CN113851077A - Constant current source driving module of LED display screen and constant current source gain control method - Google Patents
Constant current source driving module of LED display screen and constant current source gain control method Download PDFInfo
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- 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
- G09G3/22—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 using controlled light sources
- G09G3/30—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 using controlled light sources using electroluminescent panels
- G09G3/32—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 using controlled light sources using electroluminescent panels semiconductive, e.g. using light-emitting diodes [LED]
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Abstract
The invention relates to an LED display screen constant current source driving module and a constant current source gain control method, which comprise an REXT loop module, a first voltage clamping module and a second voltage clamping module, wherein the REXT loop module is connected with an external resistor R _ EXT to clamp the voltage of the REXT loop module to a third voltage; the current mirror circuit comprises a first current mirror connected with the REXT loop module and one or more second current mirrors connected with the first current mirror, wherein an input channel of the first current mirror and an output channel of the second current mirror are MOS tube groups formed by connecting a plurality of MOS tubes; and the current mirror is connected with a processor or a register and is used for configuring the access number of the MOS tubes so as to realize the mirror image proportion adjustment of the first current mirror and the second current mirror, and the adjustment of the output current is realized by adjusting the mirror image proportion of the current mirrors, so that the influence of the offset voltage of the operational amplifier on the constant current output precision is reduced. When the current gain is set to be smaller, the | VGS | (the absolute value of VGS) of each MOS tube in the current mirror can be in a reasonable interval, and therefore the precision of constant current output is improved.
Description
Technical Field
The invention relates to a constant current source, in particular to a constant current source driving module of an LED display screen and a constant current source gain control method.
Background
The constant current source is a component widely used in a circuit, is a wide-frequency-spectrum high-precision alternating current stabilized current power supply, and has the advantages of high response speed, high constant current precision, capability of stably working for a long time, suitability for various loads, and the like. The simplest constant current source is a constant current diode. In fact, the application of the constant current diode is relatively few, and besides the constant current characteristic of the constant current diode is not very good, the current specification is relatively small, and the price is relatively high, which is also an important reason. The most common simple constant current source uses two triodes of the same type, the relatively stable be voltage of the triodes is used as a reference, and the current value is I ═ Vbe/R1. The constant current source has the advantages of simplicity, feasibility, free control of the current value, no use of special elements and contribution to reduction of the product cost. The disadvantage is that the be voltage of different types of tubes is not a fixed value, and even the same type has certain individual difference. At the same time, the voltage will fluctuate somewhat at different operating currents. And therefore not suitable for precise constant current requirements. In order to output current accurately, an operational amplifier is usually used as feedback, and a field effect transistor is used to avoid errors caused by be current of a triode. The fet may be replaced by a triode if the current does not need to be particularly accurate.
For example, fig. 1 is a conventional constant current source driving generation circuit, and R _ EXT in the above figure is an external resistor of the driving chip.
Assuming that the gains of all the amplifiers in the figure are infinite, the generation principle of the constant current source is as follows:
1) generating a band gap reference voltage VBG from the Bandgap;
2) the current gain control module amplifies or reduces the VBG according to a certain proportion to generate a reference potential VREF1, namely VREF1 is Igain VBG, the proportion Igain is current gain, and the size of the proportion Igain is controlled by a register;
3) the source terminal potential of NM0 is clamped to VREF1 by amplifier AMP1, so the source-drain current flowing through PM0 is: i0 ═ VREF1/R _ EXT;
4) the PM1 and the PM0 are current mirrors, and the current ratio of the current mirrors (the source-drain current of the PM1 is greater than that of the PM 0) is K, so that the magnitude of the source-drain current of the PM1 is I1 ═ K × VREF1/R _ EXT;
5) when the constant current source channels are started, the amplifiers AMP3 and AMP _ C clamp the drain end potentials of NM1 and NM _ C0 to VREF2 respectively, the potentials of all ports of NM _ C0 of the constant current source output channels are the same as the potentials of all ports of NM1, the output current of the channels is proportional mirror image of the magnitude of NM1 source-drain current, the mirror image proportion is J, and then the output constant current magnitude (absolute value) of the constant current source channels at the moment is IOUT (Igain) J K VBG/R _ EXT.
