Photovoltaic micro inverter current detection circuit

Abstract

The utility model provides a current detection circuit of a photovoltaic micro inverter. The current detection circuit of the photovoltaic micro inverter at least comprises a conversion circuit, an electric energy circuit and a detection circuit, the electric energy circuit is used for storing or transmitting electric energy according to the connection or disconnection of the conversion circuit; and the detection circuit is used for outputting a preset voltage when the conversion circuit is switched on and the electric energy circuit stores electric energy so as to detect a current signal based on the preset voltage. According to the invention, the measurement error of the current signal can be eliminated, and the measurement precision is improved.

Description

Technical Field

[0001] The present application relates to the technical field of detection circuits, and particularly to a current detection circuit for a photovoltaic micro-inverter. Background Art

[0002] The existing current detection circuit for a photovoltaic micro-inverter is as Figure 1 shown. The power MOS transistor V1 conducts when the DC / DC conversion drive signal is at a high level and cuts off when the DC / DC conversion drive signal is at a low level.

[0003] The DC / DC conversion drive signal is sent from the corresponding pin of the MCU chip.

[0004] When the power MOS transistor V1 conducts, the solar (photovoltaic) cell (hereinafter referred to as the photovoltaic cell) forms a current loop through the power transformer T1, the current transformer B1, and the power MOS transistor V1, and supplies electric power to the high-voltage DC power supply Vdd through the power transformer T1 and the diode V2 to achieve energy transfer.

[0005] When the power MOS transistor V1 conducts, since there is a current flowing through the primary side of the current transformer B1, an induced voltage is generated on the secondary side of the current transformer B1. The induced voltage generates an induced current through the resistor R3, the diode V3, the resistors R4, R5, and the capacitor C1, and forms a voltage corresponding to the current on the primary side of the current transformer B1 on the capacitor C1, so that the corresponding analog-to-digital conversion (hereinafter referred to as ADC) pin of the MCU obtains a corresponding voltage, and a corresponding current digital signal is obtained.

[0006] Figure 1 In [reference], the diode V3 is used to pass the forward induced current and cut off the reverse induced current. Since the forward voltage drop of the diode and the passing current have a non-linear relationship, rather than a constant value. And the voltage drop curves of each diode are different. In addition, the forward conduction turn-on voltage UT of each diode is also different. The characteristics of the diode are as Figure 2 shown.

[0007] In mass production, when the same current passes through the current transformer B1, due to these characteristics of the diode V3, the sampling values obtained by the MCU are different, resulting in measurement errors and affecting photovoltaic energy transfer. Utility Model Content

[0008] The present application provides a current detection circuit for a photovoltaic micro-inverter to solve the above technical problems.

[0009] Specifically, the present application provides a current detection circuit for a photovoltaic micro-inverter, which at least includes a conversion circuit, a power circuit, and a detection circuit.

[0010] The electric energy circuit is used to store or transmit electric energy according to the conduction or cut-off of the conversion circuit.

[0011] The detection circuit is used to output a preset voltage when the conversion circuit is conducting and the electric energy circuit is storing electric energy, so as to detect a current signal based on the preset voltage.

[0012] Furthermore, the conversion circuit at least includes a first resistor, a second resistor, and a power MOS transistor.

[0013] Furthermore, the electric energy circuit at least includes a power transformer and a first diode.

[0014] Furthermore, the detection circuit at least includes a first circuit form and a second circuit form.

[0015] When the detection circuit is in the first circuit form, the detection circuit at least includes a current transformer, a third resistor, a second diode, a fourth resistor, an operational amplifier, a seventh resistor, a first capacitor, and a second capacitor.

[0016] When the detection circuit is in the second circuit form, the detection circuit further includes a fifth resistor and a sixth resistor.

[0017] Furthermore, the current detection circuit of the photovoltaic micro-inverter further includes a DC / DC conversion drive pin, an ADC pin, a first power supply, a second power supply, and a photovoltaic cell.

[0018] Furthermore, the gates of the first resistor, the second resistor, and the power MOS transistor are connected in sequence.

[0019] Any point of the connection of the first resistor and the second resistor is connected to the DC / DC conversion drive pin.

[0020] The drain of the power MOS transistor is connected to the input end of the current transformer and the input end of the power transformer in sequence.

[0021] Furthermore, the output end of the power transformer is respectively connected to the positive electrode of the first diode and the ground, and the negative electrode of the first diode is connected to the first power supply.

[0022] Furthermore, both ends of the third resistor and the second diode are connected to the output end of the current transformer, and the negative electrode of the second diode is connected to the fourth resistor.

