The function of converting electricity in the voltage parameter can be performed by various devices such as generators, chargers and transformer devices. To one degree or another, all of them are capable of changing the characteristics of energy, but not always their use justifies itself in terms of technical and ergonomic qualities. This is partly due to the fact that the task of transforming the current for most regulators is not a key one - in any case, if we talk about both direct and alternating current. It is these limitations that motivated manufacturers of electrical equipment to develop a switching converter, which compares favorably with its compact size and voltage stabilization accuracy.
Device detection
Numerous radio engineering devices, means of automation and communication rarely do without single-phase and three-phase power devices for current transformation in the ranges from units to hundreds of volt-amperes. Pulse devices are used for narrower tasks. An electrical converter of a pulse type is a device thattransforms the voltage in small time intervals with a duration of the order of 1-2 microns / sec. The voltage pulses are rectangular in shape and repeat at a frequency of 500-20,000 Hz.
Traditional voltage-adjustable converters typically control the device's resistance rating. It can be a thyristor or a transistor through which current flows continuously. It is his energy that causes the controller device to heat up, due to which part of the power is lost. Against this background, a pulse voltage converter looks more attractive in terms of its technical and operational properties, since its design provides for a minimum of parts, which leads to a decrease in electrical interference. The adjusting element of the converter is a key that operates in different modes - for example, in an open and closed state. And in both cases, the minimum amount of thermal energy is released during operation, which also increases the performance of the equipment.
Inverter assignment
Wherever a change in the parameters of electricity is required, pulse transformers are used in one or another operational configuration. At the first stage of their wide distribution, they were used mainly in pulse technology - for example, in triode generators, gas lasers, magnetrons and differentiating radio equipment. Further, as the device improved, they began to be used in most typical representatives of electrical equipment. And it wasn't necessarilyspecialized equipment. Again, in different versions, a pulse converter can be present in computers and TVs, in particular.
Another, but less well-known function of transformers of this type is protective. In itself, impulse regulation can be considered as a protective measure, but the goals of adjusting voltage parameters are initially different. Nevertheless, special modifications provide equipment protection against short circuits under load. This is especially true for equipment operating in idling modes. There are also pulse devices that prevent overheating and excessive voltage increases.
Design of the device
The converter consists of several windings (at least two). The first and main is connected to the network, and the second is sent to the target device. Windings can be made of aluminum or copper alloys, but in both cases, as a rule, additional varnish insulation is used. The wires are wound on an insulating base, which is fixed on the core - the magnetic circuit. In low-frequency converters, the cores are made of transformer steel or a soft magnetic alloy, and in high-frequency converters, they are based on ferrite.
The low-frequency magnetic circuit itself is formed by sets of plates W, G or U-shaped. Ferrite cores are usually made in one piece - such parts are present in welding inverters and galvanic isolation transformers. Low power high frequency transformers andcompletely dispense with the core, since its function is performed by the air environment. For integration into electrical devices, the design of the magnetic circuit is provided by a frame. This is the so-called pulse converter unit, which is closed with a protective cover with markings and warning labels. If during the repair process it is necessary to turn on the device with the cover removed, this operation is performed through an RCD or an isolation transformer.
If we talk about converters that are used in modern radio and electrical engineering, then there will be a significant difference between them and classic voltage transformers. The most noticeable reduction in size and weight. Pulse devices can weigh several grams and still perform the same.
Features of operational processes
As already noted, keys are used to regulate the current in pulse transformers, which themselves can become sources of high-frequency interference. This is typical for stabilizing models that operate in current switching mode.
At the moments of switching, sensitive current and voltage drops can occur, which create conditions for anti-phase and common-mode interference at the input and output. For this reason, a switching power converter with a stabilizer function provides for the use of filters that eliminate interference. To minimize unwanted electromagnetic factors, the switch is switched at times when the switch is not conducting current.(when open). This method of dealing with interference is also used in resonant converters.
Another feature of the working process of the devices under consideration is the negative differential resistance at the input when the voltage is stabilized under load. That is, as the input voltage increases, the current decreases. This factor must be taken into account to ensure the stability of the converter, which is connected to sources with a high internal resistance.
