Switching power supply and vehicle

Abstract

The application relates to a switching power supply and a vehicle, and relates to the field of electronic circuits. The switching power supply comprises a power transformer, a positive temperature coefficient thermistor and a primary side flyback circuit. The primary side flyback circuit is connected to the primary winding of the power transformer. The positive temperature coefficient thermistor is connected in parallel to the two ends of the first secondary winding of the power transformer. The switching power supply utilizes the characteristic that the resistance of the positive temperature coefficient thermistor presents a positive temperature characteristic. In the starting stage of the switching power supply, because the ambient temperature is low, the resistance of the positive temperature coefficient thermistor is small, so that the load of the switching power supply is large in the starting moment, and the power supply can be started stably. With the working of the switching power supply, the ambient temperature rises, the resistance of the positive temperature coefficient thermistor increases, when the output voltage of the output end of the first secondary winding is unchanged, the power consumption of the positive temperature coefficient thermistor is reduced, the current on the power transformer and the output end loop is small, and the heat generation is small, so that the power transformer is prevented from being disabled due to overheating.

Description

Technical Field

[0001] This application relates to the field of power electronics technology, and in particular to a switching power supply and a vehicle. Background Technology

[0002] Electric vehicles can use switching power supplies to power their load devices. As the battery voltage of electric vehicles gradually increases, more low-voltage power is drawn from the high-voltage battery. This results in the power transformer of the switching power supply being designed with a high input voltage and a low output voltage, placing increasingly higher demands on the load. If the load is too large, the vehicle cannot start; if the load is too small, power consumption is high, and the power transformer is prone to failure.

[0003] In existing solutions, a dummy load resistor can be added to the secondary side of the switching transformer to ensure the switching power supply can start normally. However, the dummy load will cause the transformer winding current to increase, which will affect the power of other components in the power supply link. Especially when the transformer output voltage is large and the load is constant, the increased transformer winding current can easily cause the switching transformer to overheat and fail, thus resulting in low reliability. Utility Model Content

[0004] In view of the above problems, this application provides a switching power supply and a vehicle, which can optimize and ensure the normal startup of the switching power supply and avoid transformer failure due to overheating.

[0005] In a first aspect, this application provides a switching power supply, which includes a power transformer, a positive temperature coefficient thermistor, and a primary-side flyback circuit. The primary-side flyback circuit is connected to the primary winding of the power transformer; the positive temperature coefficient thermistor is connected in parallel across the first secondary winding of the power transformer.

[0006] This switching power supply utilizes the characteristic of a positive temperature coefficient (PTC) thermistor, where the resistance exhibits a positive temperature characteristic. During the startup phase, due to the low ambient temperature, the resistance of the PTC thermistor is small, resulting in a large load at startup and enabling stable power supply startup. This is based on the formula I = U / R, where U is the voltage across the first secondary winding, R is the equivalent impedance of all loads connected to the first secondary winding, and I is the startup current flowing through the first secondary winding. Adding a PTC thermistor increases the equivalent impedance R. When the voltage U across the first secondary winding remains constant, the startup current of the first secondary winding decreases, thus enabling stable power supply startup.

[0007] The existing solution uses a dummy load resistor with a fixed resistance. As the switching power supply operates, this dummy load resistor generates significant heat, increasing the load on the power transformer. In contrast, the solution in this application addresses this issue by increasing the resistance of the positive temperature coefficient thermistor as the ambient temperature rises with the operation of the switching power supply. When the output voltage at the output terminal of the first secondary winding remains constant, according to the power formula P = U... 2 As can be seen from the equation / R, the power consumption of the positive temperature coefficient thermistor is reduced, the current in the power transformer and output circuit is decreased, and the heat generation is reduced, thus preventing the power transformer from failing due to overheating. This implementation method only requires one positive temperature coefficient thermistor to achieve automatic adjustment, and also effectively reduces the hardware cost and complexity of the equipment.

[0008] In one possible implementation, the power transformer is a printed circuit board (PCB) transformer.