[0023] The other end of the fourth resistor is connected to the positive electrode of the operational amplifier, the positive power supply of the operational amplifier is connected to the second power supply, and the second power supply is also connected with a second capacitor.

[0024] The output terminal of the operational amplifier is convergently connected to a seventh resistor, and the other end of the seventh resistor is respectively connected to a first capacitor and an ADC pin.

[0025] The other ends of the first capacitor and the second capacitor are both grounded.

[0026] Further, when the detection circuit is in the second circuit form, the fifth resistor and the sixth resistor are connected, and any point of the connection line of the fifth resistor and the sixth resistor is connected to the negative input terminal of the operational amplifier.

[0027] The other end of the fifth resistor is grounded, and the other end of the sixth resistor is convergently connected to the seventh resistor with the output terminal of the operational amplifier.

[0028] Further, the output terminal of the current transformer, the junction of the third resistor and the positive electrode of the second diode, the photovoltaic cell, the first resistor, the source electrode of the power MOS transistor, and the negative power supply of the operational amplifier are all grounded.

[0029] Compared with the prior art, the beneficial effects of the present application are as follows:

[0030] The present application provides a current detection circuit for a photovoltaic micro-inverter, which at least includes a conversion circuit, a power circuit, and a detection circuit; the power circuit is used for storing or transmitting electric energy according to the conduction or cut-off of the conversion circuit; the detection circuit is used for outputting a preset voltage when the conversion circuit is conducting and the power circuit is storing electric energy, so as to detect a current signal based on the preset voltage. The present application can eliminate the measurement error of the current signal, thereby improving the measurement accuracy. Description of the Drawings

[0031] Figure 1 It is a current detection circuit diagram of a photovoltaic micro-inverter in the prior art.

[0032] Figure 2 For Figure 1 The forward voltage-current characteristic curve diagram of the diode described above.

[0033] Figure 3 It is a current detection circuit diagram of the photovoltaic micro-inverter described in the present application.

[0034] Figure 4 It is another circuit form of the current detection circuit diagram of the photovoltaic micro-inverter described in the present application. Detailed Embodiments

[0035] The present application provides a current detection circuit for a photovoltaic micro-inverter to solve the technical problem of large measurement error in the prior art.

[0036] The following further describes in detail a current detection circuit for a photovoltaic micro-inverter of the present application in conjunction with specific embodiments and the accompanying drawings. Embodiment

[0037] Please refer to Figure 3 , the present application provides a current detection circuit for a photovoltaic micro-inverter, which at least includes a conversion circuit, a power circuit, and a detection circuit.

[0038] The power circuit is used to store or transmit electrical energy according to the conduction or cutoff of the conversion circuit.

[0039] The detection circuit is used to output a preset voltage when the conversion circuit is conducting and the power circuit is storing electrical energy, so as to detect a current signal based on the preset voltage.

[0040] Further, the conversion circuit at least includes a first resistor R1, a second resistor R2, and a power MOS transistor V1.

[0041] Further, the power circuit at least includes a power transformer T1 and a first diode V2.

[0042] Further, the detection circuit at least includes a first circuit form and a second circuit form.

[0043] When the detection circuit is in the first circuit form, the detection circuit at least includes a current transformer B1, a third resistor R3, a second diode V3, a fourth resistor R4, an operational amplifier N1, a seventh resistor R7, a first capacitor C1, and a second capacitor C2.

[0044] Please refer to Figure 3 , when the detection circuit is in the second circuit form, the detection circuit further includes a fifth resistor R5 and a sixth resistor R6.

[0045] Further, the current detection circuit for the photovoltaic micro-inverter further includes a DC / DC conversion drive pin, an ADC pin, a first power supply Vdd, a second power supply VCC, and a photovoltaic cell G1.

[0046] Further, the gates of the first resistor R1, the second resistor R2, and the power MOS transistor V1 are connected in sequence.

[0047] Any point of the connection of the first resistor R1 and the second resistor R2 is connected to the DC / DC conversion drive pin.

[0048] The drain of the power MOS transistor V1 is sequentially connected to the input end of the current transformer B1 and the input end of the power transformer T1.

[0049] Further, the output terminal of the power transformer T1 is respectively connected to the positive electrode of the first diode V2 and the ground, and the negative electrode of the first diode V2 is connected to the first power supply Vdd.

[0050] Further, both ends of the third resistor R3 and the second diode V3 are connected to the output terminal of the current transformer B1, and the negative electrode of the second diode V3 is connected to the fourth resistor R4.

