CN114448229A

CN114448229A - Charge pump circuit

Info

Publication number: CN114448229A
Application number: CN202011202792.2A
Authority: CN
Inventors: 文宇
Original assignee: SG Micro Beijing Co Ltd
Current assignee: SG Micro Beijing Co Ltd
Priority date: 2020-11-02
Filing date: 2020-11-02
Publication date: 2022-05-06
Anticipated expiration: 2040-11-02
Also published as: CN114448229B

Abstract

The application discloses charge pump circuit, including first to fourth switch, flying capacitor, output capacitance, drive circuit and the control circuit of series connection between voltage input end and ground in proper order, control circuit is suitable for output a control signal, and drive circuit is suitable for the basis control signal output drive signal is with the switching on and the shutoff of control each switch. The duty ratio of the control signal is gradually increased in a first time period when the charge pump circuit is started, and the duty ratio of the control signal is unchanged in a second time period after the first time period, so that the charging time of the charge pump in each charging period can be reduced when the charge pump circuit 200 is started, the starting time of the charge pump circuit 200 is prolonged, the transient current is prevented from being too large when the charge pump circuit is started, the impact on a power supply is reduced, and the circuit stability is improved.

Description

Charge pump circuit

Technical Field

The present invention relates to the field of electronic technologies, and in particular, to a charge pump circuit.

Background

Charge pumps, also known as switched load capacitive voltage converters, are converters that store energy using a so-called "fast" or "pumped" load capacitance. The input voltage can be increased or decreased, and the negative voltage generator can also be used for generating negative voltage and is widely applied to power supplies, memories and radio frequency chips.

Fig. 1 shows a schematic diagram of a charge pump circuit according to the prior art. As shown in fig. 1, the charge pump circuit 100 includes first to fourth switches Q1-Q4, a flying capacitor CFly, an output capacitor Cout, and a driving circuit 110, which are sequentially connected between a voltage input terminal Vin and ground. The flying capacitor CFly has a first terminal connected to an intermediate node between the first switch Q1 and the second switch Q2, and a second terminal connected to an intermediate node between the third switch Q3 and the fourth switch Q4. The output capacitor Cout is connected between the voltage output terminal Vout and ground. The driving circuit 110 is configured to output a driving signal to control the first to fourth switches Q1-Q4 to be turned on and off, thereby obtaining a stable output voltage.

When the charge pump circuit 100 is in the charging stage, the first switch Q1 and the third switch Q3 are turned on, current flows through the first switch Q1 and the flying capacitor CFly to the source end of the third switch Q3, and then flows through the third switch Q3 to charge the output capacitor Cout; when the charge pump circuit 100 is in the freewheeling stage, the second switch Q2 and the fourth switch Q4 are turned on, and the current flows from the upper end of the flying capacitor CFly through the second switch Q2 to the first end of the output capacitor Cout, then flows into the output capacitor Cout, and then flows from the source end of the fourth switch Q4 to the second end of the flying capacitor CFly. The working principle of the switched capacitor type charge pump is that the high-current charging with high speed and high efficiency is achieved by continuously repeating the charging cycle.

The prior art charge pump circuit 100 suffers from the following problems: when the charge pump circuit 100 is just powered on, the charge on the flying capacitor CFly is gradually filled, so that the charging current at this time is large, and due to the parasitic inductance in the circuit, large fluctuation is generated on the power supply voltage, which may cause the internal control circuit to operate abnormally.

Disclosure of Invention

In view of the above problems, an object of the present invention is to provide a charge pump circuit that solves the problem of a large instantaneous current at the time of starting the charge pump circuit.

According to an embodiment of the present invention, there is provided a charge pump circuit including: the first switch, the second switch, the third switch and the fourth switch are sequentially connected between the voltage input end and the ground in series; a first terminal of the flying capacitor is connected to an intermediate node of the first switch and the second switch, and a second terminal of the flying capacitor is connected to an intermediate node of the third switch and the fourth switch; an output capacitor connected between the voltage output terminal and ground; the control circuit is suitable for outputting a control signal; and a driving circuit adapted to output a driving signal to control on and off of each switch according to the control signal, wherein a duty ratio of the control signal is gradually increased in a first period in which the charge pump circuit is started, and the duty ratio of the control signal is not changed in a second period after the first period.

