CN111030480A

CN111030480A - Switching power supply system and constant voltage control circuit

Info

Publication number: CN111030480A
Application number: CN201911401088.7A
Authority: CN
Inventors: 朱臻; 胡黎强; 卢鹏飞; 郜小茹; 陈一辉; 孙顺根
Original assignee: Shanghai Bright Power Semiconductor Co Ltd
Current assignee: Shanghai Bright Power Semiconductor Co Ltd
Priority date: 2019-12-30
Filing date: 2019-12-30
Publication date: 2020-04-17
Also published as: WO2021136083A1; CN112039353A

Abstract

The application provides a switching power supply system, which comprises a first controller, a second controller, a power inductor and an output capacitor. The ground terminal of the first controller is coupled to the ground terminal of the switching power supply system and has a first reference level. The first controller is used for generating a PWM voltage signal according to an output voltage from a switching power supply system and converting the PWM voltage signal into a first driving signal based on a first reference level. The ground terminal of the second controller is separated from the ground terminal of the first controller, and has a second reference level. The second controller is configured to convert the first driving signal into a second driving signal based on the second reference level and generate the output voltage at the output capacitor through the power inductor.

Description

Switching power supply system and constant voltage control circuit

Technical Field

The present disclosure relates to switching power supply systems, and particularly to a Buck (Buck), Buck-Boost (Buck-Boost) or Flyback (Flyback) switching power supply system.

Background

The Buck (Buck), Buck-Boost (Buck-Boost) or Flyback (Flyback) type alternating current-direct current conversion (AC-DC) switching power supply system has a very simple structure and reliable performance. The switch power supply systems with the structures have wide application in the aspects of small household appliance slave power supply, Internet of things intelligent switch power supply and intelligent induction power supply. Since the input of the AC-DC power supply is usually a higher AC voltage, the chip ground potential of the switching power supply controller is higher than the system ground potential for chip manufacturing process reasons. Such limitations often require the addition of potential conversion circuits or components when sampling the feedback signal.

Fig. 1 illustrates a known buck auxiliary power supply system. The system 100 includes a rectifier bridge (D1, D2, D3, D4), an input capacitor Cin, a power inductor L, a freewheeling diode DX, a current sampling resistor Rs, an output capacitor Co, a supply diode Ds, a supply filter capacitor Cf, and a constant voltage control circuit 101. The constant voltage control circuit 101 is, for example, a constant voltage control chip BP2525X manufactured by shanghai crystal feng source semiconductor gmbh. The control circuit 101 has a controller 102 and a power switch M1 therein.

When the system 100 is operating, the output voltage Vo is input to the control circuit 101 via the diode Ds as an output feedback control signal. The signal is processed by a controller 102 within the control circuit 101 to generate a PWM signal. The PWM signal controls the on and off times of the power switch M1, which in turn controls the output voltage. Such a negative feedback loop causes the output voltage to be modulated at a value predetermined by the internal reference voltage of the controller 102.

There are some disadvantages to the above control approach. First, the output voltage error is large. This is because the output voltage can only be sampled when the power switch M1 is off and the power inductor L is in the demagnetized state (the freewheeling diode Dx is in the on-state). At this time, the chip ground (VSS) is lower than the system Ground (GND) by the forward conduction voltage drop VF of the diode Dx_DX. In addition, the output voltage is fed back to FB of the control circuit 101 via the diode Ds&VCC pin, so the feedback voltage is lower than the actual output voltage by the forward conduction voltage drop VF of the diode Ds_DS. Therefore, the feedback voltage actually received by the chip (relative to chip ground) is Vo-VF_DS+VF_DX. Since the forward conduction voltage drop VF of the diode is affected by various factors such as temperature, current, mutual matching, and the like, these uncertain factors are finally reflected as an error of the output voltage. The second is a relatively poor dynamic response. Because the control circuit 101 cannot receive the feedback signal of the output voltage in real time in this control mode, an effective feedback signal can be obtained only in the demagnetization stage. Therefore, if the load suddenly changes in a time period other than the demagnetization stage, the control circuit 101 cannot respond in time and modulates the PWM signal. Furthermore, since the output voltage ratio is low, usually 3V to 12V, in most applications of the constant voltage mode, the power loss on the follow current tube Dx is large, which results in a decrease in the efficiency of the entire power supply system.

Content of application

The application provides a switching power supply system which can improve output precision and dynamic response.

