Current limit module and control module for power converters and associated method

A power converter comprising:

• an input port configured to receive an input voltage;
• an output port configured to provide an output voltage;
• a switching module comprising at least a main switch configured to conduct on and off switching in response to a pulse width modulated signal so as to convert the input voltage into the output voltage, wherein a switching current flows through the main switch, and wherein the percentage of the on time of the main switch in a switching cycle is referred to as a duty cycle;
• and
• a control module having a first input terminal configured to receive a feedback signal indicative of the output voltage, a second input terminal configured to receive a reference signal indicative of an desired value of the output voltage, a third input terminal configured to receive a first current sense signal indicative of the switching current, a fourth input terminal configured to receive a first current limit threshold indicative of a maximum allowable value of a peak value of the switching current, and a control output terminal configured to provide the pulse width modulated signal, wherein the control module is configured to compensate the first current sense signal with a ramp compensation signal to generate a second current sense signal, and is further configured to superpose a threshold compensation signal indicative of the duty cycle with the first current limit threshold to provide a second current limit threshold, and is further configured to compare the second current sense signal with the second current limit threshold to provide a second comparison signal, and wherein the second comparison signal triggers the pulse width modulated signal to turn the main switch off when the second current sense signal exceeds the second current limit threshold.

A method for controlling a power converter, wherein the power converter comprises a main switch and is configured to convert an input voltage to an output voltage based on driving the main switch to switch on and off, and wherein a switching current flows through the main switch, and wherein the percentage of the on time of the main switch in a switching cycle is referred to as a duty cycle, the method comprising:

• sensing the output voltage to provide a feedback signal indicative of the output voltage;
• sensing the switching current to provide a first current sense signal indicative of the switching current;
• compensating the first current sense signal with a ramp compensation signal to provide a second current sense signal;
• generating a difference signal indicative of a difference between the feedback signal and a reference signal, wherein the reference signal is indicative of a desired value of the output voltage;
• comparing the second current sense signal with the difference signal to output a first comparison signal;
• providing a first current limit threshold indicative of a maximum allowable value of a peak value of the switching current, and superposing a threshold compensation signal indicative of the duty cycle to the first current limit threshold to provide a second current limit threshold;
• comparing the second current sense signal with the second current limit threshold to generate a second comparison signal;
• turning the main switch off in response to the second comparison signal when the second current sense signal is larger than the second current limit threshold, and turning the main switch off in response to the first comparison signal when the second current sense signal is smaller than the second current limit threshold and larger than the difference signal;
• and
• turning the main switch on in response to a clock signal.