A dead-time compensation method and system for a bidirectional boost converter

Abstract

The application discloses a dead-time compensation method and system of a bidirectional boost converter. The dead-time compensation method comprises the following steps: S1: obtaining the inductor current, input voltage and output voltage of the bidirectional boost converter, and calculating the output frequency of the switch tube of the bidirectional boost converter working in a critical conduction mode according to the inductor current, input voltage and output voltage of the bidirectional boost converter; S2: calculating the reference duty ratio of the switch tube through a loop control module; S3: dynamically correcting the reference duty ratio of the switch tube according to the output frequency of the switch tube and the direction of the inductor current, so as to obtain the corrected duty ratio of the switch tube; and S4: generating the driving signal of the switch tube according to the output frequency and the corrected duty ratio of the switch tube, and driving the switch tube in the bidirectional boost converter according to the driving signal of the switch tube. The application can not affect the output voltage when the current polarity is reversed, and can guarantee the stability of the control loop.

Description

Technical Field

[0001] This invention relates to the field of boost converter technology, and in particular to a dead-zone compensation method and system for a bidirectional boost converter. Background Technology

[0002] like Figure 1 In a bidirectional boost converter, DC1 is the low-side DC power supply, DC2 is the high-side DC power supply, L is the boost inductor, the arrow indicates the current reference direction, QH is the upper switch, and QL is the lower switch. Drivers TH and TL are used to drive switches QH and QL, respectively. If both switches QH and QL on the same bridge arm are turned on simultaneously, a short circuit in the bridge arm will inevitably occur. To prevent short circuits, the trigger signals of the two switches on the same bridge arm are usually spaced out for a certain period of time, called the "dead time." Since the inductor current cannot change abruptly, the freewheeling switch of the inductor is in the on state during the dead time, causing the duty cycle of the switch to be different from the given duty cycle. The resulting effect is called the "dead time effect."

[0003] The bidirectional boost converter operates in TCM (critical conduction mode or critical current mode). The controller controls the output voltage by adjusting the duty cycle and adjusts the switching frequency to make the bidirectional boost converter operate in TCM mode.

[0004] like Figure 2 As shown, when the switching period is T, the duty cycle is D, Thon is the conduction time of the upper switch, TLon is the conduction time of the lower switch, and Tdb is the fixed dead time. Adjusting the switching frequency introduces a "dead time effect." The dead time Tdb is fixed, while the switching period T varies. When the load is light, the current changes slowly, and the period T automatically lengthens (frequency decreases); when the load is heavy, the current changes quickly, and the period T automatically shortens (frequency increases). Under a long period (Tmax), the ratio of Tdb / Tmax is small, and the duty cycle distortion caused by the dead time effect is small; under a short period (Tmin), the ratio of Tdb / Tmax is large, and the dead time "eats up" a considerable proportion, causing the effective duty cycle to deviate significantly from the given value D. Figure 2 When the duty cycles are equal and the switching periods are Tmax and Tmin respectively, the state of the upper and lower switches in the dead zone is related to the direction of the inductor current (the freewheeling switch is on and the non-freewheeling switch is off). This causes the duty cycles of the upper and lower switches to be different from the set duty cycle D. The "dead zone effect" causes fluctuations in the output voltage and current. The feedback of the fluctuating voltage and current will cause fluctuations in the switching frequency, resulting in controller oscillation. Therefore, when adjusting the frequency, the duty cycle needs to be corrected at the same time to decouple the two. The measure to correct the duty cycle is "dead zone compensation".

[0005] Existing dead-time compensation methods generally employ an open-loop approach, which determines the polarity of the compensation voltage and the timing of the compensation based on the polarity of the inductor current. For example, when I... L >0 (boost mode), the dead time is equivalent to adding an extra Tdb of conduction time to the upper switching transistor (QH); when I L <0 (buck mode), the dead time is equivalent to adding an extra Tdb of conduction time to the lower switch (QL). To compensate, the upper switch is determined to be conducting during the dead time based on the polarity of the inductor current. Therefore, the given duty cycle should be reduced by Tdb / T (T is the current cycle) so that the actual conduction time of the upper switch is equal to the required conduction time. Conversely, if the lower switch is conducting during the dead time, the given duty cycle should be increased by Tdb / T.

[0006] However, changes in the polarity of the inductor current under different operating conditions are often difficult to detect accurately. In particular, when the inductor current is close to 0, it is very easy to misjudge the direction. Furthermore, the polarity reversal and inaccurate timing of the dead zone compensation cause the duty cycle plus Tdb / T to suddenly become minus Tdb / T, which will cause a sudden change in the voltage amplitude. Due to the feedback effect, this will eventually lead to controller oscillation.

