Patent Publication Number: US-2022239221-A1

Title: Voltage regulator

Description:
RELATED APPLICATIONS 
     This application claims the benefit of Chinese Patent Application No. 201710720368.9, filed on Aug. 21, 2017, which is incorporated herein by reference in its entirety. 
     FIELD OF THE INVENTION 
     The present invention generally relates to the field of power electronics, and more particularly to voltage regulators. 
     BACKGROUND 
     A switched-mode power supply (SMPS), or a “switching” power supply, can include a power stage circuit and a control circuit. When there is an input voltage, the control circuit can consider internal parameters and external load changes, and may regulate the on/off times of the switch system in the power stage circuit. Switching power supplies have a wide variety of applications in modern electronics. For example, switching power supplies can be used to drive light-emitting diode (LED) loads. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic block diagram of an example switched capacitor converter. 
         FIG. 2  is a waveform diagram of example operation of the switched capacitor converter of  FIG. 1 . 
         FIG. 3  is a schematic block diagram of a first example voltage regulator, in accordance with embodiments of the present invention. 
         FIG. 4  is a waveform diagram of example control signal operation for the first example voltage regulator, in accordance with embodiments of the present invention. 
         FIG. 5  is an equivalent circuit diagram of the first example voltage regulator operating in a first state, in accordance with embodiments of the present invention. 
         FIG. 6  is an equivalent circuit diagram of the first example voltage regulator operating in a second state, in accordance with embodiments of the present invention. 
         FIG. 7  is a schematic block diagram of a second example voltage regulator, in accordance with embodiments of the present invention. 
         FIG. 8  is a waveform diagram of example control signal operation for the second example voltage regulator, in accordance with embodiments of the present invention. 
         FIG. 9  is an equivalent circuit diagram of the second example voltage regulator operating in a first state, in accordance with embodiments of the present invention. 
         FIG. 10  is an equivalent circuit diagram of the second example voltage regulator operating in a second state, in accordance with embodiments of the present invention. 
         FIG. 11  is a schematic block diagram of a third example voltage regulator, in accordance with embodiments of the present invention. 
         FIG. 12  is a waveform diagram of example control signal operation for the third example voltage regulator, in accordance with embodiments of the present invention. 
         FIG. 13  is an equivalent circuit diagram of the third example voltage regulator operating in a first state, in accordance with embodiments of the present invention. 
         FIG. 14  is an equivalent circuit diagram of the third example voltage regulator operating in a second state, in accordance with embodiments of the present invention. 
         FIG. 15  is a schematic block diagram of a fourth example voltage regulator, in accordance with embodiments of the present invention. 
         FIG. 16  is a waveform diagram of example control signal operation for the fourth example voltage regulator, in accordance with embodiments of the present invention. 
         FIG. 17  is an equivalent circuit diagram of the fourth example voltage regulator operating in a first state, in accordance with embodiments of the present invention. 
         FIG. 18  is an equivalent circuit diagram of the fourth example voltage regulator operating in a second state, in accordance with embodiments of the present invention. 
         FIG. 19  is a schematic block diagram of a fifth example voltage regulator, in accordance with embodiments of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Reference may now be made in detail to particular embodiments of the invention, examples of which are illustrated in the accompanying drawings. While the invention may be described in conjunction with the preferred embodiments, it may be understood that they are not intended to limit the invention to these embodiments. On the contrary, the invention is intended to cover alternatives, modifications and equivalents that may be included within the spirit and scope of the invention as defined by the appended claims. Furthermore, in the following detailed description of the present invention, numerous specific details are set forth in order to provide a thorough understanding of the present invention. However, it may be readily apparent to one skilled in the art that the present invention may be practiced without these specific details. In other instances, well-known methods, procedures, processes, components, structures, and circuits have not been described in detail so as not to unnecessarily obscure aspects of the present invention. 
     Referring now to  FIG. 1 , shown is a schematic block diagram of an example switched capacitor converter. Referring also to  FIG. 2 , shown is a waveform diagram of example operation of the switched capacitor converter of  FIG. 1 . A switched capacitor converter may realize voltage or current conversion by controlling the charge and discharge of capacitors through switches. Here, an input port can receive input voltage Vin. Switch Q 1  can connect between node “a” of capacitor C and a first node of a voltage input port, and may be turned on and off under the control of control signal G 1 . Switch Q 2  can connect between node “a” of capacitor C and a first node of an output port, and can be turned on and off under the control of control signal G 2 . Also control signals G 1  and G 2  may be complementary, such that when control signal G 1  is high, control signal G 2  is low, and vice versa. 
     Node “b” of capacitor C can connect to a second node of the input port and a second node of the output port. The second node of the input port and the second node of the output port may be a reference node (e.g., a ground node). Output capacitor Co can also be configured in the output port to smooth output voltage Vout. Thus, capacitor C May intermittently discharge to the output port by alternately turning switches Q 1  and Q 2  on and off, thereby realizing power transmission and voltage/current conversion. However, in this structure, the input port and the output port share a common ground, and capacitor C intermittently outputs an output current to the output port, which can lead to larger undesirable current pulsation on an input source and the output capacitor. Further, this example isolated converter may utilize coils with a larger volume that is not conducive to a miniaturized system. 
