Isolated 1W and 2W Converters Meet the Needs of Many Applications

Unregulated or Regulated Converters

RECOM offers isolated DC/DC converters in both regulated and unregulated versions. The choice between the two depends on the specific application. If the supply voltage is regulated and the load remains relatively constant, an unregulated DC/DC converter may offer the ideal solution. This is because an unregulated DC/DC converter still offers voltage level conversion, galvanic isolation, and short-circuit protection (/P versions) while also being significantly cheaper than a regulated DC/DC converter.

Conversely, if the supply voltage or load is not stable, a regulated converter is needed since it is designed to maintain the output voltage at the desired value despite input voltage or load variations. A regulated DC/DC converter will maintain a fixed output voltage if the input voltage varies (for example, if it is battery-powered) or if the load is variable, including no-load conditions.

In some low-power designs, a semi-regulated solution offers the best compromise. An unregulated converter incorporating a linear low-dropout (LDO) voltage regulator on the secondary side of the transformer maintains the output at the desired value, irrespective of load conditions. The tradeoff is that the additional regulation stage reduces the overall efficiency and increases the cost compared to an unregulated converter, although it has the advantage that if the load is suddenly removed, the output voltage remains stable and the converter continues to be short-circuit protected.

Here are some of the many areas where these versatile devices are used. Both regulated and unregulated converters are included, depending on the application.

Gate Drive Power Supplies

Isolated DC/DC converters are widely used in gate drivers in high-voltage inverters. For instance, a photovoltaic (PV) solar panel produces a high-voltage DC output that is converted to AC by a high-voltage three-phase inverter. The DC rail voltage can be 1000V or higher, and the inverter module is often floated by a few hundred volts above the ground; therefore, isolation is required for both functional and safety purposes.

Though control signals can be isolated using optocouplers, isolated DC/DC drivers are needed for an isolated gate driver power supply. RECOM offers a range of isolated DC/DC converter modules that provide a simple power solution for IGBT, SiC MOSFET, or GaN HEMT power devices.

The optimum RECOM DC/DC converter families vary by power switch technology and can be categorized as follows:

• IGBT power devices: RECOM’s DC/DC converters RH, RV, RP, RGZ, RKZ, RxxPxx, and RxxP2xx provide asymmetric outputs of +15V and -9V, making them ideal for powering IGBT drivers with only a single DC/DC converter.


• SiC MOSFETs: The RxxP22005 and RKZ-xx2005 series feature asymmetric outputs of +20V and -5V to switch the SiC MOSFET efficiently and effectively. The RxxP21503 series provides asymmetric output voltages of +15 and -3V, which are needed to efficiently switch second-generation SiC MOSFETs.


• GaN HEMTs: High slew-rate GaN transistor drivers reach optimal performance switching at +6V through RECOM’s DC/DC converters of the RP-xx06 and RxxP06 series, which feature high isolation voltage and low isolation capacitance. Further, in GaN applications where higher noise and interference must be considered, RECOM also offers converters with +9V output, which can be split with a Zener diode into +6V and -3V to provide a negative gate voltage on the turn-off, ensuring that the gate voltage stays below the turn-on threshold.

Isolated Serial Links in Industrial Applications

A fieldbus is a generic term used to describe a serial bus system in industrial applications that connects e-sensors and actuators to each other as well as to multiple master devices such as PLCs or industrial PCs. Fieldbuses often run over long distances and often include a feature such as differential twisted pair connections to accomplish high-speed and high-reliability data communication. The signal and power isolation between the bus and each system connection is critical to protect from overvoltage transients between the cable network and the systems connected to it. Further, the isolation eliminates ground loops in the network, reduces signal distortion and errors, and provides protection from voltage/ground mismatches.

For instance, the Controller Area Network (CAN) bus was originally developed for automobile use, but its robust protocol has found ready adoption in industrial applications. It specifies a maximum cable length of 40 meters and up to 30 nodes. Other fieldbus standards with similar DC/DC requirements include Modbus, Profibus, and Interbus.

An example of an isolated DC/DC converter suitable for isolated fieldbus interface power is RECOM’s RxxCT(E)xx family of regulated converters that provide 0.5W or 1W at 5V or 3.3V output from a nominal 5V input—all in an SMD-16 package. Additionally, isolation is provided with a 5kVAC reinforced rating.

