Switching converter and its transient enhancement circuit, chip and electronic device

Abstract

The application discloses a switching converter, a transient enhancement circuit thereof, a chip and electronic equipment. The switching converter comprises an error amplifier and a compensation network. The error amplifier is used for amplifying a feedback voltage of the switching converter and a reference voltage. The compensation network is used for converting a current amplified by the error amplifier into a voltage signal to control a switching duty cycle of a power switch tube. The transient enhancement circuit comprises a comparison module, a transconductance amplifier and a current control module. The comparison module is used for comparing the feedback voltage with a first threshold voltage and generating a mode control signal according to a comparison result. The transconductance amplifier is controlled by the mode control signal and is used for differentially transconducting and amplifying the feedback voltage and a second threshold voltage to generate a compensation current. The current control module is used for providing the compensation current to the compensation network according to a state of the mode control signal and a direction of the compensation current to improve a response speed of the compensation network.

Description

Technical Field

[0001] This invention relates to the field of integrated circuit technology, and in particular to a switching converter and its transient enhancement circuit, chip, and electronic device. Background Technology

[0002] With the increasing demand for power electronic products and the development of semiconductor technology, power management chips are being used more widely in portable computers, mobile phones, personal digital assistants, and other portable or non-portable electronic devices. Switching converters use power switches to control the transfer of electrical energy from the input to the output, thus providing a constant output voltage and / or output current. In existing Buck-type switching converters, the reference voltage and feedback voltage are differentially amplified by an error amplifier. The resulting differential current is converted into a voltage signal on a compensation network, thereby adjusting the switching duty cycle of the power switches. Therefore, the transconductance capability of the error amplifier and the configuration of the compensation network play a decisive role in the response speed and stability of the closed-loop system.

[0003] To improve the transient response speed of Buck-type switching converters, existing technologies optimize the transconductance of the error amplifier and the compensation network to increase the loop bandwidth, thereby giving the system a better transient response. However, this can lead to a deterioration in system stability.

[0004] Therefore, a new switching converter and its transient enhancement circuit are needed to solve the above problems. Summary of the Invention

[0005] In view of the above problems, the purpose of this invention is to provide a switching converter and its transient enhancement circuit, chip and electronic device, thereby enhancing the transient response speed of the switching converter without changing the small-signal bandwidth and stability of the loop.

[0006] According to one aspect of the present invention, a transient enhancement circuit for a switching converter is provided. The switching converter includes an error amplifier and a compensation network. The error amplifier amplifies a feedback voltage of the switching converter and a reference voltage. The compensation network converts the amplified current from the error amplifier into a voltage signal to control the switching duty cycle of a power switch. The transient enhancement circuit includes: a comparison module for comparing the feedback voltage with a first threshold voltage and generating a mode control signal based on the comparison result; a transconductance amplifier controlled by the mode control signal for differentially amplifying the feedback voltage and a second threshold voltage to generate a compensation current; and a current control module for providing the compensation current to the compensation network according to the state of the mode control signal and the direction of the compensation current to improve the response speed of the compensation network.

[0007] Optionally, the first threshold voltage includes a first high threshold voltage and a first low threshold voltage, and the comparison module includes: a first comparator, with its positive input terminal connected to the first low threshold voltage and its inverting input terminal connected to the feedback voltage, for providing a first mode control signal based on the comparison result of the first low threshold voltage and the feedback voltage; and a second comparator, with its positive input terminal connected to the feedback voltage and its inverting input terminal connected to the first high threshold voltage, for providing a second mode control signal based on the comparison result of the first high threshold voltage and the feedback voltage.

[0008] Optionally, the second threshold voltage includes a second high threshold voltage and a second low threshold voltage, and the transient enhancement circuit further includes: a first switch connected between the positive input terminal of the transconductance amplifier and the second low threshold voltage; and a second switch connected between the positive input terminal of the transconductance amplifier and the second high threshold voltage.

[0009] Optionally, the second low threshold voltage is lower than the first low threshold voltage, the second high threshold voltage is higher than the first high threshold voltage, and the reference voltage is higher than the first low threshold voltage and lower than the first high threshold voltage.

[0010] Optionally, the first switch and the second switch are controlled to conduct in a non-overlapping manner by the first mode control signal and the second mode control signal, respectively.

[0011] Optionally, the current control module includes: a third switch connected between the output of the transconductance amplifier and the compensation network; and a current detection module for controlling the conduction and de-conduction of the third switch according to the state of the mode control signal and the direction of the compensation current.

