A control circuit for a power converter and a power converter

Abstract

The utility model provides a control circuit and power converter of power converter, including first operational amplifier, second operational amplifier and / or third operational amplifier, and the compensation circuit that connects between the output of first operational amplifier and reference ground, when including second operational amplifier, the output of second operational amplifier is connected with compensation circuit and separates at least one compensation resistance with the output of first operational amplifier, when including third operational amplifier, the output of third operational amplifier is connected with compensation circuit and separates at least one compensation resistance with the output of first operational amplifier. Because on the basis of existing first operational amplifier, increased second operational amplifier and / or third operational amplifier, make second operational amplifier and / or third operational amplifier not function when power converter is in steady state, accelerate the response speed of compensation voltage when the output voltage of power converter overshoots or falls, thereby can optimize the dynamic characteristic of system under the premise of not influencing system stability.

Description

Technical Field

[0001] This utility model relates to the field of power electronics technology, and in particular to a control circuit and a power converter for a power converter. Background Technology

[0002] Most power converters currently consist of a power stage circuit and a control circuit. The power stage circuit can include Buck, Boost, Buck-Boost, AC / DC, and other circuit structures. Taking the Boost circuit as an example, its circuit structure can be as follows: Figure 1 As shown, the power converter 10 includes a power stage circuit 30 and a control circuit 20. The control circuit 20 can be composed of a compensation voltage generation circuit 21, a comparator circuit CMP, and a logic circuit 22.

[0003] The control circuit 20 first samples the output voltage VOUT of the power converter 10 through the feedback circuit 211, which consists of feedback resistors R1 and R2, to obtain the feedback voltage VFB1. The feedback voltage VFB1 and the reference voltage VREF1 can be used as the input terminals of the first operational amplifier EA1. The output current IEA1 of the first operational amplifier EA1 is proportional to the voltage difference between its positive and negative input terminals. The output terminal of the first operational amplifier EA1 is usually connected to the compensation circuit 212, which consists of compensation resistor Rc and compensation capacitor Cc. The output current IEA1 of the first operational amplifier EA1 flows through the compensation circuit 212 and generates a compensation voltage Vc. The compensation voltage Vc and the current sampling value IL_sense of the inductor L1 are passed through the comparator circuit CMP and the logic circuit 22 to generate a pulse width modulation (PWM) signal to drive the power transistor M1, ultimately stabilizing the output voltage VOUT at the set value.

[0004] From a stability perspective, a smaller compensation resistor Rc and a larger compensation capacitor Cc result in a larger phase margin and gain margin, leading to better system stability. From a dynamic characteristics perspective, a larger compensation resistor Rc and a smaller compensation capacitor Cc allow the compensation voltage Vc to adjust faster during dynamic processes such as input voltage VIN transitions and load transitions, enabling the system to reach a new steady state more quickly. However, the downside is that the phase margin and gain margin of the system will decrease, resulting in poorer system stability.

[0005] The above analysis shows that system stability and dynamic characteristics are contradictory. As the application scenarios of power converters increasingly demand higher requirements for dynamic characteristics, how to optimize dynamic characteristics without affecting system stability has become an urgent problem to be solved. Utility Model Content

[0006] The purpose of this invention is to provide a control circuit and power converter for a power converter, which can optimize the dynamic characteristics of the system without affecting the system stability.

[0007] This invention provides a control circuit for a power converter, including a first operational amplifier and a compensation circuit. The compensation circuit includes a compensation resistor unit and a compensation capacitor unit connected in series. The output terminal of the first operational amplifier is connected to a first terminal of the compensation resistor unit, and the compensation capacitor unit is connected between a second terminal of the compensation resistor unit and a reference ground. The compensation resistor unit includes at least one compensation resistor, and the compensation capacitor unit includes at least one compensation capacitor. When a second operational amplifier is included, the output terminal of the second operational amplifier is connected to the compensation circuit and is separated from the output terminal of the first operational amplifier by at least one compensation resistor. When a third operational amplifier is included, the output terminal of the third operational amplifier is connected to the compensation circuit and is separated from the output terminal of the first operational amplifier by at least one compensation resistor.

[0008] Preferably, when the second operational amplifier is included, the output terminal of the second operational amplifier is connected to the second terminal of the compensation resistor unit; when the third operational amplifier is included, the output terminal of the third operational amplifier is connected to the second terminal of the compensation resistor unit.

[0009] Preferably, the second operational amplifier is configured to generate a current flowing from the output terminal of the second operational amplifier to the compensation circuit when the output voltage of the power converter drops; the third operational amplifier is configured to generate a current flowing from the compensation circuit to the output terminal of the third operational amplifier when the output voltage of the power converter overshoots.

[0010] Preferably, when the second operational amplifier is included, the output current of the second operational amplifier is 0 when the power converter is in a steady state or when the output voltage overshoots; when the third operational amplifier is included, the output current of the third operational amplifier is 0 when the power converter is in a steady state or when the output voltage drops.

