Continuous comparator with improved calibration
View Patent ↗An auto-calibrated current sensing comparator is provided. A secondary dynamic comparator shares the same inputs and acts to adjust a calibration control of the current sensing comparator. The calibration control may be in the form of adjusting the offset of the current sensing comparator or adjusting a propagation delay that is added to its output.
1. A circuit comprising:
a power switch;
a continuous comparator that monitors a current across the power switch;
a dynamic comparator which shares inputs of the continuous comparator;
the dynamic comparator being adapted to provide a logic signal;
a calibration control adapted to calibrate the continuous comparator;
wherein a clock for the dynamic comparator is coupled with a control signal for changing a state of the power switch; and
wherein the calibration control comprises a counter coupled with an output of the dynamic comparator and one of a variable comparator offset or a variable propagation delay that is directly connected to the continuous comparator; the counter being adapted to receive the logic signal;
wherein the counter operates to increment or decrement the variable comparator offset or the variable propagation delay.
2. The circuit of claim 1 , wherein the continuous comparator is a zero crossing comparator.
3. The circuit of claim 1 , wherein the continuous comparator is a current limit comparator.
4. A switched mode power supply including a circuit that comprises:
a power switch;
a continuous comparator that monitors a current across the power switch;
a dynamic comparator which shares inputs of the continuous comparator;
the dynamic comparator being adapted to provide a logic signal;
a calibration control adapted to calibrate the continuous comparator;
wherein a clock for the dynamic comparator is coupled with a control signal for changing a state of the power switch; and
wherein the calibration control comprises a counter coupled with an output of the dynamic comparator and one of a variable comparator offset or a variable propagation delay that is directly connected to the continuous comparator;
the counter being adapted to receive the logic signal; wherein the counter operates to increment or decrement the variable comparator offset or the variable propagation delay.
5. The switched mode power supply of claim 4 , wherein the continuous comparator is a zero crossing comparator.
6. The switched mode power supply of claim 4 , wherein the continuous comparator is a current limit comparator.
7. A method of operating a power switch in a circuit, comprising:
monitoring a current across the power switch with a continuous comparator; and
calibrating the continuous comparator using a calibration control comprising a counter and one of a variable comparator offset or a variable propagation delay that is directly connected to the continuous comparator;
wherein calibrating the continuous comparator is based on an operation of a dynamic comparator which shares inputs of the continuous comparator;
wherein the dynamic comparator is clocked by a control signal for changing a state of the power switch; the dynamic comparator being adapted to provide a logic signal;
wherein an output of the dynamic comparator increments or decrements the counter Which in turn adjusts the calibration applied to the continuous comparator;
the counter being adapted to receive the logic signal.
8. The method of claim 7 , wherein said calibrating the continuous comparator comprises varying one of the offset or the propagation delay that is applied to the continuous comparator.
9. The method of claim 7 , wherein the continuous comparator is a zero crossing comparator or a current limit comparator.
10. The method of claim 7 , wherein the circuit comprises a switched mode power supply.
11. The method of claim 10 , wherein the switched mode power supply comprises a buck converter, boost converter, or a buck-boost converter and wherein one or more continuous comparators are provided, comprising a zero crossing comparator and/or a current limit comparator.