Reference voltage generating circuit of positive and negative pressure source driving circuit

Abstract

The application discloses a reference voltage generating circuit, which provides stable and accurate positive and negative voltages for a load circuit, and has the characteristics that an operational amplifier is used to receive a positive reference voltage +VREF at a first input end; a transistor is connected to an output end of the operational amplifier at a gate, and connected to a second input end of the operational amplifier and a first end of a first resistance string at a source; the first resistance string comprises a plurality of first resistances connected in series, and the second ends of the plurality of first resistances output a plurality of different first voltages respectively; a current mirror is used to work between a positive voltage VSP and a negative voltage VSN, and the current mirror is connected to a drain of the transistor and a second end of a second resistance string; and the second resistance string comprises a plurality of second resistances connected in series, and the second ends of the plurality of second resistances output a plurality of different second voltages respectively, wherein the first end of the second resistance string and the second end of the first resistance string are connected to a ground potential GND.

Description

Technical Field

[0001] This application belongs to the field of positive and negative voltage reference voltage generation circuits, and relates to the design of positive and negative voltage source drive circuits for liquid crystal displays. Background Technology

[0002] Liquid crystal displays (LCDs) are common output devices in modern electronic systems. An LCD contains many liquid crystal cells. By applying voltage across each liquid crystal cell, the light transmittance of the cell can be controlled, thus displaying different grayscale levels. By controlling the grayscale settings of the three primary colors individually, the color of each pixel can be controlled.

[0003] To control the voltage across liquid crystal cells or other load circuits, a positive and negative voltage source driving circuit is needed. To save energy and cost, a design with a smaller chip area is urgently required. This design should not only save costs but also reduce the power consumed by the positive and negative voltage source driving circuit. Summary of the Invention

[0004] This application proposes a reference voltage generation circuit, a positive and negative voltage source driving circuit using such a reference voltage generation circuit, and a liquid crystal display to address the shortcomings of the prior art. The purpose is to provide a stable and accurate positive and negative voltage for the load circuit, save chip area and energy consumption during operation, increase product competitiveness, and promote environmental protection.

[0005] To achieve the above objectives, this application adopts the following technical solution:

[0006] According to an embodiment of this application, a reference voltage generation circuit is provided, characterized in that it comprises: an operational amplifier, the first input terminal of which is used to receive a positive reference voltage +VREF; a transistor, the gate of which is connected to the output terminal of the operational amplifier, and the source of which is connected to the second input terminal of the operational amplifier and the first end of a first resistor string; the first resistor string comprising a plurality of first resistors connected in series, the second ends of which respectively output a plurality of different first voltages; a current mirror, operating between a positive voltage VSP and a negative voltage VSN, the current mirror being connected to the drain of the transistor and the second end of the second resistor string; and a second resistor string comprising a plurality of second resistors connected in series, the second ends of which respectively output a plurality of different second voltages, wherein the first end of the second resistor string and the second end of the first resistor string are connected to ground potential GND.

[0007] Furthermore, in order to provide both positive and negative voltages simultaneously, the plurality of different first voltages are respectively located between the positive voltage VSP and the ground potential GND, and the plurality of different first voltages are respectively located between the ground potential GND and the negative voltage VSN.

[0008] Furthermore, in order to select one of a plurality of positive voltages and a plurality of negative voltages as the positive reference voltage VREF_VGMP and the negative reference voltage VREF_VGMN respectively, the reference voltage generation circuit is characterized in that the above-mentioned reference voltage generation circuit further includes a first multiplexer and a second multiplexer. The first multiplexer is used to receive the plurality of different first voltages and select one of the plurality of different first voltages to output the positive reference voltage VREF_VGMP to the positive operational amplifier. The second multiplexer is used to receive the plurality of different second voltages and select one of the plurality of different second voltages to output the negative reference voltage VREF_VGMN to the negative operational amplifier.

[0009] Furthermore, in order to obtain a temperature-stable reference power supply, the positive reference voltage +VREF is derived from a bandgap reference circuit, which operates between the positive voltage VSP and the ground potential GND.

[0010] Furthermore, in order to better output negative voltage, the current mirror is characterized in that it is a current mirror with four transistors.

[0011] According to an embodiment of this application, a positive and negative voltage source driving circuit is provided, characterized in that it includes: a bandgap reference circuit, operating between a positive voltage VSP and a ground potential GND, for providing a positive reference voltage +VREF; a reference voltage generating circuit, for receiving the positive reference voltage +VREF and outputting a positive reference voltage VREF_VGMP to a positive operational amplifier and outputting a negative reference voltage VREF_VGMN to a negative operational amplifier; and the positive operational amplifier and the negative operational amplifier, respectively, outputting a positive voltage and a negative voltage to a load circuit.

[0012] Furthermore, in order to select one of a plurality of positive voltages and a plurality of negative voltages as the positive reference voltage VREF_VGMP and the negative reference voltage VREF_VGMN respectively, the reference voltage generation circuit is characterized in that the above-mentioned reference voltage generation circuit further includes a first multiplexer and a second multiplexer. The reference voltage generation circuit is used to receive the positive reference voltage +VREF to generate a plurality of different first voltages and a plurality of different second voltages to the first multiplexer and the second multiplexer respectively. The first multiplexer selects one of the plurality of different first voltages to output the positive reference voltage VREF_VGMP to the positive operational amplifier, and the second multiplexer selects one of the plurality of different second voltages to output the negative reference voltage VREF_VGMN to the negative operational amplifier.

[0013] Furthermore, in order to provide both positive and negative voltages simultaneously, the plurality of different first voltages are respectively located between the positive voltage VSP and the ground potential GND, and the plurality of different first voltages are respectively located between the ground potential GND and the negative voltage VSN.