     In one embodiment, a voltage regulator can include: (i) N energy storage capacitors, each having first nodes connected together, where N is a positive integer; (ii) N input capacitors connected in series between two nodes of an input port; (iii) N input switch circuits, each being connected in parallel with a corresponding one of the N input capacitors, where each of the N input switch circuits is configured to selectively couple a second node of a corresponding one of the N energy storage capacitors to a first node or a second node of the corresponding input capacitor; (iv) a first output switch circuit configured to selectively couple the first nodes of the N energy storage capacitors to a first node or a second node of an output port; and (v) where the N input switch circuits and the first output switch circuit are controlled to switch among different states such that an output voltage of the voltage regulator is proportional to an input voltage of the voltage regulator. 
     Referring now to  FIG. 3 , shown is a schematic block diagram of a first example voltage regulator, in accordance with embodiments of the present invention. In this particular example, the voltage regulator can include input capacitors Cn 1  and Cn 2 , energy storage capacitors C 1  and C 2 , input switch circuits IN 1  and IN 2 , output switch circuit OUT 1  and isolation capacitor C′. One node of each of energy storage capacitors C 1  and C 2  can connect to a node “a”, and nodes b 1  and b 2  of energy storage capacitors C 1  and C 2  can connect to input switch circuits IN 1  and IN 2 , respectively. Input capacitors Cn 1  and Cn 2  can connect in series between two nodes n 0  and n 2  (e.g., n 2  is a ground node) of an input port. Input capacitor Cn 1  can connect between nodes n 0  and n 1 , and input capacitor Cn 2  can connect between node n 1  and node n 2 . Input switch circuit IN 1  can connect in parallel with input capacitor Cn 1 , in order to selectively couple node b 1  of energy storage capacitor C 1  to node n 0  or n 1 . Input switch circuit IN 2  can connect in parallel with input capacitor Cn 2 , in order to selectively couple node b 2  of energy storage capacitor C 2  to node n 1  or n 2 . For example, the voltage may further include output capacitor Cout at an output port. 
     Input switch circuit IN 1  can include switches Q 1  and Q 2  connected in series. A common node of switches Q 1  and Q 2  can connect to node b 1  of energy storage capacitor C 1 , in order to form a half-bridge circuit. Input switch circuit IN 2  can include switches Q 3  and Q 4  connected in series. A common node of switches Q 3  and Q 4  can connect to node b 2  of energy storage capacitor C 2 , in order to form a half-bridge circuit. Switches Q 1  and Q 2  may respectively be controlled by control signals GH and GL. Switches Q 3  and Q 4  can respectively be controlled by control signals GH and GL. 
     Referring now to  FIG. 4 , shown is a waveform diagram of example control signal operation for the first example voltage regulator, in accordance with embodiments of the present invention. As shown in  FIG. 4 , control signals GH and GL can be inverted with each other, such that switches Q 1  and Q 2  are complementary with each other, and switches Q 3  and Q 4  are complementary with each other. That is, switches Q 2  and Q 4  may simultaneously be turned off while switches Q 1  and Q 3  are simultaneously turned on, and switches Q 1  and Q 3  may simultaneously be turned off while switches Q 2  and Q 4  are simultaneously turned on. 
     Output switch circuit OUT 1  can connect with node “a” of energy storage capacitors C 1  and C 2 , to selectively couple node “a” to node o 1  or o 2  (e.g., node o 2  is a ground node of the output port in  FIG. 3 ) of the output port. Output switch circuit OUT 1  can include switches Q 5  and Q 6  connected in series. A common node of switches Q 5  and Q 6  can connect to node “a” of energy storage capacitors C 1  and C 2 , in order to form a half-bridge circuit. Switches Q 5  and Q 6  may respectively be controlled by control signals GH′ and GL′. As shown in  FIG. 4 , control signals GH′ and GL′ are inverted from each other, such that switches Q 5  and Q 6  are complementary with each other. Control signal GH′ may be in phase with control signal GH for controlling the input switch circuit. 
     That is, in the circuit shown in  FIG. 3 , switches Q 2 , Q 4 , and Q 6  may simultaneously be turned off while switches Q 1 , Q 3 , and Q 5  are simultaneously turned on, and switches Q 2 , Q 4 , and Q 6  may simultaneously be turned on while switches Q 1 , Q 3 , and Q 5  are simultaneously turned off. Switches Q 1 -Q 6  may alternately turned on and off under control of control signals GH, GL, GH′, and GL′, such that the voltage regulator is switched between a “first” state and a “second” state. Isolation capacitor C′ can connect between node o 2  (e.g., a ground node) of the output port and node n 2  of the input port. Alternatively, isolation capacitor C′ may also between node o 2  of the output port and node n 0 , or between nodes o 2  and n 1 . In this example, isolation capacitor C′ may function to isolate the input port from the output port while forming a current return path between the input port and the output port. 
     Referring now to  FIG. 5 , shown is an equivalent circuit diagram of the first example voltage regulator operating in a first state, in accordance with embodiments of the present invention. In this particular example, in the first state, switches Q 1 , Q 3 , and Q 5  may be turned on while switches Q 2 , Q 4 , and Q 6  are turned off. Node “a” can connect with energy storage capacitors C 1  and C 2 , and to node o 1  of the output port through switch Q 5 . Input capacitor Cn 1 , energy storage capacitors C 1  and C 2 , and isolation capacitor C′ can be charged by the input port and input capacitor Cn 2 , and output voltage Vout may be provided between nodes o 1  and o 2  of the output port. In this way, multiple current paths may be formed. One current path can begin from node n 0 , sequentially pass through switch Q 1 , energy storage capacitor C 1 , switch Q 5 , the output port, and isolation capacitor C′, and return to node n 2  of the input port. 
