PREVENTION OF MISSING PULSES IN A POWER CONVERSION CIRCUIT

Abstract

PREVENTION OF MISSING PULSES IN A POWER CONVERSION CIRCUIT This topic relates to a power conversion circuit (200), particularly for automotive traction motor applications, which includes an inductor (L), a semiconductor switch (D), a control circuit (202), and a resistor (R). The inductor (L) is connected between an input terminal and an auxiliary switch (SB). The semiconductor switch (D) is connected to a capacitor (C_out) and a load (R_load). The capacitor (C_out) and the load (R_load) are connected in parallel. Furthermore, the control circuit (202) is configured to regulate the switching operation of the auxiliary switch (SB). The resistor (R) is connected in parallel to one reverse-biased side of the semiconductor switch (SB) and also in parallel with the auxiliary switch (SB).

Description

Title of the invention: PREVENTION OF MISSING PULSES IN A POWER CONVERSION CIRCUIT FIELD OF THE INVENTION

[0001] The present subject matter relates to a power conversion circuit for a DC power supply with switching elements. More particularly, the present subject matter relates to the elimination of missing pulse prevention in a power conversion circuit of a power conversion apparatus in automotive applications.

[0002] CONTEXT

[0003] A power conversion circuit for generating a DC power supply with switching elements, such as a metal oxide semiconductor field effect transistor (MOSFET), an insulated gate bipolar transistor (IGBT), typically includes, for example, an inverter that converts DC to AC (or vice versa) and a DC-DC converter. This type of power conversion device is commonly used, in automotive applications, with traction motors. A DC-DC converter typically includes a boost converter for raising an input voltage to a high level required by a load. To do this, electrical energy is stored in an inductor and returned to the load that requires a higher voltage.

[0004] In conventional power conversion circuits, switching elements are provided on the high side and the low side. By complementary operation of the high side switching elements and the low side switching elements (e.g., by providing a switching pulse), power is supplied to an inductive load. A diode is coupled in antiparallel to the switching elements and operates as a freewheeling diode when the inductive load is powered. The reverse recovery properties of the diode are generally poor and vary from diode to diode. At the time of reverse recovery, a current (reverse recovery current) flows in the opposite direction of the diode. Due to the poor recovery properties of the diode, a large surge current, due to the reverse recovery current, is generated when the high side switching element is turned on.When the high-side switching elements and the low-side switching element are turned off simultaneously, a circulating current in the forward direction flows from the inductive load to the low-side diode. In this state, when the element . When the high-side switching element is turned on, the load current flows to the current flowing through the high-side switching element. At this time, a voltage in the opposite direction is applied to the diode and a large reverse recovery current is superimposed to generate a current surge and a voltage surge. In addition, there is a high risk of missing the next switching pulse if the recovery is delayed, resulting in a disturbance in the current flow. This disturbance can lead to unstable operation of the power conversion device with larger ripple in the load voltage and can cause total harmonic distortion (THD).

[0005] Therefore, the technical problem to be solved by the present subject is how to provide an energy conversion apparatus having reduced disturbances due to reverse recovery current. Summary of the invention

[0006] The present object aims to solve the above-mentioned technical problem in conventional energy conversion devices. The present object finds a particularly advantageous application in rotating electrical machines such as alternators, alternator starters, or reversible machines or electric motors. A reversible machine is a rotating electrical machine which can operate reversibly, on the one hand as an electric generator in the alternator function, and on the other hand as an electric motor, for example to start the thermal engine of a motor vehicle. The rotating electrical machine described here can also be used as a traction motor for hybrid or electric vehicles. 1. The present subject matter relates to a power conversion circuit for automotive traction motor applications, comprising: an inductor connected between an input terminal and a booster switch; a semiconductor switch connected to a capacitor and a load, the capacitor and the load being connected in parallel; a control circuit configured to regulate the switching operation of the booster switch; and a resistor connected in parallel to a reverse-biased side of the semiconductor switch and connected in parallel to the booster switch. Accordingly, during the reverse-biased operation of the semiconductor switch, the reverse recovery current of this switch begins to flow through the resistor. This strategic arrangement therefore minimizes or largely eliminates problems associated with reverse recovery, such as recovery time.In particular, the phenomenon of missing impulse (delay . in switching) is eliminated through a dedicated path provided to release the energy stored in the semiconductor switch.

