A parallel structure high-efficiency envelope tracking power supply and control method thereof

Abstract

The present invention discloses a parallel structure high-efficiency envelope tracking power supply and a control method thereof, comprising a parallel switching converter and a linear amplifier, wherein the switching converter and the linear amplifier respectively work in a current source form and a voltage source form; the output current of the switching converter fits the load current in a triangular wave form, and the linear amplifier is used to compensate for the difference current between the load current and the output current of the switching converter. The present invention can reduce the voltage borne by the power tube during operation, reduce the switching frequency of the CSC, greatly reduce the loss of the VLA, and significantly improve the efficiency of the parallel structure envelope tracking power supply.

Description

Technical Field

[0001] The present invention relates to the technical field of wireless communications, and in particular to a control method for a parallel-structured high-efficiency envelope tracking power supply. Background Art

[0002] Mobile communications have developed rapidly in the past few decades, bringing great convenience to people's lives and becoming an important industry for global economic development. The construction of a large number of base stations ensures network coverage, but it also causes the electricity costs of communication operators to increase exponentially. On the one hand, the current full-load power consumption of a single 5G base station is about 4kW, which is equivalent to 3 times that of a 4G base station; on the other hand, in the future, the number of 5G base stations will also greatly exceed that of 4G base stations. Therefore, it is very important to reduce the energy consumption of mobile communication base stations.

[0003] After the third generation (3G) mobile communication system, high spectrum efficiency modulation methods such as Quadrature Amplitude Modulation (QAM) and Orthogonal Frequency Division Multiplexing (OFDM) have been widely adopted. This type of modulation method makes the envelope of the RF signal no longer constant and presents a large peak-to-average power ratio (PAPR). At this time, in order to amplify the RF signal without distortion, a linear power amplifier (LPA) is required to amplify its power. However, the constant voltage powered LPA is inefficient in the power back-off area. At present, the technologies to improve PA efficiency mainly include Doherty technology and envelope tracking (ET) technology. Among them, Doherty technology requires the use of a main power amplifier and an auxiliary power amplifier to work together, which is costly. In addition, since the auxiliary power amplifier uses a nonlinear power amplifier, the linearity at the peak of the RF signal is poor and the operating frequency band is narrow. ET technology can work in any frequency band. By detecting the envelope of the RF signal and using it as a reference signal for the power modulator, the output voltage of the power modulator tracks the reference signal and supplies power to the LPA, so that the LPA always works in a state close to saturation, thereby improving the efficiency of the LPA. The power modulator is the so-called ET power supply, which is the core of ET technology.

[0004] With the development of wireless communication technology, the RF envelope bandwidth continues to increase, so the ET power supply needs to have a higher tracking bandwidth. The original intention of the ET power supply is to improve the efficiency of the power amplifier system, and as a part of the system, its own efficiency should also be high. The switch-linear hybrid (SLH) ET power supply integrates the advantages of high efficiency of the switching converter and high bandwidth of the linear amplifier, and has become the mainstream architecture of the ET power supply. The parallel structure SLH ET power supply is composed of a current-controlled led switched-mode converter (CSC) working in the form of a current source and a voltage-controlled linear amplifier (VLA) working in parallel. Among them, the output current of the CSC fits the load current to reduce the output current of the VLA, thereby reducing the loss of the VLA. However, when the output voltage swing is large, the output power of the VLA is still large, which limits the improvement of the overall efficiency of the parallel structure SLH ET power supply. Summary of the invention

[0005] The purpose of the present invention is to provide a parallel structure high-efficiency envelope tracking power supply and a control method thereof, so that the first power tube Q of the AB class VLA u And the second power tube Q d They work at higher and lower load voltages respectively to reduce the voltage that the power tube is subjected to during operation, thereby significantly reducing the loss of VLA and improving the efficiency of the parallel structure (envelope tracking power supply) ET power supply. In addition, in order to achieve the first power tube Q u And the second power tube Q d In order to realize time-sharing operation, the present invention also proposes a triangular wave current control method, which makes the output current of the switching converter fit the load current in the form of a triangular wave. Compared with the traditional hysteresis current control, this method can reduce the switching frequency of the switching converter.

