Power supply for Unch. Switching power supply circuit for an amplifier. Diagram of rectifiers and voltage stabilizers
Making a good power supply for a power amplifier (UPA) or other electronic device is a very responsible task. The quality and stability of the entire device depends on the power source.
In this publication I will tell you about making a simple transformer power supply for my homemade amplifier low frequency power "Phoenix P-400".
Such a simple power supply can be used to power various low-frequency power amplifier circuits.
Preface
For the future power supply unit (PSU) for the amplifier, I already had a toroidal core with a wound primary winding of ~220V, so there was no problem of choosing “switching PSU or based on a network transformer.”
U pulse sources power supplies are small in size and weight, have high output power and high efficiency. Power supply based on a network transformer - has heavy weight, is easy to manufacture and set up, and you don’t have to deal with dangerous voltages when setting up the circuit, which is especially important for beginners like me.
Toroidal transformer
Toroidal transformers, in comparison with transformers with armored cores made of W-shaped plates, have several advantages:
- less volume and weight;
- higher efficiency;
- better cooling for windings.
The primary winding already contained approximately 800 turns of 0.8 mm PELSHO wire; it was filled with paraffin and insulated with a layer of thin fluoroplastic tape.
By measuring the approximate dimensions of the transformer iron, you can calculate its overall power, so you can estimate whether the core is suitable for obtaining the required power or not.
Rice. 1. Dimensions of the iron core for the toroidal transformer.
- Overall power (W) = Window area (cm 2) * Sectional area (cm 2)
- Window area = 3.14 * (d/2) 2
- Sectional area = h * ((D-d)/2)
For example, let's calculate a transformer with iron dimensions: D=14cm, d=5cm, h=5cm.
- Window area = 3.14 * (5cm/2) * (5cm/2) = 19.625 cm2
- Cross-sectional area = 5cm * ((14cm-5cm)/2) = 22.5 cm 2
- Overall power = 19.625 * 22.5 = 441 W.
The overall power of the transformer I used turned out to be clearly less than I expected - about 250 watts.
Selection of voltages for secondary windings
Knowing the required voltage at the output of the rectifier after the electrolytic capacitors, you can approximately calculate the required voltage at the output of the secondary winding of the transformer.
Numeric value DC voltage after the diode bridge and smoothing capacitors will increase by approximately 1.3..1.4 times compared to the alternating voltage supplied to the input of such a rectifier.
In my case, for UMZCH power supply you need bipolar DC voltage - 35 volts on each arm. Accordingly, each secondary winding must have AC voltage: 35 Volts / 1.4 = ~25 Volts.
Using the same principle, I made an approximate calculation of the voltage values for the other secondary windings of the transformer.
Calculation of the number of turns and winding
To power the remaining electronic units of the amplifier, it was decided to wind several separate secondary windings. A wooden shuttle was made to wind the coils with enameled copper wire. It can also be made from fiberglass or plastic.
Rice. 2. Shuttle for winding a toroidal transformer.
Winding was done with enameled copper wire, which was available:
- for 4 power windings UMZCH - wire with a diameter of 1.5 mm;
- for other windings - 0.6 mm.
I selected the number of turns for the secondary windings experimentally, since I did not know the exact number of turns of the primary winding.
The essence of the method:
- We wind 20 turns of any wire;
- We connect the primary winding of the transformer to the ~220V network and measure the voltage on the wound 20 turns;
- We divide the required voltage by that obtained from 20 turns - we will find out how many times 20 turns are needed for winding.
For example: we need 25V, and from 20 turns we get 5V, 25V/5V=5 - we need to wind 20 turns 5 times, that is, 100 turns.
The calculation of the length of the required wire was done as follows: I wound 20 turns of wire, made a mark on it with a marker, reeled it off and measured its length. I divided the required number of turns by 20, multiplied the resulting value by the length of 20 turns of wire - I got approximately the required length of wire for winding. By adding 1-2 meters of reserve to the total length, you can wind the wire onto the shuttle and safely cut it off.
