An LED driving device capable of directly regulating current and having power supply and temperature monitoring functions

Abstract

The present invention discloses an LED driving device which can directly regulate current and has power supply monitoring and temperature monitoring functions. The system includes an LED driving module, a reference source module, a power supply monitoring module, a temperature monitoring module and a reference voltage monitoring module. The LED driving module uses a current mirror array to regulate the driving current; the reference source module provides a reference voltage and a bias current; the power supply monitoring module, the temperature monitoring module and the reference voltage monitoring module respectively monitor the power supply voltage, the internal temperature of the chip and the reference voltage in real time. Different from the traditional LED driving technology (which often requires an off-chip resistor or a large-area on-chip resistor switch array), the device of the present invention can directly regulate the LED driving current, the chip area is small and easy to use. In addition, the present invention also has a mode switching function, which solves the problem that the traditional structure cannot respond quickly at low load. Without introducing additional pins, the present invention realizes the power supply voltage and temperature monitoring inside the chip, the supply and monitoring of the reference voltage and current, avoids system damage and failure caused by voltage fluctuations and abnormal temperature at the driving end, effectively improves the reliability of the operation of the LED driving system and the service life of the LED, and can be applied to environments with a temperature range of ‑40°C to 125°C.

Description

Technical Field

[0001] The invention belongs to the field of LED control, and in particular relates to an LED driving device and an LED driving circuit. Background Art

[0002] The continuous development of new optical design technologies has made the application of light-emitting diodes (LEDs) in lighting more extensive. In current applications, in order to avoid excessive driving current driving a small LED load and causing damage to the LED, the LED driving circuit needs to adjust the output driving current according to the size of the LED load. The existing technology mainly uses two methods to adjust the current. Method 1 (such as Figure 2 The structure in the figure) can change the driving current by controlling the reference voltages Vref1 and Vref2, but its control structure still requires off-chip resistors and a large-area resistor array on the chip to obtain a more accurate driving current. Method 2 (such as Figure 3 The structure in FIG. 1 is used to adjust the driving current by controlling the size of the resistor. In order to increase the matching of the resistors to obtain higher accuracy, large-area switches and resistor arrays are often required. The above two methods, whether using off-chip resistors or resistor arrays, undoubtedly increase the area and cost of the chip. At the same time, because the power tube of the LED driving system has no external load driving current when the LED is unloaded, and is also limited by the parasitic capacitance and resistance of the power tube, the output end of the driving circuit cannot respond quickly, and the voltage at the LED end will be unstable. When extreme voltage occurs, the LED is often damaged. In this regard, existing solutions (such as Figure 4 As shown in the figure), voltage overshoot is avoided by increasing the regulation of input and output detection circuits, but its operation is based on the reference voltage. In actual applications, the reference voltage may fluctuate due to the coupling capacitance between lines or the moment of startup, which may lead to the risk of misjudgment. In addition, when the drive system is working normally, a large current flows through the power tube for a long time, which may cause excessive temperature and affect performance and service life.

[0003] Therefore, it is necessary to design an LED driving system that can respond quickly under no-load or light-load conditions, whose driving current does not depend on the regulating resistor and has both power supply monitoring and temperature monitoring, so as to solve the above technical problems. Summary of the invention

[0004] The object of the present invention is to provide an LED driving device which can directly regulate current and has power supply monitoring and temperature monitoring functions, so as to solve the problems in the prior art proposed in the above background technology, such as large resistance area, need to connect off-chip resistance, slow response under light load conditions, and the service life of the LED being affected by power supply voltage fluctuations and excessive temperature.

[0005] To achieve the above object, the present invention provides the following technical solutions: an LED driving device capable of directly regulating current and having power supply monitoring and temperature monitoring functions, comprising an LED driving module, which controls a main current mirror by selecting a signal Sel<1:n>, changes the magnitude of a regulating current Ictrl, and provides a proportionally amplified driving current for an LED load after being mirrored by a slave current mirror;

[0006] The reference source module provides stable and reliable reference voltage, bias voltage and reference current for the entire LED driver;

[0007] The reference voltage monitoring module monitors the reference voltage output by the reference source module in real time to prevent the reference voltage from being too low, which may cause the entire LED driver to be unable to operate correctly according to the current state;

[0008] The power supply monitoring module monitors the power supply voltage of the system in real time to ensure that the entire LED driver operates within a safe voltage range;

[0009] The temperature monitoring module monitors the on-chip temperature in real time to prevent the chip from overheating and failure.