In a general constant current source driving chip, J × K is a fixed value, VBG is a bandgap reference voltage, and after the resistance value of the external resistor R _ EXT is selected, the proportion Igain can be adjusted by a configuration register, so that the magnitude of the current output by the constant current is adjusted, and the control of the current gain is realized.
According to the current formula of IOUT, the accuracy of VREF1 will directly affect the accuracy of the constant current output. According to the circuit structure, the offset voltage VOS of the operational amplifier AMP1 is directly superposed on the VREF 1. For the same chip, the offset voltage VOS of the operational amplifier AMP1 is a fixed value and does not change with the change of the current gain Igain. Therefore, the smaller the current gain Igain is set, the smaller VREF1 is, the greater the influence of VOS on the constant current output accuracy is, and the worse the accuracy of the constant current output is.
In a typical constant current source driver chip, the current gain Igain is wide in range, and the ratio of the adjustable maximum current to the adjustable minimum current is usually more than 8 times. For the gain control method, the adjustment range of VREF1 is required to be more than 8 times. The maximum voltage of VREF1 is typically not very large due to the limited supply voltage. In order to satisfy the adjustable range of the current gain, the minimum voltage value of VREF1 can only be set to be very small, which is not favorable for improving the constant current output precision.
And when the current gain Igain is small, I0, I1 and IOUT are all reduced proportionally, and the parameters of PM0, PM1, NM1 and NM _ C0 of each channel need to meet the requirement of normal operation at the maximum output current, so when the output current is minimum, PM0, PM1, NM1 and NM _ C0 of each channel have small | VGS | (absolute value of VGS), which deteriorates the two sets of current mirrors mentioned above and also deteriorates the precision of the output constant current source.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provides an LED display screen constant current source driving module and a constant current source gain control method. When the current gain is set to be smaller, the | VGS | (the absolute value of VGS) of each MOS tube in the current mirror can be in a reasonable interval, and therefore the precision of constant current output is improved.
The purpose of the invention is realized by the following technical scheme:
the utility model provides a LED display screen constant current source drive module, includes:
the REXT loop module is connected with the external resistor R _ EXT to clamp the voltage of the external resistor R _ EXT to a third voltage;
the current mirror circuit comprises a first current mirror connected with the REXT loop module and one or more second current mirrors connected with the first current mirror, wherein an input channel of the first current mirror and an output channel of the second current mirror are MOS tube groups formed by connecting a plurality of MOS tubes;
and the processor or the register is connected with the current mirrors and is used for configuring the access number of the MOS tubes so as to realize the mirror proportion adjustment of the first current mirror and the second current mirror.
In the invention, the mirror proportion of the current mirror is configured by using the processor or the register, and the processor or the register can synchronously adjust the sizes of the MOS tubes in the current mirror, so that the | VGS | (the absolute value of VGS) of each MOS tube is in a reasonable interval, thereby improving the precision of constant current output.
For PMOS, operating in saturation, the current formula is as follows:
in the formula, mu, Cox、VTHCan be regarded as a constant, VOSPIs the offset voltage between PM0 and PM 1.
Because of the wide range of IOUT required, the IOUT maximum may be more than 10 times the IOUT minimum, while I0Proportional to IOUT, then I0Also more than 10 times. According to I0Is calculated according to the formula if
Remains unchanged, then VGSMay vary over a wide range. When IOUT is large, VGSIs also larger, VOSPThe proportion occupied in the current formula is small, and the current precision is high at the moment; when IOUT is small, VGSIs also smaller, VOSPThe current formula occupies a larger proportion, and the current precision is obviously reduced at the moment.
