# Switch Mode Power Supply Circuit Diagram With Explanation

## Switch Mode Power Supply Circuit Diagram With Explanation

A switch-mode power supply (SMPS) is a type of power supply that uses a switching regulator to convert DC input voltage to a regulated DC output voltage. Switch-mode power supplies are used in a wide variety of applications, from portable electronic devices to industrial power systems. The basic principle of a switch-mode power supply is to use a switching transistor to alternately switch the input voltage on and off. This creates a square wave output voltage that is then filtered to produce a regulated DC output voltage. The switching frequency of the power supply is typically in the range of 50 kHz to 1 MHz. The main advantage of switch-mode power supplies over linear power supplies is that they are much more efficient. This is because the switching transistor is only turned on for a short period of time, during which time it dissipates very little power. In contrast, a linear power supply dissipates power continuously, even when the output voltage is not changing. Switch-mode power supplies also have a number of other advantages over linear power supplies, including: * Smaller size and weight * Higher power density * Better regulation * Lower noise * Longer life The main disadvantage of switch-mode power supplies is that they can be more complex to design and manufacture than linear power supplies. However, the advantages of switch-mode power supplies typically outweigh the disadvantages, and they are now the most common type of power supply used in electronic devices. ### Switch-Mode Power Supply Circuit Diagram The following diagram shows a basic switch-mode power supply circuit:

The circuit consists of the following components: * A transformer to convert the input voltage to a higher or lower voltage * A switching transistor to switch the input voltage on and off * A diode to rectify the output voltage from the transformer * A capacitor to filter the output voltage * A regulator to regulate the output voltage The operation of the circuit is as follows: 1. The input voltage is applied to the transformer. 2. The switching transistor is turned on, which causes the primary winding of the transformer to be energized. 3. The current flowing through the primary winding of the transformer creates a magnetic field. 4. When the switching transistor is turned off, the magnetic field collapses. 5. The collapse of the magnetic field induces a voltage in the secondary winding of the transformer. 6. The diode rectifies the output voltage from the transformer. 7. The capacitor filters the output voltage. 8. The regulator regulates the output voltage. The output voltage of the switch-mode power supply is typically regulated to a very tight tolerance, typically ±2%. This is much tighter than the regulation of a linear power supply, which is typically ±10%. ### Explanation of Switch-Mode Power Supply Operation The operation of a switch-mode power supply can be divided into two phases: the on-time phase and the off-time phase. During the on-time phase, the switching transistor is turned on and the primary winding of the transformer is energized. This causes a current to flow through the primary winding of the transformer and creates a magnetic field. When the switching transistor is turned off, the magnetic field collapses. This collapse of the magnetic field induces a voltage in the secondary winding of the transformer. The polarity of the induced voltage is opposite to the polarity of the input voltage. The diode rectifies the output voltage from the transformer, which means that it converts the AC voltage to a DC voltage. The capacitor filters the output voltage, which means that it removes any unwanted ripple from the DC voltage. The regulator regulates the output voltage to a very tight tolerance. This is done by comparing the output voltage to a reference voltage and then adjusting the duty cycle of the switching transistor to compensate for any changes in the input voltage. The duty cycle of the switching transistor is the ratio of the on-time to the total time period. The higher the duty cycle, the more power is delivered to the load. Switch-mode power supplies are very efficient because they only draw power from the input voltage during the on-time phase. This is in contrast to linear power supplies, which draw power from the input voltage continuously. Switch-mode power supplies are also very compact and lightweight because they do not require a large heat sink to dissipate the heat generated by the switching transistor. ### Conclusion Switch-mode power supplies are a very efficient and compact way to convert

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