阅读说明：本技术 一种逆变电路 (Inverter circuit ) 是由 林川川 李启国 肖隆兴 赵小坤 于 2019-10-16 设计创作，主要内容包括：本发明提供一种逆变电路,包括至少一条支路及驱动模块,每条支路的两端均分别连接至直流电源的正极和负极,每条支路上均设有两个导通方向相同的开关元件,驱动模块分别对应输出第一PWM驱动信号和第二PWM驱动信号至处于同一支路上的两个开关元件,以控制每条支路上的其中一个开关元件导通,另一个开关元件关断,该逆变电路还包括第一检测模块和第一比较模块；第一检测模块与处于同一支路上的两个开关元件的公共端相连,用于检测公共端输出的电压信号；第一比较模块用于将检测到的公共端输出的电压信号与预设的PWM信号作比较；若检测到的公共端输出的电压信号与预设的PWM信号相匹配,则判定开关元件的开关状态正常；否则判定开关元件的开关状态异常。(The invention provides an inverter circuit, which comprises at least one branch circuit and a driving module, wherein two ends of each branch circuit are respectively connected to the anode and the cathode of a direct-current power supply, two switching elements with the same conduction direction are arranged on each branch circuit, the driving module respectively and correspondingly outputs a first PWM driving signal and a second PWM driving signal to the two switching elements on the same branch circuit so as to control the conduction of one switching element on each branch circuit and the turn-off of the other switching element, and the inverter circuit also comprises a first detection module and a first comparison module; the first detection module is connected with the common end of the two switching elements on the same branch and used for detecting a voltage signal output by the common end; the first comparison module is used for comparing the detected voltage signal output by the public end with a preset PWM signal; if the detected voltage signal output by the common terminal is matched with a preset PWM signal, judging that the switching state of the switching element is normal; otherwise, the switching state of the switching element is judged to be abnormal.)

1. An inverter circuit comprises at least one branch and a driving module, wherein two ends of each branch are respectively connected to the anode and the cathode of a direct-current power supply, two switching elements which are identical in conduction direction and are mutually connected in series are arranged on each branch, and the driving module respectively and correspondingly outputs a first PWM (pulse width modulation) driving signal and a second PWM driving signal to the two switching elements on the same branch so as to control one switching element on each branch to be conducted and the other switching element to be switched off;

the first detection module is connected with a common end of the two switch elements on the same branch and used for detecting a voltage signal output by the common end;

the first comparison module is connected with the first detection module and used for comparing the detected voltage signal output by the public end with a preset PWM signal;

if the detected voltage signal output by the common terminal is matched with a preset PWM signal, judging that the switching state of the switching element is normal; and if the detected voltage signal of the common terminal is not matched with a preset PWM signal, judging that the switching state of the switching element is abnormal.

2. The inverter circuit according to claim 1, further comprising a protection module for activating a circuit protection function when a switching state of the switching element is abnormal.

3. The inverter circuit according to claim 2, wherein the protection module is the driving module, the driving module is connected to an output end of the first comparison module, and when the first comparison module determines that the switching state of the switching element is abnormal, the driving module stops sending the driving signal to the switching element to protect the inverter circuit.

4. The inverter circuit according to claim 1, wherein the first comparing module compares the detected voltage signal outputted from the common terminal with a preset PWM signal after a first delay time elapses from the start of the detection of the voltage signal outputted from the common terminal by the first detecting module;

the magnitude of the first delay time is determined by the dead time of the phase and/or the time required for transmitting the voltage signal output by the common terminal to the first comparison module.

5. The inverter circuit according to claim 1, wherein the first detection module comprises an optical coupler, and the optical coupler is connected between the common terminal and the first comparison module, and is configured to step down a voltage signal of the common terminal and send the voltage signal to the first comparison module.

6. The inverter circuit of claim 1, wherein the first detection module further comprises a first current limiting resistor for reducing current flowing through the first detection module.

