Abstract:
The circuit of voltage multiplier with programmable output, which compares the feedback voltage of the output with a reference voltage, whether the pumping circuit functions to pump the output voltage or not is controlled by a clock generator so as to sustain the output voltage within a prescribed range, moreover, by using a voltage regulator to supply a stable output voltage to the load.

Description:
FIELD OF THE INVENTION 
   The present invention relates to a circuit of voltage multiplier, especially for a circuit of voltage multiplier with low-power-consumption and programmable output. 
   BACKGROUND OF THE INVENTION 
   DC power is the most frequently used voltage source for electronic equipments. For the use of electronic equipments with different driving voltages, a DC-DC converter usually will be used to change the magnitude of a voltage. Please refer to  FIG. 1 , which is a well-known DC-DC voltage converter. It is composed of a bandgap  1 , a pumping CKT  2 , and a regulator  3 . A user can choose the properties of the components according to the required supply voltage. Assume that the user needs a 7.2v output voltage Vout and a 2.4˜3.6 system voltage Vcc, who may choose a 1.2v bandgap  1  and a six-times pumping CKT  2 . The system voltage Vcc is first dropped to 1.2v by the bandgap  1 , then is pumped to the 7.2v output voltage by the six-times pumping CKT  2 , finally is regulated by the regulator  3  to supply the regulated 7.2v output voltage Vout. If customers do not mind the slight variation of the voltage, the regulator  3  can be not used. 
   The aforementioned voltage converter, which is dropped by the bandgap  1  and then pumped by the multiple pumping CKT  2  such that the power consumption is quite serious. Therefore, please refer to  FIG. 2 , an operation method that directly uses the system voltage Vcc to be the source voltage of the pumping CKT  2  has been developed recently. Similarly assume that the user needs a 7.2v output voltage Vout and a 2.4˜3.6 system voltage Vcc, who only needs a triple pumping CKT  2 , then regulated by the regulator  3  to supply a regulated 7.2v output voltage Vout. As a result, the operation efficiency for the pumping CKT  2  can be improved and the total power consumption is reduced. 
   In case the working voltage for the system voltage Vcc has a wider range whereas the operation method that directly uses the system voltage Vcc to be the source voltage of the pumping CKT  2  has to be adopted. For example, assume that a 5.0v output voltage Vout is needed whereas the system voltage Vcc is 2.0v˜3.6v, uses double pumping CKT  2  when the system voltage Vcc=3.0˜3.6v; uses triple pumping CKT  2  when the system voltage Vcc=2.0˜2.5v; when the system voltage Vcc=2.5˜3.0v then the multiple for the pumping CKT  2  should be switched between double and triple. Moreover, by way of the regulator  3  to drop and regulate the output voltage Vout can be regulated at 5.0v. Although this operation method can be applied on the case of wider system voltage Vcc, but when the system voltage Vcc=2.5˜3.0v then the multiple for the pumping CKT  2  will switch between double and triple, which substantially affects the voltage-converting efficiency. 
   Obviously, the aforementioned DC-DC voltage converter can supply voltage in accordance with the user&#39;s requirements. However, voltage-drop is unavoidable during the process of the voltage converting so as to supply the required voltage to the load, which leads to the unnecessary power consumption. 
   SUMMARY OF THE INVENTION 
   Consequently, the main purpose of the current invention is to provide a circuit of voltage multiplier with low-power-consumption. The second purpose of the current invention is to provide a circuit of voltage multiplier with programmable output. 
   The present invention is a circuit of voltage multiplier with programmable output, which is composed of a pumping CKT, a CLK generator, and a comparator. The pumping CKT has an input terminal, a control terminal, and an output terminal. The CLK generator connects to the control terminal of the pumping CKT. The clock single is generated to control the operation of the pumping CKT such that the pumping CKT pumps the input voltage at the input terminal to be the output voltage at the output terminal of the pumping CKT. The comparator has two input terminals and one output terminal. The output terminal of the comparator connects to the CLK generator. One of the input terminals of the comparator connects to the output terminal of the pumping CKT, and the other input terminal of the comparator connects to a reference voltage. According to this, when the output voltage at the output terminal of the pumping CKT is lower than the reference voltage, the CLK generator is activated by the comparator to drive the pumping CKT to pump until the output voltage at the output terminal of the pumping CKT is higher than the reference voltage. At this time, the CLK generator shuts down by way of the comparator. Therefore, the output voltage at the output terminal of the pumping CKT can be controlled to supply the load merely by programming the reference voltage. 
   Besides, for avoiding the efficiency loss and the life reduction resulted from the pumping CKT too frequently switching, the feedback voltage derived from the output terminal of the pumping CKT can be divided into the first feedback signal and the second feedback signal by a voltage divider circuit. With the help of a multiplexer, the two feedback signals connect to the comparator at the same time. According to this, when the first feedback signal is lower than the reference voltage, the CLK generator is activated by the comparator to drive the pumping CKT to pump until the second feedback voltage is higher than the reference voltage. At this time, the CLK generator shuts down by way of the comparator. Consequently, the switching rate of the pumping CKT can be reduced. 

