Current detection circuit and detection method thereof

Abstract

A current detection circuit is used for detecting input current of a switching power conversion circuit receiving an input voltage, and the current detection circuit includes a current sensing unit, a first set of unidirectional conducting elements, a demagnetization circuit, a second set of unidirectional conducting elements, a first switch, a second switch, a control unit and a detection unit. The current sensing unit is coupled to a power switch of the switching power conversion circuit, and the first set of unidirectional conducting elements, the demagnetization circuit and the second set of unidirectional conducting elements are connected in parallel to the current sensing unit. The first switch and the second switch are coupled to the first set of unidirectional conducting elements or the second set of unidirectional conducting elements, and the control unit correspondingly controls the first switch and the second switch according to the input voltage in a first direction voltage or a second direction voltage. The present application also relates to a current detection method of a current detection circuit.

Description

Technical Field

[0001] This invention relates to a current detection circuit and a detection method thereof, and particularly to a general-purpose current detection circuit and a current detection method. Background Technology

[0002] As power quality becomes increasingly important in the electrical industry, more and more electronic devices are incorporating power factor correction (PFCC) circuits at their input terminals to improve power quality. PFCC circuits primarily control the input current waveform to follow the input voltage waveform; therefore, a current sensing circuit is necessary to obtain the input current waveform for the switching control of the PFCC circuit. However, the current sensing circuits used in general PFCC circuits often have limitations. The main difference lies in the type and architecture of the PFCC circuit; bridged and bridgeless circuit architectures have different switching control methods, resulting in incompatibility between the current sensing circuits of these two architectures. Specific current sensing circuits must be used to accurately detect the input current, making the control process more complex and cumbersome.

[0003] like Figure 1 As shown, the main reason for the incompatibility of current sensing circuits is the need to consider whether the current transformer (CT) will saturate. Saturation mainly stems from the lack of a suitable demagnetizing path. However, ensuring a suitable demagnetizing path inevitably increases the difficulty of control or the complexity of the circuit itself. The current sensing circuit of a bridged power factor correction circuit is generally incompatible with a bridgeless current sensing circuit because the bridgeless current sensing circuit needs to independently determine the positive and negative half-cycle signals, thus requiring two sets of current transformers (CTs) to detect the positive and negative half-cycles separately, thereby increasing the size of the circuit.

[0004] Therefore, how to design a universal current detection circuit and its current detection method that can be compatible with various switching power conversion circuit architectures, such as power factor correction circuits or DC-DC conversion circuits, is a major research topic that the inventors of this disclosure intend to conduct. Summary of the Invention

[0005] To address the aforementioned problems, this invention provides a current detection circuit to overcome the limitations of existing technologies. Therefore, the current detection circuit of this invention is used to detect the input current of a switching power conversion circuit, and the current detection circuit includes a current comparison unit, a first unidirectional conducting element group, a demagnetizing circuit, a second unidirectional conducting element group, a first switch, a second switch, a control unit, and a detection unit. The current comparison unit has a primary winding and a secondary winding, the primary winding being coupled to the power switch of the switching power conversion circuit. The first unidirectional conducting element group is connected in parallel to the secondary winding and includes a first unidirectional conducting element and a second unidirectional conducting element connected in reverse series; the node between the first unidirectional conducting element and the second unidirectional conducting element is a first node. The demagnetizing circuit is connected in parallel to the secondary winding and provides a demagnetizing path for the current comparison unit. The second unidirectional conducting element group is connected in parallel to the secondary winding and includes a third unidirectional conducting element and a fourth unidirectional conducting element connected in reverse series; the common contact point of the third unidirectional conducting element and the first unidirectional conducting element has opposite polarities, and the node between the third unidirectional conducting element and the fourth unidirectional conducting element is a second node. The first switch is connected in series with either the first or fourth unidirectional conducting element, and the second switch is connected in series with either the second or third unidirectional conducting element. The control unit is used to control the on or off state of the first and second switches, and the detection unit is coupled to the first and second nodes.

