Charge pump circuit

A charge pump circuit is provided. The charge pump circuit includes a pump unit, first through sixth switches, a fly capacitor and an output capacitor. In a first period, an input voltage and a first voltage charge at least one internal capacitor of the pump unit via a first terminal and a second terminal of the pump unit. In the second period, the internal capacitor of the pump unit provides charges to the fly capacitor via the second switch and generates a first output voltage. In the third period, the fly capacitor supplies the charges to the output capacitor via the fourth switch to generate a second output voltage.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the priority benefit of Taiwan application serial no. 97100661, filed on Jan. 8, 2008. The entirety of the above-mentioned patent application is hereby incorporated by reference herein and made a part of this specification.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention generally relates to a charge pump circuit, and more particularly, to a charge pump circuit having comparatively fewer capacitor components.

2. Description of Related Art

Typically, in an electronic circuit, voltages of different levels are often needed for operation of the circuit. Therefore, a charge pump is often employed in such an electronic circuit for generating voltages of different level.

FIG. 1is a circuit diagram of a conventional charge pump. Referring toFIG. 1, there is shown a charge pump circuit100including switches101through108, capacitors109through112. The charge pump circuit100utilizes two control signals PH1(in first periods) and PH2(in second periods) for alternately controlling on/off states of the switches101through108. When the control signal PH1is at a high level, the switches101,104,106and108are turned on, in which an equivalent circuit is as shown inFIG. 2A. In this case, an input voltage VIN charges the capacitor109to hold a voltage difference at two terminals thereof that equals to VIN. When the control signal PH2is at a high level, the switches102,103,105, and107are turned on, in which an equivalent circuit is as shown inFIG. 2B. In this case, the input voltage VIN and charges stored in the capacitor109charge the capacitors110and111to 2VIN, and generate an output voltage Vout1with a level of 2VIN.

Then, when the control signal PH1is again shifted to the high level, in which the capacitor110stores charges of 2VIN, the output voltage Vou1is sustained as 2VIN. Meanwhile, the capacitor112is charged by charges stored in the capacitor111, so as to generate another output voltage Vout2with a level of −2VIN.

FIG. 3is a circuit diagram of another conventional charge pump. Referring toFIG. 3, there is shown a charge pump circuit300including switches301through306, capacitors307through309. The charge pump circuit300utilizes four control signals PH1(in first periods) through PH4(in fourth periods) for alternately controlling on/off states of the switches301through306. When the control signal PH1is at a high level, the switches301and304are turned on, in which the charge pump circuit300has an equivalent circuit as shown inFIG. 4A. In this case, an input voltage VIN charges the capacitor307to hold a voltage difference between two terminals thereof identical to VIN. When the control signal PH2is at the high level, the switches302, and303are turned on, in which the charge pump circuit300has an equivalent circuit as shown inFIG. 4B. The capacitor307has a terminal coupled to the input voltage VIN. The capacitor308is charged to 2VIN by the input voltage VIN and charges stored in the capacitor307, and thus outputting an output voltage Vout1with a voltage level of 2VIN.

When the control signal PH3is at a high level, the switches301and304are turned on, in which the charge pump circuit300has an equivalent circuit as shown inFIG. 4C. In this case, the capacitor308stores charges of 2VIN, and therefore the output voltage Vout1sustains a voltage level of 2VIN. On the other hand, the input voltage VIN charges the capacitor307to hold a voltage difference between two terminals thereof that equals to VIN. When the control signal PH4is at the high level, the switches305and306are turned on, in which the charge pump circuit300has an equivalent circuit as shown inFIG. 4D. In this case, the capacitor309is discharged by the charges stored in the capacitor307, so as to generate another output voltage Vout2with a voltage level of −VIN.

