Fast Inductive Load Turn-off (Fast Demagnetization)

Traditionally, inductive loads (such as a solenoid drive) use a free-wheeling diode in parallel with the load to discharge stored energy to reach the Off status (zero current). This process is called Demagnetization.

The PointMax high-speed counter/SSI module has the fast inductive load turn-off feature. If the inductive load is within the module's specified inductance and current rating, then no free-wheeling diode is required. Demagnetization is performed faster when compared to using an external free-wheeling diode. For the module inductance and current rating specifications, see the PointMax I/O System Specifications Technical Data, publication 5034-TD001.

There are two possible demagnetization scenarios. Typically, inductive load demagnetization happens as illustrated in Demagnetization Example 1. In this scenario, demagnetization happens entirely through the high-side active clamp switch and the output voltage is at a negative voltage of (SA voltage + VCL) during the demagnetization phase.

However in some situations, demagnetization happens as illustrated in Demagnetization Example 2. The demagnetization happens through the combination of high-side active clamp switch and low-side switch. The output voltage switches between a negative voltage of (SA voltage + VCL) and approximately 0 volts during the demagnetization phase.