On-board charger, DC-DC converter and control method

Abstract

An on-board charger, a DCDC converter and a control method are provided, including: an input end of a high-voltage DC converter circuit is connected to an output end of a power factor correction circuit, an input end of a low-voltage DC converter circuit is connected to an output end of the high-voltage DC converter circuit or an output end of the power factor correction circuit, and an output end of the low-voltage DC converter circuit is connected to a low-voltage battery, the low-voltage DC converter circuit includes a main power tube and a controllable switch tube, the controller uses a current loop soft start to generate a driving signal for the main power tube during startup of the low-voltage DC converter circuit, gradually increasing the current through the inductor, the current predetermined value of the current loop depends on the current reference value output from the voltage loop and the output result of the soft start function, after the startup of the low-voltage DC converter circuit is completed, the voltage loop and the current loop are cascaded to generate a driving signal for the main power tube, and the voltage loop outputs a current reference value to the input end of the current loop, thereby reducing the shock current to the main power tube during startup of the LVDC.

Description

[Technical Field]

[0001] This application claims priority to a Chinese patent application bearing application number 202111575228.X and entitled "On-board charger, DC-DC converter, and control method" filed with the State Intellectual Property Office of the People's Republic of China on December 21, 2021, the entire contents of which are incorporated herein by reference.

[0002] The present application relates to the field of power electronics technology, and more particularly to an on-board charger, a DC-DC converter, and a control method. [Background technology]

[0003] As the global energy shortage continues, new energy vehicles are currently attracting increasing attention. The power battery packs of new energy vehicles generally need to be charged, and many new energy vehicles include an on-board charger (OBC). The OBC generally includes a power factor correction (PFC), a high-voltage direct current (DC) converter (HVDC), and a low-voltage direct current (LVDC). The PFC is connected to the AC power source, the HVDC is connected to the high-voltage battery, and the LVDC is connected to the low-voltage battery. The LVDC can extract power from the DC bus and supply it to the low-voltage battery and low-voltage electrical appliances, such as air conditioners, pumps, and headlights.

[0004] LVDCs usually operate under low voltage and high current conditions. For example, if the LVDC uses a buck circuit, the flywheel diode in the buck circuit is usually replaced with a MOS tube, so that the current flows through the MOS tube during flywheel operation, resulting in the on-state and reverse recovery loss of the original flywheel diode. Generally, the driving signals of the main power tube and the MOS tube in the buck circuit can adopt a complementary method.

[0005] However, currently, when LVDC is started, the main power tube receives a relatively large shock current, which poses a serious risk to the safety of the main power tube. Summary of the Invention [Problem to be solved by the invention]

[0006] To solve the above problems, the present application provides an on-board charger, a DC-DC converter, and a control method that can reduce the shock current to the main power pipe when the LVDC is started and protect the safety of the main power pipe. [Means for solving the problem]

[0007] To achieve the above objectives, the embodiments of the present application provide the following technical solutions. An embodiment of the present application provides an on-board charger, comprising: a power factor correction circuit, a high-voltage DC conversion circuit, a low-voltage DC conversion circuit, and a controller, wherein an input terminal of the high-voltage DC conversion circuit is connected to an output terminal of the power factor correction circuit; an input terminal of the low-voltage DC conversion circuit is connected to an output terminal of the high-voltage DC conversion circuit or an output terminal of the power factor correction circuit; an output terminal of the low-voltage DC conversion circuit is used to connect to a low-voltage battery and a low-voltage load; and the low-voltage DC conversion circuit comprises a main power tube and a controllable switch tube; The controller generates a drive signal for the main power tube using a current loop soft start, so as to gradually increase the current flowing through the inductor connected in series with the main power tube when the low-voltage DC converter circuit is started up, and the predetermined current value of the current loop depends on the current reference value output from the voltage loop and the output result of the soft start function. After the start-up of the low-voltage DC converter circuit is completed, the controller generates a drive signal for the main power tube by cascading the voltage loop and the current loop, and the voltage loop is used to output the current reference value to the input end of the current loop.

[0008] Preferably, the input of the current loop includes the output current of the low-voltage DC converter circuit and the output result of the small value acquisition unit, the current loop is used to compare the output current of the low-voltage DC converter circuit with the output result of the small value acquisition unit, and generate the driving signal of the main power tube according to the comparison result, and the small value acquisition unit is used to take the smaller value of the output result of the voltage loop and the output result of the soft start function; When the error between the output current of the low-voltage DC converter circuit and the output result of the small value acquisition unit is within a preset range, the activation of the low-voltage DC converter circuit is completed.

[0009] Preferably, the input of the voltage loop includes a preset voltage reference value and the output voltage of the low-voltage DC converter circuit, and the voltage loop is used to generate the current reference value based on the preset voltage reference value and the output voltage of the low-voltage DC converter circuit, and output it to the input end of the current loop.

[0010] Preferably, the soft start function is a soft start ramp function, and the output result of the soft start ramp function is a current that gradually increases over time to a preset current value.

[0011] Preferably, the controller is further used to control the controllable switch tube to be turned off when the low-voltage DC converter circuit is started up, and after the low-voltage DC converter circuit is started up, the controller controls the main power tube and the controllable switch tube to perform complementary switching operations.

