In recent years, radio amateurs have increasingly used power amplifiers on microcircuits. For many applications, it becomes impractical to assemble an amplifier using separate elements; such amplifiers in most cases require the establishment of a protection device, setting the quiescent current of the output stage, etc. Integrated amplifiers are actually designed according to the “soldered in and ready” principle. Various versions of such amplifiers have already been repeatedly recommended on the pages of the magazine, however, the maximum (i.e., with nonlinear distortion of 10%) output power of amplifiers on a single chip is usually limited to 100...120 W, at least when using chips from an affordable price category. Even when using two TDA7294 microcircuits in a bridge connection, the load power does not exceed 200 W. But what if you need to assemble a more powerful amplifier, for example, for a disco? An integrated circuit power amplifier is described here that allows output power of up to 300 W per channel.
The amplifier uses a STK4231-II hybrid chip manufactured by SANYO. This chip is a dual-channel chip, so only one chip is required for the bridged connection option. When assembling an amplifier on such a chip, a little more parts are required than for an amplifier on the TDA7294, but it has a number of advantages and, most importantly, allows you to get a significantly more powerful amplifier. The microcircuit is much easier to attach to a heat sink, since its substrate is not connected to the heat-conducting surface of the case and can be directly connected to the heat sink or amplifier case (for the TDA7294 microcircuit, the minus of the power supply is connected to the substrate). This can often be decisive, since isolating the heat sink from the case is sometimes not easy.
Main technical parameters:
Rated output power, W…….250
Maximum output power, W… 320
Load resistance, Ohm………5.3
Reproducible frequency range, kHz… 0.02…20
Harmonic coefficient, no more than, %…….0.4
Input voltage, mV………………….500
Amplifier circuit
The amplifier is powered by an unstabilized bipolar voltage source of 2x(45...55) V. The input signal to one of the amplifiers of the DA2 microcircuit is supplied directly to pin 3, and to the second (pin 20) through an inverting buffer amplifier on op-amp DA1. The op-amp is powered by voltage stabilizers +15 and -15 V, made on DA3, DA4 microcircuits. If necessary, these same stabilizers can also power a pre-amplifier with tone controls or crossover filters. The gain of the power amplifier can be changed by selecting feedback resistors R6 and R11. Their resistance in both arms of the amplifier should be the same.
Transistors VT1 - VT4 have a current protection unit that prevents the microcircuit from failing in the event of an overload. As the current through one of the resistors R18, R28 increases, the voltage drop across it increases, which leads to the opening of transistor VT2 or VT1, respectively. This, in turn, leads to the operation of the thyristor analogue on transistors VT3, VT4, and the microcircuit is blocked. To disable the lock, you must turn the amplifier off and on again. If there is no need for a protection device, then you don’t have to solder transistors VT1 - VT4 and related elements into the board - this will not affect the operation of the amplifier. You can use other types of protection devices with the amplifier, taking into account the fact that when resistors R25, R31 are connected to the common wire, the amplifier is blocked.
The microcircuit has a unit that prevents clicks in the speakers when turning the power on and off. To do this, pin 8 of the DA2 microcircuit receives a constant voltage supplied through the VD2 diode and correction circuits from the winding of the power transformer.
The amplifier is tested in operation with a real load with a resistance of 5.3 Ohms; the output power is slightly less with a load resistance of 8 ohms.
Location of parts on the printed circuit board
In the design, you can use resistors C5-16 with a power of 5 W (R16-R18, R28-R30), MLT-1 (R22, R31, R38, R39), the rest - MLT-0.25 or MLT-0.5. Oxide capacitors - K50-35 or imported for a voltage of 63 V. The remaining capacitors are film (K73 groups) or ceramic (except for the TKE H50 and H90 groups).
Op-amp DA1 can be replaced with K140UD7, KR140UD17, TL071, etc. Transistors KT502E can be replaced with 2SA1207, KT814G, VT3 - with 2SC2911, KT815G, VT4 - with 2SA1209, KT814G. Chokes L1, L2 are wound with a wire with a diameter of 1 mm on resistors R17, R29 turn to turn in one layer along the length of the resistor.
