SEPIC buck-boost circuit based on electric drive system, power supply and vehicle

Abstract

The utility model relates to an SEPIC boost-buck circuit based on an electric drive system, a power supply and a vehicle, which belong to the technical field of new energy automobile power electronics and comprise a direct current input voltage source Vdc, an energy storage inductor L1, a switching device FET1, a capacitor C1, a motor three-phase winding of the electric drive system, an electric drive inversion unit, a diode D1 and a capacitor C2. According to the utility model, through the on-off of the switching device FET1, the switching device FET2, the switching device FET3, the switching device FET4, the switching device FET5, the switching device FET6 and the switching device FET7 and the energy storage of the capacitor C1, not only can the boost function of the whole circuit be realized, but also the buck function can be realized when a low-voltage platform vehicle faces a high-voltage charging pile, and no extra buck circuit is needed.

Description

Technical Field

[0001] The utility model belongs to the technical field of power electronics for new energy vehicles, and specifically relates to a SEPIC buck-boost circuit, a power supply and a vehicle based on an electric drive system. Background Art

[0002] With the development of new energy vehicle technology, the voltage platform of the whole vehicle is getting higher and higher, and is gradually transitioning from 400V to 800V. However, most of the charging piles in China are still 400V. In order to realize charging under the 800V platform, the vehicle must be equipped with a boost module.

[0003] The boost circuits of existing boost modules mostly use Boost boost circuits, and the circuit structure is as follows: Figure 1 As shown, it includes inductor L2, switch tube Q1 and diode D2. The working process can be divided into two parts: charging and discharging. Charging process: During charging, switch tube Q1 is turned on, which can be understood as a MOS tube, which is equivalent to a line directly connecting the drain and the source, which is equivalent to short-circuiting the MOS tube. At this time, the input voltage flows through capacitor C3 for filtering, inductor L2, switch tube Q1. As inductor L2 is continuously charged, the current on inductor L2 increases linearly. When it reaches a certain time, inductor L2 stores a certain amount of energy. During this process, diode D2 is reverse biased and cut off, and capacitor C4 (capacitor C4 has The power is charged because the capacitor C4 was charged during the last discharge) to provide energy to the load RL to maintain the load operation; Discharge process: When the switch tube is not conducting, the switch tube Q1 is equivalent to being disconnected. Due to the reverse electromotive force of the inductor L2, the current of the inductor L2 cannot change suddenly, but will discharge slowly and gradually. Since the original electrical circuit has been disconnected, the inductor L2 can only discharge through the diode D2, the load RL, and the capacitor C3 circuit, that is, the inductor L2 starts to charge the capacitor C4, and before charging C4, C4 already provides voltage, so the voltage across the capacitor C4 increases. However, the Boost boost circuit can only boost voltage. If you want to reduce voltage, you need a buck circuit or linear regulator configured separately in the vehicle. Utility Model Content

[0004] The purpose of the utility model is to provide a SEPIC buck-boost circuit, power supply and vehicle based on an electric drive system to solve the problems existing in the prior art, in view of the defect that a boost module in the prior art adopts a Boost boost circuit to boost the voltage, but when the vehicle power supply is stepped down, a buck circuit or a linear regulator needs to be additionally configured, and the structure is relatively complicated.

[0005] In order to achieve the above purpose, the utility model provides the following technical solutions:

[0006] In the first aspect, the utility model provides a SEPIC buck-boost circuit based on an electric drive system, comprising a DC input voltage source Vdc, an energy storage inductor L1, a switching device FET1, a capacitor C1, a three-phase winding of a motor of the electric drive system, an electric drive inverter unit, a diode D1 and a capacitor C2;

[0007] The first end of the energy storage inductor L1 is connected to the positive electrode of the DC input voltage source Vdc, the second end of the energy storage inductor L1 is connected to the drain of the switching device FET1 and the positive electrode of the capacitor C1, the negative electrode of the capacitor C1 is connected to the first input end of the electric drive inverter unit, the second input end of the electric drive inverter unit is connected to the first end of the three-phase winding of the motor, the output end of the electric drive inverter unit is connected to the positive electrode of the diode D1, the negative electrode of the diode D1 is connected to the positive electrode of the capacitor C2 and the positive electrode of the load R1, the negative electrode of the DC input voltage source Vdc, the source of the switching device FET1, the second end of the three-phase winding of the motor, the negative electrode of the capacitor C2 and the negative electrode of the load R1 are all grounded, and the gate of the switching device FET1 and the signal input end of the electric drive inverter unit are all connected to the output end of the electric drive system.

