A bias voltage power supply circuit and method for LCD screen

Abstract

The present invention discloses a bias voltage power supply circuit and method for an LCD screen, wherein the first end of an energy storage unit is electrically connected to the input end of a DC-DC power chip, the second end is commonly connected to the output end of the DC-DC power chip, the first end of a first coupling unit, and the first end of a second coupling unit, the second end of the first coupling unit is electrically connected to the first end of a first rectifier unit, the second end of the second coupling unit is electrically connected to the first end of a second rectifier unit, the second end of the first rectifier unit and the second end of the second rectifier unit are electrically connected to a first output unit and a second output unit, respectively; the first output unit and the second output unit are used to output positive voltage and negative voltage to the LCD screen, respectively. By using a DC-DC power chip, a coupling capacitor, and a rectifier bridge to form a bias voltage circuit for an LCD screen, instead of a traditional bias power chip circuit, positive voltage and negative voltage are obtained and output to the LCD screen, thereby eliminating the need to use a blind hole process, reducing process complexity, and at the same time, reducing the cost of the circuit.

Description

Technical Field

[0001] The present invention relates to the technical field of bias voltage of LCD screens, and in particular to a bias voltage power supply circuit and method for LCD screens. Background Art

[0002] LCD bias voltage refers to the voltage used to control the deflection of liquid crystal molecules in a liquid crystal display (LCD). A reasonable bias voltage can make the liquid crystal molecules produce corresponding deflection angles under different voltage states, thereby accurately controlling the light transmittance of each pixel and achieving accurate image display. By adjusting the bias voltage, the contrast of the LCD display can be changed, making the image clearer and more vivid, meeting the display needs of different users. It can usually be generated by a dedicated power management chip or circuit, such as the MAX1578 chip, which contains three advanced charge pumps for LCD bias power supply, which can provide fixed +5V, +15V and -10V voltages without the need for external diodes, meeting the voltage requirements of small active matrix TFT-LCD displays. It can also be used. Figure 1 The bias power supply circuit composed of U1702: 5V (VBAT_SYS) voltage is input to U1702 (bias voltage IC, and the U1702 chip directly converts the output VSP / VSN positive and negative voltages.

[0003] However, since the PCB package size of the bias voltage chip is small, the PCB design needs to adopt a blind hole process, which is costly. At the same time, the cost of the bias voltage chip is generally relatively high. Summary of the invention

[0004] In the prior art, the bias voltage of the LCD screen is obtained by using a power supply circuit composed of a bias voltage chip. Due to the small package size, the process is not only complicated but also the cost is high.

[0005] In view of the above problems, a bias voltage power supply circuit and method for an LCD screen are proposed. The bias voltage circuit of the LCD screen is composed of a DC-DC power supply chip, a coupling capacitor, and a rectifier bridge, which replaces the traditional bias power supply chip circuit to obtain positive voltage and negative voltage, and output them to the LCD screen, thereby eliminating the need to use a blind hole process, reducing the process complexity, and at the same time reducing the cost of the circuit.

[0006] In a first aspect, a bias voltage power supply circuit for an LCD screen includes:

[0007] DC-DC power supply chip;

[0008] Energy storage unit;

[0009] A first coupling unit and a second coupling unit;

[0010] A first rectifying unit and a second rectifying unit;

[0011] A first output unit and a second output unit;

[0012] The first end of the energy storage unit is electrically connected to the input end of the DC-DC power supply chip, the second end is commonly connected to the output end of the DC-DC power supply chip, the first end of the first coupling unit, and the first end of the second coupling unit, the second end of the first coupling unit is electrically connected to the first end of the first rectifier unit, the second end of the second coupling unit is electrically connected to the first end of the second rectifier unit, and the second end of the first rectifier unit and the second end of the second rectifier unit are electrically connected to the first output unit and the second output unit respectively;

[0013] The first output unit and the second output unit are used to output a positive voltage and a negative voltage to the LCD screen respectively.

