Patent Publication Number: US-2023133557-A1

Title: Power supply device with protection function when water ingress occurs

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the priority benefit of Taiwanese application no. 110140666, filed on Nov. 2, 2021. The entirety of the above-mentioned patent application is hereby incorporated by reference herein and made a part of this specification. 
     BACKGROUND 
     Technical Field 
     The disclosure relates to a power supply device, and in particular, to a power supply device with a protection function when a water ingress occurs. 
     Description of Related Art 
     In a housing of a conventional power supply device, high-frequency welding ultrasonic bars are adopted for welding. To avoid an appearance defect due to an overflow of ultrasonic bars after welding, conventionally, the ultrasonic bars are separately arranged. However, the design may cause gaps between the ultrasonic bars of the upper housing and the lower housing after welding, which may lead to a safety issue when a water ingress occurs in the power supply device. Therefore, how to provide the power supply device with a protection function when the water ingress occurs in the power supply device has become a research focus for those skilled in the art. 
     SUMMARY 
     The disclosure is directed to a power supply device capable of providing a protection function when a water ingress occurs in the power supply device. 
     The power supply device of the disclosure includes a housing, a power converter, a controller, multiple humidity sensitive capacitors, and a feedback circuit. The power converter, the controller, the humidity sensitive capacitors, and the feedback circuit are respectively configured in the housing. The housing has multiple joints. The controller controls the power converter to provide an output voltage. The multiple humidity sensitive capacitors are respectively configured in the housing and adjacent to a corresponding joint of the joints. The multiple humidity sensitive capacitors jointly provide a sensing capacitance value. The feedback circuit is coupled to the power converter, the controller, and the multiple humidity sensitive capacitors. The feedback circuit changes a gain value and a compensation bandwidth of the output voltage in response to a change of the sensing capacitance value. When humidity of at least one of the multiple joints increases, the sensing capacitance value is reduced, so that the gain value and the compensation bandwidth are reduced. 
     Based on the above, when the humidity of at least one of the multiple joints increases, the sensing capacitance value is reduced. Therefore, the gain value and the compensation bandwidth are reduced. The voltage value of the output voltage is thus reduced. In this way, in the disclosure, the power supply device is provided with a water ingress protection function. 
     In order to make the aforementioned features and advantages of the disclosure comprehensible, embodiments accompanied with drawings are described in detail below. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a schematic diagram of a power supply device according to a first embodiment of the disclosure. 
         FIG.  2    is a schematic diagram illustrating a relation between a capacitance value of a humidity sensitive capacitor and relative humidity according to an embodiment of the disclosure. 
         FIG.  3    is a schematic circuit diagram of a power supply device according to a second embodiment of the disclosure. 
         FIG.  4    is a schematic diagram of loop gain in multiple humidity states according to an embodiment of the disclosure. 
         FIG.  5    is a schematic diagram of a power supply device according to a third embodiment of the disclosure. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     Some embodiments of the disclosure accompanied with the drawings will now be described in detail. In the reference numerals recited in description below, the same reference numerals shown in different drawings will be regarded as the same or similar elements. These embodiments are only a part of the disclosure and do not disclose all possible implementations of the disclosure. To be more precise, these embodiments are only examples of the appended claims of the disclosure. 
     Referring to  FIG.  1   ,  FIG.  1    is a schematic diagram of a power supply device according to a first embodiment of the disclosure. In the embodiment, a power supply device  100  includes a housing  110 , a power converter  120 , a controller  130 , humidity sensitive capacitors CX 1  to CX 4 , and a feedback circuit  140 . The power converter  120 , the controller  130 , the humidity sensitive capacitors CX 1  to CX 4 , and the feedback circuit  140  are respectively configured in the housing  110 . The housing  110  has joints J1 to J4. For example, the joints J1 to J4 are respectively a joint of the housing  110  and an AC inlet cable, joints of an upper part of the housing  110  and a lower part of the housing  110 , and a joint of the housing  110  and an SR enhancing portion of the transmission cable. The joints J1 to J4 are positions where a water ingress may occur in the power supply device. The controller  130  controls the power converter  120  to provide an output voltage VO. 
