CN217693770U

CN217693770U - LED drive circuit, chip and electronic equipment

Info

Publication number: CN217693770U
Application number: CN202221481347.9U
Authority: CN
Inventors: 梁浩贤
Original assignee: Chipsea Technologies Shenzhen Co Ltd
Current assignee: Chipsea Technologies Shenzhen Co Ltd
Priority date: 2022-06-13
Filing date: 2022-06-13
Publication date: 2022-10-28
Anticipated expiration: 2032-06-13

Abstract

The embodiment of the application provides a LED drive circuit, chip and electronic equipment, LED drive circuit includes: a first input end of the first operational amplifier is used for inputting a reference voltage; the control end of each first transistor is connected with the output end of the first operational amplifier, the first end of each first transistor is connected with the second input end of the first operational amplifier, and the second end of each first transistor is used for being connected with an LED. The LED driving circuit can greatly reduce the current mismatch error between different LEDs and improve the matching degree between different LEDs.

Description

LED drive circuit, chip and electronic equipment

Technical Field

The application relates to the technical field of electronics, in particular to an LED driving circuit, a chip and electronic equipment.

Background

When a forward voltage is applied to a light-emitting diode (LED), holes injected from the P region into the N region and electrons injected from the N region into the P region recombine with the electrons in the N region and the holes in the P region near the PN junction, respectively, to generate spontaneous emission fluorescence. From the electrical characteristics, the LED lamp beads can be regarded as diodes with different voltage drops, and the voltage stabilizing capability is very strong. According to different colors, the LED lamp beads can be divided into four types, namely red light, yellow light, blue light, white light and the like, the voltage drop of the first two types is below 2V, and the voltage drop of the second two types is about 3V. Under the same power supply voltage, the LED lamp bead with higher voltage drop is difficult to maintain the constant current characteristic.

The dimming and control of the flashing and brightness of the LED lamp is called LED driving. The LED driving can be divided into a constant voltage mode and a constant current mode, and the constant current mode is the mainstream LED driving mode at present because the driving mode of the constant voltage mode is greatly influenced by the characteristics of the LED and the external environment, such as temperature, process, voltage, etc. The constant current mode LED driving uses constant current driving, and each LED is driven by a corresponding current mirror and a clamping operational amplifier, so that the defect of the constant voltage mode can be improved, but the driving currents of different LEDs have large mismatch.

SUMMERY OF THE UTILITY MODEL

The embodiment of the application provides an LED drive circuit, a chip and electronic equipment, so as to solve the technical problems.

In a first aspect, an embodiment of the present application provides an LED driving circuit, which includes:

a first operational amplifier, wherein a first input end of the first operational amplifier is used for inputting a reference voltage;

the control end of each first transistor is connected with the output end of the first operational amplifier, the first end of each first transistor is connected with the second input end of the first operational amplifier, and the second end of each first transistor is used for being connected with an LED (light-emitting diode), so that the current mismatch error between different LEDs can be greatly reduced.

Optionally, the LED driving circuit further comprises:

and each controller is connected between the output end of the first operational amplifier and the control end of one first transistor so as to control the first transistor to work or stop.

Optionally, the LED driving circuit further includes:

the current limiting circuit comprises a plurality of second ends, and an LED is connected between the second end of each current limiting circuit and the second end of one first transistor.

Optionally, each of the current limiting circuits includes a plurality of current limiting units, each of the current limiting units includes a second operational amplifier, a second transistor, a third transistor, and a first resistor, a first end of the second transistor and a first end of the third transistor are both used for inputting a power supply voltage, a control end of the second transistor and a control end of the second transistor are both connected to an output end of the second operational amplifier, a second end of the second transistor is used for connecting an LED, and a second end of the third transistor is grounded through the first resistor.

Optionally, the current limiting circuit comprises:

the current generation circuit comprises a second operational amplifier, a third transistor and a first resistor, wherein a first end of the third transistor is used for inputting power supply voltage, a control end of the third transistor is connected with an output end of the second operational amplifier, and a second end of the third transistor is grounded through the first resistor;

each current mirror branch comprises a second transistor, the first end of the second transistor is used for inputting power supply voltage, the control end of the second transistor is connected with the output end of the second operational amplifier, and the second end of the second transistor is used for being connected with the second end of one first transistor to form an LED.

Optionally, the LED driving circuit includes a plurality of driving units, each of the driving units includes one of the current limiting circuits and one of the first transistors, each of the driving units includes a common output terminal, the common output terminal is connected to the second terminal of the current limiting circuit and the second terminal of the first transistor, and the common output terminals of any two of the driving units are used for connecting two terminals of an LED to drive the LED.

Optionally, a second terminal of the second transistor of the current limiting circuit is connected to the common output terminal.

Optionally, the number of common outputs is greater than or equal to 3.

In a second aspect, an embodiment of the present application further provides a chip, which includes the LED driving circuit described above.

In a third aspect, an embodiment of the present application further provides an electronic device, which includes a plurality of LEDs and the chip as described above, where the chip is connected to the plurality of LEDs.

Optionally, the chip includes at least three driving pins, the number of the LEDs is greater than the number of the driving pins, and each of the driving pins is connected to an anode of at least one LED and a cathode of at least one LED.