   
     BRIEF DESCRIPTION FOR THE DRAWINGS 
       FIG. 1  is the block diagram for a well-known DC-DC voltage converter. 
       FIG. 2  is the block diagram for another well-known DC-DC voltage converter. 
       FIG. 3  is the block diagram for the DC-DC voltage converter of the first embodiment of the present invention. 
       FIG. 4  is the block diagram for the DC-DC voltage converter of the second embodiment of the present invention. 
       FIG. 5  is the timing diagram for the second embodiment of the present invention. 
       FIG. 6  is the block diagram for the first embodiment of the present invention with the regulator. 
       FIG. 7  is the block diagram for the second embodiment of the present invention with the regulator. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENT 
   The detailed descriptions for content and technology of this invention associated with figures are as follows. 
   Please refer to  FIG. 3 , which is the first embodiment of the present invention. The multiple circuit of this invention is composed of a pumping CKT  10 , a CLK generator  20 , and a comparator  30 . 
   The pumping CKT  10  has an input terminal  10   a,  a control terminal  10   c,  and an output terminal  10   b.    
   The CLK generator  20  connects to the control terminal  10   c  of the pumping CKT  10 , and the clock signal generated by the CLK generator  20  controls the pumping CKT  10  to start or stop. The pumping CKT  10  pumps the input voltage Vcc at the input terminal  10   a  of the pumping CKT  10  to be the output voltage Vout at the output terminal  10   b  of the pumping CKT  10 . 
   The comparator  30  has two input terminals  30   a  and one output terminal  30   b . The output terminal  30   b  of the comparator  30  connects to the CLK generator  20 . One of the input terminals  30   a  of the comparator  30  connects to the output terminal  10   b  of the pumping CKT  10 , and the other input terminal  30   a  of the comparator  30  connects to a reference voltage Vref. 
   When the circuit starts, the CLK generator  20  will drive the pumping CKT  10  to pump the output voltage Vout at the output terminal  10   b  of the pumping CKT  10  continuously. The output voltage Vout at the output terminal  10   b  of the pumping CKT  10  will feedback to the comparator  30  continuously until the output voltage Vout at the output terminal  10   b  of the pumping CKT  10  is higher than the reference voltage Vref. The CLK generator  20  is turned off by way of the signals generated by the comparator  30  so as to stop driving the pumping of the pumping CKT  10 . At this time, the output voltage Vout at the output terminal  10   b  of the pumping CKT  10  will keep dropping due to the consumption of a load (which is not shown in the figure) until the output voltage Vout at the output terminal  10   b  of the pumping CKT  10  is lower than the reference voltage Vref. The CLK generator  20  is turned on by way of the signals generated by the comparator  30  so as to drive the pumping of the pumping CKT  10 . Accordingly, a recurring operation loop is formed. Therefore, the output voltage Vout at the output terminal  10   b  of the pumping CKT  10  can be controlled to supply the load (which is not shown in the figure) merely by programming the reference voltage Vref. 
   Please refer to  FIG. 4 , which shows the second embodiment of this invention. The multiple circuit of this invention is composed of a pumping CKT  10 , a CLK generator  20 , a comparator  30 , and a voltage divider  50 . 
   The CLK generator  20  connects to the control terminal  10   c  of the pumping CKT  10 , and the clock signal generated by the CLK generator  20  controls the pumping CKT  10  to start or stop. The pumping CKT  10  pumps the input voltage Vcc at the input terminal  10   a  of the pumping CKT  10  to be the output voltage Vout at the output terminal  10   b  of the pumping CKT  10 . 
   The pumping CKT  10  has an input terminal  10   a,  a control terminal  10   c,  and an output terminal  10   b.    
   The CLK generator  20  connects to the control terminal  10   c  of the pumping CKT  10 , and the discontinuous clock single generated by the CLK generator  20  controls the pumping CKT  10  to start or stop. The pumping CKT  10  pumps the input voltage Vcc at the input terminal  10   a  of the pumping CKT  10  to be the output voltage Vout at the output terminal  10   b  of the pumping CKT  10 . 
   The comparator  30  has two input terminals  30   a  and one output terminal  30   b . The output terminal  30   b  of the comparator  30  connects to the CLK generator  20 . One of the input terminals  30   a  of the comparator  30  connects to the reference voltage Vref. 
   The multiplexer  40  has an output terminal  40   b , a selected terminal  40   c , a first input terminal  40   a   1 , and a second input terminal  40   a   2 . The output terminal  40   b  of the multiplexer  40  connects to the other input terminal  30   a  of the comparator  30 . The selected terminal  40   c  of the multiplexer  40  connects to the output terminal  30   b  of the comparator  30 . 
   The voltage divider has an input terminal  50   a  and an output terminal  50   b . There are a first resistor Ra, a first connection point A, a third resistor Rc, a second connection point B, and a second resistor Rb in series between the input terminal  50   a  and the output terminal  50   b . The input terminal  50   a  of the voltage divider  50  connects to the output terminal  10   b  of the pumping CKT  10 , the first connection point A connects to the first input terminal  40   a   1  of the multiplexer  40 , the second connection point B connects to the second input terminal  40   a   2 , and the output terminal  50   b  of the voltage divider is grounded. 
   Please refer to  FIG. 5 , which is a timing diagram for the output voltage Vout at the output terminal  10   b  of the pumping CKT  10 , for the pumping CKT, and for the CLK generator  20  of this invention. As shown in the figure, the time interval can be divided into Ti interval (initial interval), Ta interval, and Tb interval. In the beginning, there are Ti interval and Ta interval. When the circuit is started, the CLK generator  20  will drive the pumping CKT to pump continuously so as to increase the output voltage Vout at the output terminal  10   b  of the pumping CKT  10 . Through the voltage divider  50 , the output voltage Vout at the output terminal  10   b  produces the first feedback voltage Vref 1  at the first connection point A and the second feedback voltage Vref 2  at the second connection point B. The relations among the first feedback voltage Vref 1 , the second feedback voltage Vref 2 , the output voltage Vout at the output terminal  10   b , the first resistor Ra, the second resistor Rb, and the third resistor Rc are: 
             V     ref   ⁢           ⁢   1       =       V   out     ⁡     (         R   b     +     R   c           R   a     +     R   b     +     R   c         )                     V     ref   ⁢           ⁢   2       =       V   out     ⁡     (       R   b         R   a     +     R   b     +     R   c         )             
In the beginning, the multiplexer selects the second input terminal  40   a   2  as the channel so that the second feedback voltage Vref 2  can continuously feedback to the comparator  30  until the second feedback voltage Vref 2  is higher than the reference voltage Vref. The CLK generator  20  is now turned off by way of the signals generated by the comparator  30  so as to stop the function of the pumping CKT  10 . At the same time, the comparator  30  produces signals to change the channel of the multiplexer  40  to the first input terminal  40   a   1 . At this time, the signal for the input terminal  30   a  of the comparator  30  changes to the first feedback voltage Vref 1 . However, because the second feedback voltage Vref 2  is smaller than the first feedback voltage Vref 1  now, when the multiplexer  40  chooses the first input terminal  40   a   1  to be the channel, it will not change the state of the comparator  30  to produce clock signal.
 