A switching power supply system according to one aspect of the present application includes a first controller, a second controller, a power inductor, and an output capacitor. The first controller is provided with a feedback end, a driving signal output end, a synchronization end and a grounding end, the grounding end of the first controller is coupled with the grounding end of the switching power supply system and is provided with a first reference level, the first controller comprises a PWM generator, a driving signal converter and a transistor, the PWM generator is coupled with the feedback end and is used for generating a PWM voltage signal according to output voltage from the feedback end and outputting the PWM voltage signal to the driving signal converter, the driving signal converter is coupled with the driving signal output end and is used for converting the PWM voltage signal into a first driving signal based on the first reference level, and the transistor is coupled between the synchronization end and the grounding end. The second controller is provided with a driving signal input end and a grounding end, the driving signal input end is coupled with the driving signal output end of the first controller, the grounding end of the second controller is coupled with the synchronous end of the first controller and is provided with a second reference level, the second controller comprises a driving signal detector, a first driver and a main power tube, the driving signal detector is coupled with the driving signal input end and is used for converting the first driving signal into a second driving signal based on the second reference level and outputting the second driving signal to the first driver, the output end of the first driver is coupled with the control end of the main power tube, and the output end of the main power tube is coupled with the grounding end of the second controller. The first end of the power inductor is coupled to the ground terminal of the second controller to generate an output voltage, and the second end of the power inductor is coupled to the feedback terminal of the first controller. The first end of the output capacitor is coupled to the feedback end of the first controller, and the second end of the output capacitor is coupled to the ground end of the switching power supply system.

In an embodiment of the present application, a ground terminal of the first controller is directly connected to a ground terminal of the switching power supply system.

In an embodiment of the present application, the first terminal of the output capacitor is directly connected to a feedback terminal of the first controller.

In an embodiment of the present application, the first controller is powered by the feedback terminal.

In an embodiment of the present application, the second controller further has a power supply terminal, and the switching power supply system further includes a rectifying circuit and an input capacitor. The rectifying circuit is coupled with the grounding end of the first controller and the power end of the second controller. The input capacitor is coupled to a ground terminal of the first controller and a power terminal of the second controller.

In an embodiment of the present application, the first driving signal is a PWM current signal.

In an embodiment of the application, the transistor is a synchronous rectification power transistor, and the first controller further includes a second driver, an input terminal of the second driver is coupled to the output terminal of the PWM generator, and an output terminal of the second driver is coupled to a control terminal of the synchronous rectification power transistor.

In an embodiment of the present application, the first controller and the second controller are each a die and are packaged in the same chip.

In an embodiment of the present application, the first controller and the second controller are independently packaged chips.

In an embodiment of the present application, the PWM generator includes a voltage dividing circuit, an operational amplifier, a sawtooth generator, and a comparator. The voltage division circuit is used for dividing the output voltage into feedback voltage. The operational amplifier is used for generating an amplified difference voltage according to a reference voltage and the feedback voltage. The sawtooth generator is used for providing sawtooth voltage. The comparator is used for comparing the difference voltage with the sawtooth wave voltage to generate the PWM voltage signal.

In one embodiment of the present application, the PWM generator includes a voltage dividing circuit, an operational amplifier, a sawtooth generator, a comparator, and a synchronous rectification signal generator. The voltage division circuit is used for dividing the output voltage into feedback voltage. The operational amplifier is used for generating an amplified difference voltage according to a reference voltage and the feedback voltage. The sawtooth generator is used for providing sawtooth voltage. The comparator is used for comparing the difference voltage with the sawtooth wave voltage to generate the PWM voltage signal. The synchronous rectification signal generator is used for generating a synchronous rectification PWM signal which is not overlapped with the PWM voltage signal according to the PWM voltage signal.

In an embodiment of the present application, the sawtooth wave generator is further configured to generate a low-frequency sawtooth wave at an initial start of the switching power supply system.

A constant voltage controller according to another aspect of the present application, for a switching power supply system, includes a first controller and a second controller. The first controller is provided with a feedback end, a driving signal output end, a synchronization end and a grounding end, the grounding end of the first controller is suitable for being coupled with the grounding end of the switching power supply system and is provided with a first reference level, the first controller comprises a PWM generator, a driving signal converter and a transistor, the PWM generator is coupled with the feedback end and is used for generating a PWM voltage signal according to output voltage from the feedback end and outputting the PWM voltage signal to the driving signal converter, the driving signal converter is coupled with the driving signal output end and is used for converting the PWM voltage signal into a first driving signal based on the first reference level, and the transistor is coupled between the synchronization end and the grounding end. The second controller is provided with a driving signal input end and a grounding end, the driving signal input end is coupled with the driving signal output end of the first controller, the grounding end of the second controller is coupled with the synchronous end of the first controller and is provided with a second reference level, the second controller comprises a driving signal detector, a first driver and a main power tube, the driving signal detector is coupled with the driving signal input end and is used for converting the first driving signal into a second driving signal based on the second reference level and outputting the second driving signal to the first driver, the output end of the first driver is coupled with the control end of the main power tube, and the output end of the main power tube is coupled with the grounding end of the second controller.

