TWM623901U - Integrated circuit with current detection and overcurrent protection for inverter - Google Patents

Abstract

The present invention provides a current detection and overcurrent protection integrated circuit for an inverter, comprising: an operational amplifier circuit for externally receiving a current sense circuit representing a transient current flowing through a semiconductor electronic switch in the inverter a low-pass averaging circuit for low-pass filtering the current sampling signal to generate a current sampling average signal; and an overcurrent protection circuit for sampling the current The signal is compared with an overcurrent protection threshold to generate an overcurrent protection signal and output the overcurrent protection signal to the outside. The current detection and overcurrent protection integrated circuit for an inverter according to the present inventive embodiment realizes two functions of current detection and overcurrent protection through a single circuit, so the electronic devices used for realizing the inverter can be saved, and the reduction of System cost of the inverter.

Description

Current sensing and overcurrent protection ICs for inverters

This creation relates to the field of circuits, especially to an integrated circuit for current measurement and overcurrent protection for inverters.

An inverter is a power conversion device that converts a DC voltage into an AC voltage. A common implementation is the use of semiconductor electronic switches (eg, Metal-Oxide-Semiconductor Field-Effect Transistor, MOSFET). , Insulated Gate Bipolar Junction Transistor (Insulated Gate Bipolar Transistor, IGBT, etc.) switching action at a specific time converts DC voltage into AC voltage. In order to ensure the stable and reliable operation of semiconductor electronic switches, the inverter needs to have two basic functions, current detection and overcurrent protection.

Current detection includes detection of both transient and average currents flowing through semiconductor electronic switches. Usually, the detection results of both the transient current and the average current flowing through the semiconductor electronic switch are required to be accurate and linear, and the transient current signal and the average current signal respectively characterize the transient current and the average current flowing through the semiconductor electronic switch. Periods are on the order of microseconds to milliseconds.

The overcurrent protection is used to detect the maximum value of the transient current flowing through the semiconductor electronic switch, and generate the overcurrent protection signal according to the detected maximum value and the overcurrent protection threshold. Generally, it is required to generate an overcurrent protection signal for enabling the semiconductor electronic switch to change from the ON state to the OFF state when the maximum value of the transient current flowing through the semiconductor electronic switch is detected to be greater than the overcurrent protection threshold, the overcurrent protection signal The period is on the order of microseconds.

Traditionally, the above two functions of the inverter are implemented by different circuits, which increases the system cost of the inverter.

In view of one or more of the problems mentioned above, the present creation proposes a current detection and overcurrent protection integrated circuit for an inverter.

A current detection and overcurrent protection integrated circuit for an inverter according to an embodiment of the present invention includes an operational amplifier circuit for externally receiving a current representing a transient current flowing through a semiconductor electronic switch in the inverter sense signals and amplify the current sense signals to generate current sampling signals; a low-pass averaging circuit for low-pass filtering the current sampling signals to generate current sampling average signals; and an overcurrent protection circuit for measuring the current The sampled signal is compared with the overcurrent protection threshold to generate an overcurrent protection signal and output the overcurrent protection signal to the outside.

The current detection and overcurrent protection integrated circuit for an inverter according to the present inventive embodiment realizes two functions of current detection and overcurrent protection through a single circuit, so the electronic devices used for realizing the inverter can be saved, and the reduction of System cost of the inverter.

100: Overcurrent protection integrated circuit

102: Operational amplifier circuit

104: Low-pass averaging circuit

106: Overcurrent protection circuit

102-1: Differential filter circuit

102-2: Voltage Bias Circuit

102-3: Adjustable Gain Circuit

102-4: Operational Amplifier

Vcs: Current sensing signal

Voffset: DC offset

N: the gain factor for the voltage-biased current sense signal set by the adjustable gain circuit 102-3

