Ripple control method of charge pump circuit, control circuit and charge pump system

Abstract

The application provides a ripple control method, a control circuit and a charge pump system of a charge pump circuit. The charge pump circuit comprises an input capacitor. The input capacitor is charged in a first working stage, and the input capacitor is discharged to a load in a second working stage. In the second working stage, load information is sampled, and a discharge current of the input capacitor is controlled according to a sampling signal representing the load information, so that a variation of an output voltage is in a first interval. The application can ensure that the output ripple of the charge pump circuit is small.

Description

Technical Field

[0001] This invention relates to the field of power electronics, and in particular to a ripple control method, control circuit, and charge pump system for a charge pump circuit. Background Technology

[0002] In existing technologies, charge pump circuits use clock signals to control the energy storage and release processes to obtain the output voltage. However, during the energy storage and release process, the output voltage ripple of the charge pump circuit is large, which in turn affects the reliability of the charge pump system. Summary of the Invention

[0003] The purpose of this invention is to provide a ripple control method and control circuit for a charge pump circuit, which solves the problem of large output voltage ripple in the prior art.

[0004] To achieve the above objectives, the present invention provides a ripple control method for a charge pump circuit, wherein the charge pump circuit includes an input capacitor, the input capacitor is charged in a first operating phase, the input capacitor is discharged to a load in a second operating phase, in the second operating phase, load information is sampled, and the discharge current of the input capacitor is controlled according to the sampled signal characterizing the load information, such that the change in the output voltage of the charge pump circuit in the second operating phase is within a first range.

[0005] Optionally, the input capacitor voltage and the output voltage are subtracted to obtain a difference signal; when the difference signal is greater than a fourth threshold, the input capacitor is discharged; when the difference signal is less than a fifth threshold, the input capacitor is charged; the fifth threshold is less than the fourth threshold.

[0006] Optionally, a first sampling signal is obtained by sampling the load current, and a second sampling signal is obtained by sampling the output voltage. When the second sampling signal rises to a first threshold, the discharge current of the input capacitor is controlled according to the first sampling signal, so that the discharge current of the input capacitor is equal to the load current.

[0007] Optionally, a first sampling signal is obtained by sampling the load current, and the discharge current of the input capacitor is controlled to be greater than the load current according to the first sampling signal, and the difference between the discharge current and the load current is less than a second threshold.

[0008] Optionally, the output voltage is sampled to obtain a second sampling signal. When the second sampling signal rises to a first threshold, the discharge current is controlled to stabilize the output voltage.

[0009] Optionally, the output voltage is sampled to obtain a second sampling signal. When the second sampling signal rises to a first threshold, the discharge current is controlled to decrease, thereby reducing the output voltage. When the second sampling signal falls to the third threshold, the discharge current is controlled to increase, thereby increasing the output voltage.

[0010] The present invention also provides a ripple control circuit for a charge pump circuit, the charge pump circuit including an input capacitor, the input capacitor being charged in a first operating phase, and the input capacitor discharging to a load in a second operating phase, including...

[0011] The sampling circuit samples the load information and outputs a sampling signal characterizing the load information when the charge pump circuit enters the second working stage.

[0012] The first control circuit receives the sampling signal and outputs a first control signal. The first control signal controls the discharge current of the input capacitor, so that the change in the output voltage of the charge pump circuit in the second working stage is in the first range.

[0013] Optionally, the first control circuit includes a differential circuit.

[0014] The differential circuit receives the input capacitor voltage and the output voltage, calculates the difference, and outputs a differential signal.

[0015] When the difference signal is greater than the fourth threshold, the first control circuit controls the input capacitor to discharge; when the difference signal is less than the fifth threshold, the first control circuit controls the input capacitor to charge; the fifth threshold is less than the fourth threshold.

[0016] Optionally, the sampling circuit includes a load current sampling circuit and an output voltage sampling circuit.

[0017] The load current sampling circuit samples the load current and outputs a first sampling signal;

[0018] The output voltage sampling circuit samples the output voltage and outputs a second sampling signal;

[0019] When the second sampling signal rises to the first threshold, the first control circuit controls the discharge current of the input capacitor according to the first sampling signal, so that the discharge current is equal to the load current.

[0020] Optionally, the ripple control circuit further includes a discharge current sampling circuit, and the first control circuit further includes a first comparator, a first operational amplifier, and a driver circuit.

[0021] In the second working stage, the discharge current sampling circuit samples the discharge current of the input capacitor and outputs a second sampling signal;

[0022] The first comparator receives the second sampled signal and the first threshold at its first and second input terminals, respectively, and outputs a first comparison signal.

