CN2137363Y

CN2137363Y - Dc voltage isolated measuring device

Info

Publication number: CN2137363Y
Application number: CN 92225826
Authority: CN
Inventors: 杨民
Original assignee: NANCHANG ACADEMY OF NONFERROUS METALLURGY
Current assignee: NANCHANG ACADEMY OF NONFERROUS METALLURGY
Priority date: 1992-06-23
Filing date: 1992-06-23
Publication date: 1993-06-30
Anticipated expiration: 2002-06-23

Abstract

The utility model relates to a direct current voltage isolated measuring device and is mainly composed of a switch three-pole pipe, a base pole inputting coupling circuit of the switch three-pole pipe, an isolated transformer and a variable voltage dividing resistance cross connected at the two ends of the secondary coil of the isolated transformer. The first coil of the isolated transformer is connected in series on a switch three-pole pipe collecting electricity pole branch. The direct current voltage isolated measuring device has simple circuits and fewer components and is provided with a detecting outputting end without the common earth. Because the isolated transformer working far away from the magnetization curve saturation region is adopted, the direct current voltage isolated measuring device has the advantages of high accuracy, good linearity, high stability and reliability. The direct current voltage isolated measuring device is mainly used for a microcomputer control system or other automatic control systems and carries out the isolated measurement for a direct connected system without the electricity and the common earth or a direct current voltage in a unit.

Description

DC voltage isolated measuring device

The utility model relates to the device that adopts the Digital Measuring Technique measuring voltage, further relates to a kind of microcomputer control system and other automatic control system of being mainly used in to not altogether and do not have a device that DC voltage in electric direct-connected system or the unit is carried out isolation detection.

In microcomputer control system and other automatic control system, consider the anti-interference of system, the floating dummy status of mutual power supply and the inconsistency of level, when detecting the external voltage value, generally all need to take electric isolation method.Have now DC voltage isolation detection mode is mainly contained " straight one hands over always " mode and adopts Hall element mode, the former is an alternating voltage with the DC voltage inversion earlier, by being DC voltage with ac voltage rectifier again behind the isolating transformer, the dc voltage value before the DC voltage after the measurement rectification can obtain to isolate.This isolation detection device circuit more complicated, required components and parts are many, and reliability and precision owe poor, and latter's circuit is simple, reliable operation, but owing to reasons such as the not high and volume of precision are bigger, seldom adopt at present.

The purpose of this utility model is to propose a kind of DC voltage isolation detection device that is mainly used in Control System of Microcomputer and other automatic control system.

The utility model comes down to a kind of six end active networks of being furnished with shell.This six ends active network has two groups of input ends altogether, one group is detected voltage input end, be connected across the two ends of detected DC voltage, another group is to detect the control input end, be connected to the delivery outlet that microsystem is isolated through photoelectricity, also have one group and do not measure output terminal altogether, be connected to the input port of microsystem A/D analog to digital converter, for adopting the Digital Measuring Technique measuring voltage.

This six ends active network is by switch triode and base stage input coupling circuit thereof; primary coil is serially connected in the isolating transformer of switch triode collector branch road; be connected across the variable divider resistance at isolating transformer secondary coil two ends; and the fly-wheel diode that is connected across isolating transformer primary coil two ends, be connected across the voltage dependent resistor (VDR) between switch triode collector and emitter and be connected across, the protection diode between switch triode base stage and emitter forms.

The switch triode emitter is connected to detected voltage input end and detects holding of control input end commonly, it is common, be serially connected in an other end that is connected to detected voltage input end of the isolating transformer primary coil of collector branch road, be connected to the divider resistance of direct supply and switch triode base stage input coupling circuit two ends that capacitance is formed by one and be connected to respectively and detect the two ends, control input end, be connected across the end of variable divider resistance at isolating transformer secondary coil two ends and movable end and be connected to respectively and do not measure the output terminal two ends altogether.

