Circuit for eliminating spike voltage based on liquid crystal display

Abstract

The application relates to a liquid crystal display-based circuit for eliminating sharp peak voltage. The liquid crystal display-based circuit for eliminating sharp peak voltage comprises an input module, an absorption module and an output module. The absorption module comprises a resistor R2, a capacitor C2, a switch tube Q1 and a transformer T1. The first end of the resistor R2 is electrically connected with the input module and the first end of the capacitor C2 respectively, the second end of the resistor R2 is electrically connected with the second end of the capacitor C2, the first end of the capacitor C2 is electrically connected with the transformer T1, the first end of the switch tube Q1 is electrically connected with the transformer T1, and the second end of the switch tube Q1 is grounded. The output module is electrically connected with the transformer T1. The scheme provided by the application can eliminate high-frequency interference voltage and sharp peak voltage in input voltage, reduce overvoltage burnout damage to a switch MOS tube, and prolong the service life of a product.

Description

Technical Field

[0001] This invention relates to the field of liquid crystal display technology, and in particular to a circuit for eliminating voltage spikes in a liquid crystal display. Background Technology

[0002] Liquid crystal display (LCD) is a passive light-emitting flat panel display technology that mainly utilizes the change in light transmittance of liquid crystal molecules under the action of an electric field. Combined with polarizers, glass substrates, TFT arrays, color filters, and backlight modules, the LCD screen displays image pixels.

[0003] In related technologies, the power input of LCD monitors is currently susceptible to high-frequency interference and voltage spikes from the 220V AC power grid. Despite the protection measures of varistor, it is currently impossible to block the high-voltage impact of continuous high-frequency voltage spikes, which can cause instantaneous overvoltage burnout of the switching transistors in the power supply system, resulting in the LCD monitor showing a black screen or being unable to power on. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a circuit based on a liquid crystal display to eliminate voltage spikes. This circuit can eliminate high-frequency interference voltage and voltage spikes in the input voltage, reduce overvoltage burn-out damage to the switching MOSFET, and extend the product's service life.

[0005] The objective of this invention is achieved through the following technical solution: The first aspect of this application provides a circuit for eliminating voltage spikes in a liquid crystal display, comprising: an input module; an absorption module including a resistor R2, a capacitor C2, a switching transistor Q1, and a transformer T1, wherein the first end of the resistor R2 is electrically connected to the input module and the first end of the capacitor C2, the second end of the resistor R2 is electrically connected to the second end of the capacitor C2, the first end of the capacitor C2 is electrically connected to the transformer T1, the first end of the switching transistor Q1 is electrically connected to the transformer T1, and the second end of the switching transistor Q1 is grounded; and an output module electrically connected to the transformer T1.

[0006] The absorption module also includes a diode D2, the first end of which is electrically connected to the second end of the capacitor C2, and the second end of the diode D2 is electrically connected to the first end of the switching transistor Q1.

[0007] The output module includes a resistor R1 and a capacitor C1. The first end of the resistor R1 is electrically connected to the transformer T1, and the second end of the resistor R1 is electrically connected to the first end of the capacitor C1.

[0008] The output module also includes a diode D1 and a capacitor C3. The first end of the diode D1 is electrically connected to the first end of the resistor R1, the second end of the diode D1 is electrically connected to the first end of the capacitor C3, and the second end of the capacitor C3 is grounded.

[0009] Compared with the prior art, the present invention has at least the following advantages: This application eliminates high-frequency interference signals in the input voltage by setting up an absorption module, and absorbs instantaneous high voltage spikes, ensuring that the power supply system of the LCD can withstand the impact damage of continuous high-frequency spikes in the power grid, effectively protecting the switching transistors. Attached Figure Description

[0010] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly described below.

[0011] Figure 1 This is a functional block diagram of a circuit for eliminating voltage spikes based on a liquid crystal display according to an embodiment of the present invention; Figure 2 This is a circuit diagram of a liquid crystal display-based circuit for eliminating voltage spikes according to an embodiment of the present invention. Detailed Implementation

[0012] Embodiments of this application will now be described in more detail with reference to the accompanying drawings. While embodiments of this application are shown in the drawings, it should be understood that this application may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to make this application more thorough and complete, and to fully convey the scope of this application to those skilled in the art.

