The operation of almost any electronic circuit requires the presence of one or more constant voltage sources, and in the vast majority of cases a stabilized voltage is used. Stabilized power supplies use either linear or switching stabilizers. Each type of converter has its own advantages and, accordingly, its own niche in power supply circuits. The undoubted advantages of switching stabilizers include higher efficiency values, the ability to obtain high output current values ​​and high efficiency with a large difference between the input and output voltages.

The operating principle of a buck pulse stabilizer

Figure 1 shows a simplified diagram of the power section of the IPSN.

Rice. 1.

Field effect transistor VT performs high-frequency current switching. In pulse stabilizers, the transistor operates in switching mode, that is, it can be in one of two stable states: full conduction and cutoff. Accordingly, the operation of the IPSN consists of two alternating phases - the energy pumping phase (when the VT transistor is open) and the discharge phase (when the transistor is closed). The operation of the IPSN is illustrated in Figure 2.

Rice. 2. Operating principle of IPSN: a) pumping phase; b) discharge phase; c) timing diagrams

The energy pumping phase continues throughout the time interval T I. During this time, the switch is closed and conducts current I VT. Next, the current passes through the inductor L to the load R, shunted by the output capacitor C OUT. In the first part of the phase, the capacitor supplies current I C to the load, and in the second half, it takes part of the current I L from the load. The magnitude of the current I L continuously increases, and energy is accumulated in the inductor L, and in the second part of the phase - on the capacitor C OUT. The voltage across the diode V D is equal to U IN (minus the voltage drop across the open transistor), and the diode is closed during this phase - no current flows through it. The current I R flowing through the load R is constant (the difference I L - I C), accordingly, the voltage U OUT at the output is also constant.

The discharge phase occurs during the time T P: the switch is open and no current flows through it. It is known that the current flowing through the inductor cannot change instantly. The current IL, constantly decreasing, flows through the load and closes through the diode V D. In the first part of this phase, the capacitor C OUT continues to accumulate energy, taking part of the current I L from the load. In the second half of the discharge phase, the capacitor also begins to supply current to the load. During this phase, the current I R flowing through the load is also constant. Therefore, the output voltage is also stable.

Main settings

First of all, we note that according to their functional design, they distinguish between IPSN with adjustable and fixed output voltage. Typical switching circuits for both types of IPSN are presented in Figure 3. The difference between them is that in the first case, the resistor divider, which determines the value of the output voltage, is located outside the integrated circuit, and in the second, inside. Accordingly, in the first case, the value of the output voltage is set by the user, and in the second, it is set during the manufacture of the microcircuit.

Rice. 3. Typical switching circuit for IPSN: a) with adjustable and b) with fixed output voltage

The most important parameters of IPSN include:

