A dc-dc converter current limiting device and method

Abstract

The application is a DCDC converter current limiting device, belonging to the electrical field: including: a sampling module for sampling the output of the DCDC converter to obtain output voltage and output current; a virtual resistance adjusting module for receiving the output current from the sampling module, increasing the virtual resistance when the output current is greater than the current limiting value, and decreasing the virtual resistance when the output current is less than the current limiting value, and the virtual resistance is decreased to zero at the minimum; a virtual output voltage module for receiving the virtual resistance from the virtual resistance adjusting module, connecting the virtual resistance and the actual load in series as an equivalent load, receiving the output voltage and output current from the sampling module, and outputting the virtual output voltage; a DCDC converter for receiving the virtual output voltage from the virtual output voltage module, controlling the DCDC converter, and making the virtual output voltage follow the given value of the output voltage; when in the constant current working condition, the device feedback channel contains the output voltage, the response to the output side voltage disturbance is fast, and the output current fluctuation caused is small.

Description

Technical Field

[0001] This invention belongs to the field of electrical engineering and relates to a current limiting device and method for DC-DC converters. Background Technology

[0002] The DC-DC converter in rail transit vehicles operates in both constant voltage and constant current modes. When in constant voltage mode, if the output current reaches the current limit, it must switch to constant current mode. If the output current falls below the current limit, it must exit constant current mode. Current technology uses voltage closed-loop control in constant voltage mode and switches to current closed-loop control in constant current mode. During current limiting, the DC-DC converter is affected by output current fluctuations, causing frequent switching between the two modes. Rail transit vehicle DC-DC converters have large capacities and low switching frequencies. The controller bandwidth is small due to the switching frequency, resulting in long settling times and large current fluctuations during mode switching. This places high demands on the regulator design. Furthermore, in constant current mode, there is only a current loop, leading to poor immunity to voltage disturbances and large output current fluctuations when the output voltage fluctuates.

[0003] like Figure 1 The diagram shows a current limiting device module for a DC-DC converter in the prior art. The DC-DC converter current limiting device includes a constant voltage control module 1, a constant current control module 2, a mode selection module 3, and a drive module 4.

[0004] In the existing technology, under constant voltage conditions, the constant voltage control module 1 performs voltage closed-loop control to enable the DC-DC converter to output a constant voltage; under constant current conditions, the constant current control module 2 performs current closed-loop control to enable the DC-DC converter to output a constant current; both the constant voltage control module 1 and the constant current control module 2 output control quantities to the mode selection module 3, which selects the actual operating condition according to the judgment conditions and outputs the corresponding operating condition control quantity to the drive module 4.

[0005] The mode selection module 3 of the prior art selects the operating condition by comparing the output current and the current limit value. When the output current is greater than the current limit value, it directly switches from constant voltage operating condition to constant current operating condition. When the output current is less than the current limit value, it directly switches from constant current operating condition to constant voltage operating condition.

[0006] The drawback of this solution is that it is affected by output current fluctuations during current limiting, and the DC-DC converter frequently switches between constant voltage and constant current modes, resulting in large fluctuations in output voltage and output current. While increasing delays and hysteresis can reduce the switching frequency, this introduces problems such as slow response, large fluctuations, and difficulty in exiting constant current mode.

[0007] like Figure 1The diagram shows a schematic of a current limiting device module for a prior art DC-DC converter. In the prior art, under constant voltage conditions, the constant voltage control module 1 performs voltage closed-loop control to ensure that the DC-DC converter outputs a constant voltage; under constant current conditions, the constant current control module 2 performs current closed-loop control to ensure that the DC-DC converter outputs a constant current. Both the constant voltage control module 1 and the constant current control module 2 output control quantities to the mode selection module 3. The mode selection module 3 selects the actual operating condition according to the judgment conditions and outputs the corresponding operating condition control quantity to the drive module 4.

[0008] The existing technology's mode selection module 3 selects the operating condition by comparing the output control quantities of the constant voltage control module 1 and the constant current control module 2. Based on the actual circuit topology, it outputs the maximum or minimum value to the drive module 4 to achieve switching between constant voltage and constant current operating conditions.