     In the embodiment, the humidity sensitive capacitors CX 1  to CX 4  are respectively configured in the housing  110 . The humidity sensitive capacitors CX 1  to CX 4  are respectively configured at corresponding joints of the joints J1 to J4 in the housing  110 . For example, in the embodiment, the humidity sensitive capacitors CX 1  to CX 4  are configured one-to-one at the joints J1 to J4. The humidity sensitive capacitor CX 1  is designed to be adjacent to the joint J1. The humidity sensitive capacitor CX 2  is designed to be adjacent to the joint J2. The rest may be deduced by analogy. In the embodiment, the humidity sensitive capacitors CX 1  to CX 4  jointly provide a sensing capacitance value SCV. The sensing capacitance value SCV changes in response to humidity (e.g. relative humidity) of the joints J1 to J4. In the embodiment, the humidity sensitive capacitors CX 1  to CX 4  are coupled in series. Therefore, the sensing capacitance value SCV is approximately a series capacitance provided by the humidity sensitive capacitors CX 1  to CX 4  coupled in series. 
     In some embodiments, a number of the humidity sensitive capacitors is greater than a number of the joints. At least two of the humidity sensitive capacitors are designed to be adjacent to the same joint. In the disclosure, the number of and the arrangement of the humidity sensitive capacitors are not limited to this embodiment. 
     In the embodiment, the feedback circuit  140  is coupled to the power converter  120 , the controller  130 , and the humidity sensitive capacitors CX 1  to CX 4 . The feedback circuit  140  changes a gain value and a compensation bandwidth of the output voltage VO in response to a change of the sensing capacitance value SCV. When humidity of at least one of the joints J1 to J4 increases, the sensing capacitance value SCV is reduced, so that both of the gain value and the compensation bandwidth are reduced. For example, when the water ingress occurs at the joint J1, a capacitance value of the humidity sensitive capacitor CX 1  is reduced. The sensing capacitance value SCV is reduced. Therefore, both of the gain value and the compensation bandwidth of the output voltage VO are reduced. A voltage value of the output voltage VO is reduced. In this way, when the water ingress occurs, the power supply device  100  may have a water ingress protection function. 
     Specifically, in the embodiment, the feedback circuit  140  provides a pole frequency fp and provides a null frequency fz in response to the change of the sensing capacitance value SCV. The pole frequency fp is greater than the null frequency fz. Therefore, in the embodiment, when the humidity of at least one of the joints J1 to J4 increases, the sensing capacitance value SCV is reduced and the feedback  140  increases the null frequency fz. Both of the gain value and the compensation bandwidth are reduced. In addition, when the humidity of the joints J1 to J4 decreases, the sensing capacitance value SCV is increased and the null frequency fz is reduced. Hence, the gain value and the compensation bandwidth are increased. 
     Referring to  FIG.  1    and  FIG.  2    together,  FIG.  2    is a schematic diagram illustrating a relation between a capacitance value of a humidity sensitive capacitor and relative humidity according to an embodiment of the disclosure. In the embodiment, the humidity sensitive capacitors CX 1  to CX 4  have a capacitance value C_CX. The capacitance value C_CX and relative humidity H are negatively correlated. In the embodiment, the capacitance value C_CX drops linearly based on the relative humidity H. For example, when the relative humidity H at the joint J1 is equal to 0%, the capacitance value C_CX of the humidity sensitive capacitor CX 1  adjacent to the joint J1 is equal to 75 nanofarads (nF). When the relative humidity H at the joint J1 is equal to 10%, the capacitance value C_CX of the humidity sensitive capacitor CX 1  is equal to 72 nF. When the relative humidity H at the joint J1 is equal to 20%, the capacitance value C_CX of the humidity sensitive capacitor CX 1  is equal to 69 nF. The rest may be deduced by analogy. 
     In some embodiments, the capacitance value C_CX drops nonlinearly based on the relative humidity H. For example, the capacitance value C_CX is inversely proportional to the relative humidity H. 