Optionally, the control circuit includes: the reference voltage generating module is suitable for generating a second reference voltage according to the first reference voltage; the triangular wave signal generating module is suitable for generating a triangular wave voltage signal; the control signal generation module is suitable for generating the control signal according to the second reference voltage and the triangular wave voltage signal; and the duty ratio adjusting module is used for generating an adjusting signal according to the power supply voltage, and the adjusting signal is used for adjusting the second reference voltage to change the duty ratio of the control signal.

Optionally, the reference voltage generating module includes: the positive phase input end of the operational amplifier is used for receiving the first reference voltage, and the negative phase input end of the operational amplifier is connected with the output end; the first resistor and the second resistor are sequentially connected between the output end of the operational amplifier and the ground, and a first node between the first resistor and the second resistor is used for providing the second reference voltage.

Optionally, the duty cycle adjusting module includes: a first current source providing a first current; a first capacitor, a first terminal of which is connected to the power supply voltage, and a second terminal of which is connected to the first current source at a second node, so as to receive the first current and provide a gate control voltage at the second node; and a first transistor, a first terminal of the first transistor being connected to the first node, a second terminal of the first transistor being connected to ground, and a control terminal of the first transistor being connected to the second node to receive the gate control voltage, wherein the first transistor is configured to provide a current path from the first node to ground, and the adjustment signal is a current flowing through the first transistor.

Optionally, during a first time period when the charge pump circuit is started, the gate control voltage is gradually decreased, and the on-resistance of the first transistor is gradually increased, so that the second reference voltage is gradually increased, and during a second time period after the first time period, the gate control voltage is smaller than the on-threshold of the first transistor, and the first transistor is turned off, so that the second reference voltage is fixed.

Optionally, the triangular wave signal generating module includes: a second current source providing a second current; a second capacitor, wherein a first end of the second capacitor and the second current source are connected to a third node to receive the second current and provide the triangular wave voltage signal at the third node; a first comparator, a first input end of which is connected with the output end of the operational amplifier, and a second input end of which is connected with the third node; and a second transistor providing a short-circuit path from the third node to ground, a control terminal of the second transistor being connected to an output terminal of the first comparator.

Optionally, the control signal generating module includes: and a second comparator, wherein a first input end of the second comparator receives the triangular wave voltage signal, a second input end of the second comparator receives the second reference voltage, and an output end of the second comparator is used for providing the control signal.

Optionally, the driving circuit controls the second switch and the fourth switch to turn off when controlling the first switch and the third switch to be turned on, and controls the first switch and the third switch to turn off when controlling the second switch and the fourth switch to be turned on.

The charge pump circuit comprises first to fourth switches, a flying capacitor, an output capacitor, a driving circuit and a control circuit, wherein the first to fourth switches, the flying capacitor, the output capacitor, the driving circuit and the control circuit are sequentially connected between a voltage input end and the ground in series, the control circuit is suitable for outputting a control signal, and the driving circuit is suitable for outputting the driving signal according to the control signal so as to control the on and off of each switch. The duty ratio of the control signal is gradually increased in a first time period when the charge pump circuit is started, and the duty ratio of the control signal is unchanged in a second time period after the first time period, so that the charging time of the charge pump in each charging period can be reduced when the charge pump circuit is started, the starting time of the charge pump circuit is prolonged, the phenomenon that the instantaneous current is too large when the charge pump circuit is started is avoided, the impact on a power supply is reduced, and the stability of the circuit is improved.

Drawings

The above and other objects, features and advantages of the present invention will become more apparent from the following description of the embodiments of the present invention with reference to the accompanying drawings, in which:

fig. 1 shows a schematic diagram of a charge pump circuit according to the prior art;

FIG. 2 shows a schematic diagram of a charge pump circuit according to an embodiment of the invention;

FIG. 3 shows a schematic diagram of the control circuit of FIG. 2;

FIG. 4 shows an output schematic of a control circuit according to an embodiment of the invention.

Detailed Description

Various embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. In the various figures, like elements are identified with the same or similar reference numerals. For purposes of clarity, the various features in the drawings are not necessarily drawn to scale.