VOP: Current sampling signal

Vcs+Voffset: Current sensing signal

N×Vcs: Linearly amplified signal

R1: The first adjustable resistance circuit

R2: Second adjustable resistance circuit

R3: Adjustable Resistor Circuit

R4: Resistor circuit

I1: current source

C: Capacitor

2: Current sampling signal

3: Overcurrent protection signal

4: Current sampling average signal

1021: Current Sensor

1021:1041: Bypass switch

1061: Comparator

1062: Adjustable Threshold

The present creation can be better understood from the following description of the specific implementation manner of the present creation in conjunction with the accompanying drawings, wherein: FIGS. 1A and 1B illustrate a current detection and overcurrent protection product for an inverter according to an embodiment of the present creation Example circuit diagram of the bulk circuit; Figure 2 shows an example waveform diagram of a number of signals associated with the operational amplifier circuit shown in Figures 1A and 1B; Figure 3 shows the input to the low-pass averaging circuit shown in Figures 1A and 1B Example waveform diagrams of signals and output signals; FIG. 4 shows example waveform diagrams of input and output signals of the comparator shown in FIGS. 1A and 1B .

Features and exemplary embodiments of various aspects of the present invention are described in detail below. In the following detailed description, numerous specific details are set forth in order to provide a complete overview of the present invention. face understanding. However, it will be apparent to those skilled in the art that the invention may be practiced without some of these specific details. The following description of the embodiments is merely intended to provide a better understanding of the present creation by illustrating an example of the present creation. This creation is by no means limited to any specific configuration set forth below, but covers any modification, substitution and improvement of elements and components without departing from the spirit of this creation. In the drawings and the following description, well-known structures and techniques have not been shown in order to avoid unnecessarily obscuring the present invention. In addition, it should be noted that the term "A and B are connected" used herein may mean "A and B are directly connected" or "A and B are indirectly connected via one or more other elements".

In view of the fact that the two functions of current detection and overcurrent protection are respectively implemented by different circuits in a conventional inverter, the system cost of the inverter is increased. Overcurrent protection integrated circuit.

1A and 1B illustrate example circuit diagrams of a current detection and overcurrent protection integrated circuit 100 for an inverter according to an embodiment of the present invention. As shown in FIGS. 1A and 1B, the current detection and overcurrent protection integrated circuit 100 for an inverter includes an operational amplifier circuit 102, a low-pass averaging circuit 104, and an overcurrent protection circuit 106, wherein: the operational amplifier circuit 102 uses receiving a current sensing signal representing the transient current flowing through the semiconductor electronic switches in the inverter from outside, and amplifying the current sensing signal to generate a current sampling signal 2; the low-pass averaging circuit 104 is used for sampling the current The signal is low-pass filtered to generate a current sampling average signal; the overcurrent protection circuit 106 is used to compare the current sampling signal with the overcurrent protection threshold to generate an overcurrent protection signal, and output the overcurrent protection signal to the outside.

Here, the current sampling signal 2 and the current sampling average signal 4 can respectively represent the transient current and the average current flowing through the semiconductor electronic switches in the inverter, and the overcurrent protection signal can be used when the current sampling signal 2 is greater than the overcurrent protection threshold. A semiconductor electronic switch can be changed from an on state to an off state. The current detection and overcurrent protection integrated circuit for an inverter according to the present inventive embodiment realizes two functions of current detection and overcurrent protection through a single circuit, so the electronic devices used for realizing the inverter can be saved, and the reduction of System cost of the inverter.

As shown in FIG. 1A , in some embodiments, the operational amplifier circuit 102 may It has two signal input terminals, and the two signal input terminals are respectively used to connect the positive output terminal and the negative output terminal of the current sensor 1021 for providing the current sensing signal. That is, the current sensing signal may be input to the operational amplifier circuit 102 through a differential input method.

As shown in FIG. 1B , in some embodiments, the operational amplifier circuit 102 may have a signal input terminal and a ground terminal, the one signal input terminal is used for receiving the current sensing signal, and the ground terminal is used for providing the current sensing signal in conjunction with The ground terminal of the current sensor is connected through the circuit board. That is, the current sensing signal may be input to the operational amplifier circuit 102 through a single-ended input method. Since an equivalent differential circuit is formed inside the operational amplifier circuit 102 when the ground terminal of the current sensor and the ground terminal of the operational amplifier circuit 102 are connected through the circuit board, the operational principle of the operational amplifier circuit 102 shown in FIGS. 1A and 1B is the same. .