• Range of permissible input voltage values ​​U IN_MIN…U IN_MAX.
• The maximum value of the output current (load current) I OUT_MAX.
• Nominal value of the output voltage U OUT (for IPSN with a fixed output voltage value) or range of output voltage values ​​U OUT_MIN ...U OUT_MAX (for IPSN with an adjustable output voltage value). Often reference materials indicate that the maximum value of the output voltage U OUT_MAX is equal to the maximum value of the input voltage U IN_MAX. In reality this is not entirely true. In any case, the output voltage is less than the input voltage, at least by the amount of voltage drop across the key transistor U DROP. With an output current value equal to, for example, 3A, the value of U DROP will be 0.1...1.0V (depending on the selected IPSN microcircuit). Approximate equality of U OUT_MAX and U IN_MAX is possible only at very low load current values. Note also that the process of stabilizing the output voltage itself involves a loss of several percent of the input voltage. The declared equality of U OUT_MAX and U IN_MAX should be understood only in the sense that there are no other reasons for reducing U OUT_MAX other than those indicated above in a specific product (in particular, there are no explicit restrictions on the maximum value of the fill factor D). The value of the feedback voltage U FB is usually indicated as U OUT_MIN. In reality, U OUT_MIN should always be several percent higher (for the same stabilization reasons).
• Accuracy of output voltage setting. Set as a percentage. It makes sense only in the case of IPSN with a fixed output voltage value, since in this case the voltage divider resistors are located inside the microcircuit, and their accuracy is a parameter controlled during manufacturing. In the case of IPSN with an adjustable output voltage value, the parameter loses its meaning, since the accuracy of the divider resistors is selected by the user. In this case, we can only talk about the magnitude of the output voltage fluctuations relative to a certain average value (the accuracy of the feedback signal). Let us recall that in any case, this parameter for switching voltage stabilizers is 3...5 times worse compared to linear stabilizers.
• Voltage drop across open transistor R DS_ON. As already noted, this parameter is associated with an inevitable decrease in the output voltage relative to the input voltage. But something else is more important - the higher the resistance value of the open channel, the more energy is dissipated in the form of heat. For modern IPSN microcircuits, values ​​up to 300 mOhm are a good value. Higher values ​​are typical for chips developed at least five years ago. Note also that the value of R DS_ON is not a constant, but depends on the value of the output current I OUT.
• Duty cycle duration T and switching frequency F SW. The duration of the working cycle T is determined as the sum of the intervals T I (pulse duration) and T P (pause duration). Accordingly, the frequency F SW is the reciprocal of the operating cycle duration. For some part of the IPSN, the switching frequency is a constant value determined by the internal elements of the integrated circuit. For another part of the IPSN, the switching frequency is set by external elements (usually an external RC circuit), in this case the range of permissible frequencies F SW_MIN ... F SW_MAX is determined. A higher switching frequency allows the use of chokes with a lower inductance value, which has a positive effect on both the dimensions of the product and its price. Most ISPS use PWM control, that is, the T value is constant, and during the stabilization process the T I value is adjusted. Pulse frequency modulation (PFM control) is used much less frequently. In this case, the value of T I is constant, and stabilization is carried out by changing the duration of the pause T P. Thus, the values ​​of T and, accordingly, F SW become variable. In reference materials in this case, as a rule, a frequency is specified corresponding to a duty cycle equal to 2. Note that the frequency range F SW_MIN ...F SW_MAX of an adjustable frequency should be distinguished from the tolerance gate for a fixed frequency, since the tolerance value is often indicated in reference materials manufacturer.
• Duty factor D, which is equal to the percentage
  the ratio of T I to T. Reference materials often indicate “up to 100%”. Obviously, this is an exaggeration, since if the key transistor is constantly open, then there is no stabilization process. In most models released on the market before approximately 2005, due to a number of technological limitations, the value of this coefficient was limited above 90%. In modern IPSN models, most of these limitations have been overcome, but the phrase “up to 100%” should not be taken literally.
• Efficiency factor (or efficiency). As is known, for linear stabilizers (fundamentally step-down) this is the percentage ratio of the output voltage to the input, since the values ​​of the input and output current are almost equal. For switching stabilizers, the input and output currents can differ significantly, so the percentage ratio of output power to input power is taken as efficiency. Strictly speaking, for the same IPSN microcircuit, the value of this coefficient can differ significantly depending on the ratio of the input and output voltages, the amount of current in the load and the switching frequency. For most IPSN, maximum efficiency is achieved at a load current value of the order of 20...30% of the maximum permissible value, so the numerical value is not very informative. It is more advisable to use the dependence graphs that are provided in the manufacturer’s reference materials. Figure 4 shows efficiency graphs for a stabilizer as an example. . Obviously, using a high-voltage stabilizer at low actual input voltage values ​​is not a good solution, since the efficiency value drops significantly as the load current approaches its maximum value. The second group of graphs illustrates the more preferable mode, since the efficiency value weakly depends on fluctuations in the output current. The criterion for the correct choice of a converter is not so much the numerical value of the efficiency, but rather the smoothness of the graph of the function of the current in the load (the absence of a “blockage” in the region of high currents).

Rice. 4.

The given list does not exhaust the entire list of IPSN parameters. Less significant parameters can be found in the literature.

Special Features
pulse voltage stabilizers

In most cases, IPSN have a number of additional functions that expand the possibilities of their practical application. The most common are the following:

• The “On/Off” or “Shutdown” load shutdown input allows you to open the key transistor and thus disconnect the voltage from the load. As a rule, it is used for remote control of a group of stabilizers, implementing a certain algorithm for applying and turning off individual voltages in the power supply system. In addition, it can be used as an input for emergency power off in case of an emergency.
• Normal state output “Power Good” is a generalizing output signal confirming that the IPSN is in normal operating condition. The active signal level is formed after the completion of transient processes from the supply of input voltage and, as a rule, is used either as a sign of the serviceability of the ISPN, or to trigger the following ISPN in serial power supply systems. The reasons why this signal can be reset: the input voltage drops below a certain level, the output voltage goes beyond a certain range, the load is turned off by the Shutdown signal, the maximum current value in the load is exceeded (in particular, the fact of a short circuit), temperature shutdown of the load and some other. The factors that are taken into account when generating this signal depend on the specific IPSN model.
• The external synchronization pin “Sync” provides the ability to synchronize the internal oscillator with an external clock signal. Used to organize joint synchronization of several stabilizers in complex power supply systems. Note that the frequency of the external clock signal does not have to coincide with the natural frequency of the FSW, however, it must be within the permissible limits specified in the manufacturer’s materials.
• The Soft Start function provides a relatively slow increase in output voltage when voltage is applied to the input of the IPSN or when the Shutdown signal is turned on at the falling edge. This function allows you to reduce current surges in the load when the microcircuit is turned on. The operating parameters of the soft start circuit are most often fixed and determined by the internal components of the stabilizer. Some IPSN models have a special Soft Start output. In this case, the startup parameters are determined by the ratings of external elements (resistor, capacitor, RC circuit) connected to this pin.
• Temperature protection is designed to prevent chip failure if the crystal overheats. An increase in the temperature of the crystal (regardless of the reason) above a certain level triggers a protective mechanism - a decrease in the current in the load or its complete shutdown. This prevents further rise in die temperature and damage to the chip. Returning the circuit to voltage stabilization mode is possible only after the microcircuit has cooled. Note that temperature protection is implemented in the vast majority of modern IPSN microcircuits, but a separate indication of this particular condition is not provided. The engineer will have to guess for himself that the reason for the load shutdown is precisely the operation of the temperature protection.
• Current protection consists of either limiting the amount of current flowing through the load or disconnecting the load. The protection is triggered if the load resistance is too low (for example, there is a short circuit) and the current exceeds a certain threshold value, which can lead to failure of the microcircuit. As in the previous case, diagnosing this condition is the concern of the engineer.