[0014] In conjunction with the bias voltage power supply circuit for an LCD screen described in the first aspect of the present invention, in a first possible implementation manner, the DC-DC power supply chip includes:

[0015] Input pins and output pins;

[0016] An input power source and a first end of the energy storage unit are electrically connected to the input pin, and a second end of the energy storage unit is electrically connected to the output pin;

[0017] The output pin is used to output a PWM waveform of a specified frequency.

[0018] In combination with the first possible implementation manner of the first aspect of the present invention, in a second possible implementation manner, the bias voltage power supply circuit of the LCD screen further includes a feedback unit;

[0019] The DC-DC power supply chip also includes a feedback pin;

[0020] The first output unit is electrically connected to the feedback pin through the feedback unit.

[0021] In combination with the second possible implementation manner of the first aspect of the present invention, in a third possible implementation manner, the first rectifying unit includes:

[0022] A first rectifier diode and a second rectifier diode;

[0023] The anode of the first rectifier diode and the cathode of the second rectifier diode are connected together and then electrically connected to the second end of the first coupling unit;

[0024] The cathode of the first rectifier diode is electrically connected to the second output unit, and the anode of the second rectifier diode is grounded;

[0025] The first output unit is used to output a positive voltage.

[0026] In combination with the second possible implementation manner of the first aspect of the present invention, in a fourth possible implementation manner, the second rectifying unit includes:

[0027] a third rectifier diode and a fourth rectifier diode;

[0028] The cathode of the third rectifier diode and the anode of the fourth rectifier diode are connected together and then electrically connected to the second end of the second coupling unit;

[0029] The anode of the third rectifier diode is electrically connected to the second output unit, and the cathode of the fourth rectifier diode is grounded;

[0030] The second output unit is used for outputting a negative voltage.

[0031] In combination with the first possible implementation manner of the first aspect of the present invention, in a fifth possible implementation manner, the bias voltage power supply circuit of the LCD screen further includes an enabling control unit;

[0032] The DC-DC power supply chip also includes an enable control pin;

[0033] The first end of the enabling control unit is electrically connected to the control unit, and the second end is electrically connected to the enabling control pin.

[0034] In combination with the first possible implementation manner of the first aspect of the present invention, in a sixth possible implementation manner, the first output unit includes:

[0035] A first filtering module;

[0036] The first filtering module is used to filter the output positive voltage.

[0037] In combination with the first possible implementation manner of the first aspect of the present invention, in a seventh possible implementation manner, the second output unit includes:

[0038] A second filtering module;

[0039] The second filtering module is used to filter the output negative voltage.

[0040] In a second aspect, a bias voltage power supply method for an LCD screen adopts the bias voltage power supply circuit for an LCD screen described in the first aspect, comprising:

[0041] Step 100: inputting the power supply voltage to be converted into a DC-DC power supply chip, and using an energy storage unit to store energy, the DC-DC power supply chip performs pulse width modulation on the power supply voltage and outputs a PWM waveform;

[0042] Step 200, superimposing the voltage waveform output by the energy storage unit with the PWM waveform, and performing a first coupling and a second coupling on the AC voltage waveform obtained after superposition, to obtain a first sinusoidal waveform and a second sinusoidal waveform respectively;

[0043] Step 300: Perform a first rectification and a second rectification on the first sinusoidal waveform and the second sinusoidal waveform respectively to obtain a positive voltage and a negative voltage respectively.

[0044] In conjunction with the bias voltage power supply method for an LCD screen described in the first aspect of the present invention, in a first possible implementation manner, the method further includes:

[0045] Step 400, performing a first filtering and a second filtering on the positive voltage and the negative voltage respectively;

[0046] Step 500: output the positive voltage and negative voltage obtained after filtering to the LCD screen respectively.

