Power supplies

The first problem which when designing any devices face and beginning and skilled radio fans — is power supply problem. In the present chapter various network power supplies (micropowerful, average capacity, powerful) will be considered.

At a choice and development of the power supply (further SP) it is necessary to consider p a number of the factors defined by service conditions, properties of loading, requirements to safety etc.

First of all, of course, it is necessary to pay attention of font to compliance of electric parameters of SP to requirements of the fed device, namely:

· • supply voltage;

· • a consumed current;

· • demanded level of stabilization of supply voltage;

· • admissible level of a pulsation of supply voltage. SP characteristics are important also. influencing its operational qualities:

· • existence of systems of protection;

· • massogabaritny sizes.

Being an integral part of radio-electronic equipment, means of secondary power supply should correspond rigidly to certain requirements which are defined both requirements to the equipment as a whole, and conditions shown to power supplies and their work as a part of this equipment. Any of the SP parameters, overstepping the bounds of admissible requirements, brings a discord in operation of the device. Therefore before beginning SP assembly to an expected design, attentively analyse all available options and choose such SP which will correspond as much as possible to all requirements and your possibilities.

Exists four main types of network power supplies:

· • bestransformatorny, with the extinguishing resistor or the condenser.

· • linear, executed according to the classical circuit:

the lowering transformer - the rectifier - the filter

- the stabilizer.

· • the secondary pulse: the lowering transformer - the filter - the high-frequency converter of 20-400 kHz.

· • the pulse high-voltage high-frequency: the filter

- the rectifier ~220 B - pulse high-frequency

the converter 20-400kgts. Linear power supplies differ limiting simplicity and reliability, lack of high-frequency hindrances. High degree of availability of accessories and simplicity of manufacturing does them by the beginning radio designers most attractive to repetition. Besides, purely economic calculation is in certain cases important also — application of linear SP is unequivocally justified in the devices consuming to 500 мА which demand enough small-sized SP. It is possible to carry to such devices:

· • chargers for accumulators;

· • power units of radio receivers, АОНов, alarm system systems etc.

It should be noted font that some designs which are not demanding a galvanic outcome with an industrial network, it is possible to feed via extinguishing condenser or the resistor, thus consumed current can reach hundreds мА.

Efficiency and rationality of application of linear SP considerably decreases at consumption currents more than 1 A.Prichinami of it the following phenomena are:

· • fluctuations of mains voltage affect factor of stabilization; to

· • on an entrance of the stabilizer it is necessary to establish to font tension which will be obviously higher than minimum admissible tension at any fluctuations in a network, and it means that when these fluctuations are high. it is necessary to establish the overestimated tension that in turn influences the transistor through passage (unfairly big power failure on transition, and as a result — a high thermal emission);

· • the big consumed current demands application of dimensional radiators on straightening diodes and the regulating transistor, worsens a thermal mode and overall dimensions of the device as a whole.

are Rather simple in manufacturing and operation secondary pulse converters of tension, they are distinguished by simplicity of manufacturing and low cost of accessories. Economically also is technologically justified to design SP according to the circuit of the secondary pulse converter for devices with a current of consumption 1-5 And, for uninterrupted SP to video surveillance and protection systems, for amplifiers of low frequency, radio stations, chargers.

the Best distinctive feature of secondary converters before linear — massogabaritny characteristics of the rectifier, the filter, the converter, the stabilizer. However they are distinguished by big level of hindrances therefore when designing it is necessary to pay attention to shielding and suppression of high-frequency components in the food tire.

gained Recently rather wide circulation the pulse SP constructed on the basis of the high-frequency converter with a bestransformatorny entrance. These devices, eating from an industrial network ~110B/220B, do not contain in the structure of bulky low-frequency power transformers, and transformation of tension is carried out by the high-frequency converter on frequencies of 20-400 kHz. Such power supplies possess on an order the best massogaba-ritny indicators in comparison with linear, and their efficiency can reach 90 % and more. SP with the pulse high-frequency converter essentially improve many characteristics of the devices fed from these sources, and can be applied practically in any radio amateur designs. However they are distinguished by rather high level of complexity, high level of hindrances in the food tire, low reliability, high prime cost, inaccessibility of some components. Thus, it is necessary to have very strong reasons for application of pulse SP on the basis of the high-frequency converter in amateur equipment (in industrial devices it is in most cases justified). As such bases can serve: probability of fluctuations of entrance tension within ~100-300 Century. possibility to create SP with capacity from tens watt to hundreds kilowatt on any target tension, emergence of available hi-tech decisions on the basis of IMS and other modern components.

1. With a galvanic outcome from a network on оптронах

Micropowerful SP with a galvanic outcome from a network ~220 B it is possible to execute the power supply with application оптронов, having included them it is consecutive for increase in target tension (fig. 3.2-1.) . Transfer of energy is carried out by means of the unidirectional light stream inside оптрона (оптрон contains svetoizluchayushchy and absorbing elements), thus, galvanic communication with a network does not arise.

On one оптопаре is allocated with sans-serif 0,5-0,7 In for АОД101. АОД302 and 4 In — for АОТ102, АОТ110 (inflow 0,2 мА). For ensuring demanded values of tension and a current оптопары join consistently or in parallel. As a buffer accumulating element it is possible to use an ionistor, the accumulator or capacity on 100-1000 мкФ. Light-emitting diodes запитываются through capacity no more than 0.2 мкФ in order to avoid destruction. It is necessary to remember that efficiency оптронов falls over time (approximately for 25 % for 15000 business hours).