In the embodiment of the application, a first transistor in the LED driving circuit cooperates with a first operational amplifier to form a loop circuit for driving an LED, wherein the first operational amplifier cooperates with the first transistor to generate a driving current for driving the LED. It can be understood that the loops driving all the LEDs share the same first operational amplifier, that is, the operational amplifier generating the driving current driving all the LEDs is the same, the driving current difference driving the loops of different LEDs is only derived from different first transistors, and compared with the driving currents generated by different operational amplifiers and different transistors, the LED driving circuit according to the embodiment of the present application can greatly reduce the current mismatch error between different LEDs, and improve the matching degree between different LEDs.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings used in the description of the embodiments will be briefly introduced below. It is obvious that the drawings in the following description are only some embodiments of the application, and that for a person skilled in the art, other drawings can be derived from them without inventive effort.

For a more complete understanding of the present application and its advantages, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, wherein like reference numerals represent like parts in the following description.

Fig. 1 is a related art LED constant current LED driving circuit.

Fig. 2 is a first schematic diagram of an LED driving circuit according to an embodiment of the present disclosure.

Fig. 3 is a second schematic diagram of an LED driving circuit according to an embodiment of the present disclosure.

Fig. 4 is a schematic diagram of the LED driving circuit shown in fig. 3 in which the controller includes a switch.

Fig. 5 is a fourth schematic diagram of an LED driving circuit according to an embodiment of the present application.

Fig. 6 is a fifth schematic diagram of an LED driving circuit according to an embodiment of the present disclosure.

Fig. 7 is a sixth schematic diagram of an LED driving circuit according to an embodiment of the present application.

Fig. 8 is a seventh schematic diagram of an LED driving circuit according to an embodiment of the present disclosure.

Fig. 9 is a schematic diagram of another form of the LED driver circuit shown in fig. 8.

Fig. 10 is a ninth schematic diagram of an LED driving circuit according to an embodiment of the present application.

Fig. 11 is a schematic diagram of another form of the LED driving circuit shown in fig. 10.

Fig. 12 is a tenth schematic diagram of an LED driving circuit according to an embodiment of the present application.

Fig. 13 is a schematic structural diagram of a driving unit in the driving circuit shown in fig. 8.

Fig. 14 is a first schematic diagram of a chip and an LED provided in an embodiment of the present application.

Fig. 15 is a second schematic diagram of a chip and an LED provided in an embodiment of the present application.

Fig. 16 is a third schematic diagram of a chip and an LED provided in an embodiment of the present application.

Detailed Description

The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. It should be apparent that the described embodiments are only a few embodiments of the present application, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without inventive step, are within the scope of the present application.

In the embodiments of the present application, at least one means one or more; plural means two or more. In the description of the present application, the terms "first," "second," "third," and the like are used for descriptive purposes only and are not to be construed as indicating or implying relative importance, nor order.

Reference throughout this specification to "one embodiment" or "some embodiments," or the like, means that a particular feature, structure, or characteristic described in connection with the embodiment is included in one or more embodiments of the present application. Thus, the terms "including," "comprising," "having," and variations thereof in this specification mean "including, but not limited to," unless expressly specified otherwise.

It is to be noted that "connected" in the embodiments of the present application may be understood as an electrical connection, and the connection of two electrical components may be a direct or indirect connection between the two electrical components. For example, a and B may be connected directly, or indirectly through one or more other electrical components.

In the related art, the LED driving is a constant current driving generated by a current mirror and a clamping circuit, specifically referring to fig. 1, fig. 1 is a related art LED constant current driving circuit. The clamping action of the clamping operational amplifier can enable the M2 to work in a linear region, even if the drain-source voltage of the M2 is small, the LED forward voltage drop is large; meanwhile, the output impedance can be increased by clamping the operational amplifier, and the current flowing through M2 can be more constant. But because the drive current for each LED is generated by a different current mirror and clamp operational amplifier, there can be a large mismatch in drive current between the LEDs.

In order to solve the above problem, an LED driving circuit according to this embodiment is provided, where the LED driving circuit of this embodiment may be applied to an electronic device, the electronic device may include the LED driving circuit and a plurality of LEDs connected thereto, and the LED driving circuit may drive the plurality of LEDs. As an example, the plurality of LEDs may include LEDs of multiple colors, such as a red LED, a blue LED, a green LED, and the like, and the LED driving circuit may drive any one of the plurality of LEDs to display, so as to present different colors to a user through the LED displays of different colors, so as to prompt different information. For example, different colored LEDs may be displayed to indicate that the electronic device is in different charging states, different colored LEDs may be displayed to indicate that the electronic device receives different information, etc. Alternatively, the electronic device may be a mobile phone, a tablet computer, a wearable device, a charger or a charger, and the like. The wearable device can be a smart bracelet, a smart watch, a wireless headset or smart glasses and other devices.

Referring to fig. 2, fig. 2 is a first schematic diagram of an LED driving circuit according to an embodiment of the present disclosure. The LED driving circuit 10 is used to drive an LED, and the LED driving circuit 10 may include a first operational amplifier 14 and a plurality of first transistors M1. A first input end of the first operational amplifier 14 is used for inputting a reference voltage VREF; a control terminal of each first transistor M1 is connected to the output terminal of the first operational amplifier 14, a first terminal of each first transistor M1 is connected to the second input terminal of the first operational amplifier 14, and a second terminal of each first transistor M1 is used for connecting to the LED.