[0047] The bias voltage power supply circuit and method for an LCD screen described in the present invention utilizes a DC-DC power supply chip, a coupling capacitor, and a rectifier bridge to form a bias voltage circuit for the LCD screen, replacing a traditional bias power supply chip circuit to obtain positive voltage and negative voltage, which are output to the LCD screen, thereby eliminating the need for a blind hole process, reducing process complexity, and at the same time, reducing circuit costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0049] Figure 1 A bias voltage power supply circuit diagram for an LCD screen in the prior art;

[0050] Figure 2 This is a schematic diagram of the connection of the bias voltage power supply circuit module of the LCD screen in the present invention;

[0051] Figure 3 A bias voltage power supply circuit diagram of the LCD screen in the present invention;

[0052] Figure 4 A schematic flow chart of a specific embodiment of a bias voltage power supply method for an LCD screen in the present invention;

[0053] Figure 5 A schematic flow chart of another specific embodiment of the bias voltage power supply method for an LCD screen of the present invention;

[0054] Parts and serial numbers:

[0055] 100 - DC-DC power supply chip, 200 - energy storage unit, 300 - first coupling unit, 400 - second coupling unit, 500 - first rectifying unit, 600 - second rectifying unit, 700 - first output unit, 800 - second output unit, 900 - LCD screen. DETAILED DESCRIPTION

[0056] The following will be combined with the accompanying drawings in the invention to clearly and completely describe the technical solutions in the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments in the present invention, other embodiments obtained by ordinary technicians in this field without creative work are all within the scope of protection of the present invention.

[0057] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more related listed items.

[0058] It should be noted that when an element is referred to as being "fixed to" or "disposed on" another element, it can be directly on the other element or indirectly on the other element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or indirectly connected to the other element.

[0059] It should be understood that the orientation or position relationship indicated by terms such as "length", "width", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside" and "outside" are based on the orientation or position relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0060] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of this application, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0061] In the prior art, the bias voltage of the LCD screen 900 is obtained by using a power supply circuit composed of a bias voltage chip. Due to the small package size, the process is not only complicated, but also the cost is high. Figure 1 , Figure 1 The bias voltage power supply circuit diagram in the prior art; LCD screen 900 bias voltage control as shown in FIG. Figure 1 :5V (VBAT_SYS) voltage is input to U1702 (bias voltage IC, and the U1702 chip directly converts the output VSP / VSN positive and negative voltages (VSN). Due to the small package size, the PCB design needs to use a blind hole process, which is costly and the chip price is relatively expensive.

[0062] In view of the above problems, a bias voltage power supply circuit and method for an LCD screen 900 are proposed.

[0063] In a first aspect, a bias voltage supply circuit for an LCD screen 900 is provided, such as Figure 2 , Figure 2 Schematic diagram of the connection of the bias voltage power supply circuit module of the LCD screen 900 in the present invention; including a DC-DC power chip 100, an energy storage unit 200, a first coupling unit 300 and a second coupling unit 400, a first rectifier unit 500 and a second rectifier unit 600, a first output unit 700 and a second output unit 800; the first end of the energy storage unit 200 is electrically connected to the input end of the DC-DC power chip 100, and the second end is electrically connected to the output end of the DC-DC power chip 100, the first end of the first coupling unit 300, the first end of the second rectifier unit 600, the first output unit 700 and the second output unit 800. The first ends of the two coupling units 400 are connected in common, the second end of the first coupling unit 300 is electrically connected to the first end of the first rectifying unit 500, the second end of the second coupling unit 400 is electrically connected to the first end of the second rectifying unit 600, the second end of the first rectifying unit 500 and the second end of the second rectifying unit 600 are electrically connected to the first output unit 700 and the second output unit 800 respectively; the first output unit 700 and the second output unit 800 are used to output a positive voltage (VSP) and a negative voltage (VSN) to the LCD screen 900 respectively. By using the DC-DC power chip 100, coupling capacitors, and a rectifier bridge to form a bias voltage circuit of the LCD screen 900, instead of the traditional bias power chip 100 circuit, a positive voltage (VSP) and a negative voltage (VSN) are obtained and output to the LCD screen 900, so that there is no need to use a blind hole process, which reduces the process complexity and the circuit cost.

