Abstract:
A voltage conversion device capable of enhancing conversion efficiency includes a charge pump for generating output voltage linear to input voltage according to the input voltage, a feedback unit for generating a feedback signal according to the output voltage generated by the charge pump, and a regulating unit for outputting and adjusting the input voltage according to the feedback signal provided by the feedback unit, so as to keep the output voltage unchanged.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention is related to a voltage conversion device capable of enhancing conversion efficiency, and more particularly, a voltage conversion device capable of automatically adjusting a charge pump output voltage under different switch-on resistors and different load currents, to maintain at a preset level. 
     2. Description of the Prior Art 
     A charge pump is often used in a booster circuit or a voltage multiplier circuit. For example, a prior art liquid crystal display (LCD) device can utilize a charge pump to raise an output voltage from a lower voltage source, to provide a higher operating voltage for drivers such as source drivers or gate drivers. As shown in  FIG. 1  and  FIG. 2 , the charge pump can be seen as a dual-end element, for converting an input voltage Vi into a positive multiple output voltage Vo ( FIG. 1 ) or a negative multiple output voltage Vo ( FIG. 2 ). 
     The prior art provides many methods for implementing charge pumps and related circuits. For example,  FIG. 3  illustrates a schematic diagram of a constant charge pump  300 . The constant charge pump  300  includes a level shifter circuit  302  and a charge-exchange-control switch circuit  304 . Clock signals CLK, XCK and control signals S 1 , S 2  provided by the level shifter circuit  302  effectively drive the charge-exchange-control switch circuit  304 , so that the constant charge pump  300  converts an input voltage Vi to an output voltage Vo accurately for voltage boosting or voltage multiplying. However, the constant charge pump  300  is only suitable for operating with a smaller load change. If the constant charge pump  300  is applied on a design that has a larger load change, under a low load condition, the efficiency of the charge pump  300  seriously decays, and the charge pump  300  might not be able to operate when the load is too large. 
     The prior art further provides a capacitor push-pull charge pump  400 , as shown in  FIG. 4 . The capacitor push-pull charge pump  400  includes a level shifter circuit  402  and a charge-exchange-control switch circuit  404 . The charge-exchange-control switch circuit  404  is the same as the charge-exchange-control switch circuit  304  in  FIG. 3 , while in the level shifter circuit  402 , the output transistors of the level shifter circuit  302  is replaced by output capacitors. Under this condition, the capacitor push-pull charge pump  400  can adjust the amplitude of the clock control signals according to charge loads, so as to automatically reduce the transforming charges, in order to provide a higher efficiency. However, the clock signal level of the capacitor push-pull charge pump  400  cannot reach a full voltage, and the output voltage Vo is not stable and varies with the load. 
     In short, there is an equivalent resistor (switch-on resistor) when the charge pump switch is on. A load current passing through the switch-on resistor decreases the average of a direct current level of the output voltage, and the greater the switch-on resister is, the more the load current varies, and the more the average voltage decreases. If the switch rate of the charge pump is adjusted to restrain the drop of the average voltage, the output voltage Vo might be greater than the voltage requirement of the load circuit power source, and cause serious efficiency loss. 
     In order to solve the above-mentioned problems, a prior art charge pump can couple a voltage regulator to the output end, to generate the output voltage Vo as shown in  FIG. 5  and  FIG. 6 . However, there are two defects in the charge pump: one is a voltage stabilization capacitor CL should be attached, another is the charge pump multiplies the input voltage to a very high output voltage VCC or VEE, then decreases the voltage with the voltage regulator, which loses efficiency. 
     SUMMARY OF THE INVENTION 
     It is therefore a primary objective of the claimed invention to provide a voltage conversion device capable of enhancing a voltage conversion efficiency. 
     The present invention discloses a voltage conversion device capable of enhancing a voltage conversion efficiency, which comprises a charge pump for generating an output voltage linearly related to an input voltage, a feedback unit for generating a feedback signal according to the output voltage generated by the charge pump, and a regulating unit for outputting and adjusting the input voltage according to the feedback signal provided by the feedback unit, for keeping the output voltage at a predefined level. 
     These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates a schematic diagram of a prior art charge pump for generating positive output voltages. 
