A switch capacitor-flyback composite converter for vehicle lighting and a control method thereof

Abstract

This application provides a switched-capacitor-flyback composite converter for vehicle lighting and its control method, belonging to the field of power electronic energy conversion technology. The converter includes: an input filter capacitor, a switched-capacitor unit, a flyback converter unit, and an RCD snubber circuit unit. The switched-capacitor unit is used to regulate the input voltage applied to the flyback converter unit, the flyback converter unit is used to achieve electrical isolation and transfer energy to the external load, and the RCD snubber circuit unit is used to handle the residual energy generated by the leakage inductance of the transformer. The advantages of this application are that the use of cascaded switched-capacitor units for pre-voltage adjustment can improve voltage gain, and the number of switched-capacitor sub-units can be flexibly adjusted according to the rated voltage of the vehicle lighting load. The logic of coarse adjustment of the number of switched-capacitor sub-units and fine adjustment of the duty cycle of the main switch is simple. The switched-capacitor unit has no magnetic components and a compact structure, which can reduce the size of the devices and effectively improve the system power density.

Description

Technical Field

[0001] This application belongs to the field of power electronic energy conversion technology, specifically relating to a switched capacitor-flyback composite converter for vehicle lighting and its control method. Background Technology

[0002] The power converter of an automotive lighting system is a key component of the automotive electronic system, responsible for converting the low-voltage DC input of the vehicle battery into a stable high-voltage output required by the lighting load. Because vehicle batteries experience wide voltage fluctuations under conditions such as engine start-stop and sudden load changes, this converter must simultaneously meet the stringent requirements of the automotive environment for high efficiency, high power density, high reliability, and low electromagnetic interference.

[0003] Existing technologies typically employ various high-voltage gain topologies to achieve low-voltage to high-voltage conversion, with Boost converters being the most widely used. They operate based on the fundamental principles of inductor energy storage and diode freewheeling, and achieve flexible adjustment of the output voltage by regulating the duty cycle of the power switching transistors. In the low to medium voltage gain range, they offer advantages such as simple structure, convenient control, and low cost.

[0004] However, to achieve a significant voltage boost, the Boost converter must operate at an extremely high duty cycle. This results in excessively long on-time of the switching devices, leading to a cumulative increase in switching and conduction losses, severely reducing the overall system efficiency. Furthermore, high-gain operation requires large-capacity inductors to store energy, significantly increasing the size and weight of magnetic components and directly limiting the improvement of system power density. Moreover, this topology lacks inherent electrical isolation characteristics, failing to meet the electrical safety protection requirements of automotive systems. Summary of the Invention

[0005] This application addresses the problems of existing Boost converters requiring extremely high duty cycles to achieve high voltage gain, which limits power density improvement, and the lack of natural electrical isolation characteristics, thus failing to meet the electrical safety protection requirements of automotive systems. It provides a switched capacitor-flyback composite converter for automotive lighting and its control method, which can simultaneously meet the electrical safety protection requirements of automotive systems and effectively improve system power density without requiring high duty cycle operation.

[0006] Firstly, to solve the above problems, the technical solution adopted in this application is a switched capacitor-flyback composite converter for vehicle lighting, comprising: an input filter capacitor, a switched capacitor unit, a flyback converter unit, and an RCD absorption circuit unit.

[0007] The input filter capacitor is connected in parallel with the external input power supply. The switched capacitor unit is connected between the external input power supply and the flyback converter unit. The switched capacitor unit is used to regulate the input voltage applied to the flyback converter unit. The flyback converter unit is used to achieve electrical isolation and transfer energy to the external load.

[0008] The switched capacitor unit is composed of the first to the mth switched capacitor subunits cascaded together, where m is a positive integer greater than or equal to 1; i is any positive integer from 1 to m, and the ith switched capacitor subunit includes the ith flying capacitor, the ith positive charging switch, the ith discharging switch, and the ith negative charging switch.

[0009] When i=1, the first terminal of the first flying capacitor is connected to the first terminal of the first positive charging switch, the second terminal of the first positive charging switch is connected to the positive terminal of the external input power supply, the second terminal of the first flying capacitor is connected to the first terminal of the first negative charging switch, the second terminal of the first negative charging switch is connected to the negative terminal of the external input power supply, the second terminal of the first flying capacitor is connected to the first terminal of the first discharging switch, and the second terminal of the first discharging switch is connected to the positive terminal of the external input power supply.