[0023] The first operational amplifier receives the first sampled signal at its first input terminal and receives the second sampled signal at its second input terminal; the first operational amplifier outputs an error amplification signal.

[0024] The driving circuit receives the first comparison signal, the error amplification signal, and the difference signal, and outputs a driving signal to drive the first adjustment transistor, which is connected between the input capacitor and the output terminal of the charge pump circuit.

[0025] Optionally, the sampling circuit includes a load current sampling circuit and an output voltage sampling circuit.

[0026] The load current sampling circuit samples the load current and outputs a first sampling signal; the output voltage sampling circuit samples the output voltage and outputs a second sampling signal.

[0027] The first control circuit controls the discharge current of the input capacitor to be greater than the load current according to the first sampling signal, and the difference between the discharge current and the load current is less than a second threshold.

[0028] Optionally, the first control circuit includes a first operational amplifier and a driver circuit.

[0029] The sampling circuit samples the output voltage and outputs a second sampling signal;

[0030] The first operational amplifier receives a first threshold at its first input terminal, receives a second sampling signal at its second input terminal, and outputs the first control signal from its first operational amplifier.

[0031] The driving circuit receives the first control signal and the difference signal, and outputs a driving signal to drive the first adjustment tube, which is connected between the input capacitor and the output terminal of the charge pump circuit.

[0032] Optionally, the sampling circuit samples the output voltage and outputs a second sampling signal. The first control circuit includes a first comparator, a second comparator, and a drive circuit.

[0033] The first comparator receives the second sampling signal and the first threshold, respectively, and outputs a first comparison signal;

[0034] The second comparator receives the second sampling signal and the third threshold, respectively, and outputs a second comparison signal;

[0035] The driving circuit receives the first comparison signal and the second comparison signal, and outputs a driving signal to drive the first adjustment tube.

[0036] The present invention also provides a charge pump system, including a charge pump circuit and any of the above-described ripple control circuits, wherein the ripple control circuit receives a sampling signal characterizing the load information of the charge pump circuit for controlling the output voltage of the charge pump circuit.

[0037] Compared with the prior art, the present invention has the following advantages: The present invention controls the discharge current of the input capacitor by sampling load information, so that the change range of the output voltage before and after the input capacitor discharges is not large, thereby effectively controlling the output voltage ripple. Attached Figure Description

[0038] Figure 1 This is a block diagram of the charge pump system of the present invention;

[0039] Figure 2 This is a schematic diagram of a first embodiment of the ripple control circuit for the charge pump circuit of the present invention;

[0040] Figure 3 This is a schematic diagram of a second embodiment of the ripple control circuit for the charge pump circuit of the present invention.

[0041] Figure 4 This is a schematic diagram of the ripple control circuit of the charge pump circuit of the present invention in embodiment three.

[0042] Figure 5 This is a waveform diagram of the output voltage of the charge pump circuit of the present invention. Detailed Implementation

[0043] The preferred embodiments of the present invention are described in detail below with reference to the accompanying drawings, but the present invention is not limited to these embodiments. The present invention covers any substitutions, modifications, equivalent methods, and solutions made within the spirit and scope of the present invention.

[0044] To provide the public with a thorough understanding of the present invention, specific details are described in detail in the following preferred embodiments of the invention, but those skilled in the art can fully understand the invention without these details.

[0045] The invention is described more specifically in the following paragraphs by way of example with reference to the accompanying drawings. It should be noted that the drawings are in a simplified form and use non-precise proportions, in order to facilitate and clearly illustrate the purpose of the embodiments of the invention.

[0046] like Figure 1The diagram illustrates the control block diagram of the charge pump system of the present invention, including a charge pump circuit, a load information sampling circuit U01, and a first control circuit U02 for receiving load information. The charge pump circuit includes an input capacitor, and the charge pump circuit stores and releases energy through the charging and discharging of the input capacitor. The first control circuit U02 controls the discharge current of the input capacitor according to the load information, ensuring that the change in output voltage during the discharge process of the input capacitor of the charge pump circuit is within a first interval. Depending on the actual application requirements, for example, in applications with high output voltage ripple requirements, the first interval is set relatively small, thereby controlling the output voltage of the charge pump circuit to meet precision control requirements; or the first interval is set to be below 30% of the output voltage.

