Switching regulator with dynamic current limiting and drive circuit for the switching regulator

A drive circuit functioning as an active harmonic filter for driving a switching regulator having an intermediate circuit, an intermediate circuit capacitor, disposed in a shunt path of the intermediate circuit, a diode, and a power switch connected in parallel with the intermediate circuit capacitor through the diode and controls a charging current of the intermediate circuit capacitor, the drive circuit comprising:

• a first control amplifier receiving an actual output voltage from the intermediate circuit of the switching regulator and an adjustable desired output voltage, said first control amplifier generating a first control voltage from the actual output voltage and the adjustable desired output voltage;
• a multiplier connected to said first control amplifier and receiving the first control voltage and a rectified input voltage from the intermediate circuit of the switching regulator, said multiplier generating a desired current level from the first control voltage and the rectified input voltage;
• a second control amplifier receiving, from said multiplier, the desired current level and a signal derived from an actual output current level of the intermediate circuit of the switching regulator, said second control amplifier generating a second control voltage in accordance with the desired current level and the signal derived from the actual output current level;
• a third control amplifier receiving the actual output current level of the intermediate circuit of the switching regulator and a current-limiting desired value, said third control amplifier generating a third control voltage for controlling a maximum current level through the power switch from the actual output current level of the intermediate circuit of the switching regulator and the current-limiting desired value;
• a PWM driver circuit receiving at least the second and third control voltages and generating corresponding control pulses for controlling a duty ratio of the power switch;
• and
• a start circuit dynamically increasing a current limiting level for the power switch during a specific start time after a switch-on instant of the switching regulator from an initially low level up to a current-limiting desired value at an end of the specific start time, without the drive circuit limiting the duty ratio of the power switch during the start time.