Abstract:
A high voltage control switch including a voltage controller and a control switch is provided. The high voltage control switch splits the control switching of high voltages into two ranges. The voltage controller determines the on and off voltages appropriate for the application based on the range the input signal is in. The control switch then outputs the appropriate voltages determined by the voltage controller based on a logic input. As such, the high voltage control switch provides fast and reliable operation for high voltage switching applications.

Description:
RELATED APPLICATIONS 
       [0001]    This application claims priority to U.S. Provisional Patent Application No. 61/031,568, filed Feb. 26, 2008, incorporated by reference herein. 
     
    
     FIELD OF INVENTION 
       [0002]    The present invention relates to a control circuit, more particularly, a high voltage control switch circuit. 
       BACKGROUND 
       [0003]    It is well known in the art that transistors are often used to perform standard switching functions in integrated circuits. While modern day transistors make reliable switches in many circuit applications, there are also many circuit applications that place severe operational constraints on the switch transistor. In particular, many applications require the interfacing of transistors with signals having magnitudes significantly greater than the power supply voltage for the transistor. 
         [0004]    The interfacing of a transistor with signals having magnitudes greater than the voltage rating of the transistor puts the transistor at risk for a voltage breakdown, and also decreases the switching speed of the transistor when the channels of transistors become too narrow for the necessary current flow. Transistors with high voltage ratings exist for such applications, but are accordingly restricted to only high voltage switching applications. As such, a control switch circuit that can handle high voltage switching applications, while retaining the versatility of handling lower voltage applications is desired. 
       SUMMARY 
       [0005]    A high voltage control switch, including a high voltage controller and a control switch is provided. The high voltage control switch splits the control switching of high voltages into two ranges. The voltage controller determines the on and off voltages appropriate for the application based on the range the input signal is in. The control switch then outputs the appropriate voltages determined by the voltage controller based on a logic input. 
         [0006]    In one embodiment, the high voltage controller comprises inverter-like circuits for the determination of both the on and the off voltages. In another embodiment, the high voltage controller comprises differential amplifier circuits. Further, alternative embodiments can be hybrids comprising both an inverter-like circuit and a differential amplifier circuit. 
         [0007]    These features will become apparent to those of ordinary skill in the art by reading the following detailed description, with appropriate reference to the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]      FIG. 1  is a circuit diagram of a high voltage control switch, according to an embodiment of the present invention. 
           [0009]      FIG. 2  is a circuit diagram of a high voltage controller, according to an embodiment of the present invention. 
           [0010]      FIG. 3  is a circuit diagram of a high voltage controller, according to an alternative embodiment of the present invention. 
           [0011]      FIG. 4  is a circuit diagram of a high voltage controller, according to an alternative embodiment of the present invention. 
           [0012]      FIG. 5  is a circuit diagram of a control switch, according to an embodiment of the present invention. 
