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Peekaboo, hello again! Thank you so much for such an unrealistically warm reception of my first post, I did not expect that you will like it so much.
In the comments to that post, they asked to tell more about the choice of products, so today’s post will be about how we choose, store and check the quality of future food. Some of this is purely industrial history, the other is useful in home cooking.
In industrial production, good minced meat can be made from good meat. But in the process of cutting this very meat, a large mass of bones will certainly remain. In order not to throw them away, the production grinds the bones into an emulsion, adds a stabilizer and dye, and kneads the minced meat. It is even useful, except for the stabilizer and dye. And the taste is indistinguishable.
But no one will give you a discount on these bones, they will sell minced meat as natural.
We always twist minced meat ourselves. And we make, for example, yokes and meatballs out of it:
At the same time, we use one little secret: we do not add 11 herbs and spices to the minced bread (instead of it – a little breadcrumbs).
According to Soviet GOST, a cutlet should contain 20% onion, 30% bread, 50% meat. Bread, sometimes soaked in milk, is needed to give the liquid minced boneless chicken at least some shape suitable for modeling. But then the client tells you: “You brought me a cutlet that is bread.”
Therefore, for chicken cutlets, we make minced chicken breast – it is well molded by itself. But in fact – no matter what part it is made of. The meat grinder will grind everything, and according to a good technical map, any novice butcher will collect delicious minced meat from which juicy cutlets will turn out. Well, if the cutlet turns out to be dry at the exit, then either it was overcooked, or the cook could not stand the percentage of fat.
We never take freshly caught fish and I don’t recommend you to take it. Only the one that went through the shock freezing. Because for those 3-5 days that the fish spent in the ice, all the parasites will die in it.
Salmon before baking
Good fishing companies freeze the fish immediately after the catch – right on the trawler or immediately upon arrival at the port. And small ones can ignore it.
You come to the store, you see a beautiful fish on ice. Feel free to ask the seller if it has been frozen. If you do not trust – freeze at home yourself. In a regular home freezer, this will take 5 days (a long time, but what can you do). The main thing then is to defrost not in the sink – so the ice that has formed in the fibers will not destroy them, and you will not get bad-smelling cotton wool for dinner. You need to put the fish on a dish, if you’re worried – then in a tight bag, and stuff it in the refrigerator. It will take another day, but at the exit you will have a wonderful fish, which is at least for a steak, even for sushi.
So that you don’t slip a delay, pay attention to 3 things:
– the head must be available;
– eyes should also be and they should be transparent, not cloudy;
– if you press your finger on the back, where there is more meat – it should spring back. Simply put, the dent from the finger should return to its original even state.
These three points are enough for the consumer.
We don’t have river fish on our menu, but I also have a couple of tips for my fishing friends. Firstly, even crucian carp from your favorite proven pond and even from an aquarium in a supermarket should also be frozen right away. And secondly, before freezing, you need to inspect the tail and fins. If you fluff them up, spread them, you can easily notice the red worms. There are a lot of infected fish.
Meat and poultry
We order cows, pigs, chicken and ducks exclusively in freezing.
This is not exactly the kind of frost you are used to seeing in stores. Chicken, for example, comes in a meter by meter plate. Here, of course, it is not possible to look at each one; it is possible to check the quality of raw materials only through processing.
Chicken plate. You can build a house beyond the Arctic Circle
We load the stove into defrosting, then we weigh it – we write down the result and compare it with the dry weight indicated on the box. We roll it properly in spices, send it to the combi steamer and bake. There, the chicken again loses weight – we record and compare with statistical data. This is the only way to understand whether good raw materials have arrived, or whether there is more ice and gel in it than chicken. In production, such comparative work never stops.
By the way, at the dawn of experience, we realized that an expensive fillet costs us less than an inexpensive chicken carcass. At home, you will cut off the wings and legs with a knife, and send them to the oven, and the excess to the broth.
And when you have 4 tons of chicken with bones, necks and other things, you can’t really use a knife. This requires a separate boning plant with corresponding costs. Or additionally load the butcher, put him a stainless table with a sink for waste and a cleaner – because out of four tons, something will fly past. And these are also separate and considerable expenses, so that a carcass for 150 r / kg comes out golden. This is what butcher shops do, and it’s quite a profitable business if you resell the chicken.