         FIG. 2  illustrates a schematic diagram of a prior art charge pump for generating negative output voltages. 
         FIG. 3  illustrates a diagram of a prior art constant charge pump. 
         FIG. 4  illustrates a diagram of a prior art capacitor push-pull charge pump. 
         FIG. 5  illustrates a diagram of a prior art charge pump for generating positive output voltages coupled to a voltage regulator. 
         FIG. 6  illustrates a diagram of a prior art charge pump for generating negative output voltages coupled to a voltage regulator. 
         FIG. 7  illustrates a diagram of a voltage conversion device of the present invention capable of enhancing voltage conversion efficiency. 
         FIG. 8  illustrates a schematic diagram of a regulating unit of an embodiment of the present invention. 
         FIG. 9  illustrates a schematic diagram of a feedback unit of an embodiment of the present invention. 
         FIG. 10-13  illustrate schematic diagrams of circuits of a feedback unit shown in  FIG. 9 . 
         FIG. 14  illustrates a schematic diagram of a regulating unit of an embodiment of the present invention. 
         FIG. 15  illustrates a schematic diagram of a feedback unit of an embodiment of the present invention. 
         FIG. 16-20  illustrate schematic diagrams of circuits of embodiments for realizing the feedback unit shown in  FIG. 15 . 
         FIG. 21-29  illustrate schematic diagrams of circuits of embodiments for realizing the feedback unit of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Please refer to  FIG. 7 , which illustrates a schematic diagram of a voltage conversion device  200  according to the present invention. The voltage conversion device  200  can enhance voltage conversion efficiency, and includes a charge pump  202 , a regulating unit  201 , and a feedback unit  203 , to transform an input voltage Vi into an output voltage Vo. The charge pump  202  can be any type of charge pump, for multiplying the input voltage Vi into a specific multiplication output voltage Vo. The feedback unit  203  is coupled to the charge pump  202 , for outputting a feedback signal If to the regulating unit  201  according to the output voltage Vo of the charge pump  202 . The regulating unit  201  outputs and adjusts the input voltage Vi according to the feedback signal If outputted from the feedback unit  203 , so that the output voltage Vo of the charge pump  202  keeps in an expected level. Moreover, in  FIG. 7 , a current I L  generated from an equivalent current source  204  represents the load current of the charge pump  202 . 
     The feedback unit  203  of the voltage conversion device  200  can generate the feedback signal If according to the voltage Vo outputted from the charge pump  202 , and the regulating unit  201  can adjust the input voltage Vi accordingly, so that the voltage Vo remains at a preset level. Preferably, the feedback signal If is a forward or inverse current. When the load current I L  increases and causes the output voltage Vo to drop, the current value of the feedback signal If increases, and the level of the input voltage Vi outputted from the regulating unit  201  is elevated, to keep the output voltage Vo of the charge pump  202  at the expected level. In other words, when the load current I L  changes, the voltage Vi outputted from the regulating unit  201  is automatically adjusted due to the change of the current flowing through the feedback route, so as to keep the output voltage Vo of the charge pump  202  at an expected level. 
     In short, the present invention voltage conversion device  200  automatically adjusts the output voltage of the charge pump through a voltage-to-current feedback control method, so as to keep the output voltage of the charge pump at an expected level under circumstances of different switch-on resistances and different currents. As a result, the present invention does not need an extra voltage stabilization capacitor or voltage regulator, and can reduce efficiency waste. 
     Note that, the voltage conversion device  200  shown in  FIG. 7  is a diagram of an embodiment of the present invention, and those skilled in the art can design circuits accordingly. The followings explain embodiments of the regulating unit  201  and the feedback unit  203  under different applications. A voltage VDD represents a system voltage, voltages V 3 , V 4 , V 6 , V 7  represent specific direct current voltages, and GND represents a ground end. 
