Patent Publication Number: US-9431892-B1

Title: High voltage start-up circuit with adjustable start-up time

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to and/or benefit from Chinese Application No. 201510437350.9, filed on Jul. 23, 2015, entitled “HIGH VOLTAGE START-UP CIRCUIT WITH ADJUSTABLE START-UP TIME,” the specification of which is incorporated by reference herein in its entirety. 
     TECHNICAL FIELD 
     The present disclosure relates to a high voltage start-up circuit with adjustable start-up time, which is applicable to power management integrated chips, and belongs to the technical field of power semiconductors. 
     BACKGROUND 
       FIG. 1  shows the working waves of the traditional start-up mode of a start-up circuit. At the start time instant of the time span T 1 , the system is powered on and the start-up begins, then the VDD voltage continuously rises. At the end time instant of the time span T 1 , the VDD voltage reaches the threshold value VTH 1 , and the chip starts to work normally. The time span T 2  is a normal working stage. When an abnormal event occurs at a certain time instant during the time span T 2 , the VDD voltage falls. When the VDD voltage falls to the threshold value VTH 2 , the under voltage latching signal UVLO is activated, and the chip goes into a restart stage of the time span T 3 . The VDD voltage rises and reaches the threshold value VTH 1  again at the end time instant of the time span T 3 , and the chip starts to work normally and re-detects for any abnormal event. If the abnormal event still exists or any other abnormal event occurs, the restart process described above will be repeated until the time instant when the abnormal event is eliminated. After the successive restart process is over, the chip goes into the normal working stage of the time span T 5 . 
     The traditional start-up mode can ensure that the chip starts up normally and restarts when an abnormal event occurs, but in the traditional start-up mode, the power-on start-up time of the chip and the restart time of the chip are fixed and un-adjustable. What&#39;s more, the power-on start-up speed of the chip is identical to the restart speed of the chip. For example, when the power-on start-up is faster, the restart time will be shorter, thus resulting in larger input power during the restart and more power consumption. If the restart speed is lowered in order to decrease the power consumption during the restart, the power-on start-up speed will also be lowered, and may come to such a level that does not meet the application requirements. 
     SUMMARY 
     The present disclosure aims at overcoming the defects in the prior art, and providing a high voltage start-up circuit with adjustable start-up time, which effectively solves the contradiction between the power-on start-up and the restart. The present disclosure is capable of adjusting the power-on start-up time and the restart time of different chips according to application requirements, thereby realizing better application effects. 
     The objectives of the present disclosure are achieved by the following technical schemes: 
     According to one embodiment, a high voltage start-up circuit with adjustable start-up time includes a first NMOS transistor, a second NMOS transistor, a diode, a first resistor, a second resistor, a third resistor, a first comparator and a first counter; wherein the drain electrode of the first NMOS transistor is connected with a first terminal of the first resistor, the gate electrode of the second NMOS transistor and the negative terminal of the diode; the source electrode of the first NMOS transistor, together with the positive terminal of the diode, is connected to the power ground; the drain electrode of the second NMOS transistor, together with a second terminal of the first resistor, is connected with a port SW of a chip; the source electrode of the second NMOS transistor, together with a first terminal of the second resistor, is connected with a power port VDD of the chip; a second terminal of the second resistor is connected with a first terminal of the third resistor and a first input end of the first comparator; a second terminal of the third resistor is connected to the power ground; an output end of the first comparator is connected with an input end of the first counter; a first output end and a second output end of the first counter are respectively configured to be connected with a PWM controller; the first comparator is configured to detect voltage level of the power port VDD of the chip and generate a control signal Ctrl 1 ; the first counter is configured to count the number of rising edges or falling edges of the control signal Ctrl 1 , and generate a first initial start-up enable signal to regulate the power-on start-up time of the chip and a first restart enable signal to regulate the restart time of the chip. 