In artiodactyls, tenderloin is most valued. The price tag is appropriate. But we don’t use it: it’s a restaurant story. There you can cook filet mignon and sell it with a markup of 1,000%.
We take butts from beef. Too lazy to google – this is the part of the back closest to the pope. And we even make our roast beef out of it – due to the cooking technology, it turns out to be tender.
Pork has carbonade. This part is almost not involved in movement, therefore the least sinewy.
For lovers of beef tenderloin, I can give you a little advice. Be vigilant during the purchase, because you can bring home an eye muscle from a dishonest seller. It looks almost the same as a tenderloin without a head. The deception will be revealed somewhere in the fourth hour of cooking, when you realize that for some reason the meat does not become soft. Therefore, it is better to see the photo once, and then choose the correct clipping – with the head (the real clipping should resemble an Alien, sorry for the comparison, but everyone will understand and remember it that way).
Tenderloin – Right
Well, the main life hack in choosing any meat and vegetables: don’t be fooled by “eco”. But this is a fairly general and voluminous advice, we will talk about it at the end.
It’s better not to take store-bought kebabs in principle. First, everyone has their favorite spices. Secondly, as a rule, not the first freshness meat is cut into kebabs, and it is impossible to check this.
First, garlic will be added to it, which will kill all odors. And then they will fill it with vinegar – it will completely decompose everything that was already in a half-decomposed state. You will only find out about this when you get sick.
If you want barbecue, buy a piece of pork neck, cut it. If you want to save money – take a spatula. In a blender, grind three onions with salt and pepper into porridge, stuff everything together in a bag. And when you arrive at the dacha, you will have an excellent marinated soft barbecue. And it will be more useful and cheaper than the store.
Cooking barbecue according to this very recipe, Hodor controls the process
Cottage cheese and sour cream
Curd and sour cream “products” are much cheaper in production and, as a result, for the consumer. If you have the task of reducing the cost of raw materials, you can mix cottage cheese and curd product 50 to 50. For example, if we talk about cheesecakes, then the taste of the finished cheesecake will practically not change from this (of course, if you do not make a completely unsuccessful proportion).
Birth of cottage cheese pancake
Sour cream and cottage cheese products also have an advantage: they can be stored in the refrigerator for at least a month. Nevertheless, we do not buy a curd product for one simple reason: I don’t like it, I don’t eat it, and I don’t want customers to eat it. Well, we don’t need such terms either: the same sour cream, due to its bacteria, can perfectly lie for a week in a refrigerated warehouse, and then quietly for another 5 days in a client’s refrigerator.
If you don’t want to run into “sour cream”, pay attention to the name. If it is, say, not sour cream, but some kind of “sour cream”, then this is definitely a product. And look at the ingredients. If there is something else besides cream and sourdough, this is a reason to choose another manufacturer. Sometimes the additive E171 is prescribed – titanium dioxide. It is harmless in small quantities and is needed to give sour cream a white color.
Purchased sour cream from the Kirzhach Dairy Plant
There is such a thing as a cheese product on store shelves. It is easy to distinguish it, as in the case of sour cream. The label should say “cheese”. And nothing else. Color and drawing (holes) – uniform.
If you press on a real cheese, it will restore its original shape, dents remain on the cheese product.
Cheese cannot contain anything vegetable. The amount of protein – from 11%, the more – the tastier. It is better to avoid the presence of E235 – these are the antibiotics Pimaricin or Natamycin from mold, which are not very useful for humans.
Well, cheese with a good composition cannot be cheap. If you have bought and doubt the integrity of the manufacturer, you can check the quality of the house:
– fold the slice in half, without pushing through the fold – the cheese will not crumble (of course, we do not mean any parmesan);
– but if you roll it into a ball, it will crumble. And the cheese product will behave like plasticine.
And also, for those who like to get confused – you can store the cheese in a closed container along with a couple of pieces of refined sugar. Sugar will take away excess moisture, and the cheese will stay fresh longer.