[0011] Preferably, when the second operational amplifier is included, the first input terminal of the second operational amplifier receives a reference voltage, and the second input terminal receives a feedback voltage characterizing the output voltage of the power converter; when the voltage at the first input terminal of the second operational amplifier is greater than the voltage at its second input terminal, a current flows from the output terminal of the second operational amplifier to the compensation circuit, and the magnitude of the output current of the second operational amplifier is proportional to the voltage difference between the first and second input terminals of the second operational amplifier; when the voltage at the first input terminal of the second operational amplifier is less than the voltage at its second input terminal, the output current of the second operational amplifier is 0.

[0012] Preferably, when the third operational amplifier is included, the first input terminal of the third operational amplifier receives a reference voltage, and the second input terminal receives a feedback voltage characterizing the output voltage of the power converter; when the voltage at the first input terminal of the third operational amplifier is less than the voltage at its second input terminal, the output terminal of the third operational amplifier generates a current flowing from the compensation circuit to the output terminal of the second operational amplifier, and the magnitude of the output current of the third operational amplifier is proportional to the voltage difference between the second input terminal and the first input terminal of the third operational amplifier; when the voltage at the first input terminal of the third operational amplifier is greater than the voltage at its second input terminal, the output current of the third operational amplifier is 0.

[0013] Preferably, when the second operational amplifier is included, the first input terminals of both the first operational amplifier and the second operational amplifier receive a first reference voltage; the second input terminal of the first operational amplifier receives a first feedback voltage characterizing the output voltage of the power converter, and the second input terminal of the second operational amplifier receives a second feedback voltage characterizing the output voltage of the power converter; wherein, under the same output voltage conditions, the second feedback voltage is greater than the first feedback voltage.

[0014] Preferably, when the second operational amplifier is included, the first input terminal of the first operational amplifier receives a first reference voltage, and the first input terminal of the second operational amplifier receives a second reference voltage; the second input terminals of both the first and second operational amplifiers receive a first feedback voltage characterizing the output voltage of the power converter; wherein the second reference voltage is less than the first reference voltage.

[0015] Preferably, when the third operational amplifier is included, the first input terminals of both the first operational amplifier and the third operational amplifier receive a first reference voltage; the second input terminal of the first operational amplifier receives a first feedback voltage characterizing the output voltage of the power converter, and the second input terminal of the third operational amplifier receives a third feedback voltage characterizing the output voltage of the power converter; wherein, under the same output voltage conditions, the third feedback voltage is less than the first feedback voltage.

[0016] Preferably, when a third operational amplifier is included, the first input terminal of the first operational amplifier receives a first reference voltage, and the first input terminal of the third operational amplifier receives a third reference voltage; the second input terminals of both the first and second operational amplifiers receive a first feedback voltage characterizing the output voltage of the power converter; wherein the third reference voltage is greater than the first reference voltage.

[0017] This utility model also provides a power converter, including a power stage circuit and a control circuit as described above; the control circuit generates a switching control signal according to a compensation voltage, and the switching control signal is used to control the switching state of the power transistor in the power stage circuit; wherein, the compensation voltage is the voltage at the first terminal of the compensation resistor unit.

[0018] The present invention provides a control circuit and a power converter for a power converter, including a first operational amplifier, a second operational amplifier, and / or a third operational amplifier, and a compensation circuit composed of a compensation resistor unit and a compensation capacitor unit connected in series. The output terminal of the first operational amplifier is connected to the first terminal of the compensation resistor unit, and the compensation capacitor unit is connected between the second terminal of the compensation resistor unit and a reference ground. When the second operational amplifier is included, its output terminal is connected to the compensation circuit and separated from the output terminal of the first operational amplifier by at least one compensation resistor. When the third operational amplifier is included, its output terminal is connected to the compensation circuit and separated from the output terminal of the first operational amplifier by at least one compensation resistor. By adding a second operational amplifier and / or a third operational amplifier to the existing first operational amplifier, the second and / or third operational amplifiers are not active when the power converter is in a steady state. They accelerate the response speed of the compensation voltage when the output voltage of the power converter overshoots or drops, thereby optimizing the dynamic characteristics of the system without affecting system stability. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the structure of a power converter in the prior art;

[0020] Figure 2 This is a schematic diagram of the compensation voltage generation circuit according to the first embodiment of this application;

[0021] Figure 3 This is a schematic diagram of the compensation voltage generation circuit according to the second embodiment of this application;

[0022] Figure 4 This is a schematic diagram of the compensation voltage generation circuit according to the third embodiment of this application;

[0023] Figure 5 This is a schematic diagram of the compensation voltage generation circuit according to the fourth embodiment of this application;

[0024] Figure 6 This is a schematic diagram of the compensation voltage generation circuit according to the fifth embodiment of this application;

[0025] Figure 7 This is a schematic diagram of the compensation voltage generation circuit according to the sixth embodiment of this application;

[0026] Figure 8(a) shows a simulation result of the dynamic response of the power converter of this application;

[0027] Figure 8(b) shows the simulation results of the dynamic response of an existing power converter;

[0028] Figure 9(a) shows another simulation result of the dynamic response of the power converter in this application;

[0029] Figure 9(b) shows the simulation results of the dynamic response of another existing power converter. Detailed Implementation

[0030] The preferred embodiments of the present invention will be 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 that can be made within the spirit and scope of the present invention.

[0031] In order to enable the public to have a thorough understanding of the present invention, specific details are described in detail in the following preferred embodiments of the present invention, but those skilled in the art can fully understand the present invention without these details.