For example: you need 100 turns of wire, the length of 20 wound turns is 1.3 meters, we find out how many times 1.3 meters each need to be wound to get 100 turns - 100/20 = 5, we find out the total length of the wire (5 pieces of 1, 3m) - 1.3*5=6.5m. We add 1.5 m for reserve and get a length of 8 m.
For each subsequent winding, the measurement should be repeated, since with each new winding the wire length required by one turn will increase.
To wind each pair of 25 Volt windings, two wires were laid in parallel on the shuttle (for 2 windings). After winding, the end of the first winding is connected to the beginning of the second - we have two secondary windings for a bipolar rectifier with a connection in the middle.
After winding each pair of secondary windings to power the UMZCH circuits, they were insulated with thin fluoroplastic tape.
In this way, 6 secondary windings were wound: four for powering the UMZCH and two more for power supplies for the rest of the electronics.
Diagram of rectifiers and voltage stabilizers
Below is a schematic diagram of the power supply for my homemade power amplifier.
Rice. 2. Schematic diagram power supply for a homemade low-frequency power amplifier.
To power the LF power amplifier circuits, two bipolar rectifiers are used - A1.1 and A1.2. The remaining electronic units of the amplifier will be powered by voltage stabilizers A2.1 and A2.2.
Resistors R1 and R2 are needed to discharge electrolytic capacitors when the power lines are disconnected from the power amplifier circuits.
My UMZCH has 4 amplification channels, they can be turned on and off in pairs using switches that switch the power lines of the UMZCH scarf using electromagnetic relays.
Resistors R1 and R2 can be excluded from the circuit if the power supply is permanently connected to the UMZCH boards, in which case the electrolytic capacitors will be discharged through the UMZCH circuit.
KD213 diodes are designed for a maximum forward current of 10A, in my case this is enough. The D5 diode bridge is designed for a current of at least 2-3A, assembled from 4 diodes. C5 and C6 are capacitances, each of which consists of two capacitors of 10,000 μF at 63V.
Rice. 3. Schematic diagrams of DC voltage stabilizers on microcircuits L7805, L7812, LM317.
Explanation of names on the diagram:
- STAB - voltage stabilizer without adjustment, current no more than 1A;
- STAB+REG - voltage stabilizer with regulation, current no more than 1A;
- STAB+POW - adjustable voltage stabilizer, current approximately 2-3A.
When using LM317, 7805 and 7812 microcircuits, the output voltage of the stabilizer can be calculated using a simplified formula:
Uout = Vxx * (1 + R2/R1)
Vxx for microcircuits has the following meanings:
- LM317 - 1.25;
- 7805 - 5;
- 7812 - 12.
Calculation example for LM317: R1=240R, R2=1200R, Uout = 1.25*(1+1200/240) = 7.5V.
Design
This is how it was planned to use the voltage from the power supply:
- +36V, -36V - power amplifiers on TDA7250
- 12V - electronic volume controls, stereo processors, output power indicators, thermal control circuits, fans, backlighting;
- 5V - temperature indicators, microcontroller, digital control panel.
The voltage stabilizer chips and transistors were mounted on small radiators that I removed from non-working computer power supplies. The cases were attached to the radiators through insulating gaskets.
The printed circuit board was made of two parts, each of which contains a bipolar rectifier for the UMZCH circuit and the required set of voltage stabilizers.
Rice. 4. One half of the power supply board.
Rice. 5. The other half of the power supply board.
Rice. 6. Ready-made power supply components for a homemade power amplifier.
Later, during debugging, I came to the conclusion that it would be much more convenient to make voltage stabilizers on separate boards. Nevertheless, the “all on one board” option is also not bad and is convenient in its own way.
Also, the rectifier for UMZCH (diagram in Figure 2) can be assembled by mounted mounting, and the stabilizer circuits (Figure 3) in the right amount- on separate printed circuit boards.
The connection of the electronic components of the rectifier is shown in Figure 7.
Rice. 7. Connection diagram for assembling a bipolar rectifier -36V + 36V using wall-mounted installation.
Connections must be made using thick insulated copper conductors.
A diode bridge with 1000pF capacitors can be placed separately on the radiator. Installation of powerful KD213 diodes (tablets) on one common radiator must be done through insulating thermal pads (thermal rubber or mica), since one of the diode terminals has contact with its metal lining!
