CN117475938A - Multi-channel LED backlight system and constant current control circuit and method thereof - Google Patents
Multi-channel LED backlight system and constant current control circuit and method thereof Download PDFInfo
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- G—PHYSICS
- G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
- G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
- G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
- G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
- G09G3/34—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters by control of light from an independent source
- G09G3/3406—Control of illumination source
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- H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]
- H05B45/30—Driver circuits
- H05B45/345—Current stabilisation; Maintaining constant current
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Abstract
A multi-channel LED backlight system, a constant current control circuit and a constant current control method thereof are provided. The constant current control circuit includes: the channel setting current generator generates a plurality of channel setting currents according to the reference voltage and the size of the external resistor; a plurality of channel voltage generators for generating a plurality of channel voltages according to the plurality of channel setting currents; and a plurality of LED channel drivers for generating a plurality of LED driving currents for the plurality of LED channels according to the plurality of channel voltages. Each LED channel driver includes an operational amplifier. The operational amplifier comprises an operational amplifier input pair tube, an offset voltage storage pair tube and an offset voltage storage capacitor, the offset voltage storage pair tube stores the offset voltage of the operational amplifier input pair tube on the offset voltage storage capacitor before the operational amplifier generates LED driving current, and the offset voltage of the operational amplifier input pair tube is overlapped to the operational amplifier input pair tube when the operational amplifier generates the LED driving current so as to eliminate the influence of the offset voltage of the operational amplifier input pair tube on the LED driving current, thereby improving the matching between channel currents.
Description
The application is a divisional application of an invention patent application of which the application date is 11/13/2020, the application number is 202011268020.9, and the invention name is a multi-channel LED backlight system, a constant current control circuit and a constant current control method.
Technical Field
The invention relates to the field of circuits, in particular to a multipath LED backlight system and a constant current control circuit and method thereof.
Background
In a multiple Light Emitting Diode (LED) backlight system, in order to ensure uniform brightness of the entire screen, it is required that the LED driving currents for the respective LED channels must be precisely matched.
In an LED backlight system employing a low frequency (e.g., 100Hz to 1000 Hz) Pulse Width Modulation (PWM) dimming method, after setting the maximum LED driving current for each LED channel, the brightness of the LEDs is adjusted by adjusting the duty ratio of the LED driving current for each LED channel. The current matching is performed for the maximum LED drive current for each LED channel. When the brightness of the LEDs is small, increasing the brightness of the LEDs by increasing the duty ratio of the LED driving current for each LED channel does not affect the matching of the maximum LED driving current for each LED channel, but the screen may have a flickering phenomenon, which has a certain effect on the health of eyes.
In an LED backlight system employing an analog dimming method, the brightness of LEDs is adjusted by adjusting the magnitude of LED driving current for each LED channel. When the brightness of the LEDs is small, increasing the brightness of the LEDs by increasing the LED driving current for each LED channel does not cause flickering of the screen, but it is necessary to ensure matching between the LED driving currents for each LED channel, thereby ensuring uniform brightness of the entire screen.
Disclosure of Invention
In view of one or more of the problems set forth above, the present invention provides a novel multi-channel LED backlight system and constant current control circuit and method thereof.
According to an embodiment of the invention, a constant current control circuit for a multi-channel LED backlight system comprises: a channel setting current generator operable to generate a plurality of channel setting currents for the plurality of LED channels, respectively, according to the reference voltage and the magnitude of the external resistor; a plurality of channel voltage generators operable to generate a plurality of channel voltages for the plurality of LED channels, respectively, according to the plurality of channel set currents; and a plurality of LED channel drivers operable to generate a plurality of LED drive currents for the plurality of LED channels, respectively, from the plurality of channel voltages, wherein each of the plurality of LED channel drivers includes an operational amplifier and a drive current generation resistor, the operational amplifier generates an LED drive current for a corresponding one of the plurality of LED channels according to a magnitude of the corresponding one of the plurality of channel voltages and the drive current generation resistor, the operational amplifier includes an operational amplifier input pair, an offset voltage storage pair, and an offset voltage storage capacitor, the offset voltage storage pair stores an offset voltage of the operational amplifier input pair on the offset voltage storage capacitor before the operational amplifier generates the LED drive current, and the operational amplifier superimposes the offset voltage of the operational amplifier input pair stored on the offset voltage storage capacitor on the operational amplifier input pair to eliminate an influence of the offset voltage of the operational amplifier input pair on the LED drive current.