[0007] The above background information is provided only to aid in understanding the concept and technical solution of this invention. It does not necessarily belong to the prior art of this patent application. In the absence of clear evidence that the above information was disclosed on the filing date of this patent application, the above background information should not be used to evaluate the novelty and inventiveness of this application. Summary of the Invention

[0008] To address the aforementioned technical problems, this invention proposes a dead-time compensation method and system for a bidirectional boost converter, which can ensure the stability of the control loop without affecting the output voltage when the current polarity reverses.

[0009] To achieve the above objectives, the present invention adopts the following technical solution:

[0010] In a first aspect, the present invention discloses a dead-time compensation method for a bidirectional boost converter, comprising the following steps:

[0011] S1: Obtain the inductor current, input voltage, and output voltage of the bidirectional boost converter, and calculate the output frequency of the switching transistor that enables the bidirectional boost converter to operate in critical conduction mode based on the inductor current, input voltage, and output voltage of the bidirectional boost converter.

[0012] S2: Calculate the reference duty cycle of the switching transistor through the loop control module;

[0013] S3: Dynamically correct the reference duty cycle of the switching transistor based on the output frequency of the switching transistor and the direction of the inductor current to obtain the corrected duty cycle of the switching transistor;

[0014] S4: Generate a drive signal for the switch based on the output frequency and corrected duty cycle of the switch, and drive the switch in the bidirectional boost converter according to the drive signal of the switch.

[0015] Preferably, in step S1, based on the inductor current, input voltage, and output voltage of the bidirectional boost converter, the output frequency of the switching transistor that enables the bidirectional boost converter to operate in critical conduction mode is calculated using the following formula:

[0016] f = 1 / (((L m / V DC1 ) + Lm / (V DC2 -V DC1 ))*abs(I L ))

[0017] In the formula, f represents the output frequency of the switching transistor, Lm represents the inductance, and V DC1 Indicates the input voltage, V DC2 Indicates the output voltage, I L The value represents the magnitude of the inductor current, and abs() represents the absolute value function.

[0018] Preferably, the output frequency of the switching transistor of the bidirectional boost converter operating in critical conduction mode calculated in step S1 is between a preset lower frequency limit and a preset upper frequency limit, and when the amplitude of the inductor current approaches zero, the output frequency of the switching transistor of the bidirectional boost converter operating in critical conduction mode is equal to the preset upper frequency limit.

[0019] Preferably, step S3 specifically includes: dynamically calculating the dead-time compensation amount based on the difference between the output frequency of the switching transistor and the preset upper frequency limit, and correcting the reference duty cycle of the switching transistor in combination with the direction of the inductor current to obtain the corrected duty cycle of the switching transistor; wherein, when the polarity of the inductor current reverses, the dead-time compensation amount is smoothly transitioned by the continuous change in the direction of the difference between the output frequency of the switching transistor and the preset upper frequency limit and the instantaneous value of the inductor current.

[0020] Preferably, in step S3, the reference duty cycle of the switching transistor is dynamically corrected according to the following formula based on the output frequency of the switching transistor and the direction of the inductor current:

[0021] DL * (f) = DL + DLcomp(f)

[0022] When IL >0, DLcomp(f) = (fmax - f)*Tdb

[0023] When I L <0, DLcomp(f) = (f - fmax)*Tdb

[0024] In the formula, DL * (f) represents the corrected duty cycle of the lower switching transistor, DL represents the reference duty cycle of the lower switching transistor, Tdb is the dead time, and I L f represents the amplitude of the inductor current, f represents the output frequency of the switching transistor, and fmax represents the preset upper frequency limit.

[0025] Preferably, the loop control module adopts a voltage feedback-based PI controller, and step S2 specifically includes: calculating the reference duty cycle in real time through the PI controller to stabilize the output voltage at the set value.

[0026] Preferably, step S4 includes: generating two complementary PWM signals for the switching transistors based on the output frequency and the corrected duty cycle of the switching transistors; and controlling the two switching transistors in the bidirectional boost converter based on the two complementary PWM signals.

[0027] Secondly, this invention discloses a dead-time compensation system for a bidirectional boost converter, comprising a frequency calculation module, a loop control module, a dead-time compensation module, and a PWM generator, wherein...

[0028] The frequency calculation module is used to obtain the inductor current, input voltage and output voltage of the bidirectional boost converter, and calculate the output frequency of the switching transistor that enables the bidirectional boost converter to operate in the critical conduction mode based on the inductor current, input voltage and output voltage of the bidirectional boost converter.

[0029] The loop control module is used to calculate the reference duty cycle of the switching transistor;

[0030] The dead-time compensation module is used to dynamically correct the reference duty cycle of the switching transistor based on the output frequency of the switching transistor and the direction of the inductor current, so as to obtain the corrected duty cycle of the switching transistor.

[0031] The PWM generator is used to generate a drive signal for the switching transistor based on the output frequency and corrected duty cycle of the switching transistor, and to drive the switching transistor in the bidirectional boost converter according to the drive signal of the switching transistor.