[0012] Optionally, the current detection module includes a detection resistor connected between the output terminal of the transconductance amplifier and ground.

[0013] According to a second aspect of the present invention, a switching converter is provided, comprising: a power switch for controlling power transfer from the input to the output of the switching converter; a feedback circuit for providing a feedback voltage based on the output voltage of the switching converter; an error amplifier for amplifying the feedback voltage and a reference voltage; a compensation network for converting the amplified current from the error amplifier into a voltage signal; a comparator for comparing the voltage signal with a superimposed signal of an inductor sampling signal and a ramp signal, and outputting a pulse width modulation signal based on the comparison result to control the switching duty cycle of the power switch; and a transient enhancement circuit as described above for improving the response speed of the compensation network.

[0014] According to a third aspect of the present invention, a chip is provided, comprising the transient enhancement circuit as described above.

[0015] According to a fourth aspect of the present invention, an electronic device is provided, comprising a switching converter as described above or a chip as described above.

[0016] The present invention provides a switching converter and its transient enhancement circuit, chip and electronic device, which select whether to activate a transconductance amplifier based on the comparison result of the feedback voltage of the output voltage of the switching converter and the first low threshold voltage / first high threshold voltage. After the transconductance amplifier is activated, the feedback voltage and the second low threshold voltage / second high threshold voltage are differentially amplified by transconductance to obtain a compensation current. When the direction of the compensation current is in the same direction as the direction of the current amplified by the error amplifier, the compensation current is provided to the compensation network to accelerate the response speed of the compensation network, thereby enhancing the transient response speed of the switching converter. Attached Figure Description

[0017] The above and other objects, features and advantages of the present invention will become more apparent from the following description of embodiments of the invention with reference to the accompanying drawings, in which:

[0018] Figure 1 A schematic diagram of a switching converter according to an embodiment of the present invention is shown;

[0019] Figure 2 A circuit diagram of a switching converter according to an embodiment of the present invention is shown;

[0020] Figure 3 A schematic diagram of the structure of the comparison module according to an embodiment of the present invention is shown;

[0021] Figure 4 A schematic diagram showing the input current of the compensation network according to an embodiment of the present invention as a function of the feedback voltage is shown. Detailed Implementation

[0022] Various embodiments of the invention will now be described in more detail with reference to the accompanying drawings. In the various drawings, the same elements or modules are indicated by the same or similar reference numerals. For clarity, the various parts in the drawings are not drawn to scale.

[0023] It should be understood that, in the following description, "circuit" may include single or combined hardware circuits, programmable circuits, state machine circuits, and / or elements capable of storing instructions executed by the programmable circuit. When an element or circuit is said to be "connected" to another element or "connected" between two nodes, it may be directly coupled or connected to the other element, or there may be intermediate elements; the connection between elements may be physical, logical, or a combination thereof. Conversely, when an element is said to be "directly coupled to" or "directly connected" to another element, it means that there are no intermediate elements between them.

[0024] Furthermore, it should be noted that in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0025] In this application, the MOS transistor (Metal-Oxide-Semiconductor Field-Effect Transistor) includes a first terminal, a second terminal, and a control terminal.

[0026] For example, the first terminal, the second terminal, and the control terminal of a PMOS transistor can be the source, the drain, and the gate, respectively, while the first terminal, the second terminal, and the control terminal of an NMOS transistor can be the drain, the source, and the gate, respectively.

[0027] Figure 1 A schematic diagram of a switching converter according to an embodiment of the present invention is shown; Figure 2 A circuit diagram of a switching converter according to an embodiment of the present invention is shown.

[0028] like Figure 1 and Figure 2 As shown, this switching converter adopts a Buck topology and uses power switches M1 and M2 to control the power transfer from the input to the output, thereby generating an output voltage Vout based on the input voltage VIN. The switching converter includes a main power circuit 100, a control circuit 200, a transient enhancement circuit 300, and a feedback circuit 400.

[0029] The main power circuit 100 is used to provide the output voltage Vout. The main power circuit 100 includes power switches M1 and M2 connected in series between the input terminal and the ground terminal GND, an inductor L connected between the intermediate node of power switches M1 and M2 and the output terminal of the switching converter, and an output capacitor Cout connected between the output terminal of the switching converter and the ground terminal GND.

[0030] Feedback circuit 400 is used to provide feedback voltage Vfb for the output voltage Vout. Feedback circuit 400 includes resistors R1 and R2.

