Low-temperature liquid crystal display module

Abstract

The utility model provides a low-temperature liquid crystal display module, which belongs to the field of low-temperature displays and comprises a control power supply module, a backlight driving power supply module, a main control circuit, a temperature control module, a display screen and a communication interface, the control power supply module provides 5V and 3.3 V power supplies of the digital control circuit for the display module; the backlight driving power supply module is used for lightening a backlight LED of the liquid crystal display screen; the main control circuit is used for receiving a host command and refreshing display information of the liquid crystal screen; and the temperature control module is used for heating the display screen and feeding back the current screen temperature. The display screen adopts a common industrial display screen, is used for displaying graphic image data information and the like, adopts a display panel in Jingdong and a new-phase micro driving chip, and has a working temperature range of-20 DEG C to + 50 DEG C. After compensation by the temperature control module of the module, the working temperature range is expanded to-41 DEG C to + 50 DEG C, and the working temperature range is expanded to-40 DEG C to + 50 DEG C. And the working temperature of the liquid crystal display module is expanded.

Description

TECHNICAL FIELD

[0001] The utility model relates to low temperature display technology field especially relates to a low temperature liquid crystal display module. BACKGROUND

[0002] In the field of field portable detection equipment, it is usually required to carry out detection operation outdoors, and the detection equipment is generally required to have good outdoor environmental temperature adaptability, such as extreme environmental temperature in the range of -40 DEG C to +50 DEG C, and the display screen for device operation interaction cannot meet the outdoor extreme environment requirement due to the limitation of the characteristics of liquid crystal, when the temperature is too low, the liquid crystal display will appear ghosting blur phenomenon or cannot normally display.

[0003] The general liquid crystal screen in the prior art generally works at a low temperature of -20 DEG C, and the liquid crystal screen is difficult to work at a lower temperature, therefore, the utility model provides a low temperature liquid crystal display module, through screen preheating and temperature control, a domestic liquid crystal display module capable of adapting to a low temperature environment of -41 DEG C is designed. UTILITY MODEL CONTENTS

[0004] The utility model discloses a low temperature liquid crystal display module, the display screen adopts ordinary industrial display screen and is used for displaying graphic image data information etc., adopts the display panel of Jingdongfang and the driving chip of new Xiangwei, has the working temperature range of -20 DEG C to +50 DEG C, and the working temperature range is extended to -41 DEG C to +50 DEG C after the compensation of the temperature control module of the module, greatly expands the working temperature of the liquid crystal display module, can adapt to the low temperature environment of -41 DEG C.

[0005] To achieve the above object, the utility model provides the following technical scheme:

[0006] A low temperature display module comprises a control power module, a backlight driving power module, a main control circuit, a temperature control module, a display screen and a communication interface.

[0007] The control power module is composed of a switching power supply chip and inductance capacitor diode elements to form a Buck voltage reduction control circuit, and the 12V power supply input of the module is reduced to 5V output, the 5V output is connected to an LDO voltage reduction chip to be converted into a 3.3V power supply, and the control power module provides 5V and 3.3V power supplies for the main control circuit of the module.

[0008] The backlight driving power module is composed of a switching power supply chip and inductance capacitor diode elements to form a Boost voltage increase control circuit, and the 12V input voltage of the module is converted into 24V voltage to drive the backlight LED of the display screen.

[0009] The main control circuit is composed of a microcontroller, a clock circuit, a storage unit and the like, and is used for display screen content refreshing, data storage, temperature compensation of the display screen in a low temperature state and the like.

[0010] The temperature control module is composed of a PCB heating plate and a temperature sensor, and is used for heating the display screen and feeding back the heating temperature.

[0011] The display screen adopts a common industrial display screen, has a working temperature range of-20℃ to +50℃, and has a working temperature range of-41℃ to +50℃ after compensation by the temperature control module of the module, and is used for displaying graphic image data information and the like.

[0012] The communication interface is composed of an RS232 interface conversion chip and a surge suppression protection device, and is used for data interaction between the module and a host.

[0013] Preferably, the low-temperature liquid crystal display module can normally work in an ambient temperature of-41℃ to +50℃.

[0014] Preferably, all key elements and important components of the low-temperature liquid crystal display module adopt domestic devices, the liquid crystal screen manufacturer is BOE, the liquid crystal driving IC manufacturer is Xinxing Microelectronics, the switching power supply chip manufacturer is Sunban Micro, the LDO chip and the communication interface chip manufacturer is Chipai Micro, and the main control MCU and the Flash memory manufacturer is Megachips.

