Patent Publication Number: US-2022216782-A1

Title: Power conversion device

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims priority based on  35  USC  119  from prior International Patent Application No. PCT/JP2019/038502 filed on Sep. 30, 2019, the entire contents of which are incorporated herein by reference. 
    
    
     BACKGROUND 
     The disclosure may relate to a power conversion device equipped with an output circuit and a microcomputer that controls the output circuit. 
     A power conversion device is used in which a power supply chip, which functions as an output circuit, and a microcomputer chip, which functions as a microcomputer controlling the output circuit, are mounted on the same frame and packaged together. In such a power conversion device, an internal power source of the output circuit supplies power to the microcomputer. When a voltage of an input power supply drops or an abnormal or the like occurs, the output circuit stops the power supply to the microcomputer. 
     Upon stopping the power to the microcomputer, if the microcomputer is in the process of writing, the data may be corrupted. Therefore, the applicant has proposed a technology that outputs a stop signal from the output circuit to the microcomputer and then stops the internal power source when the microcomputer gets ready to be stopped (see, for example, Patent Document 1). 
     Patent Document 1: Japanese Patent Application Publication No. 2019-013130 
     SUMMARY 
     However, in the technology described above, the output circuit outputs the stop signal to the microcomputer, and the microcomputer that has received the stop signal starts a stop process so as to output a stop permission signal to the output circuit to permit the stop. Therefore, two control lines for stopping the power supply may be required between the output circuit and the microcomputer, and also the output circuit may not be able to immediately stop the power supply even when the microcomputer is ready to be stopped. 
     An object of an embodiment of the disclosure may be to provide a power conversion device capable of simplifying a control line for stopping power supply between an output circuit and a microcomputer and capable of immediately stopping the power supply by the output circuit in a state where the microcomputer is ready to be stopped. 
     An aspect of the disclosure may be a power conversion device that may include: an output circuit configured to perform a power conversion operation of converting input power into a predetermined output power and outputting the output power; and a microcomputer configured to be supplied with power from an internal power source of the output circuit and control the power conversion operation by the output circuit, wherein the microcomputer is configured to output to the output circuit a status signal that notifies whether the microcomputer is in a power shutdown permit period in which the power supply to the microcomputer is permitted to be stopped or in a power shutdown inhibit period in which the power supply to the microcomputer is not permitted to be stopped, and the output circuit includes a power supply stop circuit configured, when receiving the operation stop signal that instructs to stop the power conversion operation, to stop the power supply from the internal power source to the microcomputer on a condition where the status signal indicates that the microcomputer is in the power shutdown permit period. 
     According to the above aspect, a control line for stopping the power supply can be simplified to one line that notifies the status signal from the microcomputer to the output circuit. Also, since the status signal notifies if the microcomputer is in the power shutdown permit period, the output circuit can immediately stop the power supply to the microcomputer when the microcomputer is in the state where the microcomputer is ready to be stopped. 
    
    
     
       BREIF DESCRIPTION OF DRAWING 
         FIG. 1  is a diagram illustrating a circuit configuration of a power conversion device according to a first embodiment; 
         FIG. 2  is a timing chart illustrating operations of components of the power conversion device illustrated in  FIG. 1 ; 
         FIG. 3  is a timing chart illustrating operations of the components of the power conversion device illustrated in  FIG. 1 ; 
         FIG. 4  is a timing chart illustrating operations of the components of the power conversion device illustrated in  FIG. 1 ; 
         FIG. 5  is a circuit diagram illustrating a power conversion device according to a second embodiment; 
         FIG. 6  is a timing chart illustrating operations of components of the power conversion device illustrated in  FIG. 5 ; 
         FIG. 7  is a timing chart illustrating operations of the components of the power conversion device illustrated in  FIG. 5 ; and 
         FIG. 8  is a timing chart illustrating operations of the components of the power conversion device illustrated in  FIG. 5 . 
     
    
    
     DETAILED DESCRIPTION 
     One or more embodiments are explained with referring to drawings. In the respective drawings referenced herein, the same constituents are designated by the same reference numerals and duplicate explanation concerning the same constituents may be omitted. All of the drawings are provided to illustrate the respective examples only. No dimensional proportions in the drawings shall impose a restriction on the one or more embodiments. For this reason, specific dimensions and the like should be interpreted with the following descriptions taken into consideration. In addition, the drawings include parts whose dimensional relationship and ratios are different from one drawing to another. 