[0010] When i≥2, the first terminal of the i-th flying capacitor is connected to the first terminal of the i-th positive charging switch, the second terminal of the i-th positive charging switch is connected to the first terminal of the (i-1)-th flying capacitor, the second terminal of the i-th flying capacitor is connected to the first terminal of the i-th negative charging switch, the second terminal of the i-th negative charging switch is connected to the negative terminal of the external input power supply, the second terminal of the i-th flying capacitor is connected to the first terminal of the i-th discharging switch, and the second terminal of the i-th discharging switch is connected to the first terminal of the (i-1)-th flying capacitor.

[0011] The flyback converter unit includes a transformer, a main switch, a rectifier diode, and an output filter capacitor. The first end of the primary winding of the transformer is connected to the first end of the m-th flying capacitor of the m-th switched capacitor subunit. The second end of the primary winding of the transformer is connected to the first end of the main switch. The second end of the main switch is connected to the negative terminal of the external input power supply. The first end of the secondary winding of the transformer is connected to the anode of the rectifier diode. The cathode of the rectifier diode is connected to the anode of the external load. The second end of the secondary winding of the transformer is connected to the cathode of the external load. The output filter capacitor is connected in parallel with the external load.

[0012] The RCD snubber circuit unit includes a snubber diode, a snubber capacitor, and a snubber resistor. The anode of the snubber diode is connected to the second terminal of the primary winding of the transformer, and the cathode of the snubber diode is connected to the second terminal of the snubber capacitor and the second terminal of the snubber resistor, respectively. The first terminal of the snubber capacitor and the first terminal of the snubber resistor are both connected to the first terminal of the primary winding of the transformer. The RCD snubber circuit unit is used to absorb the energy released by the leakage inductance of the transformer and suppress voltage spikes when the main switch is turned off.

[0013] In this technical solution, a cascaded switched capacitor unit is used to pre-regulate the voltage of the flyback converter unit, raising the input voltage of the flyback converter unit so that the flyback converter unit can meet the output voltage requirements without a high duty cycle, reducing the working stress of the power devices. Simultaneously, electrical isolation is achieved through the flyback converter unit, adapting to the safety protection requirements of automotive systems. The switched capacitor unit has no magnetic components and a compact structure, reducing the size of the flyback converter unit and effectively improving the overall power density of the system. The RCD snubber circuit unit, through effective processing of leakage inductance energy, not only reduces the voltage stress of the main switching transistor but also reduces high-frequency oscillations caused by parasitic parameters, improving the reliability of the switching devices and reducing high-frequency oscillations caused by leakage inductance.

[0014] Secondly, this application also provides a control method for a switched capacitor-flyback composite converter for vehicle lighting, comprising the following steps:

[0015] Step 1: Calculate the quotient obtained by dividing the rated voltage of the external load by the transformer turns ratio, and calculate the ratio of the quotient to the external input power supply. If the ratio is less than 2, all switched capacitor sub-units are in an unoperated state. If the ratio is greater than or equal to 2, round down the ratio and subtract 1 to obtain the number of switched capacitor sub-units in operation. The number of switched capacitor sub-units in operation shall not exceed the maximum number of switched capacitor sub-units.

[0016] Step 2: Using the drive signal of the main switching transistor as a reference, control the charging and discharging of the switched capacitor subunit that is put into operation.

[0017] Step 3: Acquire the actual voltage of the external load, compare the rated voltage of the external load with the actual voltage of the external load in real time to obtain the error signal, and adjust the duty cycle of the main switch transistor according to the error signal.

[0018] Step 4: When the rated voltage of the external load changes, repeat steps 1 to 3.

[0019] Furthermore, in step one, after determining the number of switched capacitor sub-units in operation, all switched capacitor sub-units not in operation are in a conduction bypass state except for those in operation.

[0020] Furthermore, in step two, j is any sequence number of the switched capacitor sub-unit that is put into operation. The j-th positive charging switch, j-th discharging switch, and j-th negative charging switch of the switched capacitor sub-unit that is put into operation all have the same driving cycle as the main switching transistor. When the main switching transistor starts its conduction phase, the conduction phase of the j-th discharging switch starts synchronously, and the cutoff phases of the j-th positive charging switch and the j-th negative charging switch start synchronously. The duty cycle of the j-th positive charging switch, the j-th discharging switch, and the j-th negative charging switch is fixed at 0.5.