[0013] It should be understood that although the terms "first," "second," "third," etc., may be used in this application to describe various information, this information should not be limited to these terms. These terms are only used to distinguish information of the same type from one another. For example, without departing from the scope of this application, first information may also be referred to as second information, and similarly, second information may also be referred to as first information. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0014] Unless otherwise expressly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0015] Liquid crystal display (LCD) is a passive light-emitting flat panel display technology that mainly utilizes the change in light transmittance of liquid crystal molecules under the action of an electric field. Combined with polarizers, glass substrates, TFT arrays, color filters, and backlight modules, the LCD screen displays image pixels.

[0016] In related technologies, the power input of LCD monitors is currently susceptible to high-frequency interference and voltage spikes from the 220V AC power grid. Despite the protection measures of varistor, it is currently impossible to block the high-voltage impact of continuous high-frequency voltage spikes, which can cause instantaneous overvoltage burnout of the switching transistors in the power supply system, resulting in the LCD monitor showing a black screen or being unable to power on.

[0017] To address the aforementioned issues, this application provides a circuit for eliminating voltage spikes based on a liquid crystal display. This circuit can eliminate high-frequency interference voltages and voltage spikes in the input voltage, reduce overvoltage burn-out damage to the switching MOSFET, and extend the product's lifespan.

[0018] The technical solutions of the embodiments of this application are described in detail below with reference to the accompanying drawings.

[0019] See Figure 1 A circuit for eliminating voltage spikes based on a liquid crystal display includes: an input module 100, an absorption module 200, and an output module 300. The absorption module 200 includes a resistor R2, a capacitor C2, a switch Q1, and a transformer T1. The first end of the resistor R2 is electrically connected to the input module and the first end of the capacitor C2. The second end of the resistor R2 is electrically connected to the second end of the capacitor C2. The first end of the capacitor C2 is electrically connected to the transformer T1. The first end of the switch Q1 is electrically connected to the transformer T1, and the second end of the switch Q1 is grounded. The output module 300 is electrically connected to the transformer T1.

[0020] It should be noted that this application, by setting up an absorption module 200, eliminates high-frequency interference signals in the input voltage and absorbs instantaneous high voltage spikes, ensuring that the power supply system of the LCD monitor can withstand the impact damage of continuous high-frequency voltage spikes in the power grid, effectively protecting the switching transistors. The input module is used to input 220V AC power.

[0021] Specifically, in one embodiment, the absorption module 200 further includes a diode D2, the first end of which is electrically connected to the second end of the capacitor C2, and the second end of the diode D2 is electrically connected to the first end of the switching transistor Q1.

[0022] Specifically, in one embodiment, the output module 300 includes a resistor R1 and a capacitor C1. The first end of the resistor R1 is electrically connected to the transformer T1, and the second end of the resistor R1 is electrically connected to the first end of the capacitor C1.

[0023] Specifically, in one embodiment, the output module 300 further includes a diode D1 and a capacitor C3. The first end of the diode D1 is electrically connected to the first end of the resistor R1, the second end of the diode D1 is electrically connected to the first end of the capacitor C3, and the second end of the capacitor C3 is grounded.

[0024] The circuit principle of this application is explained below: When the LCD is working normally, the VCC voltage is transmitted to the circuit through the input module. It is first connected to one end of resistor R2 and capacitor C2, then to one end of the primary winding of transformer T1, and the other end is connected to the drain of switching transistor Q1. The input module transmits the PWM pulse width modulation signal sent by the MCU chip pin to the gate bias of switching transistor Q1, controls the working state of the switching transistor, and thus realizes the change of the output of the switching regulated power supply.

[0025] When the PWM signal is high, the switching transistor Q1 turns on when the gate voltage is greater than the threshold. The VCC voltage forms a path with the primary winding of transformer T1 for power supply. When current flows through the primary winding, an alternating current is generated, which, through the internal iron core, produces an alternating magnetic flux. According to the principle of electromagnetic induction, the transformer generates a magnetic field. Because the iron core provides a closed path with low magnetic reluctance, the primary magnetic flux is coupled to the secondary winding through the iron core, thereby inducing an electromotive force in the secondary winding for output. The freewheeling diode D2 is cut off due to reverse bias, and its elimination / absorption operation is in a dormant state. The primary magnetic flux is the medium for energy transfer, determined by the input voltage and frequency.