[0032] The present invention will be described in more detail below 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 present invention.

[0033] refer to Figure 1 In order to optimize the dynamic characteristics of the power converter 10, one existing method is to optimize the response speed of the first operational amplifier EA1. However, in current power converters, the operational amplifiers of the control circuit are the focus of the design and can basically achieve high-speed dynamic response. Therefore, further optimization of the operational amplifiers will not have a significant impact on the overall dynamic characteristics of the system.

[0034] Another approach is to connect a capacitor in parallel with the feedback resistor R1 to introduce a feedforward function. While this method can improve the dynamic response speed of the first op-amp EA1, it will change the phase margin and gain margin of the system, thus affecting the stability of the system. Furthermore, if the value of the feedforward capacitor is not well designed, it can lead to serious instability of the system.

[0035] Another approach is to use alternative control circuit structures, such as hysteresis control circuits. However, while this method can better optimize dynamic characteristics, it may result in poorer output voltage ripple and load regulation. Overall, existing control circuit structures remain the most widely used.

[0036] Based on this, this application proposes a control circuit for a power converter, which adds a second operational amplifier and / or a third operational amplifier to the existing control circuit that only includes a first operational amplifier. This allows the second and / or third operational amplifiers to be inactive when the power converter is in a steady state, and to accelerate the adjustment speed of the compensation voltage when the output voltage of the power converter overshoots or drops. When the second operational amplifier is included, its output terminal is connected in the compensation circuit at a position separated from the output terminal of the first operational amplifier by at least one compensation resistor. When the third operational amplifier is included, its output terminal is connected in the compensation circuit at a position separated from the output terminal of the first operational amplifier by at least one compensation resistor. This allows for the optimization of the dynamic characteristics of the system without affecting the system stability.

[0037] Figure 2 A schematic diagram of the compensation voltage generation circuit according to the first embodiment of this application is shown. Figure 2 As shown, the compensation voltage generation circuit 21 may include a first operational amplifier EA1, a second operational amplifier EA2, a feedback circuit 211, and a compensation circuit 212. The compensation voltage generation circuit 21 can be connected with... Figure 1 The comparison circuit CMP and logic circuit 22 shown together form the control circuit 20.

[0038] The feedback circuit 211 is connected between the output voltage terminal of the power converter 10 and the reference ground, and includes feedback resistors R1, R2 and R3 connected in series; the compensation circuit 212 is connected between the output terminal of the first operational amplifier EA1 and the reference ground, and includes compensation resistor Rc and compensation capacitor Cc connected in series.

[0039] The output terminal of the second operational amplifier EA2 is connected to the intermediate node of the compensation resistor Rc and the compensation capacitor Cc. The positive input terminals of both the first operational amplifier EA1 and the second operational amplifier EA2 receive the first reference voltage VREF1. The negative input terminal of the first operational amplifier EA1 is connected to the intermediate node of the feedback resistors R2 and R3 to receive the first feedback voltage VFB1, which characterizes the output voltage VOUT. The negative input terminal of the second operational amplifier EA2 is connected to the intermediate node of the feedback resistors R1 and R2 to receive the second feedback voltage VFB2, which characterizes the output voltage VOUT. The second feedback voltage VFB2 is greater than the first feedback voltage VFB1.

[0040] The current IEA1 is the output current of the first op-amp EA1, the current IEA2 is the output current of the second op-amp EA2, and the compensation voltage Vc is the voltage at the connection point between the output of the first op-amp EA1 and the compensation resistor Rc.

[0041] The first op-amp EA1 and the second op-amp EA2 are both transconductance operational amplifiers, which are circuit structures with functions similar to current-mode operational amplifiers.

[0042] In steady state, the first reference voltage VREF1 = the first feedback voltage VFB1 < the second feedback voltage VFB2, that is, the voltage at the positive input terminal of the second op-amp EA2 is less than the voltage at the negative input terminal, the second op-amp EA2 does not function and has no impact on the stability of the system.

[0043] When the output load switches from heavy load to light load, the output voltage VOUT has an overshoot. The first reference voltage VREF1 < the first feedback voltage VFB1 < the second feedback voltage VFB2, and the second op-amp EA2 does not function.

[0044] When the output load switches from light to heavy load, the output voltage VOUT drops. The first feedback voltage VREF1 is greater than the second feedback voltage VFB2, and the second op-amp EA2 starts to function. Compared to the traditional structure, the currents IEA2 and IEA1 charge the compensation capacitor Cc simultaneously, so the compensation voltage Vc rises at a faster rate, and the voltage drop of the output voltage VOUT is smaller.

[0045] Therefore, the circuit structure in this embodiment can optimize the dynamic performance of the output load switching from light load to heavy load.

[0046] Specifically, in steady state or when the output voltage VOUT is overshooting, the voltage at the positive input terminal of the second operational amplifier EA2 is less than the voltage at the negative input terminal, and the current IEA2 generated at its output terminal is 0, presenting a high impedance state. When the output voltage VOUT drops, the voltage at the positive input terminal of the second operational amplifier EA2 is greater than the voltage at the negative input terminal, and a current IEA2 is generated at its output terminal, flowing from the output terminal of the second operational amplifier EA2 to the compensation circuit 212.

