LED drive display circuit

Abstract

The present invention discloses an LED driving display circuit, comprising a scanning circuit, a driving circuit and an LED array circuit, wherein the LED array circuit comprises LED lamp tubes; the common end of each row of LED lamp tubes in the LED array circuit is connected to the first power supply end through a first switch tube, and the common end of each row of LED lamp tubes in the LED array circuit is connected to the second power supply end through a second switch tube, and the scanning circuit is used to control the on-off state of all the first switch tubes and the second switch tubes, and the other end of each column of LED lamp tubes in the LED array circuit is respectively connected to each driving end of the driving circuit in a one-to-one correspondence. The LED driving display circuit of the present invention sets a time-sharing scanning mode for LED red tubes and LED blue-green tubes, and sets a bias voltage so that even if there is a reverse leakage in the LED lamp tube, it cannot light up the corresponding LED lamp.

Description

Technical Field

[0001] The present invention relates to the technical field of LED driving, and in particular to an LED driving display circuit. Background Art

[0002] In the LED driving circuit in the prior art, when reverse leakage occurs in the same column of LEDs, the LED lights that should be in the off state may easily appear dim. There are two different situations in the specific circuit, namely, there are differences between the common anode connection method and the common cathode connection method.

[0003] like Figure 1 As shown, it is a simplified schematic diagram of the driver board with a normal common anode connection. If one color of D11 leaks in the reverse direction (taking red as an example), the equivalent schematic diagram of the reverse leakage is as follows Figure 2 As shown. When scanning the nth row, Q1-Qn-1 is disconnected and Qn is turned on. At this time, if the driver IC is not turned on, D1n should be off under normal circumstances. However, due to the reverse leakage of D11 and the existence of row capacitance, this provides a closed loop for D1n to turn on. The loop is formed as described below, and the current charges C1 through Qn, D1n, and R1. The above is the mechanism for the LEDs in the same column of the common anode connection to have reverse leakage, causing other LEDs that should be black to be dark.

[0004] like Figure 3 As shown, it is a simplified schematic diagram of the driver board with a normal common cathode connection. If D11 leaks in the reverse direction, its equivalent schematic diagram in the reverse direction is as follows Figure 4 As shown. When scanning the kth (1≤k≤n) row, Qk is turned on and the others are turned off. At this time, if the driver IC is turned on, D1k is lit and the first row capacitor is charged. After switching to scanning the k+1 row, if the driver IC is not turned on at this time, under normal circumstances, D1k+1 should be extinguished. However, due to the reverse leakage of D11, the discharge of the first row capacitor will continue to light up D1k+1. The formation of the circuit is as follows. The above is the mechanism for the other LEDs to be brighter due to the reverse leakage of the LEDs in the same column of the common cathode connection. Summary of the invention

[0005] In order to overcome the deficiencies of the prior art, the object of the present invention is to provide an LED driving display circuit, which can solve the technical problem of dimming of LED due to reverse leakage.

[0006] The purpose of the present invention is achieved by the following technical solutions:

[0007] An LED drive display circuit comprises a scanning circuit, a drive circuit and an LED array circuit, wherein the LED array circuit comprises LED lamp tubes, and the number of the LED lamp tubes is N*M, wherein N≥1, M≥1;

[0008] The common end of each row of LED lamp tubes in the LED array circuit is connected to the first power supply end through the first switch tube, and the common end of each row of LED lamp tubes in the LED array circuit is connected to the second power supply end through the second switch tube. The scanning circuit is used to control the on and off states of all the first switch tubes and the second switch tubes. The other ends of each column of LED lamp tubes in the LED array circuit are respectively connected to each driving end of the driving circuit one by one.

[0009] Furthermore, the scanning circuit is used to control the first switch tube or the second switch tube connected to the scanning row of the LED array to be turned on, and to generate a line bias voltage at the stop scanning row of the LED array.

