WO2022041590A1

WO2022041590A1 - Current detection circuit, power factor correction circuit, and current detection method

Info

Publication number: WO2022041590A1
Application number: PCT/CN2020/137654
Authority: WO
Inventors: 李锐; 刘宏森; 朱益波; 兰正宇; 郑煦
Original assignee: 杭州中恒电气股份有限公司
Priority date: 2020-08-31
Filing date: 2020-12-18
Publication date: 2022-03-03
Also published as: CN112202330A

Abstract

The present invention relates to the field of switched-mode power supply power electronics, and discloses a current detection circuit. The current detection circuit and a switching circuit are connected in series between a first connection point and a second connection point. The current detection circuit comprises a current transformer and a secondary circuit. A primary winding of the current transformer is connected in series between the switching circuit and the second connection point, and a secondary winding of the current transformer and the secondary circuit are connected in series. The current transformer is used for converting, when the switching circuit is turned on, a current to be detected into a secondary current, and the secondary circuit is used for converting the secondary current into a detection voltage. The current detection circuit does not need to use a rectifying circuit to rectify the current to be detected and then detect same, such that the problem of high costs caused by a large number of elements of the rectifying circuit is solved, and the costs of the current detection circuit can be reduced. The present invention further discloses a power factor correction circuit and a current detection method.

Description

A current detection circuit, power factor correction circuit and current detection method

technical field

The invention relates to the field of switching power supply power electronics, in particular to a current detection circuit, a power factor correction circuit and a current detection method.

Background technique

Before the AC input signal is provided to the electrical equipment, a bridgeless Power Factor Correction (PFC) circuit is usually used to perform power factor correction on the AC input signal to improve the power efficiency of the electrical equipment. In order to control the working mode of the bridgeless PFC circuit, a current detection circuit is required to detect the AC input current of the bridgeless PFC circuit. In the related art, it is difficult for the current detection circuit to directly detect the AC input current, and the current The rectifier circuit in the detection circuit rectifies the AC input current, and then samples the current output by the rectifier circuit to calculate the AC input current. However, the rectifier circuit has a large number of electronic components, which increases the cost of the current detection circuit.

Aiming at the problem of high cost caused by the large number of components in the current detection circuit in the related art, no effective solution has been proposed yet.

SUMMARY OF THE INVENTION

In order to overcome the deficiencies of the prior art, one of the purposes of the present invention is to provide a current detection circuit, which converts the current to be measured into a secondary current through a current transformer, and converts the secondary current into a detection voltage through the secondary circuit, The problem of high cost caused by the large number of components of the current detection circuit is solved, and the cost of the current detection circuit can be reduced.

One of the objects of the present invention adopts the following technical solutions to realize:

A current detection circuit, the current detection circuit and the switch switching circuit are connected in series between a first connection point and a second connection point, the first connection point and the second connection point are respectively connected to a working circuit, the The first connection point is connected to one end of the AC circuit through the first inductor, the second connection point is connected to the other end of the AC circuit, and the current detection circuit includes: a current transformer and a secondary circuit;

Wherein, the primary winding of the current transformer is connected in series between the switch switching circuit and the second connection point, and the secondary winding of the current transformer is connected in series with the secondary circuit;

The current transformer is used for converting the current to be measured output from the AC circuit into a secondary current when the switching circuit is turned on; the secondary circuit is used for converting the secondary current into a detection voltage.

Further, the secondary side circuit includes a first switch unit, a second switch unit and a voltage conversion unit;

Wherein, the first end of the first switch unit is connected to the opposite end of the secondary winding, the second end of the first switch unit is connected to the voltage conversion unit, and the first switch unit is used for The current to be measured is turned on in a positive half cycle and turned off when the current to be measured is in a negative half cycle;

The first end of the second switch unit is connected to the same name end of the secondary winding, the second end of the second switch unit is connected to the voltage conversion unit, and the second switch unit is used for turning off when the current is in a positive half cycle and turning on when the current to be measured is in a negative half cycle;

The first end of the voltage conversion unit is connected to the first switch unit, the second end of the voltage conversion unit is connected to the second switch unit, and the voltage conversion unit is used for converting the secondary side current into all the detection voltage.