One last note regarding the parameters and functions of the IPSN. In Figures 1 and 2 there is a discharge diode V D. In fairly old stabilizers, this diode is implemented precisely as an external silicon diode. The disadvantage of this circuit solution was the high voltage drop (approximately 0.6 V) across the diode in the open state. Later designs used a Schottky diode, which had a voltage drop of approximately 0.3 V. In the last five years, designs have used these solutions only for high-voltage converters. In most modern products, the discharge diode is made in the form of an internal field-effect transistor operating in antiphase with the key transistor. In this case, the voltage drop is determined by the resistance of the open channel and at low load currents gives an additional gain. Stabilizers using this circuit design are called synchronous. Please note that the ability to operate from an external clock signal and the term “synchronous” are not related in any way.

with low input voltage

Considering the fact that in the STMicroelectronics range there are approximately 70 types of IPSN with a built-in key transistor, it makes sense to systematize all the diversity. If we take as a criterion a parameter such as the maximum value of the input voltage, then four groups can be distinguished:

1. IPSN with low input voltage (6 V or less);

2. IPSN with input voltage 10…28 V;

3. IPSN with input voltage 36…38 V;

4. IPSN with high input voltage (46 V and above).

The parameters of stabilizers of the first group are given in Table 1.

Table 1. IPSN with low input voltage

Name	Exit current, A	Input voltage, V		Day off voltage, V		Efficiency, %	Switching frequency, kHz		Functions and flags
	I OUT	V IN		V OUT		h	FSW	R DSON	On/Off	Sync. Pin	Soft Start	Pow Good
	Max	Min	Max	Min	Max	Max	Type
L6925D	0,8	2,7	5,5	0,6	5,5	95	600	240	+	+	+	+
L6926	0,8	2,0	5,5	0,6	5,5	95	600	240	+	+	+	+
L6928	0,8	2,0	5,5	0,6	5,5	95	1450	240	+	+	+	+
PM8903A	3,0	2,8	6,0	0,6	6,0	96	1100	35	+	+	+	+
ST1S06A	1,5	2,7	6,0	0,8	5,0	92	1500	150	+	–	+	–
ST1S09	2,0	4,5	5,5	0,8	5,0	95	1500	100	*	–	+	+
ST1S12	0,7	2,5	5,5	0,6	5,0	92	1700	250	+		+	–
ST1S15	0,5	2,3	5,5	Fix. 1.82 and 2.8 V		90	6000	350	+	–	+	–
ST1S30	3,0	2,7	6,0	0,8	5,0	85	1500	100	*	–	+	+
ST1S31	3,0	2,8	5,5	0,8	5,5	95	1500	60	+	–	+	–
ST1S32	4,0	2,8	5,5	0,8	5,5	95	1500	60	+	–	+	–
* – the function is not available for all versions.

Back in 2005, the line of stabilizers of this type was incomplete. It was limited to microcircuits. These microcircuits had good characteristics: high accuracy and efficiency, no restrictions on the duty cycle value, the ability to adjust the frequency when operating from an external clock signal, and an acceptable RDSON value. All this makes these products in demand today. A significant drawback is the low maximum output current. There were no stabilizers for load currents of 1 A and higher in the line of low-voltage IPSN from STMicroelectronics. Subsequently, this gap was eliminated: first, stabilizers for 1.5 and 2 A ( and ) appeared, and in recent years - for 3 and 4 A ( , And ). In addition to increasing the output current, the switching frequency has increased and the open channel resistance has decreased, which has a positive effect on the consumer properties of the final products. We also note the emergence of IPSN microcircuits with a fixed output voltage ( and ) - there are not very many such products in the STMicroelectronics line. The latest addition, with an RDSON value of 35 mOhm, is one of the best in the industry, which, combined with extensive functionality, promises good prospects for this product.

The main application area for products of this type is battery-powered mobile devices. A wide input voltage range ensures stable operation of the equipment at different battery charge levels, and high efficiency minimizes the conversion of input energy into heat. The latter circumstance determines the advantages of switching stabilizers over linear ones in this area of ​​user applications.

In general, this group of STMicroelectronics is developing quite dynamically - approximately half of the entire line has appeared on the market in the last 3-4 years.

Switching buck stabilizers
with input voltage 10…28 V

The parameters of the converters of this group are given in Table 2.

