Voltage-Current Double-Loop Control Circuit, Method, and Switching Converter

Abstract

Embodiments of the present invention relate to a voltage-current double-loop control circuit, method, and switching converter. The control circuit includes a first error amplification circuit, a second error amplification circuit, an addition circuit, and a control signal generation module. The first error amplification circuit compares a voltage feedback signal and a voltage reference signal to generate a first error signal; the second error amplification circuit compares a current sampling signal and a current reference signal and generates a second error signal; the addition circuit adds the voltage feedback signal, the current sampling signal, the first error signal, and the second error signal to generate an error signal; the control signal generation module generates a control signal based on the error signal and a ramp signal for controlling a controllable switch tube in the switching converter. The control circuit has a fast response speed for both the current loop and the voltage loop, and at the same time avoids the appearance of continuous pulses during small-current charging, reducing the charging current ripple.

Description

Technical Field

[0001] The present invention relates to an electronic circuit, and more particularly, to a voltage-current dual-loop control circuit, method, and switching converter for a switching converter. Background Art

[0002] With the wide application of portable devices, the demand for charging devices has also increased rapidly. In the architecture of a general typical charging circuit, there will be two loops, namely a current loop and a voltage loop, for providing a current and a voltage suitable for battery charging. To ensure the accuracy of current and voltage sampling, the error amplifier requires a large gain. At the same time, to ensure the stability of the loop, it is often necessary to reduce the system bandwidth. Because of this, the response speed of the system often becomes very slow, and when charging the battery with a small current, there will be a situation where multiple pulses are continuously turned on at once, resulting in a large ripple current in the charging current of the battery.

[0003] Therefore, we expect to propose a voltage-current dual-loop control circuit, method, and switching converter with a fast dynamic response speed. Summary of the Invention

[0004] The object of the present invention is to solve the problems such as slow system response speed and large ripple current in the prior art, and to propose a voltage-current dual-loop control circuit, method, and switching converter commonly used in charging circuits.

[0005] The present invention proposes a voltage-current dual-loop control circuit for a switching converter. The switching converter includes at least one controllable switch tube. The control circuit is characterized in that it includes: a ramp signal generation module for generating a ramp signal; a first error amplification circuit for receiving a voltage feedback signal and a voltage reference signal, and comparing the voltage feedback signal and the voltage reference signal to generate a first error signal, wherein the voltage feedback signal represents the output voltage of the switching converter, and the first error signal represents the difference between the voltage feedback signal and the voltage reference signal; a second error amplification circuit for receiving a current sampling signal and a current reference signal, and comparing the current sampling signal and the current reference signal to generate a second error signal, wherein the current sampling signal represents the output current of the switching converter, and the second error signal represents the difference between the current sampling signal and the current reference signal; an addition circuit for adding the voltage feedback signal, the current sampling signal, the first error signal, and the second error signal to generate an error signal; and a control signal generation module for receiving the error signal and the ramp signal, and generating a control signal based on the error signal and the ramp signal, the control signal being used to adjust the on and off times of the at least one controllable switch tube.

[0006] The present invention further provides a switching converter, comprising: at least one controllable switching transistor; and the control circuit as described above for generating a control signal for controlling the on and off switching of the at least one controllable switching transistor, thereby generating the required voltage signal and current signal.

[0007] The present invention further provides a control method for a switching converter, the switching converter comprising at least one controllable switching transistor, characterized in that the control method comprises: comparing a voltage feedback signal with a voltage reference signal and amplifying the error therebetween to generate a first error signal, wherein the voltage feedback signal represents the output voltage of the switching converter; comparing a current sampling signal with a current reference signal and amplifying the error therebetween to generate a second error signal, wherein the current sampling signal represents the output current of the switching converter; adding the voltage feedback signal, the current sampling signal, the first error signal and the second error signal to generate an error signal; and generating a control signal according to the error signal and a ramp signal, wherein the control signal is used to control the at least one controllable switching transistor.

[0008] In summary, due to the adoption of the above technical features, the voltage feedback signal and the current sampling signal will be introduced into the adder to jointly generate an error. Therefore, the error can directly reflect the real-time information on the voltage feedback signal and the current sampling signal. The response speed of the system to the current loop and the voltage loop will be increased, and at the same time, the occurrence of continuous pulses during small-current charging is avoided, thereby reducing the charging current ripple. Description of the Drawings

[0009] Figure 1 Shown is a circuit schematic diagram of a switching converter for battery charging according to an embodiment of the present invention;

[0010] Figure 2 Shown is a circuit schematic diagram of a switching converter according to another embodiment of the present invention.

