Power supply for energizing DC load from AC or DC source

Claim 1

A power supply for energizing an electrical DC motor, comprising: an AC socket for receiving a plug to be connected to an AC source; rectifier means for rectifying the AC when the AC source is connected to the AC socket, and for supplying DC voltage to the DC motor, said rectifier means including a first rectifier circuit for rectifying the AC of the AC source, a switching circuit for converting the rectified output from the first rectifier circuit to AC of a frequency higher than the AC source, a transformer receiving the AC from said switching circuit, and a second rectifier circuit for rectifying the output of said transformer; a battery compartment for receiving a rechargeable battery; a charging circuit for charging a rechargeable battery, when received within said compartment, with rectified AC from said rectifier means; a manual switch connected to the rectifier means, the DC motor, and the battery, wherein said manual switch may be manually opened or closed; and a control circuit effective: (a) when the manual switch is closed and the AC socket is not connected to an AC source, to connect the battery to the motor; (b) when the manual switch is closed and the AC socket is connected to an AC source, to connect the AC source to the motor and to disconnect the battery from the motor and from said charging circuit; and (c) when the manual switch is open and the AC socket is connected to an AC source, to connect the battery to said charging circuit; said control circuit including a controller which controls the duty cycle of said switching circuit to regulate the output thereof in accordance with the output of said second rectifier circuit, a comparator circuit which senses the voltage applied to the load device from the AC source, and a transistor circuit controlled by said comparator circuit to disconnect the battery from the DC motor when the comparator senses the presence of a DC voltage applied to the DC motor from the AC source.