What is Isolated DC/DC converters

Isolated DC/DC converters are required in a broad range of applications including power metering, 

industrial programmable logic controllers (PLCs), insulated-gate bipolar transistor (IGBT) driver power supplies, industrial fieldbus, and industrial automation. These converters often are used to provide galvanic isolation, improve safety, and enhance noise immunity. 

Moreover, they can be used to generate multiple output voltage rails including dual-polarity rails.

In terms of output voltage regulation accuracy, isolated DC/DC converters usually fall into three categories: regulated, unregulated, and semi-regulated.Isolated DC/DC converters typically use a transformer to electrically isolate the output from the input of the power stage.

Unregulated isolated DC/DC converters(open-loop isolated DC/DC converters), are widely used in applications that don’t require precise output voltage. 

A typical example is the push-pull converter with fixed 50% duty cycle  

The control circuitry consists of only an oscillator along with two gate drivers, which generates two complimentary fixed 50% duty cycle gate signals to drive Q1 and Q2. The transformer turns ratio is selected to deliver the desired output voltage. Neither a feedback circuitry nor a signal isolator is required, which reduces cost and solution size.

Copy from https://www.edn.com/design/power-managementTOPPOWER is one of the lead manufacturer of isolated DC/DC converter(regulated, unregulated) in China