[0009] In one possible implementation, the switching power supply further includes a temperature sampling circuit, which is used to sample the temperature of the positive temperature coefficient thermistor when the power transformer is operating.

[0010] In one possible implementation, the positive temperature coefficient (PTC) thermistor is surface-mounted onto the PCB-based transformer. This implementation makes good use of the surface-mount characteristics of the PCB-based transformer, allowing direct placement of the PTC thermistor Rp. This facilitates the layout of the PTC thermistor Rp, optimizes the load regulation during power-on, monitors the transformer temperature, provides over-temperature protection, and ensures stable operation of the system using this switching power supply.

[0011] In one possible implementation, the PCB-type transformer includes multiple PCBs, each PCB having windings.

[0012] In one possible implementation, when the switching power supply is operating, the PCB with the highest operating temperature among the multilayer PCBs is the first PCB; the positive temperature coefficient thermistor is attached to the first PCB. That is, the positive temperature coefficient thermistor is attached near the coil on the PCB-based transformer where heat generation is most severe and the temperature is highest, thereby effectively ensuring the stable and reliable operation of the power transformer.

[0013] In one possible implementation, the temperature sampling circuit is located on the first PCB.

[0014] In one possible implementation, the switching power supply further includes a controller connected to the output of the temperature sampling circuit.

[0015] In one possible implementation, the power transformer further includes a second secondary winding, the output of which is connected to a second load device.

[0016] In this implementation, the power transformer can simultaneously transmit power to both the first and second load devices, improving circuit utilization and integration.

[0017] Secondly, this application also provides a vehicle that includes the switching power supply provided in the first aspect and any implementation thereof, and further includes a power battery pack. The power battery pack is connected to the primary-side flyback circuit of the switching power supply. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 A schematic diagram of a switching power supply provided for an embodiment of this application;

[0020] Figure 2 A schematic diagram of another switching power supply provided in an embodiment of this application;

[0021] Figure 3 A schematic diagram of a PCB-type transformer used in a switching power supply provided in an embodiment of this application;

[0022] Figure 4 A schematic diagram of another switching power supply provided in an embodiment of this application;

[0023] Figure 5 This is a schematic diagram of a vehicle provided in an embodiment of this application. Detailed Implementation

[0024] To enable those skilled in the art to better understand the solution of this application, the application scenario of the technical solution of this application will be described first below.

[0025] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be described below with reference to the accompanying drawings.

[0026] The terms "first" and "second" used in this application description are for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated.

[0027] In this application, unless otherwise expressly specified and limited, the term "connection" shall be interpreted broadly. For example, "connection" may be a fixed connection, a detachable connection, or an integral part; it may be a direct connection or an indirect connection through an intermediate medium.

[0028] See Figure 1 The figure is a schematic diagram of a switching power supply provided in an embodiment of this application.

[0029] The switching power supply is specifically a flyback switching power supply, including: a power transformer 12, a positive temperature coefficient thermistor Rp, and a primary-side flyback circuit 11.

[0030] The primary-side flyback circuit 11 is connected to the primary winding L1 of the power transformer 12.

[0031] A positive temperature coefficient (PTC) thermistor Rp is connected in parallel across the two ends of the first secondary winding L2 of the power transformer 12.

[0032] Furthermore, the secondary side of the switching power supply also includes a secondary circuit 13, which is connected to both ends of the first secondary winding L2. The secondary circuit 13 can also be called a power module, and can have one or more functions such as rectification, boost conversion, and buck conversion. This application embodiment does not specifically limit the functionality. The output terminal of the secondary circuit 13 can provide an output voltage Vout to the load device.

[0033] The resistance of Rp exhibits a positive temperature characteristic; its resistance increases as the temperature of Rp rises and decreases as the temperature of Rp falls. In one possible implementation, Rp should be positioned as close as possible to the first secondary winding L2 of the power transformer 12, thereby enabling it to respond quickly and sensitively to temperature changes in the first secondary winding L2 and corresponding resistance changes.

[0034] The working principle of this switching power supply is explained in detail below.

