Patent ID: 7427889

Claim:
A voltage regulator coupled to a first voltage source and a second voltage source, the voltage regulator comprising: a first pump circuit coupled to the first voltage source for charging/discharging; a second pump circuit coupled to the second voltage source for charging/discharging; and a control circuit comprising: a first resistor having a first end coupled to the second voltage source; a second resistor having a first end coupled to an output terminal of the second pump circuit; a third resistor having a first end coupled to an output terminal of the first pump circuit; a first current mirror coupled to the first voltage source, a second end of the first resistor, and a second end of the second resistor for generating a first current flowing through the first resistor and a second current flowing through the second resistor; a second current mirror coupled to the first voltage source, and a second end of the third resistor, for generating a third current flowing through the third resistor; a first voltage comparison circuit having a first input terminal coupled to a reference voltage source and a second input terminal coupled to the second end of the first resistor for controlling operations of the first current mirror and the second current mirror according to voltage levels of the two input terminals of the first voltage comparison circuit; a voltage divider coupled to the first voltage source and the second voltage source; a second voltage comparison circuit having a first input terminal coupled to an output terminal of the voltage divider and a second input terminal coupled to the second end of the second resistor for controlling operations of second pump circuit according to voltage levels of the two input terminals of the second voltage comparison circuit; and a third voltage comparison circuit having a first input terminal coupled to the output terminal of the voltage divider and a second input terminal coupled to the second end of the third resistor for controlling operations of the first pump circuit according to voltage levels of the two input terminals of the third voltage comparison circuit.