LED drive circuit, backlight system and electronic equipment

Abstract

The utility model provides an LED driving circuit, a backlight system and an electronic device, wherein a first end of a voltage conversion module of the circuit receives an input voltage, and a second end thereof is connected to an anode of an LED through a first switch tube or a current detection module; wherein when the voltage conversion module is coupled to the anode of the LED through the current detection module, the current detection module can detect the magnitude of a current flowing through the LED, and the control module controls the magnitude of a voltage output by the voltage conversion module to match the voltage required by the LED according to the magnitude of the current flowing through the LED and an LED characteristic lookup table; when the voltage conversion module is coupled to the anode of the LED through the first switch tube, the power consumption can be reduced due to the small impedance of the first switch tube.

Description

Technical Field

[0001] The utility model relates to the field of display technology, in particular to an LED drive circuit, a backlight system and an electronic device. Background Art

[0002] LED is a current-type working device. In order to ensure the stability of the light output of the LED, the current flowing through the LED must be stable.

[0003] In the current LED driving circuit, a bipolar junction transistor (BJT) can be used as a regulating tube, which forms a constant current source with the detection sampling resistor to power the LED light string (such as Figure 1 As shown), a constant current source can also be formed based on an operational amplifier (op-amp), a detection sampling resistor and an adjustment tube to power the LED light string (as shown Figure 2 However, since the detection sampling resistor and the adjustment tube are connected in series with the LED light string, additional power consumption is caused during the LED operation process. At the same time, in order to maintain the current flowing through the LED path unchanged, the impedance of the adjustment tube will increase accordingly, which increases the impedance in the LED path and makes it difficult to improve the working efficiency of the driving circuit.

[0004] Therefore, how to reduce the impedance in the LED path, improve the working efficiency of the driving circuit, and accurately provide the matching driving current for the LED has become a technical problem that the industry urgently needs to solve. Utility Model Content

[0005] The utility model provides an LED driving circuit, a backlight system and an electronic device to solve the problem of how to reduce the impedance in the LED path, improve the working efficiency of the driving circuit, and accurately provide a matching driving current for the LED.

[0006] According to a first aspect of the utility model, there is provided an LED driving circuit, comprising: a voltage conversion module, a first switch tube, an LED, a current detection module and a control module;

[0007] The first end of the voltage conversion module receives an input voltage, and the second end thereof is respectively coupled to the first end of the first switch tube and the first end of the current detection module, the second end of the first switch tube and the second end of the current detection module are both coupled to the anode of the LED, and the control end of the first switch tube receives a switch control signal; the output end of the current detection module is coupled to the input end of the control module, and the output end of the control module is coupled to the control end of the voltage conversion module.

[0008] Optionally, the on and off of the first switch tube is controlled by the switch control signal;

[0009] The current detection module is configured as follows:

[0010] When the first switch tube is turned off, the current detection module is controlled to be in a working state, so that the second end of the voltage conversion module is coupled to the anode of the LED through the current detection module to detect the magnitude of the current flowing through the LED;

[0011] When the first switch tube is turned on, the current detection module is controlled to be in an open circuit state, so that the second end of the voltage conversion module is coupled to the anode of the LED through the first switch tube;

[0012] The control module is configured to:

[0013] When the first switch tube is turned off, the voltage output by the voltage conversion module is controlled to match the voltage required by the LED according to the current flowing through the LED and the LED characteristic lookup table.

[0014] Optionally, the LED characteristic lookup table includes the corresponding relationship between the junction temperature, forward current and forward voltage of the LED.

[0015] Optionally, the current detection module includes a detection resistor, a second switch and a current detection unit;

[0016] The first end of the second switch is coupled to the second end of the voltage conversion module, the second end of the second switch is coupled to the first end of the detection resistor, and the second end of the detection resistor is coupled to the anode of the LED;

[0017] The first input terminal of the current detection unit is coupled to the first terminal of the detection resistor, the second input terminal thereof is coupled to the second terminal of the detection resistor, and the output terminal thereof outputs a first signal; wherein the first signal includes information on the magnitude of the current flowing through the LED.