[0064] In this embodiment, the DC-DC power supply chip 100 performs pulse width modulation on the input 5V power supply voltage and outputs a PWM waveform. The energy storage unit 200 is used to maintain a stable output of the output voltage. After the output PWM waveform is superimposed on the voltage waveform of the energy storage unit 200, a sine waveform is output through the first coupling unit 300 and the second coupling unit 400 respectively, and then rectified by the first rectifying unit 500 and the second rectifying unit 600 to obtain a positive voltage (VSP) and a negative voltage (VSN) to be output to the LCD screen 900.

[0065] In this embodiment, the first coupling unit 300 and the second coupling unit 400 respectively use coupling capacitors (C5 and C6) to convert the output PWM waveform into a sinusoidal waveform.

[0066] Preferably, if Figure 3 , Figure 3 This is a bias voltage power supply circuit diagram of the LCD screen 900 in the present invention; the DC-DC power supply chip 100 includes an input pin VIN and an output pin SW; the first end of the input power supply and energy storage unit 200 is electrically connected to the input pin VIN, and the second end of the energy storage unit 200 is electrically connected to the output pin SW; the output pin SW is used to output a PWM waveform of a specified frequency.

[0067] In this embodiment, the frequency of the PWM waveform is preferably 1.2 MHz, and the energy storage unit 200 is equivalent to being connected in parallel at both ends of the DC-DC power chip 100, storing energy when the switch is turned on, and outputting electrical energy when the switch tube is turned off to maintain the stability of the output voltage.

[0068] In this embodiment, the energy storage unit 200 uses an energy storage inductor L1 , which is connected in parallel at two ends of the DC-DC power chip 100 and is commonly connected with the first coupling unit 300 and the second coupling unit 400 .

[0069] Preferably, the bias voltage power supply circuit of the LCD screen 900 further includes a feedback unit; the DC-DC power chip 100 further includes a feedback pin FB; the first output unit 700 is electrically connected to the feedback pin FB via the feedback unit. The feedback unit is used to provide feedback to the voltage signal output by the first output unit 700 and make adjustments to maintain the stability of the output.

[0070] like Figure 3 The feedback unit includes resistors (R2, R3) and capacitor C4, and its circuit structure is as follows: Figure 3 shown.

[0071] Preferably, the first rectifier unit 500 includes a first rectifier diode D1 and a second rectifier diode D2; the anode of the first rectifier diode D1 and the cathode of the second rectifier diode D2 are connected together and electrically connected to the second end of the first coupling unit 300; the cathode of the first rectifier diode D1 is electrically connected to the second output unit 800, and the anode of the second rectifier diode D2 is grounded; the first output unit 700 is used to output a positive voltage (VSP).

[0072] Preferably, the second rectifier unit 600 includes a third rectifier diode D3 and a fourth rectifier diode D4; the cathode of the third rectifier diode D3 and the anode of the fourth rectifier diode D4 are connected together and electrically connected to the second end of the second coupling unit 400; the anode of the third rectifier diode D3 is electrically connected to the second output unit 800, and the cathode of the fourth rectifier diode D4 is grounded; the second output unit 800 is used to output a negative voltage (VSN).

[0073] In this embodiment, the enabling control unit includes a resistor R1 and a capacitor C3 , which are electrically connected to the control unit or the MCU and are used to control the start-up of the DC-DC power chip 100 .

[0074] Preferably, the first output unit 700 includes a first filtering module; the first filtering module is used to filter the output positive voltage (VSP).

[0075] In this embodiment, the first output unit 700 further includes a conversion resistor R5, and the first filtering module includes capacitors C9 and C10. The circuit structure is as follows: Figure 3 shown.

[0076] Preferably, the second output unit 800 includes a second filtering module; the second filtering module is used to filter the output negative voltage (VSN).

