Microcontroller operated current limited switching power supply for circuit protective devices

• US 20100220507A1
• Filed: 02/27/2009
• Published: 09/02/2010
• Est. Priority Date: 02/27/2009
• Status: Active Grant

• Current Assignee: Schneider Electric USA, Inc. (Schneider Electric SE)
• Original Assignee: Square D Company (Schneider Electric SE)
• Inventors: Mackenzie, John K., Larson, Brett, Schroeder, Jeremy D.
• Granted Patent: US 8,237,419 B2
• Time in Patent Office: Days
• US Class Current: 363/126
• CPC Class Codes: H02M 1/32 Means for protecting converters other than automatic disconnection
• CPC Class Codes: H02M 7/2176 comprising a passive stage to generate a rectified sinusoidal voltage and a controlled switching element in series between such stage and the output

Abstract

An AC to DC power supply for small heat sensitive electronic device. The power supply being dynamically controlled to operate symmetrically about the lowest point of the AC source voltage waveform for minimum excess heat production.

Claims

1. A thermally efficient switching power supply for a protective circuit, the power supply comprising:

a source of AC power;

a rectifier for converting the AC power to DC;

a power supply capacitor for storing a DC voltage;

a voltage regulator selectively receiving power from one of the rectifier or the power supply capacitor, the voltage regulator supplying regulated power to all components of the protective circuit;

a power supply switch electrically between the rectifier and the power supply capacitor for selectively providing power from the rectifier to the power supply capacitor and the voltage regulator, and;

a microprocessor powered by the regulated power and controlling all functions of the protective circuit including dynamic control of the power supply switch with respect to the lowest point of the AC power source voltage waveform.

2. The power supply of claim 1, wherein the microprocessor monitors the charge on the power supply capacitor.

3. The power supply of claim 2, wherein the microprocessor monitors the AC source voltage waveform.

4. The power supply of claim 3, wherein the microprocessor determines the minimum time required to sufficiently charge the power supply capacitor for operation of the protective circuit.

5. The power supply of claim 4, wherein the microprocessor initiates closing of the power supply switch at a point near the lowest point on the AC source voltage waveform that will provide the determined minimum time for charging the power supply capacitor when the power supply switch remains CLOSED symmetrically about the lowest point on the AC source voltage waveform.

6. The power supply of claim 5, wherein the lowest point on the AC source voltage waveform is the zero crossing.

7. The power supply of claim 3, wherein the microprocessor detects fault conditions and voltage sags in the AC power source.

8. The power supply of claim 7, wherein the microprocessor determines the minimum time for charging the power supply capacitor based on the detected fault condition or voltage sag and initiates closing of the power supply switch at a point on the AC source voltage waveform that will provide the determined minimum time for charging the power supply capacitor when the power supply switch remains CLOSED symmetrically about the lowest point on the AC source voltage waveform.

9. The power supply of claim 1, further including at least one voltage dropping resistor electrically between the power supply switch and the rectifier for reducing the voltage applied to the power supply switch and for dissipating heat in the power supply circuit.

10. The power supply of claim 1, further including at least one current limiting resistor electrically between the power supply switch and the voltage regulator for limiting current in the power supply circuit.

11. The power supply of claim 10, wherein the value of the current limiting resistor is selected to limit the maximum current flow through the trip solenoid and the power supply switch.

12. The power supply of claim 11, wherein the range of the voltages on both sides of the power supply switch is known and is used to determine the value of the current limiting resistor.

13. A thermally efficient switching power supply for a protective circuit, the power supply comprising:

a source of AC power;

a rectifier for converting the AC power to DC;

a power supply capacitor for storing a DC voltage;

a voltage regulator selectively receiving power from one of the rectifier or the power supply capacitor, the voltage regulator supplying regulated power to all components of the protective circuit;

a power supply switch electrically between the rectifier and the power supply capacitor for selectively providing power from the rectifier to the power supply capacitor and the voltage regulator;

at least one voltage dropping resistor electrically between the rectifier and the power supply switch for reducing the voltage applied to the power supply switch and dissipating heat;

a current limiting resistor electrically between the power supply switch and the voltage regulator for limiting current flow through the power supply switch, and;

a microprocessor powered by the regulated power and controlling all functions of the protective circuit including dynamic control of the power supply switch such that the power supply switch is CLOSED symmetrically about the lowest point of the AC power source voltage waveform for the minimum time required to charge the power supply capacitor.

14. A thermally efficient switching power supply for a protective circuit, the power supply comprising:

a source of AC power;

a rectifier for converting the AC power to DC;

a power supply capacitor for storing a DC voltage;

a voltage regulator selectively receiving power from one of the rectifier or the power supply capacitor, the voltage regulator supplying regulated power to all components of the protective circuit;

a power supply switch electrically between the rectifier and the power supply capacitor for selectively providing power from the rectifier to the power supply capacitor and the voltage regulator, and;

a microprocessor powered by the regulated power and controlling all functions of the protective circuit including dynamic control of the power supply switch such that the power supply switch is CLOSED symmetrically about the zero crossing of the AC power source voltage waveform for the minimum time required to charge the power supply capacitor.