[0035] During the startup phase of the switching power supply, since the power transformer 12 has not yet been energized and heated, the ambient temperature is low, and the resistance of the positive temperature coefficient thermistor Rp is small. The voltage U across the first secondary winding L2, the equivalent impedance R of all loads connected to the first secondary winding L2, and the startup current I flowing through the first secondary winding L2 satisfy the following equation:

[0036] I = U / R (1)

[0037] In this embodiment of the application, since a positive temperature coefficient thermistor Rp is connected in parallel across the first secondary winding L2, it is equivalent to increasing R. When the voltage U across the first secondary winding L2 remains unchanged, according to equation (1), it can be determined that the starting current I of the first secondary winding L2 decreases, and the switching power supply can start stably.

[0038] As the switching power supply operates, the power transformer 12 is energized and heats up. This heat accumulation causes the ambient temperature to rise, increasing the resistance of the positive temperature coefficient thermistor Rp. The voltage U across the first secondary winding L2 is the same as the voltage across the temperature coefficient thermistor Rp. At this time, the heating power P of the temperature coefficient thermistor Rp, the voltage U across the first secondary winding L2, and the resistance of the temperature coefficient thermistor Rp satisfy the following equation:

[0039] P = U 2 / Rp (2)

[0040] According to equation (2), as Rp increases, when the output voltage U of the first secondary winding L2 remains unchanged, the power consumption P of the positive temperature coefficient thermistor Rp decreases, which reduces the current in the power transformer 12 and the output circuit, and reduces the heat generation, thus preventing the power transformer from failing due to overheating.

[0041] The existing solution uses a dummy load resistor with a fixed resistance value. As the switching power supply operates, the dummy load resistor generates significant heat, which increases the burden on the power transformer and can easily cause the device to overheat and fail.

[0042] This method requires only a positive temperature coefficient thermistor Rp to achieve automatic adjustment, and also effectively reduces the hardware cost and complexity of the equipment.

[0043] Furthermore, in the solution provided in the embodiments of this application, the positive temperature coefficient thermistor Rp can also be used for voltage feedback control, which will be described in detail below with reference to the accompanying drawings.

[0044] See Figure 2 This figure is a schematic diagram of another switching power supply provided in an embodiment of this application.

[0045] The switching power supply also includes a temperature sampling circuit 14 and a controller 15.

[0046] The primary-side flyback circuit 11 is connected to the primary winding L1 of the power transformer 12. A positive temperature coefficient thermistor Rp is connected in parallel across the first secondary winding L2 of the power transformer 12. The secondary side of the switching power supply also includes a secondary circuit 13, which is connected across the first secondary winding L2. The output of the secondary circuit 13 can provide an output voltage Vout to the first load device 30.

[0047] The primary side of the switching power supply can be powered by the battery pack of the electric vehicle.

[0048] Temperature sampling circuit 14 is used to acquire the temperature of positive temperature coefficient thermistor Rp when the power transformer is working, and send the sampling result to controller 15. In one possible implementation, temperature sampling circuit 14 uses a temperature sensor to acquire the temperature sampling result.

[0049] The controller 15 is connected to the output terminal of the temperature sampling circuit 14. The controller 15 can also be called a microcontroller unit (MCU). The controller can be an application-specific integrated circuit (ASIC), a programmable logic device (PLD), a digital signal processor (DSP), or a combination thereof. The PLD can be a complex programmable logic device (CPLD), a field-programmable gate array (FPGA), a generic array logic (GAL), or any combination thereof. This application embodiment does not specifically limit the specific type of PLD.

[0050] After the controller 15 obtains the temperature sampling result of the PTC, it can detect the temperature of the power transformer 12 based on the temperature sampling result. When the temperature of the power transformer 12 is higher than the preset temperature, the controller 15 can perform the corresponding protection action.

[0051] The protective actions that controller 15 can perform include, but are not limited to, controlling the switching power supply to shut down and reducing the load connected to the output of the switching power supply. By performing these protective actions, the power transformer 12 is ensured to operate within a stable and reliable temperature range.

