Improved battery discharge limiter. Encyclopedia of radio electronics and electrical engineering

Encyclopedia of radio electronics and electrical engineering / Chargers, batteries, galvanic cells

 Comments on the article

The discharge limiter disconnects the load from the battery when the voltage drops below a pre-set threshold. A description of a device for a similar purpose is published in [1]. However, it does not have a threshold hysteresis. As a result, when the battery voltage under load is less than the threshold, and without load - more, the device will periodically disconnect and connect the load until the voltage of the battery without load is below the threshold. The proposed device does not have this disadvantage, since its design provides for a hysteresis of the response threshold.

Fig. 1

The discharge limiter circuit is shown in fig. 1. It consists of two main elements - a DA1 parallel voltage regulator chip and a high-current p-channel switching field-effect transistor VT1. The DA1 microcircuit is used as a comparator [2], which controls the battery voltage, the VT1 transistor is used as an electronic switch that breaks the load power supply circuit.

The device works as follows. A current of no more than 1 mA flows through the DA0,5 chip. independent of the voltage at its control input, as long as it is less than the turn-on threshold of the microcircuit (about 2,5 V). When the voltage at the control input exceeds the turn-on threshold of the microcircuit, the current through it will increase significantly

The operating threshold of the device is set by a trimming resistor R1. The controlled voltage is supplied to the control input of the microcircuit through the R3C2 low-pass filter so that the device responds to the average value of the supply voltage, and not to its instantaneous changes. The larger the capacitance of capacitor C2, the less sensitive it is to ripples of this voltage.

When the battery voltage exceeds the set threshold, a few milliamps of current flows through the microcircuit, the voltage drop across the resistor R2 is enough to keep the transistor VT1 in the open state, so the load is connected to the battery. Due to the fact that the resistance of the open channel of the transistor VT1 is hundredths of an ohm, the voltage loss on it, even at a current of several amperes, is small.

When the battery voltage becomes less than the set threshold, the current through the microcircuit will drop, the voltage across the resistor R2 will be insufficient to open the transistor VT1, as a result of which it will close and break the load supply circuit. When a discharged battery is connected, transistor VT1 will generally remain closed.

In order for the switching to take place more clearly, a positive feedback is introduced into the device through the resistor R4. Due to this, the device has a hysteresis: the load is disconnected at a lower supply voltage than its connection. The hysteresis value can be adjusted by selecting the resistor R4. For the ratings indicated in the diagram, the hysteresis was 0,4 V at a supply voltage of 9 V and 0,6 V at a supply voltage of 12 V. If the supply voltage is below the response threshold and increases, then the voltage at the control input of the microcircuit also increases. But since the load is de-energized, the voltage at the control input comes from the resistor R1 engine through the divider R3R4. Therefore, the load is connected at a voltage on the engine of the resistor R1, several hundred millivolts greater than the turn-on threshold of the microcircuit.

When the current through the microcircuit begins to grow, the transistor VT1 opens and a voltage appears at the output. Through the resistor R4, it enters the control input of the microcircuit, the voltage on it increases, which leads to the fact that the current through it increases even more and, ultimately, the transistor VT1 opens completely. When the supply voltage decreases, the reverse process occurs.

Since the field-effect transistor VT1 starts to open at a gate-source voltage of 2,5 ... 3 V, the device can operate in the supply voltage range from 5 ... 7 V to 20 V. It can use the TL431 chip, the pin numbers of which in the diagram are indicated in brackets, switching transistors with p-canapes from the list given in [3], trimmer resistor SPZ-19, constants - MLT, C2-33, oxide capacitor - K50-35, non-polar - K10-17.

Fig. 2

When using small-sized parts for surface mounting, the dimensions of the device can be made small. For an example in fig. Figure 2 shows a sketch of the PCB using the TL431CD chip in the SO-8 package and the IRLML6402P transistor in the SOT-23 package. This transistor has an on-state channel resistance of 0,06 ohms and a low on-state leakage current (several microamps). It provides current switching up to 2...3 A. Trimmer resistor R1 - POZ3AN. Oxide capacitor - imported tantalum size D. Resistors - P1-12.

The adjustment is carried out with a real load and a battery. Before turning on for the first time, the engine of the tuning resistor R1 is set to the lower position according to the diagram. Resistor R2 is selected so that when the DA1 chip is off, the transistor VT1 is closed, and when it is on, it is open. The threshold is set by the engine of the tuning resistor R1, and its hysteresis is set by the selection of the resistor R4. It should be noted that these adjustments are interrelated, so it may be necessary to repeat them one by one to achieve the required parameters. The hysteresis value is set so that when the battery voltage drops, the load is disconnected without reconnection.

Literature

1. Nechaev I. Battery discharge limiter. - Radio, 2004, No. 6, p. 38.
2. Nechaev I. Unusual application of the KR142EN19A microcircuit. - Radio, 2003, No. 5, p. 53, 54.
3. Powerful field-effect switching transistors from International Rectifier. - Radio, 2001, No. 5, p. 45.

Author: I. Nechaev

See other articles Section Chargers, batteries, galvanic cells.

Read and write useful comments on this article.