It should be understood that in the following description, "circuitry" may comprise singly or in combination hardware circuitry, programmable circuitry, state machine circuitry, and/or elements capable of storing instructions executed by programmable circuitry. When an element or circuit is referred to as being "connected to" another element or element/circuit is referred to as being "connected between" two nodes, it may be directly coupled or connected to the other element or intervening elements may be present, and the connection between the elements may be physical, logical, or a combination thereof. In contrast, when an element is referred to as being "directly coupled" or "directly connected" to another element, it is intended that there are no intervening elements present.

The invention is further illustrated with reference to the following figures and examples.

Fig. 2 shows a schematic structural diagram of a charge pump circuit according to an embodiment of the present invention. As shown in fig. 2, the charge pump circuit 200 includes first to fourth switches Q1-Q4, a flying capacitor CFly, an output capacitor Cout, a driving circuit 210 and a control circuit 220, which are sequentially connected between the voltage input terminal Vin and ground. The flying capacitor CFly has a first terminal connected to an intermediate node between the first switch Q1 and the second switch Q2, and a second terminal connected to an intermediate node between the third switch Q3 and the fourth switch Q4. The output capacitor Cout is connected between the voltage output terminal Vout and ground. The control circuit 220 is configured to provide a control signal CTRL, and the driving circuit 210 is configured to output a driving signal according to the control signal CTRL to control the first to fourth switches Q1-Q4 to turn on and off, so as to obtain a stable output voltage.

Further, the driving circuit 210 generates a first driving signal Vg1, a second driving signal Vg2, a third driving signal Vg3 and a fourth driving signal Vg4 according to the control signal CTRL. The first driving signal Vg1 is connected to the control terminal of the first switch Q1 to control the on and off of the first switch Q1, the second driving signal Vg2 is connected to the control terminal of the second switch Q2 to control the on and off of the second switch Q2, the third driving signal Vg3 is connected to the control terminal of the third switch Q3 to control the on and off of the third switch Q3, and the fourth driving signal Vg4 is connected to the control terminal of the fourth switch Q4 to control the on and off of the fourth switch Q4. The first drive signal Vg1 and the second drive signal Vg3 are in-phase signals, the second drive signal Vg2 and the fourth drive signal Vg4 are in-phase signals, and the first drive signal Vg1 and the third drive signal Vg3 are in-phase signals with the second drive signal Vg2 and the fourth drive signal Vg 4. In a specific embodiment, the first to fourth switches Q1-Q4 are selected from N-Channel-Metal-Oxide-Semiconductor field effect transistors (N-MOSFETs), and when the driving signal is high, the corresponding switch is turned on, and when the driving signal is low, the corresponding switch is turned off. And the high level time of the first drive signal Vg1 and the third drive signal Vg3 and the second drive signal Vg2 and the high level time of the fourth drive signal Vg4 are not overlapped (that is, a certain dead time exists between the first drive signal Vg1 and the third drive signal Vg3 and the second drive signal Vg2 and the fourth drive signal Vg 4), so that the first to fourth switches Q1-Q4 are prevented from being turned on at the same time.

When the charge pump circuit 200 is in the charging stage, the first switch Q1 and the third switch Q3 are turned on, the current passes through the first switch Q1 and the flying capacitor CFly to the source end of the third switch Q3, and then flows through the third switch Q3 to charge the output capacitor Cout; when the charge pump circuit 200 is in the freewheeling stage, the second switch Q2 and the fourth switch Q4 are turned on, and the current flows from the upper end of the flying capacitor CFly through the second switch Q2 to the first end of the output capacitor Cout, then flows into the output capacitor Cout, and then flows from the source end of the fourth switch Q4 to the second end of the flying capacitor CFly, so as to achieve fast and efficient large-current charging through continuous repeated charging cycles.

