The latest broad purpose and high performance power supplies

From high end bench-top models to high precision, dual range and affordable variants in wide combinations of voltage and current, manufacturers offer diverse power supply product lines to meet user requirements for a variety of applications

By Richa Chakravarty

The primary function of a power supply is to convert one form of electrical energy to another and hence power supplies are sometimes referred to as electric power converters. Today, power supplies include both broad purpose and high performance options for a variety of applications. They are used in test environments, including R&D, and in production—in the semiconductor, nanotechnology and superconductor industries. Their high sourcing accuracy and built-in control functions make them ideal for ‘hall effect’ measurements, resistance measurements using delta mode, pulsed measurements and differential conductance measurements.

Types of power supplies

There are various kinds of power supplies to meet the diverse requirements from the design and manufacturing verticals. Generally, they can be categorised into DC power supplies, AC-to-DC supplies, linear power supplies, programmable and switch mode power supplies. A linear voltage regulator is used to convert a varying DC voltage to a constant, often specific, lower DC voltage. Linear power supplies provide a current limiting function to protect the power supply and load from over current (excessive, potentially destructive current). Linear regulators can also reduce the magnitude of ripple and noise on the output voltage.

A programmable power supply is one that can be remotely controlled through an analogue input or digital interface. These supplies are used in a wide variety of applications, including automated equipment testing, crystal growth monitoring, semiconductor fabrication and in X-ray generators.

In SMPS, switching occurs at a very high frequency (typically 10kHz — 1MHz). The SMPSs have an absolute limit on their minimum current output. They are only able to output above a certain power level and cannot function below that point. In a no-load condition, the frequency of the power slicing circuit increases to a great speed. In such cases, the SMPS protection circuits briefly turn on but then shut down when no load is detected.

The latest in the market

In response to the design and manufacturing requirements of the electronics industry, power supply makers offer diverse product lines. These range from high end, bench-top models to high precision, dual range, affordable variants in wide combinations of voltage and current to help meet the varied application requirements.

Programmable multi-channel DC power supplies: Meeting a broad range of needs with general purpose bench and system power supplies, Tektronix’s DC power supply offers a wide voltage and current range, plus a fine setting resolution, so that users can precisely generate the power needed to satisfy many different applications. With less than 5mVp-p noise, users can be confident about this DC power supply’s output value. The available numeric keypad makes voltage and current set up fast and accurate. “With our PWS series, customers can generate the power they need for their applications—simply and accurately. Our programmable multi-channel DC power supplies offer an excellent combination of performance, versatility and ease of use including fully isolated channels, fully programmable channels and all channel measurements displayed simultaneously,” informs Naresh Narasimhan, country marketing manager, Tektronix India.

Keithley’s broad range of power supplies offers superior accuracy, 0.1mA current measurement resolution, an external trigger, and both USB and GPIB interfaces. It offers convenience features such as the display of both setting values and actual output values, a keypad for fast data entry, and list mode sequence operation. Battery simulating/fast transient response power supplies are designed to test portable, battery operated products such as smartphones, wireless chipsets, Bluetooth headsets, tablet computers, digital cameras and GPS receivers. They can capture load current pulses as narrow as 50µs and sleep mode currents as low as a few µA. High voltage supplies with outputs up to 10,000V facilitate high voltage device and material testing.

Hi-tech single channel programmable DC power supplies: GW Instek has also rolled out its brand new PSU series of single channel programmable switching DC power supplies featuring CV/CC priority, an adjustable slew rate and series/parallel operation. The PSU series, with a high power density design, provides 1520W output power produced by 1U height. Additional features include rear panel output and multiple remote control interfaces. These make the PSU series most suitable for production line and rack mounted ATE application. These power supplies offer the maximum voltage output of 120V for series connection and maximum current output of 800A for parallel connection. “The PSU of series programmable DC power supplies is designed to meet the test requirements of the V-I characteristics curve for power semiconductor components or power industry parts that need a fast response such as DC-DC converters, hybrid powered battery modules and automotive parts,” shares Sumit Sharma, marketing manager, India, Good Will Instrument Co Ltd.

Along with this, GW Instek has introduced its PSW series, which comprises single output multi-range programmable switching DC power supplies covering a power range up to 1080W. This series of products includes 15 models with the combination of 30V, 80V, 160V, 250V and 800V rated voltages and 360W, 720W and 1080W maximum output powers. The multi-range feature allows flexible and efficient configuration of voltage and current within the rated power range. As the PSW series can be connected in series for a maximum of two units or in parallel for a maximum of three units, the capability of connecting multiple PSW units for a higher voltage or a higher current output covers a broad range of applications.

