Buck-boost switching power supply circuit with bypass mode and control method thereof

Abstract

A buck-boost switching power supply circuit with a bypass mode and a control method thereof. The buck-boost switching power supply circuit comprises: a power switch circuit including an input switch unit and an output switch unit for switching two terminals of an inductor to perform buck-boost conversion; at least one low-dropout voltage regulator coupled to at least one output upper bridge switch of the output switch unit to convert at least one low-dropout voltage into at least one output voltage; and a bypass control circuit for generating a bypass control signal based on a conversion voltage difference between an input voltage and a corresponding low-dropout voltage; wherein the bypass control signal controls the corresponding bypass switch to electrically connect the input voltage to the corresponding low-dropout node when the corresponding conversion voltage difference is lower than a reference voltage.

Description

Technical Field

[0001] The present invention relates to a buck-boost switching power supply circuit, and more particularly to a buck-boost switching power supply circuit with a bypass mode. The present invention also relates to a control method for the buck-boost switching power supply circuit. Background Art

[0002] Please refer to FIG1 , which shows a known single-input multiple-output buck-boost switching power converter. The low-dropout voltages VINLDO[1], VINLDO[2], and VINLDO[3] of this known single-input multiple-output buck-boost switching power converter are converted into output voltages VOUT[1], VOUT[2], and VOUT[3] respectively through corresponding low-dropout voltage regulators. When the input voltage VIN is close to the low-dropout voltages VINLDO[1], VINLDO[2], and VINLDO[3], the switching loss of the single-input multiple-output buck-boost switching power converter is relatively increased, thereby resulting in a low overall power conversion efficiency.

[0003] In view of this, the present invention addresses the above-mentioned deficiencies in the prior art and proposes a buck-boost switching power supply circuit that can reduce switching losses in a bypass mode to improve efficiency when the input voltage is close to the low dropout voltage. Summary of the Invention

[0004] In one aspect, the present invention provides a buck-boost switching power supply circuit for converting an input voltage into at least one output voltage, comprising: a power switch circuit including an input switch unit and an output switch unit, wherein the input switch unit is used to switch a first end of an inductor between the input voltage and a ground potential, and the output switch unit is used to switch a second end of the inductor between at least one low voltage difference node and the ground potential, so as to convert the input voltage at the at least one low voltage difference node into at least one corresponding low voltage difference voltage, and the at least one low voltage difference node is correspondingly coupled to at least one output upper bridge switch in the output switch unit; at least one low voltage difference regulator (low voltage difference regulator) The invention also provides a first embodiment of the present invention, comprising a first dropout regulator (LDO) coupled to the at least one output high-side switch to convert the at least one low dropout voltage into the at least one output voltage; a bypass control circuit for generating a bypass control signal according to a conversion voltage difference between the input voltage and the corresponding low dropout voltage; and a bypass switching circuit, wherein the bypass control signal controls the bypass switching circuit to electrically connect the input voltage to the corresponding low dropout node when the corresponding conversion voltage difference is lower than a reference voltage, so that the buck-boost switching power supply circuit operates in a bypass mode.

[0005] In one embodiment, the bypass switching circuit includes the corresponding output high-side switch and an input high-side switch in the input switch unit. When the corresponding conversion voltage difference is lower than the reference voltage, the bypass control circuit generates the corresponding bypass control signal to control the corresponding output high-side switch and the corresponding input high-side switch to be conductive, so as to electrically connect the input voltage to the corresponding low-voltage difference node via the inductor.

[0006] In one embodiment, the bypass switching circuit includes at least one bypass switch, which is directly electrically connected between the input voltage and the corresponding low voltage difference node, so that when the corresponding conversion voltage difference is lower than the reference voltage, the corresponding bypass switch is controlled to be turned on to directly electrically connect the input voltage to the corresponding low voltage difference node.

[0007] In one embodiment, the conversion voltage difference is the absolute value of the difference between the input voltage and the corresponding low dropout voltage.

[0008] In one embodiment, the reference voltage includes a first reference voltage and a second reference voltage, wherein when the difference of the corresponding low-dropout voltage minus the input voltage is lower than the first reference voltage, and the difference of the input voltage minus the corresponding low-dropout voltage is lower than the second reference voltage, the corresponding bypass control signal is enabled, wherein the first reference voltage and the second reference voltage have one of the following relationships: (1) the first reference voltage is equal to the second reference voltage, and both the first reference voltage and the second reference voltage are not zero; (2) the first reference voltage is equal to zero, and the second reference voltage is not zero; (3) the second reference voltage is equal to zero, and the first reference voltage is not zero; or (4) the first reference voltage is not equal to the second reference voltage, and both the first reference voltage and the second reference voltage are not zero.

[0009] In one embodiment, the bypass control circuit includes: a threshold control circuit for generating an upper threshold and a lower threshold based on the reference voltage; and a comparison circuit for comparing a signal to be compared with the upper threshold and the lower threshold, and when the signal to be compared is between the upper threshold and the lower threshold, enabling the corresponding bypass control signal to electrically connect the input voltage to the corresponding low voltage difference node, wherein the signal to be compared, the upper threshold and the lower threshold have one of the following relationships: (1) the signal to be compared is the corresponding conversion voltage difference, the upper threshold is the first reference voltage, and the lower threshold is the second reference voltage; (2) the signal to be compared is the corresponding low voltage difference voltage, the upper threshold is the sum of the input voltage and the first reference voltage, and the lower threshold is the difference between the input voltage and the second reference voltage; (3) the signal to be compared is the input voltage, the upper threshold is the sum of the corresponding low voltage difference voltage and the second reference voltage, and the lower threshold is the difference between the corresponding low voltage difference voltage and the first reference voltage.

[0010] In one embodiment, the input switch unit includes: an input high-bridge switch coupled between the input voltage and the first end of the inductor; and an input low-bridge switch or an input low-bridge diode coupled between the ground potential and the first end of the inductor; wherein the input high-bridge switch and the input low-bridge switch or the input low-bridge diode are used to switch the first end of the inductor between the input voltage and the ground potential.

[0011] In one embodiment, the output switching unit includes: an output low-bridge switch coupled between the ground potential and the second end of the inductor; and at least one output high-bridge switch respectively coupled between the at least one low voltage difference node and the second end of the inductor; wherein the output low-bridge switch and the at least one output high-bridge switch are used to switch the second end of the inductor between the at least one low voltage difference node and the ground potential, thereby generating the corresponding at least one low voltage difference voltage at the at least one low voltage difference node.

[0012] In one embodiment, the buck-boost switching power supply circuit operates in a buck mode and a boost mode according to the input voltage and the corresponding low dropout voltage when the corresponding conversion voltage difference is not lower than the reference voltage.

[0013] In one embodiment, the buck-boost switching power supply circuit operates in the boost mode when the difference between the corresponding low voltage dropout voltage and the input voltage is not lower than the first reference voltage, and operates in the buck mode when the difference between the input voltage and the corresponding low voltage dropout voltage is not lower than the second reference voltage.

[0014] In one embodiment, the buck-boost switching power supply circuit further operates in a buck-boost mode according to the input voltage and the corresponding low-dropout voltage when the corresponding converted voltage difference is not lower than the reference voltage.

[0015] In one embodiment, the conversion voltage difference is operated in a corresponding mode from large to small according to one of the following orders: (1) the boost mode, the buck-boost mode, the bypass mode, and the buck mode; (2) the boost mode, the bypass mode, the buck-boost mode, and the buck mode; (3) the boost mode, the buck-boost mode, the bypass mode, the buck-boost mode, and the buck mode.