[0047] When the voltage at the positive input terminal of the second operational amplifier EA2 is greater than the voltage at the negative input terminal, the magnitude of the current IEA2 can be a fixed value, such as 10mA; or it can be proportional to the voltage difference between its positive and negative input terminals. For example, the magnitude of the current IEA2 can be the ratio of the voltage difference between its positive and negative input terminals to its own transconductance coefficient gm2, that is, current IEA2 = (VREF1 - VFB2) * gm2.

[0048] For example, the control circuit 20 in this application can control the power converter 10 in peak current mode. Of course, the control circuit 20 in this application can also use other control modes, which are not limited here.

[0049] The control circuit for the power converter proposed in this application adds a circuit structure with a function similar to a current-mode operational amplifier, namely a second operational amplifier EA2, to the existing control circuit. The second operational amplifier EA2 does not function when the power converter is in a steady state. When the output voltage VOUT drops, it outputs a current IEA2 flowing to the compensation capacitor Cc, which accelerates the rise of the compensation voltage Vc and reduces the drop of the output voltage VOUT. Furthermore, the output terminal of the second operational amplifier EA2 is connected to the compensation capacitor Cc, which solves the instability problem caused by directly connecting the output terminal of the second operational amplifier EA2 to the compensation voltage Vc. Thus, it can accelerate the adjustment speed of the compensation voltage Vc when the output voltage VOUT drops without affecting the stability of the power converter.

[0050] Figure 3 A schematic diagram of the compensation voltage generation circuit according to the second embodiment of this application is shown. Figure 3 As shown, the compensation voltage generation circuit 21 may include a first operational amplifier EA1, a third operational amplifier EA3, a feedback circuit 211, and a compensation circuit 212.

[0051] The output of the third operational amplifier EA3 is connected to the intermediate node of the compensation resistor Rc and the compensation capacitor Cc. The positive inputs of both the first operational amplifier EA1 and the third operational amplifier EA3 receive the first reference voltage VREF1. The negative input of the first operational amplifier EA1 is connected to the intermediate node of the feedback resistors R1 and R2, and is used to receive the first feedback voltage VFB1, which characterizes the output voltage VOUT. The negative input of the third operational amplifier EA3 is connected to the intermediate node of the feedback resistors R2 and R3, and is used to receive the third feedback voltage VFB3, which characterizes the output voltage VOUT. The third feedback voltage VFB3 is less than the first feedback voltage VFB1.

[0052] The current IEA3 is the output current of the third op-amp EA3, and the compensation voltage Vc is the voltage at the connection point between the output of the first op-amp EA1 and the compensation resistor Rc.

[0053] The third operational amplifier, EA3, is a transconductance operational amplifier, which is a circuit structure with functions similar to a current-mode operational amplifier.

[0054] In steady state, the first reference voltage VREF1 = the first feedback voltage VFB1 > the third feedback voltage VFB3, that is, the voltage at the positive input terminal of the third op-amp EA3 is greater than the voltage at the negative input terminal, the third op-amp EA3 does not function and has no impact on the system stability.

[0055] When the output load switches from heavy load to light load, the output voltage VOUT experiences overshoot. The first reference voltage VREF1 is less than the third feedback voltage VFB3, and the third op-amp EA3 begins to function. Compared to the traditional structure, the output current IEA3 of the third op-amp EA3 and the output current IEA1 of the first op-amp EA1 simultaneously discharge the compensation capacitor Cc. Therefore, the output voltage Vc of the first op-amp EA1 drops at a faster rate, resulting in a smaller voltage overshoot in the output voltage VOUT.

[0056] When the output load changes from light load to heavy load, the output voltage VOUT drops. The first feedback voltage VREF1 > the first feedback voltage VFB1 > the third feedback voltage VFB3, and the third op-amp EA3 does not function.

[0057] Therefore, the circuit structure in this embodiment can optimize the dynamic performance of the output load switching from light load to heavy load.

[0058] Specifically, in steady state or when the output voltage VOUT drops, the voltage at the positive input terminal of the third op-amp EA3 is greater than the voltage at the negative input terminal, and the current IEA3 generated at its output terminal is 0, exhibiting a high impedance state. When the output voltage VOUT overshoots, the voltage at the positive input terminal of the third op-amp EA3 is less than the voltage at the negative input terminal, and a current IEA3 is generated at its output terminal flowing from the compensation circuit 212 to the third op-amp EA3.

[0059] When the voltage at the positive input terminal of the third operational amplifier EA3 is less than the voltage at the negative input terminal, the magnitude of the current at its output terminal can be a constant value or proportional to the voltage difference between its positive and negative input terminals. For example, the magnitude of the current IEA3 can be the ratio of its own transconductance coefficient gm3 to the voltage difference between its positive and negative input terminals, i.e., current IEA3 = (VFB3 - VREF1) * gm3.

[0060] The control circuit for the power converter proposed in this application adds a third operational amplifier EA3 to the existing control circuit. This third operational amplifier EA3 does not function when the power converter is in steady state. When the output voltage VOUT overshoots, it outputs a current IEA3 flowing from the compensation capacitor Cc, which accelerates the decrease rate of the compensation voltage Vc and reduces the overshoot of the output voltage VOUT. Furthermore, the output terminal of the third operational amplifier EA3 is connected to the compensation capacitor Cc, thereby accelerating the adjustment speed of the compensation voltage Vc when the output voltage VOUT overshoots without affecting the stability of the power converter.