[0021] Furthermore, in step three, when the actual voltage of the external load is higher than the rated voltage, the duty cycle of the main switch is reduced; when the actual voltage of the external load is lower than the rated voltage, the duty cycle of the main switch is increased. This adjustment method can quickly correct the actual voltage of the external load, making the actual voltage of the external load approach the rated voltage, thus meeting the stable operating requirements of the external load.

[0022] Furthermore, in step four, when it is necessary to increase the number of switched capacitor sub-units put into operation, the newly put-in switched capacitor sub-units are pre-charged. Pre-charging can suppress the inrush current and voltage fluctuations at the moment the switched capacitor sub-units are put into operation, avoid damage to power devices, and improve the reliability of the system's gear switching process.

[0023] As can be seen from the above technical solutions, this application has the following advantages:

[0024] 1. Voltage gain and flexible expansion: The cascaded switched capacitor unit pre-adjustment effectively improves the voltage gain, and the number of switched capacitor sub-units can be flexibly adjusted according to the rated voltage of the external load to adapt to different vehicle lighting load requirements.

[0025] 2. Reduced control complexity: The control logic, which coarsely adjusts the number of switched capacitor sub-units and finely adjusts the duty cycle of the main switch, ensures timing synchronization and clear adjustment rules, eliminating the need for complex control algorithms and reducing control difficulty.

[0026] 3. Increased power density: The switched capacitor unit has no magnetic components and a compact structure. At the same time, the flyback converter unit does not require high duty cycle operation, which can reduce the size of the devices and thus improve the overall power density of the system.

[0027] Other features and advantages of this application will be set forth in the following description and will be apparent in part from the description or may be learned by practicing the application. The objectives and other advantages of this application are realized and obtained through the structures particularly pointed out in the description, claims and drawings.

[0028] To make the above-mentioned objectives, features and advantages of this application more apparent and understandable, preferred embodiments are described below in detail with reference to the accompanying drawings. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in the specific embodiments of this application or the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0030] Figure 1 This is a schematic diagram of the topology of a specific embodiment of this application.

[0031] Figure 2 This is a schematic diagram of the control algorithm structure for a specific implementation of this application.

[0032] Figure 3 This is a timing diagram illustrating the control logic for the normal operation of the flying capacitor in a specific embodiment of this application.

[0033] Figure 4 This is a timing diagram of the control logic during soft-start of the flying capacitor in a specific embodiment of this application.

[0034] Figure 5 This is a schematic diagram of the operating mode when the duty cycle of the main switch is less than or equal to 0.5 in a specific embodiment of this application.

[0035] Figure 6 This is a schematic diagram of the operating mode when the duty cycle of the main switch is greater than 0.5 in a specific embodiment of this application. Detailed Implementation

[0036] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0037] Example 1: A switched capacitor-flyback composite converter for vehicle lighting, such as... Figure 1 As shown, it includes: input filter capacitors Switched capacitor unit, flyback converter unit, RCD snubber circuit unit.

[0038] Input filter capacitor With external input power The switched capacitor units are connected in parallel to the external input power supply. Between the flyback converter and the flyback unit, a switched capacitor unit is used to regulate the input voltage applied to the flyback converter, which in turn provides electrical isolation and transfers energy to the external load. .

[0039] The switched capacitor unit is composed of cascaded switched capacitor subunits from the first to the mth, where m is a positive integer greater than or equal to 1; i is any positive integer from 1 to m, and the i-th switched capacitor subunit includes the i-th flying capacitor. i-th positive terminal charging switch i-th discharge switch The i-th negative terminal charging switch .

[0040] When i=1, the first flying capacitor The first terminal and the first positive terminal charging switch The first end is connected, the first positive charging switch The second terminal is connected to the external input power supply. The positive terminal is connected, and the first flying capacitor is connected. The second terminal is connected to the first negative terminal charging switch. The first end is connected, the first negative terminal charging switch The second terminal is connected to the external input power supply. The negative terminal is connected, and the first flying capacitor is connected. The second end is connected to the first discharge switch The first end is connected to the first discharge switch. The second terminal is connected to the external input power supply. The positive terminals are connected.