     Another current path can begin from node n 0 , sequentially pass through input capacitor Cn 1 , switch Q 3 , energy storage capacitor C 2 , switch Q 5 , the output port, and isolation capacitor C′, and return to node n 2  of the input port. Another current path can begin from node n 1  connected with input capacitor Cn 2 , sequentially pass through switch Q 3 , energy storage capacitor C 2 , switch Q 5 , the output port and isolation capacitor C′, and return to energy storage capacitor Cn 2 . For example, given that a current flowing through the output port has a magnitude of 2, a current flowing from the input port has a magnitude of 3/2, a current flowing through input capacitor Cn 2  has a magnitude of ½, and a current flowing through input capacitor Cn 1  has a magnitude of ½. The current flowing through energy storage capacitor C 1  and the current flowing through energy storage capacitor C 2  may have the same magnitude (e.g., 1), and flow to node “a”. The current flowing through isolation capacitor C′ and the current flowing through the output port may have the same magnitude (e.g., 2). 
     Also, in the example circuit shown in  FIG. 5 , Vcn 1 +Vcn 2 =Vin; Vc 1 −Vc 2 =Vcn 1 ; and Vcn 2 −Vc 2 −Vc′=Vout. Vcn 1  may denote a voltage across input capacitor Cn 1 , Vcn 2  may denote a voltage across input capacitor Cn 2 , Vin may denote a voltage across the input port, Vc 1  may denote a voltage across energy storage capacitor C 1 , Vc 2  may denote a voltage across energy storage capacitor C 2 , Vc′ denotes a voltage across isolation capacitor C′, and Vout may denote a voltage across the output port. 
     Referring now to  FIG. 6 , shown is an equivalent circuit diagram of the first example voltage regulator operating in a second state, in accordance with embodiments of the present invention. In this particular example, in the second state, switches Q 2 , Q 4 , and Q 6  can be turned on, while switches Q 1 , Q 3 , and Q 5  may be turned off. As shown, input capacitor Cn 1 , energy storage capacitors C 1  and C 2  and isolation capacitor C′ may discharge, in order to charge input capacitor Cn 2 , and provide a current to the input port. In this way, multiple current paths may be formed. A current path can begin from energy storage capacitor C 1 , sequentially pass through switch Q 2 , input capacitor Cn 1 , nodes n 0  and n 2  of the input port, isolation capacitor C′, nodes o 1  and o 2  of the output port, and switch Q 6 , and return to node “a” of energy storage capacitor C 1 . Another current path can begin from energy storage capacitor C 1 , sequentially pass through switch Q 2 , input capacitor Cn 2 , isolation capacitor C′, nodes o 1  and o 2  of the output port, and switch Q 6 , and return to node “a” of energy storage capacitor C 1 . 
     Another current path can begin from energy storage capacitor C 2 , sequentially pass through switch Q 4 , isolation capacitor C′, nodes of and o 2  of the output port, and switch Q 6 , and return to node “a” of energy storage capacitor C 2 . For example, a direction of the current flowing through each of the capacitors in the second state is opposite to a direction of the current flowing through the capacitor in the first state. In the second state, node o 1  of the output port may float. Correspondingly, e.g., given that a current flowing through energy storage capacitor C 1  has a magnitude of 1, a current flowing from the input port (from the group node) has a magnitude of ½, a current flowing through input capacitor Cn 2  has a magnitude of ½, a current flowing through input capacitor Cn 1  has a magnitude of ½, a current flowing through energy storage capacitor C 2  has a magnitude of 1, and a current flowing through isolation capacitor C′ has a magnitude of 2. In a case that the voltage regulator is in the first state for the same duration as in the second state, an average current flowing through the output port has a magnitude of, e.g., 1. 
     In the example circuit shown in  FIG. 6 , Vcn 1 +Vcn 2 =Vin; Vc 1 −Vc 2 =Vcn 2 ; and Vc 2 +Vc′=0. When the voltage regulator switches between the first and second states at a relatively high frequency, a voltage of the capacitor may not change rapidly among different states. Therefore, parameters in the first state may be substantially the same as parameters in the second state. Therefore, according to the above equations, Vcn 1 =Vcn 2 =Vin/2, and further, Vout=Vcn 2 =Vin/2. 
     That is, output voltage Vout of the voltage regulator in this particular example is ½ of input voltage Vin, which corresponds to the number of the provided input capacitors. Here, the two input capacitors and the two input switch circuits respectively correspond to the two input capacitors form two input circuits, and the output switch circuit may form an output circuit. The two input circuits can connect to the output circuit through the two energy storage capacitors, respectively. The input switch circuits and the output switch circuit can be controlled to be switched among states, to control the energy storage capacitors and the input capacitors to charge and discharge, in order to realize power conversion. A step down ratio of the voltage regulator can be set by changing the number of input circuits and the number of energy storage capacitors, thereby obtaining a relatively high step down ratio with a relatively small circuit volume. Also, an isolation capacitor may be provided in this example, in order to isolate the input port from the output port without a transformer, thereby avoiding an influence of current ripple of the input voltage and the output capacitance. 
