Patent Publication Number: US-2018034291-A1

Title: Power plug apparatus and over temperature protection method thereof

Description:
BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to a plug apparatus and a protection method thereof and especially relates to a power plug apparatus and over temperature protection method thereof. 
     Description of the Related Art 
     The power plug apparatus is a very common apparatus. The power plug apparatus is used to connect the power socket and the load apparatus, so that the alternating current power can be transmitted from the power socket to the load apparatus to drive the load apparatus. Therefore, the power plug apparatus is very important. 
     The related art power plug apparatus has the over temperature protection function, so that when the temperature of the related art power plug apparatus is too high, the alternating current power can be disconnected (namely, turned off or cut off). However, the disadvantage of the related art power plug apparatus is that the communication of the over temperature protection function of the related art power plug apparatus and the load apparatus is not accurate. 
     SUMMARY OF THE INVENTION 
     In order to solve the above-mentioned problems, an object of the present invention is to provide a power plug apparatus. 
     In order to solve the above-mentioned problems, another object of the present invention is to provide an over temperature protection method. 
     In order to achieve the object of the present invention mentioned above, the power plug apparatus of the present invention is applied to a power socket and a load apparatus. The power plug apparatus comprises a plug, a first temperature sensor and a micro-control unit. Moreover, the plug is plugged and connected to the power socket. The first temperature sensor is arranged in the plug. The micro-control unit is electrically connected to the first temperature sensor and the load apparatus. The first temperature sensor senses a temperature and transmits to the micro-control unit, so that the micro-control unit sends a control signal to the load apparatus. According to the control signal, the load apparatus receives a charging current. Moreover, the micro-control unit determines whether the temperature is higher than a first temperature value and not higher than a second temperature value. If the temperature is higher than the first temperature value and not higher than the second temperature value, the control signal is a first signal value and the charging current is a first current value. Moreover, the micro-control unit determines whether the temperature is higher than the second temperature value. If the temperature is higher than the second temperature value, the control signal is a second signal value and the load apparatus stops receiving the charging current. 
     Moreover, the control signal is a duty cycle of a pulse width modulation. For example, the control signal is a pulse width modulation signal with the duty cycle. 
     Moreover, the first temperature value is between 70 degrees centigrade and 79 degrees centigrade. The second temperature value is between 81 degrees centigrade and 90 degrees centigrade. The first signal value is the duty cycle of the pulse width modulation greater than or equal to 8%, and less than 10%. The second signal value is the duty cycle of the pulse width modulation less than 8%. 
     Moreover, the power plug apparatus further comprises a switch electrically connected to the plug and the load apparatus. When the control signal is the second signal value, the switch keeps turning on. 
     Moreover, the switch is a relay. 
     Moreover, the power plug apparatus further comprises a live wire and a neutral wire. The live wire is electrically connected to the plug, the switch, the load apparatus and the micro-control unit. The neutral wire is electrically connected to the plug, the switch, the load apparatus and the micro-control unit. Moreover, the switch comprises a live wire switch and a neutral wire switch. The live wire switch is electrically connected to the live wire and the micro-control unit. The neutral wire switch is electrically connected to the neutral wire and the micro-control unit. 
     Moreover, the power plug apparatus further comprises a ground wire, a ground monitoring circuit, a current detecting circuit, a residual current device and a second temperature sensor. The ground wire is electrically connected to the plug and the load apparatus. The ground monitoring circuit is electrically connected to the live wire, the neutral wire, the ground wire and the micro-control unit. The current detecting circuit is electrically connected to the live wire and the micro-control unit. The residual current device is electrically connected to the live wire, the neutral wire and the micro-control unit. The second temperature sensor is electrically connected to the micro-control unit. 
     Moreover, the power plug apparatus further comprises an auxiliary power circuit electrically connected to the live wire, the neutral wire and the micro-control unit. 
     Moreover, the power plug apparatus further comprises a voltage conversion circuit matching voltages of the micro-control unit and the load apparatus. 
     Moreover, the first temperature sensor is a thermistor. 
     Moreover, if the temperature is not higher than the first temperature value, the control signal is a normal signal value, so that the charging current is a normal current value. 
     Moreover, the normal signal value is greater than the first signal value. The first signal value is greater than the second signal value. The normal current value is greater than the first current value. 
     Moreover, the control signal is a voltage level. For example, the control signal is a voltage signal with the voltage level. 