[0010] Preferably, the LED driving module comprises: a logic AND gate AND1, a main current mirror array, a slave current mirror, an amplifier AMP1, and a control current (Ictrl) of the main current mirror array is set to times the reference current Iref_2n, the formula is as follows:

[0011] (1);

[0012] According to the proportional relationship of the current mirror, the driving current I_Drv of the LED load is derived as follows:

[0013] (2);

[0014] According to the proportional relationship of the response current mirror, when the response current mirror is started, the output response current formula is:

[0015] (3).

[0016] Preferably, the reference source module includes: a voltage limiting circuit, a bandgap reference and a reference voltage current output unit, which outputs multiple reference voltages and currents with driving capability and high power supply noise suppression ratio, including power supply reference voltages Vvp1 and Vvp2, temperature reference voltages Vtp1, Vtp2, Vtp3 and Vtp4, bias voltage Vbiasp (generating a bias voltage corresponding to a reference current) and reference current Iref_2n.

[0017] Preferably, the reference voltage monitoring module and the Schmitt trigger can be adjusted in design according to actual needs, and its input end receives the reference voltage Vref. When the reference voltage gradually stabilizes and is greater than the flip threshold of the Schmitt trigger, a low-level signal is output, and the enable signal En_2 can be obtained through inverter processing.

[0018] Preferably, the power supply voltage monitoring module includes: series resistors R1 and R2, comparator Cmp1, and comparator Cmp2. The module compares the divided voltage Vin_fb of the system voltage Vin with the reference voltage Vvp1 corresponding to the maximum tolerable system voltage and the reference voltage Vvp2 corresponding to the minimum tolerable system voltage at the same time. When Vin_fb is between Vvp1 and Vvp2, it can be considered that the system voltage is in a safe voltage range.

[0019] Preferably, the temperature monitoring module includes: a switch tube SW1, a pnp transistor Q1, a four-position selection switch SW2, a comparator Cmp3, and a logic gate AND5. Temperature sampling voltage signal The corresponding formula is as follows:

[0020] (4);

[0021] According to formula (4), VT = kT / q, the emitter current Iref_2n is the fixed reference current of the input, is the saturation current, and the derivative with respect to temperature T is obtained. The rate of change with temperature is as follows:

[0022] (5);

[0023] It can be seen from formula (5) that The rate of change with temperature is also related to its own size. In the CMOS process, its rate of change is negative within a specific temperature range, that is, it is negatively correlated with temperature. The level is gradually decreasing. When the temperature reaches the maximum tolerable temperature, When the voltage is lower than the temperature monitoring reference voltage Vtp1, the output of the comparator Cmp3 turns to 0.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] The present invention avoids the traditional method of regulating the resistor array, saving part of the area of ​​the resistor array; it has a mode switching function, which can convert no load or heavy load into two different working modes of light load and heavy load, increase the response speed of the entire system, and avoid problems such as voltage overshoot when the load is switched.

[0026] At the same time, the present invention has a more complete bias voltage and current supply system, and has reference voltage, power supply voltage and temperature monitoring and protection functions, which effectively increases the reliability and service life of the LED and the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is the overall architecture of the LED driving device proposed by the present invention.

[0028] Figure 2 It is a schematic diagram of the existing LED driving structure based on reference voltage regulation;

[0029] Figure 3 It is a schematic diagram of an existing LED driving structure based on adjusting the resistance value;

[0030] Figure 4 A schematic diagram of an existing LED driver structure with output and input detection;

[0031] Figure 5 A schematic diagram of an LED driving module in the LED driving device proposed by the present invention;

[0032] Figure 6 A schematic diagram of a main current mirror array of an LED driving module in an LED driving device proposed by the present invention;

[0033] Figure 7 A schematic diagram of a response current mirror array of an LED driving module in the LED driving device proposed by the present invention;

[0034] Figure 8 This is a structural schematic diagram of a reference voltage and current supply module in the LED driving device proposed by the present invention;

[0035] Fig. 9 A schematic diagram of a reference voltage monitoring module in the LED driving device proposed by the present invention;

[0036] Fig.10 A schematic diagram of a power supply voltage monitoring module in the LED driving device proposed by the present invention;

[0037] Fig.11 It is a schematic diagram of the temperature monitoring module in the LED driving device proposed by the present invention. Implementation

[0038] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0039] The following will be combined with the drawings in the embodiments of the present invention. The technical solutions in the embodiments of the present invention are clearly and completely described. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments in the present invention, all other embodiments obtained by the skilled person in the art without creative work are within the scope of protection of the present invention.

