A reverse buck-boost switching power supply and an anti-ringing circuit thereof

Abstract

This application provides a reverse buck-boost switching power supply and its anti-ringing circuit. The anti-ringing circuit includes a zero-current detection circuit for detecting the inductor current in the reverse buck-boost switching power supply based on the switching node voltage and output voltage of the power supply, as well as a control signal. The control signal is used to control the on / off state of the switching transistor in the reverse buck-boost switching power supply. The anti-ringing unit performs an action based on the detection result to short-circuit the inductor in the reverse buck-boost switching power supply when the inductor current is less than or equal to zero, thus reducing the inductor current to zero and preventing oscillation. This eliminates the ringing phenomenon caused by the inductor current and switching node voltage in the reverse buck-boost switching power supply, eliminates electromagnetic interference, and improves the stability of the reverse buck-boost switching power supply.

Description

Technical Field

[0001] This invention belongs to the field of power electronics technology, and more specifically, relates to a reverse buck-boost switching power supply and its anti-ringing circuit. Background Technology

[0002] like Figure 1 As shown, a conventional asynchronous boost switching power supply 300 is illustrated. The control system 301 provides a pulse width modulation (PWM) signal to the power switch N1, causing the power switch N1 to periodically turn on and off, raising the input voltage VIN to the output voltage VOUT. The control system 301 includes a PWM comparator and an oscillator 305, respectively connected to corresponding terminals of an RS flip-flop 306. These two components together determine the duty cycle signal D. The duty cycle signal D passes through a driver 307 and is then connected to the gate terminal of the power switch N1. This closed-loop feedback controls the on-time of the power switch, thereby controlling the current of the inductor L1. Figure 2 As shown, this diagram illustrates some control and switching signal waveforms of an asynchronous boost switching power supply 300. Since the inductor current direction cannot change abruptly, when the current drops below 0mA, the voltage at the switching node SW is clamped to a negative voltage by the parasitic body diode. The inductor L1, Schottky diode D1, and parasitic capacitance form a self-resonant circuit, causing the SW node voltage to oscillate. This oscillating voltage / current signal generates additional EMI radiation and, through parasitic capacitance coupling, introduces noise into both the input and output signals.

[0003] Existing technologies propose an anti-ringing solution, such as Figure 3 As shown, the voltage at node SW is detected by detection unit 201. When the voltage at node SW drops below 0V, an EN_AR signal is generated to open the charge bypass circuit 202. The structure of the charge bypass circuit 202 is as follows: Figure 5 As shown, the charge bypass circuit 202 can short-circuit the two ends of inductor L1 together, bringing the inductor current IL to zero and preventing oscillation. The effect is as follows: Figure 4 Curve 251 in the diagram illustrates this. That is, this existing technology eliminates ringing by reducing the voltage at the switching node SW to a negative voltage and short-circuiting the voltage at the switching node SW to the input voltage VIN. However, for reverse buck-boost switching power supplies, the above anti-ringing solution is no longer applicable due to architectural limitations. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide a reverse buck-boost switching power supply and its anti-ringing circuit, which is used to eliminate the ringing phenomenon of inductor current and switching node voltage in the reverse buck-boost switching power supply, eliminate electromagnetic interference, and improve the stability of the reverse buck-boost switching power supply.

[0005] The first aspect of the present invention discloses an anti-ringing circuit for a reverse buck-boost switching power supply, comprising: an anti-ringing unit and a zero-current detection circuit;

[0006] The zero-current detection circuit is used to detect the inductor current in the reverse buck-boost switching power supply based on the switching node voltage and output voltage of the reverse buck-boost switching power supply, as well as a control signal; wherein, the control signal is a signal used to control the on / off state of the switching transistor in the reverse buck-boost switching power supply.

[0007] The anti-ringing unit is used to perform an action based on the detection result, so as to short-circuit the inductor in the reverse buck-boost switching power supply when the inductor current is less than or equal to zero.

[0008] Optionally, when the zero-current detection circuit detects the inductor current in the reverse buck-boost switching power supply based on the switching node voltage and output voltage of the power supply, and the control signal, it is specifically used for:

[0009] The voltage at the switching node and the output voltage are compared to obtain a comparison result;

[0010] The comparison result is compared with the control signal by performing a logical operation according to preset rules to obtain the detection result.

[0011] Optionally, the preset rule is the comparison result priority rule.

[0012] Optionally, the control signal is a PWM (Pulse Width Modulation) signal.

[0013] Optionally, the zero-current detection circuit includes: a comparator and an RS flip-flop;

[0014] The non-inverting input of the comparator is used to receive the voltage of the switching node;

[0015] The inverting input of the comparator is used to receive the output voltage;

[0016] The output of the comparator is directly or indirectly connected to the S terminal of the RS flip-flop.

