Patent Publication Number: US-2021173420-A1

Title: Power supply unit with adaptive feedback control loops

Description:
PRIORITY 
     This application claims priority of European patent application EP 19 213 715.6 filed on Dec. 5, 2019, which is incorporated by reference herewith. 
     FIELD OF THE INVENTION 
     The present invention relates to a power supply unit, preferably for a power analyzer, a method for operating a power supply unit and a power analyzer comprising a power supply unit, wherein the power supply unit comprises a feedback control unit for selectively controlling the output level of the voltage or the output level of the current to output terminals of the power supply unit on a preset value, and means for sensing the actual output level of the voltage and current, respectively, and sending a signal representing the sensed output level to the feedback control unit. 
     BACKGROUND OF THE INVENTION 
     A power supply or a power supply unit is a device or assembly for supplying power to devices or assemblies, like an electrical or electronic load, that requires different voltages and currents than those provided by a source, like mains supply or batteries. Some power supply units are separate, standalone pieces of equipment, while others are built into the load appliances that they power. Power supply units are also referred to as electric power converters, since the main function of a power supply unit is to convert electric current from the source to the correct voltage, current and/or frequency to power the connected electric load. 
     Power supply units are used in and for a great variety of different electric and electronic devices. One of them are power analyzers. A power analyzer is used to measure the flow of power in an electrical system. Power analyzers are able to measure a variety of parameters associated to power consumption and generation. Power analyzers are used for measuring a host of aspects of electrical power for applications, which include testing power electronics, inverters, motors and drives, lighting, home appliances, office equipment, industrial machinery and more. 
     Power supply units are categorized in various ways. One type of a power supply unit is a DC power supply unit, wherein the most common one is a switched-mode power supply (SMPS). The SMPS is powered from a DC source or from an AC source and supplies constant DC voltage to its load. In a SMPS the AC mains input is directly rectified and then filtered to obtain a DC voltage. The resulting DC voltage is then switched on and off at a higher frequency by electronic switching, thus producing an AC current that will pass through a high frequency transformer or inductor. After the inductor or transformer secondary, the high frequency AC is rectified and filtered to produce the DC output voltage. 
     A SMPS is for example described in the EP 2 659 578 A2. From there, it is derivable that an uncontrolled source of voltage (or current, or power) is applied to the input of a power system with the expectation that the voltage (or current, or power) at the output will be very well controlled, wherein the basis of controlling the output is to compare it to some form of reference, and any deviation between the output and the reference becomes an error. In this document beneath others a feedback control is described, wherein negative feedback is used to reduce an error to an acceptable value, as close to zero as is required by the system. 
     Another power supply is described in the EP 1 853 985 A2, which comprises a voltage control loop and a current control loop. In more detail, from this document a power supply circuit is known that includes two pass transistors that conduct current from a voltage supply terminal to an output terminal, wherein one of the pass transistors is smaller whereas the other is larger. In this document, current through the smaller transistor is controlled by the voltage control loop such that the voltage on the output terminal is regulated to a predetermined voltage, and current through the larger transistor is controlled by a high gain current control loop such that the current flowing through the larger transistor is a multiple of the current flowing through the smaller pass transistor. 
     A problem that can arise in the above-described power supply units or generally in power supply units with at least two control loops/feedback control loops, for example a voltage control loop and a current control loop, is that depending on which one of the control loops is selected/prioritized, there is a risk that in the other control loop respectively the other variable (the voltage or the current) a transient overshoot/oscillation occurs, which could even destroy the load or the device under test (DUT) connected to the power supply unit. 
     In general, when a stationary process is excited by a change (like a load change or connecting a load to the power supply unit) a free oscillation occurs and, as a result of damping (according to, for example, feedback control), a new stationary process decays (oscillating) or becomes aperiodic (creeping). 
     A transient overshoot/oscillation can for example arise when the load or the DUT connected to the power supply unit varies or a load or DUT is connected to the power supply unit, due to necessary adjustment processes. Such a transient overshoot/oscillation is for example shown in the  FIGS. 3 and 4 , wherein in  FIG. 3 , a transient overshoot of the voltage  13 , respectively a voltage transient oscillation, is shown, whereas in  FIG. 4 , a transient overshoot of the current  14 , respectively a current transient oscillation, is shown. 
     Presently, such problems are addressed by manual selection of the priority of one of the feedback control loops. 
     There is a need to provide a power supply unit that avoids transient overshoots or oscillations when, for example, a new load or DUT is connected to the power supply unit or the load or DUT is varied, without a manual selection of a priority of a feedback control loop. 
     This object is achieved by means of the features of the independent claims. The dependent claims further develop the central idea of the present invention. 