Table 2. IPSN with input voltage 10…28 V

Name	Exit current, A	Input voltage, V		Day off voltage, V		Efficiency, %	Switching frequency, kHz	Open channel resistance, mOhm	Functions and flags
	I OUT	V IN		V OUT		h	FSW	R DSON	On/Off	Sync. Pin	Soft Start	Pow Good
	Max	Min	Max	Min	Max	Max	Type
L5980	0,7	2,9	18,0	0,6	18,0	93	250…1000	140	+	+	+	–
L5981	1,0	2,9	18,0	0,6	18,0	93	250…1000	140	+	+	+	–
L5983	1,5	2,9	18,0	0,6	18,0	93	250…1000	140	+	+	+	–
L5985	2,0	2,9	18,0	0,6	18,0	93	250…1000	140	+	+	+	–
L5986	2,5	2,9	18,0	0,6	18,0	93	250…1000	140	+	+	+	–
L5987	3,0	2,9	18,0	0,6	18,0	93	250…1000	140	+	+	+	–
L5988D	4,0	2,9	18,0	0,6	18,0	95	400…1000	120	+	+	+	–
L5989D	4,0	2,9	18,0	0,6	18,0	95	400…1000	120	+	–	+	+
L7980	2,0	4,5	28,0	0,6	28,0	93	250…1000	160	+	+	+	–
L7981	3,0	4,5	28,0	0,6	28,0	93	250…1000	160	+	+	+	–
ST1CC40	2,0	3,0	18,0	0,1	18,0	n.d.	850	95	+	–	+	–
ST1S03	1,5	2,7	16,0	0,8	12,0	79	1500	280	–	–	+	–
ST1S10	3,0	2,7	18,0	0,8	16,0	95	900	120	+	+	+	–
ST1S40	3,0	4,0	18,0	0,8	18,0	95	850	95	+	–	+	–
ST1S41	4,0	4,0	18,0	0,8	18,0	95	850	95	+	–	+	–
ST763AC	0,5	3,3	11,0	Fix. 3.3		90	200	1000	+	–	+	–

Eight years ago this group was represented only by microcircuits , and with input voltage up to 11 V. The range from 16 to 28 V remained empty. Of all the listed modifications, only , but the parameters of this IPSN poorly correspond to modern requirements. We can assume that during this time the nomenclature of the group under consideration has been completely updated.

Currently, the base of this group is microcircuits . This line is designed for the entire range of load currents from 0.7 to 4 A, provides a full set of special functions, the switching frequency is adjustable within a fairly wide range, there are no restrictions on the duty cycle, the efficiency and open-channel resistance values ​​meet modern requirements. There are two significant disadvantages in this series. Firstly, there is no built-in discharge diode (except for microcircuits with the D suffix). The accuracy of output voltage regulation is quite high (2%), but the presence of three or more external elements in the feedback compensation circuit cannot be considered an advantage. The microcircuits differ from the L598x series only in a different input voltage range, but the circuit design, and, consequently, the advantages and disadvantages are similar to the L598x family. As an example, Figure 5 shows a typical connection circuit for a three-amp microcircuit. There is also a discharge diode D and compensation circuit elements R4, C4 and C5. The F SW and SYNCH inputs remain free, therefore, the converter operates from an internal oscillator with the default frequency F SW.

1.7.4. Switching stabilizer circuit

The switching stabilizer circuit is not much more complicated than a conventional one (Fig. 1.9), but it is more difficult to configure. Therefore, for insufficiently experienced radio amateurs who do not know the rules of working with high voltage (in particular, never work alone and never adjust a switched-on device with both hands - only one!), I do not recommend repeating this scheme.

In Fig. Figure 1.9 shows the electrical circuit of a pulse voltage stabilizer for charging cell phones.

The circuit is a blocking oscillator implemented on transistor VT1 and transformer T1. Diode bridge VD1 rectifies the alternating mains voltage, resistor R1 limits the current pulse when turned on, and also serves as a fuse. Capacitor C1 is optional, but thanks to it the blocking generator operates more stably, and the heating of transistor VT1 is slightly less (than without C1).

When the power is turned on, transistor VT1 opens slightly through resistor R2, and a small current begins to flow through winding I of transformer T1. Thanks to inductive coupling, current also begins to flow through the remaining windings. At the upper (according to the diagram) terminal of winding II there is a small positive voltage, through the discharged capacitor C2 it opens the transistor even more strongly, the current in the transformer windings increases, and as a result the transistor opens completely, to a state of saturation.

After some time, the current in the windings stops increasing and begins to decrease (transistor VT1 is completely open all this time). The voltage on winding II decreases, and through capacitor C2 the voltage at the base of transistor VT1 decreases. It begins to close, the voltage amplitude in the windings decreases even more and changes polarity to negative. Then the transistor turns off completely. The voltage on its collector increases and becomes several times higher than the supply voltage (inductive surge), however, thanks to the chain R5, C5, VD4, it is limited to a safe level of 400...450 V. Thanks to the elements R5, C5, generation is not completely neutralized, and after some time the polarity of the voltage in the windings changes again (according to the principle of operation of a typical oscillating circuit). The transistor begins to open again. This continues indefinitely in a cyclical mode.