     Firstly, when the polarities of the output voltage Vo and the input voltage Vi are the same, the feedback signal If outputted from the feedback unit  203  can either flow from the feedback unit  203  to the regulating unit  201 , or flow from the regulating unit  201  to the feedback unit  203 . Please refer to  FIG. 8 , which illustrates a schematic diagram of a regulating unit  800 . The regulating unit  800  is an embodiment of the regulating unit  201  shown in  FIG. 7 , which is applicable when the output voltage Vo and the input voltage Vi have the same polarities and the feedback signal If is an inverse current (flown out from the regulating unit  800 ). The regulating unit  800  includes a voltage output end  802 , a feedback end  804 , an operational amplifier  301 , a p-type metal oxide semiconductor transistor (PMOS transistor) P 30  and resistors R 31 , R 32 . The regulating unit  800  can output the voltage Vi through the voltage output end  802 , and receive the feedback signal If (output current) through the feedback end  804 . The negative input end of the operational amplifier  301  is coupled to a reference voltage Vr, the positive input end is coupled to the resistors R 31 , R 32  and the feedback end  804 , and the output end is coupled to a gate of the PMOS transistor P 30 . Utilizing the regulating unit  800 , when the output voltage Vo of the charge pump  202  decreases, the current value of the feedback signal If increases, so that the current flowing through the resistor R 31  increases, causing the voltage Vi to arise. When the output voltage Vo of the charge pump  202  resumes to an preset value, the current value of the feedback signal If decreases, so that the current flowing through the resistor R 31  decreases and the voltage Vi resumes to the set value. 
     The regulating unit  800  is applicable when the output voltage Vo and the input voltage Vi have the same polarities and the feedback signal If flows out from the regulating unit  800 , and there are many embodiments of the corresponding feedback unit  203 . Please refer to  FIG. 9 , which illustrates a schematic diagram of a feedback unit  900 . The feedback unit  900  realizes the feedback unit  203 , which operates with the regulating unit  800 . The feedback unit  900  comprises an output voltage reception end  902 , a feedback signal end  904 , a voltage division circuit  906 , and a voltage to current conversion circuit  908 . The voltage division circuit  906  receives the output voltage Vo from the charge pump  202  through the output voltage reception end  902 , in order to generate a division voltage to the voltage to current conversion circuit  908 , so as to generate the feedback signal If (inverse current) through the feedback signal end  904 . 
     Please further refer to  FIG. 10-13 , which illustrate schematic diagrams of circuits  1000 ,  1100 ,  1200 ,  1300 . The circuits  1000 ,  1100 ,  1200 ,  1300  are utilized to realize the feedback unit  900  in  FIG. 9 . In  FIG. 10 , resistors R 311 , R 312  realize the voltage division circuit  906 , a PMOS transistor P 311  is the voltage to current amplifier, and n-type metal oxide semiconductor transistors (NMOS transistors) N 311 , N 312  form a current mirror, in order to realize the voltage to current conversion circuit  908 , with an operation method narrated as the followings. The voltage Vo is divided by the resistors R 311 , R 312  and utilizes the PMOS transistor P 311  to switch on a certain current, and the current is drawn through the current mirror formed by the NMOS transistors N 311 , N 312 , to generate the feedback signal If. When the load current I L  of the output voltage Vo of the charge pump  202  increases and causes the output voltage Vo to decrease, the gate voltage of the PMOS transistor P 311  decreases correspondingly. Due to an increase of the voltage difference between the source and gate of the PMOS transistor P 311 , the switch-on current increases accordingly, and the current value of the feedback signal If also increases, so that the voltage Vi outputted from the regulating unit  800  in  FIG. 8  increases, and the output voltage Vo of the charge pump  202  increases accordingly. Finally, the regulating unit  800  automatically adjusts the output voltage Vi until the output voltage Vo of the charge pump  202  increases to a preset value. On the other hand, when the load current I L  of the output voltage Vo of the charge pump  202  decreases and causes the output voltage Vo to increase, the gate voltage of the PMOS transistor P 311  increases correspondingly. Due to a decrease of a voltage difference between the source and gate of the PMOS transistor P 311 , the switch-on current decreases accordingly, and the current value of the feedback signal If also decreases. The current drop of the feedback signal If decreases the voltage Vi outputted from the regulating unit  800 , and can decrease the output voltage Vo of the charge pump  202 . Eventually, the regulating unit  800  automatically adjusts the output voltage Vi until the output voltage Vo of the charge pump  202  decreases to a preset value. Hence, when the output voltage Vo of the charge pump  202  varies with the load current I L , the regulating unit  800  and the circuit  1000  can automatically resume the output voltage Vo of the charge pump  202  to the preset value, and are not affected by the switch-on resistor effect or different load currents. In other words, the regulating unit  800  and the circuit  1000  can provide similar steady voltages without an extra voltage regulator or a voltage stabilization capacitor, so as to prevent efficiency loss. 
