A soft-switching motor drive circuit topology

Abstract

The present invention provides a soft-switching motor drive circuit topology, characterized in that it includes a power supply (1), a main switch (2), a first auxiliary switch (3), a second auxiliary switch (4), a first diode (5), a second diode (6), a first capacitor (7), a second capacitor (8), an inductor (9) and an inverter (10); the power supply is a DC power supply. The beneficial effects of the present invention are: the overall topology circuit has a relatively small volume, and better balances the relationship between the system volume and the realization of the resonance function, so as to achieve the purpose of improving the power density of the driver, and has lower heat generation and a low EMI level.

Description

Technical Field

[0001] The present invention relates to a motor drive circuit or driver, and particularly to a soft-switching motor drive circuit topology circuit. Background Art

[0002] The traditional main circuit topology of a motor drive is a three-phase bridge inverter circuit, which realizes the drive control of the motor by the high-frequency PWM action of the power switches. The on and off actions of the power switches are realized under the action of their respective gate drive pulses. At the moment of on or off, the voltage across the switch or the current flowing through the switch is not zero, and it is forced to turn on or off. Such a switch is called a "hard" switch. This "hard" turn-on or "hard" turn-off will cause high switching losses, increase the heat generation of the switch module, and thus increase the requirement for system heat dissipation. In addition, the "hard" switch will cause extremely high dv / dt or di / dt in the circuit system, thereby generating high EMI. The above disadvantages make it very difficult for a drive system using this circuit topology to achieve a high power density.

[0003] With the improvement of technology and production development requirements, more and more motor drivers require a high power density and a smaller volume size to be more easily integrated and installed in special use spaces or occasions. The "soft" switching technology has emerged. Using the "soft" switching technology, theoretically, the power consumption can be reduced, thereby improving the power density of the driver, reducing the system size, and reducing EMI. For example, the patents shown below have realized the soft switching technology, but they also have their own disadvantages.

[0004] For example, the patent with the invention patent application number CN 106533224A submitted a resonant DC link soft-switching inverter and its modulation method. The topology circuit in this patent realizes the ZVS (zero voltage) switching of the power switches on the inverter leg. The claimed advantages of this patent are that it eliminates the current reverse process of the auxiliary resonant inductor, thus alleviating the magnetic saturation problem of the inductor; by a specially improved SPWM modulation method, the operating frequency of the resonant circuit is reduced, and the conduction loss of the resonant circuit is reduced. These are the main problems solved by this patent.

[0005] However, the topological circuit proposed in the patent also has its disadvantages: first, the resonant circuit uses two inductors, and the peak current of one of the inductors reaches or exceeds the load current during resonance. Although the inductor flows with a pulse current during resonance, the total inductor equivalent current is very large during operation, and the current increases with the increase of the load current. This causes the coil cross-sectional area of the inductor to be designed to be larger, so that the overall inductor (9) size is larger. Although the back-stage inverter realizes soft switching, reduces the heat generation of the inverter bridge part, and can reduce the heat sink requirements, the existence of the large-size inductor makes it impossible to reduce the overall size of the driver, and there is no way to talk about the realization of a high-power density driver; secondly, the topological circuit can only achieve further reduction of the power consumption of the resonant circuit in conjunction with its improved special SPWM modulation method, which is another advantage claimed by the invention; however, for the current high-performance motor drive, especially the SVPWM (space vector PWM) modulation method generally used in servo drive, if it is used in the topological circuit, the advantages claimed by the invention may be greatly reduced.

[0006] Another invention, application publication number, CN106787903A, proposes a resonant extremely soft switching inverter circuit for brushless DC motor drive. The claimed advantage of the resonant circuit scheme proposed in the invention is that it eliminates the power switch connected in series to the DC bus in the traditional resonant circuit, thereby eliminating the conduction loss of this part to improve the system efficiency; in addition, the invention claims that the resonant circuit used uses fewer resonant components than the traditional resonant circuit, thereby reducing the circuit cost and complexity, and reducing the overall volume size of the inverter.