[0016] In one embodiment, at least one of the low-dropout voltage regulators is a negative voltage generating circuit, wherein the negative voltage generating circuit includes: a negative charge pump coupled to the corresponding low-dropout voltage node, for converting the corresponding low-dropout voltage into a negative low-dropout voltage; and at least one negative low-dropout voltage regulator coupled to the negative charge pump, for converting the negative low-dropout voltage into at least one corresponding negative output voltage.

[0017] In another aspect, the present invention provides a control method for controlling a buck-boost switching power supply circuit, for converting an input voltage into at least one output voltage, the buck-boost switching power supply circuit comprising a power switch circuit, the power switch circuit comprising an input switch unit and an output switch unit, wherein the input switch unit is used to switch a first end of an inductor between the input voltage and a ground potential, and the output switch unit is used to switch a second end of the inductor between at least one low voltage difference node and the ground potential, so as to convert the input voltage at the at least one low voltage difference node into a ground potential. The at least one low voltage difference voltage corresponds to the at least one low voltage difference node, and the at least one low voltage difference node is correspondingly coupled to the at least one output upper bridge switch in the output switch unit; the control method includes: using at least one low voltage difference regulator to convert the at least one low voltage difference voltage into the at least one output voltage; generating a bypass control signal according to a conversion voltage difference between the input voltage and the corresponding low voltage difference voltage; and when the corresponding conversion voltage difference is lower than a reference voltage, the bypass control signal controls the input voltage to be electrically connected to the corresponding low voltage difference node, so that the buck-boost switching power supply circuit operates in a bypass mode.

[0018] In one embodiment, when the corresponding conversion voltage difference is lower than the reference voltage, the bypass control signal controls the corresponding output high-bridge switch and the input high-bridge switch to be turned on, so as to electrically connect the input voltage and the corresponding low voltage difference node through the inductor.

[0019] In one embodiment, when the corresponding conversion voltage difference is lower than the reference voltage, the corresponding bypass switch in at least one bypass switch is controlled to be turned on to directly electrically connect the input voltage to the corresponding low voltage difference node, wherein the at least one bypass switch is directly electrically connected between the input voltage and the corresponding low voltage difference node.

[0020] In one embodiment, the conversion voltage difference is the absolute value of the difference between the input voltage and the corresponding low dropout voltage.

[0021] In one embodiment, the reference voltage includes a first reference voltage and a second reference voltage, wherein when the difference of the low dropout voltage minus the input voltage is lower than the first reference voltage, and the difference of the input voltage minus the low dropout voltage is lower than the second reference voltage, the corresponding bypass control signal is enabled, wherein the first reference voltage and the second reference voltage have one of the following relationships: (1) the first reference voltage is equal to the second reference voltage, and both the first reference voltage and the second reference voltage are not zero; (2) the first reference voltage is equal to zero, and the second reference voltage is not zero; (3) the second reference voltage is equal to zero, and the first reference voltage is not zero; or (4) the first reference voltage is not equal to the second reference voltage, and both the first reference voltage and the second reference voltage are not zero.

[0022] In one embodiment, the step of generating the bypass control signal includes: generating an upper threshold value and a lower threshold value based on the reference voltage; and comparing a signal to be compared with the upper threshold value and the lower threshold value, and when the signal to be compared is between the upper threshold value and the lower threshold value, enabling the corresponding bypass control signal to electrically connect the input voltage to the corresponding low voltage difference node, wherein the signal to be compared, the upper threshold value and the lower threshold value have one of the following relationships: (1) the signal to be compared is the corresponding conversion voltage difference, the upper threshold value is the first reference voltage, and the lower threshold value is the second reference voltage; (2) the signal to be compared is the corresponding low voltage difference voltage, the upper threshold value is the sum of the input voltage and the first reference voltage, and the lower threshold value is the difference between the input voltage and the second reference voltage; (3) the signal to be compared is the input voltage, the upper threshold value is the sum of the corresponding low voltage difference voltage and the second reference voltage, and the lower threshold value is the difference between the corresponding low voltage difference voltage and the first reference voltage.

[0023] In one embodiment, the buck-boost switching power supply circuit operates in a buck mode and a boost mode according to the input voltage and the corresponding low dropout voltage when the corresponding conversion voltage difference is not lower than the reference voltage.

[0024] In one embodiment, when the difference between the corresponding low voltage difference voltage and the input voltage is not lower than the first reference voltage, the buck-boost switching power supply circuit is controlled to operate in the boost mode, and when the difference between the input voltage and the corresponding low voltage difference voltage is not lower than the second reference voltage, the buck-boost switching power supply circuit is controlled to operate in the buck mode.

[0025] In one embodiment, when the corresponding conversion voltage difference is not lower than the reference voltage, the step-up / down switching power supply circuit is further operated in a buck boost mode according to the input voltage and the corresponding low voltage dropout voltage.

[0026] In one embodiment, the conversion voltage difference decreases from large to small, and the buck-boost switching power supply circuit is operated in the corresponding mode according to one of the following orders: (1) the boost mode, the buck-boost mode, the bypass mode, and the buck mode; (2) the boost mode, the bypass mode, the buck-boost mode, and the buck mode; (3) the boost mode, the buck-boost mode, the bypass mode, the buck-boost mode, and the buck mode.

[0027] In one embodiment, the control method of the present invention for controlling a buck-boost switching power supply circuit further includes: converting the corresponding low dropout voltage into a negative low dropout voltage; and converting the negative low dropout voltage into the corresponding at least one negative output voltage.

[0028] An advantage of the present invention is that the present invention can achieve higher efficiency and lower switching loss when the input voltage is close to the low dropout voltage.

[0029] Another advantage of the present invention is that the input voltage is directly bypassed to the input terminal of the low-dropout regulator, thereby increasing the voltage drop space of the low-dropout regulator.

[0030] Another advantage of the present invention is that the present invention can save the layout area of ​​the bypass switch.

[0031] The following detailed description through specific embodiments will make it easier to understand the purpose, technical content, characteristics and effects achieved by the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] FIG. 1 is a schematic diagram showing a conventional single-input multiple-output buck-boost switching power converter.

[0033] Figure 2 FIG. 1 is a circuit diagram showing a buck-boost switching power supply circuit according to an embodiment of the present invention.

[0034] Figure 3A FIG. 4 is a circuit diagram showing a buck-boost switching power supply circuit according to another embodiment of the present invention.

[0035] Figure 3B The diagram is a comparison table showing signals in a bypass control circuit of a buck-boost switching power supply circuit according to an embodiment of the present invention.

[0036] Figure 3C FIG. 4 is a circuit diagram showing a buck-boost switching power supply circuit according to yet another embodiment of the present invention.

[0037] Figure 3D According to an embodiment of the present invention, Figure 3A and Figure 3C A circuit diagram of another embodiment of a bypass control circuit of a buck-boost switching power supply circuit.

[0038] Figure 4 FIG. 1 is a characteristic diagram showing an operating mode of a buck-boost switching power supply circuit according to an embodiment of the present invention.

[0039] Figure 5 Yes Display Figure 3A Schematic diagram of the signal waveform of the circuit.

[0040] Figure 6 FIG. 4 is a circuit diagram showing a buck-boost switching power supply circuit according to another embodiment of the present invention.

[0041] Figure 7 FIG. 4 is a circuit diagram showing a buck-boost switching power supply circuit according to yet another embodiment of the present invention.

[0042] Figure 8 FIG. 4 is a circuit diagram showing a buck-boost switching power supply circuit according to another embodiment of the present invention.

[0043] Figure 9 FIG. 4 is a circuit diagram showing a buck-boost switching power supply circuit according to yet another embodiment of the present invention.

[0044] Figure 10 FIG. 4 is a circuit diagram showing a buck-boost switching power supply circuit according to another embodiment of the present invention.

[0045] Figure 11 FIG. 4 is a circuit diagram showing a buck-boost switching power supply circuit according to yet another embodiment of the present invention.

