What Is an IPD?
An IPD (Intelligent Power Device) is a power IC that contains a power switch, various protection circuits against overheating and overcurrent, and control circuits on a single chip.
Sometimes called an IPS (Intelligent Power Switch) or Smart Switch, an IPD is a high-performance semiconductor power switch capable of absorbing back energy due to inductive loads.
An IPD is available in two types: high-side switches, which are placed on the current side with respect to the external load, and low-side switches, which are placed on the GND side.
Uses of IPDs
IPDs are used as switches to drive inductive loads such as motors, solenoids, heaters, and lamps that may generate back energy.
Uses of IPDs are particularly prevalent in the automotive field, where they are used in a variety of safety-critical automotive components such as ECUs (engine control units), ADAS (advanced driver assistance systems), transmission control units, hydraulic suspension control units, power distribution modules, etc. They are also used in motor drives, solenoids, and other automotive components with strict safety requirements.
It is also used in industrial equipment with motor and solenoid drives and in home appliances such as air conditioners, ventilation fans, and ceiling fans.
Principle of IPDs
IPDs consist of a power device for driving, a current sensor, an overcurrent protection circuit, a temperature sensor, and an overheat protection circuit.
When an inductive load such as a motor or solenoid is driven, a magnetic field is generated around the inductive load. When the drive current is turned off, the current supply ceases and the magnetic field collapses. The electromagnetic induction caused by the change in the magnetic field induces a current in the reverse direction, generating a back EMF. The back EMF generated at this time is proportional to the speed of the current change and can be a high voltage spike far exceeding the supply voltage.
When such a back EMF is generated, IPDs detect the overcurrent by the current sensor and turn off the MOSFET of the overcurrent protection circuit to shut off the current. When it detects that the overcurrent has dissipated, it turns on the MOSFET of the protection circuit again to restore it. The same protection system also works against overheating.
There are two types of IPDs: high-side switches and low-side switches.
High-side switches are inserted between an external load and the power supply and are suitable for circuits with multiple loads connected to a single power supply. Since the battery is fixed and the car body is grounded, high-side switches are often used in automobiles, where the on-board devices are at GND potential when the switch is in the off state.
Low-side switches are inserted between an external load and GND and are suitable for circuits with loads connected to multiple power sources.