Buck-boost switching type power supply circuit and control method thereof

Abstract

The invention discloses a buck-boost switching type power supply circuit and a control method thereof. The buck-boost switching type power supply circuit comprises a bypass control circuit used for determining whether the buck-boost switching type power supply circuit is operated in a bypass mode according to a bypass enable signal; when the conversion voltage difference between the input voltage and the output voltage is smaller than the reference voltage, the bypass control circuit controls the input power supply to be electrically connected with the output power supply, and enables the buck-boost switching type power supply circuit to operate in a bypass stage of a bypass mode. Before and / or after the bypass stage, the bypass control circuit controls the buck-boost switching type power supply circuit to operate in a first transition stage and / or a second transition stage. In the first transition stage or the second transition stage, the bypass control circuit controls the output voltage to gradually change towards the input voltage or the target voltage until the conversion voltage difference is smaller than the first reference voltage or the output voltage is equal to the target voltage.

Description

Technical Field

[0001] The present invention relates to a buck-boost switching power supply circuit, and in particular to a buck-boost switching power supply circuit which can smoothly enter a bypass mode regardless of the size of the load current and a control method thereof. Background Art

[0002] Known buck-boost switching power converters are often required to operate in a low-power saving mode in applications related to rechargeable batteries. In the power saving mode, since the buck-boost switching power converter is still switching the power switch therein, there will be switching losses, which will reduce the conversion efficiency. Therefore, in the power saving mode, the input and output ends are further kept in an electrically connected state without switching the power switch (that is, entering the bypass mode), thereby improving the conversion efficiency. In typical applications, an additional switch is required as a bypass path to electrically connect the input and output ends when entering and exiting the bypass mode. In actual applications, there is a situation where the voltage difference between the input voltage and the output voltage is relatively large. At the moment when the bypass path is short-circuited, a relatively large current will be generated. Because of this instantaneous current change, the output jitters (damping) too much, causing the aforementioned switch, the inductor therein, or the subsequent circuit to burn out.

[0003] See also Figure 1 , which shows a signal waveform diagram of a known buck-boost switching power converter, wherein the upper figure illustrates the input voltage VIN (dashed straight line), the output voltages VOUT1 and VOUT2 in two situations, and the bypass control signals SBYPS1 and SBYPS2 for enabling the bypass mode Bypass in the above two situations, respectively. Among them, when the bypass control signals SBYPS1 and SBYPS2 for enabling the bypass mode Bypass are at a high level, it indicates that the buck-boost switching power converter enters the enabled bypass mode Bypass. As mentioned above, this known buck-boost switching power converter is used in applications related to rechargeable batteries, and enters the bypass mode Bypass when the voltage difference between the input voltage VIN and the output voltage VOUT1 or VOUT2 is less than a reference voltage, and the input voltage VIN is greater than or equal to a first threshold. As Figure 1 As shown in FIG. 1 , when the conventional buck-boost switching power converter switches from the buck-boost mode to the bypass mode, the instantaneous change amplitude of the inductor current IL is too large, such as Figure 1As shown in the lower figure, the output voltage VOUT1 will ring. The excessive ringing amplitude of the output voltage VOUT1 will not only cause greater stress on the components, but also cause the buck-boost switching power converter to erroneously trigger the overvoltage protection mechanism and leave the bypass mode when the output voltage VOUT1 exceeds the second threshold. Although the second threshold preset by the overvoltage protection mechanism can be increased to the third threshold to avoid erroneous triggering, the probability of overvoltage damage to the system will increase in this way.

[0004] In view of this, the present invention aims at addressing the above-mentioned deficiencies of the prior art and proposes a buck-boost switching power supply circuit which can smoothly enter the bypass mode regardless of the load current. Summary of the invention

[0005] In one aspect, the present invention provides a buck-boost switching power supply circuit for converting an input power supply into an output power supply, comprising: a 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 to the input power supply or a ground potential, and the output switch unit is used to switch a second end of the inductor to the output power supply or the ground potential to convert the input power supply into the output power supply; and a bypass control circuit, which is used to determine whether the buck-boost switching power supply circuit operates in a bypass mode according to a bypass enable signal; wherein, when the bypass enable signal is an enable level, the buck-boost switching power supply circuit operates in the bypass mode, and when the absolute value of a conversion voltage difference between an input voltage of the input power supply and an output voltage of the output power supply is less than a first reference voltage , the bypass control circuit controls the power switch circuit so that the input power supply and the output power supply are bypassed and electrically connected, and the buck-boost switching power supply circuit operates in a bypass stage of the bypass mode; wherein, in the bypass mode, before the bypass stage, the bypass control circuit controls the buck-boost switching power supply circuit to operate in a first transition stage, and / or after the bypass mode, the bypass control circuit controls the buck-boost switching power supply circuit to operate in a second transition stage; wherein in the first transition stage, the bypass control circuit controls the output voltage to gradually change toward the input voltage in a feedback regulation manner until the conversion voltage difference is less than the first reference voltage, and the first transition stage is ended; wherein in the second transition stage, the bypass control circuit controls the output voltage to gradually change toward a target voltage in a feedback regulation manner until the output voltage is equal to the target voltage.