[0012] Preferably, the controller further controls the controllable switch tube to be turned on when the main power tube is off during the startup of the low-voltage DC converter circuit, and the duty ratio of the controllable switch tube is smaller than the duty ratio of the main power tube; and after the startup of the low-voltage DC converter circuit is completed, the controller controls the main power tube and the controllable switch tube to perform complementary switching operations.

[0013] The present application provides a step-down DC-DC converter, comprising: a controller; a main power tube; and a controllable switch tube; and further comprising an inductor connected in series with the main power tube; and an output end of the step-down DC-DC converter is used to connect to a battery; The controller generates a driving signal for the main power tube using a current loop soft start to gradually increase the current flowing through the inductor when the step-down DC-DC converter is started up, and the predetermined current value of the current loop depends on the current reference value output from the voltage loop and the output result of the soft start function. After the start-up of the step-down DC-DC converter is completed, the controller generates a driving signal for the main power tube by cascading the voltage loop and the current loop, and the voltage loop is used to output the current reference value to the input terminal of the current loop.

[0014] Preferably, the input of the current loop includes the output current of the low-voltage DC converter circuit and the output result of the small value acquisition unit, the current loop is used to compare the output current of the low-voltage DC converter circuit with the output result of the small value acquisition unit, and generate a driving signal for the main power tube according to the comparison result, and the small value acquisition unit is used to take the smaller value of the output result of the voltage loop and the output result of the soft start function.

[0015] Preferably, the input of the voltage loop includes a preset voltage reference value and the output voltage of the low-voltage DC converter circuit, and the voltage loop is used to generate the current reference value based on the preset voltage reference value and the output voltage of the low-voltage DC converter circuit and output it to the input end of the current loop.

[0016] Preferably, the soft start function is a soft start ramp function, and the output result of the soft start ramp function is a current that gradually increases over time to a preset current value.

[0017] Preferably, the controller further controls the controllable switch tube to be turned on when the main power tube is off during the startup of the low-voltage DC converter circuit, and the duty ratio of the controllable switch tube is smaller than the duty ratio of the main power tube; and after the startup of the low-voltage DC converter circuit is completed, the controller controls the main power tube and the controllable switch tube to perform complementary switching operations.

[0018] The present application provides a control method for an on-board charger, the on-board charger including a power factor correction circuit, a high-voltage DC conversion circuit, a low-voltage DC conversion circuit, and a controller, the input terminal of the high-voltage DC conversion circuit is connected to the output terminal of the power factor correction circuit, the input terminal of the low-voltage DC conversion circuit is connected to the output terminal of the high-voltage DC conversion circuit, and the output terminal of the low-voltage DC conversion circuit is used to connect to a low-voltage battery, the low-voltage DC conversion circuit includes a main power tube and a controllable switch tube, The method comprises: generating a drive signal for the main power tube using a current loop soft start to gradually increase a current flowing through an inductor connected in series with the main power tube when the low-voltage DC converter circuit is started, wherein the predetermined current value of the current loop depends on a current reference value output from a voltage loop and an output result of a soft start function; After the start-up of the low-voltage DC converter circuit is completed, a voltage loop and a current loop are cascaded to generate a driving signal for the main power tube, and the voltage loop is used to output a current reference value to the input end of the current loop.

[0019] Preferably, the step of generating a drive signal for the main power tube using a current loop soft start when starting the low-voltage DC conversion circuit specifically includes: The input of the current loop includes the output current of the low-voltage DC converter circuit and the output result of the small value acquisition unit, the current loop compares the output current of the low-voltage DC converter circuit with the output result of the small value acquisition unit, and generates a driving signal for the main power tube based on the comparison result, and the small value acquisition unit takes the smaller value of the output result of the voltage loop and the output result of the soft start function.

[0020] Preferably, the step of generating the driving signal of the main power tube in a cascaded form of the voltage loop and the current loop specifically includes: The input of the voltage loop includes a preset voltage reference value and the output voltage of the low-voltage DC converter circuit, and the voltage loop generates the current reference value based on the preset voltage reference value and the output voltage of the low-voltage DC converter circuit and outputs it to the input end of the current loop.

[0021] Preferably, the method further includes the steps of: when the low-voltage DC converter circuit is started, the controllable switch tube is turned on when the main power tube is off, and the duty ratio of the controllable switch tube is controlled to be smaller than the duty ratio of the main power tube; and after the low-voltage DC converter circuit is started, the main power tube and the controllable switch tube are controlled to perform complementary switching operations.

