voltage V at switch S 6 two ends
S6Be substantially equal to V
OUT_HWith V
OUT_LDifference.That is to say, by adopting output voltage V
OUT_L, no matter under switch closed condition or switch off state, the operating voltage at switch S 6 and diode D6 two ends all keeps less than V respectively
OUT_HTherefore, can adopt the relatively low switch block of rated voltage (for example, switch S 6 and diode D6), to reduce power consumption and the cost of drive circuit 600.
Figure 7 shows that the load that be used for to drive according to the embodiment of the invention, such as LED string 206, the circuit diagram of drive circuit 700.Number identical parts with Fig. 2, Fig. 3 among Fig. 7 and have similar function.Fig. 7 is described in connection with Fig. 2 to Fig. 5.
In the embodiment shown in fig. 7, the switching regulaor 208 with 206 couplings of LED string is boost converters.Energy storage component 220 comprises the inductance L 7 with power line 241 couplings.Switch block 222 comprises switch S 7 and diode D7.In one embodiment, switch S 7 can be the N-type metal oxide semiconductor transistor.The drain electrode of the anode of diode D7 and switch S 7 is coupled to common node together, and this common node is coupled to power line 241 by inductance L 7.The source electrode of switch S 7 and power line 242 couplings.The negative electrode of diode D7 for example is coupled to reference node 244(, ground by LED string 206 and current inductor 210).
In addition, when switch controlling signal 230 was logic low potential, switch block 222 worked in switch off state.Under switch off state, switch S 7 disconnects, and diode D7 forward bias.Therefore, the TA of inductance L 7 end and power line 241 electric coupling, TB end and ground electric coupling." then the power line 241 of flowing through, inductance L 7, diode D7, LED string 206 and ground flow to power line 241 from ground through double conversion device 304 to electric current I 2.Inductive current flow to the TB end from the TA end.Electric current I 2 " reduce, thereby inductance L 7 discharges is 206 power supplies of LED string, and is capacitor C 7 chargings.Therefore, on-off controller 204 is regulated the electric current of led light source 206 by the duty ratio of by-pass cock control signal 230.
Advantageously, be under the switch closed condition voltage V at diode D7 two ends at switch block 222
D7Less than V
OUT_HBe under the switch off state at switch block 222, the voltage at switch S 7 two ends is less than V
OUT_HThat is to say, by adopting output voltage V
OUT_L, no matter under switch closed condition or switch off state, the operating voltage at switch S 7 and diode D7 two ends all keeps less than V respectively
OUT_HTherefore, switch S 7 and diode D7 can adopt the relatively low switch block of rated voltage, to reduce power consumption and the cost of drive circuit 700.
Drive circuit 700 also can adopt Fig. 4 A, Fig. 4 B and embodiment illustrated in fig. 5 in double conversion device 304.If adopt the double conversion device 304 shown in Fig. 4 A and Fig. 4 B, be under the switch closed condition electric current I 1 at switch block 222 " from flow through secondary coil 406 and flow to power line 241 of power line 242.Be under the switch off state electric current I 2 at switch block 222 " flow through from ground electric capacity 414 and secondary coil 406 and flow to power line 241.If adopt double conversion device 304 as shown in Figure 5, be under the switch closed condition electric current I 1 at switch block 222 " from flow through secondary coil 506 and flow to power line 241 of power line 242.Be under the switch off state electric current I 2 at switch block 222 " flow through from ground electric capacity 516 and secondary coil 506 and flow to power line 241.Within the protection range of claim, switching regulaor 208 can also have other structures, is not limited to buck converter topology among Fig. 3 and Fig. 6 and the boost converter structure among Fig. 7.
Figure 8 shows that according to the embodiment of the invention be used for driving a plurality of loads, a plurality of LED string 806_1 to 806_ for example, the circuit diagram of drive circuit 800.Fig. 8 numbers identical parts with Fig. 2 and has similar function.Fig. 8 is described in connection with Fig. 2, Fig. 3, Fig. 6 and Fig. 7.
