CN115734422A - Switch control circuit, bias current generation circuit, LED drive circuit and method - Google Patents
Switch control circuit, bias current generation circuit, LED drive circuit and method Download PDFInfo
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- CN115734422A CN115734422A CN202111022187.1A CN202111022187A CN115734422A CN 115734422 A CN115734422 A CN 115734422A CN 202111022187 A CN202111022187 A CN 202111022187A CN 115734422 A CN115734422 A CN 115734422A
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Abstract
The embodiment of the application provides a switch control circuit, a bias current generating circuit, an LED driving circuit and a method. The signal input end of the switch control circuit is connected with the signal detection end in the port constant-current operational amplifier loop, and the control end of the switch control circuit is connected with the controlled end in the bias current generating circuit; the switch control circuit is used for outputting an impact pulse to control the on-off of a switch element used for controlling the generation of impact current in the bias current generation circuit, the impact current is used for controlling the port constant-current operational amplifier loop, the impact pulse is controlled by a comparison result between port sampling current and preset reference current, and the port sampling current is determined after the port constant-current in the port constant-current operational amplifier loop is sampled. The method is used for solving the problem that in the prior art, the dynamic response of ports in and between the constant current LED driving chips is inconsistent, so that low-gray display is generated on the LED display screen.
Description
Technical Field
The application relates to the technical field of LED driving, in particular to a switch control circuit, a bias current generating circuit, an LED driving circuit and a method.
Background
In a conventional multi-channel constant current LED driving chip, a PWM (Pulse width modulation) method is usually adopted for display control. With the continuous development of display technology, the requirements for display screens are higher and higher. In order to meet the requirement of low gray display consistency at a high gray level, the port constant current value is more influenced by the dynamic response speed under the condition that the PWM opening width is smaller, so that the effect of the port dynamic response consistency on low gray display is particularly important.
At present, an LED display screen driving circuit generally uses an impact circuit to improve the response speed of a port, and the traditional impact circuit is greatly influenced by process, temperature and application conditions and is easy to generate the condition of inconsistent dynamic response of ports in a chip and between chips. Further, inconsistent dynamic response of the ports can cause display problems such as low gray color blocks on the LED display screen.
Disclosure of Invention
The switch control circuit, the bias current generation circuit, the LED drive circuit and the method are provided aiming at the defects of the existing mode, and the problem that in the prior art, the dynamic response of ports in and among constant current LED drive chips is inconsistent, so that low-gray display is generated on an LED display screen is solved.
In a first aspect, an embodiment of the present application provides a switch control circuit, where a signal input end of the switch control circuit is connected to a signal detection end in a port constant-current operational amplifier loop, and a control end of the switch control circuit is connected to a controlled end in a bias current generation circuit;
the switch control circuit is used for outputting an impact pulse to control the on-off of a switch element used for controlling the generation of the impact current in the bias current generation circuit, the impact current is used for controlling the port constant-current operational amplifier loop, the impact pulse is controlled by a comparison result between port sampling current and preset reference current, and the port sampling current is determined after the port constant-current in the port constant-current operational amplifier loop is sampled.
In some embodiments, the switch control circuit comprises a current comparator;
the current comparator includes: the device comprises a reference current module, a port current sampling module and a control module;
the first end of the control module is respectively connected with the reference current module and the controlled end of the bias current generating circuit, and the port current sampling module is respectively connected with the second end of the control module and the signal detection end of the port constant-current operational amplifier loop;
the reference current module is used for generating the reference current;
the port current sampling module is used for generating the port sampling current;
and the control module is used for comparing the port sampling current with the reference current and outputting the impact pulse according to a comparison result.
In some embodiments, the control module comprises:
the size of the port sampling switch tube is 1/k of that of the port switch tube in the port constant-current operational amplifier loop, and k is a sampling proportion; the drain electrode of the switch tube is connected with the first end of the control module, the source electrode of the switch tube is connected with the second end of the control module, and the grid electrode of the switch tube is connected with the control end of the port switch tube.
In some embodiments, the control module is operative to:
when the port sampling current is smaller than the reference current, outputting a first impact pulse to control the switch element to be closed;
and when the port sampling current is greater than or equal to the reference current, outputting a second impact pulse to control the switching element to be opened.
In some embodiments, the switch control circuit further comprises:
a buffer connected between the output terminal of the current comparator and the controlled terminal of the bias current generating circuit.
In some embodiments, the current comparator further comprises:
and the controllable switch is connected between the reference current module and the first end of the control module and is used for being opened or closed under the control of a current detection signal of the port constant current.
