Voltage feedback circuit and control circuit for switching converter

Abstract

The invention provides a voltage feedback circuit and a control circuit for a switching converter. The switching converter comprises a high-side power switching tube and a low-side power switching tube, and the common end of the high-side power switching tube and the low-side power switching tube serves as a switching node. The voltage feedback circuit comprises a first divider resistor, a second divider resistor, a first transistor and a line loss compensation circuit, wherein the first divider resistor and the second divider resistor are connected between the output end of the switching converter and the reference ground in series. The common end of the first divider resistor and the second divider resistor outputs a feedback signal representing the output voltage. When the first transistor is conducted, the line loss compensation circuit generates a line loss compensation current signal at the common end of the first divider resistor and the second divider resistor according to the voltage of the switch node, and the line loss compensation current signal is in direct proportion to the voltage of the switch node. The voltage feedback circuit can compensate circuit line loss and voltage drop, and more accurate output voltage is provided for a load.

Description

Technical Field

[0001] This invention relates to the field of switching power supply technology, and more specifically, to a voltage feedback circuit and control circuit for a switching converter. Background Technology

[0002] In the field of switching power supply chip technology, especially when powering portable electronic devices, power adapters often require long power cords to bridge external devices. For example, power cords for laptops, car navigation systems, or dashcams can be 2 to 3 meters long. Excessive cord length leads to significant parasitic resistance in the output lines between the switching power supply and the load. This resistance generates substantial line loss voltage drops when current flows, preventing the electronic device from operating at full power. Furthermore, large variations in output current result in significant changes in the output voltage downstream of the power cord, affecting the normal operation of the load. In constant voltage output mode, such variations are unacceptable in some situations.

[0003] Therefore, how to automatically increase the system output voltage according to the magnitude of the output load current and compensate for the voltage drop caused by the parasitic resistance of long-distance power lines has become a problem that must be faced in the design of power supply for long-distance power lines. Summary of the Invention

[0004] The purpose of this invention is to provide a voltage feedback circuit and control circuit for a switching converter to solve the above-mentioned problems.

[0005] To achieve the above objectives, the present invention provides a voltage feedback circuit for a switching converter. The switching converter includes a high-side power switch and a low-side power switch, which converts an input voltage into an output voltage. The common terminal of the high-side and low-side power switches serves as a switching node. The voltage feedback circuit includes: a first voltage divider resistor and a second voltage divider resistor, which are connected in series between the output terminal of the switching converter and a reference ground. The common terminal of the first and second voltage divider resistors serves as the output terminal of the voltage feedback circuit, used to output a feedback signal representing the output voltage; a first transistor having a first terminal, a second terminal, and a control terminal, the second terminal of which is coupled to the switching node, and the control terminal of which is coupled to a compensation control signal; and a line loss compensation circuit having a first terminal, a second terminal, and a third terminal, the first terminal of which is coupled to the first terminal of the first transistor, the second terminal of which is connected to the reference ground, and the third terminal of which is coupled to the common terminal of the first and second voltage divider resistors. When the first transistor is turned on, the line loss compensation circuit generates a line loss compensation current signal at its third terminal based on the voltage of the switching node, and the line loss compensation current signal is proportional to the voltage of the switching node.

[0006] The present invention also provides a control circuit for a switching converter. The switching converter includes a high-side power switch and a low-side power switch, and is used to convert an input voltage into an output voltage. The control circuit includes: a voltage feedback circuit as described above, for providing a feedback signal representing the output voltage; and a control circuit that receives the feedback signal and generates a high-side switching control signal and a low-side switching control signal based on the feedback signal, for controlling the on-time and off-time of the high-side power switch and the low-side power switch, respectively.