[0014] Furthermore, to eliminate the need for two similar circuits in the reference voltage generation circuit, and instead utilize only a single operational amplifier to save chip area and power consumption, the reference voltage generation circuit is characterized by comprising: an operational amplifier, the first input of which is used to receive the positive reference voltage +VREF; a transistor, the gate of which is connected to the output of the operational amplifier, and the source of which is connected to the second input of the operational amplifier and the first end of the first resistor string; the first resistor string comprising a plurality of first resistors connected in series, the second ends of which respectively output the plurality of different first voltages; a current mirror operating between the positive voltage VSP and the negative voltage VSN, the current mirror being connected to the drain of the transistor and the second end of the second resistor string; the first end of the second resistor string being connected to the ground potential GND, the second resistor string comprising a plurality of second resistors connected in series, the second ends of which respectively output the plurality of different second voltages.

[0015] Furthermore, in order to better output negative voltage, the current mirror is characterized in that it is a current mirror with four transistors.

[0016] Furthermore, for application in small and medium-sized liquid crystal displays, the positive voltage VSP is characterized by being between 5V and 6V, and the negative voltage VSN is between -5V and -6V.

[0017] According to an embodiment of this application, a liquid crystal display is provided, characterized in that it comprises: a plurality of liquid crystal cells; a plurality of liquid crystal control units that control the plurality of liquid crystal cells respectively; and a positive and negative voltage source driving circuit, wherein the positive and negative voltage source driving circuit comprises: a bandgap reference circuit, operating between a positive voltage VSP and a ground potential GND, for providing a positive reference voltage +VREF; a reference voltage generating circuit, for receiving the positive reference voltage +VREF and outputting a positive reference voltage VREF_VGMP to a positive operational amplifier and outputting a negative reference voltage VREF_VGMN to a negative operational amplifier; and the positive operational amplifier and the negative operational amplifier respectively outputting a positive voltage and a negative voltage to one of the plurality of liquid crystal control units, for controlling the grayscale level of one of the plurality of liquid crystal cells.

[0018] Furthermore, in order to select one of a plurality of positive voltages and a plurality of negative voltages as the positive reference voltage VREF_VGMP and the negative reference voltage VREF_VGMN respectively, the reference voltage generation circuit is characterized in that the above-mentioned reference voltage generation circuit further includes a first multiplexer and a second multiplexer. The reference voltage generation circuit is used to receive the positive reference voltage +VREF to generate a plurality of different first voltages and a plurality of different second voltages to the first multiplexer and the second multiplexer respectively. The first multiplexer selects one of the plurality of different first voltages to output the positive reference voltage VREF_VGMP to the positive operational amplifier, and the second multiplexer selects one of the plurality of different second voltages to output the negative reference voltage VREF_VGMN to the negative operational amplifier.

[0019] Furthermore, to eliminate the need for two similar circuits in the reference voltage generation circuit, and instead utilize only a single operational amplifier to save chip area and power consumption, the reference voltage generation circuit is characterized by comprising: an operational amplifier, the first input of which is used to receive the positive reference voltage +VREF; a transistor, the gate of which is connected to the output of the operational amplifier, and the source of which is connected to the second input of the operational amplifier and the first end of the first resistor string; the first resistor string comprising a plurality of first resistors connected in series, the second ends of which respectively output the plurality of different first voltages; a current mirror operating between the positive voltage VSP and the negative voltage VSN, the current mirror being connected to the drain of the transistor and the second end of the second resistor string; and the second resistor string, wherein the first end of the second resistor string is connected to the ground potential GND, the second resistor string comprising a plurality of second resistors connected in series, the second ends of which respectively output the plurality of different second voltages.

[0020] Furthermore, in order to better output negative voltage, the current mirror is characterized in that it is a current mirror with four transistors.

[0021] Furthermore, for application in small and medium-sized liquid crystal displays, the positive voltage VSP is characterized by being between 5V and 6V, and the negative voltage VSN is between -5V and -6V.

[0022] According to an embodiment of this application, a reference voltage generation circuit is provided, characterized in that it comprises: an operational amplifier, the first input terminal of which is connected to ground potential GND; a transistor, the gate of which is connected to the output terminal of the operational amplifier, the source of which is connected to the first end of a first resistor string, and the drain of which is connected to a positive voltage VSP; the first resistor string comprising a plurality of first resistors connected in series, the second ends of which respectively output a plurality of different first voltages; a second resistor string comprising a plurality of second resistors connected in series, the second ends of which respectively output a plurality of different second voltages, the first end of the second resistor string and the second end of the first resistor string being connected to the second input terminal of the operational amplifier; and a variable component, wherein the first end of the variable component is connected to the second end of the second resistor string, the second end of the variable component is connected to a negative voltage VSN, and the resistance values ​​of the first resistor string and the second resistor string are the same.

[0023] Furthermore, in order to ensure that the first resistor string, the second resistor string, and the variable component all carry the same current, the first resistor string is characterized in that the voltage VP at the first end of the first resistor string is a positive reference voltage +VREF, and the second resistor string is characterized in that the voltage VN at the second end of the second resistor string is a negative reference voltage -VREF, wherein the absolute voltage values ​​of the positive reference voltage +VREF and the negative reference voltage -VREF are the same.

[0024] Furthermore, in order to realize the variable component, it is characterized in that the aforementioned variable component is one of the following or any combination thereof: a variable resistor; and a current source.

[0025] Furthermore, for application in small and medium-sized liquid crystal displays, the positive voltage VSP is characterized by being between 5V and 6V, and the negative voltage VSN is between -5V and -6V.