In an embodiment of the present application, a ground terminal of the first controller is adapted to be directly connected to a ground terminal of the switching power supply system.

In an embodiment of the present application, the feedback terminal of the first controller is adapted to directly input the output voltage of the switching power supply system.

In an embodiment of the application, the first controller is adapted to be powered by the feedback terminal.

Compared with the prior art, the first controller is used as a main controller and is grounded with the switching power supply system, and the second controller is separated from the ground of the first controller, so that the output voltage can be continuously fed back to the first controller in real time. Therefore, the output voltage and the feedback end of the first controller do not need to be isolated through a diode, and the precision and the dynamic response performance of the output voltage are improved.

Drawings

The accompanying drawings, which are included to provide a further understanding of the application and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the application and together with the description serve to explain the principle of the description. In the drawings:

fig. 1 is a schematic diagram of a conventional buck slave power system.

Fig. 2 is a schematic diagram of a buck switching power supply system according to an embodiment of the present application.

Fig. 3 is a schematic diagram of a PWM generator of a main controller in a master-slave buck constant voltage control circuit according to an embodiment of the present application.

Fig. 4 is a waveform diagram illustrating operation of the system shown in fig. 2.

Fig. 5 is a schematic diagram of a driving signal converter of a main controller in a master-slave buck constant voltage control circuit according to an embodiment of the present application.

Fig. 6 is a schematic diagram of a driving signal detector of a slave controller in a master-slave step-down constant voltage control circuit according to an embodiment of the present application.

Fig. 7 is a schematic diagram of another master-slave buck constant voltage control circuit according to an embodiment of the present application, in which a master controller transmits a PWM signal to a slave controller.

Fig. 8 is a schematic diagram of a master-slave buck power supply system according to another embodiment of the present application.

Detailed Description

In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings used in the description of the embodiments will be briefly introduced below. It is obvious that the drawings in the following description are only examples or embodiments of the application, from which the application can also be applied to other similar scenarios without inventive effort for a person skilled in the art. Unless otherwise apparent from the context, or otherwise indicated, like reference numbers in the figures refer to the same structure or operation.

As used in this application and the appended claims, the terms "a," "an," "the," and/or "the" are not intended to be inclusive in the singular, but rather are intended to be inclusive in the plural unless the context clearly dictates otherwise. In general, the terms "comprises" and "comprising" merely indicate that steps and elements are included which are explicitly identified, that the steps and elements do not form an exclusive list, and that a method or apparatus may include other steps or elements.

The relative arrangement of the components and steps, the numerical expressions, and numerical values set forth in these embodiments do not limit the scope of the present application unless specifically stated otherwise. Meanwhile, it should be understood that the sizes of the respective portions shown in the drawings are not drawn in an actual proportional relationship for the convenience of description. Techniques, methods, and apparatus known to those of ordinary skill in the relevant art may not be discussed in detail but are intended to be part of the specification where appropriate. In all examples shown and discussed herein, any particular value should be construed as merely illustrative, and not limiting. Thus, other examples of the exemplary embodiments may have different values. It should be noted that: like reference numbers and letters refer to like items in the following figures, and thus, once an item is defined in one figure, further discussion thereof is not required in subsequent figures.

It should be noted that the terms "first", "second", and the like are used to define the components, and are only used for convenience of distinguishing the corresponding components, and the terms have no special meanings unless otherwise stated, and therefore, the scope of protection of the present application is not to be construed as being limited. Further, although the terms used in the present application are selected from publicly known and used terms, some of the terms mentioned in the specification of the present application may be selected by the applicant at his or her discretion, the detailed meanings of which are described in relevant parts of the description herein. Further, it is required that the present application is understood not only by the actual terms used but also by the meaning of each term lying within.

It will be understood that when an element is referred to as being "on," "connected to," "coupled to," or "contacting" another element, it can be directly on, coupled or coupled to, or contacting the other element or intervening elements may be present. In contrast, when an element is referred to as being "directly on," "directly coupled to" or "directly contacting" another element, there are no intervening elements present. Similarly, when a first component is said to be "in electrical contact with" or "electrically coupled to" a second component, there is an electrical path between the first component and the second component that allows current to flow. The electrical path may include capacitors, coupled inductors, and/or other components that allow current to flow even without direct contact between the conductive components.

