US 8,569,966 B2Granted

Starting circuit for buck converter

AssigneeOsram Sylvania Inc.

InventorsNitin Kumar, Shashank Bakre, Markus Ziegler

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Abstract

A ballast to energize a lamp is provided. The ballast comprises a buck converter connected to an inverter via a switching component. The buck converter includes a transistor, a capacitor, a diode, and an inductor. The switching component has a predetermined breakover voltage value and is configured to provide a start up signal to the inverter when voltage at the switching component increases to the predetermined breakover voltage value. A control circuit is configured to monitor the voltage at the switching component while the voltage at the switching component increases to the predetermined breakover voltage, and is configured to generate a gate drive pulse at a gate terminal of the transistor when the voltage at the switching component reaches a predetermined voltage that is less than the breakover voltage of the switching component.

Claims20

Dependent claims

A ballast comprising:

a rectifier that receives an alternating current (AC) voltage signal from an AC power supply and produces a rectified voltage signal therefrom;
a power factor correction circuit connected to the rectifier to provide a corrected voltage signal as a function of the rectified voltage signal;
a buck converter connected to the power factor correction circuit to step down the corrected voltage signal, the buck converter comprising:
an input terminal connected to the power factor correction circuit to receive the corrected voltage signal;
an output terminal to provide the stepped down voltage signal;
a transistor having a drain terminal, a gate terminal, and a source terminal, wherein the drain terminal is connected to the input terminal;
a capacitor having a first terminal connected to the output terminal and having a second terminal connected to ground potential;
a diode having an anode connected to ground potential and having a cathode connected to the source terminal of the transistor;
and
an inductor having a first terminal connected to the source terminal of the transistor and to the cathode of the diode, and having a second terminal connected to the first terminal of the capacitor;
an inverter connected to the output terminal of the buck converter circuit to receive a start up signal and, in response, to generate an oscillating voltage signal to energize the lamp;
a switching component connected between the output terminal of the buck converter circuit and the inverter to provide the start up signal to the inverter, the switching component having a predetermined breakover voltage value, wherein the switching component is configured to provide the start up signal to the inverter when a voltage at the switching component increases to the predetermined breakover voltage value;
a sensing circuit configured to sense the voltage at the switching component;
and
a control circuit connected to the buck converter and to the sensing circuit to drive the buck converter, the control circuit configured to monitor the sensed voltage from the sensing circuit while the voltage at the switching component increases to the predetermined breakover voltage and to generate a gate drive pulse at the gate terminal of the transistor when the sensed voltage reaches a predetermined voltage that is less than the breakover voltage of the switching component.

12 more elements

A ballast comprising:

a buck converter to generate a direct current (DC) buck voltage output, the buck converter having a particular peak DC buck voltage value associated therewith;
an inverter connected to buck converter circuit to receive a start up signal and, in response, to generate an oscillating voltage signal to energize a lamp;
a switching component connected between the buck converter and the inverter to provide the start up signal to the inverter, the switching component having a predetermined breakover voltage value, wherein the switching component is configured to provide the start up signal to the inverter when voltage at the switching component increases to the predetermined breakover voltage value;
a sensing circuit configured to sense the voltage at the switching component;
and
a control circuit connected to the buck converter and the sensing circuit to drive the buck converter, the control circuit configured to monitor the sensed voltage from the sensing circuit while the voltage at the switching component increases to the predetermined breakover voltage and to drive the buck converter to generate a voltage pulse having the particular peak DC buck voltage value when the sensed voltage reaches a predetermined voltage that is less than the breakover voltage of the switching component.

3 more elements

Dependencies are inferred from the claim text.