Voltage stabilizer on chip КР142ЕН19 with protection

In article the voltage stabilizer with reliable pulse protection is described. If the target current of the stabilizer some time exceeds a threshold of operation of protection, the stabilizer is switched off for some seconds for cooling of the regulating transistor, then joins and disconnected again, failure in loading will not be eliminated yet. As the regulating transistor in such mode the most part of time is closed, the average capacity disseminated by it even at short circuit of an exit is no more, than in a regular mode. In the offered stabilizer the knot of pulse protection on the gerkonovy relay which has been switched on in a silnotochny chain is applied. Such knot contains few additional details, almost does not reduce stabilizer efficiency, and the main thing, a current of operation of gerkonovy protection very poorly depends on temperature. The factor of stabilization of the device exceeds 400. The minimum power failure between an entrance and an exit - 0,5 V.Skhema of the stabilizer it is shown in drawing.

the Basic element of the stabilizer - chip КР142ЕН19 (DA1). If tension on an operating entrance (a conclusion 1) chips concerning the cathode (a conclusion 2) exceeds a threshold of its opening (2,5 In), the current of the anode increases with a steepness about 2 ma/mv. Tension on the anode of the open chip, defined by its internal device, - not less than 2,5 Century. This chip has feature: if tension on an entrance appears more than it is necessary for its complete opening, it can be switched off. Thus it ceases to operate the stabilizer therefore on its exit there can be an entrance tension. The overload of an entrance of a chip can occur because of a throw of target tension which arises at disconnection of loading from the working stabilizer. Thus the current arriving in loading before its shutdown, starts to charge the condenser established on an exit of the stabilizer. It leads to increase in target tension while the signal which has passed through the stabilizer of a mistake will not close the regulating transistor. Obviously, emission of tension will be that less, than it is more than a capacity of the condenser on an exit of the device and than quicker passes through the stabilizer a mistake signal. Experiments with shutdown of loading showed that the capacity not less than 1000 мкФ on each ampere of a target current has enough, that chip shutdown in the described stabilizer could not arise.