     Referring now to  FIG. 7 , shown is a schematic block diagram of a second example voltage regulator, in accordance with embodiments of the present invention. In this particular example, the voltage regulator can include input capacitors Cn 1  to Cn 3 , energy storage capacitors C 1 -C 3 , input switch circuits IN 1 -IN 3 , output switch circuit OUT 1 , and isolation capacitor C′. Input capacitors Cn 1 -Cn 3  can sequentially be connected in series between two nodes n 0  and n 3  of the input port. One node of each of energy storage capacitors C 1 -C 3  can connect to a node “a”, and the other nodes of energy storage capacitors C 1 -C 3  may connect to input switch circuits IN 1 -IN 3 , respectively. Input switch circuit INi can connect in parallel with input capacitor Cni, in order to selectively couple node “bi” of energy storage capacitor Ci corresponding to input switch circuit INi to one of two nodes of input capacitor Cni, where i=1, 2, or 3. Output switch circuit OUT 1  can connect across the output port, in order to selectively couple the node “a” to node o 1  or o 2  of the output port. Isolation capacitor C′ can connect between node o 2  of the output port and a node connected to any one of the input capacitors (that is, any one of nodes n 0  to n 3 ). 
     In  FIG. 7 , isolation capacitor C′ can connect between node o 2  of the output port and ground node n 3  of the input port. For example, the voltage regulator may further include output capacitor Cout connected across the output port. Input switch circuit IN 1  can include switches Q 1  and Q 2  connected in series. Input switch circuit IN 2  can include switches Q 3  and Q 4  connected in series. Input switch circuit IN 3  can include switches Q 5  and Q 6  connected in series. Therefore, three half-bridge circuits may be formed, which correspond to input capacitors Cn 1 -Cn 3 , respectively. A common node of the switches in input switch circuit INi can connect to node “bi” of energy storage capacitor Ci corresponding to input switch circuit INi. 
     Referring also to  FIG. 8 , shown is a waveform diagram of example control signal operation for the second example voltage regulator, in accordance with embodiments of the present invention. The two switches of input switch circuit INi can be turned on or turned off under the respective control of control signals GH and GL inverted from each other. The two switches are thus complementary with each other. In input switch circuit INi, one of the switches may be turned on while the other of the switches is turned off, in order to selectively couple node “bi” of input switch circuit INi to one of two nodes of input capacitor Cni corresponding to input switch circuit INi. 
     Output switch circuit OUT 1  can include switches Q 7  and Q 8  connected in series. Switches Q 7  and Q 8  can connect in series across the output port, in order to form a half-bridge circuit. Switches Q 7  and Q 8  can be controlled by control signals GH′ and GL′, respectively. As shown, control signals GH′ and GL′ may be inverted from each other, such that switches Q 7  and Q 8  are complementary with each other. Control signal GH′ may be in phase with control signal GH for controlling the input switch circuit. That is, in the circuit shown in  FIG. 7 , switches Q 1 , Q 3 , Q 5 , and Q 7  can simultaneously be turned on while switches Q 2 , Q 4 , Q 6 , and Q 8  are simultaneously turned off, and switches Q 1 , Q 3 , Q 5 , and Q 7  may simultaneously be turned off while switches Q 2 , Q 4 , Q 6 , and Q 8  are simultaneously turned on. Switches Q 1 -Q 8  may alternately be turned on and off under control of control signals GH, GL, GH′, and GL′, such that the voltage regulator is switched between a first state and a second state. 
     Referring now to  FIG. 9 , shown is an equivalent circuit diagram of the second example voltage regulator operating in a first state, in accordance with embodiments of the present invention. In this particular example, in the first state, switches Q 1 , Q 3 , Q 5 , and Q 7  may be turned on, while switches Q 2 , Q 4 , Q 6 , and Q 8  are turned off. As shown, node “a” can connect to node o 1  of the output port through switch Q 7 . Input capacitor Cn 1 , energy storage capacitors C 1 -C 3 , and isolation capacitor C′ can be charged by the input port and input capacitor Cn 3 , such that a current flows through nodes of and o 2  of the output port, and output voltage Vout may be provided between nodes o 1  and o 2  of the output port. In this way, multiple current paths may be formed. 
     A current path can begin from node n 0  of the input port, sequentially pass through switch Q 1 , energy storage capacitor C 1 , switch Q 7 , nodes of and o 2  of the output port and isolation capacitor C′, and return to node n 3  of the input port. Another circuit path can begin from node n 0  of the input port, sequentially pass through input capacitor Cn 1 , switch Q 3 , energy storage capacitor C 2 , switch Q 7 , nodes o 1  and o 2  of the output port, and isolation capacitor C′, and return to node n 3  of the input port. Another current path can begin from node n 2  connected to input capacitor Cn 3 , sequentially pass through switch Q 5 , energy storage capacitor C 3 , switch Q 7 , nodes o 1  and o 2  of the output port and isolation capacitor C′, and return to node n 3  connected to input capacitor Cn 3 . 
     If, for example, a current flowing through the output port has a magnitude of 2, a current flowing from the input port has a magnitude of 4/3, a current flowing through input capacitor Cn 3  has a magnitude of ⅔, a current flowing through input capacitor Cn 1  has a magnitude of ⅔, and a current flowing through input capacitor Cn 2  has a magnitude of 0, currents flowing through energy storage capacitors C 1 -C 3  have the same magnitude, which is ⅔, and a current flowing through the isolation capacitor and a current flowing through the output port have the same magnitude (e.g., 2). In this example circuit, Vcn 1 +Vcn 2 +Vcn 3 =Vin; Vc 1 −Vc 2 =Vcn 1 ; Vc 2 −Vc 3 =Vcn 2 ; and Vcn 3 −Vc 3 −Vc′=Vout. Vcni may denote a voltage across input capacitor Cni, where i=1, 2 or 3. Vci may denote a voltage across energy storage capacitor Ci, where i=1, 2 or 3. Vc′ may denote a voltage across isolation capacitor C′. Vin may denote a voltage across the input port, and Vout may denote a voltage across the output port. 
