The integration of a transformer with a full wave rectifier circuit allows for the adjustment of AC voltage amplitude before rectification. This setup is crucial in developing efficient, transformer-based power supplies, offering the advantage of voltage scaling alongside rectification. This experiment focuses on constructing such a circuit to demonstrate voltage scaling and rectification, followed by smoothing the rectified voltage to achieve a more constant DC output.
Objective
The aim is to build a transformer-coupled full wave rectifier circuit, utilizing a specific transformer to achieve a desired winding ratio for voltage scaling. Subsequently, the experiment will explore the effect of adding capacitors for voltage smoothing, moving towards the creation of a simple, unregulated DC power supply.
Materials and Setup
- Transformer with a 1:5 winding ratio (Model: HPH1-019L used)
- Full wave bridge rectifier configuration
- Capacitors for smoothing (10nF and 47µF used for comparison)
- Red Pitaya or equivalent for signal generation and oscilloscope measurements
- Resistors (1kΩ for load simulation)
Circuit Assembly
- Transformer and Rectifier Configuration: Assemble the circuit as shown, incorporating the transformer with the full wave rectifier. Ensure the winding ratio is correctly applied to scale the input voltage appropriately.
- Setup Overview: Arrange the setup to include the transformer and the rectifier, with the Red Pitaya set to generate a sine wave at an appropriate frequency (100kHz found to be effective).
Conducting the Experiment
- Signal Generation and Measurement: Initiate a high-frequency sine wave from the Red Pitaya. Observe and measure the rectified output using the oscilloscope.
- Smoothing the Voltage: Experiment with different capacitor values (10nF and 47µF) across the rectifier’s output to analyze the smoothing effect on the rectified voltage.
Analysis and Observations
- Voltage Scaling and Rectification: The transformer's winding ratio effectively scales the input voltage, which is then rectified to a DC voltage oscillating between 0V and
- Smoothing Effect of Capacitors: Larger capacitance values result in better smoothing of the rectified voltage, with the 47µF capacitor demonstrating a more stable DC output than the 10nF capacitor. However, increasing capacitance can also lead to source overloading, indicated by distortion in the input voltage's shape.
Relevant Equation
The peak output voltage of a full wave rectified signal, before smoothing, can be estimated as:
where VDIODE is the forward voltage drop of the diodes used in the rectification process, typically around 0.7V for silicon diodes.
Conclusion
This experiment offers a comprehensive look at constructing a full wave rectifier with a transformer for voltage scaling, followed by smoothing the output using capacitors to approach a steady DC supply. The findings underscore the importance of component selection and circuit design in power supply development, highlighting how transformer winding ratios and capacitor values influence the final output. Encouraging further exploration, such as examining output voltage variations under different load conditions, this experiment lays the groundwork for understanding and designing simple, yet effective, unregulated DC power supplies.