     Referring to  FIG.  3   ,  FIG.  3    is a schematic circuit diagram of a power supply device according to a second embodiment of the disclosure. For ease of description, the housing is not shown in the embodiment. In the circuit topology of the embodiment, a power supply device  200  includes a power converter  220 , a controller  230 , the humidity sensitive capacitors CX 1  to CX 4 , and a feedback circuit  240 . The feedback circuit  240  includes a coupling circuit  241  and a voltage regulator circuit  242 . The coupling circuit is coupled to the controller  230 . The voltage regulator circuit  242  is coupled to the coupling circuit  241 , the power converter  220 , and the humidity sensitive capacitors CX 1  to CX 4 . The voltage regulator circuit  242  causes the coupling circuit  241  to provide a feedback signal SFB according to a change of the output voltage VO. The controller  230  regulates a frequency of a control signal GD 1  according to the feedback signal SFB to stabilize the voltage value of the output voltage VO. 
     In the embodiment, the voltage regulator circuit  242  includes a voltage regulator  2421  and voltage dividing resistors RO 1  and RO 2 . A first end of the voltage regulator  2421  is coupled to the coupling circuit  241 . A second end of the voltage regulator  2421  is coupled to a reference low voltage that is a grounding end GND 2 . A reference end of the voltage regulator  2421  is configured to provide a reference value R. The voltage regulator  2421  causes the coupling circuit  241  to provide the feedback signal SFB according to the change of the output voltage VO. The voltage dividing resistor RO 1  is coupled between an output end of the power converter  220  and the reference end of the voltage regulator  2421 . The voltage dividing resistor RO 2  is coupled between the reference end of the voltage regulator  2421  and the second end of the voltage regulator  2421 . The voltage regulator  2421  may be realized by an element TL 431 . 
     The coupling circuit  241  may be realized by a photocoupler (e.g. an element PC 817 ). The coupling circuit  241  includes a light-emitting diode and a coupling transistor. An anode of the light-emitting diode is coupled to the output voltage VO. A cathode of the light-emitting diode is coupled to the first end of the voltage regulator  2421 . The coupling transistor is coupled between the controller  230  and a grounding end GND 1 . In the embodiment, the voltage dividing resistors RO 1  and RO 2  divide the voltage value of the output voltage VO to obtain a divided voltage value of the output voltage VO. The voltage regulator  2421  receives the divided voltage value and compares the divided voltage value and the reference value R. When the divided voltage value and the reference value R are different, a voltage value of the first end of the voltage regulator  2421  changes to affect a light-emitting result of the light-emitting diode. Therefore, the feedback signal SFB generated by the coupling transistor also changes. The controller  230  regulates the frequency of the control signal GD 1  based on a charging result caused by the feedback signal SFB to stabilize the voltage value of the output voltage VO. 
     For example, the feedback circuit  240  further includes a capacitor CB. When the voltage value of the output voltage VO increases, the divided voltage value received by the voltage regulator  2421  increases. Therefore, the voltage value of the first end of the voltage regulator  2421  is correspondingly reduced. A brightness of the light-emitting diode increases. Therefore, a current value of the feedback signal SFB provided by the coupling transistor increases so that a charging result of the capacitor CB is affected. The controller  230  reduces an operation period of the control signal GD 1  according to the charging result of the capacitor CB. Therefore, the voltage value of the output voltage VO is reduced. Conversely, when the voltage value of the output voltage VO decreases, the controller  230  increases the operation period of the control signal GD 1 . Therefore, the voltage value of the output voltage VO is increased. Therefore, the voltage value of the output voltage VO may be stabilized. 
     In the embodiment, the voltage regulator circuit  242  further includes compensation capacitors CC 1  and CC 2 , and a compensation resistor RC. The compensation capacitor CC 1  is coupled between the reference end of the voltage regulator  2421  and the first end of the voltage regulator  2421 . The compensation capacitor CC 2 , the compensation resistor RC, and the humidity sensitive capacitors CX 1  to CX 4  are coupled in series to form an element series. The element series is coupled between the reference end of the voltage regulator  2421  and the first end of the voltage regulator  2421 . In the embodiment, the pole frequency (the pole frequency fp shown in  FIG.  1   ) is determined according to a capacitance value of the compensation capacitor CC 1  and a resistance value of the compensation resistor RC. Since the capacitance value of the compensation capacitor CC 1  and the resistance value of the compensation resistor RC are not changed, the pole frequency is constant. The pole frequency may be determined through 
     