[0006] In order to achieve the above technical objectives, the technical solution adopted by the present invention is:

[0007] A parallel structure high-efficiency envelope tracking power supply, the parallel structure high-efficiency envelope tracking power supply comprises a parallel switching converter and a linear amplifier, the switching converter and the linear amplifier respectively work in a current source mode and a voltage source mode;

[0008] The output current of the switching converter fits the load current in a triangular wave form, and the linear amplifier is used to compensate for the difference current between the load current and the output current of the switching converter.

[0009] Furthermore, the switching converter adopts a Buck converter, including an input voltage Vin , switch tube Q, freewheeling diode D and filter inductor L;

[0010] The source of the switch tube Q, the cathode of the freewheeling diode D and one end of the filter inductor L are connected to each other, and the other end of the filter inductor L is connected to the load resistor R LD Connect one end of the freewheeling diode D to the anode and load resistor R LD The other ends are grounded.

[0011] Furthermore, the linear amplifier adopts a class AB linear amplifier, including a first power tube Q u , the second power tube Q d , bias voltage v bias , sampling unit and voltage regulator;

[0012] The first power tube Q u The drain voltage V in Connect the first power tube Q u The source of the second power tube Q d The drain of the second power tube Q d The source is grounded;

[0013] The output end of the sampling unit is connected to a voltage regulator;

[0014] The voltage regulator and the first power tube Q u And the second power tube Q d The first power tube Q is controlled according to the value of the output voltage vo. u And the second power tube Q d Time-sharing work;

[0015] The bias voltage v bias Used to avoid crossover distortion in linear amplifiers.

[0016] Furthermore, the voltage regulator collects the output voltage v o Make a judgment, when v o >V in / 2, the first power tube Q u work, otherwise, the second power tube Q d Work.

[0017] Furthermore, the loss p of the linear amplifier is loss_VLA It is expressed as:

[0018]

[0019] In formula (1), i VLA Represents the output current of the linear amplifier.

[0020] Further, the switching converter includes an output current sampling module, a load current fitting module, an intersection search module and a control signal calculation module;

[0021] The output current sampling module is used to sample the output current of the switching converter by theoretical calculation; specifically, in the discrete domain, the value i of the inductor current at the nth sampling moment CSC (n) and the value of the inductor current i at the n-1th sampling moment CSC (n-1) satisfies formula (2):

[0022]

[0023] In formula (2), f s represents the sampling frequency, S Q (n-1) represents the control signal of the switch tube Q at the n-1th sampling moment, S Q =1 and S Q =0 means the switch is on and off, v o Indicates the load voltage of the envelope tracking power supply;

[0024] The load current fitting module is used to fit the load current i in the form of a triangular wave. o ;

[0025] The intersection finding module is used to determine the load current i o and the boundary current i int and find the intersection point that satisfies i o >i int The valley point and the point that satisfies i o int The peak point of the boundary current i int =V in / (2R LD );

[0026] The control signal calculation module determines the load current i at the intersection o Whether to increase or decrease, if i o Gradually increase, then take the intersection point as the starting point, let S Q =1, calculate the rising trajectory of the inductor current forward and backward respectively; if i o Gradually decrease, let S Q = 0 and calculate i CSC The downward trajectory of o >i int The valley point of S Q =0, reverse prediction i CSC The downward trajectory of S Q =1, forward prediction i CSC ​The rising trajectory of o int The peak point of S Q =1, reverse prediction i CSC The rising trajectory of S Q =0, forward prediction i CSC The descending trajectory of the switch tube Q is finally generated.

[0027] The present invention also discloses a control method for a parallel structure high-efficiency envelope tracking power supply, wherein the control method is used to control the parallel structure high-efficiency envelope tracking power supply;

[0028] The control method comprises the following steps:

[0029] The output current of the switching converter is used to fit the load current in a triangular wave form, and a linear amplifier is used to compensate for the difference current between the load current and the output current of the switching converter;

[0030] According to the output voltage v o The value of controls the first power tube Q u And the second power tube Q d Time-sharing operation minimizes the power consumption of the linear amplifier.