[0007] According to an example of the present subject matter, the power conversion circuit comprises a rectifier circuit for supplying power to the input terminal. Thus, in automotive applications, such as traction motors, alternating current (AC) is converted to direct current (DC) which is then supplied to the input terminal of the power conversion circuit. Such a rectifier circuit is an electrical power converter for an AC / DC and / or DC / AC converter.

[0008] According to an example of the present subject, the resistance is a function of the reverse recovery energy stored in the semiconductor switch and the switching frequency of the switching elements in the rectifier circuit. Accordingly, due to the dedicated path for the reverse recovery current, switching losses are minimized, resulting in higher conversion efficiency, and thus better power conversion. In addition, the reduced switching losses result in less heat dissipation, allowing a more reliable and compact power converter to be designed. Furthermore, the power converter's ability to improve power conversion stability and reduce losses makes it suitable for high-power applications.Another advantage is that the power converter components are less stressed due to the minimization of reverse recovery problems, which extends the life of the boost converter.

[0009] According to an example of the present subject matter, a dedicated switch is connected in series with the resistor. Accordingly, a switching operation of the dedicated switch facilitates current flow through the dedicated path only when reverse recovery energy flows from the semiconductor switch. In other words, the dedicated switch is configured to close at the time when reverse recovery energy, in the form of a reverse recovery current, is generated by the semiconductor switch. In one example, the control circuit is further configured to regulate the switching operation of the dedicated switch.

[0010] According to an example of the present subject matter, the control circuit is further configured to regulate the switching operation of the dedicated switch.

[0011] According to an example of the present subject, the semiconductor switch is a diode.

[0012] The present subject matter also relates to a method for operating the power conversion circuit, configured as described above. The method comprises receiving an input voltage from the rectifier at the input terminal of the power conversion circuit; controlling the switching operation of the boost switch using the control circuit; increasing the input voltage using the boost converter circuit of the power conversion circuit; removing the current from reverse recovery of the semiconductor switch by applying the resistor; and supplying the increased output voltage to the load connected in parallel to the capacitor.

[0013] According to an example of the present subject matter, the method comprises selecting appropriate values ​​for the resistor in order to optimize the elimination of reverse recovery energy.

[0014] Various modifications to the disclosed embodiments, as well as other embodiments of the subject matter, will become apparent to those skilled in the art upon reference to the description of the subject matter. It is therefore contemplated that such modifications may be made without departing from the scope of the present subject matter. Brief description of the drawings

[0015] The features, aspects and advantages of the present invention will be better understood in light of the following description and the accompanying figures. The description refers to the accompanying drawings, in which:

[0016] [Fig.l] illustrates a boost converter circuit, configured in accordance with the present subject matter;

[0017] [Fig.2] illustrates a power conversion circuit which includes the boost converter circuit configured in accordance with the present subject matter; and

[0018] [Fig. 3] illustrates a flowchart for a method of selecting appropriate values ​​for a resistor in the power converter, configured in accordance with an example of the present subject matter.

[0019] The figures are not necessarily to scale and the size of certain parts may be exaggerated to more clearly illustrate the example shown. In addition, the drawings provide examples and / or examples consistent with the description, but the description is not limited to the examples and / or examples provided in the drawings. DETAILED DESCRIPTION

[0020] In the following description, reference is made to the accompanying drawings, which form an integral part of the invention, and in which are illustrated specific embodiments in which the invention may be embodied. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention, and it is understood that the embodiments may be combined, or that other embodiments may be used, and that structural and logical modifications may be made without departing from the scope of the present invention. The following detailed description is therefore not to be construed in a limiting sense, and the scope of the present invention is defined by the appended claims and their equivalents.

[0021] [Fig.l] illustrates a boost converter circuit 100, configured in accordance with the present subject matter. The boost converter circuit 100 comprises an inductor L, a semiconductor switch D, and a resistor R. The inductor L is connected between an input terminal and a boost switch (SB). The semiconductor switch D is connected to a capacitor C_out and a load R_load. Furthermore, the resistor R is connected in parallel to an inverted side of the semiconductor switch D. Furthermore, the resistor is connected such that it is parallel to the boost switch SB.

