Switch control circuit, bias current generating circuit, LED driving circuit and method

Abstract

The embodiments of the present application provide a switch control circuit, a bias current generating circuit, an LED driving circuit and a method. The signal input terminal of the switch control circuit is connected to the signal detection terminal in the port constant current operational amplifier loop, and the control terminal of the switch control circuit is connected to the controlled terminal in the bias current generating circuit; the switch control circuit is used to output a shock pulse to control the opening and closing of the switch element used to control the generation of the shock current in the bias current generating circuit, and the shock current is used to control the port constant current operational amplifier loop. The shock pulse is controlled by the comparison result between the port sampling current and the preset reference current, and the port sampling current is determined by sampling the port constant current in the port constant current operational amplifier loop. The present application is used to solve the problem of low gray display on the LED display screen caused by inconsistent port dynamic response within and between constant current LED driver chips in the prior art.

Description

Technical Field

[0001] The present application relates to the field of LED driving technology. Specifically, the present application relates to a switch control circuit, a bias current generating circuit, an LED driving circuit and a method. Background Art

[0002] Traditional multi-channel constant-current LED driver chips typically use PWM (Pulse Width Modulation) for display control. With the continuous advancement of display technology, the requirements for display screens are becoming increasingly stringent. To meet the demand for consistent low-grayscale display at high grayscale levels, the dynamic response speed of the port is particularly important for low-grayscale display, as the smaller the PWM on-width, the greater the impact of the port constant current value on the dynamic response speed.

[0003] Currently, LED display driver circuits typically use surge circuits to improve port response speed. However, these conventional surge circuits are significantly affected by process, temperature, and application conditions, and can easily lead to inconsistent dynamic response of ports within and between chips. Furthermore, these inconsistent dynamic response of ports can cause display issues such as low-gray blocks on LED displays. Summary of the Invention

[0004] In response to the shortcomings of existing methods, this application proposes a switch control circuit, a bias current generating circuit, an LED driving circuit and a method to solve the problem of low gray display on LED display screens caused by inconsistent dynamic response of ports within and between constant current LED driver chips in the existing technology.

[0005] In a first aspect, an embodiment of the present application provides a switch control circuit, wherein a signal input terminal of the switch control circuit is connected to a signal detection terminal in a port constant current operational amplifier loop, and a control terminal of the switch control circuit is connected to a controlled terminal in a bias current generating circuit;

[0006] The switch control circuit is used to output a surge pulse to control the opening and closing of a switch element in the bias current generating circuit for controlling the generation of surge current. The surge current is used to control the port constant current operational amplifier loop. The surge pulse is controlled by a comparison result between a port sampling current and a preset reference current. The port sampling current is determined by sampling the port constant current in the port constant current operational amplifier loop.

[0007] In some embodiments, the switch control circuit includes a current comparator;

[0008] The current comparator includes: a reference current module, a port current sampling module and a control module;

[0009] The first end of the control module is connected to the reference current module and the controlled end of the bias current generating circuit respectively, and the port current sampling module is connected to the second end of the control module and the signal detection end of the port constant current operational amplifier loop respectively;

[0010] The reference current module is used to generate the reference current;

[0011] The port current sampling module is used to generate the port sampling current;

[0012] The control module is used to compare the port sampling current with the reference current, and output the impact pulse according to the comparison result.

[0013] In some embodiments, the control module includes:

[0014] A port sampling switch tube, whose size is 1 / k of the size of the port switch tube in the port constant current operational amplifier loop, where k is the sampling ratio; whose drain is connected to the first end of the control module, whose source is connected to the second end of the control module, and whose gate is connected to the control end of the port switch tube.

[0015] In some embodiments, the control module operates:

[0016] When the port sampling current is less than the reference current, a first impulse pulse is output to control the switch element to close;

[0017] When the port sampling current is greater than or equal to the reference current, a second impulse pulse is output to control the switch element to open.

[0018] In some embodiments, the switch control circuit further includes:

[0019] A buffer is connected between the output terminal of the current comparator and the controlled terminal of the bias current generating circuit.

[0020] In some embodiments, the current comparator further includes:

[0021] A controllable switch is connected between the reference current module and the first end of the control module, and is used to open or close under the control of the current detection signal of the port constant current.