Further, the control circuit 220 is further configured to provide the control signal CTRL with a variable duty cycle for a first time period when the charge pump circuit 200 is activated, and provide the control signal CTRL with a fixed duty cycle for a second time period after the first time period. In a specific embodiment, the control circuit 220 gradually increases the duty ratio of the control signal CTRL during a first time period when the charge pump circuit 200 is started, and keeps the duty ratio of the control signal CTRL during a second time period, so that the charging time of the charge pump in each charging cycle can be reduced when the charge pump circuit 200 is started, the starting time of the charge pump circuit 200 can be prolonged, overshoot at the voltage output terminal when the charge pump circuit is started can be avoided, and the stability of the output voltage can be improved.

Fig. 3 shows a schematic diagram of the control circuit in fig. 2. In a specific embodiment, as shown in fig. 2, the control circuit 220 includes a reference voltage generating module 201, a triangular wave signal generating module 202, a control signal generating module 203, and a duty ratio adjusting module 204. The reference voltage generation module 201 is adapted to generate a second reference voltage Vref2 from the first reference voltage Vref 1. The triangular wave signal generating module 202 is adapted to generate a triangular wave voltage signal RAMP. The control signal generating module 203 is adapted to generate the control signal CTRL according to the second reference voltage Vref2 and the triangular wave voltage signal RAMP. The duty cycle adjustment module 204 is configured to generate an adjustment signal according to the power supply voltage Vcc, wherein the adjustment signal is used to adjust the second reference voltage Vref2 to change the duty cycle of the control signal CTRL.

Further, the reference voltage generating module 201 includes an operational amplifier OPA, a first resistor R1, and a second resistor R2. The non-inverting input terminal of the operational amplifier OPA is configured to receive the first reference voltage Vref1, and the inverting input terminal is connected to the output terminal. A first resistor R1 and a second resistor R2 are sequentially connected between the output terminal of the operational amplifier OPA and ground, and a first node P1 between the first resistor R1 and the second resistor R2 is used for providing the second reference voltage Vref 2.

Wherein the second reference voltage Vref2 is obtained by the following formula:

Vref2＝Vref1×R2/(R1+R2)

where R1 and R2 denote resistance values of the first resistor and the second resistor, respectively, and Vref1 denotes a voltage value of the first reference voltage.

The duty cycle adjustment module 204 includes a first current source I1, a first capacitor C1, and a first transistor M1. The first current source I1 is used to provide a first current. A first terminal of a first capacitor C1 is connected to the power supply voltage Vcc, and a second terminal of the first capacitor C1 and the first current source I1 are connected to a second node P2, so as to receive the first current and provide a gate control voltage at the second node P2. The first terminal of the first transistor M1 is connected to the first node P1, the second terminal of the first transistor M1 is connected to ground, and the control terminal of the first transistor is connected to the second node P2 to receive the gate control voltage. Wherein the first transistor M1 is used for providing a current path from the first node P1 to ground, and the adjusting signal is a current flowing through the first transistor M1.

The second reference voltage Vref2 at this time is obtained by the following equation:

Vref2＝Vref1/(1+R1/R2//Rm1)

where R1 and R2 respectively denote resistance values of the first resistor and the second resistor, Vref1 denotes a voltage value of the first reference voltage, Rm1 denotes an on-resistance of the first transistor M1, and R2// Rm1 denotes a parallel resistance value of the second resistor and the on-resistance of the first transistor M1.

In a specific embodiment, the first transistor M1 is selected from N-type MOSFET, the power supply starts to power up at the first time period when the charge pump circuit 200 is started, the voltage of the second node P2 is greater than the turn-on threshold of the first transistor M1, the first transistor M1 is turned on, the voltage of the second node P2 gradually decreases (i.e., the gate control voltage gradually decreases) as the current charges the first capacitor C1, and the turn-on resistance of the first transistor gradually increases, so that the second reference voltage Vref2 gradually increases. In a second time period after the first time period, the voltage of the second node P2 is less than the turn-on threshold of the first transistor M1, and the first transistor M1 is turned off, so that the second reference voltage Vref2 is fixed.