[0007] Other features and advantages of the present invention will be described in detail in the following detailed description section. Attached Figure Description

[0008] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the following detailed description to explain the invention, but do not constitute a limitation thereof. In the drawings: Figure 1 The diagram shown is a circuit schematic of a switching converter according to an embodiment of the present invention. Figure 2 The diagram shown is a circuit diagram of a voltage feedback circuit according to an embodiment of the present invention. Figure 3 The diagram shown is a circuit diagram of a voltage feedback circuit according to yet another embodiment of the present invention. Figure 4 The diagram shown is a circuit schematic of a voltage feedback circuit according to an embodiment of the present invention.

[0009] In all the different views, the same reference numerals refer to the same parts. The accompanying drawings provided are for illustrative purposes, demonstrating embodiments, principles, concepts, etc., and are not drawn to scale. Detailed Implementation

[0010] To better understand the above-mentioned objectives, features, and advantages of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that, unless otherwise specified, the embodiments and features described in these embodiments can be combined with each other.

[0011] Numerous specific details are set forth in the following description to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and therefore the scope of protection of the invention is not limited to the specific embodiments disclosed below. Throughout this specification, references to “one embodiment” or “an embodiment” mean that a particular feature, structure, or characteristic described in connection with that embodiment is included in at least one embodiment of the invention. Therefore, the phrases “in one embodiment” or “in an embodiment” appearing throughout this specification do not necessarily refer to the same embodiment. The verbs “comprising” and “having” are used herein as open-ended restrictions, neither excluding nor requiring the presence of any unrecited features. Unless expressly stated otherwise, the features recited in the dependent claims may be freely combined with each other. The use of “a” or “an” (i.e., the singular) to define an element throughout the document does not exclude the possibility of a plurality of such elements. Furthermore, the described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. Unless otherwise specified, the term “connection” 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, which may be direct or may be via one or more other elements. Conversely, when a component is referred to as "directly connected to" or "directly coupled to" another component, no intermediate component exists. The term "and / or" as 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 assumed to be the voltage between that node and a reference potential (typically ground). See below. Figures 1 to 4 This describes a voltage feedback circuit and a control circuit provided according to some embodiments of the present invention.

[0012] Figure 1 The diagram shown is a circuit schematic of a switching converter according to an embodiment of the present invention. The switching converter includes a high-side power switch HS and a low-side power switch LS. By controlling the on-time and off-time of the high-side power switch HS and the low-side power switch LS, the input voltage VIN can be converted into an output voltage VOUT. Figure 1 As shown, the switching converter includes a switching unit 10 and a control circuit.

[0013] exist Figure 1In the illustrated embodiment, the switching unit 10 is schematically a BUCK topology, including a high-side power switch HS and a low-side power switch LS. The high-side power switch HS and the low-side power switch LS are connected in series between the input voltage VIN and the reference ground GND. The common terminal of the high-side power switch HS and the low-side power switch LS serves as the switching node SW, and the voltage across the switching node SW is the node voltage VSW. The output inductor L is coupled between the switching node SW and the output terminal of the switching converter. The output capacitor COUT is coupled between the output terminal of the switching converter and the reference ground GND.

[0014] See also Figure 1 The control circuit is schematically shown to include a voltage feedback circuit and a control circuit 30. The voltage feedback circuit is coupled to the output of the switching converter and is used to generate a feedback signal VFB, which represents the output voltage VOUT of the switching converter. Figure 1 In the embodiment shown, the voltage feedback circuit includes a first voltage divider resistor R1, a second voltage divider resistor R2, a first transistor M1, and a line loss compensation circuit 20.

[0015] The first voltage divider resistor R1 and the second voltage divider resistor R2 are connected in series between the output terminal of the switching converter and the reference ground. The common terminal FB of the first voltage divider resistor R1 and the second voltage divider resistor R2 serves as the output terminal of the voltage feedback circuit, used to output the feedback signal VFB representing the output voltage VOUT.

[0016] The first transistor M1 has a first terminal, a second terminal, and a control terminal. The first terminal of the first transistor M1 is coupled to a line loss compensation circuit 20, the second terminal of the first transistor M1 is coupled to a switching node SW, and the control terminal of the first transistor M1 is coupled to a compensation control signal CTL2-d.