           [0013]      FIG. 6  is a test result plot of a high voltage control switch, according to an embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0014]      FIG. 1  is a circuit diagram of a high voltage control switch  100 , according to an embodiment of the present invention. The high voltage control switch  100  comprises a high voltage controller  102 , a control switch  104 , a sense input  106 , a Von signal  108 , a Voff signal  110 , a logic input  112 , an output  114 , an inverted output  115 , a −2V source  116 , a 5V source  118 , an 8V source  120 , and a 15V source  122 . The sense input  106  reads the input signal to the high voltage control switch  100 . The Von signal  108  and Voff signal  110  represent the voltage used to turn a device on or off at the outputs  114  and  115 . The logic input  112  is a binary signal that determines whether the device at the outputs  114  and  115  should be switched on or off. Note that the specific voltage values discussed here are simply values used in a working model of an exemplary embodiment of the present invention, which has been designed to receive input signals in the range of 0-13V. Alternative voltages can be used to adapt to different applications. 
         [0015]    The high voltage controller  102  receives inputs from the sense input  106 , the −2V source  116 , the 5V source  118 , the 8V source  120 , and the 15V source  122 , and outputs the Von signal  108  and the Voff signal  110 . The control switch  104  receives inputs from the logic input  112 , the 5V source  118 , as well as the Von signal  108  and Voff signal  110  from the high voltage controller  102 . 
         [0016]    In operation, the high voltage controller  102  reads the sense input  106  and based on the input signal, determines the appropriate Von signal  108  and Voff signal  110 . In the working model of the present invention presented here, if the sense input  106  is greater than 5V, the high voltage controller  102  will use the 15V source  122  for the Von signal  108 , and the 5V source  118  for the Voff signal  110 . The choice of using the 15V source  122  for the Von signal  108  when the input signal at the sense input  106  has a maximum of 13V is not arbitrary. A 15V source  122  is selected because it is sufficiently higher than 13V without entering a voltage breakdown stage. The 5V source  118  is selected for the Voff signal  110  because while it is not lower than 5V, it is sufficiently low. This is because the threshold voltage for the sense input  106  is 5V such that if the input signal is greater than 5V, a 5V Voff signal will be sufficiently low to switch the device off. 
         [0017]    On the other hand, when the sense input  106  is less than 5V, the high voltage controller  102  will use the 8V source  120  for the Von signal  108 , and the −2V source  116  for the Voff signal  110 . This is so the Von signal  108  will be sufficiently greater than 5V, and the Voff signal  110  will be sufficiently low while avoiding issues resulting from current leakage. 
         [0018]    The Von signal  108  and Voff signal  110  are received by the control switch  104 . The control switch  104  reads the logic input  112  and, depending on whether the logic input  112  indicates switching the device on or off, provides the outputs  114  and  115  with the Von signal  108  or the Voff signal  110 . 
         [0019]    Based on the high voltage control switch  100  described above, there are four possible outputs based on two binary inputs. If the sense input  106  is greater than 5V and the logic input  112  indicates “on,” the output  114  will be 15V. If the sense input  106  is greater than 5V and the logic input  112  indicates “off,” the output will be 5V. If the sense input  106  is less than 5V and the logic input  112  indicates “on,” the output will be 8V. And finally, if the sense input  106  is less than 5V and the logic input  112  indicates “off,” the output will be −2V. Table 1 summarizes the possible input and output combinations. 
         [0000]    
       