[0017] The R terminal of the RS flip-flop is used to receive the PWM signal;

[0018] The Q terminal of the RS flip-flop serves as the output terminal of the zero-current detection circuit.

[0019] Optionally, the zero-current detection circuit further includes a counting circuit;

[0020] One input terminal of the counting circuit is connected to the output terminal of the comparator;

[0021] Another input terminal of the counting circuit is used to receive the control signal;

[0022] The output terminal of the counting circuit is connected to the S terminal of the RS flip-flop;

[0023] The counting circuit is equipped with a preset trigger count value.

[0024] Optional, the pre-designed value is greater than or equal to 2.

[0025] Optionally, the anti-ringing unit includes: a switching unit and a driving unit;

[0026] The input terminal of the drive unit serves as the input terminal of the anti-ringing unit;

[0027] The output terminal of the drive unit is connected to the control terminal of the switch unit.

[0028] The first end of the switching unit and one end of the inductor are both connected to analog ground;

[0029] The second end of the switching unit and the other end of the inductor are both connected to the switching node.

[0030] Optionally, the switching unit includes two switching transistors connected in series with a common input terminal.

[0031] Optionally, each of the switching transistors in the switching unit is a power transistor with a built-in anti-parallel diode; or,

[0032] When each of the switching transistors in the switching unit is a power transistor without an anti-parallel diode, the switching unit further includes: two diodes; the two diodes correspond one-to-one with the two power transistors, and each diode is connected in parallel with the corresponding power transistor, and the direction of the diodes is opposite to that of the corresponding power transistors.

[0033] Optionally, in the switching unit, the output terminal of the first switching transistor serves as the first terminal of the switching unit, and the control terminal of the first switching transistor is connected to its own output terminal.

[0034] The output terminal of the second switching transistor serves as the second terminal of the switching unit;

[0035] The control terminal of the second switching transistor serves as the control terminal of the switching unit.

[0036] Optionally, the anti-ringing unit further includes: a level conversion circuit; in the switching unit, the output terminal of the first switching transistor serves as the first terminal of the switching unit, and the output terminal of the second switching transistor serves as the second terminal of the switching unit;

[0037] The control terminal of the first switching transistor is connected to the control terminal of the second switching transistor through the level conversion circuit, and the connection point serves as the control terminal of the switching unit.

[0038] Optionally, the drive unit includes a two-stage inverter.

[0039] The second aspect of this invention discloses a reverse buck-boost switching power supply, comprising: a control system, a drive circuit, an output capacitor, an anti-ringing circuit as described in any one of the first aspects of this invention, and two switching transistors;

[0040] One end of the two switching transistors connected in series serves as the input terminal of the reverse buck-boost switching power supply.

[0041] The other end of the two switching transistors connected in series is connected to one end of the output capacitor, and the connection point serves as the output terminal of the reverse buck-boost switching power supply.

[0042] The other end of the output capacitor is grounded.

[0043] The control system is used to control the on / off state of each of the switching transistors through the drive circuit.

[0044] Optionally, the control system includes: a feedback network, an error amplifier, a PWM comparator, an oscillator, an RS flip-flop, a filter circuit, and a driver; wherein:

[0045] The inverting input of the error amplifier is connected to the output of the reverse buck-boost switching power supply through the feedback network;

[0046] The non-inverting input of the error amplifier is used to receive a reference voltage signal;

[0047] The output terminal of the error amplifier is connected to the inverting input terminal of the PWM comparator and one end of the filter circuit, respectively.

[0048] The non-inverting input of the PWM comparator is used to receive the ramp signal;

[0049] The output terminal of the PWM comparator is connected to the R terminal of the RS flip-flop;

[0050] The S terminal of the RS flip-flop is connected to the output terminal of the oscillator;

[0051] The Q terminal of the RS flip-flop is connected to the input terminal of the driver;

[0052] The output terminal of the driver serves as the output terminal of the control system.

[0053] The other end of the filter circuit is grounded.

[0054] Optionally, the filtering circuit includes a filter resistor and a filter capacitor connected in series.