[0031] Furthermore, according to the output voltage v o The value of controls the first power tube Q u And the second power tube Q d Time-sharing means:

[0032] The output voltage v collected by the sampling unit o Make a judgment, when v o >V in / 2, the first power tube Q u work, otherwise, the second power tube Q d Work.

[0033] Furthermore, the control method further includes:

[0034] The output current of the switching converter is sampled by theoretical calculation; specifically, in the discrete domain, the value of the inductor current at the nth sampling moment i CSC (n) and the value of the inductor current i at the n-1th sampling moment CSC (n-1) satisfies formula (2):

[0035]

[0036] In formula (2), f s represents the sampling frequency, S Q ​(n-1) represents the control signal of the switch tube Q at the n-1th sampling moment, S Q =1 and S Q =0 means the switch is on and off, v o Indicates the load voltage of the envelope tracking power supply;

[0037] Fit the load current in the form of a triangle wave;

[0038] Determine the load current i o and the boundary current i int and find the intersection point that satisfies i o >i int The valley point and the point that satisfies i o int The peak point of the boundary current i int =V in / (2R LD );

[0039] Determine the load current i at the intersection o Whether to increase or decrease, if i o Gradually increase, then take the intersection point as the starting point, let S Q =1, calculate the rising trajectory of the inductor current forward and backward respectively; if i o Gradually decrease, let S Q = 0 and calculate i CSC The downward trajectory of o >i int The valley point of S Q =0, reverse prediction i CSC The downward trajectory of S Q =1, forward prediction i CSC The rising trajectory of o int The peak point of S Q =1, reverse prediction i CSC The rising trajectory of S Q =0, forward prediction i CSC The downward trajectory of

[0040] Generate the control signal waveform of the switch tube Q and the inductor current i CSC Waveform.

[0041] Compared with the prior art, the present invention has the following beneficial effects:

[0042] First, the parallel structure high-efficiency envelope tracking power supply and control method thereof of the present invention, for an ET power supply formed by connecting a switching converter and a class AB linear amplifier in parallel, makes the first power tube Q of the linear amplifier u And the second power tube Q​​d Working at higher and lower load voltages respectively can naturally reduce the Q of the first power tube without increasing the complexity of the circuit. u And the second power tube Q d The voltage it withstands during operation can greatly reduce the loss of linear amplifiers.

[0043] Second, the parallel structure high-efficiency envelope tracking power supply and control method thereof of the present invention are to realize the first power tube Q u And the second power tube Q d For the time-sharing operation of the switching converter, a triangle wave current control method is proposed, which can reduce the switching frequency of the switching converter and make the inductor current better fit the load current, further improving the efficiency of the parallel structure SLH ET power supply. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 It is a circuit schematic diagram of an implementation example of the parallel structure high-efficiency envelope tracking power supply circuit of the present invention.

[0045] Figure 2 The key current and voltage waveforms of the parallel structure SLH ET power supply of the present invention are shown in FIG. 1 , where (a) is the current waveform of the switching converter CSC when the conventional hysteresis current control is adopted, and (b) is the current waveform of the power tube Q u And power tube Q d The voltage waveform diagram of (c) is the voltage waveform diagram of (c) that can satisfy Q u and Q d Key current waveforms for time-sharing operation.

[0046] Figure 3 The figure shows the typical current waveform and control signal waveform of the switching converter when using triangular wave current control. DETAILED DESCRIPTION

[0047] The embodiments of the present invention are further described in detail below in conjunction with the accompanying drawings.

[0048] Example 1

[0049] The present invention provides a high-efficiency envelope tracking power supply circuit with a parallel structure. Figure 1A high-efficiency envelope tracking power supply circuit is formed by connecting a current-controlled switched-mode converter (CSC) in a current source form and a voltage-controlled linear amplifier (VLA) in a voltage source form in parallel. The parallel structure high-efficiency envelope tracking power supply circuit of the present invention includes a switching converter CSC and a class AB linear amplifier VLA. The output current of the switching converter fits the load current in a triangular wave form, and the linear amplifier is used to compensate for the difference current between the load current and the output current of the switching converter.

