CN110504832B - Control circuit and method for high-voltage BUCK switch converter - Google Patents

Control circuit and method for high-voltage BUCK switch converter Download PDF

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Publication number
CN110504832B
CN110504832B CN201910886049.4A CN201910886049A CN110504832B CN 110504832 B CN110504832 B CN 110504832B CN 201910886049 A CN201910886049 A CN 201910886049A CN 110504832 B CN110504832 B CN 110504832B
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signal
feedback
coupled
power switch
reference ground
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CN110504832A (en
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李伊珂
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Jingyi Semiconductor Co ltd
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Jingyi Semiconductor Co ltd
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M3/00—Conversion of dc power input into dc power output
    • H02M3/02—Conversion of dc power input into dc power output without intermediate conversion into ac
    • H02M3/04—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters
    • H02M3/10—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M3/145—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
    • H02M3/155—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Dc-Dc Converters (AREA)

Abstract

A control circuit for use in a high voltage BUCK switching converter is disclosed. The switching converter includes a power tube, a diode, and an integrated circuit. The source of the power switch and the cathode common of the diode serve as the ground pin of the integrated circuit. The control circuit includes a feedback circuit for detecting a voltage difference between the ground pin of the integrated circuit and the reference ground of the switching converter after freewheeling of the diode is turned off and for sending it to the integrated circuit for determining a load change condition. The control circuit can be used for a high-voltage BUCK switch converter, can rapidly detect load change, and is beneficial to improving the dynamic response speed of a system.

Description

Control circuit and method for high-voltage BUCK switch converter
Technical Field
The invention relates to an electronic circuit, in particular to a control circuit and a control method for a high-voltage BUCK switching converter.
Background
In high drop-out applications, power regulators (such as switch mode voltage regulators) are widely used in a variety of electronic devices. The high-voltage drop switch converter is widely applied to circuits such as a small household appliance control panel power supply, an industrial control power supply, LED illumination and the like due to the characteristics of simple circuit, few peripheral circuit elements, small loss, low heat and the like.
For example, fig. 1 shows a schematic circuit configuration of a conventional high-voltage BUCK switching converter. The high-voltage BUCK switching converter comprises a rectifying circuit, an input filter capacitor C IN and a high-voltage BUCK switching circuit. The high-voltage BUCK switching circuit comprises an integrated circuit 501, a diode D, an output inductor L OUT, an output capacitor C OUT and a feedback circuit 502.
IN general, integrated circuit 501 includes an input pin IN, a feedback pin FB, and a ground pin GND2. The integrated circuit 501 includes a power switch having a drain coupled to the input pin IN, a source coupled to the ground pin GND2 of the integrated circuit 501, and a diode D electrically connected to the logic ground GND1 of the high voltage BUCK switching converter. The feedback pin FB receives a feedback signal representing the output voltage signal V OUT at the output terminal OUT, and controls the power switch to turn on and off according to the feedback signal, so as to convert the dc input voltage V DC at two ends of the input capacitor C IN into the output voltage signal V OUT.
In the high-voltage BUCK switching converter shown in fig. 1, since the ground pin GND2 of the integrated circuit 501 and the logic ground GND1 of the AC-DC switching converter are at two different potentials, it is difficult to directly collect the output voltage signal V OUT in real time for control adjustment to the integrated circuit 501. Typically, a feedback circuit 502 is coupled between the output terminal OUT and the ground pin GND2 of the integrated circuit 501. When the main switch in the integrated circuit 501 is turned off and the diode D is turned on, the ground pin GND2 of the integrated circuit 501 is electrically connected to the logic ground GND1, and a fixed voltage difference (a conduction voltage drop of the diode D) exists between the ground pin GND2 and the logic ground GND1, so that the feedback signal generated by the feedback circuit 502 can represent the output voltage signal V OUT.
However, when the high-voltage BUCK switching converter operates in light load or no load, the voltage of the feedback pin FB is zero, the voltage of the ground pin GND2 is equal to the value of the output voltage signal V OUT, and the output voltage signal V OUT is discharged and maintained by the output capacitor C OUT. Meanwhile, in order to improve efficiency, the system usually enters a frequency adjustment mode, and the system operating frequency is low. Once the system is restored to heavy load from light load or no load, the feedback signal received on the feedback pin FB is collected during the on period of the last period diode D, so that the change of the load cannot be reflected timely, and meanwhile, the next switching period cannot come immediately due to low working frequency, so that the transient response speed of the system is slow. The output capacitor C OUT is insufficient to maintain the load demand, the output voltage signal V OUT is severely powered down, and the system cannot work normally. Therefore, for high voltage BUCK switching converter systems, a dummy load is typically connected to ensure that the entire system does not operate at very low frequency conditions, but the dummy load increases power consumption, resulting in inefficiency of the system.
Therefore, it is desirable to provide a high-voltage BUCK switching converter with fast transient response and low power consumption.
Disclosure of Invention
Aiming at one or more problems in the prior art, a control circuit and a control method for high-voltage BUCK switch conversion are provided.
In one aspect, the present invention provides a high voltage BUCK switching converter comprising: a diode; the power switch is provided with a first end, a second end and a control end, wherein the first end of the power switch receives input voltage, the second end of the power switch is coupled with the cathode of the diode, the control end of the power switch receives a control signal, the anode of the diode is electrically connected to a first reference ground, and the common end of the second end of the power switch and the cathode of the diode is used as a second reference ground; an inductor coupled between the second reference ground and an output of the switching converter; a first feedback circuit coupled between the second reference ground and the output terminal of the switching converter and generating a first feedback signal representative of the output voltage signal during diode turn-on; the second feedback circuit is connected between the first reference ground and the second reference ground, detects the voltage difference between the first reference ground and the second reference ground, and generates a second feedback signal representing the voltage difference between the first reference ground and the second reference ground after the power switch and the diode are turned off; and the control circuit receives the first feedback signal and the second feedback signal and generates a control signal according to the first feedback signal and the second feedback signal to control the on and off of the power switch, wherein the control circuit is integrated in an integrated circuit, and the second reference ground is the reference ground of the integrated circuit.