     In order to achieve the other object of the present invention mentioned above, the over temperature protection method of the present invention comprises following steps. (a) A temperature sensor senses a temperature of a plug and transmits to a micro-control unit. (b) The micro-control unit sends a control signal to a load apparatus. (c) According to the control signal, the load apparatus receives a charging current. (c1) If the temperature is not higher than a first temperature value, the micro-control unit adjusts the control signal as a normal signal value, so that the charging current is a normal current value. (c2) If the temperature is higher than the first temperature value and is not higher than a second temperature value, the micro-control unit adjusts the control signal as a first signal value, so that the charging current is a first current value. Moreover, the first current value is less than the normal current value. (c3) After step (c2), if the temperature is lower than a first hysteresis temperature, the control signal recovers as the normal signal value. Moreover, the first hysteresis temperature is lower than the first temperature value. (c4) If the temperature is higher than the second temperature value, the micro-control unit adjusts the control signal as a second signal value, so that the charging current is zero. Moreover, the second temperature value is higher than the first temperature value. (c5) After step (c4), if the temperature is lower than a second hysteresis temperature, the control signal recovers as the first signal value. Moreover, the second hysteresis temperature is lower than the second temperature value. 
     Moreover, the normal signal value is greater than the first signal value. The first signal value is greater than the second signal value. 
     An advantage of the present invention is that the communication of the over temperature protection function of the power plug apparatus and the load apparatus is more accurate. 
    
    
     
       BRIEF DESCRIPTION OF DRAWING 
         FIG. 1  shows a block diagram of the first embodiment of the power plug apparatus of the present invention. 
         FIG. 2  shows a block diagram of the second embodiment of the power plug apparatus of the present invention. 
         FIG. 3  shows a block diagram of the third embodiment of the power plug apparatus of the present invention. 
         FIG. 4  shows a block diagram of the fourth embodiment of the power plug apparatus of the present invention. 
         FIG. 5  shows a diagram of the plug and the first temperature sensor of the present invention. 
         FIG. 6  shows a block diagram of the application embodiment of the power plug apparatus of the present invention. 
         FIG. 7  shows a flow chart of the over temperature protection method of the present invention. 
         FIG. 8  shows a diagram of the temperature versus the duty cycle of the pulse width modulation of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Please refer to following detailed description and figures for the technical content of the present invention. The following detailed description and figures are referred for the present invention, but the present invention is not limited to it. 
       FIG. 1  shows a block diagram of the first embodiment of the power plug apparatus of the present invention. A power plug apparatus  10  is applied to a power socket  20  and a load apparatus  30 . The power plug apparatus  10  comprises a plug  102 , a first temperature sensor  104  and a micro-control unit  108 . 
     The plug  102  is plugged and connected to the power socket  20 , and is electrically connected to the load apparatus  30 . The first temperature sensor  104  is arranged in the plug  102  to sense a temperature of the plug  102 . The micro-control unit  108  is electrically connected to the first temperature sensor  104  and the load apparatus  30 . 
     The first temperature sensor  104  senses the temperature of the plug  102  and informs the micro-control unit  108  of the temperature of the plug  102 . In an embodiment of the present invention, the first temperature sensor  104  is, for example but not limited to, a negative temperature coefficient (NTC) thermistor. According to the temperature detected by the NTC thermistor, a voltage dividing value  142  is generated by the NTC thermistor and another resistor (not shown in  FIG. 1 ), and then the voltage dividing value  142  is sent to the micro-control unit  108 . When the micro-control unit  108  receives the voltage dividing value  142 , the micro-control unit  108  sends the control signal  112  to the load apparatus  30 . 
     According to the control signal  112 , the load apparatus  30  receives a charging current  114  from the power socket  20  through the plug  102 . In an embodiment of the present invention, the load apparatus  30  utilizes the constant current mode function to set the magnitude of the charging current  114  or to stop receiving the charging current  114 . Moreover, the control signal  112  sent by the micro-control unit  108  can be a duty cycle of a pulse width modulation (For example, a pulse width modulation signal with the duty cycle). In other embodiments of the present invention, the micro-control unit  108  has an in-built digital-to-analog interface, so that the control signal  112  can be an analog voltage level (For example, an analog voltage signal with a voltage level). 