[0026] According to an embodiment of this application, a positive and negative voltage source driving circuit is provided, characterized in that it comprises: an operational amplifier, the first input terminal of which is connected to ground potential GND; a transistor, the gate of which is connected to the output terminal of the operational amplifier, the source of which is connected to the first end of a first resistor string, and the drain of which is connected to a positive voltage VSP; the first resistor string comprising a plurality of first resistors connected in series, the second ends of which respectively output a plurality of different first voltages to a first multiplexer; a second resistor string comprising a plurality of second resistors connected in series, the second ends of which respectively output a plurality of different second voltages to a second multiplexer, the first end of the second resistor string and the second end of the first resistor string being connected to the second input terminal of the operational amplifier; and a variable component. The variable component has its first terminal connected to the second terminal of the second resistor string, and its second terminal connected to the negative voltage VSN. The resistance values ​​of the first resistor string and the second resistor string are the same. The first multiplexer receives multiple different first voltages and selects one from these first voltages to output a positive reference voltage VREF_VGMP to a positive operational amplifier. The second multiplexer receives multiple different second voltages and selects one from these second voltages to output a negative reference voltage VREF_VGMN to a negative operational amplifier. The positive and negative operational amplifiers respectively output positive and negative voltages to the load circuit.

[0027] Furthermore, for application in small and medium-sized liquid crystal displays, the positive voltage VSP is characterized by being between 5V and 6V, and the negative voltage VSN is between -5V and -6V.

[0028] According to an embodiment of this application, a liquid crystal display is provided, characterized in that it comprises: a plurality of liquid crystal cells; a plurality of liquid crystal control units that control the plurality of liquid crystal cells respectively; and a positive and negative voltage source driving circuit, wherein the positive and negative voltage source driving circuit comprises: an operational amplifier, the first input terminal of which is connected to ground potential GND; a transistor, the gate of which is connected to the output terminal of the operational amplifier, the source of which is connected to the first end of a first resistor string, and the drain of which is connected to a positive voltage VSP; the first resistor string, which comprises a plurality of first resistors connected in series, the second ends of which respectively output a plurality of different first voltages to a first multiplexer; and a second resistor string, which comprises a plurality of second resistors connected in series, the second ends of which respectively output a plurality of different second voltages to a second multiplexer, the first end of the second resistor string and the second end of the first resistor string being connected to the first voltage source of the operational amplifier. Two input terminals; a variable component, wherein the first terminal of the variable component is connected to the second terminal of the second resistor string, and the second terminal of the variable component is connected to the negative voltage VSN, wherein the resistance values ​​of the first resistor string and the second resistor string are the same; a first multiplexer and a second multiplexer, the first multiplexer being used to receive the plurality of different first voltages and select one of the plurality of different first voltages to output a positive reference voltage VREF_VGMP to a positive operational amplifier, the second multiplexer being used to receive the plurality of different second voltages and select one of the plurality of different second voltages to output a negative reference voltage VREF_VGMN to a negative operational amplifier; and the positive operational amplifier and the negative operational amplifier respectively output positive voltage and negative voltage to one of the plurality of liquid crystal control units for controlling the grayscale level of one of the plurality of liquid crystal units.

[0029] Furthermore, for application in small and medium-sized liquid crystal displays, the positive voltage VSP is characterized by being between 5V and 6V, and the negative voltage VSN is between -5V and -6V.

[0030] Due to the adoption of the above-described solutions, the beneficial effects of this application are as follows: One of the technical solutions provided by this application can reduce the use of bandgap reference circuits and operational amplifiers. Another technical solution provided by this application does not even require the use of bandgap reference circuits, and only a single operational amplifier is needed. This can significantly reduce chip area and reduce power consumption during operation. Attached Figure Description

[0031] Figure 1 This is a block diagram of a positive and negative voltage source driving circuit 100 according to an embodiment of this application.

[0032] Figure 2 This is a block diagram of the positive voltage reference voltage generating circuit 111 and the negative voltage reference voltage generating circuit 112 according to an embodiment of this application.

[0033] Figure 3 This is a block diagram of the positive voltage reference voltage generating circuit 111 and the negative voltage reference voltage generating circuit 112 according to an embodiment of this application.

[0034] Figure 4 This is a block diagram of a positive voltage reference voltage generating circuit 411 and a negative voltage reference voltage generating circuit 412 according to another embodiment of this application.

[0035] Figure 5 According to Figure 4 A block diagram of the embodiment shown.

[0036] Figure 6 This is a block diagram of the reference voltage generation circuit 610, the first multiplexer 231, and the second multiplexer 232 according to an embodiment of this application.

[0037] Figure 7 for Figure 6 A block diagram of the reference voltage generation circuit 610 in the illustrated embodiment.

[0038] Figure 8 for Figure 6 A block diagram of the reference voltage generation circuit 610 in the illustrated embodiment. Detailed Implementation

[0039] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other implementation methods obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0040] The terms “first,” “second,” “third,” etc. (if present) in the specification, claims, and drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that the objects described herein may be used interchangeably where appropriate. In the description of this application, “plural” means two or more, unless otherwise expressly and specifically defined. Furthermore, the terms “comprising” and “having,” and any variations thereof, are intended to cover non-exclusive inclusion. Some block diagrams shown in the drawings are functional entities and do not necessarily correspond to physically or logically independent entities. Such functional entities may be implemented in software, in one or more hardware circuits or integrated circuits, or in different network and / or processor devices and / or microcontroller devices.

[0041] In the description of this application, it should be understood that the terms "center", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", and "outer" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or component referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0042] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections, electrical connections, or connections that allow for communication; they can refer to direct connections or indirect connections via 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 aforementioned terms in this application according to the specific circumstances.

[0043] To make the objectives, features and advantages of this application more apparent and understandable, the application will be further described in detail below with reference to the drawings and specific embodiments.

[0044] Please refer to Figure 1 The diagram shown is a block diagram of a positive and negative voltage source driving circuit 100 according to an embodiment of this application. The positive and negative voltage generating circuit 100 operates between a positive voltage VSP and a negative voltage VSN. The positive voltage generating portion of the positive and negative voltage generating circuit 100 operates between the positive voltage VSP and the ground potential GND. Similarly, the negative voltage generating portion of the positive and negative voltage source driving circuit 100 operates between the ground potential GND and the negative voltage VSN. Figure 1 As can be seen, the part above the ground potential GND is the positive voltage generating section, which generates a positive voltage to the load circuit 130. The part below the ground potential GND is the negative voltage generating section, which generates a negative voltage to the load circuit 130.