[0052] In one possible implementation, reducing the load connected to the output of the switching power supply specifically includes disconnecting some of the load devices connected to the output of the switching power supply. When disconnecting load devices, lower priority load devices can be disconnected first according to a preset priority order. For example, when the temperature of the power transformer 12 is higher than a preset temperature, the first load device 30 has the lowest priority, so the first load device 30 can be disconnected first.

[0053] In one possible implementation, the power transformer 12 used in the switching power supply is specifically a printed circuit board (PCB) transformer. The temperature coefficient thermistor Rp is attached to the PCB transformer, as detailed below with reference to the accompanying drawings.

[0054] See Figure 3 The figure is a schematic diagram of the PCB board transformer used in the switching power supply provided in the embodiment of this application.

[0055] The PCB board transformer may include a multi-layer PCB 40. The PCB board transformer has a coil 42 placed on the PCB 40, and then a magnetic core (not shown in the figure) is embedded into a pre-drilled magnetic core hole 41 on the PCB. Rp is attached to the PCB board transformer.

[0056] During the operation of the PCB-type transformer, the temperature of the coils on each layer of PCB 40 may differ. To effectively ensure the stable and reliable operation of the power transformer 12, in this embodiment, the Rp is attached near the coil on the PCB-type transformer where the heat generation is most severe and the temperature is highest. That is, among the multi-layer PCB 40, the PCB with the highest operating temperature is the first PCB, and the positive temperature coefficient thermistor Rp is attached to the first PCB, specifically near the winding on the first PCB. The temperature sampling circuit 14 can also be set on the first PCB.

[0057] In this embodiment, the surface mount characteristics of the PCB board transformer are reasonably utilized, and the positive temperature coefficient thermistor Rp can be directly placed for surface mounting. This facilitates the layout of the positive temperature coefficient thermistor Rp, which can optimize the load regulation rate at the moment of power supply startup, monitor the temperature of the power transformer, and provide over-temperature protection for the power transformer, ensuring that the system using this switching power supply can operate stably.

[0058] In another possible implementation, the switching power supply may also include a second secondary winding, which will be described in detail below with reference to the accompanying drawings.

[0059] See Figure 4 This figure is a schematic diagram of another switching power supply provided in an embodiment of this application.

[0060] The primary-side flyback circuit 11 is connected to the primary winding L1 of the power transformer 12. A positive temperature coefficient thermistor Rp is connected in parallel across the first secondary winding L2 of the power transformer 12. The secondary side of the switching power supply also includes a secondary circuit 13, which is connected across the first secondary winding L2. The output of the secondary circuit 13 can provide an output voltage Vout to the first load device 30.

[0061] The power transformer 12 of the switching power supply shown in the figure also includes a second secondary winding L3, the output terminal of which is connected to a second load device 40.

[0062] The second load device 40 may have a built-in power conversion circuit to convert the AC power output from L3 into the required operating current. The power conversion circuit may have one or more functions such as rectification, boost, and buck.

[0063] The specific type of the second load device 40 is not limited in the embodiments of this application.

[0064] In one possible implementation, a power conversion circuit may also be included between the second secondary winding L3 and the second load device 40, which can convert the AC power output from L3 into the operating current required by the second load device 40.

[0065] In one possible implementation, the second load device 40 can be an integrated circuit (IC) chip, which has the characteristics of relatively low power consumption and relatively small operating current. Therefore, the second secondary winding L3 will usually not overheat. Thus, a positive temperature coefficient thermistor Rp can be omitted to reduce hardware costs and improve efficiency.

[0066] In this implementation, the power transformer can simultaneously transmit power to both the first load device 30 and the second load device 40, improving circuit utilization and integration. Furthermore, the use of a positive temperature coefficient thermistor Rp prevents the power transformer from failing due to overheating, as explained below.

[0067] During the startup phase of the switching power supply, the resistance of the positive temperature coefficient thermistor Rp is small due to the low ambient temperature. Since the load connected to the second secondary winding L3 remains unchanged at this time, the solution of this application embodiment connects the positive temperature coefficient thermistor Rp in parallel across the first secondary winding L2, which is equivalent to increasing R. When the voltage U across the first secondary winding L2 remains unchanged, it can be determined according to equation (1) that the startup current I of the first secondary winding L2 decreases, and the switching power supply can start stably.