[0041] When i ≥ 2, the i-th flying capacitor The first terminal and the i-th positive terminal charging switch The first end is connected, and the i-th positive terminal is the charging switch. The second terminal and the (i-1)th flying capacitor The first terminal is connected, and the i-th flying capacitor is connected. The second terminal is connected to the i-th negative terminal charging switch The first terminal is connected, and the i-th negative terminal is the charging switch. The second terminal is connected to the external input power supply. The negative terminal is connected, and the i-th flying capacitor is connected. The second terminal is connected to the i-th discharge switch The first end is connected, and the i-th discharge switch is connected. The second terminal and the (i-1)th flying capacitor Connect the first end.

[0042] The flyback converter unit includes a transformer and a main switch transistor. rectifier diodes Output filter capacitor The first terminal of the transformer primary winding and the m-th flying capacitor of the m-th switched capacitor subunit. The first end is connected, and the second end of the transformer primary winding is connected to the main switch tube. The first end is connected to the main switch transistor. The second terminal is connected to the external input power supply. The negative terminal is connected to the rectifier diode, and the first terminal of the transformer secondary winding is connected to the rectifier diode. The anode of the rectifier diode is connected to the cathode. Cathode and external load The anode of the transformer is connected to the ground, and the second end of the secondary winding of the transformer is connected to the external load. The cathode is connected, and the output filter capacitor is connected. With external load in parallel.

[0043] The RCD absorption circuit unit includes an absorption diode. Absorption capacitor and absorption resistance Absorption diode The anode is connected to the second terminal of the primary winding of the transformer, and the absorption diode is used. The cathodes are respectively connected to absorption capacitors. The second end and the absorption resistor The second terminal; absorption capacitor First end and absorption resistor The first terminal is connected to the first terminal of the primary winding of the transformer. The RCD snubber circuit unit is used in the main switching transistor. When cut off, it absorbs the energy released by the transformer leakage inductance and suppresses voltage spikes.

[0044] Example 2: Based on the switched capacitor-flyback hybrid converter for vehicle lighting provided in Example 1, this example further provides a control method for the switched capacitor-flyback hybrid converter for vehicle lighting, such as... Figure 2 As shown, it includes the following steps:

[0045] Step 1: Calculate the external load Rated voltage Divide by transformer turns ratio The obtained quotient, and the quotient is compared with the external input power supply. If the ratio is less than 2, the switched capacitor subunit is in an unoperated state. If the ratio is greater than or equal to 2, the ratio is rounded down and subtracted by 1 to obtain the number of switched capacitor subunits in operation, k. The number of switched capacitor subunits in operation, k, does not exceed the maximum number of switched capacitor subunits.

[0046] Once the number k of switched capacitor subunits to be put into operation is determined, the k switched capacitor subunits to be put into operation are controlled by the main switching transistor of the flyback converter unit. Under control, all other non-operational switched capacitor sub-units are in a bypass state. q represents any sequence number of a non-operational switched capacitor sub-unit. At this time, the positive terminal charging switch of the q-th non-operational switched capacitor sub-unit... All are on, the qth discharge switch With the qth negative terminal charging switch All deadlines have passed.

[0047] Step two, using the main switch transistor The driving signal is used as a reference to control the charging and discharging of the switched capacitor sub-unit that is put into operation.

[0048] In this embodiment, the control system of this solution is implemented using a DSP controller, wherein the sampling circuit and the driving circuit are implemented in hardware, and the control algorithm is implemented in software.

[0049] j represents any sequence number of the switched capacitor sub-unit that is put into operation, and the j-th positive terminal charging switch of the switched capacitor sub-unit that is put into operation. The j-th discharge switch The j-th negative terminal charging switch All are related to the main switching transistor The drive cycles are the same, when the main switching transistor When turned on, the j-th discharge switch Synchronous conduction, j-th positive terminal charging switch The j-th negative terminal charging switch Synchronization cutoff; j-th positive terminal charging switch Discharge switch j The j-th negative terminal charging switch The duty cycle is fixed at 0.5, and the j-th positive terminal charging switch... With the j-th negative terminal charging switch With the same phase, the j-th positive terminal charging switch With the j-th discharge switch Phase complementarity.

[0050] In the initial state, the main switching transistor is controlled by the PI controller. The initial duty cycle is set to 0.5, and the PI controller outputs a control signal to the PWM generator; the PWM generator generates a reference drive signal for the main switch, and outputs this drive signal to the main switch. On the other hand, the reference drive signal is provided to the drive signal generator; the drive signal generator outputs the corresponding drive signal to the switched capacitor subunit that is put into operation based on the reference drive signal.

