WO2023273294A1

WO2023273294A1 - Front-end auxiliary circuit of high-power capacitive load instrument

Info

Publication number: WO2023273294A1
Application number: PCT/CN2022/071106
Authority: WO
Inventors: 王永国; 林彦辰; 张隽毅
Original assignee: 杭州米福科技有限公司
Priority date: 2021-06-29
Filing date: 2022-01-10
Publication date: 2023-01-05
Also published as: CN113381593A; CN113381593B

Abstract

Disclosed in the present invention is a front-end auxiliary circuit of a high-power capacitive load instrument, comprising an input filter circuit, a rectifier circuit, a boost circuit, and an output filter circuit that are successively connected. The input filter circuit is connected to a power frequency power grid, and the output end of the output filter circuit is connected to a capacitive load; the input filter circuit comprises a first subcircuit and a second subcircuit, and a varistor and four X-capacitors are successively connected in parallel between a live wire and a neutral wire of the firs subcircuit; the second subcircuit is provided with four common mode inductors on a live wire and a neutral wire, the live wire and the neutral wire are respectively connected in parallel to a gas discharge tube on each common mode inductor, and a Y-capacitor is connected in parallel between the loop of each common mode inductor and protective earthing; the output filter circuit comprises four large-capacity electrolytic capacitors connected in parallel with each other, two safety capacitors, and a common mode inductor. According to the present invention, the interference or disturbance of high-order harmonics of the high-power capacitive instrument to the power frequency power grid can be reduced, and risks of the instrument operating at high power are greatly reduced.

Description

A front-end auxiliary circuit of a high-power capacitive load instrument

technical field

The invention belongs to the technical field of electronic circuits, in particular to a front-end auxiliary circuit of a high-power capacitive load instrument.

Background technique

With the development of the type and quantity of electrical appliances, the impact of the instrument on the power grid and the environment is required to meet the standards, and at the same time, it must have a certain immunity to the disturbance that may occur in the power grid, that is, the instrument is required to achieve electromagnetic compatibility (EMC). A very important part of electromagnetic compatibility is to reduce the interference or disturbance of electrical equipment on the power frequency grid. The purpose is to make the input voltage and intake current of the instrument or equipment consistent and reduce the impact of high-order harmonic current on the grid.

Capacitive loads generally refer to loads with capacitance parameters, that is, loads that conform to the characteristics of current leading voltage. When the capacitive load is charged and discharged, the voltage cannot change suddenly, the corresponding power factor is negative, and the corresponding power factor of the inductive load is positive.

For capacitive loads, many related circuits have been designed in the prior art. For example, the Chinese patent document whose publication number is CN1777010A discloses a matching circuit between a pulse power supply and a capacitive load; the Chinese patent document whose publication number is CN101662233A discloses a A circuit for driving single or multiple capacitive loads.

In view of the capacitive load’s characteristic that the voltage of the capacitor cannot be changed suddenly, when the power supply voltage is less than the capacitor voltage, the current taken by the instrument from the grid is zero; The waveform of the current is a pulse wave. It can be seen from the Fourier series expansion of the pulse wave that many high-order harmonics will be generated at this time, which will cause serious interference to the power grid.

Adding a common-mode inductance to the power grid input terminal can reduce the impact of the high-frequency harmonics of the instrument on the power grid. The larger the inductance, the better the filtering effect, but the increase in the inductance will cause excessive energy to be stored in the common-mode inductance, thereby affect the performance of the circuit.

Contents of the invention

The invention provides a front-end auxiliary circuit of a high-power capacitive load instrument, which can be used for driving the high-power capacitive load and adjusting the power factor, and has stable operation and low radiation interference.

A front-end auxiliary circuit of a high-power capacitive load instrument, including an input filter circuit, a rectifier circuit, a boost circuit and an output filter circuit connected in sequence; the input end of the input filter circuit is connected to the power frequency grid, and the output filter circuit The output of the circuit is connected to a capacitive load;

The input filter circuit includes a first sub-circuit and a second sub-circuit, and the first sub-circuit has a piezoresistor R1 and two X capacitors connected in parallel in sequence between the live line and the neutral line;

The second sub-circuit is provided with at least four common-mode inductors on the live wire and the neutral wire, and a gas discharge tube is connected in parallel to each common-mode inductor on the neutral wire and the live wire, and the circuit between each common-mode inductor and the protective ground There is a Y capacitor connected in parallel between them;

The rectifier circuit is used to convert the AC power after the input filter circuit into DC power, and the boost circuit is used to boost the DC power output by the rectifier circuit;

The output filtering circuit includes four 680uF large-capacity electrolytic capacitors, two 0.47uF safety capacitors and a common-mode inductor L6 connected in parallel.