       
         
           
             Equation 
             ⁢ 
                 
             
               
                 ( 
                 1 
                 ) 
               
               . 
             
           
         
       
       
         
           
             
               
                 
                   fp 
                   = 
                   
                     1 
                     
                       2 
                       ⨯ 
                       π 
                       ⨯ 
                       R_RC 
                       ⨯ 
                       C_CC1 
                     
                   
                 
               
               
                 
                   Equation 
                   ⁢ 
                       
                   
                     ( 
                     1 
                     ) 
                   
                 
               
             
           
         
       
     
     In Equation (1), fp represents the pole frequency. R_RC represents the resistance value of the compensation resistor RC. C_CC 1  represents the capacitance value of the compensation capacitor CC 1 . 
     The null frequency (the null frequency fz shown in  FIG.  1   ) is determined according to a capacitance value of the compensation capacitor CC 2 , the resistance value of the compensation resistor RC, and the sensing capacitance value provided by the humidity sensitive capacitors CX 1  to CX 4 . Note that the sensing capacitance value may change, so the null frequency may change based on the change of the sensing capacitance value. The null frequency may be determined through Equations (2) and (3). 
     
       
         
           
             
               
                 
                   fz 
                   = 
                   
                     1 
                     
                       2 
                       ⨯ 
                       π 
                       ⨯ 
                       R_RC 
                       ⨯ 
                       CT 
                     
                   
                 
               
               
                 
                   Equation 
                   ⁢ 
                       
                   
                     ( 
                     2 
                     ) 
                   
                 
               
             
           
         
       
       
         
           
             
               
                 
                   CT 
                   = 
                   
                     1 
                     
                       
                         1 
                         C_CC2 
                       
                       + 
                       
                         1 
                         C_CX1 
                       
                       + 
                       
                         1 
                         C_CX2 
                       
                       + 
                       
                         1 
                         C_CX3 
                       
                       + 
                       
                         1 
                         C_CX4 
                       
                     
                   
                 
               
               
                 
                   Equation 
                   ⁢ 
                       
                   
                     ( 
                     3 
                     ) 
                   
                 
               
             
           
         
       