Fig. 2 is a schematic diagram of a buck switching power supply system according to an embodiment of the present application. Referring to fig. 2, the system 200 of the present embodiment may include a rectifier bridge 210, an input capacitor Cin, a constant voltage controller 220, a power inductor L, and an output capacitor Co. The rectifier bridge 210 typically includes 4 diodes D1, D2, D3, and D4. The input capacitor Cin is coupled to the output of the rectifier bridge 210. The constant voltage controller 220 may include a first controller 221 and a second controller 226 that are relatively independent. Here, the first controller 221 may serve as a Master controller (Master), and the second controller 226 may serve as a Slave controller (Slave).

The first controller 221 has a feedback terminal FB, a driving signal output terminal Sout, a synchronization terminal SYN, and a ground terminal VSL. The first controller 221 may include a PWM generator 222, a driving signal converter 223, and a second driver 224, and a synchronous rectification power tube M2. In some embodiments, the synchronous rectification power transistor M2 may be a separate power transistor instead of being part of the first controller 221. Ground terminal VSL is coupled to the ground GND of the switching power supply system 100. Further, this coupling does not cause isolation at any time, and may be a direct connection, for example. That is, the first controller 221 and the switching power supply system 100 are commonly grounded, and the level of the ground is assumed as the first reference level. The PWM generator 222 is coupled to the feedback terminal FB for generating PWM voltage signals PWM1 and PWM2 according to the output voltage Vo from the feedback terminal FB. Wherein the PWM1 is output to the driving signal converter 223 and the PWM2 is output to the second driver 224. The driving signal converter 223 is coupled to the driving signal output terminal Sout for converting the PWM voltage signal PWM1 into the PWM current signal I_PWM1. PWM current signal I_PWM1Is based on a first reference level. The second driver 224 is used for generating a driving signal DR2 according to the PWM2 and outputting the driving signal DR2 to the control terminal of the synchronous rectification power tube M2. A synchronous rectification power tube M2 is coupled between the synchronous terminal SYN and a ground terminal VSL.

The second controller 226 has a driving signal input terminal S_INA power supply terminal VH and a ground terminal VSH. The second controller 226 may include a linear regulator (LDO)227, a drive signal detector 228, a first driver 229, and a power tube M1. In some embodiments, the power transistor M1 may be a separate power transistor rather than a part of the second controller 226. Drive signal input terminal S_INIs coupled to the driving signal output terminal Sout of the first controller 221. The ground terminal VSH is coupled to the synchronization terminal SYN of the first controller 221, and the level thereof is set as a second reference level. Obviously, the second reference level is higher than the first reference level. The driving signal detector 228 is coupled to the driving signal input terminal S_INFor applying a PWM current signal I_PWM1Converted into a voltage driving signal PDR1, and output to the first driver 229. The voltage drive signal PDR1 is based on a second reference level. The output terminal of the first driver 229 is coupled to the control terminal of the power transistor M1, and the output terminal of the power transistor M1 is coupled to the ground terminal VSH.

Although the first controller 221 converts the PWM voltage signal PWM1 into the PWM current signal I in the present embodiment_PWM1It is understood that the PWM voltage signal PWM1 may be converted to a voltage signal based on the first reference level in other embodiments. Accordingly, the secondThe driving signal detector 228 of the controller 226 may convert the voltage signal based on the first reference level into a voltage signal based on the second reference level. In the embodiment of the present application, therefore, it is only necessary to convert the PWM voltage signal PWM1 into the first driving signal based on the first reference level in the first controller 221, and then convert the first driving signal into the second driving signal based on the second reference level in the second controller 226.

The rectifying circuit 210 is coupled to the power supply terminal VH of the second controller 226 and the ground terminal VSL of the first controller 221. The first controller 221 is powered by Vo from the feedback terminal FB without being powered by the power supply terminal VH. The LDO 227 takes power from the power source terminal VH and generates a voltage VDH supplied to the first driver 229 and the drive signal detector 228. The input capacitor Cin is coupled to the power supply terminal VH of the second controller 226 and the ground terminal VSL of the first controller 221.

The first terminal of the power inductor L is coupled to the ground terminal VSH of the second controller 226 to generate the output voltage Vo, and the second terminal thereof is coupled to the feedback terminal of the first controller 221 to use the output voltage Vo as the feedback voltage. The first terminal of the output capacitor Co is coupled to the feedback terminal FB of the first controller 221, and the second terminal is coupled to the ground terminal GND of the switching power supply system 200. Further, the first terminal of the output capacitor Co is directly connected to the feedback terminal of the first controller 221, and there is no device for generating a voltage difference therebetween.