[0006] From another perspective, the present invention provides a control method for a buck-boost switching power supply circuit for converting an input power supply into an output power supply, comprising: when a bypass enable signal is at an enable level, operating a buck-boost switching power supply circuit in a bypass mode; when the absolute value of a conversion voltage difference between an input voltage of the input power supply and an output voltage of the output power supply is less than a first reference voltage, controlling the input power supply and the output power supply to be bypassed and electrically connected, and operating the buck-boost switching power supply circuit in a bypass stage of the bypass mode; in the bypass mode In the formula, before the bypass stage, the buck-boost switching power supply circuit is controlled to operate in a first transition stage, and / or after the bypass mode, the buck-boost switching power supply circuit is controlled to operate in a second transition stage; in the first transition stage, the output voltage is controlled to gradually change toward the input voltage in a feedback regulation manner until the conversion voltage difference is less than the first reference voltage, and the first transition stage is terminated; and in the second transition stage, the output voltage is controlled to gradually change toward a target voltage in a feedback regulation manner until the output voltage is equal to the target voltage.

[0007] In one embodiment, when not operating in the bypass mode, the bypass control circuit enables the bypass enable signal based on a conversion-related voltage difference between the input voltage and an output-related voltage being less than a second reference voltage, or based on an external instruction, wherein the second reference voltage is greater than the first reference voltage; wherein the output-related voltage is the output voltage or the target voltage.

[0008] In one embodiment, in the bypass stage, when a regulated voltage difference between the input voltage and the target voltage is greater than a third reference voltage, the bypass control circuit disables the bypass enable signal to control the buck-boost switching power supply circuit to end the bypass stage of the bypass mode and start the second transition stage.

[0009] In one embodiment, in the first transition stage of the bypass mode, the bypass control circuit gradually changes a fourth reference voltage according to the input voltage and the target voltage, and gradually adjusts the output voltage in a feedback regulation manner according to the fourth reference voltage, thereby causing the output voltage to gradually change toward the input voltage until the absolute value of the conversion voltage difference is less than the first reference voltage, wherein an initial value of the fourth reference voltage is related to the target voltage.

[0010] In one embodiment, in the second transition stage, the bypass control circuit gradually changes a fourth reference voltage according to the input voltage and the target voltage, and gradually adjusts the output voltage in a feedback regulation manner according to the fourth reference voltage, thereby causing the output voltage to gradually change toward the target voltage until the output voltage is equal to the target voltage, wherein an initial value of the fourth reference voltage is related to the target voltage.

[0011] In one embodiment, in the bypass stage, an output upper bridge switch in the output switch unit and an input upper bridge switch in the input switch unit are both turned on to electrically connect the input power source and the output power source via the inductor.

[0012] In one embodiment, the buck-boost switching power supply circuit also includes a bypass switch, which is directly electrically connected between the input power supply and the output power supply. During the bypass stage, the bypass control circuit controls the bypass switch to be turned on to directly electrically connect the input power supply and the output power supply.

[0013] In one embodiment, the bypass control circuit controls the output voltage in a feedback regulation manner during the first transition stage and / or during the second transition stage, thereby preventing the output voltage from overshooting or undershooting.

[0014] In one embodiment, the input switch unit includes: an input upper bridge switch coupled between the input power supply and the first end of the inductor; and an input lower bridge switch or an input lower bridge diode coupled between the ground potential and the first end of the inductor; wherein 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 to the input power supply or the ground potential.

[0015] In one embodiment, the output switch unit includes: an output lower bridge switch coupled between the ground potential and the second end of the inductor; and an output upper bridge switch coupled between the output power supply and the second end of the inductor; wherein the output lower bridge switch and the output upper bridge switch are used to switch the second end of the inductor to the output power supply or the ground potential.

[0016] In one embodiment, during the first transition stage, the bypass control circuit controls the buck-boost switching power supply circuit to enter a forced continuous conduction mode (FCCM).

[0017] In one embodiment, in the second transition stage, the bypass control circuit controls the buck-boost switching power supply circuit to enter or not enter a forced continuous conduction mode.

[0018] In one embodiment, the target voltage is the initially set output voltage or a set voltage updated during the bypass phase.

[0019] In one embodiment, the buck-boost switching power supply circuit enters the bypass stage of the bypass mode after the absolute value of the conversion voltage difference is less than the first reference voltage and the output upper bridge switch and the input upper bridge switch are both turned on.

[0020] In one embodiment, the buck-boost switching power supply circuit also includes an error amplifier circuit, wherein the bypass control circuit includes a reference voltage generating circuit, and the error amplifier circuit generates an error amplification signal based on the fourth reference voltage and an output voltage related signal related to the output voltage, and the error amplification signal is used to generate multiple switching signals for controlling the power switch circuit, wherein the bypass control circuit is also used to control the buck-boost switching power supply circuit to stop supplying power to at least one of the reference voltage generating circuit and the error amplifier circuit during the bypass stage, wherein the fourth reference voltage is generated by the reference voltage generating circuit based on the target voltage and the input voltage.

[0021] In one embodiment, the control method further includes: enabling the bypass enable signal based on a conversion-related voltage difference between the input voltage and an output-related voltage being less than a second reference voltage, or based on an external instruction, wherein the second reference voltage is greater than the first reference voltage; wherein the output-related voltage is the output voltage or the target voltage.

[0022] In one embodiment, the control method also includes: in the bypass stage, when an adjusted voltage difference between the input voltage and the target voltage is greater than a third reference voltage, the bypass enable signal is disabled to control the buck-boost switching power supply circuit to end the bypass stage of the bypass mode and start the second transition stage.

[0023] In one embodiment, in the first transition stage, the step of controlling the output voltage to gradually change toward the input voltage in a feedback regulation manner until the conversion voltage difference is less than the first reference voltage includes: in the first transition stage of the bypass mode, gradually changing a fourth reference voltage according to the input voltage and the target voltage; and gradually adjusting the output voltage in a feedback regulation manner according to the fourth reference voltage, thereby causing the output voltage to gradually change toward the input voltage until the absolute value of the conversion voltage difference is less than the first reference voltage; wherein an initial value of the fourth reference voltage is related to the target voltage.