[0022] In a second aspect, an embodiment of the present application provides a bias current generating circuit, wherein a controlled end of the bias current generating circuit is connected to the control end of the switch control circuit as described in the above embodiment, and an output end of the bias current generating circuit is connected to the input end of the port constant current operational amplifier loop;

[0023] The bias current generating circuit comprises:

[0024] A surge current source, used to generate surge current;

[0025] A switching element is connected between the impulse current source and the ground, and is used to open or close under the control of the impulse pulse output by the switch control circuit, so as to provide a constant current operational amplifier bias current containing the impulse current to the port constant current operational amplifier loop.

[0026] In some embodiments, it further includes:

[0027] Port bias current source, used to generate bias current;

[0028] A first control device, having an input terminal connected to the first current source; a port bias current source connected between an output terminal and ground; a branch formed by the series connection of the surge current source and the switch element connected in parallel to both ends of the port bias current source; and a control terminal connected to the output terminal;

[0029] A second control device, whose input end is connected to the second current source; whose control end is connected to the control end of the first control device; and whose output end is connected to the input end of the port constant current op amp loop, is used to output the constant current op amp bias current to the port constant current op amp loop, and the constant current op amp bias current includes the bias current.

[0030] In a third aspect, an embodiment of the present application provides an LED driving circuit, comprising: the switch control circuit as described in the above embodiment, the bias current generating circuit as described in the above embodiment, and the port constant current operational amplifier loop;

[0031] The signal input end of the switch control circuit is connected to the signal detection end of the port constant current operational amplifier loop, the control end of the switch control circuit is connected to the controlled end of the bias current generating circuit, and the output end of the bias current generating circuit is connected to the input end of the port constant current operational amplifier loop.

[0032] In a fourth aspect, an embodiment of the present application provides a switch control method applicable to the switch control circuit as described in the above embodiment, the method comprising:

[0033] Acquire a port constant current in a port constant current operational amplifier loop, and sample the port constant current to determine a port sampling current;

[0034] The port sampling current is compared with the preset reference current, and a surge pulse is output according to the comparison result to control the opening and closing of a switching element in a bias current generating circuit for controlling the generation of surge current. The surge current is used to control the port constant current operational amplifier loop.

[0035] Compared to the prior art, the switch control circuit and switch control method provided in the embodiments of the present application have the following technical effects:

[0036] The signal input terminal of the switch control circuit is connected to the signal detection terminal in the port constant current operational amplifier loop, and the control terminal of the switch control circuit is connected to the controlled terminal in the bias current generating circuit; the switch control circuit is used to output a surge pulse to control the opening and closing of a switch element in the bias current generating circuit for controlling surge current generation, the surge current being used to control the port constant current operational amplifier loop, the surge pulse being controlled by a comparison result between a port sampling current and a preset reference current, the port sampling current being determined by sampling the port constant current in the port constant current operational amplifier loop. In this way, the surge pulse generated by the present application is only related to the port constant current, so that the surge current is generated by the surge pulse and the surge current source, and is less affected by process, temperature, and power supply voltage. Therefore, the port dynamic response is less affected by process, temperature, power supply voltage, and other application conditions, so that the problem of low gray display on the LED display screen caused by inconsistent port dynamic response within and between constant current LED driver chips in the prior art can be solved without changing the port constant current operational amplifier loop, thereby improving the consistency of low gray display and achieving the purpose of higher image restoration of the LED display screen. At the same time, the pulse width of the inrush current can be adaptively adjusted according to the port constant current to meet application requirements within the port constant current range.

[0037] Furthermore, by applying an additional large current pulse (i.e., the above-mentioned impact current) to the bias current when the port constant current is turned on, the response speed of the port constant current op amp loop is improved, thereby improving the turn-on response speed of the port switch tube and the port response speed, which can meet the requirements of high grayscale levels.

[0038] The bias current generating circuit provided in the embodiment of the present application has the following technical effects:

[0039] The controlled end of the bias current generating circuit is connected to the control end of the switch control circuit as described in the above embodiment, and the output end of the bias current generating circuit is connected to the input end of the port constant current operational amplifier loop; the bias current generating circuit includes: an impact current source for generating an impact current; a switch element, connected between the impact current source and the ground, for opening or closing under the control of the impact pulse output by the switch control circuit, so as to provide the port constant current operational amplifier loop with a constant current operational amplifier bias current containing the impact current. In this way, the impact current generated by the present application is less affected by the process, temperature, and power supply voltage, and has the characteristics of high precision, so that the port dynamic response is less affected by the process, temperature, power supply voltage and other application conditions, and can solve the problem of low gray display on the LED display screen caused by inconsistent port dynamic response within and between constant current LED driver chips in the prior art, thereby improving the consistency of low gray display on the LED display screen.