[0061] In one embodiment, such as Figure 4 As shown, the compensation voltage generation circuit 21 may include a first operational amplifier EA1, a second operational amplifier EA2, a third operational amplifier EA3, a feedback circuit 211, and a compensation circuit 212.

[0062] The feedback circuit 211 may include feedback resistors R1, R2, R3 and R4 connected in series.

[0063] The outputs of the second operational amplifier EA2 and the third operational amplifier EA3 are both connected to the intermediate node of the compensation resistor Rc and the compensation capacitor Cc. The negative input of the first operational amplifier EA1 is connected to the intermediate node of the feedback resistor R2 and the feedback resistor R3, and is used to receive the first feedback voltage VFB1, which represents the output voltage VOUT. The negative input of the second operational amplifier EA2 is connected to the intermediate node of the feedback resistor R1 and the feedback resistor R2, and is used to receive the second feedback voltage VFB2, which represents the output voltage VOUT. The negative input of the third operational amplifier EA3 is connected to the intermediate node of the feedback resistor R3 and the feedback resistor R4, and is used to receive the third feedback voltage VFB3, which represents the output voltage VOUT. The second feedback voltage VFB2 is greater than the first feedback voltage VFB1, and the third feedback voltage VFB3 is less than the first feedback voltage VFB1.

[0064] In steady state, the second feedback voltage VFB2 > the first reference voltage VREF1 = the first feedback voltage VFB1 > the third feedback voltage VFB3, and neither the second op-amp EA2 nor the third op-amp EA3 has any function.

[0065] When the output load switches from heavy load to light load, the output voltage VOUT has an overshoot. The second feedback voltage VFB2 > the first feedback voltage VFB1 > the third feedback voltage VFB3 > the first reference voltage VREF1. The second op-amp EA2 does not work, and the third op-amp EA3 works.

[0066] When the output load changes from light load to heavy load, the output voltage VOUT drops. The first reference voltage VREF1 > the second feedback voltage VFB2 > the first feedback voltage VFB1 > the third feedback voltage VFB3. The third op-amp EA3 does not work, while the second op-amp EA2 works.

[0067] Therefore, the circuit structure in this embodiment can simultaneously optimize the dynamic performance of the output load switching from heavy load to light load and from light load to heavy load.

[0068] Specifically, in steady state, the voltage at the positive input terminal of the second op-amp EA2 is less than the voltage at its negative input terminal, and the voltage at the positive input terminal of the third op-amp EA2 is greater than the voltage at its negative input terminal. The currents IEA2 and IEA3 generated at the output terminals of both the second and third op-amp EA2 are zero. When the output voltage VOUT overshoots, the voltage at the positive input terminal of the second op-amp EA2 is less than the voltage at its negative input terminal, and the voltage at the positive input terminal of the third op-amp EA2 is less than the voltage at its negative input terminal. The current IEA2 generated at the output terminal of the second op-amp EA2 is zero, and the current IEA3 generated at the output terminal of the third op-amp EA2 flows from the compensation circuit 212 to its output terminal. When the output voltage VOUT drops, the voltage at the positive input terminal of the second op-amp EA2 is greater than the voltage at its negative input terminal, and the voltage at the positive input terminal of the third op-amp EA2 is greater than the voltage at its negative input terminal. The current IEA2 generated at the output terminal of the second op-amp EA2 flows to the compensation circuit 212, and the current IEA3 generated at the output terminal of the third op-amp EA2 is zero.

[0069] The control circuit for the power converter proposed in this application adds a second operational amplifier EA2 and a third operational amplifier EA3 to the existing control circuit. The second and third operational amplifiers EA2 and EA3 are inactive when the power converter is in steady state. When the output voltage VOUT drops, they output a current IEA2 flowing to the compensation capacitor Cc, accelerating the rise of the compensation voltage Vc and reducing the drop in output voltage VOUT. When the output voltage VOUT overshoots, they output a current IEA3 flowing from the compensation capacitor Cc, accelerating the fall of the compensation voltage Vc and reducing the overshoot of output voltage VOUT. Furthermore, the output terminals of both the second and third operational amplifiers EA2 and EA3 are connected to the compensation capacitor Cc. Therefore, without affecting the stability of the power converter, the adjustment speed of the compensation voltage Vc during dynamic processes can be accelerated.

[0070] In some embodiments, such as Figure 5 As shown, the compensation voltage generation circuit 21 may include a first operational amplifier EA1, a second operational amplifier EA2, a feedback circuit 211, and a compensation circuit 212. The feedback circuit 211 includes a feedback resistor R1 and a feedback resistor R2 connected in series.

[0071] The positive input terminal of the first operational amplifier EA1 receives a first reference voltage VREF1, and the positive input terminal of the second operational amplifier EA2 receives a second reference voltage VREF2, wherein the second reference voltage VREF2 is less than the first reference voltage VREF1. The negative input terminals of both the first operational amplifier EA1 and the second operational amplifier EA2 are connected to the intermediate node of the feedback resistor R1 and the feedback resistor R2 to receive the first feedback voltage VFB1, which characterizes the output voltage VOUT.