2. The micropowerful stabilizer with small consumption

In some radio amateur designs are required the micropowerful stabilizers consuming in a mode of stabilization microamperes. On fig. 3.2-4 the schematic diagram of such stabilizer with an internal current of consumption 10 мкА and a current of stabilization 100 мА is provided.

For the elements specified on the circuit tension of stabilization makes Uвых=3.4 B, for its change instead of a light-emitting diode of HL1 it is possible to turn on consistently KD522 diodes (on everyone power failure makes 0.7 In: on transistors

VT1, VT2 — 0,3 In). Entrance tension of this stabilizer (Uвх) no more than 30 V.Dolzhny to be applied transistors with the maximum factor of strengthening.

3. Power supplies with dividing condensers

In micropowerful power supplies with galvanic communication with an industrial network are usually applied so-called dividing condensers which represent no other than the shunting resistance included consistently in a power-supply circuit. It is known that the condenser established in a chain of an alternating current, possesses resistance which depends on frequency and is called as jet. (Under condition of application in the industrial - networks ~220 B, 50 Hz) it is possible to calculate capacity of the dividing condenser on the following formula:

For an example: the charger for nickel - cadmium accumulators 12В in capacity 1 And / can be zapitano from a network via the dividing condenser h. For nickel - cadmium accumulators the charging current makes 10 % from face value, i.e. 100 мА in our case. Further, considering power failure on the stabilizer about 3-5 In, we receive that on an entrance of the charger it is necessary to provide tension ~18 In at a working current 100 мА. Substituting these data, we receive:

on the first formula:

Thus, we choose With = 1,5 мкФ with the doubled working tension 500 In (condensers of types can be applied:

MBM, MGBP, MBT).

the Full circuit of the charger with the dividing condenser is provided by sans-serif on fig. 3.2-2. The device is suitable for a charging of accumulators a current no more than 100 мА at tension of a charge no more 15В. The tuning R2 resistor establish necessary value of tension of a charge. R1 carries out a role of the limiter of a current at the beginning of a charge, and tension allocated on it moves on a light-emitting diode. On intensity of a luminescence of a light-emitting diode it is possible to judge — it is how discharged by joint stock bank.

At operation of this power supply (and any other SP without a galvanic outcome with a network) it is necessary to remember font security measures. The device and the charged battery are all the time under potential of an industrial network. In certain cases such restrictions do impossible normal operation of devices therefore it is necessary to provide a galvanic outcome of SP from a network.

the Low-power power supply with the dividing condenser, but with a galvanic outcome from an industrial network it is possible to make on the basis of the transitional transformer or the relay

the magnetic actuator, and their working tension can be and 220 V.Na fig. 3.2-3 are lower the schematic diagram of such power supply is shown.

the Capacity of the dividing condenser pays off with the accounting of parameters of the transformer (i.e., knowing factor of transformation. at first count tension which it is necessary to provide on a transformer entrance, and then, having convinced of an admissibility of such tension for the applied transformer, count condenser parameters).

the Capacity given by such power supply, quite can feed a room call, the receiver, an audioplayer.

4. Power supplies with dividing condensers

In micropowerful power supplies with galvanic communication with an industrial network are usually applied so-called dividing condensers which represent no other than the shunting resistance included consistently in a power-supply circuit. It is known that the condenser established in a chain of an alternating current, possesses resistance which depends on frequency and is called as jet. (Under condition of application in the industrial - networks ~220 B, 50 Hz) it is possible to calculate capacity of the dividing condenser on the following formula:

For an example: the charger for nickel - cadmium accumulators 12В in capacity 1 And / can be zapitano from a network via the dividing condenser h. For nickel - cadmium accumulators the charging current makes 10 % from face value, i.e. 100 мА in our case. Further, considering power failure on the stabilizer about 3-5 In, we receive that on a charger entrance not roundимо to provide tension ~18 In at a working current 100 мА. Substituting these data, we receive:

on the first formula:

Thus, we choose With = 1,5 мкФ with the doubled working tension 500 In (condensers of types can be applied:

MBM, MGBP, MBT).

the Full circuit of the charger with the dividing condenser is provided by sans-serif on fig. 3.2-2. The device is suitable for a charging of accumulators a current no more than 100 мА at tension of a charge no more 15В. The tuning R2 resistor establish necessary value of tension of a charge. R1 carries out a role of the limiter of a current at the beginning of a charge, and tension allocated on it moves on a light-emitting diode. On intensity of a luminescence of a light-emitting diode it is possible to judge — it is how discharged by joint stock bank.

At operation of this power supply (and any other SP without a galvanic outcome with a network) it is necessary to remember font security measures. The device and the charged battery are all the time under potential of an industrial network. In certain cases such restrictions do impossible normal operation of devices therefore it is necessary to provide a galvanic outcome of SP from a network.

the Low-power power supply with the dividing condenser, but with a galvanic outcome from an industrial network it is possible to make on the basis of the transitional transformer or the relay

the magnetic actuator, and their working tension can be and 220 V.Na fig. 3.2-3 are lower the schematic diagram of such power supply is shown.

the Capacity of the dividing condenser pays off with the accounting of parameters of the transformer (i.e., knowing factor of transformation. at first count tension which it is necessary to provide on a transformer entrance, and then, having convinced of an admissibility of such tension for the applied transformer, count condenser parameters).

the Capacity given by such power supply, quite can feed a room call, the receiver, an audioplayer.