     Further, controlled by an output signal of the first comparator, a second input end of the first comparator is configured to select either an input of a threshold value K×VTH 1  or an input of a threshold value K×VTH 2 , wherein the input of the threshold value K×VTH 1  and the input of the threshold value K×VTH 2  are generated by the chip; ratio K is the voltage division ratio for the VDD voltage, which depends on a circuit structure constructed by the second resistor and the third resistor, wherein: 
               K   =       R   3         R   2     +     R   3           ;         
VTH 1  is a threshold value of the VDD voltage when the control signal Ctrl 1  inverts to a high level, VTH 2  is a threshold value of the VDD voltage when the control signal Ctrl 1  inverts to a low level, wherein VTH 1  is greater than VTH 2 ; the threshold value VTH 2  is greater than a threshold value of the VDD voltage set for an event of an internal power down of the chip; when the output signal of the first comparator is a high level, the second input end thereof selects the input of the threshold value K×VTH 2 ; when the output signal of the first comparator is a low level, the second input end thereof selects the input of the threshold value K×VTH 1 .
 
     Further, the control signal Ctrl 1  controls the high voltage start-up circuit to work or stop working, thus causing a rise or a fall of the VDD voltage, thereby generating an inversion of the the control signal Ctrl 1 ; type and number of the edges of the control signal Ctrl 1 , which are counted by the first counter, are configurable. 
     Further, for the power-on start-up, the type and number of the edges of the control signal Ctrl 1  is configured to be falling edge and N 1 , wherein N 1  can be any positive integer; for the restart, the type and number of the edges of the control signal Ctrl 1 , is configured to be falling edge and N 2 , wherein N 2  can be any positive integer. 
     During the power-on start-up period, the high voltage start-up circuit works in the rise period from the VDD voltage to the threshold value VTH 1 , and stops working in the fall period from the threshold value VTH 1  to the threshold value VTH 2 . After the control signal Ctrl 1  has experienced N 1  (N 1  can be any positive integer) rising edges or falling edges, the first initial start-up enable signal is activated. After the VDD voltage reaches the threshold value VTH 1  again and the chip&#39;s start-up is completed, the chip goes into the normal working stage. If an abnormal event occurs at any time instant thereafter, the high voltage start-up circuit shields the normal output of the chip. As the energy transmission is ceased, the VDD voltage begins to fall; when it falls to the threshold value VTH 2 , the control signal Ctrl 1  is triggered to be active and the high voltage start-up circuit begins to work; after a period of time, the VDD voltage is charged up to the threshold value VTH 1 , and the high voltage start-up circuit stops working. At this time instant, as the normal output of the chip is still shielded, the VDD voltage begins to fall once again. The process mentioned above is repeated again and again. During this period of time, the first counter counts the number of the rising edges or the falling edges of the control signal Ctrl 1 . When the first counter counts up to N 2  (N 2  can be any positive integer), the first restart enable signal is activated. If the abnormal event has been eliminated at this time instant, after the VDD voltage is charged up to the threshold value VTH 1 , the restart process ends; if the abnormal event has not been eliminated yet, the VDD voltage begins to fall once again, and the chip goes into the restart stage; when the first counter counts up to N 2 , the first restart enable signal is activated again to make a judgment. The threshold value VTH 2  is greater than the threshold value of VDD set for the event of the internal power down, so the internal power will never power down during the restart stage, and the internal circuit keeps its state all the time for performing the regular detection of the high voltage start-up circuit. 
     According to another embodiment, the high voltage start-up circuit further includes a second comparator, a second counter, a one-of-two data selector, and an OR gate; wherein a first input end of the second comparator is connected with the second terminal of the second resistor; an output end of the second comparator is connected with a second input end of the one-of-two data selector and an input end of the second counter; a first output end and a second output end of the second counter are respectively configured to be connected with the PWM controller; a first input end of the one-of-two data selector is connected with the output end of the first comparator; the selection terminal of the one-of-two data selector is connected with an output end of the OR gate; a first input end and a second input end of the OR gate are respectively connected with the first output end and the second output end of the first counter; the second comparator is configured to detect the voltage level of the power port VDD and generate a control signal Ctrl 2 , wherein the control signal Ctrl 2  is an internal power signal or an indication signal of the internal power; the second counter is configured to count the number of rising edges or falling edges of the control signal Ctrl 2 , and generate a second initial start-up enable signal and a second restart enable signal. 
     Further, an output end of the one-of-two data selector is connected with the gate electrode of the first NMOS transistor. 