[0007] However, the disadvantage of this invention is that the switch tube of the lower arm of the inverter bridge is connected in parallel with a resonant capacitor, which together with other resonant elements constitutes a resonant circuit; while the three power switches of the upper bridge arm are not connected in parallel with the resonant capacitor, which destroys the symmetry and consistency of the working characteristics of the power switches on the upper and lower arms of the three-phase bridge, and will cause large harmonics in the current and voltage components of the motor and inconsistent working dynamic processes of the switch tubes of the upper and lower bridge arms, thereby affecting the working reliability; In addition, this invention designs a single-phase transformer connected in parallel in the DC bus loop and completes the resonance of the circuit together with other auxiliary switches. When the circuit resonates, the current amplitude flowing through the primary side of the transformer can be as high as twice the load current. This large current amplitude directly leads to an increase in the wire diameter of the transformer coil, thereby increasing the size of the transformer. When integrated into the circuit system, it is impossible to achieve a reduction in the overall driver size, and achieving high power density is even more empty talk.

[0008] Therefore, on the one hand, the resonance of the circuit must be achieved in order to realize the soft switching function; on the other hand, it is necessary to avoid excessively increasing the system cost and the system volume due to the resonant circuit, which ultimately fails to improve the power density of the driver.

[0009] Therefore, there is an urgent need in the market for a motor driver that not only has a soft-switching function, but also has a relatively small overall size of the resonant circuit topology, which better balances the relationship between the system size and the realization of the resonant function, thereby achieving the purpose of improving the power density of the driver, and has low heat generation and a low EMI level. Summary of the Invention

[0010] To solve the above technical problems, a method for a soft-switching motor drive topology circuit is disclosed in the present invention, and the technical solution of the present invention is implemented as follows:

[0011] A soft-switching motor drive circuit topology, characterized in that it includes a power supply, a main switch (2), an auxiliary switch one (3), an auxiliary switch two (4), a diode one (5), a diode two (6), a capacitor one (7), a capacitor two (8), an inductor (9) and an inverter (10); the power supply is a DC power supply; the power supply, the main switch (2), the auxiliary switch one (3), and the diode one (5) intersect at point a; the diode two (6), the main switch (2), and the auxiliary switch two (4) intersect at point b; point b is connected to point c; the capacitor one (7), the capacitor two (8), and the inverter (10) intersect at point c and point h; the auxiliary switch one (3), the diode two (6), and the diode intersect at point d; the diode, the auxiliary switch two (4), and one end of the capacitor one (7) and the capacitor two (8) intersect at point e; the power supply and the diode two (6) intersect at point f; the other ends of the capacitor one (7) and the capacitor two (8) are connected to point g, point f is connected to point g, and point g is connected to point h.

[0012] Preferably, the main switch (2), the auxiliary switch one (3), and the auxiliary switch two (4) are power semiconductor switches.

[0013] Preferably, the diode two (6), the diode C, and the diode one (5) are power diodes.

[0014] Preferably, the capacitor one (7) and the capacitor two (8) are capacitors.

[0015] Preferably, the inductor (9) is a power inductor (9).

[0016] Preferably, the type of the main switch (2) is the same as that of the power switches on the bridge arm of the inverter (10).

[0017] Preferably, a capacitor C (11) is connected in parallel with the diode two (6).

[0018] Preferably, the peak value of the current flowing through the inductor (9) is determined by circuit parameters and control.

[0019] Implementing the technical solution of the present invention can solve the technical problems in the prior art, such as a large number of power devices in the system resonance unit, complex control, a relatively large volume size of the resonance unit, and the inability to balance the relationship between the system volume size and the realization of the resonance function, which in turn leads to a low power density of the driver, high heat generation, and a high EMI level. Implementing the technical solution of the present invention can achieve a system resonance unit with fewer power devices, simple control, a relatively small volume size, and a better balance between the system volume size and the realization of the resonance function, thereby enabling a high power density of the driver, having a lower heat generation and a low EMI level. Description of the Drawings

[0020] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only one embodiment of the present invention. For those of ordinary skill in the art, without creative efforts, other implementation manners can also be obtained based on these drawings.

[0021] Figure 1 It is a topological diagram of a soft-switching motor drive circuit;

[0022] Figure 2 It is a path diagram of the initial state of a soft-switching motor drive circuit topology circuit;

[0023] Figure 3 It is a path diagram of t0 - t1 of a soft-switching motor drive circuit topology circuit;

[0024] Figure 4 It is a path diagram of t1 - t2 of a soft-switching motor drive circuit topology circuit;

[0025] Figure 5 It is a path diagram of t2 - t3 of a soft-switching motor drive circuit topology circuit;

[0026] Figure 6 It is a path diagram of t3 - t4 of a soft-switching motor drive circuit topology circuit;

[0027] Figure 8 It is a topological diagram of a preferred embodiment of the circuit topology of a soft-switching motor drive circuit topology circuit.

