Switching regulator circuits

A current-mode switching regulator comprising at least

• a main switch which controls the current flow through the inductor;
• a comparator which controls the main switch based on the current in the inductor and a reference signal fed back from a voltage output of the regulator, whereby the duty cycle of said main switch, and hence a peak current in the inductor, will change to compensate for a change in output voltage;
• a signal generator for generating a ramp signal and using this for slope compensation by offsetting one of the comparator input signals relative to the other with said ramp signal;
• and
• current limiting circuitry for generating a limit-adjustment signal corresponding to a proportion of the compensatory ramp signal, said proportion being dependent on the duty cycle of more than one previous clock period of the regulator, and using said limit-adjustment signal to clamp one of the comparator input signals;
• thereby substantially maintaining the inductor current limit independent of duty cycle.

A current-mode switching regulator comprising at least

• a main switch which controls the current flow through the inductor;
• a comparator which controls the main switch based on the current in the inductor and a reference signal fed back from a voltage output of the regulator, whereby the duty cycle of said main switch, and hence a peak current in the inductor, will change to compensate for a change in output voltage;
• a signal generator for generating a ramp signal and using this for slope compensation by offsetting one of the comparator input signals relative to the other with said ramp signal;
• and
• current limiting circuitry for generating a limit-adjustment signal corresponding to a proportion of the compensatory ramp signal, said proportion being dependent on the duty cycle of more than one previous clock period of the regulator, and using said limit-adjustment signal to obtain a limit signal for comparison with a signal representative of the current in the inductor, whereby the limit signal or the signal representative of the current in the inductor is offset relative to the other with said ramp signal;
• thereby substantially maintaining the inductor current limit independent of duty cycle.

A current mode switching regulator comprising:

• current limiting circuitry for monitoring a first signal indicative of the current flow through the regulator with respect to a current limit reference signal so as to prevent current flowing through the regulator above a current limit;
• and
• slope compensation circuitry for applying a time varying offset to at least one of the first signal and the current limit reference signal which are monitored by the current limiting circuitry;
• wherein the current limiting circuit comprises an adjustment circuit for compensating for the effect of the time varying offset on the current limit;
• and
• wherein the adjustment circuit provides an adjustment based on the duty cycle of more than one previous cycle of the regulator.

A current mode switching regulator comprising:

• an inductor;
• a main switch for controlling the current flow through the conductor;
• a current monitor for generating a first signal based on the current flow through the conductor;
• current limiting circuitry for monitoring said first signal with respect to a current limit reference signal and, based on said monitoring, arranged to generate a switch control signal if the current flow through the inductor reaches a current limit so as to prevent current flowing through the regulator above the current limit;
• slope compensation circuitry for applying a time varying offset to at least one of the first signal and the current limit reference signal which is monitored;
• wherein the current limiting circuit is arranged to provide an adjustment to the monitoring of the first signal with respect to the current limit reference signal so as to compensate for the effect of the time varying offset applied to the first signal or current limit reference signal, the amount of adjustment being based on an adjustment signal and wherein the current limiting circuitry comprises an adjustment circuit for monitoring the duty cycle of a plurality of cycles and generating said adjustment signal having a value based on the duty cycles of more than one previous cycle.

A method of providing current limit control in a current mode switching regulator comprising the steps of:

• taking a first signal indicative of the current in the regulator;
• taking a current limit reference signal;
• wherein at least one the first signal and the current limit reference signal has a slope compensation time varying offset applied thereto;
• generating an adjustment signal having a value based on the duty cycle of more than one previous cycle;
• monitoring the first signal with respect to the current limit reference signal so as to determine if the current in the regulator reaches a current limit wherein said monitoring step includes using said adjustment signal to compensate for any slope compensation applied to the first signal and the current limit reference signal.