The first end of the first transistor M1 may also be grounded through the second resistor R2. A first transistor M1 cooperates with the first operational amplifier 14 and the second resistor R2 to form a loop circuit for driving the LED, wherein the first operational amplifier 14, the first transistor M1 and the second resistor R2 cooperate to generate a driving current for driving the LED. It can be understood that the same first operational amplifier 14 is shared by the driving loops of all the LEDs, that is, the operational amplifier that generates the driving currents for driving all the LEDs is the same, and the driving current difference of the loops for driving different LEDs only comes from different first transistors M1, so that the LED driving circuit 10 of the present embodiment can greatly reduce the current mismatch error between different LEDs compared to the driving currents generated by different operational amplifiers and different transistors. For example, the current mismatch error between different LEDs can be controlled to within 1%. The matching degree of different LEDs is improved, the driving currents of different LEDs are similar, and therefore the brightness of different LEDs is similar or identical. In one embodiment, the second terminal of the first transistor M1 may be connected to a cathode of the LED, and an anode of the LED may be connected to the power voltage VBAT to drive the LED. As another embodiment, the second end of the first transistor M1 may be connected to a cathode of the LED, and an anode of the LED may be connected to the power voltage VBAT through the protection circuit to drive the LED and protect the LED at the same time.

The power supply voltage VBAT may be set as required, such as 12V, 9V, 5V, or 3.3V, and the value of the power supply voltage is not limited in this embodiment. The supply voltage VBAT may be provided by a battery or other circuitry such as an LDO (low dropout linear regulator). As an example, when the LED driving circuit is applied to battery level indication, the supply voltage VBAT may be the output voltage of the battery.

The reference voltage VREF may also be set according to needs, such as 200mV or 300mV, and the value of the reference voltage VREF is not limited in this embodiment.

As an embodiment, each of the first transistors M1 may operate in a saturation region, so as to output a constant driving current in cooperation with the first operational amplifier 14.

To better understand the operation of the first transistor, as described below with reference to fig. 2, the first operational amplifier 14, a first transistor M1 and a second resistor R2 cooperate to form a constant current source to generate a constant driving current to drive the LED. As an example, the drive current I _LED Can be controlled by reference voltage VREF and resistance R of resistor R2 ₂ The determination can be specifically referred to as the formula: I.C. A _LED ＝VREF/R ₂ . It will be appreciated that the drive current to drive the LED is determined by the resistance of the second resistor R2. The output voltage of the first operational amplifier follows the reference voltage VREF input by the first input end of the first operational amplifier, the voltage drop of the first transistor M1 can be ignored, the voltage at the two ends of the second resistor R2 is VREF, and the current flowing through the second resistor R2 is VREF/R ₂ 。

In some embodiments, please refer to fig. 3, wherein fig. 3 is a second schematic diagram of an LED driving circuit according to an embodiment of the present disclosure. The LED driving circuit 10 may further include a plurality of controllers 142, and each controller 142 is connected between the output terminal of the first operational amplifier 14 and a control terminal of one first transistor M1 to control the first transistor M1 to be turned on or off. The LED driving circuit 10 can control the state, such as on or off, of each first transistor M1 through the controller 142, so as to control the corresponding LED of the first transistor M1.

As an embodiment, the LED driving circuit 10 may further include a processing unit (not shown in the figure), and the processing unit controls the first transistor M1 connected thereto to be turned off through one controller 142, so that the LED corresponding to the first transistor M1 cannot operate. Similarly, the processing unit controls the conduction of the first transistor M1 connected thereto through one controller 142, and then the LED corresponding to the first transistor M1 can operate.

As an example, as shown in fig. 4, the controller 142 may include a switch, one end of the switch is connected to the output terminal of the first operational amplifier, and the other end of the switch is connected to the control terminal of the first transistor M1, so that the first transistor is turned on or off by turning on or off the switch. For example, when the plurality of switches are controlled to be simultaneously turned on, the first transistors corresponding to the plurality of switches are simultaneously turned on, so that the plurality of LEDs are controlled to emit light simultaneously. When the plurality of switches are controlled to be conducted in turn, the first transistors corresponding to the plurality of switches are conducted in turn, so that the plurality of LEDs are controlled to emit light in turn. In practical application, the number, sequence and time of the conduction of the plurality of switches can be controlled according to the working requirement of the LED.

In some embodiments, please refer to fig. 5, and fig. 5 is a fourth schematic diagram of an LED driving circuit according to an embodiment of the present disclosure. The LED driving circuit may further include a current limiting circuit 12, a first terminal of the current limiting circuit 12 is used for inputting the power voltage VBAT, the current limiting circuit 12 includes a plurality of second terminals, and a second terminal of each current limiting circuit 12 is connected to the second terminal of one of the first transistors M1. The current limiting circuit 12 can limit the current flowing through the LED not to be too large, and avoid the LED from overcurrent, thereby protecting the LED from being damaged easily.