[0017] The line loss compensation circuit 20 has a first terminal, a second terminal, and a third terminal. The first terminal of the line loss compensation circuit 20 is coupled to the first terminal of the first transistor M1. The second terminal of the line loss compensation circuit 20 is connected to the reference ground GND. The third terminal of the line loss compensation circuit 20 is coupled to the common terminal FB of the first voltage divider resistor R1 and the second voltage divider resistor R2. When the first transistor M1 is turned on, the line loss compensation circuit 20 generates a line loss compensation current signal Ic at its third terminal according to the node voltage VSW. The line loss compensation current signal Ic is proportional to the node voltage VSW.

[0018] In one embodiment, the line loss compensation current signal Ic cannot increase indefinitely with the node voltage VSW. Only when the line loss compensation current signal Ic is less than a first current value is it proportional to the node voltage VSW. When the line loss compensation current signal Ic is greater than or equal to the first current value, it remains at the first current value. The first current value can be flexibly designed according to the application.

[0019] In one embodiment, the compensation control signal CTL2-d and the control signal CTL2 of the low-side power switch LS are synchronized. It should be noted that in one embodiment, "synchronization" means that the first transistor M1 and the low-side power switch LS are turned on and off synchronously. In another embodiment, "synchronization" can also mean that after the low-side power switch LS is turned on, the first transistor M1 is turned on only after a short blanking time. The blanking time is mainly to shield the voltage spikes and oscillations generated by the power switch during switching. In one embodiment, the line loss compensation current signal Ic is a current signal, with the current flowing from the common terminal FB of the first voltage divider resistor R1 and the second voltage divider resistor R2 to the reference ground GND. After adding the compensation current signal Ic, the adjusted output voltage VOUT_reg = VFB × (R1 + R2) / R2 + Ic × R1. This allows for compensation of the line loss voltage between the switching converter output and the load through the compensation current signal Ic, where the line loss compensation voltage is Ic × R1. When the low-side power switch LS is turned on, the node voltage VSW is IL × Ron, where IL is the inductor current and Ron is the on-resistance of the low-side power switch LS. A larger voltage VSW indicates a larger current and thus a higher line loss voltage. Since this technical solution sets the line loss compensation current signal Ic to be proportional to the node voltage VSW, a higher node voltage VSW results in a larger adjusted output voltage VOUT_reg, allowing for greater line loss compensation.

[0020] exist Figure 1 In the illustrated embodiment, the high-side power switch HS, the low-side power switch LS, and the first transistor M1 are all schematically represented as N-type metal-oxide-semiconductor field-effect transistors (MOSFETs). However, those skilled in the art will understand that the high-side power switch HS, the low-side power switch LS, and the first transistor M1 can also be other suitable controllable semiconductor power switching devices. Furthermore, the switching unit can be other suitable types of isolated or non-isolated topologies besides the BUCK topology, such as BOOST topology, BUCK-BOOST topology, etc.

[0021] Figure 2 The diagram shown is a schematic representation of a voltage feedback circuit according to an embodiment of the present invention. See also... Figure 2 In the embodiment shown, the line loss compensation circuit 20 in the voltage feedback circuit includes a current sampling circuit 21, a first current mirror 22, and a second current mirror 23.

[0022] The current sampling circuit 21 has a first terminal, a second terminal and a third terminal. The first terminal of the current sampling circuit 21 is coupled to the first terminal of the first transistor M1, the second terminal of the current sampling circuit 21 is connected to the reference ground, and the third terminal of the current sampling circuit 21 generates a current sampling signal Isen, which is proportional to the voltage VSW of the switching node.

[0023] The first current mirror 22 has a common terminal, a first current terminal and a second current terminal. The common terminal of the first current mirror 22 is coupled to the supply voltage VCC. The first current terminal of the first current mirror 22 is coupled to the third terminal of the current sampling circuit 21. The first current mirror 22 mirrors the current sampling signal Isen and generates a first mirrored current signal Im1 at its second current terminal.