     In  FIG. 11 , resistors R 321 , R 322  realize the voltage division circuit  906  in  FIG. 9 , and a PMOS transistor P 321 , an NMOS transistor N 321  and a current source  132  realize the voltage to current conversion circuit  908  in  FIG. 9 , with an operation method narrated as the follows. The voltage Vo is divided by the resistors R 321 , R 322  and utilizes the PMOS transistor to switch on a specific current. The current source  132  biases the PMOS transistor P 321 . The common node of the drain of the PMOS transistor P 321  and the current source  132  is coupled to the gate of the NMOS transistor N 321 , and draws current from the drain of the NMOS transistor, in order to generate the feedback signal If. When the load current I L  of the output voltage Vo of the charge pump  202  increases and causes the output voltage Vo to decrease, the gate voltage of the PMOS transistor P 321  decreases; thus, the gate voltage of the NMOS transistor N 321  increases, and the current value of the feedback signal If also increases. The raise of the current value of the feedback signal If increases the voltage Vi of the regulating unit  800  shown in  FIG. 8 , and increases the output voltage Vo of the charge pump  202 . Finally, the regulating unit  800  can automatically adjust the voltage Vi until the output voltage Vo of the charge pump  202  rises to the preset value. On the other hand, when the load current I L  of the output voltage Vo of the charge pump  202  decreases and causes the output voltage Vo to increase, the gate voltage of the PMOS transistor P 321  increases; thus, the gate voltage of the NMOS transistor N 321  decreases, and the current value of the feedback signal If also decreases. And the drop of the current value of the feedback signal If decreases the voltage Vi outputted from the regulating unit  800 , and also decreases the output voltage Vo of the charge pump  202 . In the same way, the regulating unit  800  regulates the voltage Vi automatically until the output voltage Vo of the charge pump  202  decreases to the preset value. 
     In  FIG. 12 , resistors R 331 , R 332  realize the voltage division circuit  906  in  FIG. 9 . PMOS transistors P 331 , P 332  form a differential amplifier, NMOS transistors N 331 , N 332  form a current mirror, and an NMOS transistor N 333  forms an active load. The PMOS transistors P 331 , P 332  and the NMOS transistors N 331 , N 332 , N 333  are used for realizing the voltage to current conversion circuit  908  in  FIG. 9 , with an operation method narrated as the followings. The common node of the resistors R 331 , R 332  are coupled to a gate of the PMOS transistor P 331 , and a gate of the PMOS transistor P 332  is coupled to a reference voltage Vref. When the load current I L  of the output voltage Vo of the charge pump  202  increases and causes the output voltage Vo to decrease, the gate voltage of the PMOS transistor P 331  decreases; thus, current generated from the current source  133  flowing through the PMOS transistor P 331  increases. With the current mirror formed by the NMOS transistors N 331 , N 332 , the current value of the feedback signal If increases. The current raise of the feedback signal If increases the voltage Vi outputted from the regulating unit  800  shown in  FIG. 8 , and increases the output voltage Vo of the charge pump  202 . Finally, the regulating unit  800  automatically regulates the voltage Vi until the output voltage Vo of the charge pump  202  rises to the preset value. On the other hand, when the load current I L  of the output voltage Vo of charge pump  202  decreases and causes the output voltage Vo to increase, the gate voltage of the PMOS transistor P 331  increases, so that more of the current from the current source  133  flows through the PMOS transistor P 332  and the NMOS transistor N 333 , and the current flowing through the PMOS transistor P 331  decreases. After reflected by the current mirror formed by the NMOS transistors N 331 , N 332 , the current value of the feedback signal If decreases. The current drop of the feedback signal If decreases the voltage Vi outputted from the regulating unit  800 , and decreases the output voltage Vo of the charge pump  202 . In the same way, the regulating unit  800  eventually regulates the output voltage Vi automatically until the output voltage Vo of the charge pump  202  decreases to the preset value. 