[0024] In one embodiment, in the second transition stage, the step of controlling the output voltage to gradually change toward the target voltage in a feedback regulation manner until the output voltage is equal to the target voltage includes: in the second transition stage, gradually changing a fourth reference voltage according to the input voltage and the target voltage; and gradually adjusting the output voltage in a feedback regulation manner according to the fourth reference voltage, thereby causing the output voltage to gradually change toward the target voltage until the output voltage is equal to the target voltage, wherein an initial value of the fourth reference voltage is related to the target voltage.

[0025] In one embodiment, the buck-boost switching power supply circuit includes a power switch circuit, which includes an input switch unit and an output switch unit, wherein the step of controlling the input power supply and the output power supply to be bypassed and electrically connected, and making the buck-boost switching power supply circuit operate in the bypass stage of the bypass mode includes: in the bypass stage, controlling an output upper bridge switch in the output switch unit and an input upper bridge switch in the input switch unit so that they are both turned on, so as to electrically connect the input power supply and the output power supply via an inductor.

[0026] In one embodiment, the buck-boost switching power supply circuit includes a bypass switch, which is directly electrically connected between the input power supply and the output power supply, wherein the step of controlling the input power supply and the output power supply to be electrically connected by bypassing each other and making the buck-boost switching power supply circuit operate in the bypass stage of the bypass mode includes: in the bypass stage, controlling the bypass switch to be turned on to directly electrically connect the input power supply and the output power supply.

[0027] In one embodiment, the control method further includes: in the first transition stage, controlling the buck-boost switching power supply circuit to enter a forced continuous conduction mode (FCCM).

[0028] In one embodiment, the control method further includes: in the second transition stage, controlling the buck-boost switching power supply circuit to enter or not enter a forced continuous conduction mode.

[0029] In one embodiment, the buck-boost switching power supply circuit includes an error amplifier circuit, a power switch circuit and a reference voltage generating circuit. The error amplifier circuit generates an error amplifier signal according to the fourth reference voltage and an output voltage related signal related to the output voltage. The error amplifier signal is used to generate a plurality of switching signals for controlling the power switch circuit. The control method further includes: during the bypass stage, controlling the buck-boost switching power supply circuit to stop supplying power to at least one of the reference voltage generating circuit and the error amplifier circuit. The fourth reference voltage is generated by the reference voltage generating circuit according to the target voltage and the input voltage.

[0030] The advantage of the present invention is that the present invention can enter the bypass mode from the boost mode / buck mode / boost-boost mode, and can smoothly enter the bypass mode regardless of the size of the load current. No additional transistor switch is required as a path for the bypass mode, and the input upper bridge switch and the output upper bridge switch can be directly used.

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

[0032] Figure 1 The figure is a schematic diagram showing signal waveforms of a known buck-boost switching power supply circuit.

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

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

[0035] Figure 4 The invention is a circuit block diagram showing a bypass control circuit of a buck-boost switching power supply circuit according to an embodiment of the invention.

[0036] Figure 5 According to an embodiment of the present invention, Figure 3 Schematic diagram of the signal waveform of the circuit.

[0037] Figure 6 According to another embodiment of the present invention, Figure 3 Schematic diagram of the signal waveform of the circuit.

[0038] Figure 7 According to yet another embodiment of the present invention, Figure 3 Schematic diagram of the signal waveform of the circuit.

[0039] Figure 8 According to another embodiment of the present invention, Figure 3 Schematic diagram of the signal waveform of the circuit.

[0040] Explanation of symbols in the figure

[0041] 10: Buck-boost switching power supply circuit

[0042] 101: Power Switching Circuit

[0043] 1011: Input switch unit

[0044] 1012: Output switch unit

[0045] 103: Control circuit

[0046] 1031: Switch control circuit

[0047] 1032: Error amplifier circuit

[0048] 1033: Bypass control circuit

[0049] 10331: Reference voltage generation circuit

[0050] 1034: Analog-to-digital conversion circuit

[0051] 20: Control method of buck-boost switching power supply circuit

[0052] 201-209, 2051, 2052, 2061, 2062: Steps

[0053] A: Input upper bridge switch

[0054] B: Input lower bridge switch

[0055] Buck-Boost: Buck-Boost mode

[0056] By_en: bypass enable signal

[0057] Bypass: Bypass mode

[0058] C: Output lower bridge switch

[0059] D: Output upper bridge switch

[0060] DVIN: digital input voltage signal

[0061] E: Bypass switch

[0062] EAO: Error Amplified Signal

[0063] IL: Inductor current

[0064] L: Inductance

[0065] LX1: First End

[0066] LX2: Second end

[0067] SBYPS, SBYPS1, SBYPS2: bypass control signal

[0068] SFCCM: Forced continuous conduction control signal

[0069] t1~t8, t1', t5': time point

[0070] VA, VB, VC, VD, VE: switching signals

[0071] VFB: Output voltage related signal

[0072] VIN, VIN_S: input voltage

[0073] VOUT, VOUT1, VOUT2, VOUT_S: output voltage

[0074] VOUT_targ: target voltage

[0075] Vref1: first reference voltage

[0076] Vref2: Second reference voltage

[0077] Vref3: The third reference voltage

[0078] Vref4: fourth reference voltage DETAILED DESCRIPTION

[0079] The drawings in the invention are all schematic, and are mainly intended to show 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.

[0080] Figure 2 FIG. 1 is a circuit diagram showing a buck-boost switching power supply circuit according to an embodiment of the present invention. Figure 2 As shown, the buck-boost switching power supply circuit 10 of the present invention is used to convert input power into output power. The buck-boost switching power supply circuit 10 includes a power switch circuit 101 and a control circuit 103. 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 LX1 of the inductor L to the input power or the ground potential, and the output switch unit 1012 is used to switch the second end LX2 of the inductor L to the output power or the ground potential to convert the input power into the output power.