[0024] The second current mirror 23 has a common terminal, a first current terminal and a second current terminal. The common terminal of the second current mirror 23 is connected to the reference ground GND. The first current terminal of the second current mirror 23 receives the first mirrored current signal Im1. After mirroring the first mirrored current signal Im1, the second current mirror 23 generates a compensation current signal Ic at its second current terminal.

[0025] exist Figure 2 The illustrated embodiment further shows a circuit diagram of a current sampling circuit 21. As shown, the current sampling circuit includes an operational amplifier OP and a second transistor M2. The operational amplifier OP has a first input terminal, a second input terminal, and an output terminal. The first input terminal of the operational amplifier OP serves as the first terminal of the current sampling circuit 21, and the second input terminal of the operational amplifier OP serves as the second terminal of the current sampling circuit 21. The second transistor M2 has a first terminal, a second terminal, and a control terminal. The first terminal of the second transistor M2 is coupled to the first input terminal of the operational amplifier OP, the second terminal of the second transistor M2 serves as the third terminal of the current sampling circuit 21, and the control terminal of the second transistor M2 is coupled to the output terminal of the operational amplifier OP.

[0026] The current sampling signal Isen flowing through the first transistor M1 and the second transistor M2 is Isen = VSW / Ron1 = IL × Ron / Ron1, where Ron1 is the on-resistance of the first transistor. The current sampling signal Isen is processed by the first current mirror 22 and the second current mirror 23 to obtain the compensation current signal Ic = K × IL × Ron / Ron1, where K is the total mirror ratio of the first current mirror 22 and the second current mirror 23.

[0027] In some embodiments, the line loss compensation circuit 20 further includes a third resistor R3, which is coupled between the first terminal of the current sampling circuit 21 and the first terminal of the first transistor M1. After adding the third resistor R3, the compensation current signal Ic = K × IL × Ron / (Ron1 + R3). In this way, the value of the current sampling signal Isen can be adjusted by the third resistor R3 to further adjust the magnitude of the compensation current signal Ic.

[0028] In one embodiment, in order to make the compensation current signal Ic follow the changes in temperature and process, the third resistor R3 can be an active resistor composed of multiple transistors connected in series.

[0029] exist Figure 2 In the described embodiment, transistors M1 and M2 are schematically represented as N-type MOSFETs. The first terminal of transistors M1 and M2 is the source of the N-type MOSFET, the second terminal of transistors M1 and M2 is the drain of the N-type MOSFET, and the control terminal of transistors M1 and M2 is the gate of the N-type MOSFET. It should be understood that this is merely illustrative and does not constitute a limitation of the invention. In other embodiments, transistors M1 and M2 may also employ other suitable semiconductor devices.

[0030] Figure 3 The diagram shown is a circuit schematic of a voltage feedback circuit according to yet another embodiment of the present invention. See also... Figure 3 In the illustrated embodiment, the line loss compensation circuit 20 in the voltage feedback circuit further includes a current limiting circuit 24. The current limiting circuit 24 receives a current limit Ilim and a second mirrored current signal Im2, compares the second mirrored current signal Im2 with the current limit Ilim, and generates a current adjustment signal Ireg to pull down the control terminal voltage of the second transistor M2. The second mirrored current signal Im2 is proportional to the current sampling signal Isen. In this embodiment, the second mirrored current signal Im2 can be generated by a first current mirror 23, which also has a third current terminal. The first current mirror 23 mirrors the current sampling signal Isen and provides the second mirrored current signal Im2 at its third current terminal. When the second mirrored current signal Im2 is greater than the current limit Ilim, the current adjustment signal Ireg pulls down the control terminal voltage of the second transistor M2 to reduce the value of the current sampling signal Isen flowing through the second transistor M2. It can be understood that the current limit Ilim can characterize the first current value of the compensation current signal Ic.

