Isolation detection circuit of DC bus voltage

Abstract

The invention discloses an isolation detection circuit of DC bus voltage, which comprises optical coupling elements and single-power dual-operational amplifiers. The output phototriodes of the two optical coupling elements BG1 and BG2 are connected in series, and the connection point is connected with the in-phase or out-phase input end of the first operational amplifier U1 to supply power at a low-voltage side through a DC power supply +E; one of the optical coupling elements is a detection optocoupler BG1, and the LED thereof is serially connected with a high-voltage resistor R1 to detect the DC bus voltage; the other one of the optical coupling elements is a feedback control optocoupler BG2; the two input ends of the operational amplifier U1 are connected with the opposite angles of the electrical bridge of equal-arm resistors R3, R4, R5 and R6 powered by the DC power supply, and the output of the operational amplifier U1 is serially connected with the LED of the feedback optocoupler; and the input current of the feedback optocoupler is converted into voltage through a resistor R7 and subjected to in-phase amplification by the operational amplifier U2 before output. The invention provides a new method for detecting a DC bus, which has the advantages of simple circuit, low cost, high measurement precision, good isolation effect and broad popularization and application prospect.

Description

technical field [0001] The invention relates to a voltage detection circuit, in particular to a switched reluctance motor speed control device and an isolation detection circuit for the DC bus voltage of the main circuit in the frequency conversion motor speed control. Background technique [0002] In the switched reluctance motor speed control device, the power inverter circuit is powered by the DC bus voltage. This is the output voltage of a three-phase bridge rectifier power supply with appropriate filter capacitors connected in parallel. After the AC grid is closed, the DC bus voltage rises slowly through the current-limiting resistor first, and then the current-limiting resistor is short-circuited. The power inverter circuit is allowed to work only when the DC bus voltage has reached a sufficiently large value. [0003] If the motor is in the state of power generation, the DC bus voltage will rise further, and its value is even greater than the peak value of the three...

AI Technical Summary

Problems solved by technology

[0007] In addition to the need for an isolated operational amplifier and auxiliary power supply on the DC bus side, the linear optocoupler solution has a major disadvantage, that is, the current in the output light-emitting diode is very small, the anti-interference ability is poor when detecting the DC bus voltage, and the detection error is relatively large.

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