[0023]Example 1
[0024]The embodiment of the present invention provides a positive bias high-end current detection circuit, such asfigure 1As shown, it includes a current transformer sampling module 1 for isolating and sampling high-end current and a positive bias detection module 2 for outputting a positive bias of the high-end current sampled by the current transformer sampling module 1. The current transformer The sampling module 1 is electrically connected to the positive bias detection module 2.
[0025]In this way, the current transformer sampling module 1 is used to isolate and sample the high-end current, and the positive bias detection module 2 is used to detect the positive bias output of the high-end current sampled by the current transformer sampling module 1, thereby abandoning the single-resistance low-end sampling current method and avoiding Ground potential fluctuations cause inaccurate sampling, reduce sampling current distortion and avoid output uncertainty when the load is zero, low cost, high accuracy, and improve product reliability.
[0026]The current transformer sampling module 1 includes a sampling module 11 and a magnetic reset module 12, and the sampling module 11 is electrically connected to the magnetic reset module 12.
[0027]In this way, the current transformer of the sampling module 11 is used to isolate and sample the high-end current, and the current transformer is magnetically reset by the magnetic reset module 12.
[0028]The positive bias detection module 2 includes a high impedance resistance module 21 and a positive bias output module 22, and the high impedance resistance module 21 is electrically connected to the positive bias output module 22.
[0029]In this way, the high-impedance resistance module 21 makes the sampling current energy consumption negligible, and the positive bias output module 22 makes the sampling voltage positively biased to output for current detection.
[0030]The sampling module 11 includes a current transformer T2, a diode D1, a first capacitor C1, a second capacitor C2, a first resistor R1, and a second resistor R2. The first pin of the current transformer T2 is connected to the live wire ACL, so The second pin of the current transformer T2 is connected in parallel with the second capacitor C2 and the motor B2 and then connected to the neutral line ACN, and the third pin of the current transformer T2 is connected in series with the diode D1 and then in parallel with one end of the first capacitor C1 and the first resistor One end of R1, the other end of the first capacitor C1 is grounded, and the other end of the first resistor R1 is connected in series with the second resistor R2 and then grounded.
[0031]In this way, when the voltage of the live wire ACL is at the AC half-wave high level, the current transformer T2 starts to be excited, and the upper half winding is left positive and right negative. Through the end of the same name and the turns ratio relationship, the lower half winding is also left positive and right negative. The diode D1 is turned on to discharge the first capacitor C1 and the first resistor R1, and clamp the output voltage of the transformer to V_T2=(IO*N1/N2)*(R1+R2), at the same time it passes through the high frequency filter capacitor and the second capacitor C2 Filter out the inductive current of the motor itself to reduce the high-frequency interference to the current of the current transformer.
[0032]The magnetic reset module 12 includes a third capacitor C3 and a third resistor R3, one end of the third capacitor C3 is connected to the third pin of the current transformer T2, and the other end of the third capacitor C3 is connected in series with a third resistor R3 Connect the common terminal of the diode D1 and the first resistor R1.
[0033]In this way, when the live wire ACL voltage is AC half-wave low level, the excitation of the current transformer T2 starts, and the upper half winding is left negative and right positive, and the lower half winding is also left negative and right positive through the relationship of the same name terminal and the turns ratio. D1 is off, and the first capacitor C1 is discharged through the first resistor R1. Since the capacitor voltage cannot change suddenly, the negative half cycle is considered unchanged due to the large release impedance. At this time, the current transformer passes through the third resistor R3 and the third capacitor C3. RCL damped oscillation for magnetic reset, wherein the resistance of the first resistor R1 is 10kΩ, the resistance of the second resistor R2 is 1kΩ, and the resistance of the third resistor R3 is 100Ω.
[0034]In this way, by repeating the AC high wave high and low voltage of the ACL live wire, the average current sampling and isolation output of the AC motor B1 is realized, and the voltage is V_R1.