There may be bugs in cereals. Therefore, if a bag of living creatures is found somewhere, it is immediately sent to the scrap. Otherwise, the bugs will spread over all the other bags.
At home, it is better to store any cereal or flour in glass or plastic under a lid. So the chance that these bugs will crawl to you from some other products is minimal. And if everything is open, and an infected product is accidentally caught, after some time the bugs will be everywhere. It’s easier to immediately burn the entire shelf and throw it away and buy new cereals. And a normal container.
We do not recommend taking by weight in supermarkets for the same reason. Even if no one sneezed into the cereal, it almost certainly contains insects.
Therefore – only in the package
You might also get another surprise. When we bought bulgur for the first time, we chose the top Russian producer – Mistral. They took bags of 5 kg, sifted them – and there were stones in them! Mineral blend scientifically.
Wrote to the supplier and received a response:
“According to complaints about the presence of mineral impurities, we explain that the cleaning of cereals is carried out on a stoner (not with hands!), The efficiency of which is 95-98%, i.e. single pebbles may be present in the groats, but their content is not more than 0.05%, which is permissible according to GOST.
GOST 276-2021 Wheat groats. Based on this GOST, our specifications for bulgur were developed.”
It turns out that for 5 kg of cereal there will be a teaspoon of stones.
So we try to keep an eye on it – chefs sort out bulgur, but some inclusions can still remain.
Here he is, this insidious type
It must be understood that one producer can have many different brands of cereals at different prices. And all this cereal is poured from one equipment, just one in a luhari package, and the other in a simpler package. Grandmother will buy cheaper, come home, sift and wash everything – she has been doing this all her life. And some hipster will buy elite cereals, will not sift anything, he will eat gravel – and he will also be satisfied. Well, a pebble will come across – maybe it’s just a hard grain.
So the only advice in choosing cereals is: buy what you like, but be sure to sift at home. Or don’t sift, birds, get out, they swallow stones on purpose so that they are better digested :).
Italian Barilla has been on the menu since the very opening. There, in Italy, this is the most budget option, and in Russia – the best. Moreover, we buy Russian-made pasta, they are excellently made here.
Tried different ones. Makfa did not like the consistency, it is for a more budget segment. All sorts of different Fedekins-Schebekins are generally fine, we used them in lasagna, but spaghetti didn’t go in, and they prevail on our menu.
Salt comes in different degrees of salinity, we ourselves went nuts when we found out. We used the usual cookbook, which is NaCl, and then ordered iodized granular. And the campaign was called so not from the word “iodine”, but from the word “poison” – because all the food was wildly oversalted.
The client complains, we go to the technical maps – the technical maps have not changed. The whole chain was checked, it turned out that the salt itself was to blame. You try it on the tongue – the same, but different in the boiler.
Berries, vegetables, fruits
We buy strawberries in the village at the ruins directly with troughs. From May – excellent Krasnodar, after it until mid-July – delicious near Moscow. Yes, the berries are crooked, slanted – but fragrant and very tasty.
And the fact that all year round in supermarkets there is a model appearance – Egypt is different and so on – then inside the water is water. The buyer chooses by appearance, so the shops take the one that is prettier.
The main rule: the most unsightly berry has the best taste. This applies to both fruits and vegetables. And what is polished with wax on the outside is the same inside.
And the second rule: take seasonal products in season. Here we have a casserole with strawberries – one of the top positions. But the season ended, and we removed it, because only the plastic one remained on sale. If you buy it, you will have to raise the cost – an off-season berry is more expensive, and the taste will fall. Customers will wait for their favorite casserole, but it is not clear what to receive.
The flag of Naturland turned out somehow
We don’t have many canned products. Peas, corn, cucumbers, tomatoes and olives – everything we work with in the kitchen.
There is no stew at all. But there are tips for choosing from the experience of our chef 🙂
Beef stew should not be pink. Meat in the composition: not less than 56%, in good – about 70%. Sometimes manufacturers are cunning, they write the content of the meat product. That is, not only meat, but lived, skin and other things – look at this carefully.