[0022] Preferably, the soft start function is a soft start ramp function, and the output result of the soft start ramp function is a current that gradually increases over time to a preset current value. [Effects of the Invention]

[0023] According to the above technical solution, the present application has the following beneficial effects: In the technical solution provided by this application, in order to reduce the current impact on the main power tube during the startup of the low-voltage DC converter circuit, the voltage loop is initially disabled and only the current loop is enabled. Because the voltage loop is disabled, a voltage soft-start control method is not adopted, but a current soft-start control method is adopted. The input parameters of the voltage loop are the output voltage and a preset voltage reference value. When the low-voltage DC converter circuit is started, the output voltage is relatively small, so the output result of the voltage loop is invalid, i.e., the voltage loop is disabled and only the current loop is enabled in the entire control loop. Because the current loop control includes a current soft-start, a soft current start method is adopted during the startup phase of the low-voltage DC converter circuit, and the current flowing through the main power tube is controlled to gradually increase, thereby minimizing the impact of the forward current on the main power tube. In order to more clearly explain the technical solutions in the embodiments of the present application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below. Obviously, the drawings in the following description are some embodiments of the present application. Those skilled in the art can derive other drawings from these drawings without creative efforts. [Brief explanation of the drawings]

[0024] [Figure 1] 1 is a schematic diagram of an on-board charger provided by an embodiment of the present application; [Figure 2] 1 is a schematic diagram of an LVDC in an on-board charger provided by an embodiment of the present application; [Figure 3] 1 is a schematic diagram of a dual-loop control in which a voltage loop and a current loop are cascaded, as provided by an embodiment of the present application. [Figure 4] Current soft start technical solution provided by the embodiment of the present application [Figure 5] An equivalent diagram when S1 is on and S2 is off provided by an embodiment of the present application. [Figure 6] An equivalent diagram when S1 is off and S2 is on provided by an embodiment of the present application. [Figure 7] Schematic diagram of a low-voltage DC conversion circuit in the prior art [Figure 8]1 is a flowchart of a control method for an on-board charger according to an embodiment of the present application; DETAILED DESCRIPTION OF THE INVENTION

[0025] In order to facilitate a better understanding of the technical solutions provided by the embodiments of the present application, before introducing the methods provided by the embodiments of the present application, application scenarios of the embodiments of the present application will be first introduced.

[0026] Example of an on-board charger Please refer to FIG. 1, which is a schematic diagram of an on-board charger provided by an embodiment of the present application.

[0027] The OBC provided by the embodiment of the present application includes three ports, namely, an AC end, a high voltage end, and a low voltage end, as shown in Figure 1. The OBC includes PFC, HVDC, and LVDC, where the input end of the PFC is used to connect to an AC power source, the input end of the HVDC is connected to the output end of the PFC, the output end of the HVDC is used to connect to a high voltage battery, the input end of the LVDC is connected to the output end of the HVDC, and the output end of the LVDC is used to connect to a low voltage battery.

[0028] In this embodiment, the LVDC is used as a step-down converter, taking a Buck circuit as an example. The Buck circuit includes a main power tube S1, an inductor, and a controllable switch tube S2. The first terminal of S1 is connected to the positive input terminal of the LVDC, the second terminal of S1 is connected to the positive output terminal of the LVDC via an inductor, the first terminal of S2 is connected to the second terminal of S1, and the second terminal of S2 is connected to the negative input terminal and negative output terminal of the LVDC. An output capacitor is connected in parallel to the output terminal of the LVDC. The controllable switch tube S2 can be a flywheel diode in a conventional Buck circuit. To reduce the power consumption of the diode, a controllable switch tube can be used instead, for example, a MOS tube, whose conduction loss and switching loss are both smaller than those of a diode.

[0029] In the prior art, to solve the problem of excessively large start-up current impact when LVDC power is turned on, a controllable switch is usually connected in series with the output end and cooperated with voltage soft start control, but connecting a controllable switch in series with the output end increases the hardware cost.

[0030] In this application, to solve the impact of forward current on S1 when the LVDC is started, a current soft start method is used for power-on and startup. Specifically, in this application, the voltage loop and the current loop are cascaded to generate the drive signal for S1, and the current reference value is generated by the output of the voltage loop. However, when the LVDC is started, the voltage loop does not function, and the soft start at the input end of the current loop functions. That is, the drive signal for S1 is realized by the current loop soft start control, that is, the current of S1 gradually increases, thereby reducing the impact current of S1.

[0031] In order to make the above objects, features and advantages of the present application clearer and more comprehensible, the following examples of the present application will be described in more detail in combination with drawings and specific embodiments.

[0032] Please refer to FIG. 2, which is a schematic diagram of the LVDC in the on-board charger provided by the embodiment of the present application.

[0033] It should be understood that the on-board charger architecture provided by the present application does not need to include a controllable switch at the output end of the LVDC of the on-board charger of the present application, i.e., the inductor L is directly connected to the positive output end of the LVDC, as shown in Fig. 1. Also, a controllable switch may be included at the output end of the LVDC of the on-board charger, for example, for safety reasons, a controllable switch may be added to the output end and kept on in a non-fault state, and it is not necessary to operate in accordance with the voltage loop and the current loop.

[0034] The technical solution provided by the present application will be explained in detail below in conjunction with FIGS.

[0035] The on-board charger provided in this embodiment includes a power factor correction circuit PFC, a high-voltage DC converter circuit HVDC, a low-voltage DC converter circuit LVDC, and a controller 100. The input terminal of the high-voltage DC converter circuit HVDC is connected to the output terminal of the power factor correction circuit PFC, the input terminal of the low-voltage DC converter circuit LVDC is connected to the output terminal of the high-voltage DC converter circuit HVDC, and the output terminal of the low-voltage DC converter circuit LVDC is used to connect to a low-voltage battery, and the low-voltage DC converter circuit LVDC includes a main power tube and a controllable switch tube.

