Constant current source segment detection module and control method for an LED display driver chip

Abstract

The present invention relates to a constant current source segment selection detection module and a control method for an LED display driving chip, including a MOS transistor forming an R_EXT current mirror with the first current mirror input channel of the constant current source driving chip, and a current detection module connected to the R_EXT current mirror; wherein, the input channel of the first current mirror is composed of a MOS transistor component with an adjustable width-to-length ratio, and is used to connect the input current I0 and the off-chip resistor R_EXT; the R_EXT current mirror is used to generate an image current Icmp[x] of the input current I0; the current detection module compares the image current Icmp[x] with the reference current [IRB, IRT], and when Icmp[x] is not within the range of the reference current [IRB, IRT], adjusts the image ratio A[X] of the R_EXT current mirror until IRB < Icmp[x] < IRT; wherein, IRB is the lower limit value of the reference current, and IRT is the upper limit value of the reference current. The present invention is used to detect the internal current of the driving chip and control it within a certain range. When it is set to be relatively small, the chip power consumption can be reduced.

Description

Technical Field

[0001] The present invention relates to the field of constant current source control, and particularly to a constant current source segment selection detection module and a control method for an LED display driving chip. Background Art

[0002] Refer to Figure 1 As shown, it is a constant current source driving generation circuit in a commonly used common anode LED display constant current source driving chip. R_EXT in the above figure is an external resistor of the driving chip.

[0003] Suppose Figure 1 the gains of all amplifiers in are infinite, and the generation principle of the constant current source is as follows:

[0004] Generate the required reference potential VREF1 from Bandgap;

[0005] The source terminal potential of NM0 is clamped to VREF1 by amplifier AMP1, so the source-drain current magnitude flowing through PM0 is: I0 = VREF1 / R_EXT;

[0006] PM1 and PM0 are current mirrors. Suppose the current ratio of the current mirror (the source-drain current of PM1 to the source-drain current of PM0) is K. Then the source-drain current magnitude of PM1 is I1 = K * VREF1 / R_EXT;

[0007] When the constant current source channel is turned on, amplifiers AMP3 and AMP_C clamp the drain terminal potentials of NM1 and NM_C0 to VREF2 respectively. The potentials of all ports of NM_C0 in the constant current source output channel are the same as those of all ports of NM1. The output current magnitude of the channel is a proportional mirror image of the source-drain current magnitude of NM1. Suppose the mirror ratio is J. Then the output constant current magnitude (absolute value) of the constant current source channel at this time is IOUT = J * K * VREF / R_EXT.

[0008] In a general constant current source driving chip, J * K is a fixed value. Therefore, the output constant current magnitude of the constant current source channel is usually determined by the resistance magnitude of the external resistor R_EXT.

[0009] The output constant current range of the constant current channels of general constant current source driver chips is relatively wide (for the vast majority of chips on the market, the maximum output value is more than 10 times the minimum output value). At this time, the current change is adjusted through R_EXT. Then, the change amounts of I0, I1, and IOUT above are all more than 10 times. The parameters of PM0, PM1, NM1, and NM_C0 of each channel need to meet the requirement of normal operation under the maximum output current. When the output current is the smallest, the |VGS| (the absolute value of VGS) of PM0, PM1, NM1, and NM_C0 of each channel will be very small, which will make the above-mentioned two groups of current mirrors worse, and the accuracy of the output constant current source will also become worse.

[0010] In order to meet the output constant current range and accuracy of the constant current chip, the constant current driver chip usually performs segmented processing on the output current range:

[0011] To meet the accuracy of the minimum output current, it is necessary to increase the W*L of PM0, PM1, NM1, and NM_C0, that is, increase the area of the above 4 devices. The most effective method is to increase L;

[0012] Due to the limitation of the power supply voltage VDD, |VGS| of PM0, PM1, NM1, and NM_C0 < VDD. If the W / L of PM0, PM1, NM1, and NM_C0 remains unchanged, the output constant current range is small. To increase the output constant current range, while ensuring that all |VGS| are within a reasonable range, it is necessary to gradually increase the W / L (width-to-length ratio) of PM0, PM1, NM1, and NM_C0, that is, perform segmented processing on the output current range.

[0013] The current I1 flowing through NM1 is inversely proportional to the size of R_EXT. The drain voltage of NM1 is a fixed potential VREF2, then the gate voltage VG of NM1 increases as R_EXT decreases. Therefore, by detecting the gate voltage VG of NM1, it can be determined whether the chip is operating in the correct current segment. The voltage detection module compares the VG voltage with the designed reference voltages VRB and VRT respectively, and the comparison results are output to the segment selection control module. The segment selection control module generates corresponding control signals according to the comparison results to control the adjustment of the width-to-length ratio of PM0, PM1, NM1, and NM_C0. When it is detected that VRB < VG < VRT, the width-to-length ratio of each MOS transistor remains unchanged; when it is detected that VG < VRB or VG > VRT, the width-to-length ratio of each MOS transistor is adjusted accordingly.