Further, the live line of the first sub-circuit is also provided with a fuse F1 with a parameter of 10A/250V.

Further, in the second sub-circuit, the number of common-mode inductors is four, and the inductances of the four common-mode inductors are 15mH, 20mH, 25mH, and 12mH respectively; the first three common-mode inductors use beryllium molybdenum cores, The fourth common mode inductor uses a high flux manganese zinc core.

Optionally, the total capacity of all Y capacitors in the second sub-circuit is 6000pF, including eight 500pF Y capacitors and two 1000pF Y capacitors; wherein, two 1000pF Y capacitors are connected in parallel between the loop of the fourth common-mode inductor and between protective earths.

Further, the rectifier circuit includes two rectifier bridge modules, the two input ends of one rectifier bridge are connected in parallel to the live wire, and the two input ends of the other rectifier bridge are connected in parallel to the neutral wire; each rectifier bridge The two output terminals are respectively connected in parallel to the DC output lines.

Further, the boost circuit adopts a boost boost circuit, including an inductor L5 and a diode D3 connected in series on the positive bus of the DC output line, between the positive terminal of the diode D3 and the negative bus, and between the negative terminal of the diode D3 and the negative bus A V-groove field effect transistor Q1 and a capacitor C13 are connected in parallel therebetween.

The output filter circuit includes four 680uF large-capacity electrolytic capacitors and two 0.47uF safety capacitors connected in parallel, which are output after being filtered by the common mode inductor L6.

The boost circuit is externally connected to the main control chip circuit; the main control chip circuit is connected to the power frequency grid through the chip power supply circuit; a protection circuit is connected between the output end of the output filter circuit and the main control chip circuit, and the described The protection circuit includes an undervoltage protection circuit, an overtemperature protection circuit and an overcurrent (short circuit) protection circuit.

Further, the undervoltage protection circuit includes a voltage comparator U1, the positive input terminal of the voltage comparator U1 is connected to the resistor R2 and one end of the regulator tube D4, and the other end of the resistor R2 is connected to the first auxiliary power supply, The other ends of the regulator tube D4 are respectively grounded; the negative input end of the voltage comparator U1 is connected to the sampling voltage;

The output end of the voltage comparator U1 is connected to one end of the resistor R3 and the anode of the optocoupler OPT1, the other end of the resistor R3 is connected to the first auxiliary power supply, and the cathode of the optocoupler OPT1 is grounded; the output end of the optocoupler is connected to the single chip microcomputer MCU connection.

Further, the overcurrent (short circuit) protection circuit includes a voltage comparator U2, the positive input terminal of the voltage comparator U2 is connected to the resistor R7 and one end of the regulator tube D5, and the other end of the resistor R7 is connected to the second Auxiliary power supply connection, the other end of the regulator tube D5 is grounded;

The negative input terminal of the voltage comparator U2 is respectively connected to one end of the voltage dividing resistor R6, the voltage dividing resistor R5 and the capacitor C18, and the other end of the voltage dividing resistor R6 is respectively connected to the output terminal of the rectifier circuit and one end of the sampling resistor R4, The other end of the sampling resistor R4, the voltage dividing resistor R5 and the capacitor C18 is grounded;

The output terminal of the voltage comparator U2 is respectively connected with one end of the resistor R8 and the cathode of the diode D6, the other end of the resistor R8 is respectively connected with the second auxiliary power supply and the Vin pin of the power chip U3, and the anode of the diode D6 is respectively connected with the power supply The ADJ pin of the chip U3, one end of the resistor R9, and one end of the resistor R10 are connected, and the other end of the resistor R9 is respectively connected with the Vout pin of the power supply chip U3 and the VDD pin of the main control chip U4. The GNDs of the control chip U4 are all grounded.

