Adjusting inductor switching frequency to compensate for inductance that deviates from a stated magnitude in order to maintain constant output current from a primary-side power converter
First Claim
1. A method comprising:
- (a) receiving a feedback signal indicative of a first time and of an input voltage of a power converter, wherein an inductor current ramps up through a primary winding of the power converter during a ramp-up time and stops ramping up at the first time, and wherein the primary winding exhibits an inductance whose magnitude deviates from a stated nominal magnitude;
(b) generating an inductor switch control signal that has a switching frequency; and
(c) adjusting the switching frequency of the inductor switch control signal based on the ramp-up time to compensate for the deviating magnitude of the inductance and to maintain a constant output current of the power converter.
2 Assignments
0 Petitions
Accused Products
Abstract
A comparing circuit and a control loop are used to maintain the peak level of current flowing through an inductor of a flyback converter. An inductor switch control signal controls a switch through which the inductor current flows. The inductor current increases at a ramp-up rate during a ramp time and stops increasing at the end of the ramp time. The comparing circuit generates a timing signal that indicates a target time at which the inductor current would reach a predetermined current limit if the inductor current continued to increase at the ramp-up rate. The control loop then receives the timing signal and compares the target time to the end of the ramp time. The pulse width of the inductor switch control signal is increased when the target time occurs after the end of the ramp time. Adjusting the frequency and pulse width controls the peak of the inductor current.
77 Citations
24 Claims
-
1. A method comprising:
-
(a) receiving a feedback signal indicative of a first time and of an input voltage of a power converter, wherein an inductor current ramps up through a primary winding of the power converter during a ramp-up time and stops ramping up at the first time, and wherein the primary winding exhibits an inductance whose magnitude deviates from a stated nominal magnitude; (b) generating an inductor switch control signal that has a switching frequency; and (c) adjusting the switching frequency of the inductor switch control signal based on the ramp-up time to compensate for the deviating magnitude of the inductance and to maintain a constant output current of the power converter. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
-
-
11. A device comprising:
-
a primary winding that exhibits an inductance whose magnitude deviates from a stated nominal magnitude, wherein an inductor current ramps up through the primary winding during a ramp-up time and stops ramping up at a first time; a switch that is controlled by an inductor switch control signal, wherein the inductor switch control signal has a switching frequency; and an oscillator that generates a switching frequency signal, wherein the switching frequency signal governs the switching frequency of the inductor switch control signal, and wherein the oscillator generates the switching frequency signal based on the ramp-up time to compensate for the deviating magnitude of the inductance and to maintain a constant output current of the device. - View Dependent Claims (12, 13, 14, 15)
-
-
16. A power converter that outputs an output current, comprising:
-
a secondary side comprising a secondary winding; and a primary side comprising a primary winding, an auxiliary winding, an oscillator and a switch, wherein an inductor current ramps up through the primary winding when the switch is on, wherein the switch is controlled by an inductor switch control signal, wherein the oscillator generates a switching frequency signal using feedback from magnetic coupling between the auxiliary winding and the secondary winding, wherein the switching frequency signal has a first frequency, wherein the inductor switch control signal has a second frequency that depends on the first frequency, wherein no feedback from the secondary side is used to control the second frequency, and wherein the oscillator controls the first frequency based on a ramp-up time when the switch is on such that the output current remains constant. - View Dependent Claims (17, 18, 19)
-
-
20. A system comprising:
-
an inductor switch that is turned on by an inductor switch control signal; an inductor whose actual inductance deviates from a stated inductance, wherein an inductor current flows through the inductor and ramps up during a ramp-up time to a peak current while the inductor switch is turned on, and wherein the inductor switch control signal has a switching frequency; and means for maintaining the peak current at a constant magnitude while adjusting the switching frequency based on the ramp-up time to compensate for the actual inductance deviating from the stated inductance. - View Dependent Claims (21, 22, 23, 24)
-
Specification