[0009] The disadvantage of this scheme is that the constant voltage control module 1 and the constant current control module 2 usually achieve closed-loop control through PI or PID regulators. Due to the influence of the integral element I, the regulator in the module that has not yet output is in a saturated state. When the operating conditions are switched, it must first desaturate before it can switch. The switching time is long, and the output voltage and output current fluctuate greatly during this period, which can easily lead to overvoltage and overcurrent problems. Summary of the Invention

[0010] To address the issue of significant output current fluctuations during switching between constant voltage and constant current operating conditions, this invention provides a current limiting device for a DC-DC converter, comprising:

[0011] Used to sample the output of the DC-DC converter to obtain the output voltage u o and output current i o The sampling module;

[0012] Used to receive the output current i transmitted by the sampling module o Adjusting the virtual resistance r v When the output current i o Greater than the current limit value i lim When the virtual resistance r is increased v When the output current i o Less than the current limit value i lim When the virtual resistance r is reduced v A virtual resistance adjustment module that can be reduced to zero;

[0013] Used to receive the virtual resistance r transmitted by the virtual resistance adjustment module v , virtual resistor r v Connected in series with the actual load as an equivalent load, it receives the output voltage u transmitted by the sampling module. o and output current i o The virtual output voltage u ovThe virtual output voltage module;

[0014] Used to receive the virtual output voltage u transmitted by the virtual output voltage module. ov Control the DC-DC converter to make the virtual output voltage u ov Follows the output voltage setpoint u ref .

[0015] Furthermore: the sampling module includes a function for sampling when the output voltage u of the DC-DC converter... o and output current i o When the output voltage u contains high-frequency ripple components, it affects the output voltage u. o and output current i o The filtering module that performs filtering.

[0016] A current limiting method for a DC-DC converter includes the following steps:

[0017] The output voltage u of the DC-DC converter o and output current i o Perform sampling;

[0018] Based on the output current i o Adjusting the virtual resistance r v When the output current i o Greater than the current limit value i lim When the virtual resistance r is increased v When the output current i o Less than the current limit value i lim When, the virtual resistance r v Reduced to a minimum of zero;

[0019] virtual resistance r v Connected in series with the actual load as an equivalent load, the voltage across the equivalent load is the virtual output voltage u. ov ;

[0020] Based on the virtual output voltage u ov Control the DC-DC converter to make the virtual output voltage u ov Follows the output voltage setpoint u ref .

[0021] Furthermore: when the output voltage u o and output current i o When the output voltage u contains high-frequency ripple components, it affects the output voltage u. o and output current i o Perform filtering.

[0022] Furthermore, the virtual resistance regulator is a P regulator, a PI regulator, or a PID regulator.

[0023] Furthermore, the constant voltage control module employs a voltage regulator.

[0024] The present invention provides a current limiting device and current limiting method for a DC-DC converter. When in constant current mode, the device feedback channel includes the output voltage, which can respond quickly to voltage disturbances on the output side and cause small fluctuations in the output current. When switching between constant voltage mode and constant current mode, the constant voltage control module is always in working state, the switching time is short, the switching process is smooth, and the output voltage and output current fluctuations are small during the switching. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 A schematic diagram of a current limiting device module for a DC-DC converter in the prior art;

[0027] Figure 2 This is a schematic diagram of the DC-DC converter current limiting device module provided in Embodiment 1 of the present invention;

[0028] Figure 3 This is an optional implementation of the sampling module for the current limiting device of the DC-DC converter provided in Embodiment 1 of the invention.

[0029] Figure 4 This is one implementation of the virtual resistance adjustment module, virtual output voltage module, and constant voltage control module of the DC-DC converter current limiting device provided in Embodiment 1 of the present invention;

[0030] Figure 5 The equivalent circuit diagram of the DC-DC converter provided in Embodiment 1 of the present invention;

[0031] Figure 6 This is a flowchart of the DC-DC converter current limiting method provided in Embodiment 2 of the present invention. Detailed Implementation

[0032] It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of the present invention can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and embodiments.

[0033] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0034] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0035] Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps described in these embodiments do not limit the scope of the invention. It should also be understood that, for ease of description, the dimensions of the various parts shown in the drawings are not drawn to actual scale. Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters in the following drawings denote similar items; therefore, once an item is defined in one drawing, it need not be further discussed in subsequent drawings.

[0036] In the description of this invention, it should be understood that the orientation or positional relationship indicated by directional terms such as "front, back, up, down, left, right", "horizontal, vertical, horizontal" and "top, bottom" is generally based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing this invention and simplifying the description. Unless otherwise stated, these directional terms 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, and therefore should not be construed as a limitation on the scope of protection of this invention. The directional terms "inner" and "outer" refer to the inner and outer contours relative to the outline of each component itself.

[0037] For ease of description, spatial relative terms such as "above," "over," "on the upper surface of," "above," etc., are used herein to describe the spatial positional relationship of a device or feature as shown in the figures to other devices or features. It should be understood that spatial relative terms are intended to encompass different orientations in use or operation besides the orientation of the device as described in the figures. For example, if the device in the figures is inverted, a device described as "above" or "above" other devices or structures would subsequently be positioned as "below" or "under" other devices or structures. Thus, the exemplary term "above" can include both "above" and "below." The device may also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatial relative descriptions used herein will be interpreted accordingly.