[0046] Figure 12A FIG. 1 is a characteristic diagram showing an operating mode of a buck-boost switching power supply circuit according to an embodiment of the present invention.

[0047] Figure 12B FIG. 1 is a characteristic diagram showing an operating mode of a buck-boost switching power supply circuit according to another embodiment of the present invention.

[0048] Figure 12CFIG. 1 is a characteristic diagram showing an operating mode of a buck-boost switching power supply circuit according to another embodiment of the present invention.

[0049] Figure 13 According to an embodiment of the present invention, Figure 3C The circuit is Figure 12A Schematic diagram of signal waveform when operating in the operating mode.

[0050] Figure 14 A control method of a buck-boost switching power supply circuit is shown according to yet another embodiment of the present invention.

[0051] Figure 15 A control method of a buck-boost switching power supply circuit is shown according to another embodiment of the present invention.

[0052] Explanation of symbols in the figure

[0053] 10, 20, 30, 40, 50, 60, 70, 80, 90: Buck-boost switching power supply circuit 100: Control method of buck-boost switching power supply circuit

[0054] 101, 201, 301, 401, 501, 601, 701, 801, 901: power switch circuit 1001, 10011, 10012, 1002, 1003, 10031a, 10031b: steps 1011, 2011, 3011, 4011, 5011, 6011, 7011, 8011, 9011: input switch unit

[0055] 1012, 2012, 3012, 4012, 5012, 6012, 7012, 8012, 9012: Output switch unit

[0056] 102[1:n], 202[1]~202[n], 302[1]~302[n], 402[1], 402[2], 502[1], 502[2], 602[1], 602[2], 702, 902[1]: Low-dropout voltage regulator

[0057] 103, 203, 203', 303, 403, 503, 603, 703, 803, 903: Bypass control circuit

[0058] 104[1:n], 204[1:n], 304[1:n], 404[1:n], 504[1:n], 604[1:n], 704, 804, 904: low voltage dropout nodes

[0059] 2031[k], 3031[k]: Threshold control circuit

[0060] 2032[k], 2032'a[k], 2032'b[k], 3032[k]: Comparison circuit

[0061] 2033a[k], 2033b[k], 3033a[k], 3033b[k]: switch

[0062] 2034'[k]:NAND gate

[0063] 305, 405, 505, 605, 705, 805, 905: conversion control circuit

[0064] 402[n], 502[n-x+1], 502[n], 602[n], 802, 902[2]: Negative voltage generating circuit

[0065] 406, 506[1]~506[x], 606, 806, 906: Negative charge pump

[0066] 407, 507[1]~507[x], 607[1]~607[x], 807, 907: Negative low dropout regulators

[0067] 408, 508, 608, 708, 808, 908: Bypass switching circuit

[0068] A: Input upper bridge switch

[0069] B: Input lower bridge switch

[0070] C: Output lower bridge switch

[0071] CPOL[k], CPOU[k]: comparison results

[0072] Cs1[k], Cs2[k]: control signals

[0073] D[1:n], D[1]~D[n]: output upper bridge switch

[0074] E[1:n], E[1]~E[n]: Bypass switch

[0075] L: Inductance

[0076] LX1: First End

[0077] LX2: Second end

[0078] NVINLDO, NVINLDO[1]~NVINLDO[x]: negative low dropout voltage

[0079] NVOUT, NVOUT[1]~NVOUT[x]: negative output voltage

[0080] VA, VB, VC, VD[1:n]: control signals

[0081] VE[1:n], VE[k], VE[1], VE[2] to VE[n]: bypass control signals

[0082] VIN: input voltage

[0083] VIN_S: input voltage sensing signal

[0084] VINLDO, VINLDO[1:n], VINLDO[1], VINLDO[2], VINLDO[3], VINLDO[n-x+1], VINLDO[n]: Low dropout voltage

[0085] VINLDO[1:n]_S, VINLDO[k]_S: low dropout voltage sensing signal

[0086] Vref1: first reference voltage

[0087] Vref2: second reference voltage

[0088] VTC, VTC[k]: signals to be compared

[0089] VthL, VthL[k]: lower threshold

[0090] VthM1: First intermediate threshold

[0091] VthM2: Second intermediate threshold

[0092] VthU, VthU[k]: upper threshold

[0093] VOUT[1:n], VOUT[1], VOUT[2], VOUT[3]: output voltage DETAILED DESCRIPTION

[0094] The drawings in the present invention are schematic diagrams, mainly intended to illustrate the coupling relationship between various circuits and the relationship between various signal waveforms. The circuits, signal waveforms and frequencies are not drawn according to scale.

[0095] Figure 2 FIG2 is a circuit diagram illustrating a buck-boost switching power supply circuit according to an embodiment of the present invention. The buck-boost switching power supply circuit 10 of the present invention includes a power switch circuit 101, a low-dropout voltage regulator 102[1:n], a bypass switching circuit 105, and a bypass control circuit 103. Where n is a positive integer greater than or equal to 1.

[0096] The power switch circuit 101 includes an input switch unit 1011 and an output switch unit 1012. The input switch unit 1011 is used to switch the first end of the inductor L (such as Figure 2 LX1 shown in Figure 2 ) between the input voltage VIN and the ground potential. The output switch unit 1012 is used to switch the second end of the inductor L (such as

[0097] LX2 shown in Figure 2 ) between the low dropout nodes 104[1:n] and the ground potential. The low dropout nodes 104[1:n] respectively have corresponding low dropout voltages VINLDO[1:n]. From one perspective, the power switch circuit 101 and the inductor L together form a buck-boost switching power supply circuit for converting the input voltage VIN into the low dropout voltages VINLDO[1:n], where the input voltage VIN can be greater than, equal to, or less than the low dropout voltages VINLDO[1:n].

[0098] Please continue to refer to Figure 4 . Figure 4 FIG.

[0099] shows an operating mode characteristic diagram of the buck-boost switching power supply circuit according to an embodiment of the present invention. In one embodiment, the buck-boost switching power supply circuit of the present invention can operate in a bypass mode. The buck-boost switching power supply circuit of the present invention operates in the bypass mode when the conversion voltage difference is lower than the reference voltage. Figure 4 Taking

[0100] as an example, the above reference voltage may include a first reference voltage Vref1 and a second reference voltage Vref2. In this embodiment, when VINLDO - VIN < Vref1 and VIN - VINLDO < Vref2, it operates in the bypass mode. Figure 2 In one embodiment, as Figure 2 As shown, the bypass switching circuit 105 includes bypass switches E[1:n]. When the corresponding conversion voltage difference is lower than the reference voltage, the bypass control signal VE[1:n] controls the corresponding bypass switches E[1:n] to electrically connect the input voltage VIN to the corresponding low voltage difference node 104[1:n]. Figure 2 In the illustrated embodiment, the bypass switches E[1:n] are directly electrically connected between the input voltage VIN and the corresponding low-dropout voltage node 104[1:n]. When the corresponding converted voltage difference is lower than the reference voltage, the corresponding bypass switch E[1:n] is controlled to directly electrically connect the input voltage VIN to the corresponding low-dropout voltage node 104[1:n]. In one embodiment, the converted voltage difference is the absolute value of the difference between the input voltage VIN and the corresponding low-dropout voltage VINLDO[1:n].