[0051] When the main switch transistor At the start of the conduction phase, the j-th discharge switch The conduction phase begins synchronously, and the j-th positive terminal charging switch... The j-th negative terminal charging switch The cutoff phase begins synchronously; at this time, the j-th flying capacitor in the switched capacitor subunit that is put into operation... External input power supply The primary winding of the transformer forms a series conducting circuit, with the first terminal of the primary winding at a high potential and the second terminal at a low potential. According to the principle of transformer polarity, the secondary winding of the transformer induces a corresponding polarity, with the first terminal of the secondary winding at a low potential and the second terminal at a high potential. Because the first terminal of the secondary winding is connected to the rectifier diode... Anode connected, rectifier diode In reverse cutoff state, external load No current flows.

[0052] In the main switch transistor With the initial duty cycle at 0.5, when the main switch transistor... When entering the cutoff state, the j-th discharge switch Synchronization cutoff, j-th positive terminal charging switch The j-th negative terminal charging switch Synchronous conduction; at this time, the j-th flying capacitor in the switched capacitor subunit that is put into operation... With external input power They are connected in parallel, with an external input power supply. For the j-th flying capacitor Charging begins. Simultaneously, the current in the transformer's primary winding decreases. According to Lenz's law, the polarity of the induced voltage in the primary winding reverses, with the first terminal of the primary winding at a low potential and the second terminal at a high potential. Based on the principle of like terminals in transformers, a corresponding polarity is induced in the secondary winding, with the first terminal of the secondary winding at a high potential and the second terminal at a low potential. The first terminal of the secondary winding is connected to the rectifier diode... Anode connected, rectifier diode Forward conduction, external load There is an electric current flowing.

[0053] Step 3, collect external load data actual voltage external load Rated voltage With external load actual voltage The system performs real-time comparisons to obtain an error signal, which is then output to the PI controller. The PI controller adjusts the main switching transistor based on the error signal. The duty cycle is set, and the corresponding control signal is output to the PWM generator; the PWM generator generates the reference drive signal for the main switch, and outputs the drive signal to the main switch. On the other hand, the reference drive signal is provided to the drive signal generator; the drive signal generator outputs the corresponding drive signal to the switched capacitor subunit that is put into operation based on the reference drive signal.

[0054] When external load actual voltage Higher than rated voltage At that time, reduce the main switching transistor The duty cycle when the external load actual voltage Below rated voltage At that time, increase the main switching transistor Duty cycle.

[0055] In this embodiment, the j-th positive electrode charging switch Discharge switch j The j-th negative terminal charging switch The states correspond to different operating modes, when the main switch transistor duty cycle At that time, the working mode is as follows Figure 5 As shown, the magnitude and direction of the voltage across the magnetizing inductor of the transformer primary winding differ in each mode. Based on the inductance characteristics, the magnetizing inductor current and the magnetizing inductor voltage satisfy the following relationship:

[0056] (1)

[0057] in, , These are the magnetizing inductor voltage and the magnetizing inductor current, respectively. The magnetizing inductance value is determined by the magnetizing inductance voltage, which in turn determines the rate of change of the magnetizing inductance current. Under different operating modes, the magnetizing current exhibits different trends. Within one switching cycle, according to the volt-second balance principle, when the volt-second product of the magnetizing inductor voltage during the conduction and turn-off phases is equal, the average current remains constant, i.e., satisfying:

[0058] (2)

[0059] in, , These are the main switching transistors. Transformer primary winding inductance voltage and main switch transistor during conduction Inductor voltage at cutoff Main switch transistor duty cycle, Main switch transistor The drive cycle, i.e., the control cycle, is the period when the j-th flying capacitor in the switched capacitor subunit is put into operation. With external input power When energy is supplied and transferred to the primary winding of a transformer in series, the magnetizing inductor voltage is:

[0060] (3)

[0061] in, For external input power, For the first flying capacitor The voltage values ​​at both ends, For external load The actual voltage, The transformer turns ratio This refers to the number of switched capacitor subunits put into operation. In this embodiment, the external input power supply... The voltage is 12V, and the external load is... The rated operating voltage is 48V, therefore the system requires a target voltage gain of approximately 4 times. This topology introduces cascaded switched capacitor units, utilizing the voltage superposition effect of the flying capacitors to pre-raise the input voltage of the flyback converter unit, thereby sharing the boosting task and effectively reducing the impact on the transformer turns ratio. Requirements. Under the specific application conditions of this 12V to 48V boost converter, the transformer turns ratio... The value can be 2. Substituting formula (3) into formula (2), we can simplify to:

[0062] (4)

[0063] When the j-th flying capacitor in the switched capacitor subunit is put into operation The voltage is stabilized at the external input power supply. When it is nearby, it can be approximated as Therefore, the voltage gain at this time The expression is:

[0064] (5)

[0065] In summary, During the cycle, the main switching transistor The j-th discharge switch in the switched capacitor subunit is turned on and put into operation. On, the j-th positive terminal charging switch is activated. The j-th negative terminal charging switch As of now, the j-th flying capacitor in the switched capacitor subunit that has been put into operation... External input power supply The primary winding of the transformer forms a series conducting circuit, and the j-th flying capacitor... In the discharge state, corresponding Figure 3 Mode 2 in the middle.

[0066] exist During the cycle, the main switching transistor As of now, the j-th discharge switch within the switched capacitor subunit that has been put into operation... On, the j-th positive terminal charging switch is activated. The j-th negative terminal charging switch As of now, the j-th flying capacitor in the switched capacitor subunit that has been put into operation... External input power supply The series circuit formed by the primary winding of the transformer is cut off, and the j-th flying capacitor... Stop discharging.

[0067] exist During the cycle, the main switching transistor As of now, the j-th discharge switch within the switched capacitor subunit that has been put into operation... End of charge, j-th positive terminal charging switch The j-th negative terminal charging switch The j-th flying capacitor in the switched capacitor subunit is turned on and put into operation. With external input power Parallel connection, external input power supply Start with the j-th flying capacitor To charge, corresponding Figure 3 Mode 1 in the text.

[0068] When the main switch transistor duty cycle At that time, the working mode is as follows Figure 6 As shown, compared to At that time, external input power When the j-th flying capacitor is given While charging, the transformer's primary winding inductance is also excited. Therefore, within one switching cycle, according to the volt-second balance principle, we can obtain:

[0069] (6)

[0070] in, For the j-th positive terminal charging switch The j-th negative terminal charging switch The duty cycle is fixed at 0.5. Represents the j-th flying capacitor While charging, the primary winding of the transformer is powered by an external input power source. Excitation is performed using one times the voltage. Represents external input power supply The series-connected switched capacitor subunit excites the primary winding of the transformer. This represents the stage where the secondary winding of the transformer releases energy. Simplifying equation (6) yields the voltage gain. for:

[0071] (7)

[0072] Therefore, it can be seen that by introducing the switched capacitor unit and the main switching transistor... Duty cycle The adjustment can not only increase the equivalent input voltage of the transformer primary winding, but also change the external load. actual voltage The size is adjusted to achieve voltage gain enhancement and power adjustability, thus resulting in the final voltage gain. The expression is:

[0073] (8)

[0074] External load The expression for the output power is: ,and Therefore, substituting into formula (8), we can obtain the output power expression as follows:

[0075] (9)

[0076] According to formula (9), the output power is determined not only by the number of input switched capacitor subunits, but also by the number of main switching transistors. duty cycle Therefore, only when the two work together and are closely integrated in control can the stability of output voltage and power be guaranteed.

[0077] In summary, During the cycle, the main switching transistor The j-th discharge switch in the switched capacitor subunit is turned on and put into operation. On, the j-th positive terminal charging switch is activated. The j-th negative terminal charging switch As of now, the j-th flying capacitor in the switched capacitor subunit that has been put into operation... External input power supply The primary winding of the transformer forms a series conducting circuit, and the j-th flying capacitor... In the discharge state, corresponding Figure 4 Mode 2 in the middle.

[0078] exist During the cycle, the main switching transistor The j-th discharge switch in the switched capacitor subunit is turned on and put into operation. End of charge, j-th positive terminal charging switch The j-th negative terminal charging switch The j-th flying capacitor in the switched capacitor subunit is turned on and put into operation. With external input power Parallel connection, external input power supply Start with the j-th flying capacitor Charging is performed simultaneously with the external power input. Connected in parallel with the primary winding of the transformer, external input power supply Excitation of the primary winding of the transformer is performed at one voltage, corresponding to Figure 4 Mode 1 in the text.

