Monday, December 19, 2011

Renesas intros high-commutation power semiconductor device for motor drive in electric household appliances

TOKYO, JAPAN: Renesas Electronics Corp. announced the availability of a high-commutation triac, the BCR8LM-14LK, supporting rated RMS on-state current (IT (RMS) of 8-ampere (A) and rated repetitive peak off-voltage (VDRM) of 700 V, which can be triggered directly by a microcontroller (MCU).

The new triac can be used to drive loads such as AC (alternating current) motors, solenoids, and heaters in electric household appliances (white goods) such as washing machines and refrigerators.

Triacs are used for controlling power supply switching in AC circuits. Due to their high gate trigger current (IGT), a dedicated circuit is required to amplify the output current of a conventional MCU. A lower gate trigger current typically has a trade-off with other performance.

The new triac maintains the performance of existing TRIAC products, while achieving a low gate trigger current of 12 milliamperes (mA) or less, allowing it to be driven directly by a MCU. This eliminates the need for an amplified circuit, required previously, and makes it possible to build drive circuits that are more compact, cost less because they use fewer parts, and consume less power.

In the field of electric household appliances (white goods), demand has increased in recent years for smaller and more power-efficient drive circuits for loads such as AC motors, solenoids, and heaters due to considerations of visual design and energy efficiency. This has created a need for triac products that require no dedicated driver circuit and can be driven directly by an MCU. However, a triac typically has a gate trigger current of 30mA or more.

Reducing this to around 12 mA to accommodate the low-current output of a typical microcontroller resulted in a worsening of the commutation characteristics, and the rate of critical off-voltage rise (dv/dt), which is important for preventing malfunctions. The new triac employs a basic structure designed to reduce the gate trigger current. It utilizes a special device structure and process optimizations to achieve a gate trigger current of only 12 mA or less without degrading other important TRIAC characteristics.

The BCR8LM-14LK device is the industry’s first triac with a voltage tolerance in the 700 V class to maintain high commutation characteristics of ((dv/dt)c) 10 V/μs while achieving a gate trigger current of 12 mA or less. Unlike conventional triac products, it requires no dedicated driver circuit. This makes it possible to use a much simpler drive circuit for AC motors and the like and contributes to reduced component cost and lower power consumption.

Renesas intends to extend the series with new products having RMS on-state current ratings of 12 A, 16 A, and 20 A, in addition to the 8 A of the BCR8LM-14LK device. In addition to the insulated TO-220FL (UL-approved) package, a lineup of non-insulated packages will be offered to meet a broad range of customer requirements.

Samples of Renesas' BCR8LM-14LK triac will be available in January 2012, priced at $1 per unit. Mass production is scheduled to begin in March 2012 and is expected to reach a combined volume of 3,000,000 units per month in March 2013.

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