As an implementation manner, please refer to fig. 6, wherein fig. 6 is a fifth schematic diagram of an LED driving circuit provided in the embodiment of the present application. The current limiting circuit 12 includes a plurality of current limiting units 120, each current limiting unit 120 may include a second operational amplifier 122, a second transistor M2, a third transistor M3, and a first resistor R1, a first end of the second transistor M2 and a first end of the third transistor M3 are both used for inputting the power supply voltage VBAT, a control end of the second transistor M2 and a control end of the second transistor M2 are both connected to an output end of the second operational amplifier 122, a second end of the second transistor M2 is used for connecting the LED, and a second end of the third transistor M3 is grounded through the first resistor R1.

The third transistor M3 may operate in a saturation region, and the second operational amplifier 122, the third transistor M3 and the first resistor R1 may cooperate to generate a reference current limiting value. When the driving current driving the LED is less than the reference current limit value, the second transistor M2 operates in a linear region. When the driving current driving the LED reaches the reference current limit value, the second transistor M2 operates in a saturation region to limit the driving current from continuing to rise. At this time, the current flowing through the second transistor M2 is mirrored by the current flowing through the third transistor M3 according to a predetermined ratio.

As an example, in each current limiting unit 120, the second operational amplifier 122, the third transistor M3 and the first resistor R1 form a current source, which can generate the current isc.ref, and the second transistor M2 and the third transistor M3 form a current mirror, which can proportionally copy the current isc.ref of the third transistor M3. When the LED works normally and no overcurrent exists, the second transistor M2 works in a linear region, and at the moment, the second transistor M2 and the third transistor M3 have no mirror image relationship; when the LED is overcurrent, the second transistor M2 operates in a saturation region, and the second transistor M2 and the third transistor M3 form a mirror image relationship, so that the current flowing through the second transistor M2 can be limited to k × isc.ref, where k is a mirror image ratio of the current mirror and depends on a ratio between the size of the second transistor M2 and the size of the second transistor M3. The second transistor M2 and the third transistor M3 may be selected to have a suitable size according to the overcurrent protection requirement, so that k × isc.ref is set to a smaller value that does not overcurrent the LED, thereby implementing overcurrent protection of the LED.

As another implementation manner, please refer to fig. 7, wherein fig. 7 is a sixth schematic diagram of an LED driving circuit provided in the embodiment of the present application. The current limiting circuit 12 may include a current generating circuit 12a and a plurality of current mirror legs 12b. The current generating circuit 12a includes a second operational amplifier 122, a third transistor M3 and a first resistor R1, a first input terminal of the second operational amplifier is used for accessing a reference voltage VREF, a control terminal of the third transistor M3 is connected to an output terminal of the second operational amplifier 122, a first terminal of the third transistor M3 is used for inputting a power voltage VBAT, a second terminal of the third transistor M3 is grounded through the first resistor R1, and a second terminal of the third transistor M3 is further connected to a second input terminal of the second operational amplifier.

Each current mirror branch 12b includes a second transistor M2, a first end of the second transistor M2 is used for inputting the power voltage VBAT, a control end of the second transistor M2 is connected to the output end of the second operational amplifier 122, and a second end of the second transistor M2 is used for connecting the second end of one first transistor M1 to the LED.

The second operational amplifier 122, the third transistor M3 and the first resistor R1 form a current source (i.e., a current generating circuit) capable of generating a current isc.ref, and each of the second transistors M2 and the third transistor M3 forms a current mirror to reproduce the current isc.ref of the third transistor M3 in proportion. When the LED works normally and no overcurrent exists, the second transistor M2 works in a linear region, and at the moment, the second transistor M2 and the third transistor M3 have no mirror image relationship; when the LED is overcurrent, the second transistor M2 operates in saturation region, and the second transistor M2 and the third transistor M3 form a mirror image relationship, and the current flowing through the second transistor M2 can be limited to k isc.ref, where k is the mirror image proportion of the current mirror, and depends on the ratio between the size of the second transistor M2 and the size of the second transistor M3. The second transistor M2 and the third transistor M3 may be selected to have a suitable size according to the overcurrent protection requirement, so that k × isc.ref is set to a smaller value that does not overcurrent the LED, thereby implementing overcurrent protection of the LED. The current mirror branches 12b may share one current generating circuit 12a, that is, the current limiting circuits corresponding to the LEDs may share one reference current source (i.e., the current generating circuit 12 a), which may optimize the circuit, reduce the usage of components, and reduce the cost.

As an example, the first transistor M1 in the above embodiments may be an NMOS transistor, and the second transistor M2 and the third transistor M3 may be PMOS transistors.

In some embodiments, please refer to fig. 8 and 9 in combination, in which fig. 8 is a seventh schematic diagram of an LED driving circuit provided in the embodiments of the present application, and fig. 9 is a schematic diagram of another form of the LED driving circuit shown in fig. 8. The LED driving circuit 10 may include a plurality of driving units 11, each driving unit 11 includes a current limiting unit 120 and a first transistor M1, each driving unit 11 includes a common output terminal LEDCNTL, the common output terminal LEDCNTL connects a second terminal of a second transistor M2 in the current limiting unit 120 and a second terminal of the first transistor M1, and the common output terminals LEDCNTL of any two driving units 11 are used for connecting two terminals of an LED to drive the LED.