Further, the first switch unit includes a third switch tube and a first Zener diode, the third switch tube is connected in parallel with the first Zener diode, and the cathode of the first Zener diode is connected to the secondary Zener diode. a side winding, and the anode of the first Zener diode is connected to the voltage conversion unit.

Further, the third switch tube is any one of a MOSFET tube, an IGBT tube, a GaN tube, a triode, a thyristor and a relay.

Further, the second switch unit includes a fourth switch tube and a second Zener diode, the fourth switch tube is connected in parallel with the second Zener diode, and the cathode of the second Zener diode is connected to the secondary Zener diode. side winding, and the anode of the second Zener diode is connected to the voltage conversion unit.

Further, the fourth switch tube is any one of a MOSFET tube, an IGBT tube, a GaN tube, a triode, a thyristor and a relay.

Further, the voltage conversion unit includes a sampling resistor and a DC power supply, the sampling resistor is connected between the first switch unit and the positive pole of the DC power supply, and the connection between the sampling resistor and the DC power supply is connected. The node is connected to the second switch unit, and the negative electrode of the DC power source is grounded.

The second purpose of the invention is to provide a power factor correction circuit, which converts the current to be measured into the secondary current through the current transformer, and converts the secondary current into the detection voltage through the secondary circuit, which solves the problem of the components of the current detection circuit. The problem of high cost is caused by a large number, and the cost of the power factor correction circuit is reduced as a whole.

The second purpose of the present invention adopts the following technical solutions to realize:

A power factor correction circuit includes an AC power supply, a first inductor, a switch switching circuit, a working circuit and a current detection circuit which is one of the objectives of the present invention; the first connection point is connected to the AC power supply through the first inductor. one end, the second connection point is connected to the other end of the AC power supply;

Wherein, the working circuit includes a rectifier circuit and a load circuit, the rectifier circuit includes a first bridge arm, a second bridge arm, a third bridge arm and a fourth bridge arm; one end of the first bridge arm and the first bridge arm One end of the three bridge arms is connected to the load circuit, the other end of the first bridge arm is connected to one end of the second bridge arm and is connected to the first connection point, and the third bridge arm is connected to the first connection point. The other end is connected to one end of the fourth bridge arm and is connected to the second connection point, and the other end of the second bridge arm is connected to the other end of the fourth bridge arm and is connected to the load circuit.

Further, the load circuit includes a filter capacitor and a load resistor, the filter capacitor and the load resistor are connected in parallel, the positive electrode of the filter capacitor is connected to one end of the first bridge arm, and the negative electrode of the filter capacitor is connected to the the other end of the second bridge arm.

The third purpose of the invention is to provide a current detection method, which is suitable for high frequency and high power density applications by calculating the resistance value of the sampling resistor and the turns ratio of the current transformer in the voltage secondary circuit.

The third purpose of the present invention adopts the following technical solutions to realize:

A current detection method, applied to the current detection circuit of the second purpose of the present invention, the method comprising:

Get the detection voltage;

Calculated according to the detection voltage, the resistance value of the sampling resistor in the secondary circuit and the turns ratio of the primary winding and the secondary winding in the current transformer to obtain the current to be measured output from the AC power supply.

Compared with the prior art, the beneficial effects of the present invention are:

The invention does not need to use a rectifier circuit to rectify the current to be measured output from the AC power supply before detection, saves the components of the rectifier circuit, saves the drawing space, reduces the cost of the current detection circuit, and reduces the cost of the rectifier circuit. Components can reduce the failure rate of the overall circuit, thereby improving the reliability of the current detection circuit.

Description of drawings

1 is a schematic diagram of a circuit structure of a power factor correction circuit according to Embodiment 1 of the present invention;

2 is a schematic diagram of the current flow of the current to be measured in Embodiment 1 of the present invention;

FIG. 3 is a flow chart of a current detection method according to Embodiment 3 of the present invention.

In the figure: 90, switch switching circuit; 100, secondary circuit; 101, first switch unit; 102, second switch unit; 103, voltage conversion unit; 1, first connection point; 2, second connection point.

detailed description

The present invention will be described in more detail below with reference to the accompanying drawings. It should be noted that the following description of the present invention with reference to the accompanying drawings is only illustrative and not restrictive. The sampling resistance and the load resistance in each embodiment are both resistance networks, which may be a resistance element, or a circuit in which several resistance elements with different and/or the same resistance value are connected in series and/or in parallel, and the first inductance is an inductance. The network can be an inductive element, or it can be a series and/or parallel circuit of several inductive elements with different and/or the same resistance value. A circuit with different and/or identical capacitive elements in series and/or parallel. The various embodiments may be combined with each other to form other embodiments not shown in the following description.