Generally, with respect to a charge pump circuit, built-in capacitors occupy a large area of the integrated circuit (IC), and thus the production cost is increased. On the other hand, external capacitors also occupy additional areas on the circuit board, and thereby increase the production cost, and even make the product bulky. Further, although the conventional charge pump circuit100is capable of outputting output voltages 2VIN and −2VIN. The output voltages Vout1, Vout2both require a stabilization capacitor, which increases the production cost. Furthermore, although the conventional charge pump circuit300uses capacitors one less than the charge pump circuit100, it produces a negative voltage of only −VIN. The conventional charge pump circuit300employs four control signals (correspondingly in four periods) for generating output voltages of 2VIN and −VIN, and therefore has a lower efficiency, and a lower maximum load capability.

SUMMARY OF THE INVENTION

Accordingly, the present invention is directed to a charge pump circuit for providing different output voltages, so as to reduce capacitors used therein and save a production cost thereof.

The present invention provides a charge pump circuit, which is adapted for generating a first output voltage and a second output voltage according to an input voltage. The charge pump circuit includes a pump unit, a first switch, a second switch, a third switch, a fourth switch, a fifth switch, a fly capacitor, and a six switch. The pump unit includes at least one internal capacitor, a first terminal, a second terminal, a third terminal, and a fourth terminal. The first terminal is coupled to the input voltage. The second terminal is coupled to a first voltage, so as to charge the internal capacitor with the input voltage and the first voltage during a first period, and allow the internal capacitor to provide a first output voltage to the fourth terminal during a second period and a third period in accordance with a voltage level of the third terminal.

The first switch includes a first terminal and a second terminal. The first terminal of the first switch is coupled to a second voltage, and the second terminal of the first switch is coupled to the third terminal of the pump unit. The first switch is maintained off during the first period, and maintained on during the second period and the third period. The second switch includes a first terminal and a second terminal. The first terminal of the second switch is coupled to the fourth terminal of the pump unit. The second switch is maintained off during the first period, and maintained on during the second period and the third period. The third switch includes a first terminal and a second terminal. The first terminal of the third switch is coupled to the second terminal of the second switch. The third switch is maintained on during the first period and the second period, and maintained off during the third period. The first terminal of the third switch is also coupled to the output terminal of the first output voltage. The fourth switch includes a first terminal and a second terminal. The first terminal of the fourth switch is coupled to a third voltage. The fourth switch is maintained on during the first period and the second period, and maintained off during the third period. The fifth switch includes a first terminal and a second terminal. The first terminal of the fifth switch is coupled to a fourth voltage. The fifth switch is maintained off during the first period and the second period, and maintained on during the third period.

The fly capacitor includes a first terminal and a second terminal. The first terminal of the fly capacitor is coupled to the second terminal of the third switch and the second switch of the fifth switch. The second terminal of the fly capacitor is coupled to the second terminal of the fourth switch. Further, the second terminal of the fly capacitor is coupled to the second terminal of the third voltage during the second period, for charging the fly capacitor with the first output voltage and the third voltage. During the third period, the fly capacitor provides the second output voltage to the second terminal of the fly capacitor in accordance with a voltage level of the fourth voltage. The second terminal of the fly capacitor is coupled to the third voltage, so as to provide the first output voltage to the first terminal of the fly capacitor during the first period in accordance with a voltage level of the third voltage. The sixth switch includes a first terminal and a second terminal. The first terminal of the sixth switch is coupled to the second terminal of the fly capacitor. The sixth switch is maintained off during the first period and the second period, and maintained on during the third period. The second terminal of the sixth switch is coupled to the output terminal of the second output voltage.

The present invention provides a charge pump circuit. The charge pump circuit includes a pump unit, a first switch, a second switch, a third switch, a fourth switch, a fly capacitor and a fifth switch. The pump unit includes an input terminal, and an output terminal. The input terminal of the pump unit receives an input voltage, and the output terminal of the pump unit provides a first output voltage. The first switch includes a first terminal and a second terminal. The first terminal of the first switch is coupled to the output terminal of the pump unit. The first switch is maintained off during the first period, and maintained on during the second period and the third period. The second terminal of the first switch is coupled to the output terminal of the first output voltage.