5. LINEAR POWER SUPPLIES

traditional linear power supplies are more and more forced out Now by the pulse. However, despite it, they continue to remain very convenient and practical decision in most cases radio amateur designing (sometimes and in industrial devices). Reasons for that a little: first, linear power supplies are structurally enough simple and are easily adjusted, secondly, they do not demand application of expensive high-voltage components and, at last, they it is much more reliable than pulse SP.

Typical linear the SP contains sans-serif in the structure: the network lowering transformer, the diode bridge with the filter and the stabilizer which will transform not stabilized tension received from a secondary winding of the transformer through the diode bridge and the filter, to the target stabilized tension, and, this target tension always below not stabilized entrance tension of the stabilizer. The main lack of such circuit is the low efficiency and need of reservation of capacity practically in all elements of the device (i.e. installation of components allowing big loadings, than expected for SP as a whole is required, for example, the SP in capacity of 10 W need the transformer in capacity not less than 15 W, etc.) . The reason of it is the principle on which stabilizers of linear SP function. It consists in dispersion on a regulating element of some capacity of Ppac = Iнагр * (Uвх - Uвых).Из formulas follows that than more difference between entrance and target tension of the stabilizer, subjects the big capacity is necessary for disseminating on a regulating element. On the other hand, than entrance tension of the stabilizer is more unstable, and than more it depends on change of a current of loading, especially high it should be in relation to target tension. Thus it is visible that stabilizers of linear SP function in rather narrow framework of admissible entrance tension, and this framework is still narrowed at presentation of rigid requirements to device efficiency. But reached in linear SP extent of stabilization and suppression of pulse hindrances much more surpass other circuits. Let's consider slightly in more detail stabilizers applied in linear SP.

Protozoa (so-called parametrical) stabilizers are based by sans-serif on use of features of volts-ampernykh of characteristics of some semi-conductor devices — generally stabilitrons. They are distinguished by high target resistance. low level of stabilization and low efficiency. Such stabilizers are applied only at small loadings, usually — as elements of circuits (for example, as sources of basic tension). Examples of parametrical stabilizers and a formula for calculation are given on fig. 3.3-1.

Consecutive linear stabilizers through passage differ the following characteristics: tension on loading does not depend on entrance tension and a loading current, high values of a current of loading are allowed, the high factor of stabilization and small target resistance is provided. The block diagram of the standard linear stabilizer is presented on fig. 3.3-2. The basic principle on which its work — comparison of target tension with some stabilized

basic tension and management on the basis of results of this comparison by the main power element of the stabilizer (on the block diagram — the so-called VT1 transistor through passage working in a linear mode, but it can be and group of components) on which the superfluous capacity (see the formula given above dissipates) is based.

In most cases radio amateur designing as power supplies of devices can be applied by sans-serif linear SP on the basis of chips of linear stabilizers of a series To (KR) 142. They possess very good parameters, have the built-in chains of protection against overloads, chains a thermolump-pensatsii, etc., are easily available and simple in application (the majority of stabilizers of this series are completely realized in IS, which (have only three conclusions). However when designing linear SP of big capacity (25-100 W) thinner approach is required, namely: use of special transformers with armored cores (having bigger KDP), direct use of only integrated stabilizers is impossible in view of insufficiency of their capacity, i.e. additional power components and, as a result, additional chains of protection against an overload, an overheat and an overstrain are necessary. Such SP allocate a lot of heat, assume installation of many components on big radiators and, respectively, enough габаритны; for achievement of high factor of stabilization of target tension special circuit decisions are required.

6. The stabilizer with a loading current to 5А

On fig. 3.3-3 is given the base circuit for creation of the powerful stabilizers providing a current of loading to 5 And. that it is quite enough for a zapityvaniye of the majority radio amateur a design. The circuit is executed with application of a chip of the stabilizer of the KP142 series and the external transistor through passage.

At a small current of consumption the VT1 transistor is closed by sans-serif and the stabilizer chip works only, but at increase in a consumed current, the tension allocated for R2 and VD5, opens the VT1 transistor, and the main part of a current of loading starts to flow through its transition. The R1 resistor serves as the current sensor on an overload. Than resistance of R1 more, subjects on a smaller current protection (the VT1 transistor is closed) works. The filtering throttle of L 1 serves for suppression of a pulsation of an alternating current at the maximum loading.

According to the provided circuit it is possible to assemble stabilizers on tension of 5-15 Century. Power VD1-VD4 diodes should be calculated on a current not less than 10 A.Rezistorom R4 exact fine tuning of target tension (base value is set by type of an applied chip of the stabilizer of the KP142 series) is carried out. Power elements are established on radiators in the area not less than 200 см^2.