[0032] Preferably, the output frequency of the bidirectional boost converter operating in critical conduction mode, calculated by the frequency calculation module, is between a preset lower frequency limit and a preset upper frequency limit. Furthermore, when the amplitude of the inductor current approaches zero, the output frequency of the bidirectional boost converter operating in critical conduction mode is equal to the preset upper frequency limit.

[0033] Thirdly, the present invention discloses a computer-readable storage medium storing a computer program, wherein the computer program is configured to be run by a processor to perform the dead-zone compensation method for the bidirectional boost converter described in the first aspect.

[0034] Compared with the prior art, the beneficial effects of the present invention are as follows: The dead-time compensation method and system for bidirectional boost converter proposed in the present invention dynamically adjust the switching frequency in the critical conduction mode, and dynamically correct the reference duty cycle of the switching transistor by the output frequency of the switching transistor and the direction of the inductor current, so that the duty cycle of the switching transistor and the switching frequency are decoupled, the change of switching frequency will not cause the gain change, the dead-time compensation value is zero when the inductor current alternates between positive and negative, and even if the detection is inaccurate at the moment of current polarity reversal, it will not cause the gain change; thus, the output voltage is not affected when the current polarity reverses, ensuring the stability of the control loop.

[0035] Other beneficial effects of the embodiments of the present invention will be further described below. Attached Figure Description

[0036] Figure 1 This is a schematic diagram of the bidirectional boost converter.

[0037] Figure 2 It refers to the on-time zone of the switching transistors in a bidirectional boost converter;

[0038] Figure 3 This is a flowchart of the dead-zone compensation method for a bidirectional boost converter according to Embodiment 1 of the present invention;

[0039] Figure 4 This is a block diagram of the dead-time compensation system for the bidirectional boost converter in Embodiment 2 of the present invention, controlling the bidirectional boost converter.

[0040] Figure 5 It is a waveform diagram of the two-way boost control variables;

[0041] Figure 6 This is a comparison diagram of dead zone compensation effects. Detailed Implementation

[0042] The embodiments of the present invention will be described in detail below. It should be emphasized that the following description is merely exemplary and not intended to limit the scope and application of the present invention.

[0043] It should be noted that when a component is referred to as "fixed to" or "set on" another component, it can be directly on or indirectly on that other component. When a component is referred to as "connected to" another component, it can be directly connected to or indirectly connected to that other component. Furthermore, a connection can be used for both fixing and circuit / signal connectivity.

[0044] It should be understood that the terms "length", "width", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", and "outer" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the embodiments of the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the present invention.

[0045] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of embodiments of the present invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0046] like Figure 3 As shown, Embodiment 1 of the present invention discloses a dead-time compensation method for a bidirectional boost converter, comprising the following steps:

[0047] S1: Obtain the inductor current, input voltage, and output voltage of the bidirectional boost converter, and calculate the output frequency of the switching transistor that enables the bidirectional boost converter to operate in critical conduction mode based on the inductor current, input voltage, and output voltage of the bidirectional boost converter.

[0048] This step S1 specifically includes: based on the inductor current, input voltage, and output voltage of the bidirectional boost converter, the output frequency of the switching transistor that makes the bidirectional boost converter operate in critical conduction mode is calculated using the following formula (1):

[0049] In the formula, f represents the output frequency of the switching transistor, and L m Inductance, V DC1 Indicates the input voltage, V DC2 Indicates the output voltage, IL The value represents the magnitude of the inductor current; abs() represents the absolute value function.

[0050] The calculated bidirectional boost converter operates in critical conduction mode with the output frequency of the switching transistor between a preset lower frequency limit and a preset upper frequency limit.

[0051] When the amplitude of the inductor current approaches or equals zero, as shown in formula (2), the output frequency of the switching transistor in the critical conduction mode of the bidirectional boost converter is equal to the preset upper frequency limit, that is:

[0052] Where fmax represents the preset upper limit of frequency.

[0053] S2: Calculate the reference duty cycle of the switching transistor through the loop control module;

[0054] The loop control module employs a voltage feedback-based PI controller. Step S2 specifically includes: calculating the reference duty cycle in real time using the PI controller to stabilize the output voltage at the set value. That is, the controller generates the reference duty cycle D by sampling the deviation between the output voltage and the set value and performing PI calculations.

[0055] S3: The reference duty cycle of the switching transistor is dynamically corrected based on the output frequency of the switching transistor and the direction of the inductor current to obtain the corrected duty cycle of the switching transistor.

[0056] This step S3 dynamically adjusts the compensation amount based on the frequency difference to dynamically correct the reference duty cycle of the switching transistor. Specifically, it includes: dynamically calculating the dead zone compensation amount based on the difference between the output frequency of the switching transistor and the preset upper frequency limit, and correcting the reference duty cycle of the switching transistor in combination with the inductor current direction to obtain the corrected duty cycle of the switching transistor; wherein, when the polarity of the inductor current reverses, the dead zone compensation amount is smoothly transitioned by the continuous change of the difference between the output frequency of the switching transistor and the preset upper frequency limit and the direction of the instantaneous value of the inductor current.

