Accurate zero current detector circuit in switching regulators
A switching regulator circuit includes a gate driver circuit driving a first switch and a second switch to generate a first voltage at a first node. Further, the switching regulator includes an LC filter circuit responsive to the first voltage to generate a desired output voltage. Moreover, the switching regulator includes a regulator circuit coupled to the LC filter circuit to control the gate driver circuit. The regulator circuit accurately controls variations in trip point. The trip point is a voltage at which the second switch is switched OFF by the gate control circuit. The regulator circuit includes one of a Delay Locked Loop (DLL) and a Pulse width modulator (PWM) controller.
1. A regulator circuit for controlling variations at a trip point of a switching regulator circuit, the regulator circuit comprising:
a first comparator operable to receive a first reference signal and a feedback signal to generate a first voltage signal, wherein the first reference signal is a first predetermined voltage at a first instance and the feedback signal is a voltage across a switch;
a second comparator operable to receive a second reference signal and the feedback signal to generate a second voltage signal, wherein the second reference signal is a second predetermined voltage at a second instance, wherein difference in time between the first instance and the second instance is proportional to value of an inductor current in the switching regulator circuit;
a reference delay circuit to delay the first voltage signal by a predetermined time period; and
a Delay Locked Loop (DLL) to modify a zero current detector output, the DLL comprising:
a Phase Frequency Detector (PFD) operable to receive the first voltage signal delayed and the second voltage signal to output a phase difference signal;
a charge pump to generate a control voltage signal based on the phase difference signal; and
a voltage controlled delay line (VCDL) to generate a delayed zero current detector output based on the control voltage signal, wherein the delayed zero current detector output controls variations in a trip point of the switching regulator, wherein the trip point is an instance at which the inductor current flowing in the switching regulator circuit is equal to zero.
2. The regulator circuit as claimed in claim 1 , wherein the first predetermined voltage is equal to a voltage of the parasitic diode when the parasitic diode starts conducting the inductor current.
3. The regulator circuit as claimed in claim 1 , wherein the second reference signal is magnitude of the feedback voltage when damped oscillation commences in an inductor and a parasitic capacitance.