[0006] To address the aforementioned problems, this invention provides a current detection method for a current detection circuit, overcoming the limitations of existing technologies. Therefore, the current detection method of this invention is used to control a current detection circuit to detect the input current of a switching power conversion circuit. The current detection circuit includes a current-conducting unit, a magnetic discharge circuit, a first and a second unidirectional conducting element connected in reverse series, a third and a fourth unidirectional conducting element connected in reverse series, a first switch, and a second switch. The current detection method includes the following steps: controlling the first switch to conduct based on a first directional voltage of the input voltage of the switching power conversion circuit, thereby generating a first current path from the current-conducting unit and the first unidirectional conducting element to the fourth unidirectional conducting element, and a first magnetic discharge path of the current-conducting unit through the magnetic discharge circuit. Controlling the second switch to conduct based on a second directional voltage of the input voltage, thereby generating a second current path from the current-conducting unit and the second unidirectional conducting element to the third unidirectional conducting element, and a second magnetic discharge path of the current-conducting unit through the magnetic discharge circuit. Measuring the voltage across the first node between the first and second unidirectional conducting elements and the second node between the third and fourth unidirectional conducting elements to obtain the input current corresponding to the voltage across the voltage. The first directional voltage and the second directional voltage are located in the opposite directions of zero voltage.

[0007] The main objective and technical effect of this invention is that the universal current detection circuit of this invention can detect the input current of a single half-cycle or the entire AC sine wave through a single current ratio unit. Regardless of the current detection circuit, it can provide a specific current path and a demagnetization path. Therefore, it can be compatible with various power factor correction circuit architectures and can also be used with DC-DC conversion circuits. This achieves the technical effect of simple circuits, reduced circuit cost and size, and easier control.

[0008] To gain a deeper understanding of the techniques, means, and effects employed by this invention to achieve its intended purpose, please refer to the following detailed description and accompanying drawings. It is believed that the purpose, features, and characteristics of this invention can be understood in a thorough and specific manner from these drawings. However, the drawings are provided for reference and illustration only and are not intended to limit the scope of this invention. Attached Figure Description

[0009] Figure 1 Here is a circuit block diagram of an existing current detection circuit;

[0010] Figure 2 This is a circuit block diagram of the current detection circuit of the present invention;

[0011] Figure 3 A block diagram showing the specific coupling positions of the first switch and the second switch in this invention;

[0012] Figure 4A This is a current path diagram when the control unit of the present invention controls the first switch to be turned on;

[0013] Figure 4B This is a diagram showing the magnetic leakage path when the control unit of the present invention controls the first switch to be turned on;

[0014] Figure 4C This is a current path diagram when the control unit of the present invention controls the second switch to be turned on;

[0015] Figure 4D This is a diagram showing the magnetic leakage path when the control unit of the present invention controls the second switch to be turned on;

[0016] Figure 5A This is a circuit diagram of the first embodiment of the magnetic discharge circuit of the present invention;

[0017] Figure 5B This is a circuit diagram of the second embodiment of the magnetic discharge circuit of the present invention;

[0018] Figure 5C This is a circuit diagram of the third embodiment of the magnetic discharge circuit of the present invention;

[0019] Figure 6A This is a circuit diagram of the first embodiment of the current detection method of the present invention;

[0020] Figure 6B This is a circuit diagram of the second embodiment of the current detection method of the present invention;

[0021] Figure 7A This is a first embodiment of the application of the current detection circuit of the present invention;

[0022] Figure 7B This is a second embodiment of the application of the current detection circuit of the present invention;

[0023] Figure 7C For the current detection circuit used in the application scenarios of the second embodiment;

[0024] Figure 8A This is a schematic diagram of the circuit waveforms of the current detection circuit of the present invention applied to a power factor correction circuit; and

[0025] Figure 8B This is a schematic diagram of the circuit waveform when the current detection circuit of the present invention is applied to a DC-DC conversion circuit.

[0026] Explanation of reference numerals in the attached figures:

[0027] 100, 100-1, 100-2… Current detection circuit

[0028] CT… Flow Regulator

[0029] 1… Specific flow unit

[0030] 12… Primary winding

[0031] 14… Secondary winding

[0032] 2…First unidirectional conduction element group

[0033] 22…First unidirectional conduction element

[0034] 24…Second unidirectional conduction element

[0035] 3, 3-1, 3-2, 3-3… Exhaust circuit

[0036] 32… Leakage resistor

[0037] ZD1…First Zener Diode

[0038] ZD2…Second Genna diode

[0039] 4…Second unidirectional conduction element group

[0040] 42…Third unidirectional conduction element

[0041] 44… Fourth unidirectional conduction element

[0042] Q1…First Switch

[0043] Q2…Second switch

[0044] 5…Control Unit

[0045] 6…Detection Unit

[0046] R…detection resistor

[0047] 7…Rate adjustment circuit

[0048] Q…switch

[0049] Ra…Rate Adjustment Resistor

[0050] N1…First node

[0051] N2…Second node

[0052] 200… Switching power conversion circuit

[0053] SW, SW-1 to SW-4… power switches

[0054] Iin…Input current

[0055] Isw…Switching Current

[0056] Ic…coupling current

[0057] Vin…Input Voltage

[0058] Vc1…First clamping voltage

[0059] Vc2…Second clamping voltage

[0060] Vr…Transpressure

[0061] Li1…First Current Path

[0062] Li2…Second Current Path

[0063] Lv1…First leakage path

[0064] Lv2…Second leakage path

[0065] Positions of Pa, Pb, P1~P4… Detailed Implementation

[0066] The technical content and detailed description of the present invention are explained below with reference to the accompanying drawings:

[0067] Please see Figure 2 This is a circuit block diagram of the current detection circuit of the present invention, which can be further referenced. Figure 1The current detection circuit 100 is coupled to a power factor correction circuit or a DC-DC conversion circuit (collectively referred to here as the switching power conversion circuit 200) and is used to detect the input current Iin of the switching power conversion circuit 200. The current detection circuit 100 is primarily coupled to the power switch SW of the switching power conversion circuit 200 (the specific coupling location will be further explained later) to operate according to the switching of the power switch SW. The current detection circuit 100 includes a current comparison unit 1, a first unidirectional conducting element group 2, a magnetizing circuit 3, a second unidirectional conducting element group 4, a first switch Q1, a second switch Q2, and a control unit 5. The primary winding 12 of the current comparison unit 1 is coupled to the power switch SW of the switching power conversion circuit 200 to generate a coupling current Ic in the secondary winding 14 based on the switching current Isw of the power switch SW. The current comparison unit 1 can be a current comparator, a coupling inductor, or other sensing element used to sense current through coupling.

[0068] The first unidirectional conducting element group 2 is connected in parallel to the secondary winding 14 of the current comparison unit 1, and includes a first unidirectional conducting element 22 and a second unidirectional conducting element 24 connected in reverse series. The demagnetizing circuit 3 is connected in parallel to the secondary winding 14 of the current comparison unit 1, and provides a demagnetizing path when the current comparison unit 1 needs to demagnetize. The second unidirectional conducting element group 4 is connected in parallel to the secondary winding 14 of the current comparison unit 1, and includes a third unidirectional conducting element 42 and a fourth unidirectional conducting element 44 connected in reverse series. 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 N2. The first unidirectional conducting element 22 is coupled to the third unidirectional conducting element 42 with opposite polarities (i.e., the polarities of the common connection point are opposite), and the second unidirectional conducting element 22 is coupled to the fourth unidirectional conducting element 44 with opposite polarities (i.e., the polarities of the common connection point are opposite). It is worth mentioning that in one embodiment of the present invention, the unidirectional conducting element is illustrated as a diode, but this is not a limitation. Any electronic component capable of unidirectional conduction (e.g., but not limited to, silicon controlled rectifiers, thyristors, etc.) should be included within the scope of this embodiment. Furthermore, the first unidirectional conducting element 22, the second unidirectional conducting element 24, the third unidirectional conducting element 42, and the fourth unidirectional conducting element 44, if... Figure 2 The opposite direction shown can constitute another embodiment, which can still perform the function of input current Iin detection, and will not be described in detail here.

[0069] The first switch Q1 can be selectively connected in series with either the first unidirectional conducting element 22 or the fourth unidirectional conducting element 44, and the second switch Q2 can be selectively connected in series with either the second unidirectional conducting element 24 or the third unidirectional conducting element 42 (the specific series connection positions will be further explained later). The control unit 5 controls the first switch Q1 and the second switch Q2 accordingly based on the input voltage Vin of the switching power conversion circuit 200 being a first-direction voltage (e.g., but not limited to, a positive voltage) or a second-direction voltage (e.g., but not limited to, a negative voltage), where the first-direction voltage and the second-direction voltage are in opposite directions to zero voltage. That is, if the first-direction voltage is positive, then the second-direction voltage is negative, in the opposite direction to zero voltage, and vice versa. The control unit 5 mainly controls the first switch Q1 or the second switch Q2 to conduct according to whether the input voltage Vin is positive or negative; therefore, the first switch Q1 and the second switch Q2 are mainly responsible for current detection of the voltage in one direction.