[0057] The reference duty cycle of the switching transistor is dynamically corrected according to the output frequency of the switching transistor and the direction of the inductor current, as follows:

[0058] In the formula, D * (f) represents the corrected duty cycle of the switching transistor, D represents the reference duty cycle of the switching transistor, and Dcomp(f) is the compensation duty cycle.

[0059] Since the switching transistors are divided into upper and lower switching transistors, and their duty cycles are complementary, if D represents the duty cycle of the upper switching transistor, then 1-D represents the duty cycle of the lower switching transistor; conversely, if D represents the duty cycle of the lower switching transistor, then 1-D represents the duty cycle of the upper switching transistor. The specific duty cycle of D can be set according to actual requirements.

[0060] However, it should be noted that different switching transistors represented by D have different current definitions and different compensation duty cycles Dcomp(f), which will be explained in detail below.

[0061] Case 1): Assume that... Figure 1 As shown, the current flowing from the high-voltage region to the low-voltage region is considered positive, that is, the current flowing into DC1 is considered positive; and D is defined as the duty cycle of the upper switching transistor QH, then:

[0062] Case 2): Assuming as Figure 1 As shown, the current flowing from the high-voltage region to the low-voltage region is considered positive, that is, the current flowing into DC1 is considered positive; and D is defined as the duty cycle of the lower switching transistor QL, then:

[0063] Case 3): Assuming that the current flowing from the low-voltage region to the high-voltage region is considered positive, that is, the current flowing out of DC1 is considered positive; and D is defined as the duty cycle of the upper switching transistor QH, then:

[0064] Case 4): Assuming that the current flowing from the low-voltage region to the high-voltage region is considered positive, that is, the current flowing out of DC1 is considered positive; and D is defined as the duty cycle of the lower switching transistor QL, then:

[0065] Among them, DH * (f) represents the corrected duty cycle of the upper switching transistor, DH represents the reference duty cycle of the upper switching transistor, DHcomp(f) is the compensated duty cycle of the upper switching transistor, and DL * (f) represents the corrected duty cycle of the lower switching transistor, DL represents the reference duty cycle of the lower switching transistor, and DLcomp(f) is the compensated duty cycle of the lower switching transistor. L The value represents the amplitude of the inductor current, f represents the output frequency of the switching transistor, fmax represents the preset upper frequency limit, and Tdb is the dead time.

[0066] Combining formula (2), we can obtain:

[0067] S4: Generate a drive signal for the switching transistor based on the output frequency and corrected duty cycle of the switching transistor, and drive the switching transistor in the bidirectional boost converter according to the drive signal of the switching transistor.

[0068] This step S4 specifically includes: generating two complementary PWM signals for the switching transistors based on the output frequency and the corrected duty cycle of the switching transistors; and controlling the two switching transistors in the bidirectional boost converter based on the two complementary PWM signals.

[0069] like Figure 4 As shown, Embodiment 2 of the present invention discloses a dead-time compensation system for a bidirectional boost converter, including a frequency calculation module 20, a loop control module 30, a dead-time compensation module 40, and a PWM generator 50, wherein...

[0070] The frequency calculation module 20 is used to obtain the inductor current, input voltage and output voltage of the bidirectional boost converter 10, and calculate the output frequency of the switching transistor that makes the bidirectional boost converter 10 work in the critical conduction mode based on the inductor current, input voltage and output voltage of the bidirectional boost converter 10.

[0071] The loop control module 30 is used to calculate the reference duty cycle of the switching transistor;

[0072] The dead-time compensation module 40 is used to dynamically correct the reference duty cycle of the switching transistor based on the output frequency of the switching transistor and the direction of the inductor current, so as to obtain the corrected duty cycle of the switching transistor.

[0073] The PWM generator 50 is used to generate a drive signal for the switching transistor based on the output frequency and the corrected duty cycle of the switching transistor, and to drive the switching transistor in the bidirectional boost converter according to the drive signal of the switching transistor.

[0074] When the loop control module 30 with voltage feedback calculates the reference duty cycle of the switching transistor, it adjusts the reference duty cycle of the switching transistor to stabilize the output voltage at the set value.

[0075] The frequency calculation module 20 calculates the output frequency of the switching transistor that makes the bidirectional boost converter work in the critical conduction mode based on the inductor current, input voltage and output voltage of the bidirectional boost converter. The formula for the output frequency is detailed in formula (1).

[0076] The frequency calculation module 20 calculates that the bidirectional boost converter operates in critical conduction mode, and the output frequency of the switching transistor is between the preset lower frequency limit and the preset upper frequency limit.

[0077] When the amplitude of the inductor current approaches zero or equals zero, as shown in formula (2), the output frequency of the switching transistor of the bidirectional boost converter 10 in critical conduction mode is equal to the preset upper frequency limit.