[0028] In the above drawings, each reference numeral represents:

[0029] 1 - Power supply, 2 - Main switch (2), 3 - Auxiliary switch one (3), 4 - Auxiliary switch two (4), 5 - Diode one (5), 6 - Diode two (6), 7 - Capacitor one (7), 8 - Capacitor two (8), 9 - Inductor (9), 10 - Inverter (10), 11 - C capacitor (11).

[0030] Figure 7 It is the path diagram of each time period of a soft - switch motor drive circuit topology circuit.

[0031] In Figure 7 each figure number mark respectively represents:[[]]END]]

[0032] T1 - State of the main switch (2), T2 - State of the auxiliary switch one (3), T3 - State of the auxiliary switch two (4), V cr1 - Voltage of capacitor one (7), V cr2 - Voltage of capacitor two (8), i Lr - Current of inductor (9), i cr2 - Current of diode two (6), i DC - Load current. Specific implementation manner

[0033] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the scope of protection of the present invention.

[0034] In a specific embodiment, such as Figures 1-6As shown, a soft-switching motor drive circuit topology, characterized in that it includes a power supply (1), a main switch (2), a first auxiliary switch (3), a second auxiliary switch (4), a first diode (5), a second diode (6), a first capacitor (7), a second capacitor (8), an inductor (9) and an inverter (10); the power supply (1) is a DC power supply (1); the power supply (1), the main switch (2), the first auxiliary switch (3), and the first diode (5) intersect at point a; the second diode (6), the main switch (2), and the second auxiliary switch (4) intersect at point b; point b is connected to point c; the first capacitor (7), the second capacitor (8), and the inverter (10) intersect at point c and point h; the first auxiliary switch (3), the second diode (6), and the diode intersect at point d; the diode, the second auxiliary switch (4), and one end of the first capacitor (7) and the second capacitor (8) intersect at point e; the power supply (1) and the second diode (6) intersect at point f; the other ends of the first capacitor (7) and the second capacitor (8) are connected to point g, point f is connected to point g, and point g is connected to point h; the main switch (2), the first auxiliary switch (3), and the first diode (5) are power switches; the first capacitor (7) and the second capacitor (8) are capacitors; the inductor (9) is a power inductor (9); the type of the main switch (2) is the same as that of the power switches on the bridge arm of the inverter (10) to ensure that their power levels are the same.

[0035] In this specific embodiment, at the initial state, i.e., at t0, the main switch (2) is in the conducting state, the first auxiliary switch (3) and the second auxiliary switch (4) are in the off state, and the switching tubes of the inverter (10) are also in the conducting state. The direction of current flow is a, b, c, h, g, f. Then, the main switch (2) is turned off, and the first capacitor (7) discharges. After the discharge of the first capacitor (7) is completed and the voltage drops to 0, at this time, i.e., at t1, the input voltage of the inverter (10) drops to 0, and the power switches on the inverter (10) achieve zero-voltage state switching, thereby realizing ZVS switching. After the power switches of the inverter (10) achieve ZVS state switching, the first auxiliary switch (3) is turned on, and the current flows along the direction of a, d, e, g, f to charge the second capacitor (8) until the voltage of the second capacitor (8) reaches the voltage of the power supply (1). At the moment of t2, then the second auxiliary switch (4) is turned on. At this time, the direction of the current is a, d, e, b, c, h, g, f. At this time, the current flowing through the inductor (9) continues to increase until the current of the inductor (9) reaches the peak value. At this time, i.e., at t3, the first auxiliary switch (3) is turned off. At this time, the direction of the current flow is from a, b, c, h, g, (f, d, e) / (e), b. At the same time, since the inductor (9) changes to the freewheeling state, the voltage at the rear stage of the second auxiliary switch (4) is higher than the voltage of the front-stage DC bus, and the DC voltage is instantly elevated, higher than the voltage of the power supply (1), which causes the first diode (5) connected in parallel with the main switch (2) to conduct forward. After the first diode (5) conducts forward, the main switch (2) also conducts simultaneously, thereby realizing the zero-voltage turn-on of the main switch (2). After the main switch (2) is turned on, the voltage of the power supply (1) supplies current to the load through the main switch (2). At the same time, because the second auxiliary switch (4) is still in the conducting state, the freewheeling continues, and the capacitor continues to discharge, which causes the current at point c to be higher than the load current, and then causes the first capacitor (7) to be charged. When the freewheeling ends, i.e., at t4, the second auxiliary switch (4) is disconnected, thereby returning to the initial state. Through the resonant working process of the above circuit, not only the soft-switching function is realized, but also the overall volume size of the resonant circuit topology is relatively small, which better balances the relationship between the system volume size and the realization of the resonant function, so as to achieve the purpose of improving the power density of the driver, and has a lower heat generation and a low EMI level.