[0031] Figure 4 The diagram shown is a circuit schematic of a voltage feedback circuit according to an embodiment of the present invention. Figure 4The illustrated embodiment further shows the specific circuit diagrams of the first current mirror 22, the second current mirror 23, and the current limiting circuit 24. The first current mirror 22 includes transistors M31-M33, and the second current mirror 23 includes transistors M41 and M42.

[0032] exist Figure 4 In the illustrated embodiment, the current limiting circuit 24 includes a third current mirror 241 and a fourth current mirror 242. The third current mirror 241 has a common terminal, a first current terminal, and a second current terminal. The common terminal of the third current mirror 241 is connected to a reference ground. The first current terminal of the third current mirror 241 receives the current limit, and the second current terminal of the third current mirror 241 receives the second mirrored current signal Im2. Figure 4 As shown, the third current mirror 241 includes transistors M51-M52. The fourth current mirror 242 has a common terminal, a first current terminal, and a second current terminal. The common terminal of the fourth current mirror 242 is connected to a reference ground. The first current terminal of the fourth current mirror 242 and the second current terminal of the third current mirror 241 are coupled together to receive the second mirrored current signal Im2. The second current terminal of the fourth current mirror 241 is coupled to the control terminal of the second transistor M2 to provide a current regulation signal Ireg. Figure 4 As shown, the fourth current mirror 242 includes transistors M61-M62.

[0033] exist Figure 4 In the embodiment shown, when the second mirror current signal Im2 is greater than the current limit Ilim, transistors M51 and M52 will flow current, that is, generate a current regulation signal Ireg to pull down the control terminal voltage of the second transistor M2, thereby reducing the current sampling signal Isen, and finally making the second mirror current signal Im2 limited to equal the current limit Ilim.

[0034] When the second mirror current signal Im2 is less than the current limit Ilim, that is, less than the current Im62 flowing through transistor M62, the potential of the drain connection point of transistors M62 and M52 is very low. At this time, transistors M51 and M52 are not conducting, the current adjustment signal Ireg is zero, and the current sampling signal Isen is not affected by the current limit Ilim.

[0035] exist Figure 4 In the embodiments described, transistors M41, M42, M51, M52, M61, and M62 are all illustrated as N-type MOSFETs, while transistors M31, M32, and M33 are P-type MOSFETs. However, this is merely illustrative and not intended to limit the invention. In other embodiments, transistors M31, M32, M33, M41, M42, M51, M52, M61, and M62 may also employ other suitable semiconductor devices.

[0036] The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the specific details of the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention, and these simple modifications all fall within the protection scope of the present invention. It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the present invention will not describe the various possible combinations separately. Furthermore, various different embodiments of the present invention can also be arbitrarily combined, as long as they do not violate the spirit of the present invention, they should also be considered as the content disclosed by the present invention.

Claims

1. A voltage feedback circuit for a switching converter, characterized in that, The switching converter includes a high-side power switch and a low-side power switch. The switching converter is used to convert an input voltage into an output voltage. The common terminal of the high-side power switch and the low-side power switch serves as a switching node. The voltage feedback circuit includes: The first voltage divider resistor and the second voltage divider resistor are connected in series between the output terminal of the switching converter and the reference ground. The common terminal of the first voltage divider resistor and the second voltage divider resistor serves as the output terminal of the voltage feedback circuit, which is used to output a feedback signal representing the output voltage. A first transistor has a first terminal, a second terminal, and a control terminal. The second terminal of the first transistor is coupled to the switching node, and the control terminal of the first transistor is coupled to a compensation control signal. A line loss compensation circuit has a first terminal, a second terminal, and a third terminal. The first terminal of the line loss compensation circuit is coupled to the first terminal of a first transistor, the second terminal of the line loss compensation circuit is connected to a reference ground, and the third terminal of the line loss compensation circuit is coupled to the common terminal of a first voltage divider resistor and a second voltage divider resistor. When the first transistor is turned on, the line loss compensation circuit generates a line loss compensation current signal at its third terminal according to the voltage of the switching node. The line loss compensation current signal is proportional to the voltage of the switching node.

