Transient over voltage protection circuit for electrical power converters
First Claim
1. In an electrical power converter having a rectifier means for converting an input AC voltage to an unregulated DC intermediate voltage, said intermediate voltage appearing on first and second output terminals of said rectifier means, and a DC-to-DC converter for converting said unregulated DC intermediate voltage into one or more regulated output DC voltages, including first and second input terminals, a transient overvoltage protection circuit comprising:
- a first switch connected in series between one of said first and second output terminals of said rectifier means and a corresponding one of said first and second input terminals of said converter, said first switch being in a normally closed state so as to create a conductive path between said respective output and input terminals;
means for electrically coupling the other of said first and second output terminals to the other of said first and second input terminals;
a capacitor connected between said first and second input terminals of said converter;
means for detecting when the voltage across said capacitor exceeds a first predetermined value and for causing said first switch to switch to a current limit state in response thereto, wherein said current limit state comprises the periodic switching of said first switch between a normally closed state and an open state, said first switch being caused to open when the voltage across said capacitor reaches said first predetermined value and to close when the voltage across said capacitor drops to a second predetermined value; and
means for maintaining said first switch in said current limit state until the voltage across said capacitor drops below said second predetermined value.
1 Assignment
0 Petitions
Accused Products
Abstract
A transient voltage protection circuit includes a normally closed switch connected between a rectifier circuit and a DC to DC converter. This switch is caused to switch to a current limit state when the voltage input to the DC to DC converter exceeds a first predetermined value, thereby protecting the DC to DC converter from voltages that exceed the converter'"'"'s operational limits. The switch is returned to its normally closed state when the voltage input to the converter drops below a second predetermined lower value. A capacitor connected across the input terminals of the converter is charged up when the switch is closed and functions to supply power to the DC to DC converter when the switch is in its current limit state. The current limit state of the switch comprises the periodic switching of said switch between a normally closed state and an open state, said switch being caused to open when the voltage across said capacitor reaches said first predetermined value and to close when the voltage across the capacitor drops to said second predetermined lower value.
107 Citations
18 Claims
-
1. In an electrical power converter having a rectifier means for converting an input AC voltage to an unregulated DC intermediate voltage, said intermediate voltage appearing on first and second output terminals of said rectifier means, and a DC-to-DC converter for converting said unregulated DC intermediate voltage into one or more regulated output DC voltages, including first and second input terminals, a transient overvoltage protection circuit comprising:
-
a first switch connected in series between one of said first and second output terminals of said rectifier means and a corresponding one of said first and second input terminals of said converter, said first switch being in a normally closed state so as to create a conductive path between said respective output and input terminals; means for electrically coupling the other of said first and second output terminals to the other of said first and second input terminals; a capacitor connected between said first and second input terminals of said converter; means for detecting when the voltage across said capacitor exceeds a first predetermined value and for causing said first switch to switch to a current limit state in response thereto, wherein said current limit state comprises the periodic switching of said first switch between a normally closed state and an open state, said first switch being caused to open when the voltage across said capacitor reaches said first predetermined value and to close when the voltage across said capacitor drops to a second predetermined value; and means for maintaining said first switch in said current limit state until the voltage across said capacitor drops below said second predetermined value. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
-
-
11. In an electrical power converter having a rectifier means for converting an input AC voltage to a DC intermediate voltage, said intermediate voltage appearing on first and second output terminals of said rectifier means, and a DC-to-DC converter for converting said unregulated DC intermediate voltage into one or more regulated output DC voltages, including first and second input terminals, a transient overvoltage protection circuit comprising:
-
a first switch connected in series between one of said first and second output terminals of said rectifier means and a corresponding one of said first and second input terminals of said converter, said first switch being in a normally closed state so as to create a conductive path between said respective output and input terminals; means for electrically coupling the other of said first and second output terminals to the other of said first and second input terminals; a capacitor connected between said first and second input terminals of said converter; means for detecting when the voltage across said capacitor exceeds a first predetermined value; a second switch being in a normally opened state and being responsive to said means for detecting, said second switch being caused to close upon the detection of a voltage across said capacitor which exceeds said first predetermined value, the closure of said second switch causing said first switch to switch to a current limit state wherein said first switch opens and closes at a periodic rate wherein said periodic rate is a function of the rate at which said capacitor charges and discharges; and means for maintaining said first switch in said current limit state until the voltage across said capacitor drops below a second predetermined value. - View Dependent Claims (12, 13)
-
-
14. In an electrical power converter having a rectifier means for converting an input AC voltage to an intermediate DC voltage, said intermediate DC voltage appearing on first and second output terminals of said rectifier means, and a DC-to-DC converter for converting said intermediate DC voltage into one or more regulated output DC voltages, including first and second input terminals, a transient overvoltage protection circuit comprising:
-
a current limit means connected in series between said first output terminal of said rectifier means and said first input terminal of said converter creating a conductive path between said respective output and input terminals, said current limit means being in a fully conductive state upon normal operation of said electrical power converter; means for electrically coupling said second output terminal to said second input terminal; a capacitor connected between said first and second input terminals of said converter; and overvoltage detection means for detecting when the voltage across said capacitor exceeds a maximum voltage level, said current limit means being responsive thereto to switch to a partially conductive state to limit the amount of current in said conductive path to below a maximum current value, said current limit means remaining in said partially conductive state until the voltage across said capacitor returns to a normal voltage level. - View Dependent Claims (15, 16, 17, 18)
-
Specification