[0051] The other end of the fourth resistor R4 is connected to the positive input terminal of the operational amplifier N1, and the positive power supply of the operational amplifier N1 is connected to the second power supply VCC, and the second power supply VCC is also connected to a second capacitor C2.

[0052] The output terminal of the operational amplifier N1 is converged and connected to the seventh resistor R7, and the other end of the seventh resistor R7 is respectively connected to the first capacitor C1 and the ADC pin.

[0053] The other ends of the first capacitor C1 and the second capacitor C2 are both grounded.

[0054] Further, when the detection circuit is in the second circuit form, the fifth resistor R5 and the sixth resistor R6 are connected, and any point of the connection of the fifth resistor R5 and the sixth resistor R6 is connected to the negative input terminal of the operational amplifier N1.

[0055] The other end of the fifth resistor R5 is grounded, and the other end of the sixth resistor R6 is converged with the output terminal of the operational amplifier N1 and connected to the seventh resistor R7.

[0056] Further, the output terminal of the current transformer B1, the convergence point of the positive electrode of the third resistor R3 and the second diode V3, the photovoltaic cell G1, the first resistor R1, the source electrode of the power MOS transistor V1, and the negative power supply of the operational amplifier N1 are all grounded.

[0057] In this embodiment, as Figure 3 shown, when the power MOS transistor V1 is turned on, the primary and secondary sides of the current transformer B1 are in-phase induction, so the voltage U1 generated on the secondary side of the current transformer B1 is positive, and the voltage U3 after passing through the operational amplifier N1 is also positive. Since the operational amplifier N1 operates in the in-phase state and U2 = U1. Therefore, U3=(1 + R6 / R5)U1, that is, U3 is always greater than or equal to U1 and U2. Since the power transformer T1 is in anti-phase induction, the power transformer T1 stores electrical energy at this time.

[0058] When the power MOS transistor V1 switches from conduction to cut-off, the primary current of the power transformer T1 and the primary current of the current transformer B1 will decrease. The inductance in their primaries will prevent the current from decreasing, causing the induced voltages across the primary and secondary windings of the power transformer T1 and the induced voltages across the primary and secondary windings of the current transformer B1 to be out of phase.

[0059] That is, the secondary of the power transformer T1 starts to transfer electrical energy to the high-voltage DC Vdd (i.e., the first power supply Vdd) through the diode V2. At this time, U1 becomes negative. However, due to the presence of the diode V3, U1 is forced to be a very small negative value.

[0060] Since the operational amplifier N1 is powered by a single positive-polarity power supply VCC (i.e., the second power supply VCC), when U1 is negative, the operational amplifier N1 cannot output a negative value and is forced to make U3 = 0. At this time, the output voltage U0 on the first capacitor C1 is discharged through the seventh resistor R7.

[0061] After the power MOS transistor V1 is cut off, since there is no current in the primary of the current transformer B1, there is no induced voltage in the secondary of the current transformer B1. That is, U1 = 0, which causes U3 = 0, resulting in U0 also becoming 0.

[0062] Figure 4 is another circuit form of the present application, which is actually Figure 3 a variation. In Figure 3 , the sixth resistor R6 = 0. In this way, the fifth resistor R5 has no function, and removing the fifth resistor R5 constitutes Figure 4 the circuit form of Figure 4 . In Figure 3 , U3 = U1. In Figure 3 , U3=(1 + R6 / R5)U1. By changing the ratio of R6 / R5, the amplification factor of the operational amplifier N1 is changed, thereby adjusting U3 to meet the amplitude requirement of the MCU sampling. That is, in

[0063] , U3 ≥ U1. Thus, it can be seen that the present application utilizes the characteristic that the operational amplifier N1 powered by a single positive-polarity power supply VCC can only linearly pass positive-polarity voltage signals and cannot pass negative-polarity voltage signals to detect the corresponding positive-polarity current signals, without the error effects on measurement caused by different forward conduction turn-on voltages of each diode and the non-linear relationship between conduction current and voltage during mass production, thereby improving the measurement accuracy. At the same time, the second diode V3 is used to limit the negative voltage generated by the current transformer B1 to a negative voltage close to 0, avoiding the current transformer B1 generating an excessive negative voltage that may damage the operational amplifier N1.

