Current detection circuit, power conversion device test equipment

Abstract

Disclosed are a current detection circuit and a power conversion device test equipment using the same. The current detection circuit comprises first to fourth operational amplifiers. The first and second operational amplifiers are two voltage followers configured to process output signals from a current sensor of the power conversion device test equipment and transmit the output signals to a third operational amplifier; the third operational amplifier is a differential amplifier configured to convert voltage signals from the first and second operational amplifiers into a single-ended signal and output the single-ended signal to a fourth operational amplifier; and the fourth operational amplifier is an inverting amplifier with an integral capacitor configured to process and filter the single-ended signal from the third operational amplifier, and an output signal of the fourth operational amplifier is output as a first output signal of the current detection circuit. The current detection circuit is suitable for detecting various forms of current.

Description

Technical Field

[0001] This application relates to a current detection circuit, which is suitable for testing equipment for various power conversion devices. Background Technology

[0002] In the field of current testing within the power conversion device (such as power electronic converter) manufacturing industry, manufacturers often prioritize fully automated test benches to reduce costs and increase production capacity. However, the input or output current forms of different power conversion devices vary significantly. For example, there are DC current, pulse current, sinusoidal AC, PWM modulated AC, and so on. The current magnitude also varies depending on the power rating, requiring different current detection circuits or amplification factors to be designed for different current forms and magnitudes during testing, adapting to the different signal processing equipment on the test bench as the product range expands. However, using the same test equipment makes the design of the current detection circuit more complex, costly, and time-consuming, and sometimes even reduces accuracy.

[0003] Current current detection circuits currently use current transformers, shunts, and Hall effect current sensors. Current transformers are only relatively accurate for sinusoidal AC current detection. Shunts consume a lot of energy and generate significant heat at high power levels. Hall effect current sensors have a wide range of applications but require specific circuit designs, generally necessitating custom development based on input and output requirements. Often, automated testing equipment customizes current detection circuits according to the input and output current characteristics and magnitude of the product under test, resulting in limited scalability and compatibility, and high time and customization costs. Utility Model Content

[0004] This application aims to improve the current detection circuit of test equipment used for power conversion devices (such as power electronic converters, frequency converters, tightening gun drivers, servo drivers, etc.).

[0005] According to one embodiment of this application, a current detection circuit is provided, which is suitable for power conversion device test equipment. The current detection circuit includes an input stage and an output stage, wherein the input stage includes a first operational amplifier, a second operational amplifier, and a third operational amplifier, and the output stage includes a fourth operational amplifier. The first and second operational amplifiers are two voltage followers configured to process the output signal from the current sensor of the power conversion device test equipment and then input it into the third operational amplifier. The third operational amplifier is a differential amplifier configured to convert voltage signals from the first and second operational amplifiers into single-ended signals and output them to the fourth operational amplifier. The fourth operational amplifier is an inverting amplifier with an integrating capacitor, configured to condition and filter the single-ended signal from the third operational amplifier, and the output signal of the fourth operational amplifier is output as the first output signal of the current detection circuit.

[0006] In one embodiment of the current detection circuit, the non-inverting input terminal of the first operational amplifier and the non-inverting input terminal of the second operational amplifier are respectively connected to a current sensor to receive the output signal of the current sensor. The inverting input and output of the first operational amplifier are combined, and then connected to the inverting input of the third operational amplifier through the first resistor; the inverting input and output of the second operational amplifier are combined, and then connected to the non-inverting input of the third operational amplifier through the second resistor.

[0007] In one embodiment of the current detection circuit, the inverting input terminal of the third operational amplifier is connected to the output terminal of the third operational amplifier via a third resistor; the non-inverting input terminal of the third operational amplifier is connected to the common power supply terminal via a fourth resistor; and the output terminal of the third operational amplifier is connected to the inverting input terminal of the fourth operational amplifier via a fifth resistor.

[0008] In one embodiment of the current detection circuit, the non-inverting input terminal of the fourth operational amplifier is connected to the common power supply terminal, and the inverting input terminal is connected to the output terminal of the fourth operational amplifier via an integrating capacitor and a sixth resistor connected in parallel. The sixth resistor is an adjustable resistor.

[0009] In one embodiment of the current detection circuit, the resistance value of the sixth resistor is adjusted based on the required amplification factor of the current detection circuit.

[0010] In one embodiment of the current detection circuit, the output signal line led out from the output terminal of the fourth operational amplifier is equipped with an output protection circuit. The output protection circuit includes protection branches connected between the output signal line of the fourth operational amplifier and different positive and negative power supply voltages, and each protection branch is provided with a switch and a diode.

[0011] In one embodiment of the current detection circuit, the output stage further includes a fifth operational amplifier, which is an inverting amplifier configured to invert the output signal from the fourth operational amplifier, and the output signal of the fifth operational amplifier is output as the second output signal of the current detection circuit.

