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Technology File - Safety Technology

Power Control Unit

The brain of the plug-in hybrid vehicle, expertly controlling electricity.

The power control unit converts AC/DC power and appropriately adjusts the electrical voltage. Plug-in hybrid vehicles powered by motors are equipped with a power control unit that consists of an inverter, a boost converter, and a DC/DC converter. Low loss elements are used to achieve superb loss reductions.

The Prius PHV features a more compact power control unit, making it possible to mount it directly above the transaxle and place the auxiliary battery in the engine room, creating a more spacious interior.

The same power control unit is used in hybrid vehicles.


Converting electricity and supplying it from the battery to the motor.

Motors cannot be operated by connecting them directly to the battery. The inverter converts DC supplied by the battery to AC to turn the electric motors and to use in the generator. Conversely, it converts AC generated by the electric motors and the generator into DC to recharge the battery. Dual side cooling, which directly cools power elements, is featured in the Prius PHV, improving cooling efficiency and enabling inverter downsizing and weight reduction.

Boost converter

Controlling voltage and boosting low voltages.

The boost converter controls the voltages of the motor and generator. It steplessly increases the normal roughly 350 V DC supply voltage to a maximum of 600 V DC as required. This means more power can be generated from a small current to bring out high performance from the high output motors, enhancing overall power control unit efficiency.

DC/DC converter

Steps down voltage precisely, enabling electricity to be used for purposes other than driving.

The DC/DC converter steps down the supply voltage from the high voltage battery. It steps down the roughly 350 V DC supply voltage from the battery to 12 V DC, to be used by engine ancillary systems which assist with motor operation and electronic devices such as headlights.

Power Control Unit

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Specifications may differ depending on country, region, or model.