Derating is the practice of setting a lower value than the maximum output power specified in the data sheet to reduce the possibility of failure. By derating, most equipment, including power supplies, can work without reducing the lifetime.

This function synchronizes the oscillation frequencies of multiple converters. The oscillation frequencies of converters of the same model are almost the same, in other words slightly different. In this situation, the input may oscillate at a lower frequency. To avoid it, there is a function to synchronize the frequencies between converters.

TCT circuit automatically supplies only required amount of the current to the base of a switching transistor to saturate it. Due to this function, unnecessary carriers are not accumulated at the base of the transistor, enabling fast switching. The TCT circuit is a Bellnix’s original circuit (patented).

　This is the range of input voltages in that power supply works with no problem. It may work with the voltages even outside this range, but it is not guaranteed that the satisfactory performance can be drawn out compared to the specs. Further, the power supply itself may also be damaged depending on the control method and conditions.

It is the ambient temperature range in that the power supply is workable. Also known as the usable temperature range. In many cases, it is specified in conjunction with Temperature Derating section in the datasheet. Temperature derating is defined with input voltage, ambient temperature, forced air cooling and so on.

It is the output voltage guaranteed under certain input/output conditions. As for the conditions, it is often written that “The value at the input voltage of xx V, output voltage of xx V, output current of xx A, ambient temperature of xx °C unless specified” outside the spec table.

It is a protective feature that works when the ambient temperature is abnormally high or when the temperature of internal components is high. This function keeps watching the temperature of a part of the converter and stops the converter’s work when its temperature exceeds a specified value (hysteresis upper limit). Typically, a hysteresis is set for the temperature detection to enable the protection at the upper limit of the hysteresis and automatically recover when the temperature lowers to the lower limit.

It is a function that controls the power supply output to ON/OFF by an external signal separately from input voltage. When multiple power supplies are used, this function is used, for example, to set a time difference in the rise time and fall time among those power supplies.

As some turn ON with an external signal LOW and OFF with an external signal HIGH, and vice versa, please check the specifications.

Note: There is a pin for external signal. Not all converters have this function.

When input voltage (VIN) reaches the minimum operating voltage at power-on, this function does not allow the DC-DC converter to suddenly start working so as to prevent the occurrence of a rush current and/or overshoot. By this function, the rise time (soft start time) is set to ensure smooth start-up of the DC-DC converter.

Note: There is a pin for external signal. Not all converters have this function.

This is a function to stabilize the output voltage at the load. Also known as remote sensing or sensing functions. Normally, as converter and load cannot be placed close together, a slight resistance exists between the converter and the load, causing a voltage drop. The higher output current, the lower load voltage due to the resistance between the converter and the load.

These phenomena can be suppressed by assigning the sensing pin separately from the output pin and connecting it to the load position.

When the output voltage sensing function is used, as the load increases, the voltage at the output pin increases to keep the voltage at the sensing point constant. The upper limit of this range is the maximum voltage at the output pin. It may be set so that overvoltage protection will be enabled if the output voltage exceeds it.

It is the time required until the output voltage rises to 90% after input source is applied. It is the sum of delay time and rise time.

It is the time that output voltage remains in a specified voltage range after the input is cut off.

It means a power supply that keeps the output voltage constant against load fluctuations.

It means a power supply that keeps the output current constant against load fluctuations.

As it is adopted for high-efficiency converters, it is called as a synonym for high efficiency. Basically, it refers to a circuit type that increases efficiency (reduces loss) by replacing the part for rectification using a diode with an FET. The diode induces 0.5 V voltage drop when current flows through. In other words, if 10 A flows, the loss of 5W occurs. FET is just a low resistor when it is ON. If the resistance value is 5 m-ohm, the voltage drop of 0.05 V will occur if 10 A flows. In other words, if10A flows, the loss of 0.5 W occurs.

POL stands for Point of Load and is a DC-DC converter located as a dedicated power supply circuit close to LSI such as FPGA or ASIC. The distance between the LSI and the power circuit can be 1 cm or so, therefore, static voltage drops can be suppressed by reducing the resistance components of the power trace. In addition, as the inductor components can also be reduced, even if the current significantly changes due to the chip operation, the voltage fluctuation due to it can be suppressed. By this reason, it is used for a power supply that a fast response speed is required.

