Isolated high frequency power supply for an indicator light

• Main Authors: STEVEN C SCHMALZ, LAWRENCE J RYCZEK, MICHAEL G TARANOWSKI, ISAAC GRUBER
• Format: Patent
• Language: English
• Published: 09.09.1998
• Edition: 6
• Subjects: BASIC ELECTRIC ELEMENTS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; ELECTRIC HEATING; ELECTRIC LIGHTING NOT OTHERWISE PROVIDED FOR; ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR; ELECTRICITY; INDUCTANCES; MAGNETS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS; PRINTED CIRCUITS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES; TRANSFORMERS

An incandescent or LED indicator light LP1 is connected to a secondary winding 14 of an isolating transformer T1, a primary winding 16 of the transformer being operated at high frequency by an operational amplifier based relaxation oscillator U1 which drives an FET Q1 connected to primary winding 16. The circuit can be energised by a low frequency AC input supply 22 or a test input 26 which are connected to a logic OR circuit D3, D4 so that half-wave rectified AC is applied to the input of a linear regulator U2 which supplies the oscillator U1. The light LP1 thus receives high frequency pulses during the positive half waves of the AC input, but not during the negative half waves (Fig.7). The circuit is built on a printed circuit board (4, Figs.1,2) and is disposed in an indicator light housing adapted to be mounted through an opening in a panel. The transformer is of planar form and has a ferrite top plate (20) and the secondary winding 14 on one side of the PCB (4), and a ferrite E-core (18) and the primary winding 16 on the other side of the PCB (4) with the legs of the E-core (18) extending through openings in the PCB.