[0045] In one embodiment, the load circuit 130 may be one or more liquid crystal control units within a liquid crystal display (LCD). The liquid crystal control unit can be used to control the grayscale level of the liquid crystal cells, thereby controlling the color of the LCD. Those skilled in the art will understand that although this embodiment uses a liquid crystal control unit of an LCD as an example of the load circuit 130, the positive and negative voltage source driving circuit 100 provided in this application is not limited to providing a voltage across the liquid crystal control unit. For example, in addition to the liquid crystal control unit, the thin-film transistor (TFT) circuit of the LCD also requires a negative voltage to turn off the transistor circuit to reduce or avoid leakage current.

[0046] The positive voltage generation section of the positive and negative voltage source driving circuit 100 sequentially includes a positive voltage reference voltage generation circuit 111 and a positive operational amplifier 121. Similarly, the negative voltage generation section of the positive and negative voltage source driving circuit 100 sequentially includes a negative voltage reference voltage generation circuit 112 and a negative operational amplifier 122. The positive operational amplifier 121 generates a voltage between the positive voltage GSP and the ground potential GND. Similarly, the negative operational amplifier generates a voltage between the ground potential GND and the negative voltage GSN. The positive voltage reference voltage generation circuit 111 generates the positive voltage reference voltage VREF_VGMP required by the positive voltage operational amplifier 121. Similarly, the negative voltage reference voltage generation circuit 112 generates the negative voltage reference voltage VREF_VGMN required by the negative voltage operational amplifier 122.

[0047] In small-to-medium-sized LCD applications, the liquid crystal switching voltage is below 6 volts. Therefore, for a fully positive half-voltage LCD panel architecture, the positive voltage VSP is approximately 5V~6V, and the negative voltage VSN is approximately -5V~-6V. Thus, unlike applications in large-sized LCDs, when used in small-to-medium-sized LCDs, a medium-voltage component (e.g., 6V) can be used to complete the design of the positive and negative voltage generation circuit 100.

[0048] Please refer to Figure 2 The diagram shows a block illustration of a positive reference voltage generation circuit 111 and a negative reference voltage generation circuit 112 according to an embodiment of this application. The positive reference voltage generation circuit 111 operates between a positive voltage VSP and a ground potential GND. The positive reference voltage generation circuit 111 includes a first bandgap reference circuit 211, a first reference voltage generation circuit 221, and a first multiplexer 231. The first bandgap reference circuit 211 generates a positive reference voltage +VREF. After receiving the positive reference voltage +VREF, the first reference voltage generation circuit 221 generates multiple different first voltages and transmits them to the first multiplexer 231. The first multiplexer 231 selects the desired positive reference voltage VREF_VGMP from the multiple different first voltages.

[0049] The negative reference voltage generation circuit 112 operates between the ground potential GND and the negative voltage VSN. The negative reference voltage generation circuit 112 includes a second bandgap reference circuit 212, a second reference voltage generation circuit 222, and a second multiplexer 232. The second bandgap reference circuit 212 generates a negative reference voltage -VREF. After receiving the negative reference voltage -VREF, the second reference voltage generation circuit 222 generates multiple different second voltages and sends them to the second multiplexer 232. The second multiplexer 232 selects the desired negative reference voltage VREF_VGMN from these multiple different second voltages.

[0050] Those skilled in the art will understand that bandgap reference circuits 211 and 212 are commonly used circuits for generating precise reference voltages, exhibiting excellent temperature stability. The aforementioned bandgap or energy gap refers to the band gap between the low-energy valence band and the high-energy conduction band of a semiconductor.

[0051] Please refer to Figure 3 As shown, it is a block diagram of a positive voltage reference voltage generating circuit 111 and a negative voltage reference voltage generating circuit 112 according to an embodiment of this application. Figure 2 The first reference voltage generation circuit 221 shown may include Figure 3 The first operational amplifier 311, the first transistor 321, and the first resistor string 331 are shown. Figure 2 The second reference voltage generation circuit 222 shown may include Figure 3 The second operational amplifier 312, the second transistor 322, and the second resistor string 332 are shown.

[0052] The first input terminal of the first operational amplifier 311 receives a positive reference voltage +VREF from the first bandgap reference circuit 211. The first transistor 321 can be an N-type transistor. Figure 3 In this embodiment, the output of the first operational amplifier 311 is connected to the gate of the first transistor 321 to control the switching of the first transistor 321. The drain of the first transistor 321 is connected to a positive voltage VSP. The source of the first transistor 321 is connected to the second input of the first operational amplifier 311 and the first terminal of the first resistor string 331. The second terminal of the first resistor string 331 is connected to ground potential GND.

[0053] The first resistor string 331 may contain multiple first resistors, which may be connected in series. Except for the first terminal of the first first resistor, which is connected to the source of the first transistor 321, the first terminal of each first resistor is connected to the second terminal of the preceding first resistor. Except for the second terminal of the last first resistor, which is connected to ground potential, the second terminal of each first resistor is connected to the first terminal of the next first resistor. Multiple lines can be connected to multiple inputs of the first multiplexer 231 at the connection points of the multiple first resistors. Because the number of first resistors varies, the first voltages of the multiple inputs of the first multiplexer 231 are all different. The first voltages of the multiple lines output via the first resistor string 331 are between the positive voltage VSP and the ground potential GND.

