Arrangement and approach for coupling power supplies using controlled switching techniques

An arrangement for selectively coupling one of a primary power supply and a backup power supply to an output for operating a circuit, the arrangement comprising:

• a primary switch to couple the primary power supply to the output;
• a backup switch to couple the backup power supply to the output;
• and
• a controller circuit to control the operation of the switches for selectively coupling the primary and backup supplies to the output as a function of a voltage level of the primary backup power supplies and a predetermined threshold voltage, the controller circuit including
• a levelshifter circuit to supply a voltage input to the primary and backup switches for controlling the switches in on and off states in response to a high voltage input, and
• a high voltage supply circuit to selectively supply the high voltage input using the higher of the primary and backup power supply voltages, and including
• two PMOS transistors between the primary power supply and the backup power supply,
• a first of the two PMOS transistors has its source electrode coupled to the primary power supply and its gate coupled to the backup power supply,
• a second of the two PMOS transistors has its source electrode coupled to the backup power supply and its gate coupled to a voltage input provided by the levelshifter, and
• the drain electrodes of the PMOS transistors are coupled to supply said high voltage input.

A switch controller arrangement for controlling power supply switches for selectively connecting primary and backup power supplies to an output node, the arrangement comprising:

• a levelshifter circuit to supply a control voltage to each of the power supply switches for independently controlling the switches in on and off states in response to a high voltage input at a high voltage input node and in response to comparisons of a level of the primary power supply to a predetermined backup-mode threshold voltage and to the backup power supply;
• and
• a high voltage supply circuit connected to the high voltage input node to selectively couple a high voltage to the levelshifter circuit for use in supplying said control voltage, by
• coupling said high voltage using the backup power supply voltage under operating conditions in which the primary power supply voltage is lower than the backup power supply voltage, and
• coupling said high voltage using the primary power supply voltage under conditions in which the primary power supply voltage is higher than the backup power supply voltage.

A switch controller arrangement for controlling power supply switches for selectively connecting primary and backup power supplies to an output node, the arrangement comprising:

• a levelshifter circuit to supply a control voltage to each of the power supply switches for independently controlling the switches in on and off states in response to a high voltage input at a high voltage input node;
• and
• a high voltage supply circuit connected to the high voltage input node to selectively couple a high voltage to the levelshifter circuit for use in supplying said control voltage, by
• coupling said high voltage using the backup power supply voltage under operating conditions in which the primary power supply voltage is lower than the backup power supply voltage, and
• coupling said high voltage using the primary power supply voltage under conditions in which the primary power supply voltage is higher than the backup power supply voltage wherein the high voltage supply circuit includes
• a first PMOS transistor having source, drain and gate electrodes, the source electrode coupled to the primary power supply, the drain electrode coupled to the high voltage input node, and the gate electrode coupled to the backup power supply, and
• a second PMOS transistor having source, drain and gate electrodes, the source electrode coupled to the backup power supply, the drain electrode coupled to the high voltage input node, and the gate electrode coupled to a voltage input provided by the levelshifter.

A method for selectively coupling one of a primary power supply and a backup power supply to an output for operating a circuit, the method comprising:

• comparing a level of the primary power supply to a predetermined backup-mode threshold voltage and to the backup power supply, and in response,
• selectively coupling the primary and backup supplies to the output as a function of a voltage level of the primary and backup power supplies and a predetermined backup-mode threshold voltage, by
• supplying a voltage input to the primary and backup switches for controlling the switches in on and off states, and
• selectively supplying a high voltage input, using the higher of the primary and backup power supply voltages, to facilitate the control of the primary and backup switches and mitigate parasitic shorting between the power supplies.