In a second aspect, an embodiment of the present application provides a bias current generating circuit, where a controlled end of the bias current generating circuit is connected to a control end of the switch control circuit according to the above embodiment, and an output end of the bias current generating circuit is connected to an input end of a port constant-current operational amplifier loop;
the bias current generating circuit includes:
the impact current source is used for generating impact current;
and the switching element is connected between the impact current source and the ground and is used for being opened or closed under the control of the impact pulse output by the switching control circuit so as to provide a constant-current operational amplifier bias current containing the impact current for the port constant-current operational amplifier loop.
In some embodiments, further comprising:
a port bias current source to generate a bias current;
a first control device, the input end of which is connected with a first current source; the port bias current source is connected between the output end of the current source and the ground, and a branch formed by connecting the impact current source and the switching element in series is connected to the two ends of the port bias current source in parallel; the control end is connected with the output end;
a second control device, the input end of which is connected with a second current source; the control end of the first control device is connected with the control end of the first control device; the output end of the constant current operational amplifier is connected with the input end of the port constant current operational amplifier loop and used for outputting the constant current operational amplifier bias current to the port constant current operational amplifier loop, and the constant current operational amplifier bias current comprises the bias current.
In a third aspect, an embodiment of the present application provides an LED driving circuit, including: the switch control circuit, the bias current generating circuit and the port constant current operational amplifier loop circuit are provided with the same structure;
the signal input end of the switch control circuit is connected with the signal detection end of the port constant-current operational amplifier loop, the control end of the switch control circuit is connected with the controlled end of the bias current generating circuit, and the output end of the bias current generating circuit is connected with the input end of the port constant-current operational amplifier loop.
In a fourth aspect, an embodiment of the present application provides a switch control method, which is applied to the switch control circuit according to the foregoing embodiment, and the method includes:
acquiring a port constant current in a port constant current operational amplifier loop, sampling the port constant current, and determining a port sampling current;
and comparing the port sampling current with a preset reference current, and outputting an impact pulse according to a comparison result to control the on-off of a switch element used for controlling the generation of the impact current in the bias current generating circuit, wherein the impact current is used for controlling the port constant-current operational amplifier loop.
Compared with the prior art, the switch control circuit and the switch control method provided by the embodiment of the application have the following technical effects:
the signal input end of the switch control circuit is connected with the signal detection end in the port constant-current operational amplifier loop, and the control end of the switch control circuit is connected with the controlled end in the bias current generating circuit; the switch control circuit is used for outputting an impact pulse to control the on-off of a switch element used for controlling the generation of the impact current in the bias current generation circuit, the impact current is used for controlling the port constant-current operational amplifier loop, the impact pulse is controlled by a comparison result between port sampling current and preset reference current, and the port sampling current is determined after the port constant-current in the port constant-current operational amplifier loop is sampled. Therefore, the impact pulse generated by the method is only related to the port constant current, so that the impact current is generated by the impact pulse and an impact current source, and the impact current is slightly influenced by the process, the temperature and the power supply voltage. Therefore, the dynamic response of the port is slightly influenced by the process, the temperature, the power supply voltage and other application conditions, so that the problem of low-gray display generated on an LED display screen due to inconsistent dynamic response of the ports in and among the constant-current LED driving chips in the prior art can be solved on the premise of not changing a port constant-current operational amplifier loop, the low-gray display consistency is improved, and the aim of higher LED display screen picture restoration is fulfilled. Meanwhile, the pulse width of the impact current can be adaptively adjusted according to the port constant current, so that the application requirement in the range of the port constant current is met.
Furthermore, an extra large current pulse (namely the impulse current) is applied to the bias current when the port constant current is started, so that the response speed of the port constant current operational amplifier loop is improved, the starting response speed of the port switch tube is improved, the port response speed is improved, and the requirement of high gray level number can be met.
The bias current generating circuit provided by the embodiment of the application has the following technical effects:
the controlled end of the bias current generating circuit is connected with the control end of the switch control circuit in the embodiment, and the output end of the bias current generating circuit is connected with the input end of the port constant-current operational amplifier loop; the bias current generating circuit includes: the impact current source is used for generating impact current; and the switching element is connected between the impact current source and the ground and is used for being opened or closed under the control of the impact pulse output by the switching control circuit so as to provide a constant-current operational amplifier bias current containing the impact current for the port constant-current operational amplifier loop. Therefore, the impact current generated by the method is little influenced by the process, the temperature and the power supply voltage, and has the characteristic of high precision, so that the dynamic response of the port is little influenced by the process, the temperature, the power supply voltage and other application conditions, the problem of low-gray display generated on an LED display screen due to inconsistent dynamic response of the ports in and among the constant-current LED driving chips in the prior art can be solved, and the consistency of low-gray display of the LED display screen is improved.