[0072] For example, the first reference voltage VREF1 can be the sum of the second reference voltage VREF2 and the voltage of the first voltage source V1.

[0073] In this embodiment, during steady-state operation or when the output voltage VOUT is overshooting, the voltage at the positive input terminal of the second operational amplifier EA2 is less than the voltage at the negative input terminal, and the current IEA2 generated at its output terminal is 0. When the output voltage VOUT drops, the voltage at the positive input terminal of the second operational amplifier EA2 is greater than the voltage at the negative input terminal, and the current IEA2 generated at its output terminal flows from the second operational amplifier EA2 to the compensation circuit 212.

[0074] In other embodiments, such as Figure 6 As shown, the compensation voltage generation circuit 21 may include a first operational amplifier EA1, a third operational amplifier EA3, a feedback circuit 211, and a compensation circuit 212. The feedback circuit 211 includes a feedback resistor R1 and a feedback resistor R2 connected in series.

[0075] The positive input terminal of the first operational amplifier EA1 receives a first reference voltage VREF1, and the positive input terminal of the third operational amplifier EA3 receives a third reference voltage VREF3, wherein the third reference voltage VREF3 is greater than the first reference voltage VREF1. The negative input terminals of both the first operational amplifier EA1 and the third operational amplifier EA3 are connected to the intermediate node of the feedback resistor R1 and the feedback resistor R2 to receive the first feedback voltage VFB1, which represents the output voltage VOUT.

[0076] For example, the first reference voltage VREF1 can be the voltage difference between the third reference voltage VREF3 and the second voltage source V2.

[0077] In this embodiment, when the output voltage VOUT is in steady state or drops, the voltage at the positive input terminal of the third operational amplifier EA3 is greater than the voltage at the negative input terminal, and the current IEA3 generated at its output terminal is 0. When the output voltage VOUT overshoots, the voltage at the positive input terminal of the third operational amplifier EA3 is less than the voltage at the negative input terminal, and the current IEA3 generated at its output terminal flows from the compensation circuit 212 to the third operational amplifier EA3.

[0078] It should be noted that it is also possible to... Figure 5 Add on the basis Figure 6 The third operational amplifier EA3 is shown in the diagram. In this case, the second reference voltage VREF2 must be less than the first reference voltage VREF1, and the third reference voltage VREF3 must be greater than the first reference voltage VREF1. Under these circumstances, the characteristics and operating states of the second operational amplifier EA2 and the third operational amplifier EA3 can be referred to the above... Figure 5 and Figure 6 The characteristics and operating states of the second operational amplifier EA2 and the third operational amplifier EA3 are not described in detail here.

[0079] Figure 7A schematic diagram of another control circuit according to an embodiment of this application is shown. Figure 7 As shown, the compensation voltage generation circuit 21 may include a first operational amplifier EA1, a second operational amplifier EA2, a feedback circuit 211, and a compensation circuit 212.

[0080] The feedback circuit 211 includes feedback resistors R1, R2, ..., Rn connected in series. The compensation circuit 212 includes a compensation resistor unit 2121 and a compensation capacitor unit 2122 connected in series. The compensation resistor unit 2121 includes compensation resistors Rc1, Rc2, ..., Rcn connected in series. The compensation capacitor unit 2122 includes compensation capacitors Cc1, Cc2, ..., Ccn connected in series.

[0081] The output of the second operational amplifier EA2 is connected to the compensation circuit 212, and is separated from the output of the first operational amplifier EA1 by at least one compensation resistor. The connection between the negative input terminals of the first operational amplifier EA1 and the second operational amplifier EA2 and the feedback circuit 211 must satisfy the condition that the second feedback voltage VFB2 is greater than the first feedback voltage VFB1.

[0082] It should be noted that... Figure 7 The second operational amplifier EA2 is replaced with the third operational amplifier EA3, while the rest of the structure remains unchanged. In this case, the connection between the negative input terminals of the first operational amplifier EA1 and the third operational amplifier EA3 and the feedback circuit 211 must satisfy the condition that the third feedback voltage VFB3 is less than the first feedback voltage VFB1. The connection between the output terminal of the third operational amplifier EA3 and the compensation circuit 212 must still be separated from the output terminal of the first operational amplifier EA1 by at least one compensation resistor Rc. However, the connection position between the output terminal of the third operational amplifier EA3 and the compensation circuit 212 can be the same as or different from the connection position between the output terminal of the second operational amplifier EA2 and the compensation circuit 212. For example, when the output terminal of the second operational amplifier EA2 is connected to the midpoint between compensation resistors Rc2 and Rc3, the output terminal of the third operational amplifier EA3 can be connected to the midpoint between compensation resistors Rc2 and Rc3, or it can be connected to the midpoint between compensation capacitors Cc1 and Cc2. This application does not limit the connection position between the output terminals of the second operational amplifier EA2 and the third operational amplifier EA3 and the compensation circuit 212.