[0036] In a preferred embodiment, as Figure 8 shown, a third capacitor (11) is connected in parallel with the second diode (6).

[0037] In this preferred embodiment, a capacitor with a relatively small power capacity, i.e., the third capacitor (11), is connected in parallel across the second diode (6) for the purpose of assisting the instant elevation of the voltage of the rear-stage DC bus during the freewheeling of the inductor (9), so as to force the first diode (5) to conduct, which helps to more easily realize the zero-voltage conduction of the main switch (2) under light load.

[0038] In a preferred embodiment, the peak value of the current flowing through the inductor (9) is determined by circuit parameters and control. In this preferred embodiment, it is required that the peak current flowing through the inductor (9) does not exceed the load current or the rated design current of the driver. If the peak current of the inductor (9) exceeds the load current, it may cause damage to the inverter (10) due to overload; the specific peak value can be determined as other current values according to the design requirements, and the magnitude of the current value determines the final size of the inductor (9). Since the inductor (9) current is pulsed and appears only once in each resonant cycle after each soft-switching transition, the effective current is actually very small, and the size of the inductor (9) coil is small; specifically, in terms of operation, by controlling the on-off time of the switching transistor in the resonant circuit, the peak value of the current flowing through the inductor (9) can be controlled.

[0039] It should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A soft-switching motor drive circuit topology, characterized in that: It includes a power supply, a main switch (2), a first auxiliary switch (3), a second auxiliary switch (4), a first diode (5), a second diode (6), a first capacitor (7), a second capacitor (8), an inductor (9) and an inverter (10); The power supply is a DC power supply; The power supply, the main switch (2), the first auxiliary switch (3) and the first diode (5) intersect at point a; The first diode (5), the main switch (2) and the second auxiliary switch (4) intersect at point b; Point b is connected to point c; The first capacitor (7) and the inverter (10) intersect at point c and point h; The first auxiliary switch (3), the second diode (6) and the inductor (9) intersect at point d; One end of the inductor (9), the second auxiliary switch (4) and the second capacitor (8) intersect at point e; The power supply and the second diode (6) intersect at point f; The other ends of the first capacitor (7) and the second capacitor (8) are connected to point g, point f is connected to point g, and point g is connected to point h; The main switch (2), the first auxiliary switch (3) and the first diode (5) are power switches; The peak value of the current flowing through the inductor (9) is determined by circuit parameters and control; The positive pole of the second diode (6) is connected to point f, and the negative pole is connected to point d; The positive pole of the first diode (5) is connected to point b, and the negative pole is connected to point a.

2. The soft-switching motor drive circuit topology circuit according to claim 1, characterized in that: The main switch (2), the first auxiliary switch (3) and the second auxiliary switch (4) are power semiconductor switches; 3. A soft-switching motor drive circuit topology according to claim 2, characterized in that: The power capacities of the first auxiliary switch (3) and the second auxiliary switch (4) are smaller than that of the main switch (2); 4. A soft-switching motor drive circuit topology circuit according to claim 1, characterized in that: The second diode (6) and the first diode (5) are power diodes; 5. A soft-switching motor drive circuit topology circuit according to claim 1, characterized in that: The inductor (9) is a power inductor (9); 6. The soft-switching motor drive circuit topology according to claim 1, characterized in that: The type of the main switch (2) is the same as that of the power semiconductor switch on the bridge arm of the inverter (10); 7. A soft-switching motor drive circuit topology according to any one of claims 1-6, characterized in that: A third capacitor (11) is connected in parallel with the second diode (6).

Images