[0040] The LED driving circuit provided in the embodiment of the present application has the following technical effects:

[0041] The LED driver circuit includes: a switch control circuit as described in the above embodiment, a bias current generating circuit as described in the above embodiment, and a port constant current operational amplifier loop; the signal input terminal of the switch control circuit is connected to the signal detection terminal of the port constant current operational amplifier loop, the control terminal of the switch control circuit is connected to the controlled terminal of the bias current generating circuit, and the output terminal of the bias current generating circuit is connected to the input terminal of the port constant current operational amplifier loop. In this way, the above-mentioned impact current is applied to the bias current when the port constant current is turned on without changing the port constant current operational amplifier loop. This impact current is less affected by process, temperature, and power supply voltage, can achieve consistency of port response, improve the response speed of the port constant current operational amplifier loop, and thus improve the port response speed, which can meet the requirements of high grayscale levels.

[0042] Additional aspects and advantages of the present application will be given in part in the following description, which will become apparent from the following description, or will be learned through practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] The above and / or additional aspects and advantages of the present application will become apparent and easily understood from the following description of the embodiments in conjunction with the accompanying drawings, in which:

[0044] Figure 1 A schematic diagram of the structure of a switch control circuit provided in an embodiment of the present application;

[0045] Figure 2 A schematic diagram of the structure of a port constant current operational amplifier loop provided in an embodiment of the present application;

[0046] Figure 3 A schematic structural diagram of a bias current generating circuit provided in an embodiment of the present application;

[0047] Figure 4 A schematic diagram of the structure of an LED driving circuit provided in an embodiment of the present application;

[0048] Figure 5 A schematic flow chart of a switch control method provided in an embodiment of the present application. DETAILED DESCRIPTION

[0049] The present application is described in detail below. Examples of embodiments of the present application are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar components or components having the same or similar functions. In addition, if the detailed description of the known technology is not necessary for the features of the present application shown, it will be omitted. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present application and are not to be construed as limiting the present application.

[0050] Those skilled in the art will understand that, unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by those skilled in the art to which this application belongs. It should also be understood that terms such as those defined in common dictionaries should be understood to have meanings consistent with their meanings in the context of the prior art and, unless specifically defined as such, will not be interpreted in an idealized or overly formal sense.

[0051] It will be understood by those skilled in the art that, unless expressly stated otherwise, the singular forms "a", "an", "said" and "the" used herein may also include the plural forms. It should be further understood that the term "comprising" used in the specification of the present application refers to the presence of the features, integers, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or groups thereof. It should be understood that when we refer to an element as being "connected" or "coupled" to another element, it may be directly connected or coupled to the other element, or there may be intermediate elements. In addition, "connected" or "coupled" as used herein may include wireless connections or wireless couplings. The term "and / or" used herein includes all or any units and all combinations of one or more associated listed items.

[0052] See also Figure 1 , is a schematic structural diagram of a switch control circuit provided in an embodiment of the present application, wherein the switch control circuit 1 has a signal input terminal connected to a signal detection terminal in a port constant current operational amplifier loop 2, and a control terminal of the switch control circuit 1 is connected to a controlled terminal in a bias current generating circuit 3;

[0053] The switch control circuit 1 is used to output a shock pulse Vpulse to control the opening and closing of the switching element K used to control the generation of the shock current in the bias current generating circuit 3. The shock current is used to control the port constant current operational amplifier loop 2. The shock pulse Vpulse is controlled by the comparison result between the port sampling current and the preset reference current. The port sampling current is determined by sampling the port constant current in the port constant current operational amplifier loop 2.

[0054] The present invention provides a switch control circuit in which the surge pulse Vpulse generated by the present invention is only related to the port constant current. This allows the surge current, generated by the surge pulse Vpulse and the surge current source, to be minimally affected by process, temperature, and power supply voltage. Consequently, the port dynamic response is minimally affected by process, temperature, power supply voltage, and other application conditions. This allows the circuit to address the prior art issue of inconsistent port dynamic response within and between constant current LED driver chips, resulting in low-grayscale display on LED displays, without changing the port constant current op amp loop. This improves low-grayscale display consistency and achieves higher image reproduction on LED displays. Furthermore, the pulse width of the surge current can be adaptively adjusted based on the port constant current to meet application requirements within the port constant current range. Furthermore, by applying an additional high-current pulse (i.e., the surge current) to the bias current when the port constant current is turned on, the response speed of the port constant current op amp loop is improved, thereby increasing the turn-on response speed of the port switch and the port response speed, enabling the circuit to meet high grayscale requirements.