In order to satisfy the output range and precision of IOUT, the areas of PM0 and PM1 need to be made large to reduce the offset voltage VOSPAnd further decrease VOSPThe effect on current accuracy.
For NMOS, the current calculation formula is as follows
Similar to PMOS, when IOUT is larger, VGSIs also larger, VOSNThe proportion occupied in the current formula is small, and the current precision is high at the moment; when IOUT is small, VGSIs also smaller, VOSNThe proportion occupied in the current formula is large, and the current precision is reduced.
Further, the second current mirrors are sequentially connected with the output channels of the first current mirrors, or each second current mirror is respectively connected with the output channels of the first current mirrors.
Further, the method also comprises the following steps:
and the voltage control module is connected to the input end of the REXT loop module and is used for adjusting the first voltage to a second voltage and outputting the second voltage to the REXT loop module.
Further, the processor or the register is connected with the voltage control module and is used for configuring the scaling of the voltage control module.
In order to further improve the precision of constant current output, the invention also takes input voltage VREF, namely the first voltage regulation in the scheme as regulation control, thereby reducing the requirement of input voltage, leading the input voltage, namely VREF mentioned in the background technology to be designed to be relatively larger, and reducing the influence of offset voltage of the operational amplifier on the precision of constant current output.
Further, the method also comprises the following steps:
and the voltage output module is connected to the input end of the voltage control module and is used for inputting a first voltage to the voltage control module.
Further, the voltage output module is a band gap voltage source.
The band-gap voltage source has the advantages that the voltage reference irrelevant to temperature can be realized, so that the voltage fluctuation caused by temperature drift is eliminated, and the constant current output precision is further improved.
Further, the method also comprises the following steps:
and the voltage output module is connected to the input end of the REXT loop module and is used for inputting a first voltage to the REXT loop module.
Further, the voltage output module is a band gap voltage source.
Further, the first current mirror and the second current mirror are mirror images formed by a single MOS tube and a MOS tube group.
Further, the MOS tube group is provided with a switching element controlled by the processor or the register, and is used for controlling the access number of the MOS tubes in the first MOS tube group and the second MOS tube group.
Further, when the first current mirror is formed by P-type MOS (metal oxide semiconductor) tubes, and the second current mirror is sequentially connected with the first current mirror, the output channels of the odd-numbered second current mirrors are formed by connecting a plurality of N-type MOS tubes, and the output channels of the even-numbered second current mirrors are formed by connecting a plurality of P-type MOS tubes;
when the second current mirror is respectively connected with the output channel of the first current mirror, the output channel of the second current mirror is formed by connecting a plurality of N-type MOS tubes.
A constant current source gain control method comprising:
step 1): clamping the voltage at one end of the external resistor R _ EXT to a third voltage through a REXT loop module;
step 2): the current end of the REXT loop module is connected with one or more current mirrors in sequence, wherein the input side of the first current mirror is formed by connecting a plurality of MOS tubes in parallel, and the output side is a single MOS tube;
the input side of the second current mirror is composed of a single MOS (metal oxide semiconductor) tube, and the output side of the second current mirror is formed by connecting a plurality of MOS tubes in parallel;
step 3): and the control instruction of a processor or a register is configured to adjust the MOS tube access number of the input side of the first current mirror and the output side of the second current mirror so as to realize the mirror proportion adjustment of the current mirrors.
Further, the method also comprises the following steps:
outputting a first voltage to a REXT loop module by a voltage output module;
or;
the voltage output module outputs a first voltage to the voltage control module, and the voltage control module outputs a second voltage to the REXT loop module;
or;
the second voltage is output directly by the voltage control module to the REXT loop module.
Further, the control instructions through the configuration processor or register are used to adjust the scaling of the voltage control module.
