CN104090145B - Inverter circuit current sampling circuit combined with mutual inductor and sampling resistor - Google Patents

Abstract

The invention provides an inverter circuit current sampling circuit combined with a transformer and a sampling resistor, including a high-frequency transformer, a resistance current sampling circuit, a transformer current sampling circuit, a switching tube driving waveform tracking circuit, a logic current sampling superimposition circuit and a reverse Addition synthesis circuit; high-frequency transformer collects signals from motor phase voltage; resistance current sampling circuit is used to sample the current when the power tube of the lower bridge arm is turned on; transformer current sampling circuit is used to output the half-bridge arm inverter circuit Current change rate sampling; logical current sampling superposition circuit is used to realize the additive synthesis of the output voltage of the resistance current sampling circuit and the output voltage of the transformer current sampling circuit when the power tube of the lower bridge arm of the half-bridge arm inverter circuit is turned on; reverse addition The synthesizing circuit is used for the additive synthesis of the transformer current sampling circuit and the logic type current sampling superposition circuit. The invention solves the time delay phenomenon in the sampling of the traditional Hall sensor, and greatly improves the current sampling efficiency.

Description

A current sampling circuit of an inverter circuit combined with a transformer and a sampling resistor

technical field

The invention relates to an inverter circuit current sampling circuit.

Background technique

The currently commonly used inverter circuit current sampling method basically uses the current Hall sensor to sample the current. The traditional sampling circuit using the Hall sensor is shown in Figure 2. Although it is simple to use, it has electrical isolation, short response time, and easy measurement. The obvious advantage of wide frequency range, but there will be a certain delay (generally less than 40us), when the sampling current frequency is high, the delay phenomenon is more obvious, which reduces the efficiency of current sampling. In addition, it is expensive, bulky, and costly.

Contents of the invention

The technical problem to be solved by the present invention is to provide a current sampling circuit of an inverter circuit combined with a transformer and a sampling resistor, so as to solve the shortcoming of time delay of the traditional current sampling circuit and improve sampling efficiency.

The technical scheme adopted by the present invention to solve the above-mentioned technical problems is: an inverter circuit current sampling circuit combined with a transformer and a sampling resistor, the inverter circuit is a half-bridge arm inverter circuit, and it is characterized in that it includes High-frequency transformer, resistance current sampling circuit, transformer current sampling circuit, switching tube drive waveform tracking circuit, logic current sampling superposition circuit and reverse addition synthesis circuit;

Among them, the primary coil of the high-frequency transformer collects signals from the phase voltage of the motor;

The resistance current sampling circuit is used to sample the current when the power tube of the lower arm of the half-bridge arm inverter circuit is turned on; by connecting a sampling resistor in series between the source of the lower arm tube Q2 of the half-bridge arm inverter circuit and the ground R9, by collecting the voltage signal CU at both ends of the sampling resistor R9, and then passing through a reverse amplification circuit, realizes sampling the current when the lower bridge arm power tube Q2 of the half bridge arm inverter circuit is turned on.

The transformer current sampling circuit collects the output voltage of the secondary coil of the high-frequency transformer for sampling the output current change rate of the half-bridge arm inverter circuit;

The logic type current sampling superposition circuit is used to realize the additive synthesis of the output voltage of the resistance current sampling circuit and the output voltage of the transformer current sampling circuit when the power tube of the lower bridge arm of the half-bridge arm inverter circuit is turned on. When the power tube of the lower bridge arm is cut off, the output voltage of the circuit is maintained when it is turned on;

The switching tube drives the waveform tracking circuit, the input signal is the driving signal of the power tube of the lower bridge arm of the half-bridge arm inverter circuit, and the output terminal is used to control the logic type current sampling superposition circuit;

The reverse addition synthesis circuit is used for the addition synthesis of the transformer current sampling circuit and the logic type current sampling superposition circuit, and realizes the sampling of the output current of the half-bridge arm.

According to the above scheme, the transformer current sampling circuit realizes the sampling of the rate of change of the output current of the half-bridge arm inverter circuit by passing the collected output voltage CTU of the secondary coil of the high-frequency transformer through the current-to-voltage amplifying circuit.

According to the above scheme, the logic-type current sampling superposition circuit includes a switch tube and a superposition circuit, the control terminal of the switch tube is connected to the output end of the switch tube driving waveform tracking circuit, and a connection terminal of the switch tube is connected to the output terminal of the switch tube drive waveform tracking circuit. The transformer current sampling circuit is connected to the resistance current sampling circuit, the other connection terminal of the switch tube is connected to the superposition circuit, and the output terminal of the superposition circuit outputs the output voltage VO3 of the logic type current sampling superposition circuit.