Drive circuit 800 comprises converter circuit 202, is used in the first power line (for example power line 241) generation the first output voltage (output voltage V for example
OUT_H), and produce the second output voltage (output voltage V for example at the second power line (for example power line 242)
OUT_L), wherein the second output voltage is less than the first output voltage.Drive circuit 800 comprises a plurality of switching regulaors that are coupled with converter circuit 202, be respectively applied to regulate the electric current of a plurality of light sources (for example LED string 806_1 to 806_3), each switching regulaor comprises switch block and energy storage component, wherein, when the switch block in each switching regulaor works in the first state (for example switch closed condition), corresponding energy storage component charging; When the switch block in each switching regulaor works in the second state (for example switch off state), corresponding energy storage component discharge; Regulate the electric current of corresponding light source by the duration of regulating the energy storage component charging and discharging.Converter circuit 202 provides the second output voltage (output voltage V for example
OUT_L), thereby when the first state and the second state, the operating voltage at switch block two ends all keeps less than the first output voltage (output voltage V for example
OUT_H).
More particularly, in the embodiment shown in fig. 8, drive circuit 800 is used for driving a plurality of light sources (for example a plurality of LED strings).Although the embodiment of Fig. 8 has shown three LED string 806_1,806_2 and 806_3, drive circuit 800 can comprise the LED string of other numbers.Each LED string 806_1 to 806_3 is coupled to the circuit similar to the drive circuit 300 of Fig. 3.For example, LED string 806_1 is coupled to the switching regulaor that comprises switch block (diode D8_1, switch S 8_1) and energy storage component (inductance L 8_1); LED string 806_2 is coupled to the switching regulaor that comprises switch block (diode D8_2, switch S 8_2) and energy storage component (inductance L 8_2); LED string 806_3 is coupled to the switching regulaor that comprises switch block (diode D8_3, switch S 8_3) and energy storage component (inductance L 8_3).
On-off controller 804_1 to 804_3 also produces error signal VEA_1, VEA_2 and VEA_3, each error signal indicates respectively corresponding LED string 806_1 to 806_3 for producing the required forward voltage of expectation current value, namely under the driving of corresponding forward voltage, each electric current of the light-emitting diode chain 806_1 to 806_3 that flows through has the expectation current value.Drive circuit 800 also comprises feeding back selects circuit 812, and this feedback selects circuit 812 to receive error signal VEA_1 to VEA_3, and which LED string has maximum forward voltage among the judgement LED string 806_1 to 806_3.Thereby feedback selects circuit 812 to produce feedback signal 810, and these feedback signal 810 indications have the electric current of the LED string of Maximum Forward Voltage.Therefore, in one embodiment, converter circuit 202 is according to feedback signal 810 regulation output voltage V
OUT_H, to satisfy the power demands of the LED string with Maximum Forward Voltage.Because output voltage V
OUT_HCan satisfy the power demands of the LED string with Maximum Forward Voltage, the power demands of other LED strings also can be met so.
In one embodiment, when the switch S 8_1 to S8_3 in the switch block is in the first state (for example switch closed condition), switch block conducting the first current path so that the electric current of inductance L 8_1 to L8_3 is flowed through power line 241 and reference node 244(for example, ground); When the switch S 8_1 to S8_3 in the switch block is in described the second state (for example switch off state), switch block conducting the second current path, power line 241 and the power line 242 so that electric current of inductance L 8_1 to L8_3 is flowed through.In another embodiment, when the switch S 8_1 to S8_3 in the switch block is in the first state (for example switch closed condition), switch block conducting the first current path so that the electric current of inductance L 8_1 to L8_3 is flowed through power line 241 and reference node 244(for example, ground); When the switch S 8_1 to S8_3 in the switch block is in described the second state (for example switch off state), switch block conducting the second current path so that the electric current of inductance L 8_1 to L8_3 is flowed through power line 242 and reference node 244(for example, ground).In yet another embodiment, when the switch S 8_1 to S8_3 in the switch block is in the first state (for example switch closed condition), switch block conducting the first current path, power line 241 and the power line 242 so that electric current of inductance L 8_1 to L8_3 is flowed through; When the switch S 8_1 to S8_3 in the switch block is in described the second state (for example switch off state), switch block conducting the second current path so that the electric current of inductance L 8_1 to L8_3 is flowed through power line 241 and reference node 244(for example, ground).