For the filtering scheme ( electrolytic capacitors 10000 µF each, resistors and ceramic capacitors 0.1-0.33 µF) can be a quick fix assemble a small panel - a printed circuit board (Figure 8).
Rice. 8. An example of a panel with slots made of fiberglass for mounting smoothing rectifier filters.
To make such a panel you will need a rectangular piece of fiberglass. Using a homemade cutter (Figure 9), made from a hacksaw blade for metal, we cut the copper foil along its entire length, then cut one of the resulting parts perpendicularly in half.
Rice. 9. A homemade cutter made from a hacksaw blade, made on a sharpening machine.
After this, we mark and drill holes for the parts and fastenings, clean the copper surface with fine sandpaper and tin it using flux and solder. We solder the parts and connect them to the circuit.
Conclusion
This simple power supply was made for a future homemade audio power amplifier. All that remains is to supplement it with a diagram smooth start(Soft start) and standby mode.
UPD: Yuri Glushnev sent a printed circuit board for assembling two stabilizers with voltages +22V and +12V. It contains two STAB+POW circuits (Fig. 3) on LM317, 7812 microcircuits and TIP42 transistors.
Rice. 10. Printed circuit board for voltage stabilizers for +22V and +12V.
Download - (63 KB).
Another printed circuit board designed for the STAB+REG adjustable voltage regulator circuit based on LM317:
Rice. 11. Printed circuit board for an adjustable voltage stabilizer based on the LM317 chip.
I present to your attention the circuit I tested of a fairly simple switching power supply unit UMZCH. The power of the unit is about 200W (but can be overclocked to 500W).
Brief characteristics:
Input voltage - 220V;
Output voltage - +-26V (drawdown 2-4V at full load);
Conversion frequency - 100 kHz;
The maximum load current is 4A.
Block diagram
The power supply is built on the IR2153 chip according to the strannicmd circuit
Construction and details.
The power supply is assembled on a printed circuit board made of single-sided fiberglass. Drawing printed circuit board in Sprint-Layout for the iron you will find at the end of the article.
An input inductor from any computer or monitor power supply, an input capacitor is used at the rate of 1 µF per 1 W. Next, a flat low-frequency diode bridge GBUB of approximately 3A can be used as switches IRF 840, IRFI840GLC, IRFIBC30G, VT1 - BUT11, VT3 - c945, output diodes it is better to use assemblies more quickly in this circuit, I installed Schottky MBR 1545, the output chokes are made of pieces of ferrite 4 cm and ? 3 mm long, 26 turns of PEV-1 wire, but I think that you can also use a group stabilization choke on a ring of atomized iron (the haven't tried it).
Most of the parts can be found in computer power supplies.
Printed circuit board
PSU assembly
Transformer
Transformer for your needs, you can calculate
This transformer is wound on one ring K32X19X16 made of ferrite grade M2000NM (ring of blue color), the primary winding is wound evenly around the entire ring and is 34 turns of MGTF 0.7 wire. Before winding the secondary windings, you need to wrap the primary winding with fluoroplastic tape. Winding II is evenly wound with PEV-1 0.7 wire folded in half and is 6+6 turns with a tap from the middle. Winding III (self-powered IR) is uniformly wound 3+3 turns with twisted pair (one pair of wires) with a tap from the middle.
Setting up power supply
ATTENTION!!! THE PRIMARY CIRCUIT OF THE PSU IS UNDER MAINS VOLTAGE, SO PRECAUTIONS SHOULD BE FOLLOWED WHEN SETTING UP AND OPERATING.
It is advisable to start the unit for the first time by connecting it through a current-limiting resistor to the fuse, which is an incandescent lamp with a power of 60 W and a voltage of 220 V, and the IR should be powered from a separate 12 V power supply (the self-supply winding is turned off). When the power supply is turned on, do not load it heavily through the lamp. As a rule, a correctly assembled power supply does not require adjustment. When you turn it on for the first time through the power supply lamp, the lamp should light up and immediately go out (blink), but if so, then everything is fine and you can check the power at the output. All OK! then we turn off the lamp, set the fuse and connect the self-power of the microcircuit; when the power supply starts, the LED that is located between the first and third legs should blink and the power supply will start.