     The micro-control unit  108  determines whether the temperature of the plug  102  is not higher than a first temperature value (for example, the first temperature value can be set to be between 70 degrees centigrade and 79 degrees centigrade). If the temperature is not higher than the first temperature value, the control signal  112  sent by the micro-control unit  108  is a normal signal value, such as a normal duty cycle of the pulse width modulation (for example, greater than or equal to 10%, and less than or equal to 85%, such as 33.3%) or a normal voltage level, so that the charging current  114  is a normal current value (for example, 20 amperes). 
     For example, if the first temperature value is set as 77 degrees centigrade, when the temperature is not higher than 77 degrees centigrade, the control signal  112  sent by the micro-control unit  108  is the normal signal value (the duty cycle of the pulse width modulation is 33.3%). When the control signal  112  received by the load apparatus  30  is the normal signal value (the duty cycle of the pulse width modulation is 33.3%), the charging current  114  set and received by the load apparatus  30  is 20 amperes. Moreover, the load apparatus  30  can follow flowing equation to set the charging current  114 : (the duty cycle of the pulse width modulation)*0.6*100=the charging current  114 . Therefore, 33.3%*0.6*100=20. 
     The micro-control unit  108  further determines whether the temperature of the plug  102  is higher than the first temperature value and not higher than a second temperature value (for example, the second temperature value can be set to be between 81 degrees centigrade and 90 degrees centigrade). If the temperature is higher than the first temperature value and not higher than the second temperature value, the control signal  112  sent by the micro-control unit  108  is a first signal value, such as a first duty cycle of the pulse width modulation (for example, greater than or equal to 8%, and less than 10%, such as 9%) or a first voltage value, so that the charging current  114  is a first current value (for example, 6 amperes). Moreover, the first signal value is less than the normal signal value. For example, the first duty cycle of the pulse width modulation is less than the normal duty cycle (in other embodiments, the first voltage value is less than the normal voltage value). The first current value is less than the normal current value. 
     For example, if the second temperature value is defined as 85 degrees centigrade, when the temperature is higher than 77 degrees centigrade and not higher than 85 degrees centigrade, the duty cycle of the pulse width modulation of the control signal  112  sent by the micro-control unit  108  is 9% (or the first voltage value). When the duty cycle of the pulse width modulation of the control signal  112  received by the load apparatus  30  is 9%, the charging current  114  set and received by the load apparatus  30  is 6 amperes. Namely, when the temperature is slightly increasing, the charging current  114  is decreasing to decrease the temperature. 
     The micro-control unit  108  further determines whether the temperature of the plug  102  is higher than the second temperature value. If the temperature is higher than the second temperature value, the control signal  112  sent by the micro-control unit  108  is a second signal value. For example, the duty cycle of the pulse width modulation is a second duty cycle (less than 8%, such as 7.5%) or a second voltage level, so that the load apparatus  30  stops receiving the charging current  114 . Moreover, the second signal value is less than the first signal value. For example, the second duty cycle of the pulse width modulation is less than the first duty cycle, or the second voltage value is less than the first voltage value. 
     For example, when the temperature is higher than 85 degrees centigrade, the duty cycle of the pulse width modulation of the control signal  112  controlled by the micro-control unit  108  is 7.5%. When the duty cycle of the pulse width modulation of the control signal  112  received by the load apparatus  30  is 7.5%, the load apparatus  30  stops receiving the charging current  114 . Namely, when the temperature is too high, the load apparatus  30  will stop receiving the charging current  114  to decrease the temperature. In another word, the charging current  114  is set as zero at this time. 
     When the temperature is decreasing to be in a safe range (for example, not higher than 77 degrees centigrade or 85 degrees centigrade), the load apparatus  30  can receive the charging current  114  again. Moreover, in other embodiments, when the duty cycle of the pulse width modulation is greater than 85%, and less than or equal to 96%, the load apparatus  30  can follow flowing equation to set the charging current  114 : (the duty cycle of the pulse width modulation−64%)*2.5*100=the charging current  114 . When the duty cycle of the pulse width modulation is greater than 96%, and less than or equal to 97%, the charging current  114  set and received by the load apparatus  30  is 80 amperes. When the duty cycle of the pulse width modulation is greater than 97%, the load apparatus  30  will stop receiving the charging current  114 . 
     Moreover, the micro-control unit  108  at least comprises following functions: 
     1. The temperature of the plug  102  can be monitored accurately at all times by utilizing the analog-to-digital interface. 