[0054] The second input terminal of the second operational amplifier 312 receives the negative reference voltage -VREF from the second bandgap reference circuit 212. The second transistor 322 can be a P-type transistor. Figure 3 In this embodiment, the output of the second operational amplifier 312 is connected to the gate of the second transistor 321 to control the switching on and off of the second transistor 322. The drain of the second transistor 322 is connected to the negative voltage VSN. The source of the second transistor 322 is connected to the first input of the second operational amplifier 312 and the first terminal of the second resistor string 322. The second terminal of the second resistor string 322 is connected to the ground potential GND.

[0055] The second resistor string 332 can contain multiple second resistors, which can be connected in series. Except for the first terminal of the first second resistor, which is connected to the source of the second transistor 322, the first terminal of each second resistor is connected to the second terminal of the preceding first resistor. Except for the second terminal of the last second resistor, which is connected to ground potential, the second terminal of each second resistor is connected to the first terminal of the next second resistor. Multiple lines can be connected to multiple inputs of the second multiplexer 232 at the connection points of the multiple second resistors. Because the number of second resistors varies, the second voltages of the multiple inputs of the second multiplexer 232 are all different. The second voltages of the multiple lines output via the second resistor string 332 are between ground potential GND and negative voltage VSN.

[0056] exist Figure 2 and Figure 3 The illustrated embodiment includes two bandgap reference circuits 211 and 212 and two reference voltage generation circuits 221 and 222, used to generate a positive reference voltage VREF_VGMP and a negative reference voltage VREF_VGMN, respectively. This application also includes other embodiments that can reduce the number of bandgap reference circuits, further reducing chip area and power consumption, and increasing product competitiveness.

[0057] Please refer to Figure 4 The diagram shows a block illustration of a positive reference voltage generation circuit 411 and a negative reference voltage generation circuit 412 according to another embodiment of this application. The positive reference voltage generation circuit 411 includes the previously described first bandgap reference circuit 211 and first multiplexer 231, as well as a reference voltage generation circuit 421. The negative reference voltage generation circuit 412 does not include the previously described second bandgap reference circuit 212, but includes the previously described second multiplexer 232 and a simplified reference voltage generation circuit 422.

[0058] Please refer to Figure 5 As shown, it is based on Figure 4 The illustrated embodiment is a block diagram. The positive voltage reference generation circuit 411 includes the previously described first operational amplifier 311, first transistor 321, and first resistor string 331. In addition, Figure 5 The illustrated embodiment also includes a current mirror structure. This current mirror structure comprises four transistors 531-534, which can be configured as follows: Figure 5 The current mirror shown, with four transistors, is used as a power supply for the negative voltage reference generation circuit 412. Those skilled in the art will understand that, in addition to... Figure 5 Besides the four transistor current mirrors shown, there are other types of current mirrors. This application is not limited to... Figure 5 The example shown.

[0059] When the second input (negative terminal) of the first operational amplifier 331 is connected to the first transistor 321 and the first resistor string 331, negative feedback causes the voltage VP to approach the positive reference voltage +VREF of the first input (positive terminal) of the first operational amplifier 331. Since the voltage VP crosses the first resistor string 331, a current I1 is generated. This current I1 is then supplied to the second resistor string 332 through the aforementioned current mirror structure.

[0060] When the resistances of the first resistor string 331 and the second resistor string 332 are equal, and the current flowing through both the first resistor string 331 and the second resistor string 332 is current I1, then the voltage VN will be equal to -VP. Since the negative feedback mentioned earlier causes VP to approach or equal the positive reference voltage +VREF, the voltage VN will be equal to -(+VREF), which is equal to the negative reference voltage -VREF. In other words, the simplified reference voltage generation circuit 422 can include the aforementioned current mirror structure and the second resistor string 332. For a description of the second resistor string 332, please refer to the previous embodiments; it will not be repeated here.

[0061] Please refer to Figure 6The diagram shown is a block diagram of a reference voltage generation circuit 610 and a first multiplexer 231 and a second multiplexer 232 according to an embodiment of this application. This reference voltage generation circuit 610 does not require any bandgap reference circuit to provide a positive reference voltage +VREF or a negative reference voltage -VREF. Compared to... Figures 1 to 3 Two examples of bandgap reference circuits, and compared to Figure 4 and Figure 5 An embodiment of a single bandgap reference circuit, Figure 6 The reference voltage generation circuit 610 shown can save chip area and power consumption.

[0062] The reference voltage generation circuit 610 can also generate multiple voltages for the aforementioned first multiplexer 231, to select one of them as the positive reference voltage VREF_VGMP. Similarly, the reference voltage generation circuit 610 can generate multiple voltages for the aforementioned second multiplexer 232, to select one of them as the negative reference voltage VREF_VGMN.

[0063] Please refer to Figure 7 As shown, it is Figure 6 A block diagram of a reference voltage generation circuit 610 in the illustrated embodiment. The reference voltage generation circuit 610 includes an operational amplifier 710, a transistor 720, a first resistor string 731, a second resistor string 732, and a variable resistor 740.

[0064] The first input terminal (positive terminal) of operational amplifier 710 is connected to ground potential GND. The output terminal of operational amplifier 710 is connected to the gate of transistor 720 to control the switching of transistor 720. Transistor 720 can be an N-type transistor. Figure 7 In this embodiment, the drain of transistor 720 is connected to a positive voltage VSP. The source of transistor 720 is connected to the first terminal of the first resistor string 731. The second input (negative terminal) of operational amplifier 710 is connected to the second terminal of the first resistor string 731 and the first terminal of the second resistor string 732. The second terminal of the second resistor string 732 is connected to the first terminal of variable resistor 740. The second terminal of variable resistor 740 is connected to a negative voltage VSN.