[0026] When the PWM signal is low, the gate voltage is less than the threshold, and the switch Q1 is turned off. The current through the primary winding gradually decreases, and the transformer T1 generates a back electromotive force. Since the windings inside the transformer have inductor characteristics, the current cannot change abruptly. Therefore, when the current path is forcibly cut off, an extremely high voltage spike is instantaneously generated, causing the Vds voltage of the switch Q1 to rise sharply. At this time, the spike voltage and the VCC voltage are superimposed on the switch Q1, and the total voltage across the switch Q1 is: Vds = VCC + Vor + Vs, where Vds is the voltage between the drain and source of the switch Q1, VCC is the input voltage, Vor is the voltage reflected from the secondary winding to the primary winding, and Vs is the spike voltage. When the Vds voltage rises sufficiently to forward conduct the freewheeling diode D2, the absorption / elimination module instantly starts working. The freewheeling diode D2 finds a new path for the reverse electromotive force, charging capacitor C2 through it. Due to the characteristic that the voltage across a capacitor cannot change abruptly, the voltage spike and interference signal are quickly absorbed during the charging process of capacitor C2, keeping the peak voltage of Vds of switching transistor Q1 within a safe voltage range. This prevents overvoltage burnout of switching transistor Q1 due to excessive reverse electromotive force and voltage spikes. Because capacitor C2 plays a leading role in absorbing / eliminating voltage spikes, after capacitor C2 is fully charged, it slowly discharges through resistor R2. The voltage spike is absorbed during the charging and discharging process of capacitor C2 and eliminated as heat energy through resistor R2, thereby eliminating the impact damage of voltage spikes, effectively protecting switching transistor Q1 from overvoltage damage, reducing the rate of change of output voltage, and improving the overall EMI performance of the circuit.

[0027] When current flows through the primary winding of transformer T1, an alternating magnetic field is generated. This field is transmitted to the secondary winding via the iron core coupling, inducing a positive electromotive force, which is then connected to one end of diode D1. Based on the diode's characteristics, the AC signal is rectified, and the other end of diode D1 outputs a unidirectional DC signal. This DC signal contains a certain amount of AC ripple, which is then connected to capacitors C1 and C3 and resistor R1 to filter out interference. The capacitors, with their AC-passing and DC-blocking characteristics, filter out the high-frequency AC ripple, resulting in a smoother and more stable VCC OUT output voltage.

[0028] The solution of this application has been described in detail above with reference to the accompanying drawings. In the above embodiments, the descriptions of each embodiment have different focuses; for parts not described in detail in a certain embodiment, please refer to the relevant descriptions of other embodiments. Those skilled in the art should also understand that the actions and modules involved in the specification are not necessarily essential to this application. Furthermore, it is understood that the steps in the method of this application embodiment can be adjusted, combined, and deleted according to actual needs, and the modules in the device of this application embodiment can be combined, divided, and deleted according to actual needs. The various embodiments of this application have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen to best explain the principles, practical application, or improvement of the technology in the market, or to enable others skilled in the art to understand the embodiments disclosed herein.

Claims

1. A circuit for eliminating voltage spikes based on a liquid crystal display, characterized in that, include: Input module; The absorption module includes a resistor R2, a capacitor C2, a switch Q1, and a transformer T1. The first end of the resistor R2 is electrically connected to the input module and the first end of the capacitor C2. The second end of the resistor R2 is electrically connected to the second end of the capacitor C2. The first end of the capacitor C2 is electrically connected to the transformer T1. The first end of the switch Q1 is electrically connected to the transformer T1. The second end of the switch Q1 is grounded. The output module is electrically connected to the transformer T1.

2. The circuit for eliminating voltage spikes based on a liquid crystal display according to claim 1, characterized in that, The absorption module also includes a diode D2, the first end of which is electrically connected to the second end of the capacitor C2, and the second end of the diode D2 is electrically connected to the first end of the switching transistor Q1.

3. The circuit for eliminating voltage spikes based on a liquid crystal display according to claim 1, characterized in that, The output module includes a resistor R1 and a capacitor C1. The first end of the resistor R1 is electrically connected to the transformer T1, and the second end of the resistor R1 is electrically connected to the first end of the capacitor C1.

4. The circuit for eliminating voltage spikes based on a liquid crystal display according to claim 3, characterized in that, The output module also includes a diode D1 and a capacitor C3. The first end of the diode D1 is electrically connected to the first end of the resistor R1, the second end of the diode D1 is electrically connected to the first end of the capacitor C3, and the second end of the capacitor C3 is grounded.

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