Active voice band filter

A network device, comprising:

• a direct current (DC) power supply including an input DC bus that provides a particular range of DC voltage, and
• an active voice-band filter, where the active voice-band filter includes:
• a regulator to regulate an input current to the regulator and to convert DC voltage from the input bus to a higher DC voltage at an output of the regulator,
• an output voltage feedback loop, connected to the output of the regulator, for generating an output voltage value, and
• a current control loop for generating a control signal to regulate an input current of the regulator, where the control signal is based on an input bus current measurement and a reference voltage value, the reference voltage value being calculated using both of the output voltage value and an input bus voltage signal,
• where the regulator regulates the input current to the regulator, based on the control signal, to reject voice band range current harmonics from the higher DC voltage.

A method for filtering voice band noise in direct current (DC) power lines, the method comprising:

• receiving, by a telecommunications networking device, a DC input with variable voltage and low frequency cyclical load variation;
• determining, by a resistive network, a scaled input voltage value;
• determining, by another resistive network, an input current value;
• converting, by a regulator, the DC input with variable voltage to a regulated DC output voltage;
• providing, by an output voltage feedback loop, an output voltage error signal for the regulated DC output voltage;
• providing, by a calculation component, a reference voltage, for a current control loop, based on the scaled input voltage value and the output voltage error signal;
• receiving, at a pulse width modulator, a control signal from the current control loop based on the reference voltage;
• and
• regulating, by the regulator, another converting of the DC input with variable voltage to a regulated DC output voltage based on the control signal.

An active voice band filter, comprising:

• means for receiving a DC input with variable voltage and low frequency cyclical load variation;
• means for determining a scaled input voltage value;
• means for determining an input current value;
• means for converting the DC input with variable voltage to a regulated DC output voltage;
• means for providing an output voltage error signal for the regulated DC output voltage;
• means for providing a reference voltage, for a current control loop, based on the scaled input voltage value and the output voltage error signal;
• means for receiving a control signal from the current control loop based on the reference voltage;
• and
• means for regulating another converting of the DC input with variable voltage to a regulated DC output voltage based on the control signal.