When needs detect DC voltage, or in sense cycle, the delivery outlet output losing side ripple that microsystem is isolated through photoelectricity detects control signal, and its width is set according to the A/D analog-to-digital conversion rate of microsystem.Detecting the control input end is that the switch triode base stage obtained bias current by divider resistance and capacitance from direct supply after high level promptly was high-impedance state by low transition, enters the saturation conduction state.The DC voltage of detected voltage input end is by between collector that was added in switch triode originally and emitter and become on the primary coil that all is added in isolating transformer, induce the voltage that is approximately linear proportional relationship with detected DC voltage on the variable divider resistance of isolating transformer primary side, scale-up factor is determined by the transformation ratio of isolating transformer.Although the voltage on the variable divider resistance is exponential damping, because be constant switch triode conducting moment to A/D analog to digital conversion start-up time, and to set by microsystem software is strict, above-mentioned linear proportional relationship can be similar to establishment.After detection finished, detection control input end saltus step again was a low level, and capacitance back discharge, switch triode lose bias current and be in cut-off state again.The vital role of capacitance is when detecting the control input end and be in high-impedance state for a long time for some reason, can prevent to bear detected DC voltage for a long time between isolating transformer primary coil and switch triode collector and emitter and cause damage owing to the long-term conducting of switch triode makes.

The utility model circuit is simple, the employing components and parts are few, be provided with and do not measure output terminal altogether, can realize the DC voltage isolation detection, adopt the isolating transformer that works in away from the magnetization curve saturation region, because it has high-precision transformation ratio and good linearty, and not influenced by variation of ambient temperature, therefore, the utlity model has the measuring accuracy height, the good and stable and reliable operation characteristics of the linearity.

Accompanying drawing is an electrical schematic diagram of the present utility model.

Below in conjunction with embodiment and contrast accompanying drawing the utility model is made an explanation:

Embodiment is one and is useful for direct current cadmium-nickel accumulator screen to carry out the battery total voltage be that 180-270 volt and control busbar voltage are the DC voltage isolation detection devices of 220 volts measurements that the microsystem main frame is 8031 single-chip microcomputers, and the A/D analog-digital chip is 0809.The delivery outlet output width that process photoelectricity is isolated is that 5 milliseconds losing side ripple detects control signal.

Terminal A1, B1 are detected voltage input ends, and terminal A2, B2 detect the control input end, and wherein terminal B1, B2 are connected to common.Terminal A3, B3 do not measure output terminal altogether.

Switch triode BG adopts 2SD870, withstand voltage 1500 volts; Preventing from unexpected superpotential to occur and cause the voltage dependent resistor (VDR) YM selection parameter of damage between its collector and emitter is 400 volts of voltages, electric current 1000 peaces; Isolating transformer Tr adopts the common power transformer, and 5 volt-amperes of capacity, transformation ratio are 220/6.3, silicon sheet core band screen layer; Protection diode D1, sustained diode 2 adopt 1N4001, and variable divider resistance W adopts 1000 Europe, 0.25 watt of potentiometer; Direct supply E is 12 volts, and divider resistance R1, R2 are respectively 88 Europe, 39 Europe, and capacitance C adopts 10 microfarads, withstand voltage 50 volts of electrochemical capacitors.

Claims

1; a kind of DC voltage isolation detection device; be the six end active networks of being furnished with shell; two groups of input ends are altogether arranged; one group of detected voltage input end; be connected across the two ends of detected DC voltage; it is characterized in that another group detects the control input end; be connected to the delivery outlet that microsystem is isolated through photoelectricity; also have one group and do not measure output terminal altogether; be connected to the input port of microsystem A/D analog to digital converter; this six ends active network is by switch triode and base stage input coupling circuit thereof; primary coil is serially connected in the isolating transformer of switch triode collector branch road; be connected across the variable divider resistance at isolating transformer secondary coil two ends; and the fly-wheel diode that is connected across isolating transformer primary coil two ends; the protection diode that is connected across the voltage dependent resistor (VDR) between switch triode collector and emitter and is connected across between switch triode base stage and emitter is formed; the switch triode emitter is connected to detected voltage input end and detects holding of control input end commonly; it is common; be serially connected in an other end that is connected to detected voltage input end of the isolating transformer primary coil of collector branch road; be connected to the divider resistance of direct supply and switch triode base stage input coupling circuit two ends that capacitance is formed by one and be connected to respectively and detect the two ends, control input end, be connected across the end of variable divider resistance at isolating transformer secondary coil two ends and movable end and be connected to respectively and do not measure the output terminal two ends altogether.