Advantageously, owing to the output voltage V that has adopted on the power line 242
OUT_L, so switch block corresponding to each LED string all can select the lower switch block of rated voltage, thus power consumption and the cost of drive circuit 800 reduced.
Figure 9 shows that the flow chart 900 according to embodiment of the invention light source driving method.The embodiment of the invention is take the structure of drive circuit 200 as example, and Fig. 9 is described in conjunction with each figure of Fig. 2 to Fig. 8.Although Fig. 9 discloses some specific step, these steps are as just example.The present invention is equally applicable to distortion or other steps of step shown in Figure 9.
In step 902, provide the first output voltage (such as V at the first power line
OUT_H), thereby be light source (such as LED string 206) power supply.
In step 904, provide the second output voltage less than described the first output voltage (such as V at the second power line
OUT_L).
In step 906, switch block (such as switch block 222) works in the first state (such as switch closed condition), energy storage component under this first state (such as energy storage component 220) charging.
In step 908, switch block works in the second state (such as switch off state), energy storage component discharge under this second state.
In step 910, by regulating the duration of energy storage component charging and discharging, namely be in the duration of described the first state and described the second state by regulating described switch block, regulate the electric current of the light source of flowing through.In one embodiment, energy storage component comprises inductance.In one embodiment, switch block comprises transistor and diode.
In step 912, the second output voltage that provides is so that when switch block was in the first state and the second state, the operating voltage at switch block two ends all kept less than the first output voltage.In the embodiment shown in fig. 3, the first current path of conducting energy storage component, the first power line and reference node so that the electric current of energy storage component is flowed through, thus be the energy storage component charging.The second current path of conducting energy storage component, the first power line and the second power line so that the electric current of energy storage component is flowed through, thus be the energy storage component discharge.In the embodiment shown in fig. 6, the first current path of conducting energy storage component, the first power line and reference node so that the electric current of energy storage component is flowed through, thus be the energy storage component charging.The second current path of conducting energy storage component, the second power line and reference node so that the electric current of energy storage component is flowed through, thus be the energy storage component discharge.In the embodiment shown in fig. 7, the first current path of conducting energy storage component, the first power line and the second power line so that the electric current of energy storage component is flowed through, thus be the energy storage component charging.The second current path of conducting energy storage component, the first power line and reference node so that the electric current of energy storage component is flowed through, thus be the energy storage component discharge.
As previously mentioned, the present invention discloses a kind of drive circuit and driving method for driving load.Advantageously, because the second output voltage on the second power line, during the first state and the second state, the operating voltage at switch block two ends keeps less than the first output voltage.Therefore, the lower switch block of rated voltage be can select, thereby power consumption and the cost of drive circuit reduced.
Wording and expression in this use all are illustrative rather than definitive thereof, use these wording and express not and will get rid of outside invention scope at any equivalent (or part equivalent) of the characteristic of this diagram and description, may have various modifications within the scope of the claims.Other modification, variant and alternative also may exist.Therefore, claim is intended to contain all these type of equivalents.
Claims (23)
1. a light source driving circuit is characterized in that, described light source driving circuit comprises:
Converter circuit provides the first output voltage to think described light source power supply at the first power line, and provides the second output voltage at the second power line, and wherein, described the second output voltage is less than described the first output voltage;
Energy storage component is by regulating the electric current of the described light source of flowing through for described energy storage component charging and discharging; And
Switch block is coupled to described converter circuit and described energy storage component, when described switch block works in the first state, and described energy storage component charging; When described switch block works in the second state, described energy storage component discharge;
Wherein, described converter circuit provides described the second output voltage, and with when described the first state and described the second state, the operating voltage at described switch block two ends all keeps less than described the first output voltage.
