In this DIY electronics project, we will design and build a precision power supply circuit using the 10JL2CZ47 power transistor, a versatile component ideal for regulating and controlling the output voltage in a power supply. The project focuses on creating a stable DC output with adjustable voltage and current regulation, which can be used for powering sensitive electronic devices, prototypes, or testing equipment.

The 10JL2CZ47 is a bipolar junction transistor (BJT) with high voltage and current ratings, making it suitable for power supply circuits where stability and precision are essential. We will use this transistor as the primary regulating component in a linear power supply, incorporating key elements such as a feedback control loop and voltage regulation to achieve the desired output.

In this project, the 10JL2CZ47 will play a critical role in providing the necessary voltage and current regulation, while other components, like resistors, capacitors, and diodes, will help shape the overall performance and stability of the power supply.

Components Needed

To build this precision power supply, we will need the following components:

· 10JL2CZ47 NPN Power Transistor (1 piece)

· LM723 Voltage Regulator IC (or similar, such as TL431 for adjustable voltage)

· Resistors:

o 10 kΩ for voltage divider feedback

o 1 kΩ for current sensing

o 0.33 Ω for current limiting

· Capacitors:

o 100nF for stability (on the regulator IC)

o 470µF and 100µF for output smoothing

· Diodes:

o 1N5408 (for flyback protection and reverse polarity protection)

· Potentiometer: 10 kΩ for adjusting output voltage

· Heat Sink: For the 10JL2CZ47 transistor (important for thermal dissipation)

· Transformer: 12V AC to 18V AC step-down transformer (depending on required output voltage)

· Bridge Rectifier: To convert AC to DC

· Multimeter: For voltage and current measurement during testing

· Wires and Connectors: For interconnecting components

Understanding the 10JL2CZ47 Power Transistor

The 10JL2CZ47 is an NPN power transistor designed to handle high voltages and currents, making it suitable for power regulation and switching applications. Here are its key specifications:

· Voltage Rating (Vce): 80V

· Current Rating (Ic): 10A, which is ideal for moderate power applications.

· Power Dissipation (Pd): 75W, making it capable of handling substantial power with proper heat management.

· Current Gain (hFE): High gain, which allows it to operate efficiently even at lower base currents.

· Low Saturation Voltage (Vce(sat)): Ensures minimal power loss during operation.

Given these characteristics, the 10JL2CZ47 is well-suited for applications like power supply circuits, motor control, and audio amplifiers where moderate to high power handling is required.

Project Overview: Precision Power Supply

The goal of this project is to build a precision linear power supply that can output a stable and adjustable DC voltage (e.g., 0V to 12V or 0V to 18V) suitable for powering devices like sensors, microcontrollers, and audio circuits.

The 10JL2CZ47 transistor will regulate the output voltage by adjusting the current flowing through the load. A feedback loop, consisting of a voltage reference (such as the LM723 voltage regulator) and a feedback network (voltage divider), will maintain a stable output voltage across a range of input and load conditions.

In the design, we will implement a current-limiting circuit to protect the power supply from overloading, and we’ll also include filter capacitors to smooth out any ripple from the rectified DC voltage.

Circuit Design Overview

1. AC Input: We begin with an AC supply, which will be stepped down to a lower AC voltage using a transformer. The output of the transformer will be fed into a bridge rectifier to convert the AC voltage to DC.

2. Voltage Regulation: The LM723 voltage regulator will regulate the output voltage based on the feedback from a voltage divider. The 10JL2CZ47 power transistor will be used to control the current flowing to the load and maintain the desired output voltage.

3. Current Limiting: A current-sensing resistor will be placed in series with the output to monitor and limit the current supplied to the load. This will prevent overloading the power supply and protect sensitive components.

4. Output Smoothing: The rectified DC will have ripple due to the AC-to-DC conversion, so we will use large filter capacitors (100µF and 470µF) to smooth out the ripple and provide a clean DC output.

5. Output Adjustability: The potentiometer will be used to adjust the output voltage within a set range.

Step-by-Step Guide

Step 1: AC to DC Conversion

Transformer:

o Start by connecting the 12V to 18V AC transformer to the AC input. The secondary side of the transformer will provide the lower AC voltage needed for the rectification process.

Bridge Rectifier:

o Use a bridge rectifier to convert the AC voltage into pulsating DC. Connect the four diodes of the bridge rectifier to the transformer’s secondary terminals.

o The positive output from the bridge rectifier will be connected to the input of the filter capacitor, and the negative output will be connected to the ground.

Smoothing Capacitors:

o Use a 470µF capacitor across the output of the rectifier to smooth out the large ripple from the DC signal.

o Add a 100µF capacitor near the output to further reduce any remaining ripple.Step 2: Voltage Regulation with LM723 and 10JL2CZ47

1. LM723 Voltage Regulator:

o The LM723 voltage regulator IC will be used to control the output voltage. It provides a stable voltage reference and allows for adjustable output voltage using a feedback network.

o Connect the input of the LM723 to the output of the rectifier. Connect the adjustment pin (pin 5) to a potentiometer (10 kΩ), which will set the desired output voltage. The LM723 will adjust its output to regulate the voltage based on this feedback.

2. 10JL2CZ47 Power Transistor:

o Connect the base of the 10JL2CZ47 to the output of the LM723 through a 10 kΩ resistor. This will allow the LM723 to control the base current of the transistor and regulate the current to the load.

o Connect the collector of the 10JL2CZ47 to the positive output terminal of the power supply.

o The emitter of the transistor will be connected to the output terminal of the power supply, where the load will be attached.

Step 3: Current Limiting

Current Sense Resistor:

o Place a 0.33 Ω resistor in series with the output to monitor the current drawn by the load.

o Connect the voltage drop across this resistor to the LM723's current sense input to enable the current-limiting function.

Adjustable Current Limiting:

o You can further fine-tune the current limit by adjusting the feedback network on the LM723, allowing for protection of both the power supply and the load.

Step 4: Testing and Adjusting the Output Voltage

Initial Power-Up:

o Once everything is connected, plug in the AC power and measure the output voltage with a multimeter.

o Use the potentiometer to adjust the output voltage to the desired level (e.g., 5V, 12V, or 18V).

Current Limit Test:

o Test the current limit by connecting different loads and ensuring that the output current is properly limited based on the current sense resistor.

Ripple Checking:

o Measure the ripple voltage across the output with an oscilloscope. Adjust the filter capacitors if necessary to reduce any remaining ripple.

Step 5: Final Adjustments

Heat Dissipation:

o Attach a heat sink to the 10JL2CZ47 power transistor to ensure it remains within safe thermal limits during operation.

Fine-Tuning:

o After confirming that the power supply is working as expected, you can make small adjustments to the feedback loop or add more filtering capacitance if needed to further reduce ripple.

Conclusion

In this DIY project, we’ve designed and built a precision power supply using the 10JL2CZ47 power transistor. This linear power supply provides a stable and adjustable DC output suitable for powering a wide range of devices. We utilized the LM723 voltage regulator, the 10JL2CZ47 transistor for power regulation, and a series of capacitors and diodes for filtering and protection.

By carefully selecting components, including a current-limiting circuit and feedback control loop, we’ve created a robust and reliable power supply for various applications. This project is an excellent example of how to use high-power transistors in a DIY setting to manage voltage and current regulation with precision, and it provides a solid foundation for creating other power-based projects in the future.