A constant current control circuit for an LED backlight system according to another embodiment of the present invention includes: a channel setting current generator operable to generate a channel setting current according to the reference voltage and the magnitude of the external resistor; a channel voltage converter operable to convert a channel setting current into a plurality of channel voltages for a plurality of LED channels, respectively; and a plurality of LED channel drivers operable to generate a plurality of LED drive currents for the plurality of LED channels, respectively, from the plurality of channel voltages, wherein each of the plurality of LED channel drivers includes an operational amplifier and a drive current generation resistor, the operational amplifier generates an LED drive current for a corresponding one of the plurality of LED channels according to a magnitude of the corresponding one of the plurality of channel voltages and the drive current generation resistor, the operational amplifier includes an operational amplifier input pair, an offset voltage storage pair, and an offset voltage storage capacitor, the offset voltage storage pair stores an offset voltage of the operational amplifier input pair on the offset voltage storage capacitor before the operational amplifier generates the LED drive current, and the operational amplifier superimposes the offset voltage of the operational amplifier input pair stored on the offset voltage storage capacitor on the operational amplifier input pair to eliminate an influence of the offset voltage of the operational amplifier input pair on the LED drive current.
The constant current control method for the multi-channel LED backlight system comprises the following steps: generating a plurality of channel setting currents for a plurality of LED channels respectively by a channel setting current generator according to the reference voltage and the size of the external resistor; generating, by a plurality of channel voltage generators, a plurality of channel voltages for a plurality of LED channels, respectively, according to a plurality of channel set currents; and generating, by the plurality of LED channel drivers, a plurality of LED drive currents for the plurality of LED channels, respectively, according to the plurality of channel voltages, wherein each of the plurality of LED channel drivers includes an operational amplifier and a drive current generation resistor, the operational amplifier generates an LED drive current for a corresponding one of the plurality of LED channels according to a magnitude of the corresponding one of the plurality of channel voltages and the drive current generation resistor, the operational amplifier includes an operational amplifier input pair tube, an offset voltage storage pair tube, and an offset voltage storage capacitor, the offset voltage storage pair tube stores an offset voltage of the operational amplifier input pair tube on the offset voltage storage capacitor before the operational amplifier generates the LED drive current, and superimposes the offset voltage of the operational amplifier input pair tube stored on the offset voltage storage capacitor on the operational amplifier input pair tube when the operational amplifier generates the LED drive current, so as to eliminate an influence of the offset voltage of the operational amplifier input pair tube on the LED drive current.
The constant current control method for the multi-channel LED backlight system comprises the following steps: generating a channel setting current by a channel setting current generator according to the reference voltage and the size of the external resistor; converting, by a channel voltage converter, a channel setting current into a plurality of channel voltages for a plurality of LED channels, respectively; the operational amplifier generates LED driving currents for the corresponding one of the plurality of LED channels according to the corresponding one of the plurality of channel voltages, the operational amplifier comprises an operational amplifier input pair tube, an offset voltage storage pair tube and an offset voltage storage capacitor, the offset voltage storage pair tube stores offset voltages of the operational amplifier input pair tube on the offset voltage storage capacitor before the operational amplifier generates the LED driving currents, and the offset voltages of the operational amplifier input pair tube stored on the offset voltage storage capacitor are superposed on the operational amplifier input pair tube when the operational amplifier generates the LED driving currents so as to eliminate influences of the offset voltages of the operational amplifier input pair tube on the LED driving currents.
The multi-channel LED backlight system comprises the constant current control circuit.
According to the constant current control system and the constant current control method for the multi-channel LED backlight system, the current matching precision among all LED channels in the multi-channel LED backlight system can be improved.
