FIELD

The present disclosure relates to power measurements in switched mode power supplies.

BACKGROUND

This section provides background information related to the present disclosure which is not necessarily prior art.

An AC-DC switched mode power supply (SMPS) commonly includes a filter, a power factor correction (PFC) circuit, and a control circuit. The control circuit may calculate an input current, an input voltage, an input power, etc. of the SMPS based on sensed parameters. Typically, the SMPS employs a power-metering chip for measuring input current and input voltage, calculating input power, etc.

SUMMARY

This section provides a general summary of the disclosure, and is not a comprehensive disclosure of its full scope or all of its features.

According to one aspect of the present disclosure, a SMPS includes a line rail, a neutral rail, a filter coupled between the line rail and the neutral rail and having an input for receiving an AC input voltage and an AC input current, an X-capacitance, and an output, a PFC circuit coupled to the output of the filter and having an input for receiving a PFC AC current, and a control circuit coupled to the PFC circuit. The control circuit is configured to generate an analog signal representing a difference between an AC line voltage and an AC neutral voltage, compare the analog signal and a defined threshold to determine zero crossings of the analog signal, determine a frequency of the AC input voltage or the AC input current based on at least two of the zero crossings of the analog signal, determine a reactive current flowing through the X-capacitance in the filter based on the determined frequency, and determine the AC input current of the SMPS based on the determined reactive current and the PFC AC current.

According to another aspect of the present disclosure, a method for determining an AC input current of a SMPS is disclosed. The SMPS includes a line rail, a neutral rail, a filter coupled between the line rail and the neutral rail, and a PFC circuit coupled to the output of the filter. The method includes generating an analog signal representing a difference between an AC line voltage and an AC neutral voltage, comparing the analog signal and a defined threshold to determine zero crossings of the analog signal, determining a frequency of an AC input voltage or an AC input current based on at least two of the zero crossings of the analog signal, determining a reactive current in the filter based on the determined frequency, and determining the AC input current of the SMPS based on the determined reactive current and a PFC AC current.

According to another aspect of the present disclosure, a SMPS includes a line rail, a neutral rail, a filter coupled between the line rail and the neutral rail, and having an input for receiving an AC input voltage and an AC input current, a PFC circuit coupled to the output of the filter, and a control circuit having a differential amplifier and a digital controller. The differential amplifier is configured to generate an analog signal representing a difference between an AC line voltage and an AC neutral voltage. The digital controller is configured to determine the AC input voltage and a frequency of the AC input voltage or the AC input current based on the analog signal.

According to another aspect of the present disclosure, a SMPS includes a filter having an input for receiving an AC input current, an X-capacitance, and an output, a PFC circuit coupled to the output of the filter, and a control circuit coupled to the PFC circuit. The control circuit is configured to determine a value of an AC input electrical parameter of the SMPS, estimate a value of the AC input electrical parameter of the SMPS based on a defined efficiency and an output power of the SMPS, determine an average value of the AC input electrical parameter if a difference between the determined value of the AC input electrical parameter and the estimated value of the AC input electrical parameter is less than a defined tolerance threshold, determine an accuracy of the determined value of the AC input electrical parameter based on the average value of the AC input electrical parameter, and report the determined value of the AC input electrical parameter to an external device if the accuracy of the determined value of the AC input electrical parameter is less than a defined accuracy threshold.

According to another aspect of the present disclosure, a method for reporting an AC input electrical parameter of a SMPS is disclosed. The SMPS includes a filter and a PFC circuit. The method includes determining a value of the AC input electrical parameter of the SMPS, estimating a value of the AC input electrical parameter of the SMPS based on a defined efficiency and an output power of the SMPS, if a difference between the determined value of the AC input electrical parameter and the estimated value of the AC input electrical parameter is less than a defined tolerance threshold, determining an average value of the AC input electrical parameter, determining an accuracy of the determined value of the AC input electrical parameter based on the average value of the AC input electrical parameter, and if the accuracy of the determined value of the AC input electrical parameter is less than a defined accuracy threshold, reporting the determined value of the input electrical parameter to an external device.

According to another aspect of the present disclosure, a SMPS includes a line rail, a neutral rail, a filter coupled between the line rail and the neutral rail, a PFC circuit coupled to the filter, a DC/DC power circuit coupled to the PFC circuit, and a control circuit. The filter includes an input for receiving an AC input voltage and an AC input current, an X-capacitance, and an output. The PFC circuit includes an input for receiving a PFC AC current, at least one power switch, and an output. The DC/DC power circuit includes at least one power switch and a transformer. The control circuit is coupled to the PFC circuit for controlling the at least one power switch of the PFC circuit and to the DC/DC power circuit for controlling the at least one power switch of the DC/DC power circuit. The control circuit includes at least one differential amplifier, a primary side digital controller, a secondary side digital controller, and an isolation device coupled between the primary side digital controller and the secondary side digital controller. The differential amplifier is configured to generate an analog signal representing a difference between an AC line voltage and an AC neutral voltage. The primary side digital controller is configured to determine the AC input voltage based on the analog signal, determine a frequency of the AC input voltage or the AC input current based on the analog signal, determine a reactive current flowing through the X-capacitance based on the determined frequency, and determine the AC input current based on the determined reactive current and the PFC AC current.

Further aspects and areas of applicability will become apparent from the description provided herein. It should be understood that various aspects of this disclosure may be implemented individually or in combination with one or more other aspects. It should also be understood that the description and specific examples herein are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.