[0036] When the low-voltage DC converter circuit is started, i.e., when the LVDC is powered on, the controller 100 generates a drive signal for the main power tube S1 using a current loop soft start to gradually increase the current flowing through the inductor L connected in series with the main power tube S1. The predetermined current value of the current loop depends on the current reference value output from the voltage loop and the output result of the soft start function. After the low-voltage DC converter circuit is started, the controller 100 generates a drive signal for the main power tube by cascading the voltage loop and the current loop. The voltage loop is used to output the current reference value to the input terminal of the current loop.

[0037] The start-up of the low-voltage DC converter circuit is completed when the difference between the output current of the low-voltage DC converter circuit and the output result of the small value acquisition unit is within a predetermined range, for example, within plus or minus 15%, and the difference between the two can be positive or negative. Here, the predetermined range is set to prevent repeated hiccups in the circuit.

[0038] In particular, reference can be made to FIG. 3, which is a schematic diagram of dual-loop control in which the voltage loop and the current loop are cascaded, as provided by an embodiment of the present application.

[0039] That is, in the technical solution provided by the embodiments of the present application, to reduce the impact of forward current on S1 during LVDC startup, the voltage loop LV is initially disabled and only the current loop LI is enabled. Because the voltage loop LV is disabled, a voltage soft start control method is not adopted, but a current soft start control method is adopted. The input parameters of the voltage loop LV are the output voltage Vout and the preset voltage reference value Vref. During LVDC startup, Vout is relatively small, so the output result of the voltage loop LV is invalid, i.e., the voltage loop LV is disabled, and only the current loop LI is enabled in the entire control loop. Because the control of the current loop LI includes a current soft start, a soft current start method is used during the LVDC startup phase to gradually increase the current through S1, thereby minimizing the impact of forward current on S1.

[0040] The current soft start technical solution provided by the embodiment of the present application will be introduced in more detail below in conjunction with FIG.

[0041] Please refer to FIG. 4, which is a specific schematic diagram of the dual loop control provided by the embodiment of the present application.

[0042] The input of the current loop includes the output current Iout of the low-voltage DC converter circuit and the output result of the small value acquisition unit min. The current loop LI is used to compare the output current Iout of the low-voltage DC converter circuit with the output result of the small value acquisition unit min and generate a drive signal for the main power tube based on the comparison result. The small value acquisition unit min is used to take the smaller value of the output result of the voltage loop LV and the output result of the current soft start function. That is, during the LVDC startup, since the value of Vout is small, when the voltage loop LV compares Vref and Vout, the output result is relatively large and min takes the smaller value of the input parameter. Therefore, LV does not function for min and min only outputs the output result of the current soft start function. Therefore, in the dual-loop control loop, only the current loop LI functions during the LVDC startup phase.

[0043] The present embodiment does not limit the specific implementation of the soft-start function, but rather only requires that the current through S1 gradually increase. For example, in one possible implementation, the soft-start function is a soft-start ramp function, whose output is a current that gradually increases over time to a preset current value. Because the startup phase does not continue continuously, the startup phase time can be determined according to the LVDC startup time and the slope of the soft-start ramp function. A preset current value can be set according to the slope and startup phase time. When the current reaches the preset current value, the soft-start function terminates its operation, i.e., the current soft-start process is completed. During the LVDC startup phase, only the current loop functions, and the current loop also has the function of current soft-start. This ensures that the forward current through S1 gradually increases from a low to a high level to avoid excessive shock to S1, thereby protecting the safety of S1. The soft-start function can also be expressed as a preset map or table, and control can be performed according to the data in the map or table. For example, it may be another variable mathematical function, for example, adjusted depending on the magnitude of Vout.

[0044] The input of the voltage loop LV includes a preset voltage reference value Vref and an output voltage Vout of the low-voltage DC converter circuit, and the voltage loop LV is used to generate a current reference value based on the preset voltage reference value Vref and the output voltage Vout of the low-voltage DC converter circuit, and output it to the input terminal of the current loop LI.

[0045] After the start-up of LVDC is completed, Vout gradually increases, in this case the output result of voltage loop LV is valid, which in turn affects the output result of min, and the output result of min is the current reference value affected by voltage loop LV, in this case the current loop LI compares the current reference value output from voltage loop LV with Iout, and generates the drive signal of S1 according to the comparison result.

[0046] In addition, the current loop parameters are variable, and two different sets of parameters can be used before and after the LVDC is started. Changing some characteristic parameters for different processes is important for improving response speed, etc. In the charging pile provided by this application, the voltage reference value Vref of the voltage loop is directly used as the desired output voltage value of the LVDC, and no voltage soft start processing is performed. The current reference value of the current loop is jointly determined by the current soft start ramp function and the output of the voltage loop, and min is the smaller value of the two compared and used as the current reference value of the current loop.

[0047] With this control method, when the output of the LVDC is connected to a battery-like load, the inductor current gradually increases in the forward direction, and the output voltage gradually increases from the battery's open-circuit voltage. When the preset current or desired output voltage is reached, the circuit operation enters steady state and the startup process is complete. When the output of the LVDC is connected to a resistive load, the inductor current gradually increases in the forward direction, and the LVDC output voltage gradually increases from zero. When the preset current or desired output voltage is reached, the LVDC enters steady state operation. When the output of the LVDC is connected to a mixed load consisting of a battery and a resistive load connected in parallel, the LVDC output voltage gradually increases from the battery's open-circuit voltage. When the preset current or desired output voltage is reached, the LVDC enters steady state operation, and the output current is automatically distributed in proportion to the battery's equivalent internal resistance and the resistive load.