[0055] As can be seen from the above technical solution, the present invention provides a power supply anti-ringing circuit for a reverse buck-boost switch. Its zero-current detection circuit is used to detect the inductor current in the reverse buck-boost switch based on the switching node voltage and output voltage of the reverse buck-boost switch, as well as a control signal. The control signal is used to control the on / off state of the switching transistor in the reverse buck-boost switch. Its anti-ringing unit is used to perform an action based on the detection result, short-circuiting the inductor in the reverse buck-boost switch when the inductor current is less than or equal to zero, thus reducing the inductor current to zero and preventing oscillation. This eliminates the ringing phenomenon of the inductor current and switching node voltage in the reverse buck-boost switch, eliminates electromagnetic interference, and improves the stability of the reverse buck-boost switch. Attached Figure Description

[0056] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0057] Figure 1 This is a schematic diagram of a conventional asynchronous boost switching power supply provided by existing technology;

[0058] Figure 2 It is a timing diagram of some control signal and switching signal waveforms of a conventional asynchronous boost switching power supply provided by existing technology;

[0059] Figure 3 This is a schematic diagram of an anti-ringing solution provided by existing technology;

[0060] Figure 4 This is a timing diagram of the signal waveforms of anti-ringing solutions provided by existing technologies;

[0061] Figure 5 This is a schematic diagram of a charge bypass circuit provided by existing technology;

[0062] Figure 6 This is a schematic diagram of a reverse buck-boost switching power supply and its anti-ringing circuit provided in an embodiment of the present invention;

[0063] Figure 7 This is a schematic diagram of a zero-current detection circuit in an anti-ringing circuit provided by an embodiment of the present invention;

[0064] Figure 8 This is a schematic diagram of an anti-ringing unit in an anti-ringing circuit provided in an embodiment of the present invention;

[0065] Figure 9 This is a schematic diagram of another anti-ringing unit in an anti-ringing circuit provided in an embodiment of the present invention;

[0066] Figure 10 It is a timing diagram of some control signal and switching signal waveforms of a common reverse buck-boost switching power supply provided by existing technology;

[0067] Figure 11 This is a timing diagram of the corresponding signal waveforms in the reverse buck-boost switching power supply provided in the embodiment of the present invention. Detailed Implementation

[0068] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0069] In this application, the terms "comprising," "including," or any other variations thereof are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0070] like Figure 1As shown, a conventional asynchronous boost switching power supply 300 is illustrated; wherein, inductor L1 is connected to VIN and switching node SW, power switch N1 is disposed between switching node SW and ground potential GND, Schottky diode D1 is disposed between switching node SW and output voltage VOUT, capacitor COUT is disposed between output voltage VOUT and ground potential GND, and control system 301 provides a pulse width modulation signal to power switch N1, and power switch N1 periodically turns on and off to raise input voltage VIN to output voltage VOUT. In the control system 301, the feedback network 302 divides the output voltage VOUT into a feedback voltage VFB, which is connected to the input of the error amplifier 303 together with the reference voltage signal VREF. The output signal EA_OUT of the error amplifier 303 and the ramp signal RAMP are input to the two ends of the PWM comparator 304. The output of the PWM comparator is connected to the R terminal of the RS flip-flop 306, and the output of the oscillator 305 is connected to the S terminal of the RS flip-flop 306. The two together determine the duty cycle signal D. The duty cycle signal D is connected to the gate terminal of the power switch N1 after passing through the driver 307. That is, the opening time of the power switch is controlled through closed-loop feedback, thereby controlling the current of the inductor L1.

[0071] like Figure 2 The diagram illustrates the control and switching signal waveforms of a switching power supply 300. Waveform 360 shows the duty cycle signal D, waveform 361 shows the switching node SW, and waveform 362 shows the inductor L1 current. During the high period of the duty cycle signal D, power switch N1 is open, the voltage at switching node SW is pulled low, and the current IL of inductor L1 rises linearly. When the low period of the duty cycle signal D occurs, power switch N1 is closed, the inductor current begins to decrease linearly, and the switching node SW is pulled high. Since the direction of the inductor current cannot change abruptly, when the current drops below 0mA, the voltage at switching node SW is clamped to a negative voltage by the parasitic body diode. Inductor L1, Schottky diode D1, and parasitic capacitance form a self-resonant circuit, and the voltage at switching node SW begins to oscillate. However, the oscillating voltage / current signal generates additional EMI radiation and, through parasitic capacitance coupling, affects the input and output signals with noise.

[0072] Existing technologies propose an anti-ringing scheme by reducing the voltage of the switching node SW to a negative voltage, thus short-circuiting the SW voltage to the input voltage VIN, thereby eliminating ringing. However, for reverse buck-boost switching power supplies, the above anti-ringing scheme is no longer applicable due to architectural limitations.

[0073] Based on this, embodiments of the present invention disclose an anti-ringing circuit for a reverse buck-boost switching power supply, which solves the problem that in the prior art, due to the influence of the architecture, the above-mentioned anti-ringing scheme is no longer applicable to reverse buck-boost switching power supplies, that is, it cannot solve the ringing phenomenon of reverse buck-boost switching power supplies.