It is also understood that the plurality of current limiting units 120 and the plurality of first transistors M1 may be divided into a plurality of driving units 11, each driving unit 11 includes one current limiting unit 120 and one first transistor M1, that is, the common output terminal LEDCNTL of each driving unit 11 is simultaneously connected to the second terminal of the second transistor M2 in the current limiting unit 120 and the second terminal of the first transistor M1, and two driving units 11 may be connected to both terminals of the LED, so as to drive the LED. As an example, the current limiting unit 120 and the first transistor M1 in any one of the two driving units 11 may alternatively operate according to a control signal, and the two driving units 11 may implement that the current limiting unit 120 in one driving unit 11 and the first transistor M1 in the other driving unit 11 cooperate to drive an LED according to the control signal. Specifically, in the two driving units 11 connected to the two ends of the LED, the current limiting unit 120 of one driving unit 11 operates, the first transistor M1 of the other driving unit 11 operates, that is, the positive electrode of the LED is connected to the current limiting unit 120 of one driving unit 11, the negative electrode of the LED is connected to the first transistor M1 of the other driving unit 11, the working current flows into the LED from the current limiting unit 120 of one driving unit 11, and then flows into the first transistor M1 of the other driving unit 11, so as to drive the LED, that is, the two driving units 11 cooperate to drive the LED.

Taking fig. 9 as an example, wherein each driving unit 11 can have three states, the first state (Sink) is that the first transistor M1 is turned on and the second transistor M2 is turned off, i.e. the common output terminal LEDCNTL corresponds to the first terminal of the first transistor M1. It can be understood that the common output terminal LEDCNTL is at a low potential. In the second state (Source), the first transistor M1 is turned off, and the second transistor M2 is turned on, i.e. the common output terminal LEDCNTL corresponds to the second terminal of the second transistor M2. It can be understood that the common output terminal LEDCNTL is at a high potential. In the third state (Floating), the first transistor M1 is turned off and the second transistor M2 is also turned off, i.e. the common output LEDCNTL is Floating or disconnected. The common output end LEDCNTL of any one of the driving units 11 in the Source state and the common output end LEDCNTL of any one of the driving units 11 in the Sink state can cooperate to realize driving of the LED. Because the state of each common output end LEDCNTL can be flexibly controlled, the LEDs can be connected between any two common output ends LEDCNTL, and the connection direction of the LEDs is not limited, that is, two LEDs with different directions can be connected between any two common output ends LEDCNTL. If there are N common outputs, there may be N x (N-1) LEDs connected to drive at least N x (N-1) LEDs. When N is greater than 2, the number of common output terminals LEDCNTL may be substantially less than the number of LEDs, i.e., the driving of a plurality of LEDs may be implemented through fewer ports.

As an example, please refer to fig. 10, and fig. 10 is a ninth schematic diagram of an LED driving circuit according to an embodiment of the present application. The 3 common outputs LEDCNTL can drive 6 LEDs. 3 public output end LEDCNTL include public output end LEDCNTLA, public output end LEDCNTLB and public output end LEDCNTLC, public output end LEDCNTLA connects the negative pole of LED1, the positive pole of LED3, the positive pole of LED5 and the negative pole of LED6, public output end LEDCNTLB connects the positive pole of LED1, the negative pole of LED2, the negative pole of LED3 and the positive pole of LED4, public output end LEDCNTLC connects the positive pole of LED2, the negative pole of LED4, the negative pole of LED5 and the positive pole of LED6, be in different states through controlling public output end LEDCNTL, thereby can control different LEDs, can refer to table 1 specifically.

Table 1:

LEDCNTLA	LEDCNTLB	LEDCNTLC	driven LED
				Sink	Source	Floating	LED1
Floating	Sink	Source	LED 2
				Source	Sink	Floating	LED 3
Floating	Source	Sink	LED 4
				Source	Floating	Sink	LED 5
Sink	Floating	Source	LED 6

Continuing with FIG. 11, in some examples, the three second transistors M2 in FIG. 11 may correspond to the three switches A _ RLOEN, B _ RLOEN and C _ RLOEN in FIG. 10, and the three first transistors M1 in FIG. 11 may correspond to the three switches A _ SELB, B _ SEL and C _ SEL in FIG. 10. When the second transistor M2 is turned on and the first transistor M1 is turned off, the driving unit 11 is in a source state; when the second transistor M2 is turned off and the first transistor M1 is turned on, the driving unit 11 is in a sink state; when the second transistors M2 and M1 and the first transistor are both off, the driving unit 11 is in the floating state.

Of course, in other examples, 3 common outputs LEDCNTL may also drive 3, 4, or 5 LEDs as desired.

It will be appreciated that the number of common output terminals LEDCNTL may have other values. For example, the number of the common output terminals LEDCNTL may be 4, and the number of the LEDs that can be controlled by the 4 common output terminals LEDCNTL may be between 4 and 12. Of course, in other examples, the LED driving circuit 10 may have a larger number of driving units 11, such as 5, 6, or more, each driving unit 11 has one common output end LEDCNTL, and the plurality of common output ends LEDCNTL may drive a larger number of LEDs.