Compared with the prior art, the present invention has the following beneficial effects:

1. The input filter circuit of the present invention adopts a gas discharge tube connected in parallel on the common-mode inductor, and utilizes the gas discharge tube to absorb the excessive energy stored in the common-mode inductor due to increasing the inductance; the common-mode inductor with high inductance is guaranteed It can not only reduce the interference of the instrument's high-order harmonics to the power frequency grid, but also inhibit the excessive energy stored in the high-inductance common-mode inductor from adversely affecting the instrument. At the same time, a plurality of Y capacitors are scattered and connected in parallel between the loops of each inductor and the protective grounding to further reduce the interference or disturbance of the high-order harmonics of the instrument on the power frequency grid. At the same time, the influence of the machine to the ground leakage current caused by the Y capacitor capacity is still controlled within the allowable range of IEC60601-1.

2. In the rectifier circuit of the present invention, the input ends of each rectifier bridge are connected in parallel as a lead wire at one end, which cleverly allows the two rectifier bridges to be electrically connected in parallel, increases the output current of the rectifier bridge, and at the same time facilitates the wiring of the PCB board , to ensure that the leads of the rectifier bridge can have a sufficiently large area of copper.

3. The present invention adds overcurrent (short circuit) protection during operation, overtemperature protection of the power tube and undervoltage protection when the power frequency grid voltage is too low to the main control chip circuit. There is a reliable guarantee when running at high power.

Description of drawings

Fig. 1 is the overall structural diagram of the front-end auxiliary circuit of a kind of high-power capacitive load instrument of the embodiment of the present invention;

Fig. 2 is the structural diagram of the first sub-circuit in the input filter circuit;

Fig. 3 is the structural diagram of the second sub-circuit in the input filter circuit;

Figure 4 is a structural diagram of a rectifier circuit;

Fig. 5 is a structural diagram of a boost circuit;

Fig. 6 is the structural diagram of output filter circuit;

FIG. 7 is a structural diagram of an undervoltage protection circuit;

FIG. 8 is a structural diagram of an overcurrent protection circuit.

detailed description

The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be noted that the following embodiments are intended to facilitate the understanding of the present invention, but do not limit it in any way.

As shown in Figure 1, a front-end auxiliary circuit of a high-power capacitive load instrument includes an input filter circuit A, a rectifier circuit B, a boost circuit C and an output filter circuit D connected in sequence. After the network power supply enters the line, it is output after filtering, rectifying, boosting, and output filtering.

The input terminal of the input filter circuit A is connected to the power frequency grid, and the output terminal of the output filter circuit is connected to the capacitive load. The boost circuit is externally connected to the main control chip circuit H; the main control chip circuit H is connected to the power frequency grid through the chip power supply circuit G; a protection circuit is connected between the output terminal of the output filter circuit D and the main control chip circuit H, and the protection circuit includes Voltage protection circuit, over-temperature protection circuit and over-current (short circuit) protection circuit, etc. A soft switch circuit E is also connected between the input filter circuit A and the chip power supply circuit G.

The input filter circuit includes a first subcircuit and a second subcircuit.

As shown in FIG. 2 , the first sub-circuit has a varistor R1 and four X capacitors connected in parallel between the live line L and the neutral line N, respectively for absorbing surge voltage and power supply filtering. A fuse F1 is also provided on the live line of the first sub-circuit, with a parameter of 10A/250V. In this embodiment, the capacities of the four X capacitors are all 0.47uF. In FIG. 2, the X capacitors C1 and C2 respectively represent two capacitors connected in parallel.

As shown in Figure 3, the second sub-circuit is equipped with four common-mode inductors L1, L2, L3 and L4 on the live line L and the neutral line N, and a gas discharge is connected in parallel to each common-mode inductor on the neutral line and the live line Tubes, respectively corresponding to the gas discharge tubes GDT1 ~ GDT8, use the gas discharge tube to absorb the excessive energy stored in the common mode inductor due to the increase of the inductance during operation, and ensure that the common mode inductor with high inductance can reduce the high-order harmonics of the instrument Interference to the power frequency grid can also inhibit the excessive energy stored in the high-inductance common-mode inductance from adversely affecting the instrument.

The inductances of the four common-mode inductors L1, L2, L3 and L4 are 15mH, 20mH, 25mH, and 12mH respectively; the first three common-mode inductors use beryllium molybdenum cores, and the fourth common-mode inductor uses manganese with high magnetic flux Zinc core.