[0055] In some embodiments, the switch control circuit 1 includes a current comparator 11;

[0056] The current comparator 11 includes: a reference current module 111, a port current sampling module 112 and a control module 113;

[0057] The first end of the control module 113 is connected to the reference current module 111 and the controlled end of the bias current generating circuit 3 respectively, and the port current sampling module 112 is connected to the second end of the control module 113 and the signal detection end of the port constant current operational amplifier loop 2 respectively;

[0058] The reference current module 111 is configured to generate the reference current;

[0059] The port current sampling module 112 is used to generate the port sampling current;

[0060] The control module 113 is configured to compare the port sampling current with the reference current, and output the impulse pulse Vpulse according to the comparison result.

[0061] In this application, see Figure 1 The reference current module 111 can be a constant current source for generating a preset reference current. The reference current module 111 is provided between the third power supply Vdd and the first terminal of the control module 113. In addition, the first terminal of the control module 113 is connected to the output terminal A of the current comparator 11, and the output terminal A of the current comparator 11 is connected to the controlled terminal of the bias current generating circuit 3. The port current sampling module 112 can be a constant current source, which is connected between the second terminal of the control module 113 and ground. Secondly, the port current sampling module 112 is connected to the signal detection terminal of the port constant current operational amplifier loop 2 (i.e., the signal input terminal of the switch control circuit 1) to detect the port constant current in the port constant current operational amplifier loop 2, so that its constant current value (i.e., the port sampling current) is determined by sampling the port constant current. Therefore, the first terminal of the control module 113 is connected to the controlled terminal of the bias current generating circuit 3 (i.e., the control terminal of the switch control circuit 1). The control module 113 is operable to compare the reference current with the port sampling current and output a surge pulse Vpulse to the bias current generating circuit 3 based on the comparison result. The pulse width of the surge pulse can be adaptively adjusted to the port constant current.

[0062] It should be noted that, see Figure 2 , is a structural schematic diagram of a port constant current operational amplifier loop provided in an embodiment of the present application, wherein the port constant current operational amplifier loop 2 includes a port switch tube M0, a port constant current source Is0, and a constant current operational amplifier U0. The port switch tube M0 is preferably an nmos tube, the gate of the port switch tube M0 is connected to the output terminal of the constant current operational amplifier U0, and the inverting terminal of the constant current operational amplifier U0 is connected to the source of the port switch tube M0 to form a negative feedback loop, thereby achieving constant current output and effectively reducing power consumption. The port constant current source Is0 is used to generate a port constant current. The port constant current source Is0 is connected between the source of the port switch tube M0 and the ground, and the drain of the port switch tube M0 is connected to the external load OUT. The signal detection terminal in the port constant current operational amplifier loop 2 is connected to the port constant current source Is0, so that the switch control circuit 1 detects the port constant current generated by the port constant current source Is0 in real time to generate a port sampling current. In addition, the non-inverting terminal of the constant current operational amplifier U0 (i.e., the input terminal of the constant current operational amplifier loop) is connected to the output terminal of the bias current generating circuit 3 to obtain the constant current operational amplifier bias current from the bias current generating circuit 3.

[0063] Therefore, the present application outputs an impulse pulse Vpulse through the switching control circuit 1 to control the generation of the impulse current to form a constant current operational amplifier bias current containing the impulse current, so as to provide a constant current operational amplifier bias current containing an additional large current pulse to the constant current operational amplifier U0. At this time, under the action of the gate voltage output by the constant current operational amplifier U0 to the port switch tube M0 and the port constant current of the source of the port switch tube M0, the port constant current operational amplifier loop 2 is driven to respond quickly, thereby improving the turn-on response speed of the port switch tube M0.

[0064] In a preferred embodiment, the port sampling current is 1 / k of the port constant current, where k is the sampling ratio. More specifically, , Iout is the port constant current. Therefore, in this embodiment, the impact pulse Vpulse is controlled by the port sampling current, and the port sampling current is determined by the port constant current. The port constant current is less affected by the process and temperature, thereby generating a high-precision impact pulse Vpulse, which enables the generation of a high-precision impact current that is less affected by the process, temperature, and application conditions. The dynamic response of the port is less affected by the process, temperature, and application conditions, which can improve the consistency of the low-gray display of the LED display. At the same time, the impact pulse width can be adaptively adjusted with the port constant current. Since the larger the port constant current, the greater the acceleration demand of the port switch tube M0, the impact pulse width is shorter when the port constant current is smaller, and the impact pulse width is longer when the port constant current is larger.