[0040] See also Figures 1 to 11 The present invention provides a technical solution: an LED driving device which can directly regulate current and has power supply monitoring and temperature monitoring functions, such as Figure 1 As shown. The main functional modules included in the system are: LED drive circuit, which adjusts the drive current on the LED load by selecting the magnitude of the control current of the main current mirror, which is more direct and clear than the traditional way of adjusting the resistor, and the chip layout is relatively simpler; reference source circuit, which provides the system with reference voltage, reference current and current bias voltage; reference voltage monitoring circuit, which monitors the state of the reference voltage in real time; power supply voltage monitoring circuit, which monitors whether the system voltage is within the operating voltage range allowed by the system in real time; temperature monitoring circuit, which monitors whether the current ambient temperature is within the operating temperature range allowed by the system in real time.

[0041] LED driver module such as Figure 5 As shown, the enable signal is controlled by the system enable signal En_start and the fourth enable signal En_4 at the same time, and the two signals must indicate the start command at the same time to turn on the LED driver module. The bias voltages of the main current mirror and the response current mirror are both provided by Vbisp. According to the principle of the current mirror, the main current mirror and the response current mirror output currents Ictrl and Istart that are proportional to the reference current Iref_2n. The main current mirror array is shown in FIG. Figure 6 As shown, the response current mirror is as Figure 7 Its working mode is as follows:

[0042] Mode 1: No-load or heavy-load switching to light-load conditions. At this time, the current flowing from the load LED on the drain of nm3 is zero or very small, and the V_Drv voltage takes a long time to stabilize. At this time, the mode switching signal En_mode instructs the switch tube nm4 to turn on, and Istart starts to inject current from the drain of nm3 through nm4. At this time, because the size of PMa is 100 times that of PM0, their gates are connected to the bias voltage Vbiasp in common, and the response current mirror output current Istart is 100 times the reference current Iref_2n, as shown in formula (3). The response current mirror provides current charging, so that the drive output terminal responds quickly and enters a stable state;

[0043] Mode 2: LED heavy load condition, at this time the mode switching signal En_mode instructs the switch tube nm4 to turn off, and the drain of nm3 needs to flow a larger drive current to drive the LED heavy load. At this time, the output current of the main current mirror is increased proportionally, assuming that the proportional coefficient is , then the control current Ictrl is as shown in formula (1). Due to the negative feedback of the operational amplifier AMP1, the drain voltages of nm2 and nm3 are limited to the same level, which makes the current mirror composed of nm2 and nm3 more accurate. According to the width-to-length ratio of nm2 and nm3, assuming that it is m, that is, the width-to-length ratios of nm3 and nm4 are 1×(W2 / L2) and

[0044] m×(W2 / L2), then the corresponding current on nm3 is Inm3=m×Ictrl, and the driving current of the load LED is I_Drv, as shown in formula (2). As described above, the present invention controls the output driving current by controlling the magnitude of the current of the main current mirror, which saves the area of ​​the resistor array compared to the traditional method of controlling the resistor array.

[0045] Reference source module such as Figure 8 As shown, it includes: a voltage limiting circuit, a bandgap reference and a reference voltage and current output unit, which outputs multiple reference voltages and reference currents with driving capability and high power supply noise suppression ratio, including power supply reference voltages Vvp1 and Vvp2, temperature reference voltages Vtp1, Vtp2, Vtp3 and Vtp4, a bias voltage Vbiasp (generating a bias voltage corresponding to a reference current) and a reference current Iref_2n.

[0046] Reference voltage monitoring module such as Fig. 9 As shown, the reference voltage monitoring module and the Schmitt trigger can be adjusted and designed according to actual needs. Its input terminal receives the reference voltage Vref. When the reference voltage gradually stabilizes and is greater than the flip threshold of the Schmitt trigger, a low-level signal is output. The enable signal En_2 can be obtained through simple logic processing.

