Switch mode power supply for a telephone entry system or the like

A power supply for supplying DC voltage comprising:

• a full wave rectifier receiving an input line voltage;
• a pair of inductors connected at least one end to one side of said full-wave rectifier;
• a pair of transistors each connected at one conduction terminal to a second end of a corresponding one of said pair of inductors and connected at a second conduction terminal to an opposite side of said full wave rectifier;
• and
• a complementary driver driving a control terminal of each of said pair of transistors;
• a pair of diodes, anodes of said pair of diodes each connected to a corresponding one of said pair of inductors at said second side, cathodes of said pair of diodes being connected together;
• and
• a filter capacitor connected at an unregulated DC voltage output between said cathodes and said other side of said full wave rectifier.

An access control system selectively providing access to a building, said access control system comprising:

• a main control unit telephonically in communication with entities within a building, said main control unit being mountable at an entrance to said building;
• a switch mode power supply providing power from an input line voltage to said main control unit, said switch mode power supply comprising:
• a full wave rectifier receiving an input line voltage,
• a pair of inductors connected at least one end to one side of said full-wave rectifier,
• a pair of transistors each connected at one conduction terminal to a second end of a corresponding one of said pair of inductors and connected at a second conduction terminal to an opposite side of said full wave rectifier,
• a complementary driver driving a control terminal of each of said pair of transistors,
• a pair of diodes, anodes of said pair of diodes each connected to a corresponding one of said pair of inductors at said second side, cathodes of said pair of diodes being connected together,
• a filter capacitor connected at an unregulated voltage output between said cathodes and said other side of said full wave rectifier, and
• at least one voltage regulator providing regulated voltage from said unregulated voltage;
• a display on said main control unit displaying contact codes for selected ones of a plurality of building tenants;
• at least one code entry unit receiving access codes, each said code entry unit providing received said access codes to said main control unit;
• and
• at least one controlled door, access through each said controlled door being provided by said main control unit in response to a correct access code entered at one said code entry unit, said main control unit logging system activity.

A power supply for supplying DC voltage comprising:

• a rectifier having an input signal input and a rectified signal output node;
• a first circuit comprising:
• a first switch coupled to the first inductor;
• a second circuit comprising:
• a second inductor coupled to the rectified signal output node;
• a second switch coupled to the second inductor;
• an oscillator coupled to selectively switch the first and second switches, wherein the oscillator has an output signal frequency substantially greater than a frequency of an input signal as is provided at the input signal input of the rectifier.