All about the switching power supply

The principle of realization of secondary power through the use of additional devices that provide energy to the circuit has been used for a long time in most electrical appliances. These devices are power supplies. They serve to convert the voltage to the required level. BP can be both built-in, and separate elements. There are two principles of electricity conversion. The first is based on the use of analog transformers, and the second is based on the use of pulsed power supplies. The difference between these principles is quite large, but, unfortunately, not everyone understands it. In this article we will understand how the switching power supply works and how it differs from the analog one. Let's get started. Go!

Pulse Power Supply Board

The first transformer transformers appeared. Their principle of operation is that they change the voltage structure with the help of a power transformer, which is connected to the 220 V network. There the amplitude of the sinusoidal harmonic decreases, which is sent further to the rectifier device. Then, the voltage is smoothed by a parallel-connected capacity, which is selected by the permissible power. Voltage regulation at the output terminals is provided by changing the position of the trimming resistors.

We now turn to a pulsed power supply. They appeared a little later, however, immediately gained considerable popularity due to a number of positive features, namely:

  • Accessibility picking;
  • Reliability;
  • Possibilities to extend the operating range for output voltages.

All devices that incorporate the principle of pulsed power, practically no different from each other.

The elements of a pulsed power supply are:

  • Linear power supply;
  • Standby power supply;
  • TPI;
  • Generator (RFI, control);
  • Key transistor;
  • Optopara;
  • Chain Management.

To choose a power supply with a specific set of parameters, use the ChipHunt website.

Let's finally figure out how the switching power supply works. It applies the principles of interaction of elements of the inverter circuit and it is thanks to this that a stabilized voltage is achieved.

First, the rectifier receives the normal voltage of 220 V, then the amplitude is smoothed using capacitors of the capacitive filter. After that, the rectification of the passing sinusoids by the output diode bridge is performed. Then there is a conversion of sinusoids into high frequency pulses. Conversion can be performed either with galvanic separation of the power network from the output circuits, or without performing such isolation.

If the power supply unit is electrically isolated, then high-frequency signals are sent to the transformer, which performs the electrical isolation. To increase the efficiency of the transformer increases the frequency.

The operation of a pulsed power supply unit is based on the interaction of three chains:

  • PWM controller (controls the conversion of pulse width modulation);
  • Cascade power switches (consists of transistors, which are included in one of three schemes: bridge, half-bridge, with a midpoint);
  • Pulse transformer (has a primary and secondary windings, which are mounted around the magnetic core).

If the power supply is without isolation, the high frequency isolation transformer is not used, and the signal is sent directly to the low pass filter.

Comparing the pulse power supply with analog, you can see the obvious advantages of the first. UPSs have less weight, while their efficiency is much higher. They have a wider range of supply voltages and built-in protection. The cost of such BP, as a rule, lower.

Among the shortcomings can be identified the presence of high-frequency noise and power limitations (both at high and at low loads).

You can check the UPS using an incandescent lamp. Please note that you should not connect the lamp to the break of the remote transistor, since the primary winding is not designed to pass a direct current, so in no case should it be allowed to pass.

If the lamp is lit, it means that the power supply is working normally, but if it is not, the power supply unit does not work. A short flash indicates that the UPS is blocked immediately after starting. Very bright light indicates the absence of output voltage stabilization.

Now you will know what the principle of operation of the pulsed and conventional analog power supplies is based on. Each of them has its own particular structure and work, which should be understood. You can also check the UPS operation with a standard incandescent lamp. Write in the comments this article was useful for you and ask any interesting questions on the topic considered.