Replacing the SD4842P67K65 chip with the FSDH321 in the S-12-12 power supply. Encyclopedia of radio electronics and electrical engineering

Encyclopedia of radio electronics and electrical engineering / Power Supplies

 Comments on the article

The S-12-12 compact switching power supply provides a stabilized voltage of 12 V at a load current of up to 1 A. It is usually used to power LED lamps, video surveillance systems and burglar alarm systems. After working for a short time, this block broke down for me, after which it lay for several years waiting for the SD4842P67K65 chip or its close analogue from the SD484x series. Since it was not possible to purchase such a microcircuit, it was decided to install the more common FSDH321 in the block. Both of them have the same functional purpose, similar parameters and are produced in the DIP-8 package.

The inclusion diagram of the SD4842P67K65 microcircuit in the S-12-12 block is shown in fig. 1. The positional designations of the elements correspond to those printed on the block board. The FSDH321 chip was installed instead of it and connected according to the diagram shown in fig. 2. Previously missing resistor R11' and zener diode VD8' were added.

Rice. 1. Scheme of switching on the SD4842P67K65 microcircuit in the S-12-12 block

Rice. 2. Scheme of switching on the FSDH321 chip in the S-12-12 block

I soldered an additional heat sink to pins 6-8 of the FSDH321 chip - a copper plate 0,6 mm thick with a cooling surface area of ​​2 cm².

In addition to replacing the microcircuit, the 1N4007 (D5) diode in the power supply was replaced by a faster UF4007 diode. The same diode can be installed in place of D6. In parallel with the oxide capacitors C8 and C9, ceramic capacitors with a capacitance of 1 uF in a surface mount package were connected. They were soldered between the terminals of the capacitors C8 and C9 on the side of the printed conductors.

It is desirable to make the first connection of the repaired power supply to the network through an incandescent lamp 230 V, 25 W.

It must be said that when the unit was first turned on, the Schottky diode SR3100 (D7) in the output voltage rectifier immediately failed. A possible reason for this could be the higher operating frequency of the new microcircuit or the fact that the author reduced the capacitance of the capacitor C5 to 22 nF (according to the typical FSDH321 microcircuit). After returning the old 100 nF capacitor to this place and replacing the SR3100 Schottky diode with a MUR460 high-speed silicon diode, the unit's performance was restored. The voltage swing between the terminals of the diode D7 is about 60 V at a load current of 1 A and about 85 V without load.

A load consuming a current of 1 A was connected to the output of the repaired PSU. After 20 minutes of operation, the temperature of the case of the U1 microcircuit reached 92 ^оC at room temperature 24 ^оC. The body temperature of the diode D7 was 88 ^оC, and the temperature of the magnetic circuit of the pulse transformer T1 - 69 ^оC. After reducing the load current to 0,6 A, the temperature of the microcircuit case dropped to 65 ^оC. The measurements were taken on the board removed from the case.

It is not surprising that this block in the factory version could not withstand prolonged operation. Based on the results obtained, the maximum current of its load should be considered 0,6 A at a voltage of 12 V or 1 A at a voltage of 9 V. To obtain an output voltage of 9 V, the resistance of the resistor R6 was reduced to 5,1 kOhm. The exact value of the output voltage is set by the tuning resistor R10.

The FSDH321 integrated circuit is marked on the case as DH321, under the same name it can be sold. The measured conversion frequency is 102 kHz. The built-in protection of the FSDH321 chip begins to reduce the output voltage only when the unit load current is more than 2 A, which is quite a lot. Therefore, to protect against overload, you can connect a self-resetting fuse with a current of 0,65 ... 1,1 A in series with the load. When the output is short-circuited, the unit makes attempts to start approximately once a second. After the same time, the output voltage appears after the unit is connected to the network.

Instead of the FSDH321 chip, you can install the FSDH0265RN. If SD4843P67K65 or SD4844P67K65 chips are available, they can be used to replace a failed SD4842P67K65 chip without any rework to the block. They are designed for increased output power - 14 and 16 watts, respectively.

The MUR460 diode can be replaced with, for example, UF5403, FR303G, SRP300J. Instead of a BZV55C-18 zener diode, a TZMC-18 or 1N4746A will do. A faulty EL817 optocoupler can be replaced by any four-pin optocoupler with the numbers 817 in the designation. For example, LTV817, PC817, PS817. With a load permanently connected to the unit, consuming a current of at least 50 mA, the resistor R9 can be removed from it. This will increase the efficiency of the unit and reduce heat generation inside its case.

The distance from the metal screen of the S-12-12 block to some solder points on its board does not exceed 2 mm. To reduce the probability of a short circuit between the primary circuit of the unit and the screen, an insulating film 784 mm thick is glued to the bottom of the screen with XB-0,5 varnish from the inside. The inner side surfaces of the screen are densely, without gaps, painted with the same varnish.

Author: A. Butov

See other articles Section Power Supplies.

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 Short daylight hours affect mental ability 17.11.2022 Scientists have found that dim winter lighting aggravates cognition by reducing the connectivity of neurons in the brain. These conclusions were reached by scientists from the University of Michigan in the course of experiments with grass mice. They, like humans, are awake during the day and sleep at night. This allows a much more accurate comparison of these animals and humans compared to conventional non-diurnal laboratory mice. Professor Lily Yang and her team of researchers studied grass mice to understand how light modulates brain function and behavior. Two groups of rodents were kept under different conditions for a month. The first lived under dim light - 50 lux, as in a room. The rest - for 1000 lux, like in a supermarket. This model simulated seasonal changes in lighting in winter and summer. Then the mice had to go through the maze. The first group coped with the task worse. In rodents, the ligaments of neurons in the hippocampus of the brain have decreased by almost a third - it is responsible for memory. They also had worse mood and cognitive function. Therefore, scientists concluded that people need to spend more time in the yard in winter - at least half an hour. Street lighting is bright enough even on a cloudy day. And in cloudless - about 10 lux.

Other interesting news:

▪ Hydrogel and sunlight can desalinate water

▪ The smallest laser

▪ Plants help fight the flu

▪ Magnetic system that converts heat into mechanical motion

▪ Antidepressants for alcoholism

News feed of science and technology, new electronics

Interesting materials of the Free Technical Library:

▪ site section Lightning protection. Article selection

▪ article There is still gunpowder in the flasks. Popular expression

▪ article Which word synagogue was replaced in the movie The Diamond Arm due to censorship? Detailed answer

▪ article Electric gas welder. Job description

▪ article Attachment to the multimeter for measuring temperature. Encyclopedia of radio electronics and electrical engineering

▪ article The map and the figure are the same. Focus Secret

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