Well, what can we say about one of the most repeated power amplifier circuits - the Lanzar circuit was developed back in the 70s of the last century. On a modern high-precision elementary base, Lanzar began to sound even better. In theory, the circuit is excellent for wideband acoustics, distortion at half the volume only 0.04%- full-fledged Hi-Fi.
The output stage of the amplifier is built on a pair 2SA1943 And 2SC5200, all stages are assembled on complementary pairs that are as close as possible in terms of parameters, the amplifier is built entirely on a symmetrical basis. The rated output power of the amplifier is 230-280 watts, but much more can be removed by increasing the input supply voltage.
The values of the limiting resistors of the differential stages are selected based on the input voltage. Below is the table.
Power supply ±70 V - 3.3 kOhm...3.9 kOhm
Power supply ±60 V - 2.7 kOhm...3.3 kOhm
Power supply ±50 V - 2.2 kOhm...2.7 kOhm
Power supply ±40 V - 1.5 kOhm...2.2 kOhm
Power supply ±30 V - 1.0 kOhm...1.5 kOhm
These resistors are selected with a power of 1-2 watts; during operation, heat generation may be observed on them.
The regulating transistor was replaced with a domestic one KT815, at that time there was no other one at hand. It is designed to regulate the quiescent current of the output stages; it does not overheat during operation, but is mounted on a common heat sink with the transistors of the output stage.
It is advisable to do the first start of the circuit from the mains power supply; connect a 100-150 watt incandescent lamp in series with the mains winding of the transformer; if there are problems, then burn a minimum of parts. In general, Lanzar’s circuit is not critical to the installation and components; I tried it even with a wide range of components used, using domestic radio components - the circuit shows high parameters even in this case. Lanzar's circuit diagram has two main versions - on bipolar transistors and using field switches in the penultimate stage, in my case first version.
The second pre-output stage operates in a pure class " A", therefore, during operation, the transistors overheat. Transistors of this cascade must be installed on a heat sink, preferably a common one, do not forget about insulation - mica plates and insulating washers for screws.
Right assembled circuit starts without any problems. We do the first launch with INPUT SHORT TO GROUND
, i.e. The amplifier input is connected to the middle point from the power supply. If nothing explodes after launch, then you can disconnect the input from the ground. Next we connect the load - the speaker and turn on the amplifier. To make sure the amplifier is working, just touch the bare input wire. If a peculiar roar appears in the head, then the amplifier is working! Next, you can strengthen all the power parts with heat sinks and send an audio signal to the amplifier input. After 15-20 minutes of operation at 30-50% of the maximum volume, you need to adjust the quiescent current. The photo shows everything in detail; it is advisable to use a digital multimeter as a voltage indicator.
Amplifier output power measurement
How to set the quiescent current
The low-pass filter and adder are built on two microcircuits. It is designed for smooth adjustment of phase, volume and frequency. The adder is designed to sum the signals of both channels to obtain a more powerful signal. In industrial car amplifiers high power This is exactly the principle of filtering and summing the signal, but the adder can be excluded from the circuit if desired and only a low-pass filter can be used. The filter cuts off all frequencies, leaving only a limit between 35-150 Hz.
Phase adjustment allows you to match the subwoofer with speaker systems, in some cases it is also excluded.
This unit is powered by a stabilized bipolar voltage source +/-15 Volts. Power can be provided using an additional secondary winding, or you can use a bipolar voltage stabilizer to reduce the voltage from the main winding.
For this purpose, a bipolar stabilizer has been assembled. Initially, the voltage is reduced by zener diodes, then amplified bipolar transistors and served on linear stabilizers voltage type 7815
And 7915
. At the output of the stabilizer, a stable bipolar power supply is formed, which powers the adder and low-pass filter unit.
Stabilizers and transistors can get hot, but this is quite normal; if desired, they can be mounted on heat sinks, but in my case there is active cooling by a cooler, so heat sinks were not useful, and besides, the heat dissipation is within normal limits, since the low-pass filter unit itself consumes very little.