[0070] Specifically, this invention can be used to detect the input current Iin of an AC / DC or DC / DC switching converter. The switching AC / DC converter is preferably a power factor correction circuit, and the first directional voltage and the second directional voltage mainly refer to the input voltage Vin being in the positive or negative half-cycle (AC). The control unit 5 mainly controls the first switch Q1 or the second switch Q2 to conduct according to whether the input voltage Vin is in the positive or negative half-cycle (i.e., a single switch handles a single half-cycle). The switching DC / DC converter can be a DC conversion circuit, and the first directional voltage and the second directional voltage mainly refer to whether the input voltage Vin is positive or negative. The control unit 5 mainly controls the first switch Q1 or the second switch Q2 to conduct according to whether the input voltage Vin is positive or negative. When the input voltage Vin has only a single directional voltage (e.g., only a positive voltage), only that single switch will remain on.

[0071] 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 voltage Vr across its terminals based on 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, current will flow through the first node N1 and the second node N2, generating a voltage Vr, which corresponds to the input current Iin. Therefore, by measuring this voltage Vr, the magnitude of the input current Iin can be accurately determined. It is worth mentioning that, in one embodiment of the present invention, the first switch Q1 and the second switch Q2 can be semiconductor elements that can be used as switches, such as MOSFETs, IGBTs, or BJTs, and preferably MOSFETs with 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-to-digital controller composed of circuits, a microcontroller with programmed control, or other chips or microcircuit elements.

[0072] Please see Figure 3 This is a block diagram showing the specific coupling positions of the first switch and the second switch of the present invention. See also the attached diagram. Figures 1-2 The first switch Q1 can be coupled to one of four positions Pa, primarily by being connected in series before or after the first unidirectional conducting element 22 or the fourth unidirectional conducting element 44. Specifically, the first coupling position Pa is between one end of the secondary winding 14 of the current-conducting unit 1 and the first unidirectional conducting element 22; the second coupling position Pa is between the first unidirectional conducting element 22 and the first 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 other end of the secondary winding 14 of the current-conducting unit 1. Similarly, the second switch Q2 can also be coupled to one of four positions Pb, primarily by being connected in series before or after the second unidirectional conducting element 22 or the third unidirectional conducting element 42. The specific positions are similar to those of the first switch Q1 and will not be described further here.

[0073] Please see Figure 4A This is a current path diagram when the control unit of the present invention controls the first switch to be turned on. Figure 4B This is a diagram showing the magnetic leakage path when the control unit of the present invention controls the first switch to be turned on. Figure 4C This is a current path diagram when the control unit of the present invention controls the second switch to be turned on. Figure 4D This is a diagram showing the magnetic leakage path when the control unit of the present invention controls the second switch to be turned on. Figures 4A-4D In the embodiments, with Figure 3 Taking one of the switch coupling positions as an example, and assuming that the voltage in the first direction is a positive voltage and the voltage in the second direction is a negative voltage.

[0074] Specifically, in Figure 4A In the circuit, control unit 5 controls the first switch Q1 to turn on and the second switch Q2 to turn off based on the first direction voltage, forming a first current path Li1 in conjunction with the first unidirectional conducting element 22 and the fourth unidirectional conducting element 44. Specifically, the first current path Li1 is formed by connecting one end of the secondary winding 14 of the current-conducting unit 1, the first unidirectional conducting element 22, the first switch Q1, the first node N1, the detection unit 6, the second node N2, and the fourth unidirectional conducting element 44 back to the other end of the secondary winding 14. Since the power switch SW of the switching power conversion circuit 200 continuously switches between on and off according to the pulse width modulation signal, and when the power switch SW is turned off, the direction of the coupling current Ic changes. Therefore, in... Figure 4B In the process, although the control unit 5 continuously controls the first switch Q1 to be turned on and controls the second switch Q2 to be turned off, the demagnetizing circuit 3 provides the first demagnetizing path Lv1 through the demagnetizing circuit 3 from the other end of the secondary winding 14 to avoid saturation of the specific current unit 1.

[0075] Furthermore, when the power switch SW switches on and off, the current-limiting unit 1 also couples the switching current Isw to the coupling current Ic. However, when the power switch SW is off, the energy stored in the current-limiting unit 1 must be discharged as quickly as possible to avoid the risk of overcurrent damage to the internal components of the current detection circuit 100 due to saturation of the current-limiting unit 1 and the generation of saturation current. Therefore, when the power switch SW is off, the demagnetizing circuit 3 provides a first demagnetizing path Lv1, allowing the energy stored in the current-limiting unit 1 to be quickly discharged through the demagnetizing circuit 3.