[0101] Figure 3A FIG1 is a circuit diagram showing a buck-boost switching power supply circuit with a single input and at least one output according to another embodiment of the present invention. In this embodiment, the inductor L, the power switch circuit 201, the low-dropout regulator 202[1:n], and the bypass switch E[1:n] are similar to Figure 2 The inductor L, power switch circuit 101, low voltage dropout regulator 102[1:n], bypass switch E[1:n], and their description are omitted. Figure 3A As shown, the input switch unit 2011 includes an input high-bridge switch A and an input low-bridge switch B (or, in one embodiment, an input low-bridge diode). The input high-bridge switch A is coupled between the input voltage VIN and the first terminal LX1 of the inductor L, while the input low-bridge switch B is coupled between the ground potential and the first terminal LX1 of the inductor L. Control signals VA and VB are used to control the input high-bridge switch A, or the input high-bridge switch A and the input low-bridge switch B, to switch the first terminal LX1 of the inductor L between the input voltage VIN and the ground potential. The output switch unit 2012 includes an output low-bridge switch C and at least one output high-bridge switch D[1:n]. The output low-bridge switch C is coupled between the ground potential and the second terminal LX2 of the inductor L, while the output high-bridge switches D[1:n] are respectively coupled between the low-dropout voltage VINLDO[1:n] and the second terminal LX2 of the inductor L. Control signals VC and VD[1:n] are used to control the output low-side switch C and the output high-side switch D[1:n] to switch the second end LX2 of the inductor L to the corresponding low-dropout voltage VINLDO[1:n] and the ground potential, thereby converting the input voltage VIN to the corresponding low-dropout voltage VINLDO[1:n]. The low-dropout node 204[1:n] is coupled to the output high-side switch D[1:n] in the output switch unit 2012. Where n is a positive integer greater than or equal to 1.

[0102] like Figure 3A As shown, the bypass control circuit 203 includes a threshold control circuit 2031[k] and a comparison circuit 2032[k]. The threshold control circuit 2031[k] is used to generate an upper threshold value VthU[k] and a lower threshold value VthL[k] according to a reference voltage, as well as a plurality of control signals Cs1[k] and Cs2[k]. The plurality of control signals Cs1[k] and Cs2[k] are used to control switches 2033a[k] ​​and 2033b[k], respectively, so that the lower threshold value VthL[k] and the upper threshold value VthU[k] are input to the comparison circuit 2032[k]. The comparison circuit 2032[k] is used to compare a comparison signal VTC[k] with the upper threshold value VthU[k] and the lower threshold value VthL[k]. When the comparison signal VTC[k] is between the upper threshold value VthU[k] and the lower threshold value VthL[k], the bypass control signal VE[k] is enabled, and the bypass switch E[k] is turned on to enter the bypass mode, so as to electrically connect the input voltage VIN to the corresponding low voltage difference node 204[k]. It should be noted that Figure 3A In the embodiment shown, in the embodiment where n is greater than 1, only one or more of the n channels may enter the bypass mode, while the other channels still maintain the normal operation mode such as the boost mode or the buck mode. It should be noted that the aforementioned sequence number k is any one of 1 to n. In addition, it should be noted that the bypass control circuit 203 of the buck-boost switching power supply circuit 20 of the present invention is not limited to Figure 3A The architecture shown, any other feasible architecture can also be used, Figure 3A The illustrated architecture is only used to illustrate the present invention and is not intended to limit the scope of the present invention.

[0103] Figure 3BThis is a comparison table of signals in the bypass control circuit of a buck-boost switching power supply circuit according to an embodiment of the present invention, which lists embodiments of the comparison signal VTC[k], the upper threshold value VthU[k] and the lower threshold value VthL[k]. In one embodiment, the comparison signal VTC[k], the upper threshold value VthU[k], and the lower threshold value VthL[k] have one of the following relationships: (1) the comparison signal VTC[k] is the conversion voltage difference VINLDO[k]-VIN, the upper threshold value VthU[k] is the first reference voltage Vref1, and the lower threshold value VthL[k] is the second reference voltage Vref2; (2) the comparison signal VTC[k] is the low voltage difference voltage VINLDO[k], the upper threshold value VthU[k] is the sum of the input voltage VIN and the first reference voltage Vref1, and the lower threshold value VthL[k] is the difference between the input voltage VIN and the second reference voltage Vref2; (3) the comparison signal VTC[k] is the input voltage VIN, the upper threshold value VthU[k] is the sum of the low voltage difference voltage VINLDO[k] and the second reference voltage Vref2, and the lower threshold value VthL[k] is the difference between the low voltage difference voltage VINLDO[k] and the first reference voltage Vref1.

[0104] Specifically, in one embodiment, when the compared signal VTC[k] is the input voltage sensing signal VIN_S, the upper threshold VthU[k] is the value obtained by adding the second reference voltage Vref2 to the low dropout voltage sensing signal VINLDO[k]_S, and the lower threshold VthL[k] is the value obtained by subtracting the first reference voltage Vref1 from the low dropout voltage sensing signal VINLDO[k]_S. In another embodiment, when the compared signal VTC[k] is the low dropout voltage sensing signal VINLDO[k]_S, the upper threshold VthU[k] is the value obtained by adding the first reference voltage Vref1 to the input voltage sensing signal VIN_S, and the lower threshold VthL[k] is the value obtained by subtracting the second reference voltage Vref2 from the input voltage sensing signal VIN_S. In another embodiment, when the comparison signal VTC[k] is the value of the low dropout voltage sensing signal VINLDO[k]_S minus the input voltage sensing signal VIN_S, the upper threshold VthU[k] is the first reference voltage Vref1, and the lower threshold VthL[k] is the second reference voltage Vref2. The input voltage sensing signal VIN_S is the sensing signal corresponding to the input voltage VIN, and the low dropout voltage sensing signal VINLDO[k]_S is the sensing signal corresponding to the low dropout voltage VINLDO[k].

[0105] Figure 3C FIG. 1 is a circuit diagram showing a buck-boost switching power supply circuit according to another embodiment of the present invention. In this embodiment, the inductor L, the power switch circuit 301, and the low-dropout regulator 302[1:n] are similar to Figure 2 The inductor L, power switch circuit 101, low voltage dropout regulator 102[1:n], the input switch unit 3011, the output switch unit 3012, the bypass control circuit 303 of this embodiment are similar to Figure 3A The input switch unit 2011, the output switch unit 2012, and the bypass control circuit 203 are omitted. Figure 3A The difference between the embodiments of the present invention and the present invention is that the bypass mode of this embodiment controls the input high-bridge switch A and the output high-bridge switch D[1:n] to be conductive. That is, the bypass switching circuit 308 of this embodiment includes the corresponding output high-bridge switch D[1:n] and an input high-bridge switch A in the input switch unit. Therefore, this embodiment does not require an additional bypass switch, which can save the layout area of ​​the additional bypass switch. When the conversion voltage difference is lower than the reference voltage, the bypass control circuit 303 generates a bypass control signal VE[1:n] to the conversion control circuit 305. The conversion control circuit 305 generates control signals VA, VB, VC, and VD[1:n] based on the bypass control signal VE[1:n] to control the corresponding output high-bridge switch D[1:n] and the input high-bridge switch A, thereby electrically connecting the input voltage VIN to the corresponding low-voltage difference node 304[1:n] via the inductor L. In one embodiment, the conversion control circuit 305 is also used to control the aforementioned switches in other modes (such as buck mode or boost mode) to perform corresponding power conversion. It should be noted that the bypass mode in this embodiment is that all n channels enter the bypass mode at the same time. It should be noted that the bypass control circuit 303 of the buck-boost switching power supply circuit 30 of the present invention is not limited to Figure 3C The architecture shown, any other feasible architecture can also be used, Figure 3C The illustrated architecture is only used to illustrate the present invention and is not intended to limit the scope of the present invention.