[0014] There are two common methods for adjusting the width-to-length ratio:

[0015] Keep the aspect ratios of PM0 and PM1 unchanged, that is, keep the mirror ratio K of I1 to I0 unchanged. To keep J*K unchanged, the mirror ratio J of IOUT to I1 remains unchanged. As the output current increases, gradually increase the W / L of NM1 and NM_C0, and the increasing ratios of the two are the same.

[0016] Keep the aspect ratios of PM0 and NM1 unchanged. As the output current increases, gradually increase the W / L of NM_C0, then the mirror ratio J of IOUT to I1 gradually increases. To keep J*K unchanged, the mirror ratio K of I1 to I0 needs to be gradually decreased, that is, the W / L of PM1 needs to be gradually decreased.

[0017] In order to meet the range and accuracy of the output constant current, the design values of I1 in the above two schemes are both relatively large.

[0018] For Method 1, as the required IOUT current increases, I1 increases in the same proportion, so the power consumption of the chip increases.

[0019] For Method 2, the mirror ratio K is gradually decreased. Compared with Method 1, the power consumption will be slightly reduced. However, since the W / L of PM1 is gradually decreased, the area of PM1 is gradually decreased, and the accuracy of PM1 and PM0 will be gradually reduced. Moreover, the mirror ratios J and K need to change simultaneously and J*K remains unchanged, which is not convenient for the design of the aspect ratios of MOS transistors in each current segment.

[0020] For the above two methods, since the aspect ratio of PM0 remains unchanged, as mentioned before, the aspect ratio of PM0 needs to meet the requirement of normal operation at the maximum output current. Then, when the output current is the smallest, the |VGS| (absolute value of VGS) of PM0 and PM1 will be very small, the accuracy of this current mirror becomes poor, and the accuracy of the output constant current source also becomes poor. Summary of the Invention

[0021] The purpose of the present invention is to overcome the deficiencies of the prior art and provide a constant current source selection and detection module and control method for an LED display driving chip, which is used to detect the internal current of the driving chip, control it within a certain range, and can reduce the chip power consumption when it is set to be relatively small.

[0022] The purpose of the present invention is achieved by the following technical solutions:

[0023] A constant current source selection and detection module for an LED display driving chip includes:

[0024] MOS transistors forming an R_EXT current mirror with the first current mirror input channel of the constant current source driving chip, and a current detection module connected to the R_EXT current mirror;

[0025] Among them, the input channel of the first current mirror is composed of a MOS transistor component with an adjustable width-to-length ratio, and is used to connect the input current I0 and the off-chip resistor R_EXT;

[0026] The R_EXT current mirror is used to generate the mirror current Icmp[x] of the input current I0;

[0027] The current detection module compares the mirror current Icmp[x] with the reference currents [IRB, IRT]. When Icmp[x] is not within the range of the reference currents [IRB, IRT], the mirror ratio A[X] of the R_EXT current mirror is adjusted until IRB < Icmp[x] < IRT;

[0028] Among them, IRB is the lower limit value of the reference current, and IRT is the upper limit value of the reference current.

[0029] In the present invention, the principle of the current mirror is utilized to construct the mirror current of the input current of the driving chip, that is, the mirror current of the external resistor R_EXT. This current is used as the detection result to be compared with the reference current. In this solution, in order to reduce the internal power consumption of the chip, that is, to avoid the excessive internal current of the chip (i.e., the output current I1 of the first current mirror), the mirror ratio of the first current mirror is adjusted according to the amplitude of the input current I0, so that the output current of the first current mirror always remains unchanged or remains within a small fluctuation range. When I1 is designed to be small enough, the internal power consumption of the chip can be reduced, and at the same time, it can also ensure that the |VGS| (the absolute value of VGS) of each MOS transistor in the current mirror is at a relatively large value, and the accuracy of the current mirror will not change significantly with the change of the magnitude of the output constant current, which is beneficial to improving the accuracy of the constant current output.

[0030] Further, the current detection module is composed of two comparators and a logic circuit;

[0031] The two comparators are respectively connected to the logic circuit. The reference terminals of the two comparators respectively input the reference current IRB and the reference current IRT, and their comparison terminals are respectively connected to the mirror current Icmp[x];

[0032] The logic circuit outputs a control instruction according to the comparison result to adjust the mirror ratio A[X] of the R_EXT current mirror until IRB < Icmp[x] < IRT;

[0033] Further, the R_EXT current mirror is one or two, and respectively outputs the mirror current Icmp[x], where x is the number corresponding to the R_EXT current mirror.

[0034] Further, when there are two R_EXT current mirrors, Icmp[1] = Icmp[2], or Icmp[1] = kIcmp[2], where k is a coefficient.

