Patent Publication Number: US-2020278134-A1

Title: Electronic continuous-flow heater and method for operating such a heater

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority from Application No. EP 19160106.1 filed Feb. 28, 2019, the entire content of which is incorporated herein by reference. 
     FIELD OF THE INVENTION 
     The present invention relates to an electronic continuous-flow heater for heating a liquid, comprising an electrically heatable heating channel arrangement with at least one electric heating element, an electronic control system, comprising at least one microprocessor, which is configured to electrically control the heating element, and a display device connected by means of the electronic control system. The invention further relates to a method for operating such an electronic continuous-flow heater. 
     BACKGROUND OF THE INVENTION 
     A control and safety device for a continuous-flow heater is known from document DE 44 16 798 A1. It discloses control means, provided with voltage monitoring means, which detect an overvoltage or undervoltage of the supply voltage in the known manner. The voltage monitoring means are also connected to the RESET input of the microcontroller to cause the control means to reset when a threshold value of the supply voltage is detected. 
     Although the control means or the electronic control system are reset in this way to a defined state in the event that undervoltage occurs, when performing a reset of the electronic control system, any display or display device connected will also regularly perform a reset and thus lose the display content previously displayed. After such an undervoltage event has occurred, it is no longer possible for the user, operator or the specialist staff to see afterwards the reason for which a reset was performed or why the continuous-flow heater is not in a functional state. 
     SUMMARY OF THE INVENTION 
     It is therefore the object of the present invention to propose a continuous-flow heater which displays information about the respective device status even when it is without power or mains voltage. The object is also to provide a continuous-flow heater which, in the event of undervoltage, provides details of the undervoltage and/or overvoltage fault event that has occurred. The object is further to propose a corresponding method for operating such a continuous-flow heater. 
     The object is achieved by an arrangement with the features referred to hereinbefore in that the display device is designed as a bistable digital display, such that the display content remains visible even in the absence of the display supply voltage of the display device. Advantageously, it is thus achieved that the display device of the continuous-flow heater according to the invention always indicates the display content even when it is in the de-energised state or is without supply voltage. In addition, it is possible in this manner for the user and/or the specialist staff to see on the continuous-flow heater that an undervoltage has occurred. In this way, such an error status can always be seen directly from the display content of the display device, irrespective of whether or not the continuous-flow heater is being properly supplied with mains voltage. According to an alternative embodiment of the invention, the display device is also designed to indicate display contents in shades of grey or in colour. In this case, the display device is configured in each case such that the display content is retained even when the display device is in the de-energised state. 
     One advantageous development of the invention is characterised in that the display surface of the display device is formed by an electronic paper. This has the advantage that the display device only has to be written on if the relevant display content is to change. In addition, the display content most recently written on the display device remains visible even if the display device is no longer supplied with the display supply voltage. 
     According to an advantageous development, it is provided that the electronic control system has at least one electrical energy storage device for buffering the operating voltage of the electronic control system and the electronic control system has an undervoltage detection circuit for detecting an undervoltage of the mains and/or heating element voltage. Advantageously, the operating voltage of the electronic control system is thus maintained, at least temporarily, even when an undervoltage occurs, such that it is possible to write a display content on the display device which provides information about the type of undervoltage that has occurred or the type of error. Furthermore, the electronic control system can thus be brought into a defined state before the supply voltage of the electronic control system finally breaks down. 
     A preferred embodiment of the invention is characterised in that the electronic control system is configured to cause the display device to output an undervoltage message in the event that an undervoltage is detected by the undervoltage detection circuit. This has the advantage that each undervoltage event can be seen on the display device of the continuous-flow heater even when said continuous-flow heater is in the de-energised state. 
     The object is further achieved by a corresponding method with the features referred to hereinbefore in that the display device, as a bistable digital display, is controlled by the control device, such that the display content remains visible even in the absence of the display supply voltage of the display device. 
     According to an advantageous embodiment of the invention, the operating voltage of the electronic control system is buffered by the electronic control system and an undervoltage of the mains and/or heating element voltage is detected by an undervoltage detection circuit of the electronic control system. 
     An advantageous embodiment is characterised in that the electronic control system causes the display device to output an undervoltage message in the event that an undervoltage is detected by the undervoltage detection circuit. 
     According to a further advantageous embodiment, it is provided to cause the control device to write a display content for identifying a technical test, which is carried out on the continuous-flow heater, on the display device at the factory before the continuous-flow heater is disconnected from the power supply after the test has been completed. In this way, it can be seen from the display device, particularly in the de-energised state of the continuous-flow heater, whether the continuous-flow heater has successfully passed the required technical function test at the factory. Furthermore, it can be seen from this that the device in question is new. 