     In  FIG. 13 , resistors R 341 , R 342  realize the voltage division circuit  906  in  FIG. 9 , and an operational amplifier  341  and an NMOS transistor N 341  realize the voltage to current conversion circuit  908  in  FIG. 9 , with an operation method narrated as the followings. The voltage Vo is divided by the resistors R 341 , R 342 , and is coupled to the negative input end of the operational amplifier  341 , while the positive input end of the operational amplifier  341  is coupled to a reference voltage Vref, and the output end of the operational amplifier  341  is coupled to the gate of the NMOS transistor N 341 . When the load current I L  of the output voltage Vo of the charge pump  202  increases and causes the output voltage Vo to decrease, the gate voltage of the NMOS transistor N 341  increases; thus, the current value of the feedback signal If generated from the drain of the NMOS transistor N 341  increases. The current raise of the feedback signal If increases the voltage Vi outputted from the regulating unit  800  in  FIG. 8 , which makes the output voltage Vo of the charge pump  202  increase. Finally, the regulating unit  201  automatically adjusts the output voltage Vi until the output voltage Vo of the charge pump  202  rises to a preset value. On the other hand, when the load current I L  of the output voltage Vo of the charge pump  202  decreases and causes the output voltage Vo to increase, the gate voltage of the NMOS transistor N 341  decreases, so that the current generated from the drain of the NMOS transistor N 341  decreases. The drop of the current value of the feedback signal If decreases the voltage Vi outputted from the regulating unit  800  shown in  FIG. 8 , and can decrease the output voltage Vo of the charge pump  202 . In the same way, the regulating unit  800  eventually regulates the voltage Vi automatically until the output voltage Vo of the charge pump  202  drops to the preset value. 
     Note that the regulating unit  800  shown in  FIG. 8  and the feedback unit  900  shown in  FIG. 9  are applicable when the output voltage Vo and the input voltage Vi have the same polarities and the feedback signal If is an inverse current (flown from the regulating unit  800  to the feedback unit  900 ).  FIG. 10-13  are embodiments of the feedback unit  900 . Moreover, the present invention further provides other embodiments for conditions when the feedback signal If is forward current. 
     Please refer to  FIG. 14 , which is a schematic diagram of a regulating unit  1400 . The regulating unit  1400  is an embodiment of the regulating unit  201  shown in  FIG. 7 , which is applicable when the output voltage Vo and the input voltage Vi have the same polarities and the feedback signal If is an forward current (flowing into the regulating unit  1400 ). A circuit structure of the regulating unit  1400  resembles the regulating unit  800  in  FIG. 8 , but adds a current source  1406  and a resistor R 41 , and a feedback end  1404  is moved to the negative input end of the operational amplifier  301  (leaving out the reference voltage Vr), with an operation method narrated as the followings. When the output voltage Vo of the charge pump  202  decreases, the current value of the received feedback signal If increases, so that the current flowing through the resistor R 41  increases, raising the drain current of a PMOS transistor P 30 , and so does the voltage Vi outputted from the voltage output end  1402 . When the output voltage Vo of the charge pump  202  resumes to a preset value, the current value of the feedback signal If decreases, and the current flowing through the resistor R 41  decreases, so that the voltage Vi resumes to the preset value. 
     The regulating unit  1400  is applicable when the output voltage Vo and the input voltage Vi have the same polarities and the feedback signal If current flows into the regulating unit  201 , while there are many embodiments of the corresponding feedback unit  203 . Please refer to  FIG. 15 , which illustrates a schematic diagram of a feedback unit  1500 . The feedback unit  1500  is utilized for realizing the feedback unit  203 , which coordinates with the regulating unit  1400 . The feedback unit  1500  comprises an output voltage reception end  1502 , a feedback signal end  1504 , a voltage division circuit  1506 , and a voltage to current conversion circuit  1508 . The voltage division circuit  1506  receives the output voltage Vo from the charge pump  202  through the output voltage reception end  1502  to generate a divided voltage to the voltage to current conversion circuit  1508 , so as to generate a feedback signal If (forward current) through the feedback signal end  1504 . 