The second switch includes a first terminal and a second terminal. The second switch is maintained on during the first period and the second period, and maintained off during the third period. The third switch includes a first terminal and a second terminal. The first terminal of the third switch is coupled to a first voltage. The third switch is maintained on during the first period and the second period, and maintained off during the third period. The fourth switch includes a first terminal and a second terminal. The first terminal of the fourth switch is coupled to a second voltage. The fourth switch is maintained off during the first period and the second period, and maintained on during the third period.

The fly capacitor includes a first terminal and a second terminal. The first terminal of the fly capacitor is coupled to the second terminal of the second switch and the second switch of the fourth switch. The second terminal of the fly capacitor is coupled to the second terminal of the third switch. Further, the second terminal of the fly capacitor is coupled to the first voltage during the second period, for charging the fly capacitor with the first output voltage and the first voltage. During the third period, the fly capacitor provides the second output voltage to the second terminal of the fly capacitor in accordance with a voltage level of the second voltage. The second terminal of the fly capacitor is coupled to the first voltage during the first period, so as to allow the fly capacitor to provide the first output voltage in accordance with a voltage level of the first voltage. The fifth switch includes a first terminal and a second terminal. The first terminal of the fifth switch is coupled to the second terminal of the fly capacitor. The fifth switch is maintained off during the first period and the second period, and maintained on during the third period. The second terminal of the fifth switch is coupled to the output terminal of the second output voltage.

The present invention employs a fly capacitor for serving as a stabilization capacitor for performing output voltage function during different periods, and therefore the number of the stabilization capacitors used therein may be reduced. Furthermore, the present invention is adapted to generate a relative high output voltage when using less control signals. As such, the present invention is featured with a higher efficiency and a larger maximum load current.

DESCRIPTION OF THE EMBODIMENTS

First Embodiment

FIG. 5is a circuit diagram of a charge pump according to a first embodiment of the present invention. Referring toFIG. 5, there is shown a charge pump circuit500including a first switch SW1, a second switch SW2, a third switch SW3, a fourth switch SW4, a fifth switch SW5, a sixth switch SW6, a fly capacitor Cf2, and an output capacitor Cout.

The pump unit510includes a first terminal T1, a second terminal T2, a third terminal T3, and a fourth terminal T4. The first terminal T1of the pump unit510is coupled to an input voltage Vin, and the second terminal T2of the pump unit510is coupled to a first voltage V1, i.e., a grounding voltage GND. The pump unit510further includes an internal capacitor Cf1, a seventh switch SW7, and an eighth switch SW8. The seventh switch SW7includes a first terminal and a second terminal. The internal capacitor Cf1includes a first terminal and a second terminal. The first terminal of the seventh switch SW7is coupled to the first terminal T1of the pump unit510, and the second terminal of the seventh switch SW7is coupled to the first terminal of the internal capacitor Cf1. The first terminal of the internal capacitor Cf1also serves as the fourth terminal T4of the pump unit510. The eighth switch SW8includes a first terminal and a second terminal. The first terminal of the eighth switch SW8serves as the second terminal T2of the pump unit510. The second terminal of the eighth switch SW8is coupled to the second terminal of the internal capacitor Cf1. The second terminal of the internal capacitor Cf1serves as the third terminal T3of the pump unit510.

The first switch SW1includes a first terminal and a second terminal. The first terminal of the first switch SW1is coupled to a second voltage V2, e.g., an input voltage Vin. The second terminal of the first switch SW1is coupled to the third terminal T3of the pump unit510. The second switch SW2includes a first terminal and a second terminal. The first terminal of the second switch SW2is coupled to the fourth terminal T4of the pump unit510. The third switch SW3includes a first terminal and a second terminal. The first terminal of the third switch SW3is coupled to the second terminal of the second switch SW2. The first terminal of the third switch SW3is coupled to a first output voltage VO1. The fourth switch SW4includes a first terminal and a second terminal. The first terminal of the fourth switch SW4is coupled to a third voltage V3, e.g., a grounding voltage GND. The fifth switch SW5includes a first terminal and a second terminal. The first terminal of the fifth switch SW5is coupled to a fourth voltage V4, e.g., a grounding voltage GND.