[0018] Optionally, the resistance value of the detection resistor matches the on-resistance of the first switch tube.

[0019] Optionally, the voltage conversion module includes an AC / DC converter or a DC / DC converter.

[0020] Optionally, a digital-to-analog converter is also included;

[0021] The output end of the control module is coupled to the control end of the voltage conversion module through the digital-to-analog converter.

[0022] According to a second aspect of the present invention, a backlight system is provided, comprising the LED driving circuit as described in any one of the first aspects of the present invention.

[0023] According to a third aspect of the present utility model, an electronic device is provided, comprising the LED driving circuit as described in any one of the first aspects of the present utility model.

[0024] In the LED driving circuit, backlight system and electronic device provided by the utility model, the first end of the voltage conversion module of the circuit receives the input voltage, and the second end thereof is connected to the anode of the LED through the first switch tube or the current detection module; wherein, when the voltage conversion module is coupled to the anode of the LED through the current detection module, the current detection module can detect the magnitude of the current flowing through the LED, and the control module controls the magnitude of the voltage output by the voltage conversion module to match the voltage required by the LED according to the magnitude of the current flowing through the LED and the LED characteristic lookup table; when the voltage conversion module is coupled to the anode of the LED through the first switch tube, the power consumption can be reduced due to the small impedance of the first switch tube. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the embodiments of the utility model or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the utility model. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0026] Figure 1 It is a structural schematic diagram of an LED driving circuit in an embodiment of the prior art;

[0027] Figure 2 is a structural schematic diagram of an LED driving circuit in another embodiment of the prior art;

[0028] Figure 3 This is a schematic diagram of the structure of an LED driving circuit in one embodiment of the utility model;

[0029] Figure 4 This is a schematic diagram of an LED characteristic lookup table in an embodiment of the present invention. Figure 1 ;

[0030] Figure 5 This is a schematic diagram of an LED characteristic lookup table in an embodiment of the present invention. Figure 2 ;

[0031] Figure 6 This is a schematic diagram of the structure of an LED driving circuit in another embodiment of the utility model;

[0032] Figure 7 It is a structural schematic diagram of an LED driving circuit in another embodiment of the utility model;

[0033] Figure 8It is a flow chart of an LED driving method in one embodiment of the utility model.

[0034] Description of reference numerals:

[0035] 10- voltage conversion module;

[0036] 20-current detection module;

[0037] 30- control module;

[0038] Vbkl-input voltage;

[0039] Q1-first switch tube;

[0040] Q2-second switch;

[0041] R1- detection resistor;

[0042] 201-current detection unit;

[0043] 40-Digital to analog converter. DETAILED DESCRIPTION

[0044] The following will be combined with the drawings in the embodiments of the utility model to clearly and completely describe the technical solutions in the embodiments of the utility model. Obviously, the described embodiments are only part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments in the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.

[0045] The terms "first", "second", "third", "fourth", etc. (if any) in the specification and claims of the present utility model and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the utility model described here can be implemented in an order other than those illustrated or described here. In addition, the terms "including" and "having" and any of their variations are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0046] The following specific embodiments are used to describe the technical solution of the utility model in detail. The following specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described in detail in some embodiments.

[0047] In view of the fact that it is difficult to reduce the impedance in the LED path, improve the working efficiency of the driving circuit, and accurately provide the LED with a matching driving current in the prior art, the utility model provides an LED driving circuit, a backlight system and an electronic device, wherein the first end of the voltage conversion module of the circuit receives an input voltage, and the second end thereof is connected to the anode of the LED through a first switch tube or a current detection module; wherein, when the voltage conversion module is coupled to the anode of the LED through the current detection module, the current detection module can detect the magnitude of the current flowing through the LED, and the control module controls the magnitude of the voltage output by the voltage conversion module to match the voltage required by the LED according to the magnitude of the current flowing through the LED and the LED characteristic lookup table; when the voltage conversion module is coupled to the anode of the LED through the first switch tube, the power consumption of the circuit can be reduced due to the small impedance of the first switch tube.