[0050] (I) Switching Converter CSC

[0051] The switching converter CSC of this embodiment is a Buck converter, including an input voltage V in , switch tube Q, freewheeling diode D, filter inductor L; the source of the switch tube Q, the cathode of the freewheeling diode D and one end of the filter inductor L are connected to each other, and the other end of the filter inductor L is connected to the load resistor R Ld Connect one end of the freewheeling diode D to the anode and load resistor R Ld The other ends are grounded.

[0052] (B) Class AB Linear Amplifier VLA

[0053] The linear amplifier VLA of this embodiment includes a first power tube Q u And the second power tube Q d , bias voltage v bias , output voltage sampling unit and voltage regulator; the VLA adopts closed-loop control to track the envelope reference signal. The output current of the VLA compensates the difference current between the load current and the CSC output current; the first power tube Q u One end is connected to the input voltage V in The other end is connected to the second power tube Q d One end of the sampling unit is connected to the first power tube Q u And the second power tube Q d This end is used to supply power to the load, and the second power tube Q d The other end of the sampling unit is grounded; the output end of the sampling unit is connected to the voltage regulator; the voltage regulator is connected to the first power tube Q u And the second power tube Q d The bias voltage v bias Used to avoid crossover distortion in Class AB VLAs.

[0054] Example 2

[0055] The present invention proposes a method for reducing the loss of a class AB VLA. Specifically, the method comprises: when the output current i of the linear amplifier VLA is VLA When it is greater than zero, the first power tube Q u Work and produce loss, on the contrary, the second power tube Q d In this working mode, the loss of the linear amplifier VLA of this embodiment can be expressed as:

[0056]

[0057] Figure 2 (a) is the current waveform of the switching converter CSC when the conventional hysteresis current control is adopted. u And the second power tube Q d Works over almost the entire load voltage range. Figure 2 (b) shows the first power tube Q u And the second power tube Q d The voltage waveform. From formula (1), we can see that when i vLA is greater than zero and the load voltage v o When the first power tube Q u The loss is large; when i VLA is less than zero and v o When it is larger, the second power tube Q d Therefore, in order to reduce the loss of VLA, it is expected that when v o When it is smaller, i VLA is less than zero, that is, the output current of CSC is greater than the load current, so that the second power tube Q d Management work; and when v o When it is larger, i VLA is greater than zero, that is, the output current of CSC is less than the load current, so that the first power tube Q u The first power tube Q u And the second power tube Q d The current values ​​are approximately equal, then when V in -v o >v o , that is, v o <V in / 2, the second power tube Q d The loss is less than the first power tube Q u loss; when V in -v o <v o , that is, v o >V in / 2, the second power tube Q d The loss is greater than the first power tube Qu Therefore, v o =V in / 2 or i o =V in / 2R Ld As the mode switching point of the two power tubes. For the convenience of description, V in / 2R Ld Defined as i int . Figure 2 (c) in the figure shows the first power tube Q that can be satisfied by the present invention. u And the second power tube Q d The key current waveform of time-sharing operation is CSC Fitting i in a way similar to a triangular wave current o , so this current control method is defined as triangular wave current control. o >i int When CSC o On the contrary, when i o int When CSC >i o .

[0058] Example 3

[0059] This embodiment also provides a control method for the above-mentioned parallel structure high-efficiency envelope tracking power supply circuit. Figure 3 , this embodiment provides typical current and control signal waveforms when triangular wave current control is adopted.

[0060] First, this embodiment uses theoretical calculation to replace the actual current sampler to sample the CSC output current. In the discrete domain, the value of the inductor current at the nth sampling moment i CSC (n) and the value of the inductor current i at the n-1th sampling moment CSC (n-1) satisfies formula (2):

[0061]

[0062] Among them, f s and S Q They are respectively represented as the sampling frequency and the control signal of the switch tube Q, S Q =1 and S Q =0 means the switch is on and off, v o is the load voltage of the ET power supply.