[0035] Further, the control strategy of the logic circuit is as follows:

[0036] When it is detected that IRB < Icmp[x] < IRT, the chip operates in current segment X, and the mirror ratio of the R_EXT current mirror is A[X];

[0037] When it is detected that Icmp[x] < IRB, the current segment in which the chip operates changes from the Xth segment to the (X - 1)th segment, the mirror ratio of the R_EXT current mirror changes from A[X] to A[X - 1], the mirror current Icmp[x] increases, and the next round of detection is carried out until it is detected that IRB < Icmp[x] < IRT;

[0038] When it is detected that Icmp[x] > IRT, the current segment in which the chip operates changes from the Xth segment to the (X + 1)th segment, the mirror ratio of the R_EXT current mirror changes from A[X] to A[X + 1], the mirror current Icmp[x] decreases, and the next round of detection is carried out until it is detected that IRB < Icmp < IRT;

[0039] Among them, A[1] to A[X] gradually decrease, and the value of X is the number of current segments of the constant - current source driving chip.

[0040] Further, the MOS transistor assembly is formed by connecting multiple MOS transistors, and a switching element is arranged in its connection circuit.

[0041] Further, the logic circuit is connected to a processor or a register, and the processor or the register is connected to the switching element to control the number of MOS transistors accessed in the MOS transistor assembly;

[0042] Or,

[0043] The logic circuit is directly connected to the switching element to control the number of MOS transistors accessed in the MOS transistor assembly.

[0044] Further, the connection method of each MOS transistor in the MOS transistor assembly is series or parallel.

[0045] Further, the switching element is a diode or a relay switch.

[0046] Further, the first current mirror is connected to one or more second current mirrors, and its connection methods include:

[0047] The first current mirror is connected to one or more second current mirrors in sequence, and the current mirror connected at the end serves as the constant - current output channel;

[0048] Or;

[0049] The first current mirror is respectively connected to one or more second current mirrors, and each second current mirror serves as a constant current output channel respectively.

[0050] A method for detecting and controlling the selection of constant current sources in an LED display driving chip, which is used to implement selection detection control in the constant current source selection detection module of the driving chip, including:

[0051] 1) Obtain the mirror current Icmp[x] of the input current I0;

[0052] 2) Compare the mirror current Icmp[x] with the reference current [IRB, IRT]. When Icmp[x] is not within the range of the reference current [IRB, IRT], adjust the mirror ratio A[X] of the R_EXT current mirror of the driving chip;

[0053] 3) Repeat step 2) until IRB < Icmp[x] < IRT.

[0054] Finally, it also includes the control and adjustment of the output current, that is, adjusting the mirror ratio J[X] of the second current mirror of the driving chip, so that the output current IOUT = I1 * J[X], where I1 is the output current of the first current mirror, that is, the input current of the second current mirror.

[0055] Further, the specific steps of step 2) include:

[0056] When it is detected that IRB < Icmp[x] < IRT, the chip operates in current segment X, and the mirror ratio of the R_EXT current mirror is A[X];

[0057] When it is detected that Icmp[x] < IRB, the current segment in which the chip operates changes from the Xth segment to the (X - 1)th segment, the mirror ratio of the R_EXT current mirror changes from A[X] to A[X - 1], the mirror current Icmp[x] increases, and the next round of detection is performed until it is detected that IRB < Icmp[x] < IRT;

[0058] When it is detected that Icmp[x] > IRT, the current segment in which the chip operates changes from the Xth segment to the (X + 1)th segment, the mirror ratio of the R_EXT current mirror changes from A[X] to A[X + 1], the mirror current Icmp[x] decreases, and the next round of detection is performed until it is detected that IRB < Icmp < IRT.

[0059] The beneficial effects of the present invention are as follows: By detecting Icmp[x], it can directly ensure that the current magnitude of a single MOS transistor in the current mirror of the driving chip is within a reasonable operating range, enabling the |VGS| (absolute value of VGS) of each MOS transistor to be at a relatively large value. The accuracy of the current mirror will not vary significantly with the magnitude of the output constant current, which is conducive to improving the accuracy of the constant current output. When the accuracy of the constant current output is satisfied, the value of current I1 can be designed to be small enough, which is beneficial to reducing the power consumption of the chip. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] Figure 1 is the schematic diagram of the output current selection segment detection of the prior art;

[0061] Figure 2 is the schematic diagram of the present invention;

[0062] Figure 3 is the schematic diagram of the current detection module;

[0063] Figure 4 is the connection schematic diagram of the P-type MOS transistor;

[0064] Figure 5 is the connection schematic diagram of the N-type MOS transistor;

[0065] Figure 6 is the example circuit of the present invention applied to the common-anode constant current driving chip;

[0066] Figure 7 is the example circuit of the present invention applied to the common-cathode constant current driving chip. DETAILED DESCRIPTION OF THE INVENTION

[0067] The technical solutions of the present invention will be further described in detail below in conjunction with specific embodiments, but the protection scope of the present invention is not limited to the following.