[0064] In summary, the present application provides a current detection circuit for a photovoltaic micro-inverter, which at least includes a conversion circuit, an electrical energy circuit, and a detection circuit; the electrical energy circuit is used to store or transmit electrical energy according to the conduction or cut-off of the conversion circuit; the detection circuit is used to output a preset voltage when the conversion circuit is conducting and the electrical energy circuit stores electrical energy, so as to detect a current signal based on the preset voltage. The present application can eliminate the measurement error of the current signal, thereby improving the measurement accuracy.

[0065] Although example embodiments have been described herein with reference to the accompanying drawings, it should be understood that the above example embodiments are merely exemplary and are not intended to limit the scope of the present application thereto. Those of ordinary skill in the art can make various changes and modifications therein without departing from the scope and spirit of the present application. All such changes and modifications are intended to be included within the scope of the present application as claimed in the appended claims.

[0066] It should be noted that, in this document, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the term "comprising", "including" or any other variant thereof is intended to cover a non-exclusive inclusion, such that a process, method, article or device comprising a series of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article or device. Without further limitation, an element defined by the phrase "comprising a..." does not exclude the existence of additional identical elements in the process, method, article or device comprising the element.

[0067] Although the description of the present application is made in conjunction with the above specific embodiments, it is obvious that those skilled in the art can make many substitutions, modifications and variations based on the above content. Therefore, all such substitutions, improvements and variations are included within the spirit and scope of the appended claims.

Claims

1. A current detection circuit for a photovoltaic micro-inverter, characterized in that, It includes at least a conversion circuit, a power circuit, and a detection circuit; The power circuit is used for storing or transmitting electric energy according to the conduction or cut-off of the conversion circuit; The detection circuit is used for outputting a preset voltage when the conversion circuit is conducting and the power circuit is storing electric energy, so as to detect a current signal based on the preset voltage.

2. The current detection circuit of the photovoltaic micro-inverter according to claim 1, characterized in that, The conversion circuit includes at least a first resistor, a second resistor, and a power MOS transistor.

3. The photovoltaic micro-inverter current detection circuit according to claim 2, wherein The power circuit includes at least a power transformer and a first diode.

4. The photovoltaic micro-inverter current detection circuit according to claim 3, wherein, The detection circuit includes at least a first circuit form and a second circuit form; When the detection circuit is in the first circuit form, the detection circuit includes at least a current transformer, a third resistor, a second diode, a fourth resistor, an operational amplifier, a seventh resistor, a first capacitor, and a second capacitor; When the detection circuit is in the second circuit form, the detection circuit further includes a fifth resistor and a sixth resistor.

5. The current detection circuit of the photovoltaic micro-inverter according to claim 4, wherein The current detection circuit of the photovoltaic micro-inverter further includes a DC / DC conversion drive pin, an ADC pin, a first power supply, a second power supply, and a photovoltaic cell.

6. The photovoltaic micro-inverter current detection circuit according to claim 5, wherein, The gates of the first resistor, the second resistor, and the power MOS transistor are connected in sequence; Any point of the connection of the first resistor and the second resistor is connected to the DC / DC conversion drive pin; The drain of the power MOS transistor is connected in sequence to the input end of the current transformer and the input end of the power transformer.

7. The current detection circuit of the photovoltaic micro-inverter according to claim 6, characterized in that The output end of the power transformer is respectively connected to the positive electrode of the first diode and grounded, and the negative electrode of the first diode is connected to the first power supply.

8. The photovoltaic micro-inverter current detection circuit according to claim 7, characterized in that, Both ends of the third resistor and the second diode are connected to the output end of the current transformer, and the negative electrode of the second diode is connected to the fourth resistor; The other end of the fourth resistor is connected to the positive input end of the operational amplifier, and the positive power supply of the operational amplifier is connected to the second power supply, and the second power supply is also connected to a second capacitor; The output end of the operational amplifier is converged and connected to the seventh resistor, and the other end of the seventh resistor is respectively connected to the first capacitor and the ADC pin; The other ends of the first capacitor and the second capacitor are both grounded.

9. The current detection circuit of the photovoltaic micro-inverter according to claim 8, characterized in that, When the detection circuit is in the second circuit form, the fifth resistor and the sixth resistor are connected, and any point of the connection of the fifth resistor and the sixth resistor is connected to the negative input end of the operational amplifier; The other end of the fifth resistor is grounded, and the other end of the sixth resistor is converged with the output end of the operational amplifier and connected to the seventh resistor.

10. The photovoltaic micro-inverter current detection circuit according to claim 9, characterized in that, The output end of the current transformer, the convergence point of the positive electrodes of the third resistor and the second diode, the photovoltaic cell, the first resistor, the source of the power MOS transistor, and the negative power supply of the operational amplifier are all grounded.

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