Example 1

Embodiment 1 provides a current detection circuit. Please refer to FIG. 1. The current detection circuit and the switch switching circuit 90 are connected in series between the first connection point 1 and the second connection point 2. The first connection point 1 and the second connection point 90 are connected in series. The connection points 2 are respectively connected to the working circuit, the first connection point 1 is connected to one end of the AC circuit via the first inductor L1, the second connection point 2 is connected to the other end of the AC circuit, and the current detection circuit includes a current transformer CT1 and a secondary side circuit 100. The primary winding of the current transformer CT1 is connected in series between the switching circuit 90 and the second connection point 2 , and the secondary winding of the current transformer CT1 is connected in series with the secondary circuit 100 . The same-named end of the primary winding and the same-named end of the secondary winding in the current transformer CT1 are both close to the second connection point 2 , and the synonymous end of the primary winding and the synonymous end of the secondary winding are both close to the first connection point 1 .

The switching circuit 90 is turned on, which can control the current to be measured output from the AC circuit to flow back to the AC circuit through the current transformer CT1. The switch switching circuit 90 is turned off, which can control the current to be measured output from the AC circuit to flow back to the AC circuit through the working circuit. By turning the switching circuit 90 on or off alternately, the AC circuit can be controlled to provide AC power to the working circuit, or the AC circuit can be controlled to stop supplying power to the working circuit and the AC current output from the AC circuit can be detected as the current to be measured.

2 is a schematic diagram of the current flow of the current to be measured output from the AC circuit, and FIG. 2(a) is a schematic diagram of the flow of the current to be measured when the switching circuit 90 is turned on when the current to be measured is a positive half cycle; FIG. 2(b) is a schematic diagram of the flow of the current to be measured when the switching circuit 90 is turned off when the current to be measured is a positive half cycle; When the circuit 90 is turned on, a schematic diagram of the flow of the current to be measured; FIG. 2(d) is a schematic diagram of the flow of the current to be measured when the switching circuit 90 is turned off when the current to be measured is in a negative half cycle.

The switch switching circuit 90 includes a first switch S1 and a second switch S2, the source of the first switch S1 is connected to the source of the second switch S2, the drain of the first switch S1 is connected to the first connection point, The drain of the second switch S2 is connected to the different terminal of the current transformer, and the gate of the first switch S1 and the gate of the second switch S2 are connected to the external control circuit. The first switch transistor S1 and the second switch transistor S2 may be any one of a MOSFET transistor, an IGBT transistor, a GaN transistor, a triode, a thyristor, and a relay. In this embodiment, the first switch transistor S1 and the second switch transistor S2 are both NMOS transistors. The first switch S1 and the second switch S2 are simultaneously turned on under the control of the external control circuit, so that the current to be measured output from the AC circuit flows back to the AC circuit through the current transformer CT1.

The current transformer CT1 converts the current to be measured into the secondary current when the switch switching circuit 90 is turned on. The secondary circuit 100 converts the secondary current into a detection voltage, and the waveform envelope of the detection voltage matches the waveform envelope of the current to be measured. Therefore, the detection of the current to be measured can be realized by detecting the voltage.

The current detection circuit does not need to use a rectifier circuit to rectify the current to be measured and then detects it, which saves the components of the rectifier circuit, thereby saving the drawing space, and solves the problem of high cost caused by the large number of components in the rectifier circuit of the current detection circuit. , the cost of the current detection circuit is reduced, and the failure rate of the whole circuit can be reduced by reducing the components of the rectifier circuit, thereby improving the reliability of the current detection circuit.