7. The inverter circuit of claim 1, further comprising a second detection module and a second comparison module;

the second detection module is connected with the control end of the switch element and used for detecting the first PWM driving signal;

the second comparison module is connected with the second detection module and used for comparing the detected first PWM driving signal with a preset PWM standard signal;

if the detected first PWM driving signal is matched with a preset PWM standard signal, judging that the first PWM driving signal is normal; and if the detected first PWM driving signal is not matched with a preset PWM standard signal, judging that the first PWM driving signal is abnormal.

8. The inverter circuit according to claim 7, wherein a circuit protection function is activated when it is determined that the first PWM drive signal is abnormal.

9. The inverter circuit according to claim 7,

the second comparison module compares the detected first PWM driving signal with the preset PWM standard signal only when a second delay time elapses from the start of the detection of the first PWM driving signal by the second comparison module;

the magnitude of the second delay time is determined by the time required for the first PWM driving signal to be transmitted to the second comparison module.

10. The inverter circuit of claim 7, wherein the second detection module further comprises a second current limiting resistor for reducing current through the second detection module.

11. The inverter circuit according to claim 1, wherein the switching element is an IGBT.

Technical Field

The invention relates to the technical field of power supplies, in particular to an inverter circuit.

Background

Switching elements such as Insulated Gate Bipolar Transistors (IGBTs) are core switching elements in inverters. The switching element can be turned on by applying a driving signal to the control terminal of the switching element, thereby controlling the switching element to be turned on and off. The inverter converts dc power to ac power by switching elements such as IGBTs.

However, when the inverter converts the dc power into the ac power by turning on and off the switching element, if the switching element cannot be normally switched on and off, the circuit protection needs to be started in time, so as to avoid the controller from being burned out or the control from being failed. For how to monitor whether the switching element can be normally switched, the prior art generally monitors and collects the driving signal of the switching element and compares the driving signal with a preset PWM signal to determine whether the driving signal meets the expectation. When the driving signal is normal, the controller judges that the switching element can be normally switched on and off, so that the circuit protection is not started; when the unexpected distortion of the driving signal occurs, the controller judges that the switching element can not be normally switched, thereby starting the circuit protection. However, when the driving signal is normal and the switching element itself fails, the prior art cannot monitor the failure of the switching element itself and determine that the switching element cannot be normally switched to start the circuit protection, which may cause the controller to burn out or the control to fail.

Disclosure of Invention

The invention aims to provide an inverter circuit which can monitor the fault of a switching element and judge that the switching element can not be switched normally when a driving signal is normal and the switching element has a fault.

The invention provides an inverter circuit, which comprises at least one branch circuit and a driving module, wherein two ends of each branch circuit are respectively connected to the anode and the cathode of a direct-current power supply, two switching elements which are identical in conduction direction and mutually connected in series are arranged on each branch circuit, the driving module respectively and correspondingly outputs a first PWM (pulse width modulation) driving signal and a second PWM driving signal to the two switching elements on the same branch circuit so as to control one switching element on each branch circuit to be conducted, and the other switching element is switched off, and the inverter circuit also comprises a first detection module and a first comparison module;

the first detection module is connected with the common end of the two switching elements on the same branch and used for detecting a voltage signal output by the common end;

the first comparison module is connected with the first detection module and used for comparing the detected voltage signal output by the public end with a preset PWM signal;

if the detected voltage signal output by the common terminal is matched with a preset PWM signal, judging that the switching state of the switching element is normal; and if the detected voltage signal of the common terminal is not matched with the preset PWM signal, judging that the switching state of the switching element is abnormal.

Furthermore, the inverter circuit further comprises a protection module for starting a circuit protection function when the switching state of the switching element is abnormal.

Further, the protection module is a driving module, the driving module is connected with the output end of the first comparison module, and when the first comparison module determines that the switching state of the switching element is abnormal, the driving module stops sending a driving signal to the switching element so as to protect the inverter circuit.