It is better to choose a stew made according to GOST, and not according to TU. G OST is the state standard, it is watched more closely, and TU is technical specifications – each manufacturer decides for himself what to put. Of course, the specifications also have frames, but they can be with errors.
When choosing olives, the first thing to look at is the dry weight. That is, the weight of the olives themselves, without water – the more the better. Size matters only in the restaurant theme – some Kalamata olives can be 3 times more expensive, but they taste about the same, non-gourmets may not be able to distinguish. We don’t need this for food.
We don’t have caviar dishes, but of course we take them home, so we can also tell something from experience.
I prefer the caviar that I can taste from the counter. I have not taken cans since I bought one for 6,000 rubles and found an incomprehensible mess inside.
The color of caviar must be uniform and bright. Pink – it means that it has already lain down a little, the grains have deformed and stuck together.
Ideally, of course, salt yourself. Take fresh fish with caviar, gut it. The best salting: vodka, salt, sugar, dill and butter. It’s fast, safe and looks good. Recipe from our chef 🙂
Salt – and then on pancakes and potato pancakes
Sturgeon spawning lasts somewhere from the end of October to January. At this time, a lot of caviar is sold by weight, and for the price it is just right. If you want, you can buy a lot at once, put them in jars and put them in the freezer. Defrost it in the refrigerator – and you can eat.
Each category of eggs has its own weight: C0 weighs 55-60 grams, C1 – 50 grams, C2 – 45 and below. It is more convenient for us to work with C1, so when compiling the technical maps, we took into account precisely these 50 grams.
Any egg can be dangerous, no matter where it is bought – in the market or in the store. Therefore, the eggs must be washed, or better, soaked for 15 minutes in vinegar. It kills salmonella, which, by the way, is not contained in the egg itself, but on the shell. Don’t believe the rumors that the egg is porous and that vinegar or dirty water will seep through the shell. These are the fables of the flat earthers.
Salmonella also dies during heat treatment. Fried eggs from fresh eggs, fried without “snot”, are completely harmless.
The taste of all chicken eggs is about the same. If you want – look at the yolk, the more yellow it is – the more natural.
My purely personal opinion: all stories about eco-friendly products are a fairy tale to shake out your wallets.
Imagine a huge poultry farm that passes hundreds of tons of chickens every day. If they have salmonella, this whole colossus will be closed for 3 months. Firstly, these are hundreds of people who need to pay salaries, and secondly, thousands of chicken heads that will fly straight into hell. And these are losses that you and I never dreamed of.
Not a single poultry farm wants to stand up. Every corner is cleaned to a shine, the right substrate is everywhere, the right inoculation is put in every chicken ass. All rules are followed so that you will never find fault with anything.
Once, in my memory, one of these supplying factories was closed. Chicken in all stores instantly rose in price by 45-50 rubles. 3 months the plant was disinfected and checked. They burned the chicken, brought in a new one, it also went through a full cycle of checks.
Now imagine a farmer with his eco-farm. One of his 50 chickens gets sick – so he won’t even do anything, they will all take a break from this infection themselves. Losses: 50 chickens. And the farmer will buy new chickens and populate them in the same cages. Same thing with beef, pork and the rest.
I was on farms where there is not enough money for a hardware breast pump. There are cows with a huge udder, and a milkmaid with furious eyes and a cry “if only not to be confused with a bull” rushes between them. This is what they call an “eco-farm”.
No eco, only hardcore
But a cow should not be left unfinished, she gets sick from this and can die. A dairy cow needs to be milked strictly according to the schedule and in certain volumes. Only hardware can do this. On a large farm, such a cow got into a stall, she was hooked up to the apparatus, as in the “Matrix”, food was brought up in front, and the excess was taken away from behind. And the farmer had enough hands for that, well done.
Eco lovers often remember antibiotics, with which “all store-bought meat is pumped up”. Well, any farmer cuts his animals in the same way. Of the 50 chicks he bought, 15 will hatch on the way to the farm, 15 will be in the process of growing up. Do you think the farmer will leave the remaining 20 to the mercy of fate? Of course not, he will protect them with all possible vaccinations. Even if he takes the best ones and tells everyone about it. Will the plant take the worst ones? Hardly.