<< Back

Latest news of science and technology, new electronics:

Machine for thinning flowers in gardens 02.05.2024

In modern agriculture, technological progress is developing aimed at increasing the efficiency of plant care processes. The innovative Florix flower thinning machine was presented in Italy, designed to optimize the harvesting stage. This tool is equipped with mobile arms, allowing it to be easily adapted to the needs of the garden. The operator can adjust the speed of the thin wires by controlling them from the tractor cab using a joystick. This approach significantly increases the efficiency of the flower thinning process, providing the possibility of individual adjustment to the specific conditions of the garden, as well as the variety and type of fruit grown in it. After testing the Florix machine for two years on various types of fruit, the results were very encouraging. Farmers such as Filiberto Montanari, who has used a Florix machine for several years, have reported a significant reduction in the time and labor required to thin flowers. ... >>

Advanced Infrared Microscope 02.05.2024

Microscopes play an important role in scientific research, allowing scientists to delve into structures and processes invisible to the eye. However, various microscopy methods have their limitations, and among them was the limitation of resolution when using the infrared range. But the latest achievements of Japanese researchers from the University of Tokyo open up new prospects for studying the microworld. Scientists from the University of Tokyo have unveiled a new microscope that will revolutionize the capabilities of infrared microscopy. This advanced instrument allows you to see the internal structures of living bacteria with amazing clarity on the nanometer scale. Typically, mid-infrared microscopes are limited by low resolution, but the latest development from Japanese researchers overcomes these limitations. According to scientists, the developed microscope allows creating images with a resolution of up to 120 nanometers, which is 30 times higher than the resolution of traditional microscopes. ... >>

Air trap for insects 01.05.2024

Agriculture is one of the key sectors of the economy, and pest control is an integral part of this process. A team of scientists from the Indian Council of Agricultural Research-Central Potato Research Institute (ICAR-CPRI), Shimla, has come up with an innovative solution to this problem - a wind-powered insect air trap. This device addresses the shortcomings of traditional pest control methods by providing real-time insect population data. The trap is powered entirely by wind energy, making it an environmentally friendly solution that requires no power. Its unique design allows monitoring of both harmful and beneficial insects, providing a complete overview of the population in any agricultural area. “By assessing target pests at the right time, we can take necessary measures to control both pests and diseases,” says Kapil ... >>

Random news from the Archive The most popular place on Earth for lightning 11.03.2024 Lightning is not only a beautiful natural phenomenon, but also a serious threat to human life and health. The pursuit of understanding and predicting these phenomena remains an urgent task for the scientific community, as this will help improve human safety and protection from lightning strikes. There are places on our planet where lightning sometimes becomes not only a frequent occurrence, but also a deadly threat to the environment and living organisms. Modern technologies make it possible to accurately determine the most dangerous areas where lightning strikes most often. There are places on our planet where lightning sometimes becomes not only a frequent occurrence, but also a deadly threat to the environment and living organisms. Modern technologies make it possible to accurately determine the most dangerous areas where lightning strikes most often. Meteorologist and lightning researcher Professor Chris Wagaski from the University of Wisconsin-Madison in the US, along with his colleagues, conducted an extensive study, the results of which have attracted the attention of many. The statistics are astonishing: There are approximately 23,4 million lightning strikes, 55,5 million lightning strikes, and 36,8 million ground strike points in the United States each year. Scientists also shared statistics on deaths and injuries from lightning strikes, noting that about 250 thousand people die or are injured in the world every year. This happens especially often in developed countries, where many are forced to work outdoors during thunderstorms. Between 2003 and 2023, an average of 28 people were killed by lightning strikes each year in the United States. Florida, according to Chris Wagaski, is the most dangerous place for cloud-to-ground lightning strikes. In 2023 alone, 120 lightning strikes were recorded in one area of ​​the state, making Florida one of the most dangerous places on Earth due to high lightning activity. Despite the high accuracy of lightning detection with modern technologies (up to 97%), these natural phenomena remain unpredictable, requiring further research to better understand their nature.

Other interesting news:

▪ Personal air conditioner

▪ In the heat is not up to love

▪ STM32L4P5/Q5 - STM32L4+ family in small packages

▪ New Bluetooth devices from PHILIPS SEMICONDUCTOR

▪ White sharks make animals stressed

News feed of science and technology, new electronics

Interesting materials of the Free Technical Library:

▪ section of the site Instructions for use. Article selection

▪ article Slander, slander, let something remain. Popular expression

▪ article Where is the lake, which hides a whole park under water every year? Detailed answer

▪ article Iceland moss. Legends, cultivation, methods of application

▪ article Voltage polarity converter on switched capacitors. Encyclopedia of radio electronics and electrical engineering

▪ article VHF tuner on the KS1066XA1 chip. Encyclopedia of radio electronics and electrical engineering

Leave your comment on this article:

All languages ​​of this page

Arabic	Hebrew	Polish
Bengali	Hindi	Portuguese
Chinese	Italian	Spanish
English	Japanese	Turkish
French	Korean	Ukrainian
German	Malay	Vietnamese

Home page | Library | Articles | Website map | Site Reviews

www.diagram.com.ua
2000-2024