For an example, we will give voltage stabilizer calculation with the following characteristics:

UóÙÕ - 12 In; Iнаг - 3 A; by Uвх - 20 Century

we Choose a voltage stabilizer 12 In in the KP142 series — КР142ЕН8Б. We choose the transistor through passage, capable to disseminate the maximum capacity of loading Rras = to Uвх* Iнагр = 20 • 3= 60 W (capacity of the transistor it is desirable to choose in 1.5-2 times bigger) — suit i extended КТ818А (Rras = 100 W, Iк Max = 15 And). As VD1-VD5 any power diodes suitable on a current, for example, КД202Д can be used.

7. PULSE POWER SUPPLIES

Unlike the traditional linear SP assuming clearing of excessive not stabilized tension on a linear element through passage, pulse SP use other methods and the physical phenomena for generation of the stabilized tension, namely: effect of accumulation of energy in inductance coils, and also possibility of high-frequency transformation and transformation of the saved-up energy to constant tension. There are three standard circuits of creation of pulse SP (see fig. 3.4-1): raising (target tension is higher entrance), lowering (target tension is lower entrance) and inverting (target tension has opposite in relation to entrance polarity). Apparently from drawing, they differ only in the way of connection of inductance, for the rest, the principle of work remains invariable, namely.

the Key element (usually apply bipolar or MDP transistors), about 20-100 kHz working with frequency, periodically for short time (no more than 50 % of time) прикла

дывает to the inductance coil the full entrance not stabilized tension. Pulse current. proceeding thus via the coil, provides accumulation of a stock of energy in its magnetic field 1/2LI^2 on each impulse. The energy reserved thus from the coil will be transferred in loading (or directly, with use of the straightening diode, or through a secondary winding with the subsequent straightening), the condenser of the target smoothing filter provides constancy of target tension and a current. Stabilization of target tension is provided with automatic adjustment of width or frequency of following of impulses on a key element (the feedback chain is intended for tracking target tension).

Such, though rather difficult, the circuit allows to increase efficiency of all device essentially. The matter is that, in this case, except the loading in the circuit there are no the power elements disseminating considerable capacity. Key transistors work in a mode of a saturated key (i.e. power failure on them is not enough) also disseminate capacity only in rather short time intervals (time of giving of an impulse). In addition, at the expense of increase of frequency of transformation it is possible to increase essentially capacity and to improve massogabaritny characteristics.

Important technological advantage of pulse SP is construction possibility on their basis of small-sized network SP with a galvanic outcome from a network for a food of the most various equipment. Such SP are under construction without use of the bulky low-frequency power transformer according to the circuit of the high-frequency converter. It is, actually, standard circuit of pulse SP with tension fall where as entrance tension the straightened mains voltage is used, and as an accumulative element — the high-frequency transformer (small-sized and with high efficiency) from which secondary winding the target stabilized stress (this transformer is removed provides also galvanic outcome with a network).

it is possible to carry font To shortcomings of pulse SP: existence of high level of pulse noise on an exit, high, complexity and low reliability (especially at handicraft manufacturing), need of application of expensive high-voltage high-frequency components which in case of the slightest malfunction easily fail "all in a crowd" (thus. as a rule, it is possible to observe impressing pyrotechnic effects). To fans to rummage in interiors of devices with a screw-driver and a soldering iron when designing network pulse SP it is necessary to be the extremely careful as many elements of such circuits are under a high voltage.

8. The effective pulse stabilizer of low level of complexity

On the element base similar to applied in described above (fig. 3.3-3) the linear stabilizer, it is possible to construct a pulse voltage stabilizer. At the same characteristics it will possess considerably smaller dimensions and the best thermal mode. The schematic diagram of such stabilizer is provided on fig. 3.4-2. The stabilizer is accurate according to the standard circuit with tension fall (fig. 3.4-1a).

At the first inclusion when the C4 condenser is discharged and is connected by sans-serif to an exit rather powerful loading, the current proceeds through IS of the linear DA1 stabilizer. The power failure caused by this current on R1 unlocks the key VT1 transistor which right there enters into a saturation mode as inductive resistance of L1 is great and via the transistor rather big current proceeds. Power failure on R5 opens the basic key element — the VT2 transistor. Current. accruing in L1, charges С4, thus through feedback on R8 there is zapi-

before the stabilizer and the key transistor. The energy reserved in the coil, feeds loading. When tension on С4 falls below tension of stabilization, DA1 and the key transistor opens. The cycle repeats with frequency of 20-30 kHz.

R3 Chain. R4, С2 will set level of target tension. It can be regulated smoothly in small limits, from Ucт DA1 to Uвх. However if Uвых to lift it is closely to Uвх, there is некото paradise an instability at the maximum loading and the raised level of a pulsation. For suppression high-frequency pulsations on an exit of the stabilizer the L2 filter, С5 is switched on.

the Circuit is rather simple and most effective for this level of complexity. All power elements VT1, VT2, VD1, DA1 are supplied with small radiators. Entrance tension of nanosecond should exceed 30 Century that is maximum for Kr142en8 stabilizers. Vypryamitelnye diodes to apply on a current not less than 3 And.

9. The device of an uninterrupted food on the basis of the pulse stabilizer

On fig. 3.4-3 is offered to sans-serif by size to consideration the device for an uninterrupted food of systems of protection and video surveillance on the basis of the pulse stabilizer combined with the charger. Systems of protection against an overload, an overheat, tension throws are entered into the stabilizer on an exit, short circuit.

the Stabilizer has the following parameters:

· • Entrance tension, Uвx — 20-30 In:

· • The target stabilized tension, Uvyx-12B:

· • Rated current of loading, number Iнагр — 5А;

· • A current of operation of system of protection against an overload, Iзащ — 7А;.