Drawings
The invention will be better understood from the following description of specific embodiments thereof, taken in conjunction with the accompanying drawings, in which:
FIG. 1 illustrates an example system block diagram of a multi-channel LED backlight system according to an embodiment of this disclosure;
FIG. 2 illustrates an example system block diagram of a constant current control circuit for a multiple LED backlight system in accordance with an embodiment of the invention;
fig. 3 shows an example circuit diagram of the constant current control circuit shown in fig. 2;
FIG. 4 illustrates an example system block diagram of a constant current control circuit for a multiple LED backlight system in accordance with an embodiment of the invention;
fig. 5 shows an example circuit diagram of the constant current control circuit shown in fig. 4;
fig. 6 shows an example circuit diagram of an LED channel driver for a constant current control circuit according to an embodiment of the present invention.
Detailed Description
Features and exemplary embodiments of various aspects of the invention are described in detail below. In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the invention. It will be apparent, however, to one skilled in the art that the present invention may be practiced without some of these specific details. The following description of the embodiments is merely intended to provide a better understanding of the invention by showing examples of the invention. The present invention is in no way limited to any particular configuration and algorithm set forth below, but rather covers any modification, substitution, and improvement of elements, components, and algorithms without departing from the spirit of the invention. In the drawings and the following description, well-known structures and techniques have not been shown in order to avoid unnecessarily obscuring the present invention.
Fig. 1 shows an example system block diagram of a multi-channel LED backlight system 100 according to an embodiment of the invention. In the multiple LED backlight system 100 shown in fig. 1, current begins to flow through the LEDs when the output voltage Vout of the switch-mode power supply system 102 increases above the on-voltage of the LEDs; the constant current control circuit 104 includes a channel current control module 1042 and n LED channel drivers 1044-1 to 1044-n (n is an integer greater than 0), the channel current control module 1042 being operable to set the magnitude of LED drive currents for each LED channel, the LED channel drivers 1044-1 to 1044-n being operable to generate n LED drive currents for the n LED channels, respectively; the headroom control module 106 is operable to detect the voltages at the LED pins LED1 through LEDn respectively connected to the respective LED channels and to feed back the detected minimum voltage VLED to the switched mode power supply system 102 for controlling the output voltage Vout for optimizing the system efficiency.
Fig. 2 shows an example system block diagram of a constant current control circuit 104 for a multiple LED backlight system 100 according to an embodiment of the invention. As shown in fig. 2, in some embodiments, the constant current control circuit 104 includes a channel setting current generator 1042-1, a channel voltage converter 1042-2, and n LED channel drivers 1044-1 to 1044-n, where: the channel setting current generator 1042-1 is operable to generate a channel setting current I1 according to the reference voltage Vref and the magnitude of the external resistor of the pin ISET; the channel voltage converter 1042-2 is operable to convert the channel setting current I1 into n channel voltages V1 to Vn for the plurality of LED channels, respectively; the LED channel drivers 1044-1 to 1044-n are operable to generate n LED drive currents for n LED channels, respectively, from the n channel voltages V1 to Vn. Here, it should be understood that the channel setting current generator 1042-1 and the channel voltage converter 1042-2 are components of the channel current control module 1042, i.e., the channel current control module 1042 includes the channel setting current generator 1042-1 and the channel voltage converter 1042-2.
Fig. 3 shows an example circuit diagram of the constant current control circuit 104 shown in fig. 2. As shown in fig. 3, in some embodiments, the operational amplifier OPC31 is used to realize the function of the channel setting current generator 1042-1, i.e. generating the channel setting current I1 according to the reference voltage Vref and the magnitude of the external resistor R3C of the ISET pin; the PMOS current mirrors PM31 and PM32 and the resistor R30 are used to realize the function of the channel voltage converter 1042-2, that is, the mirror current generated by mirroring the channel setting current I1 by the PMOS current mirrors PM31 and PM32 is converted into n channel voltages V1 to Vn on the resistor R30; the operational amplifiers OP31 to OP3n and the resistors R31 to R3n are used to realize the functions of the LED channel drivers 1044-1 to 1044-n, i.e., to generate n LED channel currents for n LED channels, respectively, according to the n channel voltages V1 to Vn.
