Hardware Protection – OverVoltage and OverCurrent

Three major power supply (Figure 1) architectures are defined for any engineer:
1.Linear Regulators.
2.Pulse width modulated switching (PWM).
3.High resonant technology switching.

Some important parameters can described in the followig texts:

Vin(low), Vin(high) – minimum and maximum allowed input voltages, hence input voltage range.
Iin(max) – maximum average input current.

Vout(min), Vout(max) – minimum and maximum allowed output voltages, hence output voltage range.
Vout(abs) – maximum allowed output voltage this limit is set by load specs. Iout(rated), Iout(min) – maximum and minimum output current provided to the load. Isc – short circuit output current.

When some of these inputs/outputs parameters are not correlated with their optimal values or just when some external event disturbs the system, like dropout, surge, transients, ripple voltages, the entire system is vulnerable and need to be protected. Everyone knows that is better preventing than curing. The solution for this is permanent monitoring and auto controlling. In most of the cases an electronic circuit is build for controlling a specific load (it’s the output terminal). The load can be a sensor, a resistive circuit or even a microcontroller (Figure 2).

Current Protection:
Depending on power line, load and control circuit layout, two basic architectures are available: low-side switch and high-side switch (figure 3 e 4).

Sometimes an embedded system is designed to control loads which run on high current or voltage. Most of the processors run at 3.3V or 5V, so the outputs are not able for switching on/off some loads connected to 12V, 24V or even more. The solution is to use some very fast turn on/off transistors, MOS technology, which are often named simply β€œ MOSFET switches” (Figure 6 and 7).

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