In some embodiments, the secondary circuit 100 includes a first switch unit 101 , a second switch unit 102 and a voltage conversion unit 103 . The first end of the first switch unit 101 is connected to the opposite end of the secondary winding, the second end of the first switch unit 101 is connected to the voltage conversion unit 103, the first switch unit 101 is turned on when the current to be measured is in the positive half cycle, and the first A switch unit 101 is turned off when the current to be measured is in a negative half cycle. The first end of the second switch unit 102 is connected to the same-named end of the secondary winding, the second end of the second switch unit 102 is connected to the voltage conversion unit 103, the second switch unit 102 is turned off when the current to be measured is in the positive half cycle, the first The two switch units 102 are turned on when the current to be measured is in a negative half cycle. The first terminal of the voltage conversion unit 103 is connected to the first switch unit 101 , the second terminal of the voltage conversion unit 103 is connected to the second switch unit 102 , and the voltage conversion unit 103 converts the secondary current into a detection voltage.

The first switch unit 101 and the second switch unit 102 only need to be turned on alternately, so that the detection voltage and the current to be measured are in the positive half cycle at the same time, or the detection voltage and the current to be measured are in the negative half cycle at the same time. The complete detection of the positive half cycle and the negative half cycle of the current, so the control wave timing requirements of the first switch unit 101 and the second switch unit 102 are simple, the timing accuracy is not high, and it has a certain anti-interference ability.

In some embodiments, the first switch unit 101 includes a third switch tube and a first Zener diode D7, the third switch tube is connected in parallel with the first Zener diode D7, and the cathode of the first Zener diode D7 is connected to the secondary winding The synonym terminal, the anode of the first Zener diode D7 is connected to the voltage conversion unit 103 .

As an optional technical solution, the first Zener diode D7 can be replaced by a combination of diodes in parallel with resistors or by a combination of diodes in parallel with capacitors, so as to provide a reset voltage for the current transformer CT1 while protecting the third switch tube. The first Zener diode D7 can also be replaced by a diode, but the diode will be damaged after the reverse breakdown of the current, and can no longer play the role of protecting the third switch tube.

As an optional technical solution, the third switch tube is any one of a MOSFET tube, an IGBT tube, a GaN tube, a triode, a thyristor and a relay.

In some embodiments, the second switch unit 102 includes a fourth switch tube and a second Zener diode D8, the fourth switch tube is connected in parallel with the second Zener diode D8, and the cathode of the second Zener diode D8 is connected to the secondary winding. The same name terminal, the anode of the second Zener diode D8 is connected to the voltage conversion unit 103 .

As an optional technical solution, the second Zener diode D8 can be replaced by a combination of diode parallel resistances or a combination of diode parallel capacitors, so as to provide a reset voltage for the current transformer CT1 and protect the fourth switch tube at the same time. The second Zener diode D8 can also be replaced by a diode, but the diode will be damaged after the reverse breakdown of the current, and can no longer play the role of protecting the fourth switch tube.

As an optional technical solution, the fourth switch tube is any one of a MOSFET tube, an IGBT tube, a GaN tube, a triode, a thyristor and a relay.

In this embodiment, both the third switch tube and the fourth switch tube use a combination of a body diode and an N-channel enhancement type MOSFET tube. The third switch transistor includes a first body diode D5 and a first NMOS transistor S3, the cathode of the first body diode D5 is connected to the drain of the first NMOS transistor S3, and the anode of the first body diode D5 is connected to the source of the first NMOS transistor S3 . The fourth switch tube includes a second body diode D6 and a second NMOS tube S4, the cathode of the second body diode D6 is connected to the drain of the second NMOS tube S4, and the anode of the second body diode D6 is connected to the source of the second NMOS tube S4 .

When the current to be measured is in a positive half cycle, the first switch unit 101 is turned on, and the fourth switch tube in the second switch unit 102 is turned off. When the switch switching circuit 90 is turned on, the secondary current flows from the opposite end of the secondary winding in the current transformer CT1 to the first switching unit 101 to the voltage conversion unit 103 to the second Zener diode D8 and back to the same name of the secondary winding end. When the switch switching circuit 90 is turned off, the current transformer CT1 is reset, and the secondary current flows from the same-named end of the secondary winding in the current transformer CT1 to the second Zener diode D8, to the voltage conversion unit 103, to the first switch unit 101 and back The synonymous end of the secondary winding, at this time, the secondary current flows from the cathode of the second Zener diode D8 to the anode, and the regulator voltage of the second Zener diode D8 provides the reset voltage for the current transformer CT1, while the second Zener diode D8 provides a reset voltage. D8 can protect the fourth switch tube.