The fly capacitor Cf2includes a first terminal and a second terminal. The first terminal of the fly capacitor Cf2is coupled to the second terminal of the third switch SW3and the second terminal of the fifth switch SW5. The second terminal of the fly capacitor Cf2is coupled to the second terminal of the fourth switch SW4. The sixth switch SW6includes a first terminal and a second terminal. The first terminal of the sixth switch SW6is coupled to the second terminal of the fly capacitor Cf2. The output capacitor Cout includes two terminals, one of which is coupled to the grounding terminal GND, and the other is coupled to the second terminal of the sixth switch SW6.

The structure and interrelationship between components of the charge pump circuit500are discussed in brief above. And below, the operation of the charge pump circuit500will be further illustrated in more detail. First, when the charge pump circuit500enters a first period, a control signal PH1is at a high level, and control signals PH2and PH3are at a low level. In this case, the third switch SW3, the fourth switch SW4, the seventh switch SW7, and the eighth switch SW8are maintained on, while the first switch SW1, the second switch SW2, the fifth switch SW5, and the sixth switch SW6are maintained off, in which an equivalent circuit of the charge pump circuit500is as shown inFIG. 6A. Meanwhile, the input voltage Vin and the first voltage V1, i.e., the grounding voltage GND, are respectively coupled to the two terminals of the internal capacitor Cf1and charge the internal capacitor Cf1thereby, until a voltage difference between the two terminals of the internal capacitor Cf1equals to the input voltage Vin.

Then the charge pump circuit500enters the second period, in which the control signal PH2is at the high level, and the control signals PH1and PH3are at the low level. In this case, the first switch SW1, the second switch SW2, the third switch SW3, and the fourth switch SW4are maintained on, while the fifth switch SW5, the sixth switch SW6, the seventh switch SW7and the eighth switch SW8are maintained off, in which an equivalent circuit of the charge pump circuit500is shown inFIG. 6B. Meanwhile, the second terminal of the internal capacitor Cf1is coupled to the second voltage V2, i.e., input voltage Vin, so that a voltage level at the first terminal of the internal capacitor Cf1is raised from Vin to 2Vin. The internal capacitor Cf1then charges the fly capacitor Cf2to 2Vin and provides the first output voltage VO1with a voltage level of 2Vin.

Then the charge pump circuit500enters the third period, in which the control signal PH3is at the high level, and the control signals PH1and PH2are at the low level. In this case, the first switch SW1, the second switch SW2, the fifth switch SW5, and the sixth switch SW6are maintained on, and the third switch SW3, the fourth switch SW4, the seventh switch SW7and the eighth switch SW8are maintained off, in which an equivalent circuit of the charge pump circuit500is as shown inFIG. 6C. Meanwhile, the first output voltage VO1is maintained at the voltage level of 2Vin. On the other hand, the first terminal of the fly capacitor Cf2is coupled to the fourth voltage V4, i.e., the grounding voltage GND, so as to discharge the output capacitor Cout by the charges stored in the fly capacitor Cf2, and thereby generate a second output voltage VO2with a voltage level of −2Vin.

According to the first embodiment, the first voltage, the second voltage, the third voltage, and the fourth voltage can be set as voltages respectively with different voltage levels. The aforementioned first period, second period, and third period are used for identifying the sequence of turning on the switches, without restricting the practical order of processing. Further, first output voltage and second output voltage with other multiplying factors can also be provided according to the present invention, as illustrated in embodiments given below.

Second Embodiment

FIG. 7is a circuit diagram of a charge pump according to a second embodiment of the present invention. Referring toFIG. 7, there is shown a charge pump circuit700. The charge pump circuit700includes a pump unit710, a first switch SW1, a second switch SW2, a third switch SW3, a fourth switch SW4, a fifth switch SW5, a sixth switch SW6, a fly capacitor Cf2, and an output capacitor Cout.