The LED drive circuit provided by the embodiment of the application has the following technical effects:
the LED drive circuit comprises: the switch control circuit, the bias current generating circuit and the port constant current operational amplifier loop circuit are provided with the same structure; the signal input end of the switch control circuit is connected with the signal detection end of the port constant-current operational amplifier loop, the control end of the switch control circuit is connected with the controlled end of the bias current generating circuit, and the output end of the bias current generating circuit is connected with the input end of the port constant-current operational amplifier loop. Therefore, on the premise of not changing the port constant-current operational amplifier loop, the impact current is applied to the bias current when the port constant-current operational amplifier loop is started, the impact current is slightly influenced by the process, the temperature and the power supply voltage, the port response consistency can be realized, the response speed of the port constant-current operational amplifier loop is improved, the port response speed is improved, and the requirement of high gray level number can be met.
Additional aspects and advantages of the present application will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the present application.
Drawings
The foregoing and/or additional aspects and advantages of the present application will become apparent and readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:
fig. 1 is a schematic structural diagram of a switch control circuit according to an embodiment of the present disclosure;
fig. 2 is a schematic structural diagram of a port constant-current operational amplifier loop provided in an embodiment of the present application;
fig. 3 is a schematic structural diagram of a bias current generating circuit according to an embodiment of the present disclosure;
fig. 4 is a schematic structural diagram of an LED driving circuit according to an embodiment of the present disclosure;
fig. 5 is a schematic flowchart of a switch control method according to an embodiment of the present application.
Detailed Description
Reference will now be made in detail to the present application, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the same or similar parts or parts having the same or similar functions throughout. In addition, if a detailed description of the known art is not necessary for illustrating the features of the present application, it is omitted. The embodiments described below with reference to the accompanying drawings are exemplary only for explaining the present application and are not construed as limiting the present application.
It will be understood by those within the art that, unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the prior art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.
As used herein, the singular forms "a", "an", "the" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and/or "comprising," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. It will be understood that when an element is referred to as being "connected" or "coupled" to another element, it can be directly connected or coupled to the other element or intervening elements may also be present. Further, "connected" or "coupled" as used herein may include wirelessly connected or wirelessly coupled. As used herein, the term "and/or" includes all or any element and all combinations of one or more of the associated listed items.
Referring to fig. 1, a schematic structural diagram of a switch control circuit provided in an embodiment of the present application is shown, in the switch control circuit, a signal input end of the switch control circuit 1 is connected to a signal detection end in a port constant current operational amplifier loop 2, and a control end of the switch control circuit 1 is connected to a controlled end in a bias current generation circuit 3;
the switch control circuit 1 is configured to output an impulse pulse Vpulse to control the bias current generation circuit 3 to control the on/off of a switch element K for generating an impulse current, where the impulse current is used to control the port constant current operational amplifier loop 2, the impulse pulse Vpulse is controlled by a comparison result between a port sampling current and a preset reference current, and the port sampling current is determined by sampling the port constant current in the port constant current operational amplifier loop 2.
According to the switch control circuit provided by the embodiment of the application, the impact pulse Vpulse generated by the switch control circuit is only related to the constant current of the port, so that the impact current is generated by the impact pulse Vpulse and the impact current source, and the impact current is slightly influenced by the process, the temperature and the power supply voltage. Therefore, the dynamic response of the port is slightly influenced by the process, the temperature, the power supply voltage and other application conditions, so that the problem of low-gray display generated on an LED display screen due to inconsistent dynamic response of the ports in and among the constant-current LED driving chips in the prior art can be solved on the premise of not changing a port constant-current operational amplifier loop, the low-gray display consistency is improved, and the aim of higher LED display screen picture restoration is fulfilled. Meanwhile, the pulse width of the impact current can be adaptively adjusted according to the port constant current, so that the application requirement in the range of the port constant current is met. Furthermore, an extra large current pulse (namely the impulse current) is applied to the bias current when the port constant current is started, so that the response speed of the port constant current operational amplifier loop is improved, the starting response speed of the port switch tube is improved, the port response speed is improved, and the requirement of high gray level number can be met.