[0106] Figure 3D According to an embodiment of the present invention, Figure 3A and Figure 3C A circuit diagram of another embodiment of a bypass control circuit of a buck-boost switching power supply circuit. The comparison signal VTC[k], the upper threshold value VthU[k] and the lower threshold value VthL[k] of this embodiment can also be used. Figure 3BIn the embodiment listed, the bypass control circuit 203' includes a threshold control circuit 2031[k] and comparison circuits 2032'a[k] and 2032'b[k]. The threshold control circuit 2031[k] is configured to generate an upper threshold value VthU[k] and a lower threshold value VthL[k] based on a reference voltage. The comparison circuit 2032'a[k] is configured to compare the comparison signal VTC[k] with the upper threshold value VthU[k] to generate a comparison result CPOU[k]. The comparison circuit 2032'b[k] is configured to compare the comparison signal VTC[k] with the lower threshold value VthL[k] to generate a comparison result CPOL[k]. When the comparison signal VTC[k] is less than the upper threshold value VthU[k] and greater than the lower threshold value VthL[k], the bypass control signal VE[k] is enabled via the NAND gate 2034'[k], thereby entering the bypass mode.

[0107] Please continue reading Figure 4 In one embodiment, the buck-boost switching power supply circuit of the present invention can operate in a boost mode, a bypass mode, or a buck mode. The buck-boost switching power supply circuit of the present invention operates in the bypass mode when the corresponding conversion voltage difference is lower than a reference voltage, and operates in a buck mode and a boost mode, respectively, based on the input voltage VIN and the corresponding low dropout voltage VINLDO, when the corresponding conversion voltage difference is not lower than the reference voltage.

[0108] In one embodiment, the reference voltage may include a first reference voltage and a second reference voltage. Figure 4As shown, the first reference voltage is Vref1, the second reference voltage is Vref2, the upper threshold is VthU, and the lower threshold is VthL. When the difference between the low dropout voltage VINLDO[k] and the input voltage VIN is lower than the first reference voltage Vref1, and the difference between the input voltage VIN and the low dropout voltage VINLDO[k] is lower than the second reference voltage Vref2, the bypass control signal VE[k] is enabled, causing the buck-boost switching power supply circuit of the present invention to operate in the bypass mode. In one embodiment, the buck-boost switching power supply circuit of the present invention operates in the boost mode when the difference between the low dropout voltage VINLDO[k] and the input voltage VIN is not lower than the first reference voltage Vref1, and operates in the buck mode when the difference between the low dropout voltage VINLDO[k] and the input voltage VIN is not lower than the second reference voltage Vref2. In one embodiment, the first reference voltage Vref1 and the second reference voltage Vref2 have one of the following relationships: (1) the first reference voltage Vref1 is equal to the second reference voltage Vref2, and both the first reference voltage Vref1 and the second reference voltage Vref2 are not zero; (2) the first reference voltage Vref1 is equal to zero, and the second reference voltage Vref2 is not zero; (3) the second reference voltage Vref2 is equal to zero, and the first reference voltage Vref1 is not zero; or (4) the first reference voltage Vref1 is not equal to the second reference voltage Vref2, and both the first reference voltage Vref1 and the second reference voltage Vref2 are not zero.

[0109] Figure 5 Yes Display Figure 3A Schematic diagram of the signal waveform of the circuit. Input voltage VIN, low voltage difference voltage VINLDO[1], VINLDO[2], VINLDO[n], bypass control signal VE[1], VE[2], VE[n] are as follows: Figure 5 It should be noted that Figure 5 This is an embodiment showing that the first reference voltage Vref1 is zero and the second reference voltage Vref2 is not zero, but it is not intended to limit the scope of the present invention. Figure 5 As shown, only one or more channels may enter bypass mode, while the other channels operate normally.

[0110] Figure 6 FIG. 1 is a circuit diagram showing a buck-boost switching power supply circuit according to another embodiment of the present invention. The power switch circuit 401, input switch unit 4011, output switch unit 4012, low voltage dropout regulator 402[1], 402[2], inductor L, bypass control circuit 403, conversion control circuit 405 and bypass switching circuit 408 of this embodiment are similar to FIG. Figure 3CThe power switch circuit 301, input switch unit 3011, output switch unit 3012, low voltage dropout regulator 302[1]~302[n], inductor L, bypass control circuit 303, conversion control circuit 305 and bypass switching circuit 308 are not described in detail. The bypass control circuit 403 of this embodiment can also be used Figure 3D In the embodiment, the bypass switching circuit 408 of this embodiment can also be used Figure 3A This embodiment is similar to Figure 3C The difference between the embodiments of the present invention and the present invention lies in that a low-dropout (LDO) regulator in the buck-boost switching power supply circuit 40 of this embodiment corresponds to a negative voltage generating circuit 402[n], which is configured to convert the LDO voltage VINLDO[n] into a negative output voltage NVOUT (corresponding to the output voltage VOUT[n]). The negative voltage generating circuit 402[n] includes a negative charge pump 406 and a negative LDO regulator 407. The negative charge pump 406 is coupled to the LDO node 404[n] to convert the LDO voltage VINLDO[n] into a negative LDO voltage NVINLDO. The negative LDO regulator 407 is coupled to the negative charge pump 406 to convert the negative LDO voltage NVINLDO into a negative output voltage NVOUT. In this embodiment, n is a positive integer greater than or equal to 2.

[0111] Figure 7 FIG. 1 is a circuit diagram showing a buck-boost switching power supply circuit according to another embodiment of the present invention. The power switch circuit 501, input switch unit 5011, output switch unit 5012, low voltage dropout regulators 502[1], 502[2], inductor L, bypass control circuit 503, conversion control circuit 505 and bypass switching circuit 508 of this embodiment are similar to FIG. Figure 3C The power switch circuit 301, input switch unit 3011, output switch unit 3012, low voltage dropout regulator 302[1]~302[n], inductor L, bypass control circuit 303, conversion control circuit 305 and bypass switching circuit 308 are not described in detail. The bypass control circuit 503 of this embodiment can also be used Figure 3D In the embodiment, the bypass switching circuit 508 of this embodiment can also be used Figure 3A This embodiment is similar to Figure 3CThe difference between the embodiments is that in the buck-boost switching power supply circuit 50 of this embodiment, some of the multiple low-dropout voltage regulators correspond to negative voltage generating circuits 502[n-x+1]~502[n], which are used to convert the low-dropout voltages VINLDO[n-x+1]~VINLDO[n] into negative output voltages NVOUT[1]~NVOUT[x] (corresponding to the output voltages VOUT[n-x+1]~VOUT[n], respectively). The negative voltage generating circuits 502[n-x+1]~502[n] respectively include negative charge pumps 506[1]~506[x] and multiple negative low-dropout voltage regulators 507[1]~507[x]. A plurality of negative charge pumps 506[1] to 506[x] are respectively coupled to corresponding low-voltage dropout nodes 504[n-x+1] to 504[n] for converting corresponding low-voltage dropout voltages VINLDO[n-x+1] to VINLDO[n] into corresponding negative low-voltage dropout voltages NVINLDO[1] to NVINLDO[x]. A plurality of negative low-voltage dropout regulators 507[1] to 507[x] are respectively coupled to the plurality of negative charge pumps 506[1] to 506[x] for converting corresponding negative low-voltage dropout voltages NVINLDO[1] to NVINLDO[x] into corresponding negative output voltages NVOUT[1] to NVOUT[x]. Wherein x is a positive integer greater than or equal to 1. In this embodiment, n is a positive integer greater than or equal to 3.