The only “eco” that I trust grows in the garden of my mother-in-law and father-in-law. But the volumes there, you know, are not industrial.
I thought I would write a couple of tips in a couple of hours, but a sheet came out in a hundred screens. I hope some of you find this information useful 🙂
In the market of components for personal computers (including power supplies for PCs and servers), there are many companies, ranging from supercorporations to little-known small manufacturers. Despite this diversity, most power supplies are built on a similar principle, although on a different element base. Knowing these principles, you can understand the operation of any source of supply voltage.
Device and general block diagram Description of ATX computer power supply circuits
Device and general structural diagram
The structure of the IIP for a computer.
The power supply for the PC is built according to the usual traditional circuitry, typical for pulsed power supplies with voltage stabilization. But the ATX standard computer power supply circuit has additional specific nodes that allow you to control the module with signals from the motherboard. Each block is discussed in detail below.
The input circuits protect the network from interference generated by the power supply during operation. In addition to the filter, they contain elements to protect the PSU from power surges and short circuits inside the unit.
Typical construction of the input circuits of the supply voltage source.
The typical circuit contains a fuse that blows when the current consumption rises above the nominal value, as well as a varistor. In normal mode, its resistance is high and it does not participate in the operation of the node. With surges in the network, its resistance decreases, the current through it increases, thereby accelerating the burnout of the fuse-link. The input circuits also contain filtering elements:
Real power supplies may not contain all of the specified elements, and vice versa, they may contain additional ones (two common-mode chokes, a thermistor to limit the charge current of the rectifier capacitors, etc.).
Usually done in a full-wave bridge. Smoothing capacitors are connected in series. The purpose of such inclusion is twofold:
Rectifier operation in full-wave bridge mode (a) and doubler (b).
In parallel with the capacitors, resistors are often installed to quickly discharge the capacitances when the power is turned off, as well as to equalize the mid-point voltage – it can differ from half Upit due to different leakage currents of oxide capacitors. To protect against overvoltages, varistors or zener diodes can be installed in parallel with the capacitors.
The inverter is used to convert the rectified mains voltage into pulsed. Most often they are performed on a push-pull half-bridge circuit. The half-bridge is a compromise between push-pull and bridge converters – it is free from voltage spikes that impose increased requirements on the parameters of transistors, it uses transformers without a midpoint in the primary winding and it uses only two transistors. But only half of the supply voltage is applied to the primary winding (it is formed due to the midpoint of the smoothing filter).
Various inverter circuits.
In some sources, single-cycle forward inverters are also used (for flyback inverters, with increasing power, the dimensions and weight of pulse transformers increase significantly).
Key management scheme
In stabilized power supplies, the switches are controlled by pulse-width modulation. Pulses are applied to the control electrodes of the transistors, following with the same frequency, but with adjustable duration. To increase the voltage, the duration of the pulses also increases. To lower the output level, the transistors turn on for a shorter time. Chips are usually used to organize PWM. They “on board” have a complete set of nodes from the generator and error amplifier to the output transistor switches (however, low enough power to do without external power transistors).
The voltage from the primary winding of the pulse transformer is converted into a reduced pulse voltage on the secondary windings, and then rectified and smoothed.
Scheme of secondary circuits of BP KYP-150 W.
Windings are usually made with a tap from the midpoint. In this case, the rectifiers are executed according to the bridge circuit. The most energy-intensive channels (+5 and +12 volts) are powered from the top of the bridges (powerful valves or assemblies are installed for them), and negative voltages are removed from the lower diodes (they are less powerful). Further, the rectified voltages are smoothed out using LC circuits (they also include group stabilization inductor windings). For voltage +3.3 VDC, a separate rectifier is usually used, or it is formed from the +5 VDC channel using an additional linear regulator.
Standby voltage circuit
The Stand By voltage is needed to power the section of the PC motherboard circuit responsible for starting the computer. It is also used to power the PWM chip and the inverter driver before the PSU is started. Typically, the node is made in the form of a separate generator, powered by a high-voltage rectifier.