In some embodiments, the switch control circuit 1 comprises a current comparator 11;
the current comparator 11 includes: a reference current module 111, a port current sampling module 112 and a control module 113;
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, and the port current sampling module 112 is connected to the second end of the control module 113 and the signal detecting end of the port constant current operational amplifier loop 2;
the reference current module 111 is configured to generate the reference current;
the port current sampling module 112 is configured to generate the port sampling current;
the control module 113 is configured to compare the port sampling current with the reference current, and output the impulse pulse Vpulse according to a comparison result.
In the present application, referring to fig. 1, the reference current module 111 may be a constant current source for generating a predetermined reference current, the reference current module 111 is disposed between the third power Vdd and the first end of the control module 113, in addition, the first end of the control module 113 is connected to the output end a of the current comparator 11, and the output end a of the current comparator 11 is connected to the controlled end of the bias current generating circuit 3. The port current sampling module 112 may be a constant current source connected between a second terminal of the control module 113 and ground. Next, the port current sampling module 112 is connected to a signal detection end (i.e., a signal input end of the switch control circuit 1) of the port constant current operational amplifier loop 2, and is configured to detect the port constant current in the port constant current operational amplifier loop 2, so that a constant current value (i.e., a port sampling current) of the port constant current operational amplifier loop 2 is determined after 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 2 (i.e., the control terminal of the switch control circuit 1), and the control module 113 is operable to compare the magnitudes of the reference current and the port sampling current, and output the impulse pulse Vpulse to the bias current generating circuit 3 according to the comparison result. The impulse pulse width can be adjusted by self-adapting port constant current.
It should be noted that, referring to fig. 2, for a structural schematic diagram of a port constant-current operational amplifier loop provided in the embodiment of the present application, 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 switching tube M0 is preferably an nmos tube, the grid electrode of the port switching tube M0 is connected with the output end of the constant-current operational amplifier U0, and the inverting end of the constant-current operational amplifier U0 is connected with the source electrode of the port switching tube M0 to form a negative feedback loop, so that constant-current output is realized, and power consumption can be effectively reduced. The port constant current source Is0 Is used for generating a port constant current, the port constant current source Is0 Is connected between the source electrode of the port switch tube M0 and the ground, and the drain electrode of the port switch tube M0 Is connected with an external load OUT. The signal detection end in the port constant-current operational amplifier loop 2 Is connected with 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 the port sampling current. In addition, the non-inverting terminal (i.e. the input terminal of the port constant current operational amplifier loop) of the constant current operational amplifier U0 is connected to the output terminal of the bias current generating circuit 3, so as to obtain the constant current operational amplifier bias current from the bias current generating circuit 3.
Therefore, the impact pulse Vpulse is output by the switch control circuit 1 and used for controlling the generation of the impact current to form a constant-current operational amplifier bias current containing the impact current, so that the constant-current operational amplifier bias current containing extra large-current pulses is provided for the constant-current operational amplifier U0, and at the moment, the constant-current operational amplifier loop 2 is driven to quickly respond under the action of the gate voltage output to the port switch tube M0 by the constant-current operational amplifier U0 and the port constant-current of the source electrode of the port switch tube M0, so that the opening response speed of the port switch tube M0 is improved.
In a preferred embodiment, the port sampling current is 1/k of the port constant current, and k is a sampling ratio. More specifically, the present invention is to provide a novel,
iout is port constant current. Therefore, in the embodiment, the impulse pulse Vpulse is controlled by the port sampling current, the port sampling current is determined by the port constant current, and the port constant current is slightly influenced by the process and the temperature, so that the high-precision impulse pulse Vpulse can be generated, the high-precision impulse current which is slightly influenced by the process, the temperature and the application condition can be generated, the dynamic response of the port is slightly influenced by the process, the temperature and the application condition, and the consistency of low-gray display of the LED display screen can be improved. Meanwhile, the impulse pulse width can be adjusted in a self-adaptive mode along with the port constant current, and as the port constant current is larger, the acceleration requirement of the port switching tube M0 is larger, the impulse pulse width is shorter when the port constant current is smaller, and the impulse pulse width is longer when the port constant current is larger.
In some embodiments, the control module 113 includes:
the size of the port sampling switch tube M1 is 1/k of the size of the port switch tube M0 in the port constant-current operational amplifier loop 2, and k is a sampling proportion; the drain thereof is connected to the first end of the control module 113, the source thereof is connected to the second end of the control module 113, and the gate V0 thereof is connected to the control end of the port switch M0.