         
               
               
               
             
               
               
               
               
             
           
               
                   
                 TABLE 1 
               
               
                   
                   
               
               
                   
                 Von 108 
                 Voff 110 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 Sense input 106 &gt;5 V 
                 15 V 
                   5 V 
               
               
                   
                 Sense Input 106 &lt;5 V 
                  8 V 
                 −2 V 
               
               
                   
                   
               
             
          
         
       
     
         [0020]      FIG. 2  is a circuit diagram of a high voltage controller  200  that may be used as the high voltage controller  102  in  FIG. 1 , according to an embodiment of the present invention. 
         [0021]    The high voltage controller circuit  200  comprises a Von controller circuit  202  and a Voff controller circuit  250 . In this embodiment, both the Von controller circuit  202  and the Voff controller circuit  250  are inverter-like circuits, comprising stacked transistors. 
         [0022]    The Von controller circuit  202  includes a 15V source  204 , a current source  206 , an input signal  208 , a 5V source  210 , an 8V source  212 , and a ground source  214  as the inputs, and a Von signal  240  as the output. When referencing  FIG. 1 , the 15V source  204  corresponds to the 15V source  122 , the input signal  208  corresponds to the sense input  106 , the 5V source  210  corresponds to the 5V source  118 , the 8V source  212  corresponds to the 8V source  120 , and the Von signal output  240  corresponds to the Von signal  108 . 
         [0023]    The Von controller circuit  202  also includes p-channel transistors  216 ,  218 ,  220 ,  222 ,  224 ,  226 , and  228 ; n-channel transistors  230  and  232 ; resistors  234  and  236 ; and capacitor  238 . The sources of p-channel transistors  216 ,  218 ,  220 ,  222  and  224  are each coupled to the 15V source  204 . The gates of p-channel transistors  216 ,  218  and  220  are each coupled to the current source  206 , as is the drain of p-channel transistor  216 . The drain of p-channel transistor  218 , the source of p-channel transistor  226 , and the gate of p-channel transistor  222  all share a common node. The gate and drain of p-channel transistor  226  are both coupled to the source of p-channel transistor  228 . The gates of p-channel transistor  228  and n-channel transistor  230  are both coupled to the input signal  208  by the resistor  234 . The drain of p-channel transistor  228  is coupled to the 5V source  210 , while the source of n-channel  230  is coupled to the 5V source  210  by the resistor  236  and to the ground source  214  by the capacitor  238 . The drains of p-channel transistors  220 ,  222  and n-channel transistor  230  and the gates of p-channel transistor  224  and n-channel transistor  232  all share a common node. The source of n-channel transistor  232  is coupled to the 8V source  212 , and the drains of p-channel transistor  224  and n-channel transistor  232  are both coupled to the Von signal output  240 . The resistor  234  may have a resistance of approximately 1 kilo-Ohms and the resistor  236  may have a resistance of approximately 10 kilo-Ohms. The resistor  236  can alternatively be replaced by a short circuit for faster performance. The capacitor may have a capacitance of approximately 10 pico-Farads. 
         [0024]    The Voff controller circuit  250  includes a −2V source  256  in addition to the inputs in Von controller circuit  202 , and a Voff signal  270  as the output. When referencing  FIG. 1 , the −2V source  256  corresponds to the −2V source  116 , and the Voff signal output  270  corresponds to the Voff signal  110 . 
         [0025]    The Voff controller circuit  250  also includes p-channel transistors  260  and  262 , n-channel transistors  258 ,  264 , and  266 , and a resistor  268 . The gates of n-channel transistor  258  and p-channel transistor  260  are both coupled to the input signal  208 . The drain of n-channel transistor  258  and the sources of p-channel transistors  260  and  262  are each coupled to the 5V source  210 . The source of n-channel transistor  258  and the gate of n-channel transistor  264  are both coupled to the −2V source  256  by the resistor  268 . The drains of p-channel transistor  260  and n-channel transistor  264  and the gates of p-channel transistor  262  and n-channel transistor  266  all share a common node. The sources of n-channel transistors  264  and  266  are both coupled to the −2V source  256  and the drains of p-channel transistor  262  and n-channel transistor  266  are both coupled to the Voff signal output  270 . The resistor  268  may have a resistance of approximately 50 kilo-Ohms. 
         [0026]      FIG. 3  is a circuit diagram of a high voltage controller  300  that may be used as the high voltage controller  102  in  FIG. 1 , according to an embodiment of the present invention. 
         [0027]    The high voltage controller circuit  300  comprises a Von controller circuit  302  and a Voff controller circuit  350 . In this embodiment, both the Von controller circuit  302  and the Voff controller circuit  350  are differential amplifier circuits. 
