TWI780791B - Current detection circuit and current detection method of the same - Google Patents

Abstract

A detection circuit is used to detect an input current of a switching power conversion circuit that receives an input voltage, and the current detection circuit includes a specific current unit, a first unidirectional-conducting element group, a magnetic bleeder circuit, a second unidirectional-conducting element group, a first switch, a second switch, a control unit and a detection unit. The specific current unit is coupled to a power switch of the switching power conversion circuit, and the first unidirectional-conducting element group, the magnetic bleeder circuit and the second unidirectional-conducting element group are connected in parallel with the specific current unit. The first switch and the second switch are coupled to the first or second unidirectional-conducting element group, and the control unit correspondingly controls the first switch and the second switch according to the input voltage in first or second direction voltage so that the detection unit detects the input current.

Description

Current detection circuit and its detection method

The invention relates to a current detection circuit and a detection method thereof, in particular to a general-purpose current detection circuit and a current detection method.

As the quality of power is increasingly required in the current electric power field, more and more electronic equipment will be equipped with power factor correction circuits at the input end to improve power quality. The power factor correction circuit mainly controls the waveform of the input current to follow the waveform of the input voltage, so a current detection circuit is necessary to obtain the waveform of the input current to facilitate the switching control of the power factor correction circuit. However, most current detection circuits used in general power factor correction circuits have limitations in use. The main difference lies in the type of structure of the power factor correction circuit. The switch control method of the circuit structure with bridge or without bridge is not the same. As a result, the current detection circuit of the two circuit structures is not compatible, and a specific current must be used. Only the detection circuit can detect the input current correctly, and the control is complicated and cumbersome.

As shown in Figure 1, the main reason for the incompatibility of the current detection circuits is that it is necessary to consider whether the current transformer CT (Current Transformer) will be saturated. The saturation mainly comes from the lack of a suitable magnetic leakage path. However, it will inevitably increase the difficulty of control if there is a suitable magnetic leakage path, or increase the Plus the complexity of the circuit itself. The current detection circuit of the power factor correction circuit with a bridge usually cannot be shared with the current detection circuit without a bridge, because the current detection circuit without a bridge needs to judge the positive and negative half-cycle signals by itself, thus requiring two sets of current comparators CT to detect them separately Plus or minus half a cycle, thereby increasing the size of the volume.

Therefore, how to design a general-purpose current detection circuit and its current detection method to be compatible with various switching power conversion circuit architectures, such as power factor correction circuits or DC conversion circuits, etc., is the author of this case. a major topic.

In order to solve the above problems, the present invention provides a current detection circuit to overcome the problems of the prior art. Therefore, the current detection circuit of the present invention is used to detect the input current of the switching power conversion circuit, and the current detection circuit includes a specific current unit, a first unidirectional conduction element group, a magnetic leakage circuit, a second unidirectional conduction element group, a second A switch, a second switch, a control unit and a detection unit. The ratio current unit has a primary winding and a secondary winding, and the primary winding is coupled to a power switch of the switching power conversion circuit. The first unidirectional conduction element group is connected with the secondary winding in parallel, and includes the first unidirectional conduction element and the second unidirectional conduction element in reverse series; the node between the first unidirectional conduction element and the second unidirectional conduction element is first node. The flux leakage circuit is connected in parallel with the secondary winding, and is used for providing a flux leakage path of the ratio current unit. The second unidirectional conduction element group is connected with the secondary winding in parallel, and includes the third unidirectional conduction element and the fourth unidirectional conduction element in reverse series; the common contact polarity of the third unidirectional conduction element and the first unidirectional conduction element On the contrary, and the node between the third unidirectional conduction element and the fourth unidirectional conduction element is the second node. The first switch is connected in series with the first unidirectional conduction element or the fourth unidirectional conduction element, and the second switch is connected in series with the second unidirectional conduction element or the third unidirectional conduction element. control sheet The unit is used to control the turn-on or turn-off of the first switch and the second switch, and the detection unit is coupled to the first node and the second node.

