Ideal diode module / Controllers (PMIC) - Heisener
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Ideal diode module/Controllers

Ideal diode characteristics

An ideal semiconductor should behave as a switch. In other words, an ideal diode should show infinite conductance when active, behaving as a closed circuit. Also, it should show infinite resistance when inactive, behaving as an open circuit. Since it shows infinite conductance in operating mode, there is apparently no potential drop across it.

Need for an Ideal diode module

A practical general-purpose semiconductor diode, however, is quite different in terms of its current-voltage characteristics. Unlike an ideal diode, a practical semiconductor diode does not show infinite conductance on forward biasing but it follows some relations with the forward voltage. In fact, the conduction does not start significantly unless the forward current rises above a certain threshold called knee voltage.

Practical diodes also don’t show infinite resistance on reversed biasing as there is always a small reverse saturation current or leakage current.

Since there is a voltage drop equal to the knee voltage across the diode when it is forward biased. This potential drop produces heat as per the Joule’s heat law. This heat does not only result in unnecessary power loss, but also imposes limitations on the power ratings of the diode.

Due to these limitations of a standard semiconductor diode, ideal diode modules are preferred over general diode in a number of applications.

Construction and working of an Ideal diode module

The basic circuit of an ideal diode module consists of a normal diode connecting the input and output sides of the circuit with its positive end towards the input. There is a power MOSFET connected across the diode with its drain and source connected to the positive and negative sides of the diode, respectively. There is also a control unit which measures the voltage across the diode and controls the gate of the MOSFET accordingly. When the control unit finds a positive potential drop across the diode, it switches ON the FET and the diode is short-circuited, removing the potential drop across it. Thus, heating issues are almost completely eliminated.

Applications

In power backup systems and battery charging systems, it is very important to prevent the current from the main power supply from flowing into the backup systems and damaging them. An ideal diode module is highly suitable for this purpose as it does not only prevent the reverse current but also eliminates any power dissipation in the form of heat. The ideal diode module can also be used in electrical systems where non-rechargeable batteries are used as a backup to the main power supply to prevent reverse current from flowing into the batteries and damaging them.

PMIC - OR Controllers, Ideal Diodes

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