[0074] See Figure 6 The anti-ringing circuit 109 of the reverse buck-boost switching power supply 100 includes: an anti-ringing unit 160 and a zero-current detection circuit 170.

[0075] The zero-current detection circuit 170 is used to detect the inductor L1 current in the reverse buck-boost switching power supply 100 based on the switching node voltage and output voltage of the reverse buck-boost switching power supply 100, as well as the control signal.

[0076] The control signal is used to control the on / off state of the switching transistors in the reverse buck-boost switching power supply 100; generally, this control signal is output by the control system 101 in the reverse buck-boost switching power supply 100. The switching node voltage is the voltage of the switching node SW in the reverse buck-boost switching power supply 100; the switching node SW is the connection point between two switching transistors in the reverse buck-boost switching power supply 100; this connection point is also grounded through inductor LI. VOUT is the output voltage, which is the voltage at the output terminal of the reverse buck-boost switching power supply 100.

[0077] Specifically, the zero-current detection circuit 170 has three receiving pins; the first receiving pin is located at the switching node SW in the reverse buck-boost switching power supply 100; the second receiving pin is located at the output terminal of the reverse buck-boost switching power supply 100; and the third receiving pin is located at the output terminal of the control system 101.

[0078] The anti-ringing unit 160 is used to perform an action based on the detection result to short-circuit the inductor LI in the reverse buck-boost switching power supply 100 when the current of inductor LI is less than or equal to zero.

[0079] Specifically, when the detection result indicates that the current of inductor LI is less than or equal to zero, the anti-ringing unit 160 short-circuits the inductor LI and pulls the switch node SW to ground; when the detection result indicates that the current of inductor LI is greater than zero, the anti-ringing unit 160 does not operate, that is, the inductor LI is not short-circuited; the switch node SW is still connected to ground through the inductor LI.

[0080] In this embodiment, when the inductor current is less than or equal to zero, the inductor in the reverse buck-boost switching power supply is short-circuited to bring the inductor current to zero, avoiding oscillation. This eliminates the ringing phenomenon caused by eliminating inductor L1 current and switching node voltage in the reverse buck-boost switching power supply 100, eliminates electromagnetic interference, and improves the stability of the reverse buck-boost switching power supply 100. At the same time, the circuit implementation is simple, has no special requirements for the process, and is compatible with most BCD (Bipolar-CMOS-DMOS) processes.

[0081] In practical applications, the zero-current detection circuit 170 is used to detect the inductor L1 current in the reverse buck-boost switching power supply 100 based on the switching node voltage and output voltage VOUT of the reverse buck-boost switching power supply 100, as well as the control signal. The specific process is as follows:

[0082] (1) Compare the switching node voltage and the output voltage to obtain the comparison result.

[0083] Specifically, the switching node voltage and the output voltage can be compared. When the switching node voltage is greater than the output voltage, a first comparison result is output; when the switching node voltage is less than the output voltage, a second comparison result is output. Of course, the specific process of comparing the switching node voltage and the output voltage to obtain the comparison result is not limited to the above example. As long as the comparison result can characterize the relationship between the switching node voltage and the output voltage, it is acceptable. It will not be elaborated here, and all of them are within the protection scope of this application.

[0084] (2) Perform logical operations on the comparison results and control signals according to preset rules to obtain the detection results.

[0085] Optionally, the preset rule is the comparison result priority rule; of course, it is also possible that the preset rule is the control signal priority rule or other rules, which will not be elaborated here, and all are within the protection scope of this application.

[0086] Under the comparison result priority rule, the detection result is primarily determined by the comparison result, with the control signal serving as an auxiliary factor. If the comparison result is valid but the control signal is invalid, the detection result is valid. When the detection result is valid, the current of the inductor L1 is zero. Of course, the above logical operation process is merely an example; other operational processes will not be elaborated upon here, but are all within the scope of protection of this application.

[0087] It should be noted that this control signal can be a PWM signal, also known as a duty cycle signal (e.g., ...). Figure 6 As shown in D); of course, it can also be other signals, which will not be elaborated here, and are all within the protection scope of this application.

[0088] In any of the above embodiments, see Figure 7 The zero-current detection circuit 170 includes a comparator 171 and an RS flip-flop 173.

[0089] The non-inverting input of comparator 171 serves as the first receiving pin of zero-current detection circuit 170 and is connected to the switching node SW in reverse buck-boost switching power supply 100 to receive the switching node voltage.

[0090] The inverting input of comparator 171 serves as the second receiving pin of zero-current detection circuit 170 and is connected to the output of reverse buck-boost switching power supply 100 to receive the output voltage.