[0038] Furthermore, it should be noted that the use of terms such as "first" and "second" to define components is merely for the purpose of distinguishing the corresponding components. Unless otherwise stated, the above terms have no special meaning and therefore should not be construed as limiting the scope of protection of this invention.

[0039] Figure 2 This is a schematic diagram of the DC-DC converter current limiting device module provided in this embodiment, as shown below. Figure 2 As shown, the DC-DC converter current limiting device includes a sampling module 110, a virtual resistance adjustment module 120, a virtual output voltage module 130, and a constant voltage control module 140.

[0040] The sampling module 110 is used to sample the output of the DC-DC converter to obtain the output voltage u. o and output current i o The input terminal of the sampling module 110 is connected to the main circuit of the DC-DC converter.

[0041] The virtual resistance adjustment module 120 is used to receive the output current i transmitted by the sampling module 110. o Adjusting the virtual resistance r v When the output current i o Greater than the current limit value i lim When the virtual resistance r is increased v When the output current i o Less than the current limit value i lim When the virtual resistance r is reduced v Reduced to a minimum of zero;

[0042] The virtual output voltage module 130 is used to receive the virtual resistance r transmitted by the virtual resistance adjustment module 120. v , virtual resistor r vConnected in series with the actual load as an equivalent load, the voltage across the equivalent load is the virtual output voltage u. ov That is, virtual resistance r v With output current i o The product of the sampling module 110 and the output voltage u o The sum of these is the virtual output voltage u. ov ;

[0043] The constant voltage control module 140 is used to receive the virtual output voltage u transmitted by the virtual output voltage module 130. ov Control the DC-DC converter to make the virtual output voltage u ov Follows the output voltage setpoint u ref Changes;

[0044] Figure 3 This is one optional implementation of the sampling module for the DC-DC converter current limiting device provided in this embodiment, such as... Figure 3 As shown, the sampling module 110 includes a filtering module 111, which, when the output voltage u... o and output current i o When the output voltage u contains high-frequency ripple components, the filter module 111 adjusts the output voltage u. o and output current i o Perform filtering to remove the output voltage u o and output current i o The high-frequency ripple component in the image.

[0045] Figure 4 This is a control block diagram illustrating one implementation of the virtual resistance adjustment module, virtual output voltage module, and constant voltage control module of the DC-DC converter current limiting device provided in this embodiment. Figure 4 As shown, the virtual resistance adjustment module 120 uses the filter module 111, and the virtual resistance adjustment module 120 adjusts the output current i o With the current limiting value i lim The difference is used as the input of the virtual resistance regulator;

[0046] Virtual resistance regulators can employ P, PI, PID, and other regulators.

[0047] With virtual resistance r v The output of the virtual resistance adjustment module 120 is set, and the lower limit of the output limit of the virtual resistance adjustment module 120 is set to zero.

[0048] The virtual output voltage module 130 will use the virtual resistance r v With output current i o After multiplying, then add the output voltage u. o The virtual output voltage u is obtained by adding them together. ov .

[0049] The constant voltage control module 140 implements closed-loop voltage control, setting the output voltage setpoint u. ref With virtual output voltage u ov The voltage error signal is obtained by subtraction, and the constant voltage control module 140 adopts a voltage regulator;

[0050] When the voltage error signal is input to the voltage regulator, the voltage regulator output gradually increases when the voltage error signal is greater than zero, and gradually decreases when the voltage error signal is less than zero.

[0051] Figure 5 This is the equivalent circuit diagram of the DC-DC converter provided in this embodiment. Figure 5 The DC-DC converter is equivalent to an ideal voltage source u s and internal resistance r s R is the actual load, and r is the virtual resistance. v As a virtual load connected in series with the actual load, a virtual output voltage u is formed. ov This is the voltage across the equivalent load.

[0052] Combination Figure 4 The virtual resistance adjustment module 120, virtual output voltage module 130, and constant voltage control module 140 shown illustrate the working principle of the current limiting device for the DC-DC converter in this embodiment. Figure 5 We can obtain:

[0053] u ov =u o +r v i o =(R+r v )i o

[0054] The constant voltage control module 140 uses voltage closed-loop control to control the virtual output voltage u. ov Follows the output voltage setpoint u ref In steady state, u ov =u ref It can be seen that by adjusting the virtual resistance r v The output current i can be changed o When the output current i o Greater than the current limit value i lim At that time, the virtual resistance regulator adjusts the virtual resistance r. v Increase, causing the output current i o Decrease; when the output current i o Less than the current limit value i lim At that time, the virtual resistance regulator adjusts the virtual resistance i. o Decrease, causing the output current i o Increase. Therefore, gradually decrease the output current i.o With the current limiting value i lim The error between them will eventually stabilize the output current at the current limit value i. lim To ensure effective control, the constant voltage control module 140 should adjust faster than the virtual resistance adjustment module 120.