     Please further refer to  FIG. 16-20 , which illustrate schematic diagrams of circuits  1600 ,  1700 ,  1800 ,  1900 , and  2000 . The circuits  1600 ,  1700 ,  1800 ,  1900 ,  2000  realize the feedback unit  1500  shown in  FIG. 15 . In  FIG. 16 , resistors R 411 , R 412  realize the voltage division circuit  1506 , and a PMOS transistor P 411  realizes the voltage to current conversion circuit  1508 , with an operating method narrated as the followings. The voltage Vo is divided by the resistors R 411 , R 412  to utilize the PMOS transistor P 411  to switch on a certain current, and output the current through a drain of the PMOS transistor P 411 , which is the feedback signal If. When the load current I L  of the output voltage Vo of the charge pump  202  increases and causes the output voltage Vo to decrease, the gate voltage of the PMOS transistor P 411  decreases. Due to an increase of a voltage difference between the gate and the source of the PMOS transistor P 411 , the switch-on current increases, and the current value of the feedback signal I L  also increases. The current raise of the feedback signal If increases the voltage Vi outputted from the regulating unit  1400  shown in  FIG. 14 , and raises the output voltage Vo of the charge pump  202 . Finally, the regulating unit  1400  automatically regulates the output voltage Vi until the output voltage Vo of the charge pump  202  rises to the preset value. On the another hand, when the load current I L  of the output voltage Vo of the charge pump  202  decreases and causes the output voltage Vo to increase, the gate voltage of the PMOS transistor P 411  increases. Due to a decrease of a voltage difference between the gate and the source of the PMOS transistor P 411 , the switch-on current decreases, and the current value of the feedback signal If also decreases. The current drop of the feedback signal If decreases the voltage Vi outputted from the regulating unit  1400  shown in  FIG. 14 , and decreases the output voltage Vo of the charge pump  202 . In the same way, the regulating unit  1400  eventually adjusts the output voltage Vi automatically until the output voltage Vo of the charge pump  202  drops to the preset value. Hence, when the output voltage Vo of the charge pump  202  varies with the load current I L , the regulating unit  1400  and the circuit  1600  can automatically resume the output voltage Vo of the charge pump  202  to the preset value, and are not affected by the switch-on resistance effect or different load currents. In other words, without connecting to a voltage regulator or a voltage stabilization capacitor, the regulating unit  1400  and the circuit  1600  can provide a similar stable output voltage, in order to prevent efficiency loss. 
     In  FIG. 17 , resistors R 421 , R 422  realize the voltage division circuit  1506  shown in  FIG. 5 , and PMOS transistors P 421 , P 422  and a current source  142  realize the voltage to current conversion circuit  1508  shown in  FIG. 15 , with an operating method narrated as the followings. The voltage Vo is coupled to the gate of the PMOS transistor P 421  through the resistors R 421 , R 422 . The current source  142  biases the PMOS transistor P 421 . A common node of the source of the PMOS transistor P 421  and the current source  142  is coupled to the gate of the PMOS transistor P 422 , and the current outputted from the drain of the PMOS transistor P 422  is the feedback signal If. When the load current I L  of the output voltage Vo of the charge pump  202  increases and causes the output voltage Vo to decrease, the gate voltage of the PMOS transistor P 421  decreases; thus, the gate voltage of the PMOS transistor P 422  decreases, and the current value of the feedback signal If rises. The current raise of the feedback signal If increases the voltage Vi outputted from the regulating unit  1400  shown in  FIG. 14 , and raises the output voltage Vo of the charge pump  202 . Finally, the regulating unit  1400  automatically regulates the output voltage Vi until the output voltage Vo of the charge pump  202  rises to a preset value. On the other hand, when the load current I L  of the output voltage Vo of the charge pump  202  decreases and causes the output voltage Vo to increase, the gate voltage of the PMOS transistor P 421  increases, the gate voltage of the PMOS transistor P 422  increases, and the current value of the feedback signal If decreases. The current drop of the feedback signal If decreases the voltage Vi outputted from the regulating unit  1400  shown in  FIG. 14 , and can decrease the output voltage Vo of the charge pump  202 . In the same way, the regulating unit  1400  eventually regulates the output voltage Vi automatically until the output voltage Vo of the charge pump  202  drops to the preset value. 