[0047] Power supply voltage monitoring module such as Fig.10 As shown, the power supply voltage monitoring module includes: series resistors R1 and R2, comparator Cmp1, and comparator Cmp2. The specific monitoring method is as follows:

[0048] Step 1: The power supply voltage sampling circuit collects the power supply voltage according to a certain ratio to obtain a signal Vin_cmp and sends it to the inverting input terminal of the first comparator Cmp1 and the non-inverting input terminal of the second comparator Cmp2;

[0049] Step 2: The non-inverting input terminal of the first comparator receives the third reference voltage Vvp1, and Vvp1 corresponds to the maximum value of the power supply voltage fluctuation. When the power supply voltage fluctuation is on the high side, i.e., Vin_cmp > Vvp1, the first comparator outputs a low level, causing the third indication signal to be directly set to zero, indicating that other circuits of the system do not start; when Vin_cmp < Vvp1, the first comparator outputs a high level, and Step 4 is performed;

[0050] Step 3, which is actually carried out synchronously with Step 2. The inverting input terminal of the second comparator receives the third reference voltage Vvp2, and Vvp2 corresponds to the minimum value of the power supply voltage fluctuation. When the power supply voltage fluctuation is on the low side, i.e., Vin_cmp < Vvp2, the second comparator outputs a low level, causing the third indication signal to be directly set to zero, indicating that other circuits of the system do not start; when Vin_cmp > Vvp2, the second comparator outputs a high level, and Step 4 is performed;

[0051] Step 4: When both the first comparator and the second comparator output high levels simultaneously, it means that the power supply voltage is within the acceptable voltage range for system operation, causing the third enable signal En_3 to be set to a high level, indicating that other circuit modules of the system can start; conversely, if any one of the comparators outputs a low level, the third enable signal En_3 is set to a low level, indicating that other circuit modules of the system are turned off.

[0052] The temperature monitoring module is as Fig.11 shown. Since the reference current Iref_2n is basically fixed under temperature changes, according to Formulas (4) and (5), the temperature sampling output Vtem exhibits a negative temperature characteristic due to the characteristics of the first pnp transistor Q1. When the temperature rises, the temperature sampling voltage Vtem decreases with the temperature. The monitoring steps are as follows:

[0053] Step 1: When the temperature is higher than the preset maximum value, Vtem will drop below the high-temperature monitoring reference voltage Vtp1. At this time, the comparator Cmp3 detects that the voltage at the non-inverting input terminal is less than that at the inverting input terminal, and the output of the comparator flips, changing from the original high level to a low level. After passing through the fourth AND gate AND4, a low-level fourth indication signal En_4 is directly output. When En_4 is set to a low level, as Figure 1 shown, En_4 will be sent to the LED driver module, indicating that the LED driver module does not start temporarily. En_4 will be sent to the digital controller, and after digital processing, a Sel_vtp signal will be sent out. Sel_vtp controls the switching of the four-bit selection switch SW2 to switch the reference voltage at its input terminal to the potential Vtp2 corresponding to the system restart temperature;

[0054] Step 2: After step 1, the system starts to cool down. When the temperature gradually decreases, the corresponding Vtem will gradually rise. When Vtem>Vtp2, the comparator Cmp3 detects that the voltage at the in-phase input terminal is greater than the inverting input terminal, and the output of the comparator flips again, from the low level during overtemperature to the high level. At this time, the fourth indication signal En_4 is also at a high level (here the third enable signal is assumed to be high, because En_4 is controlled by the output result of Cmp3 only when the third enable signal is high), indicating that the LED driver module is started. At the same time, En_4 will be sent to the digital controller, which will send out the Sel_vtp signal again after digital processing to switch the reference voltage to the potential Vtp1 corresponding to the critical temperature of the system. Here, Vtp3 and Vtp4 are reserved as selectable reference voltage gears to adapt to different temperature ranges.