[0068] Refer to Figure 2 As shown, a constant current source selection segment detection module of an LED display driving chip is applicable to a constant current source driving chip to achieve the constant current output control of the constant current source driving chip. To achieve the technical effects of the present invention, the constant current source driving chip in this solution refers to a constant current output channel composed of a first current mirror and a second current mirror with adjustable mirror ratios. The purpose of the present invention is to adjust the current I1 between the first current mirror and the second current mirror to be within a preset range value, so that its fluctuation range is small, or remains unchanged. When I1 is designed to be small enough, it can reduce the power consumption of the chip, and at the same time ensure that the |VGS| (absolute value of VGS) of each MOS transistor in the current mirror is at a relatively large value. The accuracy of the current mirror will not vary significantly with the magnitude of the output constant current, which is conducive to improving the accuracy of the constant current output.

[0069] The present invention aims to provide a detection scheme for output current control. A constant current source selection and detection module of an LED display driving chip includes:

[0070] A MOS transistor that forms an R_EXT current mirror with the first current mirror input channel of the constant current source driving chip, and a current detection module connected to the R_EXT current mirror;

[0071] Among them, the input channel of the first current mirror is composed of a MOS transistor component with adjustable width-to-length ratio, and is used to connect the input current I0 and the external resistor R_EXT;

[0072] The R_EXT current mirror is used to generate an image current Icmp[x] of the input current I0;

[0073] The current detection module compares the image current Icmp[x] with the reference current [IRB, IRT]. When Icmp[x] is not within the range of the reference current [IRB, IRT], the image ratio A[X] of the R_EXT current mirror is adjusted until IRB < Icmp[x] < IRT. Among them, IRB is the lower limit value of the reference current, and IRT is the upper limit value of the reference current.

[0074] In the present invention, using the current mirror principle, an image current of the input current of the driving chip is constructed, that is, an image current of the external resistor R_EXT. This current is used as the detection result to be compared with the reference current. In this solution, in order to reduce the internal power consumption of the chip, that is, to avoid excessive internal current of the chip (i.e., the output current I1 of the first current mirror), the image ratio of the first current mirror is adjusted according to the amplitude of the input current I0, so that the output current of the first current mirror always remains unchanged or within a small fluctuation range. When I1 is designed small enough, the internal power consumption of the chip can be reduced, and at the same time, it can also ensure that the |VGS| (the absolute value of VGS) of each MOS transistor in the current mirror is at a relatively large value, and the accuracy of the current mirror will not change greatly with the change of the output constant current, which is beneficial to improving the accuracy of the constant current output.

[0075] For PMOS, working in the saturation region, the current formula is as follows:

[0076]

[0077] In the formula, μ, C ox , V TH can be regarded as constants, and V OSP is the offset voltage between PM0 and PM1.

[0078] Since the required range of IOUT changes greatly, the maximum value of IOUT may be more than 10 times the minimum value of IOUT, and I 0 is proportional to IOUT, then I0 The variation range is also more than 10 times. According to I 0 's calculation formula, if remains unchanged, then V GS will vary within a large range. When IOUT is large, V GS is also large, and V OSP accounts for a smaller proportion in the current formula, and the current accuracy is higher at this time; when IOUT is small, V GS is also small, and V OSP accounts for a larger proportion in the current formula, and the current accuracy is significantly reduced at this time.

[0079] To meet the output range and accuracy of IOUT, the areas of PM0 and PM1 need to be made very large to reduce the offset voltage V OSP , and further reduce the influence of V OSP on the current accuracy.

[0080] For NMOS, working in the linear region, the current calculation formula is as follows

[0081]

[0082] Similar to PMOS, when IOUT is large, V GS is also large, and V OSN accounts for a smaller proportion in the current formula, and the current accuracy is higher at this time; when IOUT is small, V GS is also small, and V OSN accounts for a larger proportion in the current formula, and the current accuracy decreases.

[0083] Optionally, in a constant current source selection and detection module of an LED display driving chip, in this solution, the R EXT current mirror can be one or two to respectively perform comparison detection corresponding to IRB and IRT. Refer to Figure 4 shown, in this embodiment, the first current mirror is composed of a P-type MOS transistor component PM0 and a MOS transistor MP1. Among them, PM0 is the equivalent circuit of the MOS transistor component, and its actual circuit is as Figure 4 shown and is composed of multiple P-type MOS transistors connected in parallel. By controlling the number of MOS transistors connected in PM0, the mirror ratio K of the first current mirror can be adjusted. Among them, the output current of the first current mirror is I1, and this current I1 is also the input current of the second current mirror. It can be seen from Figure 4 that the essence of the second current mirror is composed of an N-type MOS transistor NM1 and NM_C0. NM1 is connected to MP1 as the input end of the second current mirror, and NM_C0 is used as a constant current output channel. Among them, NM_C0 is composed of multiple N-type MOS transistors connected in parallel, and its principle refers to Figure 5 to make the mirror ratio J of the second current mirror adjustable.