[0112] Figure 8 FIG. 1 is a circuit diagram showing a buck-boost switching power supply circuit according to another embodiment of the present invention. The power switch circuit 601, input switch unit 6011, output switch unit 6012, low voltage dropout regulator 602[1], 602[2], inductor L, bypass control circuit 603, conversion control circuit 605 and bypass switching circuit 608 of this embodiment are similar to FIG. Figure 3C The power switch circuit 301, input switch unit 3011, output switch unit 3012, low voltage dropout regulator 302[1]~302[n], inductor L, bypass control circuit 303, conversion control circuit 305 and bypass switching circuit 308 are not described in detail. The bypass control circuit 603 of this embodiment can also be used Figure 3D In the embodiment, the bypass switching circuit 608 of this embodiment can also be used Figure 3A This embodiment is similar to Figure 3CThe difference between the embodiments is that a low voltage dropout regulator in the buck-boost switching power supply circuit 60 of this embodiment corresponds to a negative voltage generating circuit 602[n], which is used to convert the low voltage dropout voltage VINLDO[n] into at least one negative output voltage NVOUT[1]~NVOUT[x] (corresponding to the output voltage VOUT[n]). The negative voltage generating circuit 602[n] includes a negative charge pump 606 and at least one negative low voltage dropout regulator 607[1]~607[x]. The negative charge pump 606 is coupled to the low voltage dropout node 604[n] to convert the low voltage dropout voltage VINLDO[n] into a negative low voltage dropout voltage NVINLDO. The multiple negative low voltage dropout regulators 607[1]~607[x] are respectively coupled to the negative charge pump 606 to convert the negative low voltage dropout voltage NVINLDO into corresponding negative output voltages NVOUT[1]~NVOUT[x]. In this embodiment, n is a positive integer greater than or equal to 2.

[0113] Figure 9 FIG. 1 is a circuit diagram showing a buck-boost switching power supply circuit according to another embodiment of the present invention. Figure 3C The difference is that this embodiment only includes a single output upper bridge switch D and a single low voltage dropout regulator 702. The input switch unit 7011, the output lower bridge switch C, the low voltage dropout regulator 702, and the conversion control circuit 705 of this embodiment are similar to Figure 3C The input switch unit 3011, the output lower bridge switch C, the low voltage dropout regulator 302[1:n], and the conversion control circuit 305 are shown in FIG. However, in this embodiment, n is 1, so the detailed description thereof is omitted. The bypass control circuit 703 of this embodiment can be used Figure 3C or Figure 3D The bypass control circuit 703 generates a bypass control signal VE to the conversion control circuit 705. The conversion control circuit 705 generates control signals VA, VB, VC, and VD according to the bypass control signal VE to control the output high-side switch D and the input high-side switch A to electrically connect the input voltage VIN to the low-voltage dropout node 704 via the inductor L.

[0114] Figure 10 FIG. 1 is a circuit diagram showing a buck-boost switching power supply circuit according to another embodiment of the present invention. Figure 6 The difference between the embodiment of FIG1 and FIG2 is that the embodiment of FIG1 only includes a single output upper bridge switch D, and the single low-dropout voltage regulator of the embodiment corresponds to a negative voltage generating circuit 802. The input switch unit 8011, the output lower bridge switch C, the conversion control circuit 805, the bypass control circuit 803, the negative voltage generating circuit 802, the negative charge pump 806, and the negative low-dropout voltage regulator 807 of the embodiment are similar to those of FIG1 and FIG2. Figure 6The input switch unit 4011, the output lower bridge switch C, the conversion control circuit 405, the bypass control circuit 403, the negative voltage generating circuit 402[n], the negative charge pump 406, and the negative low dropout voltage regulator 407 are omitted for detailed description. Figure 3C or Figure 3D The bypass control circuit 803 generates a bypass control signal VE to the conversion control circuit 805. The conversion control circuit 805 generates control signals VA, VB, VC, and VD according to the bypass control signal VE to control the output high-side switch D and the input high-side switch A to electrically connect the input voltage VIN to the low-voltage dropout node 804 via the inductor L.

[0115] Figure 11 FIG. 1 is a circuit diagram showing a buck-boost switching power supply circuit according to another embodiment of the present invention. Figure 6 The difference between the embodiment of the present invention and the embodiment of the present invention is that the present invention only includes a single output upper bridge switch D, and the present invention only includes a low voltage dropout regulator 902[1] and another low voltage dropout regulator (corresponding to the negative voltage generating circuit 902[2]). The bypass control circuit 903 of the present embodiment can be used Figure 3C or Figure 3D The input switch unit 9011, the output lower bridge switch C, the conversion control circuit 905, the bypass control circuit 903, the low voltage difference regulator 902[1], the negative voltage generating circuit 902[2], the negative charge pump 906, and the negative low voltage difference regulator 907 of this embodiment are similar to Figure 6 The input switch unit 4011, the output low-bridge switch C, the conversion control circuit 405, the bypass control circuit 403, the low-voltage dropout regulator 402[1], the negative voltage generating circuit 402[n], the negative charge pump 406, and the negative low-voltage dropout regulator 407 are omitted for detailed description. The bypass control circuit 903 generates a bypass control signal VE to the conversion control circuit 905. The conversion control circuit 905 generates control signals VA, VB, VC, and VD according to the bypass control signal VE to control the output high-bridge switch D and the input high-bridge switch A to electrically connect the input voltage VIN to the low-voltage dropout node 904 via the inductor L.

[0116] Figures 12A-12C 1 is a characteristic diagram showing the operation mode of a buck-boost switching power supply circuit according to several embodiments of the present invention. It should be noted that Figure 12A 、 Figure 12B or Figure 12C Applicable to Figure 3A 、 Figure 3C 、 Figures 6-11 Likewise, Figure 4 Also applicable to Figure 3A 、 Figure 3C 、 Figures 6-11 Any one of the embodiments. Figure 12A As shown, the first reference voltage is Vref1, the second reference voltage is Vref2, the upper threshold is VthU, the lower threshold is VthL, the first intermediate threshold is VthM1, and the second intermediate threshold is VthM2. Figure 4 The difference is that the buck-boost switching power supply circuit of this embodiment also operates in a buck-boost mode according to the input voltage VIN and the corresponding low voltage dropout voltage VINLDO when the corresponding conversion voltage difference is not lower than the reference voltage. Figure 12A As shown, the conversion voltage difference (taking VINLDO-VIN as an example) is operated in the corresponding mode from large to small according to the following sequence: boost mode, buck-boost mode, bypass mode, buck-boost mode, and buck mode.

[0117] like Figure 12B As shown, the first reference voltage is Vref1, the second reference voltage is Vref2, the upper threshold is VthU, the lower threshold is VthL, and the first intermediate threshold is VthM1. Figure 12A The difference is that this embodiment only has a buck boost mode above the bypass mode. Figure 12B As shown, the conversion voltage difference decreases from large to small (taking VINLDO-VIN as an example), and operates in the corresponding mode according to the following sequence: boost mode, buck-boost mode, bypass mode, and buck mode.

[0118] Figure 12C FIG. 1 is a characteristic diagram showing the operation mode of a buck-boost switching power supply circuit according to another embodiment of the present invention. Figure 12C As shown, the first reference voltage is Vref1, the second reference voltage is Vref2, the upper threshold is VthU, the lower threshold is VthL, and the second intermediate threshold is VthM2. Figure 12A The difference is that this embodiment only has a buck boost mode below the bypass mode. Figure 12C As shown, the conversion voltage difference decreases from large to small, and the corresponding mode is operated according to one of the following sequences: boost mode, bypass mode, buck-boost mode, and buck mode.

[0119] Figure 13 According to an embodiment of the present invention, Figure 3C The circuit is Figure 12A Schematic diagram of signal waveforms when operating in the operation mode. Input voltage VIN, low voltage dropout voltage VINLDO[k], control signals VA, VD[k] are as follows Figure 13 It should be noted that Figure 13This is an embodiment showing that the first reference voltage Vref1 is zero and the second reference voltage Vref2 is non-zero, but it is not intended to limit the scope of the present invention. Specifically, in buck mode, the corresponding output high-bridge switch D[k] is constantly on, that is, the corresponding control signal VD[k] is constantly high, and the input high-bridge switch A is switched to perform buck conversion. In buck-boost mode, the corresponding output high-bridge switch D[k] and the input high-bridge switch A are both switched to perform buck-boost conversion. In bypass mode, the corresponding output high-bridge switch D[k] and the input high-bridge switch A are both constantly on, so that the input voltage VIN and the corresponding low-dropout voltage VINLDO[k] are electrically connected through the inductor L. In boost mode, the input high-bridge switch A is constantly on, and the corresponding output high-bridge switch D[k] is switched to perform boost conversion.

