Switching power supply and power factor correction controller therefor having improved input current sensing

A controller for a power factor correction converter, comprising:

• switch control circuitry configured to generate a switch control signal for modulating an input current received from a rectified alternating-current supply to form an output voltage across an energy storage element in response to the switch control signal, wherein the switch control circuitry comprises:
• a gain modulator configured to combine an output voltage error signal with an instantaneous input voltage sensing signal and the gain modulator having an output node;
• an input current sensor configured to draw a current signal from the output node of the gain modulator, wherein the current signal is representative of an instantaneous input current sensing signal, wherein the input current sensor comprises:
• a transistor having a first controlled terminal, a second controlled terminal and a control terminal;
• and an amplifier having a first input terminal coupled to a ground node, a second input terminal coupled to a current sensing resistor and an output terminal coupled to the control terminal of the transistor, thereby a voltage at the output node is representative of the instantaneous input voltage sensing signal, the instantaneous input current sensing signal and the output voltage error signal;
• and
• a comparator configured to compare the voltage at the output node to a ramp signal to form a switch modulation signal that controls timing of the switch control signal.

An input current sensor for a power factor correction converter comprising:

• a transistor having a first controlled terminal, a second controlled terminal and a control terminal;
• and
• an amplifier having a first input terminal coupled to a ground node, a second input terminal coupled to a current sensing resistor and an output terminal coupled to the control terminal of the transistor,
• wherein the input current sensor is configured to draw a current signal from an output node of a gain modulator, wherein the current signal is representative of an instantaneous input current sensing signal, the instantaneous input current sensing signal being representative of an input current for the power factor correction converter.