As shown in FIGS. 1A and 1B , the operational amplifier circuit 102 includes a differential filter circuit 102-1, a voltage bias circuit 102-2, an adjustable gain circuit 102-3, and an operational amplifier 102-4, wherein: the differential filter circuit 102- 1 is used to differentially filter the current sensing signal; the voltage bias circuit 102-2 is used to perform voltage bias on the differentially filtered current sensing signal; the adjustable gain circuit 102-3 is used to set the voltage bias The gain coefficient of the current sensing signal is set; the operational amplifier 102-4 is used to amplify the voltage-biased current sensing signal with the gain coefficient set by the adjustable gain circuit 102-3. Here, the input terminal of the differential filter circuit 102 - 1 is used as the input terminal of the operational amplifier circuit 102 , and the output terminal of the operational amplifier 102 - 4 is used as the output terminal of the operational amplifier circuit 102 .

Electronic noise is generated when the semiconductor electronic switches in the inverter operate, and the electronic noise is superimposed on the current sensing signal provided by the current sensor. Since the amplitude of the current sensing signal is small, the superposition of electronic noise will result in poor signal-to-noise ratio of the current sensing signal, which is not suitable for direct use. The differential filtering circuit 102-1 can reduce the common-mode noise of the current-sensing signal by performing differential filtering on the current-sensing signal (that is, the differentially filtered current-sensing signal does not include common-mode noise or includes smaller common mode noise). Here, since the equivalent impedance of the differential filter circuit 102-1 is relatively large, other effects on the current sensing signal will not be produced.

Typically, the starting voltage of the current sense signal provided by the current sensor is relatively low, outside the linear operating range of operational amplifier 102-4. The voltage bias circuit 102-2 may superimpose a DC bias on the differentially filtered current sense signal so that the voltage biased current sense signal enters the linear operating region of the operational amplifier 102-4.

Assuming that the current sensing signal provided by the current sensor is Vcs, the DC offset superimposed on the differentially filtered current sensing signal by the voltage bias circuit 102-2 is Voffset, which is set by the adjustable gain circuit 102-3 The gain coefficient for the voltage-biased current sensing signal is N, and the current sampling signal VOP=N×(Vcs+Voffset) output by the operational amplifier 120 - 4 . FIG. 2 shows a number of signals associated with the operational amplifier circuit 102-4 shown in FIGS. 1A and 1B (ie, the current sense signal Vcs, the differentially filtered current sense signal, the voltage biased current sense Example waveform diagrams of the signal Vcs+Voffset, and the current sampling signal VOP).

In some embodiments, the current sampling signal may be DC-blocked by software or hardware to obtain a linearly amplified signal N×Vcs of the current sensing signal Vcs. The linearity and signal-to-noise ratio of the linearly amplified signal of the current sensing signal are relatively high.

As shown in FIGS. 1A and 1B , in some embodiments, the adjustable gain circuit 102 - 3 may include first and second adjustable resistance circuits R1 and R2 , wherein the first end of the first adjustable resistance circuit R1 is connected to The first output end and the second end of the differential filter circuit 102-1 are connected to the inverting input end of the operational amplifier 102-4 and the first end of the second adjustable resistance circuit R2, and the first end of the second adjustable resistance circuit R2 The second terminal of the first adjustable resistance circuit is connected to the inverting input terminal of the operational amplifier 102-4, and the second terminal is connected to the output terminal of the operational amplifier 102-4. The first and second adjustable resistance circuits may be implemented as adjustable resistances, adjustable equivalent resistances, or combinations thereof (ie, the adjustable gain circuit 102-3 may include adjustable resistances, adjustable equivalent resistances, or their combination). In different applications, the adjustable gain circuit 102-3 can set different gain coefficients, for example, 4, 8, 16, 32, etc., which are suitable for different power level applications.

