Method for detecting capacitance value of bootstrap capacitor on line
A bootstrap capacitance and capacitance technology, which is applied in capacitance measurement, electrical variable measurement, resistance/reactance/impedance measurement, etc., can solve problems such as failure of power devices, failure to charge, large heat generation, etc., to ensure normal operation, Reduce downtime and stop production, and the effect of economic benefits is obvious
Pending Publication Date: 2021-11-16
长沙市创安电气有限公司
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Problems solved by technology
[0003] It can be seen that the role of the bootstrap capacitor is very important. The selection of the capacitance value of the capacitor is very critical. If the capacitance value is too small, it will not be able to store enough charge to complete the turn-on of the power tube of the upper bridge. The voltage value of the upper bridge power tube cannot be turned on
In view of this, bootstrap capacitors cannot be connected in parallel like power supply capacitors to increase the reliability and redundancy of the system. At the same time, bootstrap capacitors generally need to be installed close to power devices, which generate a lot of heat when they work. exacerbated the capacitance drop of the bootstrap capacitor
Once the capacitance of the bootstrap capacitor drops, it will cause the failure of the entire power device
Method used
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Embodiment 1
[0019] The method for on-line detection of the bootstrap capacitance provided by the present invention can be used in power switch circuits of single-phase full bridge, two-phase, three-phase and multi-phase full bridge, and a three-phase circuit is taken as an example now.
[0020] like figure 2 As shown, T1, T3, and T5 are power transistors of the three-phase upper bridge, and each of these three power transistors has a bootstrap circuit including a resistor, a bootstrap capacitor, and a bootstrap diode. T2, T4, T6 are the power tubes of the three-phase lower bridge. Now take the process of detecting the bootstrap capacitor of the T1 bootstrap circuit as an example as follows: 1. Turn off T3, T4, T5, T6; 2. Turn on T2 for a certain fixed time S1, so as to charge the bootstrap capacitor of the bootstrap circuit of T1 with a certain charge Q1; 3. Turn off T2, turn on T4, and switch the pulse sequence of the continuous turn-on time of S2 and turn-off time of S3 in the power t...
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The invention discloses a method for detecting the capacitance value of a bootstrap capacitor on line. The method comprises the steps that: the bootstrap capacitor is charged with the electric quantity of an electric quantity Q at a fixed time T, the electric quantity Q is consumed through continuous switching, and a total switching frequency is calculated as X1; the bootstrap capacitor is charged with the electric quantity of an electric charge quantity Q again within the fixed time T, the electric charge quantity Q is consumed through continuous switching, a total switching frequency is calculated as X2, the real-time capacitance value C2 of the bootstrap capacitor is obtained through calculation according to the formula that C2 = C1 * X1 / X2, wherein C1 is the fixed capacitance value of the bootstrap capacitor. According to the method, the decreasing proportion of the capacitance value of the bootstrap capacitor is judged, an alarm can be given or a client can be reminded in advance, normal operation of a power device can be guaranteed, shutdown and production halt are reduced, and economic benefits are obvious.
Description
technical field [0001] The invention relates to the technical field of capacitance detection, in particular to a method for online detection of the capacitance of a bootstrap capacitor. Background technique [0002] The bootstrap circuit is widely used in electric drive devices, its principle is as attached figure 1 As shown, when the N-side IGBT is turned on, the power supply VD charges the bootstrap capacitor through the current-limiting resistor and the bootstrap diode, thereby providing driving power for the P-side IGBT. [0003] It can be seen that the role of the bootstrap capacitor is very important. The selection of the capacitance value of the capacitor is very critical. If the capacitance value is too small, it will not be able to store enough charge to complete the turn-on of the power tube of the upper bridge. The voltage value of the upper bridge cannot be turned on. In view of this, bootstrap capacitors cannot be connected in parallel like power supply capaci...
Claims
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IPC IPC(8): G01R27/26
CPCG01R27/2605
Inventor 周清泉刘金周
Owner 长沙市创安电气有限公司