         [0028]    The Von controller circuit  302  includes a 15V source  304 , a current source  306 , an input signal  308 , a 5V source  310 , an 8V source  312 , and a −2V source  314  as the inputs and a Von signal  342  as the output. When referencing  FIG. 1 , the 15V source  304  corresponds to the 15V source  122 , the input signal  308  corresponds to the sense input  106 , the 5V source  310  corresponds to the 5V source  118 , the 8V source  312  corresponds to the 8V source  120 , the −2V source  314  corresponds to the −2V source  116 , and the Von signal output  342  corresponds to the Von signal  108 . 
         [0029]    The Von controller circuit  302  also includes p-channel transistors  316 ,  318 ,  320 ,  322 , and  328 , n-channel transistors  324 ,  326 ,  330 ,  332 ,  334 ,  336  and  338 , and resistor  340 . The sources of p-channel transistors  328 ,  316   318 ,  320  and  322  are each coupled to the 15V source  304 . The drain of p-channel transistor  328  is coupled to its gate and also to the drain of n-channel transistor  336 . The gate of n-channel transistor  330  is coupled to the signal input  308  by resistor  340 . The drain of the n-channel transistor  334  and the gates of n-channel transistors  334 ,  336  and  338  all share a common node and are coupled to the current source  306 . The sources of n-channel transistors  334 ,  336  and  338  are all coupled to the −2V source  314 . The sources of n-channel transistors  330  and  332  and the drain of n-channel transistor  338  all share a common node. The drains of p-channel transistor  316  and n-channel transistor  330  and the gates of p-channel transistors  316  and  322  all share a common node. The drains of p-channel transistor  318  and n-channel transistor  332  and the gates of p-channel transistors  318 ,  320  and n-channel transistor  324  all share a common node. The drains of p-channel transistor  320  and n-channel transistor  324 , and the gate of n-channel transistor  326  all share a common node. The gate of n-channel transistor  332  is coupled to the 5V source  310 , the sources of n-channel transistors  324  and  326  are both coupled to the 8V source  312 , and the drains of p-channel transistor  322  and n-channel transistor  326  are both coupled to the Von signal output  342 . The resistor  340  may have a resistance of approximately 1 kilo-Ohms. 
         [0030]    The Voff controller circuit  350  includes the inputs for Von controller circuit  302 , and a Voff signal  368  as the output. When referencing  FIG. 1 , the Voff signal output  368  corresponds to the Voff signal  110 . 
         [0031]    The Voff controller circuit  350  also includes p-channel transistors  354 ,  356 ,  360 , and  364  and n-channel transistors  358 ,  362 ,  366 . The source of p-channel transistor  354  is coupled to the 15V source  304 , and the gate of p-channel transistor  356  is coupled to the input signal  308 . The source of p-channel transistor  364  and the gate of p-channel transistor  360  are both coupled to the 5V source  310 , and the sources of n-channel transistors  358 ,  362 , and  366  are each coupled to the −2V source  314 . The gate of p-channel transistor  354  is connected to the gate and drain of the p-channel transistor  328  in the Von controller circuit  302 . The drain of p-channel transistor  354  and the sources of p-channel transistors  356  and  360  all share a common node. The gates of n-channel transistors  358  and  362 , the drain of p-channel transistors  360 , and the drain of n-channel transistor  362  all share a common node. The drains of p-channel transistor  356  and n-channel transistor  358  and the gates of p-channel transistor  364  and n-channel transistor  366  all share a common node. The drains of p-channel transistor  364  and n-channel transistor  366  are both coupled to the Voff signal output  368 . 
         [0032]    As mentioned before, high voltage controller circuit  200  comprises two inverter-like circuits, while high voltage controller circuit  300  comprises two differential amplifier circuits. While either of the high voltage controller circuits  200  and  300  can be used as the high voltage controller  102  in the high voltage control switch  100 , each has distinct characteristics. The key difference is that the high voltage controller circuit  300  with differential amplifier circuits operates faster than, but also consumes more current than the high voltage controller circuit  200 . 
         [0033]      FIG. 4  is a circuit diagram of a high voltage controller  400  that may be used as the high voltage controller  102  in  FIG. 1 , according to an embodiment of the present invention. The high voltage controller circuit  400  is a hybrid between the high voltage controller circuits  200  and  300 , implementing the inverter-like circuit  202  for the Von controller and the differential amplifier circuit  350  for the Voff controller. When combining the controllers, the gate of p-channel transistor  354  is coupled to the current source  206  or  306 . This hybrid high voltage controller provides a compromise between operation speed and current consumption. Similarly, the use of a differential amplifier circuit for the Von controller and an inverter-like circuit for the Voff controller is feasible. 