[0081] Figure 3 is a circuit diagram showing a buck-boost switching power supply circuit according to another embodiment of the present invention. Figure 2 and Figure 3 The control circuit 103 includes a switch control circuit 1031, an error amplifier circuit 1032, a bypass control circuit 1033 and an analog-to-digital conversion circuit 1034. The analog-to-digital conversion circuit 1034 is used to generate a digital input voltage signal DVIN according to the input voltage VIN. The error amplifier circuit 1032 compares the fourth reference voltage Vref4 with the output voltage related signal VFB related to the output voltage VOUT to generate an error amplified signal EAO.

[0082] The switch control circuit 1031 is used to control the power switch circuit 101 in a pulse width modulation manner according to the error amplification signal EAO in a regulation operation mode to convert the input power into the output power, and generate a plurality of switching signals VA, VB, VC, VD for controlling the power switch circuit 101 and a switching signal VE for controlling the bypass switch E.

[0083] The bypass control circuit 1033 is used to control the buck-boost switching power supply circuit 10 to enter and exit the bypass mode according to the bypass enable signal By_en, the digital input voltage signal DVIN and the target voltage VOUT_targ. The operation details will be described in detail later.

[0084] The switch control circuit 1031 is also used to control the power switch circuit 101 to operate in the bypass stage according to the bypass control signal SBYPS in the bypass mode, and to control the power switch circuit 101 to enter the forced continuous conduction mode in the first transition stage and / or the second transition stage according to the forced continuous conduction control signal SFCCM, wherein the operation details of each mode and each stage will be described in detail later.

[0085] Continue to refer to Figure 3 The input switch unit 1011 includes an input upper bridge switch A and an input lower bridge switch B (in one embodiment, the input lower bridge switch B may also be an input lower bridge diode). The input upper bridge switch A is coupled between the input power supply and the first end LX1 of the inductor L, and the input lower bridge switch B or the input lower bridge diode is coupled between the ground potential and the first end LX1 of the inductor L. The input upper bridge switch A and the input lower bridge switch B or the input lower bridge diode are used to switch the first end LX1 of the inductor L to the input power supply or the ground potential.

[0086] Please refer to Figure 3 The output switch unit 1012 includes an output lower bridge switch C and an output upper bridge switch D. The output lower bridge switch C is coupled between the ground potential and the second end LX2 of the inductor L, and the output upper bridge switch D is coupled between the output power supply and the second end LX2 of the inductor L. The output lower bridge switch C and the output upper bridge switch D are used to switch the second end LX2 of the inductor L to the output power supply or the ground potential.

[0087] Please refer to Figure 3 In one embodiment, when the bypass enable signal By_en is at the enable level, the buck-boost switching power supply circuit 10 operates in the bypass mode, and when the difference between the input voltage VIN of the input power supply and the output voltage VOUT of the output power supply, that is, the absolute value of the conversion voltage difference is less than the first reference voltage Vref1, it enters the bypass stage. Specifically, the bypass control circuit 1033 controls the power switch circuit 101 to bypass the input power supply and the output power supply and electrically connect them, so that the buck-boost switching power supply circuit 10 operates in the bypass stage of the bypass mode.

[0088] Please refer to Figure 3 In the bypass mode, before entering the bypass stage, the bypass control circuit 1033 controls the buck-boost switching power supply circuit 10 to operate in the first transition stage, and / or after the bypass mode, the bypass control circuit 1033 controls the buck-boost switching power supply circuit 10 to operate in the second transition stage.

[0089] like Figure 3 As shown, in the first transition stage, the bypass control circuit 1033 controls the output voltage VOUT to gradually change toward the input voltage VIN in a feedback regulation manner until the conversion voltage difference is less than the first reference voltage Vref1, and the first transition stage is ended. It should be noted that the so-called gradual change is to change the output voltage VOUT at a speed that avoids causing the ringing amplitude of the output voltage VOUT to exceed the threshold of the overvoltage protection mechanism.

[0090] like Figure 3 As shown, in the second transition stage, the bypass control circuit 1033 controls the output voltage VOUT to gradually change toward the target voltage VOUT_targ in a feedback regulation manner until the output voltage VOUT is equal to the target voltage VOUT_targ.

[0091] In one embodiment, in the first transition stage of the bypass mode, the bypass control circuit 1033 gradually changes the fourth reference voltage Vref4 according to the input voltage VIN and the target voltage VOUT_targ, and gradually adjusts the output voltage VOUT in a feedback regulation manner according to the fourth reference voltage Vref4, thereby causing the output voltage VOUT to gradually change toward the input voltage VIN until the absolute value of the converted voltage difference is less than the first reference voltage Vref1, wherein the initial value of the fourth reference voltage Vref4 is related to the target voltage VOUT_targ.

[0092] In one embodiment, in the second transition stage, the bypass control circuit 1033 gradually changes the fourth reference voltage Vref4 according to the input voltage VIN and the target voltage VOUT_targ, and gradually adjusts the output voltage VOUT in a feedback regulation manner according to the fourth reference voltage Vref4, thereby causing the output voltage VOUT to gradually change toward the target voltage VOUT_targ until the output voltage VOUT is equal to the target voltage VOUT_targ, wherein the initial value of the fourth reference voltage Vref4 is related to the target voltage VOUT_targ.