[0015] The low-temperature liquid crystal display module has the advantages that:

[0016] (1) The display screen adopts a common industrial display screen, is used for displaying graphic image data information and the like, adopts a display panel of BOE and a driving chip of Xinxing Microelectronics, has a working temperature range of-20℃ to +50℃, and has a working temperature range of-41℃ to +50℃ after compensation by the temperature control module of the module, so that the working temperature of the liquid crystal display module is greatly expanded, and the low-temperature environment of-41℃ can be adapted.

[0017] (2) In the utility model, the output voltage after the inductor is stabilized and filtered through C16 and C17, and is fed back to the Vsense pin of U2 through the voltage dividing resistors R7 and R10, the power supply chip U2 compares the voltage of the Vsense pin with the 0.8V reference voltage, and then controls the duty cycle of the SW pin, so that the output voltage is stabilized at 5V through the closed-loop control. The 5V output is converted into a 3.3V power supply through the LDO voltage reduction chip U1 (CBM1117-3.3), and the energy storage and decoupling capacitors are arranged at the input end and the output end respectively to improve the voltage stability. The control power supply module provides 5V and 3.3V power supplies for the main control circuit of the module.

[0018] (3)The utility model discloses, current charges energy storage capacitor C38 and C39 through diode D2, and output voltage is fed back to the FB pin of U5 through voltage dividing resistor R33 and R34, and power supply chip U5 compares the switch duty ratio of SW pin according to the FB pin with 1.23V reference voltage and controls, makes output voltage steady at the set value. Backlight drive power module is used for lighting display screen backlight 7 series LED. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 It is the structure schematic diagram of the utility model module;

[0020] Figure 2 It is the circuit schematic diagram of the utility model module;

[0021] Figure 3 It is the circuit schematic diagram of the utility model control power module;

[0022] Figure 4 It is the circuit schematic diagram of the utility model module main control module;

[0023] Figure 5 It is the circuit schematic diagram of the utility model module backlight drive power module;

[0024] Figure 6 It is the circuit schematic diagram of the utility model module temperature control module;

[0025] Figure 7 It is the mainboard PCB layout of the utility model module;

[0026] Figure 8 It is the heating PCB layout of the utility model module. DETAILED DESCRIPTION

[0027] The technical solutions in the embodiments of the utility model will be described clearly and completely below with reference to the drawings in the embodiments of the utility model. Obviously, the described embodiments are only part of the embodiments of the utility model, not all the embodiments. Based on the embodiments in the utility model, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of the utility model.

[0028] In the description of this utility model, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", etc., indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this utility model and simplifying the description, and are not intended to indicate or imply that the device or component referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this utility model.

[0029] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this utility model, "a plurality of" means two or more, unless otherwise explicitly specified.

[0030] Example: Figures 1-8 As shown, this embodiment provides a low-temperature liquid crystal display module, which includes a control power module, a backlight drive power module, a main control circuit, a temperature control module, a display screen, and a communication interface.

[0031] The control power supply module consists of a Buck step-down control circuit composed of a switching power supply chip U3 (SGM61232) and components such as inductors, capacitors, and diodes. This circuit steps down the module's 12V input power to a 5V output. The SW pin of U3 in the circuit has a fixed output switching frequency of 540kHz. When this pin is on, the input power charges inductor L2; when it is off, the freewheeling diode D7 maintains the current. After passing through the inductor, the output voltage is regulated and filtered by C16 and C17, and then fed back to the Vsense pin of U2 through voltage divider resistors R7 and R10. The power supply chip U2 compares the voltage at the Vsense pin with a 0.8V reference voltage, thereby controlling the duty cycle of the SW pin. Through this closed-loop control, the output voltage is stabilized at 5V. The 5V output is connected to an LDO step-down chip U1 (CBM1117-3.3) to convert it to a 3.3V power supply. Energy storage and decoupling capacitors are placed at the input and output terminals respectively to improve voltage stability. The control power module provides 5V and 3.3V power to the module's main control circuit;

[0032] The backlight driving power module is composed of a switching power supply chip U5 (SGM6607A) and inductance, capacitance and diode elements to form a Boost voltage boost control circuit to convert the 12V input voltage of the module into 24V voltage. The SW pin of U5 in the circuit has a switching frequency of 1.1MHz, when the pin output is low, the input power charges the inductor L1; when the pin is off, the current cannot change abruptly, so the current charges the energy storage capacitors C38 and C39 through the diode D2, and the output voltage is fed back to the FB pin of U5 through the voltage dividing resistors R33 and R34, and the power supply chip U5 compares the FB pin with the 1.23V reference voltage to control the switching duty cycle of the SW pin, so that the output voltage is stabilized at the set value. The backlight driving power module is used to light the display screen backlight 7 in series with the LED.