As shown in FIGS. 1A and 1B, in some embodiments, the voltage bias circuit 102-2 may include an adjustable resistance circuit R3 and a current source I1, wherein the first end of the adjustable resistance circuit R3 is connected to the differential filter circuit 102- The second output terminal of 1, the second terminal is connected to the non-inverting input terminal of the operational amplifier 102-4 and the second terminal of the current source I1, and the first terminal of the current source I1 is connected for inversion. The power supply voltage and the second terminal of the inverter current detection and overcurrent protection integrated circuit 100 are connected to the second terminal of the adjustable resistance circuit R3 and the non-inverting input terminal of the operational amplifier 102-4. Here, the adjustable resistance circuit R3 may include at least one of an adjustable resistance and an adjustable equivalent resistance.

As shown in FIGS. 1A and 1B , in some embodiments, the low-pass averaging circuit 104 includes a resistor circuit R3 and an external capacitor connection terminal. The first terminal of the resistor circuit R3 is connected to the output terminal of the operational amplifier circuit 102 , and the second terminal is connected to the output terminal of the operational amplifier circuit 102 . An external capacitor connection terminal, the external capacitor connection terminal is used to connect the external capacitor C that forms an RC filter circuit together with the resistor circuit R3. Typically, the operating current of the inverter (ie, the current flowing through the semiconductor electronic switches in the inverter) changes instantaneously, thus characterizing the current flowing through the semiconductor electronic switches in the inverter (ie, characterizing the inverter The current sampling signal of the working current) also changes in real time. The power of the inverter can be obtained by detecting the envelope of the current sampling signal. RC filtering can eliminate the current pulsation caused by the semiconductor electronic switch, and obtain the envelope of the current sampling signal, that is, the current sampling average signal. FIG. 3 shows example waveform diagrams of the input signal (ie, current sampled signal 2 ) and output signal (ie, current sampled averaged signal 4 ) of the low-pass averaging circuit 104 shown in FIGS. 1A and 1B . RC filtering replaces complex software processing algorithms and requires less signal processor. In addition, since the capacitor C is external, it can be adapted to the needs of different terminal applications by selecting capacitors with different capacitance values.

As shown in FIGS. 1A and 1B , in some embodiments, the low-pass averaging circuit 104 may further include a bypass switch 1041 for bypassing the resistive circuit R4 . When the bypass switch 1041 is closed, the current sampling signal 2 can be measured directly through the external capacitor connection terminal (ie, the external capacitor connection terminal can provide the current sampling signal to the outside). It is very easy to debug the circuit through the oscilloscope observation.

As shown in FIGS. 1A and 1B , in some embodiments, the overcurrent protection circuit 106 includes a comparator 1061 and an adjustable threshold 1062 generating circuit, the first input terminal of the comparator 1061 is connected to the output terminal of the operational amplifier circuit 102 , the first The two input terminals are connected to the adjustable threshold 1062 generating circuit, and the output terminal is used as the output terminal of the overcurrent protection circuit 106 . Usually, the operation time of the comparator 1061 does not exceed 1 microsecond, the operational amplifier circuit 102 has partially eliminated the electronic noise and no delay is generated, so the abnormal current sensing signal can cause the overcurrent protection signal 3 to be generated within 4 microseconds Variety. back After the signal processing circuit of the terminal detects the change of the overcurrent protection signal, it can immediately take protective action on the semiconductor electronic switch to achieve the purpose of overcurrent protection. FIG. 4 shows example waveform diagrams of the input signal (ie, the current sampling signal 2 ) and the output signal (ie, the overcurrent protection signal 3 ) of the comparator 1061 shown in FIGS. 1A and 1B . It can be seen from FIG. 4 that when the current sampling signal 2 exceeds the overcurrent protection threshold, the level polarity of the overcurrent protection signal 3 is reversed.

In some embodiments, the adjustable threshold generation circuit is implemented as an adjustable resistive voltage divider circuit or a digital-to-analog converter. By setting different overcurrent protection thresholds, it can adapt to the needs of different terminal applications.

The current detection and overcurrent protection integrated circuit for the inverter according to the embodiment of the present invention can be implemented independently or integrated into the control chip of the inverter as a module. The advantages brought by the current detection and overcurrent protection integrated circuit for the inverter of the creative embodiment, namely, the saving of peripheral filter circuits, bias circuits, amplifying feedback circuits, averaging circuits, threshold voltage divider circuits, etc.; at the same time, The adjustable gain of the operational amplifier circuit, the adjustable threshold of the comparator, and the external capacitor of the low-pass averaging circuit can meet the requirements of different end products.