Specifically, as shown in fig. 3, each of the LED channel drivers 1044-1 to 1044-n, for example, the LED channel driver 1044-m includes an operational amplifier OP3m and a driving current generation resistor R3m, wherein the operational amplifier OP3m generates an LED driving current for a corresponding one of the n LED channels (i.e., the LED channel to which the LED pin LEDm is connected) according to the corresponding one of the channel voltages V1 to Vn and the magnitude of the driving current generation resistor R3 m. Here, m is an integer, and 1.ltoreq.m.ltoreq.n.
In the constant current control circuit 104 shown in fig. 3, matching of LED driving currents between LED channels is mainly affected by matching of the resistor R30 and the resistors R31 to R3n and offset voltages of the operational amplifiers OP31 to OP3 n. Because the matching between the resistor R30 and the resistors R31 to R3n is difficult to achieve equalization, and meanwhile, when the channel setting current I1 is smaller, the voltages of the resistors R31 to R3n are too low, the offset voltages of the operational amplifiers OP31 to OP3n have a great influence on the LED driving currents output to the LED channels, and the conventional field effect transistor (MOS) operational amplifier is difficult to achieve extremely low offset voltages (within 1 mV), which may cause poor matching consistency of the LED driving currents between the LED channels.
In view of one or more of the above problems, the present invention provides a novel constant current control circuit and method for a multi-channel LED backlight system to improve the accuracy of matching of LED drive currents between individual LED channels.
Fig. 4 shows an example system block diagram of a constant current control circuit 104' for a multiple LED backlight system 100 according to an embodiment of the invention. As shown in fig. 4, in some embodiments, the constant current control circuit 104 'includes a channel setting current generator 1042-1', n channel voltage generators 1042-21 to 1042-2n, and n LED channel drivers 1044-1 'to 1044-n', where: the channel setting current generator 1042-1' is operable to generate n channel setting currents Ich1 to Ichn for n LED channels, respectively, according to the reference voltage Vref and the magnitude of the external resistor of the ISET pin; the channel voltage generators 1042-21 to 1042-2n are operable to generate n channel voltages V1 'to Vn' from n channel setting currents Ich1 to Ichn; the LED channel drivers 1044-1 'to 1044-n' are operable to generate n LED drive currents for n LED channels, respectively, from the n channel voltages V1 'to Vn'. Similarly, it should be appreciated that the channel setting current generator 1042-1 'and the channel voltage generators 1042-21 to 1042-2n are components of the channel current control module 1042', i.e. the channel current control module 1042 'comprises the channel setting current generator 1042-1' and the channel voltage generators 1042-21 to 1042-2n.
Fig. 5 shows an example circuit diagram of the constant current control circuit 104' shown in fig. 4. As shown in fig. 5, in some embodiments, the operational amplifier OPC51 and the n triode current mirrors including PMOS transistors PM51 and PM1 to PMn, the triodes Q51 and Q1 to Qn of the emitters of these PMOS transistors, and the negative feedback resistors R51 and R53-1 to R53-n of the emitters of these PMOS transistors are used to realize the function of the channel setting current generator 1042-1', i.e., the operational amplifier OPC51 generates the channel setting source current Ic according to the reference voltage Vref and the magnitude of the external resistor R5c of the ISET pin, the channel setting source current Ic generates the channel setting currents Ich1 to Ichn via the mirror images of the n triode current mirrors; the channel voltage generating resistors Rc1 to Rcn are used for realizing the functions of the channel voltage generators 1042-21 to 1042-2n, i.e. the channel voltage generating resistors Rc1 to Rcn generate the channel voltages V1 'to Vn' according to the channel setting currents Ich1 to Ichn, respectively; the operational amplifiers OP1 to OPn and the driving current generating resistors R1 to Rm are used to realize the functions of the LED channel drivers 1044-1 'to 1044-n', i.e., to generate n LED driving currents for n LED channels, respectively, according to the channel voltages V1 'to Vn'.