In order to solve the above problems, the present invention provides a current detection method of a current detection circuit to overcome the problems of the prior art. Therefore, the current detection method of the present invention is used to control the current detection circuit to detect the input current of the switching power conversion circuit; The conducting element, the third unidirectional conducting element and the fourth unidirectional conducting element connected in reverse series, the first switch and the second switch, the current detection method includes the following steps: according to the first direction of the input voltage of the switching power conversion circuit The voltage controls the conduction of the first switch to generate the ratio current unit, the first current path from the first unidirectional conduction element to the fourth unidirectional conduction element, and the first flux leakage path through the flux leakage circuit through the ratio current unit. Control the conduction of the second switch according to the second directional voltage of the input voltage, so as to generate the second current path of the ratio current unit, the second current path from the second unidirectional conduction element to the third unidirectional conduction element, and the second leakage through the flux leakage circuit of the ratio current unit. magnetic path. measuring the cross-voltage between the first node between the first unidirectional conducting element and the second unidirectional conducting element and the second node between the third unidirectional conducting element and the fourth unidirectional conducting element, to obtain a corresponding input current across the voltage. Wherein, the voltage in the first direction and the voltage in the second direction are located in opposite directions of the zero voltage.

The main purpose and effect of the present invention is that the universal current detection circuit of the present invention can only detect the input current of a single half cycle or the entire AC sine wave through a single ratio current unit, no matter which current detection circuit can provide a specific current The path and the flux leakage path are compatible with various power factor correction circuit structures, and can also be used in common with DC conversion circuits to achieve the effect of simple circuit itself, reduced circuit cost and volume, and easier control.

In order to further understand the technology, means and effects that the present invention adopts to achieve the predetermined purpose, please refer to the following detailed description and accompanying drawings of the present invention, and believe that the purpose, characteristics and A deep and specific understanding of the characteristics can be obtained from this, but the accompanying drawings are only for reference and illustration, and are not intended to limit the present invention.

100, 100-1, 100-2: current detection circuit

CT: current ratio

1: specific flow unit

12: Primary winding

14: Secondary winding

2: The first unidirectional conduction element group

22: The first unidirectional conduction element

24: The second unidirectional conduction element

3, 3-1, 3-2, 3-3: magnetic leakage circuit

32: Leakage resistance

ZD1: The first zener diode

ZD2: Second Zener diode

4: The second unidirectional conduction element group

42: The third unidirectional conduction element

44: The fourth unidirectional conduction element

Q1: First switch

Q2: Second switch

5: Control unit

6: Detection unit

R: sense resistor

7: Magnification adjustment circuit

Q: switch

Ra: magnification adjustment resistor

N1: the first node

N2: second node

200: Switching power conversion circuit

SW, SW-1~SW-4: power switch

Iin: input current

Isw: switch current

Ic: coupling current

Vin: input voltage

Vc1: the first clamping voltage

Vc2: the second clamping voltage

Vr: cross voltage

Li1: the first current path

Li2: Second current path

Lv1: The first magnetic leakage path

Lv2: The second magnetic leakage path

Pa, Pb, P1~P4: position

Fig. 1 is a circuit block diagram of a known current detection circuit; Fig. 2 is a circuit block diagram of a current detection circuit of the present invention; Fig. 3 is a schematic block diagram of the specific coupling positions of the first switch and the second switch of the present invention; Fig. 4A is The current path diagram when the control unit of the present invention controls the conduction of the first switch; FIG. 4B is a magnetic leakage path diagram when the control unit of the present invention controls the conduction of the first switch; FIG. 4C is the current path when the control unit of the present invention controls the conduction of the second switch Figure; Figure 4D is the magnetic leakage path diagram when the control unit of the present invention controls the second switch to be turned on; Figure 5A is the circuit diagram of the first embodiment of the magnetic leakage circuit of the present invention; Figure 5B is the second embodiment of the magnetic leakage circuit of the present invention Circuit schematic diagram; Figure 5C is a schematic circuit diagram of the third embodiment of the magnetic leakage circuit of the present invention; Figure 6A is a schematic circuit diagram of the first embodiment of the current detection method of the present invention; Figure 6B is a schematic circuit diagram of the second embodiment of the current detection method of the present invention ; FIG. 7A is the first embodiment of the application of the current detection circuit of the present invention; FIG. 7B is the second embodiment of the application of the current detection circuit of the present invention; FIG. 7C is the current detection circuit used in response to the application of the second embodiment ; FIG. 8A is a schematic diagram of a circuit waveform in which the current detection circuit of the present invention is applied to a power factor correction circuit; and FIG. 8B is a schematic diagram of a circuit waveform in which the current detection circuit of the present invention is applied to a DC conversion circuit.