[0022] According to the present subject, the boost converter circuit 100 is powered by an input voltage Vin from a converter 104 to power the input terminal. The input terminal may also be a battery or a power source to provide the input voltage Vin. The converter 104 includes switches that are powered by a source voltage Vs and output the input voltage Vin to the boost converter circuit 100. In the example of [Fig.l], the converter 104 is a single-phase or polyphase type rectifier. The inductor L is connected in series with the input terminal. The inductor L stores and releases energy during switching cycles. The boost switch SB, typically a transistor, controls the circuit by opening and closing to control the energy flow. The semiconductor switch D allows current to flow in only one direction, thus preventing reverse current flow.Capacitor C_out smooths the output voltage by storing the charge. The load R_load represents, for example, a traction motor or any other load connected to the output. The input terminal is connected to inductor L and boost switch SB in series. Semiconductor switch D and capacitor C_out are connected in parallel to load R_load. An additional dedicated path for resistor R is provided in the boost converter 100 circuit in the reverse direction of semiconductor switch D. Semiconductor switch D, in one example, is a diode.

[0023] According to the present subject matter, when the boost switch SB is closed, energy is stored in the inductor L. When the boost switch SB is open, the inductor L releases the stored energy, resulting in an increase in the output voltage. The semiconductor switch D in the boost converter circuit 100, during an OFF phase of the boost switch SB, the semiconductor switch D conducts to provide a path for the energy from the inductor L to reach the load R_load. When the boost switch SB turns back on, there is a brief interval, or "reverse recovery time," during which the semiconductor switch D transitions from the conductive state to the off state, and a reverse recovery current I„ flows in a reverse biased direction 102 due to the stored energy, or reverse recovery energy, in the semiconductor switch D. The reverse recovery current follows the dedicated path provided by resistor R.

[0024] According to one aspect of the present subject matter, the resistance of the resistor R is a function of the stored reverse recovery energy. However, the resistance may be determined based on other factors, such as the application, circuit voltage, etc. Furthermore, the appropriate resistor R may be selected based on the rail voltage and the storage energy in the semiconductor switch D.

[0025] The present subject matter also relates to a power conversion circuit 200 for automotive traction motor applications that includes the boost converter circuit 100 as described in the preceding description. [Fig. 2] illustrates a power conversion circuit 200 that includes the boost converter circuit 100, configured in accordance with the present subject matter, and a control circuit 202. The inductor L, the semiconductor switch D, and the resistor R are configured in the manner described for [Fig. 1]. The control circuit 202 is configured to regulate the switching operation of the boost switch SB, thereby providing an optimal switching operation of the boost switch SB according to the requirements demanded by the load R_load.

[0026] According to the example illustrated in [Fig.2], the power conversion circuit 200 further comprises a rectifier circuit 204. The rectifier circuit 204 operates to convert alternating current (AC) into direct current (DC). The rectifier circuit 204 provides the input voltage Vin which is "increased" in a boost function of the boost converter circuit 100 to a higher level, i.e. to an increased output voltage Vout, required by the load R_load. The rectifier circuit 204 may be incorporated in an electrical energy converter (not shown) which operates in rectifier mode (to convert alternating current into direct current) or in inverter mode (to convert direct current into alternating current). The rectifier circuit 204 may be of the polyphase type to operate with a polyphase traction motor.

[0027] In the example of [Fig. 2], the rectifier circuit 204 converts the AC voltage at the input phases A, B and C into DC power for the boost converter circuit 100. In the example of [Fig. 2], the rectifier is a three-phase rectifier. The rectifier circuit 204 is equipped with switching elements S1, S2, S3, S4, S5, S6. During operation, at any time, two of the switching elements S1, S2, S3, S4, S5, S6, one at the top and one at the bottom of the other two branches (phases), will be in the ON state while the rest of the switching elements S1, S2, S3, S4, S5, S6 will be in the OFF state. During operation, when the semiconductor switch D transitions from the conductive state to the off state, the reverse recovery current flows in the reverse biased direction 102 to take the dedicated path provided by the resistor R. For example, during a first mode, switches SI and S6 are in the ON state, current flows through input phase A, SI, L, D, R_load, S6 and then input phase C, in that order. In the above-mentioned example, semiconductor switch D is forward biased. During a subsequent mode of operation, switches SI and S6 are in the OFF state and semiconductor switch D is reverse biased. During this reverse bias time, the reverse recovery energy is discharged and directed to resistor R supplied in the reverse bias direction of semiconductor switch D. The resistance of resistor R is therefore also a function of the switching frequency of switching elements SI, S2, S3, S4, S5, S6 in rectifier circuit 204.

[0028] Therefore, in the example where the load R_load is a traction motor, the increased output voltage (i.e., Vout) is transmitted to the traction motor, facilitating efficient operation and allowing for better control of the traction motor speed and torque. The power conversion circuit 200 ensures that the traction motor receives an appropriate voltage level for optimal performance, thereby improving the overall efficiency and functionality of the traction system.