Specifically, as shown in fig. 5, a transistor current mirror m including a PMOS transistor PM51, any one of PMOS transistors PM1 to PMn, transistors Q51 and Qm of the emitters of the PMOS transistors PM51 and PMm, and negative feedback resistors R51 and R53-m of the emitters of the PMOS transistors PM51 and PMm generates a channel setting current Ichm by mirroring a channel setting source current Ic; any one of the channel voltage generation resistors Rc1 to Rcn generates a channel voltage Vm' from the channel setting current Ichm by the channel voltage generation resistor Rcm; any one of the LED channel drivers 1044-1' to 1044-n ' includes an operational amplifier OPm and a driving current generation resistor Rm, the operational amplifier OPm generating an LED driving current for an LED channel to which the LED pin LEDm is connected according to the channel voltage Vm ' and the magnitude of the driving current generation resistor Rm.
The constant current control circuit 104' has the following technical advantages with respect to the constant current control circuit 104: 1) The adoption of the three-stage tube current mirror can achieve accurate current mirror matching; 2) The negative feedback resistance of the emitter is added in the triode current mirror, so that the matching precision of the current mirror can be further improved; 3) For any one LED channel m of the LED channels 1 to n, only an accurate resistive power matching between the channel voltage generating resistor Rcm and the driving current generating resistor Rm needs to be achieved.
It should be appreciated that all three of the above technical advantages of the constant current control circuit 104' need not necessarily be realized to improve the accuracy of matching of LED drive currents between individual LED channels. Conversely, in some embodiments, the accuracy of matching of LED drive currents between individual LED channels may be improved to some extent by implementing one or more of the above three technical advantages of the constant current control circuit 104', as desired.
In some embodiments, the accuracy of matching of LED drive currents between individual LED channels may also be improved by improving the LED channel driver. Fig. 6 shows an example circuit diagram of an LED channel driver for a constant current control circuit according to an embodiment of the present invention. It should be appreciated that by applying the LED channel driver shown in fig. 6 to the constant current control circuit 104 shown in fig. 2 and the constant current control circuit 104' shown in fig. 4, the matching accuracy of the LED driving currents between the respective LED channels can also be improved to some extent. That is, each of the LED channel drivers 1044-1 to 1044-n (e.g., LED channel driver 1044-m) and each of the LED channel drivers 1044-1' to 1044-n ' (e.g., LED channel driver 1044-m ') may be implemented in the form of the LED channel drivers shown in fig. 6 to improve the matching accuracy of the LED driving currents between the respective LED channels.
Here, it is assumed that fig. 6 shows an example circuit diagram of any one of the LED channel drivers 1044-m or 1044-m'. As shown in fig. 6, the LED channel driver 1044-m or 1044-m' includes an op-amp input pair of pipes PM65 and PM66 and an offset voltage storage pair of pipes PM62 and PM63; the operational amplifier input connects the VR terminals of the tubes PM65 and PM66 (i.e., the positive input terminals of the operational amplifiers OP3m or OPm in the LED channel drivers 1044-m or 1044-m ') with the channel voltage Vm or Vm'. Normally, the operational amplifier OP3m or OPm has the following two operating phases: in a first phase, i.e., before the LED driving current is generated, the switch SW1 is closed to connect the VN terminal (i.e., the inverting terminal of the operational amplifier OP3m or OPm in the LED channel driver 1044-m or 1044-m') and the VR terminal of the operational amplifier input pair pipes PM65 and PM66 together, while the switches SW2 and SW5 are turned off to open the resistive feedback loop, and the switches SW3 and SW4 are closed to cause the offset voltage storage capacitor C1 to store the offset voltage of the operational amplifier input pair pipes; and in the second stage, when the LED driving current is generated, the switch SW1 is opened, the switches SW2 and SW5 are closed, a resistor feedback loop is formed to perform constant current control on the LED driving current, meanwhile, the switches SW3 and SW4 are turned off to convert the offset voltage stored in the offset voltage storage capacitor C1 in the first stage into current through the offset voltage storage tubes PM62 and PM63 and then are overlapped on the Drain ends of the operational amplifier input pair tubes PM65 and PM66, and therefore the influence of the offset voltage of the operational amplifier OP3m or OPm on the LED driving current output to the LED channel m is eliminated.
That is, the operational amplifier OP3m or OPm includes an operational amplifier input pair tube, an offset voltage storage pair tube, and an offset voltage storage capacitor, the offset voltage storage pair tube stores an offset voltage of the operational amplifier input pair tube on the offset voltage storage capacitor before the operational amplifier generates the LED driving current, and the offset voltage of the operational amplifier input pair tube stored on the offset voltage storage capacitor is superimposed on the operational amplifier input pair tube when the operational amplifier generates the LED driving current, so as to eliminate an influence of the offset voltage of the operational amplifier input pair tube on the LED driving current.