     In  FIG. 18 , resistors R 431 , R 432  realize the voltage division circuit  1506  shown in  FIG. 15 , and the voltage to current conversion circuit  1508  is realized by PMOS transistors P 431 , P 432 , P 433 , an NMOS transistor N 431  and a current source  143 , with an operation method narrated as the followings. The voltage Vo is divided by the resistors R 431 , R 432 , and is coupled to the gate of the PMOS transistor P 431 . The current source  143  biases the PMOS transistor P 431 . A common node of the drain of the PMOS transistor P 431  and the current source  143  is coupled to the gate of the NMOS transistor N 431 , and the current flown through the drain of the NMOS transistor N 431  then to the current mirror formed by the PMOS transistors P 432 , P 433  is the feedback signal If. When the load current I L  of the output voltage Vo of the charge pump  202  increases and causes the output voltage Vo to decrease, the gate voltage of the PMOS transistor P 431  decreases, which raises the gate voltage of the NMOS transistor N 431 , and increases the current flowing through the current mirror formed by the PMOS transistors P 432 , P 433 , and the current value of the feedback signal If increases correspondingly. The current increase of the feedback signal If increases the voltage Vi outputted from the regulating unit  1400  shown in  FIG. 14 , and can raise the output voltage of the charge pump  202 . Finally, the regulating unit  1400  automatically regulates the output voltage Vi until the output voltage Vo of the charge pump  202  rises to a preset value. One the other hand, when the load current I L  of the output voltage Vo of the charge pump  202  decreases and causes the output voltage Vo to increase, the gate voltage of the PMOS transistor P 431  increases, and the gate voltage of the NMOS transistor N 431  decreases; thus, the current of the current mirror formed by the PMOS transistors P 432 , P 433  decreases, and the current value of the feedback signal If also decreases. The current drop of the feedback signal If decreases the voltage Vi outputted from the regulating unit  1400  shown in  FIG. 14 , and decreases the output voltage Vo of the charge pump  202 . Similarly, the regulating unit  1400  eventually adjusts the output voltage Vi automatically until the output voltage Vo of the charge pump  202  drops to the preset value. 
     In  FIG. 19 , resistors R 441 , R 442  realize the voltage division circuit  1506  shown in  FIG. 15 . NMOS transistors N 441 , N 442  form a differential amplifier, PMOS transistors P 442 , P 443  form a current mirror, and a PMOS transistor P 441  forms an active load. The NMOS transistors N 441 , N 442  and the PMOS transistors P 441 , P 442 , P 443  and the current source  144  realize the voltage to current conversion circuit  1508  shown in  FIG. 15 , with an operation method narrated as the followings. The voltage Vo divided by the resistors R 441 , R 442  is coupled to the gate of the NMOS transistor N 441 , and the gate of the NMOS transistor N 442  is coupled to a reference voltage Vref. When the load current I L  of the output voltage Vo of the charge pump  202  increases and causes the output voltage Vo to decrease, the gate voltage of the NMOS transistor N 441  decreases, so that current generated by the current source  144  flowing into the NMOS transistor N 442  increases, and the current value of the feedback signal If flown through the current mirror formed by the PMOS transistors P 442 , P 443  increases accordingly. The current increase of the feedback signal If increases the voltage Vi outputted from the regulating unit  1400  shown in  FIG. 14 , which raises the output voltage Vo of the charge pump  202 . Finally, the regulating unit  1400  automatically adjusts the output voltage Vi until the output voltage Vo of the charge pump  202  rises to a preset value. On the other hand, when the load current I L  of the output voltage Vo of the charge pump  202  decreases and causes the output voltage Vo to increase, the gate voltage of the NMOS transistor N 441  increases, so that the current generated from the current source  144  flowing through the NMOS transistor N 441  and the PMOS transistor P 441  increases, and the current value of the feedback signal If flown through the current mirror formed by the PMOS transistors P 442 , P 443  decreases. The current drop of the feedback signal If decreases the voltage-Vi outputted from the regulating unit  1400  shown in  FIG. 14 , and can decrease the output voltage Vo of the charge pump  202 . Similarly, the regulating unit  1400  eventually regulates the output voltage Vi automatically until the output voltage Vo of the charge pump  202  drops to the preset value. 
