Intrinsically safe universal switching power supply

An intrinsically safe switching power supply for generating one or more voltage outputs, said switching power supply comprising:

• (a) a circuit board having a plurality of layers, and including an opening for receiving a transformer;
• (b) a first stage having an input for receiving a supply voltage and including a converter circuit for converting said supply voltage to a DC level and having circuitry for producing an output voltage from said DC level, and said first stage including primary windings, said primary windings being formed as conductive tracking on one layer of said circuit board;
• (c) a second stage coupled to said first stage through said transformer and said second stage including secondary windings for coupling said output voltage produced by said first stage through said transformer, said second stage including circuitry for generating one or more voltage outputs, and said secondary windings being formed as conductive tracking on another layer of said circuit board, and said circuit board including an output layer for said voltage outputs;
• (d) said second stage including a sub-stage for generating an intrinsically safe voltage output, and said sub-stage comprising a plurality of separate secondary windings for coupling said output voltage produced by said first stage and circuitry for generating said intrinsically safe voltage output, and said separate secondary windings comprising conductive tracking formed on another layer of said circuit board, and said layer carrying the conductive tracking for said intrinsically safe voltage output being isolated from said other layers in said circuit board.

A switching power supply for generating one or more voltage outputs, and one of the voltage outputs comprising an intrinsically safe voltage output, said switching power supply comprising:

• (a) an input stage having an input stage for receiving a supply voltage and a circuit for converting said supply voltage a DC level input;
• (b) a first stage coupled to said input stage for receiving said DC level and said first stage having first stage circuit for producing an output voltage from said DC level;
• (c) a second stage coupled to said first stage and having a circuit for receiving said output voltage produced by said first stage and including a circuit for generating one or more voltage outputs and an intrinsically safe voltage output;
• (d) a planar core transformer for isolating said second stage from said first stage;
• (e) said first stage including primary windings electromagnetically coupled to said planar core transformer, and said primary windings comprising a plurality of conductive tracks formed on one layer in a multi-layer circuit board;
• (f) said second stage including secondary windings electromagnetically coupled to said planar core transformer, and said secondary windings comprising a plurality of conductive tracks formed on one or more layers in the multi-layer circuit board;
• (g) a start-up stage coupled to said first stage and said input stage, said start-up stage including circuitry for starting said power supply during a low period.

A switching power supply for generating one or more voltage outputs, said switching power supply comprising:

• (a) an input stage having an input for receiving a supply voltage and a circuit for converting said voltage to a DC level;
• (b) a first stage coupled to said input stage for receiving said DC level and said first stage having a circuit for generating an output voltage from said DC level;
• (c) a second stage coupled to said first stage and having a circuit for receiving said output voltage produced by said first stage and including circuitry for generating one or more voltage outputs and an intrinsically safe voltage output;
• (d) a planar core transformer for isolating said second stage from said first stage;
• (e) said first stage including primary windings electromagnetically coupled to said planar core transformer, and said primary windings comprising a plurality of conductive tracks formed on a layer of a multi-layer circuit board;
• (f) said second stage including secondary windings electromagnetically coupled to said planar core transformer, and said secondary windings comprising a plurality of conductive tracks formed on another layer of said multi-layer circuit board, and said other layer being isolated from said layer carrying said conductive tracks for said primary windings;
• (g) said circuit for generating an output voltage in said first stage including a switching device and a controller coupled to said switching device, said switching device being coupled to said primary windings, and said switching device switching a current through said primary windings under the control of said controller.