[0033] The main control circuit is composed of a microcontroller, a clock circuit, a storage unit and the like, and is used for display screen content refreshing, data storage and temperature compensation of the display screen in a low temperature state and the like. The microcontroller U6 (GD32F450ZI) has a TFT-LCD interface TLI and an image processing accelerator IPA, the TLI provides parallel digital RGB (R0-7 / G0-7 / B0-7) and line field synchronization (HSYNC / VSYNC), clock (PIXCLK) and data enable (DE) signals, can directly drive the LCD or TFT display panel, and the IPA has specific image format conversion and transmission functions, so that the microcontroller can be conveniently connected with the display panel and display controlled; the clock circuit adopts an active crystal oscillator with a frequency of 8MHz and a power supply of 3.3V to provide a stable clock source for the microcontroller; the storage unit adopts a 128Mbit Flash memory device (GD25Q128ESIGR) connected with the microcontroller U5 through a hardware SPI interface, and is used for storing a character library and a graphics library.

[0034] The temperature control module is composed of a PCB heating plate and a temperature sensor, and is used for heating the display screen and feeding back the heating temperature. The PCB heating plate is designed in a customized manner, has a size consistent with the length and width of the display screen, has a wire laid on one side close to the display screen, uses the wire resistance to heat, and has two temperature sensor chips placed on the other side of the PCB to feed back the temperature of the heating plate; the microcontroller of the main control circuit reads the temperature measurement value of the temperature sensor chip through an IIC interface, and if the temperature is lower than -20℃, the heating switch Q1 is turned on, and the 12V power supply of the module is applied to the PCB heating plate; when the temperature is higher than -20℃, the heating switch Q1 is turned off.

[0035] The display screen adopts a common industrial display screen, uses a display panel of Jingdongfang and a driving chip of Xinxiangwei, has a working temperature range of -20℃ to +50℃, and after compensation by the temperature control module of the module, the working temperature range is expanded to -41℃ to +50℃, and is used for displaying graphic image data information and the like.

[0036] The communication interface is composed of RS232 interface conversion chip (CBM3232A) and surge suppression protection device, used for data interaction between the module and the host.

[0037] Circuit principle:

[0038] 1. The control power module is composed of switching power supply chip U3 (SGM61232) and inductance capacitor diode, etc. elements to form Buck step-down control circuit, which reduces the 12V power input of the module to 5V output, and the 5V output is connected to LDO step-down chip U1 (CBM1117-3.3) to convert to 3.3V power supply, which supplies power to the digital circuit part in the circuit. The 12V power input is connected to the circuit board through the 3 / 4 pin of the socket P1, connected to the power input pin VIN of the switching chip U3 after the energy storage capacitors C10 / C12 / C13, the enable pin of U3 is obtained by dividing the power input voltage through R30 and R36, the COMP pin of U3 is connected to ground through the series connection of capacitor C9 and resistor R9, the SS pin of U3 is connected to ground through capacitor C15, the switching output pin SW of U3 is externally connected to inductor L2 and freewheeling diode D7, the SW pin fixedly outputs 540KHz switching frequency, charges the inductor L2 when turned on, and maintains the current by the freewheeling diode D7 when turned off, the output voltage after the inductor is stabilized and filtered through C16 and C17, and the output voltage is fed back to the Vsense pin of U3 through the voltage dividing resistors R7 and R10, the power supply chip U3 compares the voltage of the Vsense pin with the 0.8V reference voltage, and then controls the switching duty cycle of the SW pin, through the closed-loop control, the output voltage is stabilized at 5V. The 5V voltage output is connected to the LDO step-down chip U1 (CBM1117-3.3) after the energy storage filter capacitors C1 and C3, which converts the 5V power supply to 3.3V power supply, and the 3.3V output is connected to the energy storage filter capacitors C4 and C2 to improve the voltage stability, and R1 and D1 are connected as the indicator lamp for power supply start. Since there are many devices powered by 3.3V, multiple decoupling capacitors need to be added in the circuit, C24-C35 and C18 / C19 / C42 are connected in parallel between the 3.3V power supply and the ground wire.