[0065] In some embodiments, the control module 113 includes:

[0066] The port sampling switch tube M1 has a size of 1 / k of the size of the port switch tube M0 in the port constant current op amp loop 2, where k is the sampling ratio; its drain is connected to the first end of the control module 113, its source is connected to the second end of the control module 113, and its gate V0 is connected to the control end of the port switch tube M0.

[0067] In this example, see Figure 1 The port sampling switch tube M1 is preferably an nmos tube, and the drain of the port sampling switch tube M1 is connected to the first end of the control module 113 (ie Figure 1 The output terminal A of the current comparator 11 in the port sampling switch tube M1 is connected, a port current sampling module 112 is connected between the source of the port sampling switch tube M1 and the ground, and the gate V0 of the port sampling switch tube M1 is connected to the gate of the port switch tube M0 in the port constant current operational amplifier loop 2 (that is, the output terminal of the constant current operational amplifier), so that the gate voltage of the port sampling switch tube M1 is the same as the gate voltage of the port switch tube M0, and the port sampling switch tube M1 is controlled by the gate voltage of the port switch tube M0.

[0068] In some embodiments, the control module 113 operates:

[0069] When the port sampling current is less than the reference current, a first impulse pulse is output to control the switch element K to close;

[0070] When the port sampling current is greater than or equal to the reference current, a second impulse pulse is output to control the switch element K to open.

[0071] In this embodiment, the port sampling current Iout_sampling and the reference current Ibref change linearly with the current gain ratio. Therefore, the pulse width of the impulse pulse always changes linearly with the current gain under the control of different currents, that is, the impulse pulse Vpulse always changes linearly with the port constant current. Flipped when. Specifically, the control module 113 compares the size of the port sampling current Iout_sampling with the reference current Ibref. More specifically, when the port constant current source Is0 in the port constant current operational amplifier loop 2 is turned on, a port constant current is generated. At this time, the output terminal A of the current comparator 11 is initially set to a low state. When the port sampling current Iout_sampling is less than the reference current Ibref, the shock pulse Vpulse begins to rise, and the shock pulse is turned on, that is, the first shock pulse is output at point A to control the switching element K to close, thereby generating a shock current and forming a constant current operational amplifier bias current, so that a constant current operational amplifier bias current containing an additional large current pulse is provided to the constant current operational amplifier U0, thereby improving the opening response speed of the port switch tube M0. Further, as the port constant current gradually increases, when the port sampling current Iout_sampling is equal to the reference current Ibref, at this time Furthermore, when the port sampling current Iout_sampling is greater than the reference current Ibref, the impulse pulse is turned off, that is, a second impulse pulse is output at point A to control the switch element K to turn on.

[0072] In some embodiments, the switch control circuit 1 further includes:

[0073] The buffer 12 is connected between the output terminal of the current comparator 11 and the controlled terminal of the bias current generating circuit 3 .

[0074] In this example, see Figure 1The input end of the buffer 12 is connected to the output end A of the current comparator 11, and the output end of the buffer 12 is connected to the output end of the switch control circuit 1. This enables the buffer 12 to collect the impact pulse signal in real time and temporarily store the impact pulse signal sent to the bias current generating circuit 3, playing a coordination and buffering role for the switch control circuit 1 and the bias current generating circuit 3, and realizing the synchronization of data transmission.

[0075] In some embodiments, the current comparator 11 further includes:

[0076] The controllable switch 114 is connected between the reference current module 111 and the first end of the control module 113 , and is configured to be opened or closed under the control of the current detection signal of the port constant current.

[0077] In this embodiment, the controllable switch 114 is connected to the signal input terminal of the switch control circuit 1. When the port constant current source Is0 in the port constant current op amp loop 2 is turned on, a port constant current is generated. When the controllable switch 114 detects the port constant current, a corresponding first current detection signal is generated to control the controllable switch 114 to close and the current comparator 11 to turn on. Secondly, if the port constant current source Is0 in the port constant current op amp loop 2 is not turned on and the controllable switch 114 does not detect the port constant current, a corresponding second current detection signal is generated to control the controllable switch 114 to open. At this time, the voltage at point A is initially low.