[0093] like Figure 3 As shown, when not operating in the bypass mode (e.g., in the aforementioned regulation operation mode), the bypass control circuit 1033 enables the bypass enable signal By_en according to the conversion-related voltage difference between the input voltage VIN and the output-related voltage being less than the second reference voltage Vref2, or the bypass control circuit 1033 enables the bypass enable signal By_en according to an external instruction, wherein the second reference voltage Vref2 is greater than the first reference voltage Vref1. In one embodiment, the output-related voltage is the output voltage VOUT or the target voltage VOUT_targ.

[0094] Continue to refer to Figure 3 In one embodiment, in the bypass stage, the output upper bridge switch D in the output switch unit 1012 and the input upper bridge switch A in the input switch unit 1011 are both turned on to electrically connect the input power supply and the output power supply via the inductor L.

[0095] Continue to refer to Figure 3 In another embodiment, the buck-boost switching power supply circuit 10 further includes a bypass switch E, which is directly electrically connected between the input power supply and the output power supply. In the bypass stage, the bypass control circuit 1033 controls the bypass switch E to be turned on to directly electrically connect the input power supply and the output power supply.

[0096] The bypass control circuit 1033 controls the output voltage VOUT in a feedback regulation manner during the first transition stage and / or during the second transition stage, thereby preventing the output voltage from overshooting or undershooting.

[0097] In one embodiment, the target voltage VOUT_targ is the initially set output voltage VOUT. In another embodiment, the target voltage VOUT_targ may be a set voltage updated during the bypass stage. In one embodiment, the buck-boost switching power supply circuit 10 enters the bypass stage of the bypass mode only when the absolute value of the conversion voltage difference is less than the first reference voltage Vref1.

[0098] Figure 4 FIG. 1 is a circuit block diagram showing a bypass control circuit of a buck-boost switching power supply circuit according to an embodiment of the present invention. Figure 4 As shown, the bypass control circuit 1033 includes a reference voltage generating circuit 10331, which is used to generate a fourth reference voltage Vref4 according to the target voltage VOUT_targ and the digital input voltage signal DVIN. In one embodiment, the bypass control circuit 1033 is also used to control the buck-boost switching power supply circuit 10 to stop supplying power to at least one of the reference voltage generating circuit 10331 and the error amplifier circuit 1032 during the bypass stage, so as to achieve power saving effect and increase power conversion efficiency under extremely light load.

[0099] Please also see Figure 3 and Figure 5 , Figure 5 According to an embodiment of the present invention, Figure 3 The input voltage VIN, the output voltage VOUT, the target voltage VOUT_targ, the bypass control signal SBYPS, the forced continuous conduction control signal SFCCM, the bypass enable signal By_en, the inductor current IL and the first reference voltage Vref1 are shown in FIG. Figure 5 .like Figure 5As shown, this embodiment enables or disables the bypass enable signal By_en according to an external instruction. In one embodiment, when the bypass enable signal By_en is enabled and enters the bypass mode, the first transition stage is entered at time point t1. In the first transition stage, the bypass control circuit 1033 controls the output voltage VOUT to gradually change toward the input voltage VIN in a feedback regulation manner until the conversion voltage difference is less than the first reference voltage Vref1, and then the first transition stage is ended. In this embodiment, the conversion voltage difference is equal to the absolute value of the difference between the input voltage VIN and the output voltage VOUT. It should be noted that the so-called gradual change is to change the output voltage VOUT at a speed that avoids causing the ringing amplitude of the output voltage VOUT to exceed the threshold of the overvoltage protection mechanism. Specifically, for example, the gradual change of the output voltage VOUT is achieved by gradually adjusting the fourth reference voltage Vref4 as mentioned above.

[0100] Continue to refer to Figure 5 When the absolute value of the conversion voltage difference between the input voltage VIN and the output voltage VOUT is less than the first reference voltage Vref1 (time point t2), the bypass control circuit 1033 controls the buck-boost switching power supply circuit 10 to end the first transition stage and enter the bypass stage of the bypass mode. As mentioned above, in the bypass stage, the input power supply and the output power supply are electrically connected via the output upper bridge switch D and the input upper bridge switch A and the inductor L in the input switch unit 1011, or are electrically connected via the bypass switch E. Therefore, after time point t2 and between time point t3, the output voltage VOUT is equal to the input voltage VIN.

[0101] Continue to refer to Figure 5 In one embodiment, when the bypass enable signal By_en is disabled at time point t3 and decides to leave the bypass mode, the second transition stage is entered. As described above, in the second transition stage, the bypass control circuit 1033 controls the output voltage VOUT to gradually change toward the target voltage VOUT_targ in a feedback adjustment manner until the output voltage VOUT is equal to the target voltage VOUT_targ. In this embodiment, the target voltage VOUT_targ is the same as the initial value and does not change.

[0102] Continue to refer to Figure 5 In one embodiment, in the first transition stage (from time point t1 to time point t2) and the second transition stage (from time point t3 to time point t4), as shown by the inductor current IL, the bypass control circuit 1033 controls the buck-boost switching power supply circuit 10 to enter the forced continuous conduction mode (FCCM) to perform conversion between the input power supply and the output power supply.

[0103] Please also see Figure 3 and Figure 6 , Figure 6 According to another embodiment of the present invention, Figure 3 Schematic diagram of the signal waveform of the circuit. Figure 6 An embodiment similar to Figure 5 The embodiment is different in that, in Figure 6 In the embodiment, in the second transition stage (time point t3 to time point t4), the bypass control circuit 1033 controls the buck-boost switching power supply circuit 10 not to enter the forced continuous conduction mode. Specifically, in the present embodiment, in the second transition stage (time point t3 to time point t4), the forced continuous conduction control signal SFCCM (solid line) is prohibited, the inductor current IL is not switched and is 0, that is, the output voltage VOUT only decreases according to the consumption of the load (solid line), wherein the dotted line forced continuous conduction control signal SFCCM and the dotted line output voltage VOUT are the waveforms of the forced continuous conduction mode.