The first switch SW1includes a first terminal and a second terminal. The first terminal of the first switch SW1is coupled to a second voltage V2, e.g., an input voltage Vin. The second terminal of the first switch SW1is coupled to the third terminal T3of the pump unit710. The second switch SW2includes a first terminal and a second terminal. The first terminal of the second switch SW2is coupled to the fourth terminal T4of the pump unit710. The third switch SW3includes a first terminal and a second terminal. The first terminal of the third switch SW3is coupled to the second terminal of the second switch SW2. The first terminal of the third switch SW3is also coupled to an output terminal of a first output voltage VO1. The fourth switch SW4includes a first terminal and a second terminal. The first terminal of the fourth switch SW4is coupled to a third voltage V3, e.g., a grounding voltage GND. The fifth switch SW5includes a first terminal and a second terminal. The first terminal of the fifth switch SW5is coupled to a fourth voltage V4, e.g., a grounding voltage GND.

The fly capacitor Cf2includes a first terminal and a second terminal. The first terminal of the fly capacitor Cf2is coupled to the second terminal of the third switch SW3and the second terminal of the fifth switch SW5. The second terminal of the fly capacitor Cf2is coupled to the second terminal of the fourth switch SW4. The sixth switch SW6includes a first terminal and a second terminal. The first terminal of the sixth switch SW6is coupled to the second terminal of the fly capacitor Cf2. The output capacitor Cout includes two terminals, one of which is coupled to the grounding terminal GND, and the other is coupled to the second terminal of the sixth switch SW6.

The pump unit710includes internal capacitors Cf1_1through Cf1_M, in which M is a positive integer greater than 0, first internal switches ISW1_1through ISW1_M, second internal switches ISW2_1through ISW2_M, and third internal switches S1through SM−1. Each of the internal capacitors Cf1_1through Cf1_M, the first internal switches ISW1_1through ISW1_M, the second internal switches ISW2_1through ISW2_M, and the third internal switches S1through SM−1includes a first terminal and a second terminal. The pump unit710includes a first terminal T1, a second terminal T2, a third terminal T3, and a fourth terminal T4. The first terminal T1of the pump unit710is coupled to an input voltage Vin, and the second terminal T2of the pump unit710is coupled to a first voltage V1, i.e., a grounding voltage GND. The second terminal of the internal capacitor Cf1_1is coupled to the third terminal T3of the pump unit710. The first terminal of the internal capacitor Cf1_M is coupled to the fourth terminal T4of the pump unit710. The first internal switches ISW1_1through ISW1_M are respectively coupled between the first terminals of corresponding internal capacitors Cf1_1through Cf1_M and the first terminal T1of the pump unit710. The second internal switches ISW2_1through ISW2_M are respectively coupled between the second terminals of corresponding internal capacitors Cf1_1through Cf1_M and the second terminal T2of the pump unit710.

The third internal switches S1through SM−1are coupled in a manner that the first terminal of the iththird internal switch Siis coupled to the first terminal of the ithinternal capacitor Cf1_i, and the second terminal of the iththird internal switch Siis coupled to the second terminal of the i+1thinternal capacitor Cf1_i+1, in which 0<i<M.

The structure and interrelationship between components of the charge pump circuit700are discussed in brief above. And below, the operation of the charge pump circuit700will be further illustrated in more detail. First, the charge pump circuit500enters a first period, in which a control signal PH1is at a high level, and control signals PH2and PH3are at a low level. In this case, the first internal switches ISW1_1through ISW1-M, the second internal switches ISW2_1through ISW2-M, the third switch SW3, and the fourth switch SW4are maintained on, while the first switch SW1, the second switch SW2, the fifth switch SW5, the sixth switch SW6, and the third internal switches S1through SM−1are maintained off. In such a way, the internal capacitors Cf1_1through Cf1_M are connected in parallel and coupled between the first terminal T1and the second terminal T2of the pump unit710. Meanwhile, the input voltage Vin and the first voltage V1, i.e., the grounding voltage GND, charge the internal capacitors Cf1_1through Cf1_M connected in parallel until a voltage difference between the two terminals of the internal capacitors Cf1_1through Cf1_M equals to the input voltage Vin.

