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

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 and a power-consuming load 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;
• and
• at least one programmable integrated circuit programmed to:
• control the PSU to supply DC output power through the DC current loop to the PSU power output with the PSU power output being connected to the transformer by the output power switch,
• monitor the DC output power supplied through the DC current loop to the PSU power output and determine an expected voltage drop across the sense resistor that corresponds to a value of the monitored DC output power,
• monitor a voltage drop across the sense resistor while the monitored DC output power is supplied through the DC current loop to the PSU power output,
• compare the expected voltage drop to the monitored voltage drop across the sense resistor while the monitored DC output power is supplied through the DC current loop to the PSU power output,
• control the output power switch to disconnect the PSU power output to the transformer if the monitored voltage drop does not equal the expected voltage drop, and
• control the output power switch to maintain the PSU power output connected to the transformer if the monitored voltage drop equals the expected voltage drop.

A method of operating a power supply unit (PSU) system including primary side circuitry and secondary side circuitry that are separated by a transformer, the method comprising:

• receiving a power input in the primary side circuitry of the PSU, the primary side circuitry of the PSU including a primary side winding of the transformer;
• receiving power in the secondary side circuitry from the primary side circuitry, the 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 and an output power switch coupled within the DC output current loop between the transformer and a PSU power output;
• and
• using at least one programmable integrated circuit to control the output power switch coupled within the DC output current loop between the transformer and the PSU power output to selectively connect and disconnect the PSU power output from the transformer;
• using at least one programmable integrated circuit to monitor a voltage drop across a sense resistor coupled within one of the first or second DC current loop paths between the transformer and the output power switch while a test current is flowing across the sense resistor that is produced through a test current path that includes the DC current loop and 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 while the PSU power output is selectively 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
• using the at least one programmed integrated circuit 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.

A method of operating a power supply unit (PSU) system including primary side circuitry and secondary side circuitry that are separated by a transformer, the method comprising:

• receiving a power input in the primary side circuitry of the PSU, the primary side circuitry of the PSU including a primary side winding of the transformer;
• receiving power in the secondary side circuitry from the primary side circuitry, the 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 and an output power switch coupled within the DC output current loop between the transformer and a PSU power output;
• using at least one programmable integrated circuit to control the output power switch coupled within the DC output current loop between the transformer and the PSU power output to selectively connect and disconnect the PSU power output from the transformer;
• using at least one programmable integrated circuit to monitor a voltage drop across a sense resistor coupled within one of the first or second DC current loop paths between the transformer and the output power switch while controlling the PSU to supply a DC output power through the DC current loop to the PSU power output while the PSU power output is selectively connected to the transformer by the output power switch;
• and
• using the at least one programmed integrated circuit to:
• monitor the DC output power supplied through the DC current loop to the PSU power output and determine an expected voltage drop across the sense resistor that corresponds to a value of the monitored DC output power,
• monitor a voltage drop across the sense resistor while the monitored DC output power is supplied through the DC current loop to the PSU power output,
• compare the expected voltage drop to the monitored voltage drop across the sense resistor while the monitored DC output power is supplied through the DC current loop to the PSU power output,
• control the output power switch to disconnect the PSU power output to the transformer if the monitored voltage drop does not equal the expected voltage drop, and
• control the output power switch to maintain the PSU power output connected to the transformer if the monitored voltage drop equals the expected voltage drop.