In another embodiment, please refer to fig. 12, wherein fig. 12 is a tenth schematic diagram of an LED driving circuit according to an embodiment of the present disclosure. The main difference between the present embodiment and the above embodiments is the structure of the driving unit, that is, the LED driving circuit 10 may include a plurality of driving units 11, each driving unit 11 includes a second transistor M2 and a first transistor M1, a first terminal of the second transistor M2 is used for inputting the power voltage VBAT, each driving unit 11 includes a common output terminal LEDCNTL, the common output terminal LEDCNTL is connected to a second terminal of the second transistor M2 and a second terminal of the first transistor M1, and the common output terminals LEDCNTL of any two driving units 11 are used for connecting two terminals of an LED to drive the LED. The control end of the second transistor M2 is used for inputting a control signal CNTL, and the control signal CNTL can control the on or off of the second transistor M2, and in cooperation with the on or off of the first transistor M1, the state of the common output end LEDCNTL can be a high level, a low level or floating. The control signal CNTL may be sent by a processing unit in the LED driving circuit, or may be sent by a control circuit outside the LED driving circuit.

Because the state of each common output end LEDCNTL can be flexibly controlled, the LEDs can be connected between any two common output ends LEDCNTL, and the connection direction of the LEDs is not limited, that is, two LEDs with different directions can be connected between any two common output ends LEDCNTL. If there are N common outputs, there may be N x (N-1) LEDs connected to drive at least N x (N-1) LEDs. When N is greater than 2, the number of common output terminals LEDCNTL may be substantially less than the number of LEDs, i.e., the driving of a plurality of LEDs may be implemented through fewer ports. As an example, 3 common outputs LEDCNTL may drive 4 LEDs as shown in fig. 12. As another example, in connection with fig. 10 or fig. 11,3 common output terminals LEDCNTL may drive 6 LEDs.

It should be noted that each LED in the above embodiments may be a single LED, or may be a combination of a plurality of LEDs connected in series and parallel. For example, a plurality of LEDs connected in series in the same direction, or a plurality of LEDs connected in parallel, or a plurality of LEDs connected in series and parallel in series can be regarded as one larger LED. It should be noted that the colors of the plurality of LEDs may be set as needed, and as an example, the plurality of LEDs may be LEDs of the same color. As another example, the plurality of LEDs may be different color LEDs.

As an embodiment, referring to fig. 8, the LED driving circuit 10 may further include a reference voltage generating circuit 13, and the reference voltage generating circuit 13 may output a reference voltage VREF and transmit the reference voltage VREF to the first operational amplifier 14 and each of the driving units 11. In other embodiments, the reference voltage generating circuit 13 may also generate a bias current and transmit the bias current to the first operational amplifier and current limiting circuit.

In some embodiments, referring to fig. 13, fig. 13 is a schematic structural diagram of a driving unit in the driving circuit shown in fig. 8. In each of the driving units 11, the second terminal of the first transistor M1 and the second terminal of the second transistor M2 may be connected and serve as a common output terminal LEDCNTL. Each drive unit 11 may also include a controller 142. As an embodiment, the controller 142 may include a Level Shifter (Level Shifter) and a switch, and controls the operation or the turn-off of the first transistor M1 through the switch. As another embodiment, the controller 142 may also control the channel or the turn-off of the first transistor M1 through other structures. As an example, the controller 142 may include only a Level Shifter (Level Shifter), and not include a switch, an output terminal of the Level Shifter (Level Shifter) is connected to the control terminal of the first transistor M1, and the output terminal of the Level Shifter (Level Shifter) may output different voltages, so as to control the first transistor to be turned on or off.

In some embodiments, each driving unit 11 may further include a current unit 121, and the current unit 121 includes a second operational amplifier 122 and a third transistor M3, wherein the third transistor M3 is connected to the second transistor M2 to form a current mirror.

The embodiment of the application also provides a chip, and the chip can comprise the LED driving circuit in any one of the embodiments. The Chip may be, but is not limited to, an SOC (System on Chip) Chip or an SIP (System in package) Chip. The chip shares the same first operational amplifier through the loops driving all the LEDs, namely the operational amplifier generating the driving current for driving all the LEDs is the same, the driving current difference of the loops driving different LEDs only comes from different first transistors, and compared with the driving currents generated through different operational amplifiers and different transistors, the chip of the embodiment can greatly reduce the current mismatch error between different LEDs. For example, the current mismatch error between different LEDs can be controlled to within 1%. And the driving currents of different LEDs can be similar, and the matching degree of different LEDs is improved, such as the brightness of different LEDs is similar or the same.

As an implementation manner, please refer to fig. 14, where fig. 14 is a first schematic diagram of a chip and an LED provided in an embodiment of the present application. The chip 20 may include a plurality of driving pins (e.g., LEDCNTLA, LEDCNTLAB, LEDCNTLC), each of which is connected to the second terminal of one of the first transistors M1 and the second terminal of one of the current limiting circuits 12, or it may be understood that the common output terminal LEDCNTL of each of the driving units in the LED driving circuit is connected to one of the driving pins of the chip 20, and the driving pin connected to the common output terminal LEDCNTL may be connected to an external device, such as an LED. Namely, the current limiting circuit 12, the first operational amplifier 14 and the first transistor M1 are integrated on a chip, and the LED is disposed outside the chip. The specific connection structure of the common output terminal and the LED can refer to the above embodiments, and is not described herein again. Since each drive pin of the chip 20 can be multiplexed, the number of drive pins required can be less than the number of LEDs driven.

