Supposing D1 and RLOAD fixed, the exact voltage threshold of the circuit depends also on the values of R1, R3 and (much more slighty) of R2. In particular, by increasing R3 the OVP circuit acts at lower voltage levels (and, equivalently, more quickly in time) due to the weaker Q1 base current during nominal operation (i.e. when OVP is not triggered). Moreover, it is important to notice that keeping R3 high is useful for limiting power consumption in nominal operation, even though too high values (especially in relation to RLOAD) may cause Q1 to never switch on. Similarly, by increasing R1 the OVP circuit is triggered at lower voltage levels (and, equivalently, more quickly in time) since current flow through R2 is eased (R1 and R2 + Q2 can be seen as two resistive paths in parallel converging to D1) and, in turn, the switching on of Q2 fostered.

Of course, the use of this circuit can be extended to any voltage supply, OVP threshold and load values by simply acting on the choice of D1 and R3 mainly, as explained above.

Finally, component C1 acts as decoupling capacitor, good practise in order to assure a more constant supply voltage by smoothing abrupt transients and filtering noise from other circuit sections.

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After the first step of study, simulation and validation of the circuit, this has been converted into a PCB by means of Altium Designer. In sight of this, another potentially useful section of circuit has been inserted. As shown in Fig.3, two more branches containing each a MOSFET, an LED and a resistor have been inserted in order to be able to visually assess the OVP circuit state. In fact, while VIN remains below threshold the high value of VOUT makes the M1 N-MOSFET conduct and, in turn, the green LED on, whereas a low value of VOUT due to an overvoltage causes M2 MOSFET conduct and, in turn, the red LED on.