Amplitude Modulation for Pass Gate to Improve Charge Pump Efficiency

摘要

Techniques are presented for improving the efficiency of charge pumps. A charge pump, or a stage of a charge pump, provides its output through a pass gate. For example, this could be a charge pump of a voltage doubler type, where the output is supplied through pass gate transistors whose gates are connected to receive the output of an auxiliary section, also of a voltage doubler type of design. The waveforms provided to the gates of the pass gate transistors are modified so that their low values are offset to a higher value to take into account the threshold voltage of the pass gate transistors. In a voltage doubler based example, this can be implemented by way of introducing diodes into each leg of the auxiliary section.

主权项

1. A method of operating a charge pump circuit, the charge pump including one or more stages each having one or more legs, including a first leg connected between an output node for the corresponding stage and an input node for the corresponding stage receiving an input voltage for the stage, and the first leg has a first capacitor with a first plate connected to an internal node thereof and a first output transistor connected between the internal node and the output node of the corresponding stage, the method comprising:
applying a first clock signal to a second plate of first capacitor, the first clock signals value alternating between a high value and a low value; and applying a second clock signal to the gate of the first output transistor, wherein the second clock signal is of the same phase as the first clock signal, and wherein the second clock signal has a low value that is higher than the input voltage for the stage, being offset above the input voltage by an amount not more than the than the threshold voltage of the first output transistor.