Further, the triangular wave signal generating module 202 includes a first comparator CMP1, a second current source I2, a second capacitor C2, and a second transistor M2. The second current source I2 is used to provide a second current. The first terminal of the second capacitor C2 and the second current source I2 are connected to the third node P3, so as to receive the second current and provide the triangular wave voltage signal RAMP at the third node P3. An inverting input terminal of the first comparator CMP1 is connected to an output terminal of the operational amplifier OPA, a non-inverting input terminal thereof is connected to the third node P3, an output terminal thereof is connected to a control terminal of the second transistor M2, and the second transistor M2 is turned on and off according to the control of the output voltage of the first comparator CMP1, and provides a short-circuit path from the third node P3 to ground when turned on. When the second transistor M2 is turned off, the second current source I2 charges the second capacitor C2, so that the voltage of the third node P3 rises with a predetermined slope. When the voltage of the third node P3 rises to the first reference voltage Vref1, the first comparator CMP1 turns over, the second transistor M2 is turned on, the two ends of the second capacitor C2 are short-circuited and discharged, and the voltage of the third node P3 becomes 0 in a short time, so that the triangular wave voltage signal RAMP having a certain slope and amplitude is obtained. In one embodiment, the second transistor M2 is selected from an N-type MOSFET, and the first comparator CMP1 outputs a high level signal when the voltage of the third node P3 is greater than/equal to the first reference voltage Vref 1; when the third node P3 is less than the first reference voltage Vref1, the first comparator CMP1 outputs a low level signal.

The control signal generating module 203 comprises a second comparator CMP2, an inverting input terminal of the second comparator CMP2 receives the triangular wave voltage signal RAMP, a non-inverting input terminal receives the second reference voltage Vref2, and an output terminal is used for providing the control signal CTRL. When the triangular wave voltage signal RAMP is greater than the second reference voltage Vref2, the second comparator CMP2 outputs the control signal CTRL as a low level signal, and when the triangular wave voltage signal RAMP is less than the second reference voltage Vref2, the second comparator CMP2 outputs the control signal CTRL as a high level signal.

FIG. 4 shows an output schematic of a control circuit according to an embodiment of the invention. The operation of the control circuit according to an embodiment of the present invention will be described in detail with reference to fig. 3 and 4. During a first time period T1 when the charge pump circuit 200 is just started, the power supply is just powered on, and as the second reference voltage Vref2 gradually increases, the high level time of the control signal CTRL (i.e., the duty ratio of the control signal CTRL) gradually increases; in the second period T2, the voltage of the second reference voltage Vref2 is not changed any more, and thus the high level time of the control signal CTRL (i.e., the duty ratio of the control signal CTRL) is fixed.

In summary, the charge pump circuit according to the embodiment of the invention includes first to fourth switches, a flying capacitor, an output capacitor, a driving circuit, and a control circuit, which are sequentially connected in series between a voltage input terminal and a ground, wherein the control circuit is adapted to output a control signal, and the driving circuit is adapted to output a driving signal according to the control signal to control on and off of each switch. The duty ratio of the control signal is gradually increased in a first time period when the charge pump circuit is started, and the duty ratio of the control signal is unchanged in a second time period after the first time period, so that the charging time of the charge pump in each charging period can be reduced when the charge pump circuit 200 is started, the starting time of the charge pump circuit 200 is prolonged, the transient current is prevented from being too large when the charge pump circuit is started, the impact on a power supply is reduced, and the circuit stability is improved.

It should be noted that although the device is described herein as being an N-channel or P-channel device, or an N-type or P-type doped region, one of ordinary skill in the art will appreciate that complementary devices may be implemented in accordance with the present invention. It will be understood by those skilled in the art that conductivity type refers to the mechanism by which conduction occurs, for example by conduction through holes or electrons, and thus does not refer to the doping concentration but to the doping type, for example P-type or N-type. It will be understood by those of ordinary skill in the art that the words "during", "when" and "when … …" as used herein in relation to the operation of a circuit are not strict terms referring to actions occurring immediately upon initiation of a startup action, but rather there may be some small but reasonable delay or delays, such as various transmission delays, between them and the reactive action (action) initiated by the startup action. The words "about" or "substantially" are used herein to mean that the value of an element (element) has a parameter that is expected to be close to the stated value or position. However, as is well known in the art, there is always a slight deviation that makes it difficult for the value or position to be exactly the stated value. It has been well established in the art that a deviation of at least ten percent (10%) for a semiconductor doping concentration of at least twenty percent (20%) is a reasonable deviation from the exact ideal target described. When used in conjunction with a signal state, the actual voltage value or logic state (e.g., "1" or "0") of the signal depends on whether positive or negative logic is used.