[0048] Immediately after the LVDC is started, the duty cycle of the S1 drive signal generated by the current soft start is very small, and the forward current of the inductor is very small. If the S2 drive signal is complementary to the S1 drive signal, the duty cycle of the S1 drive signal is large. The negative result of the relatively large duty cycle of the S2 drive signal is that due to the battery connected to the output of the LVDC, a relatively large reverse current is generated during the start-up phase due to the long-term on-state of S2, i.e., the current in the inductor flows from the battery to the input of the LVDC.

[0049] It should be understood that the drive signals of S1 and S2 are complementary, or the switching states of S1 and S2 are complementary, meaning that when one of the two switches is on, the other is off, and they are not on at the same time. For safety reasons, there is also a certain dead time between S1 and S2.

[0050] In order to enable those skilled in the art to better understand the technical solution provided by the present application, the following will introduce the disadvantages of the start-up phase of LVDC when the duty of S2 is relatively large, with reference to the accompanying drawings.

[0051] In the application scenario of an LVDC in an on-board charger, a battery is connected to the output terminal of the LVDC, so if S2 is turned on for a long time during the startup phase, a relatively large reverse current will flow through the inductor.

[0052] Please refer to Figure 5, which is an equivalent diagram when S1 is on and S2 is off. Please refer to Figure 6, which is an equivalent diagram when S1 is off and S2 is on.

[0053] As can be seen from FIG. 5, when S1 is on and S2 is off, the input power supply Vin is connected to the circuit, and as can be seen from FIG. 6, when S1 is off and S2 is on, the input power supply Vin is not connected to the circuit.

[0054] In the prior art, in order to prevent S2 from receiving a reverse shock current from the output battery at startup, as shown in FIG. 7, a third switch S3 is connected between the inductor and the output.

[0055] Referring to FIG. 7, this is a schematic diagram of a low voltage DC converter circuit.

[0056] In Figure 7, a third switch S3 is connected to the output terminal of the low-voltage DC converter circuit, and a voltage soft-start method is used to avoid reverse current in the inductor. Specifically, the third switch S3 is turned on after the voltage on the output capacitor Vc reaches the battery voltage Vbat, thereby reducing the current shock caused by the voltage difference between the output capacitor Vc and the battery. However, the technical solution in Figure 7 increases hardware costs and reduces the charging efficiency of the entire charging pile.

[0057] In order to avoid increasing the hardware cost, i.e., not increasing the third switch S3, and to avoid the reverse shock current during startup, the technical solution provided by this application includes the following two:

[0058] Type 1: The controller is further used to control the controllable switch tube S2 to be turned off when the low-voltage DC converter circuit is started up, and to control the main power tube and the controllable switch tube S2 to perform complementary switching operations after the low-voltage DC converter circuit is started up.

[0059] In order to prevent the reverse impulse current generated by the battery from impacting S1 and S2 when the low-voltage DC converter circuit is started up, S2 is always controlled to be turned off during the start-up phase, and only after the start-up phase is finished can S2 be normally controlled to perform switching operation.

[0060] Type 2: The controller is further used to control the controllable switch tube to be turned on when the main power tube is off during the startup of the low-voltage DC conversion circuit, and the duty ratio of the controllable switch tube is smaller than the duty ratio of the main power tube; and after the startup of the low-voltage DC conversion circuit is completed, control the main power tube and the controllable switch tube to perform complementary switching operations.

[0061] In the second method, the controllable switch tube is controlled to operate at a small duty ratio to avoid a large reverse shock current, that is, the ON time of S2 is controlled to be short, but S2 must be turned on when S1 is off.

[0062] In order to avoid the generation of a large reverse inductor current, the duty ratio of S2 is limited during the startup phase of the low-voltage DC converter circuit to limit the reverse inductor current. Specifically, during the startup phase of the low-voltage DC converter circuit, the drive signal of S1 is generated using the dual-loop control introduced in the above embodiment, and the duty ratio of S2 is controlled to gradually increase from a small value based on the duty ratio of the drive signal of S1, while ensuring that S2 and S1 are not turned on simultaneously. Only after the current soft start is completed is the control of the duty ratio of the drive signal of S2 stopped, thereby controlling the complementary operation of S2 and S1.

[0063] In the technical solution provided by this application, during the startup phase of the low-voltage DC converter circuit, S1 and S2 do not perform complementary switching operations. On the premise of maintaining the principle of controlling S2 to turn on when S1 turns off, the driving signal controlling S2 is not complementary to the driving signal of S1, so as to reduce the duty ratio of S2 and shorten the on-time of S2, thereby avoiding the generation of a large reverse inductor current.

[0064] The present application does not limit the specific implementation of S2 during the LVDC startup phase, but for example, S2 can be turned off when it is detected that the LVDC output current is in the reverse direction, or the duty ratio of S2 can be limited during the current soft start phase, for example, by gradually increasing the duty ratio of S2. It is only necessary to ensure that S2 does not continuously exhibit a large duty ratio so as to prevent a large reverse current from flowing through the inductor during the LVDC startup phase.