[0104] Please also see Figure 3 and Figure 7 . Figure 7 According to yet another embodiment of the present invention, Figure 3 The input voltage VIN, the output voltage VOUT, the target voltage VOUT_targ, the bypass control signal SBYPS, the forced continuous conduction control signal SFCCM, the bypass enable signal By_en, the inductor current IL, the first reference voltage Vref1, the second reference voltage Vref2 and the third reference voltage Vref3 are shown in FIG. Figure 7 .like Figure 7 As shown, in this embodiment, the bypass enable signal By_en is enabled or disabled according to the absolute value of the conversion-related voltage difference, so as to adaptively determine whether to enter or leave the bypass mode, wherein the conversion-related voltage difference refers to the voltage difference between the input voltage VIN and the output-related voltage. In this embodiment, the output-related voltage is the target voltage VOUT_targ. In other words, in this embodiment, the conversion-related voltage difference refers to the voltage difference between the input voltage VIN and the target voltage VOUT_targ. In this embodiment, in the non-bypass mode, when the absolute value of the conversion-related voltage difference between the target voltage VOUT_targ and the input voltage VIN is less than the second reference voltage Vref2, it is determined to enter the bypass mode. On the other hand, in the bypass mode, when the absolute value of the conversion-related voltage difference between the target voltage VOUT_targ and the input voltage VIN is greater than the third reference voltage Vref3, it is determined to leave the bypass mode.

[0105] Continue reading Figure 7At time point t1, after the target voltage VOUT_targ is converted, the absolute value of the voltage difference between the target voltage VOUT_targ and the input voltage VIN (i.e., the conversion-related voltage difference) is less than the second reference voltage Vref2, so the bypass control circuit 1033 enables the bypass enable signal By_en to control the buck-boost switching power supply circuit 10 to enter the bypass mode, and enter the first transition stage at time point t1, that is, the bypass control circuit 1033 controls the output voltage VOUT to gradually change toward the input voltage VIN in a feedback regulation manner until the conversion voltage difference is less than the first reference voltage Vref1, and the first transition stage ends. At time point t2, the conversion voltage difference is less than the first reference voltage Vref1, so the bypass control circuit 1033 controls the buck-boost switching power supply circuit 10 to enter the bypass stage of the bypass mode, and electrically connects the input power supply to the output power supply. Next, in the present embodiment, at time point t3, after the target voltage VOUT_targ changes again, the conversion-related voltage difference with the input voltage VIN is greater than the third reference voltage Vref3, so the bypass control circuit 1033 controls the buck-boost switching power supply circuit 10 to leave the bypass stage of the bypass mode and enter the second transition stage (time point t3 to t4), wherein in the second transition stage, the bypass control circuit 1033 controls the output voltage VOUT to gradually change toward the target voltage VOUT_targ in a feedback regulation manner until the output voltage VOUT is equal to the target voltage VOUT_targ (time point t4), at which time the second transition stage ends and returns to the regulation operation mode (time point t4 to t5), and the output voltage VOUT is regulated to the target voltage VOUT_targ in a feedback regulation manner.

[0106] It is worth noting that before time point t1, although the target voltage VOUT_targ also changes, the conversion-related voltage difference between the input voltage VIN and the target voltage VOUT_targ is still greater than the second reference voltage Vref2, so the bypass control circuit 1033 adaptively determines that there is no need to enter the bypass mode.

[0107] Continue reading Figure 7 Then, from time point t5 to t6, it enters the first transition stage of another bypass mode again. From time point t6 to t7, it enters the bypass stage of another bypass mode. From time point t7 to t8, it enters another second transition stage. From time point t8 onwards, it enters another regulating operation mode. Each mode and stage is similar to the above, so it will not be repeated here.

[0108] Please also see Figure 3 and Figure 8 , Figure 8 According to another embodiment of the present invention, Figure 3 Schematic diagram of the signal waveform of the circuit. Figure 8 An embodiment similar to Figure 7 The difference is that Figure 8 In the embodiment of the present invention, the output-related voltage is the output voltage VOUT, that is, the conversion-related voltage difference used to determine whether to enter or exit the bypass mode refers to the voltage difference between the output voltage VOUT and the input voltage VIN.

[0109] Continue reading Figure 8 At time t1', after the target voltage VOUT_targ changes, the output voltage VOUT starts to rise in order to adjust to the target voltage VOUT_targ. Then, at time t1, the conversion-related voltage difference between the output voltage VOUT and the input voltage VIN is less than the second reference voltage Vref2, so the bypass control circuit 1033 enables the bypass enable signal By_en to control the buck-boost switching power supply circuit 10 to enter the bypass mode. The first transition stage and the bypass stage in the remaining bypass mode, as well as the second transition stage of leaving the bypass mode, are similar to Figure 7 On the other hand, at time point t5' and time point t5, the judgment and operation are similar to those at time points t1' and t1, which are not described in detail here.

[0110] As described above, the present invention can enter the bypass mode from the boost mode / buck mode / boost-boost mode. Regardless of the size of the load current, it can smoothly enter or exit the bypass mode through the first transition stage or the second transition stage, effectively avoiding the overshoot or undershoot that may be caused when the output voltage VOUT switches with the bypass mode.