In some embodiments, the first controller 221 and the second controller 226 are each relatively independent dies (Die), which may be co-packaged in one package. In other embodiments, the first controller 221 and the second controller 226 are each relatively independent chips (chips), each packaged in a different package.

In the present embodiment, since the "ground" (VSL terminal) of the first controller 221 is coupled to the system "ground" (GND), the first controller 221 is common to the output load Ro, and the second controller 226 is separated from the ground of the first controller, the output voltage Vo may be continuously sampled by the first controller 221 in real time. As shown in fig. 2, the output voltage Vo is directly fed back to the feedback input terminal FB of the first controller 221, and the signal Vo is further input to the PWM generator of the first controller 221And a generator 222. The PWM generator 222 processes the feedback signal FB to generate two signals, PWM1 and PWM2, respectively. The PWM2 signal is input to the first driver 224, and generates a synchronous driving signal DR2 to drive the synchronous rectification power tube M2; the PWM1 signal is input to the drive signal converter 223, and the PWM1 signal is converted into a synchronous current pulse signal I by the drive signal converter 223_PWM1. The signal I_PWM1The driving signal detector 228 is inputted to the second controller 226 and further restored to the synchronized voltage pulse modulation signal P by the driving signal detector 228_DR1. The signal P_DR1Further input to the second driver 229, a synchronized second driving signal DR1 is generated, and the power transistor M1 is driven.

Power transistor M1 acts as the main power transistor for switching power supply system 100 and controls the energy delivered from an Alternating Current (AC) power source to an output load. In the whole energy transfer process, the power tube M1 works in an on state and an off state, and when the driving signal DR1 is at a high level, the power tube M1 is turned on; when the driving signal DR1 is at low level, the power transistor M1 is turned off. By controlling the time of turn-on and turn-off, the energy delivered to the output load can be controlled. As shown in fig. 2, the output voltage Vo is input as a feedback signal to the PWM generator 222 of the first controller 221, and the PWM generator 222 generates a PWM1 signal by comparing the sampled output voltage Vo with an internal reference voltage. The signal PWM1 is processed by the driving signal converter 223, the driving signal detector 228 and the second driver 229 to form a synchronous driving control signal DR1, which controls the main power transistor M1. The signal is fed back from the output to the PWM generator 222, and then through the driving signal converter 223, the driving signal detector 228 and the second driver 229 are driven to control the main power transistor M1, and a complete negative feedback loop is formed by such a path that the power transistor M1 modulates the energy transmitted to the load. Since the negative feedback loop has a sufficiently high gain, the output voltage can be modulated to a predetermined value.

The power transistor M2 is a synchronous rectification power transistor, which can replace the conventional freewheeling diode and reduce the power consumption consumed on the freewheeling diode. When the power transistor M1 turns from on to off, the power inductor L forms a freewheeling loop through the load and the synchronous rectifier. In the process, the current of the power inductor L is gradually reduced from the maximum value when the power tube M1 is turned off. The power transistor M2 needs to start conducting immediately after the power transistor M1 turns off and turn off before the power inductor current decreases to 0 or before the main power transistor turns on next time. This requires the PWM generator 222 to generate a synchronous rectified drive signal PWM2 to control it. Since the conduction voltage drop limit of the power transistor M2 can be as high as 0V, and the conduction voltage drop of the conventional freewheeling diode is at least larger than its conduction threshold (usually 0.7V), the synchronous rectification structure has a greater potential for reducing loss and improving efficiency.

In summary, the embodiments of the present application are characterized by configuring a constant voltage control circuit in an AC-DC buck control system to include two independent controllers. A controller 221 as a master controller is common to the output load Ro; the other controller 226 is common to the master power transistor M1 as a slave controller. The "ground" (VSH) of the controller 226 is connected to the output voltage Vo through a power inductor L and is therefore floating. The output voltage Vo is continuously fed back to the controller 221 in real time, and the controller 221 generates the control signal PWM1 of the main power transistor M1 according to the feedback signal. The signal PWM1 is processed by the driving signal converter 223 in the controller 221 and transmitted to the driving signal converter 228 of the controller 222 through the packaging Wire 225, and is restored to the level signal PDR1 synchronized with the PWM1, and then converted into the main power transistor driving signal DR1 through the second driver 229 to drive the main power transistor M1. The embodiments of this sample application have many advantages. Firstly, after the ground potentials of the two

controllers

221 and 226 are separately set, the feedback signal is allowed to directly come from the output voltage Vo, so that the precision of the output voltage Vo is improved, and secondly, the output inductor does not need to wait for demagnetization when the feedback signal is sampled, so that the dynamic response performance is improved; moreover, the synchronous rectification structure improves the conversion efficiency.