· • Tension of operation of system of protection against an overstrain, Uвых защ — 13 In;

· • The maximum current of a charging of joint stock bank, joint stock bank Iзар Max — 0,7 And;

· • Pulsation level. Uпульс — 100 мВ,

· • Temperature of operation of system of protection against an overheat, Tzashch — 120 With;

· • Speed of switching on a food from joint stock bank, tперекл — 10мс (the RES relay - РФО.452.112).

the Principle of operation of the pulse stabilizer in the described device same, as well as at the stabilizer presented above.

the Device is added with the charger executed on the elements DA2, R7, R8, R9, R10, VD2, С7. IS of a voltage stabilizer of DA2 with a current divider on R7. R8 limits the maximum initial current of a charge, the divider of R9, R10 sets target tension of a charge, the VD2 diode protects joint stock bank from the self-category in the absence of supply voltage.

Protection against an overheat uses the R16 thermoresistor as the temperature sensor. At operation of protection the sound signaling device collected on IS DD 1 and, at the same time, loading joins is disconnected from the stabilizer, passing to a food from joint stock bank. The thermoresistor mount on a VT1 transistor radiator. Exact fine tuning of level of operation of temperature protection is carried out by resistance of R18.

the Sensor of tension is accurate on a divider of R13, R15. resistance of R15 establish exact level of operation of protection against an overstrain (13 In). At an overvoltage on a stabilizer exit (in case of an exit of the last out of operation) the S1 relay disconnects loading from the stabilizer and connects it to joint stock bank. In case of shutdown of feeding tension, the S1 relay passes to a condition "by default" - i.e. connects load of joint stock bank.

the circuit Provided here has no electronic protection against short circuit for joint stock bank. this role is carried out by the fuse in the loading power-supply circuit, calculated on the maximum consumed current.

10. Power supplies on the basis of the high-frequency pulse converter

Rather often when designing devices arise rigid requirements to the sizes of the power supply. In this case the unique exit is SP application on the basis of high-voltage high-frequency pulse converters. which are connected to a network ~220 B without use of the dimensional low-frequency lowering transformer and can provide big capacity at the small sizes and heatreturn.

the Block diagram of the standard pulse converter with a food from an industrial network is presented to sans-serif by size on rice 34-4.

the Entrance filter is intended to sans-serif by size for prevention of penetration of pulse hindrances in a network. Power keys provide giving of impulses of a high voltage on primary winding of the high-frequency transformer (can be applied one - and

duple circuits). Frequency and duration of impulses are set by the operated generator (management in width of impulses is usually applied, is more rare — frequency). Unlike transformers of a sinusoidal signal of low frequency, in pulse SP the broadband devices providing effective transfer to capacity on signals with fast fronts are applied. It imposes essential requirements of type applied магнитопровода and a transformer design. On the other hand, with increase in frequency the demanded sizes of the transformer (with preservation of the transferred capacity) decrease (modern materials allow to build powerful transformers with acceptable efficiency on frequencies to 100-400 kHz). Feature of the target rectifier is application in it not ordinary power diodes, and Shottka's high-speed diodes that is caused by high frequency of straightened tension. The target filter smoothes pulsations of target tension. Tension of feedback is compared to basic tension and then operates the generator. Pay attention to existence of a galvanic outcome in a feedback chain that is necessary if we want to provide an outcome of target tension with a network.

When manufacturing such SP arise serious requirements to applied components (that increases their cost in comparison with traditional). First, it concerns working tension of diodes of the rectifier, condensers of the filter and key transistors which less than 350 should not be In in order to avoid breakdowns. Secondly, high-frequency key transistors (working frequency of 20-100 kHz) and special ceramic condensers (usual oksidny electrolits on high frequencies will overheat in view of their high induk-

tivnost) should be applied. And. thirdly, frequency of saturation of the high-frequency transformer, defined by type applied магнитопро water (as a rule, toroidal cores are used) should be much higher than working frequency of the converter.

On fig. 3.4-5 the schematic diagram of classical SP on the basis of the high-frequency converter is provided. The filter consisting of capacities С1, С2, SZ and throttles of L1, L2, serves for are sewn up a power line from high-frequency hindrances from the converter. The generator is constructed according to the self-oscillatory circuit and combined with the key cascade. Key VT1 and VT2 transistors work in an antiphase, opening and being closed in turn. Start of the generator and reliable work are provided by the VT3 transistor working in a mode of avalanche breakdown. At tension increase on С6 through R3 the transistor opens and the condenser is discharged on the VT2 base, starting operation of the generator. Tension of feedback acts in film from an additional (III) winding of the power Tpl transformer.