[0031] Control circuit 200 provides switching control signals to power switches M1 and M2 to control their on-state. Control circuit 200 includes an error amplifier EA, a compensation network 210, a comparator 220, and a driver circuit 230. The positive input of error amplifier EA receives a reference voltage Vref, and the negative input receives a feedback voltage Vfb, used to differentially amplify the reference voltage Vref and the feedback voltage Vfb to obtain current I1. Comparison network 210 is connected between the output of error amplifier EA and ground GND, used to convert the input current I0 into a voltage signal to adjust the system's duty cycle. The positive input of comparator 220 is connected to compensation network 210, and the negative input receives a superimposed signal Vipe of the inductor sampling signal Isense and the slope signal. It compares the voltage signal provided by compensation network 210 with the superimposed signal Vipe, and provides a pulse width modulation signal based on the comparison result. The input terminal of the drive circuit 230 is connected to the output terminal of the comparator 220, and the output terminal is connected to the control terminals of the power switch M1 and the power switch M2 respectively, which is used to provide switching control signals to the power switch M1 and the power switch M2 according to the pulse width modulation signal.

[0032] The transient enhancement circuit 300 includes a comparator module 310, a transconductance amplifier 320, and a current control module 330.

[0033] The comparison module 310 is used to provide a mode control signal VA based on the comparison result of the feedback voltage Vfb and the threshold voltage VL1, and to provide a mode control signal VB based on the comparison result of the feedback voltage Vfb and the threshold voltage VH1.

[0034] The positive input terminal of the transconductance amplifier 320 receives the threshold voltage VL2 through switch k1 and the threshold voltage VH2 through switch k2. The inverting input terminal of the transconductance amplifier 320 receives the feedback voltage Vfb. The transconductance amplifier 320 is used to differentially amplify the threshold voltage VL2 / threshold voltage VH2 and the feedback voltage Vfb to obtain the compensation current I2. The switches k1 and k2 are controlled by the mode control signal VA and the mode control signal VB, respectively, to conduct in a non-overlapping manner.

[0035] The current control module 330 provides the compensation current I2 to the compensation network 210 based on the state of the mode control signals VA and VB and the direction of the compensation current I2, thereby improving the response speed of the compensation network 210. The current control module 330 includes a current detection module 331 and a switch k3. The switch k3 is connected between the output of the transconductance amplifier 320 and the common node of the error amplifier EA and the compensation network 210. The output of the current detection module 331 is connected to the control terminal of the switch k3. The input of the current detection module 331 is connected to the output of the transconductance amplifier 320 and the mode control signals VA and VB, and is used to control the on and off of the switch k3 based on the level of the mode control signals VA and VB and the direction of the compensation current I2, thereby providing the compensation current I2 to the compensation network 210. Specifically, when either the mode control signal VA or the mode control signal VB is high, the current detection module 331 is turned on. When the mode control signal VA is high, if the direction of the compensation current I2 is detected as the first direction, the control switch k3 is turned on, so that the compensation current I2 and the current I1 merge into the input current I0 and flow into the compensation network 210. If the direction of the compensation current I2 is detected as the second direction, the control switch k3 is turned off, so that the compensation current I2 will not merge with the current I1, and the input current I0 is the current I1. When the mode control signal VB is high, if the direction of the compensation current I2 is detected as the first direction, the control switch k3 is turned off, so that the compensation current I2 will not merge with the current I1, and the input current I0 is the current I1. If the direction of the compensation current I2 is detected as the second direction, the control switch k3 is turned on, so that the compensation current I2 and the current I1 merge into the input current I0 and flow into the compensation network 210.

[0036] Furthermore, the relationship between the threshold voltage and the reference voltage is: VL2 <VL1<Vref<VH1<VH2。

[0037] Furthermore, both power switch M1 and power switch M2 are NMOS transistors.

[0038] Furthermore, the current detection module 331 detects the direction of the compensation current I2 through a detection resistor connected between the output terminal of the transconductance amplifier 320 and ground. When the direction of the compensation current I2 is the first direction, the voltage of the common node of the detection resistor and the output terminal of the transconductance amplifier 320 is high. When the direction of the compensation current I2 is the second direction, the voltage of the common node of the detection resistor and the output terminal of the transconductance amplifier 320 is 0.