[0047] like Figure 2 The diagram illustrates the schematic of a first embodiment of the ripple control circuit for the charge pump circuit of the present invention. This embodiment includes four switching transistors M1-M4, an input capacitor Cf, and an output capacitor Co. The positive terminal of the input power supply is connected to both ends of the input capacitor Cf via switching transistors M1 and M3, respectively. The two ends of the output capacitor Co are connected to both ends of the input capacitor Cf via switching transistors M2 and M4, respectively. A load is connected in parallel across the output capacitor Co. In the first operating stage, switching transistors M1 and M4 are turned on, charging the input capacitor Cf to the input voltage Vin. The output capacitor Co discharges to the load, causing the output voltage Vo to decrease. In the second operating stage, switching transistors M2 and M3 are turned on, changing the high-potential voltage of the input capacitor Cf to 2Vin and the low-potential voltage to Vin. The input capacitor Cf discharges to the output capacitor Co and the load, causing the output voltage Vo to increase. Based on the charge conservation relationship before and after the input capacitor Cf discharges, we have Equation 1: Cf*Vin + Co*Vo=(Cf+Co)*(Vo+ΔVo), which further gives Equation 2: ΔVo=Cf*(Vin-Vo) / (Cf+Co). In addition, based on the principle of charge balance, we also have Equation 3:

[0048] ΔVo = Io * t / Co, where ΔVo is the change in output voltage before and after the input capacitor Cf discharges, Io is the discharge current of the input capacitor Cf, and t is the discharge time. According to equation 2, ΔVo cannot be adjusted based on the input capacitor Cf and the output capacitor Co; however, according to equation 3, the change in output voltage ΔVo can be adjusted by regulating the discharge current of the input capacitor Cf. Figure 2In the illustrated embodiment, the sampled output voltage Vo and the input capacitor voltage Vf are sampled, and the difference between the input capacitor voltage Vf and the output voltage is calculated to obtain a difference signal ΔV = Vf - Vo. When ΔV > VREF4, the difference signal ΔV controls the discharge of the input capacitor Cf, the input capacitor voltage Vf decreases, the output voltage Vo increases, and the difference signal ΔV decreases. When the difference signal ΔV < VREF5, the input capacitor Cf is controlled to charge; by setting the threshold voltages VREF4 and VREF5 to control the charge and discharge of the input capacitor Cf, the charge and discharge frequency of the input capacitor Cf can be avoided from being too high. In the second working stage, the input capacitor Cf is first controlled to discharge rapidly. When the output voltage Vo rises to the first threshold VREF1, the output voltage Vo is then controlled to be maintained at the first threshold VREF1. This avoids the discharge current of the input capacitor Cf being too large at the beginning of discharge, and the output voltage Vo rising rapidly to be much greater than the first threshold VREF1, generating a large ripple.

[0049] Specifically, refer to the embodiment of the charge pump ripple control circuit Figure 2 , which includes a first operational amplifier U201, a difference circuit U202, and a drive circuit U203. The first input terminal of the first operational amplifier U201 receives the sampled signal VFB of the output voltage Vo, its second terminal receives the first threshold VREF, and its output terminal is connected to the input terminal of the drive circuit U202; the difference circuit U202 subtracts the output voltage Vo from the output capacitor voltage Vf and outputs a difference signal ΔV. The input terminal of the drive circuit U202 also receives the difference signal ΔV to control the working stage of the adjustment transistor M2. The output terminal of the drive circuit U201 is connected to the control terminal of the adjustment transistor M2. In this embodiment, when the output voltage sampled signal VFB rises to the first threshold VREF1, the output voltage Vo is controlled to remain unchanged.

[0050] Such as Figure 3The diagram illustrates the principle of a second embodiment of the ripple control circuit for the charge pump circuit of the present invention. The parts identical to those in embodiment one will not be repeated. The difference lies in the following principle: when the output voltage rises to a first threshold, the discharge current of the input capacitor decreases, and the output voltage decreases; when the output voltage drops to a third threshold, the discharge current of the input capacitor increases, and the output voltage increases. Specifically, the ripple control circuit includes a first comparator U201, a second comparator U203, a difference circuit U203, and a drive circuit U204. The first comparator U201 receives the output voltage sampling signal VFB at its first input terminal and receives the first threshold VREF1 at its second input terminal, outputting a first comparison signal VC1. The second comparator U202 receives the third threshold VREF3 at its first input terminal and receives the output voltage sampling signal VFB at its second input terminal, outputting a second comparison signal. The difference circuit U203 calculates the difference between the output voltage Vout and the input capacitor voltage Vf, outputting a difference signal ΔV. The drive circuit receives the first comparison signal VC1, the second comparison signal VC2, and the difference signal ΔV, outputting a drive signal Vt to drive the switching transistor M2.

