These are useful terms to know when talking about DC-DC converters.
Brick converter: Dc-dc converter modules provide electrical isolation, increased load transient performance, and a modular upgrade path. The physical size of brick converters can vary slightly, but pin configurations are standard, which allows multiple sources.
Bus converter: Bus converters usually deliver an unregulated, stepped-down voltage of 9.6 to 14 V with a nominal 2000-V dc input-output isolation. They are ideal for loosely regulated 12-V dc intermediate bus architectures that power a variety of downstream non-isolated, point-of-load converters.
Controller IC: The controller IC controls the output of a dc-dc converter by employing an external power stage output (usually power MOSFETs). The power stage may be integrated in the same IC as the controller circuit, though integrated power MOSFETs have a higher on resistance than external devices.
Distributed power architecture: distributed power architecture converts the incoming ac power to a secondary dc bus voltage, using a front-end supply. This dc bus voltage can be 12, 24, or 48 V and is usually less than 60 V. This bus voltage is distributed throughout the system, connecting to dc-dc converter (point-of-load) modules associated with specific subsystems or circuit cards.
Distributed-power Open Standards Alliance (DOSA): Dc-dc converter manufacturers established DOSA to ensure future product compatibility and standardization within the power converter market. Its goal is to establish standards over a broad range of power converter form factors, footprints, feature sets, and functionality to drive product development and facilitate independent alternate product sources.
Efficiency: Efficiency is the ratio of output-to-input power (in percent), measured at a given load current with nominal line conditions (POUT/PIN).
Front-end power supply: The front-end power supply is an isolated ac-dc supply employed in distributed power architectures that usually provides a 36- to 75-V dc output (48 V nominal).
Intermediate bus architecture (IBA): The IBA inserts a level of power distribution between a front-end ac-dc power supply and a point-of-load. It employs an isolated bus converter that delivers an unregulated 9.6 to 14 V to power non-isolated point-of-load converters.
Isolation: Isolation is the electrical separation between the input and output of a power supply. A non-isolated supply has a dc path between the input and output of the supply, whereas an isolated power supply employs a transformer to eliminate the dc path between input and output.
Line regulation: Line regulation is the change in the value of a dc-dc converter’s output voltage resulting from a change in input voltage, specified as the change in ± mV or ± %.
Load regulation: Load regulation is the change in the value of a dc-dc converter’s output voltage resulting from a change in load from open circuit to maximum rated output current, specified as the change in ± mV or ± %.
Output voltage trim: Output voltage trim is the ability to “trim” the output voltage, whose adjustment range is usually about ±10%. One common usage is to compensate for the dc distribution voltage drop within the system. Trimming can be either upward or downward from the nominal setting using an external resistor or potentiometer.
Periodic and random deviation (PARD): PARD is the unwanted periodic (ripple) or aperiodic (noise) deviation of the power supply output voltage from its nominal value. It’s expressed in mV peak-to-peak or rms at a specified bandwidth.
Point-of-load (POL) converter: These converter modules are usually mounted on printed-circuit boards (PCBs), where they provide POL regulation. This is increasingly important as processors operate at low voltages, higher currents, and higher clock frequencies. They are used in distributed power architecture and intermediate bus architecture systems.
Power Management Bus (PMBus): This open standard power-management protocol has a fully defined command language that facilitates communication with power converters and other devices in a power system. It is implemented over the industry-standard SMBus serial interface and enables programming, control, and real-time monitoring of compliant power conversion products.
Power supply sequencing: Sequential turn-on and turn-off of power supplies may be required in systems with multiple operating voltages—that is, voltages must be applied and also removed in a specific sequence. Otherwise, the system may be damaged.
Pulse-frequency modulation (PFM): PFM varies the frequency of a pulse train in accordance with the instantaneous amplitude of the modulating signal at sampling intervals. The amplitude and width of the pulses is kept constant.
Pulse-width modulation (PWM): PWM varies the width of a square wave frequency signal in response to a varying dc control voltage feedback. In a dc-dc converter, this feedback allows the converter to maintain a constant output voltage.
Regulatory standards: Individual nations usually require compliance with national or international standards for dc-dc converters. Different nations can require compliance with different standards. Subjects include electromagnetic interference/electromagnetic compliance (EMI/EMC), safety, electrostatic discharge (ESD), audible noise, and power-line noise and harmonics.
Remote sense: The direct connection from a power supply’s output to its load produces a voltage drop that creates a difference between the supply’s output and the actual load voltage, which can cause an incorrect feedback voltage. Remote sense inputs connected to the load carry very low current so the voltage fed back to the power supply is the accurate load voltage.
Restriction of Hazardous Substances (RoHS): This directive restricts the use of hazardous substances in electrical and electronic equipment. Designated 2002/95/EC, it is commonly referred to as the Restriction of Hazardous Substances Directive. It took effect in July 2006 and includes power supplies.
Soft start: Soft start is the inrush current limitation provided by a circuit that slows the initial rise of current and then allows normal operation.
Switch-mode power supply (SMPS): An SMPS converts the incoming dc into a switched frequency that can be anywhere from 60 kHz to over 2 MHz. The switched frequency is then rectified and filtered to obtain a dc output. This approach provides higher efficiency than a linear power supply.
Synchronous rectifier: The synchronous rectifier usually uses a pair of power MOSFETs that turn on and off to rectify a switched voltage. This provides higher efficiency than the use of rectifier diodes because the conduction losses of the MOSFETs are lower than the diodes.
Tracking: When using multiple output power supplies whereby one or more outputs follow another with changes in line, load, and temperature, each output maintains the same proportional output voltage, within specified tracking tolerance, with respect to a common value.