Abstract: A circuit comprises a first printed circuit board (60) carrying a first set of components and a second printed circuit board (62) carrying a second set of components, with a clearance (64) between the first and second printed circuit boards. A transformer (66) has a primary side connected to the first set of components and a secondary side connected to the second set of components. One of the transformer windings, and its connection to a respective set of components, comprises a triple insulated wire. A glass, ceramic or mica spacer (70) mounted to the first and second printed circuit boards defines and sets the clearance (64) between the first and second printed circuit boards. The clearance requirement is met by providing separate printed circuit boards with spacing between them and the use of a triple insulated wire addresses or overcomes issues of creepage. Thus, high frequency and high voltage operation on the first printed circuit board is possible.