An open-loop low-power LCD controller based on an on-chip capacitor charge pump

Abstract

The present invention provides a controller of an open-loop low-power liquid crystal display based on an on-chip capacitor charge pump. The controller is used to adopt a charge pump design of an on-chip capacitor, which greatly saves peripheral devices and packaging area. The controller comprises: a low-power oscillator, a charge pump, a voltage selector, a bias generator, a buffer and a selector matrix; the low-power oscillator is used to generate a clock signal; the charge pump outputs a boosted voltage, wherein the charge pump comprises a switch element and an on-chip capacitor; the voltage selector has an input voltage that is any one of a boosted voltage, an external power supply voltage or an internal power supply voltage, and outputs a target voltage; the bias generator is used to output a group of bias voltages using the target voltage; the buffer is used to buffer a group of bias voltages to obtain a group of buffer voltages; the selector matrix inputs a group of buffer voltages and a target voltage, is used to select a target buffer voltage from a group of buffer voltages output by the buffer through digital control, and outputs the target buffer voltage to a liquid crystal display screen.

Description

Technical Field

[0001] The invention relates to the field of display driving, and in particular to a controller of an open-loop low-power liquid crystal display based on an on-chip capacitor charge pump. Background Art

[0002] At present, as a display of a portable electronic device, a segmented liquid crystal panel is generally used, in which a plurality of display pixels are arranged in a matrix. In the portable electronic device, a controller for controlling the segmented liquid crystal panel is also installed. The controller is used to drive the driver circuit of the segmented liquid crystal panel. With the continuous improvement of the integration of integrated circuits, charge pump circuits are increasingly integrated into the controller of liquid crystal displays. However, since the charge pump circuit has high requirements for power supply, in order to reduce the ripple interference of the charge pump circuit on the power supply, it is generally necessary to add a large external capacitor to its power supply port, which means that not only the cost of the power supply system is increased, but also the reliability of the entire system is reduced. Summary of the invention

[0003] The object of the present invention is to provide an open-loop low-power liquid crystal display controller based on an on-chip capacitor charge pump, which is used to adopt an on-chip capacitor charge pump design and greatly save peripheral devices and packaging area.

[0004] In a first aspect, the present invention provides a controller for a liquid crystal display, the controller comprising: a low power oscillator, a charge pump, a voltage selector, a bias generator, a buffer and a selector matrix;

[0005] The low power oscillator is used to generate a clock signal;

[0006] The charge pump inputs a power supply voltage VIN and the clock signal and outputs a boosted voltage V5, wherein the charge pump includes a switch element and an on-chip capacitor;

[0007] The voltage selector, whose input voltage is any one of the boost voltage V5, the external power supply voltage VBAT or the internal power supply voltage VBAT, outputs a target voltage VLCD;

[0008] The bias voltage generator is input with the target voltage VLCD and is used to output a set of bias voltages using the target voltage VLCD;

[0009] The buffer is input with a set of bias voltages output by the bias generator, and is used to buffer the set of bias voltages to obtain a set of buffered voltages;

[0010] The selector matrix inputs the group of buffer voltages and the target voltage VLCD, and is used to select a target buffer voltage from a group of buffer voltages output from the buffer through digital control, and output the target buffer voltage to a liquid crystal display.

[0011] The beneficial effects of the controller of the open-loop low-power liquid crystal display based on the on-chip capacitor charge pump provided by the present invention are: on the one hand, the charge pump design using the on-chip capacitor greatly saves peripheral devices and packaging area; on the other hand, the input voltage of the voltage selector is any one of the boost voltage V5, the external power supply voltage VBAT or the internal power supply voltage VBAT, so that the external power supply voltage VBAT or the internal power supply voltage VBAT can replace the charge pump, which can reduce power consumption; in addition, the bias generator can provide a group of bias voltages, so it supports multiple biases, can effectively control power consumption, and improve the average working efficiency of the controller.

[0012] Optionally, the selector matrix inputs the set of buffer voltages instead of inputting an external power supply voltage. The selector matrix can select different buffer voltages through digital control, thereby enabling LCD flashing and updating the displayed image of the liquid crystal display.

[0013] Optionally, the output end of the voltage selector is further connected to an external capacitor, and the external capacitor is used to stabilize the target voltage VLCD. This structure helps to improve the output voltage stability of the boost module and improve the average working efficiency of the charge pump.

[0014] Optionally, the bias generator is a low power consumption resistor string, and the set of bias voltages includes a target voltage VLCD, a VLCD / 2 bias voltage, a VLCD / 3 bias voltage, and a VLCD / 4 bias voltage.

[0015] Optionally, the switch element is constructed by a high-voltage MOS transistor, and the bias generator and the buffer are both low-power devices.