         [0034]      FIG. 5  is a circuit diagram of a control switch  500  that may be used as the control switch  104  in  FIG. 1 , according to an embodiment of the present invention. The control switch  500  includes a 5V source  502 , a logic input  504 , a ground source  506 , a Von signal input  508 , a Voff signal input  510 , an output  550 , and an inverted output  552 . When referencing  FIG. 1 , the 5V source  502  corresponds to the 5V source  118 , the logic input  504  corresponds to the logic input  112 , the Von signal input  508  corresponds to the Von signal  108 , the Voff signal  510  corresponds to the Voff signal  110 , the output  550  corresponds to the output  114 , and the inverted output  552  corresponds to the inverted output  115 . 
         [0035]    The control switch  500  also includes p-channel transistors  512 ,  520 ,  522 ,  524 ,  526 ,  528 , and  530 , n-channel transistors  514 ,  516 ,  518 ,  532 ,  534 ,  536 ,  538 ,  540 , and  542 , and resistors  544 ,  546 , and  548 . The gates of p-channel transistor  512  and n-channel transistors  514  and  532  are each coupled to the logic input  504 . The source and substrate of p-channel transistor  512  is coupled to the 5V source  502 . The gate and drain of n-channel transistor  536  and the gate of n-channel transistor  538  share a common node and are coupled to the 5V source  502  by resistor  544 . The sources and substrates of n-channel transistors  514 ,  536 , and  538  are each coupled to the ground source  506 . The drains of p-channel transistor  512  and n-channel transistor  514  are both coupled to the gate of n-channel transistor  534 . The sources of p-channel transistors  520 ,  522 ,  524 ,  526 ,  528 , and  530  are each coupled to the Von signal input  508 . The gates of p-channel transistors  520 ,  524 , and  530  and the drains of p-channel transistor  524  and n-channel transistor  534  all share a common node. Similarly, the gates of p-channel transistors  522 ,  526 , and  528  and the drains of p-channel transistor  522  and n-channel transistor  532  all share a common node. 
         [0036]    The sources of n-channel transistors  516 ,  518 ,  540 , and  542  are all coupled to the Voff signal input  510 . The sources and substrates of n-channel transistor  532  and  534  and the drain of n-channel transistor  538  all share a common node. The drains of p-channel transistor  520  and n-channel transistor  516  and the gates of n-channel transistors  516  and  540  all share a common node and are coupled to the Voff signal input  510  by the resistor  546 . Similarly, the drains of p-channel transistor  526  and n-channel transistor  518  and the gates of n-channel transistors  518  and  542  all share a common node and are coupled to the Voff signal input  510  by the resistor  548 . The drains of p-channel transistor  528  and n-channel transistor  540  are both coupled to the output  550 . Similarly, the drains of p-channel transistor  530  and n-channel transistor  542  are both coupled to the inverted output  552 . 
         [0037]    The resistor  544  may have a resistance of approximately 50 kilo-Ohms, and the resistors  546  and  548  may each have a resistance of approximately 20 kilo-Ohms. 
         [0038]    The voltage ratings of the transistors are optimally at least half of the intended input voltage range. In addition, when high breakdown voltage is needed, a DMOS transistor can be used. Further, a transistor package that includes a connector to the substrate is appropriate when such a connection is required. 
         [0039]      FIG. 6  is a test result plot  600  of a high voltage control switch, according to an embodiment of the present invention. The plot shows the voltage versus time relationship of the different operative modes of the high voltage control switch and supports the input and output combinations shown in Table 1. The plot includes the voltage traces of an input signal  602 , an output signal  604 , an inverted output  606 , a Von signal  608 , a Voff signal  610 , and a logic input  612 . 
         [0040]    The plot can be divided into two sections. A first section  620  is when the input signal  602  is greater than 5V, and a second section  640  is when the input signal  602  is less than 5V. Following the Von signal  608 , we see that it rises to 15V in the first section  620  and drops to 8V in the second section  640 . Similarly, the Voff signal  610  rises to 5V in the first section  620  and drops to −2V in the second section  640 . In both the first section  620  and second section  640 , the output  604  follows the Von signal  608  when the logic input  612  is high, and follows the Voff signal  610  when the logic input  612  is low. On the other hand, the inverted output  606  follows the Voff signal  610  when the logic input  612  is high, and follows the Von signal  608  when the logic input  612  is low. 
         [0041]    While exemplary embodiments have been described, persons of skill in the art will appreciate that variations may be made without departure from the scope and spirit of the invention. The true scope and spirit of the invention is defined by the appended claims, which may be interpreted in light of the foregoing.