2. light source driving circuit according to claim 1 is characterized in that, when described switch block is in described the first state, and described switch block conducting the first current path, described the first power line and reference node so that the electric current of described energy storage component is flowed through; When described switch block is in described the second state, described switch block conducting the second current path, described the first power line and described the second power line so that the electric current of described energy storage component is flowed through.
3. light source driving circuit according to claim 1 is characterized in that, when described switch block is in described the first state, and described switch block conducting the first current path, described the first power line and reference node so that the electric current of described energy storage component is flowed through; When described switch block is in described the second state, described switch block conducting the second current path, described the second power line and described reference node so that the electric current of described energy storage component is flowed through.
4. light source driving circuit according to claim 1, it is characterized in that, when described switch block is in described the first state, described switch block conducting the first current path, described the first power line and described the second power line so that the electric current of described energy storage component is flowed through; When described switch block is in described the second state, described switch block conducting the second current path, described the first power line and reference node so that the electric current of described energy storage component is flowed through.
5. light source driving circuit according to claim 1 is characterized in that, described converter circuit comprises:
Transformer with primary coil and secondary coil, described primary coil receives input voltage, and the first port of described secondary coil provides described the first output voltage, and the second port of described secondary coil provides described the second output voltage.
6. light source driving circuit according to claim 1 is characterized in that, described converter circuit comprises:
Transformer with primary coil, secondary coil and ancillary coil, described secondary coil and described ancillary coil are coupled to common node, described primary coil receives input voltage, the first port of described secondary coil provides described the first output voltage, and described ancillary coil provides described the second output voltage at described common node place.
7. light source driving circuit according to claim 1 is characterized in that, described energy storage component comprises inductance, and described switch block comprises switch and diode.
8. light source driving circuit according to claim 1 is characterized in that, described the second output voltage changes according to described the first output voltage.
9. light source driving circuit, described light source is a plurality of, it is characterized in that, described light source driving circuit comprises:
Converter circuit is used for providing the first output voltage to think described a plurality of light source power supply at the first power line, and provides the second output voltage at the second power line, and wherein, described the second output voltage is less than described the first output voltage; And
A plurality of switching regulaors with the coupling of described converter circuit, are respectively applied to regulate the electric current of described a plurality of light sources of flowing through, each described switching regulaor comprises switch block and energy storage component, wherein, when described switch block works in the first state, described energy storage component charging; When described switch block works in the second state, described energy storage component discharge; Regulate the electric current of the corresponding light source of flowing through by the duration of regulating described energy storage component charging and discharging;
Wherein, described converter circuit provides described the second output voltage, and with when described the first state and described the second state, the operating voltage at described switch block two ends all keeps less than described the first output voltage.
10. light source driving circuit according to claim 9 is characterized in that, described light source driving circuit also comprises:
Respectively with a plurality of on-off controllers of described a plurality of switching regulaors coupling, described a plurality of on-off controller receives respectively a plurality of induced signals, wherein, described a plurality of induced signal is indicated respectively the current value of the described a plurality of light sources of flowing through, described a plurality of on-off controller compares the reference signal of described a plurality of induced signals and indicative of desired current value respectively, and produce respectively a plurality of switch controlling signals according to described comparative result, thereby control described a plurality of switching regulaor, be adjusted to respectively described expectation current value with the electric current of the described a plurality of light sources of will flowing through.
11. light source driving circuit according to claim 10 is characterized in that, described light source driving circuit also comprises:
Select circuit with the feedback of described a plurality of on-off controller couplings, described feedback selects circuit to receive a plurality of error signals that produced by described a plurality of on-off controllers respectively, wherein, described a plurality of error signal indicates respectively described a plurality of light source for producing the required forward voltage of expectation current value, described feedback selects circuit to produce feedback signal according to described a plurality of error signals, described feedback signal indication has the electric current of the light source of Maximum Forward Voltage, thereby controls described first output voltage of described converter circuit.
12. light source driving circuit according to claim 9, it is characterized in that, when described switch block is in described the first state, described switch block conducting the first current path, described the first power line and reference node so that the electric current of described energy storage component is flowed through; When described switch block is in described the second state, described switch block conducting the second current path, described the first power line and described the second power line so that the electric current of described energy storage component is flowed through.