     Referring now to  FIG. 10 , shown is an equivalent circuit diagram of the second example voltage regulator operating in a second state, in accordance with embodiments of the present invention. In this particular example, in the second state, switches Q 2 , Q 4 , Q 6 , and Q 8  are turned on while switches Q 1 , Q 3 , Q 5 , and Q 7  are turned off. As shown, input capacitor Cn 3  can be charged by input capacitor Cn 1 , energy storage capacitors C 1 -C 3 , and isolation capacitor C′, and a current may be provided to the output port. Therefore, multiple current paths can be formed. A current path can begin from energy storage capacitor C 1 , sequentially pass through switch Q 2 , input capacitor Cn 1 , nodes n 0  and n 3  of the input port, isolation capacitor C′ and switch Q 8 , and return to energy storage capacitor C 1 . Another current path can begin from energy storage capacitor C 2 , sequentially pass through switch Q 4 , input capacitor Cn 3 , isolation capacitor C′, and switch Q 8 , and return to energy storage capacitor C 2 . 
     Another current path can begin from energy storage capacitor C 3 , sequentially pass through switch Q 6 , isolation capacitor C′ and switch Q 8 , and return to energy storage capacitor C 3 . In the second state, node o 1  of the output port may float. For example, a direction of the current flowing through each of the capacitors in the second state is opposite to a direction of the current flowing through the capacitor in the first state. Correspondingly, for example, a current flowing from the output port may have a magnitude of 2, a current flowing through input capacitor Cn 1  has a magnitude of ⅔, a current flowing through input capacitor Cn 2  has a magnitude of 0, a current flowing through input capacitor Cn 3  has a magnitude of ⅔, a current flowing through each of energy storage capacitors C 1  to C 3  has a magnitude of ⅔, and a current flowing through isolation capacitor C′ has a magnitude of 2. When the voltage regulator is in the first state for the same duration as the second state, an average current flowing through the output port has a magnitude of, e.g., 1. 
     In the circuit shown in  FIG. 10 , Vcn 1 +Vcn 2 +Vcn 3 =Vin; Vc 1 −Vc 2 =Vcn 2 ; Vc 2 −Vc 3 =Vcn 3 ; and Vc 3 +Vc′=0. When the voltage regulator is switched between the first state and the second state at a relatively high frequency, a voltage of the capacitor may not change rapidly among different states. Therefore, parameters in the first state may be substantially the same as parameters in the second state. As such, according to the above equations, Vcn 1 =Vcn 2 =Vcn 3 =Vin/3, and further, Vout=Vcn 3 =Vin/3. That is, the output voltage of the voltage regulator in this particular example is ⅓ of input voltage Vin, which corresponds to the number of provided input capacitors. Similarly, when N energy storage capacitors, N input capacitors and N input switch circuits are provided in a voltage regulator having a similar structure, output voltage Vout is 1/N of input voltage Vin, where N is a positive integer. In this way, a voltage regulator with any step down ratio can be implemented. 
     Referring now to  FIG. 11 , shown is a schematic block diagram of a third example voltage regulator, in accordance with embodiments of the present invention. In this particular example, the voltage regulator can include two input capacitors Cn 1  and Cn 2 , two energy storage capacitors C 1  and C 2 , and input switch circuits IN 1  and IN 2  each in a form of a half-bridge circuit. Input switch circuits IN 1  and IN 2  can effectively change a connection relation between the energy storage capacitor and the input capacitor. On an output side, the voltage regulator can include an output circuit in a form of a full-bridge circuit. For example, the voltage regulator may further include output capacitor Cout connected across the output port. The output circuit can include output switch circuits OUT 1  and OUT 2 . Output switch circuit OUT 1  can selectively couple a node “a” connected with energy storage capacitors C 1  and C 2  to node of or o 2  of the output port. Output switch circuit OUT 2  can connect in parallel with output switch circuit OUT 1 . Output switch circuit OUT 2  may selectively couple input node “c” of output switch circuit OUT 2  to node o 1  or o 2  of the output port. Output switch circuit OUT 1  can include switches Q 5  and Q 6  connected in series. A common node of switches Q 5  and Q 6  can connect to node “a”, in order to form a half-bridge circuit. Switches Q 5  and Q 6  may respectively be controlled by control signals GH′ and GL′. 
     Referring now to  FIG. 12 , shown is a waveform diagram of example control signal operation for the third example voltage regulator, in accordance with embodiments of the present invention. As shown, control signals GH′ and GL′ are inverted with respect to each other, such that switches Q 5  and Q 6  are complementary with each other. Control signal GH′ can be in phase with control signal GH for controlling the input switch circuit. Output switch circuit OUT 2  can include switches Q 7  and Q 8  connected in series. A common node of switches Q 7  and Q 8  is input node “c” of output switch circuit OUT 2 . Switches Q 7  and Q 8  may be turned on or turned off under the respective control of control signals GH′ and GL′. Therefore, in the circuit shown in  FIG. 11 , switches Q 1 , Q 3 , Q 5 , and Q 7  may simultaneously be turned on while switches Q 2 , Q 4 , Q 6 , and Q 8  may simultaneously be turned off, and switches Q 1 , Q 3 , Q 5 , and Q 7  may simultaneously be turned off while switches Q 2 , Q 4 , Q 6 , and Q 8  are simultaneously turned on. Switches Q 1 -Q 8  may alternately be turned on and off under control of control signals GH, GL, GH′ and GL′, such that the voltage regulator switches between the first and second states. Also, a node of isolation capacitor C′ can connect to input node “c” of output switch circuit OUT 2 , and the other node of isolation capacitor C′ can connect to a node connected to any one of the input capacitors. In  FIG. 11 , isolation capacitor C′ can connect between nodes “c” and n 2 . Therefore, isolation capacitor C′ can effectively isolate the input port from the output port while forming a current path from the output port to the input port. 
