Although rechargeable batteries have many advantages, they can be damaged and have a shortened life if they are over-discharged. The circuit in Figure 1 can shut down a battery-powered appliance, such as an LED flash powered by a NiMH (nickel metal hydride) battery, when the battery voltage falls below a preset limit. Although this circuit targets LED flashes, it can be applied to any battery-powered device. Since there is no guarantee that the user will remove the battery to recharge it, the circuit latches off the flash when the battery voltage drops below a usable limit, which is also a strong hint that it is time to recharge.
Although a simple non-latching voltage comparator can cut power, removing the battery load causes voltage fluctuations, and the comparator forces the flash mode again when power is restored. This circuit turns off the flash light and keeps it off unless the user manually turns the light on with switch S1.
IC1, a 600mA NCP1421 PFM step-up synchronous rectification DC/DC converter from On Semiconductor, forms the heart of the circuit, but the basic circuit is applicable to other converters that provide similar functions (Reference 1). The main features of the NCP1421 include an integrated LBI/EN (low battery input/enable) and an open-drain LBO (low battery output). The circuit operates from two AA NiMH batteries and consists of a conventional step-up regulator: an inductor, input and output capacitors, and a
and the current sensing circuit on the right side of IC1. The LED forward voltage generated by the voltage divider R3 and R2, and the voltage across the current sensing resistor R1, together generate a feedback voltage that is compared with the 1.2V nominal reference voltage of the NCP1421.
On the input side, the LBI/EN pin of IC1 is connected to the battery through a voltage divider network consisting of R4, R5, and R10. When the LBI/EN voltage exceeds 1.2V, the NCP1421 remains enabled. When the LBI/EN voltage drops below 1.2V, the LBO sense pin is low, Q3 turns on, and provides current to the base of Q1. When Q1 turns on, the base of Q2 is low, latching the virtual thyristor (SCR) formed by Q1 and Q2, IC2 is an integrated dual transistor MBT3946DW1.
In addition, Q1 locks the LBI/EN pin to a low level to prevent IC1 from turning on again when the load is removed. To restart this circuit, the power supply to the circuit must be cut off with switch S1. Resistors R4, R5, and R10 set the battery voltage breakpoint for the LBO detector. R5 also sets the amount of current that flows out of the battery when the SCR is activated. When the battery voltage drops to approximately 1.3V, the circuit shuts down, and the LBI/EN pin reaches 1.2V.
Previous article:High performance combined with a revolutionary breakthrough in size, weight and power consumption
Next article:Lithium-ion battery basics
- MathWorks and NXP Collaborate to Launch Model-Based Design Toolbox for Battery Management Systems
- STMicroelectronics' advanced galvanically isolated gate driver STGAP3S provides flexible protection for IGBTs and SiC MOSFETs
- New diaphragm-free solid-state lithium battery technology is launched: the distance between the positive and negative electrodes is less than 0.000001 meters
- [“Source” Observe the Autumn Series] Application and testing of the next generation of semiconductor gallium oxide device photodetectors
- 采用自主设计封装,绝缘电阻显著提高!ROHM开发出更高电压xEV系统的SiC肖特基势垒二极管
- Will GaN replace SiC? PI's disruptive 1700V InnoMux2 is here to demonstrate
- From Isolation to the Third and a Half Generation: Understanding Naxinwei's Gate Driver IC in One Article
- The appeal of 48 V technology: importance, benefits and key factors in system-level applications
- Important breakthrough in recycling of used lithium-ion batteries
- Innolux's intelligent steer-by-wire solution makes cars smarter and safer
- 8051 MCU - Parity Check
- How to efficiently balance the sensitivity of tactile sensing interfaces
- What should I do if the servo motor shakes? What causes the servo motor to shake quickly?
- 【Brushless Motor】Analysis of three-phase BLDC motor and sharing of two popular development boards
- Midea Industrial Technology's subsidiaries Clou Electronics and Hekang New Energy jointly appeared at the Munich Battery Energy Storage Exhibition and Solar Energy Exhibition
- Guoxin Sichen | Application of ferroelectric memory PB85RS2MC in power battery management, with a capacity of 2M
- Analysis of common faults of frequency converter
- In a head-on competition with Qualcomm, what kind of cockpit products has Intel come up with?
- Dalian Rongke's all-vanadium liquid flow battery energy storage equipment industrialization project has entered the sprint stage before production
- Allegro MicroSystems Introduces Advanced Magnetic and Inductive Position Sensing Solutions at Electronica 2024
- Car key in the left hand, liveness detection radar in the right hand, UWB is imperative for cars!
- After a decade of rapid development, domestic CIS has entered the market
- Aegis Dagger Battery + Thor EM-i Super Hybrid, Geely New Energy has thrown out two "king bombs"
- A brief discussion on functional safety - fault, error, and failure
- In the smart car 2.0 cycle, these core industry chains are facing major opportunities!
- The United States and Japan are developing new batteries. CATL faces challenges? How should China's new energy battery industry respond?
- Murata launches high-precision 6-axis inertial sensor for automobiles
- Ford patents pre-charge alarm to help save costs and respond to emergencies
- New real-time microcontroller system from Texas Instruments enables smarter processing in automotive and industrial applications
- Share the common problems of MSP430: LCD display driver
- Analysis of common defects, hazards and causes of circuit board welding
- Network port with a speed of 5G or above
- The origin of the BUCK circuit, with three evolutionary circuits
- DSP Learning (1) Introduction to Digital Signal Processors (DSPs)
- Espressif's ESP32-C3 is an extremely low-power SoC equipped with a RISC-V 32-bit single-core processor
- Please teach me a resistance measurement circuit
- Why does the STACK MODE of almost all pads in ALTIUM DESIGNER change to FULL STACK?
- 【STM32WB55 Review】——by Beifang
- 8 principles to follow in PCB stackup design