[0051] like Figure 4 The diagram illustrates the schematic of a third embodiment of the ripple control circuit for the charge pump circuit of the present invention. It includes a discharge current sampling circuit U03, a load current sampling circuit U101, a first comparator U200, a first operational amplifier U201, a difference circuit U202, and a drive circuit U203. The difference circuit U203 calculates the difference between the input capacitor voltage Vf and the output voltage Vo, outputting a difference signal ΔV. The discharge current sampling circuit U03 samples the discharge current of the input capacitor Cf and outputs a first current sampling signal VCS1. The load current sampling circuit U04 samples the load current and outputs a second current sampling signal CS2. The first comparator U200 receives the output voltage sampling signal VFB and the first threshold VREF, respectively, and outputs a first comparison signal VC1. The first operational amplifier U201 receives the first current sampling signal CS1 and the second current sampling signal CS2, respectively, and outputs a first error amplification signal VC2. The drive circuit U202 receives the first comparison signal VC1, the first error amplification signal VC2, and the difference signal ΔV. The output of the drive circuit U201 is connected to the control terminal of the regulating transistor M2. When the output voltage sampling signal VFB rises to the first threshold VREF1, the first error amplification signal VC2 controls the load current to be equal to the discharge current, so that the output capacitor Co has no charging current, thereby keeping the output voltage Vo unchanged and making the output voltage Vo ripple smaller.

[0052] In actual operation, during the charging phase of the input capacitor Cf, the output capacitor Co discharges to the load. During the discharging phase of the input capacitor Cf, the discharge current can be controlled to be slightly greater than the load current. The difference between the discharge current and the load current is less than the second threshold VREF2, so that the charging current to the output capacitor is small, and the output voltage Vo increases slowly. As long as it can be ensured that the output voltage Vo does not change much during the charging and discharging process of the output capacitor, it is acceptable.

[0053] Figure 5 The diagram illustrates the output voltage waveform of the charge pump circuit of the present invention, and is combined with... Figure 2 , Figure 3 and Figure 4 To illustrate with a schematic embodiment, during the charging phase of the input capacitor Cf, the output capacitor Co discharges to the load, causing the output voltage Vo to decrease. During the discharging phase of the input capacitor Cf, if the discharge current is not controlled, it will be large at the beginning of the discharge, causing the output voltage Vo to rise very high in a short time, as shown by solid line ① in the figure, with an output voltage ripple of ΔV01. Using the method of this invention, the discharge current is controlled so that when the output voltage Vo rises to the first threshold VREF1, the discharge current is reduced, causing the output voltage Vo to decrease. When the output voltage Vo drops to the second threshold VREF2, the discharge current is increased, causing the output voltage Vo to increase, as shown by solid line ② in the figure, with an output voltage ripple of ΔV02. Alternatively, when the output voltage Vo rises to the first threshold VREF1, the output voltage Vo is stabilized, as shown by solid line ③ in the figure, with an output voltage ripple of ΔV03. A comparison clearly shows that the output voltage ripple of this invention is much smaller than that of the prior art.

[0054] Although the embodiments are described and illustrated separately above, some common technologies are involved. Those skilled in the art can replace and integrate them between the embodiments. If there is any content not explicitly described in one embodiment, then another embodiment that is described can be referred to.

[0055] The embodiments described above do not constitute a limitation on the scope of protection of this technical solution. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the above embodiments should be included within the scope of protection of this technical solution.

Claims

1. A ripple control method for a charge pump circuit, the charge pump circuit including an input capacitor, the input capacitor being charged in a first operating phase and discharged to a load in a second operating phase, characterized in that: In the second working stage, load information is sampled, and the discharge current of the input capacitor is controlled according to the sampled signal characterizing the load information, so that the change in the output voltage of the charge pump circuit in the second working stage is in the first range. The difference between the input capacitor voltage and the output voltage is calculated to obtain the difference signal; When the difference signal is greater than the fourth threshold, the input capacitor discharges; The input capacitor is charged when the difference signal is less than the fifth threshold; the fifth threshold is less than the fourth threshold.

2. The ripple control method for the charge pump circuit according to claim 1, characterized in that: A first sampling signal is obtained by sampling the load current, and a second sampling signal is obtained by sampling the output voltage. When the second sampling signal rises to a first threshold, the discharge current of the input capacitor is controlled according to the first sampling signal, so that the discharge current of the input capacitor is equal to the load current.

3. The ripple control method for the charge pump circuit according to claim 1, characterized in that: A first sampling signal is obtained by sampling the load current. Based on the first sampling signal, the discharge current of the input capacitor is controlled to be greater than the load current, and the difference between the discharge current and the load current is less than a second threshold.