[0010] Furthermore, both the first switch tube and the second switch tube are PMOS tubes; the source of the first switch tube is connected to the first power supply terminal, the drain of the first switch tube is connected to the anode common terminal of each row of LED lamp tubes in the LED array circuit, and the gate of the first switch tube is connected to the control switch terminal in the scanning circuit; the source of the second switch tube is connected to the second power supply terminal, the drain of the second switch tube is connected to the anode common terminal of each row of LED lamp tubes in the LED array circuit, and the gate of the second switch tube is connected to the control switch terminal in the scanning circuit; the cathodes of each row of LED lamp tubes in the LED array are respectively connected to each driving terminal in the driving circuit in a one-to-one correspondence.

[0011] Furthermore, the voltage of the first power supply end is higher than the forward bias voltage of the red tube in the LED lamp tube, the voltage of the second power supply end is higher than the forward bias voltage of the blue and green tubes in the LED lamp tube, and the voltage of the first power supply end is lower than the voltage of the second power supply end.

[0012] Further, the scanning circuit includes a resistor R2, a transistor Q3, a transistor Q4, a capacitor CE1, a resistor R3, a resistor R4, a resistor R5, a fourth switch tube QC1, a reference voltage device U2 and a third switch tube group, and the third switch tube group includes N third switch tubes;

[0013] The power supply terminal VDD_LED is connected to the cathode of the reference voltage device U2 through the resistor R2, the power supply terminal VDD_LED is connected to the collector of the transistor Q3, the emitter of the transistor Q3 is connected to the collector of the transistor Q4, the bases of the transistors Q3 and Q4 are both connected to the cathode of the reference voltage device U2, the reference level of the reference voltage device U2 is connected to one end of the resistor R5, the emitter of the transistor Q3 is connected to the row bias voltage terminal VDD_Row_off, the emitter of the transistor Q3 is grounded through the capacitor CE1, and the emitter of the transistor Q3 is connected to one end of the resistor R5 through the resistor R3. , the emitter of the transistor Q3 is connected to one end of the resistor R4 through the resistor R3, the other end of the resistor R5 is connected to the drain of the fourth switch tube QC1, the anode of the reference voltage device U2, the emitter of the transistor Q4, the other end of the resistor R4 and the source of the fourth switch tube QC1 are all grounded, the gate of the fourth switch tube QC1 is connected to the bias voltage control terminal in the driving circuit, the row bias voltage terminal VDD_Row_off is connected to the source of all the third switch tubes, the drains of all the third switch tubes are respectively connected to a corresponding row voltage terminal, and the gates of all the third switch tubes are respectively connected to a corresponding control switch terminal.

[0014] Furthermore, the row bias voltage generated by the row bias voltage terminal VDD_Row_off is lower than the forward bias voltage of the red tube in the LED lamp tube, or the row bias voltage generated by the row bias voltage terminal VDD_Row_off is lower than the forward bias voltage of the blue and green tubes in the LED lamp tube, the transistor Q3 is an NPN transistor, and the transistor Q4 is a PNP transistor.

[0015] Furthermore, the first switch tube and the second switch tube are both NMOS tubes; the source of the first switch tube is connected to the first power supply terminal, the drain of the first switch tube is connected to the cathode common terminal of each row of LED lamp tubes in the LED array circuit, and the gate of the first switch tube is connected to the control switch terminal in the scanning circuit; the source of the second switch tube is connected to the second power supply terminal, the drain of the second switch tube is connected to the cathode common terminal of each row of LED lamp tubes in the LED array circuit, and the gate of the second switch tube is connected to the control switch terminal in the scanning circuit; the anodes of each row of LED lamp tubes in the LED array are respectively connected to each driving terminal in the driving circuit in a one-to-one correspondence.

[0016] Furthermore, the voltage of the first power supply end is lower than the power supply end minus the forward bias voltage of the red tube in the LED lamp tube, the voltage of the second power supply end is lower than the power supply end minus the forward bias voltage of the blue and green tubes in the LED lamp tube, and the voltage of the first power supply end is higher than the voltage of the second power supply end.