The invention has the beneficial effects that: in the present invention, the current gain control is implemented by adjusting the magnitude of the input voltage (i.e., the first voltage) and adjusting the mirror ratio between the input current and the IOUT. Therefore, the value of the input voltage can be designed to be larger, and the influence of the offset voltage of the operational amplifier on the constant current output precision is reduced. When the current gain is set to be smaller, namely when I0 is smaller, the processor or the register can synchronously adjust the size of the MOS transistors in the current mirror, so that | VGS | (absolute value of VGS) of each MOS transistor is in a reasonable interval, thereby improving the precision of constant current output.
Drawings
FIG. 1 is a schematic block diagram of the prior art;
FIG. 2 is a functional block diagram of the present invention;
FIG. 3 is a schematic diagram of a first MOS transistor bank;
fig. 4 is a schematic diagram of a second MOS transistor bank.
Detailed Description
The technical solution of the present invention is further described in detail with reference to the following specific examples, but the scope of the present invention is not limited to the following.
The invention provides an LED display screen constant current source driving module, which is mainly used for constant current source driving, for example, the constant current source driving applied to an LED display screen or the constant current source driving in other scenes.
A kind of LED display screen constant current source drive module, its minimum composition should include at least:
the REXT loop module is connected with the external resistor R _ EXT to clamp the voltage of the REXT loop module to a third voltage;
the current mirror circuit comprises a first current mirror connected with the REXT loop module and one or more second current mirrors connected with the first current mirror, wherein an input channel of the first current mirror and an output channel of the second current mirror are MOS tube groups formed by connecting a plurality of MOS tubes;
and the processor or the register is connected with the current mirrors and is used for configuring the access number of the MOS tubes so as to realize the mirror proportion adjustment of the first current mirror and the second current mirror.
The REXT loop module is used for clamping the voltage across the external resistor R _ EXT to a voltage that is required by a user or a preset voltage, that is, a third voltage referred to in the present invention, and it should be noted that the third voltage referred to in the present embodiment and the first voltage and the second voltage referred to later are merely distinguished in terms of nomenclature, and do not represent a change in voltage amplitude, and may even be that the third voltage, the first voltage, and the second voltage are identical, that is, the third voltage, the first voltage, and the second voltage are not substantially related in voltage magnitude. Among them, REXT loop module, which is mainly composed of amplifiers, is implemented by using a circuit structure known in the art without being modified by the present invention. For example, in fig. 1, that is, the prior art is configured by using an amplifier AMP1 and an N-type MOS transistor NM0, an input terminal of the amplifier AMP1 is connected to an input voltage, an output terminal thereof is connected to a gate of the N-type MOS transistor NM0, and a source of the N-type MOS transistor NM0 and another input terminal of the amplifier AMP1 are connected to an external resistor R _ EXT. In addition to the implementation shown in fig. 1, the amplifier may be directly formed by an amplifier, that is, the output terminal of the amplifier is directly connected to the external resistor R _ EXT, so that the voltage at one terminal of the external resistor R _ EXT is equal to the output voltage of the amplifier.
Optionally, in the LED display screen constant current source driving module, the second current mirrors are sequentially connected to the first current mirror output channel, or each second current mirror is connected to the first current mirror output channel.
The second current mirror is connected with the first current mirror in sequence, or the second current mirror is respectively connected with the output channel of the first current mirror. For example, as shown in fig. 2, the second current mirror is connected to the first current mirror in sequence, and when a plurality of second current mirrors are present, the second current mirrors are connected in sequence, and finally an output channel is formed. Generally, the number of the second current mirrors is one or two, when two are used, the second current mirrors can be used as common cathode wiring, when one is used, the second current mirrors can be used as common anode wiring, as a special case, the second current mirrors can also be omitted, namely, only the output of the first current mirror is used as common cathode driving, and the scheme has internal consumption of a chip, so that the scheme is not in the discussion range of the scheme.
When the second current mirrors are respectively connected to the output channels of the first current mirror, each second current mirror is used as one output channel, which is equivalent to providing a plurality of output power supplies.