[0077] In this embodiment, the second output unit 800 further includes a conversion resistor R4, and the second filtering module includes capacitors C7 and C8. The circuit structure is as follows: Figure 3 shown.

[0078] Preferably, the bias voltage power supply circuit of the LCD screen 900 also includes an enable control unit; the DC-DC power supply chip 100 also includes an enable control pin EN; the first end of the enable control unit is electrically connected to the control unit, and the second end is electrically connected to the enable control pin EN.

[0079] like Figure 3The circuit for converting direct current into positive and negative power, which is composed of a DC-DC power chip 100 and a rectifier diode component, mainly utilizes the pulse width modulation (PWM) output by pin 1 of the DC-DC chip to convert it into sinusoidal alternating current through coupling capacitors C5 and C6, and then passes through bridge rectifiers D1, D2, D3, and D4 rectifier diodes to output negative voltage (VSN) (VSN) and positive voltage (VSP) (VSP).

[0080] The normal working process is that when EN outputs high level, 5V power supply is input to the 5th pin of the DC-DC power chip 100, the DC-DC power chip 100 works, and the 1st pin SW of the DC-DC power chip 100 outputs 1.2MHZ pulse width modulation (PWM), which is converted into sinusoidal AC through the coupling capacitors C411 and C412, and then outputs positive voltage (VSP) (VSP) through the bridge rectifier circuit D1, D2 rectifier diodes (IN4148), and outputs negative voltage (VSN) (VSN) through the rectifier diodes D3 and D4 (IN4148), and then the output positive voltage (VSP) (VSP) and the voltage divider circuit composed of R4 and R5 are used for voltage feedback by the 3rd pin FB of the DC-DC power chip 100 to adjust and stabilize the output voltage.

[0081] In a second aspect, a bias voltage supply method for an LCD screen 900 is provided, such as Figure 4 , Figure 4 The present invention is a schematic flow chart of a specific embodiment of the bias voltage power supply method for the LCD screen 900; the bias voltage power supply circuit of the LCD screen 900 of the first aspect is adopted, comprising: S100, inputting the power supply voltage to be converted into the DC-DC power supply chip 100, and utilizing the energy storage unit 200 to store energy, the DC-DC power supply chip 100 pulse width modulating the power supply voltage, and outputting a PWM waveform; S200, superimposing the voltage waveform output by the energy storage unit 200 with the PWM waveform, and performing a first coupling and a second coupling on the AC voltage waveform obtained after superposition, respectively, to obtain a first sinusoidal waveform and a second sinusoidal waveform, respectively; S300, performing a first rectification and a second rectification on the first sinusoidal waveform and the second sinusoidal waveform, respectively, to obtain a positive voltage (VSP) and a negative voltage (VSN), respectively.

[0082] Preferably, if Figure 5 , Figure 5 This is a schematic flow chart of the steps of another specific embodiment of the bias voltage power supply method for the LCD screen 900 in the present invention; the method also includes: S400, performing a first filtering and a second filtering on the positive voltage (VSP) and the negative voltage (VSN), respectively; S500, converting the positive current and the negative current obtained after filtering to obtain a positive voltage (VSP) and a negative voltage (VSN), which are output to the LCD screen 900, respectively.

[0083] A bias voltage power supply circuit and method for an LCD screen 900 of the present invention is implemented. By utilizing a DC-DC power supply chip 100, a coupling capacitor, and a rectifier bridge to form a bias voltage circuit for the LCD screen 900, instead of a traditional bias power supply chip 100 circuit, a positive voltage (VSP) and a negative voltage (VSN) are obtained and output to the LCD screen 900, thereby eliminating the need for a blind hole process, reducing process complexity, and at the same time, reducing the cost of the circuit.