     Further, controlled by an output signal of the second comparator, a second input end of the second comparator is configured to select either an input of a threshold value K×VTH 3  or an input of a threshold value K×VTH 4 , wherein the input of the threshold value K×VTH 3  and the input of the threshold value K×VTH 4  are generated by the chip; ratio K is the voltage division ratio for the VDD voltage, which depends on a circuit structure constructed by the second resistor and the third resistor, wherein: 
               K   =       R   3         R   2     +     R   3           ;         
VTH 3  is a threshold value of the VDD voltage when the control signal Ctrl 2  inverts to a high level, namely, a threshold value of the VDD voltage when an internal power is set up, VTH 4  is a threshold value of the VDD voltage when the control signal Ctrl 2  inverts to a low level, namely, a threshold value of the VDD voltage when the internal power powers down, wherein VTH 3  is greater than VTH 4 , and VTH 1  is greater than VTH 2 , and VTH 2  is greater than VTH 4 ; when the output signal of the second comparator is a high level, the second input end of the second comparator selects the input of the threshold value K×VTH 4 ; when the output signal of the second comparator is a low level, the second input end of the second comparator selects the input of the threshold value K×VTH 3 .
 
     Further, the second comparator is configured to detect the voltage level of the power port VDD and generate a control signal Ctrl 2 , the first comparator is configured to detect the voltage level of the power port VDD and generate the control signal Ctrl 1 ; the control signal Ctrl 2  and the control signal Ctrl 1  are selected to control the high voltage start-up circuit to work or stop working, thus causing a rise or a fall of the VDD voltage, thereby generating an inversion of the control signal Ctrl 1  or the control signal Ctrl 2 ; during a power-on start-up stage, if the first initial start-up enable signal is inactive, the control signal Ctrl 1  controls the high voltage start-up circuit to work or not work; if the first initial start-up enable signal is active, the control signal Ctrl 2  controls the high voltage start-up circuit to work or not work; during a restart stage, if the first restart enable signal is inactive, the control signal Ctrl 1  controls the high voltage start-up circuit to work or not work; if the first restart enable signal is active, the control signal Ctrl 2  controls the high voltage start-up circuit to work or not work. 
     Further, the type and number of the edges of the control signal Ctrl 2 , which are counted by the second counter, are configurable; for the power-on start-up, the type and number of the edges of the control signal Ctrl 2  is configured to be a falling edge and N 3 , wherein N 3  can be any positive integer; when the chip restarts after an abnormal event, the type and number of the edges of the control signal Ctrl 2  is configured to be a falling edge and N 4 , wherein N 4  can be any positive integer. 
     VTH 3  is a threshold value of the VDD voltage when the internal power is set up, VTH 4  is a threshold value of the VDD voltage when the internal power powers down. During the power-on start-up period, the VDD voltage continuously rises and reaches the threshold value VTH 3 , the control signal Ctrl 2  inverts to a high level 1 and the internal power of the chip is set up. When the VDD voltage continuously rises and reaches the threshold value VTH 1 , the control signal Ctrl 1  inverts to a high level 1 and the high voltage start-up circuit stops working. But at this time instant, controlled by the high voltage start-up circuit, the normal output of the chip is shielded, so the VDD voltage starts to fall. When the VDD voltage falls to the threshold value VTH 2 , the control signal Ctrl 2  inverts to a low level 0; the high voltage start-up circuit starts to work; and the VDD voltage rises once again. The process mentioned above is repeated again and again. During this period, the first counter counts the number of the rising edges or the falling edges of the control signal Ctrl 1 . When the first counter counts up to N 1  (N 1  can be any positive integer), a signal is generated to choose the control signal Ctrl 2  as the control signal controlling the high voltage start-up circuit to work again. When the VDD voltage falls to the threshold value VTH 4 , the internal power powers down; the control signal Ctrl 2  inverts to a low level 0; the high voltage start-up circuit starts to work, and the VDD voltage rises once again. The whole process mentioned above is repeated again and again. During this period, the second counter counts the number of the rising edges or the falling edges of the control signal Ctrl 2 . When the second counter counts up to N 3  (N 3  can be any positive integer), the first and second initial start-up enable signal are active. When the VDD voltage rises to the threshold value VTH 1 , the power-on start-up stage is completed, and the chip goes into the normal working stage. If an abnormal condition occurs thereafter, the chip goes into the restart stage. When the VDD voltage falls to the threshold value VTH 2 , the control signal Ctrl 1  inverts to a low level 0; the high voltage start-up circuit starts to work; and the VDD voltage rises again. The process is repeated again and again. During this period, the first counter counts the number of the rising edges or the falling edges of the control signal Ctrl 1 . When the first counter counts up to N 2  (N 2  can be any