VT1 Transistors. VT2 establish on lamellar radiators not less than 100 см^2. VD2-VD5 diodes with Shottka's barrier are put on a small radiator 5 см^2. Data of throttles and transformatorov:l1-1. L2 reel up on rings from K12kh8kh3 ferrite 2000НМ in two wires wire ПЭЛШО 0,25: 20 rounds. TP1 — on two rings combined together, KZ 1х18.5х7 ferrite 2000НН;

winding of 1 — 82 round wire PEV-2 0,5: a winding of II — 25+25 rounds a wire PEV-2 1,0: a winding of III — 2 rounds a wire PEV-2 0.3. TP2 reel up on a ring from K10kh6kh5 ferrite 2000НН. all windings are executed by a wire PEV-2 0.3: winding of 1 — 10 rounds:

windings of II and III — on 6 rounds, both windings (and III) are reeled up by II so that borrow on a ring on 50 % of the area without concerning and without blocking each other, the winding of I is reeled up evenly on all ring and isolated by a layer лакоткани. Coils of the filter of the rectifier L3, L4 reel up on ferrite 2000НМ K 12х8х3 a wire PEV-2 1,0, quantity of rounds — 30. As key transistors VT1, VT2 can be applied КТ809А. КТ812, КТ841.

Face values of elements and namotochny data of transformers are given by sans-serif for target tension of 35 Century. In a case when other working values of parameters are required, it is necessary a sootvetstvo to change in a yushchy way quantity of rounds in a winding of 2 Tr1.

the Described circuit has the essential shortcomings caused by aspiration to minimize quantity of the applied This components and low "level of stabilization of target tension, and unstable unreliable work, and a low target current. However it is quite suitable for a food of the elementary designs of different capacity (at application of the corresponding components), such as: calculators. AONY. lighting devices, etc.

One more circuit of SP on the basis of the high-frequency pulse converter is provided by sans-serif on fig. 3.4-6. The main difference of this circuit from the standard structure presented on fig. 3.4-4 is lack of a chain of feedback. In this regard, stability of tension on target windings of VCh of the Tr2 transformer rather low also is required use of secondary stabilizers (in the circuit universal integrated stabilizers on KP142 series IS are used).

11. Pulse the stabilizer with key MDP-tranzistorom with current reading.

to Miniaturization and efficiency increase when developing and designing pulse power supplies promotes sans-serif application of a new class of semi-conductor inverters — MDP-tranzistorov, and also: powerful diodes with fast return restoration, Shottka's diodes, ultrafast diodes, field transistors with the isolated lock, integrated circuits of management of key elements. All these elements are available in the domestic market and can be used in designing of highly effective power supplies, converters, systems of ignition of internal combustion engines (DVS), systems of start of fluorescent lamps (LDS). The great interest also can cause a class of power devices in developers under the name HEXSense — MDP-tranzistory with current reading. They are ideal switching elements for pulse power supplies with ready management. Possibility read out a current of the key transistor can to be used in pulse SP for feedback on a current, pulse-width modulation demanded for the controler. It reaches simplification of a design of the power supply — an exception of it those resistors and transformers.

On fig. 3.4-7 is given by sans-serif the circuit of the pulse power supply in capacity of 230 W. Its main performance data following:

· • Entrance napryazheniye:-110 In 60Гц:

· • Target tension: 48 In the constant:

· • Loading current: 4.8 А:

· • Frequency of switching: 110 kHz:

· • Kpdpri to full loading : 78 %;

· • Efficiency at loading 1/3: 83 %.

the Circuit is constructed by sans-serif on the basis of the pulse-width modulator (ShIM) with the high-frequency converter on an exit. The principle of work consists in the following.

the Signal of management of the key transistor arrives from an exit of 6 ShIM of the DA1 controler, the factor of filling is limited 50 % to the resistor R4, R4 and SZ are времязадающи ми generator elements. A food of DA1 is provided with VD5 chain, С5, С6, R6. The R6 resistor is intended for giving of feeding tension during generator start, in the subsequent start ствуется feedback on tension through LI, VD5. This feedback turns out from an additional winding of a target throttle which works in a mode of reverse motion. Besides a generator food, tension of feedback through a chain of VD4, Cl, Rl, R2 moves on a feedback entrance on tension of DA1 (выв.2). Through R3 and С2 compensation which guarantees stability of a loop of feedback is provided.

as the key element VT2 is used by sans-serif MDP-tranzistor with reading of a current of IRC830 of International Rectifier firm. The signal of reading of a current moves from VT2 on a conclusion of 3 DA1. Tension level on a conclusion of reading of a current is set by the R7 resistor and is proportional to a drain current, С9 suppresses emissions on the forward front of an impulse of a current of a drain which can cause premature operation of the controler. VT1 and R5 are used for a task of the necessary law of management. Pay attention that the current of reading comes back to a crystal on a source conclusion. It becomes for this purpose. to avoid an error of reading of a current which can arise because of power failure on parasitic resistance of a conclusion of a source.

on the basis of this circuit possibly creation of pulse stabilizers and with other target parameters.

12. Modern gas-discharge devices

About 25 % of the electric power developed in the world, are spent by systems of artificial lighting, чтo does this area extremely attractive to application of forces in the field of increase of efficiency of use and electricity consumption reduction.

the most widespread economic light sources are Now gas-discharge lamps which are even more often applied instead of ordinary filament lamps. The principle of action of such lamps is in a luminescent luminescence of the gas concluded in a lamp at current course through it (implementation of high-voltage breakdown) that is provided with giving of a high voltage on lamp electrodes. Gas-discharge lamps can be divided into two look, the first — is lamps of high intensity of a luminescence among which are most widespread: mercury lamps, sodium lamps of a high pressure and the metalhalogen lamps, the second look — it is luminescent lamps of low pressure.