[0063] First, determine i o and i int In t i1 Time and t i2 ​​The intersection point i i1 and i i2 , at t i1 Moment, i o Gradually increase, in order to make i CSC Fitting o , let S Q =1, predict the rising trajectory of the inductor current. v1 Moment, find satisfaction o >i int The valley point i v1 , change i iv1 The value of S is reduced by 2% and used as the starting point. Q =0, reverse prediction i CSC The downward trajectory of Q =1, forward prediction i CSC The rising trajectory of i2 As the starting point, let S Q = 0, calculate the falling trajectory of the inductor current. o int The peak point i p1 For example, let S Q =1, reverse prediction i CSC The rising trajectory of Q =0, prediction i CSC The intersection of the inductor current trajectory is the switch-on or switch-off moment of the switch tube. Finally, the inductor current i that meets the requirements is obtained. CSC And the control signal S of the switch tube Q Q .

[0064] It can be seen from the above description that the present invention has the following advantages:

[0065] 1. When the output voltage of the parallel structure SLHET power supply is high, the first power tube Q of VLA u work, on the contrary, the second power tube Q d Work to reduce the voltage that the two power tubes are subjected to when they are working, thereby greatly reducing the loss of VLA and improving the overall efficiency of the parallel structure ET power supply;

[0066] 2. Compared with the traditional hysteresis current control, the proposed triangle wave current control method can reduce the switching frequency of CSC and improve the overall efficiency of ET power supply.

[0067] ​Those skilled in the art will appreciate that the embodiments of the present application can be provided as methods, systems, or computer program products. Therefore, the present application can adopt the form of complete hardware embodiments, complete software embodiments, or embodiments in combination with software and hardware. Moreover, the present application can adopt the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) that contain computer-usable program code. The scheme in the embodiments of the present application can be implemented in various computer languages, for example, object-oriented programming language Java and literal scripting language JavaScript, etc.

[0068] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0069] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture including an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0070] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process in the computer or other programmable device. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0071] Although the preferred embodiments of the present application have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications falling within the scope of the present application.

[0072] Obviously, those skilled in the art can make various changes and modifications to the present application without departing from the spirit and scope of the present application. Thus, if these modifications and variations of the present application fall within the scope of the claims of the present application and their equivalents, the present application is also intended to include these modifications and variations.

Claims

1. A parallel structure high efficiency envelope tracking power supply, characterized in that: The parallel structure high-efficiency envelope tracking power supply comprises a parallel switching converter and a linear amplifier, wherein the switching converter and the linear amplifier respectively operate in a current source mode and a voltage source mode; The output current of the switching converter fits the load current in a triangular wave form, and the linear amplifier is used to compensate for the difference current between the load current and the output current of the switching converter; The switching converter adopts a Buck converter, including an input voltage V in , switch tube Q, freewheeling diode D and filter inductor L; The source of the switch tube Q, the cathode of the freewheeling diode D and one end of the filter inductor L are connected to each other, and the other end of the filter inductor L is connected to the load resistor R LD Connect one end of the freewheeling diode D to the anode and load resistor R LD The other end of is grounded; The linear amplifier adopts a class AB linear amplifier, including a first power tube Q u , the second power tube Q d , bias voltage v bias , sampling unit and voltage regulator; The first power tube Q u The drain voltage V in Connect the first power tube Q u The source of the second power tube Q d The drain of the second power tube Q d The source is grounded; The output end of the sampling unit is connected to a voltage regulator; The voltage regulator and the first power tube Q u And the second power tube Q d The first power tube Q is controlled according to the value of the output voltage vo. u And the second power tube Q d Time-sharing work; The bias voltage v bias Used to avoid crossover distortion of linear amplifiers; The voltage regulator collects the output voltage v o Make a judgment, when v o >V in / 2, the first power tube Q u work, otherwise, the second power tube Q d Work.