     SUMMARY OF THE INVENTION 
     The present invention relates to a power supply unit, preferably for a power analyzer, comprising a feedback control unit arranged for selectively controlling the output level of the voltage or the output level of the current to output terminals of the power supply unit on a preset value, and means for sensing the actual output level of the voltage and current, respectively, and sending a signal representing the sensed output level to said feedback control unit, wherein the feedback control unit is arranged to autonomously prioritize or activate at least a first control loop for the controlling of the output level of the current or a second control loop for the controlling of the output level of the voltage, based on data generated within the power supply unit and/or externally generated data supplied to the power supply unit. 
     Advantageously, the externally generated data are data from a DUT or a load connected to the output terminals of the power supply unit, wherein the externally generated data can be sensed data, preferably representing the impedance or the capacitance, of the DUT or load. It is also possible that the externally generated data are data from a database connected to the power supply unit via a network interface of the power supply unit. 
     In a preferred embodiment, the data generated within the power supply unit are sensor data, preferably representing an electrical parameter, such as voltage, current or power transmission, of the status of the output terminals. It is also possible that the data generated within the power supply unit are data from a database in the power supply unit. 
     In a preferred embodiment, the data generated within the power supply unit or externally generated data are supplied to an Artificial Intelligence unit, such as a trained network, issuing a selection signal for prioritizing or activating the first or the second control loop, respectively. 
     The Artificial Intelligence unit can be positioned in the power supply unit or the Artificial Intelligence unit can be externally positioned and the power supply unit is connected to the Artificial Intelligence unit via a network interface of the power supply unit. 
     In a preferred embodiment, the feedback control unit is furthermore arranged to adjust at least one control parameter value of the prioritized or activated control loop, preferably also based on data generated within the power supply unit or externally generated data supplied to the power supply unit. 
     Advantageously, the power supply unit is a DC power supply and the feedback control unit comprises an analogue or a digital control algorithm. 
     The present invention further relates to a power analyzer comprising the above power supply unit. 
     The present invention further relates to a method for operating a power supply unit, preferably for a power analyzer, comprising selectively feedback controlling the output level of the voltage or the output level of the current to output terminals of the power supply unit on a preset value, sensing the actual output level of the voltage and current, respectively, for the selectively feedback controlling, and autonomously prioritizing or activating at least a first control loop for the controlling of the output level of the current or a second control loop for the controlling of the output level of the voltage, based on data generated within the power supply unit or externally generated data supplied to the power supply unit. 
     Advantageously, the method further comprises supplying to an Artificial Intelligence unit, such as a trained network, the data generated within the power supply unit or externally generated data and issuing a selection signal for prioritizing or activating the first or the second control loop, respectively. 
     In a preferred embodiment, the method further comprises adjusting at least one control parameter value of the prioritized or activated control loop, preferably also based on data generated within the power supply unit or externally generated data supplied to the power supply unit. 
     With the power supply unit and the method for operating a power supply unit of the present invention, the feedback control unit autonomously prioritizes or activates a voltage control loop or a current control loop, wherein both control loops are monitored to determine which one of the feedback control loops (the current or the voltage) should be activated or should have priority, so that a transient overshoot of the voltage or current or a voltage transient oscillation or a current transient oscillation is avoided or at least reduced, and thus, it is avoided that a load or a DUT connected to the power supply unit is destroyed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other aspects and advantages of the present invention will become more apparent when studying the following detailed description, in connection with the figures in which: 
         FIG. 1  shows schematically a power supply unit; 
         FIG. 2  shows schematically another power supply unit; 
         FIG. 3  shows schematically a diagram of a transient overshoot of a voltage; 
         FIG. 4  shows schematically a diagram of a transient overshoot of the current; and 
         FIG. 5  shows schematically a diagram without a transient overshoot of the voltage and the current. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     As already described above, a power supply unit, for example used in or for a power analyzer, can have at least two feedback control loops, like a voltage control loop and a current control loop. In case one of the two control loops is prioritized, it could happen that a transient overshoot or a transient oscillation in the variable of the other one occurs. Such transient overshoots or transient oscillations are shown for example in the  FIGS. 3 and 4 , wherein  FIG. 3  shows a transient overshoot of the voltage  13 , whereas in  FIG. 4 , a transient overshoot of the current  14  is shown. In both cases it could even happen that parts of the power supply unit or the load/DUT connected to the power supply unit are destroyed. 
     In the present invention both control loops are now monitored and then it is determined, which one of the control loops should be prioritized or activated so that a transient overshoot or a transient oscillation is avoided or at least reduced. Therefore, as shown in  FIG. 1 , a power supply unit  1  according to the present invention discloses a feedback control unit  2  selectively controlling the output level of the voltage or the output level of the current to output terminals  6  of the power supply unit  1  on a preset value. 