Further, the first comparing module compares the detected voltage signal output by the common terminal with a preset PWM signal after a first delay time elapses from the start of the detection of the voltage signal output by the common terminal by the first detecting module;

the magnitude of the first delay time is determined by the dead time of the phase and/or the time required for transmitting the voltage signal output by the common terminal to the first comparison module.

Further, the first detection module comprises an optical coupler, the optical coupler is connected between the public end and the first comparison module, and the first detection module is used for sending the voltage signal of the public end to the first comparison module after voltage reduction processing.

Furthermore, the first detection module further comprises a first current limiting resistor, and the first current limiting resistor is used for reducing the current flowing through the first detection module.

Further, the device also comprises a second detection module and a second comparison module;

the second detection module is connected with the control end of the switch element and used for detecting the first PWM driving signal;

the second comparison module is connected with the second detection module and used for comparing the detected first PWM driving signal with a preset PWM standard signal;

if the detected first PWM driving signal is matched with a preset PWM standard signal, judging that the first PWM driving signal is normal; and if the detected first PWM driving signal is not matched with the preset PWM standard signal, judging that the first PWM driving signal is abnormal.

Further, the circuit protection function is started when it is determined that the first PWM drive signal is abnormal.

Further, after a second delay time elapses since the second comparing module starts detecting the first PWM driving signal, the second comparing module compares the detected first PWM driving signal with a preset PWM standard signal;

the second delay time is determined by the time required for the first PWM driving signal to be transmitted to the second comparison module.

Furthermore, the second detection module further comprises a second current limiting resistor, and the second current limiting resistor is used for reducing the current flowing through the second detection module.

Further, the switching element is an IGBT.

The inverter circuit comprises a first detection module and a first comparison module; the first detection module is connected with the common end of the two switching elements on the same branch and used for detecting a voltage signal output by the common end; the first comparison module is connected with the first detection module and used for comparing the detected voltage signal output by the public end with a preset PWM signal; if the detected voltage signal output by the common terminal is matched with a preset PWM signal, judging that the switching state of the switching element is normal; if the detected voltage signal of the common terminal is not matched with the preset PWM signal, the switching state of the switching element is judged to be abnormal, so that when the driving signal is normal and the switching element is in fault, the inverter circuit can monitor the fault of the switching element and judge that the switching element cannot be normally switched.

Drawings

Fig. 1 is a schematic diagram of an inverter circuit in which an inverter converts dc power into three-phase ac power by switching of IGBTs.

Fig. 2 is a partial structural diagram of an inverter circuit according to an embodiment of the invention.

Detailed Description

The following detailed description of embodiments of the present invention is provided in connection with the accompanying drawings and examples. The following examples are intended to illustrate the invention but are not intended to limit the scope of the invention.

The inverter circuit comprises at least one branch circuit, wherein the branch circuits are respectively connected in parallel, two ends of each branch circuit are respectively connected to the positive electrode and the negative electrode of a direct-current power supply, and two switching elements which are identical in conduction direction and mutually connected in series are arranged on each branch circuit. The inverter circuit controls one of the switching elements on each branch circuit to be switched on, and the other switching element to be switched off, so that the conversion from direct current to alternating current is realized. The switching element may be an IGBT, a BJT, or the like, and the IGBT is taken as an example in the present invention.

Fig. 1 is a schematic diagram of an inverter circuit in which an inverter converts dc power into three-phase ac power by switching of IGBTs. As shown in fig. 1, the inverter circuit includes three branches connected in parallel, two ends of the three branches are respectively connected to the positive electrode and the negative electrode of the dc power supply, each branch is provided with two IGBTs 1, 1 'having the same conduction direction and connected in series, each IGBT is connected in parallel with a diode 2 having a conduction direction opposite to the conduction direction of the IGBT, and the common ends of the IGBTs 1, 1' connected in series in each branch are respectively connected to the three-phase winding of the motor (PMSM) to form three-phase voltages Ua, Ub, Uc. Of course, in other embodiments, the inverter circuit may include two branches to obtain two-phase alternating current; or only one branch to obtain single-phase alternating current.