13. light source driving circuit according to claim 9, it is characterized in that, when described switch block is in described the first state, described switch block conducting the first current path, described the first power line and reference node so that the electric current of described energy storage component is flowed through; When described switch block is in described the second state, described switch block conducting the second current path, described the second power line and described reference node so that the electric current of described energy storage component is flowed through.
14. light source driving circuit according to claim 9, it is characterized in that, when described switch block is in described the first state, described switch block conducting the first current path, described the first power line and described the second power line so that the electric current of described energy storage component is flowed through; When described switch block is in described the second state, described switch block conducting the second current path, described the first power line and reference node so that the electric current of described energy storage component is flowed through.
15. light source driving circuit according to claim 9 is characterized in that, described converter circuit comprises:
Transformer with primary coil and secondary coil, described primary coil receives input voltage, and the first port of described secondary coil provides described the first output voltage, and the second port of described secondary coil provides described the second output voltage.
16. light source driving circuit according to claim 9 is characterized in that, described converter circuit comprises:
Transformer with primary coil, secondary coil and ancillary coil, described secondary coil and described ancillary coil are coupled to common node, described primary coil receives input voltage, the first port of described secondary coil provides described the first output voltage, and described ancillary coil provides described the second output voltage at described common node place.
17. light source driving circuit according to claim 9 is characterized in that, described energy storage component comprises inductance, and described switch block comprises switch and diode.
18. light source driving circuit according to claim 9 is characterized in that, described the second output voltage changes according to described the first output voltage.
19. a light source driving method is characterized in that, described method comprises:
Provide the first output voltage at the first power line, be described light source power supply;
Provide the second output voltage less than described the first output voltage at the second power line;
Switch block works in the first state, so that the energy storage component charging;
Described switch block works in the second state, so that the discharge of described energy storage component; And
Be in the duration of described the first state and described the second state by regulating described switch block, regulate the electric current of described light source;
Wherein, provide described the second output voltage, so that when described the first state and described the second state, the operating voltage at described switch block two ends all keeps less than described the first output voltage.
20. light source driving method according to claim 19 is characterized in that, described method also comprises:
Conducting the first current path, described the first power line and reference node so that the electric current of described energy storage component is flowed through, thereby to described energy storage component charging; And
Conducting the second current path, described the first power line and described the second power line so that the electric current of described energy storage component is flowed through, thereby to described energy storage component discharge.
21. light source driving method according to claim 19 is characterized in that, described method also comprises:
Conducting the first current path, described the first power line and reference node so that the electric current of described energy storage component is flowed through, thereby to described energy storage component charging; And
Conducting the second current path, described the second power line and described reference node so that the electric current of described energy storage component is flowed through, thereby to described energy storage component discharge.
22. light source driving method according to claim 19 is characterized in that, described method also comprises:
Conducting the first current path, described the first power line and described the second power line so that the electric current of described energy storage component is flowed through, thereby to described energy storage component charging; And
Conducting the second current path, described the first power line and reference node so that the electric current of described energy storage component is flowed through, thereby to described energy storage component discharge.
23. light source driving method according to claim 19 is characterized in that, described energy storage component comprises inductance, and described switch block comprises transistor and diode.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US13/274,663 US8148919B2 (en) | 2008-08-05 | 2011-10-17 | Circuits and methods for driving light sources |
| US13/274,663 | 2011-10-17 |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN102905416A true CN102905416A (en) | 2013-01-30 |
| CN102905416B CN102905416B (en) | 2014-02-12 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201210156029.XA Expired - Fee Related CN102905416B (en) | 2011-10-17 | 2012-05-18 | Light source driving circuit and driving method |
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| Country | Link |
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| CN (1) | CN102905416B (en) |
| TW (1) | TWI392208B (en) |
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Also Published As
| Publication number | Publication date |
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| TWI392208B (en) | 2013-04-01 |
| TW201301734A (en) | 2013-01-01 |
| CN102905416B (en) | 2014-02-12 |
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