[0065] In the above embodiments, an on-board charger including a low-voltage DC conversion circuit is introduced. However, it should be understood that the low-voltage DC conversion circuit is a step-down DC-DC converter. The technical solutions provided by the embodiments of the present application are applicable not only to on-board chargers but also to step-down DC-DC converters that connect a battery to the output terminal. Therefore, based on the on-board charger provided by the above embodiments, the DC-DC converter provided by the present application will now be introduced.

[0066] Example of a DC-DC converter The step-down DC-DC converter provided by the present application can continue to refer to Figure 2, and will only be briefly introduced below. For detailed operating principles, please refer to the introduction of the on-board charger above, and will not be repeated here.

[0067] The step-down DC-DC converter provided by this embodiment includes a controller, a main power tube, and a controllable switch tube, and further includes an inductor connected in series with the main power tube, and the output end of the step-down DC-DC converter is used to connect to a battery; When the DC-DC converter is started, the controller uses the current loop soft start to generate a driving signal for the main power tube, so that the current flowing through the inductor is gradually increased. The predetermined current value of the current loop depends on the current reference value output from the voltage loop and the output result of the soft start function. After the DC-DC converter is started, the controller generates a driving signal for the main power tube by cascading the voltage loop and the current loop, and the voltage loop is used to output the current reference value to the input terminal of the current loop.

[0068] The current loop soft start may employ a soft start function, for example, the soft start function is a soft start ramp function, the output of which is a current that gradually increases over time to a preset current value.

[0069] The input of the current loop includes the output current of the low-voltage DC converter circuit and the output result of the small value acquisition unit, the current loop is used to compare the output current of the low-voltage DC converter circuit and the output result of the small value acquisition unit, and generate the driving signal of the main power tube according to the comparison result, and the small value acquisition unit is used to take the smaller value of the output result of the voltage loop and the output result of the soft start function.

[0070] The input of the voltage loop includes a preset voltage reference value and the output voltage of the low-voltage DC converter circuit, and the voltage loop generates a current reference value based on the preset voltage reference value and the output voltage of the low-voltage DC converter circuit and outputs it to the input terminal of the current loop.

[0071] The controller further controls the controllable switch tube to be turned on when the main power tube is off during the startup of the low-voltage DC conversion circuit, and the duty ratio of the controllable switch tube is smaller than the duty ratio of the main power tube; and after the startup of the low-voltage DC conversion circuit is completed, controls the main power tube and the controllable switch tube to perform complementary switching operations.

[0072] Based on the on-board charger provided by the above embodiments, the present application further provides a control method for an on-board charger, which will be described in detail below in conjunction with the accompanying drawings.

[0073] Method Example The present embodiment provides a control method for an on-board charger, in which the on-board charger includes a power factor correction circuit, a high-voltage DC conversion circuit, a low-voltage DC conversion circuit, and a controller, the input terminal of the high-voltage DC conversion circuit is connected to the output terminal of the power factor correction circuit, the input terminal of the low-voltage DC conversion circuit is connected to the output terminal of the high-voltage DC conversion circuit, and the output terminal of the low-voltage DC conversion circuit is used to connect to a low-voltage battery, and the low-voltage DC conversion circuit includes a main power tube and a controllable switch tube. Referring to FIG. 8, this figure is a flowchart of the control method for the on-board charger provided by the present application.

[0074] The method includes the following steps: Step S801: When the low-voltage DC converter circuit is started, a current loop soft start is used to generate a driving signal for the main power tube, so as to gradually increase the current flowing through the inductor connected in series with the main power tube, and the predetermined current value of the current loop depends on the current reference value output from the voltage loop and the output result of the soft start function. Here, the current loop soft start may employ a soft start function, for example, the soft start function is a soft start ramp function, and the output result of the soft start ramp function is a current that gradually increases over time to a preset current value.

[0075] Step S802: After the low-voltage DC conversion circuit is started, the voltage loop and the current loop are cascaded to generate the driving signal of the main power tube, and the voltage loop is used to output the current reference value to the input end of the current loop.

[0076] In the control method provided in the embodiments of the present application, the technical solution provided by the present application reduces the impact of forward current on the main power tube during startup of the LVDC converter circuit by first disabling the voltage loop and only enabling the current loop. Because the voltage loop is disabled, a voltage soft-start control method is not adopted, but a current soft-start control method is adopted. The input parameters of the voltage loop are the output voltage and a preset voltage reference value. During startup of the LVDC converter circuit, the output voltage is relatively small, so the output of the voltage loop is invalid, i.e., the voltage loop is disabled, and only the current loop functions as the overall control loop. Because the current loop control includes a current soft-start, a soft current start method is used during the startup phase of the LVDC converter circuit to gradually increase the current flowing through the main power tube, thereby minimizing the impact of forward current on the main power tube.

[0077] The step of generating a driving signal for the main power tube using a current loop soft start when the low-voltage DC conversion circuit is started specifically includes: The input of the current loop includes the output current of the low-voltage DC conversion circuit and the output result of the small value acquisition unit, the current loop compares the output current of the low-voltage DC conversion circuit with the output result of the small value acquisition unit, and generates a driving signal for the main power tube based on the comparison result, and the small value acquisition unit takes the smaller value of the output result of the voltage loop and the output result of the soft start function.