Lamps of low pressure are used by sans-serif for lighting in most cases an everyday life — in office buildings, offices, houses: they are distinguished by saturated this world. close to day (from here the name — "fluorescent lamps"). Lamps of a high pressure are used for external lighting — in streetlights, searchlights, etc.

If the ordinary filament lamp when it is included, represents constant resistive loading, all gas-discharge lamps have negative impedance characteristics. which demand current stabilization. Besides, it is necessary to consider such moments as: a resonant operating mode, protection at a lamp exit out of operation; high-voltage ignition, special management of the power tire. The main mode, which observance it is necessary for a luminescent lamp throughout all term of operation — it is a tokovy mode (in an ideal, it is necessary capacity stabilization throughout the entire period ekspluata- to

lamp tsiya). As a rule, lamps eat from an alternating voltage for equalizing of wear of electrodes (in case of a food by constant tension, service life is shorter for 50 %).

13. Magnetic and electronic ballasts

For management of gas-discharge lamps was traditionally used by sans-serif a so-called magnetic ballast (see the circuit on fig. 3.5-1), however in view of its inefficiency and unreliability, recently

the increasing distribution receive circuits of electronic control — an electronic ballast which allows to increase considerably efficiency and service life of lighting systems to make light more equal and natural to eyes.

the Base circuit of an electronic ballast with a consecutive resonance is provided by sans-serif on fig. 3.5-2. Applying electronic ballasts, it is possible to operate lamps of any capacity, it is possible to build in any additional devices the circuit (for example, the photorelay which is switching on lighting in twilight and switching off at a dawn).

14. The management circuit for a fluorescent lamp in capacity to 40Вт

to 40 W is intended to sans-serif by size For management of a fluorescent lamp (LDS) in capacity the circuit provided on fig. 3.5-3.

the Supply voltage ~220 In moves on L1 and L2 entrances. Straightened by VD1 diodes - VD4 constant tension makes about 320 V.Kondensatory S1 i S2 work as the capacitor entrance filter. Use and networks ~110В is possible, in this case a food moves on entrances of L1 (L2) and N. and VD1 diodes. VD3 (VD2, VD4) with condensers C1 and С2 work as однопо a luperiodny doubler of tension.

DA1 (IR2151) — is the circuit of management MDP-tranzistora ми with the internal generator which works directly from the food tire through R1. The internal stabilizer fixes supply voltage at 15 V.Predusmotrena's level blocking of locks at power failure below 9 Century.

At rated constant voltage of the tire of a food 230 In a target rectangular impulse has effective tension 160 In, and frequency is established by selection of R2 and С4 for approach to resonant frequency of a lamp. The lamp works in the consecutive resonant circuit consisting of consistently switched on coil of inductance of L1 and the shunting C6 condenser which costs parallel to the termistor with positive temperature factor.

Termistor (for these purposes the neon bulb can be used also) has small resistance in a cold condition and very high in hot when heats up thanks to a current proceeding through it. Purpose of a termistor — to provide smooth increase of tension on lamp electrodes at inclusion. In cases when the lamp burns constantly or very seldom

joins/is switched off by sans-serif, the termistor can be cleaned. In this case the lamp joins instantly that can result in its fast wear.

15. The supertiny circuit of management for a fluorescent lamp in capacity to 26Вт

the Following schematic diagram provided on fig. 3.5-4, allows to operate a fluorescent lamp (LDS), having thus the supertiny sizes as in it power inverters (are not applied by IS IR51H420 unites in one IS IR2151 case and MDP-klyuchi). The maximum capacity of a lamp in this case should not exceed 26 W of that it is quite enough for illumination of one workplace.

16. RAISING CONVERTERS AND TENSION MULTIPLIERS

Usually if in a design there is a network food, for receiving all feeding tension use transformers. Raising converters and multipliers of tension are applied, when it is necessary to receive tension big, than supply voltages in the nosimy devices fed from batteries or accumulators. Converters of low power (to 100-200 MWt) can be collected on discrete elements without use of transformers, in converters of big capacity the transformer is necessary. For obtaining the doubled or trebled tension it is possible to use so-called multipliers of tension (see chapter 2).

17. The Bestransformatorny doubler of tension for small-sized devices

On fig. 3.6-1 is given by sans-serif the circuit of the converter of tension 9 In -> 18В for the devices consuming no more than 100 мА at supply voltage 18В. The converter is given in structure of the practical circuit of a siren for protection and alarm system systems.

the Generator of management is executed by sans-serif according to the standard circuit. On an exit of D 1.2 rectangular impulses with frequency of 1 Hz are formed. Impulses arrive on the operated generator Dl.3, D1.4 and a chain of R3, R2, С2 which influences depth of modulation. R4, R5, SZ, С4 steal up according to resonant frequency пьезо a ceramic radiator In 1 within 1,5-3 kHz. For amplitude increase on a piezocrystal the multiplier is entered into the circuit. The signal from an exit of DD1.4 arrives on complementary to steam VT5, VT6 and further on the multiplier VD3, VD4, С5, Sb. Tension on С6 at a current of loading 50 мА and the main food 9 In makes about 16 V.Moshchnost of the multiplier it is possible to increase a little, having applied capacities of bigger face value. It is possible to feed the circuit with tension 6-15 In (15 In — the maximum for series 561 IS), in case of 15 In a food, tension on an exit of the multiplier will make nanosecond less than 25 In at loading 80 мА.