[0065] As previously described, the first resistor string 731 is composed of multiple first resistors connected in series, and the second resistor string is also composed of multiple second resistors connected in series. Except for the first terminal of the first resistor connected to the source of the transistor, the first terminals of the remaining first resistors are connected to the second terminal of the preceding first resistor. Except for the second terminal of the last first resistor connected to the first terminal of the second resistor string 732 and the second input (negative terminal) of the operational amplifier 710, the second terminals of the remaining first resistors are connected to the first terminal of the following first resistor. Multiple lines can be connected to multiple inputs of the first multiplexer 231 at the connection points of the multiple first resistors. Because the number of first resistors passing through them varies, the voltages of the multiple inputs of the first multiplexer 231 are all different. The voltages of the multiple lines output through the first resistor string 731 are between the positive voltage VSP and the ground potential GND.

[0066] Except for the first terminal of the first second resistor, which is connected to the second terminal of the first resistor string 732 and the second input terminal (negative terminal) of the operational amplifier 710, the first terminals of the remaining second resistors are connected to the second terminal of the preceding second resistor. Except for the second terminal of the last second resistor, which is connected to the first terminal of the variable resistor 740, the second terminals of the remaining second resistors are connected to the first terminal of the following second resistor. Multiple lines can be connected to multiple inputs of the second multiplexer 232 at the connection points of the multiple second resistors. Because the number of second resistors varies, the voltages at the multiple inputs of the second multiplexer 232 are all different. The voltages of the multiple lines output via the second resistor string 732 are between ground potential GND and negative voltage VSN.

[0067] Due to the negative feedback from the second terminal (negative terminal) of operational amplifier 710, the voltage at the connection between the first resistor string 731 and the second resistor string 732 approaches the voltage at the first terminal (positive terminal) of operational amplifier 710, which is ground potential GND or 0V. When the resistance value R3 of variable resistor 740 is adjusted with the negative voltage VSN, the voltage across the first and second terminals of the second resistor string 732 remains constant. Assuming the resistance value R1 of the first resistor string 731 is the same as the resistance value R2 of the second resistor string 732, and the same current I1 flows through the first resistor string 731, the second resistor string 732, and the variable resistor 740, then the resistance value R3 of variable resistor 740 can be set such that voltage VP = I1*R1 = +VREF, and voltage VN = I1*R2 = -VREF. In this way, a smaller chip area and lower power consumption can be used to simultaneously obtain a positive reference voltage +VREF and a negative reference voltage -VREF. By using the first resistor string 731, the second resistor string 732, the first multiplexer 231, and the second multiplexer 232, the positive reference voltage VREF_VGMP and the negative reference voltage VREF_VGMN can be obtained.

[0068] Please refer to Figure 8 As shown, it is Figure 6 A block diagram of the reference voltage generation circuit 610 of the illustrated embodiment. Figure 7 Compared to the embodiment shown, the aforementioned variable resistor 740 is replaced by a current source 840, and the rest are the same. Figure 7 The current remains unchanged. Similarly, the current of current source 840 can be set such that voltage VP = I1*R1 = +VREF, and voltage VN = I1*R2 = -VREF. In this way, a positive reference voltage +VREF and a negative reference voltage -VREF can be obtained simultaneously using a smaller chip area and lower power consumption. Then, through the first resistor string 731, the second resistor string 732, the first multiplexer 231, and the second multiplexer 232, the positive reference voltage VREF_VGMP and the negative reference voltage VREF_VGMN can be obtained.

[0069] According to an embodiment of this application, a reference voltage generation circuit is provided, characterized in that it comprises: an operational amplifier, the first input terminal of which is used to receive a positive reference voltage +VREF; a transistor, the gate of which is connected to the output terminal of the operational amplifier, and the source of which is connected to the second input terminal of the operational amplifier and the first end of a first resistor string; the first resistor string comprising a plurality of first resistors connected in series, the second ends of which respectively output a plurality of different first voltages; a current mirror, operating between a positive voltage VSP and a negative voltage VSN, the current mirror being connected to the drain of the transistor and the second end of the second resistor string; and a second resistor string comprising a plurality of second resistors connected in series, the second ends of which respectively output a plurality of different second voltages, wherein the first end of the second resistor string and the second end of the first resistor string are connected to ground potential GND.

[0070] Furthermore, in order to provide both positive and negative voltages simultaneously, the plurality of different first voltages are respectively located between the positive voltage VSP and the ground potential GND, and the plurality of different first voltages are respectively located between the ground potential GND and the negative voltage VSN.

[0071] Furthermore, in order to select one of a plurality of positive voltages and a plurality of negative voltages as the positive reference voltage VREF_VGMP and the negative reference voltage VREF_VGMN respectively, the reference voltage generation circuit is characterized in that the above-mentioned reference voltage generation circuit further includes a first multiplexer and a second multiplexer. The first multiplexer is used to receive the plurality of different first voltages and select one of the plurality of different first voltages to output the positive reference voltage VREF_VGMP to the positive operational amplifier. The second multiplexer is used to receive the plurality of different second voltages and select one of the plurality of different second voltages to output the negative reference voltage VREF_VGMN to the negative operational amplifier.

[0072] Furthermore, in order to obtain a temperature-stable reference power supply, the positive reference voltage +VREF is derived from a bandgap reference circuit, which operates between the positive voltage VSP and the ground potential GND.

[0073] Furthermore, in order to better output negative voltage, the current mirror is characterized in that it is a current mirror with four transistors.

[0074] According to an embodiment of this application, a positive and negative voltage source driving circuit is provided, characterized in that it includes: a bandgap reference circuit, operating between a positive voltage VSP and a ground potential GND, for providing a positive reference voltage +VREF; a reference voltage generating circuit, for receiving the positive reference voltage +VREF and outputting a positive reference voltage VREF_VGMP to a positive operational amplifier and outputting a negative reference voltage VREF_VGMN to a negative operational amplifier; and the positive operational amplifier and the negative operational amplifier, respectively, outputting a positive voltage and a negative voltage to a load circuit.