In this embodiment, please refer to fig. 1, the port sampling switch tube M1 is preferably an nmos tube, a drain of the port sampling switch tube M1 is connected to a first end of the control module 113 (i.e., an output end a of the current comparator 11 in fig. 1), the port current sampling module 112 is connected between a source of the port sampling switch tube M1 and the ground, a gate V0 of the port sampling switch tube M1 is connected to a gate of the port switch tube M0 in the port constant current operational amplifier loop 2 (i.e., an output end of the constant current operational amplifier), so that the gate voltage of the port sampling switch tube M1 is 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.
In some embodiments, the control module 113 is operative to:
when the port sampling current is smaller than the reference current, outputting a first impact pulse to control the switch element K to be closed;
and when the port sampling current is greater than or equal to the reference current, outputting a second impact pulse to control the switch element K to be opened.
In the present embodiment, the port sampling current Iout _ sampling and the reference current Ibref simultaneously and linearly vary with the current gain ratio, so the pulse width of the impact pulse always linearly varies with the current gain under the control of different currents, i.e. the impact pulse Vpulse always flips when the port constant current Iout = k × Ibref. Specifically, the control module 113 compares the port sampling current Iout _ sampling with the reference current Ibref. More specifically, when a 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, an output end a point of the current comparator 11 Is initially set low, when a port sampling current Iout _ sampling Is smaller than a reference current Ibref, an impulse pulse Vpulse starts to rise, the impulse pulse Is turned on, that Is, a first impulse pulse Is output at the point a to control the switching element K to be closed, so that an impulse current Is generated, a constant current operational amplifier bias current Is formed, a constant current operational amplifier bias current containing extra large current pulses Is provided to the constant current operational amplifier U0, and the turn-on response speed of the port switching tube M0 Is improved. Further, as the port constant current gradually increases, when the port sampling current Iout _ sampling is equal to the reference current Ibref, and Iout = k Ibref, the level of the impact pulse Vpulse is inverted. Furthermore, when the port sampling current Iout _ sampling is greater than the reference current Ibref, the impact pulse is turned off, i.e., a second impact pulse is output at point a to control the switching element K to be turned on.
In some embodiments, the switch control circuit 1 further includes:
and a buffer 12 connected between the output terminal of the current comparator 11 and the controlled terminal of the bias current generating circuit 3.
In this embodiment, please refer to fig. 1, an input end of the buffer 12 is connected to the output end a of the current comparator 11, and an output end of the buffer 12 is connected to the output end of the switch control circuit 1, so that the buffer 12 collects the impulse pulse signal in real time and temporarily stores the impulse pulse signal to be sent to the bias current generating circuit 3, thereby performing coordination and buffering functions on the switch control circuit 1 and the bias current generating circuit 3, and realizing synchronization of data transmission.
In some embodiments, the current comparator 11 further includes:
and a controllable switch 114 connected between the reference current module 111 and the first end of the control module 113, and configured to be opened or closed under the control of a current detection signal of the port constant current.
In this embodiment, the controllable switch 114 Is connected to a signal input end of the switch control circuit 1, and 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, and 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 be closed, and the current comparator 11 Is turned on. Secondly, if the port constant current source Is0 in the port constant current operational amplifier loop 2 Is not started 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 be turned on, and at this time, the voltage at the point a Is set to be low in the initial state.
Referring to fig. 3, for a schematic structural diagram of a bias current generating circuit provided in the embodiment of the present application, a controlled end of the bias current generating circuit 3 is connected to a control end of the switch control circuit 1 according to the above embodiment, and an output end V1 of the bias current generating circuit 3 is connected to an input end of the port constant-current operational amplifier loop 2;
the bias current generating circuit 3 includes:
the impulse current source Is1 Is used for generating impulse current Ipulse;
and the switching element K Is connected between the inrush current source Is1 and the ground and Is used for being opened or closed under the control of an inrush pulse Vpulse output by the switching control circuit 1 so as to provide a constant-current operational amplifier bias current containing the inrush current Ipulse to the port constant-current operational amplifier loop 2.