The STK4231 microcircuit has two versions - with indexes II and V. The connection circuit for STK4231-V differs slightly from that recommended for the STK4231-II microcircuit, in which pins 1, 2, 21 and 22 are not used. For STK4231-V, additional elements are connected to them, as shown in Fig. 3; all other terminals are connected in the same way. An amplifier with STK4231-V has a lower harmonic distortion coefficient of 0.08%.
Connection diagram STK4231-V
Such an UMZCH can be powered either from a transformer mains power supply or from a more modern pulsed one. The power of the power supply should be selected 30...40% greater than the maximum power of the amplifier itself. You should also take into account the amendment to this article: pin 12 of DD3.2 (see diagram in Fig. 2 in the article) should be connected to pin 3 of DD3.1, and not as shown in the diagram. In addition, to limit the first inrush current when turning on the UPS, it is useful to introduce a thermistor into the primary rectification circuit.
When using a switching power supply in the amplifier circuit, instead of the KD226A diode (VD2), use KD212, and reduce the capacitance of capacitor C14 to 1000 pF.
When assembling the described amplifier, special attention must be paid to attaching the microcircuits to the heat sink. The introduction of mica spacers for insulation at such an amplifier power is unacceptable. Microcircuits can heat up to 70 °C during normal operation, but it is advisable not to exceed this temperature. It is advisable to use forced cooling with a fan. The heat sink can be installed pin (needle-shaped), or, in extreme cases, ribbed, acting as the rear or side walls of the amplifier housing. It is possible to fasten the microcircuit with screws using heat-conducting paste to a copper plate 3...5 mm thick, and then a plate with the same paste to a dissipating heat sink. The dimensions of the plate should be 2...4 times larger than the dimensions of the microcircuit used. In this case, the efficiency of heat transfer will be maximum.
With proper assembly and use of known-good parts, the described amplifier does not require adjustment. When powering the pre-amplifier from stabilizers DA3, DA4, you only need to select resistors R38, R39 so that the voltage at the input of stabilizers DA3, DA4 is within 20...30 V.
This article will tell you how to assemble simple sound amplifier based on integrated circuit STK4362 SANYO company. This UMZCH has the following parameters:
Maximum supply voltage - 50 V
Number of channels – 2
Power – 10W + 10W min, at THD = 1.0%
This amplifier is not suitable for a car due to a power supply other than 12 V, but it will perfectly replace multimedia speakers with a built-in amplifier.
Schematic diagram of STK4326 from the datasheet:
Integrated circuit STK4326, wiring diagram
Not finding a ready one on the Internet printed circuit board it was decided to breed it independently. The board was made in the SprintLayout program.
Integrated circuit STK4326, printed circuit board
After which the printed circuit board was manufactured using the method LUT(laser iron). For etching, a mixture was used: hydrogen peroxide + citric acid + salt. The board in the photo is slightly different from the circuit made in SprintLayout, since after installation some places in the circuit were changed for ease of installation.
PCB for STK4362
The following components were used for installation:
Capacitors
C1, C2 – 470 pf (you can take ceramic or mica);
C3, C4, C5 – 47 uF 50 V (polar);
C6 – 1 µF 50 V (polar);
C7 – 100 uF 50 V (polar);
C8, C9 – 0.47 µF 50 V (polar);
C10, C11 – 220 µF 50 V (polar);
C12, C13 – 1000 uF 35 V (polar);
C14, C15 – 0.1 uF 50 V or more (film);
Resistance
R1, R2 – 4.7 Ohm;
R3, R4 – 120 Ohm;
R5, R6 – 1 kOhm;
R7 – 100 Ohm;
R8, R9, R10 – 100 kOhm;
Ready UMZCH on STK4326
To tin the board and mount the parts, I used solder paste ordered from Aliexpress for 300 rubles. The tube in the photo is enough for more than one board, and this greatly speeds up the process, since it contains flux and solder at the same time.
On the chip STK4048XI. We offer a slightly modified circuit of this amplifier based on STK microcircuits. If the circuit itself remains unchanged, and only the microcircuits from the list below are replaced, you can change the output power of the audio amplifier depending on your needs from 6 to 200 watts. Depending on the marking STK chips they have different levels of nonlinear distortion: II - 0.2%; V - 0.08%; X - 0.008%; XI - 0.002%.