[0078] The loop control module 30 adopts a voltage feedback-based PI controller, which calculates the reference duty cycle in real time to stabilize the output voltage at the set value.

[0079] The dead-time compensation module 40 dynamically corrects the reference duty cycle of the switching transistor according to the above formulas (3a), (3b), (4a)-(4d), (5a)-(5d) based on the output frequency of the switching transistor and the direction of the inductor current. When I L = 0 or I L → When 0, the compensation duty cycle Dcomp(f) = 0.

[0080] The PWM generator 50 generates two complementary PWM signals for the switching transistors based on the output frequency and the corrected duty cycle of the switching transistors; and controls the two switching transistors in the bidirectional boost converter based on the two complementary PWM signals.

[0081] The following detailed description, in conjunction with specific embodiments, provides a further explanation of the dead-zone compensation method for the bidirectional boost converter in Embodiment 1 and the dead-zone compensation system for the bidirectional boost converter in Embodiment 2 of the present invention.

[0082] This specific embodiment proposes a dead-zone compensation method that does not affect the output voltage when the current polarity (positive and negative direction) is reversed, including the following steps:

[0083] A1: Sampling to obtain the inductor current amplitude I L Input voltage V DC1 Output voltage V DC2 ;

[0084] Among them, such as Figure 4 As shown, the dead-time compensation system of the bidirectional boost converter 10 includes a frequency calculation module 20, a loop control module 30, a dead-time compensation module 40, and a PWM generator 50. The structure of the bidirectional boost converter 10 is as follows: Figure 1 As shown, DC1 is the input DC power supply, DC2 is the output DC power supply, L is the inductor, QH and QL represent the switching transistors, and the arrow indicates the current reference direction as the current flows into DC1.

[0085] A2: The switching frequency f is calculated using the frequency calculation module 20. The bidirectional boost converter 10 is controlled by TCM, and the frequency calculation module 20 is used to calculate the switching frequency f. The inductor current amplitude I can be calculated after sampling the instantaneous value I(L) of the inductor current. LThe output frequency f belongs to the given switching frequency operating range (fmin, fmax), and the calculation formula is:

[0086] In the formula, f represents the output frequency of the switching transistor, Lm represents the inductance of the bidirectional boost converter 10, and V DC1 V represents the input voltage of the bidirectional boost converter 10. DC2 I represents the output voltage of the bidirectional boost converter 10. L The value represents the magnitude of the inductor current, and abs() represents the absolute value function.

[0087] Where fmin represents the preset lower limit of the switching frequency, and fmax represents the preset upper limit of the switching frequency.

[0088] In TCM (Critical On Mode or Critical Current Mode), the switching frequency f is adjusted to ensure that the current drops to zero just as the switching device begins to conduct. This means the diode does not undergo a reverse recovery process, and therefore no reverse recovery current flows, i.e., soft switching. Since the current needs to rise from zero to its maximum value (current rise time) and then return to zero (current fall time) in each switching cycle, the switching frequency f can be obtained as: f = 1 / (current rise time + current fall time). According to the volt-second product formula: current rise time = L m *abs(I L ) / V DC1 Current fall time = L m *abs(I L ) / (V DC2 -V DC1 From these, we can obtain formula (1).

[0089] The switching frequency f calculated by formula (1) enables the bidirectional boost converter 10 to operate in TCM soft-switching mode.

[0090]

[0091] Formula (2) means that I L When the absolute value is less than a preset threshold, f = fmax, where the preset threshold is f. thr It can be calculated according to the following formula (7):

[0092] A3: Calculate the duty cycle D using loop control module 30;

[0093] like Figure 4The loop control module 30 shown is used for bidirectional boost output voltage control. The output is the reference duty cycle D, which refers to the proportion of the on-time to the total time within one pulse cycle.

[0094] The loop control module 30 can be a PI controller. The function of the loop control module 30 is to calculate a suitable reference duty cycle D so that the voltage V DC2 Stabilize at the set value, such as 400V.

[0095] A4: Calculate D using dead zone compensation module 40 * (f);

[0096] like Figure 4 The dead-time compensation module 40 shown adds dead-time compensation Dcomp(f) and outputs the corrected duty cycle D. * (f), in this embodiment, Figure 1 The diagram illustrates the current flowing into DC1 as positive, and D is defined as the duty cycle of the lower switching transistor QL.

[0097] In the formula, I L The value represents the amplitude of the inductor current, f represents the output frequency of the switching transistor, fmax represents the preset upper frequency limit, and Tdb is the dead time.

[0098] Combining formula (2) from step A2, we can see that:

[0099] A5: Use PWM generator 50 to drive bidirectional boost converter 10;

[0100] like Figure 4 The PWM generator 50 shown will output frequency f and compensated duty cycle DL. * (f) is converted into PWM control signals TL and TH to control the switching transistors QL and QH in the bidirectional boost converter 10. The switching transistors QL and QH are complementary and their switching frequency is f.