In yet another aspect, the present invention provides an integrated circuit for controlling a high voltage BUCK switching converter, the switching converter including a diode, an inductor, a first feedback circuit and a second feedback circuit, wherein a diode cathode is coupled to an output of the switching converter through the inductor, a diode anode is electrically connected to a first reference ground, the diode cathode acts as a second reference ground, the first feedback circuit is coupled between the second reference ground and the output of the switching converter to generate a first feedback signal representative of an output voltage, the second feedback circuit is coupled between the second reference ground and the first reference ground to detect a voltage difference between the first reference ground and the second reference ground to generate a second feedback signal representative of the voltage difference between the first reference ground and the second reference ground, the integrated circuit comprising: an input pin receiving an input voltage signal; a first feedback pin receiving a first feedback signal; a second feedback pin receiving a second feedback signal; a ground pin coupled to a second reference ground; the power switch is provided with a first end, a second end and a control end, wherein the first end of the power switch is coupled with the input pin to receive input voltage, the second end of the power switch is coupled with the grounding pin, and the control end receives a control signal; and the control circuit receives the first feedback signal and the second feedback signal and generates a control signal according to the first feedback signal and the second feedback signal to control the on and off of the power switch.
In another aspect, the present invention provides a control method for controlling a high voltage BUCK switching converter, where the high voltage BUCK switching converter includes a power switch, a diode, and an integrated circuit for controlling the high voltage BUCK switching converter, a drain of the power switch is coupled to an input terminal of the switching converter and receives an input voltage signal, a source of the power switch is coupled to a cathode of the diode, an anode of the diode is electrically connected to a first reference ground, and a common terminal of the source of the power switch and the cathode of the diode is used as a second reference ground, where the second reference ground is a reference ground of the integrated circuit, the control method includes: judging whether the power switch and the freewheeling diode are both turned off; when the power switch and the freewheeling diode are both closed, detecting the voltage difference between the first reference ground and the second reference ground, generating a second feedback signal representing the voltage difference between the first reference ground and the second reference ground, and sending the second feedback signal to the integrated circuit; judging whether the second feedback signal is lower than an undervoltage threshold, and switching on the power switch when the second feedback signal is lower than the undervoltage threshold; and judging whether the second feedback signal is higher than an overvoltage threshold value, and when the second feedback signal is higher than the overvoltage threshold value, keeping the power switch in an off state, wherein the overvoltage threshold value is larger than the undervoltage threshold value.
Drawings
Throughout the following drawings, the same reference numerals indicate the same, similar or corresponding features or functions.
FIG. 1 is a schematic circuit diagram of a conventional high voltage BUCK switching converter;
FIG. 2 shows a schematic block diagram of a high voltage BUCK switching converter 100, according to an embodiment of the present invention;
FIG. 3 shows a schematic block diagram of a high voltage BUCK switching converter 200 that includes an integrated circuit 30, according to an embodiment of the present invention;
FIG. 4 shows a schematic block diagram of a high voltage BUCK switching converter 300 including an integrated circuit 40, according to an embodiment of the present invention;
FIG. 5 shows a schematic block diagram of a high voltage BUCK switching converter 400 including an integrated circuit 50, according to an embodiment of the present invention;
FIG. 6 shows a schematic block diagram of a high voltage BUCK switching converter 500 that includes an integrated circuit 60, according to an embodiment of the present invention;
FIG. 7 shows a circuit schematic of the enable circuit 15 according to an embodiment of the invention;
fig. 8 shows a circuit schematic of an enabling circuit 15 according to a further embodiment of the invention;
FIG. 9 shows a circuit schematic of the comparison circuit 16 according to an embodiment of the invention;
fig. 10 shows a schematic circuit diagram of the control unit 17 according to an embodiment of the invention;
fig. 11 shows a schematic circuit diagram of a control unit 17 according to another embodiment of the invention;
fig. 12 shows a schematic diagram of a control method 600 for controlling a high voltage BUCK switching converter according to an embodiment of the invention.
Detailed Description
Specific embodiments of the invention will be described in detail below, it being noted that the embodiments described herein are for illustration only and are not intended to limit the invention. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. However, it will be apparent to one of ordinary skill in the art that: no such specific details are necessary to practice the invention. In other instances, well-known circuits, materials, or methods have not been described in detail in order not to obscure the invention.
Throughout the specification, references to "one embodiment," "an embodiment," "one example," or "an example" mean: a particular feature, structure, or characteristic described in connection with the embodiment or example is included within at least one embodiment of the invention. Thus, the appearances of the phrases "in one embodiment," "in an embodiment," "one example," or "an example" in various places throughout this specification are not necessarily all referring to the same embodiment or example. Furthermore, the particular features, structures, or characteristics may be combined in any suitable combination and/or sub-combination in one or more embodiments or examples. Moreover, those of ordinary skill in the art will appreciate that the illustrations provided herein are for illustrative purposes and that the illustrations are not necessarily drawn to scale. It will be understood that when an element is referred to as being "connected" or "coupled" to another element, it can be directly connected or coupled to the other element or intervening elements may be present. In contrast, when an element is referred to as being "directly connected to" or "directly coupled to" another element, there are no intervening elements present. Like reference numerals designate like elements. The term "and/or" as used herein includes any and all combinations of one or more of the associated listed items.
Fig. 2 shows a schematic block diagram of a high voltage BUCK switching converter 100 according to an embodiment of the invention. As shown in fig. 2, the high-voltage BUCK switching converter 100 includes a rectifying circuit 10, an input filter capacitor C IN, and a high-voltage BUCK switching circuit. The rectifying circuit 10 receives an ac voltage signal V AC, and the ac voltage signal V AC is rectified by the rectifying circuit 10 and filtered by the input capacitor CIN to obtain a dc input voltage signal V IN. The high-voltage BUCK switching circuit comprises a power switch 11, a diode 12, an inductor L OUT, an output capacitor C OUT, a first feedback circuit 13, a second feedback circuit 14 and a control circuit 20.