[0016] Optionally, the charge pump is a linear charge pump.

[0017] Optionally, the linear charge pump supports multiple adjustable rates.

[0018] In a second aspect, the present invention provides an integrated circuit chip, the chip comprising the controller described in any one of the first aspects. The beneficial effects can be found in the description of the first aspect.

[0019] In a third aspect, the present invention provides a communication device, the communication terminal comprising the integrated circuit chip described in the second aspect. The beneficial effects can be found in the description of the first aspect. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 A schematic diagram of a controller of an open-loop low-power liquid crystal display based on an on-chip capacitor charge pump is provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0021] In order to make the purpose, technical solutions and advantages of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. Unless otherwise defined, the technical terms or scientific terms used herein should be understood by people with general skills in the field to which the present invention belongs. "Including" and similar words used in this article mean that the elements or objects appearing before the word include the elements or objects listed after the word and their equivalents, without excluding other elements or objects.

[0022] In view of the problems existing in the prior art, an embodiment of the present invention provides an open-loop low-power liquid crystal display controller based on an on-chip capacitor charge pump. Figure 1 The circuit structure block diagram of the controller is exemplarily shown, including: a low-power oscillator 10 , a charge pump 20 , a voltage selector 30 , a bias generator 40 , a buffer 50 and a selector matrix 60 .

[0023] The low power oscillator 10 is used to generate a clock signal. For example, the center frequency of the clock signal may be 2 MHZ, and the LPOSC may be a built-in ultra-low power oscillator with an adjustable oscillation frequency. The output clock of the LPOSC is supplied to a charge pump (CP) 20 .

[0024] The charge pump 20 inputs the power supply voltage VIN and the divided clock signal, and outputs the boost voltage V5. In this embodiment, the charge pump 20 can be a linear charge pump (LCP), which supports multiple adjustable magnifications, such as 3 times magnification, 4 times magnification or 5 times magnification, etc. The linear charge pump can include multiple switching elements and on-chip capacitors, and the switching elements are constructed of high-voltage MOS tubes. The on-chip capacitor can be 200PF. Compared with the charge pump with integrated off-chip capacitors in the prior art, the charge pump with on-chip capacitors in this embodiment can save the area occupied by the off-chip, reduce the circuit design cost, and also help save the packaging area.

[0025] The voltage selector 30 has the boost voltage V5 as an input voltage and outputs the target voltage VLCD. That is, the charge pump 20 provides the output voltage of the charge pump 20 to the voltage selector 30. Alternatively, the input end of the voltage selector 30 can use the external power supply voltage VBAT or the internal power supply voltage VBAT instead of the boost voltage V5, so that in order to save power consumption, the charge pump can stop working and use the external power supply voltage VBAT or the internal power supply voltage VBAT instead of the boost voltage V5.

[0026] The bias generator 40 inputs the target voltage VLCD and is used to output a set of bias voltages using the target voltage VLCD. The target voltage VLCD is the highest voltage output by the charge pump 20 corresponding to the LCD segment. The bias generator can be a low power device or an ultra low power device.

[0027] like Figure 1 As shown, the bias generator 40 can be a low power resistor string, and the group of bias voltages includes a target voltage VLCD, a VLCD / 2 bias voltage, a VLCD / 3 bias voltage, and a VLCD / 4 bias voltage. Exemplarily, a group of bias voltages can include 0V (ground potential), +1V, +2V, and +3V. It is worth noting that the present embodiment does not limit the number and magnitude of the bias voltages.

[0028] The buffer 50 inputs a set of bias voltages output by the bias generator 40, and is used to buffer the set of bias voltages to obtain a set of buffer voltages. The buffer 50 may be an ultra-low power consumption buffer, which mainly buffers the voltage output by the buffer 50. The buffer 50 may be a resistor string to form a resistor voltage divider, and the buffer 50 may be a low power consumption device or an ultra-low power consumption device.

[0029] The selector matrix 60 inputs the group of buffer voltages and the target voltage VLCD, and is used to select a target buffer voltage from a group of buffer voltages output by the buffer through digital control, and output the target buffer voltage to a liquid crystal display. The liquid crystal display can be a segmented liquid crystal display, such as a liquid crystal display of a water meter or an electric meter. Exemplarily, the selector matrix has a total of 36 selectors for the segment code interface (8com+28seg), and selects different buffer voltages to output the segment code liquid crystal display through digital control.

[0030] The chip including the controller of the open-loop low-power liquid crystal display based on the on-chip capacitor charge pump can be applied to various communication terminals as an important component of analog integrated circuits. The communication terminal mentioned here refers to an electronic device that can be used in a mobile environment and supports a variety of communication formats such as the long-term evolution (LTE) system, the world-wide interoperability for microwave access (WiMAX) communication system, the fifth generation (5G) system, such as the new generation of wireless access technology (NR), and future communication systems such as the sixth generation (6G) system, and the electronic device includes an Internet of Things device, a mobile phone, a laptop, a tablet computer, a car computer, etc.