[0012] In one embodiment of the current detection circuit, the output terminal OUTD of the fourth operational amplifier is connected to the inverting input terminal of the fifth operational amplifier via a seventh resistor, and the inverting input terminal of the fifth operational amplifier is connected to the output terminal of the fifth operational amplifier via an eighth resistor, which is an adjustable resistor.

[0013] In another aspect, this application provides a power conversion device testing apparatus, comprising: A current sensor is used to detect the current in a power conversion device; and The current detection circuit of this application is connected to the first signal pin and the second signal pin of the current sensor, and is used to process the output signal of the current sensor and output it in a single-ended or differential manner.

[0014] In one embodiment of the power conversion device test equipment, a power voltage divider circuit is also included. The power voltage divider circuit includes a plurality of voltage divider resistors connected in series between the highest positive and negative power supply voltages, and polarized capacitors connected in parallel with each voltage divider resistor, thereby providing an intermediate power supply voltage different from the highest positive and negative power supply voltages between adjacent voltage divider resistors. The current sensor and current detection circuit use the highest positive and negative power supply voltage or the intermediate power supply voltage provided by the power voltage divider circuit as the power supply voltage.

[0015] The power conversion device testing equipment is suitable for testing power electronic converters, frequency converters, tightening gun drivers, or servo drivers.

[0016] The current detection circuit for power conversion device testing equipment according to this application is applicable to various current types and can be quickly deployed after simple debugging. It can protect against multiple output levels and is compatible with common voltage detection levels on the market. Attached Figure Description

[0017] The technical solution of this application will become clearer from the following detailed description taken in conjunction with the accompanying drawings. It is understood that these drawings are for illustrative purposes only and are not intended to limit the scope of protection of this application.

[0018] Figure 1 An exemplary structure of a current detection circuit for a power conversion device test apparatus according to this application is shown.

[0019] Figure 2 An exemplary wiring method is shown for a current sensor that can be connected to the input of the current detection circuit.

[0020] Figure 3 A voltage divider circuit for a power supply that can be used in this current sensing circuit is shown.

[0021] Figure 4 A protection circuit that can be used at the output of this current sensing circuit is shown. Detailed Implementation

[0022] This application generally relates to a rapidly deployable, highly compatible current sensing circuit for power conversion device test equipment, and power conversion device test equipment incorporating such a current sensing circuit. The power conversion device test equipment includes a current sensor for detecting the output current of a power electronic converter, and a current sensing circuit for converting the detection signal from the current sensor into an input signal permissible by subsequent signal processing equipment or signal detection equipment.

[0023] The devices that can be tested by the power conversion device testing equipment of this application can be power electronic converters, frequency converters, tightening gun drivers, servo drivers, etc.

[0024] Figure 1 An exemplary structure of a current detection circuit for a power conversion device test apparatus according to this application is shown. The main function of this current detection circuit is to process (amplify, filter) the output signal from the current sensor and output it in a single-ended or differential manner.

[0025] The current sensing circuit consists of two stages: an input stage and an output stage. The input stage includes operational amplifiers UA (first operational amplifier), UB (second operational amplifier), and UC (third operational amplifier). The output stage includes operational amplifier UD (fourth operational amplifier) ​​and an optional operational amplifier UE (fifth operational amplifier).

[0026] To ensure compatibility with both differential and single-ended output signals from the current sensor, two voltage followers, operational amplifiers UA and UB, are used to process the output signal from the current sensor and then input it into operational amplifier UC.

[0027] Specifically, the positive power supply pin V+ and the negative power supply pin V- of operational amplifier UA are connected to a +15V power supply and a -15V power supply, respectively. The -15V and +15V power supplies are connected to the common power supply terminal COM via capacitors C1 and C2, respectively. It should be noted that operational amplifier UA can also use other voltage power supplies, such as + / -5V, + / -10V, etc. Other operational amplifiers are equipped with positive and negative power supplies of the same voltage as operational amplifier UA.

[0028] The non-inverting input terminals +INA and +INB of operational amplifiers UA and UB are used to receive the output signals V1 and V2 from the current sensor, respectively.

[0029] The output voltage V of operational amplifier UA UA_OUT For: V UA_OUT =V1. The output voltage V of operational amplifier UB. UB_OUT For: V UB_OUT =V2.

[0030] The inverting input terminal -INA of operational amplifier UA meets the output terminal OUTA, and then connects to the inverting input terminal -INC of operational amplifier UC via resistor R1 (the first resistor). The inverting input terminal -INB of operational amplifier UB meets the output terminal OUTB, and then connects to the non-inverting input terminal +INC of operational amplifier UC via resistor R2 (the second resistor).

[0031] Operational amplifier UC is a differential amplifier. Considering the inherent characteristics of differential amplifiers, and to improve the robustness of the current sensing circuit, operational amplifiers UA and UB are first used to process the signal from the current sensor, providing a stable and high input impedance for operational amplifier UC. This makes the operation of operational amplifier UC more reliable. Operational amplifier UC converts the differential signal from operational amplifiers UA and UB into a single-ended signal, which is then output to operational amplifier UD.