Then the charge pump circuit700enters the second period, in which the control signal PH2is at the high level, and the control signals PH1and PH3are at the low level. In this case, the first switch SW1, the second switch SW2, the third switch SW3, the fourth switch SW4, and the third internal switches S1through SM−1are maintained on, while the fifth switch SW5, the sixth switch SW6, the first internal switches ISW1_1through ISW1-M, and the second internal switches ISW2_1through ISW2-M are maintained off. In such a way, the internal capacitors Cf1_1through Cf1_M are connected in series serving as an internal capacitor. A voltage basis terminal of the internal capacitor series, i.e., the second terminal of the internal capacitor Cf1_1, is coupled to the third terminal T3of the pump unit710. A voltage accumulating terminal of the internal capacitor series, i.e., the first terminal of the internal capacitor Cf1_M charges the fly capacitor Cf2to (M+1)×Vin via the fourth terminal T4of the pump unit710and the second switch SW2, and therefore provides a first output voltage VO1with a voltage level of (M+1)×Vin.

Then the charge pump circuit700enters the third period, in which the control signal PH3is at the high level, and the control signals PH1and PH2are at the low level. In this case, the first switch SW1, the second switch SW2, the fifth switch SW5, the sixth switch SW6, and the third internal switches S1through SM−1are maintained on, while the third switch SW3, the fourth switch SW4, the first internal switches ISW1_1through ISW1−M, and the second internal switches ISW2_1through ISW2-M are maintained off. Meanwhile, the first output voltage VO1is maintained at the voltage level of (M+1)×Vin. On the other hand, the first terminal of the fly capacitor Cf2is coupled to the fourth voltage V4, i.e., the grounding voltage GND, so as to discharge the output capacitor Cout via the sixth switch SW6, and thereby generate a second output voltage VO2with a voltage level of −(M+1)×Vin. The aforementioned first period, second period, and third period are used for identifying the sequence of turning on the switches, without restricting the practical order of processing.

Those skilled in the art may vary the quantity of internal capacitors employed in the pump unit710, i.e., selecting the value of M, so as to generate first output voltage VO1and second output voltage VO2with a corresponding multiplying factor. Further, the multiplying factor for voltage levels of the first output voltage VO1and the second output voltage VO2can also be adjusted by setting the first voltage V1, the second voltage V2, the third voltage V3, and the fourth voltage V4with different voltage levels. For example, the second voltage V2of the charge pump circuit700can be varied to the grounding voltage GND or other voltage level, so that the charge pump circuit700generates an M multiple of the output voltage plus V2and a −M multiple of the output voltage minus V2.

Third Embodiment

FIG. 8is a circuit block diagram of a charge pump according to a third embodiment of the present invention. Referring toFIG. 8, there is shown a charge pump circuit800. The charge pump circuit800includes a pump unit810, a first switch SW1, a second switch SW2, a third switch SW3, a fourth switch SW4, a fifth switch SW5, a fly capacitor Cf2, and an output capacitor Cout. The pump unit810includes an input terminal and an output terminal TO1. The input terminal of the pump unit810receives an input voltage Vin, and a first output voltage VO1is provided from the output terminal TO1of the pump unit810.

