Systems and methods to remove input voltage dependency in a power converter

A system comprising:

• a plurality of subscriber line interface circuits (SLICs), each SLIC operable to communicate with a plurality of subscriber lines;
• at least one subscriber line audio processing circuit (SLAC) coupled to each of the plurality of SLICs, the at least one SLAC operable to generate a reference voltage based upon an operating condition received from one or more of the plurality of SLICs;
• a pulse width modulated (PWM) controller operable to receive the reference voltage from the SLAC and to generate a modulated control signal based upon the reference voltage;
• a power converter operable to receive the modulated control signal and an input voltage and to generate a low supply voltage and a high supply voltage, wherein the voltage converter comprises;
• a switching circuit to selectively provide an input voltage to a switching node at a switching frequency to establish a charging cycle and a discharging cycle based upon a modulated control signal to generate a low supply voltage having a low supply voltage magnitude at a first output node of a power converter, wherein the switching circuit comprises a first capacitor coupled between the first output node of the power converter and a ground node;
• an input voltage cancellation circuit coupled to the switching node, wherein the switching circuit further comprises a first diode coupled between the input voltage cancellation circuit and the first output node of the power converter, wherein the input voltage cancellation circuit comprises a second capacitor coupled between the switching node and the first diode and a second diode coupled between the second capacitor and the ground node and wherein the switching frequency of the switching circuit is such that a bias on the second capacitor does not have adequate time to discharge during the discharging cycle of the switching circuit so as to maintain an offset across the second capacitor equal to the input voltage thereby cancelling input voltage selectively provided to the switching node by the switching circuit such that the switching node swings by an amount which is independent of an amplitude of the input voltage;
• and
• a boost circuit coupled to the switching node and to the switching circuit, the boost circuit operable to generate the high supply voltage having a high supply voltage magnitude at a second output node of the power converter, wherein the high supply voltage magnitude is a multiple of the low supply voltage magnitude.

A method comprising:

• generating, by a switching circuit, a low supply voltage having a low supply voltage magnitude at a first output node of a power converter by selectively providing an input voltage to a switching node at a switching frequency to establish a charging cycle and a discharging cycle based upon a modulated control signal;
• charging a capacitor of an input voltage cancellation circuit during the charging cycle to establish a bias on the capacitor of the input voltage cancellation circuit equal to the input voltage and maintaining the bias on the capacitor input voltage cancellation circuit during the discharging cycle to cancel, by the input voltage cancellation circuit, the input voltage selectively provided to the switching node by the switching circuit such that the switching node swings by an amount which is independent of an amplitude of the input voltage;
• and
• generating, by a boost circuit, a high supply voltage having a high supply voltage magnitude at a second output node of the power converter, wherein the high supply voltage magnitude is a multiple of the low supply voltage magnitude.