In this design amplitude on a crystal пьезоэлемен that will be quadruple, considering that it is included in an antiphase, concerning shoulders of transistors VT1, VT3. As a radiator the developed ceramic plate with a bilateral covering, so-called триморф with diameter of a crystal of 32 mm is used specially for these purposes.

18. The powerful converter for a food of electrical household appliances

On fig. 3.6-2 the schematic diagram of the powerful converter for a food of electrical household appliances (the TV, a drill, the electropump etc.) is provided from the automobile accumulator. The converter provides a target voltage of 220 V, 50 Hz on loading in capacity to 100 W. At the maximum loading the current consumed from the accumulator does not exceed 10 And.

the Quantity of details in the device is minimized by sans-serif. On a chip of DD1.1 the setting generator with frequency of 100 Hz is accurate. Exact control of frequency (that is important for normal work of equipment) carry out R1 and R2 resistors. Division of frequency on 2 and management of transistors are provided with the second half of a chip — D1.2. Transistors VT1, VT2 are switched on for providing a normal operating mode of exits of DD1.2 at the maximum current of loading. Target transistors VT3, VT4 are established on the radiators, which area not less than 350 см^2.

is intended to sans-serif For smoothing of rectangular fronts the SZ condenser which together with a target winding and loading forms resonant system. Its capacity strongly depends on character of loading. The TP1 transformer is executed on магнитопро to water of ShLM or PLM brand of dimensional capacity of 100 W. Windings of I and II contain on 17 rounds of wire PEV-2 2,0мм, the winding of III contains 750 rounds of wire PEV-2 0,7мм.

This circuit it is very easy to process font under the high-frequency converter of tension (frequency of transformation of ~25 kHz). For this purpose it is enough to lift frequency of the setting generator on D1.1 to-50 kHz, having changed capacities С1 and С2 on 180 пФ, and to replace TP1 with the high-frequency transformer. The capacity of the converter depends on loading of target transistors, the maximum current which they can give nanosecond should exceed 8А in a shoulder. For increase in a current the quantity of rounds of the transformer in 1 and the II windings decreases till 8-10. On an exit of the converter the diode bridge and VCh-filtr is established, components applied in them should provide normal work on frequency of 25 kHz.

19. PROTECTION AGAINST EXCESS of MAINS VOLTAGE

In an industrial and household network quite often can fix unforeseen throws of tension, thus tension in a network can exceed nominal for 20-40 %. Such throws can be divided into two classes:

1. Short-term — increase in amplitude within several periods.

2. Long — increase in tension within several seconds or minutes.

the First can be carried p rather to pulse hindrances that is connected with switching on lines of any powerful loadings (welding devices, engines, heating elements). They, undoubtedly, influence household appliances and, especially, on sensitive elements of power supplies of TVs, the audiocenters. which often there are in a mode on duty day and night.

20. The device of protection against pulse hindrances in a network

the Device protecting from pulse hindrances, is shown on fig. 3.7-1. The circuit consists of the following knots:

· • the power supply — VD1-VD4, R6, R7, VD5, VD7, Cl, C2;

· • the sensor comparator — Rl, R2, R3, R4, R5, HL1, VD8, DA1, R8, R9;

· • the dumping shaper with a delay on switching off — VD9, R10, DD1.1, DD1.2, VD10, R11, SZ;

· • the generator of impulses of high frequency of 25 kHz for management of a simmistor — DD 1.3, DD1.4, R 12, R 13, С4, С5, R14, TP1, VS1.

· • a sound signaling device (it is carried out at will) —

R14, R15, C6, C7, HA1, DD2.

the Power supply develops two tension: +24 In — for a food of the pulse transformer, +5 In — for a food of IS of the device.

the Knot of control of tension is accurate on Rl, R2, R3. From a divider tension arrives on a comparator entrance. Operation level on an overvoltage is established by the R2 resistor (the provision of a cursor steals up so that the comparator was on the verge of operation at 245 In on an entrance). At превysheniya on an entrance of the comparator of the set peak value it is switched and on an exit there are rectangular impulses with frequency of 25 Hz.

In an initial condition on an exit of D1.2 is supported by font the high logic level allowing operation of the generator of management of a simmistor (for its maintenance abroach). The VT1 transistor operates the pulse transformer. forming powerful impulses of tension open. Frequency of the generator is chosen equal 25 kHz for the fastest unlocking of a power key during the transition moments through "zero" (if frequency of management is insufficient, can happen so that when during inclusion there will be high-voltage emissions and the form of a sinusoidal signal will be distorted, the system will not manage to react and the distorted signal will arrive on loading).

the Differentiating chain on the elements D1.1 and D1.2 carries out a ban of operation of the generator at receipt of low level from a comparator exit (at increase of threshold tension in a network) and with a delay in 9с allows generator start when tension will decrease to threshold value of 240 Century

the Pulse TP1 transformer is reeled up on матнитопро to water of standard size К20х10х7,5 from ferrite of brand 2000НН and contains: a winding of I — 100 rounds, a winding of II — 40 rounds of wire PELShO-0,22. Windings isolate from a ring a layer лакоткани and place on the opposite sides of a ring. At loading capacity more than 300 W a simmistor it is necessary for font to establish p to

on a radiator.

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