2. The parallel structure high-efficiency envelope tracking power supply according to claim 1, characterized in that: The linear amplifier loss p loss_VLA It is expressed as: In formula (1), i VLA Represents the output current of the linear amplifier.

3. The parallel structure high efficiency envelope tracking power supply according to claim 1, characterized in that: The switching converter includes an output current sampling module, a load current fitting module, an intersection search module and a control signal calculation module; The output current sampling module is used to sample the output current of the switching converter by theoretical calculation; specifically, in the discrete domain, the value i of the inductor current at the nth sampling moment CSC (n) and the value of the inductor current i at the n-1th sampling moment CSC (n-1) satisfies formula (2): In formula (2), f s represents the sampling frequency, S Q (n-1) represents the control signal of the switch tube Q at the n-1th sampling moment, S Q =1 and S Q =0 means the switch is on and off, v o represents the load voltage of the envelope tracking power supply; The load current fitting module is used to fit the load current i in the form of a triangular wave. o ; The intersection finding module is used to determine the load current i o and the boundary current i int and find the intersection point that satisfies i o >i int The valley point and the point that satisfies i o int The peak point of the boundary current i int =V in / (2R LD );​ The control signal calculation module determines the load current i at the intersection o Whether to increase or decrease, if i o Gradually increase, then take the intersection point as the starting point, let S Q =1, calculate the rising trajectory of the inductor current forward and backward respectively; if i o Gradually decrease, let S Q = 0 and calculate i CSC The downward trajectory of o >i int The valley point of S Q =0, reverse prediction i CSC The downward trajectory of S Q =1, forward prediction i CSC The rising trajectory of o int The peak point of S Q =1, reverse prediction i CSC The rising trajectory of S Q =0, forward prediction i CSC The descending trajectory of the switch tube Q is finally generated.​ 4. A control method for a parallel structure high-efficiency envelope tracking power supply, characterized in that: The control method is used to control the parallel structure high-efficiency envelope tracking power supply described in claim 1; The control method comprises the following steps: The output current of the switching converter is used to fit the load current in a triangular wave form, and a linear amplifier is used to compensate for the difference current between the load current and the output current of the switching converter; According to the output voltage v o The value of controls the first power tube Q u And the second power tube Q d Time-sharing operation minimizes the power consumption of the linear amplifier.

5. The control method of the parallel structure high efficiency envelope tracking power supply according to claim 4, characterized in that: According to the output voltage v o The value of controls the first power tube Q u And the second power tube Q d Time-sharing means: The output voltage v collected by the sampling unit o Make a judgment, when v o >V in / 2, the first power tube Q u work, otherwise, the second power tube Q d Work.

6. The control method of the parallel structure high-efficiency envelope tracking power supply according to claim 5, characterized in that: The control method further comprises: The output current of the switching converter is sampled by theoretical calculation; specifically, in the discrete domain, the value of the inductor current at the nth sampling moment i CSC (n) and the value of the inductor current i at the n-1th sampling moment CSC (n-1) satisfies formula (2): In formula (2), f s represents the sampling frequency, S Q (n-1) represents the control signal of the switch tube Q at the n-1th sampling moment, S Q =1 and S Q =0 means the switch is on and off, v o represents the load voltage of the envelope tracking power supply; Fit the load current in the form of a triangle wave; Determine the load current i o and the boundary current i int and find the intersection point that satisfies i o >i int The valley point and the point that satisfies i o int The peak point of the boundary current i int =V in / (2R LD );​ Determine the load current i at the intersection o Whether to increase or decrease, if i o Gradually increase, then take the intersection point as the starting point, let S Q =1, calculate the rising trajectory of the inductor current forward and backward respectively; if i o Gradually decrease, let S Q = 0 and calculate i CSC The downward trajectory of o >i int The valley point of S Q =0, reverse prediction i CSC The downward trajectory of S Q =1, forward prediction i CSC The rising trajectory of o int The peak point of S Q =1, reverse prediction i CSC The rising trajectory of S Q =0, forward prediction i CSC The downward trajectory of​ Generate the control signal waveform of the switch tube Q and the inductor current i CSC Waveform.

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