What is SMPS? Working Principle and Properties of SMPS

Hello friends, in today’s article I am going to tell you what is SMPS? Functions and properties of SMPS, Main principle of SMPS, Working of SMPS, Properties of SMPS, Demerits of SMPS: If you also want to know, then keep reading this article completely. so let’s start

What is SMPS?

SMPS (Switch Mode Power Supply) – DC voltage is required in various applications. Which Doordarshan receiver is the main one where different DC voltage from 121 to 160V is required. Initially, series regulators were used to stabilizing the output voltage against the change of input voltage and change of load. Later filter circuits with SCR-controlled rectifiers became popular.

Necessary improvements were made in these, in which the use of full-wave rectifier and break quantifier is the main one. However, due to the high power dissipation, and the large size of the break quantifier, its use in today’s color vision receiver circuits has been complicated. Switch Mode Power Supply, abbreviated as SMPS, is now used in all types of color television receivers today.

SMPS Main principles

In each SMPS power supply, first, the main source voltage is rectified by a high voltage rectifier and filtered by a capacitor filter. The unregulated DC voltage obtained is chopped off at a high frequency by a switching transistor that is driven by a control circuit. In Doordarshan Grahmi this frequency is kept at 15.625 kHz.

The arc rectified voltage is given to the primary coil of a high-frequency transformer. A high-frequency alternating voltage is obtained at the output of the second coil, which is rectified by a fast recharge power diode, to obtain a pure DC voltage by isolating the alternating component by a capacitor or an inductance filter. Some part of the output DC voltage is isolated and amplified by a sensing amplifier and re-inserted into the control circuit, which regulates the duty cycle of the switch transistor and keeps the output constant. The transformer used is small. The number of coils in the coil is selected according to the required output voltage. The required different DC voltages can be obtained by taking several secondary coils in the same transformer.

Working Principle of SMPS

The working of SMPS can be understood from Figure 1. A detailed description of each section shown in this picture is being given here.

Block Diagram Of SMPS

(i) Input Rectifier Stage – If SMPS alternating current is input, then in the first stage this input alternating current is converted into rectified current. This process is called rectification. A switch is made like a voltage doubler by connecting it with a rectifier. It is necessary to work on the normal potential of 120V and 240V high supply processes. Here the rectifier gives the non-linear DC potential which is input to the filter circuit.

The current taken by this circuit from the main supply is in the form of short pulses around high values ​​of alternating current potential. These pulses have high-frequency energy which reduces the power coefficient. Some control systems are used by the SMPS to keep the value of the power coefficient constant, such as making the average input current equal to the input alternating current, etc. This stage is not required for an SMPS in which DC is invested. An SMPS designed for alternating current can also work for DC (230VAC would be 330VDC) as there will be no effect on the current passing through the rectifier but it is not used experimentally because full In this stage, only half the diodes are useful for the load. Hence, there is a risk of circuit burns due to excessive heating of the components.

If an input range switch is used, the stage from the rectifier acts as a potential doubler at low potential (120VAC) and as a rectifier at high potential (240VAC). If a range switch is not used, usually a full-wave rectifier is used and the interrupter is designed to take the rectifier output potentials as input.

What is SMPS

(ii) Inverter Stage – The inverter stage converts the rectifier (directly from the input or rectifier stage) into alternating current by driving it through a power oscillator whose output transformer is very small and operating at low frequency. This frequency is chosen over 20 kHz so that it is not heard by humans. Here the output potential is fairly regular. The switching is done like a MOSFET amplifier.

(iii) Voltage Converter and Output Rectifier – If the output is to be isolated from the input, then the converted alternating current is used to drive the primary coil of the high-frequency transformer. Due to this, the desired potential is obtained on the secondary coil. The output transformer in Figure (i) does this process.

If DC output is required, the AC output of the transformer is rectified. Silicon diodes are used for output potentials of 10 V or more. Similarly, Schottky diodes are used in rectifiers for low potentials. And MOSFETs are used for very low and their relative potential drop is also less than that of Schottky diodes. The rectifying potential obtained from this stage is passed through the filter circuit and the desired output is obtained.

A particular DC voltage is required in different applications, for example, in Doordarshan, different DC voltages are required from 12 V to 60 V. That’s why SMPS is used.

Properties of SMPS

  1. Due to the high chopping rate, the basic shape of the transformer is small.
  2. Transistor is ON only when required for the load current. Therefore, the heat loss is less in the controlled transistor. Due to this more efficiency is available
  3. Low voltage and medium voltage can be obtained from a circuit.
  4. All outputs are constant. There is a system of overload open and closed circuit protection.
  5. Interference in other circuits can be reduced by using synchronization.

Demerits of SMPS

  1. Strong interference signals are generated due to fast switching.
  2. Due to the trapping of energy, a high-frequency oscillation frequency is generated which is captured by the tuner of television.
  3. Due to the generation of strong induction voltage, there is a possibility of it corrupting the main AC source.

Now you must know what is SMPS? Functions and Properties of SMPS – What is SMPS, Main Principle of SMPS, Working of SMPS, Properties of SMPS, Demerits of SMPS |

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