[0075] Furthermore, in order to select one of a plurality of positive voltages and a plurality of negative voltages as the positive reference voltage VREF_VGMP and the negative reference voltage VREF_VGMN respectively, the reference voltage generation circuit is characterized in that the above-mentioned reference voltage generation circuit further includes a first multiplexer and a second multiplexer. The reference voltage generation circuit is used to receive the positive reference voltage +VREF to generate a plurality of different first voltages and a plurality of different second voltages to the first multiplexer and the second multiplexer respectively. The first multiplexer selects one of the plurality of different first voltages to output the positive reference voltage VREF_VGMP to the positive operational amplifier, and the second multiplexer selects one of the plurality of different second voltages to output the negative reference voltage VREF_VGMN to the negative operational amplifier.

[0076] Furthermore, in order to provide both positive and negative voltages simultaneously, the plurality of different first voltages are respectively located between the positive voltage VSP and the ground potential GND, and the plurality of different first voltages are respectively located between the ground potential GND and the negative voltage VSN.

[0077] Furthermore, to eliminate the need for two similar circuits in the reference voltage generation circuit, and instead utilize only a single operational amplifier to save chip area and power consumption, the reference voltage generation circuit is characterized by comprising: an operational amplifier, the first input of which is used to receive the positive reference voltage +VREF; a transistor, the gate of which is connected to the output of the operational amplifier, and the source of which is connected to the second input of the operational amplifier and the first end of the first resistor string; the first resistor string comprising a plurality of first resistors connected in series, the second ends of which respectively output the plurality of different first voltages; a current mirror operating between the positive voltage VSP and the negative voltage VSN, the current mirror being connected to the drain of the transistor and the second end of the second resistor string; the first end of the second resistor string being connected to the ground potential GND, the second resistor string comprising a plurality of second resistors connected in series, the second ends of which respectively output the plurality of different second voltages.

[0078] Furthermore, in order to better output negative voltage, the current mirror is characterized in that it is a current mirror with four transistors.

[0079] Furthermore, for application in small and medium-sized liquid crystal displays, the positive voltage VSP is characterized by being between 5V and 6V, and the negative voltage VSN is between -5V and -6V.

[0080] According to an embodiment of this application, a liquid crystal display is provided, characterized in that it comprises: a plurality of liquid crystal cells; a plurality of liquid crystal control units that control the plurality of liquid crystal cells respectively; and a positive and negative voltage source driving circuit, wherein the positive and negative voltage source driving circuit comprises: a bandgap reference circuit, operating between a positive voltage VSP and a ground potential GND, for providing a positive reference voltage +VREF; a reference voltage generating circuit, for receiving the positive reference voltage +VREF and outputting a positive reference voltage VREF_VGMP to a positive operational amplifier and outputting a negative reference voltage VREF_VGMN to a negative operational amplifier; and the positive operational amplifier and the negative operational amplifier respectively outputting a positive voltage and a negative voltage to one of the plurality of liquid crystal control units, for controlling the grayscale level of one of the plurality of liquid crystal cells.

[0081] Furthermore, in order to select one of a plurality of positive voltages and a plurality of negative voltages as the positive reference voltage VREF_VGMP and the negative reference voltage VREF_VGMN respectively, the reference voltage generation circuit is characterized in that the above-mentioned reference voltage generation circuit further includes a first multiplexer and a second multiplexer. The reference voltage generation circuit is used to receive the positive reference voltage +VREF to generate a plurality of different first voltages and a plurality of different second voltages to the first multiplexer and the second multiplexer respectively. The first multiplexer selects one of the plurality of different first voltages to output the positive reference voltage VREF_VGMP to the positive operational amplifier, and the second multiplexer selects one of the plurality of different second voltages to output the negative reference voltage VREF_VGMN to the negative operational amplifier.

[0082] Furthermore, to eliminate the need for two similar circuits in the reference voltage generation circuit, and instead utilize only a single operational amplifier to save chip area and power consumption, the reference voltage generation circuit is characterized by comprising: an operational amplifier, the first input of which is used to receive the positive reference voltage +VREF; a transistor, the gate of which is connected to the output of the operational amplifier, and the source of which is connected to the second input of the operational amplifier and the first end of the first resistor string; the first resistor string comprising a plurality of first resistors connected in series, the second ends of which respectively output the plurality of different first voltages; a current mirror operating between the positive voltage VSP and the negative voltage VSN, the current mirror being connected to the drain of the transistor and the second end of the second resistor string; and the second resistor string, wherein the first end of the second resistor string is connected to the ground potential GND, the second resistor string comprising a plurality of second resistors connected in series, the second ends of which respectively output the plurality of different second voltages.

[0083] Furthermore, in order to better output negative voltage, the current mirror is characterized in that it is a current mirror with four transistors.

[0084] Furthermore, for application in small and medium-sized liquid crystal displays, the positive voltage VSP is characterized by being between 5V and 6V, and the negative voltage VSN is between -5V and -6V.

[0085] According to an embodiment of this application, a reference voltage generation circuit is provided, characterized in that it comprises: an operational amplifier, the first input terminal of which is connected to ground potential GND; a transistor, the gate of which is connected to the output terminal of the operational amplifier, the source of which is connected to the first end of a first resistor string, and the drain of which is connected to a positive voltage VSP; the first resistor string comprising a plurality of first resistors connected in series, the second ends of which respectively output a plurality of different first voltages; a second resistor string comprising a plurality of second resistors connected in series, the second ends of which respectively output a plurality of different second voltages, the first end of the second resistor string and the second end of the first resistor string being connected to the second input terminal of the operational amplifier; and a variable component, wherein the first end of the variable component is connected to the second end of the second resistor string, the second end of the variable component is connected to a negative voltage VSN, and the resistance values ​​of the first resistor string and the second resistor string are the same.