[0084] Optionally, in addition to the above parallel connection method, MP1 and NM_C0 can also be connected in series. The difference is that in the parallel connection method, the widths of MP1 and NM_C0 are adjusted by changing the number of MOS transistors connected, while in the series connection method, the lengths of MP1 and NM_C0 are adjusted. The ultimate goal is to achieve the adjustment of the mirror ratio of the first current mirror and the second current mirror.

[0085] Optionally, in a constant current source segment detection module of an LED display driving chip, the mirror current Icmp[x] is implemented by MOS transistors PM3 and PM4. Among them, PM3 and PM4 respectively form an R_EXT current mirror with PM0 to output Icmp[x], that is, Icmp[1] and Icmp[2]. That is, the detection of I1 is achieved by collecting Icmp[1] and Icmp[2]. In this embodiment, it can be designed that Icmp[1] = Icmp[2] = Icmp. In actual applications, it can also be designed differently. For example, it can be designed that Icmp[1] = k * Icmp[2]. When comparing, the reference current can be amplified or reduced by the same multiple. For the sake of simpler calculation, this embodiment adopts the form of Icmp[1] = Icmp[2] = Icmp, and Icmp = A[X] * I0, where A[X] is the mirror ratio of the R_EXT current mirror. Among them, I1 = K[X] * I0, that is, I1 = (K[X] / A[X]) * Icmp. That is to say, the magnitude of I1 can be reflected by detecting the values of Icmp[1] and Icmp[2]. In other words, by controlling the output of Icmp, the output control of I1 is achieved. Because the values of K[X] and A[X] are both adjusted and implemented by the MOS transistor components of the first current mirror, that is, K[X] and A[X] change synchronously. By adjusting Icmp, the technical purpose of adjusting I1 is achieved.

[0086] Optionally, in a constant current source segment detection module of an LED display driving chip, refer to Figure 3 As shown, the current detection module consists of two comparators and a logic circuit; the two comparators are respectively connected to the logic circuit. The reference terminals of the two comparators respectively input the reference current IRB and the reference current IRT, and their comparison terminals are respectively connected to the mirror current Icmp[x]; the logic circuit outputs a control instruction according to the comparison result to adjust the mirror ratio A[X] of the R_EXT current mirror until IRB < Icmp[x] < IRT. The logic circuit is connected to a processor or a register, and the processor or the register is connected to a switching element to control the number of MOS transistors connected in the MOS transistor component; or, the logic circuit is directly connected to the switching element to control the number of MOS transistors connected in the MOS transistor component.

[0087] In the constant current source segment selection detection module of an LED display driving chip provided by the present invention, the function of the current detection module is mainly to sample and compare the mirror current Icmp[x]. That is to say, any comparison circuit known in the art can be used in this solution, and the design concept of the present invention is not limited to the current detection module disclosed in this embodiment.

[0088] Optionally, in a constant current source segment selection detection module of an LED display driving chip, the current detection module may be composed of a sampling circuit and a processor. The collected mirror current Icmp[x] is sent into a processor, and the thresholds of the preset reference currents [IRB, IRT] are set in the processor. The output of the control instruction is completed through the internal logic processing of the processor. In this solution, only one R_EXT current mirror is required, that is, the sampled current Icmp is directly sent into the processor to complete the comparison.

[0089] Optionally, in a constant current source segment selection detection module of an LED display driving chip, the current detection module may be composed of a sampling circuit and an FPGA module. The FPGA module designs the logic processing principle through programming to output control instructions. In this solution, only one R_EXT current mirror is required, that is, the sampled current Icmp is directly sent into the processor to complete the comparison.

[0090] Optionally, in a constant current source segment selection detection module of an LED display driving chip, the control strategy of the logic circuit or the processor or the FPGA module is as follows:

[0091] When it is detected that IRB < Icmp[x] < IRT, the chip operates in current segment X, and the mirror ratio of the R_EXT current mirror is A[X];

[0092] When it is detected that Icmp[x] < IRB, the current segment in which the chip operates changes from the Xth segment to the (X - 1)th segment, the mirror ratio of the R_EXT current mirror changes from A[X] to A[X - 1], and the mirror current Icmp[x] increases for the next round of detection until it is detected that IRB < Icmp[x] < IRT;

[0093] When it is detected that Icmp[x] > IRT, the current segment in which the chip operates changes from the Xth segment to the (X + 1)th segment, the mirror ratio of the R_EXT current mirror changes from A[X] to A[X + 1], and the mirror current Icmp[x] decreases for the next round of detection until it is detected that IRB < Icmp < IRT;

[0094] Among them, A[1] to A[X] gradually decrease, and the value of X is the number of current segments of the constant current source driving chip.