[0039] 2、Backlight drive power module is constituted by switching power supply chip U5 (SGM6607A) and inductance capacitor diode and other elements Boost boost control circuit, the input voltage of 12V of module is converted into 24V voltage. The input 12V power supply of module is connected to the Vin input pin of U5 after energy storage capacitor C40; the enable pin EN of U5 is connected to Vin through pull-up resistor R35, when the external 12V power supply is powered on, the chip starts working immediately; the COMP pin of U5 is grounded through resistor R32 and capacitor C41; the SW pin of U5 is connected to Vin pin through inductance L1, connected to power output end through diode D2, the power output end is stabilized through capacitor C38 and C39, and the power output voltage is fed back to the FB pin of U5 through voltage dividing resistor R33 and R34, the switching frequency of SW is 1.1MHz, when the output of this pin is low, the input power supply charges inductance L1; when the pin is off, because the current of inductance cannot be suddenly changed, the current charges energy storage capacitor C38 and C39 through diode D2, the output voltage is stabilized at the design value according to the comparison of the FB pin and 1.23V reference voltage to control the switching duty cycle of SW pin by power supply chip U5. The output voltage of backlight drive power module is used to light up the 7 series LED of display screen backlight.

[0040] 3、The main control circuit is composed of a microcontroller, a clock circuit, a storage unit, etc., and is used for display screen content refreshing, data storage, and temperature compensation of the display screen in a low temperature state, etc. The microcontroller U6 (GD32F450ZI) has a TFT-LCD interface TLI and an image processing accelerator IPA. The TLI provides parallel digital RGB and line field synchronization (HSYNC / VSYNC), clock (PIXCLK), and data enable (DE) signals, and can directly drive the LCD or TFT display panel. The IPA specifically converts and transmits image formats. The microcontroller can be conveniently connected with the display panel and display controlled. In this module, a 16-bit RGB interface (R7-3 / G7-2 / B7-3) is used to connect with the display panel, and the image color data is transmitted in time sequence according to the data clock / line synchronization / field synchronization signal requirements. The internal clock circuit of the main control circuit uses an active crystal oscillator Y1 with a frequency of 8MHz and a power supply of 3.3V to provide a stable clock source for the microcontroller. A capacitor C23 is placed between the power supply input and the ground wire of Y1 for noise decoupling. The storage unit of the main control circuit uses a 128Mbit Flash memory device (GD25Q128ESIGR), which is connected with the microcontroller U6 through a hardware SPI interface. The SPI_NSS signal is used to select the memory device U4. The SPI_SCK is a data clock signal. The SPI_MISO and SPI_MOSI signals are used for bidirectional data transmission between U4 and U6. The F_WP signal is used for U4 write protection. The F_RST is a reset signal, which is used for resetting the memory device U4 by the microcontroller U6. The data space of the storage unit is used to store the font library and graphic library required by the display screen interface. The program download interface of the main control circuit is a SWD1 interface, which mainly includes Reset, SWDIO and SWCLK signals. The Reset signal is used to reset the microcontroller U6. The SWDIO and SWCLK are used for program download and data simulation debugging functions. The Reset pin is pulled up to 3.3V power supply through a resistor R31, and is decoupled through a capacitor C37. The SWDIO pin is pulled up to 3.3V through a resistor R24. The SWCLK pin is pulled down to ground through a resistor R25.

[0041] 4、The temperature control module is composed of a PCB heating plate and a temperature sensor, which is used to heat the display screen and feedback the heating temperature. The PCB heating plate is custom designed, with the size consistent with the length and width of the display screen. Printed conductive wires are laid on one side of the PCB heating plate, which generates heat by the resistance of the printed conductive wires. Two temperature sensor chips are placed on the other side of the PCB, which are used to feedback the temperature of the heating plate. In this module, the two digital temperature sensors of the PCB heating plate are connected through two sockets P4 and P5, which provide 3.3V power supply for the sensors and read the temperature measurement value of the temperature sensor chips through the IIC interface. The temperature sensor U7 is used to sense the temperature of the main control area, which is also connected to the microcontroller through the IIC interface. The heating signal H_PWM output by the microcontroller is connected to the base of the triode Q3 through the isolation diode D4 and the resistor R3 of this module. The base and emitter of the triode Q3 are connected in parallel with the resistor R4. The collector of the triode Q3 is pulled up to 5V through the resistor R2, which is used as the control input signal of the switch tube Q1. The P2 interface is used to connect the heating printed conductive wires of the PCB heating plate. When H_PWM outputs high level, the triode Q3 is turned on, and the input end of the switch tube Q1 is pulled to low level by Q3, so that the switch tube Q1 is turned off, and the PCB heating plate stops heating. When H_PWM outputs low level, the triode Q3 is turned off, and the input end of the switch tube Q1 is pulled to 5V by R2, so that the switch tube Q1 is turned on, and the PCB heating plate starts heating. Under the logical control of the main control module, when the temperature detected by the PCB temperature sensor P4 / P5 is lower than -20℃, the heating switch Q1 is turned on, and the 12V power supply of the module is applied to the PCB heating plate. When the temperature is higher than -15℃, the heating switch Q1 is turned off. In order to prevent the switch circuit from frequently starting, a heating hysteresis of 5℃ is set in the main control logic, that is, the heating is turned on when the temperature is lower than -20℃, and the heating is turned off when the temperature is higher than -15℃.