[0039] Figure 3 A schematic diagram of the structure of the comparison module according to an embodiment of the present invention is shown, such as... Figure 3 As shown, the comparison module 310 includes comparator 311 and comparator 312. The positive input of comparator 311 is connected to a threshold voltage VL1, and the negative input is connected to a feedback voltage Vfb. It is used to compare the threshold voltage VL1 with the feedback voltage Vfb to obtain the mode control signal VA. Specifically, when the feedback voltage Vfb is greater than the threshold voltage VL1, the mode control signal VA is low (L); when the feedback voltage Vfb is less than the threshold voltage VL1, the mode control signal VA is high (H). The positive input of comparator 312 is connected to the feedback voltage Vfb, and the negative input is connected to a threshold voltage VH1. It is used to compare the threshold voltage VH1 with the feedback voltage Vfb to obtain the mode control signal VB. Specifically, when the feedback voltage Vfb is less than the threshold voltage VH1, the mode control signal VB is low (L); when the feedback voltage Vfb is greater than the threshold voltage VH1, the mode control signal VB is high (H).

[0040] Figure 4 A schematic diagram showing the input current of the compensation network according to an embodiment of the present invention as a function of the feedback voltage is shown.

[0041] The following is combined Figure 4To illustrate the transient enhancement circuit 300 of the switching converter provided by the present invention, when the load of the switching converter switches from light load to heavy load, the output voltage Vout of the switching converter undershoots, resulting in the feedback voltage Vfb undershooting. At this time, if Vref > Vfb > VL1, then VA = VB = L, the switches k1 and k2 are turned off, and the transconductance amplifier 320 does not work. Then the input current I0 of the compensation network 210 = gm1*(Vref - Vfb) = I1 (gm1 is the transconductance of the error amplifier EA); if VL2 < Vfb < VL1, then VA = H, VB = L. At this time, the transconductance amplifier 320 is activated, and the compensation current I2 = gm2*(VL2 - Vfb) (gm2 is the transconductance of the transconductance amplifier 320). The direction of the compensation current I2 is the second direction (opposite to the direction of the current I1, that is, the current flows into the transconductance amplifier 320). The current detection module 331 controls the switch k3 to turn off, so that the input current I0 of the compensation network 210 = gm1*(Vref - Vfb) = I1; as the feedback voltage Vfb is lower than the threshold voltage VL2, the direction of the compensation current I2 changes to the first direction (the same as the direction of the current I1, that is, the current flows out of the transconductance amplifier 320). The current detection module 331 controls the switch k3 to conduct. At this time, the input current I0 of the compensation network 210 = gm1*(Vref - Vfb) + gm2*(VL2 - Vfb); through the above method, during the process that the feedback voltage Vfb undershoots to below the threshold voltage VL2, the input current I0 of the compensation network 210 will gradually increase and will not mutate, so as to enhance the transient response speed of the closed-loop system without affecting the stability of the closed-loop system.

[0042] Similarly, when the load of the switching converter switches from heavy load to light load, the output voltage Vout of the switching converter overshoots, and the feedback voltage Vfb overshoots. When VH2 > Vfb > Vref, the input current I0 of the compensation network 210 = gm1*(Vref - Vfb) = I1; when VH2 < Vfb, the input current I0 of the compensation network 210 = gm1*(Vref - Vfb) + gm2*(VH2 - Vfb) = I1 + I2. Through the above method, during the process that the feedback voltage Vfb overshoots to above the threshold voltage VH2, the input current I0 of the compensation network 210 will not mutate, so as to similarly enhance the transient response speed of the closed-loop system without affecting the stability of the closed-loop system.

[0043] In other circuits of the present invention, a chip is also provided. The chip is, for example, an integrated circuit chip such as a power management chip or a radio frequency chip. The transient enhancement circuit 300 provided by the embodiments of the present invention can be integrated in the chip. The specific structure of the transient enhancement circuit in the integrated circuit chip will not be elaborated one by one here.

[0044] This invention also provides an electronic device, including the aforementioned switching converter or the aforementioned chip;

[0045] For example, the aforementioned switching converter with transient enhancement circuitry can be used in communication terminals as an important component of radio frequency integrated circuits or power management circuits. Here, "communication terminal" refers to a device that can be used in a mobile environment and supports multiple communication standards such as GSM, EDGE, TD-SCDMA, TDD-LTE, and FDD-LTE, including mobile phones, laptops, tablets, and in-vehicle computers. Furthermore, the technical solution provided by this invention is also applicable to other applications of radio frequency integrated circuits, such as communication base stations.