This creation can be realized in other specific forms without departing from its spirit and essential characteristics. The present embodiments are to be considered in all respects as illustrative and not restrictive, and the scope of the present invention is defined by the appended claims rather than the foregoing description, and within the meaning and range of equivalents of the claims. All changes are included in the scope of this creation.

100: Overcurrent protection integrated circuit

102: Operational amplifier circuit

104: Low-pass averaging circuit

106: Overcurrent protection circuit

102-1: Differential filter circuit

102-2: Voltage Bias Circuit

102-3: Adjustable Gain Circuit

102-4: Operational Amplifier

R1: The first adjustable resistance circuit

R2: Second adjustable resistance circuit

R3: Adjustable Resistor Circuit

R4: Resistor circuit

I1: current source

C: Capacitor

Claims (10)

A current detection and overcurrent protection integrated circuit for an inverter, characterized by comprising: an operational amplifier circuit for externally receiving a signal representing a transient current flowing through a semiconductor electronic switch in the inverter. a current sensing signal, and amplifying the current sensing signal to generate a current sampling signal; a low-pass averaging circuit for low-pass filtering the current sampling signal to generate a current sampling averaging signal; and an overcurrent protection circuit , which is used to compare the current sampling signal with the overcurrent protection threshold to generate an overcurrent protection signal, and output the overcurrent protection signal to the outside. The current detection and overcurrent protection integrated circuit according to claim 1, wherein the operational amplifier circuit comprises: a differential filter circuit for performing differential filtering on the current sensing signal; a voltage bias circuit for voltage biasing the differentially filtered current sense signal; an adjustable gain circuit for setting a gain factor for the voltage biased current sense signal; and an operational amplifier for utilizing the adjustable gain by the The gain factor set by the circuit amplifies the voltage-biased current sensing signal, wherein the input terminal of the differential filter circuit is used as the input terminal of the operational amplifier circuit, and the output terminal of the operational amplifier is used as the input terminal of the operational amplifier circuit. the output of the operational amplifier circuit. The current detection and overcurrent protection integrated circuit according to claim 1, wherein the operational amplifier circuit has two signal input terminals, and the two signal input terminals are respectively used for connecting the current supplying the current sensing signal The positive and negative outputs of the sensor. The current detection and overcurrent protection integrated circuit of claim 1, wherein the operational amplifier circuit has a signal input terminal and a ground terminal, the one signal input terminal is used for receiving the current sensing signal, and the ground terminal The terminal is used for connecting with the ground terminal of the current sensor that provides the current sensing signal through the circuit board. The current detection and overcurrent protection integrated circuit of claim 2, wherein the adjustable gain circuit comprises an adjustable resistance, an adjustable equivalent resistance, or a combination thereof. The current detection and overcurrent protection integrated circuit of claim 2, wherein the voltage bias circuit includes at least one of an adjustable resistance and an adjustable equivalent resistance and a current source. The current detection and overcurrent protection integrated circuit according to claim 1, wherein the low-pass averaging circuit comprises a resistor and an external capacitor connecting terminal, and the first terminal of the resistor is connected to the output terminal of the operational amplifier circuit, The second terminal is connected to the external capacitor connection terminal, and the external capacitor connection terminal is used to connect an external capacitor that forms an RC filter circuit together with the resistor. The current detection and overcurrent protection integrated circuit of claim 7, wherein the low-pass averaging circuit further comprises a bypass switch for bypassing the resistor, wherein when the bypass switch is closed At the time, the external capacitor connection terminal is used to provide the current sampling signal to the outside. The current detection and overcurrent protection integrated circuit according to claim 1, wherein the overcurrent protection circuit comprises a comparator and an adjustable threshold value generation circuit, and the first input end of the comparator is connected to the operational amplifier circuit. The output terminal and the second input terminal are connected to the adjustable threshold value generating circuit, and the output terminal is used as the output terminal of the overcurrent protection circuit. The current detection and overcurrent protection integrated circuit of claim 9, wherein the adjustable threshold generation circuit is implemented as an adjustable resistor divider circuit or a digital-to-analog converter.

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