[0091] The output of comparator 171 is directly or indirectly connected to the S terminal of RS flip-flop 173; that is, the output of comparator 171 can be directly connected to the S terminal of RS flip-flop 173 so as to directly output a signal to the S terminal of RS flip-flop 173 through its own output terminal; or, the output of comparator 171 can be connected to the S terminal of RS flip-flop 173 through a corresponding device so as to output a signal to the device through its own output terminal. The device processes the received signal and outputs the result to RS flip-flop 173.

[0092] The R terminal of the RS flip-flop 173 is used as the third receiving pin and connected to the output terminal of the control system 101 to receive PWM signals.

[0093] The Q terminal of the RS flip-flop 173 is used as the output terminal of the zero current detection circuit 170 and is connected to the input terminal of the anti-ringing unit 160.

[0094] Specifically, the output signal of comparator 171 and the duty cycle signal D are added to the S and R terminals of RS flip-flop 173, and the output signal EN_AR of RS flip-flop 173 is sent to the input terminal of anti-ringing unit 160.

[0095] In practical applications, the zero-current detection circuit 170 also includes a counting circuit 172.

[0096] The counting circuit 172 is located between the output of the comparator 171 and the S terminal of the RS flip-flop 173; the counting circuit 172 is also connected to the R terminal of the RS flip-flop 173.

[0097] Specifically, the first terminal of the counting circuit 172 is connected to the output terminal of the comparator 171, the second terminal of the counting circuit 172 is connected to the R terminal of the RS flip-flop 173, and the third terminal of the counting circuit 172 is connected to the S terminal of the RS flip-flop 173.

[0098] The counting circuit 172 is equipped with a preset trigger count value. That is, when the count value of the counting circuit 172 reaches the preset trigger count value, the counting circuit 172 outputs a signal to the RS flip-flop 173.

[0099] Specifically, the pre-designed value can be greater than or equal to 2; of course, it is also possible that the pre-designed count value is 1. No specific limitation is made here, and it can be determined according to the actual situation. All of these are within the protection scope of this application.

[0100] In this embodiment, after adding the counting circuit 172, the zero current detection circuit 170 can suppress false triggering caused by abnormal current in inductor L1, that is, it has the function of preventing false entry.

[0101] In any of the above embodiments, see Figure 8 The anti-ringing unit 160 includes: a switching unit (including N7 and N8 as shown in 7) and a drive unit (including M1 and M2 as shown in 7).

[0102] The input terminal of the drive unit is connected to the output terminal of the zero-current detection circuit 170 as the input terminal of the anti-ringing unit 160. The output terminal of the drive unit is connected to the control terminal of the switch unit to control the on / off state of the switch unit; the first terminal of the switch unit and one end of the inductor L1 are both connected to analog ground; the second terminal of the switch unit and the other end of the inductor L1 are both connected to the switch node SW.

[0103] The switching unit includes two switching transistors connected in series with a common input terminal.

[0104] Specifically, the output terminal of the first switch N7 serves as the first terminal of the switching unit and is connected to the switching node SW; the input terminal of the first switch N7 is connected to the input terminal of the second switch N8; the output terminal of the second switch N8 serves as the second terminal of the switching unit and is connected to analog ground. The first switch N7 is a high-voltage transistor, and the second switch N8 is a low-voltage transistor.

[0105] Each switching transistor in the switching unit can be a power transistor with its own anti-parallel diode, such as a MOSFET; or, each switching transistor in the switching unit can be a power transistor without an anti-parallel diode, such as a transistor.

[0106] When the switching transistors in the switching unit are power transistors without anti-parallel diodes, the switching unit also includes: two diodes; each diode corresponds one-to-one with one of the two power transistors, and each diode is connected in parallel with its corresponding power transistor, with the diodes in opposite directions. Specifically, the anode of the diode is connected to the output terminal of the power transistor, and the cathode of the diode is connected to the input terminal of the power transistor.

[0107] In practical applications, there are various forms of connection structure between the two switching transistors in this switching unit. Examples of two forms are given below.

[0108] (1) As Figure 9 As shown, the output terminal of the first switch N7 serves as the first terminal of the switching unit and is connected to the switching node SW; the control terminal of the first switch N7 is connected to its own output terminal; the output terminal of the second switch N8 serves as the second terminal of the switching unit and is connected to the analog ground; the control terminal of the second switch N8 serves as the control terminal of the switching unit and is connected to the output terminal of the drive unit.