In implementing all three of the above technical advantages of the constant current control circuit 104' and the constant current control circuit of the operational amplifier shown in fig. 6, the matching of the LED driving currents between all channels can be optimized for a wide range of currents. For example, a match of less than 3% may be made for LED drive currents of around 5 mA.
In summary, the constant current control circuit 104' according to the embodiment of the present invention may implement a constant current control method, including: generating a plurality of channel setting currents for a plurality of LED channels respectively by a channel setting current generator according to the reference voltage and the size of the external resistor; generating, by a plurality of channel voltage generators, a plurality of channel voltages for a plurality of LED channels, respectively, according to a plurality of channel set currents; and generating, by the plurality of LED channel drivers, a plurality of LED drive currents for the plurality of LED channels, respectively, according to the plurality of channel voltages, wherein each of the plurality of LED channel drivers includes an operational amplifier and a drive current generation resistor, the operational amplifier generates an LED drive current for a corresponding one of the plurality of LED channels according to a magnitude of the corresponding one of the plurality of channel voltages and the drive current generation resistor, the operational amplifier includes an operational amplifier input pair tube, an offset voltage storage pair tube, and an offset voltage storage capacitor, the offset voltage storage pair tube stores an offset voltage of the operational amplifier input pair tube on the offset voltage storage capacitor before the operational amplifier generates the LED drive current, and superimposes the offset voltage of the operational amplifier input pair tube stored on the offset voltage storage capacitor on the operational amplifier input pair tube when the operational amplifier generates the LED drive current, so as to eliminate an influence of the offset voltage of the operational amplifier input pair tube on the LED drive current.
In addition, the constant current control circuit 104 according to the embodiment of the present invention may implement a constant current control method, including: generating a channel setting current by a channel setting current generator according to the reference voltage and the size of the external resistor; converting, by a channel voltage converter, a channel setting current into a plurality of channel voltages for a plurality of LED channels, respectively; the operational amplifier generates LED driving currents for the corresponding one of the plurality of LED channels according to the corresponding one of the plurality of channel voltages, the operational amplifier comprises an operational amplifier input pair tube, an offset voltage storage pair tube and an offset voltage storage capacitor, the offset voltage storage pair tube stores offset voltages of the operational amplifier input pair tube on the offset voltage storage capacitor before the operational amplifier generates the LED driving currents, and the offset voltages of the operational amplifier input pair tube stored on the offset voltage storage capacitor are superposed on the operational amplifier input pair tube when the operational amplifier generates the LED driving currents so as to eliminate influences of the offset voltages of the operational amplifier input pair tube on the LED driving currents.
Other aspects of the constant current control method according to the embodiment of the present invention are the same as or similar to the corresponding aspects of the constant current control circuit described above with reference to fig. 2 to 6, so that a detailed description thereof will be omitted.
The present invention may be embodied in other specific forms without departing from its spirit or essential characteristics. For example, the algorithms described in particular embodiments may be modified without departing from the basic spirit of the invention. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.
Claims (8)
1. A constant current control circuit for a multiple LED backlight system, comprising:
a channel setting current generator operable to generate a plurality of channel setting currents for the plurality of LED channels, respectively, according to the reference voltage and the magnitude of the external resistor;
a plurality of channel voltage generators operable to generate a plurality of channel voltages for the plurality of LED channels, respectively, in accordance with the plurality of channel set currents; and
a plurality of LED channel drivers operable to generate a plurality of LED drive currents for the plurality of LED channels, respectively, from the plurality of channel voltages, wherein
Each of the plurality of LED channel drivers includes an operational amplifier and a driving current generating resistor, the operational amplifier generating an LED driving current for a corresponding one of the plurality of LED channels according to a corresponding one of the plurality of channel voltages and a magnitude of the driving current generating resistor,
the operational amplifier comprises an operational amplifier input pair tube, an offset voltage storage pair tube and an offset voltage storage capacitor, wherein before the operational amplifier generates the LED driving current, the forward input end and the reverse input end of the operational amplifier input pair tube are connected together, the offset voltage storage pair tube stores the offset voltage of the operational amplifier on the offset voltage storage capacitor, when the operational amplifier generates the LED driving current, the forward input end and the reverse input end of the operational amplifier input pair tube are disconnected, the offset voltage storage pair tube stacks the offset voltage of the operational amplifier stored on the offset voltage storage capacitor on the operational amplifier input pair tube so as to eliminate the influence of the offset voltage of the operational amplifier on the LED driving current,
the operational amplifier is a two-stage operational amplifier, wherein the first stage adopts a folded common-source common-gate architecture, and the second stage adopts a PMOS input common-source architecture.