Comparison with linear converter
Unlike linear devices, pulse adapters favorably feature higher performance, compact size and the possibility of galvanic isolation of circuits at the input and output. To provide additional functionality with the binding of third-party devices, the use of complex connection schemes is not required. But there are also weaknesses in the pulse converter in comparison with linear transformers. These include the following disadvantages:
- Under the condition of changing input current or voltage under load, the output signal is unstable.
- The presence of the already mentioned impulse noise on the output and input circuits.
- After sudden changes in voltage and current parameters, the system takes longer to recover from transients.
- Risk of self-oscillations that may affect the performance of the equipment. Moreover, fluctuations of this kind are associated not with the network instability of the source, but withconflicts within the stabilization scheme.
DC/DC Converter
All varieties of impulse devices of the DC / DC system are characterized by the fact that the keys are activated during the translation of special impulses in the direction of the transistor. In the future, due to the growing voltage, a logical locking of the transistors occurs, moreover, against the background of recharging the capacitor. It is this feature that distinguishes the DC-DC switching device from similar devices in independent inverter equipment.
Typically, these devices perform DC voltage monitoring under load in the process of supplying DC power to the grid. This kind of control is achieved by adjusting the voltage on the public key. Small current values make it possible to fix a high level of performance, at which the efficiency can reach 95%. Setting the peak performance of the system is a significant plus of pulse current converters, however, the implementation of the DC-DC circuit is not possible in every design. In the device, the contact network should initially act as a source - in particular, this principle is used in batteries and batteries.
Boost Converter
With the help of this transformer, the voltage is increased from 12 to 220 V. It is used in situations where there is no source with suitable power parameters, but it is necessary to provide power to the device from a standard network. In other words,an adapter must be introduced from a source with some characteristics to a consumer with different power requirements. Schematic designs of pulse voltage converters 12-220 V allow the connection of devices that operate at a frequency of 50 Hz. Moreover, the power of the equipment should not exceed the maximum power rating of the transformer. And even if the voltage parameters match, the consumer device must have protection against network overloads. This voltage correction method has several advantages:
- Possibility of a long working session at maximum load without interruption.
- Auto power output adjustment.
- Increased efficiency ensures both the stability of the operating mode of the device and the high reliability of the function of the electrical circuit.
Down-down switching converter
When using low-frequency or low-power equipment, it is quite natural that there may be a need to lower the voltage indicator. For example, this task is often encountered when connecting lighting devices - for example, LED backlighting. To lower the converter closes the regulating switching key, after which it accumulates "extra" energy. A special diode in the circuit does not allow current from the supply source to the consumer. At the same time, in self-induction systems, rectifier diodes can pass negative voltage pulses. In the operation of 24-12 V pulse converters, the output stabilization function is especially important. Both linear anddirectly impulse stabilizers. It is more profitable to use devices of the second type with width or frequency modulation. In the first case, the duration of the control pulses will be corrected, and in the second, the frequency of their occurrence. There are also stabilizers with mixed control, in which the operator can, if necessary, change the configuration for adjusting pulses in frequency and duration.
Pulse Width Converter
In the process of work, a device is used that accumulates energy as a result of transformation. It can be included in the basic structure or connected directly to the input voltage without reference to the converter. One way or another, the output will be an average voltage indicator, determined by the value of the input voltage and the duty cycle of the pulses from the switching key. The operational amplifier has a special calculator that evaluates the parameters of the input and output signals, registering the difference between them. If the output voltage is less than the reference voltage, then a modulator is connected to the regulation, which increases the duration of the open state of the switching key relative to the time of the clock generator. As the input voltage changes, the switching converter adjusts the key control circuit so that the difference between the output and the reference voltage is minimized.
Conclusion
In its pure form without connecting auxiliary deviceslike rectifiers and stabilizers, the functions of the converter are significantly reduced, although the efficiency remains at a high level. Transformation devices that rarely do without additional equipment include regulators in AC networks. At least in this case, you will have to install a smoothing filter and a rectifier at the input. Conversely, pulse converters of direct electric currents both at the input and at the output can autonomously support their main function. But even in such systems, it is important that the device can perform the task of voltage stabilization. Also, do not forget about possible interference with the active use of switching switches in the stabilizer system. In such non-grounded applications, it is recommended to connect a noise filter to the converter block.