[0078] See also Figure 3 , is a schematic structural diagram of a bias current generating circuit provided in an embodiment of the present application, wherein a controlled end of the bias current generating circuit 3 is connected to a control end of the switch control circuit 1 as described in the above embodiment, and an output end V1 of the bias current generating circuit 3 is connected to an input end of a port constant current operational amplifier loop 2;

[0079] The bias current generating circuit 3 comprises:

[0080] The impulse current source Is1 is used to generate an impulse current Ipulse;

[0081] The switching element K is connected between the impulse current source Is1 and the ground, and is used to open or close under the control of the impulse pulse Vpulse output by the switching control circuit 1, so as to provide a constant current operational amplifier bias current including the impulse current Ipulse to the port constant current operational amplifier loop 2.

[0082] At present, LED display driver circuits usually use surge current to improve port response speed. The components of traditional surge current generating circuits are greatly affected by process, temperature and application conditions, resulting in surge current being greatly affected by process, temperature and application conditions. Therefore, the dynamic response of the port generated by the surge current is greatly affected by process, temperature, power supply voltage and other application conditions. In this application, please refer to Figure 3 The surge current source Is1 can be a constant current source for generating a surge current Ipulse. The surge current source Is1 and the switch element K are connected in series in the bias current generating circuit 3 to form a branch for generating the surge current Ipulse. Specifically, the switch element K is connected to the switch control circuit 1 so as to respond to the surge pulse Vpulse output by the switch control circuit 1 to control the opening and closing of the switch element K. In this way, the conduction or cutoff of the branch is controlled by the surge pulse Vpulse. Furthermore, it only depends on the port constant current of the port constant current operational amplifier loop 2, so that the constant current operational amplifier bias current generated by the bias current generating circuit 3 can include a high-precision surge current that is less affected by process, temperature and application conditions.

[0083] In some embodiments, the bias current generating circuit 3 further includes:

[0084] The port bias current source Is2 is used to generate a bias current Ibias_IO;

[0085] A first control device M2, whose input terminal is connected to the first current source; the port bias current source Is2 is connected between its output terminal and ground; a branch formed by the series connection of the surge current source Is1 and the switch element K is connected in parallel to both ends of the port bias current source Is2; and a control terminal is connected to its output terminal;

[0086] The second control device M3 has its input end connected to the second current source; its control end is connected to the control end of the first control device M2; its output end is connected to the input end of the port constant current op amp loop 2, for outputting the constant current op amp bias current to the port constant current op amp loop 2, wherein the constant current op amp bias current includes the bias current Ibias_IO.

[0087] In this example, see Figure 3The first control device M2 and the second control device M3 can be pmos transistors. The source of the first control device M2 and the source of the second control device M3 are respectively connected to the current source, the gate of the first control device M2 is connected to the gate of the second control device M3, and the gate of the first control device M2 is connected to the drain of the first control device M2. A parallel port bias current source Is2 and a branch consisting of a surge current source Is1 and a switch element K in series are connected between the drain of the first control device M2 and the ground. In this way, illustratively, when the port sampling current is less than the reference current, the switch control circuit 1 outputs a first surge pulse, the switch element K is closed under the control of the first surge pulse, the branch is turned on, and the bias current generating circuit 3 generates a constant current op amp bias current including the surge current Ipulse and the bias current Ibias_IO, thereby improving the response speed of the port constant current op amp loop 2. In addition, when the port sampling current is greater than or equal to the reference current, the switch control circuit 1 outputs a second shock pulse, the switch element K is opened under the control of the second shock pulse, the branch is cut off, and the bias current generating circuit 3 generates a constant current operational amplifier bias current containing only the bias current Ibias_IO.

[0088] The embodiment of the present application provides a bias current generating circuit, wherein the controlled end of the bias current generating circuit is connected to the control end of the switch control circuit as described in the above embodiment, and the output end of the bias current generating circuit is connected to the input end of the port constant current operational amplifier loop; the bias current generating circuit includes: a surge current source for generating surge current; a switch element connected between the surge current source and ground, and used to open or close under the control of the surge pulse output by the switch control circuit, so as to provide the port constant current operational amplifier loop with a constant current operational amplifier bias current containing the surge current. In this way, the surge current generated by the present application is less affected by process, temperature, and power supply voltage, and has the characteristics of high precision, so that the port dynamic response is less affected by process, temperature, power supply voltage and other application conditions, and can solve the problem of low gray display on LED display screen caused by inconsistent port dynamic response within and between constant current LED driver chips in the prior art, thereby improving the consistency of low gray display on LED display screen.