     The feedback control unit  2  is connected to a power circuit  8  or power unit, wherein the power circuit  8  converts an electric current from a source  10  connected to input terminals  7  to the correct voltage, current and frequency to power a load  9  connected to the output terminals  6 , wherein the power circuit  8  is connected to the input terminals  7  for receiving for example an electric current from the source  10  and is connected to the output terminals  6  for outputting the voltage, the current or the power for the load  9 . The power circuit  8  is then controlled by the feedback control unit  2 . 
     The connection between the feedback control unit  2  and the power circuit  8  comprises a part  4  of a current control loop and a part  5  of a voltage control loop, wherein the power circuit  8  is then controlled by the feedback control unit  2  by the current control loop as well as the voltage control loop. 
     Regarding the load  9 , it should be noted that the load  9  can be for example a power analyzer, wherein the power supply unit  1  can be integrated together with the power analyzer in one housing or can be separately provided in an own housing. Further, it is possible that the power supply unit  1  does not only provide to the power analyzer but also to a DUT connected to the power analyzer voltage, current or power. In this case, the load  9  is therefore the power analyzer together with the DUT. 
     The power supply unit  1  further comprises means  3  for sensing the actual output level of the voltage and current, respectively, and sending a signal representing the sensed output level to said feedback control unit  2 . The means  3  for sensing the actual output level are connected to the output of the power circuit  8 . With the signaling representing the sensed output level received from the means  3  for sensing the actual output level, the feedback control unit  2  can then selectively control the power circuit  8  via the part  4  of the current control loop and the part  5  of the voltage control loop and thus, control the voltage, the current or the power supplied at the output of the power circuit  8  and thus, at the output terminals  6  for the load  9 . 
     Therefore, as can be also seen from  FIG. 1 , the means  3  for sensing the actual output level, the feedback control unit  2  and the part  5  form a voltage feedback loop/voltage control loop, whereas the means  3  for sensing the actual output level, the feedback control unit  2  and the part  4  form a current feedback loop/current control loop. The means  3  for sensing the actual output level and the feedback control unit  2  are used in both feedback loops/control loops. 
     According to the present invention, the feedback control unit  2  now autonomously prioritize or activate the first control loop  4  for the controlling of the output level of the current or the second control loop  5  for the controlling of the output level of the voltage, based on data generated within the power supply unit or externally generated data supplied to the power supply unit. 
     Since the feedback control unit  2  prioritizes or activates the first control loop  4  (current) or the second control loop  5  (voltage) autonomously, transient overshoots or oscillations can be avoided or at least reduced without a manual selection of a priority of one of the control loops  4  or  5 , when, for example, a new load  9  or DUT is connected to the power supply unit  1  or the load  9  or DUT is varied. This is derivable for example from  FIG. 5 , where, compared to the  FIGS. 3 and 4 , no more transient overshoots or oscillations exist in the voltage (in difference to  FIG. 3 ) as well as in the current (in difference to  FIG. 4 ). 
     Prioritizing in the present invention in particular means that one of the control loops  4  or  5  is more weighted than the other one and thus, has more influence than the other one on the controlling of the power circuit  8  by the feedback control unit  2 . 
     Activating in the present invention in particular means that one of the control loops  4  or  5  is selected and thus, one of the control loops is used for the controlling of the power circuit  8  by the feedback control unit  2 . 
     The autonomously prioritizing or activating of the first control loop  4  for the controlling of the output level of the current or the second control loop  5  for the controlling of the output level of the voltage by the feedback control unit  2  is done based on data generated within the power supply unit and/or externally generated data supplied to the power supply unit. 
     The externally generated data can be data from the DUT or the load  9  connected to the output terminals  6  of the power supply unit  1 . In particular, it can be sensed data, representing the impedance or the capacitance, of the DUT or load  9 . In this case, the impedance or the capacitance of the DUT or load  9  connected to the power supply unit  1  are measured and then transmitted from the DUT or load  9  to the feedback control unit  2  via, for example, a separate connection not shown in detail in  FIG. 1 . 
     It is also possible that the externally generated data are data from a database. For this, the power supply unit  1  is connected to database  11 , wherein the power supply unit  1  comprises a network interface  12  that is used for connecting to the database  11 . From the database  11  the externally generated data is then derivable, which are used by the feedback control unit  2  for autonomously prioritizing or activating the first control loop  4  for the controlling of the output level of the current or the second control loop  5  for the controlling of the output level of the voltage. The externally generated data in the database  11  can be for example test sequence data, DUT data, control loop parameters, test parameters or test limits. 
     Further, it is also possible that the externally generated data are data of a user input, for example via a corresponding input unit connected to the power supply unit  1  or integrated in the power supply unit  1 . 