There is a Y capacitor connected in parallel between the loop of each common mode inductor and the protective ground, corresponding to the Y capacitors C3-C12 respectively, with a total capacity of 6000pF. Eight capacitors of 500pF and two capacitors of 1000pF are scattered and connected in parallel with the loops of each inductor. Protective grounding between PEs further reduces the interference or disturbance of the high-order harmonics of the instrument on the power frequency grid.

The structure diagram of the rectifier circuit is shown in Figure 4. The two input ends of one rectifier bridge are connected in parallel and then connected to the live wire, and the two input ends of the other rectifier bridge are connected in parallel and then connected to the neutral wire; the two output ends of each rectifier bridge respectively connected in parallel to the DC output line.

In the present invention, two rectifier bridges can be flatly pasted on an aluminum heat sink back to back, thereby effectively improving the utilization space of the chassis. The two power frequency rectifier bridge stack modules D1 and D2 are not the conventional parallel connection method of two rectifier bridges. The terminals of the two rectifier bridges with the same name are connected in parallel, but the input terminals of each rectifier bridge are connected in parallel as one terminal lead, which is very clever It not only allows the two rectifier bridges to be electrically connected in parallel, but also increases the output current of the rectifier bridge, and at the same time facilitates the wiring of the PCB board, ensuring that the leads of the rectifier bridge can have a large enough area of copper. In addition, it also ensures that two rectifier bridges can be attached back to back to a metal heat sink.

As shown in Figure 5, the booster circuit includes an inductor L5 and a diode D3 connected in series on the positive busbar of the DC output line. V-shaped Slot FET Q1 and capacitor C13.

The present invention adopts the boost circuit topological circuit, utilizes the energy storage characteristics of the inductance L5, and converts the current energy into magnetic field energy storage when the V-groove field effect transistor (VMOSFET-N) Q1 is turned on. When Q1 is turned off, it converts the stored magnetic field energy into electrical energy, thereby boosting the voltage from the rectified 300VDC to 400VDC. The function of diode D3 is to let the energy on the inductor L5 have a way to release to the load, and let the machine no longer be directly affected by the voltage value of the four parallel large capacitors when it absorbs current from the power frequency grid, effectively inhibiting the machine from Interference or disturbance of power frequency grid.

As shown in Figure 6, the output filter circuit includes four 680uF large-capacity electrolytic capacitors and two 0.47uF safety capacitors connected in parallel, and the output is filtered by the common mode inductor L6. In the figure, large-capacity electrolytic capacitors C14 and C15 respectively represent two parallel capacitors of 680uF. 400V DC (400VDC) is output (400Vout) after passing through the output filter circuit.

Because there is no temperature protection, short circuit protection and undervoltage protection in the internal control circuit of the power factor control (PFC) main control chip, that is, there is no reliable guarantee during high-power operation. To this end, the circuit of the present invention adds 1. short-circuit (overcurrent) protection during work, 2. over-temperature protection of the power tube and 3. under-voltage protection when the power frequency network voltage is too low.

The chip power supply circuit includes a power frequency step-down transformer (220V-12V), a rectifier circuit composed of four 1N4007 diodes, and a power chip LM317.

As shown in Figure 7, the undervoltage protection circuit includes a voltage comparator U1, the positive input terminal of the voltage comparator U1 is connected to a resistor R2 and one end of a voltage regulator tube D4, and the other end of the resistor R2 is connected to the first auxiliary power supply for voltage regulation The other ends of the tubes D4 are respectively grounded. The negative input terminal of the voltage comparator U1 is connected to the sampling voltage. The output end of the voltage comparator U1 is connected to one end of the resistor R3 and the anode of the optocoupler OPT1, the other end of the resistor R3 is connected to the first auxiliary power supply, and the cathode of the optocoupler OPT1 is grounded; the output end of the optocoupler is connected to the MCU .

The first auxiliary power supply is +18V, and the first auxiliary power supply, the resistor R2 and the regulator tube D4 form a reference voltage. When the output voltage is lower than 340V, the sampling voltage (Vol Samp) is lower than the reference voltage, the output state of the voltage comparator U1 is reversed, and the output is high, and the optocoupler OPT1 is used to give instructions and suspend the energy output operation of the machine. The signal is transmitted to the single-chip MCU and the host computer for processing.