[0008] A further improvement of the present technical solution is that the three-phase winding of the motor includes an energy storage inductor La, an energy storage inductor Lb and an energy storage inductor Lc, the first end of the energy storage inductor La, the first end of the energy storage inductor Lb and the first end of the energy storage inductor Lc are all connected to the second input end of the electric drive inverter unit, and the second end of the energy storage inductor La, the second end of the energy storage inductor Lb and the second end of the energy storage inductor Lc are all grounded.

[0009] A further improvement of the technical solution is that the electric drive inverter unit includes a switching device FET2, a switching device FET3, a switching device FET4, a switching device FET5, a switching device FET6 and a switching device FET7;

[0010] The drain of the switching device FET2, the drain of the switching device FET3 and the drain of the switching device FET4 are all connected to the negative electrode of the capacitor C1 and the positive electrode of the diode D1, the source of the switching device FET2 and the drain of the switching device FET5 are all connected to the first end of the energy storage inductor La, the source of the switching device FET3 and the drain of the switching device FET6 are all connected to the first end of the energy storage inductor Lb, the source of the switching device FET4 and the drain of the switching device FET7 are all connected to the first end of the energy storage inductor Lc, and the source of the switching device FET5, the source of the switching device FET6 and the source of the switching device FET7 are all grounded.

[0011] A further improvement of the technical solution is that the motor of the electric drive system adopts a permanent magnet synchronous motor.

[0012] In a second aspect, the utility model provides a power supply based on an electric drive system, comprising any of the above-mentioned SEPIC buck-boost circuits based on an electric drive system.

[0013] In a third aspect, the utility model provides a vehicle, comprising the power supply based on the electric drive system described above.

[0014] The beneficial effect of the utility model is that the utility model can not only realize the boost function of the entire circuit through the on and off of the switching devices FET1, FET2, FET3, FET4, FET5, FET6 and FET7 and the energy storage of the capacitor C1, but also can realize the voltage reduction function when a low-voltage platform vehicle model faces a high-voltage charging pile, without the need to set up an additional voltage reduction circuit.

[0015] In addition, the utility model has a reliable design principle, a simple structure and a very broad application prospect.

[0016] It can be seen that compared with the prior art, the present invention has outstanding substantive features and significant progress, and the beneficial effects of its implementation are also obvious. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is the schematic diagram of the Boost circuit.

[0018] Figure 2 This is the schematic diagram of the SEPIC buck-boost circuit.

[0019] Figure 3 Schematic diagram of current flow when the switching device FET1 is closed.

[0020] Figure 4 Schematic diagram of current flow when the switching device FET1 is turned off. DETAILED DESCRIPTION

[0021] In order to enable those skilled in the art to better understand the technical solutions in the present invention, the following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0022] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0023] The key terms appearing in the present invention are explained below.

[0024] SEPIC, single ended primary inductor converter, is a DCDC converter that allows the output voltage to be greater than, less than or equal to the input voltage. The output voltage is controlled by the duty cycle of the main control switch (transistor or MOS tube). The biggest advantage of this circuit is that the input and output have the same polarity. It is especially suitable for battery-powered applications, allowing the battery voltage to be higher or lower than the required input voltage. For example, the voltage of a lithium battery is 3V to 4.2V. If the load requires 3.3V, the SEPIC circuit can achieve this conversion. Another benefit is the isolation of input and output, which is achieved through the capacitor on the main circuit. It also has a complete shutdown function. When the switch tube is turned off, the output voltage is 0V.