     Referring now to  FIG. 13 , shown is an equivalent circuit diagram of the third example voltage regulator operating in a first state, in accordance with embodiments of the present invention. In this particular example, in the first state, switches Q 1 , Q 3 , Q 5 , and Q 7  are turned on while switches Q 2 , Q 4 , Q 6 , and Q 8  are turned off. Here, node “a” can connect to node o 1  of the output port through switch Q 5 , and node “c” can connect to node o 2  of the output port through switch Q 7 . The input port and input capacitor Cn 2  may discharge, in order to charge energy storage capacitors C 1  and C 2 , isolation capacitor C′, and the output port. In this way, multiple current paths may be formed. 
     One current path may begin from the node n 0  of the input port, sequentially pass through switch Q 1 , energy storage capacitor C 1 , switch Q 5 , nodes o 1  and o 2  of the output port, switch Q 7 , and isolation capacitor C′, and return to node n 2  of the input port. Another current path can begin from node n 0  of the input port, sequentially pass through input capacitor Cn 1 , switch Q 3 , energy storage capacitor C 2 , switch Q 5 , nodes o 1  and o 2  of the output port, switch Q 7  and isolation capacitor C′, and return to node n 2  of the input port. Another current path taking input capacitor Cn 2  as a current source may sequentially pass through node n 1 , switch Q 3 , energy storage capacitor C 2 , switch Q 5 , nodes o 1  and o 2  of the output port, switch Q 7 , isolation capacitor C′, and node n 2 . If, for example, a current flowing through the output port has a magnitude of 1, a current flowing from the input port has a magnitude of ¾, a current flowing through input capacitor Cn 2  has a magnitude of ¼, and a current flowing through input capacitor Cn 1  is ¼. 
     For example, current flowing through energy storage capacitor C 1  and a current flowing through energy storage capacitor C 2  may have the same magnitude (e.g., ½), and flow to node “a”. For example, current flowing through isolation capacitor C′ and a current flowing through the output port have the same magnitude (e.g., 1). In the circuit shown in  FIG. 13 , Vcn 1 +Vcn 2 =Vin; Vc 1 −Vc 2 =Vcn 1 ; and Vcn 2 −Vc 2 −Vc′=Vout. Vcn 1  may denote a voltage across input capacitor Cn 1 . Vcn 2  may denote a voltage across input capacitor Cn 2 . Vin may denote a voltage across the input port. Vc 1  may denote a voltage across energy storage capacitor C 1 , and Vc 2  may denote a voltage across energy storage capacitor C 2 . Vc′ may denote a voltage across isolation capacitor C′. Also, Vout may denote a voltage across the output port. 
     Referring now to  FIG. 14 , shown is an equivalent circuit diagram of the third example voltage regulator operating in a second state, in accordance with embodiments of the present invention. In this particular example, in the second state, switches Q 2 , Q 4 , Q 6 , and Q 8  may be turned on while switches Q 1 , Q 3 , Q 5 , and Q 7  are turned off. As shown, node “a” can connect to node o 2  of the output port through switch Q 6 , and node “c” can connect to node o 1  of the output port through switch Q 8 . Input capacitor Cn 1 , energy storage capacitors C 1  and C 2  and isolation capacitor C′ may discharge, in order to charge the input capacitor Cn 2 , the output port and the input port. Therefore, multiple current paths may be formed, which are different from the multiple current paths in the first state. 
     A current path may begin from energy storage capacitor C 1 , sequentially pass through switch Q 2 , input capacitor Cn 1 , nodes n 0  and n 2  of the input port, isolation capacitor C′, switch Q 8 , nodes o 1  and o 2  of the output port, and switch Q 6 , and return to node “a”. Another current path may begin from the energy storage capacitor C 1 , sequentially pass through switch Q 2 , input capacitor Cn 2 , isolation capacitor C′, switch Q 8 , nodes o 1  and o 2  of the output port, and switch Q 6 , and return to node “a”. Another current path may begin from energy storage capacitor C 2 , sequentially pass through switch Q 4 , isolation capacitor C′, switch Q 8 , nodes of and o 2  of the output port, and switch Q 6 , and return to node “a”. For example, a direction of the current flowing through each of the capacitors in the second state is opposite to a direction of the current flowing through the capacitor in the first state. If, for example a current flowing through the output port has a magnitude of 1, a current flowing through energy storage capacitor C 1  and a current flowing through energy storage capacitor C 2  have the same magnitude, which is ½, a current flowing through input capacitor Cn 1  has a magnitude of ¼, a current flowing through input capacitor Cn 2  has a magnitude of ¼, and a current flowing through isolation capacitor C′ and a current flowing through the output port have the same magnitude (e.g., 1). 
     Also, in the example current shown in  FIG. 14 , Vcn 1 +Vcn 2 =Vin; Vc 1 −Vc 2 =Vcn 2 ; and Vc 2 +Vc′=Vout. If the voltage regulator is switched between the first state and the second state at a relatively high frequency, a voltage of the capacitor may not change rapidly among the different states. Therefore, parameters in the first state can be substantially the same as parameters in the second state. Therefore, according to the above equations, Vcn 1 =Vcn 2 =Vin/2; and Vout=Vcn 2 /2=Vin/4. That is, output voltage Vout of the voltage regulator in this example is ¼ of input voltage Vin, which corresponds to the double of the number of the provided input capacitors. 