[0017] Further, the scanning circuit includes a resistor R2, a transistor Q3, a transistor Q4, a capacitor CE1, a resistor R3, a resistor R4, a resistor R5, a fourth switch tube QC1, a reference voltage device U2 and a third switch tube group, and the third switch tube group includes N third switch tubes;

[0018] The power supply terminal VDD_LED is connected to the cathode of the reference voltage device U2 through the resistor R2, the power supply terminal VDD_LED is connected to the collector of the transistor Q3, the emitter of the transistor Q3 is connected to the collector of the transistor Q4, the bases of the transistors Q3 and Q4 are both connected to the cathode of the reference voltage device U2, the emitter of the transistor Q3 is connected to the row bias voltage terminal VDD_Row_off, the emitter of the transistor Q3 is grounded through the capacitor CE1, the emitter of the transistor Q3 is connected to one end of the resistor R5 through the resistor R3, and the emitter of the transistor Q3 is connected to the cathode of the reference voltage device U2 through the resistor R4. R3 is connected to one end of the resistor R4, the other end of the resistor R5 is connected to the drain of the fourth switch tube QC1, the anode of the reference voltage device U2, the emitter of the transistor Q4, the other end of the resistor R4 and the source of the fourth switch tube QC1 are all grounded, the gate of the fourth switch tube QC1 is connected to the bias voltage control terminal in the drive circuit, the row bias voltage terminal VDD_Row_off is connected to the source of all the third switch tubes, the drains of all the third switch tubes are respectively connected to a corresponding row voltage terminal, and the gates of all the third switch tubes are respectively connected to a corresponding control switch terminal through an inverter.

[0019] Further, the row bias voltage generated by the row bias voltage terminal VDD_Row_off is higher than the power supply terminal minus the forward bias voltage of the red tube in the LED lamp, or the row bias voltage generated by the row bias voltage terminal VDD_Row_off is higher than the power supply terminal minus the forward bias voltage of the blue and green tubes in the LED lamp, the transistor Q3 is an NPN transistor, and the transistor Q4 is a PNP transistor.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] The LED driving display circuit of the present invention sets a time-sharing scanning mode for the LED red tube and the LED blue and green tubes, and sets a bias voltage so that even if there is reverse leakage of the LED tube, the corresponding LED lamp cannot be lit. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a simplified schematic diagram of a driver board of the common positive connection method in the prior art;

[0023] Figure 2 This is an equivalent schematic diagram of the prior art common anode connection method when reverse leakage occurs;

[0024] Figure 3 It is a simplified schematic diagram of a driver board of the common female connection method in the prior art;

[0025] Figure 4 This is an equivalent schematic diagram of the prior art common cathode connection method when reverse leakage occurs;

[0026] Figure 5 This is a simplified schematic diagram of a common anode connection driving board of the first embodiment;

[0027] Figure 6 is a schematic diagram of a scanning circuit of Embodiment 1;

[0028] Figure 7 This is a simplified schematic diagram of a common cathode connection driving board of the second embodiment;

[0029] Figure 8 is a schematic diagram of a scanning circuit of Embodiment 2;

[0030] Fig. 9 This is the volt-ampere characteristic curve of the LED lamp. DETAILED DESCRIPTION

[0031] The present invention is further described below in conjunction with the accompanying drawings and specific implementation methods. It should be noted that, under the premise of no conflict, the various embodiments or technical features described below can be arbitrarily combined to form a new embodiment.

[0032] The basic idea of ​​the present invention to solve the dark-bright situation in the background technology is: when the LED tube should be turned off, find a way to reduce the forward bias voltage of the LED to make it lower than the forward conduction voltage of the LED. Since it is lower than the forward conduction voltage, the LED cannot be turned on, that is, the LED tube is turned off.