   The next is the Tb interval. As time passes by, the output voltage Vout at the output terminal  10   b  of the pumping CKT  10  will keep dropping due to the consumption of a load (which is not shown in the figure). Correspondingly, the first feedback voltage Vref 1  will also keep dropping until the first feedback voltage Vref 1  is lower than the reference voltage Vref. The CLK generator  20  is now turned on by way of the signals generated by the comparator  30  so as to drive the pumping of the pumping CKT  10 , and the multiplexer  40  changes to choose the second input terminal  40   a   2  to be the channel. Similarly, because the second feedback voltage Vref 2  is smaller than the first feedback voltage Vref 1  now, when the multiplexer  40  chooses the second input terminal  40   a   2  to be the channel, it will not change the state of the comparator  30 . As describe above, intervals Ta and Th will repeat uninterruptedly to form a recurring operation-such that the output voltage Vout at the output terminal of the pumping CKT  10  keeps within the interval of 
   
     
       
         
           
             
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   Therefore, the output voltage Vout at the output terminal  10   b  of the pumping CKT  10  can be controlled to supply the load (which is not shown in the figure) merely by programming the reference voltage Vref, the first resistor Ra, the second resistor Rb, or the third resistor Rc. 
   Besides, as shown in  FIGS. 6 and 7 , a regulator  60  can be added to the output terminal  10   b  of the pumping CKT  10  for the aforementioned the first and the second embodiments. The regulator  60  is composed of a comparator, a transistor Q, and resistors R 1  and R 2 . The regulator can perform the final regulation and voltage-drop on the output voltage Vout by adjusting the magnitudes of resistors R 1  and R 2 , which can supply more stable voltage to the load (which is not shown in the figure). The first resistor Ra, the second resistor Rb, and the third resistor Rc in the second embodiment can be made of a programmable variable-resistor that is made of semiconductor. By adjusting the third resistor Rc, the oscillation amplitude of the output voltage Vout at the output terminal  10   b  of the pumping CKT can be adjusted, while adjusting the first resistor Ra and the second resistor Rb the output voltage Vout at the output terminal  10   b  of the pumping CKT can be adjusted. Consequently, not only requirements for different loads can be satisfied but also the programmable adjusting can be achieved. 
   As described above, the voltage-drop is not necessary in the present invention whereas the output voltage can be multiplied to supply the load such that the unnecessary power consumption can be reduced and the output voltage can be changed by way of programming the resistance of the variable-resistor.