How Transistor Series Voltage Regulator Works?

A voltage regulator that employs transistors in line with a cargo to sustain a steady affair voltage is known as a transistor voltage regulator. Irrespective of variations to the cargo or input voltage.

Basic Components

1. Reference Voltage (Vref): A steady voltage source that offers a steady reference voltage, such a zener diode.
2. Error Amplifier: A reference voltage and output voltage comparison operational amplifier, or op-amp. and amplify the error (difference).
3. Pass Transistor (Q1): A transistor that serves as a variable resistor, typically NPN or PNP. managed by an error amplifier to regulate the voltage output.
4. Feedback Network: A resistive divider network that feeds the error amplifier some of the output voltage so it can be compared to the reference voltage.

Working Principle

1. Initial Conditions: The error amplifier’s inverter input receives a reference voltage(Vref). Through a resistive divider, the output voltage (Vout) is supplied back to the fault amplifier’s non-inverter input.
2. Error Detection: In the case that changes in the input or cargo voltage cause changes in the output voltage(Vout), the error amplifier compares the feedback voltage(Vfb) to the reference value(Vref).. Moreover, the feedback voltage (Vfb) will alter.
3. Amplification of Error: The error amplifier amplifies the difference between Vfb and Vref. This difference is called the error signal. The base (or gate) of the transistor is controlled by the error amplifier’s output through (Q1).
4. Regulation: The feedback voltage (Vfb) drops in tandem with a decrease in the output voltage (Vout). The output voltage is increased by an error amplifier. The pass transistor (Q1) can therefore carry out additional operations. By doing this, the output voltage is raised back to the appropriate level and more current is passed through the load. On the other hand, when the output voltage (Vout) rises, so does the feedback voltage (Vfb). The output voltage is decreased by the error amplifier. The pass transistor (Q1) will therefore operate less, lowering the current flowing through the load. and bring the output voltage down to the appropriate level once more.

Key Points

– Series Configuration: The load and the pass transistor are connected in series. As a result, it has direct control over the current entering the load.

– Stability: The affair voltage is kept steady by the regulator. Indeed in the event that the cargo current and input voltage vary.

– Power Dissipation: Power dispersion in a pass transistor is commensurable to the current passing through it and the voltage across it. It can produce a great deal of heat. Enough cooling is required.

Real-world example of Transistor Series Voltage Regulators’ Application

Power Supply for Electronic Devices

Scenario: 

Desktop computer power supply units (PSUs) use transistor series voltage regulators.

Components and Configuration:

1. Input Voltage Source: Offers a DC voltage that is switchable (e.g., 9V to 15V).
2. Pass Transistor (Series Transistor): Typically, NPN transistors (such the 2N3055) are connected in series with the load. It functions as an error amplifier-controlled variable resistor.
3. Error Amplifier: Maintains a constant output voltage by comparing the output voltage to a constant reference voltage(such a zener diode) and conforming the pass transistor’s base current.
4. Reference Voltage Source: 5.6V is an illustration of a stable reference voltage handed by a zener diode.
5. Output Capacitor: Reduces ripple and smoothes the output voltage.

Operation:

The input voltage is fed to the collector of the pass transistor.

The output cargo is connected to the transistor’s emitter.

The output voltage is continually observed by the error amplifier, which also compares it to a reference value.

if the output voltage frequently rises above the intended level. The transistor’s base current is decreased by the error amplifier. Lower the output voltage and raise the resistance.

In contrast, if the output voltage drops below the required level. The transistor’s base current is increased by the error amplifier. Elevate the output voltage while decreasing the resistance.

The outcome is the supply of a steady output voltage (such 12V) to the motherboard and other peripherals of the computer. This does not account for variations in load (e.g., adding or removing graphics cards or hard drives) or variations in input voltage.

Advantages:

– Provides a stable and dependable power force to sensitive electronic factors.

– Protects the computer from voltage harpoons and oscillations.

Example Circuit:

In this circuit:

– R1 is utilized to control the current flowing to the transistor’s base.

– To modify the transistor’s base current, the output voltage is supplied back to the error amplifier, which isn’t visible in this picture.

This example demonstrates how to utilize a transistor series voltage regulator to give an electrical equipment, like a desktop computer, a steady power supply.

Conclusion

Voltage regulators in the transistor series are crucial to preserving a steady and dependable power source for electronic equipment. applying a load to a passive transistor. managed by an error amplifier. The output voltage can be set by the controller to a steady value. even in the event that the load or input voltage fluctuate. By doing this, it is ensured that delicate electronic parts—like those in desktop computers—are not harmed. There will be a steady and reliable voltage. Defend these components from spikes and variations in voltage. Efficiency is the outcome. dependability and longer lifespan of electrical devices