[0033] Since LED tubes with small spacing are generally packaged as 4 pins, the anodes of the LEDs of 3 colors are connected together and led to one pin, and the cathodes are connected to one pin respectively, which is a common anode LED tube; the cathodes of the LEDs of 3 colors are connected together and led to one pin, and the anodes are connected to one pin respectively, which is a common cathode LED tube. Generally, the forward conduction voltage of the red LED is lower than the forward conduction voltage of the blue-green LED, and the voltage difference is about 1V. Since the anodes (cathodes) are connected together, to drive the corresponding tubes, it is necessary to ensure that the forward bias voltage is higher than the forward conduction voltage of the blue-green tube, so the red LED anode of the LED tube in the current scanning line has a higher bias voltage (or the cathode has a lower bias voltage). Therefore, when the red tube in the LED tube leaks reversely, it is very easy to cause dark light; therefore, it can be considered to solve this problem by time-sharing scanning of the LED red tube and the LED blue-green tube. In addition, when the equivalent leakage resistance is relatively small, it is necessary to consider adding a bias voltage to the line where the scanning is stopped to suppress the LED tube from displaying. The present invention specifically describes the common anode connection method and the common cathode connection method.

[0034] The forward conduction voltage of the blue-green tube is generally 30% higher than that of the red tube. The leakage of the blue-green tube can easily cause the red tube to dim. A higher line bias voltage can easily cause the red tube to mis-conduct. The red tube requires a relatively lower line bias voltage. When the red, green and blue are scanned at the same time, the adjustable line bias voltage range for the blue-green tube is very limited. Since the voltages of the blue and green tubes are very close, in the description of the present invention, the voltages of the blue and green tubes in the LED lamp tube are taken as one voltage. During the specific operation, those skilled in the art can select a more appropriate voltage for control according to the actual situation.

[0035] The forward voltage of LEDs produced by different manufacturers and different models of LEDs from the same manufacturer are different. The row bias voltage and LED power supply voltage need to be set according to the volt-ampere characteristic curve of the LED. The following takes the FC-B1010RGBT-HG of Nationstar Optoelectronics as an example to briefly explain how to set the row bias voltage and LED power supply voltage. Fig. 9 The volt-ampere characteristic curve of FC-B1010RGBT-HG is shown as follows:

[0036] According to the volt-ampere characteristic and considering the constant current requirement of the LED driver IC, the red LED power supply voltage VDD_R can be set to 2.8V, and the blue-green LED power supply voltage can be set to 4.0V. The row bias voltage needs to ensure that the LEDs in the rows not scanned are not bright enough. According to the above volt-ampere characteristic curve, the red row bias voltage VDD_Row_off_R can be set to 1.6V, and the blue-green row bias voltage VDD_Row_off_GB can be set to 2.6V. This setting method can be designed by those skilled in the art according to different LED characteristics.

[0037] Embodiment 1:

[0038] like Figure 5 As shown, it is a simplified schematic diagram of the common anode LED red tube and LED blue-green tube time-sharing scanning driver board. Figure 6 The corresponding row bias voltage reference circuit schematic diagram. According to the forward conduction voltage drop VF_R, VF_G, VF_B of the red, green, and blue LEDs of the LED tube, the values ​​of VDD_R and VDD_GB are appropriately adjusted to make VDD_R slightly higher than VF_R, and VDD_GB slightly higher than the larger of VF_G and VF_B. In this circuit, COLOR_SEL is the bias voltage control terminal, which enables the circuit to generate the row bias voltage of the red tube and the row bias voltage of the blue and green tubes in a time-sharing manner. This signal is generally generated by the drive control chip (such as CPU, FPGA)

[0039] By adjusting the ratio of R3 and R4, when QC1 is disconnected, the row bias voltage VDD_Row_off can be controlled to be slightly lower than the forward conduction voltage VF_R of the red LED; on this basis, the value of R5 is adjusted so that when QC1 is turned on, the row bias voltage VDD_Row_off can be controlled to be slightly lower than the lower of the forward conduction voltage VF_G of the green LED tube and the forward conduction voltage VF_B of the blue LED tube. The row bias voltage VDD_Row_off here is the bias voltage of the row where the LED is in the off state. For example, when scanning the first row, its row bias voltage is VDD_Row_1. At this time, the bias voltage of other rows is VDD_Row_off. Since the row bias voltage VDD_Row_off is less than the forward conduction voltage of the LED tube, the LED tube cannot be turned on.

