DC-to-DC converter having hysteretic current limiting
First Claim
1. A DC-to-DC converter comprising:
- a. means for charging an inductor with a current;
b. means for discharging the inductor into a capacitor, the means for discharging coupled to the means for charging; and
c. means for sensing a level of current in the inductor only when discharging the inductor, the means for sensing coupled to the means for discharging.
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Accused Products
Abstract
A DC-to-DC converter having hysteretic inductor current limiting and that does not have a resistor continuously carrying the inductor current. A voltage supply is coupled to a drain of a first transistor. A source of the first transistor is coupled to a first terminal of the inductor and to a drain of a second transistor. A source of the second transistor is coupled to ground through a resistor. A second terminal of the inductor is coupled to a first terminal of a capacitor. When the first transistor is on, the second transistor is off, causing current in the inductor to increase. The current flowing through the inductor charges the capacitor, and stores energy in the inductor as an increasing magnetic field. When the first transistor is off, the second transistor is on, and the stored energy is converted back into current, continuing to charge the capacitor. Voltage across the capacitor is regulated for powering a load by controlling the first and second transistors in a feedback loop. When the first transistor is off and the second transistor is on, a voltage across the resistor in series with the second transistor forms a signal representative of the inductor current. When the inductor current is higher than a first threshold at the start of a discharge cycle, the discharge cycle is extended until the inductor current falls below a second threshold, lower than the first threshold. Thus, the inductor current is hysteretically limited to prevent excessive current from damaging circuit elements.
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Citations
27 Claims
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1. A DC-to-DC converter comprising:
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a. means for charging an inductor with a current; b. means for discharging the inductor into a capacitor, the means for discharging coupled to the means for charging; and c. means for sensing a level of current in the inductor only when discharging the inductor, the means for sensing coupled to the means for discharging. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A method of sensing current in a DC-to-DC converter comprising the steps of:
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a. charging an inductor; b. discharging the inductor; and c. sensing a level of current in the inductor only when discharging the inductor. - View Dependent Claims (8, 9, 10, 11)
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12. A DC-to-DC converter comprising:
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a. a first transistor having a first drain, a first source and a first gate; b. a second transistor having a second drain, a second source and a second gate, wherein the second drain is coupled to the first source; c. means for controlling the first gate and the second gate coupled to the first gate and to the second gate; d. an inductor having a first terminal and a second terminal wherein the first terminal of the inductor is coupled to the first source; e. a capacitor having a first terminal and a second terminal wherein the first terminal of the capacitor is coupled to the second terminal of the inductor; and f. a resistor having a first terminal and a second terminal wherein the first terminal of the resistor is coupled to the second source and wherein the second terminal of the resistor is coupled to a supply potential. - View Dependent Claims (13, 14, 15, 16, 17, 18, 19)
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20. A DC-to-DC converter controller comprising:
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a. means for charging an inductor with a current; b. means for discharging the inductor into a capacitor for forming a first voltage across the capacitor; c. means for sensing a current in the inductor; and d. means for sensing the first voltage, wherein the inductor is charged and discharged according to a pulse-width modulation scheme for maintaining the first voltage substantially constant and wherein, after the current in the inductor exceeds a first threshold, the inductor is discharged until after the current in the inductor falls below a second threshold lower than the first threshold. - View Dependent Claims (21, 22, 23)
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24. A DC-to-DC converter comprising:
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a. a first transistor having a first drain, a first source and a first gate wherein the first drain is coupled to receive power from a supply; b. a second transistor having a second drain, a second source and a second gate wherein the second drain is coupled to the first source; c. a resistor having a first terminal and a second terminal wherein the first terminal of the resistor is coupled to the second source and wherein the second terminal of the resistor is coupled to a ground node; d. an inductor having a first terminal and a second terminal wherein the first terminal of the inductor is coupled to the first source and to the second drain; e. a capacitor having a first terminal and a second terminal wherein the first terminal of the capacitor is coupled to the second terminal of the inductor and wherein the second terminal of the capacitor is coupled to the ground node; f. an amplifier having a positive input, a negative input and an output wherein the positive input of the amplifier is coupled to a reference voltage source and wherein the negative input of the amplifier is coupled to the first capacitor terminal; g. a comparator having a positive input, a negative input and an output wherein the negative input is coupled to the output of the amplifier; h. an oscillator having a periodic ramp output wherein the periodic ramp output is coupled to the positive input of the comparator; i. a Schmitt trigger having an hysteretic transfer characteristic and having an input and an output wherein the input is coupled to the first terminal of the resistor; and j. logic circuits coupled to receive the output of the comparator and the output of the Schmitt trigger for forming a first output signal and a second output signal wherein the first output signal is coupled to the first gate and the second output signal is coupled to the second gate. - View Dependent Claims (25, 26, 27)
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Specification