2. The constant current control circuit of claim 1, wherein the channel setting current generator is further operable to:
generating channel set source current according to the reference voltage and the external resistor; and
the channel set source current is mirrored with a plurality of triode current mirrors to produce the plurality of channel set currents.
3. The constant current control circuit of claim 2, wherein each of the plurality of transistor current mirrors comprises an emitter degeneration resistor.
4. A constant current control circuit as claimed in any one of claims 1 to 3, wherein each of the plurality of channel voltage generators includes a channel voltage generation resistor through which a corresponding one of the plurality of channel setting currents generates the corresponding one of the channel voltages.
5. A constant current control circuit for an LED backlight system, comprising:
a channel setting current generator operable to generate a channel setting current according to the reference voltage and the magnitude of the external resistor;
a channel voltage converter operable to convert the channel setting current into a plurality of channel voltages for a plurality of LED channels, respectively; and
a plurality of LED channel drivers operable to generate a plurality of LED drive currents for the plurality of LED channels, respectively, from the plurality of channel voltages, wherein
Each of the plurality of LED channel drivers includes an operational amplifier and a driving current generating resistor, the operational amplifier generating an LED driving current for a corresponding one of the plurality of LED channels according to a corresponding one of the plurality of channel voltages and a magnitude of the driving current generating resistor,
the operational amplifier comprises an operational amplifier input pair tube, an offset voltage storage pair tube and an offset voltage storage capacitor, wherein before the operational amplifier generates the LED driving current, the forward input end and the reverse input end of the operational amplifier input pair tube are connected together, the offset voltage storage pair tube stores the offset voltage of the operational amplifier on the offset voltage storage capacitor, when the operational amplifier generates the LED driving current, the forward input end and the reverse input end of the operational amplifier input pair tube are disconnected, the offset voltage storage pair tube stacks the offset voltage of the operational amplifier stored on the offset voltage storage capacitor on the operational amplifier input pair tube so as to eliminate the influence of the offset voltage of the operational amplifier on the LED driving current,
the operational amplifier is a two-stage operational amplifier, wherein the first stage adopts a folded common-source common-gate architecture, and the second stage adopts a PMOS input common-source architecture.
6. A constant current control method for a multi-channel LED backlight system, comprising:
generating a plurality of channel setting currents for a plurality of LED channels respectively by a channel setting current generator according to the reference voltage and the size of the external resistor;
generating, by a plurality of channel voltage generators, a plurality of channel voltages for the plurality of LED channels, respectively, according to the plurality of channel set currents; and
generating, by a plurality of LED channel drivers, a plurality of LED drive currents for the plurality of LED channels, respectively, from the plurality of channel voltages, wherein
Each of the plurality of LED channel drivers includes an operational amplifier and a driving current generating resistor, the operational amplifier generating an LED driving current for a corresponding one of the plurality of LED channels according to a corresponding one of the plurality of channel voltages and a magnitude of the driving current generating resistor,
the operational amplifier comprises an operational amplifier input pair tube, an offset voltage storage pair tube and an offset voltage storage capacitor, wherein before the operational amplifier generates the LED driving current, the forward input end and the reverse input end of the operational amplifier input pair tube are connected together, the offset voltage storage pair tube stores the offset voltage of the operational amplifier on the offset voltage storage capacitor, when the operational amplifier generates the LED driving current, the forward input end and the reverse input end of the operational amplifier input pair tube are disconnected, the offset voltage storage pair tube stacks the offset voltage of the operational amplifier stored on the offset voltage storage capacitor on the operational amplifier input pair tube so as to eliminate the influence of the offset voltage of the operational amplifier on the LED driving current,
the operational amplifier is a two-stage operational amplifier, wherein the first stage adopts a folded common-source common-gate architecture, and the second stage adopts a PMOS input common-source architecture.