[0055] Example 2

[0056] Figure 6 This is a flowchart of the DC-DC converter current limiting method provided in this embodiment, as follows: Figure 6 As shown, this rate limiting method includes the following steps:

[0057] S601: Samples the output voltage u of the DC-DC converter o and output current i o .

[0058] Specifically, the output voltage u is sampled through a sampling circuit connected to the main circuit of the DC-DC converter. o and output current i o .

[0059] S602: Based on the output current i o Adjusting the virtual resistance r v When the output current i o Greater than the current limit value i lim When the virtual resistance r is increased v When the output current i o Less than the current limit value i lim When the virtual resistance r is reduced v The minimum value is reduced to zero.

[0060] Specifically, the virtual resistance r can be adjusted using P, PI, PID, and other regulators as virtual resistance regulators. v The virtual resistor regulator outputs current i o and the current limiting value i lim The time difference is used as the input quantity, with a virtual resistance r. v This is the output quantity, and the lower limit of the output limit is set to zero.

[0061] S603: Obtain virtual output voltage u ov , virtual resistor r v Connected in series with the actual load as an equivalent load, the voltage across the equivalent load is the virtual output voltage u. ov .

[0062] Specifically, the virtual resistance r v With output current i o After multiplying, then add the output voltage u. o The virtual output voltage u is obtained by adding them together. ov .

[0063] S604: Controls the DC-DC converter, making the virtual output voltage u ov Follows the output voltage setpoint u ref .

[0064] Specifically, the virtual output voltage u can be controlled through voltage closed-loop control using regulators such as PI and PID controllers. ov Follows the output voltage setpoint u ref .

[0065] Optionally, when the output voltage u o and output current i o When high-frequency ripple components are present, the output voltage u is affected. o and output current i o Perform filtering.

[0066] The DC-DC converter current limiting device and method provided in this embodiment of the invention, when operating under constant current conditions, include the output voltage in the system feedback channel, resulting in a fast response to output voltage disturbances and minimal output current fluctuations. Furthermore, when switching between constant voltage and constant current conditions, the constant voltage control module remains operational, with short switching times, a smooth switching process, and minimal fluctuations in output voltage and current during switching.

[0067] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A current limiting device for a DC-DC converter, characterized in that: include: Used to sample the output of the DC-DC converter to obtain the output voltage. u o and output current i o The sampling module; Used to receive the output current transmitted by the sampling module i o Adjusting the virtual resistance r v When the output current i o Greater than the rate limit i lim At that time, increase the virtual resistance r v When the output current i o Less than the current limit i lim When, reduce virtual resistance r v A virtual resistance adjustment module that can be reduced to zero; Used to receive the virtual resistance transmitted by the virtual resistance adjustment module. r v virtual resistance r v Connected in series with the actual load as an equivalent load, it receives the output voltage transmitted by the sampling module. u o and output current i o The virtual output voltage u ov The virtual output voltage module; Used to receive the virtual output voltage transmitted by the virtual output voltage module. u ov Control the DC-DC converter to make the virtual output voltage u ov Follow the output voltage setpoint u reff The constant pressure control module.

2. The DC-DC converter current limiting device according to claim 1, characterized in that: The sampling module includes a function for sampling when the output voltage of the DC-DC converter... u o and output current i o When the output voltage contains high-frequency ripple components, it affects the output voltage. u o and output current i o The filtering module that performs filtering.

3. The DC-DC converter current limiting device according to claim 1, characterized in that: The virtual resistance adjustment module uses a P regulator, PI regulator, or PID regulator.

4. The DC-DC converter current limiting device according to claim 1, characterized in that: The constant voltage control module uses a voltage regulator.

5. A current limiting method for a DC-DC converter, characterized in that: Includes the following steps: Output voltage of DC-DC converter u o and output current i o Perform sampling; Based on output current i o Adjusting the virtual resistance r v When the output current i o Greater than the rate limit i lim At that time, increase the virtual resistance r v When the output current i o Less than the current limit i lim At that time, the virtual resistance r v Reduced to a minimum of zero; virtual resistance r v Connected in series with the actual load as an equivalent load, the voltage across the equivalent load is the virtual output voltage. u ov ; Based on virtual output voltage u ov Control the DC-DC converter to make the virtual output voltage u ov Follow the output voltage setpoint u ref .

6. The current limiting method for a DC-DC converter according to claim 5, characterized in that: When the output voltage u o and output current i o When the output voltage contains high-frequency ripple components, it affects the output voltage. u o and output current i o Perform filtering.

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