[0089] See also Figure 4 , is a schematic structural diagram of an LED driving circuit provided in an embodiment of the present application, wherein the LED driving circuit comprises: a switch control circuit 1 as described in the above embodiment, a bias current generating circuit 3 as described in the above embodiment, and a port constant current operational amplifier loop 2;

[0090] The signal input end of the switch control circuit 1 is connected to the signal detection end of the port constant current operational amplifier loop 2, the control end of the switch control circuit 1 is connected to the controlled end of the bias current generating circuit 3, and the output end V1 of the bias current generating circuit 3 is connected to the input end of the port constant current operational amplifier loop 2.

[0091] In this embodiment, the port constant current op amp loop 2 transmits a port constant current to the signal input terminal of the switch control circuit 1 via its signal detection terminal. The switch control circuit 1 samples the port constant current, determines the port sampled current, compares the port sampled current with a preset reference current, and outputs a surge pulse Vpulse based on the comparison result. This surge pulse Vpulse is then transmitted via the control terminal of the switch control circuit 1 to the controlled terminal of the bias current generating circuit 3. Based on the surge pulse Vpulse, the bias current generating circuit 3 controls the opening and closing of the switch element K used to control the generation of the surge current Ipulse, thereby generating a surge current that is less affected by process, temperature, and power supply voltage. This generates a constant current op amp bias current comprising the surge current Ipulse and the bias current, and transmits this constant current op amp bias current to the input terminal of the port constant current op amp loop 2 via the output terminal V1 of the bias current generating circuit 3. The port constant current op amp loop 2 inputs the constant current op amp bias current to the non-inverting terminal of the constant current operational amplifier U0. At this time, the dynamic response of the port is less affected by the process, temperature, power supply voltage and other application conditions, thereby improving the response speed of the port constant current op amp loop 2, thereby improving the opening response speed of the port constant current switch tube M0.

[0092] An LED driving circuit provided by an embodiment of the present application includes: a switch control circuit as described in the above embodiment, a bias current generating circuit as described in the above embodiment, and a port constant current operational amplifier loop; the signal input end of the switch control circuit is connected to the signal detection end of the port constant current operational amplifier loop, the control end of the switch control circuit is connected to the controlled end of the bias current generating circuit, and the output end of the bias current generating circuit is connected to the input end of the port constant current operational amplifier loop. In this way, the above-mentioned impact current is applied to the bias current when the port constant current is turned on without changing the port constant current operational amplifier loop. The impact current is less affected by the process, temperature, and power supply voltage, and can achieve consistency of port response, thereby improving the response speed of the port constant current operational amplifier loop, thereby improving the port response speed and meeting the requirements of high grayscale levels.

[0093] See also Figure 5 , is a flow chart of a switch control method provided in an embodiment of the present application. The switch control method is applicable to the switch control circuit as described in the above embodiment, and the method includes steps S501 to S502.

[0094] S501, obtaining a port constant current in a port constant current operational amplifier loop, and sampling the port constant current to determine a port sampling current;

[0095] S502, comparing the port sampling current with a preset reference current, and outputting a surge pulse according to the comparison result to control the opening and closing of a switching element in a bias current generating circuit for controlling the generation of surge current, wherein the surge current is used to control the port constant current operational amplifier loop.

[0096] The present application provides a switch control method in which the generated impulse pulse is only related to the port constant current, so that the impulse current is generated by the impulse pulse and the impulse current source, and is less affected by the process, temperature, and power supply voltage. Therefore, the port dynamic response is less affected by the process, temperature, power supply voltage, and other application conditions. This allows the method to solve the problem of inconsistent port dynamic response within and between constant current LED driver chips in the prior art, resulting in low-gray display on the LED display, without changing the port constant current op amp loop. This improves the consistency of low-gray display and achieves the purpose of higher image restoration of the LED display. At the same time, the pulse width of the impulse current can be adaptively adjusted according to the port constant current to meet application requirements within the port constant current range. Furthermore, by applying an additional large current pulse (i.e., the above-mentioned impulse current) to the bias current when the port constant current is turned on, the response speed of the port constant current op amp loop is improved, thereby improving the turn-on response speed of the port switch tube and the port response speed, and can meet the requirements of high grayscale levels.