[0040] A specific solution is described for a specific row scanning scenario: when scanning the kth row (1≤k≤n), the red LED tube is scanned first, and the driver ICs of the green LED tube and the blue LED tube are not turned on. Figure 5 QRk is turned on and other MOS tubes are turned off. At this time, the row voltage VDD_Rowk of the kth row is the power supply voltage VDD_R of the red LED tube. Figure 6In the process, the switch tube QC1 is turned off, QRowk is turned off, and other MOS tubes are turned on. At this time, the row voltage of other stopped scanning rows is the row bias voltage VDD_Row_off, which is a voltage slightly lower than the forward conduction voltage of the LED red tube. If the red driver IC of the i-th column (1≤i≤m) is turned on, the red LED tube of Dik is normally lit; if the red driver IC of the i-th column is not turned on, the anode bias voltage of Dik red LED is VDD_R, which is a bias voltage slightly higher than its forward conduction voltage, and the cathode bias voltage is VDD_Row_off, which is a bias voltage slightly lower than its forward conduction voltage. Its forward bias is very small, less than its forward conduction voltage VF_R; therefore, even if the red LED of the row that stops scanning leaks, the red tube of Dik is still in the off state. At this time, no matter whether the red tube in Dik is on or off, the anode bias voltage of the blue and green tubes is VDD_R, and the cathode bias voltage is VDD_Row_off. From the above, it can be seen that the forward bias of the blue and green tubes is very small, which is less than its forward conduction voltage, so the blue and green tubes of Dik are in the off state.

[0041] Scan the blue and green LED tubes again, and the red LED driver IC is not conducting. Figure 5 QGBk is turned on, and other MOS tubes are turned off. The kth row voltage VDD_Rowk is the power supply voltage VDD_GB of the blue and green LED tubes. Figure 6 In the process, QROWk is disconnected and other MOS tubes are turned on. At this time, the voltage of other rows that stop scanning is the row bias voltage VDD_Row_off, which is a bias voltage slightly lower than the lower of the forward conduction voltage VF_G of the LED green tube and the forward conduction voltage VF_B of the LED blue tube. If the i-th (1≤i≤m) column green (blue) driver IC is turned on, the LED green (blue) tube of Dik is normally lit; if the i-th column green (blue) driver IC is not turned on, the anode bias voltage of the LED green tube (blue tube) in Dik is VDD_GB, which is a bias voltage slightly higher than the larger of the forward conduction voltage VF_G of the LED green tube and the forward conduction voltage VF_B of the LED blue tube, and the cathode bias voltage is VDD_Row_off, which is a bias voltage slightly lower than the lower of the forward conduction voltage VF_G of the LED green tube and the forward conduction voltage VF_B of the LED blue tube. Because the forward conduction voltage VF_G of the green LED tube is very close to the forward conduction voltage VF_B of the blue LED tube, its forward bias is very small, less than its forward conduction voltage VF_G (VF_B), so even if the green (blue) LED of the row that stops scanning leaks, the Dik green tube (blue tube) is still in the off state. At this time, regardless of the on and off conditions of the blue and green tubes in Dik, the anode bias voltage of the red LED tube in Dik is VDD_GB, and the cathode bias voltage is VDD_Row_off. From the above, it can be seen that the forward bias of the blue and green tubes is very small, less than their forward conduction voltage, so the Dik red tube is in the off state.

[0042] Embodiment 2:

[0043] Figure 7 This is a simplified schematic diagram of the common cathode connection one-nth red LED and blue-green LED time-sharing scanning driver board. Figure 8 The corresponding row bias voltage reference circuit schematic diagram is shown in Figure 2. The driver IC power supply voltage is VDD_LED. According to the forward conduction voltage drops VF_R, VF_G, and VF_B of the red, green, and blue LEDs of the LED tube, the values ​​of GND_R and GND_GB are appropriately adjusted to make GND_R slightly lower than VDD_LED minus VF_R, and GND_GB slightly lower than the larger of VDD_LED minus VF_G and VF_B. By adjusting the ratio of R3 and R4, when QC1 is disconnected, the row bias voltage GND_Row_off can be controlled to be slightly higher than the driver IC power supply voltage VDD_LED minus the red LED forward bias voltage VF_R; on this basis, the value of R5 is adjusted, and when QC1 is turned on, the row bias voltage GND_Row_off can be controlled to be slightly higher than the smaller of the driver IC power supply voltage VDD_LED minus the green LED forward conduction voltage VF_G and the blue LED forward conduction voltage VF_B.