[0101] like Figure 2 As shown, a PWM period T is divided into four time zones, where Tdb represents the dead time, THon is the on-time of the upper switch, and TLon is the on-time of the lower switch. When using the dead-time compensation module 40 of this invention, the duty cycle setting of the PWM generator 50 is DL. * (f), we can obtain:

[0102] refer to Figure 5This is a waveform diagram of the control variables of the bidirectional boost converter. The horizontal axis represents the running time, and the vertical axis represents the reference duty cycle D given by the lower switching transistor, the switching frequency f, the instantaneous inductor current I(L) (represented by the orange line in the top block diagram), and the inductor current amplitude I. L (The blue line in the top box indicates) Output voltage V DC2 .exist Figure 1 In the bidirectional boost converter, the inductor current amplitude I L It exhibits alternating positive and negative changes.

[0103] like Figure 1 In the bidirectional boost converter shown, the inductor current flows into DC1, then the inductor current amplitude I L >0, during the Tdb period, the QL body diode conducts as an inductor freewheeling current, the conduction time of the next switching transistor is: (TLon + Tdb + Tdb), and the effective duty cycle DTL(f) of the next switching transistor is:

[0104] Substituting formula (4b) into formula (3b), the output duty cycle D of loop control module 30 is obtained as follows:

[0105] Combining f = 1 / T and formulas (8), (9), and (10), the output duty cycle DL of the loop control module 30 can be obtained as:

[0106] It can be seen that the effective duty cycle DTL(f) of the lower switching transistor is decoupled from the switching frequency f, and adjusting f will not change the effective duty cycle DTL(f) of the lower switching transistor.

[0107] Assuming the inductor current in the bidirectional boost converter flows out of DC1, then the inductor current amplitude I... L <0, during the Tdb period, the body diode of QH conducts as an inductor freewheeling current, the conduction time of the lower switching transistor QL is: TLon, and the effective duty cycle DTL(f) of the lower switching transistor is:

[0108] Substituting formula (5b) into formula (3b), the output duty cycle D of loop control module 30 is obtained as follows:

[0109] Combining f = 1 / T and formulas (8), (12), and (13), the output duty cycle DL of the loop control module 30 can be obtained as:

[0110] From formulas (11) and (14), we can obtain:

[0111] DL is the original duty cycle given for the lower switching transistor calculated by the controller loop, and it is independent of f. Furthermore, fmax and Tdb are also independent of f. Therefore, the effective duty cycle DTL(f) of the lower switching transistor is decoupled from the switching frequency f. f does not affect the effective duty cycle DTL of the lower switching transistor, and DTL(fmin) = DTL(fmax). Adjusting f will not change the duty cycle DTL(f) of the lower switching transistor. Similarly, the effective duty cycle DTH of the upper switching transistor = 1 - DTL, which is also independent of f.

[0112] Figure 6 Dcomp1 is the effect diagram of the duty cycle compensation using the present invention, and Dcomp2 is the effect diagram of the traditional duty cycle compensation. Given a switching frequency f that varies with IL to achieve TCM effect, that is, the instantaneous value of the inductor current I(L) can return to zero each time, realizing soft switching. When using equation (1) of the frequency calculation module 20, the current is very small when the inductor current alternates between positive and negative, just enough to make f=fmax, as shown in the figure around 0.002s, at the inductor current amplitude I... L When the value approaches 0, when f=fmax using equation (2) of dead zone compensation module 40, Dcomp(f) = 0 (i.e. Figure 6 When Dcomp1 = 0, the inductor current alternates between positive and negative, and Dcomp(f) experiences a smooth transition without polarity reversal. This does not cause a change in gain (the ratio of output voltage to duty cycle amplitude) and has no effect on the effective duty cycle. Figure 6 As shown, at the inductor current amplitude I L When the positive and negative values ​​alternate, the range of f is very large, the gain is decoupled from f, and the amplitude I of the inductor current... L Switching between positive and negative values ​​will not cause a jump in gain.

[0113] In summary, at the inductor current amplitude I L When the positive and negative values ​​alternate, the dead zone compensation value Dcomp(f) = 0, there is no polarity reversal, and it will not cause a gain jump. Thus, even if the current polarity reversal is not detected accurately, it will not affect the dead zone compensation effect; ultimately, the influence of the dead zone effect can be eliminated.

[0114] Comparative example: If the dead-time compensation module adopts the following formula (16), when the inductor current I LWhen switching between positive and negative, the frequency calculation module output f = fmax can be obtained from formula (2); using this method, the duty cycle DTL of the switching transistor QL is decoupled from the switching frequency f, but the dead zone compensation value Dcomp is large and will jump from Tdb * fmax to -Tdb * fmax, causing a gain jump.

[0115]

[0116] The Dcomp2 calculated by the traditional formula fluctuates greatly due to the current direction and oscillates near the zero crossing, which affects the effective duty cycle.