[0068] As the switching power supply operates, the power transformer 12 is energized and heats up. The accumulated heat causes the ambient temperature to rise, and the resistance value of the positive temperature coefficient thermistor Rp increases. When the output voltage U of the first secondary winding L2 remains unchanged, according to equation (2), the power consumption P of the positive temperature coefficient thermistor Rp can be determined to decrease, which makes the current in the power transformer 12 and the output circuit smaller, and the heat generation smaller, thus avoiding the failure of the power transformer due to overheating.

[0069] Based on the power supply system provided in the above embodiments, this application also provides a vehicle, which will be described below with reference to the accompanying drawings.

[0070] See Figure 5 This figure is a schematic diagram of a vehicle provided in an embodiment of this application.

[0071] like Figure 5 As shown, the vehicle 100 may include one or more switching power supplies 101 as described in any of the embodiments. The vehicle 100 may be a battery electric vehicle (BEV), a hybrid electric vehicle (HEV), a plug-in hybrid electric vehicle (PHEV), an extended-range electric vehicle (EREV), a fuel cell vehicle (FCV), etc.

[0072] The vehicle 100 also includes a power battery pack 102, which can be connected to the switching power supply 101 via a DC bus to supply power to the switching power supply 101.

[0073] For details on the specific implementation and working principle of the switching power supply 101, please refer to the description in the above embodiments. The embodiments of this application will not be repeated here.

[0074] The switching power supply in the vehicle utilizes the positive temperature coefficient (PTC) thermistor's resistance, which exhibits a positive temperature characteristic. During the power supply's startup phase, due to the low ambient temperature, the PTC thermistor's resistance is low, resulting in a large instantaneous load and stable startup. As the power supply operates, the ambient temperature rises, increasing the PTC thermistor's resistance. When the output voltage of the first secondary winding remains constant, the PTC thermistor's power consumption decreases, reducing the current in the power transformer and output circuit, thus minimizing heat generation. This prevents the power transformer from failing due to overheating, ensuring a better user experience and improving vehicle safety.

[0075] It should be noted that the various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0076] It should also be noted that, in this document, the terms “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, and an element defined by the phrase “comprising one…” does not exclude the presence of other identical elements in the article or device that includes said element.

[0077] The above description of the disclosed embodiments enables those skilled in the art to make or use this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A switching power supply, characterized in that, The switching power supply includes: a power transformer, a positive temperature coefficient thermistor, and a primary-side flyback circuit; The primary-side flyback circuit is connected to the primary winding of the power transformer; The positive temperature coefficient thermistor is connected in parallel across the two ends of the first secondary winding of the power transformer.

2. The switching power supply according to claim 1, characterized in that, The power transformer is a printed circuit board (PCB) transformer.

3. The switching power supply according to claim 2, characterized in that, The switching power supply further includes a temperature sampling circuit, which is used to sample the temperature of the positive temperature coefficient thermistor when the power transformer is working.

4. The switching power supply according to claim 3, characterized in that, The positive temperature coefficient thermistor is attached to the PCB board transformer.

5. The switching power supply according to claim 4, characterized in that, The PCB-type transformer includes multiple PCBs, with each PCB layer containing windings.

6. The switching power supply according to claim 5, characterized in that, When the switching power supply is working, the PCB with the highest operating temperature among the multilayer PCBs is the first PCB. The positive temperature coefficient thermistor is attached to the first PCB.

7. The switching power supply according to claim 6, characterized in that, The temperature sampling circuit is located on the first PCB.

8. The switching power supply according to claim 7, characterized in that, The switching power supply also includes a controller, which is connected to the output of the temperature sampling circuit.

9. The switching power supply according to any one of claims 1-8, characterized in that, The power transformer also includes a second secondary winding, the output of which is connected to a second load device.

10. A vehicle, characterized in that, The vehicle includes one or more switching power supplies according to any one of claims 1-9, and further includes a power battery pack; The power battery pack is connected to the primary-side flyback circuit of the switching power supply.

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