Power supply having voltage blocking clamp

• US 20070115022A1
• Filed: 01/03/2007
• Published: 05/24/2007
• Est. Priority Date: 02/21/1992
• Status: Active Grant

• Current Assignee: Elster Electricity LLC (Honeywell International Inc.)
• Original Assignee: Elster Electricity LLC (Honeywell International Inc.)
• Inventors: Schleifer, Fred, Munday, Mark, Hemminger, Rodney
• Granted Patent: US 7,339,805 B2
• Time in Patent Office: Days
• US Class Current: 363/56.110
• CPC Class Codes: G01R 21/133 by using digital technique
• CPC Class Codes: G01R 21/1331 Measuring real or reactive component, measuring apparent energy
• CPC Class Codes: H02M 3/335 using semiconductor devices only
• CPC Class Codes: H02M 3/33507 with automatic control of the output voltage or current, e.g. flyback converters H02M3/33561, H02M3/33569 take precedence

Abstract

A power supply comprises a rectifier, a transformer, a switching member, a controller and a voltage blocking clamp. A power supply can receive an alternating current (AC) input voltage having any magnitude within a wide range of AC input voltage magnitudes and can produce from any such AC input voltage magnitude a direct current (DC) output voltage. The voltage blocking clamp comprises at least one transistor connected between the rectifier and the transformer and switching member that limits the amount of rectified AC input voltage applied to the transformer and switching member to a predetermined amount when the rectified input voltage exceeds that predetermined amount. When the rectified input voltage exceeds the predetermined amount, the amount of the rectified input voltage above the predetermined amount is applied to the at least one transistor instead of the transformer and switching member.

Claims

1. A power supply for receiving an alternating current (AC) input voltage having any magnitude within a wide range of AC input voltage magnitudes and producing therefrom a direct current (DC) output voltage, said power supply comprising:

a rectifier that receives and rectifies an AC input voltage having a magnitude within said wide range;

a transformer comprising a first winding and a second winding, wherein the first winding is connected to receive the rectified AC input voltage so that current flows through the first winding, and wherein a voltage across the second winding defines the output of the power supply;

a switching member connected to the first winding for permitting and preventing the flow of current through the first winding in response to a control signal;

a controller connected to the switching member that generates the control signal in response to a signal representative of the output of the power supply; and

a voltage blocking clamp comprising at least one transistor connected between the rectifier and the transformer and switching member that limits the amount of the rectified AC input voltage applied to the transformer and switching member to a predetermined amount when the rectified input voltage exceeds that predetermined amount, wherein when the rectified input voltage exceeds the predetermined amount, the amount of the rectified input voltage above the predetermined amount is applied to the at least one transistor instead of the transformer and switching member.

2. The power supply recited in claim 1, wherein the transformer comprises a third winding that generates said signal representative of the output of the power supply.

3. The power supply of claim 2, wherein the third winding is substantially similar to the second winding, so a voltage across the third winding is similar to the voltage across the second winding, and wherein said voltage across the third winding defines said signal representative of the output of the power supply.

4. The power supply recited in claim 1, wherein the voltage blocking clamp causes the switching member to be disabled when the rectified input voltage exceeds the predetermined amount.

5. The power supply recited in claim 1, wherein the voltage blocking clamp comprises a first transistor and a second transistor, and wherein when the rectified input voltage exceeds the predetermined value, the amount of the rectified input voltage above the predetermined amount is applied to the first and second transistors instead of the transformer and switching member.

6. The power supply of claim 1, wherein the switching member comprises a transistor connected between the first winding and a ground, and wherein the controller comprises an oscillator connected to a base of the transistor, and wherein the oscillator generates an oscillating signal for switching the transistor on and off to control the flow of current through the primary winding.

7. The power supply of claim 6, wherein the oscillator comprises a ring oscillator.

8. The power supply of claim 6, wherein the switching member comprises a MOSFET.

9. The power supply of claim 8, wherein the MOSFET is a 600V MOSFET.

10. The power supply of claim 1, wherein the controller comprises (a) a current sensor for sensing current flowing through the first winding and for generating a sensed current signal, (b) a reference current generator for generating a reference current signal in response to the signal reflective of the output of the power supply and (c) a comparator for comparing the sensed current signal and the reference current signal.

11. The power supply of claim 10, wherein the control signal is generated in response to the comparator determining that the sensed current signal exceeds the reference current signal.

12. The power supply of claim 10, wherein the reference current generator comprises a current-mode regulator.

13. The power supply of claim 1, wherein the wide range of AC input voltage magnitudes includes magnitudes in the range of approximately 96 to 528 volts.

14. The power supply of claim 1, wherein the predetermined amount comprises approximately 400 volts.