Inrush Current Limiter Circuit

A 7805 can be configured as a constant-current regulator to function as an inrush current limiter. Resistor R1 will maintain a voltage of 5 V across it at all times, resulting in a total current through R1 of 5 V/R1 + 5 mA, where the 5 mA represents the operating current of the regulator. In this case, R1 = 5 V/95 mA = 52.6 ohms for an output current of 100 mA.

The 7805 voltage regulator is commonly utilized in electronic circuits to provide a stable 5 V output. In the context of using it as a constant-current regulator, it is essential to configure the circuit correctly to achieve the desired current limiting functionality. The inrush current limiter is particularly useful in applications where initial power surges can damage components or affect circuit performance.

To implement this configuration, the resistor R1 is placed in series with the load. The voltage drop across R1 is directly proportional to the current flowing through it, defined by Ohm's law (V = IR). The selected value for R1 is crucial; it must be calculated based on the desired output current. For instance, if the target output current is 100 mA, R1 can be calculated as follows:

R1 = V / I = 5 V / 0.095 A = 52.6 ohms.

This calculation ensures that the total current through R1 will include both the load current and the regulator's quiescent current (5 mA). Therefore, the effective total current through the circuit becomes 100 mA plus the 5 mA from the regulator, leading to a total of 105 mA.

It is important to note that the 7805 regulator has a maximum output current rating, typically around 1 A, which allows for sufficient headroom in many applications. However, care must be taken to ensure that the power dissipation across the regulator does not exceed its thermal limits, which may require the addition of a heat sink depending on the load conditions.

In summary, configuring a 7805 as a constant-current regulator by using an appropriate resistor allows for effective inrush current limiting, protecting sensitive components from excessive current during power-up. Proper calculations and thermal management are essential for reliable operation in this configuration. A 7805 can be configured as a constant-current regulator, to serve as an inrush current limiter. Rl will have 5 V across it at all times so the total current through 11 will be 5 V/R1 + 5 mA, the 5 mA being the regulator operating current. In This ease, R{ = 5 V/95 mA = 52.6 for II current = 100 mA. 🔗 External reference