At present, an impulse current is generally used by an LED display screen driving circuit to improve a port response speed, and an element of a conventional impulse current generating circuit is greatly influenced by a process, a temperature and an application condition, so that the generated impulse current is greatly influenced by the process, the temperature and the application condition, and therefore, a port dynamic response generated by the impulse current is greatly influenced by the process, the temperature, a power supply voltage and other application conditions. In the present application, referring to fig. 3, the impact current source Is1 may be a constant current source for generating an impact current Ipulse, and the bias current generating circuit 3 Is formed by serially connecting the impact current source Is1 and the switching element K to form a branch for generating the impact current Ipulse. Specifically, the switching element K is connected to the switching control circuit 1, so as to respond to the impulse Vpulse outputted by the switching control circuit 1 to control the switching of the switching element K. Therefore, the on or off of the branch circuit is controlled by the impulse pulse Vpulse, and further, only the port constant current of the port constant current operational amplifier loop 2 is depended on, so that the constant current operational amplifier bias current generated by the bias current generating circuit 3 can include high-precision impulse current which is slightly influenced by process, temperature and application conditions.
In some embodiments, the bias current generating circuit 3 further includes:
a port bias current source Is2 for generating a bias current Ibias _ IO;
a first control device M2, the input terminal of which is connected to the first current source; the port bias current source Is2 Is connected between the output end of the impact current source and the ground, and a branch formed by connecting the impact current source Is1 and the switching element K in series Is connected to two ends of the port bias current source Is2 in parallel; the control end is connected with the output end;
a second control device M3, an input terminal of which is connected to the second current source; the control end of the first control device M2 is connected with the control end of the first control device; the output end of the constant current operational amplifier is connected with the input end of the port constant current operational amplifier loop 2 and used for outputting the constant current operational amplifier bias current to the port constant current operational amplifier loop 2, and the constant current operational amplifier bias current comprises the bias current Ibias _ IO.
In this embodiment, referring to fig. 3, the first control device M2 and the second control device M3 may be pmos transistors, the source of the first control device M2 and the source of the second control device M3 are respectively connected to a current source, the gate of the first control device M2 Is connected to the gate of the second control device M3, the gate of the first control device M2 Is connected to the drain of the first control device M2, and a parallel port bias current source Is2 and a branch formed by connecting a surge current source Is1 and a switching element K in series are connected between the drain of the first control device M2 and ground. Thus, for example, when the port sampling current is smaller than the reference current, the switch control circuit 1 outputs a first impulse pulse, the switch element K is closed under the control of the first impulse pulse, the branch is turned on, and the bias current generating circuit 3 generates a constant-current operational amplifier bias current including an impulse current Ipulse and a bias current Ibias _ IO, thereby improving the response speed of the port constant-current operational amplifier 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 impulse pulse, the switch element K is turned on under the control of the second impulse pulse, the branch is turned off, and the bias current generating circuit 3 generates a constant-current operational amplifier bias current only including the bias current Ibias _ IO.
According to the bias current generating circuit provided by the embodiment of the application, the controlled end of the bias current generating circuit is connected with the control end of the switch control circuit in the embodiment, and the output end of the bias current generating circuit is connected with the input end of the port constant-current operational amplifier loop; the bias current generating circuit includes: the impact current source is used for generating impact current; and the switching element is connected between the impact current source and the ground and is used for being opened or closed under the control of the impact pulse output by the switching control circuit so as to provide a constant-current operational amplifier bias current containing the impact current for the port constant-current operational amplifier loop. Therefore, the impact current generated by the method is little influenced by the process, the temperature and the power supply voltage, and has the characteristic of high precision, so that the dynamic response of the port is little influenced by the process, the temperature, the power supply voltage and other application conditions, the problem of low-gray display generated on an LED display screen due to inconsistent dynamic response of the ports in and among the constant-current LED driving chips in the prior art can be solved, and the consistency of low-gray display of the LED display screen is improved.
Referring to fig. 4, a schematic structural diagram of an LED driving circuit provided in an embodiment of the present application is shown, where the LED driving circuit includes: the switch control circuit 1, the bias current generating circuit 3 and the port constant current operational amplifier loop circuit 2 are arranged in the embodiment;
the signal input end of the switch control circuit 1 is connected with the signal detection end of the port constant-current operational amplifier loop 2, the control end of the switch control circuit 1 is connected with the controlled end of the bias current generating circuit 3, and the output end V1 of the bias current generating circuit 3 is connected with the input end of the port constant-current operational amplifier loop 2.
