Parallel operation is the method of connecting multiple power supplies with the same rated output voltage to increase the total available output current. A critical requirement is to ensure that all connected power supplies maintain identical output voltages during operation. While the current from each unit may vary, the total current, It, is the sum of the individual currents:
where I1 through In represent the current supplied by each individual power supply.
In a parallel configuration, even minor differences in the output voltage of each power supply can generate undesirable "circulating currents" between the units. To ensure balanced current sharing, equalizing resistors can be inserted at the output of each power supply. This method is effective in suppressing circulating currents caused by voltage differences, thereby ensuring that each unit contributes its proper share of the total current.
- Primary Applications
- Electroplating: In electroplating, multiple power supplies are often connected in parallel to provide the high currents required, which can be 100 A or more.
- Laser Cluster Drives: This is another application that demands stable, high-current power delivery.
- Other Applications: Parallel operation is also used in semiconductor manufacturing equipment and medical devices, where power supply reliability and stability are paramount.
- Key Considerations
- Current Sharing Circuits: These circuits are essential for preventing current imbalances among the power supplies. The output of each unit is regulated by either an internal control system or external circuitry to ensure each contributes equally.
- Cable Resistance Compensation: It is necessary to compensate for variations in wiring resistance to prevent uneven current distribution. This involves careful selection of cable length and cross-sectional area for all connections.
- These design considerations enable safe and stable power delivery in parallel configurations, which enhances overall system reliability.