     
     In Equations (2) and (3), fz represents the null frequency. R_RC represents the resistance value of the compensation resistor RC. C CC 2  represents the capacitance value of the compensation capacitor CC 2 . C CX 1  represents the capacitance value of the humidity sensitive capacitor CX 1 . C CX 2  represents a capacitance value of the humidity sensitive capacitor CX 2 . C_CX 3  represents a capacitance value of the humidity sensitive capacitor CX 3 . C_CX 4  represents a capacitance value of the humidity sensitive capacitor CX 4 . CT represents a capacitance value formed by the compensation capacitor CC 2  and the humidity sensitive capacitors CX 1  to CX 4  coupled in series. In other words, the capacitance value CT is approximately equal to a result of the sensing capacitance value and the capacitance value of the compensation capacitor CC 2  in series. 
     In the embodiment, when the relative humidity is equal to 0%, the humidity sensitive capacitors CX 1  to CX 4  are designed to have the capacitance values that are less than or equal to the capacitance value of the compensation capacitor CC 2 . In addition, the capacitance value of the compensation capacitor CC 1  is less than the capacitance value CT. 
     To further explain, referring to  FIG.  3    and  FIG.  4    together,  FIG.  4    is a schematic diagram of loop gain in multiple humidity states according to an embodiment of the disclosure.  FIG.  4    illustrates loop gain LG in various humidity states. In the embodiment, when the relative humidity is equal to 0%, the water ingress does not occur in the power supply device  200 . The feedback circuit  240  provides a null frequency fz 1  and the pole frequency fp. Therefore, a gain value G 1  and a compensation bandwidth BW 1  are formed. 
     When a slight water ingress occurs in the power supply device  200 , the sensing capacitance value drops. The feedback circuit  240  provides a null frequency fz 2  and the pole frequency fp. Therefore, a gain value G 2  and a compensation bandwidth BW 2  are formed. Note that the null frequency fz 2  is greater than the null frequency fz 1 . Therefore, the gain value G 2  is less than the gain value G 1 . Since the pole frequency fp is not changed, the compensation bandwidth BW 2  is less than the compensation bandwidth BW 1 . 
     For example, based on the gain value G 1 , the power converter  220  may provide the output voltage VO. The voltage value of the output voltage VO is approximately equal to 19 volts (the disclosure is not limited thereto). In addition, based on the compensation bandwidth BW 1 , the output voltage VO has a greater compensation margin and stability. When the slight water ingress occurs in the power supply device  200 , the loop gain LG drops from the gain value G 1  to the gain value G 2 . Therefore, based on the gain value G 2 , the voltage value of the output voltage VO is reduced to 5 volts. In addition, based on the compensation bandwidth BW 2 , the compensation margin of the output voltage VO may be reduced. 
     When a severe water ingress occurs in the power supply device  200 , the sensing capacitance value drops further. The feedback circuit  240  provides a null frequency fz 3  and the pole frequency fp. Therefore, a gain value G 3  and a compensation bandwidth BW 3  are formed. Note that the null frequency fz 3  is greater than the null frequency fz 2 . Therefore, the gain value G 3  is less than the gain value G 2 . Since the pole frequency fp is not changed, the compensation bandwidth BW 3  is less than the compensation bandwidth BW 2 . 
     For example, when the severe water ingress occurs in the power supply device  200 , the gain value drops to the gain value G 3 . Therefore, based on the gain value G 3 , the voltage value of the output voltage VO is reduced to less than 5 volts (e.g. approximately 0 volts). In addition, based on the compensation bandwidth BW 3 , the compensation margin of the output voltage VO is very small so that the output voltage VO cannot be reduced to 0 volts by the gain value. 
     In the embodiment, the null frequency fz 2  may be designed to be greater than or equal to 1.5 times the null frequency fz 1  and less than the null frequency fz 3 . The null frequency fz 3  may be designed to be greater than or equal to 2 times the null frequency fz 1  and slightly less than the pole frequency fp. 
     Returning to the embodiment in  FIG.  3   , the power converter  220  includes a rectifier BR, an excitation inductor LM, a transformer TR, a power switch Q 1 , an output diode DO, and an output capacitor CO. The rectifier BR generates a rectified power VR according to an input voltage VIN. A first end of the excitation inductor LM is coupled to the rectifier BR. A first end of the power switch Q 1  is coupled to a second end of the excitation inductor LM. A second end of the power switch Q 1  is coupled to the grounding end GND 1 . A control end of the power switch Q 1  is coupled to the controller  230 . The transformer TR includes a primary winding NP and a secondary winding NS. The primary winding NP is coupled to the excitation inductor LM in parallel. A first end of the secondary winding NS is coupled to an anode of the output diode DO. A second end of the secondary winding NS is coupled to the grounding end GND 2 . A cathode of the output diode DO serves as the output end of the power converter  220 . The output capacitor CO is coupled between the cathode of the output diode DO and the grounding end GND 2 . The power switch Q 1  performs switch operation based on the control signal GD 1  provided by the controller  230  so that the power converter  220  converts the rectified power VR into the output voltage VO. 
     In the embodiment, the topology of the rectifier BR and a flyback converter serves as an example of the power converter  220 ; however, the disclosure is not limited thereto. In some embodiments, the power converter  220  may be realized by other converters. 