When the temperature of the MOS switching tube of the soft switching circuit is too high, the temperature of the radiator behind it rises accordingly, and the temperature switch attached to it is closed, which pulls down the reference voltage of the power chip LM317 in the chip power supply circuit, so that the main control chip The circuit is powered off to avoid damage to the circuit due to high temperature.

As shown in Figure 8, the short circuit (overcurrent) protection circuit includes a voltage comparator U2, the positive input terminal of the voltage comparator U2 is connected with the resistor R7 and one end of the voltage regulator tube D5, and the other end of the resistor R7 is connected with the second auxiliary power supply connection, the other end of the regulator tube D5 is grounded;

The negative input terminal of the voltage comparator U2 is respectively connected to one end of the voltage dividing resistor R6, the voltage dividing resistor R5 and the capacitor C18, and the other end of the voltage dividing resistor R6 is respectively connected to the output terminal of the rectifier circuit and one end of the sampling resistor R4, and the sampling resistor The other end of R4, voltage dividing resistor R5 and capacitor C18 is grounded;

The output terminal of the voltage comparator U2 is respectively connected to one end of the resistor R8 and the cathode of the diode D6, the other end of the resistor R8 is respectively connected to the second auxiliary power supply and the Vin pin of the power chip U3, and the anode of the diode D6 is respectively connected to the power chip U3 The ADJ pin of the resistor R9, one end of the resistor R10 are connected, the other end of the resistor R9 is respectively connected to the Vout pin of the power supply chip U3, and the VDD pin of the main control chip U4, and the other end of the resistor R10 is connected to the main control chip The GNDs of U4 are all grounded.

The voltage of the second auxiliary power supply is +18V, and the second auxiliary power supply, resistor R7 and regulator D5 form a reference voltage (1.2V). In the rectification output circuit (300VDC) of the circuit, a 20mΩ sampling resistor R4 is connected in series, so that the output current can be detected without affecting the current output, and the current sampling signal is compared with the reference voltage (1.2V) after being divided by R6, R5, and C18. For comparison, adjust the voltage dividing resistors R6 and R5 to adjust the protection current threshold. When the output current exceeds the set value, the output state of the comparator U2 is reversed, and the output is low, and the voltage of the reference pin of the power chip U3 (LM317) is pulled to Low, cut off the power supply of the main control chip U4 (PFC-CHIP), so that it stops working.

Over-current (short circuit), under-voltage, over-temperature protection In addition to the above hardware protection, there is also an independent photocoupler interface, which can communicate with the single-chip microcomputer and transmit the fault information to the single-chip microcomputer and the upper PC.

The embodiments described above have described the technical solutions and beneficial effects of the present invention in detail. It should be understood that the above descriptions are only specific embodiments of the present invention, and are not intended to limit the present invention. All within the scope of the principles of the present invention Any modifications, supplements and equivalent replacements should be included within the protection scope of the present invention.

Claims

A front-end auxiliary circuit of a high-power capacitive load instrument is characterized in that it includes an input filter circuit, a rectifier circuit, a boost circuit and an output filter circuit connected in sequence; the input end of the input filter circuit is connected to the power frequency grid Connection, the output terminal of the output filter circuit is connected to the capacitive load;

The input filter circuit includes a first sub-circuit and a second sub-circuit, and the first sub-circuit has a piezoresistor R1 and four X capacitors sequentially connected in parallel between the live line and the neutral line;

The second sub-circuit is provided with at least four common-mode inductors on the live wire and the neutral wire, and a gas discharge tube is connected in parallel to each common-mode inductor on the neutral wire and the live wire, and the circuit between each common-mode inductor and the protective ground There is a Y capacitor connected in parallel between them;

The rectifier circuit is used to convert the AC power after the input filter circuit into DC power, and the boost circuit is used to boost the DC power output by the rectifier circuit;