SLAPPING TO CHIP CIRCUITS
A slap in the face of mikruham is not the easiest, but high quality amplifier LF power. The amplifier is capable of developing maximum output power 130 watts and operates over a fairly wide input voltage range. The output stage of the amplifier is built on a pair 2sa1943 2sc5200 and works in mode AB. This version was developed by the author this year, below are its main parameters. Supply voltage range = +/- 20V... +/- 60V
Nominal supply voltage (100W, 4 Ohm) = +/- 36V
Nominal supply voltage (100W, 8 Ohm) = +/- 48V
Everything is clear with power, but what about distortion?
THD+N (at Pout<=60Вт, 20кГц) <= 0,0009%
THD+N (at maximum output power, 20kHz) = 0.008%
The parts used in this module are trimming resistors, low- and medium-power transistors:
HERE VIDEO
Not bad at all, almost high-end! In fact, if you focus only on SOI, then this amplifier is full-fledged HI-END, but this is not enough for the high-end, so it was classified in the good old category hi-fi.
Although the amplifier develops only 100 watts, it is an order of magnitude more complex than similar circuits, but the assembly itself will not be difficult if all the components are available. I do not recommend rejecting the circuit values - my experience confirms this.
Low-power transistors may overheat during operation, but there is no need to worry - this is their normal operating mode. The output stage, as already said, operates in class AB, therefore, a huge amount of heat will be released that needs to be removed. In my case, they are reinforced with a common heat sink, which is more than enough, but just in case, there is also active cooling.
After assembly, we are waiting for the first launch of the circuit. To do this, I advise you to read the launch and configuration of Lanzar again - here everything is done in exactly the same way. We do the first start with the input shorted to ground, if everything is OK, then we open the input and sound a sound signal. By that time, all power components must be strengthened with a heat sink, otherwise, while admiring the music, you may not notice how the output stage switches smoke - each of them is very, very expensive. And you will learn about the protection unit. Sincerely - AKA KASYAN.
Discuss the article HOME AMPLIFIER - UMZCH UNIT
An audio frequency amplifier (AFA), or low frequency amplifier (LF) is one of the most common electronic devices. We all receive sound information using one or another type of ULF. Not everyone knows, but low-frequency amplifiers are also used in measurement technology, flaw detection, automation, telemechanics, analog computing and other areas of electronics.
Although, of course, the main use of ULF is to bring a sound signal to our ears using acoustic systems that convert electrical vibrations into acoustic ones. And the amplifier must do this as accurately as possible. Only in this case do we receive the pleasure that our favorite music, sounds and speech give us.
From the advent of Thomas Edison's phonograph in 1877 to the present, scientists and engineers have struggled to improve the basic parameters of the ULF: primarily for the reliability of the transmission of sound signals, as well as for consumer characteristics such as power consumption, size, ease of manufacture, configuration and use.
Beginning in the 1920s, a letter classification of classes of electronic amplifiers was formed, which is still used today. Classes of amplifiers differ in the operating modes of the active electronic devices used in them - vacuum tubes, transistors, etc. The main “single-letter” classes are A, B, C, D, E, F, G, H. Class designation letters can be combined in case of combining some modes. The classification is not a standard, so developers and manufacturers can use letters quite arbitrarily.
Class D occupies a special place in the classification. The active elements of the ULF output stage of class D operate in a switching (pulse) mode, unlike other classes, where the linear mode of operation of the active elements is mostly used.
One of the main advantages of Class D amplifiers is the coefficient of performance (efficiency) approaching 100%. This, in particular, leads to a reduction in the power dissipated by the active elements of the amplifier, and, as a consequence, to a reduction in the size of the amplifier due to the reduction in the size of the radiator. Such amplifiers place significantly lower demands on the quality of the power supply, which can be unipolar and pulsed. Another advantage can be considered the possibility of using digital signal processing methods and digital control of their functions in class D amplifiers - after all, it is digital technologies that prevail in modern electronics.