Moreover, it is further understood that the use of relational terms such as first and second, and the like, herein, are used solely to distinguish one from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other identical elements in a process, method, article, or apparatus that comprises the element.

In accordance with embodiments of the present invention, the foregoing examples are not intended to be exhaustive or to limit the invention to the precise form disclosed. Obviously, many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the invention and the practical application, to thereby enable others skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated. The scope of the invention should be determined from the following claims.

Claims

1. A charge pump circuit, comprising:

the first switch, the second switch, the third switch and the fourth switch are sequentially connected between the voltage input end and the ground in series;

a first terminal of the flying capacitor is connected to an intermediate node of the first switch and the second switch, and a second terminal of the flying capacitor is connected to an intermediate node of the third switch and the fourth switch;

an output capacitor connected between the voltage output terminal and ground;

the control circuit is suitable for outputting a control signal; and

a driving circuit adapted to output a driving signal to control on and off of each switch according to the control signal,

wherein the duty cycle of the control signal is gradually increased during a first period of time when the charge pump circuit is activated, and the duty cycle of the control signal is unchanged during a second period of time after the first period of time.

2. The charge pump circuit of claim 1, wherein the control circuit comprises:

the reference voltage generating module is suitable for generating a second reference voltage according to the first reference voltage;

the triangular wave signal generating module is suitable for generating a triangular wave voltage signal;

the control signal generation module is suitable for generating the control signal according to the second reference voltage and the triangular wave voltage signal; and

and the duty ratio adjusting module is used for generating an adjusting signal according to the power supply voltage, and the adjusting signal is used for adjusting the second reference voltage to change the duty ratio of the control signal.

3. The charge pump circuit of claim 2, wherein the reference voltage generation module comprises:

the positive phase input end of the operational amplifier is used for receiving the first reference voltage, and the negative phase input end of the operational amplifier is connected with the output end;

the first resistor and the second resistor are sequentially connected between the output end of the operational amplifier and the ground, and a first node between the first resistor and the second resistor is used for providing the second reference voltage.

4. The charge pump circuit of claim 3, wherein the duty cycle adjustment module comprises:

a first current source providing a first current;

a first capacitor, a first end of the first capacitor being connected to the power supply voltage, a second end of the first capacitor being connected to a second node with the first current source for receiving the first current and providing a gate control voltage at the second node; and

a first transistor having a first terminal connected to the first node, a second terminal connected to ground, and a control terminal connected to the second node to receive the gate control voltage,

wherein the first transistor is used for providing a current path from the first node to ground, and the adjusting signal is a current flowing through the first transistor.

5. The charge pump circuit of claim 4, wherein during a first time period when the charge pump circuit is activated, the gate control voltage is gradually decreased, the on-resistance of the first transistor is gradually increased, thereby gradually increasing the second reference voltage, and

in a second time period after the first time period, the gate control voltage is smaller than the turn-on threshold of the first transistor, and the first transistor is turned off, so that the second reference voltage is fixed.

6. The charge pump circuit of claim 3, wherein the triangular wave signal generating module comprises:

a second current source providing a second current;

a second capacitor, a first end of the second capacitor and the second current source being connected to a third node to receive the second current and provide the triangular wave voltage signal at the third node;

a first comparator, a first input end of which is connected with the output end of the operational amplifier, and a second input end of which is connected with the third node; and

and the second transistor provides a short-circuit path from the third node to the ground, and the control end of the second transistor is connected with the output end of the first comparator.

7. The charge pump circuit of claim 2, wherein the control signal generation module comprises:

and a second comparator, wherein a first input end of the second comparator receives the triangular wave voltage signal, a second input end of the second comparator receives the second reference voltage, and an output end of the second comparator is used for providing the control signal.

8. The charge pump circuit of claim 1, wherein the drive circuit controls the second switch and the fourth switch to turn off when controlling the first switch and the third switch to turn on, and

and when the second switch and the fourth switch are controlled to be switched on, the first switch and the third switch are controlled to be switched off.