     2. The temperature-controlling function equations and forms can be stored by utilizing the memory. According to the temperature, the load apparatus  30  adjusts the magnitude of the charging current  114  proportionally. The hysteresis functions can be utilized, so that the control signal  112  can avoid switching continually around the first temperature value (or around the second temperature value). Please refer to  FIG. 7  below and the content thereof. 
     For example, when the temperature is higher than the first temperature value and is not higher than the second temperature value so the charging current  114  decreases as the first current value (for example, 6 amperes) and thus the temperature is decreasing, the temperature has to be decreasing, for example, below 50 degrees centigrade (the first hysteresis temperature), so that the micro-control unit  108  just sends the normal signal value to the load apparatus  30 . After the load apparatus  30  sets, the charging current  114  just recovers as the normal current value (for example, 20 amperes). 
     3. The equations can be modified and written into the micro-control unit  108 , so that various temperature-controlling function equations and forms can be executed. 
       FIG. 2  shows a block diagram of the second embodiment of the power plug apparatus of the present invention. The description for the elements shown in  FIG. 2 , which are similar to those shown in  FIG. 1 , is not repeated here for brevity. The power plug apparatus  10  further comprises a voltage conversion circuit  110  and/or a switch  106 . The switch  106  is electrically connected to the plug  102  and the load apparatus  30 . The voltage conversion circuit  110  is electrically connected to the micro-control unit  108  and the load apparatus  30 . The main function of the voltage conversion circuit  110  is that when the voltages of the micro-control unit  108  and the load apparatus  30  are different, the voltage conversion circuit  110  is used for matching the voltages to adjust the amplitude of the control signal  112 . Moreover, the switch  106  can connect (namely, conduct or turn on) or disconnect (namely, cut off or turn off) the charging current  114 . The switch  106  is, for example but not limited to, a relay switch circuit. In the embodiment with the switch  106 , if the temperature is higher than the second temperature value, the control signal  112  sent by the micro-control unit  108  is the second signal value, for example, the second duty cycle of the pulse width modulation or the second voltage value, so that the load apparatus  30  stops receiving the charging current  114 . At this time, the switch  106  keeps turning on (namely, conducting), so that when the temperature is decreasing to be in the safe range (for example, not higher than 77 degrees centigrade or 85 degrees centigrade), comparing to the related art that turns off the switch  106  for over temperature protection, the load apparatus  30  can receive the charging current  114  again more quickly and safely in the present invention. 
       FIG. 3  shows a block diagram of the third embodiment of the power plug apparatus of the present invention. The description for the elements shown in  FIG. 3 , which are similar to those shown in  FIGS. 1 ˜ 2 , is not repeated here for brevity. Moreover, the power plug apparatus  10  further comprises a live wire  116  and a neutral wire  118 . The live wire  116  is electrically connected to the plug  102 , the switch  106 , the load apparatus  30  and the micro-control unit  108 . The neutral wire  118  is electrically connected to the plug  102 , the switch  106 , the load apparatus  30  and the micro-control unit  108 . The switch  106  comprises a live wire switch  120  and a neutral wire switch  122 . The live wire switch  120  is electrically connected to the live wire  116  and the micro-control unit  108 . The neutral wire switch  122  is electrically connected to the neutral wire  118  and the micro-control unit  108 . The live wire switch  120  is, for example but not limited to, a relay switch. The neutral wire switch  122  is, for example but not limited to, a relay switch. In other embodiments, the present invention can be applied to the single phase three wires system, the three phases three wires system and three phases four wires system. 
       FIG. 4  shows a block diagram of the fourth embodiment of the power plug apparatus of the present invention. The description for the elements shown in  FIG. 4 , which are similar to those shown in  FIGS. 1 ˜ 3 , is not repeated here for brevity. Moreover, the power plug apparatus  10  further comprises a ground wire  124 , a ground monitoring circuit  126 , a current detecting circuit  128 , a residual current device  130 , a second temperature sensor  132 , an auxiliary power circuit  134  and a light emitting diode  136 . The ground wire  124  is electrically connected to the plug  102  and the load apparatus  30 . The ground monitoring circuit  126  is electrically connected to the live wire  116 , the neutral wire  118 , the ground wire  124  and the micro-control unit  108 . The current detecting circuit  128  can be electrically connected to the live wire  116  (or the neutral wire  118 ) and the micro-control unit  108 . The residual current device  130  is electrically connected to the live wire  116 , the neutral wire  118  and the micro-control unit  108 . The second temperature sensor  132  is electrically connected to the micro-control unit  108 . The auxiliary power circuit  134  is electrically connected to the live wire  116 , the neutral wire  118  and the micro-control unit  108 . The light emitting diode  136  is electrically connected to the micro-control unit  108 . 