Taking into account all these trends, the Master Kit company offers wide selection of class amplifiersD, assembled on the same TPA3116D2 chip, but having different purposes and power. And so that buyers do not waste time searching for a suitable power source, we have prepared amplifier + power supply kits, optimally suited to each other.
In this review we will look at three such kits:
- (D-class LF amplifier 2x50W + power supply 24V / 100W / 4.5A);
- (D-class LF amplifier 2x100W + power supply 24V / 200W / 8.8A);
- (D-class LF amplifier 1x150W + power supply 24V / 200W / 8.8A).
First set Designed primarily for those who need minimal dimensions, stereo sound and a classic control scheme in two channels simultaneously: volume, low and high frequencies. It includes and.
The two-channel amplifier itself has unprecedentedly small dimensions: only 60 x 31 x 13 mm, not including control knobs. Dimensions of the power supply are 129 x 97 x 30 mm, weight – about 340 g.
Despite its small size, the amplifier delivers an honest 50 watts per channel into a 4 ohm load at a supply voltage of 21 volts!
The RC4508 chip, a dual specialized operational amplifier for audio signals, is used as a pre-amplifier. It allows the amplifier input to be perfectly matched to the signal source, and has extremely low nonlinear distortion and noise levels.
The input signal is supplied to a three-pin connector with a pin pitch of 2.54 mm, and power supply and speaker systems are connected using convenient screw connectors.
A small heatsink is installed on the TPA3116 chip using heat-conducting glue, the dissipation area of which is quite sufficient even at maximum power.
Please note that in order to save space and reduce the size of the amplifier, there is no protection against reverse polarity of the power supply connection (reversal), so be careful when supplying power to the amplifier.
Taking into account its small size and efficiency, the scope of application of the kit is very wide - from replacing an outdated or broken old amplifier to a very mobile sound reinforcement kit for dubbing an event or party.
An example of using such an amplifier is given.
There are no mounting holes on the board, but for this you can successfully use potentiometers that have fastenings for a nut.
Second set includes two TPA3116D2 chips, each of which is enabled in bridged mode and provides up to 100 watts of output power per channel, as well as with an output voltage of 24 volts and a power of 200 watts.
With the help of such a kit and two 100-watt speaker systems, you can sound a major event even outdoors!
The amplifier is equipped with a volume control with a switch. A powerful Schottky diode is installed on the board to protect against polarity reversal of the power supply.
The amplifier is equipped with effective low-pass filters, installed in accordance with the recommendations of the manufacturer of the TPA3116 chip, and together with it, ensuring high quality of the output signal.
The supply voltage and speaker systems are connected using screw connectors.
The input signal can be supplied either to a three-pin connector with a pitch of 2.54 mm, or using a standard 3.5 mm Jack audio connector.
The radiator provides sufficient cooling for both microcircuits and is pressed against their thermal pads with a screw located at the bottom of the printed circuit board.
For ease of use, the board also has a green LED indicating when the power is turned on.
The dimensions of the board, including capacitors and excluding the potentiometer knob, are 105 x 65 x 24 mm, the distances between the mounting holes are 98.6 and 58.8 mm. Dimensions of the power supply are 215 x 115 x 30 mm, weight about 660 g.
Third set represents l and with an output voltage of 24 volts and a power of 200 watts.
The amplifier provides up to 150 watts of output power into a 4 ohm load. The main application of this amplifier is to build a high-quality and energy-efficient subwoofer.
Compared to many other dedicated subwoofer amplifiers, the MP3116btl excels at driving large-diameter woofers. This is confirmed by customer reviews of the ULF in question. The sound is rich and bright.
The heatsink, which occupies most of the printed circuit board area, ensures efficient cooling of the TPA3116.
To match the input signal at the amplifier input, the NE5532 microcircuit is used - a two-channel low-noise specialized operational amplifier. It has minimal nonlinear distortion and wide bandwidth.
The input signal amplitude regulator with a slot for a screwdriver is also installed at the input. With its help, you can adjust the volume of the subwoofer to the volume of the main channels.
To protect against supply voltage reversal, a Schottky diode is installed on the board.
Power and speaker systems are connected using screw connectors.