Optionally, in addition to the above, the present solution further includes a voltage control module connected to an input end of the REXT loop module, and configured to adjust the first voltage to a second voltage and output the second voltage to the REXT loop module. In the scheme, a voltage control module is added, namely, the output regulation of the constant current source is divided into two parts, one part is used for regulating the size of the input voltage, and the other part is used for regulating the mirror ratio of the current mirror, so that the value of the input voltage can be designed to be larger, and the influence of the offset voltage of the operational amplifier on the constant current output precision is reduced. When the current gain is set to be smaller, namely the input current is smaller, the processor or the register can synchronously adjust the sizes of the MOS tubes in the current mirror, so that | VGS | (the absolute value of VGS) of the MOS tubes are in a reasonable interval, and the precision of constant current output is improved.
Optionally, in addition to the above, a processor or a register is connected to the voltage control module, and is configured to configure the scaling of the voltage control module, that is, a control instruction of the scaling of the voltage control module is stored in the processor or the register, where the voltage control module is implemented by using an amplifying circuit that is commonly used in the art without making a corresponding design improvement, and all the amplifying circuits known in the art can be used in this scheme.
Optionally, an LED display screen constant current source driving module includes:
the REXT loop module is connected with the external resistor R _ EXT to clamp the voltage of the REXT loop module to a third voltage;
the current mirror circuit comprises a first current mirror connected with the REXT loop module and one or more second current mirrors connected with the first current mirror, wherein an input channel of the first current mirror and an output channel of the second current mirror are MOS tube groups formed by connecting a plurality of MOS tubes;
the processor or the register is connected with the current mirrors and is used for configuring the access number of the MOS tubes so as to realize the mirror proportion adjustment of the first current mirror and the second current mirror;
and the voltage output module is connected to the input end of the voltage control module and used for inputting a first voltage to the voltage control module.
Referring to fig. 2, optionally, an LED display screen constant current source driving module includes:
the REXT loop module is connected with the external resistor R _ EXT to clamp the voltage of the REXT loop module to a third voltage;
the current mirror circuit comprises a first current mirror connected with the REXT loop module and one or more second current mirrors connected with the first current mirror, wherein an input channel of the first current mirror and an output channel of the second current mirror are MOS tube groups formed by connecting a plurality of MOS tubes;
the processor or the register is connected with the current mirrors and is used for configuring the access number of the MOS tubes so as to realize the mirror proportion adjustment of the first current mirror and the second current mirror;
a voltage control module connected to the input end of the REXT loop module for regulating the first voltage to a second voltage and outputting the second voltage to the REXT loop module
And the voltage output module is connected to the input end of the REXT loop module and is used for inputting the first voltage to the REXT loop module. The processor or the register is connected with the voltage control module and is used for configuring the scaling of the voltage control module.
Optionally, in the LED display screen constant current source driving module, the voltage output modules mentioned in this embodiment are all band gap voltage sources, that is, band voltage reference, which is referred to as band for short. The most classical bandgap reference is a temperature independent voltage reference implemented by using the sum of a voltage with positive temperature coefficient and a voltage with negative temperature coefficient, which cancel each other out.
The utility model provides a LED display screen constant current source drive module, includes:
the REXT loop module is connected with the external resistor R _ EXT to clamp the voltage of the REXT loop module to a third voltage;
the current mirror circuit comprises a first current mirror connected with the REXT loop module and one or more second current mirrors connected with the first current mirror, wherein an input channel of the first current mirror and an output channel of the second current mirror are MOS tube groups formed by connecting a plurality of MOS tubes;
the processor or the register is connected with the current mirrors and is used for configuring the access number of the MOS tubes so as to realize the mirror proportion adjustment of the first current mirror and the second current mirror;
and the voltage output module is connected to the input end of the REXT loop module and is used for inputting the first voltage to the REXT loop module.