positive integer), a signal is generated to choose the control signal Ctrl 2  as the control signal controlling the high voltage start-up circuit to work again. When the VDD voltage falls to the threshold value VTH 4 , the internal power powers down; the control signal Ctrl 2  inverts to a low level 0; the high voltage start-up circuit starts to work, and the VDD voltage rises once again. This process is repeated again and again. During this period, the second counter counts the number of the rising edges or the falling edges of the control signal Ctrl 2 . When the second counter counts up to N 4  (N 4  can be any positive integer), the first and second restart enable signals are active. The restart enable signals start the judging for the current states of the internal circuit. If the abnormal event has been eliminated, after the VDD voltage reaches the threshold value VTH 1 , the restart process ends. The chip resumes normal working. If the abnormal event has not been eliminated, the restart process described above will be repeated until the abnormal event is eliminated at one time instant during a restart period, and the restart process of the chip ends. 
     The substantive features and notable progresses of the present disclosure are as follows:
         1. With the high voltage start-up circuit with adjustable start-up time of the present disclosure, the power-on start-up time of the chip and the restart time of the chip can be adjusted flexibly, which effectively solves the contradiction between the power-on start-up and the restart. According to application requirements, different start-up times and restart times can be adjusted flexibly, thus achieving better application effects.   2. The high voltage start-up circuit can be used in self-powered high voltage applications, wherein, a self-powered circuit is included in the high voltage start-up circuit. The self-contained counter of the high voltage start-up circuit and the counter of the self-powered circuit count are implemented in a nested manner, thereby adjusting the start-up time and the restart time more flexibly, and obtaining better application effects.       

    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a more complete understanding, reference is now made to the following description taken in conjunction with the accompanying Drawings in which: 
         FIG. 1  is a schematic diagram illustrating working waves of the traditional start-up circuit; 
         FIG. 2  is a schematic diagram illustrating the high voltage start-up circuit with adjustable start-up time according to one embodiment of the present invention; 
         FIG. 3  is a schematic diagram illustrating working waves of the high voltage start-up circuit of  FIG. 2 ; 
         FIG. 4  is a schematic diagram illustrating the high voltage start-up circuit with adjustable start-up time according to another embodiment of the present invention; and 
         FIG. 5  is a schematic diagram illustrating working waves of the high voltage start-up circuit of  FIG. 4 . 
     
    
    
     DETAILED DESCRIPTION 
     The present disclosure will now be described in more detail with reference to the accompanying figures and embodiments. 
     The present disclosure provides a high voltage start-up circuit with adjustable start-up time, which is capable of flexibly adjusting the power-on start-up time of the chip and the restart time of the chip, so as to meet different application requirements. 
     As shown in  FIG. 2 , the high voltage start-up circuit with adjustable start-up time includes a first NMOS transistor M 1 , a second NMOS transistor M 2 , a diode D 1 , a first resistor R 1 , a second resistor R 2 , a third resistor R 3 , a first comparator  101  and a first counter  102 . The drain electrode of the first NMOS transistor M 1  is connected with a first terminal of the first resistor R 1 , the gate electrode of the second NMOS transistor M 2  and the negative terminal of the diode D 1 . The gate electrode of the first NMOS transistor M 1  is connected with the output end of the first comparator  101  and the input end of the first counter  102 . The source electrode of the first NMOS transistor M 1 , together with the positive terminal of the diode D 1 , is connected to the power ground. The drain electrode of the second NMOS transistor M 2 , together with a second terminal of the first resistor R 1 , is connected with the port SW of the chip. The source electrode of the second NMOS transistor M 2 , together with the first terminal of the second resistor R 2 , is connected with the power port VDD of the chip. The second terminal of the second resistor R 2  is connected with the first terminal of the third resistor R 3  and the first input end of the first comparator  101 . The second terminal of the third resistor R 3  is connected to the power ground. The output end of the first comparator  101  is connected with the input end of the first counter  102 . The first output end and the second output end of the first counter  102  are respectively connected with a PWM controller  103 , which is not included in the high voltage start-up circuit and is built in the application chip. The first comparator  101  detects the voltage level of the power port VDD of the chip and generates a control signal Ctrl 1 . The first counter  102  counts the number of the rising edges or falling edges of the control signal Ctrl 1  and generates a first initial start-up enable signal to regulate the power-on start-up time of the chip and a first restart enable signal to regulate the restart time of the chip. 