The first switch SW1includes a first terminal and a second terminal. The first terminal of the first switch SW1is coupled to the output terminal TO1of the pump unit810. The second terminal of the first switch SW1is coupled to the output terminal of the first output voltage VO1. The second switch SW2includes a first terminal and a second terminal. The first terminal of the second switch SW2is coupled to the second terminal of the first switch SW1. The third switch SW3includes a first terminal and a second terminal. The first terminal of the third switch SW3is coupled to a first voltage V1, e.g., grounding voltage GND. The fly capacitor Cf2includes a first terminal and a second terminal. The fourth switch includes a first terminal and a second terminal. The first terminal of the fourth switch is couple to a second voltage V2, e.g., the grounding voltage GND. The first terminal of the fly capacitor Cf2is coupled to the second terminal of the second switch SW2and the second terminal of the fourth switch SW4. The second terminal of the fly capacitor Cf2is coupled to the second terminal of the third switch SW3. The fifth switch SW5includes a first terminal and a second terminal. The first terminal of the fifth switch SW5is coupled to the second terminal of the fly capacitor Cf2. The output capacitor Cout includes two terminals, one of which is coupled to the grounding voltage GND, and the other is coupled to the second terminal of the fifth switch SW5and an output terminal of the second output voltage VO2.

The structure and interrelationship between components of the charge pump circuit800are discussed in brief above. And below, the application of the pump unit810will be further illustrated in more detail.

FIG. 9is a circuit diagram of the charge pump ofFIG. 8. Referring toFIG. 9, the pump unit810includes a first pump unit930, a sixth switch SW6, a seventh switch SW7, an internal capacitor Cf1, an eighth switch SW8, and a ninth switch SW9. The first pump unit930includes a first terminal T5, a second terminal T6, a third terminal T7, and a fourth terminal T8. Each of the sixth switch SW6, the seventh switch SW7, the internal capacitor Cf1, the eighth switch SW8, and the ninth switch SW9includes a first terminal and a second terminal. The first terminal T5of the first pump unit930is coupled to the input voltage Vin. The second terminal T6of the first pump unit930is coupled to a third voltage, e.g., grounding voltage GND. The first pump unit930further includes a first internal capacitor Cf_1, a tenth switch SW10, and an eleventh switch SW11. A terminal of the tenth switch SW10serves as the first terminal T5of the first pump unit930, and another terminal of the tenth switch SW10is coupled to a first terminal of the first internal capacitor Cf_1which is served as the fourth terminal T8of the first pump unit930. A terminal of the eleventh switch SW11is served as the second terminal T6of the first pump unit930, and another terminal of the eleventh switch SW11is coupled to the second terminal of the first internal capacitor Cf_1which is served as the third terminal T7of the first pump unit930.

The first terminal of the sixth switch SW6is coupled to a fourth voltage, e.g., the input voltage Vin. The second terminal of the sixth voltage SW6is coupled to the third terminal T7of the first pump unit930. The first terminal of the seventh switch SW7is coupled to the fourth terminal T8of the first pump unit930. The first terminal of the internal capacitor Cf1is coupled to the second terminal of the seventh switch SW7. The first terminal of the eighth switch SW8is coupled to the second terminal of the internal capacitor Cf1, and the second terminal of the eighth switch SW8is coupled to a third voltage V3, i.e., grounding voltage GND. The first terminal of the ninth switch SW9is coupled to the second terminal of the internal capacitor Cf1, and the second terminal of the ninth switch SW9is coupled to a fourth voltage V4, i.e., the input voltage Vin.

The structure and interrelationship between components of the pump unit810are discussed in brief above. And below, the operation of the charge pump circuit800will be further illustrated in more details. First, when the charge pump circuit800enters a second period, a control signal PH2is at a high level, and control signals PH1and PH3are at a low level. In this case, the first switch SW1, the second switch SW2, the third switch SW3, the ninth switch SW9, the tenth switch SW10, and the eleventh switch SW11are maintained on, while the fourth switch SW4, the fifth switch SW5, the sixth switch SW6, the seventh switch SW7, and the eighth switch SW8are maintained off, in which an equivalent circuit of the charge pump circuit800is shown inFIG. 10A. Meanwhile, the input voltage Vin and the third voltage V1, i.e., the grounding voltage GND, charge the first internal capacitor Cf_1of the first pump unit930, so as to obtain a voltage difference between the two terminals of the first internal capacitor Cf_1equals to the input voltage Vin.

