Systems and methods for diagnostic current shunt and overcurrent protection (OCP) for power supplies

Patent metadata

Field	Value
Publication number	US-9906143-B1
Application number	US-201615282189-A
Country	US
Kind code	B1
Filing date	Sep 30, 2016
Priority date	Sep 30, 2016
Publication date	Feb 27, 2018
Grant date	Feb 27, 2018

Abstract

Systems and methods are provided that may be implemented to provide a power supply with automatic overcurrent protection (OCP) point calibration and/or current sense resistor (Rsense) verification. The provided systems and methods may implement auto-calibration techniques on the secondary side of a power supply to achieve a more precise OCP point than is possible with conventional adapter technology, and in one example may implement auto trimming for OCP voltage threshold value.

First claim

What is claimed is:

1. A power supply unit (PSU) including a primary side and a secondary side that are separated by a transformer, comprising:
transformer circuitry having a primary side winding and a secondary side winding;
primary side circuitry including the primary side winding of the transformer and configured to receive input power at a PSU power input;
secondary side circuitry including the secondary side winding of the transformer coupled to a DC output current loop that includes first and second DC current loop paths, the secondary side circuitry configured to receive power from the primary side circuitry through the transformer and to supply direct current (DC) power to a PSU power output through the DC current loop paths of the DC output current loop;
an output power switch coupled within the DC output current loop between the transformer and the PSU power output, the output power switch being coupled to selectively connect and disconnect the PSU power output from the transformer;
a sense resistor coupled within one of the first or second DC current loop paths between the transformer and the output power switch;
at least one current shunt coupled between the first and second DC current loop paths at a node located between the sense resistor and the output power switch to provide a test current path through the current shunt and the DC current loop with the PSU power output disconnected from the transformer by the output power switch, the current shunt having a resistance value selected to yield an expected test current value through the current shunt and the DC current loop at a given output voltage from the transformer; and
at least one programmable integrated circuit coupled to control the output power switch and programmed to selectively disconnect the PSU power output from the transformer while the secondary side of the transformer is supply DC power to produce a test current through the test current path and to monitor a voltage drop across the sense resistor while the test current is flowing across the sense resistor with the PSU power output being disconnected from the transformer by the output power switch, the programmable integrated circuit being further programmed to:
compare the expected voltage drop to the monitored voltage drop across the sense resistor while the test current is flowing across the sense resistor, and
determine whether or not to control the output power switch to connect the PSU power output to the transformer based on the comparison of the monitored voltage drop across the sense resistor to the expected voltage drop across the sense resistor.

2. The PSU of claim 1 , where the at least one current shunt comprises a test switch coupled between the first and second DC current loop paths to selectively connect and disconnect the test current path through the current shunt and the DC current loop, the at least one programmable integrated circuit coupled to control the test switch to selectively connect and disconnect the test current path through the current shunt and the DC current loop.

3. The PSU of claim 1 , where the expected voltage drop is a voltage value or a range of voltage values; and where the programmable integrated circuit is programmed to:
not connect the PSU power output to the transformer with the output power switch if the monitored voltage drop across the sense resistor is greater or lesser than the expected voltage drop; and
connect the PSU power output to the transformer with the output power switch if the monitored voltage drop across the sense resistor is equal to the expected voltage drop.

4. The PSU of claim 1 , where the expected voltage drop is a voltage value or a range of voltage values; and where the programmable integrated circuit is programmed to not connect the PSU power output to the transformer with the output power switch if the monitored voltage drop across the sense resistor is greater or lesser than the expected voltage drop.

5. The PSU of claim 1 , where the expected voltage drop is a voltage value or a range of voltage values; and where the programmable integrated circuit is programmed to connect the PSU power output to the transformer with the output power switch if the monitored voltage drop across the sense resistor is equal to the expected voltage drop.

6. The PSU of claim 1 , comprising at least two different current shunts coupled in parallel between the first and second DC current loop paths at respective nodes located between the sense resistor and the output power switch, each given one of the current shunts having a resistance value selected to yield an expected test current value through the given current shunt at a given output voltage from the transformer; where each given one of the current shunts comprises a test switch coupled between the first and second DC current loop paths to selectively connect and disconnect a test current path through the given current shunt and the DC current loop, the at least one programmable integrated circuit coupled to control each of the test switches to selectively connect and disconnect the test current path through each given current shunt.

7. The PSU of claim 6 , where the at least one programmable integrated circuit is programmed to monitor a first voltage drop across the sense resistor while DC output power is flowing from the transformer through the DC current loop to the PSU power output the across the sense resistor with the PSU power output being connected to the transformer by the output power switch, the programmable integrated circuit being further programmed to compare the monitored first voltage drop to a voltage threshold (Vth) value that corresponds to an overcurrent protection (OCP) apparent power limit, and to selectively disconnect the PSU power output from the transformer when a monitored value of the first voltage drop exceeds the Vth; and where the programmable integrated circuit is further programmed to perform the following steps while the with the PSU power output disconnected from the transformer by the output power switch:
first control the test switches to selectively cause a first current value to flow through at least one of the current shunts and the DC current loop, and measure a first voltage drop value across the sense resistor while the first current value is flowing through the DC current loop;
then control the test switches to selectively cause a second and different current value to flow through at least one of the current shunts and the DC current loop, and measure a second and different voltage drop value across the sense resistor while the second current value is flowing through the DC current loop; and
then select the Vth value based on a relationship between the first and second voltage drop values and the values of the first and second test currents.

8. The PSU of claim 1 , where upon each power up cycle of the PSU the at least one programmable integrated circuit is programmed to perform the following steps:
first control the output power switch to disconnect the PSU power output from the transformer before supplying any direct current (DC) power to the PSU power output through the DC current loop paths of the DC output current loop;
then control the PSU to supply DC power from the secondary side of the transformer to produce a test current through the test current path;
monitor a voltage drop across the sense resistor while the test current is flowing across the sense resistor with the PSU power output being disconnected from the transformer by the output power switch;
compare the expected voltage drop to the monitored voltage drop across the sense resistor while the test current is flowing across the sense resistor, and
control the output power switch to connect the PSU power outp

Assignees

• Dell Products Lp

Inventors

• Yu wei cheng
• Liao Tsung Cheng
• Wood Merle
• Tan Geroncio O

Classifications

• H02H3/087

  for DC applications · CPC title

• H02M2001/0009

  Electricity · mapped topic

• H02M1/08

  Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters · CPC title

• H02H11/007

  involving automatic switching for adapting the protected apparatus to the supply voltage · CPC title

• H02H7/1213

  for DC-DC converters · CPC title