The chip can further comprise a power supply pin and a grounding pin, wherein the power supply pin can be connected with an external power supply so as to access power supply voltage, and the grounding pin can be connected with an external ground. As another embodiment, the main difference between this embodiment and the above embodiments is that this embodiment does not need to provide a current limiting circuit, please refer to fig. 11, each driving pin of the chip is connected to the second terminal of one first transistor M1 and the second terminal of one second transistor, the first terminal of the second transistor is used for inputting the power voltage, and the control terminal of the second transistor is controlled by the control CNTL. As an example, the control terminal of the second transistor may be controlled by a processing unit within the chip. It can also be understood that each driving unit in the LED driving circuit includes a second transistor M2 and a first transistor M1, the common output terminal LEDCNTL of the driving unit is connected to the second terminal of the first transistor and the second terminal of the second transistor, the common output terminal LEDCNTL of one driving unit is connected to a driving pin of the chip 20, and the driving pin can be connected to an external device, such as an LED. The specific connection structure of the common output terminal and the LED can refer to the above embodiments, and is not described herein.

The embodiment of the application further comprises an electronic device, wherein the electronic device comprises a plurality of LEDs and the chip in any one of the above embodiments. The driving circuit or chip is connected with the plurality of LEDs and drives the plurality of LEDs.

Referring to fig. 1 to 14, the electronic device uses the same first operational amplifier for driving all the loops of the LEDs, that is, the operational amplifiers generating the driving currents for driving all the LEDs are the same, and the driving current differences of the loops for driving different LEDs are only from different first transistors. For example, the current mismatch error between different LEDs can be controlled to within 1%. The driving current of different LEDs can be similar, and the matching degree of different LEDs is improved, such as the brightness of different LEDs is similar or the same.

As an embodiment, please refer to fig. 15, wherein fig. 15 is a second schematic diagram of a chip and an LED provided in the embodiment of the present application. The number of the driving pins of the chip is larger than two, the number of the LEDs is the same as that of the driving pins, and each driving pin is correspondingly connected with one LED to independently drive the LED. At this time, the driving pin of the chip may be led out from the second end of the first transistor M1, as an example, the driving circuit structure inside the chip may refer to the embodiments shown in fig. 2, fig. 3, or fig. 4, and is not described herein again.

As an embodiment, please refer to fig. 16, wherein fig. 16 is a third schematic diagram of a chip and an LED provided in the embodiment of the present application. The number of the driving pins of the chip is larger than two, the number of the driving pins can be twice of the number of the LEDs, every two driving pins are a pair and are correspondingly connected to two ends of one LED to drive the LED. At this time, each pair of driving pins of the chip may be respectively led out from the second end of the first transistor M1 and the second end of the second transistor M2 (a second end of the current limiting unit), as an example, the driving circuit structure inside the chip may refer to the embodiments shown in fig. 5, fig. 6, fig. 7, fig. 9, fig. 11, or fig. 12, and is not described herein again.

As another embodiment, the number of the driving pins of the chip is greater than two, the number of the LEDs is greater than the number of the driving pins, and one or more LEDs are connected between any two driving pins to drive the LEDs through the cooperation of the two driving pins. As an example, the driving pin of the chip may be led out, and refer to the embodiments shown in fig. 9, fig. 11, or fig. 12, which is not described herein again.

As an example, the plurality of LEDs may include LEDs of multiple colors, such as a red LED, a blue LED, a green LED, and the like, and the LED driving circuit may drive any one of the plurality of LEDs to display, so as to display different colors to a user through the LED displays of different colors, so as to prompt different information. For example, different colored LEDs may be displayed to indicate that the electronic device is in different charging states, different colored LEDs may be displayed to indicate that the electronic device receives different information, etc.

The embodiment of the present application further provides an electronic device, and a main difference between the electronic device of the present application and the electronic device of the foregoing embodiment is a chip. The electronic device comprises a chip and a plurality of LEDs, wherein the chip comprises a plurality of driving units (not shown in the figure) and a plurality of driving pins (LEDCNILA, LEDCNILB, LEDCNILC), each driving unit comprises a common output end, each common output end is connected with one driving pin, and the state of the common output end, namely the driving pin, can be high level, low level or floating. Because the state of each driving pin can be flexibly controlled, the LED can be connected between any two driving pins, and the connecting direction of the LED is not limited, namely the LED with two different directions can be connected between any two driving pins. If there are N driving pins, there may be N × N-1 LEDs connected to drive at least N × N-1 LEDs. When N is greater than 2, the number of driving pins may be substantially less than the number of LEDs, i.e., the driving of a plurality of LEDs may be achieved by fewer driving pins. As an example, as shown in fig. 12, 3 common outputs LEDCNTL, i.e., 3 driving pins, may control 4 LEDs, respectively. As another example, in connection with fig. 10 or fig. 11,3 common outputs LEDCNTL, i.e., 3 driving pins, may control 6 LEDs, respectively. The connection structure of the common output terminal can refer to the above embodiments, and is not described herein again.

As an alternative, each driving unit includes a current limiting circuit and a constant current source circuit, a first end of each current limiting circuit is used for inputting a power supply voltage, a first end of each constant current source circuit is used for grounding, and a second end of each current limiting circuit and a second end of one constant current source circuit are connected to one driving pin; the number of the driving pins is larger than two, the number of the LEDs is larger than that of the driving pins, and each driving pin is connected with the anode of at least one LED and the cathode of at least one LED.