What does a computer power supply consist of – its functions and voltage
PG signal generation and PS_ON signal processing
Separate sections of the scheme are responsible for this task. If all (or part) of the supply voltages are present, a PG (Power Good) signal is generated, signaling to the computer that the power supply is working. When a PS_ON signal is received from the motherboard, the PWM controller generator starts. Some specialized microcircuits have separate inputs for the formation and processing of these signals (LPG899, AT2005B). There are also supervisory chips that perform these functions and generate control signals. In some power supplies, these tasks are assigned to circuit sections on discrete elements.
Feedback circuits
Most power supplies use only one voltage to maintain the level (usually +12 VDC or +5 VDC). The remaining channels are included in the group stabilization system, affecting the measured voltage. This principle does not allow achieving a high stabilization coefficient, but greatly simplifies the construction of the ATX power supply circuit.
Description of ATX computer power supply circuits
Several power supply circuits of various capacities are considered as examples. The schemes are selected so that the same functional units are built on different elements.
300-watt PSU manufactured by JNC computer
Schematic diagram of the SY-300ATX power supply.
As the first example, the electrical circuit diagram of the PSU SY-300ATX 300W is shown. The input circuits are somewhat simplified. It does not have a Cx capacitor to protect against differential noise. There is also no varistor to protect against mains surges. Only the common mode protection circuit is fully implemented – on the LF1 inductor and capacitors CY1 and CY2.
The rectifier on the RL205 assembly has no special features, the C1C2 smoothing filter simultaneously performs the functions of a voltage divider. Resistors R13, R12 and varistors V1, V2 are used to equalize the midpoint and quickly discharge the capacitances when turned off. From a rectified voltage of about 310 volts, a circuit operates that generates a standby voltage.
Converting a computer power supply into a laboratory one with voltage regulation
The generator is made on the transistor Q3, the primary windings of the transformer T3 perform the function of load and feedback. The lower half of the secondary winding forms the Stand By voltage itself, which is rectified by the D7 diode, smoothed by the C13L2C14 filter. To stabilize it, another feedback loop is organized through the U1 optocoupler. If the output level rises, the optocoupler LED becomes more intense, the receiving transistor opens, covering transistor Q4, which, by reducing the voltage at the base of Q3, reduces its on-time. From two windings (the sum of the upper and lower halves), power is removed for the generator microcircuit and the preliminary stage of the inverter. It is rectified by diode D8, smoothed by capacitance C12.
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The middle point of the rectified high voltage divider is connected to one end of the primary winding of the pulse transformer T3, protected from switching surges by the snubber R16C10. The other end of the primary winding is connected to the midpoint of a half-bridge inverter formed by transistors Q1, Q2. The half bridge is isolated from the low voltage part by a transformer T2. Pulses on the secondary windings are generated by a driver on transistors Q5, Q6, which, in turn, alternately open and close under the control of pins 7 and 8 of the AT2005 chip. This chip is designed for use as a PWM controller in computer power supplies.
Like any PWM controller, it performs the following functions:
In addition, it performs tasks specific to computer PSUs:
AT2005 pinout.
The purpose of the pins of the microcircuit is indicated in the table.
Related article: Pinout of computer power supply connectors by colors and voltage
Expert opinion Alexey StanovoyElectronic engineer. I work in an appliance repair shop. I’m into circuit engineering. Ask a questionThis PSU uses the AT2005 chip. It should not be confused with the widely used AT2005B, which has a different pinout. A complete analogue of AT2005 is the LPG899 chip.
The PG signal is removed from pin 11 if the voltages at pins 1,2,3 are within normal limits. From the motherboard, the Power_ON signal comes to pin 9 – if the level goes low, the generation starts. With this construction, the control of the PWM controller does not require additional elements.
Output 12 is energized from the middle point of the driver – when the pulses disappear, the microcircuit turns off. Channel voltage +12 volts is applied to input 16 – this is how a feedback circuit is formed to regulate the voltage. With an increase in the voltage at the channel output, the duration of the pulses decreases, with a decrease, it increases. The remaining channels are stabilized using a group stabilization choke – it does not have its own letter designation on the diagram.
Fragment of the scheme of secondary circuits of a power transformer with a group stabilization choke.