     Referring to  FIG.  4    and  FIG.  5   ,  FIG.  5    is a schematic circuit diagram of a power supply device according to a third embodiment of the disclosure. In the embodiment, a power supply device  300  includes a power converter  320 , a controller  330 , humidity sensitive capacitors CX 1  to CX 4 , the feedback circuit  240 , a warning power switch QX, and a warning light  350 . The implementation of the feedback circuit  240  and humidity sensitive capacitors CX 1  to CX 4  is clearly described in the embodiments of  FIG.  1    to  FIG.  4   , and it is not repeated. In the embodiment, a first end of the warning power switch QX receives the rectified power VR. A control end of the warning power switch QX is coupled to the controller  330 . The warning light  350  is coupled to a second end of the warning power switch QX and the controller  330 . The rectified power VR serves as a driving power of the warning light  350 . 
     In the embodiment, the controller  330  receives the output voltage VO to determine an internal humidity state of the housing (the housing  110  as shown in  FIG.  1   ) according to the voltage value of the output voltage VO. In addition, the controller  330  controls the warning power switch QX and the warning light  350  based on the humidity state so that the warning light  350  displays warning signals ALM 1  and ALM 2  corresponding to different humidity states. 
     In the embodiment, to protect the warning power switch QX and the warning light  350 , a current-limiting resistor RX may be provided between the first end of the warning power switch QX and the rectifier BR of the power converter  320 . 
     In the embodiment, based on a performance of the loop gain LG shown in  FIG.  4   , the voltage value of the output voltage VO is controlled to be approximately 19 volts based on the gain value G 1 . The voltage value of the output voltage VO is controlled to be approximately 5 volts based on the gain value G 2 . The voltage value of the output voltage VO is controlled to be approximately 0 volts based on the gain value G 3 . When the voltage value of the output voltage VO is approximately equal to an operation voltage value (i.e. 19 volts), the controller  330  determines a first humidity state inside the housing. The first humidity state is a state where no water ingress occurs. When the voltage value of the output voltage VO is approximately equal to a first voltage value (i.e. 5 volts), the controller  330  determines a second humidity state inside the housing. The second humidity state is a state where the slight water ingress occurs. When the voltage value of the output voltage VO is approximately equal to a second voltage value (i.e. 0 volts), the controller  330  determines a third humidity state inside the housing. The third humidity state is a state where the severe water ingress occurs. 
     In the embodiment, in the first humidity state, the controller  330  turns off the warning power switch QX. Therefore, the warning light  350  stops operating since it cannot receive the rectified power VR. In the second humidity state, the controller  330  provides a control signal GD 2  to turn on the warning power switch QX and controls the warning light  350  to display the warning signal ALM 1 . Specifically, in the second humidity state, the controller  330  turns on the warning power switch QX and provides a control signal LEDC 1 . The warning light  350  displays the warning signal ALM 1  in response to the control signal LEDC 1 . 
     In the third humidity state, the controller  330  provides the control signal GD 2  to turn on the warning power switch QX and controls the warning light  350  to display the warning signal ALM 2 . Specifically, in the third humidity state, the controller  330  turns on the warning power switch QX and provides a control signal LEDC 2 . The warning light  350  displays the warning signal ALM 2  in response to the control signal LEDC 2 . 
     In the embodiment, a color of the warning signal ALM 1  is different from a color of the warning signal ALM 2 . For example, the color of the warning signal ALM 1  may be yellow. In the second humidity state, the color of the warning signal ALM 2  may be red. In some embodiments, a blinking pattern of the warning signal ALM 1  is different from a blinking pattern of the warning signal ALM 2 . 
     In the embodiment, the warning light  350  may be realized by at least one light-emitting diode module or light-emitting element. The warning light  350  is disposed on the housing or an output cable. In this way, a user may obtain the humidity state inside the housing from an outside of the housing. 
     In the embodiment, the difference between the power converter  320  and the power converter  220  is that the power converter  320  further includes an auxiliary diode DA and an auxiliary capacitor CA. The transformer TR further includes an auxiliary winding NA. The auxiliary diode DA, the auxiliary capacitor CA, and the auxiliary winding NA jointly form an auxiliary power supplier. A first end of the auxiliary winding NA is coupled to an anode of the auxiliary diode DA. A cathode of the auxiliary diode DA is coupled to a first end of the auxiliary capacitor CA and the controller  330 . A second end of the auxiliary capacitor CA is coupled to a second end of the auxiliary winding NA and the grounding end GND 1 . The auxiliary power supplier may provide an auxiliary power to the controller  330 . 
     In summary of the above, when the humidity of at least one of the multiple joints of the housing of the power supply device increases, the gain value and the compensation bandwidth of the output voltage are reduced. Therefore, the voltage value of the output voltage is reduced. In this way, in the disclosure, the power supply device is provided with a water ingress protection function. In addition, in some embodiments, the power supply device includes the warning light. The power supply device may control the warning light to display the different warning signals corresponding to the humidity states according to the humidity states. In this way, the user may obtain the humidity state inside the housing based on the warning signal. 
     Although the disclosure has been described with reference to the above embodiments, they are not intended to limit the disclosure. It will be apparent to one of ordinary skill in the art that modifications to the described embodiments may be made without departing from the spirit and the scope of the disclosure. Accordingly, the scope of the disclosure will be defined by the attached claims and their equivalents and not by the above detailed descriptions.