Device for increasing inrush current at low voltage of bidirectional power supply and control method thereof

Abstract

The present invention discloses a device for increasing the inrush current at low voltage of a bidirectional power supply and its control method, belonging to the field of power supplies. It includes a power conversion unit, a power detection unit, and a digital signal processing unit, solving the technical problem of improving the inrush current absorption ability at low voltage of the bidirectional power supply by changing the switching period T0 of the switching tube. The present invention dynamically adjusts the control period without affecting the reliability of the machine. Compared with the traditional method of adjusting the rising edge and falling edge times, the present invention does not affect the electromagnetic radiation of the machine.

Description

Technical Field

[0001] The present invention belongs to the technical field of power supplies, and relates to a device for increasing the inrush current of a bidirectional power supply at low voltage and a control method therefor. Background Art

[0002] A bidirectional DC power supply is a two-quadrant power supply that can both output power and absorb power. Currently, bidirectional power supplies on the market generally have the defect that they cannot absorb power at full current when the voltage is low and the current is large during power absorption.

[0003] Currently, to overcome the above defects, the common approach is to reduce the dead time Tdead to improve the power absorption ability of the bidirectional power supply: by adjusting the resistance value in the analog circuit to shorten or increase the dead time. When the dead time is reduced, the inrush current absorption ability of the bidirectional power supply at low voltage increases.

[0004] Another method is to speed up the rising edge or falling edge time of the drive to improve the power absorption ability of the bidirectional power supply: by adjusting the resistance value in the analog circuit to speed up the rising edge or falling edge time of the drive. When the rising edge and falling edge times are reduced, the inrush current absorption ability of the bidirectional power supply at low voltage increases.

[0005] In summary, the above two common methods for improving the inrush current absorption ability of a bidirectional power supply at low voltage both meet the requirements by modifying hardware parameters. Reducing the dead time will affect the reliability of the machine, and speeding up the rising edge or falling edge time will deteriorate the electromagnetic radiation of the machine. Summary of the Invention

[0006] The object of the present invention is to provide a device for increasing the inrush current of a bidirectional power supply at low voltage and a control method therefor, which solves the technical problem of improving the inrush current absorption ability of the bidirectional power supply at low voltage by changing the switching period T0 of the switching tube.

[0007] To achieve the above object, the present invention adopts the following technical solutions:

[0008] A device for increasing the inrush current of a bidirectional power supply at low voltage includes a power conversion unit, a power detection unit, and a digital signal processing unit. The power conversion unit is connected to the object to be measured, the digital signal processing unit is connected to the power conversion unit, the power detection unit is connected to the digital signal processing unit, and the power detection unit is also connected to the object to be measured.

[0009] Preferably, the power conversion unit includes a bidirectional DC-DC power module, which includes a switching transistor Q1, a switching transistor Q2, an inductor L, and a capacitor C. The D pole of the switching transistor Q1 is connected to the positive pole of the external power supply, the G pole is connected to the digital signal processing unit, and the S pole is connected to the D pole of the switching transistor Q2. The G pole of the switching transistor Q2 is connected to the digital signal processing unit, and the S pole is connected to the negative pole of the external power supply. The D pole of the switching transistor Q2 is also connected to the S pole of the switching transistor Q2 through the serially connected inductor L and capacitor C. Both ends of the capacitor C provide a bidirectional power load terminal, and the bidirectional power load terminal is connected to the object under test.

[0010] Preferably, the object under test is a power supply or a load to be tested.

[0011] A method for increasing the inrush current of a bidirectional power supply at low voltage includes the following steps:

[0012] Step 1: Establish a device for increasing the inrush current of a bidirectional power supply at low voltage;

[0013] Step 2: The power detection unit collects the current Io of the object under test and sends the current Io to the digital signal processing unit;

[0014] Step 3: The digital signal processing unit calculates the current control voltage output value Uout in real time and controls the alternating conduction of the switching transistor Q1 and the switching transistor Q2 through a PWM signal, that is, the switching cycle time T;

[0015] Step 4: The digital signal processing unit is used to adjust the PWM signal to adjust the switching cycle time T.