The output filtering circuit includes four 680uF large-capacity electrolytic capacitors, two 0.47uF safety capacitors and a common-mode inductor L6 connected in parallel.
The front-end auxiliary circuit of a high-power capacitive load instrument according to claim 1, wherein a fuse F1 is provided on the live line of the first sub-circuit, and the parameter is 10A/250V.
The front-end auxiliary circuit of the high-power capacitive load instrument according to claim 1, wherein, in the second sub-circuit, the number of common-mode inductors is four, and the inductances of the four common-mode inductors are respectively 15mH, 20mH, 25mH, 12mH; the first three common-mode inductors use beryllium molybdenum cores, and the fourth common-mode inductors use high-flux manganese-zinc cores.
The front-end auxiliary circuit of the high-power capacitive load instrument according to claim 3, wherein the total capacity of all Y capacitors in the second sub-circuit is 6000pF, including eight 500pFY capacitors and two 1000pF Y capacitors; wherein , Two 1000pF Y capacitors are connected in parallel between the loop of the fourth common mode inductor and the protective ground.
The front-end auxiliary circuit of the high-power capacitive load instrument according to claim 1, wherein the rectification circuit includes two rectification bridge modules, and the two input terminals of one rectification bridge are connected in parallel with the fire wire, and the other The two input terminals of the rectifier bridge are connected in parallel to the neutral line; the two output terminals of each rectifier bridge are respectively connected in parallel to the DC output line.
The front-end auxiliary circuit of a high-power capacitive load instrument according to claim 5, wherein the boost circuit adopts a boost circuit, comprising an inductor L5 and a diode D3 connected in series on the positive busbar of the DC output line, A V-groove field effect transistor Q1 and a capacitor C13 are connected in parallel between the positive terminal of the diode D3 and the negative bus, and between the negative terminal of the diode D3 and the negative bus.
The front-end auxiliary circuit of a high-power capacitive load instrument according to claim 1, wherein the output filter circuit includes four 680uF large-capacity electrolytic capacitors and two 0.47uF safety capacitors connected in parallel, The output is filtered by the mold inductor L6.
The front-end auxiliary circuit of a high-power capacitive load instrument according to claim 1, wherein the boost circuit is externally connected to the main control chip circuit; the main control chip circuit is connected to the power frequency grid through the chip power supply circuit ; A protection circuit is connected between the output terminal of the output filter circuit and the main control chip circuit, and the protection circuit includes an undervoltage protection circuit, an over-temperature protection circuit and an over-current protection circuit.
The front-end auxiliary circuit of a high-power capacitive load instrument according to claim 8, wherein the undervoltage protection circuit includes a voltage comparator U1, and the positive input terminal of the voltage comparator U1 is connected to a resistor R2 and One end of the regulator tube D4 and the other end of the resistor R2 are connected to the first auxiliary power supply, and the other ends of the regulator tube D4 are respectively grounded; the negative input terminal of the voltage comparator U1 is connected to the sampling voltage;

The output end of the voltage comparator U1 is connected to one end of the resistor R3 and the anode of the optocoupler OPT1, the other end of the resistor R3 is connected to the first auxiliary power supply, and the cathode of the optocoupler OPT1 is grounded; the output end of the optocoupler is connected to the single chip microcomputer MCU connection.
The front-end auxiliary circuit of a high-power capacitive load instrument according to claim 8, wherein the overcurrent protection circuit includes a voltage comparator U2, and the positive input terminal of the voltage comparator U2 is connected to the resistor R7 and One end of the regulator tube D5 is connected, the other end of the resistor R7 is connected to the second auxiliary power supply, and the other end of the regulator tube D5 is grounded;

The negative input terminal of the voltage comparator U2 is respectively connected to one end of the voltage dividing resistor R6, the voltage dividing resistor R5 and the capacitor C18, and the other end of the voltage dividing resistor R6 is respectively connected to the output terminal of the rectifier circuit and one end of the sampling resistor R4, The other end of the sampling resistor R4, the voltage dividing resistor R5 and the capacitor C18 is grounded;

The output terminal of the voltage comparator U2 is respectively connected with one end of the resistor R8 and the cathode of the diode D6, the other end of the resistor R8 is respectively connected with the second auxiliary power supply and the Vin pin of the power chip U3, and the anode of the diode D6 is respectively connected with the power supply The ADJ pin of the chip U3, one end of the resistor R9, and one end of the resistor R10 are connected, and the other end of the resistor R9 is respectively connected with the Vout pin of the power supply chip U3 and the VDD pin of the main control chip U4. The GNDs of the control chip U4 are all grounded.