For example, as shown in fig. 2, there is an example having two current mirrors, and the constant current drive source is mainly used in a common anode connection manner. When only one current mirror is provided, the common cathode connection mode is applicable. Based on the working principle of the current mirrors, the current mirrors are applicable to the connection mode of the common cathode when the number of the current mirrors is odd, and are applicable to the connection mode of the common anode when the number of the current mirrors is even. Therefore, in practical application, the number of current mirrors is designed to be three groups at most.
A constant current source driving module of an LED display screen is characterized in that a first current mirror and a second current mirror form mirror image output by a single MOS tube and an MOS tube group. The connection comprises series connection or parallel connection, based on the common knowledge, the mirror ratio of the current mirror is adjusted by the width-length ratio of the MOS tube, and the width of the MOS tube group is adjustable but the length of the MOS tube group is not adjustable by controlling the access number of the MOS tubes in the MOS tube group in a parallel connection mode, so that the mirror ratio of the current mirror is adjusted finally. The principle is the same when the serial connection mode is adopted, and the difference is that the length of the MOS tube group is adjustable and the width is not adjustable.
Furthermore, the MOS tube group is provided with a switch element controlled by the processor or the register and used for controlling the access quantity of the MOS tubes in the first MOS tube group and the second MOS tube group.
More specifically, the first current mirror is composed of P-type MOS transistors, when the second current mirror is sequentially connected to the first current mirror, the output channels of the odd-numbered second current mirrors are formed by connecting a plurality of N-type MOS transistors, and the output channels of the even-numbered second current mirrors are formed by connecting a plurality of P-type MOS transistors; when the second current mirror is respectively connected with the output channel of the first current mirror, the output channel of the second current mirror is formed by connecting a plurality of N-type MOS tubes.
Referring to fig. 3 and 4, the circuit is an example circuit (parallel connection mode) of a first MOS transistor group and a second MOS transistor group, which are different only in the type of MOS transistor used, wherein the first MOS transistor group is formed by connecting P-type MOS transistors, the second MOS transistor group is formed by connecting NP-type MOS transistors, and the two groups are completely identical in circuit implementation.
The embodiment also provides a constant current source gain control method, which is operated for the LED display screen constant current source driving module, and includes the steps of:
step 1): clamping the voltage at one end of the external resistor R _ EXT to a third voltage through a REXT loop module;
step 2): the current end of the REXT loop module is connected with one or more current mirrors in sequence, wherein the input side of the first current mirror is formed by connecting a plurality of MOS tubes in parallel, and the output side is a single MOS tube;
the input side of the second current mirror is composed of a single MOS (metal oxide semiconductor) tube, and the output side of the second current mirror is formed by connecting a plurality of MOS tubes in parallel;
step 3): and the control instruction of a processor or a register is configured to adjust the MOS tube access number of the input side of the first current mirror and the output side of the second current mirror so as to realize the mirror proportion adjustment of the current mirrors.
Further, if the constant current source driving module further includes a voltage output module or a voltage control module, the controlling step further includes:
outputting a first voltage to a REXT loop module by a voltage output module;
or;
the voltage output module outputs a first voltage to the voltage control module, and the voltage control module outputs a second voltage to the REXT loop module;
or;
the second voltage is output directly by the voltage control module to the REXT loop module.
Further, the control instructions through the configuration processor or register are used to adjust the scaling of the voltage control module.