[0111] The present invention has been described above with respect to the preferred embodiment, but the above description is only to make it easy for those skilled in the art to understand the content of the present invention, and is not used to limit the widest scope of the rights of the present invention. The various embodiments described are not limited to individual applications, but can also be used 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, converting the signal to voltage and current, current and voltage, and / or ratio conversion, and then processing or calculating according to 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 one by one here. 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 power supply into an output power supply, comprising: A power switch circuit comprises an input switch unit and an output switch unit, wherein the input switch unit is used to switch a first end of an inductor to the input power supply or a ground potential, and the output switch unit is used to switch a second end of the inductor to the output power supply or the ground potential, so as to convert the input power supply into the output power supply; and a bypass control circuit for determining whether the buck-boost switching power supply circuit operates in a bypass mode according to a bypass enable signal; in, When the bypass enable signal is at an enable level, the buck-boost switching power supply circuit operates in the bypass mode, and when the absolute value of a conversion voltage difference between an input voltage of the input power supply and an output voltage of the output power supply is less than a first reference voltage, the bypass control circuit controls the power switch circuit so that the input power supply and the output power supply are bypassed and electrically connected, and the buck-boost switching power supply circuit operates in a bypass stage of the bypass mode; Wherein, in the bypass mode, before the bypass stage, the bypass control circuit controls the buck-boost switching power supply circuit to operate in a first transition stage, and / or after the bypass mode, the bypass control circuit controls the buck-boost switching power supply circuit to operate in a second transition stage; In the first transition stage, the bypass control circuit controls the output voltage to gradually change toward the input voltage in a feedback regulation manner until the conversion voltage difference is less than the first reference voltage, thereby terminating the first transition stage; In the second transition stage, the bypass control circuit controls the output voltage to gradually change toward a target voltage in a feedback regulation manner until the output voltage is equal to the target voltage.

2. The buck-boost switching power supply circuit according to claim 1, wherein: When not operating in the bypass mode, the bypass control circuit enables the bypass enable signal based on a conversion-related voltage difference between the input voltage and an output-related voltage being less than a second reference voltage, or based on an external instruction, wherein the second reference voltage is greater than the first reference voltage; wherein the output-related voltage is the output voltage or the target voltage.

3. The buck-boost switching power supply circuit according to claim 1, wherein: In the bypass stage, when an adjusted voltage difference between the input voltage and the target voltage is greater than a third reference voltage, the bypass control circuit disables the bypass enable signal to control the buck-boost switching power supply circuit to end the bypass stage of the bypass mode and start the second transition stage.

4. The buck-boost switching power supply circuit according to claim 1, wherein: In the first transition stage of the bypass mode, the bypass control circuit gradually changes a fourth reference voltage according to the input voltage and the target voltage, and gradually adjusts the output voltage in a feedback regulation manner according to the fourth reference voltage, thereby causing the output voltage to gradually change toward the input voltage until the absolute value of the conversion voltage difference is less than the first reference voltage, wherein an initial value of the fourth reference voltage is related to the target voltage.

5. The buck-boost switching power supply circuit according to claim 1, wherein: In the second transition stage, the bypass control circuit gradually changes a fourth reference voltage according to the input voltage and the target voltage, and gradually adjusts the output voltage in a feedback regulation manner according to the fourth reference voltage, thereby causing the output voltage to gradually change toward the target voltage until the output voltage is equal to the target voltage, wherein an initial value of the fourth reference voltage is related to the target voltage.

6. The buck-boost switching power supply circuit according to claim 1, wherein: In the bypass stage, an output upper bridge switch in the output switch unit and an input upper bridge switch in the input switch unit are both turned on to electrically connect the input power source and the output power source via the inductor.

7. The buck-boost switching power supply circuit according to claim 1, wherein: The device also includes a bypass switch, which is directly electrically connected between the input power source and the output power source. In the bypass stage, the bypass control circuit controls the bypass switch to be turned on to directly electrically connect the input power source and the output power source.

8. The buck-boost switching power supply circuit according to claim 1, wherein: The bypass control circuit controls the output voltage in a feedback regulation manner during the first transition stage and / or during the second transition stage, thereby preventing the output voltage from overshooting or undershooting.

9. The buck-boost switching power supply circuit according to claim 1, wherein: The input switch unit comprises: an input upper bridge switch coupled between the input power source and the first end of the inductor; and An input lower bridge switch or an input lower 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 to the input power source or the ground potential.

10. The buck-boost switching power supply circuit according to claim 1, wherein: The output switch unit comprises: an output lower bridge switch coupled between the ground potential and the second end of the inductor; and An output upper bridge switch coupled between the output power source and the second end of the inductor; The output lower bridge switch and the output upper bridge switch are used to switch the second end of the inductor to the output power source or the ground potential.

11. The buck-boost switching power supply circuit according to claim 1, wherein: In the first transition stage, the bypass control circuit controls the buck-boost switching power supply circuit to enter a forced continuous conduction mode.

12. The buck-boost switching power supply circuit according to claim 1, wherein: In the second transition stage, the bypass control circuit controls the buck-boost switching power supply circuit to enter or not enter a forced continuous conduction mode.

13. The buck-boost switching power supply circuit according to claim 1, wherein: The target voltage is the initially set output voltage or a set voltage updated during the bypass phase.

14. The buck-boost switching power supply circuit according to claim 6, wherein: The buck-boost switching power supply circuit enters the bypass stage of the bypass mode only after the absolute value of the conversion voltage difference is less than the first reference voltage and the output upper bridge switch and the input upper bridge switch are both turned on.

15. The buck-boost switching power supply circuit according to claim 4, wherein: It also includes an error amplifier circuit, wherein the bypass control circuit includes a reference voltage generating circuit, and the error amplifier circuit generates an error amplification signal according to the fourth reference voltage and an output voltage related signal related to the output voltage, and the error amplification signal is used to generate a plurality of switching signals for controlling the power switch circuit, wherein the bypass control circuit is also used to control the buck-boost switching power supply circuit to stop supplying power to at least one of the reference voltage generating circuit and the error amplifier circuit during the bypass stage, wherein the fourth reference voltage is generated by the reference voltage generating circuit according to the target voltage and the input voltage.

