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    Abstract: IR2175 is the high-pressured rectilinear current sensor which IR (International Rectifier) the company produces, it does not need through A/D to transform then may the direct output PWM digital signal, thus simplified the motor control electric circuit’s electric current examination and the protection operation, but uses in conveniently the motor-driven system. In the article introduced the IR2175 unique feature, the pin function and the principal characteristic, have given its model application electric circuit.

    Key word: IR2175; Rectilinear current sensor; Bootstrap circuit

1 outline

In the magnetoelectric machine or in asynchronous machine’s high performance AC servomechanism control, to realize the magnetic field orientation control, needs to examine at least two electrical machinery winding’s electric current. Usually uses the following three methods to survey the magnitude of current:

(1) uses the Hall electric current sensor

(2) sampling resistance and linear light pair coordination use

(3) uses in the sampling measure of resistance cocurrent bus bar the electric current, then obtains the electric current through the expansion software and hardware design calculation.

IR2175 is the international rectification company (IR) specially not brushes the high-pressured rectilinear current sensor which for the exchange or the cocurrent electrical machinery’s actuation application designs, its built-in electric current examination and the protection circuit, may obtain the winding electric current through the series in the winding return route’s sampling resistance, will not need a/D transformation chip to be able automatic to input the simulated signal to transform the digital PWM signal output, may direct and the processor is connected. The same tradition’s Hall electric current sensor compares, IR2175 has floats low, the digital PWM output, to be possible warm to simplify the interface circuit, not to need linear merits and so on light pair and A/D switch, 8 foot PDIP or SOIC seal. The IR2175 principal characteristic is as follows:

* has the voltage to reach as high as 600V the floating input channel;

* obtains the rectilinear current feedback through the sampling resistance;

* has the direct digital PWM output interface;

* the low IQBS permission support from lifts the power source power supply;

* has the independence fast overflow output signal;

* has the very strong syntype meaconing inhibiting ability;

●IGBT under the short circuit condition has the overvoltage protection;

* uses leaks the output mode.

2 pin functions and electrical specification

2.1 pin functions

IR2175 has 8 foot PDIP and 8 foot SOIC two kind of seal patterns, its pin arrangement as shown in Figure 1. Various pins’ function is as follows:

1 foot (VCC): Low end power source end;

2 feet (PO): Digital PWM out-port;

3 feet (COM): Low end place;

4 feet (OC): The overflow signal out-port, the low level is effective;

5 feet (NC): Spatial foot;

6 feet (VB): High-end floating power source voltage terminal;

7 feet (VS): High-end floating power source bias end;

8 feet (VIN ): Sampling voltage forward input end.

2.2 recommendation electricity parameter

The IR2175 recommendation operational parameter like table 1 arranges in order. What must explain is for enables the module the normal work, when the design generally should the recommendation working condition which gives according to IR Corporation carry on.

Table 1 recommendation operational parameter

3 basic functions and characteristic

Rectilinear current sensor IR2175 is for transforms the electric current signal from electrical machinery’s high-end driving circuit to the low end driving circuit designs, like this, obtains the electric current signal can facilitate carries on processing with the control circuit. Its simulator input is the series in the phase winding return route’s sample resistance pressure drop. Along with the electrical machinery interphase current’s change, in the sample resistance will produce a very small alternating voltage signal by to take IR2175 the input. Its output is the frequency is 130kHz, take the place as the reference, the dutyfactor along with the electric current size change PWM digital signal, after undergoing the level switch, 煟 the school wishes holds the lotus root bubbles to transform take the place as the reference point signal. IR2175 output signal dutyfactor scope from 9% to 91%, when in the input sampling resistance’s pressure drop is 0, when is the interphase current is 0, output signal’s dutyfactor is 50%; Output voltage’s range of variation from - 260mV when surpasses this scope to the 260mV 煹 generation of clothes resistance both sides’ voltage value, output signal’s dutyfactor will reach maximum value 91%, this time obvious has not been able to reflect the interphase current the change, therefore the excess current winds through time the sample resistance produces the voltage should be smaller than or be equal to 260mV. For example: Regarding the 10A excess current, the sample resistance should for 26MΩ. Moreover, when input signal’s peak-to-peak value surpasses 260mV, will output a typical value in the IR2175 OC end for 2μs, the low level effective overflow signal. PO is the PWM output foot which opens leaks, what because it outputs is the digital signal, therefore is very easy and the working voltage is the 3.3~15V control circuit carries on the connection. When use only needs on PO termination one to pull the resistance then (on to pull resistance size to be possible to act according to and PO junction circuit’s input current carries on choice, its typical value for 1~10kΩ).

Below in summary, IR2175 has the remarkable function characteristic:

(1) IR2175 may supply the current feedback information, but may also provide a higher band width and the greater acceleration high speed frequency output (fo=130kHz), can satisfy the request strict servo electrical machinery application, like the high speed printing, the packaging machinery, the robot and locate automated applications and so on platform.

(2) IR2175 has 2.0μs the electric current shutdown signal output, may directly carries on the connection with the microprocessor or the digital signal processor. Existing rectilinear current sensing’s optics or the Hall effect system’s turn-off time is generally 3~4 μs, usually needs outside two to set at the comparator and a level switch operational amplifier can achieve with this same function.

(3) IR2175 does not need to establish the optical coupler, had guaranteed system performance lasting stable, is helpful in enhances the system reliability. Because gets older along with the optical coupler, the photo tube (LED) and between the receive component’s electric current transmission will be weaken gradually compared to (CTR), has the possibility to create the system failure.

(4) IR2175 uses the PWM digital signal output, and with from lifted the power source to substitute for the special-purpose accessory power supply, thus reduced the device dimension effectively, reduced the components number.