[0048] The solution of the utility model is specifically described as follows:

[0049] Please refer to Figure 3 The embodiment of the utility model provides an LED driving circuit, including: a voltage conversion module 10, a first switch tube Q1, an LED, a current detection module 20 and a control module 30;

[0050] The first end of the voltage conversion module 10 receives the input voltage Vbkl, and the second end thereof is respectively coupled to the first end of the first switch tube Q1 and the first end of the current detection module 20, the second end of the first switch tube Q1 and the second end of the current detection module 20 are both coupled to the anode of the LED, and the control end of the first switch tube Q1 receives a switch control signal; the output end of the current detection module 20 is coupled to the input end of the control module 30, and the output end of the control module 30 is coupled to the control end of the voltage conversion module 10.

[0051] exist Figure 3 In the example, the cathode of the LED is grounded. In actual applications, the cathode of the LED may also be connected to other circuits, and the present invention does not limit this.

[0052] in:

[0053] The on and off of the first switch tube Q1 is controlled by the switch control signal;

[0054] The current detection module 20 is configured as follows:

[0055] When the first switch tube Q1 is turned off, the current detection module 20 is controlled to be in a working state, so that the second end of the voltage conversion module 10 is coupled to the anode of the LED through the current detection module 20 to detect the magnitude of the current flowing through the LED;

[0056] When the first switch tube Q1 is turned on, the current detection module 20 is controlled to be in an open circuit state, so that the second end of the voltage conversion module 10 is coupled to the anode of the LED through the first switch tube Q1;

[0057] The control module 30 is configured as follows:

[0058] When the first switch tube Q1 is turned off, the voltage output by the voltage conversion module 10 is controlled to match the voltage required by the LED according to the current flowing through the LED and the LED characteristic lookup table.

[0059] Therefore, the utility model can ensure that the path where the LED is located has resistance loss only when the second end of the voltage conversion module 10 is coupled to the anode of the LED through the current detection module 20. When the second end of the voltage conversion module 10 is coupled to the anode of the LED through the first switch tube Q1, and the first switch tube Q1 is in a saturated conduction state at this time, the conduction impedance of the path where the LED is located is very low, so that the voltage output by the voltage conversion module 10 is used to drive the LED, and the additional power consumption generated is very small. Compared with the traditional constant current source drive circuit, the time that the detection resistor R1 is connected in series in the LED path is reduced, and its power consumption is greatly reduced, thereby improving the working efficiency of the LED drive circuit.

[0060] In a specific implementation manner, the first switch tube Q1 is a MOS tube. Figure 3 In the example, the MOS tube is an NMOS tube. Of course, the utility model is not limited to this, and it can also be a triode, etc. Those skilled in the art can select a suitable switch type as needed.

[0061] As an example, see Figure 4 as well as Figure 5 , the LED characteristic lookup table should include the corresponding relationship between the junction temperature, forward current and forward voltage of the LED, and for the same LED, the corresponding relationship between the junction temperature, forward current and forward voltage is unique. In practical applications, the required driving voltage can also be selected according to the LED characteristic lookup table and used as the initial output voltage of the voltage conversion module 10. Due to the discreteness of the LED itself and various fluctuations in the actual application circuit, the current flowing through the LED may deviate from the target value, so the current detection module 20 is also required to detect it.

[0062] In one implementation, please refer to Figure 6 , the current detection module 20 includes a detection resistor R1, a second switch Q2 and a current detection unit 201;

[0063] A first end of the second switch Q2 is coupled to a second end of the voltage conversion module 10, a second end of the second switch Q2 is coupled to a first end of the detection resistor R1, and a second end of the detection resistor R1 is coupled to an anode of the LED;

[0064] The first input terminal of the current detection unit 201 is coupled to the first terminal of the detection resistor R1, the second input terminal thereof is coupled to the second terminal of the detection resistor R1, and the output terminal thereof outputs a first signal; wherein the first signal includes information about the current flowing through the LED.