[0079] exist During the cycle, the main switching transistor As of now, the j-th discharge switch within the switched capacitor subunit that has been put into operation... End of charge, j-th positive terminal charging switch The j-th negative terminal charging switch The j-th flying capacitor in the switched capacitor subunit is turned on and put into operation. With external input power Parallel connection, external input power supply Continue with the j-th flying capacitor Charging is performed simultaneously with the external power input. Stop energizing the primary winding of the transformer, corresponding to Figure 4 Mode 3 in the text.

[0080] Step 4, when external load Rated voltage When changes occur, steps one through three are repeated. In this embodiment, when switching external loads... When it is necessary to increase the number of switched capacitor sub-units, the newly added switched capacitor sub-units are pre-charged.

[0081] In this embodiment, pre-charging employs soft-start technology. The quantity decision unit calculates the quantity k by comparing the number of switched capacitor subunits in operation at the current time and the previous time. ,when When it is necessary to increase the number of switched capacitor sub-units put into operation, an Enable signal is first input through the soft-start controller to put the newly added switched capacitor sub-units into a soft-start state. During the soft-start phase, the newly added switched capacitor sub-units do not participate in voltage superposition; they only use their charging branches to establish the initial voltage of the flying capacitor. After the flying capacitor reaches the preset voltage after N preset cycles, it switches to the normal operating state to participate in voltage superposition. Through this soft-start process, the inrush current and voltage fluctuations at the moment the switched capacitor sub-units are put into operation can be effectively suppressed, avoiding damage to power devices and improving the reliability of the system's voltage switching process.

[0082] Specifically, such as Figure 4 As shown, in At a certain time, when the soft-start controller receives the Enable signal, it controls the qth negative terminal charging switch in the newly added switched capacitor subunit. The circuit begins to conduct, and the qth negative terminal charging switch... The duty cycle of the main switch transistor The drive cycle gradually increases until the duty cycle reaches 0.5, thus completing the pre-charging process and enabling the qth flying capacitor in the newly added switched capacitor sub-unit to... The voltage reaches the pre-charge target value. In this embodiment, the pre-charge process is performed on 20 main switching transistors. The driving cycle.

[0083] After pre-charging is complete, the newly added switched capacitor subunit switches to the normal operating state. In the normal operating state, the q-th positive terminal charging switch in the newly added switched capacitor subunit... With the qth negative terminal charging switch The driving phases are the same, and both are related to the q-th discharge switch. The driving phases are complementary, and the qth positive electrode charging switch is also active. qth negative terminal charging switch and the qth discharge switch The duty cycle is fixed at 0.5.

[0084] like Figure 3 As shown, when the main switch transistor At the start of the conduction phase, the q-th discharge switch... The conduction phase begins synchronously, and the q-th positive terminal charging switch... With the qth negative terminal charging switch The cutoff phase begins synchronously, with the main switch transistor... Its duty cycle is not fixed. In actual control, the main switch transistor... The duty cycle depends on the external load. actual voltage Perform closed-loop regulation.