(outside 5) the electrical machinery driver electric circuit uses IR2175 to be possible to omit sets at optics or the Hall effect sensor, thus further reduces the electric circuit size, the simplification to design and to enhance the reliability.

4 model application electric circuit

Figure 2 is IR2175 applies in the three-phase AC server’s time electric circuit connection diagram, in the chart, the three-phase permanent magnetism not brushes the electric motor V and in the W phase winding return route connects 0.01Ω sampling resistance R1 and R2 separately, their both sides’ voltage may take two IR2175 electric current sensor’s input separately, VCC and VS connects one from to lift the diode, indirect of VB and VS from lifts the electric capacity. In this system, the author uses restores diode IRF107 quickly and 10μF the tantalum electric capacity to take separately from lifts the diode and from lifts the electric capacity.

VBS is one power source which fluctuates in above the VS voltage’s peak value 熢 cheats huo suo in the situation, VS is high frequency square-wave 牎 S line of ji ku pepper may produce the VBS aerosol power source, one of them uses the bootstrap circuit. This method’s merit is simple, is cheap. Figure 2 from lifts the power source is by diode D1, D2 and capacitor C1, C2 is composed, its principle of work is: When VS through carries lowly under IGBT pulls to the place, from lifts the electric capacity 煟 vast by Ying Mangbo 牨 kun ü from lifts the diode 煟 mold 犛 to guarantee by Ying Mubo load value mold Zheng Mang Gui to twine vast a lip line of charge, thus has provided power source VBS. When VS is pulled through the high-end switch to the overvoltage, VBS is the fluctuation, this time from lifts the diode by the reverse bias, thus has blocked the charge return route.

Through the bootstrap circuit may produces the high-end aerosol power source when VB and VS, the VBS power source for the minimum value (8V), the electric circuit may the normal work, recommendation VBS and the VCC voltage should maintain above 10V.

The IR2175 output signal has two processing methods:

The first kind is filters out the intelligence signal with the filter, thus restructuring simulation electric current signal. The restructuring simulation electric current signal’s simple, the most inexpensive method is filters out the PWM signal with the low pass filter the carrier. Has very many kind of low pass filters to be possible to use 煱 includes passive and the active filter. Considered simple and low cost, may choose the passive RC filter and the first-order active filter. In the typical situation, the active filter have a precise cut-off frequency, therefore, it compares the filter effect with the passive filter to be better some. Figure 3 is first-order VCVS 煹 Miao Gu刂 frequency Miao Guai towering 犅 flickers ㄆ jian the male pian fen principle chart, this is a basic gain is 19 Baht wass filter. Regarding this type’s filter, usually should choose the high gain, its cut-off frequency is 9kHz, very close actual output frequency.

The second kind is IR2175 direct and the low end numerical control electric circuit 熑 gun テ machine or the DSP 牻 good connection, this method is simple in the hardware aspect, but needs to use the software to calculate the electric current, this method may the very good limit error’s production.

5 use attention question

5.1 VS foot instant negative bias processing

The IR2175 high pressure linear transducer request has the independent instantaneous negative bias protection circuit, this is as a result of it and the gate extremely driver not synchronization. Because IR2175 is different with the gate extremely driver, it in transformation period must continue to work, this time the high-end switch is shutting off, therefore, guaranteed that electric current sensor IC does not have the instantaneous negative bias in the VS foot is very important. In the model junction circuit, generally in the COM foot and the VS foot indirect diode, outputs the indirect resistance in VS with half bridge 熂 to bestow the mark warehouse weapon mold remote che to stop remote foundation U to put in order the reef perch to be possible to carry on the clamp to the VS foot, therefore the VS foot may compare the COM foot low diode’s pressure drop. The diode should choose restores the time is smaller than 100ns restores the diode quickly. Between the VS base pin and half bridge output the resistance (R3 and R4) should 熅” jiao the peak guarantee the Zheng Yong lotus root barrel during 10~20 OMEGA scopes na to climb su fu the resistance are the electric current sensing channels, but it in non-transformation period does not have the electroresponse signal. Because transformation period produces the electroresponse signal’s duration is very short, therefore may neglect in the IR2175 input end by the operational amplifier.

5.2 dv/dt and to dutyfactor influence

In high-end aerosol therefore, but will not have in the situation which the switch will cut 熂 towering Zheng Yong Mumiao the gun deep pool ǖ mold 牐 dutyfactor not to have the fluctuation. But in half bridge electric circuit’s application, because the Vs base pin connects to half bridge’s out-port, and surveys electrical machinery’s interphase current with two IR2175, but VS base pin and IR2175 high-end electric circuit in the place or the avenue of approach with will be directing current between the bus bar to swing, will therefore each time transform time will have dv/dt. Thus, in VS foot transformation period, dv/dt will cause on the PO foot the output signal dutyfactor to have the small fluctuation, then causes the IR2175 output signal dutyfactor fluctuation, this will be transformed in the motor-driven electric circuit electrical machinery’s torque ripple, regarding this designs when should bring to the attention.

5.3 wiring suggestions

All electric power electronic circuit’s layout wiring should take reduce the parasitic inductance, the electric capacity as a foundation. In the IR2175 application, on VCC and the VBS decoupling electric capacity should as far as possible approach IC, between the sampling resistance and the VS segment should also approach IC, reduces between these two base pin’s differential pressure. Between the sample resistance and the VIN segment must short as far as possible, reduce the coupling to the electric current sampled signal in noise, maintains the wide electric current lead wire may reduce the stray inductance. The instantaneous negative bias protection circuit which are composed of R2 and D2 must as far as possible approach IC, with the aim of producing the best results.