A Low-Cost Surge Current Detection Sensor with Predictive Lifetime Display Function for Maintenance of Surge Protective Devices

In this study, a low-cost surge current detection sensor (SCDS) that can measure high current surges using a low-current toroidal coil is proposed for maintenance of a surge protective device (SPD). The proposed SCDS is designed to display the predicted lifetime of the SPD based on the magnitude of surge current and number of surges. In addition, a method for measuring high surge current using a toroidal coil that can usually measure only low current is proposed. A lightning strike counter consists of a microcontroller with a low-power liquid crystal display (LCD) driver, 3 VDC lithium battery, and signal conditioning circuit that converts amplitude information of the surge current into duration information of a negative pulse to facilitate processing in the microcontroller. In this paper, we propose a software algorithm that can calculate the remaining lifetime of SPD based on the amplitude and number of surge currents. There is also an option to select the capacity of the surge protective device and the number of phase lines, allowing it to assess the predicted lifetime for various types of Class II SPDs. The proposed SCDS is measured as 7.2 μA from the battery power consumption test, and the service life is calculated to be 11.1 years. It meets the International Standard IEC62561-6 test conditions of the lightning strike counter and is expected to be useful in the maintenance of SPDs and lightning protection systems.

Application of cascode level shifter for EMI reduction in LCD driver IC

Purpose – This paper aims to design the circuit for electromagnetic interface (EMI) reduction in liquid crystal display (LCD). Design/methodology/approach – The cascode level shifter and segmented driver circuit are applied in LCD column driver integrated circuit (IC) for EMI reduction. Cascode current mirror is used in the proposed level shifter for DC voltage biasing and reduction of the driving current which passes through the level shifter. The on-off switching currents and transient times are measured and compared between the conventional and proposed level shifters. Additionally, a segmented data latch is obtained by the timing spread solution in data latch, and applied to split the large peak switching current into a number of smaller peak current. The timing spread-operation does not actually reduce the total power of the noise, instead, it spreads the noise power evenly over the frequency bandwidth. The optimal number of latch is dependent on the operating frequency and EMI allowance. The column driver IC and clock controller are integrated in 0.18 μm CMOS technology with 1-poly and 4-metal process. Findings – The post-layout simulation shows that the proposed column driver circuit for LCD driver IC significantly reduces the peak switching current, and it results in the reduction of EMI noise level by more than 15 dB. It is obtained with 20 segmented operations in data latch at 40 MHz frequency. Originality/value – The advantage of the cascode current source is that it can provide a well-controlled bias current with an accurate current transfer ratio. To reduce the EMI noise in LCD driver circuit, the cascode current source is properly located for the DC bias block in the level shifter. The application is rarely done by others, and a significant EMI noise reduction is found. The well-controlled current source provides a high performance switching in the level shifter.

Implementation Method of μC/GUI Chinese Font Base on Embedded System

According to the current application of human-computer interaction interface is more and more complex requirements, implementation method of μC/GUI Chinese font based on the ARM embedded operating system with CortexTM-M4F kernel is designed, to download the font by PC and embedded system USB to expand FLASH memory, the μC/GUI kernel code is modified and the GB2312 Chinese characters codec driver is added, this makes up for technical blank of Chinese display in embedded system with μC/GUI library, to provide an efficient and flexible solution for no character of LCD in embedded system. The method provides a reference implementation for other LCD controllers driver and font library transplantation in μC/GUI. Experiments show that, the design method of extended Chinese font provides reference for interactive LCD driver transplantation and font realization; it has better practicability and universality in environment of μC/GUI system.

Design and Realization of TFT LCD Driver Circuit Based EPM240

This paper introduces the implement method of the controller of a CPLD TFT based on the LCD digital display, using CPLD to achieve TFT-LCD display timing generation, display image processing, double memory read-write rotation control functions, This design according to the actual demand, cut on the interface function of special display control chip, custom display control function, enhance the system reliability and design flexibility. Applied to a liquid crystal display control unit, solve practical problems in engineering.

Design and Implementation of Intelligent Tester for LED Backlight LCD Display Driving Power

In accordance with the requirement of LED LCD driving power test and the basic principle of digital DC electronic load and combined with the trend of intelligentization, miniaturization, communication of electronic load, a new scheme of intelligent tester for LED LCD driver power based on PIC is proposed. It implements working modes of setting current, testing voltage, testing current, testing frequency, multi-channel transmission etc. Intelligent testing for ten states of LED LCD's four outputs under two power mode is supported. It can also send test data to upper computer for analysis with RS485 bus.