     (First Embodiment) 
     Referring to  FIG. 1 , a power conversion device  1  (or a power converter) according to a first embodiment is a DC/DC converter that is configured to convert an input voltage Vin to an output voltage Vout and output the output voltage Vout. The power conversion device  1  is packaged with a chip-formed output circuit  10  and a chip formed microcomputer 20 mounted on a same frame. 
     The output circuit  10  includes a switching device Q 1  and a switching device Q 2 , which function as output parts  11 , an internal power source  12 , a drive circuit  13 , a power supply stop circuit  14 , and a timer circuit  15 . Note that the switching device Q 1  and the switching device Q 2  can be configured as a chip(s) or the like independent from the output circuit  10  and connected to the outside of the output circuit  10 . 
     An input capacitor C 1  is connected to both ends of the input voltage Vin, the positive side of the input voltage Vin is connected to a drain of the switching device Q 1 , and the negative side of the input voltage Vin is grounded. A source of the switching device Q 1  is connected to a drain of the switching device Q 2  and to one end of a primary winding of a transformer T 1 . The other end of the primary winding of the transformer T 1  is connected to one end of an output capacitor C 3 , and the other end of the output capacitor C 3  is grounded. A load  2  is connected to both ends of the output capacitor C 3 . 
     One end of a secondary winding of the transformer T 1  is connected to an anode of a diode D 1 , and the other end of the secondary winding of the transformer T 1  is grounded. A cathode of the diode D 1  is connected to an input of the internal power source  12  and to one end of the capacitor C 2 . The other end of the capacitor C 2  is grounded. As a result, the switching output stepped down by the transformer T 1  is rectified by the diode D 1  and then smoothed by the capacitor C 2  to generate a DC voltage, which is input to the internal power source  12 . 
     As illustrated by the bold dotted lines in  FIG. 1 , an output of the internal power source  12  is connected to and supplies power to the drive circuit  13 , the power supply stop circuit  14 , and the timer circuit  15  in the output circuit  10 , and the microcomputer  20 . 
     The drive circuit  13  outputs a Q 1  drive signal to a gate of the switching device Q 1 , and drives the switching device Q 1  by the Q 1  drive signal. The drive circuit  13  outputs a Q 2  drive signal, which has a reverse phase of the Q 1  drive signal, to the gate of the switching device Q 2 , and drives the switching device Q 2  by the Q 2  drive signal. 
     The microcomputer  20  detects the voltage between both ends of the output capacitor C 3  as the output voltage Vout, and outputs control signals to the drive circuit  13  to control duty ratios of the Q 1  drive signal and the Q 2  drive signal so that the output voltage Vout becomes constant. 
     The output circuit  10  is provided with an external input terminal  30  that accepts input of an operation stop signal, from an external source, such as a host system, to instruct the power conversion device  1  to stop operating. The operation stop signal is input via the external input terminal  30  to the power supply stop circuit  14  and the timer circuit  15 . The operation stop signal, for example, is normally at a Hi level, and a transition of the operation stop signal from the Hi level to a Low level instructs to stop the operation of the power conversion device  1 . 
     The microcomputer  20  outputs a status signal to the output circuit  10  to notify a status of the microcomputer  20 . The status signal is used to notify whether the microcomputer  20  is in a power shutdown permit period during which the power supply is permitted to be stopped, or in a power shutdown inhibit period during which the power supply is not permitted to be stopped, such as during writing to the memory. The status signal, for example, is at a Low level during the power shutdown permit period. A transition of the status signal from the Low level to a Hi level notifies the start of the power shutdown inhibit period. 
     The status signal output from the microcomputer  20  is input to the power supply stop circuit  14 . When the power supply stop circuit  14  is instructed to stop the operation of the power conversion device  1  by the operation stop signal on the condition that the microcomputer  20  is in the power shutdown permit period, the power supply stop circuit  14  outputs to the internal power source  12  a power supply stop signal that instructs the internal power source  12  to stop supplying power. In other words, when the power supply stop circuit  14  receives the operation stop signal at the Low level and the status signal at the Low level, the power supply stop circuit  14  outputs the power supply stop signal to the internal power source  12  that instructs the internal power source  12  to stop supplying power. The power supply stop signal, for example, is normally at a Hi level, and a transition of the power supply stop signal from the Hi level to the Low level instructs the internal power source  12  to stop supplying power. 
