IPDs

What is an IPD?

An IPD, or Intelligent Power Device, is a high performance semiconductor power switch with built-in protection circuits capable of absorbing energy such as inductive loads.
Depending on the region, it may also be called an IPS (Intelligent Power Switch), Smart Switch, or High Side/Low Side Switch.

IPD Feature 1 (Comparison vs MOSFET)

Typically, MOSFETs are the first components that come to mind when thinking about semiconductor switches.
However, when using a single MOSFET as a switch, the MOSFET itself may fail if the load shorts on the mounted circuit.
In contrast, IPDs incorporate circuits that protect against excessive current and heat as well as for absorbing energy (i.e. from inductive loads), allowing them to maintain switch functionality without breaking down due to abnormal conditions such as short-circuits.

[IPD vs MOSFET]

IPD Feature 2 (Comparison vs Fuse)

Fuses are components that prevent excessive current flow.
Mechanical fuses stop current flow by opening the circuit during overcurrent conditions. However, they must be replaced in order to resume normal operation.
Conversely, using an IPD as a semiconductor fuse makes it possible to detect abnormalities such as overcurrent and stop current flow. A notification function (i.e. to the MCU) is also built in that can be effective in analyzing the root cause. What’s more, IPDs are self-restoring, therefore no replacement is needed.

[IPD vs Mechanical Fuse]

IPD Feature 3 (Comparison vs Mechanical Relay)

Relays are components that switch electrical circuits ON/OFF using an external signal.
As mechanical relays have mechanical contacts, there are concerns regarding service life and reliability. In addition, relays typically generate a mechanical sound when switching.
Semiconductor relays using IPDs, on the other hand, feature no mechanical contacts, resulting in longer life, higher reliability, and quieter operation. Also, their compact lightweight form factor supports reflow soldering, and they provide not only relay functionality for switching ON/OFF, but protection as well by detecting overcurrent.

[Comparison vs Mechanical Relay]

High Side/Low Side Drive

A semiconductor switch placed in the upper circuit with respect to an external load is referred to as high-side drive (power supply side), and when mounted in the lower circuit is called low side drive (ground side).

[High Side Drive / Low Side Drive]

Usage examples for high side and low side switches

IPDs incorporate a high side switch for the upper circuit and a low side switch for the lower circuit with respect to external loads, utilizing a circuit design optimized for each location.
As shown in the figure at left below, in a circuit where various loads are connected to a single power supply voltage, such as in a vehicle where the battery voltage is fixed and body connected to ground, the output can easily become grounded, making a high-side switch more suitable for detecting abnormal conditions such as ground faults.
Conversely, low side switches are ideal for circuits in which loads are placed at various power supply voltages as shown in the figure at right below. The low side switch operates by applying an input voltage to the gate and connecting the MOSFET Source to ground. This control scheme is the same as with single MOSFETs, making it easy to replace individual MOSFETs.

[High Side / Low Side Usage Examples]

*For details on “low-side switches,” please see this article.