[0109] (2) Figure 8 As shown, the anti-ringing unit 160 further includes: a level conversion circuit 161; the output terminal of the first switch transistor N7 serves as the first terminal of the switching unit and is connected to the switch node SW; the output terminal of the second switch transistor N8 serves as the second terminal of the switching unit and is connected to analog ground; the control terminal of the first switch transistor N7 is connected to the control terminal of the second switch transistor N8 through the level conversion circuit 161, and the connection point serves as the control terminal of the switching unit. Specifically, the control terminal of the first switch transistor N7 is connected to one end of the level conversion circuit 161, and the other end of the level conversion circuit 161 is connected to the control terminal of the second switch transistor N8, which serves as the control terminal of the switching unit and is connected to the output terminal of the drive unit.

[0110] It should be noted that both schemes (1) and (2) can achieve the anti-ringing effect, but scheme (1) is better, so scheme (1) is preferred.

[0111] The zero-current detection circuit 170 outputs a high-level signal when it detects that the switching node voltage exceeds the output voltage. When a counting circuit 172 is provided, the zero-current detection circuit 170 outputs a high signal when it detects that the switching node voltage exceeds the output voltage for N consecutive cycles, where N ≥ 2. This high-level output signal, together with the duty cycle signal D, enters the S and R terminals of the RS flip-flop 173. The RS flip-flop 173 outputs the EN_AR signal, which enters the anti-ringing unit 160. After the anti-ringing circuit 109 detects that the EN_AR signal is high, it controls both the first switch N7 and the second switch N8 to close. The first switch N7 can have its gate voltage withstand range guaranteed by the level conversion circuit 161. After the first switch N7 and the second switch N8 are closed, the switching node voltage is pulled up to the GND voltage, eliminating the ringing phenomenon caused by the inductor L1 current and the SW voltage.

[0112] Another embodiment of the present invention also provides a reverse buck-boost switching power supply 100, see [link to relevant documentation]. Figure 6 It includes: a control system 101, a drive circuit 108, an output capacitor COUT, an inductor L1, an anti-ringing circuit 109 as provided in any of the above embodiments, and two switching transistors (such as...). Figure 6 (N1 and N2 shown).

[0113] One end of the two switching transistors connected in series serves as the input terminal of the reverse buck-boost switching power supply 100; the other end of the two switching transistors connected in series is connected to one end of the output capacitor COUT, and the connection point serves as the output terminal of the reverse buck-boost switching power supply 100. The other end of the output capacitor COUT is grounded. The connection point between the two switching transistors serves as the switching node SW.

[0114] One end of inductor LI is connected to the switching node SW, and the other end of inductor LI is connected to analog ground.

[0115] To distinguish the switching transistors in the anti-ringing circuit 109, the two switching transistors connected between the output and input terminals of the reverse buck-boost switching power supply 100 are named the third switching transistor N1 and the fourth switching transistor N2. Specifically, the input terminal of the third switching transistor N1 serves as the input terminal of the reverse buck-boost switching power supply 100; the output terminal of the third switching transistor N1 is connected to the input terminal of the fourth switching transistor N2; the output terminal of the fourth switching transistor N2 is connected to one end of the output capacitor COUT, and the connection point serves as the output terminal of the reverse buck-boost switching power supply 100.

[0116] The control system 101 is used to control the on / off state of each switching transistor via the drive circuit 108. Specifically, the output terminal of the control system 101 is connected to the input terminal of the drive circuit 108. The control system 101 outputs a control signal to the drive circuit 108, and the output terminal of the drive circuit 108 is connected to the control terminals of the third switching transistor N1 and the fourth switching transistor N2, so that the drive circuit 108 controls the on / off state of the third switching transistor N1 and the fourth switching transistor N2 according to the control signal.

[0117] The control signal can be a PWM signal, which causes the two switching transistors to periodically turn on and off, raising or lowering the input voltage VIN to become the output voltage.

[0118] In practical applications, the control system 101 includes: a feedback network 102, an error amplifier 103, a PWM comparator 104, an oscillator 105, an RS flip-flop 106, and a filter circuit (including, etc.) Figure 6 R1 and C1 are shown, and driver 107.

[0119] The inverting input of error amplifier 103 is connected to the output of reverse buck-boost switching power supply 100 through feedback network 102; the non-inverting input of error amplifier 103 is used to receive the reference voltage signal; the output of error amplifier 103 is connected to the inverting input of PWM comparator 104 and one end of the filter circuit, respectively; the non-inverting input of PWM comparator 104 is used to receive the ramp signal; the output of PWM comparator 104 is connected to the R terminal of RS flip-flop 106; the S terminal of RS flip-flop 106 is connected to the output of oscillator 105; the Q terminal of RS flip-flop 106 is connected to the input of driver 107; the output of driver 107 serves as the output of control system 101; the other end of the filter circuit is grounded.