The remaining elements of the high-voltage part of the circuit assemble a voltage regulator and a unit for protecting transistor VT1 from overcurrent. Resistor R4 in the circuit under consideration acts as a current sensor. As soon as the voltage drop across it exceeds 1...1.5 V, transistor VT2 will open and close the base of transistor VT1 to the common wire (forcefully close it). Capacitor C3 speeds up the reaction of VT2. Diode VD3 is necessary for normal operation of the voltage stabilizer.

The voltage stabilizer is assembled on one chip - an adjustable zener diode DA1.

To galvanically isolate the output voltage from the mains voltage, optocoupler VO1 is used. The operating voltage for the transistor part of the optocoupler is taken from winding II of transformer T1 and smoothed by capacitor C4. As soon as the voltage at the output of the device becomes greater than the nominal one, current will begin to flow through the zener diode DA1, the optocoupler LED will light up, the collector-emitter resistance of the phototransistor VO 1.2 will decrease, the transistor VT2 will open slightly and reduce the voltage amplitude at the base of VT1. It will open weaker, and the voltage on the transformer windings will decrease. If the output voltage, on the contrary, becomes less than the nominal voltage, then the phototransistor will be completely closed and the transistor VT1 will “swing” at full strength. To protect the zener diode and LED from current overloads, it is advisable to connect a resistor with a resistance of 100...330 Ohms in series with them.

Setting up

First stage: It is recommended to connect the device to the network for the first time using a 25 W, 220 V lamp, and without capacitor C1. The resistor R6 slider is set to the bottom (according to the diagram) position. The device is turned on and off immediately, after which the voltages on capacitors C4 and C6 are measured as quickly as possible. If there is a small voltage across them (according to the polarity!), then the generator has started, if not, the generator does not work, you need to look for errors on the board and installation. In addition, it is advisable to check transistor VT1 and resistors R1, R4.

If everything is correct and there are no errors, but the generator does not start, swap the terminals of winding II (or I, but not both at once!) and check the functionality again.

Second phase: turn on the device and control with your finger (not the metal pad for the heat sink) the heating of transistor VT1, it should not heat up, the 25 W light bulb should not light up (the voltage drop across it should not exceed a couple of volts).

Connect some small low-voltage lamp to the output of the device, for example, rated for a voltage of 13.5 V. If it does not light, swap the terminals of winding III.

And at the very end, if everything works fine, check the functionality of the voltage regulator by rotating the slider of the trimming resistor R6. After this, you can solder in capacitor C1 and turn on the device without a current-limiting lamp.

The minimum output voltage is about 3 V (the minimum voltage drop at the DA1 pins exceeds 1.25 V, at the LED pins - 1.5 V).

If you need a lower voltage, replace the zener diode DA1 with a resistor with a resistance of 100...680 Ohms. The next setup step requires setting the device output voltage to 3.9...4.0 V (for a lithium battery). This device charges the battery with an exponentially decreasing current (from about 0.5 A at the beginning of the charge to zero at the end (for a lithium battery with a capacity of about 1 A/h this is acceptable)). In a couple of hours of charging mode, the battery gains up to 80% of its capacity.

About details

A special design element is a transformer.

The transformer in this circuit can only be used with a split ferrite core. The operating frequency of the converter is quite high, so only ferrite is needed for transformer iron. And the converter itself is single-cycle, with constant magnetization, so the core must be split, with a dielectric gap (one or two layers of thin transformer paper are laid between its halves).

It is best to take a transformer from an unnecessary or faulty similar device. In extreme cases, you can wind it yourself: core cross-section 3...5 mm 2, winding I - 450 turns with a wire with a diameter of 0.1 mm, winding II - 20 turns with the same wire, winding III - 15 turns with a wire with a diameter of 0.6...0, 8 mm (for output voltage 4…5 V). When winding, strict adherence to the winding direction is required, otherwise the device will work poorly or not work at all (you will have to make efforts when setting it up - see above). The beginning of each winding (in the diagram) is at the top.

Transistor VT1 - any power of 1 W or more, collector current of at least 0.1 A, voltage of at least 400 V. Current gain b 2 1 e must be greater than 30. Transistors MJE13003, KSE13003 and all other types 13003 of any type are ideal companies. As a last resort, domestic transistors KT940, KT969 are used. Unfortunately, these transistors are designed for a maximum voltage of 300 V, and at the slightest increase in the mains voltage above 220 V they will break through. In addition, they are afraid of overheating, i.e. they need to be installed on a heat sink. For transistors KSE13003 and MJE13003, a heat sink is not needed (in most cases, the pinout is the same as that of domestic KT817 transistors).

Transistor VT2 can be any low-power silicon, the voltage on it should not exceed 3 V; the same applies to diodes VD2, VD3. Capacitor C5 and diode VD4 must be designed for a voltage of 400...600 V, diode VD5 must be designed for the maximum load current. The diode bridge VD1 must be designed for a current of 1 A, although the current consumed by the circuit does not exceed hundreds of milliamps - because when turned on, a rather powerful surge of current occurs, and you cannot increase the resistance of resistor Y1 to limit the amplitude of this surge - it will heat up very much.