Approximate layout of radio elements on a printed circuit board:
At all STK chips This series provides high output power and low nonlinear distortion. This allows you to get high quality sound reproduction from the amplifier.
The supply voltage is bipolar from 20 to 95 volts (varies depending on the brand of the microcircuit, see table). Amplifier load is at least 4 ohms; optimal - 8 ohms. The input impedance of the UMZCH is 55 kOhm. The quiescent current is 120 mA. Output current up to 15 amperes (depending on the microcircuit used, see table). Microcircuits of the STK40** series require the use of a radiator with an area of at least 400 mm 2. To effectively remove heat, you can screw the chip onto a heat sink using heat-conducting paste.
The list of microcircuits in the table will be incomplete without mentioning two more markings of this series, which provide an output power of the assembled amplifier of 200 watts. This STK4050II and STK4050V. The recommended voltage for the circuit on these microcircuits is not lower than 66 volts, and the maximum is 95 V.
Assembled amplifier based on STK4050 with an output power of 200 watts:
I present to your attention my new project - a portable power amplifier based on the STK4231 chip.
And so, first things first...
Idea from Sanio - STK4231
About a year ago I bought two SANYO microcircuits - STK4231. I wanted to build an amplifier based on I. Korotkov’s article “320 W amplifier on the STK4231 chip”, published in RADIO magazine No. 11, 2005.Then there were problems with the board - I simply couldn’t do it well enough because I drew it with a marker (the board is visible in my article about photoresist) and there was no desire to redraw it in SPRINT LAYOUT.
So the mikruhi remained in the box until recently.
I found an interesting article on the Internet by Finn Mikko Esala. So I assembled such an amplifier; I actually added a level indicator on the Samsung mikruha.
The amplifier is assembled according to a circuit close to the one in the datasheet.
It is necessary to keep in mind that there are two modifications of STKashki – STK4231-II and STK4231-V. The differences are that STK4231-II pins 1, 2, 21, 22 are not used and the second one has a lower harmonic coefficient - 0.08%. The connection diagram for STK4231-V is slightly different - additional elements are simply connected as shown in the figure.
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Thank you for your attention!
Igor Kotov, editor-in-chief of Datagor magazine
power unit
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🕗 08/19/08 ⚖️ 4.23 Kb ⇣ 364
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Sound amplifier 200 watt— I propose for repetition an amplifier circuit with excellent sound quality and minimal noise level. The device is made using the integrated, hybrid properties of the STK4050 microcircuit from the Japanese company Sanyo. In order to have good sound quality and its highest gain, the amplifier needs a power supply that matches the power of this circuit. And also a rectifier with a sufficient total capacitance of capacitors, which creates the necessary conditions for efficient operation of the load.
This amplifier model is perfect for use as part of a home theater or personal computer, as well as in a set of other audio systems. For example, such a sound amplifier is perfect for working with a subwoofer. The STK4050 chip has protection that prevents clicks from occurring when power is applied or turned off. There is also highly effective protection against short circuits in the load and against excess temperature components.
Universal scheme
The circuit of this device is universal in that the circuit itself cannot be changed, but only the installation of microcircuits selected from the list proposed below. This makes it possible to modulate the power you need at the output of the UMZCH in the range from 6 W to 200 W. (All pictures can be enlarged by clicking)
The figure shows the relative placement of electronic elements on the signet:
It is well known that the hybrid microcircuits of the series proposed here guarantee solid output power and low THD. This makes it possible to extract a sound picture from the amplifier with the highest quality reproduction.
The supply voltage of the device is bipolar, which ranges from 20v to 95v and is determined depending on the installed microcircuit (that is, according to the STK marking indicated in the table). The acoustics connected to the amplifier must have a resistance of 4 ohms; the best option is 8 ohms. The output resistance of the UMZCH is 55 kOhm. The quiescent current is within 120 mA. The output current reaches 15A, again depending on the installed STK, according to the table shown in the figure. For reliable operation of the STK4050 hybrid integrated circuit, a heat sink with a cooling area of 400 cm2 is required. To ensure efficient heat dissipation, the microcircuit is attached to the radiator through heat-conducting paste KPT-8.