     Upon being instructed by the operation stop signal to stop the operation of the power conversion device  1 , the timer circuit  15  starts counting the time for a preset waiting period T 0 . When the waiting period T 0  elapses, the timer circuit  15  outputs the power supply stop signal that instructs the internal power source  12  to stop supplying power. Note that in a first embodiment, the power supply stop signal output from the power supply stop circuit  14  and the power supply stop signal output from the timer circuit  15  are common. Therefore, the transition from the Hi level to Low level in the power supply stop signal output from either of the power supply stop circuit  14  or the timer circuit  15  instructs the internal power source  12  to stop supplying power. 
     Next, a power supply stop operation is explained in detail with reference to  FIGS. 2 and 4 .  FIG. 2  illustrates an example where the status signal is at the Low level when the operation stop signal transition from the Hi level to the Low level at time t 11 . 
     Referring to  FIG. 2 , at time t 11 , the operation stop signal input to the external input terminal  30  transitions from the Hi level to the Low level. With this, the power supply stop circuit  14  is instructed by the operation stop signal to stop the operation of the power conversion device  1 , and thus the power supply stop circuit  14  checks the status signal output from the microcomputer  20 . At this time, the status signal is in the Low level which indicates the microcomputer  20  is in the power shutdown permit period, and thus the power supply stop circuit  14  causes the power supply stop signal to transition from the Hi level to the Low level to instruct the internal power source  12  to stop supplying power. With this, the internal power source  12  can stop supplying power at a substantially same time when the operation stop signal instructs to stop the operation of the power conversion device  1 . 
       FIG. 3  illustrates an example where the status signal transitions from the Hi level to the Low level at time t 22  after the operation stop signal instructs to stop the operation of the power conversion device  1  at time t 21 . Referring to  FIG. 3 , at time t 21 , the operation stop signal input to the external input terminal  30  transitions from the Hi level to the Low level to stop the operation of the power conversion device  1 . Upon being instructed by the operation stop signal to stop the operation of the power conversion device  1 , the power supply stop circuit  14  checks the status signal output from the microcomputer  20 . At this time, the status signal is at the Hi level which indicates the microcomputer  20  is in the power shutdown inhibit period, and thus the power supply stop circuit  14  waits. 
     Also, upon being instructed by the operation stop signal to stop the operation of the power conversion device  1 , the timer circuit  15  starts counting for the waiting period To. Then, at time t 22 , which is before time t 23  when the waiting period To elapses, the status signal transitions from the Hi level to the Low level which indicates the microcomputer  20  is in the power shutdown permit period. With this, the power supply stop circuit  14  causes the power supply stop signal to transition from the H level to the Low level to instruct the internal power source  12  to stop supplying power. This causes the internal power source  12  to stop supplying power at a substantially same time when the microcomputer  20  gets ready to be shutdown. 
       FIG. 4  illustrates an example where the status signal keeps at the Hi level until the waiting period T 0  elapses. Referring to  FIG. 4 , at time t 31 , the operation stop signal input to the external input terminal  30  transitions from the Hi level to the Low level to stop the operation of the power conversion device  1 . Upon being instructed by the operation stop signal to stop the operation of the power conversion device  1 , the power supply stop circuit  14  checks the status signal output from the microcomputer  20 . At this time, the status signal is at the Hi level which indicates the microcomputer  20  is in the power shutdown inhibit period, and thus the power supply stop circuit  14  waits. 
     Also, upon being instructed by the operation stop signal to stop the operation of the power conversion device  1 , the timer circuit  15  starts counting for the waiting period To. Then, at time t 32  when the time elapses the waiting period T 0 , the timer circuit  15  causes the power supply stop signal to transition from the Hi level to the Low level, so as to instruct the internal power source  12  to stop supplying power. This causes the internal power source  12  to stop supplying power according to the operation stop signal. Therefore, even if the status signal is somehow stuck in the Hi level which indicates that the microcomputer  20  is in the power shutdown inhibit period, it is possible to stop the power supply from the internal power source  12  based on the operation stop signal. 