The inverter circuit further comprises a driving module 3, and the driving module 3 correspondingly outputs a first PWM driving signal and a second PWM driving signal to the IGBT1 and the IGBT 1' on the same branch circuit respectively. While the first PWM drive signal applies a forward voltage to one of the IGBTs 1, the second PWM drive signal applies a reverse voltage to the other IGBT 1'; when the first PWM driving signal applies a reverse voltage to one of the IGBTs 1, the second PWM driving signal applies a forward voltage to the other IGBT, thereby controlling one of the IGBTs on each leg to turn on, and the other IGBT to turn off.

Referring to fig. 2, the inverter circuit further includes a first detecting module and a first comparing module. The first detection module is connected to a common terminal of two IGBTs 1 on the same branch for detecting a voltage signal output by the common terminal. The first comparison module is connected with the first detection module and used for comparing the detected voltage output by the public end with a preset PWM signal. If the detected voltage output by the common terminal is matched with a preset PWM signal, judging that the switching state of the IGBT is normal; and if the detected voltage output by the common terminal is not matched with the preset PWM signal, judging that the switching state of the IGBT is abnormal.

Specifically, the preset PWM signal may be set to two voltage values including high and low levels. When the IGBT connected with the positive pole of the direct-current power supply on a certain branch needs to be turned on and the IGBT connected with the negative pole of the direct-current power supply on the branch is turned off, the first detection module detects voltage signals output by the common ends of the two IGBTs, the first comparison module compares the detected voltage signals output by the common ends with preset PWM signals, if the detected voltage signals output by the common ends are matched with the high level in the preset PWM signals, the switching states of the IGBTs 1 and 1 'connected with the positive pole of the direct-current power supply are judged to be normal, and otherwise, the switching states of the IGBTs 1 and/or the IGBT 1' are/is judged to be abnormal. Similarly, when the IGBT connected to the negative electrode of the dc power supply on the branch needs to be turned on and the IGBT connected to the positive electrode of the dc power supply on the branch needs to be turned off, the first detection module detects the voltage signal output by the common terminal of the two IGBTs, the first comparison module compares the detected voltage output by the common terminal with the preset PWM signal, and if the detected voltage signal output by the common terminal matches with the low level in the preset PWM signal, it is determined that the switching states of the IGBT1 and the IGBT1 'are normal, and otherwise, it is determined that the switching states of the IGBT1 and/or the IGBT 1' are abnormal.

Specifically, the preset PWM signal may also be the first PWM driving signal, or a signal obtained by performing delay processing on the first PWM driving signal.

Referring back to fig. 1, as mentioned above, the inverter controls one of the IGBTs 1 on each branch and the other IGBT1 off to convert dc power to ac power, that is, theoretically, only one IGBT1 on each branch is turned on. However, when the on IGBT in a branch is switched off and the off IGBT is switched on, the two IGBTs in the phase are simultaneously turned off to prevent a short circuit due to the simultaneous on of the two IGBTs, and the time during which the two IGBTs are simultaneously turned off is called a dead time. In the dead time, the current direction on the branch circuit is based on the current direction of a PMSM motor winding, and the current can flow through the upper end diode of the branch circuit and flow back to the PMSM motor through the lower end diodes of the other two branch circuits; current may also flow from the lower diode of the branch and into the PMSM machine. In the dead time, the current direction on the branch is unstable, and the voltage signal of the common end of the two series-connected IGBTs on the branch is also unstable. The dead time is passed from the beginning of the first detection module detecting the voltage signal of the common terminal, and the voltage signal of the common terminal detected in the dead time is not stable. After the dead time, the voltage signal of the public terminal detected by the first detection module is a stable signal. In addition, a certain time is required for the voltage signal of the common terminal to be transmitted to the first comparison module. Therefore, the first comparing module compares the detected voltage signal output by the common terminal with the preset PWM signal only after the first delay time elapses from the start of the detection of the voltage signal output by the common terminal by the first detecting module; the magnitude of the first delay time is determined by the dead time of the phase and/or the time required for transmitting the voltage signal output by the common terminal to the first comparison module. Therefore, unstable voltage signals output by the public end in the dead time can be avoided, and stable voltage signals output by the public end after the dead time are sent to the first comparison module to be compared with the preset PWM signals. In addition, since a certain time is required for the stable voltage signal output by the common terminal to be transmitted to the first comparison module, the time required for the voltage signal output by the common terminal to be transmitted to the first comparison module is taken into account, so that the comparison result of the first comparison module can be more accurate.