Hereby the technical contents and detailed descriptions of the present invention are described as follows in conjunction with the drawings: please refer to FIG. 2 for a circuit block diagram of the current detection circuit of the present invention, and refer to FIG. The current detection circuit 100 is coupled to a power factor correction circuit or a DC conversion circuit (herein collectively referred to as the switching power conversion circuit 200 ), and is used for detecting the input current Iin of the switching power conversion circuit 200 . Wherein, the current detection circuit 100 is mainly coupled to the power switch SW of the switching power conversion circuit 200 (the specific coupling position will be further described later), so as to operate according to the switching of the power switch SW. The current detection circuit 100 includes a current ratio unit 1, a first unidirectional conduction element group 2, a flux leakage circuit 3, a second unidirectional conduction element group 4, a first switch Q1, a second switch Q2 and a control unit 5, and the ratio current The primary winding 12 of the unit 1 is coupled to the power switch SW of the switching mode power conversion circuit 200 to generate a coupling current Ic in the secondary winding 14 according to the switching current Isw of the power switch SW. Wherein, the current ratio unit 1 may be an inductive element for inducing current through coupling, such as a current ratio device, a coupled inductor, or the like.

The first unidirectional conduction element group 2 is connected in parallel with the secondary winding 14 of the flow ratio unit 1 , and includes a first unidirectional conduction element 22 and a second unidirectional conduction element 24 connected in reverse series. The flux leakage circuit 3 is connected in parallel with the secondary winding 14 of the current ratio unit 1 , and is used to provide a flux leakage path for the ratio current unit 1 when flux leakage is required. The second unidirectional conduction element group 4 is connected in parallel with the secondary winding 14 of the flow ratio unit 1 , and includes a third unidirectional conduction element 42 and a fourth unidirectional conduction element 44 connected in reverse series. Wherein, the node between the first unidirectional conducting element 22 and the second unidirectional conducting element 24 is the first node N1, and the node between the third unidirectional conducting element 42 and the fourth unidirectional conducting element 44 is the second node N1. Node N2. The first unidirectional conduction element 22 is coupled to the third single The second unidirectional conduction element 24 is coupled to the fourth unidirectional conduction element 44 with opposite polarity (ie, the polarity of the common contact is opposite). It is worth mentioning that in one embodiment of the present invention, the unidirectional conduction element is represented by a diode, but it is not limited thereto. All electronic components that can conduct in one direction (such as but not limited to silicon controlled rectifiers, thyristors, etc.) should be included in the scope of this embodiment. In addition, if the directions of the first unidirectional conduction element 22, the second unidirectional conduction element 24, the third unidirectional conduction element 42, and the fourth unidirectional conduction element 44 are opposite to those shown in FIG. 2, another embodiment can be formed. , it can still complete the function of detecting the input current Iin, which will not be repeated here.

The first switch Q1 can be selectively coupled in series to both sides of the first unidirectional conduction element 22 or the fourth unidirectional conduction element 44 , and the second switch Q2 can be selectively coupled in series to the second unidirectional conduction element 24 Or both sides of the third unidirectional conduction element 42 (the specific positions that can be connected in series will be further described later). The control unit 5 correspondingly controls the first directional voltage (such as but not limited to, a positive voltage) or the second directional voltage (such as but not limited to a negative voltage) according to the input voltage Vin of the switching power conversion circuit 200 . The switch Q1 and the second switch Q2, and the voltage in the first direction and the voltage in the second direction are located in opposite directions of the zero voltage. That is, if the voltage in the first direction is a positive voltage, the voltage in the second direction is a negative voltage in the opposite direction of the zero voltage, and vice versa. The control unit 5 mainly controls the first switch Q1 or the second switch Q2 to turn on according to whether the input voltage Vin is a positive voltage or a negative voltage, so the first switch Q1 and the second switch Q2 are mainly responsible for the current of a single direction voltage detection.

Specifically, the present invention can be used to detect the input current Iin of an AC/DC or DC/DC switching converter. The switchable AC/DC converter can preferably be a power factor correction circuit, and the voltage in the first direction and the voltage in the second direction mainly refer to the (AC) positive half cycle or negative half cycle of the input voltage Vin. The control unit 5 mainly controls the conduction of the first switch Q1 or the second switch Q2 according to whether the input voltage Vin is a positive half cycle or a negative half cycle (that is, a single half cycle is handled by a single switch). Switched DC/DC The converter can be a DC conversion circuit, and the voltage in the first direction and the voltage in the second direction mainly refer to whether the input voltage Vin is a positive voltage or a negative voltage. The control unit 5 mainly controls the first switch Q1 or the second switch Q2 to turn on according to whether the input voltage Vin is a positive voltage or a negative voltage. When the input voltage Vin has only a single direction voltage (for example, only positive voltage), only a single switch is continuously turned on.