[0042] 5. The display module uses a standard industrial display screen. In this example, it uses a display panel from BOE and a driver chip from NewSign Microelectronics. The LCD panel has an operating temperature range of -20℃ to +50℃. After compensation by the temperature control module of this module, the operating temperature range is extended to -41℃ to +50℃, used for displaying graphic images, data information, etc. The display screen is powered by 3.3V. Two decoupling capacitors C20 / C21 and an energy storage capacitor C22 are placed at the power input port of the display screen to improve the stability of the power supply. The backlight of the display screen is a 7-LED series structure. The voltage output of the backlight driver module is connected to the positive terminal of the display screen backlight after being connected in series with a 10Ω current-limiting resistor R22. The negative terminal of the backlight is grounded through a switching circuit, which consists of transistor Q2, resistors R16 / R18 and diode D3. When the MCU control signal LCD_BL is high, transistor Q2 is turned on and the backlight is lit. When the MCU control signal LCD_BL is low, transistor Q2 is turned off and the backlight is off. The backlight brightness is adjusted by controlling the duty cycle of the LCD_BL signal, and the display brightness can be continuously adjusted between 0% and 100%.

[0043] 6. The communication interface consists of an RS232 interface conversion chip (CBM3232A) and surge suppression protection devices, used for data interaction between the module and the external host. Pin-141 (UART7-RX) of microcontroller U6 connects to Pin-12 of U2 (CBM3232), Pin-142 (UART7-TX) of U6 connects to Pin-11 of U2, and Pin-14 and Pin-13 of U2 connect to the RS232 interface of the external host. The peripheral components of U2 mainly include decoupling capacitors C6 / C7 / C14 and charge pump boost capacitors C5 / C11, MCU port protection devices D5 and D6, and external host interface protection devices R11 / R12 and D8 / D9. D5 and D6 limit the MCU port voltage to 0-3.3V to prevent overvoltage; R11 / R12 and D8 / D9 limit the external host interface voltage to ±9V to prevent damage to U2 from external wiring errors.

[0044] The above description is only a preferred embodiment of the present utility model and is not intended to limit the present utility model. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.

Claims

1. A low temperature liquid crystal display module, characterized by, The display module comprises a control power module, a backlight driving power module, a main control circuit, a temperature control module, a display screen and a communication interface. The control power module comprises a Buck voltage reduction control circuit composed of a switching power supply chip and an inductor capacitor diode. The Buck voltage reduction control circuit reduces the 12V power input of the module to 5V output, and the 5V output is connected to an LDO voltage reduction chip to be converted to a 3.3V power supply. The main control circuit is composed of a microcontroller, a clock circuit and a storage unit, and is used for display screen content refreshing, data storage and temperature compensation operation of the display screen in a low temperature state.

2. The low temperature liquid crystal display module according to claim 1, wherein, The backlight driving power module comprises a Boost voltage increase control circuit composed of a switching power supply chip and an inductor capacitor diode element, which converts the 12V input voltage of the module to 24V voltage for driving the backlight LED of the display screen.

3. The low temperature liquid crystal display module according to claim 2, wherein, The temperature control module is composed of a PCB heating plate and a temperature sensor, and is used for heating the display screen and feeding back the heating temperature.

4. The low temperature liquid crystal display module according to claim 3, wherein, The communication interface is composed of an RS232 interface conversion chip and a surge suppression protection device, and is used for data interaction between the module and the host.

5. The low temperature liquid crystal display module according to claim 4, wherein, The display screen adopts a common industrial display screen, is used for displaying graphic image data information, and has temperature adaptability expansion after temperature compensation of the liquid crystal display module by the temperature control module built in the module.

Images