LED POWER SOURCE AND DC-DC CONVERTER

• US 20100308751A1
• Filed: 06/05/2009
• Published: 12/09/2010
• Est. Priority Date: 06/05/2009
• Status: Active Grant

• Current Assignee: Current Lighting Solutions, LLC (f/k/a GE Lighting Solutions, LLC) (American Industrial Partners)
• Original Assignee: General Electric Company
• Inventors: Nerone, Louis Robert
• Granted Patent: US 7,990,070 B2
• Time in Patent Office: Days
• US Class Current: 315/312
• CPC Class Codes: H02M 1/32 Means for protecting converters other than automatic disconnection
• CPC Class Codes: H02M 1/4225 using a non-isolated boost converter
• CPC Class Codes: Y02B 70/10 Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes

Abstract

Isolated LED power sources and DC-DC converters therefor are presented in which the DC-DC converter includes a self-oscillating inverter driving an output rectifier for operating an LED array of one or more LEDs, where the inverter uses a control transformer with core having a Curie temperature set to a maximum operating temperature of one or more power supply components to reduce inductances of secondary windings in the inverter oscillation circuitry to lower the power supplied to the load so as to prevent the inverter from overheating.

Claims

1. An LED power source for operating an LED array of one or more LEDs, the power source comprising:

an input rectifier operative to receive an input AC voltage signal and to produce an initial DC voltage; and

a DC-DC converter which is operatively coupled to the input rectifier to receive the initial DC voltage, the DC-DC converter comprising;

a supply-side ground connection,

a load-side ground connection electrically isolated from the supply side ground,

a self-oscillating inverter operatively coupled to the supply-side ground connection and receiving the initial DC voltage, the inverter operative to produce an intermediate AC signal, and

an output rectifier operatively coupled to receive the intermediate AC signal from the inverter and being coupled with the load-side ground connection, the output rectifier operative to produce an output DC voltage to supply power to the LED array.

2. The LED power source of claim 1, further comprising a boost converter operatively coupled between the input rectifier and the DC-DC converter, the boost converter receiving the initial DC voltage from the input rectifier and amplifying the initial DC voltage to provide an intermediate DC voltage, the inverter converting the intermediate DC voltage to produce the intermediate AC signal.

3. The LED power source of claim 2, wherein the boost converter further comprises a power factor correction controller to control a power factor of the power source.

4. The LED power source of claim 1, wherein the DC-DC converter further comprises an inverter controller operatively coupled to the inverter, to modify a switching frequency of the inverter, to control a frequency of the intermediate AC signal to control power supplied to the LED array based at least in part on a sensed power drawn by the LED array.

5. The LED power source of claim 4, wherein the inverter controller is electrically isolated from the inverter.

6. The LED power source of claim 4, wherein the DC-DC converter further comprises a control transformer comprising:

a primary winding operatively coupled to and controlled by the inverter controller;

a secondary winding operative to control the switching frequency of the inverter; and

a core operatively coupled to the primary winding and the secondary windings, the core comprising a core material having a Curie temperature associated with a maximum operating junction temperature of a component in the power source, operative to become paramagnetic when the temperature of the core exceeds the Curie temperature of the core;

the control transformer being operative to reduce the inductance of the secondary windings to lower the power supplied to the LED array to prevent the component of the power source from overheating.

7. The LED power source of claim 4, wherein the inverter further comprises:

a resonant circuit which generates an oscillation signal, including a resonant inductance and a resonant capacitance,

first and second switches operatively connected together at a common node to receive the oscillation signal determining the switching rate of the first and second switches;

a first gate control circuit controlling the first switch, the first gate control circuit comprising an inductance operatively connected between the junction of the first and second switches and the gate of the first switch and being coupled to the resonant inductance; and

a second gate control circuit controlling the second switch, the second gate control circuit comprising an inductance operatively connected between the supply-side ground connection and the gate of the second switch and being coupled to the resonant inductance;

wherein the first and second switches induce an AC current in the resonant circuit.

8. The LED power source of claim 1, wherein the inverter further comprises:

a feedback transformer comprising;

a primary winding, and

a first and second secondary winding operatively connected to the primary winding of the feedback transformer;

a resonant circuit comprising;

a signal-to-center capacitance operatively connected to the positive rail of the initial DC voltage,

a center-to-ground capacitance operatively connected between the signal-to-center capacitance and the supply-side ground connection, and

an inductance comprising the primary winding of the feedback transformer operatively connected to the junction of the signal-to-center capacitance and the center-to-ground capacitance;

a first gate control circuit comprising;

an inductance comprising the first secondary winding of the feedback transformer operatively connected to the inductance of the resonant circuit,

a capacitance operatively connected to the inductance of the first gate control circuit, and