[0029] According to another example of the present subject, the power conversion circuit 200 further comprises a dedicated switch SR in series with the resistor R, provided in the reverse recovery path of the semiconductor switch D. The dedicated switch SR is controlled by the control circuit 202 to close only when the reverse recovery energy (in the form of the reverse recovery current Irr) begins to flow in the dedicated path provided with the resistor R.

[0030] [Fig. 3] illustrates a flowchart describing a method 300, according to the present subject matter, for selecting appropriate values ​​for the resistor R to optimize the elimination of the reverse recovery current Irr. The method 300 includes receiving an input voltage 302 Vin from the rectifier circuit 204 at the input terminal of the power conversion circuit. The rectifier circuit 204 receives the alternating current and converts it to direct current for the input of the boost converter circuit 100. The input voltage Vin may also be from a battery or a power source. The method also includes controlling 304 the switching operation of the boost switch SB. The aforementioned control 304 of the boost switch SB is facilitated by the control circuit 202 illustrated in [Fig. 2].Further, method 300 includes increasing 306 the input voltage Vin to the higher level of the boosted output voltage Vout. Boost converter circuit 100 facilitates increasing the input voltage Vin so that the load R_load, for example a traction motor, receives the voltage of . increased output Vout for optimal performance. Method 300 further involves eliminating 308 the reverse recovery current Irr from the semiconductor switch D. The reverse recovery current Irr flows in the dedicated path provided with the resistor R. Method 300 further involves providing 310 the amplified output voltage Vout to the load R_load which is connected in parallel with the capacitor C_out.

[0031] According to an example of the present subject matter, the method 300 further comprises selecting 312 appropriate values ​​for the resistor R. As explained in a previous paragraph, the resistance of the resistor R is a function of the reverse recovery energy stored in the semiconductor switch D and the switching frequency of the switching elements S1, S2, S3, S4, D5, S6 in the rectifier circuit 204. Furthermore, the selection 312 of the appropriate resistor R may depend on the rail voltage and the storage energy in the semiconductor switch D. For example, in an application where the reverse recovery current Irr is close to 50mA, the value of the resistor (in Ohms), governed by the formula where the DC bus voltage is divided by 50mA, may be chosen based on the switching frequency of the switching elements S1, S2, S3, S4, D5, S6 in the rectifier circuit 204.

[0032] Various modifications to the disclosed embodiments, as well as other embodiments of the subject matter, will become apparent to those skilled in the art upon reference to the description of the subject matter. It is therefore contemplated that such modifications may be made without departing from the scope of the present subject matter.

Claims

Claims

1. A power conversion circuit (200) for automotive traction motor applications, comprising: an inductor (L) connected between an input terminal and a boost switch (SB); a semiconductor switch (D) connected to a capacitor (C_out) and a load (R_load), the capacitor (C_out) and the load (R_load) being connected in parallel; a control circuit (202) configured to regulate the switching operation of the boost switch (SB); and a resistor (R) connected in parallel to an inverted side of the semiconductor switch (D) and connected in parallel to the boost switch (SB).

2. The power conversion circuit (200) according to claim 1 comprises a rectification circuit (204) for supplying power to the input terminal.

3. The power conversion circuit (200) of claim 2, wherein the resistance of the resistor (R) is a function of the reverse recovery energy stored in the semiconductor switch (D) and the switching frequency of the switching elements (S1, S2, S3, S4, S5, S6) in the rectifier circuit (204).

4. The power conversion circuit (200) of claim 1, wherein a dedicated switch (SR) is connected in series with the resistor (R).

5. The power conversion circuit (200) of claims 1 and 4, wherein the control circuit (202) is further configured to regulate the switching operation of the dedicated switch (SR).

6. A power conversion circuit (200) according to any preceding claim, wherein the semiconductor switch (D) is a diode.

7. A method (300) of operating the power conversion circuit (200) according to any preceding claim, the method (300) comprising: receiving the input voltage (Vin) from the rectifier circuit (204) at the input terminal of the power conversion circuit (200);

8. controlling the switching operation of the booster switch (SB) using the control circuit (202); increasing the input voltage (Vin) using the boost converter circuit (100) of the power conversion circuit (200); eliminate the reverse recovery current (Irr) of the semiconductor switch (D) by applying the resistor (R); and deliver the amplified output voltage (Vout) to the load (R_load) connected in parallel with the capacitor (C_out). The method (300) of claim 7, wherein the method (300) comprises selecting appropriate values ​​for the resistor (R) to optimize the elimination of the reverse recovery current (Irr).

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