A detection unit 6 may be included between the first node N1 and the second node N2. The main function of the detection unit 6 is to generate a cross voltage Vr at both ends of the detection unit 6 according to the current flowing through the first node N1 and the second node N2 . When the control unit 5 controls the first switch Q1 or the second switch Q2 to be turned on, a current flows across the first node N1 and the second node N2 to generate a cross voltage Vr, which corresponds to the input current Iin . Therefore, the magnitude of the input current Iin can be accurately known by measuring the cross voltage Vr. It is worth mentioning that, in an embodiment of the present invention, the first switch Q1 and the second switch Q2 can be MOSFETs, IGBTs or BJTs that can be used as switches, and are preferably MOSFETs suitable for high switching frequency response. In addition, the control unit 5 may include at least one sensor and a controller (not shown). The sensor can be used to sense, for example but not limited to, the input voltage Vin or the input current Iin, and the controller can be an analog digital controller composed of circuits, a chip or a microcircuit element such as a programmed microcontroller.

Please refer to FIG. 3 , which is a schematic block diagram of the specific coupling positions of the first switch and the second switch in the present invention, and refer to FIGS. 1-2 for complex cooperation. The first switch Q1 can be coupled to one of the four positions Pa, and can be connected in series before and after the first one-way conducting element 22 or before and after the fourth one-way conducting element 44 . Specifically, the first coupling position Pa is between one end of the secondary winding 14 of the specific flow unit 1 and the first unidirectional conduction element 22, and the second coupling position Pa is between the first unidirectional conduction element 22 and the second unidirectional conduction element 22. Between a node N1, the third coupling position Pa is between the second node N2 and the fourth unidirectional conducting element 44, and the fourth coupling position Pa is between the fourth unidirectional conducting element 44 and the specific flow unit 1 between the other ends of the secondary winding 14. Likewise, the second switch Q2 It can also be coupled to one of the four positions Pb, mainly connected in series before and after the second unidirectional conducting element 24 or before and after the third unidirectional conducting element 42 . The specific position is similar to that of the first switch Q1, and will not be repeated here.

Please refer to FIG. 4A, which is the current path diagram when the control unit of the present invention controls the first switch to be turned on; FIG. 4B is the flux leakage path diagram when the control unit of the present invention controls the first switch to be turned on; FIG. 4C is the control unit of the present invention to control the second switch. The current path diagram when it is turned on, FIG. 4D is a flux leakage path diagram when the control unit of the present invention controls the second switch to turn on. In the embodiments of FIGS. 4A-4D , one of the switch coupling positions in FIG. 3 is taken as an example, and it is assumed that the voltage in the first direction is a positive voltage, and the voltage in the second direction is a negative voltage.

Specifically, in FIG. 4A , the control unit 5 controls the first switch Q1 to turn on according to the voltage in the first direction, and controls the second switch Q2 to turn off, and cooperates with the first unidirectional conduction element 22 and the fourth unidirectional conduction element 44 to form The first current path Li1. The specific first current path Li1 is one end of the secondary winding 14 of the ratio current unit 1, the first unidirectional conduction element 22, the first switch Q1, the first node N1, the detection unit 6, the second node N2, the fourth unidirectional The conduction element 44 returns to the other end of the secondary winding 14 . Since the power switch SW of the switching power conversion circuit 200 is continuously switched on and off according to the pulse width modulation signal, and when the power switch SW is turned off, the current direction of the coupling current Ic will change. Therefore, in FIG. 4B , although the control unit 5 continues to control the first switch Q1 to be turned on and the second switch Q2 to be turned off, the flux leakage circuit 3 provides the first flux leakage through the flux leakage circuit 3 from the other end of the secondary winding 14. path Lv1 to avoid saturation over flow unit 1.

Further, when the power switch SW is switched on and off, the current ratio unit 1 also couples the switch current Isw to the coupling current Ic accordingly. However, when the power switch SW is turned off, the energy stored in the current ratio unit 1 must be discharged as soon as possible, so as to avoid the saturation current of the ratio current unit 1 and cause overcurrent damage to the internal components of the current detection circuit 100. risks of. Therefore, in the power switch When the SW is turned off, the flux leakage circuit 3 provides a first flux leakage path Lv1 , so that the energy stored on the specific current unit 1 can be quickly removed through the flux leakage circuit 3 .