Further details of the various units/components of the present application will be described hereinafter with reference to the drawings, however, it will be understood that various modifications/substitutions can be made by those skilled in the art without departing from the spirit of the present application after reading the following. The scope of protection of the application is therefore not limited to the embodiments described hereinafter.

Fig. 3 is a schematic diagram of a PWM generator of a Master chip (Master) in a Master-slave buck constant voltage control circuit according to an embodiment of the present application. Referring to fig. 3, the PWM generator 222 may include a sawtooth generator 301, a voltage dividing circuit composed of two voltage dividing resistors R1, R2, an operational amplifier (EA)302, a comparator 303, and a synchronization signal generator 304. The synchronization signal generator 304 may include an inverter, two nand gates, and two delay cells. When the output voltage Vo is inputted to the PWM generator 222, the feedback voltage FB is first formed by dividing the voltage through the voltage dividing resistors R1 and R2_INAnd input to the operational amplifier 302, and the other end of the operational amplifier 302 is coupled to an internal reference voltage Vref. The feedback voltage FB_INThe difference from the reference voltage is amplified by the operational amplifier 302 and output as a difference voltage V_EA. The difference voltage V_EAAnd a sawtooth wave voltage V output from the sawtooth wave generator 301_SAWThe two inputs of the comparator 303 are input, respectively, and the comparator 303 generates a PWM1 signal. The PWM1 signal is passed through the synchronization generator 304 to generate the synchronous rectified signal PWM2 that does not overlap with the PWM 1. As shown in fig. 2, the PWM1 and PWM2 convert into driving signals DR1 and DR2, respectively, which control the main power transistor M1 and the synchronous rectifier M2.

Fig. 4 illustrates an operation waveform diagram of the switching power supply system 100. As can be seen in FIG. 4, the internal feedback signal FB_INThe difference with Vref is amplified to a control signal V_EAThe signal and a sawtooth wave signal V_SAWOverlapped and compared by comparator 303 to form pulse modulated signal PWM 1. The PWM1 signal passes through the synchronous rectification signal generator to form a non-overlapping synchronous rectification control signal PWM 2. As shown in fig. 4, the sawtooth wave generator 301 generates a sawtooth wave with a lower frequency relative to the PWM switching frequency after entering a stable operating state when the system is initially started, so as to achieve soft start to avoid entering a deep continuous operating mode during start.

Fig. 5 is a schematic diagram of a driving signal converter of a main controller in a master-slave buck constant voltage control circuit according to an embodiment of the present application. The driving signal converter 223 may include a MOS transistor M5, a current limiting resistor R2, and a depletion mode Field Effect Transistor (FET). When PWM1 is high, MOS transistor M5 is turned on and the depletion mode FET generates a current signal, which is expressed as follows:

wherein V_PIs the pinch-off voltage of the depletion mode FET.

When the PWM1 is at low level, the MOS transistor M5 is turned off, I_FET0. Thus I_FETIs a PWM current.

Fig. 6 is a schematic diagram of a driving signal detector of a slave controller in a master-slave step-down constant voltage control circuit according to an embodiment of the present application. Referring to fig. 6, the driving signal detector 228 includes: a current mirror composed of two PMOS tubes M3 and M4, and a pull-down resistor R_PDAnd schmitt trigger SMT. Referring to fig. 2 in combination, the current PWM signal I output by the driving signal converter 223 in the first controller 221_PWMFrom S_INThe port inputs the drive signal detector 228. When I is_PWMThe signal is in a current state, and the pull-down resistor R_PDThe current mirrored by the PMOS tube M4 is pulled high, and the Schmitt trigger SMT is turned into high level; when I is_PWMThe signal is in a "no current state", and the input of the Schmitt trigger SMT is pulled down by a resistor R_PDPulled low and thus, the schmitt trigger SMT flips low. Thus, the PWM1 signal generated by the first controller 221 is restored to be completely synchronized with the PDR1 signal. The PDR1 signal is then passed through the second driver 229 to form the driving signal DR1 for the main power transistor M1.