The driving unit, the current limiting circuit and the constant current source circuit may refer to the current limiting circuit and the constant current source circuit in the above embodiments, and are not described herein again. It should be noted that, as an embodiment, the constant current source circuit may include the first operational amplifier and the plurality of first transistors in the above-described embodiment. That is, the plurality of constant current source circuits may include a common first operational amplifier and a plurality of first transistors, and the specific structure may refer to the above embodiments, which is not described herein again. As another implementation, each constant current source circuit may include a first operational amplifier and a first transistor, and the specific structure may be adjusted after referring to the above embodiment, which is not described herein again. The output common end of each driving unit is connected with the second end of each current limiting circuit and the second end of a constant current source circuit, namely the output common end of each driving unit is connected with a driving pin. The LED can be connected between the two driving pins and is driven by a current limiting circuit connected with one driving pin and a constant current source circuit connected with the other driving pin. It will be appreciated that more LEDs can be arranged reasonably by multiplexing the drive pins. As an example, each driving pin is connected to the positive electrode of 2 LEDs and the negative electrode of 2 LEDs, any 2 driving pins can drive 2 LEDs, and 3 driving pins can drive 6 LEDs. It should be noted that the LEDs may be arranged as appropriate according to the needs, for example, only 4 or 5 LEDs may be arranged.

It is understood that the electronic device in the above embodiments may be, but not limited to, a weight scale, a body fat scale, a nutrition scale, an infrared electronic thermometer, a pulse oximeter, a body composition analyzer, a mobile power supply, a wireless charger, a quick charger, a vehicle charger, an adapter, a display, a USB (Universal Serial Bus) docking station, a touch pen, a true wireless earphone, a control screen in an automobile, an intelligent wearable device, a mobile terminal, and an intelligent home device. The intelligent wearable device comprises but is not limited to an intelligent watch, an intelligent bracelet and a cervical vertebra massager. The mobile terminal includes, but is not limited to, a smart phone, a notebook computer, a tablet computer, and a POS (point of sale) machine. The intelligent household equipment comprises but is not limited to an intelligent socket, an intelligent electric cooker, an intelligent sweeper and an intelligent lamp.

In the foregoing embodiments, the descriptions of the respective embodiments have respective emphasis, and for parts that are not described in detail in a certain embodiment, reference may be made to the related descriptions of other embodiments.

Although the present application has been described with reference to the preferred embodiments, it is not intended to limit the present application to the details of the foregoing description, and it will be apparent to those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention.

Claims

1. An LED driving circuit, comprising:

a first input end of the first operational amplifier is used for inputting a reference voltage;

the control end of each first transistor is connected with the output end of the first operational amplifier, the first end of each first transistor is connected with the second input end of the first operational amplifier, and the second end of each first transistor is used for being connected with an LED.

2. The LED driving circuit of claim 1, further comprising:

a plurality of controllers, each of the controllers connected between an output of the first operational amplifier and a control terminal of one of the first transistors.

3. The LED driving circuit according to claim 1 or 2, further comprising:

and the first end of the current limiting circuit is used for inputting power supply voltage, the current limiting circuit comprises a plurality of second ends, and an LED is connected between the second end of each current limiting circuit and the second end of one first transistor.

4. The LED driving circuit according to claim 3, wherein the current limiting circuit comprises a plurality of current limiting units, each of the current limiting units comprises a second operational amplifier, a second transistor, a third transistor and a first resistor, a first end of the second transistor and a first end of the third transistor are used for inputting a power supply voltage, a control end of the second transistor and a control end of the second transistor are connected with an output end of the second operational amplifier, a second end of the second transistor is used for connecting the LED, and a second end of the third transistor is grounded through the first resistor.

5. The LED driving circuit according to claim 3, wherein the current limiting circuit comprises:

each current mirror branch comprises a second transistor, the first end of the second transistor is used for inputting power supply voltage, the control end of the second transistor is connected with the output end of the second operational amplifier, and the second end of the second transistor is used for being connected with the second end of the first transistor through an LED.

6. The LED driving circuit according to claim 4 or 5, wherein the LED driving circuit comprises a plurality of driving units, each of the driving units comprises one of the current limiting circuits and one of the first transistors, each of the driving units comprises a common output terminal, the common output terminal is connected to the second terminal of the current limiting circuit and the second terminal of the first transistor, and the common output terminals of any two of the driving units are used for connecting two terminals of an LED.

7. The LED driving circuit according to claim 6, wherein a second terminal of the second transistor of the current limiting circuit is connected to the common output terminal.

8. The LED driving circuit according to claim 6, wherein the number of common outputs is greater than or equal to 3.

9. A chip comprising the LED driving circuit according to any one of claims 1 to 8.

10. An electronic device comprising a plurality of LEDs and the chip of claim 9, said chip being connected to a plurality of said LEDs.

11. The electronic device of claim 10, wherein the chip comprises at least three driving pins, wherein the number of LEDs is greater than the number of driving pins, and wherein each driving pin is connected to a positive electrode of at least one LED and a negative electrode of at least one LED.