[0055] The contents not described in detail in this specification belong to the prior art known to the professional and technical personnel in this field. Although the present invention is described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments. Or some of the technical features thereof can be replaced by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. An LED driving device capable of directly regulating current and having power supply monitoring and temperature monitoring functions, characterized in that: It includes an LED driving module, a reference source module, a power supply voltage monitoring module, a temperature monitoring module and a reference voltage monitoring module; wherein, The first enable terminal of the LED driver module is connected to the system enable signal En_start, the second enable terminal is connected to the fourth enable signal En_4, the mode switching control terminal is connected to the mode switching signal En_mode, and the selection control terminal is connected to the selection signal Sel <1> -Sel <n> , the bias voltage input terminal is connected to the bias voltage Vbiasp, and the output terminal is V_Drv;< / n> The reference source module enable terminal is connected to the system enable signal En_start, and the output terminal is the reference voltage Vref, the power reference voltage Vvp1 and Vvp2, the temperature reference voltage Vtp1, Vtp2, Vtp3 and Vtp4, the bias voltage Vbiasp, and the reference current Iref_2n; wherein, Vtp1 <Vtp2<Vtp3<Vtp4; The input terminal of the reference voltage monitoring module is connected to Vref, and the output terminal is the enable signal En_2; The first enable terminal of the power supply voltage monitoring module is connected to the system enable signal En_start, the second enable terminal is connected to the second enable signal En_2, the reference voltage input terminal 1 is connected to Vvp1, the reference voltage input terminal 2 is connected to Vvp2, and the output terminal is the third enable signal En_3; The first enable terminal of the temperature monitoring module is connected to the system enable signal En_start, the third enable terminal is connected to the enable signal En_3, the reference voltage input terminal is connected to the temperature reference voltages Vtp1, Vtp2, Vtp3 and Vtp4, the reference current input terminal is connected to the reference current Iref_2n, the reference voltage selection terminal is connected to the selection signal Sel_vtp, and the output terminal is the fourth enable signal En_4; The working mode of the LED driving device is as follows: The reference source module is started according to the input system enable signal En_start, and the reference voltage monitoring module is started at the same time. When the reference voltage Vref reaches the expected value, the reference voltage monitoring module detects this signal and outputs a second enable signal En_2; According to the input system enable signal En_start and the second enable signal En_2, the power supply voltage monitoring module is started to monitor whether the power supply voltage is within the expected voltage range, and a third enable signal En_3 is output; According to the input system enable signal En_start and the third enable signal En_3, the temperature monitoring module is started, the system temperature is monitored, and the fourth enable signal En_4 is output and sent to the digital controller; at this time, if the temperature is within the normal range, En_4 instructs the LED driver module to start, and the digital controller does not perform any operation; if the temperature is too high, En_4 will instruct the LED driver module not to start temporarily, and the digital controller will output the temperature reference voltage selection signal Sel_vtp accordingly after receiving the over-temperature enable signal En_4, and increase the reference voltage of the temperature monitoring module by one gear. Since the temperature sampling voltage signal Vtem is negatively correlated with the temperature, the enable signal for starting the LED driver module will be given only when the temperature is lower than the set restart temperature; According to the system enable signal En_start and the fourth enable signal En_4, when the reference voltage is stable, the power supply voltage is stable and the temperature is normal, the LED driver module is started to supply power to the LED; when the LED load is switched from heavy load to light load or no load, the mode switching enable signal En_mode is used to start the response current mirror to provide current to the output end to maintain the voltage stability and fast response of the output end.

2. The LED driving device capable of directly regulating current and having power supply monitoring and temperature monitoring functions according to claim 1, characterized in that: The LED driving module includes: a logic AND gate AND1, whose input terminal 1 is connected to the system enable signal En_start, whose input terminal 2 is connected to the fourth indication signal En_4, and whose output terminal is connected to the fifth enable signal En_5; a main current mirror array, whose enable terminal is connected to En_5, whose power terminal is connected to the system voltage Vin, whose input terminal is connected to the bias voltage Vbiasp, whose output control current is Ictrl, whose output point voltage is Vctrl, and whose Ictrl is controlled by the selection signal Sel<1:n>; a slave current mirror, including two matched n-type transistors nm2 and nm3, wherein the size ratio of nm2 and nm3 is 1:m, and which share the gate voltage Vctrl, and which control the current Ictrl flows into nm2 and is amplified m times by nm3 to generate a driving current I_Drv to drive the LED; the amplifier AMP1, its positive input terminal is connected to the driving output point potential V_Drv and the drain of nm3, the negative input terminal is connected to the source of nm1 VSnm1 and the drain of nm2, the output terminal is connected to the gate of nm1 VGnm1, and the drain of nm1 is connected to the voltage Vctrl; the response current mirror array, the power supply terminal is connected to Vin, the input terminal is connected to Vbiasp, the enable terminal is connected to En_5 and the mode switching enable signal En_mode, the output current is Istart, which is injected into the current mirror through the switch tube nm4, and the gate of nm4 is connected to En_mode.