The power switch 11 has a first end coupled to the output end of the rectifying circuit 10 for receiving the input voltage V IN, a second end and a control end, and the second end of the power switch 11 is electrically connected to the first ground GND1 through the diode 12. Wherein the anode of the diode 12 is electrically connected to a first ground GND1; the cathode of the diode 12 is electrically connected to the second terminal of the power switch 11 and the common terminal of the cathode of the diode 12 and the second terminal of the power switch 11 is marked as second ground GND2. In one implementation, the second reference ground GND2 is a reference ground of an integrated circuit. The inductor L OUT is coupled between the second ground GND2 and the output OUT of the switching converter 100. The output capacitor C OUT is coupled between the output terminal OUT and the first ground GND1.
The first feedback circuit 13 is coupled between the output terminal OUT and the second ground GND2, and generates a feedback signal V FB1 representing the output voltage signal V OUT during the on period of the diode 12. In one embodiment, the first feedback circuit 13 comprises a first resistor R1 and a second resistor R2 connected in series between the output OUT and the second ground GND2, wherein a common terminal of the first resistor R1 and the second resistor R2 is coupled to be provided as the output terminal of the first feedback circuit 13
A first feedback signal V FB1. During the on period of the diode 12, the first feedback signal V FB1 is in a proportional relationship with the output voltage signal V OUT; when the diode 12 freewheels off, the current through the inductor L OUT is zero and the first feedback signal V FB1 is equal to zero.
The second feedback circuit 14, connected between the first and second reference grounds GND1 and GND2, detects a voltage difference between the first and second reference grounds GND1 and GND 2. And generates a second feedback signal V FB2 representing the voltage difference between the first reference ground GND1 and the second reference ground GND2 after the power switch 11 and the diode 12 are both turned off. When the diode 12 freewheels off, the current through the inductor L OUT is zero and the voltage at the second ground GND2 is equal to the output voltage signal V OUT. The second feedback signal V FB2 thus directly reflects the information of the output voltage V OUT after the diode 12 freewheels. In one embodiment, the second feedback signal V FB2 comprises a voltage signal; in another embodiment, the second feedback signal V FB2 comprises a current signal.
The control circuit 20 receives the first feedback signal V FB1 and the second feedback signal V FB2, generates a control signal PWM according to the first feedback signal V FB1 and the second feedback signal V FB2, and sends the control signal PWM to the control terminal of the power switch 11 for controlling the on-off switching of the power switch 11, so as to convert the dc input voltage signal V IN into the output voltage signal V OUT. In one embodiment, control circuit 20 includes an enable circuit 15, a compare circuit 16, and a control unit 17.
In the embodiment shown in fig. 2, the enable circuit 15 generates the enable signal EN, which is asserted when both the power switch 11 and the diode 12 are turned off. In one embodiment, the enable circuit 15 generates the enable signal EN according to the first feedback signal V FB1. In another embodiment, the enable circuit 15 may generate the enable signal EN according to the control signal PWM.
The comparison circuit 16 receives the enable signal EN and the second feedback signal V FB2, and when the enable signal EN is valid, the comparison circuit 16 compares the second feedback signal V FB2 with the undervoltage threshold and the overvoltage threshold respectively, so as to generate a second control signal PWM2; when the second feedback signal V FB2 is smaller than the undervoltage threshold, the second control signal PWM2 is used to turn on the power switch 11; the second control signal PWM2 is used to keep the power switch 11 continuously turned off when the second feedback signal V FB2 is greater than the overvoltage threshold. In one embodiment, the over-voltage threshold is greater than the under-voltage threshold, and when the second feedback signal V FB2 is less than the under-voltage threshold, which represents that the load is heavily loaded, the power switch 11 is turned on immediately. In one embodiment, the second control signal PWM2 comprises two signals.
The control unit 17 receives the first feedback signal V FB1 and the second control signal PWM2, and generates the control signal PWM for turning on and off the power switch 11 according to the first feedback signal V FB1 and the second control signal PWM 2.
In the embodiment shown in fig. 2, the power switch 11 is illustrated as an N-type metal oxide semiconductor field effect Transistor (Metal Oxide Semiconductor FIELD EFFECT Transistor, MOSFET), and in other embodiments, the power switch 11 may further include other suitable types of switching devices, such as a P-type MOSFET, a Junction FIELD EFFECT Transistor (JFET), an insulated gate bipolar Transistor (Insulated Gate Bipolar Transistor, IGBT), and so on.
Fig. 3 shows a schematic block diagram of a high voltage BUCK switching converter 200 including an integrated circuit 30 according to an embodiment of the invention. The structure of the high-voltage BUCK switching converter 200 and the high-voltage BUCK switching converter 100 are substantially identical, except that in the embodiment shown in fig. 3, the control circuit consisting of the enabling circuit 15, the comparing circuit 16 and the control unit 17 is integrated in one integrated circuit 30. As shown, the integrated circuit 30 includes a first feedback pin FB1, a second feedback pin FB2, a ground pin GND2, and a drive pin DRV. The first feedback pin FB1 is coupled to the first feedback circuit 13 for receiving the first feedback signal V FB1. The second feedback pin FB2 is coupled to the second feedback circuit 14 for receiving the second feedback signal V FB2. The ground pin GND2 is coupled to a second reference ground, i.e. the second terminal of the power switch 11 and the common terminal of the cathode of the diode 12. The driving pin DRV is coupled to the control terminal of the power switch 11 for providing the control signal PWM.
