CN202631606U - Current detection apparatus - Google Patents

Abstract

The utility model discloses a current detection device in power electronic direct current conversion. The device mainly includes an inductor (100), an RC network (110), an amplifier circuit (210), a charge pump circuit (220), a first-stage differential circuit (310) and a second-stage differential circuit (320). The RC network (110) converts the current flowing through the inductor (100) into a voltage signal and outputs it to the amplifying circuit (210); the amplifying circuit (210) amplifies the input voltage signal and outputs the amplified signal to the charge pump circuit ( 220); the amplifying circuit (210) is isolated from the ground plane through the charge pump circuit (220), thereby achieving the function of potential floating; the common function to eliminate the conduction voltage difference introduced by the charge pump circuit (220). The utility model can be used for lossless detection of the inductance current in the direct current conversion circuit under the condition of high voltage.

Description

A current detection device

technical field

The electronic circuit technology of the utility model particularly relates to a current detection device, which can be used for the detection of current by a power electronic system. the

Background technique

Inductive current detection technology must be used when implementing technologies such as current-mode control, over-current protection, and system parallel current sharing in power electronic systems. the

Common inductor current detection methods include series current detection resistor method, current transformer method, insulated gate transistor MOSFET cell detection method and inductance equivalent series resistance detection method. the

The series current-sensing resistor method, as shown in Figure 1, is to connect the current-sensing resistor 1 in series with the load 2. According to Ohm's law, the detected current can be determined only by detecting the voltage at both ends of the current-sensing resistor 1. The defect of this method is that the loss is too large, especially in the detection of high current, the loss cannot be ignored. the

The current transformer method is based on the principle of electromagnetic induction, using a transformer for current detection, connecting the primary winding in series to the line that needs to measure the current, and connecting the secondary winding in series to the measuring instrument and the protection circuit. The current transformer can convert the primary current with a large value into a secondary current with a small value through a certain transformation ratio. The disadvantage of this method is that it cannot detect DC current. the

The insulated gate transistor MOSFET cell detection method is to connect a detection MOSFET next to the power MOSFET in the detection circuit. The disadvantage of this method is that the applicable frequency bandwidth is too narrow, and the detection MOSFET connected in parallel will bring a large error to the original power MOSFET in the circuit. the

The inductor equivalent series resistance detection method, as shown in Figure 2, converts the current flowing through the inductor into a voltage signal, and obtains the current value by detecting the voltage signal. Since the value of the equivalent series resistance ESR of the inductor is very small, it is necessary to use an operational amplifier to amplify the detection signal. Due to the limitation of the withstand voltage of the operational amplifier, this method cannot be well applied to high-voltage occasions. the

Utility model content

The purpose of this utility model is to propose a current detection device for the above-mentioned deficiencies in the prior art, so as to reduce the detection loss and the influence on the detected circuit, and realize the accurate detection of DC and AC signals under high voltage conditions. the

In order to achieve the above object, the current detection device of the present utility model includes an inductor, and the RC network is characterized in that:

The output terminal of the RC network is connected with a potential floating voltage detection circuit, which is used to detect the voltage difference between the two ends of the detection capacitor in the RC network; the output terminal of the potential floating voltage detection circuit is connected with a differential proportional operation circuit, which is used to amplify the voltage detection circuit output, and return the reference plane of the output voltage value to the ground plane;

The voltage detection circuit with floating potential includes: an amplifier circuit and a charge pump circuit; the input terminal of the amplifier circuit is connected in parallel with the detection capacitor in the RC network; the input terminal of the charge pump circuit is connected in series with the output of the amplifier circuit;

The differential proportional operation circuit includes: a first-stage differential circuit and a second-stage differential circuit; the input end of the first-stage differential circuit is connected to the output end of the charge pump circuit; the output end of the first-stage differential circuit is connected to the second-stage differential circuit The input end of the differential circuit is connected; the output end of the second stage differential circuit is used as the output of the whole detection circuit. the

Because the utility model adopts the original power inductor in the power electronic system to measure the current, it makes full use of the equivalent series resistance of the inductor, so that no new loss is added to the detection circuit, thereby achieving the purpose of lossless measurement; at the same time, due to The utility model adds a charge pump circuit in the voltage detection circuit to make the voltage of the voltage detection circuit float, so the circuit can be well used in high-voltage occasions; in addition, because the utility model adds a differential proportional operation circuit, the charge pump circuit is eliminated. The effect of the voltage drop in the circuit on the output voltage, and bring the output voltage back to the ground plane as a reference. the