In this embodiment, the port constant current operational amplifier loop 2 sends a port constant current to the signal input terminal of the switch control circuit 1 through the signal detection terminal. The switch control circuit 1 samples the port constant current, determines the port sampling current, compares the port sampling current with a preset reference current, and outputs an impulse pulse Vpulse according to the comparison result, so that the impulse pulse Vpulse is sent to the controlled end of the bias current generation circuit 3 through the control end of the switch control circuit 1. The bias current generating circuit 3 controls the on-off of a switch element K used for controlling the generation of the impulse current Ipulse according to the impulse pulse Vpulse so as to generate the impulse current which is less affected by the process, the temperature and the power voltage, further obtain the constant current operational amplifier bias current containing the impulse current Ipulse and the bias current, and transmit the constant current operational amplifier bias current to the input end of the port constant current operational amplifier loop 2 through the output end V1 of the bias current generating circuit 3. The port constant-current operational amplifier loop 2 inputs the constant-current operational amplifier bias current to the in-phase end of the constant-current operational amplifier U0, and at the moment, the dynamic response of the port is slightly influenced by the process, the temperature, the power supply voltage and other application conditions, so that the response speed of the port constant-current operational amplifier loop 2 is increased, and the starting response speed of the port constant-current switching tube M0 is increased.
The embodiment of the application provides a LED drive circuit, through LED drive circuit includes: the switch control circuit, the bias current generating circuit and the port constant current operational amplifier loop circuit are provided with the same structure; the signal input end of the switch control circuit is connected with the signal detection end of the port constant-current operational amplifier loop, the control end of the switch control circuit is connected with the controlled end of the bias current generating circuit, and the output end of the bias current generating circuit is connected with the input end of the port constant-current operational amplifier loop. Therefore, on the premise of not changing the port constant current operational amplifier loop, the impact current is applied to the bias current when the port constant current is started, the impact current is slightly influenced by the process, the temperature and the power supply voltage, the port response consistency can be realized, the response speed of the port constant current operational amplifier loop is increased, the port response speed is increased, and the requirement of high gray level number can be met.
Referring to fig. 5, a schematic flowchart of a switching control method provided in an embodiment of the present application, where the switching control method is suitable for a switching control circuit according to the foregoing embodiment, and the method includes steps S501 to S502.
S501, acquiring a port constant current in a port constant current operational amplifier loop, sampling the port constant current, and determining a port sampling current;
and S502, comparing the port sampling current with a preset reference current, and outputting an impact pulse according to a comparison result to control the on-off of a switch element used for controlling the generation of the impact current in the bias current generating circuit, wherein the impact current is used for controlling the port constant-current operational amplifier loop.
According to the switch control method provided by the embodiment of the application, the generated impact pulse is only related to the port constant current, so that the impact current is generated by the impact pulse and the impact current source, and the impact current is slightly influenced by the process, the temperature and the power supply voltage. Therefore, the dynamic response of the port is slightly influenced by the process, the temperature, the power supply voltage and other application conditions, so that the problem of low-gray display generated on an LED display screen due to inconsistent dynamic response of the ports in and among the constant-current LED driving chips in the prior art can be solved on the premise of not changing a port constant-current operational amplifier loop, the low-gray display consistency is improved, and the aim of higher LED display screen picture restoration is fulfilled. Meanwhile, the pulse width of the impact current can be adaptively adjusted according to the port constant current, so that the application requirement in the range of the port constant current is met. Furthermore, an extra large current pulse (namely the impulse current) is applied to the bias current when the port constant current is started, so that the response speed of the port constant current operational amplifier loop is improved, the starting response speed of the port switch tube is improved, the port response speed is improved, and the requirement of high gray level number can be met.
The foregoing is only a partial embodiment of the present application, and it should be noted that, for those skilled in the art, several modifications and decorations can be made without departing from the principle of the present application, and these modifications and decorations should also be regarded as the protection scope of the present application.
Claims (10)
1. A switch control circuit is characterized in that a signal input end of the switch control circuit is connected with a signal detection end in a port constant-current operational amplifier loop, and a control end of the switch control circuit is connected with a controlled end in a bias current generating circuit;
the switch control circuit is used for outputting an impact pulse to control the on-off of a switch element used for controlling the generation of the impact current in the bias current generation circuit, the impact current is used for controlling the port constant-current operational amplifier loop, the impact pulse is controlled by a comparison result between port sampling current and preset reference current, and the port sampling current is determined after the port constant-current in the port constant-current operational amplifier loop is sampled.
2. The switch control circuit of claim 1, wherein the switch control circuit comprises a current comparator;
the current comparator includes: the device comprises a reference current module, a port current sampling module and a control module;
the first end of the control module is respectively connected with the reference current module and the controlled end of the bias current generating circuit, and the port current sampling module is respectively connected with the second end of the control module and the signal detection end of the port constant-current operational amplifier loop;
the reference current module is used for generating the reference current;
the port current sampling module is used for generating the port sampling current;
and the control module is used for comparing the port sampling current with the reference current and outputting the impact pulse according to a comparison result.
