Buck converter and control method therefor
First Claim
1. A buck converter, stepping-down an input voltage to an output voltage, comprising:
- a high-side N-type MOSFET switch, the drain electrode of the high-side N-type MOSFET switch coupled to the input voltage;
a low-side N-type MOSFET switch, the drain electrode of the low-side N-type MOSFET switch coupled to the source electrode of the high-side N-type MOSFET switch, the source electrode of the low-side N-type MOSFET switch coupled to a ground, wherein the high-side N-type MOSFET switch and the low-side N-type MOSFET switch have complementary duty cycles;
an output filter, coupled to the source electrode of the high-side N-type MOSFET switch and the drain electrode of the low-side N-type MOSFET switch, providing the output voltage;
a control circuit, controlling the high-side N-type MOSFET switch and the low-side N-type MOSFET switch;
a boot-strap capacitor, a first terminal of the boot-strap capacitor coupled to a regulating voltage, a second terminal of the boot-strap capacitor coupled to the source electrode of the high-side N-type MOSFET switch, the boot-strap capacitor being charged by the regulating voltage, the voltage of the first terminal of the boot-strap capacitor being provided to the control circuit for generating a gate driving signal controlling the high-side N-type MOSFET switch, wherein the voltage of the gate driving signal is larger than the input voltage; and
a disabling circuit, coupling to the boot-strap capacitor and the control circuit, the disabling circuit sensing the voltage across the boot-strap capacitor, and generating a control signal to control the control circuit for continuously turning off the high-side N-type MOSFET switch when the voltage crossing the boot-strap capacitor is less than a threshold voltage, and comprising;
a determining unit, coupled to the boot-strap capacitor, determining whether the voltage across the boot-strap capacitor is less than the threshold voltage and generating the control signal accordingly; and
a discharge unit, coupled to the boot-strap capacitor and the determining unit, wherein the discharge unit discharges the boot-strap capacitor to make the voltage across the boot-strap capacitor be zero according to the control signal when the voltage across the boot-strap capacitor is less than the threshold voltage.
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Accused Products
Abstract
The present disclosure provides a pair of NMOSFET switches connected in series, an output filter, a control circuit, a boot-strap capacitor and a disabling circuit. A high-side MOSFET switch is coupled to an input voltage. A low-side MOSFET switch is coupled to a ground. The high-side MOSFET switch and the low-side MOSFET switch have complementary duty cycles. The output filter is coupled to the NMOSFET switches to provide an output voltage. The boot-strap capacitor is coupled to the source of the high-side MOSFET switch. The voltage crossing the boot-trap capacitor is for making the gate voltage of the high-side MOSFET switch to be higher than the input voltage. The disabling circuit senses the voltage crossing the boot-strap capacitor, and generates a control signal to control the control circuit for continuously turning off the high-side MOSFET switch when the voltage crossing the boot-strap capacitor is less than a threshold voltage.
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Citations
9 Claims
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1. A buck converter, stepping-down an input voltage to an output voltage, comprising:
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a high-side N-type MOSFET switch, the drain electrode of the high-side N-type MOSFET switch coupled to the input voltage; a low-side N-type MOSFET switch, the drain electrode of the low-side N-type MOSFET switch coupled to the source electrode of the high-side N-type MOSFET switch, the source electrode of the low-side N-type MOSFET switch coupled to a ground, wherein the high-side N-type MOSFET switch and the low-side N-type MOSFET switch have complementary duty cycles; an output filter, coupled to the source electrode of the high-side N-type MOSFET switch and the drain electrode of the low-side N-type MOSFET switch, providing the output voltage; a control circuit, controlling the high-side N-type MOSFET switch and the low-side N-type MOSFET switch; a boot-strap capacitor, a first terminal of the boot-strap capacitor coupled to a regulating voltage, a second terminal of the boot-strap capacitor coupled to the source electrode of the high-side N-type MOSFET switch, the boot-strap capacitor being charged by the regulating voltage, the voltage of the first terminal of the boot-strap capacitor being provided to the control circuit for generating a gate driving signal controlling the high-side N-type MOSFET switch, wherein the voltage of the gate driving signal is larger than the input voltage; and a disabling circuit, coupling to the boot-strap capacitor and the control circuit, the disabling circuit sensing the voltage across the boot-strap capacitor, and generating a control signal to control the control circuit for continuously turning off the high-side N-type MOSFET switch when the voltage crossing the boot-strap capacitor is less than a threshold voltage, and comprising; a determining unit, coupled to the boot-strap capacitor, determining whether the voltage across the boot-strap capacitor is less than the threshold voltage and generating the control signal accordingly; and a discharge unit, coupled to the boot-strap capacitor and the determining unit, wherein the discharge unit discharges the boot-strap capacitor to make the voltage across the boot-strap capacitor be zero according to the control signal when the voltage across the boot-strap capacitor is less than the threshold voltage. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A control method for a buck converter, for controlling a high-side N-type MOSFET switch of the buck converter, the buck converter comprising the high-side N-type MOSFET switch coupling to an input voltage and a low-side N-type MOSFET switch coupling to a ground, the control method comprising:
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coupling a boot-strap capacitor between a regulating voltage and the source electrode of the high-side N-type MOSFET switch, wherein the source electrode of the high-side N-type MOSFET switch is coupled to the drain electrode of the low-side N-type MOSFET switch; turning-on the low-side N-type MOSFET switch, so as to make the regulating voltage charge the boot-strap capacitor through a path comprising the low-side N-type MOSFET switch; utilizing a gate driving signal to drive the high-side N-type MOSFET switch, wherein the voltage level of the gate driving signal is corresponding to the voltage across the boot-strap capacitor; sensing the voltage across the boot-strap capacitor; and turning-off the high-side N-type MOSFET switch continuously and discharging the boot-strap capacitor for making the voltage across the boot-strap capacitor be zero, when the voltage across the boot-strap capacitor is less than a threshold voltage. - View Dependent Claims (9)
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Specification