[0117] The dead-time compensation method proposed in this invention is as follows: When using formula (1) of the frequency calculation module, the current is very small when the inductor current alternates between positive and negative, just enough to make f = fmax. When using formula of the dead-time compensation module, Dcomp(f) = 0 is just enough to decouple the duty cycle of the switching transistor from the switching frequency f. Changes in f will not cause changes in gain. When the inductor current alternates between positive and negative, the dead-time compensation value is 0. Even if the detection is inaccurate at the moment of current polarity reversal, it will not cause changes in gain. Ultimately, the influence of the dead-time effect on the gain can be eliminated, making the control loop stable.

[0118] In summary, the dead-time compensation method proposed in this invention can be applied to TCM-controlled bidirectional boost converters. The duty cycle of the switching transistor and the switching frequency f are decoupled, so changes in f do not cause gain changes. When the inductor current alternates between positive and negative, the dead-time compensation value is 0. Even if the current polarity reversal is not accurately detected, it will not cause gain changes. Ultimately, the influence of the dead-time effect on the gain can be eliminated, resulting in a stable control loop.

[0119] Embodiment 3 of the present invention discloses a computer-readable storage medium storing a computer program, wherein the computer program is configured to be run by a processor to perform the steps of the dead-zone compensation method for the bidirectional boost converter in Embodiment 1 above.

[0120] Optionally, the aforementioned computer-readable storage media may include, but are not limited to, various media capable of storing computer programs, such as USB flash drives, read-only memory (ROM), random access memory (RAM), portable hard drives, magnetic disks, or optical disks.

[0121] The background section of this invention may include background information about the problems or circumstances surrounding the invention, rather than a description of prior art by others. Therefore, the content included in the background section is not an admission of prior art by the applicant.

[0122] The above description provides a further detailed explanation of the present invention in conjunction with specific / preferred embodiments, and it should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various substitutions or modifications can be made to these described embodiments without departing from the concept of the present invention, and all such substitutions or modifications should be considered within the scope of protection of the present invention. In the description of this specification, the reference to terms such as "an embodiment," "some embodiments," "preferred embodiment," "example," "specific example," or "some examples," etc., indicates that the specific features, structures, materials, or characteristics described in connection with that embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in any suitable manner in one or more embodiments or examples. Furthermore, those skilled in the art can combine and integrate different embodiments or examples and features of different embodiments or examples described in this specification without contradiction. Although the embodiments of the present invention and their advantages have been described in detail, it should be understood that various changes, substitutions, and modifications can be made herein without departing from the scope defined by the appended claims.

Claims

1. A dead-time compensation method for a bidirectional boost converter, characterized in that, Includes the following steps: S1: Obtain the inductor current, input voltage, and output voltage of the bidirectional boost converter, and calculate the output frequency of the switching transistor that enables the bidirectional boost converter to operate in critical conduction mode based on the inductor current, input voltage, and output voltage of the bidirectional boost converter. S2: Calculate the reference duty cycle of the switching transistor through the loop control module; S3: Dynamically correct the reference duty cycle of the switching transistor based on the output frequency of the switching transistor and the direction of the inductor current to obtain the corrected duty cycle of the switching transistor; S4: Generate a drive signal for the switch based on the output frequency and corrected duty cycle of the switch, and drive the switch in the bidirectional boost converter according to the drive signal of the switch. Step S3 specifically includes: dynamically calculating the dead-time compensation amount based on the difference between the output frequency of the switching transistor and the preset upper frequency limit, and correcting the reference duty cycle of the switching transistor in combination with the direction of the inductor current to obtain the corrected duty cycle of the switching transistor; wherein, when the polarity of the inductor current reverses, the dead-time compensation amount is smoothly transitioned by the continuous change of the direction of the instantaneous value of the inductor current and the difference between the output frequency of the switching transistor and the preset upper frequency limit. The switching transistor is divided into an upper switching transistor and a lower switching transistor, and the sum of the duty cycles of the upper switching transistor and the lower switching transistor is 1. When the current flows from the high-voltage region to the low-voltage region as positive, the corrected duty cycle of the upper switching transistor is: When the current flows from the high-voltage region to the low-voltage region as positive, the corrected duty cycle of the lower switching transistor is: When the current flows from the low-voltage region to the high-voltage region as positive, the corrected duty cycle of the upper switching transistor is: When the current flows from the low-voltage region to the high-voltage region as positive, the corrected duty cycle of the lower switching transistor is: Among them, DH * (f) represents the corrected duty cycle of the upper switching transistor, DH represents the reference duty cycle of the upper switching transistor, DHcomp(f) is the compensated duty cycle of the upper switching transistor, and DL * (f) represents the corrected duty cycle of the lower switching transistor, DL represents the reference duty cycle of the lower switching transistor, and DLcomp(f) is the compensated duty cycle of the lower switching transistor. L The value represents the amplitude of the inductor current, f represents the output frequency of the switching transistor, fmax represents the preset upper frequency limit, and Tdb is the dead time.