3. The LED driving device capable of directly regulating current and having power supply monitoring and temperature monitoring functions according to claim 2, characterized in that: The main current mirror array includes: pmos switch tubes S0-Sn, whose sources are connected to the system voltage Vin, the input end of the inverter INV1 is connected to the fifth enable signal En_5, and the output end is connected to the gate of S0, and the gates of S1-Sn are respectively connected to the selection signal Sel <1> -Sel <n> ; pmos current mirror tubes PM0-PMn, whose sources are respectively connected to the drains of S0-Sn, whose gates are short-connected to the bias voltage Vbiasp, whose drains are short-connected to Vctrl and output the control current Ictrl.< / n> 4. The LED driving device capable of directly regulating current and having power supply monitoring and temperature monitoring functions according to claim 1, characterized in that: The response current mirror includes: a logic NAND gate NAND1, whose input terminal 1 is connected to a mode switching enable signal, whose input terminal 1 is connected to a fifth enable signal En_5, and whose output terminal is connected to the gate of the switch tube Sa; whose source is connected to a system voltage Vin, and whose drain is connected to the source of a pmos current mirror tube PMa; whose size is 100 times that of PM0, whose gate is connected to a bias voltage Vbisp, and whose drain outputs a response current Istart.

5. The LED driving device capable of directly regulating current and having power supply monitoring and temperature monitoring functions according to claim 1, characterized in that: The reference source module includes: a voltage limiting circuit, whose power supply terminal is connected to the system voltage Vin, whose enable terminal is connected to the system enable signal En_start, and whose output is the internal power supply Vclip to supply power to the bandgap reference; a bandgap reference, whose power supply terminal is connected to Vclip and whose enable terminal is connected to En_start, and whose output is the reference voltage Vref; a reference voltage current output unit, whose input terminal is connected to Vref and outputs multiple reference voltage currents, including the power supply reference voltages Vvp1 and Vvp2, the temperature reference voltages Vtp1, Vtp2, Vtp3, and Vtp4, where Vtp1 < Vtp2 < Vtp3 < Vtp4, the bias voltage Vbiasp, and the reference current Iref_2n.

6. The LED driving device capable of directly regulating current and having power supply monitoring and temperature monitoring functions according to claim 1, characterized in that: The reference voltage monitoring module includes a Schmitt trigger, whose input terminal is connected to the monitoring reference voltage Vref, and whose output terminal is connected to the input terminal of the inverter INV2, and the output of INV2 is the second enable signal En_2.

7. The LED driving device capable of directly regulating current and having power supply monitoring and temperature monitoring functions according to claim 1, characterized in that: The power supply voltage monitoring module includes: series resistors R1 and R2 connected between the system voltage Vin and the ground, and the divided voltage potential is Vin_fb; the positive input terminal of the comparator Cmp1 is connected to the power supply reference voltage Vvp1, the negative input terminal is connected to Vin_fb, and after comparing the magnitudes of Vin_fb and Vvp1, Cmp_out1 is output; the negative input terminal of the comparator Cmp2 is connected to the power supply reference voltage Vvp2, the positive input terminal is connected to Vin_fb, and after comparing the magnitudes of Vin_fb and Vvp2, Cmp_out2 is output; the two input terminals of the logic AND gate AND2 are respectively connected to the outputs Cmp_out1 and Cmp_out2 of Cmp1 and Cmp2; the two input terminals of the logic AND gate AND3 are respectively connected to the system enable signal En_start and the second enable signal En_2, and the two input terminals of the logic AND gate AND4 are respectively connected to the outputs of AND2 and AND3, and the third enable signal En_3 is output by AND4.

8. The LED driving device capable of directly regulating current and having power supply monitoring and temperature monitoring functions according to claim 1, characterized in that: The temperature monitoring module includes: an n-type MOS switch tube SW1, whose gate is connected to the system enable signal En_start, whose drain receives the reference current Iref_2n, and whose source is connected to the emitter of the pnp-type triode Q1 and serves as the temperature sampling voltage signal Vtem; the base and collector of Q1 are shorted together and connected to the ground potential; a four-bit selection switch SW2, whose control terminal is connected to the output Sel_vtp of the digital controller, whose four input terminals are respectively connected to the temperature reference voltages Vtp1, Vtp2, Vtp3, and Vtp4, and whose output terminal is connected to the negative input terminal of the comparator Cmp3, and the positive input terminal of the comparator Cmp3 is connected to Vtem; a logic AND gate AND5, whose two input terminals are respectively connected to the output terminal of Cmp3 and the third enable signal En_3.

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