[0046] The transient enhancement circuit 300 of the switching converter provided by the present invention selects whether to activate the transconductance amplifier 320 based on the comparison result of the feedback voltage Vfb and the threshold voltage VL1 / VH1. After the transconductance amplifier 320 is activated, the feedback voltage Vfb and the threshold voltage VL2 / VH2 are differentially amplified by transconductance to obtain a compensation current I2. When the direction of the compensation current I2 is the same as the direction of the current I1 amplified by the error amplifier EA, the compensation current I2 is injected into the compensation network 210 to accelerate the response speed of the compensation network 210, thereby enhancing the transient response speed of the switching converter.

[0047] As described above, these embodiments of the present invention do not exhaustively describe all details, nor do they limit the invention to specific embodiments. Clearly, many modifications and variations can be made based on the above description. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to effectively utilize the invention and its modifications. The scope of protection of this invention should be determined by the scope defined in the claims and their equivalents.

Claims

1. A transient enhancement circuit for a switching converter, the switching converter comprising an error amplifier and a compensation network, the error amplifier amplifying the feedback voltage of the switching converter and a reference voltage, the compensation network converting the amplified current from the error amplifier into a voltage signal to control the switching duty cycle of a power switching transistor, wherein... The transient enhancement circuit includes: The comparison module is used to compare the feedback voltage with the first threshold voltage and generate a mode control signal based on the comparison result. A transconductance amplifier, controlled by the mode control signal, is used to differentially amplify the feedback voltage and the second threshold voltage to generate a compensation current; and A current control module is used to provide the compensation current to the compensation network according to the state of the mode control signal and the direction of the compensation current, so as to improve the response speed of the compensation network.

2. The transient enhancement circuit according to claim 1, wherein, The first threshold voltage includes a first high threshold voltage and a first low threshold voltage, and the comparison module includes: The first comparator has its positive input connected to the first low threshold voltage and its negative input connected to the feedback voltage, and is used to provide a first mode control signal based on the comparison result between the first low threshold voltage and the feedback voltage. The second comparator has its positive input connected to the feedback voltage and its negative input connected to the first high threshold voltage. It is used to provide a second mode control signal based on the comparison result between the first high threshold voltage and the feedback voltage.

3. The transient enhancement circuit according to claim 2, wherein, The second threshold voltage includes a second high threshold voltage and a second low threshold voltage, and the transient enhancement circuit further includes: A first switch is connected between the positive input terminal of the transconductance amplifier and the second low threshold voltage; The second switch is connected between the positive input terminal of the transconductance amplifier and the second high threshold voltage.

4. The transient enhancement circuit according to claim 3, wherein, The second low threshold voltage is lower than the first low threshold voltage, the second high threshold voltage is higher than the first high threshold voltage, and the reference voltage is higher than the first low threshold voltage and lower than the first high threshold voltage.

5. The transient enhancement circuit according to claim 3, wherein, The first switch and the second switch are controlled to conduct in a non-overlapping manner by the first mode control signal and the second mode control signal, respectively.

6. The transient enhancement circuit according to claim 5, wherein, The current control module includes: The third switch is connected between the output of the transconductance amplifier and the compensation network; A current detection module is used to control the opening and closing of the third switch according to the state of the mode control signal and the direction of the compensation current. The current detection module is activated when either the first mode control signal or the second mode control signal is at a high level. When the first mode control signal is high, if the direction of the compensation current is detected to be in the first direction, the third switch is controlled to be turned on; if the direction of the compensation current is detected to be in the second direction, the third switch is controlled to be turned off. When the second mode control signal is high, if the direction of the compensation current is detected to be in the first direction, the third switch is controlled to be turned off; if the direction of the compensation current is detected to be in the second direction, the third switch is controlled to be turned on.

7. The transient enhancement circuit according to claim 6, wherein, The current detection module includes a detection resistor connected between the output terminal of the transconductance amplifier and ground, and the current detection module detects the direction of the compensation current through the detection resistor.

8. A switching converter, comprising: Power switching transistors are used to control the power transfer from the input to the output of the switching converter. Feedback circuitry is used to provide feedback voltage based on the output voltage of the switching converter; An error amplifier is used to amplify the feedback voltage and the reference voltage; A compensation network is used to convert the current amplified by the error amplifier into a voltage signal. A comparator is used to compare the voltage signal and the superimposed signal of the inductor sampling signal and the ramp signal, and outputs a pulse width modulation signal according to the comparison result to control the switching duty cycle of the power switch. The transient enhancement circuit as described in any one of claims 1-7 is used to improve the response speed of the compensation network.

9. A chip comprising the transient enhancement circuit as described in any one of claims 1-7.

10. An electronic device comprising the switching converter of claim 8 or the chip of claim 9.

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