[0120] Figure 14 According to another embodiment of the present invention, a control method for a buck-boost switching power supply circuit is shown. The control method 100 of the buck-boost switching power supply circuit of the present invention includes step 1001, wherein at least one low-dropout voltage regulator is coupled to the at least one output high-side switch to convert the at least one low-dropout voltage VINLDO to the at least one output voltage VOUT. Next, in step 1002, a bypass control signal is generated based on a conversion voltage difference between the input voltage VIN and the corresponding low-dropout voltage VINLDO. Next, in step 1003, when the corresponding conversion voltage difference is lower than a reference voltage, the bypass control signal controls the electrical connection between the input voltage VIN and the corresponding low-dropout node. In one embodiment, step 1003 may include step 10031a or step 10031b. In step 10031a, when the corresponding conversion voltage difference is lower than the reference voltage, the bypass control signal controls the corresponding output high-side switch and the corresponding input high-side switch to electrically connect the input voltage VIN to the corresponding low-voltage-dropout node via an inductor. In step 10031b, when the corresponding conversion voltage difference is lower than the reference voltage, the corresponding bypass switch of at least one bypass switch is controlled to be conductive to directly electrically connect the input voltage VIN to the corresponding low-voltage-dropout node.

[0121] Figure 15Another embodiment of the present invention shows a control method for a buck-boost switching power supply circuit. In one embodiment, step 1001 may include steps 10011 and 10012. In step 10011, an upper threshold value VthU and a lower threshold value VthL are generated according to a reference voltage. In step 10012, a signal to be compared VTC is compared with the upper threshold value VthU and the lower threshold value VthL. When the signal to be compared VTC is between the upper threshold value VthU and the lower threshold value VthL, the corresponding bypass control signal is enabled to electrically connect the input voltage VIN to the corresponding low voltage difference node, wherein the signal to be compared VTC, the upper threshold value VthU and the lower threshold value VthL have one of the following relationships: (1) the signal to be compared VTC is the corresponding conversion voltage difference, the upper threshold value VthU is the first reference voltage Vref1, and the lower threshold value VthL is the second Reference voltage Vref2; (2) the signal to be compared VTC is the corresponding low voltage difference voltage VINLDO, the upper threshold value VthU is the sum of the input voltage VIN and the first reference voltage Vref1, and the lower threshold value VthL is the difference between the input voltage VIN and the second reference voltage Vref2; (3) the signal to be compared VTC is the input voltage VIN, the upper threshold value VthU is the sum of the corresponding low voltage difference voltage VINLDO and the second reference voltage Vref2, and the lower threshold value VthL is the difference between the corresponding low voltage difference voltage VINLDO and the first reference voltage Vref1.

[0122] As described above, the present invention provides a buck-boost switching power supply circuit and control method thereof. By utilizing a bypass mode, the circuit achieves low switching losses and high efficiency when the input voltage is close to the low-dropout voltage. Furthermore, since the input voltage is directly bypassed to the input of the low-dropout regulator, a larger voltage drop margin is available for the low-dropout regulator. Furthermore, by employing a bypass mode in which both the input high-side switch and the output high-side switch are constantly on, the present invention can reduce the layout area of ​​the bypass switches.

[0123] The present invention has been described above with respect to the preferred embodiments, but the above description is only for those skilled in the art to easily understand the content of the present invention and is not intended to limit the broadest scope of the present invention. The various embodiments described are not limited to individual applications, but can also be applied in combination. For example, two or more embodiments can be used in combination, and part of the components in one embodiment can also be used to replace the corresponding components in another embodiment. In addition, under the same spirit of the present invention, those skilled in the art can think of various equivalent changes and various combinations. For example, the present invention refers to "processing or calculating or generating an output result according to a certain signal", which is not limited to the signal itself, but also includes, when necessary, performing voltage-to-current conversion, current-to-voltage conversion, and / or ratio conversion on the signal, and then processing or calculating the converted signal to generate an output result. It can be seen that under the same spirit of the present invention, those skilled in the art can think of various equivalent changes and various combinations, and there are many combinations, which are not listed here one by one. Therefore, the scope of the present invention should cover the above and all other equivalent changes.

Claims

1. A buck-boost switching power supply circuit for converting an input voltage into at least one output voltage, comprising: A power switch circuit includes an input switch unit and an output switch unit, wherein the input switch unit is used to switch a first end of an inductor between the input voltage and a ground potential, and the output switch unit is used to switch a second end of the inductor between at least one low voltage difference node and the ground potential, so as to convert the input voltage into at least one corresponding low voltage difference voltage at the at least one low voltage difference node, and the at least one low voltage difference node is correspondingly coupled to at least one output high-side switch in the output switch unit; At least one low-dropout voltage regulator is coupled to the at least one output upper bridge switch to convert the at least one low-dropout voltage into the at least one output voltage; a bypass control circuit for generating a bypass control signal according to a conversion voltage difference between the input voltage and the corresponding low dropout voltage; as well as a bypass switching circuit, wherein the bypass control signal controls the bypass switching circuit to electrically connect the input voltage to the corresponding low voltage difference node when the corresponding conversion voltage difference is lower than a reference voltage, so that the buck-boost switching power supply circuit operates in a bypass mode; The reference voltage includes a first reference voltage and a second reference voltage, wherein when a difference between the corresponding low dropout voltage and the input voltage is lower than the first reference voltage, and a difference between the input voltage and the corresponding low dropout voltage is lower than the second reference voltage, the corresponding bypass control signal is enabled, wherein the first reference voltage and the second reference voltage have one of the following relationships: (1) The first reference voltage is equal to the second reference voltage, and both the first reference voltage and the second reference voltage are non-zero; (2) The first reference voltage is equal to zero, and the second reference voltage is not zero; (3) The second reference voltage is equal to zero, and the first reference voltage is not zero; or (4) The first reference voltage is not equal to the second reference voltage, and both the first reference voltage and the second reference voltage are not zero; The buck-boost switching power supply circuit operates in a buck mode, a boost mode and a buck-boost mode according to the input voltage and the corresponding low voltage difference voltage when the corresponding conversion voltage difference is not lower than the reference voltage.

2. The buck-boost switching power supply circuit according to claim 1, wherein: The bypass switching circuit includes the corresponding output high-bridge switch and an input high-bridge switch in the input switch unit. When the corresponding conversion voltage difference is lower than the reference voltage, the bypass control circuit generates the corresponding bypass control signal to control the corresponding output high-bridge switch and the input high-bridge switch to be turned on, so as to electrically connect the input voltage to the corresponding low-voltage difference node via the inductor.

3. The buck-boost switching power supply circuit according to claim 1, wherein: The bypass switching circuit includes at least one bypass switch, which is directly electrically connected between the input voltage and the corresponding low voltage difference node, so that when the corresponding conversion voltage difference is lower than the reference voltage, the corresponding bypass switch is controlled to be turned on to directly electrically connect the input voltage to the corresponding low voltage difference node.

4. The buck-boost switching power supply circuit according to claim 1, wherein: The conversion voltage difference is the absolute value of the difference between the input voltage and the corresponding low dropout voltage.