It is a choke with 5 windings wound on one toroidal core. Each winding is connected to its own voltage circuit. If the voltage of any channel changes, it causes a corresponding change in the remaining channels, including +12 volts. Changing this voltage activates the PWM controller and all other voltages return within the set limits.
Group stabilization choke on the board.
The pulse transformer is made with one secondary winding with an output midpoint and two symmetrical taps, from which voltage is removed for channels +5 and -5 volts. The voltage for the channel +12 VDC and -12 VDC is removed from the extreme conclusions. All voltages are rectified by push-pull bridge rectifiers and smoothed by filters, which include the corresponding winding of the group stabilization inductor, L6 chokes individual for each channel. L9 and capacitors. The cooling fan is powered from the +12 VDC channel – the stabilizer is assembled on a Q6 transistor and a ZD2 zener diode.
The +3.3 VDC channel is made from a separate rectifier on the D17 assembly and diodes D14, D15. This channel is not included in the group regulation scheme.
It will be useful to read: Scheme and assembly of a home-made PSU with voltage and current regulation
ATX 350 WP4
ATX 350 WP4 switching power supply circuit.
The next power supply has a power of 350 W. It is built according to a similar scheme, which contains a number of differences from the previous PSU:
The deeper difference lies in the application of the PWM chip and in the generation of the PG signal and the processing of the PS_ON command. To control the pulse-width modulation, the AZ7500BP chip is used – a complete analogue of the most popular TL494.
Functionality and pinout of TL494.
This microcircuit is more versatile, it contains two error amplifiers, which allows organizing stabilization not only in voltage, but also in current. T L494 allows you to more flexibly control PWM (by setting the Dead Time – pauses between pulses). But it does not contain a supervisor for the presence and level of output voltages, and this problem must be solved separately. In this circuit, the LP7510 chip is used for this. If there are three voltages – +12 VDC, +5 VDC, +3.3 VDC, a PG signal will appear at pin 8, which will inform the computer that the PSU is working. When a low-level Power_ON signal is received from the motherboard at pin 4, a high level will appear at pin 3, allowing the TL494 chip to start and the PSU to start.
Recommended reading: Schematic of a bipolar power supply
Sparkman 400W
Schematic of the Sparkman 400 W power supply.
The next power supply is Sparkman 400 W. Its main feature is a single-ended forward converter. A MOSFET SVD7N60F with a drain current of up to 7 A is used as a power transistor, which is directly controlled by the KA3842 chip. At its output 1 through the optocoupler U38 feedback is introduced, through which the output level is regulated by changing the pulse duration.
A group stabilization choke has also been applied. For a voltage of +3.3 VDC, a separate winding and a rectifier are not provided; it is formed from the +5 volt channel using a separate stabilizer on the MOSFET SD1. The WT7510 microcircuit in standard inclusion serves as a voltage supervisor, a PG signal conditioner.
The +5 V Stand By formation circuit and other nodes have no special features. The high-voltage rectifier filter is made in the form of a divider with a midpoint, which in this case is needed to switch the mains voltage from 220 VAC to 110 VAC. In the second case, the bridge rectifier becomes a mains voltage doubler.
Switching power supply – a selection of circuits for self-production
ISO 450PP 4S
PSU diagram ISO 450PP 4S.
The technical solutions described above cover almost all the circuitry needs of power supplies up to about 500 watts. So, in the ISO 450PP 4S (450 W) block diagram, nothing fundamentally described above was used.
Diagram of a 550-watt SMPS.
More powerful sources use specific technical solutions. So in the PSU IP-550DJ2 more attention is paid to protection against impulse noise. Two common-mode chokes are used, and smoothing capacitors are protected by two-anode zener diodes. The single-ended inverter uses two powerful MOSFETs. They have less switching losses, so the problem of heat dissipation is simplified. To form +5 V Stand by, an integral converter TNY276 is used.
Obviously, with an increase in the power consumed by a computer, new technical solutions will be required to create a power supply unit in the same dimensions. The trends in the development of power electronics and integrated circuits allows us to hope that these solutions will be found as needed.