In the embodiment shown in fig. 3, the second feedback circuit 14 is illustrated as two resistors R3 and R4 connected in series between the first ground GND1 and the second ground GND 2. Wherein the common terminal between the resistor R3 and the resistor R4 provides the second feedback signal V FB2 as the output terminal of the second feedback circuit 14. When both the power switch 11 and the diode 12 are turned off, the voltage at the second reference ground GND2 is equal to the output voltage V OUT. At this time, the second reference GND2 is again used as the ground pin of the integrated circuit 30, so that the voltage at the first reference GND1 is a negative value of the output voltage V OUT with respect to the integrated circuit 30. Therefore, when both the power switch 11 and the diode 12 are turned off, the second feedback signal V FB2 represents the voltage difference between the first reference ground GND1 and the second reference ground GND2, that is, represents the output voltage V OUT. In the embodiment shown in fig. 3, the second feedback signal V FB2 comprises a negative voltage signal having a value equal to-V OUT ×r4/(r3+r4). Due to the input requirements of the pins of the integrated circuit 30 for negative voltages, the value of resistor R4 is typically much greater than the value of resistor R3. For example, the value of resistor R3 may be 20k ohms and the value of resistor R4 may be 20M ohms.
Fig. 4 shows a schematic block diagram of a high voltage BUCK switching converter 300 including an integrated circuit 40 according to an embodiment of the invention. In some embodiments, the power switch 11 and the control circuit may be integrated together in an integrated circuit. As shown in fig. 4, integrated circuit 40 in high voltage BUCK switching converter 300 also integrates power switch 11 as compared to high voltage BUCK switching converter 200. IN the embodiment shown IN fig. 4, the integrated circuit 40 includes an input pin IN, a first feedback pin FB1, a second feedback pin FB2, and a ground pin GND2. The input pin IN receives the input voltage signal V IN, and the first feedback pin FB1 is coupled to the first feedback circuit 13 for receiving the first feedback signal V FB1. The second feedback pin FB2 is coupled to the second feedback circuit 14 for receiving the second feedback signal V FB2. The ground pin GND2 is coupled to the second ground GND2, i.e. the cathode of the diode 12. Inside the integrated circuit 40, the drain of the power switch 11 receives the input voltage signal V IN through the input pin IN, and the source of the power switch 11 is coupled to the ground pin GND2.
Fig. 5 shows a schematic block diagram of a high voltage BUCK switching converter 400 including an integrated circuit 50 according to an embodiment of the invention. The high-voltage BUCK switching converter 400 has substantially the same structure as the high-voltage BUCK switching converter 200 shown in fig. 3, and a control circuit composed of the enable circuit 15, the comparison circuit 16, and the control unit 17 is integrated in one integrated circuit 50. The integrated circuit 50 includes a first feedback pin FB1, a second feedback pin FB2, a ground pin GND2, and a drive pin DRV. The first feedback pin FB1 is coupled to the first feedback circuit 13 for receiving the first feedback signal V FB1. The second feedback pin FB2 is coupled to the second feedback circuit 14 for receiving the second feedback signal V FB2. The ground pin GND2 is coupled to a second reference ground, i.e. the second terminal of the power switch 11 and the common terminal of the cathode of the diode 12. The driving pin DRV is coupled to the control terminal of the power switch 11 for providing the control signal PWM.
Unlike the high voltage BUCK switching converter 200 shown in fig. 3, in the high voltage BUCK switching converter 400, a portion of the second feedback circuit 14 is integrated in the integrated circuit 50. Specifically, in the embodiment shown in fig. 5, the second feedback circuit 14 includes a sampling resistor Rs, an operational amplifier 51, a transistor 52, and a current mirror 53. The sampling resistor Rs is located outside the integrated circuit 50, and the operational amplifier 51, the transistor 52, and the current mirror 53 are integrated in the integrated circuit 50.
The sampling resistor Rs is connected between the first ground GND1 and the second feedback pin FB2. The operational amplifier 51 has a first input terminal, a second input terminal, and an output terminal. A first input terminal of the operational amplifier 51 is coupled to the ground pin GND2; a second feedback pin FB2 of the operational amplifier 51; the output of the operational amplifier 51 is coupled to the gate of the transistor 52. The drain of transistor 52 is coupled to a first current terminal of current mirror 53; a source of transistor 52 is coupled to the second feedback pin FB2. When both the power switch 11 and the diode 12 are turned off, the voltage at the second reference ground GND2 is equal to the output voltage V OUT. At this time, the second ground GND2 is used as the ground pin of the integrated circuit 60, and therefore, the voltage at the first ground GND1 is a negative output voltage V OUT with respect to the ground pin GND 2. The voltage on the second feedback pin FB2 is thus clamped by the operational amplifier 51 to be equal to the ground potential on the ground pin GND2 and the first current terminal of the current mirror 53 outputs a current signal having a value equal to V OUT/Rs. At the same time, the current mirror 53 mirrors the current and outputs a feedback current signal I FB2 at a second current output, which has a value equal to V OUT/Rs. That is, in the embodiment shown in FIG. 6, the second feedback signal V FB2 includes a current signal I FB2 having a value equal to V OUT/Rs.
Those skilled in the art will appreciate that in the embodiment shown in fig. 5, the power switch 11 may also be integrated into the integrated circuit 50. The connection of the integrated pins is shown with reference to fig. 4, and will not be described here again in order not to obscure the focus of the present invention.
Fig. 6 shows a schematic block diagram of a high voltage BUCK switching converter 500 including an integrated circuit 60 according to an embodiment of the invention. The high voltage BUCK switching converter 500 has substantially the same structure as the high voltage BUCK switching converter 200 shown in fig. 3, and a control circuit comprising the enable circuit 15, the comparison circuit 16 and the control unit 17 is integrated in one integrated circuit 60. The integrated circuit 60 includes a first feedback pin FB1, a second feedback pin FB2, a ground pin GND2, a transition pin VT, and a drive pin DRV. The first feedback pin FB1 is coupled to the first feedback circuit 13 for receiving the first feedback signal V FB1. The second feedback pin FB2 is coupled to the second feedback circuit 14 for receiving the second feedback signal V FB2. The ground pin GND2 is coupled to a second reference ground, i.e. the second terminal of the power switch and the common terminal of the cathode of the diode 12. The driving pin DRV is coupled to the control terminal of the power switch 11 for providing the control signal PWM. The transition pin VT will be described further in the following section as part of the second feedback circuit 14.