[0035]The high impedance resistor module 21 includes a fourth resistor R4, a fifth resistor R5, a sixth resistor R6, a seventh resistor R7, an eighth resistor R8, and a ninth resistor R9. One end of the fourth resistor R4 is connected to the first resistor. The common connection end of R1 and the third resistor R3. The other end of the fourth resistor R4 is connected in parallel with one end of the fifth resistor R5 and one end of the ninth resistor R9. The other end of the fifth resistor R5 is grounded. The other end of the resistor R9 is connected to the positive bias reference voltage VREF, one end of the sixth resistor R6 is connected to the common connection end of the first resistor R1 and the second resistor R2, and the other end of the sixth resistor R6 is connected in parallel with the seventh resistor R7 And one end of the eighth resistor R8, and the other end of the seventh resistor R7 is grounded. Wherein, the resistance value of the fourth resistor R4, the resistance value of the sixth resistor R6, the resistance value of the eighth resistor R8, and the resistance value of the ninth resistor R9 are all equal to 100KΩ.
[0036]In this way, when the motor B2 is disconnected, no current flows through the current transformer T2 (ie I_T2=0), so there is no excitation current, and the first resistor R1 has no voltage output, and V_R1=0. At this time, due to the connection of the forward bias Set the reference voltage VREF and connect it to the non-inverting terminal of the operational amplifier A1 through the ninth resistor R9, then its voltage VA1+=VREF*R5/(R5+R9), according to the principle of virtual break and virtual short, VA1+=VA1-=VO*R7/ (R7+R8), due to the impedance symmetry of the fifth resistor R5, the seventh resistor R7, the eighth resistor R8, and the ninth resistor R9, the output voltage V0=VREF, so that when the load current is 0, the non-inverting operational amplifier A1 The positive bias output avoids the uncertainty of the sampling current under light load conditions.
[0037]The positive bias output module 22 includes an operational amplifier A1, the fifth pin of the operational amplifier A1 is connected to the common connection end of the fifth resistor R5 and the ninth resistor R9, and the sixth pin of the operational amplifier A1 is connected to the first The common connection end of the six resistors R6 and the eighth resistor R8, and the seventh pin of the operational amplifier A1 is connected to the other end of the eighth resistor R8. Wherein, the resistance value of the fifth resistor R5 and the resistance value of the seventh resistor R7 are equal to 10KΩ.
[0038]In this way, when the current of the motor B2 is I_B2=I_T2, due to the high impedance symmetrical resistance network (>100KΩ), the loss of sampling current energy is negligible, and the voltage output of the current transformer T2 is based on V_T2=(IO*N1/N2)*(R1+R2), because the non-inverting terminal VA1+ of the operational amplifier A1 has both voltage sources V_T2 and VREF , At the same time, the input current at the non-inverting terminal is 0 (according to the principle of virtual break), according to the linear circuit superposition theorem, VA1+=VREF*R5/(R5+R9)+V_T2*R5/(R5+R4); because the op amp A1 reverse terminal VA1- There are voltage sources V_R2 and VO at the same time, and the input current at the non-inverting terminal is 0 (according to the principle of virtual disconnection). According to the linear circuit superposition theorem, VA1-=V_R2*R7/(R7+R6)+VO*R7/(R7+ R8);
[0039]According to the virtual break and virtual short, the non-inverting end and inverting end of the integrated operational amplifier A1, VA1+=VA1-, the formula is rationalized:
[0040]Vo=VREF+(V_T2-V_R2)*(R8+R7)/(R6+R7)=VREF+IO*R1*(R8+R7)/(R6+R7);
[0041]At this point, repeating the disconnection of motor B2 and the I_T2 stage, after the current transformer sampling module 1, the positive bias detection module 2 in-phase amplifying circuit, the output voltage VO follows I0 in the size of VREF~VREF+IO*R1*(R8 +R7)/(R6+R7) changes to achieve stable sampling and reliable output of high-end current.
[0042]The positive bias high-end current detection circuit of the present invention isolates and samples the high-end current through the current transformer sampling module, and detects the positive bias output of the high-end current sampled by the current transformer sampling module through the positive bias detection module, thereby discarding the single-resistor low-end The sampling current mode avoids inaccurate sampling due to ground potential fluctuations, reduces sampling current distortion and avoids the uncertainty of output when the load is zero, low cost, high accuracy, and improved product reliability.