IIOT Sensing and Control Applications

The Industrial Internet of Things (IIOT) unlocks new capabilities for factory designers. The IIOT’s vast array of connected sensors allows for numerous improvements to traditional industrial operations, including predictive maintenance, condition-based monitoring (CBM), and real-time digital modeling of industrial processes.

The harsh factory power infrastructure with its ground loops, voltage surges, and high levels of electrical noise was not designed to accommodate sensitive sensors and microcontrollers. Therefore, isolated power is a requirement in the factory environment. However, many sensors or data-acquisition circuits are designed to consume minimal amounts of power, so a 1W or 2W converter is often sufficient.

IIOT applications also include control elements. Figure 1 presents an isolated digital-to-analog (DAC) circuit suitable for a control output module in an industrial PLC or distributed control system (DCS).

The DAC operates from a single +5V supply, but the output buffer requires a +/-12V supply to provide a bidirectional output voltage range. The isolated +/-12V is supplied by R1DX-0512/H, which is a cost-efficient, low-profile, and open-frame 1W SMD isolated DC/DC dual-output DC/DC converter. An R-78E-0.5 switching regulator supplies the DAC with +5V from the +12V rail.

The R1DX family operates from 5V and offers a choice between ±5, ±9, ±12, and ±15 dual outputs. The output voltages are compatible with typical active sensors and microcontrollers or DSP front ends for the data analysis.

Medical Applications

Medical applications have strict regulatory requirements in both hospital and non-hospital environments, with prime importance placed on patient and operator safety. In medical equipment, there is often a need for DC/DC converters that may take a battery- or AC-derived DC input and convert voltage levels to practical values either required in the circuit or for powering peripherals to the equipment such as sensors. In most cases, the input voltage to the DC/DC converter is low such as 5V or 12V with a low voltage output such as +/-5V or 3.3V. Functionally, isolation is not always required but may be included to break ground loops, help control cross-talk between the sensors, reduce electromagnetic interference (EMI), or generate a negative rail voltage from a positive supply. Conversely, in situations where isolation is not needed functionally, it still may be necessary for safety reasons, even though input and output voltages are low and well within the definition of a “safe” voltage.

RECOM has many medical-grade DC/DC converters that offer higher power levels; however, it has expanded the power range with the 1W REM1, which is a medical-grade unregulated DC/DC converter in a compact SIP7 package. The REM1 features reinforced 5.2kVDC/1 minute isolation and 2MOPP*/250VAC working voltage. The REM1 is available with 3.3, 5, 12, 15, or 24V inputs and offers 3.3, 5, or 12V outputs with up to 85% efficiency. The operating temperature ranges from -40°C to +90°C. Moreover, the converter is compliant with Class B EMC and 60601-1-2 (fourth edition) medical EMC standards by using a simple external LC filter. Further, the converters are fully compliant with CB, IEC/EN, and ANSI/AAMI 60601 (third edition), RoHS2+ (10/10), and REACH safety standards as well as come with a five-year warranty.

*2MOPP = Two means of patient protection

Distributed Power Architecture (DPA) systems

A DPA system is often used in industrial controls where high-power loads are combined with low-power control devices. An AC/DC power supply typically provides a system bus voltage of 24V or 48V, which is available for motors, pumps, and similar electrical equipment.

However, the controllers, logic circuits, and other electronic devices require small volumes of 3.3V, 5V, 12V, or 15V power to operate. Low-power isolated DC/DC converters are used to provide 3.3V, 5V, 12V, 15V, +/-12V, +/-15V, and similar voltages. In a rack-based design, the DC/DC converters are point-of-load (PoL) devices placed next to wherever they are needed. This minimizes any voltage drop between the converter and the device and reduces the possibility of any noise pick-up that could cause signal degradation.

RECOM Offers Low-Power DC/DC Converters for Multiple Uses

Low-power isolated DC/DC converters are found in many industrial and medical applications with a broad range of specialized requirements. RECOM offers a wide range of regulated and unregulated designs that are optimized for these purposes.