Similar to the high voltage BUCK switching converter 400 shown in fig. 5, in the high voltage BUCK switching converter 500, a portion of the second feedback circuit 14 is integrated into the integrated circuit 60. Specifically, in the embodiment shown in fig. 6, the second feedback circuit 14 includes a resistor R5, a resistor R6, an operational amplifier 61, and a transistor 62. Resistor R5 and resistor R6 are external to integrated circuit 60, and operational amplifier 61 and transistor 62 are integrated in integrated circuit 60.
The resistor R5 and the resistor R6 are connected in series between the first ground GND1 and the second feedback pin FB2, and a common terminal between the resistor R5 and the resistor R6 is coupled to the switching pin VT. The operational amplifier 61 has a first input terminal, a second input terminal, and an output terminal. A first input terminal of the operational amplifier 61 is coupled to the ground pin GND2; a second input terminal of the operational amplifier 61 is coupled to the switching pin VT; the output of the operational amplifier 61 is coupled to the gate of the transistor 62. The drain of transistor 62 is coupled to power supply VCC; a source of transistor 62 is coupled to the second feedback pin FB2. When both the power switch 11 and the diode 12 are turned off, the voltage at the second reference ground GND2 is equal to the output voltage V OUT. At this time, the second ground GND2 is again used as the ground pin of the integrated circuit 60, and the operational amplifier 61 clamps the voltage on the switching pin VT to be equal to the voltage on the ground pin GND 2. The voltage at the first reference ground GND1 is thus a negative value of the output voltage V OUT with respect to the ground potential at the switch pin VT. The voltage on the second feedback pin FB2 is therefore a positive voltage, which is equal to V OUT x R6/R5. That is, in the embodiment shown in FIG. 6, the second feedback signal V FB2 comprises a positive voltage signal having a value equal to V OUT R6/R5.
Likewise, it will be appreciated by those of ordinary skill in the art that in the embodiment shown in FIG. 6, the power switch 11 may also be integrated into the integrated circuit 60. The connection of the integrated pins is shown with reference to fig. 4, and will not be described here again in order not to obscure the focus of the present invention.
Fig. 7 and 8 show circuit schematic diagrams of the enabling circuit 15 according to an embodiment of the invention, respectively. The enable circuit 15 is configured to generate an enable signal EN for enabling the comparison circuit 16 when both the power switch 11 and the diode 12 are turned off.
In the embodiment shown in fig. 7, the enabling circuit 15 includes a falling edge trigger circuit 151 and a delay circuit 152. The falling edge trigger circuit 151 receives the control signal PWM and generates the trigger signal Tr at the falling edge timing of the control signal PWM. The delay circuit 152 receives the trigger signal Tr and generates the enable signal EN after a certain delay. The delay time of the trigger signal Tr by the delay circuit 152 may be based on the specific application circuit design. In one embodiment, the diode 12 is considered to have been turned off during the delay period of the trigger signal Tr.
In the embodiment shown in fig. 8, the enabling circuit 15 comprises a voltage comparator having a non-inverting input, an inverting input and an output. The non-inverting input of the voltage comparator receives the zero crossing threshold signal V ZCD, the inverting input of the voltage comparator receives the first feedback signal V FB1, the voltage comparator compares the first feedback signal V FB1 with the zero crossing threshold signal V ZCD, and the enable signal EN is output at the output of the voltage comparator. In one embodiment, zero crossing threshold signal V ZCD is equal to zero or a value near zero.
Fig. 9 shows a circuit schematic of the comparison circuit 16 according to an embodiment of the invention. As shown, the comparison circuit 16 includes a first comparator 161 and a second comparator 162. The first comparator 161 and the second comparator 162 have an enable terminal, an inverting input terminal, a non-inverting input terminal, and an output terminal, respectively.
The enable terminal of the first comparator 161 receives the enable signal EN, the inverting input terminal of the first comparator 161 receives the second feedback signal V FB2, the non-inverting input terminal of the first comparator 161 receives the under-voltage threshold signal UV, and when the enable signal EN is active, the first comparator 161 compares the second feedback signal V FB2 with the under-voltage threshold signal UV and outputs the first comparison signal ca_uv at the output terminal of the first comparator 161. In one embodiment, the power switch 11 is turned on when the first feedback signal V FB1 is less than the under-voltage threshold signal UV, the first comparison signal ca_uv is active (e.g., logic high).
The enable terminal of the second comparator 162 receives the enable signal EN, the inverting input terminal of the second comparator 162 receives the second feedback signal V FB2, the non-inverting input terminal of the second comparator 162 receives the over-voltage threshold signal OV, and the second voltage comparator compares the second feedback signal V FB2 with the over-voltage threshold signal OV and outputs the second comparison signal ca_ov at the output terminal of the second comparator 162 when the enable signal EN is active. In one embodiment, when the second feedback signal V FB2 is greater than the over-voltage threshold signal OV, the second comparison signal ca_ov is active (e.g., logic low) when the power switch 11 is forced to remain in the off state, preventing the output voltage V OUT from rising higher the more the power switch 11 is turned on. In one embodiment, the over-voltage threshold signal OV is greater than the under-voltage threshold signal UV.