[0095] Optionally, the MOS transistor components in the first current mirror and the second current mirror are formed by connecting multiple MOS transistors, and switching elements are provided in the connection circuit. The control instructions mentioned above essentially control these switching elements to achieve the number of MOS transistors connected in the MOS transistor component.

[0096] Optionally, in a constant current source segment selection detection module of an LED display driving chip, the switching element is a diode or a relay switch. That is to say, the switching element in the present invention should meet the requirements of automatic control and can achieve power-on control.

[0097] Optionally, in a constant current source segment selection detection module of an LED display driving chip, the first current mirror is connected to one or more second current mirrors, and the connection methods include:

[0098] The first current mirror is connected to one or more second current mirrors in sequence, and the current mirror connected at the end is used as the constant current output channel;

[0099] Or;

[0100] The first current mirror is respectively connected to one or more second current mirrors, and each second current mirror is respectively used as a constant current output channel.

[0101] A constant current source segment selection detection control method for an LED display driving chip, which is used to implement segment selection detection control in the constant current source segment selection detection module of the driving chip, includes:

[0102] 1) Obtain the mirror current Icmp[x] of the input current I0;

[0103] 2) Compare the mirror current Icmp[x] with the reference current [IRB, IRT]. When Icmp[x] is not within the range of the reference current [IRB, IRT], adjust the mirror ratio A[X] of the R_EXT current mirror of the driving chip;

[0104] 3) Repeat 2) until IRB < Icmp[x] < IRT.

[0105] Finally, it also includes the control adjustment of the output current, that is, adjusting the mirror ratio J[X] of the second current mirror of the driving chip so that the output current IOUT = I1 * J[X], where I1 is the output current of the first current mirror, that is, the input current of the second current mirror.

[0106] Further, the specific steps of 2) include:

[0107] When it is detected that IRB < Icmp[x] < IRT, the chip works in current segment X, and the mirror ratio of the R_EXT current mirror is A[X];

[0108] When it is detected that Icmp[x] < IRB, the current segment in which the chip operates changes from the X-th segment to the (X - 1)-th segment, the mirror ratio of the R_EXT current mirror changes from A[X] to A[X - 1], the mirror current Icmp[x] increases, and the next round of detection is carried out until it is detected that IRB < Icmp[x] < IRT;

[0109] When it is detected that Icmp[x] > IRT, the current segment in which the chip operates changes from the X-th segment to the (X + 1)-th segment, the mirror ratio of the R_EXT current mirror changes from A[X] to A[X + 1], the mirror current Icmp[x] decreases, and the next round of detection is carried out until it is detected that IRB < Icmp < IRT.

[0110] Reference Figure 6 and Figure 7 As shown in

[0111] (1) The current range of the constant current output is divided into L segments, and the current values increase sequentially from the 1st segment to the L-th segment. Currently, it is operating in the X-th segment;

[0112] (2) PM3, PM4 and PM0 form a current mirror to mirror the current flowing through R_EXT to generate currents Icmp1 and Icmp2. The mirror ratio is controlled by the current detection result. Here, it is designed that Icmp1 = Icmp2 = Icmp = A[X] * I0 (A[1] to A[L] decrease sequentially);

[0113] Among them, according to the formula IOUT[X] = I0[X] * K[X] * J[X], keeping K[X] * J[X] as a constant, adjusting I0[X] so that IOUT[X] is the actual operating current, or the current operating currently.

[0114] (3) The reference current IRT is the upper limit of the current detection range, and the reference current IRB is the lower limit of the current detection range. The current detection module compares the currents Icmp1 and Icmp2 with IRT and IRB respectively. According to the detection results, the corresponding segment selection control signals (SP[L:1] and SN[L:1]) and mirror ratio control signals (SP[L:1]) are generated by the logic circuit. The segment selection control signals SP[L:1] and SN[L:1] are used to control the number of MOS transistors turned on in PM0[L:1] and NM_C0[L:1] respectively. Assume 1 ≤ X ≤ L. When SN[X] and SP[X] are valid, VGNO[X] = VGN, VGPO[X] = VGP; when S[X] is invalid, VGNO[X] = GND, VGPO[X] = VDD.

[0115] (4) When IRB < Icmp < IRT is detected, the chip operates in the correct current segment. The segment selection control signals SP[L:1] and SN[L:1] remain unchanged, the number of MOS transistors turned on in PM0[L:1] and NM_C0[L:1] remains unchanged, the mirror ratio A[X] remains unchanged, and the mirror current Icmp remains unchanged. From the above description, it can be seen that K[X] changes synchronously with A[X], that is, I1 remains unchanged and operates within the preset range value, which is also the current value with relatively low chip power consumption.