     Controlled by the output signal from the output end of the first comparator  101 , the second input end of the first comparator  101  selects either an input of the threshold value K×VTH 1  or an input of the threshold value K×VTH 2 , wherein the input of the threshold value K×VTH 1  and the input of the threshold value K×VTH 2  are generated by the chip. K is the voltage division ratio for the VDD voltage, which depends on the circuit structure constructed by the second resistor R 2  and the third resistor R 3 , wherein: 
             K   =         R   3         R   2     +     R   3         .           
VTH 1  is a threshold value of the VDD voltage when the control signal Ctrl 1  inverts to a high level, VTH 2  is the threshold value of the VDD voltage when the control signal Ctrl 1  inverts to a low level, wherein VTH 1  is greater than VTH 2 , and VTH 2  is greater than the threshold value of the VDD voltage set for the event of the internal power down of the chip. When the output signal of the first comparator  101  is a high level, the second input end of the first comparator  101  selects the input of the threshold value K×VTH 2 ; when the output signal of the first comparator  101  is a low level, the second input end of the first comparator  101  selects the input of the threshold value K×VTH 1 .
 
     The control signal Ctrl 1  controls the high voltage start-up circuit to work or stop working, thus causing a rise or a fall of the VDD voltage, thereby generating an inversion of the the control signal Ctrl 1 . The type and the number of the edges of the control signal Ctrl 1 , which are counted by the first counter  102 , are configurable. For a power-on start-up, the type and number of the edges of the control signal Ctrl 1  is configured to be a falling edge and N 1 , wherein N 1  can be any positive integer; for a restart, the type and number of the edges of the control signal Ctrl 1  is configured to be a falling edge and N 2 , wherein N 2  can be any positive integer. 
       FIG. 3  shows the working waves of the above mentioned high voltage start-up circuit with adjustable start-up time. During the time span T 1 , the chip is powered on and started up, the high voltage start-up circuit works in the rise period from the VDD voltage to the threshold value VTH 1 , and stops working in the fall period from the threshold value VTH 1  to the threshold value VTH 2 . After the control signal Ctrl 1  has experienced N 1  rising edges or falling edges (what is shown in the working waves are falling edges, and N 1  is a positive integer), the first initial start-up enable signal is activated. The start-up of the chip is completed at the end time instant of the time span T 1 , and, at this time instant, the VDD voltage reaches the threshold value VTH 1 . Thereafter the chip goes into the normal working stage of the time span T 2 . If an abnormal event occurs at any time instant thereafter, the high voltage start-up circuit shields the normal output of the chip. As the energy transmission is ceased, the VDD voltage begins to fall; when it falls to the threshold value VTH 2 , the control signal Ctrl 1  is triggered to be active and the high voltage start-up circuit begins to work; after a period of time, the VDD voltage is charged up to the threshold value VTH 1 , and the high voltage start-up circuit stops working. At this time instant, as the normal output of the chip is still shielded, the VDD voltage begins to fall once again. The process mentioned above is repeated again and again until the end time instant of the time span T 3 . During the time span T 3 , the first counter counts the number of the rising edges or the falling edges (what is shown in the working waves are falling edges) of the control signal Ctrl 1 . When the first counter counts up to N 2 , the first restart enable signal is activated. If the abnormal event has not been eliminated yet, the VDD voltage begins to fall once again, and the chip goes into a restart stage again. When the first counter counts up to N 2 , the first restart enable signal is activated again. If the abnormal event has been eliminated at this time instant, after the VDD voltage is charged up to the threshold value VTH 1 , the restart process ends, as shown in the time span T 4 . Then the chip goes into the normal working stage of the time span T 5 . The threshold value VTH 2  is greater than the threshold value of VDD set for the internal power down, so the internal power will never power down during the restart stage, and the internal circuit keeps its state all the time for performing the regular detection of the high voltage start-up circuit. 