Multi-output linear power supplies: Aplab’s model LQ6324P is basically a linear power supply with digitally controlled output settings unlike the general programmable power supplies available in the market (with SMPS). DC linear power supplies have their own advantages over the SMPS designs like very low output ripple, noise and radiation. They also offer the facility to store or recall 10 sets of output settings in internal memory. Users can even get programmable arbitrary variable outputs as required, by feeding only the coefficient of the curves. “Linear programmable power supplies are now available at almost the same cost as non-programmable units. Generally, linear DC power supplies, and programmable and non-programmable SMPS power supplies are available in the Indian market. For most testing as well as R&D purposes, users prefer linear power supplies as they have very low ripple current,” informs S A Gadkari, general manager, Aplab Ltd.

Scientech Technologies has been manufacturing linear power supplies for the past 30 years. It offers a wide range, from single output to multi-output variants, catering to the industrial and education markets’ needs. Scientech4074 is the latest multi-output power supply with 0-30V and ±15V dual tracking CVCC power supplies ideal for industries, test benches and laboratories, giving a selectable display for voltage and current parameters. “The linear power supplies we offer have a very high MTBF, excellent CV CC features and can be used even as battery chargers. We have explored untapped areas where power supplies can create miracles in the analysis of chemical compositions and in automotive applications,” adds Vivek Mantri, country manager, industrial segment, Scientech Technologies Pvt Ltd.

Making a purchase decision

Depending upon the users’ requirements, the specifications of a power supply may differ. However, there are certain aspects to be considered when buying a power supply.

Output and power requirements: Multiple outputs are vital when a power supply is used to test multiple devices at the same time. When choosing a multiple output power supply, one should consider if one needs the outputs to be isolated from one another, and also the power supply’s tracking capabilities.

Operational specifications: This is an important parameter when choosing the right kind of power supply for specific needs. A user should look at hold time, voltage/load regulation, ripples or noise, transient response, etc. A good power supply will always include protection against the output voltage exceeding a certain critical level. If, for some reason, the voltage surges beyond the critical level, most power supplies shut down that output. Ideally, while detecting an over voltage, a power supply will reset. Also, in case the power supply’s output exceeds its maximum ratings, some models will detect this condition and reset the unit. The user should be careful while checking the specifications.

Safety and certifications: Generally, all power supplies have their safety and quality certified by one or more agencies. These certifications indicate that the power supply has been tested and has passed a certain standard. Safety and quality certification is probably the most important thing to look for. Apart from other safety standards, tests that assess how much electromagnetic interference (EMI) or radio frequency interference (RFI) the power supply generates should also be considered.

Cost of ownership: Another factor that should be considered is the cost of ownership. One should take into account not only the price of the power supply but the whole product experience. This includes the cost of downtime for calibration and repair, protection for the DUT and test instruments, and the reliability of the power supply.

GW Instek’s PSU series programmable switching DC power supply

• Voltage ratings: 6V, 12.5V, 20V, 40V and 60V

• Output power rating: 1200W~1520W

• Adjustable slew rate

• Series and parallel operation (two units in series or four units in parallel)

• High efficiency and high power density

• Interface: LAN, RS-232 & RS-485, USB, analogue control interface and GPIB (optional)

GW Instek’s PSW series multi-range DC power supply

• Voltage rating: 30V, 80V, 160V, 250V and 800V

• Output power rating: 360W ~ 1080W

• Constant power output for multiple range (V&I) operation

• 1/2, 1/3 and 1/6 rack mount size design (EIA/JIS standard) for 360W/720W/1080W

• Standard interface: LAN, USB and analogue control interface

Aplab’s LQ6324P series multi-output linear DC power supply

• Digitally controlled output settings

• Stores/recalls 10 sets of output settings in the internal memory

• USB interface software provided

• Programmable arbitrary variable output by just feeding coefficient of the curve

• Fully protected against overload and short circuit

• Three independent outputs electrically isolated from each other

Keithley’s 2220-30-1 dual-channel DC power supply

• Dual output models with two 30V/1.5A (45W) channels

• All channels are independently controlled and have isolated outputs for maximum flexibility

• All channels have remote sensing to ensure that programmed voltage is accurately applied to the load

• Two 30V channels can be combined either in series to double output voltage or in parallel to double output current

• 0.03 per cent basic voltage output accuracy and 0.1 per cent current accuracy ensure quality test data

• Low noise, linear regulation with <3mVpp ripple and noise

Scientech’s 4074 multi-output linear power supply

• Three floating, independent DC supply voltages

• DC outputs of 0-30V, 0±15V (dual tracking) and 5V, of 1A each

• Constant voltage and constant current operation

• Digital display for voltage and current

• Selectable display for voltage and current

• Adjustable current limiter, low ripple, and three-year warranty

• Excellent line and load regulation