The powerful two-polar stabilized power unit of 2х44 Volts, 4 And on the canal

02/20/2017 - 04:55

In radiolyubitelsy literature was repeatedly expressed by font size opinion on need of a food of UMZCh from the stabilized power supply for providing more its natural sounding. Really, at the maximum target capacity of the amplifier of a pulsation of tension of not stabilized source can reach several volts. Thus the supply voltage can essentially decrease at the expense of the category of condensers of the filter. It is imperceptible at peak values of target tension on the highest sound frequencies, thanks to sufficient capacity of filtering condensers, but affects when strengthening low-frequency components of big level as in a musical signal they have big duration. As a result filtering condensers manage to be discharged, the supply voltage, so, and the maximum target capacity of the amplifier decreases. If the voltage reduction of a food leads to reduction of a current of rest of the target cascade of the amplifier, it can lead and to emergence of additional nonlinear distortions.

on the other hand, use of the stabilized power supply constructed on the usual circuit of the parametrical stabilizer, increases consumed by it from a network capacity and demands use of the network transformer of bigger weight and dimensions. In addition, there is a need "the heat removal disseminated by target transistors of the stabilizer. And often the capacity disseminated by target transistors by UMZCh, is equal to the capacity disseminated by target transistors of the stabilizer, i.e. a half of capacity is spent for nothing. Pulse voltage stabilizers have high efficiency, but are rather difficult in manufacturing, have big level of high-frequency hindrances and are not always reliable.

If to the power unit is not shown to font by p of rigid requirements for stability of tension and pulsation level, as the power supply it is possible to use the ordinary bipolar power unit which schematic diagram is shown on рис1.

the Powerful compound VT7 and VT8 transistors which have been switched on on the circuit of emitterny repeaters, provide rather good filtration of a pulsation of supply voltage with frequency of a network and stabilization of target tension thanks to established in a chain of bases of transistors to VD5 stabilitrons — VD10. Elements LI, L2, R16, R17, C11, eliminate with C12 possibility of high-frequency generation tendency to which speaks big factor of strengthening on a current of compound transistors. The size of the alternating voltage arriving from the network transformer, is chosen such, that at the maximum target capacity of UMZCh (that there corresponds to a current in loading 4А) tension on C1 filter condensers — С8 decreased approximately to 46... 45 Century. In this case power failure on transistors VT7, VT8 will not exceed 4 In, and the capacity disseminated by transistors will make 16 W. At reduction of the capacity consumed from the power supply, power failure on transistors VT7, VT8 increases, but the capacity disseminated on them remains to a constant because of reduction of a consumed current. The power unit works as a voltage stabilizer at small and average currents of loading, and at the maximum current — as the transistor filter. In such mode its target tension can decrease to 42... 41 In, pulsation level on an exit reaches value 200 мВ, the efficiency is equal 90 %. to

As showed to font prototyping, fuses cannot protect the amplifier and the power unit from overloads on a current because of the lag effect. For this reason the device of high-speed protection against short circuit and excess of an admissible current of the loading, transistorized VT1 — VT6 was applied. And protection functions at overloads of positive polarity carry out transistors VT1, VT2, VT5, resistors Rl, R3, R5. R7 — R9, R13 and the C9 condenser, and negative — transistors VT4, VT3, VT6, resistors R2, R4, R6, R10 — R12, R14 and the C10 condenser.

we Will consider operation of the device at overloads of positive polarity. In an initial condition at a rated load all transistors of the device of protection are closed. At increase in a current of loading starts raise power failure on the R7 resistor and if it exceeds admissible value, the VT1 transistor, and after it and VT2 and VT5 transistors starts to open. The last reduce tension on the basis of the regulating VT7 transistor, so, and tension on a power unit exit. Thus at the expense of the positive feedback provided by the R13 resistor, tension reduction on an exit of the power unit leads to acceleration of further opening of transistors VT1, VT2, VT5 and fast closing of the VT7 transistor. If resistance of the resistor of positive feedback of R13 is not enough, after operation of the device of protection tension on an exit of the power unit is not restored even after loading shutdown. In this mode it would be necessary to provide the button of start which is disconnecting, for example, for short time the R13 resistor after operation of protection and at the moment of turning on of the power unit. However, if resistance of the R13 resistor to choose such that at short circuit of loading the current was not equal to zero, tension on an exit of the power unit will be restored after operation of the device of protection at reduction of a current of loading to safe size. Practically resistance of the R13 resistor gets out such size at which reliable turning on of the power unit at restriction of a current of short circuit by value 0,1 is provided... 0,5 A.Tok operations of the device of protection are defined by the R7 resistor. The device of protection of the power unit similarly works at overloads of negative polarity.

Design and details. All details of the power unit are placed by b on one payment. An exception transistors VT7, VT8 of the block make the tsitaniye placed on separate heat-conducting paths with the area of the disseminating surface of 300 cm 2 each. Coils LI, power unit L2 (fig. 3) contain 30 — 40 rounds of the wire PEV-1 1,0 which has been reeled up on the case of the resistor C5-5 or MLT-2. Resistors R7, R12 of the power unit represent a piece of a copper wire of PEL, PEV-1 or ПЭЛШО in diameter 0,33 and length of 150 mm, the MLT-1 resistor reeled up on the case. The transformer of a food is executed on toroidal магнитопроводе from electrotechnical E320 steel, thickness of 0,35 mm, width of a tape of 40 mm, internal diameter of a magnito-wire 80, external — 130 mm. The network winding contains 700 rounds of wire ПЭЛШО 0,47, secondary — 2Х130 rounds of wire ПЭЛШО 1,2.

Each of KT825G transistors can replace p with compound transistors KT814G, КТ818Г, and КТ827А — compound transistors KT815G, КТ819Г. Instead of stabilitrons КС515А it is possible to use stabilitrons Д814А connected consistently (B, In, G, Д) and КС512А.

Check of serviceability of the power unit. for this purpose, having replaced power unit resistors R7, R12 with more high-resistance (about 0,2... 0,3 Ohm), check operability of the power unit of the device of protection. It should work at a current of loading 1... 2 A.Ubedivshis in normal operation of the power unit and UMZCh, establish resistors R7, R12 with the nominal resistance specified on the schematic diagram supervising absence of operation of the device of protection.

LITERATURE

1. Leksina Valentin and Victor. About a visibility of nonlinear distortions of the amplifier of capacity. — Radio, 1984, No. 2, page 33 — 35.
2. Solntsev Yu. What Kg is admissible? — Radio, 1985, No. 2, page 26 — 28.
3. Solntsev Yu. High-quality amplifier of capacity. — Radio, 1984, No. 5, with, 29 — 34.
4. Gumelya E. Quality and UMZCh circuitry. — Radio, 1985, No. 9, page 31 — 34. />/>/>

Radio No. 5 1990г.

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The powerful two-polar stabilized power unit of 2х44 Volts, 4 And on the canal