[0031] Compared with the prior art, the charge pump in the controller of the open-loop low-power LCD display based on the on-chip capacitor charge pump provided by the present invention can output a boost power supply with an adjustable rate, and the input voltage of the voltage selector is any one of the boost voltage V5, the external power supply voltage VBAT or the internal power supply voltage VBAT, so that the external power supply voltage VBAT or the internal power supply voltage VBAT can replace the charge pump, which can reduce power consumption; in addition, the bias generator can provide a set of bias voltages, so it supports multiple biases, can effectively control power consumption, and improve the average working efficiency of the controller. Since the present embodiment has a built-in ultra-low power oscillator, it does not require an additional crystal oscillator or PLL to provide a system clock, which greatly saves area and reduces the cost of module devices; in addition, the present embodiment integrates all functional requirements into one, meeting the different needs of customers for complex application scenarios. The charge pump is an on-chip capacitor charge pump, which greatly reduces the cost of module devices. The present invention has low power consumption, high efficiency, high integration, and greatly reduces the cost of module application.

[0032] This LCD controller is based on the combination of traditional LCD controller functions and performances in the industry, and has the following advantages:

[0033] (1) A waveform or B waveform can be selected.

[0034] (2) Supports 8 time slices and 4 bias voltages.

[0035] (3) It can automatically output segment signals and common signals by automatically reading display data registers.

[0036] (4) The time interval between frames can be changed.

[0037] (5) LCD flashing is possible.

[0038] (6) Ability to update displayed image.

[0039] (7) Can support internal VBAT, internal charge pump or external VBAT power supply

[0040] (8) Can support internal resistance voltage division, external resistance voltage division or external capacitance voltage division

[0041] (9) The internal charge pump can support the input voltage to be multiplied by 3, 4 or 5 times as the output VLCD of the LCD driver

[0042] (10) The charge pump adopts the design of on-chip capacitors, which greatly saves packaging solutions and peripheral devices.

[0043] The circuit, chip and communication terminal of the controller provided by the present invention are described in detail above. Although the embodiments of the present invention are described in detail above, it is obvious to those skilled in the art that various modifications and changes can be made to these embodiments. However, it should be understood that such modifications and changes are within the scope and spirit of the present invention as described in the claims. Moreover, the present invention described herein may have other embodiments and may be implemented or realized in a variety of ways.

Claims

1. A controller for a liquid crystal display, characterized in that: include: Low-power oscillators, charge pumps, voltage selectors, bias generators, buffers, and selector matrices; The low power oscillator is used to generate a clock signal; The charge pump inputs a power supply voltage VIN and the clock signal and outputs a boosted voltage V5, wherein the charge pump includes a switch element and an on-chip capacitor; The voltage selector has an input voltage of any one of the boost voltage V5, the external power supply voltage VBAT or the internal power supply voltage VBAT, and outputs a target voltage VLCD; when the charge pump stops working, the external power supply voltage VBAT or the internal power supply voltage VBAT replaces the boost voltage V5; The bias generator inputs the target voltage VLCD and is used to output a set of bias voltages using the target voltage VLCD; the bias generator is a low-power resistor string, and the set of bias voltages includes the target voltage VLCD, a VLCD / 2 bias voltage, a VLCD / 3 bias voltage, and a VLCD / 4 bias voltage; The buffer is input with a set of bias voltages output by the bias generator, and is used to buffer the set of bias voltages to obtain a set of buffered voltages; The selector matrix inputs the group of buffer voltages and the target voltage VLCD, and is used to select a target buffer voltage from a group of buffer voltages output from the buffer through digital control, and output the target buffer voltage to a liquid crystal display.

2. The controller according to claim 1, characterized in that: The selector matrix input the set of buffered voltages is replaced by an input external supply voltage.

3. The controller according to claim 1 or 2, characterized in that: The output end of the voltage selector is further connected to an external capacitor, and the external capacitor is used to stabilize the target voltage VLCD.

4. The controller according to claim 1, characterized in that: The bias generator and the buffer are both low power consumption devices.

5. The controller according to claim 1, characterized in that: The charge pump is a linear charge pump.

6. The controller according to claim 5, characterized in that: The linear charge pump supports multiple adjustable rates.

7. The controller according to claim 1 or 2, characterized in that: The switching element is configured by a high-voltage MOS transistor.

8. An integrated circuit chip, characterized in that: A controller comprising any one of claims 1 to 7.

9. A communication terminal, characterized in that: Comprising the integrated circuit chip as claimed in claim 8.

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