Microchip Technology Inc.

Daniel Leonescu

Scott Dearborn

Philippe Deval

Terry L Cleveland

Christian Albrecht

Philippe Gimmel

Matthew Williams

Marius Budaes

The regulated output voltage of a voltage regulator is maintained up to a current limit, I, then as the load impedance continues to decrease the output current does not increase past the current limit, I, but rather the output voltage decreases forcing the output current to also decrease to satisfy Ohm's Law: I=V/Z. When the output voltage drops below the regulated voltage value because of current limiting the voltage regulator shifts from a current limit mode to a current foldback mode wherein the output current decreases with the decrease in output voltage until the output current reaches a current foldback minimum, I, at an output voltage of substantially zero volts. As the load impedance increases so will the output voltage and current until the output voltage is back at substantially the regulation voltage value, and the output current is less than or equal to the current limit, I.

Voltage regulator having current and voltage foldback based upon load impedance

A high voltage switching regulator has significantly reduced current sensing delay between measurement of input current and generation of sensed current values, while maintaining good accuracy of the current through a power transistor using current replication and a current conveyor. High sensing accuracy of the input current ensures good load regulation, and low sensing delay ensures fixed duty cycle over a wide range of output currents and high input to output voltage ratios. A current conveyor is used to transfer high side current values to low side control circuits, e.g., pulse width modulation (PWM) control. The current conveyor is always on, e.g., some current flow is always present, thus minimizing any current measurement delay. This is accomplished by dynamically biasing the current conveyor by draining to ground a current equal to the sensed current. Wherein balancing of the current conveyor is ensured and offset at the input of the current conveyor is minimized.

Effective current sensing for high voltage switching regulators

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Bucharest, Romania

Daniel Leonescu