     The advantages associated with the method according to the invention have already been explained in detail in connection with the continuous-flow heater according to the invention, to which reference is therefore made here. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram of the electronic control system of the continuous-flow heater according to the invention; 
         FIG. 2  is a flow chart of the mode of operation of the electronic control system or the method according to the invention; 
         FIG. 3  is an example of a first display content; 
         FIG. 4  is an example of a second display content; and 
         FIG. 5  is an example of a third display content. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  shows a block diagram of the electronic control system of the continuous-flow heater according to the invention. The continuous-flow heater, which is not shown in the drawing, comprises an electrically heatable heating channel arrangement with at least one electric heating element which is preferably configured as a bare wire heating coil. The electronic control system comprises at least one microprocessor  10  which is configured to electrically control the heating element. For this purpose, the control device is connected to power electronics  11  which are configured to switch the electric heating element on or off as well as to control its heat output. Such power electronics are sufficiently well known and are therefore not to be explained in greater detail here. 
     The electronic control system is electrically connected to a display device  12 . As shown in  FIG. 1 , the display device  12  is preferably electrically connected to the microprocessor  10 . In this case, the display device  12  is designed as a bistable digital display. Once a display content is written to the display by the electronic control system, it remains visible in this way even in the absence of the display supply voltage of the display device  12 . Thus, it is always only necessary to write on the display device  12  if a changed display content is to be displayed. 
     The display surface of the display device  12  is preferably formed by an electronic paper. In other words, the display device  12  is designed as an e-paper display. The display device  12  is thus designed as a passive display on which display contents, such as texts and/or graphics are permanently displayed without requiring the presence of the display supply voltage. Once a display content is displayed, it stays there, even if there is no display supply voltage present, until a new write access with differing display content is made by the electronic control system. 
     Advantageously, the electronic control system has at least one electrical energy storage device  13  for buffering the operating voltage of the electronic control system. The energy storage device  13  preferably comprises at least one supercap or ultracap. If any undervoltages of the mains voltage occur or if a phase fails, the energy storage device  13  serves as an intermediate storage device to supply the electronic control system with power for a sufficient length of time so that it can still carry out necessary control steps before the operating voltage of the electronic control system also becomes too low. 
     The electronic control system also comprises an undervoltage detection circuit for registering or detecting an undervoltage of the mains and/or heating element voltage. For this purpose, the microprocessor  10  of the control circuit is connected via an electrical line  14  to the power electronics which provide the microprocessor  10  with a signal to query the mains and/or heating element voltage. The line  14  and line  15  shown in  FIG. 1  are intended to symbolise the connection of the said components to each other. The lines  14 ,  15  may be executed physically as electrical signal lines or as a bus system. 
     The electronic control system is further configured to cause the display device to output an undervoltage message in the event that an undervoltage is detected by the undervoltage detection circuit. The intention is to explain below the sequence during detection of a/the undervoltage based on the flow chart in  FIG. 2 . If the undervoltage detection circuit detects in step  15  that the mains and/or supply voltage of the power electronics is lower than a specified minimum voltage, then the voltage supply of the control circuit, including the microprocessor  10  and the display device  12 , is first ensured via the energy storage device  13 . The energy storage device  13  optionally comprises necessary switching components to automatically switch over to a supply by the energy storage device  13  if the regular supply voltage of the electronic control system fails. This changeover takes place in step  16 . 
     In step  17 , the display device  12  is written on with a display content which informs about the type of undervoltage. If the undervoltage detection circuit detects an undervoltage or a failure of the mains phases, the display content shown in  FIG. 3 , for example, is written on the display device  12 . If the undervoltage detection circuit detects an undervoltage of the supply voltage of the heating element, the display content shown in  FIG. 4 , for example, is outputted by the display device  12 . 
     Further preferably, the microprocessor  10  and the display device  12  are then put into a “hibernation mode” in step  18 . 
     The method according to the invention has already been well documented in connection with the previously described device according to the invention, such that only selected aspects of the method according to the invention will be enlarged upon below to avoid repetitions. 
     The method according to the invention is used to operate the electronic continuous-flow heater previously described. Electrical control of the at least one electric heating element takes place by the control device. The display device  12  is controlled as a bistable digital display by the control device. This means that the microprocessor  10  only writes a display content on the display device  12  once in each case, since the display device  12 —irrespective of whether or not it is supplied with the display supply voltage—retains the display content written once by the microprocessor. The display content thus always remains visible even in the absence of the display supply voltage of the display device  12 . 
     Once the continuous-flow heater has passed all the necessary tests for technical function and quality assurance on a test rig in the production line, the third display content shown in  FIG. 5  is preferably written on the display device  12  at the factory. In other words, the control device is caused to write a display content, namely the said third display content, for identifying a technical test, which is carried out on the continuous-flow heater, on the display device  12  at the factory before the continuous-flow heater is disconnected from the power supply after the test has been completed. Advantageously, the said display content is retained even in the de-energised state. When the continuous-flow heater is removed from its packaging, the fitter can immediately read from the display device  12  that he has received a new device that has been tested and is in perfect condition. The control device is further preferably designed to display this third display content by the display device  12  only after successful performance of the said tests. After initial commissioning, this third display content is not displayed in any other operating state.