[0120] Specifically, the feedback network 102 divides the output voltage VOUT into a feedback voltage VFB. This feedback voltage VFB, together with the reference voltage signal VREF, is connected to the input terminal of the error amplifier 103. The EA_OUT signal output by the error amplifier 103 and the ramp signal RAMP are input to both ends of the PWM comparator 104. The output terminal of the PWM comparator 104 is connected to the R terminal of the RS flip-flop 106, and the output terminal of the oscillator 105 is connected to the S terminal of the RS flip-flop 106. That is, the PWM comparator 104 and the oscillator 105 together determine the output of the flip-flop 106, namely the duty cycle signal D. The duty cycle signal D is connected to the control terminals of the third switch N1 and the fourth switch N2 after passing through the driver 107 and the drive circuit 108, thereby realizing closed-loop feedback control of the switching time of the switching transistors, and thus realizing the control of the current of the inductor L1.

[0121] The filtering circuit includes a filter resistor R1 and a filter capacitor C1 connected in series. Specifically, one end of the filter resistor R1 is connected to the output terminal of the error amplifier 103 and the inverting input terminal of the PWM comparator 104; the other end of the filter resistor R1 is connected to one end of the filter capacitor C1; and the other end of the filter capacitor C1 is grounded. Of course, it is not excluded that the positions of the filter capacitor C1 and the filter resistor R1 can be interchanged, which will not be elaborated here, and all are within the protection scope of this application.

[0122] It should be noted that, Figure 10 The waveforms show some control and switching signals of a typical reverse buck-boost switching power supply. Waveform 150 shows the duty cycle signal D, waveform 151 shows the switching node voltage, and waveform 152 shows the inductor LI current. During the high period of duty cycle signal D, the third switch N1 is on, and the second switch N8 is off. The switching node voltage is pulled up to near the input voltage VIN, and the current IL of inductor LI rises linearly. During the low period of duty cycle signal D, the third switch N1 is off, and the fourth switch N2 is on. The current of inductor LI begins to decrease linearly, and the switching node voltage is pulled down to near the output voltage VOUT. Since the direction of the inductor LI current cannot change abruptly, when the current drops below 0mA, because both the third and fourth switches N1 and N2 are off, the switching node voltage self-discharges through a self-resonant circuit formed by inductor LI and parasitic capacitance, and the switching node voltage begins to oscillate.

[0123] In this implementation, an anti-ringing circuit 109 is added, the specific timing diagram of which is as follows: Figure 11 As shown, when the current drops below 0mA, the anti-ringing circuit 109 operates to pull the switching node voltage up to the GND voltage, thereby eliminating the ringing phenomenon caused by the inductor L1 current and the switching node voltage.

[0124] The features described in the various embodiments of this specification can be substituted for or combined with each other. Similar or identical parts between embodiments can be referred to mutually. Each embodiment focuses on describing the differences from other embodiments. In particular, for system or system embodiments, since they are basically similar to method embodiments, the description is relatively simple; relevant parts can be referred to the descriptions in the method embodiments. The systems and system embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs. Those skilled in the art can understand and implement this without creative effort.

[0125] Those skilled in the art will further recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of both. To clearly illustrate the interchangeability of hardware and software, the components and steps of the various examples have been generally described in terms of functionality in the foregoing description. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementations should not be considered beyond the scope of this invention.

[0126] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. An anti-ringing circuit for a reverse buck-boost switching power supply, characterized in that, include: Anti-ringing unit and zero-current detection circuit; The zero-current detection circuit is used to detect the inductor current in the reverse buck-boost switching power supply based on the switching node voltage and output voltage of the reverse buck-boost switching power supply, as well as a control signal; wherein, the control signal is a signal used to control the on / off state of the switching transistor in the reverse buck-boost switching power supply. The anti-ringing unit is used to perform an action based on the detection result, so as to short-circuit the inductor in the reverse buck-boost switching power supply when the inductor current is less than or equal to zero.

2. The anti-ringing circuit of the reverse buck-boost switching power supply according to claim 1, characterized in that, The zero-current detection circuit is used to detect the inductor current in the reverse buck-boost switching power supply based on the switching node voltage and output voltage of the power supply, as well as the control signal. Specifically, it is used for: The voltage at the switching node and the output voltage are compared to obtain a comparison result; The comparison result is compared with the control signal by performing a logical operation according to preset rules to obtain the detection result.

3. The anti-ringing circuit of the reverse buck-boost switching power supply according to claim 2, characterized in that, The preset rule is a comparison result priority rule.

4. The anti-ringing circuit of the reverse buck-boost switching power supply according to claim 1, characterized in that, The control signal is a pulse width modulation (PWM) signal.