In the embodiment shown in fig. 9, the second control signal PWM2 comprises two signals. The first comparison signal ca_uv and the second comparison signal ca_ov are both the second control signal PWM2. In one embodiment, when the second feedback signal V FB2 is a voltage signal, the first comparator 161 and the second comparator 162 are voltage comparators; when the second feedback signal V FB2 is a current signal, the first comparator 161 and the second comparator 162 are current comparators. In other embodiments, the comparison circuit 16 may also include other suitable comparison circuits that perform similar functions.
The control unit 17 may employ various control modes, such as pulse width modulation (e.g., voltage control, current control, voltage-current dual-loop control, etc.), pulse frequency modulation (e.g., constant time on control, frequency hopping control, etc.), or a combination of pulse width modulation and pulse frequency modulation. For example, in the case of normal load of the system, a pulse width modulation control method can be adopted; under the condition of light load or no load of the system, a pulse frequency control mode can be adopted.
Fig. 10 shows a schematic circuit diagram of a control unit 17 for Constant On Time (COT) control. As shown in fig. 10, the control unit 17 includes a voltage comparator 171, an and gate 172, an or gate 173, a constant on-time generation circuit 174, and an RS flip-flop 175. Wherein the first feedback voltage signal V FB1 represents the value of the output voltage signal V OUT during freewheeling conduction of the diode 12. The second input terminal of the voltage comparator 171 receives the first feedback voltage signal V FB1, and the voltage comparator 171 compares the first feedback voltage signal V FB1 with the reference voltage signal V REF and outputs the first control signal PWM1 at the output terminal. The first control signal PWM1 is a logic high-low signal, and the first control signal PWM1 is active (e.g., logic high) when the first feedback voltage signal V FB1 is less than the reference voltage signal V REF. The and gate 172 receives the second comparison signal ca_ov and the first control signal PWM1, performs an and operation, and outputs an and signal. The or gate 173 receives the and signal and the first comparison signal ca_uv and performs an or operation to output the set signal Cs. The constant on-time generating circuit 174 generates a reset signal C R with a fixed on-time. The set terminal S of the RS flip-flop 175 receives the set signal Cs. The reset terminal R of the RS flip-flop 175 receives the reset signal C R and outputs the control signal PWM at the output terminal Q. In the embodiment shown in fig. 10, the control signal PWM is a logic high-low signal, and the power switch 11 is turned on when the control signal PWM is active (e.g., logic high); when the control signal PWM is inactive (e.g., logic low), the power switch 11 is turned off.
Fig. 11 shows a schematic circuit diagram of a control unit 17 according to another embodiment of the invention. In the embodiment shown in fig. 11, the control unit 17 includes a peak current control structure of voltage-current double loop control. As shown in fig. 11, the control unit 17 includes an error amplifier 271, a voltage comparator 272, an and gate 273, an or gate 274, a voltage comparator 275, and an RS flip-flop 276. A first input of the error amplifier 271 receives the reference voltage signal V REF, a second input of the error amplifier 173 receives the first feedback voltage signal V FB1, the error amplifier 173 compares the first feedback voltage signal V FB1 with the reference voltage signal V REF and amplifies the error, and an error signal EA is output at an output. A first input terminal of the voltage comparator 272 receives the error signal EA, a second input terminal of the voltage comparator 272 receives the RAMP signal RAMP, and the voltage comparator 272 compares the error signal EA with the RAMP signal RAMP and outputs the first control signal PWM1 at an output terminal. The first control signal PWM1 is a logic high-low signal. In one embodiment, the first control signal PWM1 is active (e.g., logic high) when the RAMP signal RAMP is greater than the error signal EA. The and gate 273 receives the second comparison signal ca_ov and the first control signal PWM1, performs an and operation, and outputs an and signal. The or gate 274 receives the and signal and the first comparison signal ca_uv and performs an or operation to output the set signal Cs. A first input terminal of the voltage comparator 275 receives the current reference signal V REF_CS, a second input terminal of the voltage comparator 275 receives the current sample signal V CS, the voltage comparator 275 compares the current reference signal V REF_CS with the current sample signal V CS, and outputs the reset signal C R at an output terminal. In one embodiment, current sample signal V CS represents the value of the current flowing through power switch 11. The set terminal S of the RS flip-flop 276 receives the comparison signal C S, the reset terminal R of the RS flip-flop 176 receives the second comparison signal C R, and the control signal PWM is output at the output terminal Q. At the position of
In the embodiment shown in fig. 11, the control signal PWM is a logic high-low signal, and the power switch 11 is turned on when the control signal PWM is active (e.g., logic high); when the control signal PWM is inactive (e.g., logic low), the power switch 11 is turned off.
Fig. 12 shows a schematic diagram of a control method 600 for controlling a high voltage BUCK switching converter according to an embodiment of the invention. The control method shown in fig. 12 can be applied to the high voltage BUCK switching converters shown in fig. 2-11 described above. As shown in the foregoing fig. 2-11, the high voltage BUCK switching converter includes a power switch 11, a diode 12, an inductance L OUT, a capacitance C OUT, a first feedback circuit 13, and an integrated circuit for controlling the high voltage BUCK switching converter. The drain of the power switch 11 is coupled to the input terminal of the switching converter for receiving the dc input voltage V IN, the source of the power switch 11 is coupled to the cathode of the diode 12, and the anode of the diode 12 is electrically connected to the first ground GND1. The inductor L OUT is coupled between the source of the power switch 11 and the output OUT of the switching converter, the first feedback circuit 13 is connected between the output OUT of the switching converter and the source of the power switch 11, and generates a first feedback signal V FB2 representing the output voltage signal V OUT during the on-period of the diode 12, the common terminal of the source of the power switch 11 and the cathode of the diode 12 being the second reference ground GND2, wherein the second reference ground GND2 is the reference ground of the integrated circuit. The control method includes steps 1301-1306.
Step 1301, it is determined whether the inductor current crosses zero, i.e. whether the power switch 11 and the freewheeling diode 12 are both turned off. When the inductor current crosses zero, i.e. both the power switch 11 and the freewheeling diode 12 are turned off, the process goes to step 1302, otherwise the determination is continued.