[0025] like Figure 2 As shown, the utility model provides a SEPIC buck-boost circuit based on an electric drive system, comprising a DC input voltage source Vdc, an energy storage inductor L1, a switch device FET1, a capacitor C1, a three-phase winding of a motor of the electric drive system, an electric drive inverter unit, a diode D1 and a capacitor C2; a first end of the energy storage inductor L1 is connected to the positive electrode of the DC input voltage source Vdc, a second end of the energy storage inductor L1 is connected to the drain of the switch device FET1 and the positive electrode of the capacitor C1, a negative electrode of the capacitor C1 is connected to the first input end of the electric drive inverter unit, and the electric drive inverter unit The second input end of the element is connected to the first end of the three-phase winding of the motor, the output end of the electric drive inverter unit is connected to the anode of the diode D1, the cathode of the diode D1 is connected to the anode of the capacitor C2 and the anode of the load R1, the cathode of the DC input voltage source Vdc, the source of the switching device FET1, the second end of the three-phase winding of the motor, the cathode of the capacitor C2 and the cathode of the load R1 are all grounded, the gate of the switching device FET1 and the signal input end of the electric drive inverter unit are all connected to the output end of the electric drive system; wherein, the motor of the electric drive system adopts a permanent magnet synchronous motor.

[0026] Specifically, the three-phase winding of the motor includes an energy storage inductor La, an energy storage inductor Lb and an energy storage inductor Lc. The first end of the energy storage inductor La, the first end of the energy storage inductor Lb and the first end of the energy storage inductor Lc are all connected to the second input end of the electric drive inverter unit, and the second end of the energy storage inductor La, the second end of the energy storage inductor Lb and the second end of the energy storage inductor Lc are all grounded.

[0027] The electric drive inverter unit includes switching device FET2, switching device FET3, switching device FET4, switching device FET5, switching device FET6 and switching device FET7; the drain of switching device FET2, the drain of switching device FET3 and the drain of switching device FET4 are all connected to the negative electrode of capacitor C1 and the positive electrode of diode D1, the source of switching device FET2 and the drain of switching device FET5 are all connected to the first end of energy storage inductor La, the source of switching device FET3 and the drain of switching device FET6 are all connected to the first end of energy storage inductor Lb, the source of switching device FET4 and the drain of switching device FET7 are all connected to the first end of energy storage inductor Lc, and the source of switching device FET5, the source of switching device FET6 and the source of switching device FET7 are all grounded.

[0028] In addition, the utility model also provides a power supply based on an electric drive system, including any of the above-mentioned SEPIC buck-boost circuits based on an electric drive system; and the utility model also provides a vehicle, including the above-mentioned power supply based on an electric drive system.

[0029] Finally, the working principle of the SEPIC buck-boost circuit based on the electric drive system is: using the switch device of the electric drive system inverter unit and the three-phase winding coil of the synchronous motor as part of the boost component, and cooperating with the energy storage inductor L1, capacitor C1, and switch device to realize the boost function. The charging process of the new energy vehicle can be regarded as the DC input power supply Vdc in the figure. The entire boost process can be divided into two parts: the switch device FET1 is closed and disconnected. Among them, the switch device FET5, the switch device FET6, and the switch device FET7 in the electric drive inverter unit are always in the disconnected state, and the switch device FET2, the switch device FET3, and the switch device FET4 are always in the closed state; the switch device FET2, the switch device FET3, the switch device FET4, the switch device FET5, the switch device FET6, and the switch device FET7 can use the inverter of the electric drive system, reducing the number of devices that need to be additionally arranged in the entire boost module.

[0030] like Figure 3 As shown, when the switch device FET1 is in the closed state, the DC input power supply Vdc flows through the energy storage inductor L1 and the switch device FET1 to form the first loop. The capacitor C1 discharges and flows through the switch device FET1 and the energy storage inductors La, Lb, and Lc to form the second loop.