[0065] The current detection unit 201 can obtain the current value flowing through the LED by detecting the voltage across the detection resistor R1. Figure 6 In the example, the output end of the current detection unit 201 is coupled to the input end of the control module 30. In a specific implementation, a differential operational amplifier can be used to detect the current flowing through the detection resistor R1, and the output end of the differential operational amplifier is coupled to the input end of the control module 30.

[0066] In a preferred embodiment, the resistance value of the detection resistor R1 can also be controlled to match the on-resistance of the first switch tube Q1, so as to avoid changes in the voltage received by the anode of the LED when the first switch tube Q1 is turned on.

[0067] Regarding the voltage conversion module 10, in one implementation, it may be an AC / DC converter or a DC / DC converter.

[0068] In this case, please refer to Figure 7 , the LED driving circuit further includes a digital-to-analog converter 40;

[0069] The output terminal of the control module 30 is coupled to the control terminal of the voltage conversion module 10 through the digital-to-analog converter 40 .

[0070] Taking the voltage conversion module 10 as an AC / DC converter as an example, in actual applications, the output end of the control module 30 can reduce or increase the duty cycle of the primary output voltage of the AC / DC converter through the digital-to-analog converter 40, thereby reducing or increasing the voltage output by the voltage conversion module 10.

[0071] In addition, the present invention also provides a method for driving an LED. Figures 3 to 7 The LED driving circuit of any embodiment shown in the figure is controlled to provide a stable driving current to the LED, and the control method comprises the following steps:

[0072] According to the working state of the first switch tube Q1, a driving current is provided to the LED, wherein:

[0073] If the first switch tube Q1 is turned off, the following steps are performed:

[0074] Control the current detection module 20 to be in a working state, so that the second end of the voltage conversion module 10 is coupled to the anode of the LED through the current detection module 20 to detect the magnitude of the current flowing through the LED;

[0075] According to the magnitude of the current flowing through the LED and the LED characteristic lookup table, the output voltage of the voltage conversion module 10 is controlled to match the voltage required by the LED;

[0076] If the first switch tube Q1 is turned on, the following steps are performed:

[0077] The current detection module 20 is controlled to be in an open circuit state, so that the second end of the voltage conversion module 10 is coupled to the anode of the LED through the first switch tube Q1.

[0078] As a specific implementation, please refer to Figure 8 In actual use, the LED driving method provided by the embodiment of the utility model is used for Figure 1 The LED driving circuit shown is controlled, including the following steps:

[0079] S51: Power on;

[0080] After power-on, the LED driving circuit works normally;

[0081] S52: Control the first switch tube Q1 to be turned off, and control the current detection module 20 to be in a working state to detect the magnitude of the current flowing through the LED;

[0082] Wherein, step S52 can be understood as: controlling the current detection module 20 to be in a working state, so that the second end of the voltage conversion module 10 is coupled to the anode of the LED through the current detection module 20 to detect the magnitude of the current flowing through the LED and obtain the first driving current value;

[0083] S53: Determine the voltage value that needs to be adjusted by the voltage conversion module 10 according to the magnitude of the current flowing through the LED and the LED characteristic lookup table;

[0084] Specifically, when the first switch tube Q1 is turned off, the driving voltage required by the corresponding LED is selected through the LED characteristic lookup table, and the control module 30 calculates the voltage value of the driving voltage and the difference between the first driving current value, determines the voltage value that the voltage conversion module 10 needs to adjust, and controls the voltage output by the voltage conversion module 10 to match the voltage required by the LED.

[0085] S54: Control the output voltage of the voltage conversion module 10 to match the voltage required by the LED;

[0086] S55: Control the first switch tube Q1 to be turned on, and control the current detection module 20 to be in an open circuit state;

[0087] Specifically, the second end of the voltage conversion module 10 is coupled to the anode of the LED through the first switch tube Q1.

