DENSO Develops High Output Power Control Unit and Battery Cooling System for Hybrids; Applied in the LS 600h
|The new structure for DENSO’s PCU handles the greater cooling requirements of the high-output unit.|
DENSO Corporation has developed a new high-output power control unit (PCU) and battery cooling system for hybrid vehicles. The products are installed on the Lexus LS 600h and the Lexus LS 600hL (earlier post).
The high-output PCU consists of a boost converter that raises the main battery voltage (288V) up to the maximum system voltage (650V), and two inverters that convert direct current (DC) into alternating current (AC) to drive the main traction motors.
Denso’s new PCU can produce higher output power by approximately 60% per unit volume, compared to the company’s conventional technology, thus improving the hybrid system performance. When the PCU is designed to produce the same output as the conventional technology, it can be reduced approximately 30% in size and approximately 20% in volume.
For this PCU, DENSO developed a new structure to handle the increased cooling requirements. To deliver a higher PCU output, the power devices must handle more power, resulting in more heat generation by the devices. Using a conventional cooling structure where power devices are mounted horizontally on a cooling unit through a heat sink so that only the side facing the cooling unit is cooled made it difficult to adequately cool the higher power devices.
In DENSO’s new cooling structure, the power devices are sandwiched between two heat sinks and inserted in layers between stacked cooling tubes. This structure allows both sides of the power devices to be cooled, which substantially enhances the cooling performance. The new cooling structure also is more compact than the conventional structure.
Since both sides of the power devices are soldered to the heat sinks, DENSO reduced the thickness of each power device to ease stress on joint portions, ensuring high reliability. The new PCU design can easily be used in hybrid systems with different output levels by changing the number of stacked power devices and cooling tubes.
Battery cooling system. In some conventional battery cooling systems, the battery blower draws only cabin air to cool the hybrid vehicle’s main battery. DENSO’s newly developed battery cooling system can use cooled air from the cooling unit of the rear air conditioning system as well as cabin air to cool the main battery.
Accordingly, the new battery cooling system provides comparable cooling performance with approximately half the amount of air required by previous models. This reduces noise from blowing air by approximately 30%, contributing to the quieter vehicle cabins of the Lexus LS600h and the Lexus LS600hL.
In addition to the high output PCU and battery cooling system, other DENSO hybrid vehicle products including the DC-DC converter, the battery-monitoring unit, the system main relays, and the current sensor are installed on the Lexus LS600h and the Lexus LS600hL.