In step 1302, a voltage difference between the first reference ground GND1 and the second reference ground GND2 is detected, and a second feedback signal V FB2 representing the voltage difference between the first reference ground GND1 and the second reference ground GND2 is generated. The first reference ground GND1 is a reference ground of the high-voltage BUCK switching converter, and the second reference ground GND2 is a reference ground of an integrated circuit controlling the high-voltage BUCK switching converter.
In step 1303, it is determined whether the second feedback signal V FB2 is greater than the overvoltage threshold, and when the second feedback signal V FB2 is greater than the overvoltage threshold, the process goes to step 1304.
Step 1304, the off state of the power switch 11 is maintained. In one embodiment, when the second feedback signal V FB2 is greater than the overvoltage threshold, the power switch 11 remains off even if the first control signal PWM1 is active.
Step 1305, determining whether the second feedback signal V FB2 is smaller than the undervoltage threshold, and when the second feedback signal V FB2 is smaller than the undervoltage light-load threshold, going to step 1306.
Step 1306, maintaining the power switch 11 off state.
Of the method steps described above, steps 1305 and 1306 are illustrated after steps 1303 and 1304, and those skilled in the art will appreciate that steps 1303 and 1305 may occur simultaneously during actual operation.
The above description of the control method and steps according to the embodiments of the present invention is merely exemplary, and is not intended to limit the present invention. In other instances, well known control steps, used control parameters, and the like have not been shown or described in detail in order to avoid obscuring the invention, in a clear, concise, and convenient manner. It will be appreciated by those skilled in the art that the step numbers used in the description of the control method and steps according to the embodiments of the present invention above are not intended to indicate the absolute sequence of steps, and that the steps are not performed in the order of step numbers, but may be performed in a different order, or may be performed concurrently and in parallel, and are not limited to just the described embodiments.
While the invention has been described with reference to several exemplary embodiments, it is to be understood that the terminology used is intended to be in the nature of words of description and of limitation. As the present invention may be embodied in several forms without departing from the spirit or essential characteristics thereof, it should also be understood that the above-described embodiments are not limited by any of the details of the foregoing description, but rather should be construed broadly within its spirit and scope as defined in the appended claims, and therefore all changes and modifications that fall within the meets and bounds of the claims, or equivalences of such meets and bounds are therefore intended to be embraced by the appended claims.

Claims (12)

1. A high voltage BUCK switching converter comprising:
A diode;
The power switch is provided with a first end, a second end and a control end, wherein the first end of the power switch receives input voltage, the second end of the power switch is coupled with the cathode of the diode, the control end of the power switch receives a control signal, the anode of the diode is electrically connected to a first reference ground, and the common end of the second end of the power switch and the cathode of the diode is used as a second reference ground;
an inductor coupled between the second reference ground and an output of the switching converter;
A first feedback circuit coupled between the second reference ground and the output terminal of the switching converter and generating a first feedback signal representative of the output voltage signal during diode turn-on;
The second feedback circuit is connected between the first reference ground and the second reference ground, detects the voltage difference between the first reference ground and the second reference ground, and generates a second feedback signal representing the voltage difference between the first reference ground and the second reference ground after the power switch and the diode are turned off; and
And the control circuit receives the first feedback signal and the second feedback signal and generates a control signal according to the first feedback signal and the second feedback signal to control the on and off of the power switch, wherein the control circuit is integrated in an integrated circuit, and the second reference ground is the reference ground of the integrated circuit.
2. The switching converter of claim 1, wherein the control circuit comprises:
The enabling circuit generates an enabling signal, and the enabling signal is valid after the power switch and the diode are both closed;
the comparison circuit receives the enabling signal and the second feedback signal, and when the enabling signal is effective, the second feedback signal is respectively compared with an undervoltage threshold value and an overvoltage threshold value to generate a first control signal; when the second feedback signal is smaller than the undervoltage threshold, the first control signal is used for conducting the power switch; when the second feedback signal is larger than an overvoltage threshold value, the first control signal is used for keeping the power switch in an off state, wherein the overvoltage threshold value is smaller than the overvoltage threshold value; and
And the control unit is used for receiving the first feedback signal and the first control signal and generating the control signal according to the first feedback signal and the first control signal.
3. The switching converter of claim 1, wherein the integrated circuit further comprises:
a first feedback pin coupled to the first feedback circuit for receiving the first feedback signal;
a second feedback pin coupled to the second feedback circuit for receiving a second feedback signal;
a ground pin coupled to a second reference ground; and
The driving pin is coupled with the control end of the power switch to provide a control signal.
4. The switching converter of claim 1, wherein the power switch is integrated within an integrated circuit, the integrated circuit further comprising:
An input pin receiving an input voltage signal;
a first feedback pin coupled to the first feedback circuit for receiving the first feedback signal;
A second feedback pin coupled to the second feedback circuit for receiving a second feedback signal; and
A ground pin coupled to a second reference ground; the first end of the power switch is coupled to the input pin, and the second end of the power switch is coupled to the ground pin.
5. The switching converter of claim 1, wherein the second feedback circuit comprises:
And a first resistor and a second resistor connected in series between the first reference ground and the second reference ground, wherein the second feedback signal comprises a voltage on a common terminal of the first resistor and the second resistor.
6. A switching converter as claimed in claim 3 or 4, wherein the second feedback circuit comprises:
The sampling resistor is provided with a first end and a second end, the first end of the sampling resistor is coupled with the first reference ground, and the second end of the sampling resistor is coupled with the second feedback pin;
the operational amplifier is provided with a first input end, a second input end and an output end, wherein the first input end of the operational amplifier is coupled with the grounding pin, and the second input end of the operational amplifier is coupled with the second feedback pin;
A current mirror having a first current terminal and a second current terminal; and
The transistor is provided with a source electrode, a drain electrode and a grid electrode, the drain electrode of the transistor is coupled with the first current end of the current mirror, the source electrode of the transistor is coupled with the second feedback pin, and the grid electrode of the transistor is coupled with the output end of the operational amplifier; the second current end of the current mirror is used as an output end of the second feedback circuit to provide a second feedback signal, and the operational amplifier, the current mirror and the transistor are integrated inside the integrated circuit.