     When the ground monitoring circuit  126 , the current detecting circuit  128 , the residual current device  130  or the second temperature sensor  132  detects/senses abnormal conditions, the micro-control unit  108  will be informed to turn off the live wire switch  120  and the neutral wire switch  122 , so that the charging current  114  will not be sent to the load apparatus  30 . 
       FIG. 5  shows a diagram of the plug and the first temperature sensor of the present invention. The plug  102  comprises a heat conductor  138  and power pins  140 . The heat conductor  138  touches the first temperature sensor  104  and the power pins  140 , so that the thermal energy of the power pins  140  can be transmitted to the first temperature sensor  104  quickly. Namely, the temperature gradient of the first temperature sensor  104  and the power pins  140  is narrowed. A media (not shown in  FIG. 5 ) can be arranged between the power pins  140  and the heat conductor  138  to fill gaps between the power pins  140  and the heat conductor  138 , so that the heat conduction is better. The heat conductor  138  is an insulator, so that the heat conductor  138  can touch the power pins  140  directly. 
       FIG. 6  shows a block diagram of the application embodiment of the power plug apparatus of the present invention. In an embodiment of the present invention, the power plug apparatus is applied to charge the vehicle as shown in  FIG. 6 . A control box  144  may be independent in the mechanism to accommodate the micro-control unit  108  and the circuits mentioned above. One terminal of the control box  144  is electrically connected to the plug  102 . The other terminal of the control box  144  is electrically connected to a power output plug  146  to connect to a vehicle  40 . In other embodiments of the present invention, the present invention can be applied to medical facilities, especially portable (namely, mobile or movable) medical instruments. The power plug apparatus can be shown as  FIG. 6 , or the micro-control unit  108  and the circuits mentioned above are built in the medical instrument. The present invention is not limited to it. 
       FIG. 7  shows a flow chart of the over temperature protection method of the present invention.  FIG. 8  shows a diagram of the temperature versus the duty cycle of the pulse width modulation of the present invention. The over temperature protection method of the present invention comprises following steps: 
     S 02 : A temperature sensor senses a temperature of a plug and transmits to a micro-control unit. 
     S 04 : The micro-control unit sends a control signal to a load apparatus. 
     S 06 : According to the control signal, the load apparatus receives a charging current. 
     If the temperature is not higher than a first temperature value, the micro-control unit adjusts the control signal as a normal signal value (the duty cycle of the pulse width modulation is the normal duty cycle) and sends the control signal to the load apparatus, so that the charging current is a normal current value. If the temperature is higher than the first temperature value and is not higher than a second temperature value, the micro-control unit adjusts the control signal as a first signal value (the duty cycle of the pulse width modulation is the first duty cycle), so that the charging current is a first current value. Moreover, the first current value is less than the normal current value. Then, if the temperature is lower than a first hysteresis temperature, the control signal recovers as the normal signal value (the duty cycle of the pulse width modulation recovers as the normal duty cycle). Moreover, the first hysteresis temperature is lower than the first temperature value. If the temperature is higher than the second temperature value, the micro-control unit adjusts the control signal as a second signal value (the duty cycle of the pulse width modulation is the second duty cycle), so that the charging current is zero. Moreover, the second temperature value is higher than the first temperature value. Then, if the temperature is lower than a second hysteresis temperature, the control signal recovers as the first signal value (the duty cycle of the pulse width modulation recovers as the first duty cycle). Moreover, the second hysteresis temperature is lower than the second temperature value. Moreover, the normal signal value (the duty cycle of the pulse width modulation is the normal duty cycle) is greater than the first signal value (the duty cycle of the pulse width modulation is the first duty cycle). The first signal value (the duty cycle of the pulse width modulation is the first duty cycle) is greater than the second signal value (the duty cycle of the pulse width modulation is the second duty cycle). 
     The advantage of the present invention is to strengthen the over temperature protection function of the power plug apparatus, and the over temperature protection function is more accurate. 
     Although the present invention has been described with reference to the preferred embodiment thereof, it will be understood that the invention is not limited to the details thereof. Various substitutions and modifications have been suggested in the foregoing description, and others will occur to those of ordinary skill in the art. Therefore, all such substitutions and modifications are intended to be embraced within the scope of the invention as defined in the appended claims.