     A second output switch circuit may additionally be provided in particular embodiments. The second output switch circuit and the first output switch circuit may form a full-bridge circuit, in order to change a connection relation of the circuit. Therefore, the output port can be connected in the current path whether in the first state or the second state, and the energy storage capacitors or the input port can constantly supply power to the output port, thereby improving reliability of the voltage of the output port. Also, the voltage regulator may have a higher step down ratio with the same number of capacitors, as compared to other approaches. Further, an isolation capacitor may be provided in order to isolate the input port from the output port without a transformer, thereby avoiding an influence of current ripple of the input voltage and the output capacitance. 
     Referring now to  FIG. 15 , shown is a schematic block diagram of a fourth example voltage regulator, in accordance with embodiments of the present invention. In this particular example, the voltage regulator can include three input capacitors Cn 1 -Cn 3 , three energy storage capacitors C 1 -C 3 , and three input switch circuits IN 1 -IN 3 . In input switch circuits IN 1 -IN 3 , switches Q 1 , Q 3 , and Q 5  may be controlled by control signal GH, and switches Q 2 , Q 4 , and Q 6  can be controlled by control signal GL. On an output side, output switch circuit OUT 1 , output switch circuit OUT 2 , and isolation capacitor C′ are provided. For example, the voltage regulator may further include output capacitor Cout connected across the output port. Output switch circuit OUT 1  can include switches Q 7  and Q 8 , and output switch circuit OUT 2  can include switches Q 9  and Q 10 . Switches Q 7  and Q 8  may respectively be controlled by control signals GH′ and GL′. 
     Referring now to  FIG. 16 , shown is a waveform diagram of example control signal operation for the fourth example voltage regulator, in accordance with embodiments of the present invention. As shown, control signals GH′ and GL′ are inverted from each other, such that switches Q 7  and Q 8  are complementary with each other, and switches Q 9  and Q 10  are complementary with each other. Also, control signal GH′ may be in phase with control signal GH for controlling the input switch circuit. In this example, switches Q 1 , Q 3 , Q 5 , Q 7 , and Q 9  may simultaneously be turned on while switches Q 2 , Q 4 , Q 6 , Q 8 , and Q 10  are simultaneously turned off, and switches Q 1 , Q 3 , Q 5 , Q 7 , and Q 9  may simultaneously be turned off while switches Q 2 , Q 4 , Q 6 , Q 8 , and Q 10  are simultaneously turned on. Therefore, switches Q 1 -Q 10  can alternately be turned on and off under control of control signals GH, GL, GH′, and GL′, such that the voltage regulator is switched between the first and second states. A node of isolation capacitor C′ can connect to input node “c” of output switch circuit OUT 2 , and the other node of the isolation capacitor C′ can connect to a node connected to any one of the input capacitors. In  FIG. 15 , isolation capacitor C′ can connect between nodes “c” and n 3 . Therefore, isolation capacitor C′ can effectively isolate the input port from the output port while forming a current path from the output port to the input port. 
     Referring now to  FIG. 17 , shown is an equivalent circuit diagram of the fourth example voltage regulator operating in a first state, in accordance with embodiments of the present invention. In this particular example, in the first state, switches Q 1 , Q 3 , Q 5 , Q 7 , and Q 9  can be turned on, while switches Q 2 , Q 4 , Q 6 , Q 8 , and Q 10  may be turned off. As shown, node “a” can connect to node o 1  of the output port through switch Q 7 , and node “c” can connect to node o 2  of the output port through switch Q 9 . The input port and input capacitor Cn 3  may discharge, in order to charge input capacitor Cn 1 , energy storage capacitors C 1  to C 3 , and isolation capacitor C′, such that a current flows through nodes o 1  and o 2  of the output port, in order to generate an output voltage Vout across the output port. Therefore, multiple current paths may be formed in this fashion. 
     A current path may begin from the input port, sequentially pass through switch Q 1 , energy storage capacitor C 1 , switch Q 7 , nodes o 1  and o 2  of the output port, switch Q 9  and isolation capacitor C′, and return to node n 3  (e.g., the ground node of the input port). Another current path may begin from the input port, sequentially pass through input capacitor Cn 1 , switch Q 3 , energy storage capacitor C 2 , switch Q 7 , nodes o 1  and o 2  of the output port, switch Q 9  and isolation capacitor C′, and return to node n 3 . Another current path may begin from node n 2  connected to input capacitor Cn 3 , sequentially pass through switch Q 5 , energy storage capacitor C 3 , switch Q 7 , nodes o 1  and o 2  of the output port, switch Q 9 , and isolation capacitor C′, and return to node n 3 . If, for example, a current flowing through the output port has a magnitude of 1, a current flowing from the input port has a magnitude of ⅔, a current flowing through the input capacitor Cn 1  and a current flowing through input capacitor Cn 3  have the same magnitude, which is ⅓, a current flowing through input capacitor Cn 2  has a magnitude of 0, currents flowing through energy storage capacitors C 1 -C 3  have the same magnitude, which is ⅓, and a current flowing through isolation capacitor C′ and a current flowing through the output port have the same magnitude (e.g., 1). In the example circuit shown in  FIG. 17 , Vcn 1 +Vcn 2 +Vcn 3 =Vin; Vc 1 −Vc 2 =Vcn 1 ; Vc 2 −Vc 3 =Vcn 2 ; and Vcn 3 −Vc 3 −Vc′=Vout. 
