Voltage-current transformation method

Abstract

The invention provides a voltage-current transformation circuit, which comprises an amplifier. Input voltage is connected with a non inverting input end of the amplifier, an inverted input end of the amplifier is grounded. The transformation circuit is characterized in that the output end of the amplifier is connected with a base electrode of Darlington circuit; a first resistance is bridged between the non inverting input end of the amplifier and a collector of the Darlington circuit; a second resistance is bridged between the inverted input end of the amplifier and the anode of a power supply; a third resistance is connected between the second resistance and the first resistance; and an emitter of the Darlington circuit is grounded by a fourth resistance. The circuit has the advantages of high accuracy, good thermal stability, linearity and anti-interference performance, and stable and reliable working performance. A plurality of the voltage-current transformation circuits can be accessed to one voltage point (common-grounded) simultaneously, meanwhile measure and transmit, and realize the common-grounded circulation detection of multiple fault signals. The circuit is high in cost performance, simple and easy in implementation.

Description

A Method of Voltage-Current Transformation technical field The invention relates to a voltage-current conversion method, which is used for various detection devices such as phase loss, overvoltage, undervoltage, device overcurrent, optical fiber disconnection, unit overtemperature, etc. in transmission instruments and high-voltage frequency converter power units. Among them, it belongs to the technical field of voltage-current conversion circuit. Background technique In the current unit series high-voltage frequency conversion technology scheme, each power unit works relatively independently. After receiving power, it goes through the process of rectification, filtering, auxiliary power start, receiving control signals, etc., and then enters normal frequency conversion and output power. During normal operation, the unit controller needs to actively detect various fault information, such as input phase loss, overvoltage, undervoltage, device overcurrent, fiber break, unit o...

AI Technical Summary

Problems solved by technology

Because as shown in Figure 1, since the negative signal end of the resistor RL1 is grounded, the resistor R1 will be short-circuited to the ground, and the resistor R1 is the key to determine the proportional coefficient in the function Io1=Vi1 / R1, and Io1 is the current on the resistor RL1, from It can be seen from this mathematical model that if R1=0, then Io1=∞, the circuit cannot work normally; Io2 is all shunted to the ground. In fact, the positive signal terminal of the resistor RL2 is the ground at this time, so there is no current output at this point.

For the roving detection of multi-channel signals, like the common ground detection, it is not possible to directly use a load-floating voltage-current converter or a load-grounding voltage-current converter with a floating input. If you want to use a load floating type For voltage-current converters or load-grounded voltage-current converters with floating input, other circuit configurations must be added, which makes the circuit structure complex; if a load-grounded voltage-current converter with input and output in different phases is used , as shown in Figure 3, because the direction of the current Io3 on the resistor RL3 is just opposite to the direction of Vi3, so each detection loop needs to add an inverting amplifier, which will also complicate the circuit

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