A complete example is shown in figure 2:
1) generating a band gap reference voltage VBG (first voltage) from a band gap (voltage output block);
2) the voltage control module amplifies or reduces VBG according to a ratio Igainv to generate a reference potential VREF (i.e., a second voltage), wherein VREF is Igainv VBG, the size of the ratio Igainv is controlled by a register S1[ P:1], and the ratio of the maximum value to the minimum value of Igainv is Gv Igainv (max)/Igainv (min);
3) REXT loop module connects off-chip resistor R _ EXT (i.e., external resistor R _ EXT), PM0, and the voltage at one end of off-chip resistor R _ EXT is clamped to VREF (i.e., a third voltage, which is substantially the same as the second voltage in this example) by an operational amplifier, I0 is the current flowing through off-chip resistor R _ EXT and PM0, and the current calculation formula is: i0 ═ VREF/R _ EXT ═ Igainv ═ VBG/R _ EXT;
the PM1 and the PM0 form a current mirror, and mirror the current I0 flowing through the R _ EXT resistor to generate a current I1, which is output to the NM 1. The size of PM1 is adjustable and is controlled by an M-bit control signal SP [ M:1 ]. The mirror ratio of I0 to I1 is K. The formula for current I1 is: i1 ═ K × I0;
NM1 and NM _ C0 form a current mirror, which mirrors current I1 to generate the output current IOUT of the channel. NM _ C0 is adjustable in size and is controlled by N-bit control signal SN [ N:1 ]. The mirror ratio of I1 to IOUT is J. The current IOUT is calculated as: IOUT J I1J K I0J K Igainv VBG/R _ EXT;
4) the adjustment of the aspect ratio of PM0, NM-C0 may be controlled by configuring registers S2[ Q:1 ]. As the aspect ratios of PM0 and NM _ C0 are adjusted, the mirror ratio J, K changes. There are L values of J x K, JK [ L:1], where [ L:1] represents from 1 to L. I.e. the desired value of J x K can be selected by means of the configuration register S2Q: 1.
Design JK [1]]＝JK[2]*Gv＝JK[3]*(Gv)2＝…＝JK[L]*(Gv)L-1According to the calculation formula of Gv, JK [ X ] can be obtained when X is more than or equal to 1 and less than or equal to L]*Igainv(min)＝JK[X+1]*Igain(max)；
As known from the calculation formula of IOUT, after R _ EXT is selected, the magnitude of the output current can be adjusted through configuration registers S1[ P:1] and S2[ Q:1], the adjustment range of IOUT is divided into L sections, and the adjustment range of each section is respectively: JK [ X ]. Igainv (max) VBG/R _ EXT-JK [ X ]. Igainv (min) VBG/R _ EXT. From the above, the current regulation lower limit value of the X-th segment is equal to the current regulation upper limit value of the X + 1-th segment, and then the L regulation ranges can be seamlessly connected, so as to realize the current gain control from JK [1] igainv (max) VBG/R _ EXT to JK [ L ] igainv (min) VBG/R _ EXT.
The above example refers to the case where there are two current mirrors, the mirror proportions of the two current mirrors are K and J, respectively, the control principle for the plurality of current mirrors is similar to that described above, and details are not repeated in this embodiment.
The foregoing is illustrative of the preferred embodiments of this invention, and it is to be understood that the invention is not limited to the precise form disclosed herein and that various other combinations, modifications, and environments may be resorted to, falling within the scope of the concept as disclosed herein, either as described above or as apparent to those skilled in the relevant art. And that modifications and variations may be effected by those skilled in the art without departing from the spirit and scope of the invention as defined by the appended claims.
Claims (14)
1. The utility model provides a LED display screen constant current source drive module which characterized in that includes:
the REXT loop module is connected with the external resistor R _ EXT to clamp the voltage of the external resistor R _ EXT to a third voltage;
the current mirror circuit comprises a first current mirror connected with the REXT loop module and one or more second current mirrors connected with the first current mirror, wherein an input channel of the first current mirror and an output channel of the second current mirror are MOS tube groups formed by connecting a plurality of MOS tubes;
and the MOS tube access quantity is configured according to the output current value so as to realize the mirror image proportion adjustment of the first current mirror and the second current mirror.
2. The LED display screen constant current source driving module according to claim 1, wherein the second current mirrors are sequentially connected to the first current mirror output channels, or each second current mirror is respectively connected to the first current mirror output channels.