[0078] The step of generating the driving signal of the main power tube in a cascaded form of the voltage loop and the current loop specifically includes: The input of the voltage loop includes a preset voltage reference value and the output voltage of the low-voltage DC conversion circuit, and the voltage loop generates a current reference value based on the preset voltage reference value and the output voltage of the low-voltage DC conversion circuit and outputs it to the input end of the current loop.

[0079] The control method provided by the embodiment of the present application further includes the steps of: when the low-voltage DC converter circuit is started, the controllable switch tube is turned on when the main power tube is turned off, and the duty ratio of the controllable switch tube is controlled to be smaller than the duty ratio of the main power tube; and after the low-voltage DC converter circuit is started, the main power tube and the controllable switch tube are controlled to perform complementary switching operations.

[0080] In order to avoid the generation of large reverse inductor current, the duty ratio of the controllable switch tube is limited in the start-up phase of the low-voltage DC converter circuit to limit the reverse inductor current.Specifically, in the start-up phase of the low-voltage DC converter circuit, the driving signal of the main power tube is generated by the double-loop control introduced in the above embodiment, and according to the duty ratio of the driving signal of the main power tube, the controllable switch tube controls the duty ratio of the controllable switch tube from small to gradually increase, while ensuring that the controllable switch tube and the main power tube are not turned on at the same time.Only after the current soft start is completed, the control of the duty ratio of the driving signal of the controllable switch tube is stopped, and the controllable switch tube can be controlled to work complementarily with the main power tube.

[0081] From the above description of the embodiments, it can be clearly understood by those skilled in the art that all or part of the steps in the methods of the above embodiments can be realized with the help of software as well as a required general-purpose hardware platform. Based on this understanding, the technical solution of the present application, or the part that contributes to the prior art, can be expressed in the form of a software product, which can be stored in a storage medium such as a ROM / RAM, a magnetic disk, or an optical disk, and includes several instructions for causing a computer device (such as a personal computer, a server, or a network communication device such as a media gateway) to execute the method described in each embodiment or a certain part of the embodiments of the present application.

[0082] In addition, each embodiment in this specification is described step by step, and the main points of each embodiment are the differences from other embodiments, and the same or similar parts between the embodiments can be referred to each other. The method disclosed in the embodiment corresponds to the system disclosed in the embodiment, so the explanation is relatively simple, and the relevant parts can be referred to the explanation of the system part.

[0083] It should be noted that, as used herein, the terms "comprise," "have," and any variations thereof are intended to encompass a non-exclusive inclusion, such that a process, method, product, or device comprising a set of elements includes not only those elements but also other elements not expressly listed or inherent to the process, method, product, or device. Absent further limitations, an element defined by the phrase "comprises one of" does not exclude the presence of other identical elements in the process, method, product, or device that includes that element. Given the above description of the disclosed embodiments, it will be apparent to those skilled in the art that various modifications to these embodiments of the present application can be implemented, and the general principles defined herein may be embodied in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application is not intended to be limited to the embodiments set forth herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. An on-board charger, The power supply includes a power factor correction circuit, a high-voltage DC converter circuit, a low-voltage DC converter circuit, and a controller, wherein the input terminal of the high-voltage DC converter circuit is connected to the output terminal of the power factor correction circuit, the input terminal of the low-voltage DC converter circuit is connected to the output terminal of the high-voltage DC converter circuit or the output terminal of the power factor correction circuit, and the output terminal of the low-voltage DC converter circuit is used to connect to a low-voltage battery and a low-voltage load, and the low-voltage DC converter circuit includes a main power tube and a controllable switch tube; The controller generates a driving signal for the main power tube using a current loop soft start, so as to gradually increase the current flowing through the inductor connected in series with the main power tube when the low-voltage DC converter circuit is started up, and the predetermined current value of the current loop is the smaller value of the current reference value output from the voltage loop and the output result of the soft start function. After the start-up of the low-voltage DC converter circuit is completed, the controller generates a driving signal for the main power tube by cascading the voltage loop and the current loop, and the voltage loop is used to output the current reference value to the input end of the current loop. An on-board charger characterized by:

2. The input of the current loop includes the output current of the low-voltage DC converter circuit and the output result of the small value acquisition unit, the current loop is used to compare the output current of the low-voltage DC converter circuit with the output result of the small value acquisition unit, and generate a driving signal for the main power tube according to the comparison result, and the small value acquisition unit is used to take the smaller value of the output result of the voltage loop and the output result of the soft start function; When the error between the output current of the low-voltage DC converter circuit and the output result of the small value acquisition unit is within a predetermined range, the startup of the low-voltage DC converter circuit is completed.

2. The charger according to claim 1.

3. The input of the voltage loop includes a preset voltage reference value and an output voltage of the low-voltage DC converter circuit, and the voltage loop is used to generate the current reference value based on the preset voltage reference value and the output voltage of the low-voltage DC converter circuit, and output the current reference value to the input terminal of the current loop.