[0011] Figure 3 Shown is a circuit schematic diagram of a switching converter according to another embodiment of the present invention.

[0012] Figure 4 Shown is a schematic flow chart of a control method according to an embodiment of the present invention.

[0013] As shown in the drawings, in all different views, the same reference numerals refer to the same parts. The drawings provided herein are all for the purpose of illustrating embodiments, principles, concepts, etc., and are not drawn to scale. Detailed Embodiments

[0014] Next, specific embodiments of the present invention will be described non - restrictively in conjunction with the accompanying drawings. References to "an embodiment" or "an embodiment" throughout the specification mean that the particular features, structures, or characteristics described in connection with that embodiment are included in at least one embodiment of the present invention. Thus, the phrases "in an embodiment" or "in an embodiment" that appear throughout the specification do not necessarily all refer to the same embodiment. The verbs "comprise" and "have" are used in this document as open limitations, which neither exclude nor require the presence of unrecited features. Unless otherwise expressly stated, the features recited in the dependent claims can be freely combined with each other. Elements defined using "a" or "an" (i.e., the singular form) throughout the document do not exclude the possibility of multiple such elements. Further, the described features, structures, or characteristics can be combined in any suitable manner in one or more embodiments. Unless otherwise specified, the term "connected" is used to specify a direct electrical connection between circuit elements, while the term "coupled" is used to specify an electrical connection between circuit elements that can be direct or can be via one or more other elements. In contrast, when an element is said to be "directly connected to" or "directly coupled to" another element, there is no intermediate element. The term "and / or" used herein includes any and all combinations of one or more of the related listed items. When referring to the voltage of a node or terminal, unless otherwise indicated, the voltage is considered to be the voltage between that node and a reference potential (usually ground). Further, when referring to the potential of a node or terminal, unless otherwise indicated, the potential is considered to refer to the reference potential. The voltage and potential of a given node or given terminal will further be designated by the same reference numeral. A signal that alternates between a first logic state (e.g., a logic - low state) and a second logic state (e.g., a logic - high state) is called a "logic signal". The high and low states of different logic signals in the same electronic circuit may be different. In particular, the high and low states of a logic signal can correspond to voltages or currents that may not be completely constant in the high or low state.

[0015] Figure 1 Shown is a circuit schematic diagram of a switching converter with voltage - current dual - loop control according to an embodiment of the present invention. In Figure 1 In the shown embodiment, the switching converter includes a switching circuit 10, a sampling circuit, a control circuit, and a capacitor Cout. In one embodiment, the switching converter can be applied to a battery charging circuit, with the load being a battery, and the switching converter is used to provide a suitable charging voltage signal and charging current signal for the battery.

[0016] The switching circuit 10 includes at least one controllable switching device. The input terminal of the switching circuit 10 receives an input voltage signal Vin, and the output terminal of the switching circuit 10 is coupled to the output terminal of the switching converter. The switching circuit 10 receives a control signal PWM. The control signal PWM controls the on and off times of at least one controllable switching device in the switching circuit 10, thereby converting the input voltage signal Vin into a desired output voltage signal Vout, and also providing a desired output current signal Iout. The switching circuit 10 can select a suitable topology according to the application scenario. For example, the switching circuit 10 can select topologies such as BUCK, BOOST, FLYBACK, etc. The at least one controllable switching device can select semiconductor power switching devices according to the application scenario, such as Metal Oxide Semiconductor Field Effect Transistor (MOSFET), Junction Field-effect Transistor (JFET), Insulated Gate Bipolar Transistor (IGBT), Double Diffusion Metal Oxide Semiconductor (DMOS), and so on. The capacitor Cout is coupled between the output terminal of the switching converter 100 and the reference ground.

