Circuit for reducing electrical power consumption

Abstract

A control circuit includes a first input coupled to a power source, a second input coupled to an output of a power supply, and an output coupled to an input of the power supply. The control circuit senses current at the power supply output. If the sensed current exceeds a threshold, the control circuit connects the power supply input to the power source. If sensed current does not exceed the threshold, the control circuit disconnects the power supply input from the power source and applies a voltage to the power supply output. If the sensed current exceeds the threshold while the power supply input is disconnected from the power source and while the control circuit is applying voltage to the power supply output, the control circuit discontinues application of voltage to the power supply output and connects the power supply input to the power source.

What is claimed is: 
     
         1 . (canceled) 
     
     
         2 . The control circuit as recited in  claim 10  wherein the load is a battery charger to charge one or more batteries in an electronic device. 
     
     
         3 . The control circuit as recited in  claim 10  wherein the control circuit is integrated into the power supply. 
     
     
         4 . (canceled) 
     
     
         5 . The method as recited in  claim 11  wherein the current sensor is a Hall Effect current sensor. 
     
     
         6 . The method as recited in  claim 11  wherein the current sensor is a resistance sensing device. 
     
     
         7 . The method as recited in  claim 11  wherein the current sensor is a magnetic sensing device. 
     
     
         8 . The method as recited in  claim 11  wherein the current sensor is a sense-FET device. 
     
     
         9 . The method as recited in  claim 11 , further comprising integrating the control circuit into the power supply. 
     
     
         10 . A control circuit to reduce electrical energy consumption by a power supply comprising:
 a first electronic switch having an input connected to a power source and having an output selectively connected to an input of the power supply to connect the input of the power supply to the power source;   a load detector having an input selectively coupled to the output of the power supply, the load detector having a first output connected to a node adapted to be connected to a load to sense load current;   a voltage source to supply a voltage;   a second electronic switch having an input connected to the output of the power supply and an output selectively coupled to the load to cause the output of the power supply to be coupled to the load when the input of the power supply is connected by the first electronic switch to the power source and to cause the voltage not to be applied to the load when the input of the power supply is selectively connected by the first electronic switch to the power source;   a third electronic switch having an input connected to the voltage source and an output selectively coupled to the load to cause the voltage to be applied to the load when the input of the power supply is not selectively connected by the first electronic switch to the power source and to cause the voltage not to be applied to the load when the input of the power supply is selectively connected by the first electronic switch to the power source;   a comparator circuit having an input connected to a second output of the load detector to compare the sensed load current to a threshold and having an output coupled to the first electronic switch, the second electronic switch, and the third electronic switch to one of a) cause the first electronic switch to connect the input of the power supply to the power source and the second electronic switch to couple the output of the power supply to the load if the sensed load current exceeds the threshold and b) cause the first electronic switch to disconnect the input of the power supply from the power source and the third electronic switch to couple the voltage to the load when the sensed load current does not exceed the threshold.   
     
     
         11 . A method to reduce electrical energy consumption by a power supply comprising:
 providing a first input adapted to be coupled to a power source;   providing a second input adapted to be coupled to an output of a power supply;   providing an output adapted to be coupled to an input of the power supply;   providing a current sensor adapted to be coupled to the second input to sense current at an output of the current sensor; and   providing circuitry coupled to the current sensor to selectively couple the input of the power supply to the power source;   wherein if the current at an output of the current sensor is sensed to exceed a threshold, the circuitry couples the input of the power supply to the power source;   wherein if the current at the output of the current sensor is sensed to not exceed the threshold, the circuitry decouples the input of the power supply from the power source and applies a voltage at an input of the current sensor while the power supply is decoupled from the power source; and   wherein if the current at the output of the current sensor is sensed to exceed the threshold while the input of the power supply is decoupled from the power source and while the circuitry is applying the voltage at the input of the current sensor, the circuitry discontinues application of the voltage at the input of the current sensor and couples the input of the power supply to the power source.   
     
     
         12 . The control circuit as recited in  claim 10  wherein the first electronic switch comprises a trial having an input connected to the power source and an output selectively connected to the input of the power supply. 
     
     
         13 . The control circuit as recited in  claim 10  wherein the load detector comprises a current sensor selected from among the group of current sensors consisting of a Hall Effect current sensor, a resistance sensing device, a magnetic sensing device, and a sense-FET device. 
     
     
         14 . The control circuit as recited in  claim 10  wherein the voltage source comprises a bridge rectifier connected to the power source to produce the voltage. 
     
     
         15 . The control circuit as recited in  claim 10  wherein the comparator circuit comprises a pair of cascaded comparators connected to the second output of the load detector.