In FIG. 4C , the control unit 5 controls the second switch Q2 to turn on, and controls the first switch Q1 to turn off, and cooperates with the second unidirectional conduction element 24 and the third unidirectional conduction element 42 to form a second current path Li2 . The specific second current path Li2 is the other end of the secondary winding 14 of the ratio current unit 1, the second unidirectional conduction element 24, the second switch Q2, the first node N1, the detection unit 6, the second node N2, the third single One end of the secondary winding 14 is returned to the conducting element 42 . In FIG. 4D , although the control unit 5 continues to control the second switch Q2 to be turned on and the first switch Q1 to be turned off, the flux leakage circuit 3 provides a second flux leakage path Lv2 through the flux leakage circuit 3 from one end of the secondary winding 14 to avoid saturation of flow cell 1. It is worth mentioning that if the directions of the first unidirectional conduction element 22, the second unidirectional conduction element 24, the third unidirectional conduction element 42, and the fourth unidirectional conduction element 44 are opposite to those shown in FIGS. 4A-4D , Then the current path and the magnetic flux leakage path are just opposite, which will not be repeated here.

Furthermore, in FIGS. 4B and 4D , since the current detection circuit 100 only generates a single first magnetic leakage path Lv1 or a second magnetic leakage path Lv2 when the ratio current unit 1 is leaking flux, there is no additional The path flows the current when the flux leaks from the first node N1 to the second node N2. Therefore, compared with the conventional current detection circuit, the current detection circuit 100 of the present invention can improve the accuracy of current detection. Moreover, due to the existence of the extra current path, additional compensation circuits are not required to compensate for the problem of current detection inaccuracy.

Please refer to FIG. 5A, which is a schematic circuit diagram of the first embodiment of the magnetic leakage circuit of the present invention, FIG. 5B is a schematic circuit diagram of the second embodiment of the magnetic leakage circuit of the present invention, and FIG. 5C is a schematic circuit diagram of the third embodiment of the magnetic leakage circuit of the present invention, See Figures 1-4D for complex coordination. In Figure 5A, the flux leakage circuit 3-1 can be a resistor 32. The resistor 32 can discharge the energy stored on the flow unit 1 as quickly as possible. However, the resistor 32 is easy to heat due to the fact that the current is too large, so the resistor 32 is usually suitable for low-power circuits.

In FIG. 5B , the flux leakage circuit 3 - 2 includes a first Zener diode ZD1 and a second Zener diode ZD2 . The first Zener diode ZD1. Wherein, the first Zener diode ZD1 and the second Zener diode ZD2 are coupled in series with opposite polarities. Specifically, when the flux leakage path is the first flux leakage path Lv1 in FIG. 4B, the second Zener diode ZD2 will reversely collapse, and the first Zener diode ZD1 is forward conduction (forward conduction The voltage is approximately 0.5V). Therefore, a first clamping voltage Vc1 is generated at both ends of the flux leakage circuit 3-2. The first clamping voltage Vc1 clamps the voltage across the flux leakage circuit 3-2 (forward conduction voltage is negligible), so as to protect other electronic components of the current detection circuit 100 and avoid the transient overvoltage of the flux leakage. Conversely, when the flux leakage path is the second flux leakage path Lv2 in Figure 4D, the first Zener diode ZD1 will reversely collapse, and the second Zener diode ZD2 is forward conduction to generate a second clamp The voltage Vc2 can also protect other electronic components of the current detection circuit 100 . It is worth mentioning that in one embodiment of the present invention, the directions of the first Zener diode ZD1 and the second Zener diode ZD2 can be exactly opposite to those shown in FIG. Protect other electronic components of the current detection circuit 100 .

In Fig. 5C, the flux leakage circuit 3-3 is usually applied to high-power circuits, and it includes a first Zener diode ZD1 and a second Zener diode ZD2 connected in series with opposite polarities, and connected in parallel The leakage resistance 32. The flux leakage circuit 3 - 3 provides two parallel flux leakage circuits, and the flux leakage resistor 32 is for the complete and rapid flux leakage of the specific current unit 1 at the moment of rapid flux leakage. However, due to the high power, a large voltage will be induced. In order to protect the components on the line and achieve effective magnetic leakage, back-to-back Zener diodes (ZD1, ZD2) are used to make an additional circuit to clamp the voltage to protect other components. Further, since in FIGS. 4A and 4C, when the first switch Q1 or the second switch Q2 is turned on to generate the first current path Li1 or the second current path Li2, the voltage across the two ends of the specific current unit 1 may be within 5V, but exist In FIGS. 4B and 4D , since the flux leakage circuit 3 is required for rapid flux leakage, the voltage across the two ends of the specific current unit 1 may be above 10V. Especially in the case of high wattage switching converters, the voltage across the specific current unit 1 may increase to more than 30V in an instant, and it may be difficult to clamp the specific current unit through a single Zener diode (ZD1, ZD2). 1 voltage across. Therefore, the zener diodes (ZD1, ZD2) can be adjusted with the wattage of the switching converter. In high wattage applications, multiple Zener diodes (ZD1, ZD2) can be connected in series to increase the cross-voltage when the Zener diodes (ZD1, ZD2) break down.