[0116] Under normal circumstances, in a fixed circuit, I1 can only fluctuate within a certain range. The reason is that the mirror ratio K of the first current mirror is determined by the number of MOS transistors in the MOS transistor component. Only when the number of MOS transistors approaches infinity can the value of K be continuous. Usually, the value of K is several fixed values. For example, in a MOS transistor component with 10 MOS transistors, the value of K is also 10 values (assumed to be 1 - 10). Only when the output current IOUT exactly operates at these 10 points can I1 be guaranteed to remain unchanged.

[0117] For example, when the output current is IOUT = 10A, the input current I0 = 1A, K = 1, and J = 10, then IOUT = 10A = 1A * 1 * 10;

[0118] If at this time, the output current IOUT becomes 20A, on the premise that J * K remains unchanged, I0 = 2A, to satisfy I1 = 1A, then K = 2 / 1 = 2, and J correspondingly becomes 5, thus maintaining I1 = 1A unchanged. In actual situations, this generally does not occur, that is, only when such a coincidence occurs can I1 be maintained unchanged.

[0119] If at this time, the output current IOUT becomes 9A, on the premise that J * K remains unchanged, I0 = 0.9A, to satisfy I1 = 1A, then K = 1 / 0.9. Obviously, the value of K does not include this value in practice, so only a K value close to it can be taken, that is, K = 1 is maintained, and in this case I1 = 0.9A. That is to say, in actual situations, it is generally impossible to maintain I1 unchanged, and this state can only be achieved under ideal conditions.

[0120] (5) When it is detected that Icmp < IRB, which means that I1 is lower than the preset value, this state causes the |VGS| of each MOS transistor in the first current mirror and the second current mirror not to be at a relatively large value, and its accuracy decreases; in this state, the segment control signals SP[L:1] and SN[L:1] change, and the current segment in which the chip operates changes from the Xth segment to the (X - 1)th segment. The number of MOS transistors turned on in PM0[L:1] and NM_C0[L:1] decreases, the mirror ratio changes from A[X] to A[X - 1], and the mirror current Icmp increases. As can be seen from the above description, K[X] changes synchronously with A[X], that is, I1 also increases, and the next round of detection is carried out until it is detected that IRB < Icmp < IRT. In this state, I1 returns to the preset range value.

[0121] (6) When it is detected that Icmp > IRT, which means that I1 is greater than the preset value, the internal power consumption of the chip is relatively large. In this state, the segment control signals SP[L:1] and SN[L:1] change, and the current segment in which the chip operates changes from the Xth segment to the (X + 1)th segment. The number of MOS transistors turned on in PM0[L:1] and NM_C0[L:1] increases, the mirror ratio changes from A[X] to A[X + 1], and the mirror current Icmp decreases, that is, I1 decreases, and the next round of detection is carried out until it is detected that IRB < Icmp < IRT. In this state, I1 returns to the preset range value.

[0122] In summary, the control strategy of the present invention mainly controls the internal current I1 of the chip within a reasonable range, so that it can not only reduce the internal power consumption of the chip, but also ensure that the |VGS| (the absolute value of VGS) of each MOS transistor is at a relatively large value, and the accuracy of the current mirror does not change significantly with the magnitude of the output constant current, which is beneficial to improving the accuracy of the constant current output. When the accuracy of the constant current output is satisfied, the value of the current I1 can be designed to be small enough, which is beneficial to reducing the power consumption of the chip.

[0123] The above is only the preferred embodiment of the present invention. It should be understood that the present invention is not limited to the form disclosed herein, and should not be regarded as excluding other embodiments, but can be used in various other combinations, modifications and environments, and can be changed within the scope of the concept described herein through the above teachings or the technology or knowledge in related fields. And the changes and modifications made by those skilled in the art without departing from the spirit and scope of the present invention should be within the protection scope of the appended claims of the present invention.

Claims

1. A constant current source selection and detection module for an LED display driver chip, characterized in that, it includes: a MOS transistor forming an R_EXT current mirror with the first current mirror input channel of the constant current source driver chip, and a current detection module connected to the R_EXT current mirror; wherein, the input channel of the first current mirror is composed of a MOS transistor component with adjustable width-to-length ratio, and is used to connect the input current I0 and the off-chip resistor R_EXT; the R_EXT current mirror is used to generate an image current Icmp[x] of the input current I0; the current detection module compares the image current Icmp[x] with the reference currents [IRB, IRT], and when Icmp[x] is not within the range of the reference currents [IRB, IRT], adjusts the number of MOS transistors connected to the input channel of the first current mirror to adjust the mirror ratio A[X] of the R_EXT current mirror until IRB < Icmp[x] < IRT; wherein, IRB is the lower limit value of the reference current, and IRT is the upper limit value of the reference current.

