AN458 APPLICATION NOTE

18/19

DUAL OUTPUT POWER SUPPLY

The application shown in fig.23 is interesting because it provides two output voltages. The main voltage, is di-

rectly controlled by the feedback loop, the second voltage is obtained through an auxiliary winding. As the aux-

iliary voltage is obtained through a completely separated winding, it is possible to obtain either a positive or a

negative voltage. Where isolation is not required between the two outputs, we can reduce the number of the

auxiliary turns improving also the tolerance of the secondary output using the configuration illustrated in fig.24.

For both this configurations, the discontinuous mode is ideal because we have a good energy transfer between

primary and secondary windings, due to the high energy stored in the coil that is function of the ripple current in

the inductor.

Figure 23. Multioutput isolated.