5. The buck-boost switching power supply circuit according to claim 1, wherein: The bypass control circuit includes: a threshold control circuit for generating an upper threshold and a lower threshold according to the reference voltage; and a comparison circuit for comparing a signal to be compared with the upper threshold and the lower threshold, and enabling the corresponding bypass control signal when the signal to be compared is between the upper threshold and the lower threshold to electrically connect the input voltage to the corresponding low voltage dropout node, wherein the signal to be compared, the upper threshold, and the lower threshold have one of the following relationships: (1) the signal to be compared is the corresponding conversion voltage difference, the upper threshold is the first reference voltage, and the lower threshold is the second reference voltage; (2) the signal to be compared is the corresponding low-dropout voltage, the upper threshold is the sum of the input voltage and the first reference voltage, and the lower threshold is the difference between the input voltage and the second reference voltage; (3) The signal to be compared is the input voltage, the upper threshold is the sum of the corresponding low voltage difference voltage and the second reference voltage, and the lower threshold is the difference between the corresponding low voltage difference voltage and the first reference voltage.

6. The buck-boost switching power supply circuit according to claim 1, wherein: The input switch unit includes: an input high-side switch coupled between the input voltage and the first end of the inductor; and an input low-bridge switch or an input low-bridge diode, coupled between the ground potential and the first end of the inductor; The input upper bridge switch and the input lower bridge switch or the input lower bridge diode are used to switch the first end of the inductor between the input voltage and the ground potential.

7. The buck-boost switching power supply circuit according to claim 1, wherein: The output switching unit includes: an output low-bridge switch coupled between the ground potential and the second end of the inductor; and The at least one output upper bridge switch is respectively coupled between the at least one low voltage difference node and the second end of the inductor; The output lower bridge switch and the at least one output upper bridge switch are used to switch the second end of the inductor between the at least one low voltage difference node and the ground potential, thereby generating the corresponding at least one low voltage difference voltage at the at least one low voltage difference node.

8. The buck-boost switching power supply circuit according to claim 1, wherein: The buck-boost switching power supply circuit operates in the boost mode when the difference between the corresponding low voltage dropout voltage and the input voltage is not lower than the first reference voltage, and operates in the buck mode when the difference between the input voltage and the corresponding low voltage dropout voltage is not lower than the second reference voltage.

9. The buck-boost switching power supply circuit according to claim 1, wherein: The conversion voltage difference is from large to small, and the corresponding mode is operated according to one of the following sequences: (1) the boost mode, the buck-boost mode, the bypass mode, and the buck mode; (2) the boost mode, the bypass mode, the buck-boost mode, and the buck mode; (3) The boost mode, the buck-boost mode, the bypass mode, the buck-boost mode, and the buck mode.

10. The buck-boost switching power supply circuit according to claim 1, wherein: At least one of the low-dropout voltage regulators is a negative voltage generating circuit, wherein the negative voltage generating circuit comprises: a negative charge pump coupled to the corresponding low-dropout node, for converting the corresponding low-dropout voltage into a negative low-dropout voltage; and At least one negative low dropout voltage regulator is coupled to the negative charge pump and is used for converting the negative low dropout voltage into at least one corresponding negative output voltage.

11. A control method for controlling a buck-boost switching power supply circuit, configured to convert an input voltage into at least one output voltage. The buck-boost switching power supply circuit includes a power switching circuit, the power switching circuit including an input switching unit and an output switching unit, wherein the input switching unit is configured to switch a first end of an inductor between the input voltage and a ground potential, and the output switching unit is configured to switch a second end of the inductor between at least one low voltage difference node and the ground potential, thereby converting the input voltage to at least one corresponding low voltage difference voltage at the at least one low voltage difference node, and the at least one low voltage difference node is correspondingly coupled to at least one output high-side switch in the output switching unit. The control method comprises: Using at least one low dropout voltage regulator, converting the at least one low dropout voltage into the at least one output voltage; generating a bypass control signal according to a conversion voltage difference between the input voltage and the corresponding low dropout voltage; and When the corresponding conversion voltage difference is lower than a reference voltage, the bypass control signal controls the input voltage to be electrically connected to the corresponding low voltage difference node, so that the buck-boost switching power supply circuit operates in a bypass mode; The reference voltage includes a first reference voltage and a second reference voltage, wherein when a difference between the low dropout voltage and the input voltage is lower than the first reference voltage, and a difference between the input voltage and the low dropout voltage is lower than the second reference voltage, the corresponding bypass control signal is enabled, wherein the first reference voltage and the second reference voltage have one of the following relationships: (1) The first reference voltage is equal to the second reference voltage, and both the first reference voltage and the second reference voltage are non-zero; (2) The first reference voltage is equal to zero, and the second reference voltage is not zero; (3) The second reference voltage is equal to zero, and the first reference voltage is not zero; or (4) The first reference voltage is not equal to the second reference voltage, and both the first reference voltage and the second reference voltage are not zero; The buck-boost switching power supply circuit operates in a buck mode, a boost mode and a buck-boost mode according to the input voltage and the corresponding low voltage difference voltage when the corresponding conversion voltage difference is not lower than the reference voltage.

12. The control method according to claim 11, wherein: When the corresponding conversion voltage difference is lower than the reference voltage, the bypass control signal controls the corresponding output upper bridge switch and the input upper bridge switch to be turned on, so as to electrically connect the input voltage and the corresponding low voltage difference node through the inductor.

13. The control method according to claim 11, wherein: When the corresponding conversion voltage difference is lower than the reference voltage, the corresponding bypass switch in at least one bypass switch is controlled to be turned on to directly electrically connect the input voltage to the corresponding low voltage difference node, wherein the at least one bypass switch is directly electrically connected between the input voltage and the corresponding low voltage difference node.

14. The control method according to claim 11, wherein: The conversion voltage difference is the absolute value of the difference between the input voltage and the corresponding low dropout voltage.

15. The control method according to claim 11, wherein: The step of generating the bypass control signal comprises: Generating an upper threshold and a lower threshold according to the reference voltage; and and comparing a signal to be compared with the upper threshold and the lower threshold. When the signal to be compared is between the upper threshold and the lower threshold, enabling the corresponding bypass control signal to electrically connect the input voltage to the corresponding low voltage dropout node, wherein the signal to be compared, the upper threshold, and the lower threshold have one of the following relationships: (1) the signal to be compared is the corresponding conversion voltage difference, the upper threshold is the first reference voltage, and the lower threshold is the second reference voltage; (2) the signal to be compared is the corresponding low-dropout voltage, the upper threshold is the sum of the input voltage and the first reference voltage, and the lower threshold is the difference between the input voltage and the second reference voltage; (3) The signal to be compared is the input voltage, the upper threshold is the sum of the corresponding low voltage difference voltage and the second reference voltage, and the lower threshold is the difference between the corresponding low voltage difference voltage and the first reference voltage.

16. The control method according to claim 11, wherein: When the difference between the corresponding low voltage difference voltage and the input voltage is not lower than the first reference voltage, the buck-boost switching power supply circuit is controlled to operate in the boost mode; and when the difference between the input voltage and the corresponding low voltage difference voltage is not lower than the second reference voltage, the buck-boost switching power supply circuit is controlled to operate in the buck mode.

17. The control method according to claim 11, wherein: The conversion voltage difference decreases from large to small, and the buck-boost switching power supply circuit operates in a corresponding mode according to one of the following sequences: (1) the boost mode, the buck-boost mode, the bypass mode, and the buck mode; (2) the boost mode, the bypass mode, the buck-boost mode, and the buck mode; (3) The boost mode, the buck-boost mode, the bypass mode, the buck-boost mode, and the buck mode.

18. The control method according to claim 11, wherein: The at least one output voltage includes at least one negative output voltage, and the control method further comprises: Converting the corresponding low dropout voltage into a negative low dropout voltage; and The negative low dropout voltage is converted into the corresponding at least one negative output voltage.

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