Please refer to FIG. 6A, which is a schematic circuit diagram of the first embodiment of the current detection method of the present invention, and FIG. 6B, which is a schematic circuit diagram of the second embodiment of the current detection method of the present invention. Refer to FIGS. 1-5C for complex cooperation. As shown in FIG. 6A , a preferred implementation manner of the detection unit 6 may be a detection resistor R, and generates a cross voltage Vr according to the current flowing through the first node N1 and the second node N2 . Since the cross voltage Vr corresponds to the input current Iin, the magnitude of the input current Iin can be detected through the cross voltage Vr. It is worth mentioning that in one embodiment of the present invention, the detection unit 6 is not limited to the detection resistor R, for example, any electronic component or circuit that can generate a cross-voltage Vr corresponding to the input current Iin at both ends of the detection unit 6 can be used. Should be included in the category of this embodiment.

As shown in FIG. 6B , the current detection circuit 100 further includes a magnification adjustment circuit 7 . The magnification adjustment circuit 7 is coupled to the detection unit 6 and used for adjusting the impedance value of the detection unit 6 according to the magnitude of the input current Iin. Specifically, for example but not limited to when detecting the input current Iin of the switching power conversion circuit 200 , the input current Iin varies according to the wattage of the switching power conversion circuit 200 and the magnitude of the input voltage Vin. Therefore, it may be difficult for the existing detection unit 6 to accurately detect the input current Iin due to insufficient current amplification. Therefore, using the magnification adjustment circuit 7 coupled to the detection unit 6 to adjust the current magnification is a preferred implementation. In this way, in the field where the input current Iin is greater than the predetermined current In combination, the magnification adjustment circuit 7 is used to lower the impedance value of the detection unit 6 to provide a general current magnification. Otherwise, the detection unit 6 is used to detect the input current Iin to provide a larger current amplification factor.

Furthermore, a preferred embodiment of the ratio adjustment circuit 7 is that the ratio adjustment circuit 7 includes a switch Q and a ratio adjustment resistor Ra. The switch Q is coupled to one end of the detection unit 6 and the control unit 5 , and one end of the magnification adjustment resistor Ra is coupled to the switch Q, and the other end of the magnification adjustment resistor Ra is coupled to the other end of the detection unit 6 . The control unit 5 can set a predetermined current, and control the switch Q to conduct according to the input current greater than or equal to the predetermined current, so as to reduce the resistance value of the detection unit 6 and provide a general current amplification factor. On the contrary, the control switch Q is turned off, so as to maintain the impedance value of the detection unit 6 and provide a larger current amplification factor. It is worth mentioning that in one embodiment of the present invention, the magnification adjustment circuit 7 is not limited to the switch Q connected in series with the magnification adjustment resistor Ra. For example, any electronic components or circuits that can adjust the impedance value of the detection unit 6 should be included in this embodiment. In the category of examples.

Please refer to FIG. 7A for the first embodiment of the application of the current detection circuit of the present invention, FIG. 7B for the second embodiment of the application of the current detection circuit of the present invention, and FIG. 7C for the current detection used in the application of the second embodiment For the circuit, refer to Figure 2~6B for complex coordination. As shown in FIG. 7A , it is a bridgeless power factor correction circuit, and the power switches (SW-1, SW-2) may operate no matter the input voltage Vin is in the positive or negative half cycle. Since the current detection circuit 100 of the present invention only needs to turn on the corresponding switches (Q1, Q2) according to the positive and negative half cycles, only a single set of current detection circuit 100 needs to be coupled to the position P1 or position P2 shown in FIG. 7A to detect complete The input current Iin of the positive and negative half cycles. It is not necessary to add an additional set of specific flow units and corresponding control methods like the conventional circuit shown in FIG. 1 . Therefore, the effect of simple circuit itself and relatively easy control can be achieved.

As shown in Figure 7B, it is a totem pole power factor correction circuit. The circuit feature is that the power switches (SW-1, SW-4) and power switches (SW-2, SW-3) are respectively based on the input voltage Vin The positive half cycle or negative half cycle and action. The current detection circuit 100 of the present invention is coupled to the position P1 or position P2 shown in FIG. 7B to detect the input current Iin of the complete positive half cycle, or coupled to the position P3 or position P4 to detect the input current Iin of the complete negative half cycle. Input current Iin. Then, the waveform of the other half cycle can be estimated according to the input current Iin waveform of a single half cycle. Alternatively, as shown in FIG. 7C, the detection point of one of the current detection circuits (100-1, 100-2) is coupled to the position P1 or position P2, and the other current detection circuit (100-1, 100- 2) The detection point is coupled to position P3 or position P4, and the feedback point of the current detection circuit (100-1, 100-2) is connected to the same point for use, and the input current Iin of the complete positive and negative half cycles can be seen waveform.