     As shown in  FIG. 4 , based on the circuit of  FIG. 2 , the high voltage start-up circuit with adjustable start-up time further includes a second comparator  201 , a second counter  202 , a one-of-two data selector  203 , and an OR gate. A first input end of the second comparator  201  is connected with the second terminal of the second resistor R 2 . The output end of the second comparator  201  is connected with the second input end of the one-of-two data selector  203  and the input end of the second counter  202 . The first output end and the second output end of the second counter  202  are respectively connected with the PWM controller  103 . The first input end of the one-of-two data selector  203  is connected with the output end of the first comparator  201 . The selection terminal Sel of the one-of-two data selector  203  is connected with the output end of the OR gate. The first input end and the second input end of the OR gate are respectively connected with the first output end and the second output end of the first counter  102 . The output end of the one-of-two data selector  203  is connected with the gate electrode of the first NMOS transistor M 1 . The second comparator  201  detects the voltage level of the power port VDD and generates a control signal Ctrl 2 . The control signal Ctrl 2  is an internal power signal or an indication signal of the internal power. The second counter  202  counts the number of the rising edges or the falling edges of the control signal Ctrl 2 , and generates a second initial start-up enable signal and a second restart enable signal. The high voltage start-up circuit makes use of the two sets of enable signals in a nested manner, so that the high voltage start-up circuit is able to adjust the power-on start-up time of the chip and the restart time of the chip more precisely. 
     Controlled by the output signal from the output end of the second comparator  201 , the second input end of the second comparator  201  selects either an input of the threshold value K×VTH 3  or an input of the threshold value K×VTH 4 , wherein the input of the threshold value K×VTH 3  and the input of the threshold value K×VTH 4  are generated by the chip. Ratio K is the voltage division ratio for the VDD voltage, which depends on the circuit structure constructed by the second resistor R 2  and the third resistor R 3 , wherein: 
             K   =         R   3         R   2     +     R   3         .           
The threshold value VTH 3  is the threshold value of the VDD voltage when the control signal Ctrl 2  inverts to a high level, namely, the threshold value of the VDD voltage when the internal power is set up. The threshold value VTH 4  is the threshold value of the VDD voltage when the control signal Ctrl 2  inverts to a low level, namely, the threshold value of the VDD voltage when the internal power powers down, wherein VTH 3  is greater than VTH 4 , VTH 1  is greater than VTH 2 , and VTH 2  is greater than VTH 4 . The threshold value VTH 1  is the threshold value of the VDD voltage when the control signal Ctrl 1  inverts to a high level. The threshold value VTH 2  is the threshold value of the VDD voltage when the control signal Ctrl 1  inverts to a low level. When the output signal of the second comparator  201  is a high level, the second input end of the second comparator  201  selects the input of the threshold value K×VTH 4 ; when the output signal of the second comparator  201  is a low level, the second input end of the second comparator  201  selects the input of the threshold value K×VTH 3 .
 
     The second comparator  201  detects the voltage level of the power port VDD and generates a control signal Ctrl 2 , the first comparator  101  detects the voltage level of the power port VDD and generates a control signal Ctrl 1 . The control signal Ctrl 2  and the control signal Ctrl 1  are selected to control the high voltage start-up circuit to work or stop working, thus causing a rise or a fall of the VDD voltage, thereby generating an inversion of the control signal Ctrl 1  or the control signal Ctrl 2 . During the power-on start-up stage, if the first initial start-up enable signal is inactive, the control signal Ctrl 1  controls the high voltage start-up circuit to work or not work; if the first initial start-up enable signal is active, the control signal Ctrl 2  controls the high voltage start-up circuit to work or not work. During the restart stage, if the first restart enable signal is inactive, the control signal Ctrl 1  controls the high voltage start-up circuit to work or not work; if the first restart enable signal is active, the control signal Ctrl 2  controls the high voltage start-up circuit to work or not work. The type and the number of the edges of the control signal Ctrl 2 , which are counted by the second counter  202 , are configurable. For the power-on start-up, the type and number of the edges of the control signal Ctrl 2  are configured to be a falling edge and N 3 , wherein N 3  can be any positive integer; when the chip restarts after an abnormal event, the type and number of the edges of the control signal Ctrl 2  are configured to be a falling edge and N 4 , wherein N 4  can be any positive integer. 