     (Second Embodiment) 
       FIG. 5  illustrates a power conversion device  1   a  according a second embodiment. Referring to  FIG. 5 , the power conversion device  1   a  according to a second embodiment includes an output circuit  10   a  with an overheat detection circuit  16  instead of the timer circuit  15  illustrated in  FIG. 1 . The output of the internal power source  12  is also connected to and supplies power to the overheat detection circuit  16 , as illustrated by the bold dotted line in  FIG. 5 . 
     The overheat detection circuit  16  is laid out in the vicinity of the switching device Q 1  and detects a junction temperature of the switching device Q 1 . When the detected junction temperature exceeds a predetermined first threshold temperature, the overheat detection circuit  16  outputs an operation stop signal to stop the operation of the power conversion device  1   a  to the power supply stop circuit  14 . In other words, a second embodiment detects an operation stop factor in the power conversion device  1   a  to generate the operation stop signal. 
     Also, when the detected junction temperature exceeds a second threshold temperature, which is preset to be higher than the first threshold temperature, the overheat detection circuit  16  outputs to the internal power source  12  the power supply stop signal that instructs the internal power source  12  to stop supplying power. The power supply stop signal output from the power supply stop circuit  14  and the power supply stop signal output from the overheat detection circuit  16  are made common. Thus, the transition from the Hi level to the Low level in the power supply stop signal output from either of the power supply stop circuit  14  or the overheat detection circuit  16  instructs the internal power source  12  to stop supplying power. 
     Next, a power supply stop operation of the power conversion device  1   a  is explained in detail with reference to  FIGS. 6 to 8 .  FIG. 6  illustrates an example where the status signal is in the Low level at time t 41  when the junction temperature reaches the first threshold temperature. Referring to  FIG. 6 , due to an abnormality in a load  2 , etc., the load current increases and the junction temperature of the switching device Q 1  rises. When the junction temperature of the switching device Q 1  exceeds the first threshold temperature at time t 41 , the overheat detection circuit  16  changes the operation stop signal from the Hi level to the Low level, so as to instruct to stop the operation of the power conversion device  1   a . When instructed to stop the operation of the power conversion device  1   a  by the operation stop signal, the power supply stop circuit  14  checks the status signal output from the microcomputer  20 . At this time, since the status signal is at the Low level indicating that the microcomputer is in the power shutdown permit period, the power supply stop circuit  14  causes the power supply stop signal to transition from the Hi level to the Low level, so as to instruct the internal power source  12  to stop supplying power. With this, the internal power source  12  stops supplying power at a substantially same time when the operation stop signal is output to stop the operation of the power conversion device  1   a.    
       FIG. 7  illustrates an example where the status signal is in the Hi level at time t 51  when the junction temperature reaches the first threshold temperature and then the status signal transitions from the Hi level to the Low level at time t 52 . Referring to  FIG. 7 , due to an abnormality in the load  2 , etc., the load current increases and the junction temperature of the switching device Q 1  rises. When the junction temperature of the switching device Q 1  exceeds the first threshold temperature at time t 51 , the overheat detection circuit  16  causes the operation stop signal to transition from the Hi level to the Low level, to instruct to stop the operation of the power conversion device  1   a . When instructed by the operation stop signal to stop the operation of the power conversion device  1   a , the power supply stop circuit  14  checks the status signal output from the microcomputer  20 . At this time, the status signal is in the Hi level indicating that the microcomputer is in the power shutdown inhibit period, and thus the power supply stop circuit  14  waits. 
     As a result, the operation of the switching device Q 1  continues and the junction temperature of the switching device Q 1  further rises. Then, at time t 52  before the junction temperature exceeds the second threshold temperature, the state signal transitions from the Hi level to the Low level indicating that the microcomputer  20  is in the power shutdown permit period. With this, the power supply stop circuit  14  causes the power supply stop signal to transition from the Hi level to the Low level to instruct the internal power source  12  to stop supplying power. With this, the internal power source  12  stops supplying power at a substantially same time when the microcomputer  20  becomes ready to be shutdown. 