It is to make a difference between detection thresholds. In the case of a protection circuit, it is to set a difference between the value to start the protective operation and the value to end it. This characteristic is often adopted in such cases of “To disable the over-temperature protection that starts the protection at 110 °C, the temperature needs to fall below 100 °C”.

When described as Withstand Voltage, it means the voltage that can be withstood against or the limit voltage that can be applied for a specified time period between specified pins that are isolated without causing isolation breakdown. Based on this definition, it may also be expressed as “Dielectric Strength” or “Isolation voltage”.

It means the voltage that occurs no problem even if it is applied between all input terminals and all output terminals. It is sometimes specified for AC, and for DC in other cases. However, it is rarely acceptable to be all the time. It is usually specified for one minute or one second. The reason it is not specified for a longer period of time is that external factors due to the environment may change if it is applied for a long period of time.

For example, when the device is brought close to a CD, it ionizes the air, making it easier for electricity to flow through the air.

It is the ambient temperature range that the off-state power supply can be left. Be careful that some products may have different pre-mounted and post-mounted storage requirements. In that case, the condition for post-mounted is called Storage Temperature Range.

It is the input current that flows when the power supply is ON (output voltage comes out) and no output current is flowing. Even if no output current is flowing, it induces a loss due to the work of the internal circuits of the power supply. It is mainly due to the losses incurred when driving the control circuit and switching elements.

This means the amount of output voltage change when the input voltage is changed within the specification range while the load is kept constant. Also known as Static Input Fluctuation. In the datasheet, the specification is often defined as the amount of output voltage change when changing the input voltage from the minimum voltage to the maximum voltage in specified input voltage range at rated load. Some products may have a specific definition on the power supply.

This means the amount of output voltage change when the load is changed within the specification while the input voltage remains constant. Also known as Static Load Fluctuation. In the datasheet, the specification is often defined by the amount of output voltage change when output current is changed from no load to rated load at rated input voltage. Some products may have a specific definition on the power supply.

It is the output current range in that the power supply works with no problem. It is often referred for no-load to rated load, however, the minimum output current may be specified on some power supplies.

Note that the condition to obtain the output voltage as specified does not match with the output current range in some products.

It is the humidity range in that the power supply is usable. Also known as Operating Humidity Range.

Also known as Overvoltage Protection. It is the function to disable the power supply output when the output voltage rises above a specified value due to the changes in the state of surrounding circuitries or the failure of power supply. The disabling voltage depends on power supply. Not all power supplies have this feature.

Also known as current limiter or overload protection. It is a protective function to prevent damage to the power supply at the event of excessive output current or output short-circuit. When an overcurrent state occurs, the output voltage drops to protect the power supply, however, when the overcurrent state is removed, its behavior depends on the type of overcurrent characteristic. There are several types of overcurrent characteristics including “Drooping characteristic”, Fold-back characteristic, “Shutdown” and “Hiccup”. Not all power supplies have this feature.

It is the ambient humidity range that an off-state power supply can be left. Be careful that some products may have different pre-mounted and post-mounted storage requirements. In that case, the condition for post-mounted is called Storage Humidity Range.

It refers to the input current that flows in the OFF state (no output voltage comes out, stopping) in a power supply that ENABLE (ON/OFF) function is hired.

It refers to the amount of output voltage change when ambient temperature is changed while input/output conditions remain constant. Normally, the amount of output voltage change is specified for 1 ℃ change such as [V/°C] or [V%/°C].

It means the frequency at which the main switch of the power supply is oscillating (switching). In many cases of separately-excited PWM control, it is almost constant over the entire input/output range. In almost cases of self-excited type and PFM control, the value will most likely vary depending on input/output conditions. Even if the same product, there will be a slight deviation due to individual differences in the parts used. By this reason, frequency synchronization is required in some applications.

It is a protective function that prevents the power supply from breakdown even if the +Vout and -Vout pins (COM pin) are shorted by a mistake at the output side. It is generally a protection against momentary shorting, not against long-term shorting. Not all power supplies have this feature.

It is called UVLO for short. Also known as an undervoltage protection circuit. It is the function to stop the power supply when the input voltage gets too low. When the input voltage drops, the input current increases if the load is constant. If the input voltage drops below the input voltage range, it may become a problem as the temperature of the input part rises (loss due to resistance component increases) due to the increase in current. In the absence of UVLO, overcurrent protection of the power supply (of pre-stage) may work at the start-up, causing a problem such that the power supply does not start up. Not all power supplies have this feature.