Renesas Introduces Photocoupler with Long External Creepage Distance of 14.5mm
Renesas Electronics Corp. announced the availability of a long-creepage-distance photocoupler, the PS9905, for inverters in applications such as industrial equipment employing the maximum commercial power supply voltage of 690V or solar power generation systems employing high voltages up to 1,000V. The new PS9905 device is a photocoupler (compound semiconductor) with an external creepage distance of 14.5 mm, exceeding the 13.8 mm specified in safety standards (IEC 61800) covering insulation to prevent electric shock, etc.
A high-speed photocoupler, the PS9924, is also available, which supports internal system communication speeds of 10 Mb/second while providing a long creepage distance of 14.5mm. Among products with creepage distances exceeding 10mm, it delivers low power consumption characteristics among the best in the industry, making it well suited for applications requiring both high insulation voltage and low power consumption.
As efforts to reduce CO2 emissions and lower energy consumption in order to protect the environment have advanced, the use of inverters in industrial applications and solar power generation systems has continued to grow rapidly as a way to achieve low-power motor control and reduce power conversion loss. These inverters comprise high-voltage circuit blocks containing power devices such as IGBTs and control circuit boxes containing devices such as microcontrollers (MCUs). Photocouplers are required to drive power semiconductor devices such as IGBTs while electrically isolating the two circuit blocks.
Renesas already mass produces compact photocouplers with a creepage distance of 8mm for driving IGBTs in inverter circuits. However such systems have come to handle increasingly higher voltages, making it possible to lower the current level, reducing power loss and allowing the use of thinner cables between inverter motors and as power cables. To address this market trend, Renesas released the PS9905 and PS9924 photocouplers for inverters in industrial systems employing 690V power supplies, use of which is expected to expand further moving forward, and inverters in 1,000V solar power generation systems. The new photocouplers have a long creepage distance of 14.5mm to meet applicable safety standards.
The IEC 61800 standard requires a creepage distance of 13.8mm or more for the reinforced insulation of 690 V power supplies and a creepage distance of 10mm or more for the basic insulation of inverters in solar power generation systems handling voltage levels of 1,000V. The new PS9905 employs design enhancements that enable a creepage distance of 14.5mm, easily meeting the safety standard. The insulation voltage is 7,500Vrms, suitable for equipment with high voltage handling.
The new PS9905 can do the work that previously required two Renesas Electronics photocouplers, each with a creepage distance of 8mm. This results in a reduction of approximately 30 percent in the mounting area. In addition, the newly developed 8-pin surface-mount package gives this high-speed photocoupler one of the smallest mounting areas in the industry among photocouplers with a creepage distance exceeding 10mm.
The photocoupler employs a light receiving IC fabricated with a BiCMOS process exclusive to Renesas Electronics, enabling it to achieve a low parasitic capacitance while keeping the circuit current (Icc) below 3mA and delivering short delay times (tPHL, tPLH) of less than 150 ns. High-speed response is among the best in the industry for photocouplers to drive IGBTs with 2.5 A output, allowing for improved output current accuracy after inverter control.
Optimizing the design of the light receiving IC incorporated into the photocoupler made it possible to achieve a long creepage distance of over 10mm and substantially lower power consumption. Input current (IFHL) is 5mA (maximum value) and circuit current (Icc) is 5mA (TYP). Power supply voltages of 3.3 and 5V are supported, and the operating temperature range is a wide −40 to 110°C. The photocoupler can then be used for communication in compact systems where the high mounting density is accompanied by a high-temperature environment.
Samples of Renesas Electronics’ new photocouplers are available now, priced at US $4.00 per unit. Mass production started today and will reach a scale of 1,000,000 units per month in October 2012.
More news and information regarding the latest developments in Smart Grid electronics can be found at Darnell’s SmartGridElectronics.Net.