The working principle of the present invention is as follows: Utilize the sampling resistance to sample the real-time current when the lower bridge arm power tube of the half bridge arm circuit is turned on, and use the high frequency transformer to sample the current change rate output by the half bridge arm inverter circuit; When it is turned on, the logic type current sampling superposition circuit is used to complete the addition and synthesis of the output voltage of the resistance current sampling circuit and the output voltage of the transformer current sampling circuit, and when the power tube of the lower bridge arm is cut off, the output voltage of the circuit when it is turned on is maintained; The switch tube drive waveform tracking circuit with isolation follower function realizes that when the drive voltage of the switch tube is low, it outputs a negative voltage, and when the drive voltage of the switch tube is high, it outputs a positive voltage; the reverse addition synthesis circuit is used to realize the transformer current sampling circuit and logic The additive synthesis of the type current sampling superposition circuit realizes the sampling of the output current of the half-bridge arm inverter circuit.

The beneficial effects of the present invention are: the present invention well solves the time delay phenomenon existing in traditional Hall sensor sampling, and greatly improves the current sampling efficiency; and the circuit hardware cost of the present invention is lower than that of the traditional Hall sensor.

Description of drawings

FIG. 1 is a schematic circuit diagram of an embodiment of the present invention.

Figure 2 is a traditional Hall component sampling circuit.

Figure 3 shows the waveform comparison between this sampling circuit and the traditional sampling circuit (low frequency 100Hz).

Figure 4 shows the waveform comparison between this sampling circuit and the traditional sampling circuit (high frequency 2KHz).

detailed description

The present invention will be further described below in conjunction with specific examples and accompanying drawings.

Fig. 1 is the circuit schematic diagram of an embodiment of the present invention, and it comprises high-frequency transformer U1, resistance current sampling circuit, transformer current sampling circuit, switching tube driving waveform tracking circuit, logic type current sampling superposition circuit and reverse addition synthesis circuit. The half-bridge inverter circuit in this embodiment is composed of two N-type MOS tubes (Q1 and Q2), and both N-type MOS tubes have reverse diodes, and the half-bridge arm inverter circuit is used to drive the motor One of the phase windings provides working current for it. Suppose there are two PWM waves with dead zone Compared with PWM_U, the two waves are originally symmetrical square waves, but because the turn-on time of the upper bridge arm of the half-bridge is faster than the turn-off time of the lower bridge arm, it is easy to have the phenomenon that the upper and lower tubes are turned on at the same time, so the two-way band A dead zone is added to the PWM wave of the dead zone. After joining the dead zone Drive the half-bridge arm inverter circuit with PWM_U wave.

Among them, the primary coil of the high-frequency transformer U1 is connected in series with the phase winding of the motor, and the signal is collected from the phase voltage of the motor; assuming that the transformation ratio of the primary coil and the secondary coil of the high-frequency transformer U1 is 1:n, the rate of change of the motor phase current will be Output as 1/n.

The resistance current sampling circuit is used for sampling the current when the lower bridge arm power transistor of the half bridge arm inverter circuit is turned on. By connecting a sampling resistor R9 in series between the source of the lower bridge arm tube Q2 of the half-bridge arm inverter circuit and the ground, by collecting the voltage signal CU at both ends of the sampling resistor R9, and then passing through an inverse amplifier circuit (the inverse amplifier circuit is a conventional circuit, in the present embodiment, the inverting amplifying circuit is composed of the fourth operational amplifier U3D, the eighth resistor R8, and the twelfth resistor R12), and realizes when the lower bridge arm power tube Q2 of the half bridge arm inverter circuit is turned on The current is sampled.

The transformer current sampling circuit collects the output voltage of the secondary coil of the high-frequency transformer for sampling the rate of change of the output current of the half-bridge arm inverter circuit; specifically, the output voltage of the secondary coil of the high-frequency transformer U1 collected is The CTU passes through the current-to-voltage amplifying circuit (the current-to-voltage amplifying circuit is a conventional circuit, and in this embodiment, the current-to-voltage amplifying circuit is composed of the second operational amplifier U3B, the third resistor R3, the fourth resistor R4, the sixth resistor R6 and the first A triode U2 and a second triode U4), to realize the sampling of the rate of change of the output current of the half-bridge arm inverter circuit.