[0017] In Figure 1 the illustrated embodiment, the sampling circuit includes an output voltage sampling circuit 21 and an output current sampling circuit 22. The output voltage sampling circuit 21 is coupled to the output terminal of the switching converter and is used to sample the output voltage signal Vout and generate a voltage feedback signal Vfb, where the voltage feedback signal Vfb represents the output voltage signal Vout. In one embodiment, the output voltage sampling circuit 20 includes a voltage divider composed of resistors. In other embodiments, the output voltage sampling circuit 20 can also directly sample the output voltage signal Vout. In Figure 1 the illustrated embodiment, the output current sampling circuit 22 is coupled to the output terminal of the switching converter and is used to sample the output current Iout of the switching converter and generate a current sampling signal Ics, where the current sampling signal Ics represents the output current Iout of the switching converter. Figure 1 The examples in are only illustrative. In other embodiments, other suitable currents can also be sampled to generate a current sampling signal Ics for representing the output current Iout of the switching converter. For example, the current sampling circuit 22 can also be coupled inside the switching circuit 10 to sample the current flowing through the switching device inside the switching circuit 10 and generate a current sampling signal Ics. Another example is that in one embodiment, the battery current can be sampled and a current sampling signal Ics can be generated.

[0018] In Figure 1 the illustrated embodiment, the control circuit 30 includes a first error amplifier circuit 31, a second error amplifier circuit 32, an adder circuit 33, a ramp signal generation module 34, and a control signal generation module 35.

[0019] The first error amplifier circuit 31 has a first input terminal, a second input terminal, and an output terminal. Its first input terminal receives a voltage feedback signal Vfb; its second input terminal receives a voltage reference signal Vref; the first error amplifier circuit 31 compares the voltage feedback signal Vfb and the voltage reference signal Vref and generates a first error signal eao1 at the output terminal, where the first error signal eao1 represents the difference between the voltage feedback signal Vfb and the voltage reference signal Vref. In one embodiment, the first error amplifier circuit 31 includes a voltage error amplifier EA1. The first input terminal of the first error amplifier circuit 31 is the inverting input terminal of the error amplifier EA1; the second input terminal of the first error amplifier circuit 31 is the non-inverting input terminal of the error amplifier EA1. In one embodiment, the first error amplifier circuit 31 includes a transconductance amplifier.

[0020] The second error amplifier circuit 32 has a first input terminal, a second input terminal, and an output terminal. Its first input terminal receives a current sampling signal Ics; its second input terminal receives a current reference signal Iref; the second error amplifier circuit 32 compares the current sampling signal Ics and the current reference signal Iref and generates a second error signal eao2 at the output terminal, where the second error signal eao2 represents the difference between the current sampling signal Ics and the current reference signal Iref. In one embodiment, the second error amplifier circuit 32 includes a voltage error amplifier EA2. The first input terminal of the second error amplifier circuit 32 is the inverting input terminal of the voltage error amplifier EA2; the second input terminal of the second error amplifier circuit 32 is the non-inverting input terminal of the error amplifier EA2. In one embodiment, the second error amplifier circuit 32 includes a transconductance amplifier.

[0021] The adder circuit 33 receives the voltage feedback signal Vfb, the current sampling signal Ics, the first error signal eao1, and the second error signal eao2, and adds the voltage feedback signal Vfb, the current sampling signal Ics, the first error signal eao1, and the second error signal eao2 to generate an error signal eao.

[0022] The ramp signal generation module 34 is used to generate a ramp signal ramp. The specific form of the ramp signal is determined by the control method selected by the switching converter.

[0023] The control signal generation module 35 receives the error signal eao and the ramp signal ramp, and generates a control signal PWM based on the error signal eao and the ramp signal ramp. In one embodiment, the control signal PWM is used to adjust the on and off times of at least one controllable switch tube in the switch circuit 10, thereby generating the desired output voltage signal Vout and output current signal Iout.

[0024] In Figure 1 the illustrated embodiment, since the voltage feedback signal Vfb and the current sampling signal Ics are introduced into the adder to jointly generate the error eao, the error eao can directly reflect the real-time information on the voltage feedback signal Vfb and the current sampling signal Ics. The response speed of the system to the current loop and the voltage loop will increase, and at the same time, the occurrence of continuous pulses during small-current charging is avoided, thereby reducing the charging current ripple.