Instead of the VD1 bridge, you can install 4 diodes of type 1N4004...4007 or KD221 with any letter index. Stabilizer DA1 and resistor R6 can be replaced with a zener diode, the voltage at the output of the circuit will be 1.5 V greater than the stabilization voltage of the zener diode.

The “common” wire is shown in the diagram for graphical purposes only and should not be grounded and/or connected to the device chassis. The high voltage part of the device must be well insulated.

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But in vain. The conversation is just beginning. Maybe a person doesn’t have a passport and just doesn’t understand what he wants from his stabilizer. But wanting and being able are two different things. Now what, jump and read on different topics?
To maintain a stable arc during manual arc welding with consumable electrodes, a pulse welding arc stabilizer type SD-3 is used in conjunction with commercially produced transformers.
When installing automation systems, the stabilizer can be used for manual argon arc welding of pipe lines and metal structures made of aluminum and its alloys with a non-consumable electrode, as well as for manual arc welding of steel pipe lines and metal structures with consumable electrodes. In the latter case, you can use electrodes designed for welding with alternating current (type MP-3) and direct current (type UONI-13/45).
The operation of the stabilizer is based on maintaining a stable burning of the arc by applying voltage pulses of reverse polarity to it at the beginning of each half-cycle. The principle of stabilizing the welding arc is as follows. When welding with alternating current, the welding arc breaks when the welding current passes through zero. Thus, at a mains frequency of 50 Hz, the arc goes out and is re-ignited at twice the mains frequency. Re-ignition of the arc occurs from a “spike” of the no-load voltage of the welding transformer, the value of which can reach 90-100 V. However, this voltage is not enough for re-ignition and stable burning of the arc. To reliably ignite the arc, at the beginning of each half-wave, the stabilizer supplies voltage pulses to the secondary winding, the amplitude value of which reaches 200 V. These pulses contribute to stable burning of the arc. The polarity of the stabilizing pulses is reversed, i.e., when a positive half-wave increases between the electrode and the workpiece, a pulse is sent from the welding transformer into the arc gap, the leading edge of which has a negative polarity.
Structurally, the arc stabilizer is an attachment that can be installed directly on the welding transformer. Before connecting it, the welding transformer must be disconnected from the network. After power is supplied to the welding transformer and the electrode briefly touches the product, the stabilizer should turn on, as indicated by the light on its front panel. If this does not happen, you need to swap the power cables from the network. If the stabilizer and welding transformer are working properly, the arc stabilizer works only during welding and turns off no later than 1 second after welding stops. One of the signs of the stabilizer’s operation is a change in the characteristic sound of a welding transformer. This sound is most audible after stopping welding for 1 second.
The welding arc stabilizer SD-3 is powered from an alternating current network with a voltage of 380 V and a frequency of 50 Hz. Permissible voltage deviation from nominal +10 and -15%. Power consumption no more than 50 V-A. Reading 1 s.
When argon arc welding of aluminum and its alloys with non-consumable electrodes, the arc stabilizer can work in conjunction with welding transformers; having an open circuit voltage of 80 V and a current of 50 to 800 A. For manual arc welding with consumable electrodes, the stabilizer can be used with transformers having an open circuit voltage of 45-80 V and a current of 80 to 300 A. The SD-3 stabilizer has dimensions of 334* 208x152 mm and weight 7 kg.

Now tell me what will happen? , will read my previous message in the flood, will be even more offended by me, and he will never understand that I just want to help him. Your right, of course.

The invention relates to welding production and can be used in the production or modernization of welding power sources. The purpose of the invention is to increase the power and stability of arc-igniting pulses by changing the circuit of the key cascade, which makes it possible to improve the operational properties of the stabilizer and expand the scope of its application. The pulse stabilizer of the welding arc contains two transformers 1, 2, two thyristors 7, 8, four diodes 10 13, capacitor 9, resistor 14. 1 or.