Please refer to FIG. 8A, which is a schematic diagram of the circuit waveform of the current detection circuit of the present invention applied to a power factor correction circuit. FIG. 8B is a schematic diagram of a circuit waveform of the current detection circuit of the present invention, applied to a DC conversion circuit. Refer to FIGS. 2-7C for complex cooperation. The waveform shown in FIG. 8A is applied to a power factor correction circuit. The input voltage Vin is AC and includes a positive half cycle and a negative half cycle. The power factor correction circuit generates the input current Iin by controlling the switching of the power switch SW, which is convenient for illustration. FIG. 8A is illustrated by a larger triangular wave. However, in fact, the power switch SW is switched at a high frequency, which should be a high-density triangular wave. When the input voltage Vin is in a positive half cycle, the control unit 5 controls the first switch Q1 to be turned on. When the first switch Q1 is turned on and the power switch SW is also turned on, the input current Iin rises (that is, the rising edge of the triangle wave). At this time, the current detection circuit 100 generates a first current path Li1. On the contrary, when the first switch Q1 is turned on and the power switch SW is turned off, the input current Iin drops (ie, the falling edge of the triangular wave). At this time, the current detection circuit 100 generates the first flux leakage path Lv1. The same is true when the input voltage Vin is in the negative half cycle, and details will not be described here.

The waveform shown in FIG. 8B is applied to a DC conversion circuit, the input voltage Vin is DC, and it is assumed that the input voltage Vin includes a positive voltage and a negative voltage (usually only one, including both for convenience). Like FIG. 8A , the power switch SW is also switched at high frequency. When the input voltage Vin is a positive voltage, the control unit 5 controls the first switch Q1 to be turned on. When the first switch Q1 is turned on, and the power switch SW is also turned on When it is turned on, the input current Iin rises (that is, the rising edge of the triangle wave). At this time, the current detection circuit 100 generates a first current path Li1. On the contrary, when the first switch Q1 is turned on and the power switch SW is turned off, the input current Iin drops (ie, the falling edge of the triangular wave). At this time, the current detection circuit 100 generates the first flux leakage path Lv1. The same is true when the input voltage Vin is a negative voltage, which will not be repeated here.

However, the above description is only a detailed description and drawings of preferred embodiments of the present invention, but the features of the present invention are not limited thereto, and are not intended to limit the present invention. The entire scope of the present invention should be applied for as follows The scope of the patent shall prevail, and all embodiments that conform to the spirit of the patent scope of the present invention and its similar changes shall be included in the scope of the present invention, and any person familiar with the art can easily think of it in the field of the present invention Changes or modifications can be covered by the scope of the following patents in this case.

100: current detection circuit

1: specific flow unit

12: Primary winding

14: Secondary winding

2: The first unidirectional conduction element group

22: The first unidirectional conduction element

24: The second unidirectional conduction element

3: Leakage circuit

4: The second unidirectional conduction element group

42: The third unidirectional conduction element

44: The fourth unidirectional conduction element

Q1: First switch

Q2: Second switch

5: Control unit

6: Detection unit

N1: the first node

N2: second node

200: Switching power conversion circuit

SW: power switch

Iin: input current

Isw: switch current

Ic: coupling current

Vin: input voltage

Claims (19)