       FIG. 5  shows the working waves of the high voltage start-up circuit of  FIG. 4 . During the time span T 1 , the chip is powered on and started up. When the VDD voltage continuously rises and reaches the threshold value VTH 3 , the control signal Ctrl 2  inverts to a high level 1 and the internal power of the chip is set up. When the VDD voltage continuously rises and reaches the threshold value VTH 1 , the control signal Ctrl 1  inverts to a high level 1 and the high voltage start-up circuit stops working. But at this time instant, controlled by the high voltage start-up circuit, the normal output of the chip is shielded, so the VDD voltage starts to fall. When the VDD voltage falls to the threshold value VTH 2 , the control signal Ctrl 2  inverts to a low level 0; the high voltage start-up circuit starts to work; and the VDD voltage rises once again. The process mentioned above is repeated again and again. During this period, the first counter counts the number of the rising edges or the falling edges (what is shown in the working waves are falling edges) of the control signal Ctrl 1 . When the first counter counts up to N 1  (N 1  can be any positive integer), a signal is generated to choose the control signal Ctrl 2  as the control signal controlling the high voltage start-up circuit to work again. When the VDD voltage falls to the threshold value VTH 4 , the internal power powers down; the control signal Ctrl 2  inverts to a low level 0; the high voltage start-up circuit starts to work, and the VDD voltage rises once again. The whole process mentioned above is repeated again and again. During this period, the second counter counts the number of the rising edges or the falling edges of the control signal Ctrl 2 . When the second counter counts up to N 3  (N 3  can be any positive integer), the first and second initial start-up enable signal are activated. When the VDD voltage rises to the threshold value VTH 1 , the power-on start-up stage is completed, and the chip goes into the normal working stage of the time span T 2 . If an abnormal condition occurs thereafter, the chip goes into the restart stage of the time span T 3 . The VDD voltage falls; when the VDD voltage falls to the threshold value VTH 2 , the control signal Ctrl 1  inverts to a low level 0; the high voltage start-up circuit starts to work; and the VDD voltage rises again. The process is repeated again and again. During this period, the first counter counts the number of the rising edges or the falling edges of the control signal Ctrl 1 . When the first counter counts up to N 2  (N 2  can be any positive integer), a signal is generated to choose the control signal Ctrl 2  as the control signal controlling the high voltage start-up circuit to work again. When the VDD voltage falls to the threshold value VTH 4 , the internal power powers down; the control signal Ctrl 2  inverts to a low level 0; the high voltage start-up circuit starts to work, and the VDD voltage rises once again. This process is repeated again and again. During this period, the second counter counts the number of the rising edges or the falling edges of the control signal Ctrl 2 . When the second counter counts up to N 4  (N 4  can be any positive integer), the first and second restart enable signals are active. The restart enable signals start the judging for the current states of the internal circuit. If the abnormal event has been eliminated, after the VDD voltage reaches the threshold value VTH 1 , the restart process ends. The restart of the chip is completed and the chip resumes normal working in the time span T 4 . 
     The high voltage start-up circuit with adjustable start-up time of the present disclosure could flexibly adjust the power-on start-up time of the chip and the restart time of the chip, and effectively solve the contradiction between the power-on start-up and the restart. According to application requirements, the present disclosure is capable of adjusting the start-up time and the restart time flexibly, thus realizing better application effects. 
     It should be understood by those skilled in the art that the present invention is not restricted to the preferred embodiments, and that various modifications or improvement may be made based on the principles of the present invention without departing from the scope of the present invention.