[0084] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A bias voltage power supply circuit for an LCD screen, characterized in that it includes: DC-DC power supply chip; Energy storage unit; A first coupling unit and a second coupling unit; A first rectifying unit and a second rectifying unit; A first output unit and a second output unit; The first end of the energy storage unit is electrically connected to the input end of the DC-DC power supply chip, the second end is commonly connected to the output end of the DC-DC power supply chip, the first end of the first coupling unit, and the first end of the second coupling unit, the second end of the first coupling unit is electrically connected to the first end of the first rectifier unit, the second end of the second coupling unit is electrically connected to the first end of the second rectifier unit, and the second end of the first rectifier unit and the second end of the second rectifier unit are electrically connected to the first output unit and the second output unit respectively; The first output unit and the second output unit are used to output a positive voltage and a negative voltage to the LCD screen respectively.

2. The bias voltage power supply circuit for an LCD screen according to claim 1, characterized in that: The DC-DC power supply chip includes: Input pins and output pins; An input power source and a first end of the energy storage unit are electrically connected to the input pin, and a second end of the energy storage unit is electrically connected to the output pin; The output pin is used to output a PWM waveform of a specified frequency.

3. The bias voltage power supply circuit for an LCD screen according to claim 2, characterized in that: The bias voltage power supply circuit of the LCD screen also includes a feedback unit; The DC-DC power supply chip also includes a feedback pin; The first output unit is electrically connected to the feedback pin through the feedback unit.

4. The bias voltage power supply circuit for an LCD screen according to claim 3, characterized in that: The first rectifying unit comprises: A first rectifier diode and a second rectifier diode; The anode of the first rectifier diode and the cathode of the second rectifier diode are connected together and then electrically connected to the second end of the first coupling unit; The cathode of the first rectifier diode is electrically connected to the second output unit, and the anode of the second rectifier diode is grounded; The first output unit is used to output a positive voltage.

5. The bias voltage power supply circuit for an LCD screen according to claim 3, characterized in that: The second rectifying unit comprises: a third rectifier diode and a fourth rectifier diode; The cathode of the third rectifier diode and the anode of the fourth rectifier diode are connected together and then electrically connected to the second end of the second coupling unit; The anode of the third rectifier diode is electrically connected to the second output unit, and the cathode of the fourth rectifier diode is grounded; The second output unit is used to output a negative voltage.

6. The bias voltage power supply circuit for an LCD panel according to claim 2, characterized in that: The bias voltage power supply circuit of the LCD screen also includes an enabling control unit; The DC-DC power supply chip also includes an enable control pin; The first end of the enabling control unit is electrically connected to the control unit, and the second end is electrically connected to the enabling control pin.

7. The bias voltage power supply circuit for an LCD screen according to claim 2, characterized in that: The first output unit comprises: A first filtering module; The first filtering module is used to filter the output positive voltage.

8. The bias voltage power supply circuit for an LCD screen according to claim 2, characterized in that: The second output unit comprises: A second filtering module; The second filtering module is used to filter the output negative voltage.

9. A method for supplying bias voltage to an LCD screen, using the bias voltage supply circuit for an LCD screen as claimed in any one of claims 1 to 8, characterized in that: include: Step 100: inputting the power supply voltage to be converted into a DC-DC power supply chip, and using an energy storage unit to store energy, the DC-DC power supply chip performs pulse width modulation on the power supply voltage and outputs a PWM waveform; Step 200, superimposing the voltage waveform output by the energy storage unit with the PWM waveform, and performing a first coupling and a second coupling on the AC voltage waveform obtained after superposition, to obtain a first sinusoidal waveform and a second sinusoidal waveform respectively; Step 300: Perform a first rectification and a second rectification on the first sinusoidal waveform and the second sinusoidal waveform respectively to obtain a positive voltage and a negative voltage respectively.

10. The bias voltage supply method for an LCD screen according to claim 9, characterized in that: The bias voltage power supply method of the LCD screen also includes: Step 400, performing a first filtering and a second filtering on the positive voltage and the negative voltage respectively; Step 500: output the positive voltage and negative voltage obtained after filtering to the LCD screen respectively.

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