[0088] In actual work, the current flowing through the LED can also be periodically detected and dynamically corrected according to the LED characteristic lookup table. In a specific implementation, step S55 also includes: returning to step S52 after a set time.

[0089] In addition, the embodiment of the utility model further provides a backlight system, including the above-mentioned LED driving circuit. As an example, the system is a TV backlight system, a display screen backlight system, and of course it can also be other LED systems that need to display.

[0090] In addition, the embodiment of the utility model further provides an electronic device, including the above-mentioned backlight system. As an example, the electronic device can be a mobile phone, a tablet, a computer, etc., and of course it can also be other devices that need to display.

[0091] In summary, the utility model receives an input voltage through the first end of the voltage conversion module, and the second end thereof is connected to the anode of the LED through the first switch tube or the current detection module; wherein, when the voltage conversion module is coupled to the anode of the LED through the current detection module, the current detection module can detect the magnitude of the current flowing through the LED, and the control module controls the magnitude of the voltage output by the voltage conversion module to match the voltage required by the LED according to the magnitude of the current flowing through the LED and the LED characteristic lookup table; when the voltage conversion module is coupled to the anode of the LED through the first switch tube, the power consumption can be reduced due to the small impedance of the first switch tube.

[0092] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the utility model, rather than to limit it. Although the utility model has been described in detail with reference to the aforementioned embodiments, ordinary technicians in this field should understand that they can still modify the technical solutions recorded in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not make the essence of the corresponding technical solution deviate from the scope of the technical solution of the embodiments of the utility model.

Claims

1. An LED driving circuit, characterized in that: include: A voltage conversion module, a first switch tube, an LED, a current detection module and a control module; The first end of the voltage conversion module receives an input voltage, and the second end thereof is respectively coupled to the first end of the first switch tube and the first end of the current detection module, the second end of the first switch tube and the second end of the current detection module are both coupled to the anode of the LED, and the control end of the first switch tube receives a switch control signal; the output end of the current detection module is coupled to the input end of the control module, and the output end of the control module is coupled to the control end of the voltage conversion module; The current detection module includes a detection resistor, a second switch and a current detection unit; The first end of the second switch is coupled to the second end of the voltage conversion module, the second end of the second switch is coupled to the first end of the detection resistor, and the second end of the detection resistor is coupled to the anode of the LED; The first input terminal of the current detection unit is coupled to the first terminal of the detection resistor, the second input terminal thereof is coupled to the second terminal of the detection resistor, and the output terminal thereof outputs a first signal; wherein the first signal includes information on the magnitude of the current flowing through the LED; Wherein, the on and off of the first switch tube is controlled by the switch control signal; The current detection module is configured as follows: When the first switch tube is turned off, the current detection module is controlled to be in a working state, so that the second end of the voltage conversion module is coupled to the anode of the LED through the current detection module to detect the magnitude of the current flowing through the LED; When the first switch tube is turned on, the current detection module is controlled to be in an open circuit state, so that the second end of the voltage conversion module is coupled to the anode of the LED through the first switch tube; The control module is configured to: When the first switch tube is turned off, the voltage output by the voltage conversion module is controlled to match the voltage required by the LED according to the current flowing through the LED and the LED characteristic lookup table.

2. The LED driving circuit according to claim 1, characterized in that: The resistance value of the detection resistor matches the on-resistance of the first switch tube.

3. The LED driving circuit according to claim 1, characterized in that: The voltage conversion module includes an AC / DC converter or a DC / DC converter.

4. The LED driving circuit according to claim 3, characterized in that: Also included is a digital-to-analog converter; The output end of the control module is coupled to the control end of the voltage conversion module through the digital-to-analog converter.

5. A backlight system, characterized in that: The LED driving circuit comprises the LED driving circuit according to any one of claims 1 to 4.

6. An electronic device, characterized in that: The LED driving circuit comprises the LED driving circuit according to any one of claims 1 to 4.

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