Pure linear regulation still provides the lowest output noise and best transient response. The disadvantage is greater physical size and weight for a given power, together with higher heat output.
For higher power levels, Aim-TTi have developed a technology that uses switch-mode pre-regulation and linear final regulation. This technique combines exceptional efficiency with noise levels that are close to that of pure linear supplies.
PowerFlex and PowerFlex+ Autoranging
Most laboratory power supplies (PSUs) offer a fixed maximum voltage and maximum current capability. Thus, for example, a 35V/20A PSU can supply up to 700 watts, but its power capability falls in direct proportion to the output voltage so that when being used at 12V, for example, the maximum power has reduced to 240W. The TTi PowerFlex system uses a modified form of mixed-mode regulation to provide higher levels of current when the voltage is set to lower values. PowerFlex supplies have an auto-ranging or semi constant power characteristic so that the current capability rises as the voltage falls and offer a near constant power output over a limited range. Thus, for example, the QPX1200 can provide up to 60V or up to 50A within a total power limit of 1200W. This means that the maximum voltage and the maximum current are not available simultaneously and care must be taken when interpreting the specifications. Although producing slightly higher noise levels than the standard mixed-mode regulation, performance is still excellent. Both the CPX and QPX series use PowerFlex with linear post regulation to provide wider output voltage and current capabilities with low noise.
The main outputs on most Aim-TTi power supplies are isolated and have automatic crossover between constant voltage (CV) and constant current (CI) modes. This allows wiring in series or parallel in order to achieve higher voltages or higher currents. The PL series also features "quad-mode" switching on dual and triple output variants which allows push-button selection of four modes of operation - isolated, series, series-tracking, or parallel.
The output channels of some Aim-TTi power supplies can be configured to give a higher maximum voltage or a higher maximum current at the same power to suit different applications extending their flexibility. For example the MX100T outputs can be 0-16V at up to 6A or 0-35V at up to 3A. This means that the maximum voltage (here 35V) and the maximum current (here 6A) are not available simultaneously as they are in different ranges and care must be taken when interpreting the specifications. In the MX series, multiple ranges can be combined with Power Sharing - see below:
On some multi-channel power supplies, the channels can be reconfigured so that two channels are wired internally to connect to the same output terminals in series or parallel, providing double the power and either double the voltage or double the current respectively. In these configurations the output terminals of the second channel are unused.