Furthermore, the inverter circuit also comprises a protection module which is used for starting a circuit protection function when the state of the IGBT switch is abnormal. The protection module can be in various forms, in this embodiment, the protection module is a driving module, the driving module 3 is connected to an output end of the first comparison module, and when the first comparison module determines that the switching state of the IGBT is abnormal, the driving module 3 stops sending a driving signal to the IGBT to protect the inverter circuit.

Further, the first detection module further comprises an optical coupler 4, and the optical coupler 4 is connected between the common end of the two IGBTs and the first comparison module, and is used for sending the voltage signal of the common end to the first comparison module after voltage reduction processing. By carrying out voltage reduction processing on the voltage signal of the public end, the voltage signal with lower level can be sent to the first comparison module, so that comparison can be carried out in a safer mode. Further, the first detection module further includes a first current limiting resistor R1, and the first current limiting resistor R1 is used for reducing the current flowing through the first detection module, so as to protect the first detection module.

Further, the inverter circuit further comprises a second detection module and a second comparison module. The second detection module is connected with a gate pole of the IGBT and used for detecting the first PWM driving signal. The second comparison module is connected with the second detection module and used for comparing the detected first PWM driving signal with a preset PWM standard signal. If the detected first PWM driving signal is matched with a preset PWM standard signal, judging that the first PWM driving signal is normal; and if the detected first PWM driving signal is not matched with the preset PWM standard signal, judging that the first PWM driving signal is abnormal. The circuit protection function may be activated when it is determined that the first PWM driving signal is abnormal.

In addition, after the second comparison module starts to detect the first PWM driving signal, the second comparison module compares the detected first PWM driving signal with a preset PWM standard signal after a second delay time elapses; the second delay time is determined by the time required for the first PWM driving signal to be transmitted to the second comparison module. By taking into account the time required for the first PWM driving signal to be transmitted to the second comparison module, the comparison result of the second comparison module can be made more accurate.

Further, the second detection module further includes a second current limiting resistor R2, and the second current limiting resistor R2 is used for reducing the current flowing through the second detection module, so as to protect the second detection module.

In summary, the inverter circuit of the present invention includes a first detecting module and a first comparing module; the first detection module is connected with the common end of the two switching elements on the same branch and used for detecting a voltage signal output by the common end; the first comparison module is connected with the first detection module and used for comparing the detected voltage signal output by the public end with a preset PWM signal; if the detected voltage signal output by the common terminal is matched with a preset PWM signal, judging that the switching state of the switching element is normal; if the detected voltage signal of the common terminal is not matched with the preset PWM signal, the switching state of the switching element is judged to be abnormal, so that when the driving signal is normal and the switching element is in fault, the inverter circuit can monitor the fault of the switching element and judge that the switching element cannot be normally switched.

The technical features of the above embodiments can be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the above embodiments are not described, but should be considered as the scope of the present specification as long as there is no contradiction between the combinations of the technical features.

The above description is only for the specific embodiments of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art can easily conceive of the changes or substitutions within the technical scope of the present invention, and the changes or substitutions should be covered within the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.