[0031] like Figure 4 As shown, when the switch device FET1 is in the off state, the DC input power supply Vdc passes through the energy storage inductor L1, and then passes through the capacitor C1 and the diode D1 to charge the load R1 to form the first loop. The energy storage inductors La, Lb, Lc pass through the diode D1 to charge the load R1 to form the second loop.

[0032] Specifically, the relationship between voltage input and output can be expressed as:

[0033]

[0034] Among them, V out is the output voltage, V dc is the charging voltage at the input terminal, and D is the on-duty ratio of the switching device FET1 within one cycle.

[0035] It can be seen from the relationship between voltage input and output that, compared with the traditional Boost circuit, this circuit can not only achieve the boost function but also the buck function. Therefore, when some low-voltage platform models face high-voltage charging piles, the buck function of the SEPIC buck-boost circuit does not require additional design, and the buck charging function can also be achieved, and the utility model uses fewer devices.

[0036] The above disclosure is only the preferred implementation mode of the utility model, but the utility model is not limited thereto. Any non-creative changes that can be thought of by technicians in this field, as well as several improvements and modifications made without departing from the principle of the utility model, should fall within the scope of protection of the utility model.

Claims

1. A SEPIC buck-boost circuit based on an electric drive system, characterized in that: It includes a DC input voltage source Vdc, an energy storage inductor L1, a switching device FET1, a capacitor C1, a three-phase winding of a motor of an electric drive system, an electric drive inverter unit, a diode D1 and a capacitor C2; The first end of the energy storage inductor L1 is connected to the positive electrode of the DC input voltage source Vdc, the second end of the energy storage inductor L1 is connected to the drain of the switching device FET1 and the positive electrode of the capacitor C1, the negative electrode of the capacitor C1 is connected to the first input end of the electric drive inverter unit, the second input end of the electric drive inverter unit is connected to the first end of the three-phase winding of the motor, the output end of the electric drive inverter unit is connected to the positive electrode of the diode D1, the negative electrode of the diode D1 is connected to the positive electrode of the capacitor C2 and the positive electrode of the load R1, the negative electrode of the DC input voltage source Vdc, the source of the switching device FET1, the second end of the three-phase winding of the motor, the negative electrode of the capacitor C2 and the negative electrode of the load R1 are all grounded, and the gate of the switching device FET1 and the signal input end of the electric drive inverter unit are all connected to the output end of the electric drive system.

2. The SEPIC buck-boost circuit based on the electric drive system according to claim 1, characterized in that: The three-phase winding of the motor includes energy storage inductor La, energy storage inductor Lb and energy storage inductor Lc. The first end of the energy storage inductor La, the first end of the energy storage inductor Lb and the first end of the energy storage inductor Lc are all connected to the second input end of the electric drive inverter unit, and the second end of the energy storage inductor La, the second end of the energy storage inductor Lb and the second end of the energy storage inductor Lc are all grounded.

3. The SEPIC buck-boost circuit based on the electric drive system according to claim 2, characterized in that: The electric drive inverter unit includes a switching device FET2, a switching device FET3, a switching device FET4, a switching device FET5, a switching device FET6 and a switching device FET7; The drain of the switching device FET2, the drain of the switching device FET3 and the drain of the switching device FET4 are all connected to the negative electrode of the capacitor C1 and the positive electrode of the diode D1, the source of the switching device FET2 and the drain of the switching device FET5 are all connected to the first end of the energy storage inductor La, the source of the switching device FET3 and the drain of the switching device FET6 are all connected to the first end of the energy storage inductor Lb, the source of the switching device FET4 and the drain of the switching device FET7 are all connected to the first end of the energy storage inductor Lc, and the source of the switching device FET5, the source of the switching device FET6 and the source of the switching device FET7 are all grounded.

4. The SEPIC buck-boost circuit based on the electric drive system according to claim 1, characterized in that: The electric drive system uses a permanent magnet synchronous motor.

5. A power supply based on an electric drive system, characterized in that: It comprises a SEPIC buck-boost circuit based on an electric drive system as described in any one of claims 1 to 4.

6. A vehicle, characterized in that: Comprising a power supply based on an electric drive system as described in claim 5.

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