     Referring now to  FIG. 18 , shown is an equivalent circuit diagram of the fourth example voltage regulator operating in a second state, in accordance with embodiments of the present invention. In this particular example, in the second state, switches Q 2 , Q 4 , Q 6 , Q 8 , and Q 10  may be turned on while switches Q 1 , Q 3 , Q 5 , Q 7 , and Q 9  can be turned off. As shown, node “a” can connect to node o 2  of the output port through switch Q 8 , and node “c” can connect to node o 1  of the output port through switch  10 . Input capacitor Cn 1 , energy storage capacitors C 1  to C 3  and isolation capacitor C′ may discharge, in order to charge the input port, the output port and input capacitor Cn 3 . In this way, multiple circuit paths may be formed. For example, a direction of the current flowing through each of the capacitors in the second state is opposite to a direction of the current flowing through the capacitor in the first state. Also, since a connection relation may accordingly be changed, a direction of a current flowing through the output port can remain unchanged while a current flowing through each of the capacitors is inverted. 
     A current path may begin from energy storage capacitor C 1 , sequentially pass through switch Q 2 , input capacitor Cn 1 , nodes n 0  and n 3  of the input port, isolation capacitor C′, switch Q 10 , nodes o 1  and o 2  of the output port, and switch Q 8 , and return to capacitor C 1 . Another current path may begin from energy storage capacitor C 2 , sequentially pass through switch Q 4 , energy storage capacitor Cn 3 , isolation capacitor C′, switch Q 10 , nodes o 1  and o 2  of the output port, and switch Q 8 , and return to energy storage capacitor C 2 . Another current path may begin from energy storage capacitor C 3 , sequentially pass through switch Q 6 , isolation capacitor C′, switch Q 10 , nodes o 1  and o 2  of the output port, and switch Q 8 , and return to energy storage capacitor C 3 . If, for example, a current flowing through the output port has a magnitude of 1, a current flowing into the input port has a magnitude of ⅓, a current flowing through each of input capacitors Cn 1  and Cn 3  has a magnitude of ⅓, a current flowing through input capacitor Cn 2  has a magnitude of 0, a current flowing through each of energy storage capacitors C 1  to C 3  has a magnitude of ⅓, and a current flowing through isolation capacitor C′ and a current flowing through the output port have the same magnitude (e.g., 1). 
     In the circuit shown in  FIG. 18 , Vcn 1 +Vcn 2 +Vcn 3 =Vin; Vc 1 −Vc 2 =Vcn 2 ; Vc 2 −Vc 3 =Vcn 3 ; and Vc 3 +Vc′=Vout. If the voltage regulator is switched between the first and second states at a relatively high frequency, a voltage of the capacitor may not change rapidly among different states. Therefore, parameters in the first state can be substantially the same as those parameters in the second state. Therefore, according to the above equations, Vcn 1 =Vcn 2 =Vcn 3 =Vin/3; and Vout=Vcn 3 /2=Vin/6. That is, output voltage Vout of the voltage regulator can, e.g., be ⅙ of the input voltage, which may correspond to the double of the number of the provided input capacitors. Similarly, e.g., in the voltage regulator having a similar structure, output voltage Vout is ½N of input voltage Vin when N energy storage capacitors, the N input capacitors and N input switch circuits are provided, where N is a positive integer. Therefore, a voltage regulator with any step down ratio can be implemented in certain embodiments. 
     Referring now to  FIG. 19 , shown is a schematic block diagram of a fifth example voltage regulator, in accordance with embodiments of the present invention. When it is not required to isolate the output port from the input port, the isolation capacitor in the above examples may be avoided, and one node of the output port may be directly connected to a node connected to any one of the N input capacitors, in order to form a current path. As shown, N input capacitors Cn 1 -CnN, N energy storage capacitors C 1 -CN, and N input switch circuits are provided in this example. Input capacitors Cn 1 -CnN may be sequentially connected in series across the input port. One nodes of N energy storage capacitors can connect together, and the other nodes of the N energy storage capacitors can connect to the input switch circuits corresponding to the N energy storage capacitors, respectively. The input switch circuit can selectively couple energy storage capacitor Ci to one of two nodes of input capacitor Cni corresponding to energy storage capacitor Ci. 
     Also, first and second output switch circuits may also be provided in the voltage regulator. The first output switch circuit can selectively couple node “a” of energy storage capacitors C 1 -CN to node of or node o 2  of the output port. The second output switch circuit can selectively couple node “c” to node o 1  or o 2  of the output port. This example differs in that, the isolation capacitor is not provided, and node “c” and node nx (x=0, 1, 2, . . . N) can connect through a wire or be arranged as one node, in order to directly form a current path. For example, output voltage Vout of the voltage regulator is ½N of input voltage Vin. Similarly, in a voltage regulator implemented without the second output switch circuit, any node of the output port may also be connected to a node connected to any one of the input capacitors through a wire. In this fashion, the number of devices can be reduced, and the area of the circuit can be reduced, when isolation of the input port from the output port is not required for a given application. 
     It should be understood that, although metal oxide semiconductor field-effect transistor (MOSFET) is used as a switch device in the examples described herein, other types of controlled switch device (e.g., a bipolar transistor [BJT], an insulated gate bipolar transistor ROM etc.), may additionally or alternatively be utilized in one or more of the switches in the voltage regulator of particular embodiments. 
     The embodiments were chosen and described in order to best explain the principles of the invention and its practical applications, to thereby enable others skilled in the art to best utilize the invention and various embodiments with modifications as are suited to particular use(s) contemplated. It is intended that the scope of the invention be defined by the claims appended hereto and their equivalents.