Description of drawings

Fig. 1 is the structural block diagram of the current detection circuit of existing application current detection resistor;

Fig. 2 is the structural block diagram of the current detection circuit of existing application inductance equivalent series resistance;

Fig. 3 is a block diagram of the utility model;

Fig. 4 is the schematic diagram of the circuit structure of the utility model. the

Detailed ways

In order to make the purpose, technical solutions and advantages of the utility model clearer, the utility model will be further described in detail below with reference to the accompanying drawings and using specific embodiments. the

The embodiment of the utility model matches the detection capacitor and the matching resistor in the RC network, so that the voltage difference at both ends of the capacitor is linearly related to the current flowing through the inductor, and the current detection is performed by using this characteristic. the

With reference to Fig. 3, the electric current detection circuit of the present utility model, comprises the voltage detection circuit 200 and the differential proportional operation circuit 300 of inductance 100, RC network 110, potential floating. The voltage detection circuit 200 includes an amplifier circuit 210 and a charge pump circuit 220 , and the differential proportional operation circuit 300 includes a first-stage differential circuit 310 and a second-stage differential circuit 320 . The input end of this RC network 110 is connected in parallel with the two ends of inductance 100, and the output end is connected with the input end of amplifying circuit 210, and the output end of this amplifying circuit 210 is connected with the input end of charge pump circuit 220, and the output of this charge pump circuit 220 terminal is connected to the input end of the first-stage differential circuit 310, and the output end of the first-stage differential circuit 310 is connected to the input end of the second-stage differential circuit 320, and the output end of the second-stage differential circuit 320 is used as the whole detection circuit output. The RC network 110 converts the current flowing through the inductor into a voltage signal, and outputs it to the amplifying circuit 210; the amplifying circuit 210 amplifies the input voltage signal, and outputs the amplified signal to the charge pump circuit 220; when the floating voltage of the inductor is high potential, the amplifying circuit 210 is isolated from the differential proportional operation circuit 300 through the charge pump circuit 220, and the amplifying circuit 210 takes the floating voltage of the inductor 100 as a reference plane to ensure that the operational amplifier 211 is not broken down; when the floating voltage of the inductor is at a low potential , through the charge pump circuit 220, the output of the amplifying circuit 210 is transmitted to the differential proportional operation circuit 300; the joint action of the first stage differential circuit 310 and the second stage differential circuit 320 eliminates the conduction voltage difference introduced in the charge pump circuit, And restore the output voltage to the ground plane as the reference plane. the

With reference to Fig. 4, the connection structure of the whole circuit of the present utility model is as follows:

The RC network 110 includes a matching resistor 111 and a detection capacitor 112; one end of the matching resistor 111 is connected to the detection capacitor 112, the other end is connected to the power supply end of the inductor 100, and the other end of the detection capacitor 112 is connected to the load end of the inductor 100; Both ends of the detection capacitor 112 are connected to the input of the amplifying circuit 210 as the output of the RC network, the potential of one end of the detection capacitor 112 connected to the inductor is floating, and the potential of the other end connected to the matching resistor is not floating. the

The amplifying circuit 210 includes an operational amplifier 211, a first resistor 212, a second resistor 213 and a charging capacitor 214; the non-inverting input terminal of the operational amplifier 211 is connected to the potential non-floating terminal of the detection capacitor 112, and the inverting input terminal is passed through the second Resistor 213 is connected to the potential floating terminal of detection capacitor 112, and the output terminal is connected to the charge pump circuit. At the same time, the output signal of operational amplifier 211 is fed back to the inverting input terminal of this operational amplifier 211 through the first resistor 212. The operational amplifier amplifies The form of the input signal is amplified; the charging capacitor 214 is used as the power supply of the operational amplifier 211, and is connected between the positive power supply terminal of the operational amplifier 211 and the negative power supply terminal of the operational amplifier 211; The floating voltages float together to ensure that the reference plane potential of the amplifying circuit 210 floats. the