2. The voltage feedback circuit according to claim 1, characterized in that, The compensation control signal is synchronized with the control signal of the low-side power switch.

3. The voltage feedback circuit according to claim 1, characterized in that, When the line loss compensation current signal is less than the first current value, the line loss compensation current signal is proportional to the voltage of the switching node; when the line loss compensation current signal is greater than or equal to the first current value, the line loss compensation current signal is equal to the first current value.

4. The voltage feedback circuit according to claim 1, characterized in that, The line loss compensation circuit includes: A current sampling circuit has a first terminal, a second terminal, and a third terminal. The first terminal of the current sampling circuit is coupled to the first terminal of a first transistor, the second terminal of the current sampling circuit is connected to a reference ground, and the third terminal of the current sampling circuit generates a current sampling signal that is proportional to the voltage of the switching node. A first current mirror has a common terminal, a first current terminal, and a second current terminal. The common terminal of the first current mirror is coupled to the supply voltage. The first current terminal of the first current mirror is coupled to the third terminal of the current sampling circuit. The first current mirror mirrors the current sampling signal and generates a first mirrored current signal at its second current terminal. The second current mirror has a common terminal, a first current terminal and a second current terminal. The common terminal of the second current mirror is connected to the reference ground. The first current terminal of the second current mirror receives a first mirrored current signal. The second current mirror mirrors the first mirrored current signal and generates a compensation current signal at its second current terminal.

5. The voltage feedback circuit according to claim 4, characterized in that, The line loss compensation circuit further includes: The third resistor is coupled between the first terminal of the current sampling circuit and the first terminal of the first transistor.

6. The voltage feedback circuit according to claim 5, characterized in that, The third resistor includes an active resistor consisting of multiple transistors connected in series.

7. The voltage feedback circuit according to claim 4, characterized in that, The current sampling circuit includes: An operational amplifier has a first input terminal, a second input terminal, and an output terminal. The first input terminal of the operational amplifier serves as the first terminal of a current sampling circuit, and the second input terminal of the operational amplifier serves as the second terminal of the current sampling circuit. The second transistor has a first terminal, a second terminal, and a control terminal. The first terminal of the second transistor is coupled to the first input terminal of the operational amplifier, the second terminal of the second transistor serves as the third terminal of the current sampling circuit, and the control terminal of the second transistor is coupled to the output terminal of the operational amplifier.

8. The voltage feedback circuit according to claim 7, characterized in that, The line loss compensation circuit further includes: The current limiting circuit receives the current limit and the second mirror current signal, compares the second mirror current signal with the current limit, and generates a current adjustment signal to pull down the control terminal voltage of the second transistor. The second mirror current signal is proportional to the current sampling signal.

9. The voltage feedback circuit according to claim 8, characterized in that, The current limiting circuit includes: A third current mirror has a common terminal, a first current terminal, and a second current terminal. The common terminal of the third current mirror is connected to a reference ground, and the first current terminal of the third current mirror receives a current limit. The fourth current mirror has a common terminal, a first current terminal, and a second current terminal. The common terminal of the fourth current mirror is connected to a reference ground. The first current terminal of the fourth current mirror and the second current terminal of the third current mirror are coupled together to receive a second mirror current signal. The second current terminal of the fourth current mirror is coupled to the control terminal of the second transistor to generate a current regulation signal.

10. A control circuit for a switching converter, characterized in that, The switching converter includes a high-side power switch and a low-side power switch, and is used to convert an input voltage into an output voltage. The control circuit includes: The voltage feedback circuit as described in any one of claims 1-9 is used to provide a feedback signal representing the output voltage; and The control circuit receives feedback signals and generates high-side switch control signals and low-side switch control signals based on the feedback signals, which are used to control the on-time and off-time of the high-side power switch and the low-side power switch, respectively.

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