5. The anti-ringing circuit of the reverse buck-boost switching power supply according to claim 4, characterized in that, The zero-current detection circuit includes: a comparator and an RS flip-flop; The non-inverting input of the comparator is used to receive the voltage of the switching node; The inverting input of the comparator is used to receive the output voltage; The output of the comparator is directly or indirectly connected to the S terminal of the RS flip-flop. The R terminal of the RS flip-flop is used to receive the PWM signal; The Q terminal of the RS flip-flop serves as the output terminal of the zero-current detection circuit.

6. The anti-ringing circuit of the reverse buck-boost switching power supply according to claim 5, characterized in that, The zero-current detection circuit further includes: a counting circuit; One input terminal of the counting circuit is connected to the output terminal of the comparator; Another input terminal of the counting circuit is used to receive the control signal; The output terminal of the counting circuit is connected to the S terminal of the RS flip-flop; The counting circuit is equipped with a preset trigger count value.

7. The anti-ringing circuit of the reverse buck-boost switching power supply according to claim 6, characterized in that, The pre-designed value is greater than or equal to 2.

8. The anti-ringing circuit of the reverse buck-boost switching power supply according to any one of claims 1-7, characterized in that, The anti-ringing unit includes: a switching unit and a driving unit; The input terminal of the drive unit serves as the input terminal of the anti-ringing unit; The output terminal of the drive unit is connected to the control terminal of the switch unit. The first end of the switching unit and one end of the inductor are both connected to analog ground; The second end of the switching unit and the other end of the inductor are both connected to the switching node.

9. The anti-ringing circuit of the reverse buck-boost switching power supply according to claim 8, characterized in that, The switching unit includes two switching transistors connected in series with a common input terminal; wherein the input terminal of the switching transistor is the end from which current flows when the switching transistor is turned on.

10. The anti-ringing circuit of the reverse buck-boost switching power supply according to claim 9, characterized in that, Each of the switching transistors in the switching unit is a power transistor with a built-in anti-parallel diode; or, When each of the switching transistors in the switching unit is a power transistor without an anti-parallel diode, the switching unit further includes: two diodes; the two diodes correspond one-to-one with the two power transistors, each diode is connected in parallel with the corresponding power transistor, and the direction of the diodes is opposite to that of the corresponding power transistors.

11. The anti-ringing circuit of the reverse buck-boost switching power supply according to claim 9, characterized in that, In the switching unit, the output terminal of the first switching transistor serves as the first terminal of the switching unit, and the control terminal of the first switching transistor is connected to its own output terminal. The output terminal of the second switching transistor serves as the second terminal of the switching unit. The control terminal of the second switching transistor serves as the control terminal of the switching unit.

12. The anti-ringing circuit of the reverse buck-boost switching power supply according to claim 9, characterized in that, The anti-ringing unit further includes: a level conversion circuit; in the switching unit, the output terminal of the first switching transistor serves as the first terminal of the switching unit, and the output terminal of the second switching transistor serves as the second terminal of the switching unit; The control terminal of the first switching transistor is connected to the control terminal of the second switching transistor through the level conversion circuit, and the connection point serves as the control terminal of the switching unit.

13. The anti-ringing circuit of the reverse buck-boost switching power supply according to claim 8, characterized in that, The drive unit includes two stages of inverters.

14. A reverse buck-boost switching power supply, characterized in that, include: The control system, the drive circuit, the output capacitor, the anti-ringing circuit as described in any one of claims 1-13, and two switching transistors; One end of the two switching transistors connected in series serves as the input terminal of the reverse buck-boost switching power supply. The other end of the two switching transistors connected in series is connected to one end of the output capacitor, and the connection point serves as the output terminal of the reverse buck-boost switching power supply. The other end of the output capacitor is grounded. The control system is used to control the on / off state of each of the switching transistors through the drive circuit.

15. The reverse buck-boost switching power supply according to claim 14, characterized in that, The control system includes: a feedback network, an error amplifier, a PWM comparator, an oscillator, an RS flip-flop, a filter circuit, and a driver; wherein: The inverting input of the error amplifier is connected to the output of the reverse buck-boost switching power supply through the feedback network; The non-inverting input of the error amplifier is used to receive a reference voltage signal; The output terminal of the error amplifier is connected to the inverting input terminal of the PWM comparator and one end of the filter circuit, respectively. The non-inverting input of the PWM comparator is used to receive the ramp signal; The output terminal of the PWM comparator is connected to the R terminal of the RS flip-flop; The S terminal of the RS flip-flop is connected to the output terminal of the oscillator; The Q terminal of the RS flip-flop is connected to the input terminal of the driver; The output terminal of the driver serves as the output terminal of the control system. The other end of the filter circuit is grounded.

16. The reverse buck-boost switching power supply according to claim 15, characterized in that, The filtering circuit includes a filter resistor and a filter capacitor connected in series.

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