a resistance operatively connected to the capacitance of the first gate drive circuit;

a second gate control circuit comprising;

an inductance comprising the second secondary winding of the feedback transformer operatively connected to the supply-side ground connection,

a capacitance and resistance in parallel operatively connected to the inductance of the second gate control circuit, and

a resistance operatively connected to the parallel capacitance-resistance of the second gate drive circuit; and

first and second switches operatively connected in series between the positive rail of the DC voltage and the supply-side ground connection, and the junction of the first and second switches is connected to the inductance of the resonant circuit, the first and second switches being controlled by the first and second gate control circuits respectively;

wherein the primary winding of the feedback transformer induces a voltage in the inductance of the first and second gate control circuits proportional to the instantaneous rate of change of current in the resonant circuit, the first and second gate control circuits alternatively switching the first and second switches operating to excite the resonant circuit.

9. An isolated, self-oscillating DC-DC converter comprising:

a supply-side ground connection;

a load-side ground connection electrically isolated from the supply side ground connection;

a self-oscillating inverter operatively coupled to the supply-side ground connection and receiving the initial DC voltage, the inverter operative to produce an intermediate AC signal; and

an output rectifier operatively coupled to receive the intermediate AC signal from the inverter and being coupled with the load-side ground connection, the output rectifier operative to produce an output DC voltage to supply power to a load.

10. The DC-DC converter of claim 9, further comprising an inverter controller operatively coupled to the inverter, to modify a switching frequency of the inverter, to control a frequency of the intermediate AC signal to control power supplied to a load based at least in part on a sensed power drawn by the load.

11. The DC-DC converter of claim 9, wherein the inverter controller is electrically isolated from the inverter.

12. The DC-DC converter of claim 9, further comprising a control transformer comprising:

a primary winding operatively coupled to and controlled by the inverter controller;

a secondary winding operative to control the switching frequency of the inverter; and

a core operatively coupled to the primary winding and the secondary windings, the core comprising a core material having a Curie temperature associated with a maximum operating junction temperature of at least one component in the power source the core being operative to become paramagnetic when a temperature of the core exceeds the Curie temperature of the core;

the control transformer being operative to reduce the inductance of the secondary windings to lower the power supplied to the LED array to prevent the component of the power source from overheating.

13. The DC-DC converter of claim 9, further comprising:

a resonant circuit which generates an oscillation signal, including a resonant inductance and a resonant capacitance;

first and second switches operatively connected together at a common node to receive the oscillation signal determining the switching rate of the first and second switches;

a first gate control circuit controlling the first switch, the first gate control circuit comprising;

an inductance operatively connected between the junction of the first and second switches and the gate of the first switch and being coupled to the resonant inductance; and

a second gate control circuit controlling the second switch, the second gate control circuit comprising;

an inductance operatively connected between the supply-side ground connection and the gate of the second switch and being coupled to the resonant inductance;

wherein the first and second switches induce an AC current in the resonant circuit.

14. A self-oscillating DC-DC converter comprising:

a self-oscillating inverter receiving the initial DC voltage, the inverter operative to produce an intermediate AC signal;

an output rectifier operatively coupled to receive the intermediate AC signal from the inverter, the output rectifier operative to produce an output DC voltage to supply power to a load; and

a control transformer comprising;

a primary winding operatively coupled to and controlled by the inverter controller;

a secondary winding operative to control the switching frequency of the inverter; and

a core operatively coupled to the primary winding and the secondary windings, the core comprising a core material having a Curie temperature associated with a maximum operating junction temperature of at least one component in the inverter and operative to become paramagnetic when a temperature of the core exceeds the Curie temperature of the core;

the control transformer being operative to reduce the inductance of the secondary windings to lower the power supplied to the LED array to prevent the component of the power source from overheating.

15. The self-oscillating DC-DC converter of claim 14, further comprising an inverter controller operatively coupled to the inverter, to modify a switching frequency of the inverter to control a frequency of the intermediate AC signal to control power supplied to the LED array based at least in part on a sensed power drawn by the LED array.

16. The self-oscillating DC-DC converter of claim 14, wherein the inverter further comprises:

a resonant circuit which generates an oscillation signal, including a resonant inductance and a resonant capacitance;

first and second switches operatively connected together at a common node to receive the oscillation signal determining the switching rate of the first and second switches;

a first gate control circuit controlling the first switch, the first gate control circuit comprising an inductance operatively connected between the junction of the first and second switches and the gate of the first switch and being coupled to the resonant inductance; and

a second gate control circuit controlling the second switch, the second gate control circuit comprising an inductance operatively connected between the supply-side ground connection and the gate of the second switch and being coupled to the resonant inductance;

wherein the first and second switches induce an AC current in the resonant circuit.