2. The dead-time compensation method for a bidirectional boost converter according to claim 1, characterized in that, In step S1, based on the inductor current, input voltage, and output voltage of the bidirectional boost converter, the output frequency of the switching transistor that enables the bidirectional boost converter to operate in critical conduction mode is calculated using the following formula: f = 1 / (((L m / V DC1 ) + L m / (V DC2 -V DC1 ))*abs(I L )) In the formula, f represents the output frequency of the switching transistor, and L m Inductance, V DC1 Indicates the input voltage, V DC2 Indicates the output voltage, I L The value represents the magnitude of the inductor current, and abs() represents the absolute value function.

3. The dead-time compensation method for a bidirectional boost converter according to claim 1, characterized in that, In step S1, the bidirectional boost converter operates in critical conduction mode. The output frequency of the switching transistor is between the preset lower frequency limit and the preset upper frequency limit. When the amplitude of the inductor current approaches zero, the output frequency of the switching transistor in the bidirectional boost converter operates in critical conduction mode and is equal to the preset upper frequency limit.

4. The dead-time compensation method for a bidirectional boost converter according to claim 1, characterized in that, The loop control module adopts a voltage feedback-based PI controller. Step S2 specifically includes: calculating the reference duty cycle in real time through the PI controller to stabilize the output voltage at the set value.

5. The dead-time compensation method for a bidirectional boost converter according to claim 1, characterized in that, Step S4 includes: generating two complementary PWM signals for the switching transistors based on the output frequency and the corrected duty cycle of the switching transistors; and controlling the two switching transistors in the bidirectional boost converter based on the two complementary PWM signals.

6. A dead-time compensation system for a bidirectional boost converter, characterized in that, It includes a frequency calculation module, a loop control module, a dead-time compensation module, and a PWM generator, among which, The frequency calculation module is used to obtain the inductor current, input voltage and output voltage of the bidirectional boost converter, and calculate the output frequency of the switching transistor that enables the bidirectional boost converter to operate in the critical conduction mode based on the inductor current, input voltage and output voltage of the bidirectional boost converter. The loop control module is used to calculate the reference duty cycle of the switching transistor; The dead-time compensation module is used to dynamically correct the reference duty cycle of the switching transistor based on the output frequency of the switching transistor and the direction of the inductor current, so as to obtain the corrected duty cycle of the switching transistor. The PWM generator is used to generate a drive signal for the switching transistor based on the output frequency and the corrected duty cycle of the switching transistor, and to drive the switching transistor in the bidirectional boost converter according to the drive signal of the switching transistor. The dead-time compensation module is used to dynamically calculate the dead-time compensation amount based on the difference between the output frequency of the switching transistor and the preset upper frequency limit, and to correct the reference duty cycle of the switching transistor in combination with the direction of the inductor current to obtain the corrected duty cycle of the switching transistor; wherein, when the polarity of the inductor current reverses, the dead-time compensation amount is smoothly transitioned by the continuous change of the direction of the instantaneous value of the inductor current and the difference between the output frequency of the switching transistor and the preset upper frequency limit. The switching transistor is divided into an upper switching transistor and a lower switching transistor, and the sum of the duty cycles of the upper switching transistor and the lower switching transistor is 1. When the current flows from the high-voltage region to the low-voltage region as positive, the corrected duty cycle of the upper switching transistor is: When the current flows from the high-voltage region to the low-voltage region as positive, the corrected duty cycle of the lower switching transistor is: When the current flows from the low-voltage region to the high-voltage region as positive, the corrected duty cycle of the upper switching transistor is: When the current flows from the low-voltage region to the high-voltage region as positive, the corrected duty cycle of the lower switching transistor is: Among them, DH * (f) represents the corrected duty cycle of the upper switching transistor, DH represents the reference duty cycle of the upper switching transistor, DHcomp(f) is the compensated duty cycle of the upper switching transistor, and DL * (f) represents the corrected duty cycle of the lower switching transistor, DL represents the reference duty cycle of the lower switching transistor, and DLcomp(f) is the compensated duty cycle of the lower switching transistor. L The value represents the amplitude of the inductor current, f represents the output frequency of the switching transistor, fmax represents the preset upper frequency limit, and Tdb is the dead time.

7. The dead-time compensation system for a bidirectional boost converter according to claim 6, characterized in that, The frequency calculation module calculates that the output frequency of the switching transistor in the critical conduction mode of the bidirectional boost converter is between the preset lower frequency limit and the preset upper frequency limit. When the amplitude of the inductor current approaches zero, the output frequency of the switching transistor in the critical conduction mode of the bidirectional boost converter is equal to the preset upper frequency limit.

8. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores a computer program, wherein the computer program is configured to be run by a processor to perform the dead-zone compensation method for the bidirectional boost converter according to any one of claims 1 to 5.

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