When the current to be measured is in a negative half cycle, the third switch tube in the first switch unit 101 is turned off, and the second switch unit 102 is turned on. When the switch switching circuit 90 is turned on, the secondary current flows from the same name terminal of the secondary winding in the current transformer CT1 through the second switching unit 102 to the voltage conversion unit 103 to the first Zener diode D7 and flows back to the secondary winding. end. When the switch switching circuit 90 is turned off, the current transformer CT1 is reset, and the secondary current flows from the opposite end of the secondary winding in the current transformer CT1 to the voltage conversion unit 103 to the second switching unit 102 through the first Zener diode D7. Back to the same-named end of the secondary winding, at this time, the secondary current flows from the cathode of the first Zener diode D7 to the anode, and the voltage of the first Zener diode D7 provides the reset voltage for the current transformer CT1, while the first Zener diode D7 provides a reset voltage. D7 can protect the third switch tube.

In some embodiments, the voltage conversion unit 103 includes a sampling resistor R2 and a DC power source V1, the sampling resistor R2 is connected between the first switch unit 101 and the positive electrode of the DC power source V1, and the node between the sampling resistor R2 and the DC power source V1 The second switch unit 102 is connected, and the negative electrode of the DC power supply V1 is grounded. The detection voltage has a negative value, but the DSP processor can only collect positive voltage. Therefore, the detection voltage is increased to a positive value through the DC power supply V1, so that the DSP processor can collect the detection voltage, which can improve the applicability of the current detection circuit. In this embodiment, the voltage of the DC power supply V1 is 1.65V. It should be noted that the voltage of the DC power supply V1 is not limited to the above-mentioned volts.

In some embodiments, the current detection circuit can be used to detect AC input currents in all bridgeless PFC circuits, and can also be used to detect AC input currents in three-phase bridgeless PFC circuits.

Embodiment 2

The second embodiment provides a power factor correction circuit. Please refer to FIG. 1 . The power factor correction circuit includes an alternating current power supply AC, a first inductor L1, a switch circuit 90, a working circuit and the current detection circuit of the first embodiment. The first connection point 1 is connected to one end of the alternating current power source AC through the first inductor L1, and the second connection point 2 is connected to the other end of the alternating current power source AC.

The working circuit includes a rectifier circuit and a load circuit, and the rectifier circuit includes a first bridge arm, a second bridge arm, a third bridge arm and a fourth bridge arm. One end of the first bridge arm is connected to one end of the third bridge arm and connected to the load circuit, the other end of the first bridge arm is connected to one end of the second bridge arm and connected to the first connection point 1, and the other end of the third bridge arm is connected to the first connection point 1. One end is connected to one end of the fourth bridge arm and is connected to the second connection point 2 , and the other end of the second bridge arm is connected to the other end of the fourth bridge arm and is connected to the load circuit.

The load circuit includes a filter capacitor C1 and a load resistor R1, the filter capacitor C1 and the load resistor R1 are connected in parallel, the positive electrode of the filter capacitor C1 is connected to one end of the first bridge arm, and the negative electrode of the filter capacitor C1 is connected to the other end of the second bridge arm. In this embodiment, the filter capacitor C1 is an electrolytic capacitor. It should be noted that the load resistor R1 can be replaced by other load devices.

In this embodiment, a diode D1 is used for the first bridge arm, a diode D2 is used for the second bridge arm, a diode D3 is used for the third bridge arm, and a diode D4 is used for the fourth bridge arm. The cathode of the diode D1 is connected to the cathode of the diode D3, and the cathode of the diode D1 is connected to the anode of the filter capacitor C1. The anode of the diode D1 and the cathode of the diode D2 are connected, and the anode of the diode D1 is connected to the first connection point 1 . The anode of diode D3 and the cathode of diode D4 are connected, and the anode of diode D3 is connected to the second connection point 2 . The anode of diode D2 is connected to the anode of diode D4, and the anode of diode D2 is connected to the cathode of filter capacitor C1.

As an optional technical solution, the first bridge arm, the second bridge arm, the third bridge arm and the fourth bridge arm may all use any one or more of semiconductor diode devices such as MOSFET transistors, IGBT transistors, and GaN transistors. combination, as long as the bridgeless power factor correction function can be realized.