[0085] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0086] Finally, it should be noted that the above-described embodiments are merely specific implementations of this application, used to illustrate the technical solutions of this application, and not to limit them. The scope of protection of this application is not limited thereto. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that any person skilled in the art can still modify or easily conceive of changes to the technical solutions described in the foregoing embodiments, or make equivalent substitutions for some of the technical features, within the scope of the technology disclosed in this application. Such modifications, changes, or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application, and should all be covered within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A switched capacitor-flyback composite converter for vehicle lighting, characterized in that, include: Input filter capacitor, switched capacitor unit, flyback converter unit, RCD snubber circuit unit; The input filter capacitor is connected in parallel with the external input power supply, and the switched capacitor unit is connected between the external input power supply and the flyback converter unit. The switched capacitor unit is used to adjust the input voltage applied to the flyback converter unit, and the flyback converter unit is used to achieve electrical isolation and transfer energy to the external load. The switched capacitor unit is composed of cascaded switched capacitor subunits from the first to the mth, where m is a positive integer greater than or equal to 1; i is any positive integer from 1 to m, and the ith switched capacitor subunit includes the ith flying capacitor, the ith positive charging switch, the ith discharging switch, and the ith negative charging switch. When i=1, the first terminal of the first flying capacitor is connected to the first terminal of the first positive charging switch, the second terminal of the first positive charging switch is connected to the positive terminal of the external input power supply, the second terminal of the first flying capacitor is connected to the first terminal of the first negative charging switch, the second terminal of the first negative charging switch is connected to the negative terminal of the external input power supply, the second terminal of the first flying capacitor is connected to the first terminal of the first discharging switch, and the second terminal of the first discharging switch is connected to the positive terminal of the external input power supply. When i≥2, the first terminal of the i-th flying capacitor is connected to the first terminal of the i-th positive charging switch, the second terminal of the i-th positive charging switch is connected to the first terminal of the (i-1)-th flying capacitor, the second terminal of the i-th flying capacitor is connected to the first terminal of the i-th negative charging switch, the second terminal of the i-th negative charging switch is connected to the negative terminal of the external input power supply, the second terminal of the i-th flying capacitor is connected to the first terminal of the i-th discharging switch, and the second terminal of the i-th discharging switch is connected to the first terminal of the (i-1)-th flying capacitor. The flyback converter unit includes a transformer, a main switch, a rectifier diode, and an output filter capacitor. The first end of the primary winding of the transformer is connected to the first end of the m-th flying capacitor of the m-th switched capacitor subunit. The second end of the primary winding of the transformer is connected to the first end of the main switch. The second end of the main switch is connected to the negative terminal of the external input power supply. The first end of the secondary winding of the transformer is connected to the anode of the rectifier diode. The cathode of the rectifier diode is connected to the anode of the external load. The second end of the secondary winding of the transformer is connected to the cathode of the external load. The output filter capacitor is connected in parallel with the external load. The RCD snubber circuit unit includes a snubber diode, a snubber capacitor, and a snubber resistor; the anode of the snubber diode is connected to the second terminal of the primary winding of the transformer, and the cathode of the snubber diode is connected to the second terminal of the snubber capacitor and the second terminal of the snubber resistor respectively; the first terminal of the snubber capacitor and the first terminal of the snubber resistor are both connected to the first terminal of the primary winding of the transformer. The RCD snubber circuit unit is used to absorb the energy released by the leakage inductance of the transformer and suppress voltage spikes when the main switch is turned off.

2. A control method for a switched capacitor-flyback composite converter for vehicle lighting as described in claim 1, characterized in that, Includes the following steps: Step 1: Calculate the quotient obtained by dividing the rated voltage of the external load by the transformer turns ratio, and calculate the ratio of the quotient to the external input power supply. If the ratio is less than 2, all switched capacitor sub-units are in an unoperated state. If the ratio is greater than or equal to 2, round the ratio down and subtract 1 to obtain the number of switched capacitor sub-units in operation. The number of switched capacitor sub-units in operation shall not exceed the maximum number of switched capacitor sub-units. Step 2: Using the drive signal of the main switch transistor as a reference, control the charging and discharging of the switched capacitor subunit that is put into operation. Step 3: Acquire the actual voltage of the external load, compare the rated voltage of the external load with the actual voltage of the external load in real time to obtain an error signal, and adjust the duty cycle of the main switch transistor according to the error signal; Step 4: When the rated voltage of the external load changes, repeat steps 1 to 3.

3. The control method for the switched capacitor-flyback composite converter for vehicle lighting according to claim 2, characterized in that, In step one, after determining the number of switched capacitor sub-units in operation, all switched capacitor sub-units not in operation are in a bypass state except for those in operation.

4. The control method for the switched capacitor-flyback composite converter for vehicle lighting according to claim 2, characterized in that, In step two, j is any sequence number of the switched capacitor subunit that is put into operation. The j-th positive charging switch, j-th discharging switch, and j-th negative charging switch of the switched capacitor subunit that is put into operation all have the same driving cycle as the main switching transistor. When the main switching transistor starts its conduction phase, the conduction phase of the j-th discharging switch starts synchronously, and the cutoff phases of the j-th positive charging switch and the j-th negative charging switch start synchronously. The duty cycle of the j-th positive charging switch, the j-th discharging switch, and the j-th negative charging switch is fixed at 0.

5.

5. The control method for the switched capacitor-flyback composite converter for vehicle lighting according to claim 2, characterized in that, In step three, when the actual voltage of the external load is higher than the rated voltage, the duty cycle of the main switch is reduced; when the actual voltage of the external load is lower than the rated voltage, the duty cycle of the main switch is increased.

6. The control method for the switched capacitor-flyback composite converter for vehicle lighting according to claim 2, characterized in that, In step four, when it is necessary to increase the number of switched capacitor sub-units put into operation, the newly added switched capacitor sub-units are pre-charged.

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