Fig. 7 is a schematic diagram of another master-slave buck constant voltage control circuit according to an embodiment of the present application, in which a master controller transmits a PWM signal to a slave controller. Referring to FIG. 7, a PWM generator 222a in the main controller 221a generates two narrow pulse control signals, respectively PWM_ON、PWM_OFFThe two paths of signals respectively correspond to the on and off of the PWM signal. These two signals are simultaneously input to the drive signal converter 223a and converted to a synchronized narrow pulse current control signal. These two signals are input to the drive signal detector 228a of the slave controller and are divided into twoThe

current comparators

71, 72 are respectively restored to PWM_ON、PWM_OFFSynchronized narrow pulse voltage signal PD_ON、PD_OFF. These two signals are further input to a clock input and a clear input of a D flip-flop 73, respectively. The data input of the D flip-flop 73 is connected to a logic "1" (i.e., high). As shown in fig. 7, when PD is present_ONThe falling edge of (D) triggers the output PDR1 of the D flip-flop to go high; and the signal PWM_OFFThe D flip-flop 73 is cleared and the output of the D flip-flop goes low. The PWM signal is thus synchronously converted to PDR 1.

Fig. 8 is a schematic diagram of a master-slave buck power supply system according to another embodiment of the present application. The system of figure 8 differs from the system of figure 2 in that the synchronous rectified power transistor M2 in the system of figure 2 is replaced by a freewheeling diode Dx in figure 8. Therefore, in the system of fig. 8, the synchronous rectification control signal is no longer required to be generated, so the control method is simpler, at the cost of higher conduction voltage drop of the freewheeling diode Dx than that of the synchronous rectifier.

Having thus described the basic concept, it will be apparent to those skilled in the art that the foregoing disclosure is by way of example only, and is not intended to limit the present application. Various modifications, improvements and adaptations to the present application may occur to those skilled in the art, although not explicitly described herein. Such modifications, improvements and adaptations are proposed in the present application and thus fall within the spirit and scope of the exemplary embodiments of the present application.

Also, this application uses specific language to describe embodiments of the application. Reference throughout this specification to "one embodiment," "an embodiment," and/or "some embodiments" means that a particular feature, structure, or characteristic described in connection with at least one embodiment of the present application is included in at least one embodiment of the present application. Therefore, it is emphasized and should be appreciated that two or more references to "an embodiment" or "one embodiment" or "an alternative embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, some features, structures, or characteristics of one or more embodiments of the present application may be combined as appropriate.

Similarly, it should be noted that in the preceding description of embodiments of the application, various features are sometimes grouped together in a single embodiment, figure, or description thereof for the purpose of streamlining the disclosure aiding in the understanding of one or more of the embodiments. This method of disclosure, however, is not intended to require more features than are expressly recited in the claims. Indeed, the embodiments may be characterized as having less than all of the features of a single embodiment disclosed above.

Numerals describing the number of components, attributes, etc. are used in some embodiments, it being understood that such numerals used in the description of the embodiments are modified in some instances by the use of the modifier "about", "approximately" or "substantially". Unless otherwise indicated, "about", "approximately" or "substantially" indicates that the number allows a variation of ± 20%. Accordingly, in some embodiments, the numerical parameters used in the specification and claims are approximations that may vary depending upon the desired properties of the individual embodiments. In some embodiments, the numerical parameter should take into account the specified significant digits and employ a general digit preserving approach. Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the range are approximations, in the specific examples, such numerical values are set forth as precisely as possible within the scope of the application.

Although the present application has been described with reference to the present specific embodiments, it will be recognized by those skilled in the art that the foregoing embodiments are merely illustrative of the present application and that various changes and substitutions of equivalents may be made without departing from the spirit of the application, and therefore, it is intended that all changes and modifications to the above-described embodiments that come within the spirit of the application fall within the scope of the claims of the application.

Claims

1. A switching power supply system comprising:

the first controller is provided with a feedback end, a driving signal output end, a synchronization end and a grounding end, the grounding end of the first controller is coupled with the grounding end of the switching power supply system and is provided with a first reference level, the first controller comprises a PWM generator, a driving signal converter and a transistor, the PWM generator is coupled with the feedback end and is used for generating a PWM voltage signal according to output voltage from the feedback end and outputting the PWM voltage signal to the driving signal converter, the driving signal converter is coupled with the driving signal output end and is used for converting the PWM voltage signal into a first driving signal based on the first reference level, and the transistor is coupled between the synchronization end and the grounding end;

the second controller is provided with a driving signal input end and a grounding end, the driving signal input end is coupled with the driving signal output end of the first controller, the grounding end of the second controller is coupled with the synchronous end of the first controller and is provided with a second reference level, the second controller comprises a driving signal detector, a first driver and a main power tube, the driving signal detector is coupled with the driving signal input end and is used for converting the first driving signal into a second driving signal based on the second reference level and outputting the second driving signal to the first driver, the output end of the first driver is coupled with the control end of the main power tube, and the output end of the main power tube is coupled with the grounding end of the second controller;

a first end of the power inductor is coupled to a ground terminal of the second controller to generate an output voltage, and a second end of the power inductor is coupled to a feedback terminal of the first controller; and

and the first end of the output capacitor is coupled with the feedback end of the first controller, and the second end of the output capacitor is coupled with the grounding end of the switch power supply system.