[0044] When scanning the kth row (1≤k≤n), the red, green and blue LED driver ICs are first scanned and are not turned on. Figure 7 QRk is turned on, other MOS tubes are turned off, and the row voltage GND_Rowk of the kth row is the red LED power supply voltage GND_R. Figure 8In the process, QC1 is disconnected, QROWk is disconnected, and other MOS tubes are turned on. At this time, the row voltage of other stopped scanning rows is the row bias voltage GND_Row_off, which is a voltage slightly higher than the driver IC power supply voltage VDD_LED minus the red LED forward conduction voltage VF_R. If the red driver IC in the i-th column (1≤i≤m) is turned on, the Dik red LED is normally lit; if the red driver IC in the i-th column is not turned on and the Di1 red LED is leaking, the anode bias voltage of the Dik red LED is GND_Row_off, which is slightly higher than the driver IC power supply voltage VDD_LED minus the red LED forward conduction voltage VF_R, and the cathode bias voltage is GND_R, which is slightly lower than VDD_LED minus the red LED forward conduction voltage VF_R. Its forward bias is very small, less than its forward conduction voltage VF_R, and the Dik red tube is off. At this time, no matter how the red tube in Dik is on or off, the anode bias voltage of the blue and green tubes in row k is GND_Row_off, and the cathode bias voltage is GND_R. From the above, we can see that the forward bias of the blue and green tubes is very small, less than their forward conduction voltage, so the blue and green tubes of Dik are in the off state. The anode and cathode bias voltages of all color tubes in other rows that stop scanning are the row bias voltage GND_Row_off, so they are all off.

[0045] Scan the blue, green and red LED driver ICs again and they are all off. Figure 7 The QGBk in the middle is turned on, the other MOS tubes are turned off, and the row voltage GND_Rowk of the kth row is the blue-green LED power supply voltage GND_GB. Figure 8In the process, QROWk is disconnected and other MOS tubes are turned on. At this time, the voltage of other rows that stop scanning is the row bias voltage GND_Row_off, which is a bias voltage slightly higher than the smaller of the driver IC power supply voltage VDD_LED minus the green LED forward conduction voltage VF_G and the blue LED forward conduction voltage VF_B. If the i-th (1≤i≤m) column green (blue) driver IC is turned on, the LED green (blue) tube of Dik is normally lit; if the i-th column green (blue) driver IC is not turned on, even if the green (blue) LED of other rows that stop scanning leaks, its anode bias voltage is GND_Row_off, which is a bias voltage slightly higher than the driver IC power supply voltage VDD_LED minus the green LED forward conduction voltage VF_G and the blue LED forward conduction voltage VF_B, and the cathode bias voltage is GND_GB, which is a bias voltage slightly lower than VDD_LED minus the larger of VF_G and VF_B. Because the forward conduction voltage VF_G of the green LED is very close to the forward conduction voltage VF_B of the blue LED, their forward bias voltage is very small, less than their forward conduction voltage VF_G (VF_B), so the Dik green tube (blue tube) is still in the off state. At this time, regardless of the on and off conditions of the blue and green tubes in Dik, the anode bias voltage of the red tube in the kth row is GND_Row_off, and the cathode bias voltage is GND_GB. From the above, it can be seen that the forward bias of the blue and green tubes is very small, less than their forward conduction voltage, so the Dik red tube is in the off state. For the other rows that stop scanning, the anode and cathode bias voltages of all color tubes are the row bias voltage GND_Row_off, so they are all off.

[0046] Therefore, the red LED and blue-green LED time-sharing scanning has introduced a row bias voltage to solve the problem of dimming caused by leakage of the LED on the scanning drive board.