The logic type current sampling superposition circuit is used to realize the additive synthesis of the output voltage of the resistance current sampling circuit and the output voltage of the transformer current sampling circuit when the power tube of the lower bridge arm of the half-bridge arm inverter circuit is turned on. When the power tube of the lower bridge arm is cut off, it keeps the output voltage of the circuit when it is turned on. The logic type current sampling superimposition circuit comprises a switch tube U6 and a superposition circuit (the superposition circuit is a conventional circuit, and in this embodiment the superposition circuit is composed of the third operational amplifier U3C, the eleventh resistor R11, the fifteenth resistor, the first capacitor), the control end of the switch tube U6 is connected to the output end of the switch tube drive waveform tracking circuit, and one connection end of the switch tube U6 is connected to the transformer current sampling circuit and the resistance current sampling circuit, and the switch tube The other connection terminal of U6 is connected with the superposition circuit, and the output terminal of the superposition circuit outputs the output voltage VO3 of the logic type current sampling superposition circuit.

The switching tube driving waveform tracking circuit, the input signal is the driving signal of the lower bridge arm power tube of the half-bridge arm inverter circuit, and the output terminal is used to control the logic type current sampling superposition circuit; the switching tube driving waveform tracking circuit is composed of the fifth operational amplifier U5A, The tenth resistor R10 and the fourteenth resistor R14 are formed. When the driving voltage of the switching tube is low, a negative voltage is output; when the driving voltage of the switching tube is high, a positive voltage is output, which plays the role of isolation follower.

The reverse addition synthesis circuit is used for the addition synthesis of the transformer current sampling circuit and the logic type current sampling superposition circuit, and realizes the sampling of the output current of the half-bridge arm. The reverse addition synthesis circuit is composed of a first resistor R1, a second resistor R2, a fifth resistor R5 and a first operational amplifier U3A. After the output voltage VO1 of the transformer current sampling circuit and the output voltage V03 of the logic type current sampling superposition circuit pass through the reverse addition circuit, the output voltage is VOUT, that is, the current sampling voltage, to realize the sampling of the output current of the half-bridge arm.

Since the upper arm tube Q1 of the half-bridge arm inverter circuit and the lower arm arm tube Q2 of the half-bridge arm inverter circuit are turned on alternately, we assume three moments here: at time t1, the gate of Q1 is at a high level Drive, conduction; Q2 is low-level drive, cut-off; motor phase winding current is I1. At time t2, the gate of Q1 is driven at low level and cuts off; Q2 is driven at high level and turned on; the current of the phase winding of the motor is I2. At time t3, the gate of Q1 is driven at a high level and turned on; Q2 is driven at a low level and turned off; the motor phase winding current is I3. The effect of the circuit of the present invention will be described below in different time periods.

(1), the moment of change from t1 to t2

At the beginning of time t2, Q1 is cut off, Q2 is turned on, U5A will output a high level, and the switch tube U6 (N-channel junction field effect transistor in this embodiment) will be turned on, and at this time, the current flowing through the phase winding of the motor The current is also I2, and the current flowing through the sampling resistor R9 is also I2. Then the voltage flowing through the two ends of the sampling resistor R9 is CU=-R9*I2.

The parameters of the fourth operational amplifier U3D, the eighth resistor R8, and the twelfth resistor R12 are designed to be an inverse amplifier circuit with a gain of -1/R9 times. At this time, the fourth operational amplifier U3D output voltage VO2=-R9*I2*( -1/R9)=I2. The rate of change of the motor phase current is (I2-I1), and the output current of the high-frequency transformer U1 is CTU=(I2-I1)/n, through the second operational amplifier U3B, the third resistor R3, the fourth resistor R4, and the sixth resistor R6, the first triode U2 and the second triode U4 constitute a current-to-voltage amplifying circuit, and the amplification factor is designed to be -n times, then the output voltage VO1=(I2-I1 )/n*(-n)=-(I2-I1).

Since the switch tube U6 is turned on, and the drain-source impedance of the switch tube U6 is small and negligible, the eleventh resistor R11 is much larger than the fifteenth resistor R15, and the first capacitor C1 is very small, so it can be regarded as the eleventh resistor R11 is short-circuited, and the fifteenth resistor R15 is connected across the output terminal and the inverting input terminal of the third operational amplifier U3C. The seventh resistor R7, the thirteenth resistor R13, the fifteenth resistor R15, and the third operational amplifier U3C form a reverse adder, and the output voltage VO3=-(VO1+VO2)=-(-I2+I1+I2) =-I1.

The first resistor R1, the second resistor R2, the fifth resistor R5 and the first operational amplifier U3A constitute a reverse addition circuit, and after VO1 and VO3 pass through the reverse addition circuit, the current sampling voltage VOUT=-(VO1+VO3) =I2. Through calculation, it can be seen that the motor phase current from the late period of t1 to the early period of t2 is equal to the output voltage of the entire sampling circuit and has the same direction.

