Abstract: A method and apparatus for utilizing leakage energy from a transformer within a power supply, including in one embodiment, a transformer having a primary winding and a secondary winding in communication with a switch and a capacitor, a rectifier and a load within the power supply.

Abstract: A synchronous rectifier MOSFET control circuit which overcomes many of the shortcomings of the prior art employs MOSFET for supplying voltage to a load when the MOSFET is in the forward biased condition (i.e., when an input voltage level exceeds the threshold voltage level by a pre-determined amount). The MOSFET control circuit is configured to turn off the MOSFET when the input voltage level dips below that pre-determined level required to maintain the MOSFET in the forward biased condition. When the MOSFET is turned off, the diode internal to the MOSFET device prevents current flow in the reverse bias direction (i.e., the internal diode prevents current flow from the output to the input), effectively isolating the load from the input voltage source, thereby allowing the capacitors to discharge their energy to the load to maintain a voltage supply to the load which is at or above the output load threshold voltage level.

Abstract: Disclosed is a telephone alert system that comprises a telephone and a device for indicating that the telephone requires attending. The indicating device includes a call holding alert mechanism for alerting a party on hold that the hold initiating party is ready to resume conversation, and a further mechanism for alerting someone that the telephone handset is inadvertently disengaged from the switchhook. Both alert mechanisms make use of the alert tone of the telephone chassis ringer for notification purposes.

Abstract: A timing circuit generates timing signals for a synchronous rectifier directly from the transformer power output winding. A phase detector detects the phase of the voltage on the output winding. A switched current source generates a digital timing signal responsive to the phase detector. The output from the current source is applied to the gate of the rectifier to control the on/off condition of the rectifier.

Abstract: A circuit measures the driving and circulating current in an H-bridge drive network directly and linearly. Voltage across two current sensing resistors are input to two precision half-wave rectifiers. The output of the rectifiers are input to a differential amplifier via a circuit of resistors. The output of the differential amplifier is a signal representative of the current in the H-bridge for both the driven periods and non-driven or freewheeling periods.