2. The switching power supply system according to claim 1, wherein a ground terminal of the first controller is directly connected to a ground terminal of the switching power supply system.

3. The switching power supply system according to claim 1, wherein the first terminal of the output capacitor is directly connected to a feedback terminal of the first controller.

4. The switching power supply system according to claim 3, wherein the first controller is powered by the feedback terminal.

5. The switching power supply system according to claim 1, wherein the second controller further has a power source terminal, the switching power supply system further comprising:

the rectifying circuit is coupled with the grounding end of the first controller and the power end of the second controller; and

an input capacitor coupled to a ground terminal of the first controller and a power terminal of the second controller.

6. The switching power supply system according to claim 1, wherein the first drive signal is a PWM current signal.

7. The switching power supply system according to claim 1, wherein the transistor is a synchronous rectification power transistor, and the first controller further comprises a second driver, an input terminal of the second driver is coupled to the output terminal of the PWM generator, and an output terminal of the second driver is coupled to the control terminal of the synchronous rectification power transistor.

8. The switching power supply system of claim 1, wherein the first controller and the second controller are each die and are packaged in the same chip.

9. The switching power supply system according to claim 1, wherein the first controller and the second controller are each independently packaged chips.

10. The switching power supply system according to claim 1, wherein the PWM generator comprises:

a voltage dividing circuit for dividing the output voltage into a feedback voltage;

an operational amplifier for generating an amplified difference voltage according to a reference voltage and the feedback voltage;

a sawtooth wave generator for providing a sawtooth wave voltage; and

a comparator for comparing the difference voltage and the sawtooth voltage to generate the PWM voltage signal.

11. The switching power supply system according to claim 7, wherein the PWM generator comprises:

a sawtooth wave generator for providing a sawtooth wave voltage;

a comparator for comparing the difference voltage and the sawtooth voltage to generate the PWM voltage signal; and

and the synchronous rectification signal generator is used for generating a synchronous rectification PWM signal which is not overlapped with the PWM voltage signal according to the PWM voltage signal.

12. The switching power supply system of claim 10, wherein the sawtooth generator is further configured to generate a low frequency sawtooth waveform at initial startup of the switching power supply system.

13. A constant voltage controller for a switching power supply system, the constant voltage controller comprising:

the first controller is provided with a feedback end, a driving signal output end, a synchronization end and a grounding end, the grounding end of the first controller is suitable for being coupled with the grounding end of the switching power supply system and has a first reference level, the first controller comprises a PWM generator, a driving signal converter and a transistor, the PWM generator is coupled with the feedback end and used for generating a PWM voltage signal according to output voltage from the feedback end and outputting the PWM voltage signal to the driving signal converter, the driving signal converter is coupled with the driving signal output end and used for converting the PWM voltage signal into a first driving signal based on the first reference level, and the transistor is coupled between the synchronization end and the grounding end;

the second controller is provided with a driving signal input end and a grounding end, the driving signal input end is coupled with the driving signal output end of the first controller, the grounding end of the second controller is coupled with the synchronous end of the first controller and is provided with a second reference level, the second controller comprises a driving signal detector, a first driver and a main power tube, the driving signal detector is coupled with the driving signal input end and is used for converting the first driving signal into a second driving signal based on the second reference level and outputting the second driving signal to the first driver, the output end of the first driver is coupled with the control end of the main power tube, and the output end of the main power tube is coupled with the grounding end of the second controller.

14. The constant voltage controller according to claim 13, wherein a ground terminal of the first controller is adapted to be directly connected to a ground terminal of the switching power supply system.

15. The constant voltage controller as claimed in claim 13, wherein the feedback terminal of the first controller is adapted to be directly input to the output voltage of the switching power supply system.

16. The constant voltage controller as claimed in claim 13, wherein the first controller is adapted to be powered by the feedback terminal.

17. The constant voltage controller of claim 13, wherein the first driving signal is a PWM current signal.

18. The constant voltage controller as claimed in claim 13, wherein the transistor is a synchronous rectification power transistor, and the first controller further comprises a second driver, an input terminal of the second driver is coupled to the output terminal of the PWM generator, and an output terminal of the second driver is coupled to the control terminal of the synchronous rectification power transistor.

19. The constant voltage controller of claim 13, wherein the first controller and the second controller are each a die and are packaged in the same chip.

20. The constant voltage controller of claim 13, wherein the first controller and the second controller are independently packaged chips, respectively.