The dimensions of the amplifier board are 73 x 77 x 16 mm, the distances between the mounting holes are 69.4 and 57.2 mm. Dimensions of the power supply are 215 x 115 x 30 mm, weight about 660 g.
All kits include MEAN WELL switching power supplies.
Founded in 1982, the company is the world's leading manufacturer of switching power supplies. Currently, MEAN WELL Corporation consists of five financially independent partner companies in Taiwan, China, the USA and Europe.
MEAN WELL products are characterized by high quality, low failure rates and long service life.
Switching power supplies, developed on a modern element base, meet the highest requirements for the quality of output DC voltage and differ from conventional linear sources in their light weight and high efficiency, as well as the presence of protection against overload and short circuit at the output.
The LRS-100-24 and LRS-200-24 power supplies used in the presented kits have an LED power indicator and a potentiometer for precise adjustment of the output voltage. Before connecting the amplifier, check the output voltage and, if necessary, set its level to 24 volts using a potentiometer.
The sources used use passive cooling, so they are completely silent.
It should be noted that all the amplifiers considered can be successfully used to design sound reproduction systems for cars, motorcycles and even bicycles. When powering amplifiers with a voltage of 12 volts, the output power will be slightly less, but the sound quality will not suffer, and the high efficiency allows you to effectively power the ULF from autonomous power sources.
We also draw your attention to the fact that all the devices discussed in this review can be purchased individually and as part of other kits on the website.
Switching power supply for ULF designed to provide power supply voltage to two-channel UMZCH. The power supply is designed to operate an amplifier with an output power of 200 W per channel. This device consists of two printed circuit boards. One board contains a mains voltage filter, an electromagnetic relay, a transformer, a diode bridge with a 1000 uF x 25v filter capacitor in its circuit. Another board contains a control module, a rectifier transformer, as well as capacitors and chokes in the filter circuit.
Bipolar transistors KT626, as well as powerful 2SK1120 MOSFET or KP707V2 must be installed on radiators with a sufficient heat dissipation area. The most effective cooling radiators are heat sinks made of thick milled aluminum. Their effectiveness lies in the fact that in addition to cooling electronic components, they also serve as side elements of the amplifier housing. The control module for powerful output switches is mounted on a small independent board, which in turn is built into the rectifier module.
UPS upgrade
To ensure more correct and reliable operation of the structure, switching power supply for ULF has been somewhat modernized. In particular, shunts were installed in the secondary windings of the transformer in the form of an RC circuit suppressing interference. The capacity of the filter capacitors was also increased to 10,000 uF x 50v and shunted with 3.3 uF 63v capacitors. Which have very low losses and high insulation resistance. Input protection has not been activated, but can be used as peak current protection if necessary. To do this, you need to apply a signal to the input from the shunt circuit or from a current transformer.
Warning
Special attention! All power paths of this power supply, with the exception of secondary circuits, are at high potential mains voltage, which poses a danger to life! During the process of setting up the structure, the greatest possible care must be taken. When performing setup work, it is advisable to connect the device to the network via an isolation transformer.
Before starting the switching power supply for the first time, there is no need to install a 2A fuse in the 320v voltage circuit yet. First, you need to debug the control circuit, and only then install a 220v incandescent lamp with a power of 60 W in place of the 2A fuse. But the most effective way to guarantee the integrity of the transistors is to turn on the device through a voltage-stepping transformer. Only when the adjustment work has been completed is the fuse put in place. Now the switching power supply can be tested with a load.
Pictured: inverter module, rectifier and filter circuit
Pictured: mains voltage filter and rectifier module
Pictured: arrangement of power switches and diodes
Transformer
Transformer T1 is wound on three rings with a diameter of 45 mm made of 2000NM1 ferrite. The primary winding contains 2×46 turns of insulated wire 0.75 mm2 (wound with two wires at once). The secondary winding is wound with a braid of 16 wires with a diameter of 0.8 mm. It contains six turns, after winding it is divided into two groups, the beginnings of one group are connected to the ends of the other. Chokes DB3 and DR2 are wound on an 8 mm ferrite rod and made with wire D = 1.2 mm.