7. A constant current control method for a multi-channel LED backlight system, comprising:
generating a channel setting current by a channel setting current generator according to the reference voltage and the size of the external resistor;
converting, by a channel voltage converter, the channel setting current into a plurality of channel voltages for a plurality of LED channels, respectively;
generating, by a plurality of LED channel drivers, a plurality of LED drive currents for the plurality of LED channels, respectively, from the plurality of channel voltages, wherein
Each of the plurality of LED channel drivers includes an operational amplifier and a driving current generating resistor, the operational amplifier generating an LED driving current for a corresponding one of the plurality of LED channels according to a corresponding one of the plurality of channel voltages and a magnitude of the driving current generating resistor,
the operational amplifier comprises an operational amplifier input pair tube, an offset voltage storage pair tube and an offset voltage storage capacitor, wherein before the operational amplifier generates the LED driving current, the forward input end and the reverse input end of the operational amplifier input pair tube are connected together, the offset voltage storage pair tube stores the offset voltage of the operational amplifier on the offset voltage storage capacitor, when the operational amplifier generates the LED driving current, the forward input end and the reverse input end of the operational amplifier input pair tube are disconnected, the offset voltage storage pair tube stacks the offset voltage of the operational amplifier stored on the offset voltage storage capacitor on the operational amplifier input pair tube so as to eliminate the influence of the offset voltage of the operational amplifier on the LED driving current,
the operational amplifier is a two-stage operational amplifier, wherein the first stage adopts a folded common-source common-gate architecture, and the second stage adopts a PMOS input common-source architecture.
8. A multiple LED backlight system comprising the constant current control circuit of any one of claims 1 to 5.
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| CN202311514697.XA CN117475938A (en) | 2020-11-13 | 2020-11-13 | Multi-channel LED backlight system and constant current control circuit and method thereof |
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| CN202011268020.9A CN112365853A (en) | 2020-11-13 | 2020-11-13 | Multi-path LED backlight system and constant current control circuit and method thereof |
| CN202311514697.XA CN117475938A (en) | 2020-11-13 | 2020-11-13 | Multi-channel LED backlight system and constant current control circuit and method thereof |
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| JP4632655B2 (en) * | 2003-11-07 | 2011-02-16 | 日本電気株式会社 | Luminescent display device |
| JP2009284150A (en) * | 2008-05-21 | 2009-12-03 | Panasonic Corp | Offset canceling circuit and display |
| CN101848575B (en) * | 2009-03-25 | 2012-11-28 | 华映视讯（吴江）有限公司 | Driving circuit for backlight system of light-emitting diode |
| CN102915701B (en) * | 2011-08-04 | 2015-09-16 | 昂宝电子（上海）有限公司 | For the system and method for the currents match of LED channel |
| CN102881251B (en) * | 2012-08-20 | 2015-08-26 | 深圳市易事达电子有限公司 | Current driving circuit |
| CN103441736B (en) * | 2013-08-27 | 2016-02-10 | 西北工业大学 | The preamplifier circuit of CMOS comparator |
| CN104111683B (en) * | 2014-06-27 | 2016-04-20 | 成都嘉纳海威科技有限责任公司 | A kind of reference source with automatically eliminating amplifier imbalance function |
| US10244591B2 (en) * | 2014-11-14 | 2019-03-26 | Texas Instruments Incorporated | Voltage/current regulator supplying controlled current with PVT adjusted headroom |
| CN106208982B (en) * | 2016-07-15 | 2019-01-18 | 天津大学 | A kind of trsanscondutance amplifier imbalance elimination structure based on output electric current storage |
| CN108092628A (en) * | 2017-12-12 | 2018-05-29 | 上海集成电路研发中心有限公司 | A kind of operational amplifier and amplifier circuit that there is imbalance to eliminate structure |
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