[0025] Figure 2 Shown is a circuit schematic diagram of a switch converter according to another embodiment of the present invention. In Figure 2 it, the switch circuit 10 is shown as a switch circuit of a BUCK topology. At least one controllable switch tube includes a main switch tube HS and a freewheeling switch tube LS. The main switch tube HS and the freewheeling switch tube LS are shown as NMOS tubes, serially coupled between the input end of the switch circuit 10 and the reference ground. The common node of the main switch tube HS and the freewheeling switch tube LS is marked as the switch node SW. The inductor L is coupled between the switch node SW and the output end of the switch circuit 10. The control signal PWM includes a first control signal PWM1 and a second control signal PWM2. Among them, the first control signal PWM1 is used to control the on and off times of the main switch tube HS, and the second control signal PWM2 is used to control the on and off times of the freewheeling switch tube LS. In one embodiment, the first control signal PWM1 and the second control signal PWM2 are logically complementary signals.

[0026] In Figure 2 the illustrated embodiment, the ramp signal generation module 34 includes a ramp signal generator for generating a ramp signal ramp with a fixed frequency.

[0027] Furthermore, Figure 2 the illustrated embodiment also shows the specific circuit schematic diagram of the control signal generation module 35. As Figure 2Among them, the control signal generation module 35 includes a voltage comparator 351 and an inverter 352. The voltage comparator 351 receives the error signal eao and the ramp signal ramp, and generates a first control signal PWM1 based on the error signal eao and the ramp signal ramp. The first control signal PWM1 becomes the second control signal PWM2 after passing through the inverter. In one embodiment, when the error signal eao is greater than the ramp signal ramp, the first control signal PWM1 is at a logic low level; when the error signal eao is less than the ramp signal ramp, the first control signal PWM1 is at a logic high level.

[0028] Figure 3 Shown is the circuit schematic diagram of a switching converter according to another embodiment of the present invention. In Figure 3 it, the circuit schematic diagram of another embodiment of the control signal generation module 35 and the circuit schematic diagram of the ramp signal generation module 34 are specifically illustrated.

[0029] In Figure 3 the illustrated embodiment, the ramp signal ramp is generated by the node voltage signal at the node SW. As Figure 3 shown, the ramp signal generation module 34 includes a voltage division circuit 341 and a filtering circuit 342. The voltage division circuit 341 is coupled to the switch node SW, divides the node voltage signal, and generates a divided voltage signal. The filtering circuit 342 is coupled to the voltage division circuit 341, filters the divided voltage signal, and generates the ramp signal ramp. In some embodiments, the voltage division circuit 341 can also be omitted according to the actual application situation.

[0030] In Figure 3 the illustrated embodiment, the control signal generation module 35 includes a voltage comparator 351, a conduction time generation circuit 353, and a logic circuit 354. The voltage comparator 351 receives the error signal eao and the ramp signal ramp, and compares the error signal eao and the ramp signal ramp to generate a set signal set. In one embodiment, the set signal set is a pulse signal. When the value of the ramp signal ramp drops to the error signal eao, the voltage comparator 351 generates a positive pulse set signal set.

[0031] In Figure 3In the illustrated embodiment, the on-time generation circuit 353 is configured to generate a constant on-time control signal Ton. The constant on-time control signal Ton is typically used to control the on-duration of the main switch HS. In actual implementation, the on-time generation module 353 may generate the constant on-time control signal Ton based on the input voltage signal Vin and the output voltage signal Vout of the switching converter. In other embodiments, the signal Vin received by the on-time generation module may not be the direct input voltage signal Vin, but other signals representing the input voltage Vin; similarly, the signal Vout received by the on-time generation module may not be the direct output voltage signal Vout, but other signals representing the output voltage Vout.

[0032] The logic circuit 354 receives the set signal set and the constant on-time control signal Ton, and performs a logic operation on the set signal set and the constant on-time control signal Ton to generate a first control signal PWM1 and a second control signal PWM2. In Figure 1 the illustrated embodiment, the logic circuit 354 is shown as an RS flip-flop. The set terminal S of the RS flip-flop receives the set signal set, and the reset terminal R of the RS flip-flop receives the constant on-time control signal Ton.

[0033] Figure 4 Shown is a schematic flow diagram of a voltage-current double-loop control method according to an embodiment of the present invention. Figure 4 The illustrated control method can be used in the aforementioned switching converter and other switching converters within the scope of protection of the present invention. The control method includes steps S1 - S4.

[0034] Step S1, compare the voltage feedback signal Vfb and the voltage reference signal Vref, and amplify the error between the two to generate a first error signal eao1.

[0035] Step S2, compare the current sampling signal Ics and the current reference signal Iref, and amplify the error between the two to generate a second error signal eao2.