[0076] exist Figure 4C In this circuit, control unit 5 controls the second switch Q2 to turn on and the first switch Q1 to turn off, forming a second current path Li2 in conjunction with the second unidirectional conducting element 24 and the third unidirectional conducting element 42. Specifically, the second current path Li2 is formed by passing the other end of the secondary winding 14 of the current-conducting unit 1, the second unidirectional conducting element 24, the second switch Q2, the first node N1, the detection unit 6, the second node N2, and the third unidirectional conducting element 42 returning to one end of the secondary winding 14. Figure 4D In this process, although control unit 5 continuously controls the second switch Q2 to be on and controls the first switch Q1 to be off, the demagnetizing circuit 3 provides a second demagnetizing path Lv2 through the demagnetizing circuit 3 from one end of the secondary winding 14 to avoid saturation of the specific current unit 1. It is worth mentioning that when the first unidirectional conducting element 22, the second unidirectional conducting element 24, the third unidirectional conducting element 42, and the fourth unidirectional conducting element 44 are... Figures 4A-4D The directions shown are exactly opposite, so the current path and the demagnetization path are also exactly opposite, which will not be elaborated here.

[0077] Furthermore, at Figure 4B ,4D In this invention, when the current-discharging unit 1 demagnetizes, the current detection circuit 100 only generates a single first demagnetizing path Lv1 or a second demagnetizing path Lv2, without any additional path for the current to flow from the first node N1 to the second node N2. Therefore, compared to existing current detection circuits, the current detection circuit 100 of this invention improves the accuracy of current detection. Furthermore, it avoids the need for additional compensation circuits to compensate for inaccurate current detection due to the presence of extra current paths.

[0078] Please see Figure 5A This is a circuit diagram of the first embodiment of the magnetic discharge circuit of the present invention. Figure 5B This is a circuit diagram of the second embodiment of the magnetic discharge circuit of the present invention. Figure 5C This is a circuit diagram of the third embodiment of the magnetic discharge circuit of the present invention, which can be further referred to. Figures 1-4D .exist Figure 5A In the circuit, the demagnetizing circuit 3-1 can be a resistor 32. Resistor 32 can quickly dissipate the energy stored in the current-carrying unit 1. However, because resistor 32 is prone to overheating when the current is too high, resistor 32 is more commonly used in low-power circuits.

[0079] exist Figure 5B In the process, the magnetizing circuit 3-2 includes a first Zener diode ZD1 and a second Zener diode ZD2. The first Zener diode ZD1 and the second Zener diode ZD2 are connected in series with opposite polarities. Specifically, when the magnetizing path is... Figure 4B When the first leakage path Lv1 is in the direction of leakage, the second Zener diode ZD2 will collapse in reverse, and the first Zener diode ZD1 will conduct in the forward direction (the forward conduction voltage is approximately 0.5V). Therefore, a first clamping voltage Vc1 will be generated across the leakage circuit 3-2. This first clamping voltage Vc1 will clamp the voltage across the leakage circuit 3-2 (the forward conduction voltage is negligible) to protect other electronic components of the current detection circuit 100 and prevent the generation of instantaneous overvoltage during leakage. Conversely, when the leakage path is... Figure 4D When the second leakage path Lv2 is reached, the first Zener diode ZD1 will collapse in reverse, and the second Zener diode ZD2 will conduct in the forward direction, generating a second clamping voltage Vc2, which 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... Figure 5B On the contrary, it can also provide a demagnetization path and protect other electronic components of the current detection circuit 100.