(2), late t2

At the end of time t2, the phase current of the motor is stable at I2, and the output of high-frequency transformer U1 is 0 at this time, then VO1=0, VO2=I2, VO3=-I2, VOUT=I2. The calculation shows that the magnitude of the phase current of the motor in the late period of t2 is equal to the output voltage of the entire sampling circuit, and the direction is the same.

(3), the moment of change from t2 to t3

At time t3, Q1 is turned on, Q2 is turned off, the switch tube U6 will be turned off, the current is I3, the current flowing through the phase winding of the motor is also 0, and the current flowing through the resistor is also 0, the output voltage of the fourth operational amplifier U3D VO2=0. Since the switch tube U6 is turned off, the fifteenth resistor R15 is disconnected, and the first capacitor C1 and the eleventh resistor R11 are connected in parallel. The time constant of the two is large enough, and the third operational amplifier U3C constitutes a holding circuit, which is the working time of t3 However, the voltage VO3=-I2 is maintained. At this time, the current change rate is (I3-I2), the output current of the high-frequency transformer U1 will be (I3-I2)/n, VO1=-(I3-I2), and the current sampling voltage VOUT=-(VO1+VO3 )=-(-I3+I2-I2)=I3. The calculation shows that the magnitude of the phase current of the motor at time t3 is equal to the output voltage of the entire sampling circuit, and the direction is the same.

Figure 3 shows the waveform comparison between the sampling circuit and the traditional sampling circuit (low frequency 100Hz); Figure 4 shows the waveform comparison between the sampling circuit and the traditional sampling circuit (high frequency 2KHz).

After the above analysis, it can be seen that the circuit meets the design requirements, and has been tested in the three-phase hybrid stepping motor subdivision driver circuit developed in the laboratory. The contents not described in detail in the description of the present invention belong to the prior art known to those skilled in the art.

Claims (3)

1. A kind of inverter circuit current sampling circuit that combines mutual inductor and sampling resistance, described inverter circuit is half-bridge arm inverter circuit, it is characterized in that: this inverter circuit current sampling circuit comprises high-frequency transformer, resistance Current sampling circuit, transformer current sampling circuit, switching tube drive waveform tracking circuit, logic current sampling superposition circuit and reverse addition synthesis circuit; Among them, the primary coil of the high-frequency transformer collects signals from the phase voltage of the motor; The resistance current sampling circuit is used to sample the current when the power tube of the lower arm of the half-bridge arm inverter circuit is turned on; by connecting a sampling circuit in series between the source of the lower arm power tube Q2 and the ground Resistor R9, by collecting the voltage signal CU at both ends of the sampling resistor R9, and then passing through a reverse amplification circuit, realizes sampling of the current when the lower bridge arm power tube Q2 of the half-bridge arm inverter circuit is turned on; The transformer current sampling circuit collects the output voltage of the secondary coil of the high-frequency transformer for sampling the output current change rate of the half-bridge arm inverter circuit; The logic type current sampling superposition circuit is used to realize the additive synthesis of the output voltage of the resistance current sampling circuit and the output voltage of the transformer current sampling circuit when the power tube of the lower bridge arm of the half-bridge arm inverter circuit is turned on. When the power tube of the lower bridge arm is cut off, the output voltage of the circuit is maintained when it is turned on; The switching tube drives the waveform tracking circuit, the input signal is the driving signal of the power tube of the lower bridge arm of the half-bridge arm inverter circuit, and the output terminal is used to control the logic type current sampling superposition circuit; The reverse addition synthesis circuit is used for the addition synthesis of the transformer current sampling circuit and the logic type current sampling superposition circuit, and realizes the sampling of the output current of the half-bridge arm. 2. the inverter circuit current sampling circuit combining transformer and sampling resistance according to claim 1, is characterized in that: described transformer current sampling circuit, by the high-frequency transformer secondary coil output voltage that gathers The CTU realizes the sampling of the rate of change of the output current of the half-bridge arm inverter circuit through the current-to-voltage amplifying circuit. 3. The inverter circuit current sampling circuit combining transformer and sampling resistance according to claim 1, characterized in that: the logic type current sampling superposition circuit comprises a switch tube and a superposition circuit, the control of the switch tube end is connected with the output end of the switching tube driving waveform tracking circuit, one connecting end of the switching tube is connected with the described transformer current sampling circuit and the resistance current sampling circuit, and the other connecting end of the switching tube is connected with the superposition circuit, The output terminal of the superposition circuit outputs the output voltage VO3 of the logic type current sampling superposition circuit.