[0086] Furthermore, in order to ensure that the first resistor string, the second resistor string, and the variable component all carry the same current, the first resistor string is characterized in that the voltage VP at the first end of the first resistor string is a positive reference voltage +VREF, and the second resistor string is characterized in that the voltage VN at the second end of the second resistor string is a negative reference voltage -VREF, wherein the absolute voltage values ​​of the positive reference voltage +VREF and the negative reference voltage -VREF are the same.

[0087] Furthermore, in order to realize the variable component, it is characterized in that the aforementioned variable component is one of the following or any combination thereof: a variable resistor; and a current source.

[0088] Furthermore, for application in small and medium-sized liquid crystal displays, the positive voltage VSP is characterized by being between 5V and 6V, and the negative voltage VSN is between -5V and -6V.

[0089] According to an embodiment of this application, a positive and negative voltage source driving circuit is provided, characterized in that it comprises: an operational amplifier, the first input terminal of which is connected to ground potential GND; a transistor, the gate of which is connected to the output terminal of the operational amplifier, the source of which is connected to the first end of a first resistor string, and the drain of which is connected to a positive voltage VSP; the first resistor string comprising a plurality of first resistors connected in series, the second ends of which respectively output a plurality of different first voltages to a first multiplexer; a second resistor string comprising a plurality of second resistors connected in series, the second ends of which respectively output a plurality of different second voltages to a second multiplexer, the first end of the second resistor string and the second end of the first resistor string being connected to the second input terminal of the operational amplifier; and a variable component. The variable component has its first terminal connected to the second terminal of the second resistor string, and its second terminal connected to the negative voltage VSN. The resistance values ​​of the first resistor string and the second resistor string are the same. The first multiplexer receives multiple different first voltages and selects one from these first voltages to output a positive reference voltage VREF_VGMP to a positive operational amplifier. The second multiplexer receives multiple different second voltages and selects one from these second voltages to output a negative reference voltage VREF_VGMN to a negative operational amplifier. The positive and negative operational amplifiers respectively output positive and negative voltages to the load circuit.

[0090] Furthermore, for application in small and medium-sized liquid crystal displays, the positive voltage VSP is characterized by being between 5V and 6V, and the negative voltage VSN is between -5V and -6V.

[0091] According to an embodiment of this application, a liquid crystal display is provided, characterized in that it comprises: a plurality of liquid crystal cells; a plurality of liquid crystal control units that control the plurality of liquid crystal cells respectively; and a positive and negative voltage source driving circuit, wherein the positive and negative voltage source driving circuit comprises: an operational amplifier, the first input terminal of which is connected to ground potential GND; a transistor, the gate of which is connected to the output terminal of the operational amplifier, the source of which is connected to the first end of a first resistor string, and the drain of which is connected to a positive voltage VSP; the first resistor string, which comprises a plurality of first resistors connected in series, the second ends of which respectively output a plurality of different first voltages to a first multiplexer; and a second resistor string, which comprises a plurality of second resistors connected in series, the second ends of which respectively output a plurality of different second voltages to a second multiplexer, the first end of the second resistor string and the second end of the first resistor string being connected to the first voltage source of the operational amplifier. Two input terminals; a variable component, wherein the first terminal of the variable component is connected to the second terminal of the second resistor string, and the second terminal of the variable component is connected to the negative voltage VSN, wherein the resistance values ​​of the first resistor string and the second resistor string are the same; a first multiplexer and a second multiplexer, the first multiplexer being used to receive the plurality of different first voltages and select one of the plurality of different first voltages to output a positive reference voltage VREF_VGMP to a positive operational amplifier, the second multiplexer being used to receive the plurality of different second voltages and select one of the plurality of different second voltages to output a negative reference voltage VREF_VGMN to a negative operational amplifier; and the positive operational amplifier and the negative operational amplifier respectively output positive voltage and negative voltage to one of the plurality of liquid crystal control units for controlling the grayscale level of one of the plurality of liquid crystal units.

[0092] Furthermore, for application in small and medium-sized liquid crystal displays, the positive voltage VSP is characterized by being between 5V and 6V, and the negative voltage VSN is between -5V and -6V.

[0093] The above description is merely a preferred embodiment of this application, but the scope of protection of this application is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in this application, based on the technical solution and application concept of this application, should be included within the scope of protection of this application.

Claims

1. A reference voltage generation circuit, characterized in that, Includes: an operational amplifier whose first input is used to receive a positive reference voltage +VREF; A transistor, the gate of which is connected to the output of the operational amplifier, and the source of which is connected to the second input of the operational amplifier and the first end of the first resistor string; the first resistor string includes a plurality of first resistors connected in series, the second ends of which output a plurality of different first voltages; a current mirror, which operates between a positive voltage VSP and a negative voltage VSN, is connected to the drain of the transistor and the second end of the second resistor string. And the second resistor string, which includes a plurality of second resistors connected in series, wherein the second terminals of the plurality of second resistors output a plurality of different second voltages, wherein the first terminal of the second resistor string and the second terminal of the first resistor string are connected to the ground potential GND.

2. The reference voltage generating circuit as described in claim 1, characterized in that, The plurality of different first voltages are respectively located between the positive voltage VSP and the ground potential GND, and the plurality of different first voltages are respectively located between the ground potential GND and the negative voltage VSN.

3. The reference voltage generating circuit as described in claim 1, characterized in that, It also includes a first multiplexer and a second multiplexer. The first multiplexer is used to receive the plurality of different first voltages and select one of the plurality of different first voltages to output a positive reference voltage VREF_VGMP to a positive operational amplifier. The second multiplexer is used to receive the plurality of different second voltages and select one of the plurality of different second voltages to output a negative reference voltage VREF_VGMN to a negative operational amplifier.

4. The reference voltage generating circuit as described in claim 1, characterized in that, The positive reference voltage +VREF mentioned above comes from the bandgap reference circuit, which operates between the positive voltage VSP and the ground potential GND.

5. The reference voltage generating circuit as described in claim 1, characterized in that, The aforementioned current mirror is a current mirror with four transistors.

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