[0080] exist Figure 5CIn this circuit, the demagnetizing circuit 3-3 is typically used in high-power circuits. It includes a first Zener diode ZD1 and a second Zener diode ZD2 connected in series with opposite polarities, and a demagnetizing resistor 32 connected in parallel with them. This demagnetizing circuit 3-3 provides two parallel demagnetizing loops. During rapid demagnetizing, the demagnetizing resistor 32 ensures that the current-carrying unit 1 can demagnetize completely and quickly. However, due to the high power, a large voltage will be induced. To protect the components on the circuit and achieve effective demagnetizing, back-to-back Zener diodes (ZD1, ZD2) are used to provide an additional loop to clamp the voltage and protect other components. Furthermore, since in Figure 4A , 4C In the process, 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 current-reducing unit 1 may be within 5V, but in Figure 4B , 4D In this system, due to the need for rapid demagnetization by the demagnetizing circuit 3, the voltage across the current-limiting unit 1 may exceed 10V. Especially in high-wattage switching converters, the voltage across the current-limiting unit 1 may momentarily spike to over 30V, making it difficult for a single Zener diode (ZD1, ZD2) to clamp the voltage across it. Therefore, the Zener diodes (ZD1, ZD2) can be adjusted according to the wattage of the switching converter. In high-wattage applications, multiple Zener diodes (ZD1, ZD2) can be connected in series to increase the voltage across the Zener diodes (ZD1, ZD2) in case of breakdown.

[0081] Please see Figure 6A This is a circuit diagram of the first embodiment of the current detection method of the present invention. Figure 6B This is a circuit diagram of the second embodiment of the current detection method of the present invention, which can be further referred to. Figures 1-5C .like Figure 6A As shown, a preferred embodiment of the detection unit 6 can be a detection resistor R, and a voltage Vr is generated based on the current flowing through the first node N1 and the second node N2. Since this voltage Vr corresponds to the input current Iin, the magnitude of the input current Iin can be detected through this 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; any electronic component or circuit that can generate a voltage Vr corresponding to the input current Iin across the detection unit 6 should be included within the scope of this embodiment.

[0082] like Figure 6BAs shown, the current detection circuit 100 also includes a rate adjustment circuit 7. The rate adjustment circuit 7 is coupled to the detection unit 6 and is used to adjust the impedance value of the detection unit 6 according to the magnitude of the input current Iin. Specifically, since the input current Iin varies depending on the wattage of the switching power conversion circuit 200 and the magnitude of the input voltage Vin when detecting, for example but not limited to, the input current Iin, may vary depending on the wattage of the switching power conversion circuit 200 and the magnitude of the input voltage Vin, the existing detection unit 6 may have difficulty accurately detecting the input current Iin due to insufficient current amplification. Therefore, it is a preferred embodiment to adjust the current amplification by coupling the detection unit 6 with the rate adjustment circuit 7. In this way, when the input current Iin is greater than a predetermined current, the impedance value of the detection unit 6 can be reduced using the rate adjustment circuit 7 to provide a general current amplification. Conversely, when the input current Iin is less than a predetermined current, the detection unit 6 is used to detect the input current Iin to provide a larger current amplification.

[0083] Furthermore, in a preferred embodiment, the rate adjustment circuit 7 includes a switch Q and a rate adjustment resistor Ra. Switch Q is coupled to one end of the detection unit 6 and the control unit 5, and one end of the rate adjustment resistor Ra is coupled to switch Q, while the other end of the rate 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 switch Q to conduct when the input current Iin is greater than or equal to the predetermined current, thereby reducing the impedance value of the detection unit 6 and providing a general current amplification rate. Conversely, it controls switch Q to turn off when the input current Iin is less than or equal to the predetermined current, thereby maintaining the impedance value of the detection unit 6 and providing a larger current amplification rate. It is worth noting that in one embodiment of the present invention, the rate adjustment circuit 7 is not limited to switch Q connected in series with the rate adjustment resistor Ra; any electronic component or circuit capable of adjusting the impedance value of the detection unit 6 should be included within the scope of this embodiment.

[0084] Please see Figure 7A This is the first embodiment of the application of the current detection circuit of the present invention. Figure 7B This is a second embodiment of the application of the current detection circuit of the present invention. Figure 7C For the current detection circuit used in the application scenarios of the second embodiment, please refer to the following: Figures 2-6B .like Figure 7A The circuit shown is a bridgeless power factor correction circuit. The input voltage Vin may activate the power switches (SW-1, SW-2) regardless of the positive or negative half-cycle. Since the current detection circuit 100 of this invention only needs to activate the corresponding switches (Q1, Q2) according to the positive and negative half-cycles, only a single current detection circuit 100 needs to be coupled to... Figure 7A By using position P1 or position P2 as shown, the input current Iin of the complete positive and negative half-cycles can be detected. There is no need to... Figure 1The existing circuit requires an additional set of current-comparing units and their corresponding control methods. Therefore, it achieves a technical effect that is both simple in circuitry and relatively easy to control.