2. The constant current source selection and detection module for an LED display driver chip according to claim 1, characterized in that, the current detection module is composed of two comparators and a logic circuit; the two comparators are respectively connected to the logic circuit, the reference terminals of the two comparators respectively input the reference current IRB and the reference current IRT, and their comparison terminals are respectively connected to the image current Icmp[x]; the logic circuit outputs a control instruction according to the comparison result to adjust the mirror ratio A[X] of the R_EXT current mirror until IRB < Icmp[x] < IRT.

3. The constant current source selection and detection module for an LED display driver chip according to claim 2, characterized in that, the R_EXT current mirror is one or two, and respectively outputs the image current Icmp[x], where x is the number of the corresponding R_EXT current mirror.

4. The constant current source selection and detection module for an LED display driver chip according to claim 3, characterized in that, when there are two R_EXT current mirrors, Icmp[1] = Icmp[2], or Icmp[1] = kIcmp[2], where k is a coefficient.

5. The constant current source selection and detection module for an LED display driver chip according to claim 4, characterized in that, the control strategy of the logic circuit is: when it is detected that IRB < Icmp[x] < IRT, the chip works in current segment X, and the mirror ratio of the R_EXT current mirror is A[X]; when it is detected that Icmp[x] < IRB, the current segment in which the chip works changes from the Xth segment to the (X - 1)th segment, the mirror ratio of the R_EXT current mirror changes from A[X] to A[X - 1], the image current Icmp[x] increases, and the next round of detection is performed until it is detected that IRB < Icmp[x] < IRT; When it is detected that Icmp[x] > IRT, the current segment in which the chip operates changes from the X-th segment to the (X + 1)-th segment, the mirror ratio of the R_EXT current mirror changes from A[X] to A[X + 1], the mirror current Icmp[x] decreases, and the next round of detection is carried out until it is detected that IRB < Icmp < IRT; Among them, A[1] to A[X] gradually decrease, and the value of X is the number of current segments for driving the chip by the constant current source.

6. A constant current source segment selection detection module for an LED display driving chip according to claim 5, characterized in that, The MOS transistor assembly is formed by connecting a plurality of MOS transistors, and a switching element is arranged in its connection circuit.

7. A constant current source segment selection detection module for an LED display driving chip according to claim 6, characterized in that, The logic circuit is connected to a processor or a register, and the processor or the register is connected to the switching element for controlling the number of MOS transistors accessed in the MOS transistor assembly; or, The logic circuit is directly connected to the switching element for controlling the number of MOS transistors accessed in the MOS transistor assembly.

8. A constant current source segment selection detection module for an LED display driving chip according to claim 7, characterized in that, The connection mode of each MOS transistor in the MOS transistor assembly is series or parallel.

9. A constant current source segment selection detection module for an LED display driving chip according to claim 8, characterized in that, The switching element is a diode or a relay switch.

10. A constant current source segment selection detection module for an LED display driving chip according to claim 9, the first current mirror is connected to one or more second current mirrors, and its connection mode includes: The first current mirror is sequentially connected to one or more second current mirrors, and the current mirror connected at the end serves as a constant current output channel; or; The first current mirror is respectively connected to one or more second current mirrors, and each second current mirror serves as a constant current output channel respectively; Among them, the constant current output channel is composed of a MOS transistor assembly with an adjustable width-to-length ratio formed by a plurality of MOS transistors.

11. A constant current source segment selection detection control method for an LED display driving chip, which is used to realize segment selection detection control in a constant current source segment selection detection module for an LED display driving chip according to any one of claims 1-10, characterized in that, includes: 1) Obtain the mirror current Icmp[x] of the input current I0; 2) Compare the mirror current Icmp[x] with the reference current [IRB, IRT]. When Icmp[x] is not within the range of the reference current [IRB, IRT], adjust the mirror ratio A[X] of the R_EXT current mirror of the driving chip; 3) Repeat 2) until IRB < Icmp[x] < IRT.

12. A constant current source segment selection detection control method for an LED display driving chip according to claim 11, characterized in that: The specific steps of 2) include: When it is detected that IRB < Icmp[x] < IRT, the chip operates in the current segment X, and the mirror ratio of the R_EXT current mirror is A[X]; When it is detected that Icmp[x] < IRB, the current segment in which the chip operates changes from the Xth segment to the (X - 1)th segment, the mirror ratio of the R_EXT current mirror changes from A[X] to A[X - 1], the mirror current Icmp[x] increases, and the next round of detection is carried out until it is detected that IRB < Icmp[x] < IRT; When it is detected that Icmp[x] > IRT, the current segment in which the chip operates changes from the Xth segment to the (X + 1)th segment, the mirror ratio of the R_EXT current mirror changes from A[X] to A[X + 1], the mirror current Icmp[x] decreases, and the next round of detection is carried out until it is detected that IRB < Icmp < IRT.

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