[0097] The above description is only part of the implementation methods of the present application. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present application. These improvements and modifications should also be regarded as the scope of protection of the present application.

Claims

1. A switch control circuit, characterized in that: The signal input terminal of the switch control circuit is connected to the signal detection terminal in the port constant current operational amplifier loop, and the control terminal of the switch control circuit is connected to the controlled terminal in the bias current generating circuit; The switch control circuit includes a current comparator, which is respectively connected to the controlled end of the bias current generating circuit and the signal detection end of the port constant current operational amplifier loop, and is used to output a surge pulse to control the opening and closing of a switching element in the bias current generating circuit used to control surge current generation. The surge current is used to control the port constant current operational amplifier loop. The surge pulse is controlled by a comparison result between a port sampling current and a preset reference current. The port sampling current is determined by sampling the port constant current in the port constant current operational amplifier loop.

2. The switch control circuit according to claim 1, wherein: The current comparator includes: a reference current module, a port current sampling module and a control module; The first end of the control module is connected to the reference current module and the controlled end of the bias current generating circuit respectively, and the port current sampling module is connected to the second end of the control module and the signal detection end of the port constant current operational amplifier loop respectively; The reference current module is used to generate the reference current; The port current sampling module is used to generate the port sampling current; The control module is used to compare the port sampling current with the reference current, and output the impact pulse according to the comparison result; the impact pulse can adapt to the port constant current adjustment.

3. The switch control circuit according to claim 2, wherein: The control module includes: A port sampling switch tube, whose size is 1 / k of the size of the port switch tube in the port constant current operational amplifier loop, where k is the sampling ratio; whose drain is connected to the first end of the control module, whose source is connected to the second end of the control module, and whose gate is connected to the control end of the port switch tube.

4. The switch control circuit according to claim 2, wherein: When the control module is in operation: When the port sampling current is less than the reference current, a first impulse pulse is output to control the switch element to close; When the port sampling current is greater than or equal to the reference current, a second impulse pulse is output to control the switch element to open.

5. The switch control circuit according to claim 2, wherein: The switch control circuit further includes: A buffer is connected between the output terminal of the current comparator and the controlled terminal of the bias current generating circuit.

6. The switch control circuit according to claim 2, wherein: The current comparator further includes: A controllable switch is connected between the reference current module and the first end of the control module, and is used to open or close under the control of the current detection signal of the port constant current.

7. A bias current generating circuit, characterized in that: The controlled end of the bias current generating circuit is connected to the control end of the switch control circuit according to any one of claims 1 to 6, and the output end of the bias current generating circuit is connected to the input end of the port constant current operational amplifier loop; The bias current generating circuit comprises: A surge current source, used to generate surge current; A switching element is connected between the impulse current source and the ground, and is used to open or close under the control of the impulse pulse output by the switch control circuit, so as to provide a constant current operational amplifier bias current containing the impulse current to the port constant current operational amplifier loop.

8. The bias current generating circuit according to claim 7, wherein: Also includes: Port bias current source, used to generate bias current; a first control device, an input terminal of which is connected to a first current source; The port bias current source is connected between its output terminal and ground, and a branch formed by the series connection of the surge current source and the switch element is connected in parallel to both ends of the port bias current source; its control terminal is connected to its output terminal; a second control device, an input terminal of which is connected to a second current source; Its control terminal is connected to the control terminal of the first control device; Its output end is connected to the input end of the port constant current operational amplifier loop, and is used to output the constant current operational amplifier bias current to the port constant current operational amplifier loop, where the constant current operational amplifier bias current includes the bias current.

9. An LED driving circuit, characterized in that: include: The switch control circuit according to any one of claims 1 to 6, the bias current generating circuit and the port constant current operational amplifier loop according to any one of claims 7 to 8; The signal input end of the switch control circuit is connected to the signal detection end of the port constant current operational amplifier loop, the control end of the switch control circuit is connected to the controlled end of the bias current generating circuit, and the output end of the bias current generating circuit is connected to the input end of the port constant current operational amplifier loop.

10. A switch control method, characterized in that: Applicable to the switch control circuit according to any one of claims 1 to 6, the method comprising: Obtaining a port constant current in a port constant current operational amplifier loop, and sampling the port constant current to determine a port sampling current; The port sampling current is compared with the preset reference current, and a surge pulse is output according to the comparison result to control the opening and closing of a switching element in a bias current generating circuit for controlling the generation of surge current. The surge current is used to control the port constant current operational amplifier loop.

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