       FIG. 8  illustrates an example where the status signal is in the Hi level at time t 61  when the junction temperature reaches the first threshold temperature, and then the junction temperature reaches the second threshold temperature at time t 62 . Referring to  FIG. 8 , when due to an abnormality of the load  2 , etc., the load current increases and the junction temperature of the switching device Q 1  rises. When the junction temperature exceeds the first threshold temperature at time t 61 , the overheat detection circuit  16  changes the operation stop signal from the Hi level to the Low level, to instruct to stop the operation of the power conversion device  1  a. When instructed by the operation stop signal to stop the operation of the power conversion device  1 , the power supply stop circuit  14  checks the status signal output from the microcomputer  20 . At this time, the status signal is in the Hi level indicating that the microcomputer is in the power shutdown inhibit period, and thus the power supply stop circuit  14  waits. 
     As a result, the operation of the switching device Q 1  continues, and the junction temperature of the switching device Q 1  further rises. Then, at time t 62  when the junction temperature exceeds the second threshold temperature, the overheat detection circuit  16  changes the power supply stop signal from the Hi level to the Low level, to instruct the internal power source  12  to stop supplying power. With this, when the junction temperature exceeds a safety temperature, the power supply from the internal power source  12  can be stopped regardless of the state of the microcomputer  20  (e.g., even in the power shutdown inhibit period). 
     As explained above, according to one or more embodiments, the power conversion device  1  includes: the output circuit  10  that executes the power conversion operation of converting the input power into the predetermined output power and outputs the output power; and the microcomputer  20  that is supplied with power output from the internal power source  12  of the output circuit  10  and controls the power conversion operation by the output circuit  10 , wherein the microcomputer  20  outputs the status signal to the output circuit  10  to notify whether it is in the power shutdown permit period or the power shutdown inhibit period, and the output circuit  10  includes the power supply stop circuit  14  that is configured, when receiving the operation stop signal that instructs to stop the power conversion operation, to stop the power supply from the internal power source  12  to the microcomputer  20  on the condition where it is confirmed that the status signal indicates that the microcomputer  20  is in the power shutdown permit period. This configuration simplifies the power shutdown control line to a single line that notifies the status signal from the microcomputer  20  to the output circuit  10 . This configuration also allows the output circuit  10  to immediately stop the power supply when the microcomputer  20  is ready to stop, since the status signal continues to notify that the microcomputer is in the power shutdown permit period or not. 
     Furthermore, in one or more embodiments, the output circuit  10  includes the timer circuit  15  that is configured, when the operation stop signal is input, to start to count for the preset waiting period To, and configured, when the waiting period T 0  elapses, to stop supplying power from the internal power source  12  to the microcomputer  20 , even if the status signal indicates that the microcomputer  20  is in the power shutdown inhibit period. With this configuration, the power supply from the internal power source  12  to the microcomputer  20  can be stopped based on the operation stop signal, even if the status signal is somehow stuck in a state (the Hi level) that indicates the microcomputer  20  is in the power shutdown inhibit period. 
     Furthermore, in one or more embodiments, the output circuit  10   a  includes the overheat detection circuit  16  configured to detect the junction temperature of the switching device Q 1  that executes the power conversion operation by the switching operation, and, when the detected junction temperature exceeds the preset first threshold temperature, to output the operation stop signal to the power supply stop circuit  14 . The overheat detection circuit  16  is further configured, when the detected junction temperature exceeds the preset second threshold temperature which is higher than the preset first threshold temperature, to cause the internal power source  12  to stop supplying power to the microcomputer  20  even if the status signal indicates that the microcomputer  20  is in the power shutdown inhibit period. With this configuration, the power supply from the internal power source  12  to the microcomputer  20  can be stopped when the junction temperature exceeds a safety temperature, regardless of the state of the microcomputer  20  (e.g., even during the power shutdown inhibit period). 
     The invention is not limited to one or more embodiments described above, and that each embodiment may be changed as appropriate within the scope of the technical concept of the invention. The number, position, shape, etc., of elements described above are not limited to one or more embodiments described above, and can be made into any number, position, shape, etc., that is suitable for implementing the invention. For example, the power conversion device  1  or  1  a in the disclosure is not limited to a DC/DC converter and may be a DC/AC converter or AC/AC converter that outputs an AC voltage, as long as it is a power conversion device that converts input power into a predetermined output power. Note that in the respective drawings, the same constituents are designated by the same reference numerals and duplicate explanation concerning the same constituents is omitted.