Comparator with extended common-mode input voltage range

A switching current regulator for driving an inductive load, including:

• a comparator comprising:
• two comparator inputs;
• two differential input stages connected in parallel, each of said two differential input stages being connected to receive a voltage from a common-mode input voltage source coupled to each of said two comparator inputs;
• a common constant current source connected to each of said two differential input stages;
• a supply voltage source having two poles connected to said comparator;
• said constant current source being connected to feed current to at least one of both of said two differential input stages, depending upon the relationship between said common-mode input voltage and said supply voltage;
• and
• a first current mirror circuit connected downstream of the outputs of both differential input stages and from which the output of said comparator is derived,
• wherein at least one of said two differential input stages operates in a common-base connection and receives its emitter supply current from said common-mode input voltage source;
• said switching regulator further including:
• flyback circuit means connected in series to a controllable switch, said flyback circuit means and series connected controllable switch being connected in parallel across said two poles of said supply voltage source;
• said inductive load connected in series with a current sensing means and in parallel to said flyback circuit means, said current sensing means producing a current sensing signal representative of the current flowing through said inductive load;
• said controllable switch being controlled by the output of said comparator;
• a reference signal source connected to said comparator for producing a reference signal such that said comparator compares said current sensing signal to said reference signal and causes said controllable switch to be activated each time said current sensing signal reaches said reference signal value;
• and
• said reference signal source being switchable between a high reference signal value which, when reached by said current sensing signal, said comparator effects an interruption of the previously conducting controllable switch and a low reference signal value which, when reached by said current sensing signal, said comparator effects switching of said controllable switch into a conducting state from the previously interrupted state.