[0016] Further, the digital signal processing unit adjusts the PWM signal according to the following steps to adjust the switching cycle T:

[0017] Step S1: Set the current switching cycle time T as the working cycle T0;

[0018] Judge whether the current control voltage output value Uout is negative: if yes, execute Step S2; if no, execute Step S6;

[0019] Step S2: Calculate the next working cycle T1 according to the following formula: T1 = T0 × (1 - Uout);

[0020] Step S3: Preset a cycle upper limit value TLIM, and judge whether T1 is less than TLIM: if yes, execute Step S1; if no, execute Step S4;

[0021] Step S4: Adjust the PWM signal so that the power conversion unit operates with the cycle upper limit value TLIM as the working cycle;

[0022] The digital signal processing unit reads the current Io of the object to be measured collected by the power detection unit in real time, and determines whether the current Io is less than 0: if yes, it operates with the cycle upper limit value TLIM as the working cycle; if not, it executes step S5;

[0023] Step S5: Determine whether to maintain for a certain time ΔT: if yes, execute step S6; if not, operate with the cycle upper limit value TLIM as the working cycle;

[0024] Step S6: Operate with the working cycle T0.

[0025] A device for increasing the inrush current under low voltage of a bidirectional power supply and its control method according to the present invention solve the technical problem of improving the inrush current absorption ability under low voltage of a bidirectional power supply by changing the switching cycle T0 of a switching tube. The present invention dynamically adjusts the control cycle without affecting the reliability of the machine. Compared with the traditional method of adjusting the rising edge and falling edge times, the present invention does not affect the electromagnetic radiation of the machine. Brief Description of the Drawings

[0026] Figure 1 It is a timing diagram of the upper and lower tubes of a typical buck circuit;

[0027] Figure 2 It is a principle block diagram of the present invention;

[0028] Figure 3 It is a circuit diagram of the DC-DC power module of the present invention;

[0029] Figure 4 It is a flowchart of the present invention. Detailed Embodiments

[0030] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0031] Embodiment 1:

[0032] As Figures 1-4 shown, a device for increasing the inrush current under low voltage of a bidirectional power supply includes a power conversion unit, a power detection unit, and a digital signal processing unit. The power conversion unit is connected to the object to be measured, the digital signal processing unit is connected to the power conversion unit, the power detection unit is connected to the digital signal processing unit, and the power detection unit is also connected to the object to be measured.

[0033] Preferably, the power conversion unit includes a bidirectional DC-DC power module, which includes a switching transistor Q1, a switching transistor Q2, an inductor L, and a capacitor C. The D pole of the switching transistor Q1 is connected to the positive pole of the external power supply, the G pole is connected to the digital signal processing unit, and the S pole is connected to the D pole of the switching transistor Q2. The G pole of the switching transistor Q2 is connected to the digital signal processing unit, and the S pole is connected to the negative pole of the external power supply. The D pole of the switching transistor Q2 is also connected to the S pole of the switching transistor Q2 through the serially connected inductor L and capacitor C. Both ends of the capacitor C provide a bidirectional power load terminal, and the bidirectional power load terminal is connected to the object under test.

[0034] The power conversion unit is used to achieve bidirectional power conversion between the power conversion unit and the object under test;

[0035] The power detection unit is coupled between the power conversion unit and the object under test, and is used to collect and output detection parameters to the digital signal processing unit;

[0036] The digital signal processing unit is used to perform PWM control on the power conversion unit.

[0037] Preferably, the object under test is a power supply or load to be tested.

[0038] The present invention improves the current absorption ability of the bidirectional power supply under low voltage by a novel means without affecting the reliability of the machine and electromagnetic radiation. The present invention changes the switching period T0 of the switching transistor, so that it can not only improve the current absorption ability of the bidirectional power supply under low voltage but also retain the original hardware characteristics.

[0039] Embodiment 2:

[0040] As Figures 1-4 shown, the method for increasing the inrush current of the bidirectional power supply under low voltage in Embodiment 2 is implemented on the basis of the device for increasing the inrush current of the bidirectional power supply under low voltage in Embodiment 1, and includes the following steps:

[0041] Step 1: Establish a device for increasing the inrush current of the bidirectional power supply under low voltage;

[0042] Step 2: The power detection unit collects the current Io of the object under test and sends the current Io to the digital signal processing unit;

[0043] Step 3: The digital signal processing unit calculates the current control voltage output value Uout in real time and controls the alternating conduction of the switching transistor Q1 and the switching transistor Q2 through a PWM signal, that is, the switching period time T;

[0044] Step 4: The digital signal processing unit adjusts the PWM signal according to the following steps to adjust the switching period time T:

[0045] Step S1: Set the current switching cycle time T as the working cycle T0;