When the current to be measured is in a positive half cycle, the first NMOS transistor S3 is turned on, and the second NMOS transistor S4 is turned off. When the switching circuit 90 is turned on, the current to be measured output from the alternating current power source AC flows through the first inductor L1 to the switching switching circuit 90 to the primary winding of the current transformer CT1 and flows back to the alternating current power source AC, and the secondary circuit 100 in the secondary circuit 100 The side current flows from the opposite end of the secondary winding in the current transformer CT1 to the first NMOS transistor S3 to the sampling resistor R2 to the second Zener diode D8 and flows back to the identical end of the secondary winding. When the switching circuit 90 is turned off, the current to be measured outputted from the AC power source AC flows from the first inductor L1 to the diode D1 to the filter capacitor C1 to the diode D4 and flows back to the AC power source AC, the current transformer CT1 is reset, and the secondary current flows from the current The same-named end of the secondary winding in the transformer CT1 flows to the second Zener diode D8, flows to the sampling resistor R2, flows to the first NMOS transistor S3 and flows back to the same-named end of the secondary winding.

When the current to be measured is in a negative half cycle, the first NMOS transistor S3 is turned off, and the second NMOS transistor S4 is turned on. When the switch switching circuit 90 is turned on, the current to be measured output from the alternating current power supply AC flows through the primary winding of the current transformer CT1 to the switching switching circuit 90 to the first inductor L1 and flows back to the alternating current power supply AC, and the secondary side circuit 100 flows back to the alternating current power supply AC. The side current flows from the same name terminal of the secondary winding in the current transformer CT1 to the second NMOS transistor S4 to the sampling resistor R2 to the first Zener diode D7 and flows back to the different terminal of the secondary winding. When the switch switching circuit 90 is turned off, the current output from the AC power source AC flows through the diode D3 to the filter capacitor C1 to the diode D2 to the first inductor L1 and flows back to the AC power source AC, the current transformer CT1 is reset, and the secondary current flows from the current transformer The synonymous end of the secondary winding in CT1 flows to the first Zener diode D7, flows to the sampling resistor R2, flows to the second NMOS transistor S4 and flows back to the synonymous end of the secondary winding.

The current detection circuit does not need to use a rectifier circuit to rectify the current to be measured and then detect it, which solves the problem of high cost caused by a large number of components in the current detection circuit, and can reduce the cost of the current detection circuit, thereby reducing the overall cost of the power factor correction circuit. . By turning the switching circuit 90 on or off alternately, the alternating current power supply AC can be controlled to provide alternating current to the working circuit, or the alternating current power supply AC can be controlled to stop supplying power to the working circuit and the alternating current output from the alternating current power supply AC can be used as the current to be measured. The detection can be real-time detected before the AC circuit supplies power to the working circuit, so as to improve the power supply safety of the working circuit, thereby improving the control accuracy of the power factor correction circuit.

Embodiment 3

According to the circuit structure and working principle of the second embodiment, the waveform envelope of the detected voltage is consistent with the waveform envelope of the current to be measured, and the excitation current is converted to the secondary side relative to the current in the primary winding of the current transformer CT1 The secondary current in the winding is very small, and the excitation current can be ignored. A current detection method can be obtained to detect the AC input current of the power factor correction circuit, which is suitable for high frequency and high power density applications. Referring to Figure 3, the current detection method includes:

S10. Obtain the detection voltage;

S20. Calculate according to the detected voltage, the resistance value of the sampling resistor in the secondary circuit, and the turns ratio of the primary winding and the secondary winding in the current transformer to obtain the current to be measured output from the AC power supply.

Specifically, denote the detection voltage as Vo, and input the detection voltage Vo into the following formula to calculate the current to be measured output from the AC power supply: i=((Vo-V1)/R)*n, where i represents the to-be-measured current Measure the current, R represents the resistance value of the sampling resistor R2 in the secondary circuit 100, V1 represents the volt value of the DC power supply, Vo represents the detection voltage, that is, the voltage at the end of the sampling resistor R2 that is not connected to the DC power supply, and n represents the current transformer CT1. The turns ratio of the primary winding to the secondary winding.

It is worth noting that, in the above embodiment, the modules and units included are only divided according to functional logic, but are not limited to the above-mentioned division, as long as the corresponding functions can be realized; in addition, each functional module and unit The specific names are only for the convenience of distinguishing from each other, and are not used to limit the protection scope of the present invention.