7. The switching converter of claim 3 or 4, wherein the integrated circuit further comprises a switching pin, the second feedback circuit comprising:
a third resistor coupled between the first reference ground and the switch pin;
A fourth resistor coupled between the second feedback pin and the switch pin;
the operational amplifier is provided with a first input end coupled with the grounding pin, a second input end coupled with the conversion pin and an output end; and
The transistor is provided with a source electrode, a drain electrode and a grid electrode, the drain electrode of the transistor is coupled with a power supply, the source electrode of the transistor is coupled with a second feedback pin, and the grid electrode of the transistor is coupled with the output end of the operational amplifier; wherein the transistor and the operational amplifier are integrated within the integrated circuit, and a source of the transistor provides the second feedback signal as an output of the second feedback circuit.
8. The switching converter of claim 2, wherein the first control signal comprises a first comparison signal and a second comparison signal, the comparison circuit comprising:
The first comparator is provided with an enabling end, a first input end, a second input end and an output end, the enabling end of the first comparator receives an enabling signal, the first input end of the first comparator receives a second feedback signal, the second input end of the first comparator receives an undervoltage threshold value signal, the first comparator compares the second feedback signal with the undervoltage threshold value signal when the enabling signal is valid, and the first comparison signal is output at the output end of the first comparator, wherein the first comparison signal is used for conducting a power switch when the second feedback signal is smaller than the undervoltage threshold value; and
The second comparator is provided with an enabling end, a first input end, a second input end and an output end, the enabling end of the second comparator receives an enabling signal, the first input end of the second comparator receives a second feedback signal, the second input end of the second comparator receives an overvoltage threshold value signal, the second comparator compares the second feedback signal with the overvoltage threshold value signal when the enabling signal is valid, and a second comparison signal is output at the output end of the second comparator, wherein the second comparison signal is used for keeping the power switch in an off state when the second feedback signal is larger than the overvoltage threshold value.
9. The switching converter of claim 2, wherein the enabling circuit comprises:
And the first voltage comparator is used for receiving the zero-crossing threshold signal and the first feedback signal, comparing the first feedback signal with the zero-crossing threshold signal and outputting an enabling signal.
10. The switching converter of claim 8, wherein the control unit comprises:
An error amplifier for receiving the first feedback signal and the reference voltage signal, comparing the first feedback signal with the reference voltage signal, amplifying the error, and outputting an error signal;
the second voltage comparator receives the error signal and the ramp signal, compares the error signal with the ramp signal and outputs a second control signal;
And an AND gate for receiving the second comparison signal and the second control signal, performing AND operation, and outputting an AND signal;
An OR gate which receives the AND signal and the first comparison signal and performs OR operation to output a setting signal;
A fifth voltage comparator for receiving the current reference signal and a current sampling signal representing a current flowing through the power switch, and comparing the current reference signal with the current sampling signal to output a reset signal; and
The RS trigger comprises a setting end, a resetting end and an output end, wherein the setting end of the RS trigger receives a setting signal, the resetting end of the RS trigger receives a resetting signal, and the output end of the RS trigger outputs a control signal.
11. An integrated circuit for controlling a high voltage BUCK switching converter, the switching converter including a diode, an inductor, a first feedback circuit and a second feedback circuit, wherein a diode cathode is coupled to an output of the switching converter through the inductor, a diode anode is electrically connected to a first reference ground, a diode cathode is used as a second reference ground, the first feedback circuit is coupled between the second reference ground and the output of the switching converter to generate a first feedback signal representative of an output voltage, the second feedback circuit is coupled between the second reference ground and the first reference ground to detect a voltage difference between the first reference ground and the second reference ground to generate a second feedback signal representative of the voltage difference between the first reference ground and the second reference ground, the integrated circuit comprising:
An input pin receiving an input voltage signal;
a first feedback pin receiving a first feedback signal;
a second feedback pin receiving a second feedback signal;
a ground pin coupled to a second reference ground;
The power switch is provided with a first end, a second end and a control end, wherein the first end of the power switch is coupled with the input pin to receive input voltage, the second end of the power switch is coupled with the grounding pin, and the control end receives a control signal; and
And the control circuit receives the first feedback signal and the second feedback signal and generates a control signal according to the first feedback signal and the second feedback signal to control the on and off of the power switch.
12. A control method for controlling a high voltage BUCK switching converter, wherein the high voltage BUCK switching converter comprises a power switch, a diode and an integrated circuit for controlling the high voltage BUCK switching converter, a drain of the power switch is coupled to an input terminal of the switching converter to receive an input voltage signal, a source of the power switch is coupled to a cathode of the diode, an anode of the diode is electrically connected to a first reference ground, a common terminal of the source of the power switch and the cathode of the diode serves as a second reference ground, wherein the second reference ground is a reference ground of the integrated circuit, the control method comprising:
Judging whether the power switch and the freewheeling diode are both turned off;
when the power switch and the freewheeling diode are both closed, detecting the voltage difference between the first reference ground and the second reference ground, generating a second feedback signal representing the voltage difference between the first reference ground and the second reference ground, and sending the second feedback signal to the integrated circuit;
Judging whether the second feedback signal is lower than an undervoltage threshold, and switching on the power switch when the second feedback signal is lower than the undervoltage threshold; and
And judging whether the second feedback signal is higher than an overvoltage threshold value, and when the second feedback signal is higher than the overvoltage threshold value, keeping the power switch in an off state, wherein the overvoltage threshold value is larger than the undervoltage threshold value.
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