[0047] The above-mentioned embodiments are only preferred embodiments of the present invention and cannot be used to limit the scope of protection of the present invention. Any non-substantial changes and substitutions made by technicians in this field on the basis of the present invention shall fall within the scope of protection required by the present invention.

Claims

1. An LED driving display circuit, comprising a scanning circuit, a driving circuit and an LED array circuit, wherein the LED array circuit comprises LED lamp tubes, and the number of the LED lamp tubes is N*M, wherein N≥1, M≥1; It is characterized in that The common end of each row of LED lamps in the LED array circuit is connected to the first power supply end through the first switch tube, and the common end of each row of LED lamps in the LED array circuit is connected to the second power supply end through the second switch tube. The scanning circuit is used to control the on and off states of the first switch tube and the second switch tube. The other ends of each column of LED lamps in the LED array circuit are connected to each driving end of the driving circuit one by one. The scanning circuit is used to control the first switch tube or the second switch tube connected to the scanning row of the LED array to be turned on, and to generate a line bias voltage at the stop scanning row of the LED array; Wherein, when the anode common end of each row of LED lamp tubes in the LED array circuit is connected to the first power supply end through the first switch tube, and the anode common end of each row of LED lamp tubes in the LED array circuit is connected to the second power supply end through the second switch tube, the row bias voltage is lower than the forward bias voltage of the red tube in the LED lamp tube or the row bias voltage is lower than the forward bias voltage of the blue and green tubes in the LED lamp tube; The scanning circuit includes a resistor R2, a transistor Q3, a transistor Q4, a capacitor CE1, a resistor R3, a resistor R4, a resistor R5, a fourth switch tube QC1, a reference voltage device U2 and a third switch tube group, wherein the third switch tube group includes N third switch tubes; The power supply terminal VDD_LED is connected to the cathode of the reference voltage device U2 through the resistor R2, the power supply terminal VDD_LED is connected to the collector of the transistor Q3, the emitter of the transistor Q3 is connected to the emitter of the transistor Q4, the bases of the transistors Q3 and Q4 are both connected to the cathode of the reference voltage device U2, the reference electrode of the reference voltage device U2 is connected to one end of the resistor R5, the emitter of the transistor Q3 is connected to the row bias voltage terminal VDD_Row_off, the emitter of the transistor Q3 is grounded through the capacitor CE1, and the emitter of the transistor Q3 is connected to one end of the resistor R5 through the resistor R3. , the emitter of the transistor Q3 is connected to one end of the resistor R4 through the resistor R3, the other end of the resistor R5 is connected to the drain of the fourth switch tube QC1, the anode of the reference voltage device U2, the collector of the transistor Q4, the other end of the resistor R4 and the source of the fourth switch tube QC1 are all grounded, the gate of the fourth switch tube QC1 is connected to the bias voltage control terminal in the driving circuit, the row bias voltage terminal VDD_Row_off is connected to the source of all the third switch tubes, the drains of all the third switch tubes are respectively connected to a corresponding row voltage terminal, and the gates of all the third switch tubes are respectively connected to a corresponding control switch terminal; The row bias voltage generated by the row bias voltage terminal VDD_Row_off is lower than the forward bias voltage of the red tube in the LED lamp tube or the row bias voltage generated by the row bias voltage terminal VDD_Row_off is lower than the forward bias voltage of the blue and green tubes in the LED lamp tube; Or when the cathode common terminal of each row of LED lamp tubes in the LED array circuit is connected to the first power supply terminal through the first switch tube, and the cathode common terminal of each row of LED lamp tubes in the LED array circuit is connected to the second power supply terminal through the second switch tube, the row bias voltage is higher than the power supply terminal minus the forward bias voltage of the red tube in the LED lamp tube, or the row bias voltage is higher than the power supply terminal minus the forward bias voltage of the blue and green tubes in the LED lamp tube; The scanning circuit includes a resistor R2, a transistor Q3, a transistor Q4, a capacitor CE1, a resistor R3, a resistor R4, a resistor R5, a fourth switch tube QC1, a reference voltage device U2 and a third switch tube group, wherein the third switch tube group includes N third switch tubes; The power supply terminal VDD_LED is connected to the cathode of the reference voltage device U2 through the resistor R2, the power supply terminal VDD_LED is connected to the collector of the transistor Q3, the emitter of the transistor Q3 is connected to the emitter of the transistor Q4, the bases of the transistors Q3 and Q4 are connected to the cathode of the reference voltage device U2, the emitter of the transistor Q3 is connected to the row bias voltage terminal GND_Row_off, the emitter of the transistor Q3 is grounded through the capacitor CE1, the emitter of the transistor Q3 is connected to one end of the resistor R5 through the resistor R3, and the emitter of the transistor Q3 is connected to the cathode of the reference voltage device U2 through the resistor R4. R3 is connected to one end of the resistor R4, the other end of the resistor R5 is connected to the drain of the fourth switch tube QC1, the anode of the reference voltage device U2, the collector of the transistor Q4, the other end of the resistor R4 and the source of the fourth switch tube QC1 are all grounded, the gate of the fourth switch tube QC1 is connected to the bias voltage control terminal in the driving circuit, the row bias voltage terminal GND_Row_off is connected to the source of all the third switch tubes, the drains of all the third switch tubes are respectively connected to a corresponding row voltage terminal, and the gates of all the third switch tubes are respectively connected to a corresponding control switch terminal through an inverter; The row bias voltage generated by the row bias voltage terminal GND_Row_off is higher than the power supply terminal minus the forward bias voltage of the red tube in the LED tube, or the row bias voltage generated by the row bias voltage terminal GND_Row_off is higher than the power supply terminal minus the forward bias voltage of the blue and green tubes in the LED tube.