     The data generated within the power supply unit  1  can be sensor data, preferably representing an electrical parameter, such as voltage, current or power transmission, of the status of the output terminals  6 , for example data sensed by the means  3  for sensing the actual output level of the voltage and current. 
     It is also possible that the data generated within the power supply unit  1  are data from a database  11  positioned in the power supply unit  1 , as it is shown in  FIG. 2 . From the database  11  in the power supply unit  1  the data is then derivable, which is used by the feedback control unit  2  for autonomously prioritizing or activating the first control loop  4  for the controlling of the output level of the current or the second control loop  5  for the controlling of the output level of the voltage. Similar, the data in the database  11  in the power supply unit  1  can be for example test sequence data, DUT data, control loop parameters, test parameters or test limits. 
     In the power supply unit  1  shown in  FIG. 1  the means  3  for sensing the actual output level are positioned separately from the feedback control unit  2 . 
     Alternatively, the means  3  for sensing the actual output level can be placed in the feedback control unit  2 , wherein then the feedback control unit  2  is directly connected to the output of the power circuit  8 . This is illustrated in  FIG. 2 , which shows a power supply unit  1  similar to that shown in  FIG. 1 , comprising a feedback control unit  2 , means  3  for sensing the actual output level, output terminals  6 , input terminals  7  and a power circuit  8 , wherein the power circuit  8  converts an electric current from a source  10  connected to input terminals  7  to the correct voltage, current and frequency to power a load  9  connected to the output terminals  6 . The only difference between the power supply unit  1  in  FIG. 2  and the power supply unit  1  in  FIG. 1  is that in the power supply unit  1  in  FIG. 2  the means  3  for sensing the actual output level are placed in the feedback control unit  2  and the database  11  is placed in the power supply unit  1 . Otherwise, the power supply unit  1  in  FIG. 2  and the power supply unit  1  in  FIG. 1  work in a similar way. 
     Further, it would be also possible that the means  3  for sensing the actual output level are placed separately from the feedback control unit  2  as shown in  FIG. 1  and the database  11  is placed in the power supply unit  1  as shown in  FIG. 2 , or that the means  3  for sensing the actual output level are placed in the power supply unit  1  as shown in  FIG. 2  and the database  11  is placed separately from the feedback control unit  2  as shown in  FIG. 1  using the network interface  12 . 
     The data generated within the power supply unit  1  or the externally generated data can be further supplied to an Artificial Intelligence unit (not shown in the figures), such as a trained network, issuing a selection signal for prioritizing or activating the first or the second control loop  4  or  5 , respectively. The Artificial Intelligence unit can be positioned in the power supply unit  1  or the Artificial Intelligence unit can be externally positioned and the power supply unit  1  is connected to the Artificial Intelligence unit via the network interface  12  or another network interface of the power supply unit  1 . 
     In the power supply unit  1  according to the present invention, the feedback control unit  2  can use one or any combination of the above described data generated within the power supply unit  1  and the externally generated data for autonomously prioritizing or activating the first control loop  4  for the controlling of the output level of the current or the second control loop  5  for the controlling of the output level of the voltage. 
     Furthermore, the feedback control unit  2  can adjust at least one control parameter value of the prioritized or activated control loop  4  or  5 , preferably also based on data generated within the power supply unit  1  or externally generated data supplied to the power supply unit  1 . 
     The power supply unit  1  can also comprise a further third control loop (not shown in the figures), for example for the power, wherein the feedback control unit  2  then autonomously prioritizes or activates the first control loop  4 , the second control loop  5  or the third control loop. 
     The feedback control unit  2  can be for example a microcontroller or microprocessor. 
     Regarding the load  9 , it should be noted that the load  9  can be integrated together with the power supply unit  1  in one housing or the power supply unit  1  can be separately provided in an own housing. 
     Thus, in the present invention both control loops are monitored and then it is determined which one of the control loops should be prioritized or activated so that a transient overshoot or a transient oscillation is avoided or at least reduced. 
     While various embodiments of the present invention have been described above, it should be understood that they have been presented by way of example only, and not limitation. Numerous changes to the disclosed embodiments can be made in accordance with the disclosure herein without departing from the spirit or scope of the invention. Thus, the breadth and scope of the present invention should not be limited by any of the above described embodiments. Rather, the scope of the invention should be defined in accordance with the following claims and their equivalents. 
     Although the invention has been illustrated and described with respect to one or more implementations, equivalent alterations and modifications will occur to others skilled in the art upon the reading and understanding of this specification and the annexed drawings. In addition, while a particular feature of the invention may have been disclosed with respect to only one of several implementations, such feature may be combined with one or more other features of the other implementations as may be desired and advantageous for any given or particular application.