     In  FIG. 20 , resistors R 451 , R 452  realize the voltage division circuit  1506  shown in  FIG. 15 , an operational amplifier  451  and a PMOS transistor P 451  realize the voltage to current conversion circuit  1508  shown in  FIG. 15 , with an operation method narrated as the followings. The voltage Vo divided by the resistors R 451 , R 452  is coupled to a positive input end of the operational amplifier  451 , while a negative input end of the operational amplifier  451  is coupled to a reference voltage Vref, and an output end of operational amplifier  451  is coupled to a gate of the PMOS transistor P 451 . When the load current I L  of the output voltage Vo of the charge pump  202  increases and causes the output voltage Vo to decrease, the gate voltage of the PMOS transistor P 451  decreases, so that the current of the feedback signal generated by the drain of the PMOS transistor P 451  increases. The current raise of the feedback signal If increases the voltage Vi outputted from the regulating unit  1400  shown in  FIG. 14 , and increases the output voltage Vo of the charge pump  202 . Finally, the regulating unit  1400  adjusts the output voltage Vi automatically until the output voltage Vo of the charge pump  202  rises to a preset value. On the other hand, when the load current I L  of the output voltage Vo of the charge pump  202  decreases and causes the output voltage Vo to increase, the gate voltage of the PMOS transistor P 451  increases, so that the current value of the feedback signal If generated from the drain of the PMOS transistor P 451  decreases. The current drop of the feedback signal If decreases the voltage Vi outputted from the regulating unit  1400  shown in  FIG. 14 . Similarly, the regulating unit  1400  eventually adjusts the output voltage Vi automatically until the output voltage Vo of the charge pump  202  drops to the preset value. 
     Note that the regulating unit  1400  shown in  FIG. 14  and the feedback unit  1500  shown in  FIG. 15  are applicable when the output voltage Vo and the input voltage Vi have same polarities and the feedback signal If is a forward current (flowing from the feedback unit  1500  to the regulating unit  1400 ), and  FIG. 16  to  FIG. 20  are embodiments of the feedback unit  1500 . 
     When the output voltage Vo and the input voltage Vi are both positive,  FIG. 8-20  reveal embodiments of the regulating unit  201  and the feedback unit  203  for forward or inverse feedback signals If. Similarly, when the output voltage Vo and the input voltage Vi have opposite polarities (meaning that the charge pump  202  generates a negative output voltage Vo), the present invention provides two kinds of embodiments depending on whether the feedback signal If is a forward or an inverse current. When the polarities of the output voltage Vo and the input voltage Vi are opposite and the feedback signal If is an inverse current (flowing into the feedback unit), the required regulating unit  20  can be realized through the regulating unit  800  shown in  FIG. 8 , and the feedback unit  203  can be realized through circuits  2100 ,  2200 ,  2300 ,  2400 ,  2500  shown in  FIG. 21-25 . When the polarities of the output voltage Vo and the input voltage Vi are opposite, and the feedback signal If is a forward current (flowing out from the feedback unit), the required regulating unit  201  can be realized through the regulating unit  1400  shown in  FIG. 14 , and the feedback unit  203  can be realized through circuits  2600 ,  2700 ,  2800 ,  2900  shown in  FIG. 26-29 . The circuits  2100 ,  2200 ,  2300 ,  2400 ,  2500 ,  2600 ,  2700 ,  2800 ,  2900  are generated through modifying or following the circuits  1000 ,  1100 ,  1200 ,  1300 ,  1600 ,  1700 ,  1800 ,  1900 ,  2000 , while the operation methods mentioned above can be referred, and will not be narrated in detail. 
     As a conclusion, with the voltage to current feedback control method, the present invention voltage conversion device can automatically adjust the charge pump output voltage with different switch-on resistances and different load currents, to maintain the expected level. When the output voltage of the charge pump varies with the load current, the regulating unit and the feedback unit of the present invention resume the output voltage of the charge pump to the preset value automatically, and are not affected by the switch-on resistance effects of different load currents. In other words, without connecting to a voltage regulator or a voltage stabilization capacitor, the present invention provides a similar stable output voltage, and avoids efficiency loss. 
     Those skilled in the art will readily observe that numerous modifications and alterations of the device and method may be made while retaining the teachings of the invention.