[0085] like Figure 7B The diagram shows a totem pole power factor correction circuit. Its key feature is that power switches (SW-1, SW-4) and (SW-2, SW-3) operate according to the positive or negative half-cycle of the input voltage Vin, respectively. The current detection circuit 100 of this invention is coupled to... Figure 7B Positions P1 or P2, as shown, can detect the complete positive half-cycle of the input current Iin; or, when coupled to positions P3 or P4, the complete negative half-cycle of the input current Iin can be detected. Then, the waveform of the other half-cycle can be inferred from the waveform of the input current Iin of one half-cycle. Alternatively, it can be done as follows: Figure 7C As shown, by coupling the detection point of one of the current detection circuits (100-1, 100-2) to position P1 or position P2, and the detection point of the other current detection circuit (100-1, 100-2) to position P3 or position P4, and connecting the feedback point of the current detection circuits (100-1, 100-2) to the same point for use, the complete positive and negative half-cycle input current Iin waveform can be observed.

[0086] Please see Figure 8A This is a schematic diagram of the circuit waveforms of the current detection circuit of the present invention applied to a power factor correction circuit. Figure 8B This is a schematic diagram of the circuit waveform of the current detection circuit of the present invention applied to a DC-DC conversion circuit. See also the attached diagram. Figures 2-7C .like Figure 8A The waveform shown is from a power factor correction circuit. The input voltage Vin is AC and includes both positive and negative half-cycles. The power factor correction circuit generates the input current Iin by controlling the switching of the power switch SW. (For illustration purposes, please refer to the diagram.) Figure 8A The diagram uses a relatively large triangular wave. However, in reality, the power switch SW switches at a high frequency, and should ideally produce a high-density triangular wave. During the positive half-cycle of the input voltage Vin, the control unit 5 controls the first switch Q1 to turn on. When the first switch Q1 is on and the power switch SW is also on, the input current Iin rises (i.e., the rising edge of the triangular wave). At this time, the current detection circuit 100 generates the first current path Li1. Conversely, when the first switch Q1 is on and the power switch SW is off, the input current Iin decreases (i.e., the falling edge of the triangular wave). At this time, the current detection circuit 100 generates the first leakage path Lv1. The same applies when the input voltage Vin is in the negative half-cycle, which will not be elaborated further here.

[0087] like Figure 8BThe waveform shown is applied to a DC-DC converter circuit, with an input voltage Vin that is DC. It is assumed that the input voltage Vin contains both positive and negative voltages (usually only one, but both are included for illustration purposes). As... Figure 8A The power switch SW also operates at high frequency. When the input voltage Vin is positive, the control unit 5 controls the first switch Q1 to turn on. When the first switch Q1 is on and the power switch SW is also on, the input current Iin rises (i.e., the rising edge of the triangular wave). At this time, the current detection circuit 100 generates the first current path Li1. Conversely, when the first switch Q1 is on and the power switch SW is off, the input current Iin decreases (i.e., the falling edge of the triangular wave). At this time, the current detection circuit 100 generates the first leakage path Lv1. The same applies when the input voltage Vin is negative, which will not be elaborated further here.

[0088] The above description is merely a detailed explanation and accompanying drawings of preferred embodiments of the present invention, and the features of the present invention are not limited thereto, nor are they intended to limit the present invention. The scope of the present invention should be determined by the claims. All embodiments that conform to the concept of the claims of the present invention and similar variations thereof should be included in the scope of the present invention. Any variations or modifications that can be easily conceived by those skilled in the art within the field of the present invention can be covered by the claims disclosed herein.

Claims

1. A current detection circuit for detecting an input current of a switching power conversion circuit, the current detection circuit comprising: A specific current unit has a primary winding and a secondary winding, the primary winding being coupled to a power switch of the switching power conversion circuit; A first unidirectional conducting element group is connected in parallel to the secondary winding, and includes a first unidirectional conducting element and a second unidirectional conducting element connected in reverse series; the node between the first unidirectional conducting element and the second unidirectional conducting element is a first node; A leakage circuit is connected in parallel to the secondary winding and is used to provide a leakage path for the specific current unit; A second unidirectional conducting element group is connected in parallel to the secondary winding, and includes a third unidirectional conducting element and a fourth unidirectional conducting element connected in reverse series; the common contact point polarity of the third unidirectional conducting element and the first unidirectional conducting element is opposite, and the node between the third unidirectional conducting element and the fourth unidirectional conducting element is a second node. A first switch is connected in series with the first unidirectional conducting element or the fourth unidirectional conducting element; A second switch is connected in series with the second unidirectional conducting element or the third unidirectional conducting element; A control unit for controlling the on / off state of the first switch and the second switch; and A detection unit is coupled to the first node and the second node. When the first switch is turned on, the secondary winding, the first unidirectional conducting element, the fourth unidirectional conducting element, the first switch, and the detection unit form a first current path; when the second switch is turned on, the secondary winding, the second unidirectional conducting element, the third unidirectional conducting element, the second switch, and the detection unit form a second current path.

