TTi CPX400SP – Single Output, 420 Watt PowerFlex DC PSUs with Digital Remote Control via USB, RS232 and LAN

The CPX Series of laboratory DC power supplies is one of Aim-TTi’s most successful product lines. Tens of thousands of CPX models are in service across the world.

PowerFlex regulation allows them to provide higher currents at lower voltages enabling the power to be tailored to suit a wider variety of applications.

The range includes single and dual output models with a total power ranging from 360 watts up to 840 watts.

The CPX series is a different type of laboratory power supply designed to meet the need for flexibility in the choice of voltage and current. A conventional PSU has a fixed current limit giving a power capability that reduces directly with the output voltage.

The TTi PowerFlex design of the CPX series enables higher currents to be generated at lower voltages within an overall power limit envelope. Each output can provide considerably higher current than a conventional PSU of the same maximum voltage and power (see power curve). Example voltage & current combinations for the CPX400D include 60V/7A, 42V/10A, 28V/15A, and 20V/20A.

Building Upon Success

The CPX400 series, now comprising five models, was developed from the CPX400A – one of the most successful power supplies ever.

Analog Controls With Digital Stability

As technology has changed, many products have moved from analog controls to digital ones. Although digital controls suit many instruments, they do not necessarily suit a bench power supply.

Customer research shows that many users prefer the speed and simplicity of conventional analog controls for setting voltage and current. Digital controls may offer greater precision, but often at the expense of ease-of-use. With this in mind, the CPX400 series retains the true analog controls of its predecessor.

The main disadvantage of analog controls is stability and security. The settings of analog potentiometers can drift over time. More importantly, the settings can be changed accidentally with potentially serious consequences.

The CPX series now incorporates S-Lock. One press of the Lock button transfers control of voltage and current from the analog controls to internal digital circuitry. This offers not just complete security, but exceptional stability as well with each setting controlled by an instrumentation quality DAC.

The two outputs of the CPX400D are completely independent and electrically isolated from each other. With V-Track selected, the two outputs remain electrically isolated, but the voltage control of the Master output sets an identical voltage on the Slave output.

This enables the user to create two rails of either polarity and to reference them to different grounds if necessary (e.g. digital ground and analog ground). Alternatively the outputs can be wired in series or parallel to create a voltage capability up to 120V or a current capability up to 40A with the voltage set using a single control.

The Both On/Both Off button is in addition to the individual switches for each output, and allow both outputs to be turned on or off synchronously by a single button press. Synchronous switching of the outputs is of increasing importance for circuitry which can be damaged if one voltage rail is present without the other.

Low Noise and Good Dynamic Response

The PowerFlex regulation system used on the CPX400 series combines a high frequency pre regulator with a linear post regulator to give both low noise and good transient response. Each output can operate in constant voltage or constant current mode with automatic crossover and mode indication.

Single Output, Ultra Compact Design

The CPX400S is a single output version of the CPX400D providing up to 60 volts and 20 amps within its 420 watt power envelope. It is housed in a ¼ rack width 3U high case that uses the minimum possible space for either bench use or rack mounting.

Separate voltage and current meters on each output give a resolution of 10mV and 10mA. The fixed resolution avoids the misinterpretation of readings that can occur with auto-ranging 3 or 3½ digit meters where the decimal point position moves as the reading changes.

Coarse and fine voltage controls are provided. The current control is logarithmic enabling low current levels to be set accurately. A View Settings button enables limit settings to be checked and adjusted at any time.

Each output incorporates remote sense terminals that can be enabled or disabled at the flick of a switch. Remote sensing is essential for maintaining precise regulation at the load and true metering of the load voltage.

Compact Design Uses Minimum Bench or Rack Space

Despite the high power output of 840 watts, the CPX400D & DP has a small bench footprint taking up less space on a crowded bench. For rack-mount applications the half-rack by 3U case size enables two units (providing four outputs) to be fitted into a single rack slot.

As an alternative to PowerFlex operation (60V/20A subject to a power limit), the CPX400 series can be used as conventional fixed range power supplies of either 60V/7A or 20V/20A at the press of a button.

Fixed range mode ensures that, whatever the load, the output can only be in constant voltage or constant current mode and never in power limit. Additionally finer resolution is provided on the current or voltage controls respectively.

A further button offers full customisation of voltage and current limits which can be set to suit the users application. This has the advantage that the controls cover the exact voltage and current range required, providing easier setting and reduced risk of error.

For example, the range could be set to 30V and 14A to create a 30 volt PSU of maximum current capability. Alternatively it could be set to 5V and 3A if this was all that was required for a particular application.

The CPX400S is a single output version of the CPX400D providing up to 60 volts and 20 amps within its 420 watt power envelope. It is housed in a ¼ rack width 3U high case that uses the minimum possible space for either bench use or rack mounting.

Three Variants

The single output version of the CPX400 is available in three variants. The CPX400S has manual control only, for conventional bench-top use. The CPX400SA adds isolated analogue remote control plus duplicate rear terminals. The CPX400DP has digital remote control via USB, RS-232 and LAN (LXI) along with duplicate rear terminals (see next page).

CPX400SA – Isolated Analogue Remote Control

Some applications require analogue remote control rather than digital. The CPX400SA has fully galvanically isolated voltage driven remote control for both voltage and current. In addition, voltage and current front panel settings are provided as non-isolated control voltages, enabling master-slave configurations to be used.

Safety Binding-post Terminals

All CPX series power supplies are fitted with the new TTi designed output terminals. As well as acting as conventional binding posts for bare wires, spade connectors, or standard 4mm plugs, these can accept a 4mm safety plug with rigid insulating sleeve, a requirement specified by an increasing number of laboratories for safety reasons. Limited opening length combined with raised insulated shoulders also make these terminals “touch proof” for voltages up to 250V.

CPX400SP, CPX400DP and CPX200DP Remote control via RS-232, USB and LAN Interfaces

The CPX400SP, CPX400DP and CPX200DP are a bus programmable version of the CPX400S, CPX400D and CPX200D respectively, and include all of their manual control features plus comprehensive digital interfaces and rear terminals.

Rear Output Terminals

Power and sense terminals are duplicated on the rear panel for rack mount applications or other situations where rear connection is more appropriate.

Digital Remote Control

To meet the varying needs of today’s engineers, a comprehensive array of interfaces is provided. RS-232, USB and LAN (Ethernet) with LXI support are provided as standard. Each of the digital bus interfaces provides full control of voltage, current, and output on/off, plus read-back of voltage, current and status. The interfaces are at ground potential and are opto-isolated from the output terminals.