3. The switch control circuit of claim 2, wherein the control module comprises:
the size of the port sampling switch tube is 1/k of that of the port switch tube in the port constant-current operational amplifier loop, and k is a sampling proportion; the drain electrode of the port switch tube is connected with the first end of the control module, the source electrode of the port switch tube is connected with the second end of the control module, and the grid electrode of the port switch tube is connected with the control end of the port switch tube.
4. The switch control circuit of claim 2, wherein the control module is operative to:
when the port sampling current is smaller than the reference current, outputting a first impact pulse to control the switch element to be closed;
and when the port sampling current is greater than or equal to the reference current, outputting a second impact pulse to control the switching element to be opened.
5. The switch control circuit of claim 2, further comprising:
a buffer connected between the output terminal of the current comparator and the controlled terminal of the bias current generating circuit.
6. The switch control circuit of claim 2, wherein the current comparator further comprises:
and the controllable switch is connected between the reference current module and the first end of the control module and is used for being opened or closed under the control of a current detection signal of the port constant current.
7. A bias current generating circuit is characterized in that a controlled end of the bias current generating circuit is connected with a control end of the switch control circuit according to any one of claims 1 to 6, and an output end of the bias current generating circuit is connected with an input end of a port constant-current operational amplifier loop;
the bias current generating circuit includes:
the impact current source is used for generating impact current;
and the switch element is connected between the impact current source and the ground and is used for being opened or closed under the control of the impact pulse output by the switch control circuit so as to provide a constant-current operational amplifier bias current containing the impact current for the port constant-current operational amplifier loop.
8. The bias current generating circuit according to claim 7, further comprising:
a port bias current source to generate a bias current;
a first control device, the input end of which is connected with a first current source; the port bias current source is connected between the output end of the current source and the ground, and a branch formed by connecting the impact current source and the switching element in series is connected to two ends of the port bias current source in parallel; the control end is connected with the output end;
a second control device, the input end of which is connected with a second current source; the control end of the first control device is connected with the control end of the first control device; the output end of the constant current operational amplifier is connected with the input end of the port constant current operational amplifier loop and used for outputting the constant current operational amplifier bias current to the port constant current operational amplifier loop, and the constant current operational amplifier bias current comprises the bias current.
9. An LED driving circuit, comprising: the switch control circuit of any one of claims 1 to 6, the bias current generating circuit of any one of claims 7 to 8, and the port constant current operational amplifier loop;
the signal input end of the switch control circuit is connected with the signal detection end of the port constant-current operational amplifier loop, the control end of the switch control circuit is connected with the controlled end of the bias current generating circuit, and the output end of the bias current generating circuit is connected with the input end of the port constant-current operational amplifier loop.
10. A switching control method applied to the switching control circuit according to any one of claims 1 to 6, the method comprising:
acquiring a port constant current in a port constant current operational amplifier loop, sampling the port constant current, and determining a port sampling current;
and comparing the port sampling current with a preset reference current, and outputting an impact pulse according to a comparison result to control the on-off of a switch element used for controlling the generation of the impact current in the bias current generating circuit, wherein the impact current is used for controlling the port constant-current operational amplifier loop.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202111022187.1A CN115734422A (en) | 2021-09-01 | 2021-09-01 | Switch control circuit, bias current generation circuit, LED drive circuit and method |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202111022187.1A CN115734422A (en) | 2021-09-01 | 2021-09-01 | Switch control circuit, bias current generation circuit, LED drive circuit and method |
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| CN115734422A true CN115734422A (en) | 2023-03-03 |
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| Application Number | Title | Priority Date | Filing Date |
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| CN202111022187.1A Pending CN115734422A (en) | 2021-09-01 | 2021-09-01 | Switch control circuit, bias current generation circuit, LED drive circuit and method |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN116633133A (en) * | 2023-07-21 | 2023-08-22 | 泉州艾奇科技有限公司 | Constant-current voltage stabilizing circuit |
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2021
- 2021-09-01 CN CN202111022187.1A patent/CN115734422A/en active Pending
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN116633133A (en) * | 2023-07-21 | 2023-08-22 | 泉州艾奇科技有限公司 | Constant-current voltage stabilizing circuit |
| CN116633133B (en) * | 2023-07-21 | 2024-05-03 | 泉州艾奇科技有限公司 | Constant-current voltage stabilizing circuit |
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