The invention relates to welding production and can be used in the production or modernization of welding power sources. The purpose of the invention is to develop a device that provides increased power and stability of arc-igniting pulses by changing the circuit of the key cascade, which makes it possible to improve the operational properties of the stabilizer and expand the scope of its application. To stabilize the process of arc welding on alternating current, at the beginning of each half-cycle of the welding voltage, a short-term powerful current pulse is applied to the arc, formed by recharging a capacitor connected to the arc power circuit using thyristor switches. In the known circuit, the capacitor cannot be recharged to the amplitude values ​​of the voltages supplying it, which reduces the power of the pulse that ignites the arc. At the same time, the power of this pulse is affected by the moment of opening of the thyristors relative to the beginning of the half-cycle of the voltage feeding the arc. This is due to the premature closing of the thyristors, since the capacitor charging current flowing through them is determined by the reactance of the capacitor. This current can keep the thyristor open as long as it exceeds the thyristor holding current. The specified condition is ensured (after the unlocking pulse arrives at the control electrode of the thyristor) for a very short time, after which the thyristor closes. The drawing shows the electrical circuit of the stabilizer. Positions 1 and 2 respectively indicate additional and welding transformers; 3 and 4 connection points to the circuits of the key thyristor cascade; 5 and 6, respectively, a welding electrode and a welded product; 7 and 8 key thyristors; 9 capacitor; 10 and 11 power diodes; 12 and 13 low-power diodes; 14 resistor. The diagram does not show the device for generating control pulses that unlock the thyristors. Control signals U y from this device are supplied to the corresponding electrodes of thyristors 7 and 8. The device operates as follows. When a positive half-wave voltage appears on the arc and thyristor 8 is turned on at the beginning of this half-cycle, capacitor 9 will instantly charge through it and diode 11. But the thyristor remains open, since until the amplitude voltage value is reached on the secondary winding of transformer 1, the current flows through the thyristor along two circuits: thyristor 8 diode 11 capacitor 9 and thyristor 8 diode 13 resistor 14. The current flowing through the first circuit is very small (not sufficient to keep the thyristor open), and through the second circuit it is sufficient to keep the thyristor open. As the voltage of a given half-cycle increases to its amplitude value, the capacitor is charged to the sum of this voltage with the voltage on the arc. Next, the voltage on the secondary winding of transformer 1 will begin to decrease and the voltage of the charged capacitor 9 will close the diode 13, which will lead to the locking of the thyristor 8 and the capacitor 9 will remain charged with the extreme value of the sum of the indicated voltages until the polarity of the voltage on the arc changes. After changing the polarity at the beginning of the next half-cycle, thyristor 7 will open with a control pulse and the capacitor will instantly recharge to the sum of the voltages acting at that moment on the secondary windings of transformers 1 and 2. Diode 12 opens, keeping thyristor 7 open until the amplitude value of the voltage on the secondary winding of transformer 1 is reached Accordingly, capacitor 9 is recharged to the sum of the amplitude value of the specified voltage and the voltage on the arc. The introduction of these elements into the electrical circuit of the stabilizer makes it possible to increase the pulse amplitude swing by two or more times and make it (swing) independent of the moment of opening of the thyristors relative to the beginning of the half-cycle of the voltage on the arc. In the above reasoning, only the amplitude value of the voltage on the secondary winding of transformer 1 is mentioned and nothing is said about the nature of the voltage change on the arc. The fact is that the electric arc has a significant stabilizing ability and during its combustion the alternating voltage on it has a rectangular shape with a flat top (meander), i.e. the voltage on the arc during the half-cycle is practically constant in amplitude (does not change in magnitude) and does not affect the nature of the charge of the capacitor 9. The use of the invention made it possible to increase the amplitude of the arc-igniting pulse by 1.8.2 times, to stabilize it when the opening moment changes over a wide range thyristors relative to the beginning of the half-cycle of the alternating voltage on the arc. By ensuring the indicated effects, it is possible to intensively destroy the oxide film during argon-arc welding of aluminum and its alloys, to stabilize the arc combustion process in a wide range of welding currents, especially in the direction of its reduction. The high quality of weld seam formation was noted.

Claim

PULSE WELDING ARC STABILIZER, including a series-connected secondary winding of a welding transformer, a circuit of back-to-back parallel connected thyristors with their control circuit, a capacitor and a secondary winding of an additional transformer, connected according to the secondary winding of the welding transformer, which is connected to the welding electrodes, characterized in that it two power and two low-power diodes and a resistor are introduced, and the power diodes are connected in series according to the thyristors, the connection point of one thyristor and the cathode of the first power diode is connected to the cathode of the first low-power diode, and the connection point of the cathode of the other thyristor and the anode of the second power diode is connected to the anode of the second low-power diode diode, anode and cathode of the first and second low-power diodes, respectively, are connected through a resistor to the capacitor plate connected to the secondary winding of an additional transformer.

Oscillator- this is a device that converts low voltage industrial frequency current into high frequency current (150-500 thousand Hz) and high voltage (2000-6000 V), the application of which to the welding circuit facilitates excitation and stabilizes the arc during welding.

The main application of oscillators is in argon-arc welding with alternating current with a non-consumable electrode of thin metals and in welding with electrodes with low ionizing properties of the coating. The electrical circuit diagram of the OSPZ-2M oscillator is shown in Fig. 1.

The oscillator consists of an oscillating circuit (capacitor C5, the movable winding of the high-frequency transformer and spark gap P are used as an induction coil) and two inductive choke coils Dr1 and Dr2, a step-up transformer PT, and a high-frequency transformer high-frequency transformer.

The oscillatory circuit generates a high-frequency current and is connected to the welding circuit inductively through a high-frequency transformer, the terminals of the secondary windings of which are connected: one to the grounded terminal of the output panel, the other through capacitor C6 and fuse Pr2 to the second terminal. To protect the welder from electric shock, a capacitor C6 is included in the circuit, the resistance of which prevents the passage of high voltage and low frequency current into the welding circuit. In case of breakdown of capacitor C6, fuse Pr2 is included in the circuit. The OSPZ-2M oscillator is designed for connection directly to a two-phase or single-phase network with a voltage of 220 V.