At repetition of the device should abstain from the changes leading to reduction of speed, for example, from use of low-frequency transistors. Especially dangerously artificially to reduce speed addition of integrating RC links to the highway of passing of a signal of a mistake for the purpose of fight against generation. As the part of target tension is submitted from a cursor of the resistor of adjustment of target tension of R12 on an entrance of management of a chip, the increase in tension between target conclusions of the stabilizer leads to increase in tension between an entrance of management of a chip and its cathode that leads to chip opening. Its target signal closes the VT3 transistor which has been switched on on the circuit with the general lock, and then and the compound regulating VT2VT1 transistor which has been switched on in a minus wire of the stabilizer that leads to current reduction through it. If the chip is closed, the VT3 transistor should be open, the current of its channel should be within 4... 10 мА. Such mode turns out, if on a lock tension about 5 In rather general plusovy wire is submitted. It appeared that giving on a lock of a part of entrance tension with pulsations leads to emergence of pulsations on a stabilizer exit with amplitude about 1 мВ. Therefore tension on a lock of the VT3 transistor is stabilized relatively the general wire by VD1 stabilitron and then also it is filtered by chains of R2C3, R5C4. Use of the field transistor allowed to reduce essentially a current via filters, and, therefore, and their dimensions. The R7 resistor prevents self-excitation. Without it the step on the VT3 transistor can самовозбудиться on frequency about 20 MHz. The described stabilizer has three extents of protection against failures both in loading, and in the stabilizer. Fast protection against short-term overloads is provided with the R8 resistor. At essential, approximately twice, excess by a current of loading of the set maximum in 2 And power failure on the R8 resistor increases to level of entrance tension, the VT2 transistor thereof is sated and ceases to strengthen a current that leads to restriction of a current of loading. The stabilizer is protected from more long failures by pulse protection on the gerkonovy K1 relay. If the current of loading exceeds a current of operation of the relay (2 And), геркон becomes isolated, and the SZ condenser is quickly discharged via the R1 resistor. Also the C4 condenser discharge via the R5 resistor thus begins. But this process proceeds much more slowly because of rather big resistance of the R5 resistor. When power failure on the C4 condenser will decrease approximately to 1 In, the VT3 transistor will be closed, switching off thereby the stabilizer. The delay of shutdown of the stabilizer is entered by a chain of R5C4 in order that the SZ condenser was in time till disconnection геркона К1.1 to be discharged almost completely. After disconnection геркона the slow charging of the SZ condenser via the R2 resistor begins. It leads to gradual opening of the VT3 transistor and stabilizer start. Similarly there is also a stabilizer start at food inclusion. If from this stabilizer to feed UMZCh, at its inclusion there will be no click in speaker systems. The described stabilizer, as well as any device with deep feedback, can be inclined to generation. When prototyping device generation was observed in the form of impulses on a stabilizer exit with amplitude about 5 мВ and frequency about 100 kHz. It appeared that tendency of the stabilizer to generation is influenced most of all by quality of the C5 condenser. To understand, why it occurs, the following reasonings help. Let's say on a stabilizer exit tension on 1 мВ casually changed. The chip will transform this tension to change of a target current 2 мА. Regulating transistors will strengthen it approximately in 500 times that as a result will lead to current change via the stabilizer and the C5 condenser on 1 And. This change of a current will cause power failure on equivalent consecutive resistance (EPS) of the condenser which will go on a feedback chain "on the second circle". If this power failure exceeds 1 мВ, there can be a generation. Obviously, stability of the stabilizer can provide the C5 condenser with EPS less than 0,001 Ohm. To make a choice, measurements of EPS of condensers of various series were carried out. On the condenser via the resistor unipolar tension with frequency of 100 kHz and scope of a current 1 moved And. EPS was calculated on tension on the condenser, measured by an oscillograph. It appeared that for condensers in capacity more than 500 мкФ EPS on frequency of 100 kHz depends generally on a condenser design, and on its capacity and rated voltage depends poorly. By results of measurements the C5 condenser is made of ten in parallel connected condensers of the K50-24 series on 470 мкФ therefore self-excitation without application of other means is suppressed. It is necessary for complete use of small resistance of the battery of C5 condensers, that the length of connecting wires from C5 condenser conclusions to right according to the circuit of a conclusion of the R13 resistor and to a point of connection of R10 and R14 resistors was as little as possible that is shown on the circuit. Tendency of the stabilizer to generation, as appears from the foregoing, increases at increase of the greatest possible amplitude of an impulse of the current, which stabilizer can submit to the C5 condenser. It can become the main problem in attempt to increase the maximum target current. To improve stability of the stabilizer it is possible selection of the R10 resistor creating local negative feedback in a chain of the cathode of a chip. At adjustment of the stabilizer this resistor close a crossing point, then with increase in number of condensers in the C5 battery eliminate generation then a crossing point clean. The stabilizer gets a stability stock, sufficient for its normal work even after partial loss of capacity of the C5 battery. The C2 condenser eliminates influence of inductance of a winding of the gerkonovy relay on stability of the stabilizer. In the stabilizer one more extent of protection - from overheating of the regulating VT1 transistor can be added. For this purpose it is enough to press to the case of this transistor of the thermorelay with the bimetallic plate, working at temperature 60... 70 °C. The closed contacts of the thermorelay include in a rupture of a chain of a drain of the VT3 transistor. Overheating of the VT1 transistor will cause disconnection of contacts of the thermorelay therefore the VT1 transistor will be closed until will be cooled.

the KP507A Transistor (VT3) is replaceable to relatives on the KP508A parameters. Chip КР142ЕН19 (DA1) is admissible to replace on КР142ЕН19А or foreign analog of TL431. SZ condensers, С4, protection used in knot as vremyazadayushchy, should be with small leak, for example, from FT series, К78, K71-4. The period of operation of pulse protection, and also duration of start of the stabilizer depends on capacity of the SZ condenser. At specified on the circuit resistance of the R2 resistor and SZ condenser capacity this period is approximately equal 3 pages. It is essential to reduce it decrease in capacity of the SZ condenser does not follow, as at too fast start a current of a charging of condensers which can be in loading structure, can exceed 2 And that will cause protection operation. Gerkonovoye of the K1 relay - self-made. On герконе KEM1 (or another similar) reel up 15 rounds of an obmotochny wire in diameter of 0,4-0,7 mm. Then specify number of rounds on operation геркона at a current of load of 2 A.Tranzistor VT1 it should be established on a heat-conducting path with the area of a cooling surface not less than 200 quarter see. At adjustment on an entrance submit tension from an exit of the laboratory power supply. Its maximum value should not exceed 30 In (limiting tension the anode cathode of a chip of DA1). Selection of the R14 resistor establish the top border of adjustment of target tension on 0,5... 1 In less entrance tension. The R8 resistor select so that power failure on it at a loading current about 2 And it was equal to a half of entrance tension.

the Stabilizer should be used

with care in bipolar sources because of its slow start. As геркон pulse protection can become isolated from strong jolting, it is not recommended to apply the offered stabilizer in onboard systems.

of S. Kanygin, Kharkov, Radio No. 10, 2006г.

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