New Industry Products

Isolated DC-DC Control ICs without Optocouplers

August 15, 2016 by Jeff Shepard

Rohm has announced the availability of isolated flyback-type dc-dc converter control ICs for inverters in high power industrial equipment such as factory automation drives, solar inverters and power storage systems. Isolation is almost always built into electronic equipment to provide protection against shock and damage. High-voltage, high-power industrial applications (including power storage systems and solar inverters which are seeing increased adoption) are no exception, requiring even more stringent reliability demands due to the harsher temperature conditions and the need for continuous, long-term operation.

Conventional solutions utilize an optocoupler and other components for flyback-type isolated power supply control. However, this presents challenges associated with current consumption and reliability (including circuit scale and product life). In contrast, the BD7F series reduces the number of external parts by nearly half by eliminating the need for an optocoupler, providing greater energy savings, reliability, and miniaturization. In addition, a newly developed adaptive ON time control method is used to improve load response time (a drawback of conventional isolated power supply ICs), while voltage fluctuation is limited to under 200mV, contributing to even higher reliability.

Theses dc-dc control ICs are rated from 1W to 10W, depending on model and the input voltage. They have a maximum input voltage rating of 45V and operate over a temperature range of -40 to +125 degrees C. They have a typical switching frequency of 400kHz. Functions include; enable, soft start, efficient light load mode, UVLO, over-current protection and thermal shutdown.

Samples, along with an evaluation board, BD7F100HFN-EVK-001, integrating the BD7F100HFN-LB, will be available for purchase. This board enable to be designed for 24V input voltage and 5V output voltage with output current range of 13.8mA to 800mA for maximum output power of 4W. The BD7F100 Series is available now with pricing from $4.30 in lots of 1,000 pieces. The BD7F200 Series is sampling now with production scheduled for October and costs from $4.69 in lots of 1,000 pieces. The BD7F100HFN-EVK-100 evaluation board will also be available in the Fall.

Key features of these isolated controllers include: High reliability isolation performance ; The BD7F series of isolated power supply control ICs are optimized for industrial equipment requiring continuous, long-term operation under extreme conditions. Utilizing state-of-the-art power BiCDMOS processes and leveraging proprietary advanced analog technology allow ROHM to detect the secondary side voltage and current from the primary side. This eliminates the need for a optocoupler or tertiary transformer winding required with conventional configurations, reducing the number of external parts by half which contributes to greater reliability, power savings, and end-product miniaturization.

Improved load response characteristics through adaptive ON time control; ON time control, typically used in conventional isolated power supply control ICs, is adopted to minimize output voltage fluctuations caused by instantaneous changes in load current. Rohm’s new adaptive ON time control method limits output voltage fluctuations to 200mV, 65% less than conventional solutions (at a load current of 1A and rise time of 100us). As a result, load response against instantaneous load current fluctuations is improved, increasing reliability considerably.

Optional evaluation board makes it easy to verify performance; In addition to the control ICs, an evaluation board (BD7F100HFN-EVK-001) is offered integrating the BD7F100HFN-LB, making it easy to evaluate isolated power supply operation (24V input, 5V/800mA output).