A current detection circuit is used to detect an input current of a switching power conversion circuit. The current detection circuit includes: a current ratio unit with a primary winding and a secondary winding. The primary winding is coupled to the switching power conversion A power switch of the circuit; a first unidirectional conduction element group, connected in parallel with the secondary winding, and including a first unidirectional conduction element and a second unidirectional conduction element in reverse series; the first unidirectional conduction element The node between the second unidirectional conduction element is a first node; a flux leakage circuit is connected in parallel with the secondary winding, and is used to provide a flux leakage path of the ratio current unit; a second unidirectional conduction element group, the secondary winding is connected in parallel, and includes a third unidirectional conduction element and a fourth unidirectional conduction element in reverse series; the common contact polarity of the third unidirectional conduction element and the first unidirectional conduction element On the contrary, and the node between the third unidirectional conduction element and the fourth unidirectional conduction element is a second node; a first switch is connected in series with the first unidirectional conduction element or the fourth unidirectional conduction element ; a second switch, connected in series with the second unidirectional conduction element or the third unidirectional conduction element; a control unit, used to control the turn-on or turn-off of the first switch and the second switch; and a detection unit , coupling the first node and the second node. The current detection circuit as described in Claim 1, wherein the control unit correspondingly controls the first switch and the second direction voltage according to an input voltage of the switching power conversion circuit in a first direction voltage or a second direction voltage Two switches, and the voltage in the first direction and the voltage in the second direction are in opposite directions of a zero voltage. The current detection circuit according to claim 2, wherein the control unit controls the first switch to turn on according to the first direction voltage, and controls the second switch to turn off; the control unit controls the second switch according to the second direction voltage The switch is turned on, and the first switch is controlled to be turned off. The current detection circuit according to claim 1, wherein when the first switch is turned on, the secondary winding, the first unidirectional conduction element, the fourth unidirectional conduction element, the first switch and the detection unit form a A first current path; when the second switch is turned on, the secondary winding, the second unidirectional conduction element, the third unidirectional conduction element, the second switch and the detection unit form a second current path. The current detection circuit as claimed in claim 1, wherein one end of the secondary winding forms a first flux leakage path through the flux leakage circuit, and the other end of the secondary winding forms a second flux leakage path through the flux leakage circuit path. The current detection circuit according to claim 1, wherein the flux leakage circuit includes: a flux leakage resistor. The current detection circuit as described in claim 1, wherein the flux leakage circuit includes: a first Zener diode, one end of which is coupled to one end of the secondary winding; and a second Zener diode, one end of which is coupled to The other end of the first Zener diode is coupled to the other end of the secondary winding; wherein, the polarity of the first Zener diode is opposite to that of the second Zener diode. The current detection circuit as claimed in claim 1, wherein the detection unit includes: a detection resistor for generating a voltage corresponding to the input current. The current detection circuit according to claim 8, further comprising: a magnification adjustment circuit, coupled in parallel with the detection unit, and used for adjusting an impedance value of the detection unit according to the magnitude of the input current. The current detection circuit as described in claim 9, wherein the magnification adjustment circuit includes: a switch; and a magnification adjustment resistor, coupled to the switch in series; wherein, the control unit controls the input current to be greater than or equal to a predetermined current. The switch is turned on. The current detection circuit according to claim 1, wherein the switching power conversion circuit is a bridgeless power factor correction circuit. The current detection circuit according to claim 1, wherein the switching power conversion circuit is a totem pole power factor correction circuit. The current detection circuit according to claim 1, wherein the switching power conversion circuit is a DC conversion circuit. A current detection method of a current detection circuit, which is used to control the current detection circuit to detect an input current of a switching power conversion circuit; the current detection circuit includes a specific current unit, a magnetic leakage circuit, and a first A unidirectional conduction element and a second unidirectional conduction element, a third unidirectional conduction element and a fourth unidirectional conduction element connected in reverse series, a first switch and a second switch, the current detection method includes the following Step: Control the conduction of the first switch according to a first direction voltage of an input voltage of the switching power conversion circuit, so as to generate a voltage ratio between the current ratio unit, the first unidirectional conduction element and the fourth unidirectional conduction element. The first current path and the specific current unit pass through a first magnetic leakage path of the magnetic leakage circuit; according to a second direction voltage of the input voltage, the second switch is controlled to conduct, so as to generate the specific current unit, the second single unit a second current path from the conduction element to the third unidirectional conduction element and a second flux leakage path through the flux leakage circuit of the current ratio unit; and measuring the distance between a first node between the first unidirectional conduction element and the second unidirectional conduction element and a second node between the third unidirectional conduction element and the fourth unidirectional conduction element a voltage across to obtain the input current corresponding to the voltage across; wherein, the voltage in the first direction and the voltage in the second direction are in opposite directions of a zero voltage. The current detection method according to claim 14, further comprising: controlling the second switch to be turned off according to the turn-on of the first switch. The current detection method according to claim 14, further comprising: maintaining the voltage across the two ends of the flux leakage circuit as a first clamping voltage according to the generation of the first flux leakage path. The current detection method according to claim 14, further comprising: controlling the first switch to be turned off according to the second switch being turned on. The current detection method according to claim 14, further comprising: maintaining the voltage across the two ends of the flux leakage circuit as a second clamping voltage according to the generation of the second flux leakage path. The current detection method according to claim 14, further comprising: adjusting an impedance value between the first node and the second node according to the magnitude of the input current.

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