For those skilled in the art, various other corresponding changes and deformations can be made according to the technical solutions and concepts described above, and all these changes and deformations should fall within the protection scope of the claims of the present invention.

Claims

A current detection circuit, characterized in that the current detection circuit and the switch switching circuit are connected in series between a first connection point and a second connection point, and the first connection point and the second connection point are respectively connected to the working a circuit, the first connection point is connected to one end of the AC circuit via a first inductor, the second connection point is connected to the other end of the AC circuit, and the current detection circuit comprises: a current transformer and a secondary circuit;

Wherein, the primary winding of the current transformer is connected in series between the switch switching circuit and the second connection point, and the secondary winding of the current transformer is connected in series with the secondary circuit;

The current transformer is used for converting the current to be measured output from the AC circuit into a secondary current when the switching circuit is turned on; the secondary circuit is used for converting the secondary current into a detection voltage.
The current detection circuit according to claim 1, wherein the secondary side circuit comprises a first switch unit, a second switch unit and a voltage conversion unit;

Wherein, the first end of the first switch unit is connected to the opposite end of the secondary winding, the second end of the first switch unit is connected to the voltage conversion unit, and the first switch unit is used for The current to be measured is turned on in the positive half cycle;

The first end of the second switch unit is connected to the same name end of the secondary winding, the second end of the second switch unit is connected to the voltage conversion unit, and the second switch unit is used for The current is turned on when the current is in the negative half cycle;

The first end of the voltage conversion unit is connected to the first switch unit, the second end of the voltage conversion unit is connected to the second switch unit, and the voltage conversion unit is used for converting the secondary side current into all the detection voltage.
The current detection circuit according to claim 2, wherein the first switch unit comprises a third switch tube and a first Zener diode, the third switch tube is connected in parallel with the first Zener diode, so The cathode of the first Zener diode is connected to the secondary winding, and the anode of the first Zener diode is connected to the voltage conversion unit.
The current detection circuit according to claim 3, wherein the third switch tube is any one of a MOSFET tube, an IGBT tube, a GaN tube, a triode, a thyristor and a relay.
The current detection circuit according to claim 2, wherein the second switch unit comprises a fourth switch transistor and a second Zener diode, the fourth switch transistor is connected in parallel with the second Zener diode, so The cathode of the second Zener diode is connected to the secondary winding, and the anode of the second Zener diode is connected to the voltage conversion unit.
The current detection circuit according to claim 5, wherein the fourth switch tube is any one of a MOSFET tube, an IGBT tube, a GaN tube, a triode, a thyristor and a relay.
The current detection circuit according to claim 2, wherein the voltage conversion unit comprises a sampling resistor and a DC power source, the sampling resistor is connected between the first switch unit and the positive electrode of the DC power source, and The node between the sampling resistor and the DC power supply is connected to the second switch unit, and the negative electrode of the DC power supply is grounded.
A power factor correction circuit, characterized in that it includes an alternating current power supply, a first inductor, a switching circuit, a working circuit, and the current detection circuit according to any one of claims 1 to 7; the first inductor is connected to one end of the AC power supply, and the second connection point is connected to the other end of the AC power supply;

Wherein, the working circuit includes a rectifier circuit and a load circuit, the rectifier circuit includes a first bridge arm, a second bridge arm, a third bridge arm and a fourth bridge arm; one end of the first bridge arm and the first bridge arm One end of the three bridge arms is connected to the load circuit, the other end of the first bridge arm is connected to one end of the second bridge arm and is connected to the first connection point, and the third bridge arm is connected to the first connection point. The other end is connected to one end of the fourth bridge arm and is connected to the second connection point, and the other end of the second bridge arm is connected to the other end of the fourth bridge arm and is connected to the load circuit.
The power factor correction circuit according to claim 8, wherein the load circuit comprises a filter capacitor and a load resistor, the filter capacitor and the load resistor are connected in parallel, and the positive electrode of the filter capacitor is connected to the first bridge One end of the arm, the negative pole of the filter capacitor is connected to the other end of the second bridge arm.
A current detection method, characterized in that, applied to the current detection circuit of claim 8, the method comprising:

Get the detection voltage;

Calculated according to the detection voltage, the resistance value of the sampling resistor in the secondary circuit and the turns ratio of the primary winding and the secondary winding in the current transformer to obtain the current to be measured output from the AC power supply.