[0046] Judge whether the current control voltage output value Uout is negative: if yes, execute Step S2; if no, execute Step S6;

[0047] Step S2: Calculate the next working cycle T1 according to the following formula: T1 = T0 × (1 - Uout);

[0048] Step S3: Preset a cycle upper limit value TLIM, and judge whether T1 is less than TLIM: if yes, execute Step S1; if no, execute Step S4;

[0049] Step S4: Adjust the PWM signal so that the power conversion unit operates with the cycle upper limit value TLIM as the working cycle;

[0050] The digital signal processing unit reads the current Io of the object to be measured collected by the power detection unit in real time, and judges whether the current Io is less than 0: if yes, keep operating with the cycle upper limit value TLIM as the working cycle; if no, execute Step S5;

[0051] Step S5: Judge whether to maintain for a certain time △T: if yes, execute Step S6; if no, keep operating with the cycle upper limit value TLIM as the working cycle;

[0052] Step S6: Operate with the working cycle T0.

[0053] The PWM controls the two power tubes Q1 and Q2 to conduct alternately. The flowchart of the PWM dynamically adjusting TO is as Figure 4 shown: Uout is the current control voltage output value calculated by the digital signal processing unit in real time; Io is the output current detected by the power detection unit:

[0054] The power detection unit sends the detected voltage value to the digital signal processing unit. The digital signal processing unit calculates the current control voltage output value Uout in real time based on the detected voltage value. An example of the calculation formula of the control voltage output value Uout can be:

[0055] Uout(n) = A1 * Uout(n + 1) + A2 * Uout(n + 2) + A3 * Uout(n + 3) + B0 * Errn(n) + B1 * Errn(n + 1) + B2 * Errn(n + 2) + B3 * Errn(n + 3);

[0056] Errn(n) = Vset - Vsamp;

[0057] Errn(n + 3) = Errn(n + 2);

[0058] Errn(n + 2) = Errn(n + 1);

[0059] Errn(n + 1) = Errn(n);

[0060] Uout(n + 3) = Uout(n + 2);

[0061] Uout(n + 2) = Uout(n + 1);

[0062] Uout(n + 1) = Uout(n);

[0063] In the above formula, Vset is the set value; Vsamp is the sampled value; where

[0064] A1, A2, A3, B0, B1, B2, B3 are loop coefficients respectively, which are constant values obtained according to actual debugging; Uout(n), Uout(n + 1), Uout(n + 2), Uout(n + 3) are the current control voltage output value, the control voltage output values of the next cycle, the next two cycles, and the next three cycles respectively; Errn(n), Errn(n + 1), Errn(n + 2), Errn(n + 3) are the differences between the current set voltage and the sampled voltage, the differences between the set voltage and the sampled voltage of the next cycle, the next two cycles, and the next three cycles respectively.

[0065] Furthermore, a voltage modulation signal is output to complete PWM driving to the bidirectional power conversion unit to adjust the voltage value of the bidirectional power conversion unit.

[0066] In step S2, since T1 > 0 and T0 > 0, so (1 - Uout) > 0 in the formula T1 = T0×(1 - Uout);

[0067] In step S5, a certain time △T is a given time constant to avoid the oscillation of the current Io during the positive and negative conversion.

[0068] Such as Figure 1 shown in the timing diagram of the upper and lower switches of the typical buck circuit, where Tdead is the dead time between the upper and lower switches, Tonrr is the rising edge time, Toffrr is the falling edge time, and T is the switching period time.

[0069] Its working principle is as follows:

[0070] When the bidirectional power supply performs the inhalation function, due to the existence of the dead time Tdead, there will be a duty cycle loss, and the duty cycle loss ratio is k = Tdead / T;

[0071] The magnitude of k determines the ability of the bidirectional power supply to draw current when operating in the absorption power mode. Through real-time calculation, the present invention dynamically adjusts T, thereby dynamically adjusting the magnitude of k. When T increases, k decreases; when T decreases, k increases, thus achieving dynamic adjustment of the current absorption ability.

[0072] When the frequency modulation scheme is not used, the bidirectional power supply can only carry a load of -120A at a voltage of 30V. When the voltage drops to 15V, the load current can only reach -3.6A.

[0073] After using the solution of the present invention, the same product can carry a load of -120A at a voltage of 15V. When the voltage drops to 7.5V, the load current is -3.6A.

[0074] In summary, without affecting the machine performance, after using the frequency modulation scheme, the voltage current absorption ability of the product has doubled.