Rice. 1. : ST - welding transformer, Pr1, Pr2 - fuses, Dr1, Dr2 - chokes, C1 - C6 - capacitors, PT - step-up transformer, VChT - high-frequency transformer, R - arrester	Rice. 2. : Tr1 - welding transformer, Dr - choke, Tr2 - step-up oscillator transformer, P - spark gap, C1 - circuit capacitor, C2 - circuit protective capacitor, L1 - self-induction coil, L2 - communication coil

During normal operation, the oscillator crackles evenly, and due to the high voltage, a breakdown of the spark gap occurs. The spark gap should be 1.5-2 mm, which is adjusted by compressing the electrodes with an adjusting screw. The voltage on the elements of the oscillator circuit reaches several thousand volts, so regulation must be performed with the oscillator turned off.

The oscillator must be registered with the local telecommunications inspection authorities; during operation, ensure that it is correctly connected to the power and welding circuit, as well as that the contacts are in good condition; work with the casing on; remove the casing only during inspection or repair and when the network is disconnected; monitor the good condition of the working surfaces of the spark gap, and if carbon deposits appear, clean them with sandpaper. It is not recommended to connect oscillators with a primary voltage of 65 V to the secondary terminals of welding transformers such as TS, STN, TSD, STAN, since in this case the voltage in the circuit decreases during welding. To power the oscillator, you need to use a power transformer with a secondary voltage of 65-70 V.

The connection diagram of oscillators M-3 and OS-1 to a welding transformer of the STE type is shown in Fig. 2. Technical characteristics of the oscillators are given in the table.

Technical characteristics of oscillators

Type	Primary voltage, V	Secondary voltage idle speed, V	Consumed Power, W	Dimensional dimensions, mm	Weight, kg
M-3 OS-1 OSCN TU-2 TU-7 TU-177 OSPZ-2M	40 - 65 65 200 65; 220 65; 220 65; 220 220	2500 2500 2300 3700 1500 2500 6000	150 130 400 225 1000 400 44	350 x 240 x 290 315 x 215 x 260 390 x 270 x 310 390 x 270 x 350 390 x 270 x 350 390 x 270 x 350 250 x 170 x 110	15 15 35 20 25 20 6,5

Pulse arc exciters

These are devices that serve to supply synchronized pulses of increased voltage to the AC welding arc at the moment of polarity change. Thanks to this, re-ignition of the arc is greatly facilitated, which allows reducing the no-load voltage of the transformer to 40-50 V.

Pulse exciters are used only for arc welding in a shielded gas environment with a non-consumable electrode. The exciters on the high side are connected in parallel to the transformer power supply (380 V), and on the output - parallel to the arc.

Powerful series exciters are used for submerged arc welding.

Pulse arc exciters are more stable in operation than oscillators; they do not create radio interference, but due to insufficient voltage (200-300 V) they do not ensure ignition of the arc without contact of the electrode with the product. There are also possible cases of combined use of an oscillator for the initial ignition of the arc and a pulse exciter to maintain its subsequent stable combustion.

Welding arc stabilizer

To increase the productivity of manual arc welding and economical use of electricity, the welding arc stabilizer SD-2 was created. The stabilizer maintains a stable burning of the welding arc when welding with alternating current with a consumable electrode by applying a voltage pulse to the arc at the beginning of each period.

The stabilizer expands the technological capabilities of the welding transformer and allows you to perform alternating current welding with UONI electrodes, manual arc welding with a non-consumable electrode of products made of alloy steels and aluminum alloys.

The diagram of external electrical connections of the stabilizer is shown in Fig. 3, a, oscillogram of the stabilizing pulse - in Fig. 3, b.

Welding using a stabilizer makes it possible to use electricity more economically, expand the technological capabilities of using a welding transformer, reduce operating costs, and eliminate magnetic blast.

Welding device "Discharge-250". This device is developed on the basis of a TSM-250 welding transformer and a welding arc stabilizer that produces pulses with a frequency of 100 Hz.

The functional diagram of the welding device and the oscillogram of the open circuit voltage at the device output are shown in Fig. 4, a, b.

Rice. 3. : a - diagram: 1 - stabilizer, 2 - cooking transformer, 3 - electrode, 4 - product; b - oscillogram: 1 - stabilizing pulse, 2 - voltage on the secondary winding of the transformer	Rice. 4. a - device diagram; b - oscillogram of open circuit voltage at the device output

The “Discharge-250” device is intended for manual arc welding with alternating current using consumable electrodes of any type, including those intended for direct current welding. The device can be used when welding with non-consumable electrodes, for example, when welding aluminum.

Stable burning of the arc is ensured by supplying the arc at the beginning of each half of the alternating voltage period of the welding transformer with a voltage pulse of direct polarity, i.e., coinciding with the polarity of the specified voltage.

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