4. The ripple control method for the charge pump circuit according to claim 1, characterized in that: The output voltage is sampled to obtain a second sampling signal. When the second sampling signal rises to a first threshold, the discharge current is controlled to stabilize the output voltage.

5. The ripple control method for the charge pump circuit according to claim 1, characterized in that: The output voltage is sampled to obtain a second sampling signal. When the second sampling signal rises to a first threshold, the discharge current is controlled to decrease, thereby reducing the output voltage. When the second sampling signal drops to the third threshold, the discharge current is increased, thereby increasing the output voltage.

6. A ripple control circuit for a charge pump circuit, the charge pump circuit including an input capacitor, the input capacitor being charged in a first operating phase and discharged to a load in a second operating phase, characterized in that: include, The sampling circuit samples the load information and outputs a sampling signal characterizing the load information when the charge pump circuit enters the second working stage. The first control circuit receives the sampling signal and outputs a first control signal. The first control signal controls the discharge current of the input capacitor, so that the change in the output voltage of the charge pump circuit in the second working stage is in the first range. The first control circuit includes a differential circuit. The differential circuit receives the input capacitor voltage and the output voltage, calculates the difference, and outputs a differential signal. When the difference signal is greater than the fourth threshold, the first control circuit controls the input capacitor to discharge; when the difference signal is less than the fifth threshold, the first control circuit controls the input capacitor to charge; the fifth threshold is less than the fourth threshold.

7. The ripple control circuit of the charge pump circuit according to claim 6, characterized in that: The sampling circuit includes a load current sampling circuit and an output voltage sampling circuit. The load current sampling circuit samples the load current and outputs a first sampling signal; The output voltage sampling circuit samples the output voltage and outputs a second sampling signal; When the second sampling signal rises to the first threshold, the first control circuit controls the discharge current of the input capacitor according to the first sampling signal, so that the discharge current is equal to the load current.

8. The ripple control circuit of the charge pump circuit according to claim 7, characterized in that: The ripple control circuit further includes a discharge current sampling circuit, and the first control circuit further includes a first comparator, a first operational amplifier, and a driver circuit. In the second working stage, the discharge current sampling circuit samples the discharge current of the input capacitor and outputs a third sampling signal; The first comparator receives the second sampled signal and the first threshold at its first and second input terminals, respectively, and outputs a first comparison signal. The first operational amplifier receives the first sampling signal at its first input terminal and the third sampling signal at its second input terminal; the first operational amplifier outputs an error amplification signal. The driving circuit receives the first comparison signal, the error amplification signal, and the difference signal, and outputs a driving signal to drive the first adjustment transistor, which is connected between the input capacitor and the output terminal of the charge pump circuit.

9. The ripple control circuit of the charge pump circuit according to claim 6, characterized in that: The sampling circuit includes a load current sampling circuit and an output voltage sampling circuit. The load current sampling circuit samples the load current and outputs a first sampling signal; the output voltage sampling circuit samples the output voltage and outputs a second sampling signal. The first control circuit controls the discharge current of the input capacitor to be greater than the load current according to the first sampling signal, and the difference between the discharge current and the load current is less than a second threshold.

10. The ripple control circuit of the charge pump circuit according to claim 6, characterized in that: The first control circuit includes a first operational amplifier and a driver circuit. The sampling circuit samples the output voltage and outputs a second sampling signal; The first operational amplifier receives a first threshold at its first input terminal, receives a second sampling signal at its second input terminal, and outputs the first control signal from its first operational amplifier. The driving circuit receives the first control signal and the difference signal, and outputs a driving signal to drive the first adjustment tube, which is connected between the input capacitor and the output terminal of the charge pump circuit.

11. The ripple control circuit of the charge pump circuit according to claim 6, characterized in that: The sampling circuit samples the output voltage and outputs a second sampling signal. The first control circuit includes a first comparator, a second comparator, and a drive circuit. The first comparator receives the second sampling signal and the first threshold, respectively, and outputs a first comparison signal; The second comparator receives the second sampling signal and the third threshold, respectively, and outputs a second comparison signal; The driving circuit receives the first comparison signal and the second comparison signal, and outputs a driving signal to drive the first adjustment transistor, which is connected between the input capacitor and the output terminal of the charge pump circuit.

12. A charge pump system, characterized in that it includes a charge pump circuit and a ripple control circuit as described in any one of claims 6-11, wherein the ripple control circuit receives a sampling signal characterizing load information of the charge pump circuit for controlling the output voltage of the charge pump circuit.

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