3. The charger according to claim 2.

4. The soft start function is a soft start ramp function, and the output result of the soft start ramp function is a current that gradually increases over time to a preset current value.

4. The charger according to claim 3.

5. The controller is further used to control the controllable switch tube to be turned off when the low-voltage DC converter circuit is started up, and after the low-voltage DC converter circuit is started up, the controller controls the main power tube and the controllable switch tube to perform complementary switching operations. The charger according to any one of claims 1 to 4.

6. The controller further controls the controllable switch tube to be turned on when the main power tube is off during the startup of the low-voltage DC converter circuit, and the duty ratio of the controllable switch tube is smaller than the duty ratio of the main power tube; and after the startup of the low-voltage DC converter circuit is completed, controls the main power tube and the controllable switch tube to perform complementary switching operations. The charger according to any one of claims 1 to 4.

7. A step-down DC-DC converter, The step-down DC-DC converter includes a controller, a main power tube, and a controllable switch tube, and further includes an inductor connected in series with the main power tube, and the output end of the step-down DC-DC converter is used to connect to a battery; The controller is used to generate a driving signal for the main power tube using a current loop soft start, so as to gradually increase the current flowing through the inductor when the step-down DC-DC converter is started up, and the predetermined current value of the current loop is the smaller value of the current reference value output from the voltage loop and the output result of the soft start function. After the start-up of the step-down DC-DC converter is completed, the driving signal for the main power tube is generated in a cascade form, with the voltage loop and the current loop being used to output the current reference value to the input terminal of the current loop. A converter characterized by:

8. The input of the current loop includes the output current of the step-down DC-DC converter and the output result of the small value acquisition unit, and the current loop is used to compare the output current of the step-down DC-DC converter with the output result of the small value acquisition unit and generate a driving signal for the main power tube according to the comparison result, and the small value acquisition unit is used to take the smaller value of the output result of the voltage loop and the output result of the soft start function.

8. The converter according to claim 7.

9. The input of the voltage loop includes a preset voltage reference value and an output voltage of the step-down DC-DC converter, and the voltage loop is used to generate the current reference value based on the preset voltage reference value and the output voltage of the step-down DC-DC converter, and output the current reference value to the input terminal of the current loop.

9. The converter of claim 8.

10. The soft start function is a soft start ramp function, and the output result of the soft start ramp function is a current that gradually increases over time to a preset current value.

9. The converter of claim 8.

11. The controller further controls the controllable switch tube to be turned on when the main power tube is off during startup of the step-down DC-DC converter, and the duty ratio of the controllable switch tube is smaller than the duty ratio of the main power tube; and after the startup of the step-down DC-DC converter is completed, controls the main power tube and the controllable switch tube to perform complementary switching operations. Converter according to any one of claims 7 to 10.

12. A method for controlling an on-board charger, comprising: The on-board charger includes a power factor correction circuit, a high-voltage DC conversion circuit, a low-voltage DC conversion circuit, and a controller, the input terminal of the high-voltage DC conversion circuit is connected to the output terminal of the power factor correction circuit, the input terminal of the low-voltage DC conversion circuit is connected to the output terminal of the high-voltage DC conversion circuit, and the output terminal of the low-voltage DC conversion circuit is used to connect to a low-voltage battery, and the low-voltage DC conversion circuit includes a main power tube and a controllable switch tube; The method comprises: When starting up the low-voltage DC converter circuit, a drive signal for the main power tube is generated using a current loop soft start, so that the current flowing through the inductor connected in series with the main power tube is gradually increased, and the predetermined current value of the current loop is the smaller value of the reference value of the current output from the voltage loop and the output result of a soft start function; After the start-up of the low-voltage DC converter circuit is completed, a voltage loop and a current loop are cascaded to generate a driving signal for the main power tube, and the voltage loop is used to output a current reference value to the input end of the current loop; A method comprising:

13. generating a drive signal for the main power tube using a current loop soft start when the low-voltage DC converter circuit is started, The input of the current loop includes the output current of the low-voltage DC converter circuit and the output result of the small value acquisition unit, the current loop is used to compare the output current of the low-voltage DC converter circuit and the output result of the small value acquisition unit, and generate a driving signal for the main power tube according to the comparison result, and the small value acquisition unit takes the smaller value of the output result of the voltage loop and the output result of the soft start function; 13. The method of claim 12, comprising:

14. generating a drive signal for the main power tube with the voltage loop and the current loop cascaded, an input of the voltage loop includes a preset voltage reference value and an output voltage of the low-voltage DC converter circuit, and the voltage loop generates the current reference value based on the preset voltage reference value and the output voltage of the low-voltage DC converter circuit and outputs the current reference value to the input terminal of the current loop; 14. The method of claim 13, comprising:

15. When the low-voltage DC converter circuit is started, the controllable switch tube is turned on when the main power tube is off, and the duty ratio of the controllable switch tube is controlled to be smaller than the duty ratio of the main power tube; after the start-up of the low-voltage DC converter circuit is completed, the main power tube and the controllable switch tube are controlled to perform complementary switching operations; The method according to any one of claims 12 to 14, further comprising:

16. The soft start function is a soft start ramp function, and the output result of the soft start ramp function is a current that gradually increases over time to a preset current value.

15. The method according to any one of claims 12 to 14.

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