16. A control method of a buck-boost switching power supply circuit, for converting an input power supply into an output power supply, comprising: When a bypass enable signal is at an enable level, a buck-boost switching power supply circuit is operated in a bypass mode; When the absolute value of a conversion voltage difference between an input voltage of the input power source and an output voltage of the output power source is less than a first reference voltage, the input power source and the output power source are controlled to be bypassed and electrically connected, and the buck-boost switching power supply circuit is operated in a bypass stage of the bypass mode; In the bypass mode, before the bypass stage, the buck-boost switching power supply circuit is controlled to operate in a first transition stage, and / or after the bypass mode, the buck-boost switching power supply circuit is controlled to operate in a second transition stage; In the first transition stage, the output voltage is controlled to gradually change toward the input voltage in a feedback regulation manner until the conversion voltage difference is less than the first reference voltage, thereby terminating the first transition stage; and In the second transition stage, the output voltage is controlled to gradually change toward a target voltage in a feedback regulation manner until the output voltage is equal to the target voltage.

17. The control method of the buck-boost switching power supply circuit according to claim 16, wherein: Also includes: The bypass enable signal is enabled based on a conversion-related voltage difference between the input voltage and an output-related voltage being less than a second reference voltage, or based on an external instruction, wherein the second reference voltage is greater than the first reference voltage; wherein the output-related voltage is the output voltage or the target voltage.

18. The control method of the buck-boost switching power supply circuit according to claim 16, wherein: Also includes: In the bypass stage, when a regulated voltage difference between the input voltage and the target voltage is greater than a third reference voltage, the bypass enable signal is disabled to control the buck-boost switching power supply circuit to end the bypass stage of the bypass mode and start the second transition stage.

19. The control method of the buck-boost switching power supply circuit according to claim 16, wherein: In the first transition phase, the step of controlling the output voltage to gradually change toward the input voltage in a feedback regulation manner until the conversion voltage difference is less than the first reference voltage includes: In the first transition phase of the bypass mode, gradually changing a fourth reference voltage according to the input voltage and the target voltage; and gradually adjusting the output voltage in a feedback regulation manner according to the fourth reference voltage, thereby causing the output voltage to gradually change toward the input voltage until the absolute value of the conversion voltage difference is less than the first reference voltage; An initial value of the fourth reference voltage is related to the target voltage.

20. The control method of the buck-boost switching power supply circuit according to claim 16, wherein: In the second transition stage, the step of controlling the output voltage to gradually change toward the target voltage in a feedback regulation manner until the output voltage is equal to the target voltage includes: In the second transition phase, gradually changing a fourth reference voltage according to the input voltage and the target voltage; and The output voltage is gradually adjusted in a feedback regulation manner according to the fourth reference voltage, thereby gradually changing the output voltage toward the target voltage until the output voltage is equal to the target voltage, wherein an initial value of the fourth reference voltage is related to the target voltage.

21. The control method of the buck-boost switching power supply circuit according to claim 16, wherein: The buck-boost switching power supply circuit includes a power switch circuit, which includes an input switch unit and an output switch unit, wherein the step of controlling the input power supply and the output power supply to be bypassed and electrically connected, and making the buck-boost switching power supply circuit operate in the bypass stage of the bypass mode includes: in the bypass stage, controlling an output upper bridge switch in the output switch unit and an input upper bridge switch in the input switch unit to be turned on, so as to electrically connect the input power supply and the output power supply via an inductor.

22. The control method of the buck-boost switching power supply circuit according to claim 16, wherein: The buck-boost switching power supply circuit includes a bypass switch, which is directly electrically connected between the input power supply and the output power supply, wherein the step of controlling the input power supply and the output power supply to be electrically connected by bypassing each other and making the buck-boost switching power supply circuit operate in the bypass stage of the bypass mode includes: in the bypass stage, controlling the bypass switch to be turned on to directly electrically connect the input power supply and the output power supply.

23. The control method of the buck-boost switching power supply circuit according to claim 16, wherein: The method also includes: in the first transition stage, controlling the buck-boost switching power supply circuit to enter a forced continuous conduction mode.

24. The control method of the buck-boost switching power supply circuit according to claim 16, wherein: The method further comprises: in the second transition stage, controlling the buck-boost switching power supply circuit to enter or not enter a forced continuous conduction mode.

25. The control method of the buck-boost switching power supply circuit according to claim 16, wherein: The target voltage is the initially set output voltage or a set voltage updated during the bypass phase.

26. The control method of the buck-boost switching power supply circuit according to claim 21, wherein: The buck-boost switching power supply circuit enters the bypass stage of the bypass mode only after the absolute value of the conversion voltage difference is less than the first reference voltage and the output upper bridge switch and the input upper bridge switch are both turned on.

27. The control method of the buck-boost switching power supply circuit according to claim 19, wherein: The buck-boost switching power supply circuit includes an error amplifier circuit, a power switch circuit and a reference voltage generating circuit. The error amplifier circuit generates an error amplifier signal according to the fourth reference voltage and an output voltage related signal related to the output voltage. The error amplifier signal is used to generate a plurality of switching signals for controlling the power switch circuit. The control method further includes: during the bypass stage, controlling the buck-boost switching power supply circuit to stop supplying power to at least one of the reference voltage generating circuit and the error amplifier circuit. The fourth reference voltage is generated by the reference voltage generating circuit according to the target voltage and the input voltage.

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