[0083] Preferably, when the compensation voltage generating circuit 21 includes a first operational amplifier EA1 and a second operational amplifier EA2, the output terminal of the second operational amplifier EA2 can be connected to the common terminal of the compensation resistor unit 2121 and the compensation capacitor unit 2122, that is, the output terminal of the second operational amplifier EA2 is connected to the intermediate node of the compensation resistor Rcn and the compensation capacitor Ccn; when the compensation voltage generating circuit 21 includes a first operational amplifier EA1 and a third operational amplifier EA3, the output terminal of the third operational amplifier EA3 can be connected to the common terminal of the compensation resistor unit 2121 and the compensation capacitor unit 2122.

[0084] It can also be in Figure 7 Adding a third operational amplifier EA3 while keeping the rest of the structure unchanged, the connection between the negative input terminals of the first operational amplifier EA1, the second operational amplifier EA2, and the third operational amplifier EA3 and the feedback circuit 211 must satisfy the following conditions: the second feedback voltage VFB2 is greater than the first feedback voltage VFB1, and the third feedback voltage VFB3 is less than the first feedback voltage VFB1. The connection method between the output terminals of the second operational amplifier EA2 and the third operational amplifier EA3 and the compensation circuit 212 can refer to the above. Figure 7 The description of replacing the second op-amp EA2 with the third op-amp EA3 will not be repeated here.

[0085] In this embodiment, the characteristics and operating states of the second operational amplifier EA2 and the third operational amplifier EA3 can be referred to the above description respectively. Figure 2 and Figure 3 The characteristics and operating states of the second operational amplifier EA2 and the third operational amplifier EA3 are not described in detail here.

[0086] It should be noted that, in addition to the above embodiments where the positive input terminals of the first operational amplifier EA1 and the second operational amplifier EA2 or the third operational amplifier EA3 receive the same reference voltage, and the negative input terminals of the first operational amplifier EA1 and the second operational amplifier EA2 or the third operational amplifier EA3 receive different feedback voltages; and where the negative input terminals of the first operational amplifier EA1 and the second operational amplifier EA2 or the third operational amplifier EA3 receive the same feedback voltage, and the positive input terminals of the first operational amplifier EA1 and the second operational amplifier EA2 or the third operational amplifier EA3 receive different reference voltages, and the negative input terminals of the first operational amplifier EA1 and the second operational amplifier EA2 receive different feedback voltages; and where the positive input terminals of the first operational amplifier EA1 and the third operational amplifier EA3 receive different reference voltages, and the negative input terminals of the first operational amplifier EA1 and the third operational amplifier EA3 receive different feedback voltages, and in this case, the second operational amplifier EA2 and the third operational amplifier EA3 can still have the characteristics and operating states of the above embodiments, which will not be repeated here.

[0087] This application also provides a power converter that can be used by... Figure 1The circuit consists of a power stage circuit 30, a comparator circuit CMP, a logic circuit 22, and a compensation voltage generation circuit 21 as described in the above embodiments.

[0088] The control circuit 20 proposed in this application can be composed of a comparator circuit CMP, a logic circuit 22, and a compensation voltage generation circuit 21 in the above embodiments. The control circuit 20 can generate a switching control signal for controlling the switching state of the power transistor M1 in the power stage circuit 30 according to the compensation voltage Vc.

[0089] Figures 8(a) and 8(b) show the circuit structure of this application, respectively. Figure 2 ) and existing circuit structures ( Figure 1 The simulation results of the dynamic response of the power converter are shown in Figure 8(a). In Figure 8(b), each division of the output voltage VOUT represents 0.06V, and in Figure 8(a), each division of the output voltage VOUT represents 0.05V. As can be seen from Figures 8(a) and 8(b), under the same input voltage VIN, the same output voltage VOUT, the same output current IOUT switching speed, and the same transconductance coefficient, when the output voltage VOUT drops, the minimum value of the output voltage VOUT of the circuit structure in this application is larger than that of the existing circuit structure. Moreover, compared with the existing circuit structure, the drop in output voltage VOUT of the circuit structure in this application is reduced by at least 20%, which greatly reduces the drop in output voltage VOUT and significantly improves the stability of the power converter.

[0090] Figures 9(a) and 9(b) show the circuit structure of this application, respectively. Figure 2 The simulation results of the dynamic response of the existing circuit structure that connects the output of the second op-amp EA2 to the compensation voltage Vc are shown in Figures 9(a) and 9(b). As can be seen from Figures 9(a) and 9(b), under the same test conditions of input voltage VIN, output voltage VOUT, output current IOUT switching speed, and output voltage VOUT drop, the existing circuit structure that connects the output of the second op-amp EA2 to the compensation voltage Vc can reduce the drop of the output voltage VOUT, but it is prone to instability and large fluctuations. In contrast, the circuit structure of the second op-amp EA2 in this application, which connects the output of the compensation resistor Rc and the compensation capacitor Cc to the intermediate node, can not only reduce the drop of the output voltage VOUT, but also has good stability and almost no fluctuations.

[0091] The control circuit for the power converter proposed in this application exhibits the same system stability as existing control circuits when the power converter is in a steady state; and when the power converter is in a dynamic state, the output voltage overshoot and sag of the power converter are smaller than those of existing control circuits. Furthermore, the design of the transconductance coefficient of the second operational amplifier EA2 or the third operational amplifier EA3 in this application is an independent closed-loop control design separate from the overall system, thus not affecting the complexity of existing control circuit parameter design.

[0092] 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.