[0075] An apparatus and its control method for increasing the current absorption of a bidirectional power supply at low voltage according to the present invention solve the technical problem of improving the current absorption ability of the bidirectional power supply at low voltage by changing the switching period T0 of the switching tube. The present invention dynamically adjusts the control period without affecting the reliability of the machine. Compared with the traditional method of adjusting the rising edge and falling edge times, the present invention does not affect the electromagnetic radiation of the machine.

[0076] In the present invention, any process or method description shown in the flowchart or described in other ways herein can be understood to represent a module, segment, or part of code including one or more executable instructions for implementing a customized logical function or process. The scope of the preferred embodiments of the present invention includes additional implementations, where the functions can be executed in a substantially simultaneous manner or in the reverse order according to the involved functions, rather than in the order shown or discussed, which should be understood by those skilled in the technical field to which the embodiments of the present invention belong.

[0077] Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those of ordinary skill in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present invention.

Claims

1. A method for increasing the inrush current at low voltage of a bidirectional power supply, which is applied to a device for increasing the inrush current at low voltage of a bidirectional power supply, and is characterized in that: The device includes a power conversion unit, a power detection unit, and a digital signal processing unit. The power conversion unit is connected to the object to be measured, the digital signal processing unit is connected to the power conversion unit, the power detection unit is connected to the digital signal processing unit, and the power detection unit is also connected to the object to be measured; The power conversion unit is a bidirectional DC-DC power module, and the bidirectional DC-DC power module includes a switching tube Q1, a switching tube Q2, an inductor L, and a capacitor C; The method includes the following steps: Step 1: Establish a device for increasing the inrush current at low voltage of a bidirectional power supply; Step 2: The power detection unit collects the current Io of the object to be measured and sends the current Io to the digital signal processing unit; Step 3: The digital signal processing unit calculates the current control voltage output value Uout in real time and controls the alternating conduction of the switching tube Q1 and the switching tube Q2 through a PWM signal, that is, the switching cycle time T; Step 4: The digital signal processing unit is used to adjust the PWM signal to adjust the switching cycle time T; The digital signal processing unit adjusts the PWM signal according to the following steps to adjust the switching cycle T: Step S1: Set the current switching cycle time T as the working cycle T0; Judge whether the current control voltage output value Uout is negative: if yes, execute step S2; if no, execute step S6; Step S2: Calculate the next working cycle T1 according to the following formula: T1 = T0×(1 - Uout); Step S3: Preset a cycle upper limit value TLIM, and judge whether T1 is less than TLIM: if yes, execute step S1; if no, execute step S4; Step S4: Adjust the PWM signal so that the power conversion unit operates with the cycle upper limit value TLIM as the working cycle; The digital signal processing unit reads the current Io of the object to be measured collected by the power detection unit in real time and judges whether the current Io is less than 0: if yes, keep operating with the cycle upper limit value TLIM as the working cycle; If no, execute step S5; Step S5: Judge whether it has been maintained for a certain time △T: if yes, execute step S6; if no, keep operating with the cycle upper limit value TLIM as the working cycle; Step S6: Operate with the working cycle T0; When the bidirectional power supply performs the inrush function, due to the existence of the dead time Tdead, there will be a duty cycle loss. The duty cycle loss ratio is k = Tdead / T; the size of k determines the inrush current capacity when the bidirectional power supply performs the inrush power. Through real-time operation, dynamically adjust T, thereby dynamically adjusting the size of k. When T becomes larger, k becomes smaller; when T becomes smaller, k becomes larger, so as to achieve dynamic adjustment of the inrush current capacity.

2. The method for increasing the inrush current at low voltage of a bidirectional power supply according to claim 1, wherein: In the two-way DC-DC power module, the D pole of the switching transistor Q1 is connected to the positive pole of the external power supply, the G pole is connected to the digital signal processing unit, the S pole is connected to the D pole of the switching transistor Q2, the G pole of the switching transistor Q2 is connected to the digital signal processing unit, and the S pole is connected to the negative pole of the external power supply. The D pole of the switching transistor Q2 is also connected to the S pole of the switching transistor Q2 through an inductor L and a capacitor C connected in series. Both ends of the capacitor C provide a two-way power load terminal, and the two-way power load terminal is connected to the object under test.

3. A method for increasing the inrush current at low voltage of a bidirectional power supply according to claim 1, characterized in that: The object under test is a power supply or a load to be tested.

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