2. The LED driving display circuit according to claim 1, characterized in that: The first switch tube and the second switch tube are both PMOS tubes; the source of the first switch tube is connected to the first power supply terminal, the drain of the first switch tube is connected to the anode common terminal of each row of LED lamp tubes in the LED array circuit, and the gate of the first switch tube is connected to the control switch terminal in the scanning circuit; the source of the second switch tube is connected to the second power supply terminal, the drain of the second switch tube is connected to the anode common terminal of each row of LED lamp tubes in the LED array circuit, and the gate of the second switch tube is connected to the control switch terminal in the scanning circuit; the cathodes of each row of LED lamp tubes in the LED array are respectively connected to each driving terminal in the driving circuit in a one-to-one correspondence.

3. The LED driving display circuit according to claim 2, characterized in that: The voltage of the first power supply end is higher than the forward bias voltage of the red tube in the LED lamp tube, the voltage of the second power supply end is higher than the forward bias voltage of the blue and green tubes in the LED lamp tube, and the voltage of the first power supply end is lower than the voltage of the second power supply end.

4. The LED driving display circuit according to claim 1, characterized in that: The transistor Q3 is an NPN transistor, and the transistor Q4 is a PNP transistor.

5. The LED driving display circuit according to claim 1, characterized in that: The first switch tube and the second switch tube are both NMOS tubes; the source of the first switch tube is connected to the first power supply terminal, the drain of the first switch tube is connected to the cathode common terminal of each row of LED lamp tubes in the LED array circuit, and the gate of the first switch tube is connected to the control switch terminal in the scanning circuit; the source of the second switch tube is connected to the second power supply terminal, the drain of the second switch tube is connected to the cathode common terminal of each row of LED lamp tubes in the LED array circuit, and the gate of the second switch tube is connected to the control switch terminal in the scanning circuit; the anodes of each row of LED lamp tubes in the LED array are respectively connected to each driving terminal in the driving circuit in a one-to-one correspondence.

6. The LED driving display circuit according to claim 5, characterized in that: The voltage of the first power supply end is lower than the power supply end minus the forward bias voltage of the red tube in the LED lamp tube, the voltage of the second power supply end is lower than the power supply end minus the forward bias voltage of the blue and green tubes in the LED lamp tube, and the voltage of the first power supply end is higher than the voltage of the second power supply end.

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