[0036] Step S3, add the voltage feedback signal Vfb, the current sampling signal Ics, the first error signal eao1, and the second error signal eao2 to generate an error signal eao.

[0037] Step S4, generate a control signal PWM based on the error signal eao and the ramp signal ramp, for controlling the on and off times of the switch in the switch circuit 10. In one embodiment, this step further includes: generating the ramp signal ramp based on the voltage at the common node SW.

[0038] Although the present invention has been described above with reference to several exemplary embodiments, those of ordinary skill in the relevant art should understand that the terms used in the disclosed embodiments of the present invention are illustrative and exemplary, rather than restrictive. They are only used to describe specific embodiments and do not limit the present invention. In addition, without departing from the principles and concepts of the present invention, those of ordinary skill in the art have made various modifications to the disclosed embodiments of the present invention in form and detail without creative efforts, and these modifications all fall within the protection scope defined by the claims of this application or their equivalent scope.

Claims

1. A voltage-current double-loop control circuit for a switching converter, the switching converter including at least one controllable switching transistor, characterized in that, The control circuit includes: a ramp signal generation module for generating a ramp signal; a first error amplification circuit that receives a voltage feedback signal and a voltage reference signal, and compares the voltage feedback signal and the voltage reference signal to generate a first error signal, wherein the voltage feedback signal represents the output voltage of the switching converter, and the first error signal represents the difference between the voltage feedback signal and the voltage reference signal; a second error amplification circuit that receives a current sampling signal and a current reference signal, and compares the current sampling signal and the current reference signal to generate a second error signal, wherein the current sampling signal represents the output current of the switching converter, and the second error signal represents the difference between the current sampling signal and the current reference signal; an addition circuit that adds the voltage feedback signal, the current sampling signal, the first error signal, and the second error signal to generate an error signal; and a control signal generation module that receives the error signal and the ramp signal, and generates a control signal based on the error signal and the ramp signal, the control signal being used to control the at least one controllable switch.

2. The control circuit according to claim 1, wherein, The frequency of the ramp signal is a fixed value.

3. The control circuit according to claim 1, wherein The at least one controllable switch includes a main switch and a freewheeling switch, and the ramp signal generation module receives a node voltage signal and generates the ramp signal according to the node voltage signal, wherein the node voltage signal represents the voltage at the common node of the main switch and the freewheeling switch.

4. The control circuit according to claim 3, wherein The ramp signal generation module includes: a voltage division circuit that receives the node voltage signal and divides the node voltage signal to generate a divided voltage signal; and a filtering circuit that receives the divided voltage signal and filters the divided voltage signal to generate a ramp signal.

5. The control circuit according to claim 1, wherein The control signal includes a first control signal and a second control signal, and the control signal generation module includes: a first voltage comparator that receives the error signal and the ramp signal, and generates the first control signal based on the error signal and the ramp signal; and an inverter that inverts the first control signal to generate the second control signal.

6. The control circuit according to claim 3, wherein The control signal generation module includes: a second voltage comparator that receives the error signal and the ramp signal, and generates a set signal based on the error signal and the ramp signal; a conduction time generation circuit that generates a constant conduction time control signal; and a logic circuit that performs a logic operation on the set signal and the constant conduction time control signal, and generates the control signal.

7. A switching converter, characterized in that, including: at least one controllable switch; and the control circuit according to any one of claims 1 to 6, for generating a control signal, the control signal being used to control the on and off times of the at least one controllable switch, so as to generate a required voltage signal and current signal.

8. A voltage-current double-loop control method for a switching converter, the switching converter including at least one controllable switching tube, characterized in that, The control method includes: comparing the voltage feedback signal and the voltage reference signal, and amplifying the error between the two to generate a first error signal, wherein the voltage feedback signal represents the output voltage of the switching converter; comparing the current sampling signal and the current reference signal, and amplifying the error between the two to generate a second error signal, wherein the current sampling signal represents the output current of the switching converter; adding the voltage feedback signal, the current sampling signal, the first error signal, and the second error signal to generate an error signal; and Generate a control signal based on an error signal and a ramp signal, wherein the control signal is used to control the at least one controllable switch.

9. The control method according to claim 8, characterized in that, The at least one controllable switch includes a main switch and a freewheeling switch, and the control method further includes generating the ramp signal based on the voltage at the common node of the main switch and the freewheeling switch.

10. The control method according to claim 8, characterized in that, The frequency of the ramp signal is a fixed value.

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