[0093] 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 control circuit for a power converter, comprising a first operational amplifier and a compensation circuit, characterized in that, It also includes a second operational amplifier and / or a third operational amplifier; the compensation circuit includes a compensation resistor unit and a compensation capacitor unit connected in series, the output terminal of the first operational amplifier is connected to the first terminal of the compensation resistor unit, and the compensation capacitor unit is connected between the second terminal of the compensation resistor unit and a reference ground; the compensation resistor unit includes at least one compensation resistor, and the compensation capacitor unit includes at least one compensation capacitor. When the second operational amplifier is included, the output terminal of the second operational amplifier is connected to the compensation circuit and is separated from the output terminal of the first operational amplifier by at least one compensation resistor. When the third operational amplifier is included, the output terminal of the third operational amplifier is connected to the compensation circuit and is separated from the output terminal of the first operational amplifier by at least one compensation resistor.

2. The control circuit according to claim 1, characterized in that, When the second operational amplifier is included, the output terminal of the second operational amplifier is connected to the second terminal of the compensation resistor unit; When the third operational amplifier is included, the output terminal of the third operational amplifier is connected to the second terminal of the compensation resistor unit.

3. The control circuit according to claim 1, characterized in that, The second operational amplifier is used to generate a current flowing from the output terminal of the second operational amplifier to the compensation circuit when the output voltage of the power converter drops; The third operational amplifier is used to generate a current flowing from the compensation circuit to the output terminal of the third operational amplifier when the output voltage of the power converter overshoots.

4. The control circuit according to claim 1, characterized in that, When the second operational amplifier is included, the output current of the second operational amplifier is 0 when the power converter is in steady state or when the output voltage is overshooting. When the third operational amplifier is included, the output current of the third operational amplifier is 0 when the power converter is in a steady state or the output voltage drops.

5. The control circuit according to claim 1, characterized in that, When the second operational amplifier is included, the first input terminal of the second operational amplifier receives a reference voltage, and the second input terminal receives a feedback voltage characterizing the output voltage of the power converter. When the voltage at the first input terminal of the second operational amplifier is greater than the voltage at its second input terminal, a current is generated at the output terminal of the second operational amplifier that flows from the output terminal of the second operational amplifier to the compensation circuit. The magnitude of the current at the output terminal of the second operational amplifier is proportional to the voltage difference between the first input terminal and the second input terminal of the second operational amplifier. When the voltage at the first input terminal of the second operational amplifier is less than the voltage at its second input terminal, the current at the output terminal of the second operational amplifier is 0.

6. The control circuit according to claim 1, characterized in that, When the third operational amplifier is included, the first input terminal of the third operational amplifier receives a reference voltage, and the second input terminal receives a feedback voltage characterizing the output voltage of the power converter. When the voltage at the first input terminal of the third operational amplifier is less than the voltage at its second input terminal, the output terminal of the third operational amplifier generates a current flowing from the compensation circuit to the output terminal of the second operational amplifier. The magnitude of the current at the output terminal of the third operational amplifier is proportional to the voltage difference between the second input terminal and the first input terminal of the third operational amplifier. When the voltage at the first input terminal of the third operational amplifier is greater than the voltage at its second input terminal, the current at the output terminal of the third operational amplifier is 0.

7. The control circuit according to claim 1, characterized in that, When the second operational amplifier is included The first input terminals of both the first operational amplifier and the second operational amplifier receive a first reference voltage; The second input terminal of the first operational amplifier receives a first feedback voltage characterizing the output voltage of the power converter, and the second input terminal of the second operational amplifier receives a second feedback voltage characterizing the output voltage of the power converter. Under the same output voltage conditions, the second feedback voltage is greater than the first feedback voltage.

8. The control circuit according to claim 1, characterized in that, When the second operational amplifier is included The first input terminal of the first operational amplifier receives a first reference voltage, and the first input terminal of the second operational amplifier receives a second reference voltage. The second input terminals of both the first operational amplifier and the second operational amplifier receive a first feedback voltage characterizing the output voltage of the power converter; Wherein, the second reference voltage is less than the first reference voltage.

9. The control circuit according to claim 1, characterized in that, When the third operational amplifier is included The first input terminals of both the first operational amplifier and the third operational amplifier receive a first reference voltage; The second input terminal of the first operational amplifier receives a first feedback voltage characterizing the output voltage of the power converter, and the second input terminal of the third operational amplifier receives a third feedback voltage characterizing the output voltage of the power converter. Wherein, under the same output voltage conditions, the third feedback voltage is less than the first feedback voltage.

10. The control circuit according to claim 1, characterized in that, When a third op-amp is included The first input terminal of the first operational amplifier receives a first reference voltage, and the first input terminal of the third operational amplifier receives a third reference voltage. The second input terminals of both the first operational amplifier and the second operational amplifier receive a first feedback voltage characterizing the output voltage of the power converter; The third reference voltage is greater than the first reference voltage.

11. A power converter, characterized in that, Includes a power stage circuit and a control circuit as described in any one of claims 1-10; The control circuit generates a switching control signal based on the compensation voltage, and the switching control signal is used to control the switching state of the power transistor in the power stage circuit. The compensation voltage is the voltage at the first terminal of the compensation resistor unit.

Images