2. The current detection circuit as claimed in claim 1, wherein the control unit controls the first switch and the second switch accordingly based on an input voltage of the switching power conversion circuit in a first direction voltage or a second direction voltage, and the first direction voltage and the second direction voltage are located in opposite directions to zero voltage.

3. The current detection circuit as described in claim 2, wherein the control unit controls the first switch to be turned on and the second switch to be turned off according to the first directional voltage; the control unit controls the second switch to be turned on and the first switch to be turned off according to the second directional voltage.

4. The current detection circuit as claimed in claim 1, wherein one end of the secondary winding forms a first magnetic discharge path through the magnetic discharge circuit, and the other end of the secondary winding forms a second magnetic discharge path through the magnetic discharge circuit.

5. The current detection circuit as described in claim 1, wherein the demagnetizing circuit comprises: One leakage magnetoresistive.

6. The current detection circuit as claimed in claim 1, wherein the demagnetizing circuit comprises: 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, and the other end of which is coupled to the other end of the secondary winding; The polarity of the first Zener diode is opposite to that of the second Zener diode.

7. The current detection circuit as claimed in claim 1, wherein the detection unit comprises: A sensing resistor is used to generate a voltage across the input current.

8. The current detection circuit as described in claim 7, further comprising: A rate adjustment circuit is connected in parallel to the detection unit and is used to adjust an impedance value of the detection unit according to the magnitude of the input current.

9. The current detection circuit of claim 8, wherein the rate adjustment circuit comprises: One switch; and A single-rate adjustment resistor is connected in series with the switch. The control unit controls the switch to turn on based on the input current being greater than or equal to a predetermined current.

10. The current detection circuit as claimed in claim 1, wherein the switching power conversion circuit is a bridgeless power factor correction circuit.

11. The current detection circuit as described in claim 1, wherein the switching power conversion circuit is a totem pole power factor correction circuit.

12. The current detection circuit as claimed in claim 1, wherein the switching power conversion circuit is a DC-DC conversion circuit.

13. A current detection method for a current detection circuit, used to control the current detection circuit to detect an input current of a switching power conversion circuit; the current detection circuit includes a current-limiting unit, a magnetizing circuit, a first unidirectional conducting element and a second unidirectional conducting element connected in reverse series, a third unidirectional conducting element and a fourth unidirectional conducting element connected in reverse series, a first switch and a second switch, and the current detection method includes the following steps: The first switch is turned on according to a first directional voltage of an input voltage of the switching power conversion circuit, so as to generate a first current path from the current unit, the first unidirectional conducting element to the fourth unidirectional conducting element and a first magnetic leakage path of the current unit through the magnetic leakage circuit. The second switch is turned on according to a second directional voltage of the input voltage, so as to generate a second current path from the current-conducting unit, the second unidirectional conducting element to the third unidirectional conducting element, and a second magnetic leakage path of the current-conducting unit through the magnetic leakage circuit; and Measure a cross voltage between a first node between the first unidirectional conducting element and the second unidirectional conducting element and a second node between the third unidirectional conducting element and the fourth unidirectional conducting element to obtain the input current corresponding to the cross voltage; in, The first directional voltage and the second directional voltage are located in the opposite direction to zero voltage.

14. The current detection method as described in claim 13, further comprising: The second switch is controlled to turn off based on the conduction of the first switch.

15. The current detection method as described in claim 13, further comprising: The voltage across the first leakage path is maintained as a first clamping voltage based on the generation of the first leakage path.

16. The current detection method as described in claim 13, further comprising: The first switch is turned off based on the conduction of the second switch.

17. The current detection method as described in claim 13, further comprising: The voltage across the two ends of the leakage circuit is maintained as a second clamping voltage based on the generation of the second leakage path.

18. The current detection method as described in claim 13, further comprising: Adjust the impedance value between the first node and the second node according to the magnitude of the input current.

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