3. The LED display screen constant current source driving module according to claim 2, further comprising:
and the voltage control module is connected to the input end of the REXT loop module and is used for adjusting the first voltage to a second voltage and outputting the second voltage to the REXT loop module.
4. The LED display screen constant current source driving module according to claim 3, wherein the processor or the register is connected to the voltage control module for configuring the scaling of the voltage control module.
5. The LED display screen constant current source driving module according to claim 3 or 4, further comprising:
and the voltage output module is connected to the input end of the voltage control module and is used for inputting a first voltage to the voltage control module.
6. The LED display screen constant current source driving module according to claim 5, wherein the voltage output module is a bandgap voltage source.
7. The LED display screen constant current source driving module according to claim 1, further comprising:
and the voltage output module is connected to the input end of the REXT loop module and is used for inputting a first voltage to the REXT loop module.
8. The LED display screen constant current source driving module according to claim 7, wherein the voltage output module is a bandgap voltage source.
9. The LED display screen constant current source driving module according to any one of claims 1-8, wherein the first current mirror and the second current mirror are mirror-image outputs formed by a single MOS transistor and a MOS transistor group.
10. The LED display screen constant current source driving module as claimed in claim 9, wherein the MOS tube set is provided with a switch element controlled by the processor or the register, for controlling the number of connected MOS tubes in the first MOS tube set and the second MOS tube set.
11. The LED display screen constant current source driving module according to claim 10, wherein the first current mirror is formed by P-type MOS transistors, and when the second current mirror is connected to the first current mirror in sequence, the output channels of the odd-numbered second current mirrors are formed by connecting a plurality of N-type MOS transistors, and the output channels of the even-numbered second current mirrors are formed by connecting a plurality of P-type MOS transistors;
when the second current mirror is respectively connected with the output channel of the first current mirror, the output channel of the second current mirror is formed by connecting a plurality of N-type MOS tubes.
12. A constant current source gain control method, comprising:
step 1): clamping the voltage at one end of the external resistor R _ EXT to a third voltage through a REXT loop module;
step 2): the current end of the REXT loop module is connected with one or more current mirrors in sequence, wherein the input side of the first current mirror is formed by connecting a plurality of MOS tubes in parallel, and the output side is a single MOS tube;
the input side of the second current mirror is composed of a single MOS (metal oxide semiconductor) tube, and the output side of the second current mirror is formed by connecting a plurality of MOS tubes in parallel;
step 3): and the control instruction of a processor or a register is configured to adjust the MOS tube access number of the input side of the first current mirror and the output side of the second current mirror so as to realize the mirror proportion adjustment of the current mirrors.
13. The constant current source gain control method of claim 12, further comprising:
outputting a first voltage to a REXT loop module by a voltage output module;
or;
the voltage output module outputs a first voltage to the voltage control module, and the voltage control module outputs a second voltage to the REXT loop module;
or;
the second voltage is output directly by the voltage control module to the REXT loop module.
14. The method of claim 13, wherein the control instruction of the configuration processor or the register is used to adjust the scaling of the voltage control module.
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| CN202110121322.1A Active CN113851078B (en) | 2020-09-03 | 2021-01-28 | LED display screen constant current source segmentation module and control method |
| CN202110121309.6A Pending CN113851077A (en) | 2020-09-03 | 2021-01-28 | Constant current source driving module of LED display screen and constant current source gain control method |
| CN202110119194.7A Pending CN113851075A (en) | 2020-09-03 | 2021-01-28 | A LED display constant current source drive module and its control method |
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| CN113851078B (en) | 2023-07-11 |
| CN113851078A (en) | 2021-12-28 |
| CN113851076A (en) | 2021-12-28 |
| CN113851075A (en) | 2021-12-28 |
| CN214752879U (en) | 2021-11-16 |
| CN113851076B (en) | 2025-05-30 |
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