Then the charge pump circuit800enters the third period, in which the control signal PH3is at the high level, and the control signals PH1and PH2are at the low level. In this case, the first switch SW1, the fourth switch SW4, the fifth switch SW5, the ninth switch SW9, the tenth switch SW10, and the eleventh switch SW11are maintained on, while the second switch SW2, the third switch SW3, the sixth switch SW6, the seventh switch SW7, and the eighth switch SW8are maintained off, in which in which an equivalent circuit of the charge pump circuit800is as shown inFIG. 10B. Meanwhile, the input voltage Vin and the third voltage V3, i.e., the grounding voltage GND, keeps charging the first internal capacitor Cf_1, and the voltage difference between two terminals of the first internal capacitor Cf_1is maintained as Vin.

Then the charge pump circuit800enters the first period, in which the control signal PH1is at the high level, and the control signals PH2and PH3are at the low level. In this case, the second switch SW2, the third switch SW3, the sixth switch SW6, the seventh switch SW7, and the eighth switch SW8are maintained on, while the first switch SW1, the fourth switch SW4, the fifth switch SW5, the ninth switch SW9, the tenth switch SW10, and the eleventh switch SW11are maintained off, in which an equivalent circuit of the charge pump circuit800is as shown inFIG. 10C. Meanwhile, the second terminal of the first internal capacitor Cf_1is coupled to the fourth voltage V4, i.e., the input terminal Vin, so that the voltage level at the first terminal of the first internal capacitor Cf_1rises from Vin to 2Vin, and charges the internal capacitor Cf1of the pump unit810to 2Vin.

Then the charge pump circuit800enters the second period again, in which the second terminal of the internal capacitor Cf1is coupled to the input voltage Vin, and the voltage level of the first terminal of the internal capacitor Cf1rises from 2Vin to 3Vin. The internal capacitor Cf1then charges the fly capacitor Cf2to 3Vin, and generates the first output voltage VO1with a voltage level of 3Vin.

Then the charge pump circuit800enters the third period again, in which the second terminal of the internal capacitor Cf1is maintained coupled with the input voltage Vin, so that the first output voltage VO1is maintained with the voltage level of 3Vin. On the other hand, the first terminal of the fly capacitor Cf2is coupled to the grounding voltage GND, and thereby discharges the output capacitor Cout by the charges stored therein, and thus generating the second output voltage VO2with a voltage level of −3Vin thereby.

In such a way, the charge pump circuit800repetitively passes through the foregoing three periods, and generates the first output voltage VO1of 3Vin and the second output voltage VO2of −3Vin. According to the current embodiment, the aforementioned first period, second period, and third period are used for identifying the sequence of turning on the switches, without restricting the practical order of processing.

Furthermore, the third embodiment may also be modified to provide the first output voltage VO1and the second output voltage VO2with other multiplying factors by replacing the internal circuit of the first pump unit930as shown inFIG. 9with a circuit of a first pump unit1130as shown inFIG. 11. Those skilled in the art should be able to know the circuit as shown inFIG. 11by referring to the foregoing embodiments illustrated above, and adaptively determine the quantity of the first internal capacitors used in the first pump unit1130, i.e., the value of M, so as to obtain the first output voltage VO1and the second output voltage VO2of corresponding multiplying factors. The details are not to be iterated hereby.

Moreover, the internal circuit structure of the pump unit810is one of the embodiments, and should not be construed as a restriction of the present invention. Those skilled in the art having been taught by the above teachings should know how to obtain output voltages M×Vin and −M×Vin with other circuits capable of providing a multiple of input voltages for the pump unit810according to the current embodiment, and is not iterated hereby.

In summary, the present invention has the following advantages.1. By employing a fly capacitor for stabilizing an output voltage under a certain control signal (in a certain period), comparatively a less number of capacitors may be employed for generating a maximum output voltage. Thus, the number of capacitors used therein may be reduced and the cost of fabricating the circuit may be reduced.2. By using less number of control signals (periods), an imbalance between charging and discharging may be avoided so as to obtain a higher output voltage, and therefore a higher efficiency and a larger maximum load current may be achieved.