Automatic gain control technique for current monitoring in current-mode switching regulators
AssigneeMicrosemi Corporation
InventorShawn Anthony Fahrenbruch
Life of this patent
Estimating the term…
Abstract
A current-mode switching regulator uses adaptive current sensing to reliably monitor an inductor current in a cost-efficient and power-efficient manner. A semiconductor switch periodically turns on to conduct the inductor current. A voltage drop across the semiconductor switch is monitored when the semiconductor switch is on. A variable gain amplifier with an automatic gain control loop generates a feedback signal from the voltage drop of the semiconductor switch when conducting to provide an indication of the inductor current to a controller. The automatic gain control loop compensates for any variations in the on-resistance of the semiconductor switch.
Claims20
A current-mode switching regulator comprising:
- at least one semiconductor switch and an inductor, wherein the semiconductor switch periodically closes to increase current conducted by the inductor;
- an automatic gain control circuit having a first terminal connected to a source terminal of the semiconductor switch and having a second terminal connected to a drain terminal of the semiconductor switch, the automatic gain control circuit configured to monitor a voltage across the semiconductor switch and to provide a feedback signal indicative of the current conducted by the inductor when the semiconductor switch is closed;
- and
- a controller configured to monitor an output voltage and to drive the semiconductor switch based on the output voltage, a reference voltage indicative of a desired output voltage, and the feedback signal.
A method of monitoring inductor current for a current-mode switching regulator, the method comprising:
- monitoring a voltage drop across a semiconductor switch, wherein the semiconductor switch periodically conducts to increase current flowing through an inductor;
- using a variable gain circuit with an automatic gain control loop to generate a current feedback signal based on the voltage drop across the semiconductor switch, wherein the current feedback signal is proportional to the current flowing through the inductor when the semiconductor switch is conducting and the automatic gain control loop adjusts a gain factor of the variable gain circuit to compensate for parameter variations in the semiconductor switch;
- and
- providing the current feedback signal to a control circuit for the semiconductor switch, wherein the control circuit adjusts pulse-widths of a driving signal for the semiconductor switch based on the current feedback signal and an output voltage feedback loop that monitors an output voltage of the current-mode switching regulator with reference to an input control signal indicative of a desired output voltage.
A current-mode switching regulator comprising:
- means for monitoring an inductor current by sensing a voltage drop across a semiconductor switch, the means for monitoring the inductor current arranged in a parallel configuration with the semiconductor switch, wherein the semiconductor switch periodically closes to conduct the inductor current;
- means for processing the voltage drop across the semiconductor switch with a variable gain amplifier to produce a feedback voltage;
- means for adjusting the variable gain amplifier to compensate for parameter variations in the semiconductor switch;
- and
- means for driving the semiconductor switch based on the feedback voltage to generate a desired output voltage for the current-mode switching regulator.
A method for monitoring current in a current-mode switching regulator, the method comprising:
- monitoring an inductor current by sensing a voltage drop across a semiconductor switch between a drain terminal of the semiconductor switch and a source terminal of the semiconductor switch, wherein the semiconductor switch periodically closes to conduct the inductor current;
- processing the voltage drop across the semiconductor switch with a variable gain amplifier to produce a feedback voltage;
- adjusting the variable gain amplifier to compensate for parameter variations in the semiconductor switch;
- and
- driving the semiconductor switch based on the feedback voltage to generate a desired output voltage.
Dependencies are inferred from the claim text.