The charge pump circuit 220 includes a first diode 221, a second diode 222 and a third diode 223; the cathode of the first diode 221 is connected to the output terminal of the operational amplifier 211, and the second diode The cathode of the tube 222 is connected to the potential floating terminal of the detection capacitor 112, and the cathode of the third diode 223 is connected to the positive power supply terminal of the operational amplifier 211; due to the single-phase conduction characteristic of the diode, only when the anode voltage of the diode is high When the diode is connected to the cathode, the diodes can be turned on, that is, when the floating voltage of the detection capacitor 112 is a high potential, the three diodes are all cut off, and only when the floating voltage of the detection capacitor 112 is lower than the anode of the diode, the three diodes can conduct. Pass. Through the action of the three diodes 221, 222, 223, the voltage detection circuit (200) is isolated from the ground plane, thereby achieving the function of potential floating. the

The first-stage differential circuit 310 includes a first-stage operational amplifier 313, a first voltage-dividing resistor 311, a second voltage-dividing resistor 312, a third resistor 314, and a fourth resistor 315; the non-inverting input of the first-stage operational amplifier 313 terminal is connected to the anode of the second diode 222, the inverting input terminal is connected to the common ground through the third resistor 314, and the output terminal is connected to the input terminal of the second stage differential circuit 320; the fourth resistor 315 is connected to the first between the inverting input terminal and the output terminal of the first stage operational amplifier 313; the first voltage dividing resistor 311 is connected between the non-inverting input terminal of the first stage operational amplifier 313 and the anode of the power supply 326, and the second voltage dividing resistor 312 is connected to the first Between the non-inverting input terminal of the first-stage operational amplifier 313 and the common ground, a voltage dividing circuit composed of the first voltage dividing resistor 311 and the second voltage dividing resistor 312 is used to make the second diode 222 in the charge pump circuit 220 obtain a high voltage. Due to the voltage drop of the charge pump circuit tube, the second diode 222 is cut off when the floating voltage of the inductor is high, and turned on when the floating voltage of the inductor is low. The first-stage operational amplifier 313 has its non-inverting input connected to the anode of the second diode 222, its inverting input connected to the common ground through the third resistor 314, and its output connected to the input of the second-stage differential circuit 320. connected; the fourth resistor 315 is connected between the inverting input terminal and the output terminal of the first-stage operational amplifier 313 . the

The second-stage differential circuit 320 includes a second-stage operational amplifier 323, a third voltage-dividing resistor 321, a fourth voltage-dividing resistor 322, a fifth resistor 324, and a sixth resistor 325; the second-stage operational amplifier (323) The non-inverting input terminal is connected to the anode of the first diode (221), the inverting input terminal is connected to the output of the first-stage operational amplifier (313) through the fifth resistor (324), and the output terminal is used as the output of the entire detection circuit; The six resistors (325) are connected between the inverting input terminal and the output terminal of the second-stage operational amplifier (323); the third voltage dividing resistor 321 is connected between the non-inverting input terminal of the second-stage operational amplifier 323 and the power supply 326 Between the anodes, the fourth voltage dividing resistor 322 is connected between the non-inverting input terminal of the second-stage operational amplifier 323 and the common ground, through the voltage dividing circuit composed of the third voltage dividing resistor 321 and the fourth voltage dividing resistor 322, the charge The first diode 221 in the pump circuit 220 obtains a voltage higher than the voltage drop of the charge pump circuit tube, so that the first diode 222 is cut off when the floating voltage of the inductor is at a high potential, and is turned on when the floating voltage of the inductor is at a low potential. . The noninverting input terminal of the second stage operational amplifier 323 is connected with the anode of the first diode 222, and the inverting input terminal is connected with the output of the first stage operational amplifier 313 through the fifth resistor 324, and the output terminal is used as the output of the whole detection circuit Output; the sixth resistor 325 is connected between the inverting input terminal and the output terminal of the second-stage operational amplifier 323 . the

The joint action of the first-stage differential circuit 310 and the second-stage differential circuit 320 eliminates the conduction voltage difference introduced in the charge pump circuit, and restores the output voltage to the ground plane as a reference plane. the

Claims (6)

1. a current sensing means comprises inductance (100), and RC network (110) is characterized in that:

The output terminal of RC network (110) is connected with the voltage detecting circuit (200) that current potential floats, and is used for detecting the voltage difference that RC network (110) detects the electric capacity two ends; The output terminal of the voltage detecting circuit (200) that this current potential floats is connected with difference ratio computing circuit (300), is used for the output of amplifying voltage testing circuit (200), and the reference planes of output voltage values are returned to the ground level is benchmark;

The voltage detecting circuit (200) that described current potential floats comprising: amplifying circuit (210) and charge pump circuit (220); The input end of amplifying circuit (210) is parallelly connected with the detection electric capacity in the RC network; The output of the input end of charge pump circuit (220) and amplifying circuit (210) is connected in series;

Described difference ratio computing circuit (300) comprising: first order difference channel (310) and second level difference channel (320); The input end of first order difference channel (310) links to each other with the output terminal of charge pump circuit (220); The output terminal of first order difference channel (310) links to each other with the input end of second level difference channel (320); The output terminal of second level difference channel (320) is as the output of whole testing circuit.

2. current sensing means as claimed in claim 1; It is characterized in that; RC network (110) comprising: build-out resistor (111) is connected with detection electric capacity (112) with detection electric capacity (112) a, end of this build-out resistor (111), and the other end is connected with the power end of inductance (100); The other end that detects electric capacity (112) links to each other with the load end of inductance (100), detects the electric capacity two ends and links to each other with amplifying circuit (210) as the output terminal of RC network again.

3. current sensing means as claimed in claim 1 is characterized in that, amplifying circuit (210) comprising: operational amplifier (211), first resistance (212), second resistance (213) and charging capacitor (214); The in-phase input end of operational amplifier (211) links to each other with the non-floating end of current potential that detects electric capacity (112), and inverting input links to each other with the current potential floating end that detects electric capacity (112) through second resistance (213), and output terminal links to each other with charge pump circuit; First resistance (212) is connected between the output terminal and inverting input of operational amplifier (211); One end of charging capacitor (214) links to each other with the positive power source terminal of operational amplifier (211), and the other end links to each other with the negative power end of operational amplifier (211).

4. current sensing means as claimed in claim 1 is characterized in that, described charge pump circuit (220) comprising: first diode (221), second diode (222), the 3rd diode (223); The negative electrode of this first diode (221) links to each other with the output terminal of said operational amplifier (211); The negative electrode of second diode (222) links to each other with the current potential floating end of said detection electric capacity (112); The negative electrode of the 3rd diode (223) links to each other with the positive power source terminal of said operational amplifier (211); Effect through described 3 diodes (221), (222), (223); Said voltage detecting circuit (200) and ground level are isolated, thereby reach the function that current potential floats.

5. current sensing means as claimed in claim 1; It is characterized in that said first order difference channel (310) comprising: first order operational amplifier (313), first divider resistance (311), second divider resistance (312), the 3rd resistance (314) and the 4th resistance (315); The in-phase input end of first order operational amplifier (313) links to each other with the anode of second diode (222), inverting input through the 3rd resistance (314) with link to each other publicly, output terminal links to each other with the input end of second level difference channel (320); The 4th resistance (315) is connected between the inverting input and output terminal of said first order operational amplifier (313); First divider resistance (311) is connected between the anode of in-phase input end and power supply (326) of said first order operational amplifier (313); Second divider resistance (312) is connected between the in-phase input end and public ground of first order operational amplifier (313), through the effect of said divider resistance (311) and (312), makes the diode (222) in the charge pump circuit (220) obtain forward voltage.

6. current sensing means as claimed in claim 1; It is characterized in that said second level difference channel (320) comprising: second level operational amplifier (323), the 3rd divider resistance (321), the 4th divider resistance (322), the 5th resistance (324) and the 6th resistance (325); The in-phase input end of second level operational amplifier (323) links to each other with the anode of first diode (221), and inverting input links to each other with the output of first order operational amplifier (313) through the 5th resistance (324), and output terminal is as the output of whole testing circuit; The 6th resistance (325) is connected between the inverting input and output terminal of said second level operational amplifier (323); The 3rd divider resistance (321) is connected between the anode of in-phase input end and power supply (326) of said second level operational amplifier (323); The 4th divider resistance (322) is connected between the in-phase input end and public ground of second level operational amplifier (323), through the effect of said divider resistance (321) and (322), makes first diode (221) in the charge pump circuit (220) obtain forward voltage.

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