Protection of radio equipment of an overstrain

11/20/2017 - 22:58

At failure both linear, and the pulse stabilizers of constant tension executed on transistors or chips, target tension can become almost equal to the entrance (straightened) tension which is usually removed from the condenser of the filter of a food, the diode bridge established on an exit. For example, at "burn-out" КР142ЕН5А which is usually used in power-supply circuits of digital devices, on tires of a food tension 7 can arrive... 15 In instead of put 5 V.Eto it is already dangerous to absolute majority of devices.

Sometimes for protection of knots of radio equipment sensitive to an overstrain use a powerful stabilitron with tension of stabilization, slightly big rated voltage of a food. The lack of such way of protection that many stabilitrons possess rather big differential resistance, and the protected device can continue to work some time, receiving tension, on 0,5. . 1,5 In more nominal. Stabilitron strongly warming up at this time can "leave on break", and protection as that will not turn out.

For protection of separate knots and radio equipment blocks from the increased tension at damage of the stabilizer or the wrong connection to the power supply, it is possible to assemble the simple adjustable block of protection (fig. 1). It joins in a rupture of a chain between an exit of the power supply and loading.

of the Fig. 1. The Pritsipialny circuit of the simple block of protection

Works with p this block as follows. At increase of entrance tension the current through VD1 stabilitron sharply increases, respectively, the current in a chain of an operating electrode of a tiristor of VS1 increases also, the tiristor opens and shunts a loading food till operation of a safety lock of FU1. The powerful wire R3 resistor prevents tiristor breakdown because of a strong throw of a current which arises in case in a power-supply circuit oksidny high-capacity condensers are established. The stabilitron of VD1 gets out on tension, approximately on 0,3... 1,5 In smaller, than rated voltage of a food. The choice of its type depends on a number of factors therefore for each case it is better to define optimum option experimentally. Adjustment of the R1 resistor it is possible to establish precisely that tension at which the tiristor will open. The C1 condenser prevents false operation of the block of protection at short pulse hindrances which can appear in a power-supply circuit. The R2 resistor protects a stabilitron and a tiristor in a case when the cursor of the tuning resistor is in the top situation. For the period of setup of this block it is desirable to replace a safety lock with the filament lamp on which ignition it is possible to judge the moment of inclusion of a tiristor.

More perfect block of protection can be collected according to the circuit provided on fig. 2.

of the Fig. 2. The Pritsipialny circuit of the block of protection with the relay

At increase of entrance tension a food of loading stops because of disconnection of contacts of the K1 relay. The chain of R3-VD2 is intended for reduction of short-term surge in tension on an exit of the block which can appear because of a lag effect of switching of contacts of the relay.

For protection of the radio-electronic devices established in the car, for example, autoradio tape recorders or alarm systems from an overvoltage in an onboard network, it is possible to assemble the protection block according to the circuit provided on fig. 3.

of the Fig. 3. The Pritsipialny circuit of the block of protection of automobile radio-electronic devices Here the cursor of the R1 resistor is established to p by center in situation at which operation of protection occurs at entrance tension 15... 16 V.Pri opening of a tiristor are disconnected relay contacts, a food of loading stops, the blinking light-emitting diode of HL1 starts to flash. C1 condensers... SZ raise a noise stability. In SB1 button pressing (without fixing) it is possible to return the protection block in a waiting mode.

Tuning resistors can be taken resistance 150... 470 Ohm of the types SPZ-38, RP1-63M, SP5-16va, SP4-1 or that is better, multiturnaround - the SPZ-39 type. Wire resistors - the C5-16MB type or self-made from a short piece of a thick high-resistance wire. Condensers - the types K10-17, KM-5. Tiristora any of the series KU228, КУ201, КУ202, Т122 will approach. The KD213A diode is replaced with the powerful diode from the series KD202, Д242, КД2999. The blinking light-emitting diode is used red color. It is possible to replace it with any of the series L56, L36, L799, L816 and others similar. It is possible to replace the electromagnetic relay of RMU type (passport ЧП4.523.332) with any, reliably working at rated entrance voltage and having rather powerful normalnozamknuty contacts.

In knots according to circuits on fig. 2 and 3 can establish the REK29 type relay from DU systems of old domestic TVs, having wound off from its coil the necessary quantity of rounds. It is possible to adapt and automobile relays suitable on a design.

For protection of the automobile equipment in a chain of the sensor of tension can use stabilitrons КС297В, Д814Д, КС213Ж, КС508А, 1N6003B. Stabilitrons of the types KS126G, КС126Д, КС139А, КС147А, КС407Б, КС439А, V.Dlya's 1 N5991 of devices will be suitable for designs on low-voltage digital chips on IMS of the K561 series, 564, КР1561 it is possible to choose the necessary stabilitron from row КС215Ж, КС216Ж, КС508Б, КС518А, 1N6005B, 1N6006B, 1N4745A.

Sources

  1. P. Horovits, U.Khill. Circuitry art. — M: World, 2001, Page 335.

Author: А.БУТОВ, village Kurba

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Protection of radio equipment of an overstrain

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