Patent ID: 9634558
Date: 2017-04-25
CPC Classifications: H02M

Claim:
1. A negative charge pump feedback circuit, comprising: a clock signal is connected to a first input terminal of an AND gate, an output terminal of the AND gate is connected to an input terminal of a negative charge pump, an output terminal of the negative charge pump outputs a negative voltage, and the feedback circuit is connected between the output terminal of the negative charge pump and a second input terminal of the AND gate, with the feedback circuit including a switch-capacitor circuit and a comparator; the switch-capacitor circuit comprises: a first capacitor, a first terminal of which is connected to the output terminal of the charge pump through a first switch and grounded through a second switch; a second capacitor, a first terminal of which is connected to a second terminal of the first capacitor, grounded though a third switch, and connected to a reverse-phase input terminal of the comparator through a fourth switch; an adjustable capacitor, which is connected in parallel to both terminals of the second capacitor; a positive-phase input terminal of the comparator is connected to a reference voltage; an output terminal of the comparator provides a feedback signal and is connected to the second input terminal of the AND gate, with the feedback signal controlling whether the clock signal is provided to the negative charge pump to thus regulate the negative voltage outputted by the negative charge pump; the first switch is connected to a first control signal used for controlling the switch state thereof, the second switch is connected to a second control signal used for controlling the switch state thereof, the third switch is connected to a third control signal used for controlling the switch state thereof, and the fourth switch is connected to a fourth control signal used for controlling the switch state thereof; the switch-capacitor circuit is made to switch constantly between two states by the control of the four control signals over the four switches; a first state of the switch-capacitor circuit is as follows: the first switch and the third switch are turned on, and the second switch and the fourth switch are turned off, with both terminals of the first capacitor being charged through the negative voltage outputted by the negative charge pump; a second state of the switch-capacitor circuit is as follows: the first switch and the third switch are turned off, the second switch and the fourth switch are turned on, and the first capacitor, the second capacitor and the adjustable capacitor are connected in parallel between the reverse-phase input terminal of the comparator and the ground, the charge of a parallel capacitor of the three capacitors in the second state being equal to that of the first capacitor in the first state, a voltage inputted to the reverse-phase input terminal of the comparator being a positive voltage and proportional to a negative voltage outputted by the negative charge pump; regulating a proportional relation between the voltage of the reverse-phase input terminal of the comparator and the negative voltage outputted by the negative charge pump by regulating capacitance of the adjustable capacitor, thereby regulating the negative voltage outputted by the negative charge pump.