[0032] The inverting input terminal -INC of operational amplifier UC is connected to the output terminal OUTC of operational amplifier UC via resistor R3 (the third resistor), and then connected to the inverting input terminal -IND of operational amplifier UD via resistor R5 (the fifth resistor). The non-inverting input terminal +INC of operational amplifier UC is connected to the common power supply terminal COM via resistor R4 (the fourth resistor).

[0033] The output voltage V of operational amplifier UC UC_OUT for: The non-inverting input (+IND) of operational amplifier UD is connected to the common power supply terminal COM. The inverting input (-IND) of operational amplifier UD is connected to the common power supply terminal COM via capacitor C3. The inverting input (-IND) of operational amplifier UD also connects to the output terminal OUTD of operational amplifier UD via an integrating capacitor C4 and a sixth resistor (adjustable resistor) R6 connected in parallel. The first output signal line led from the output terminal OUTD of operational amplifier UD is used to output the first output signal Vo1 of the current detection circuit.

[0034] Operational amplifier UD is an inverting amplifier with an integrating capacitor C4, which acts as a low-pass filter. Resistor R6 adjusts the gain (amplification factor) of operational amplifier UD. The output voltage V of operational amplifier UD... UD_OUT Calculated using the following formula: The cutoff frequency of the operational amplifier UD as a low-pass filter is: The resistance value of the sixth resistor R6 is adjusted based on the required amplification factor of the current sensing circuit.

[0035] The output terminal OUTD of operational amplifier UD is connected to the inverting input terminal -INE of operational amplifier UE via resistor R7 (the seventh resistor). The inverting input terminal -INE of operational amplifier UE is connected to the output terminal OUTE of operational amplifier UE via the eighth resistor (adjustable resistor) R8. The non-inverting input terminal +INE of operational amplifier UE is connected to the common power supply terminal COM. The second output signal line led from the output terminal OUTE of operational amplifier UE is used to output the second output signal Vo2 of the current detection circuit.

[0036] When the current sensing circuit is configured to have a single-ended output, the operational amplifier UE can be omitted. In this case, the first output signal Vo1 of the operational amplifier UD forms a single-ended output with the power supply common terminal COM.

[0037] When the current sensing circuit is configured with a differential output, the output terminal OUTD of operational amplifier UD transmits the output voltage to the inverting input terminal -INE of operational amplifier UE via resistor R7. The eighth resistor (adjustable resistor) R8 adjusts the gain of operational amplifier UE. Operational amplifier UE is an inverting amplifier that inverts the output signal from operational amplifier UD to form output signal Vo2, which, together with the output signal Vo1 of operational amplifier UD, forms a differential signal.

[0038] Output voltage V of operational amplifier UE UE_OUT for: When applying this technology, the resistance values ​​of R8 and R7 must be the same, or slightly adjusted to account for losses.

[0039] The first and second output signal lines of the current detection circuit can be connected to subsequent signal processing equipment to process the output signal of the current detection circuit; or connected to other downstream signal detection equipment. The output signal of the current detection circuit is an analog voltage signal.

[0040] Figure 2 This diagram schematically illustrates a current sensor that can be connected to the input terminals of a current detection circuit. The input terminals I+ and I- of this current sensor can be connected in series in the circuit under test. The output signals (voltages) V1 and V2 of the current sensor are output from the first signal pin OUT1 and the second signal pin OUT2, respectively. When the output signal of the current sensor is a differential signal, output signals V1 and V2 are two signals with opposite polarities. When the output signal of the current sensor is a single-ended signal, output signal V1 is the single-ended output signal of the current sensor, and output signal V2 is a 0V signal.

[0041] The positive power supply pin (+V) and negative power supply pin (-V) of the current sensor are connected to a +15V power supply and a -15V power supply, respectively. The -15V and +15V power supplies are connected to the common power supply terminal COM via capacitors C5 and C6, respectively. The current sensor can also use other power supply voltages, such as + / -5V, + / -10V, etc. The current sensor and the current detection circuit can use the same or different power supply voltages.

[0042] The power supply voltage that can be used for the current sensor and current detection circuit can be the one mentioned above. Figure 1 , Figure 2 The ±15V indicated schematically in the diagram can also be other power supply voltages. Therefore, this application uses... Figure 3 The power supply voltage divider circuit shown is used to provide different power supply voltages. For example... Figure 3 As shown, the +15V and -15V power supplies (the highest positive and negative power supply voltages) are connected in series via voltage divider resistors R01, R02, R03, R04, R05, and R06. Each capacitor is connected in parallel with a polarized capacitor C01, C02, C03, C04, C05, or C06. The positive terminal of each polarized capacitor C01, C02, C03, C04, C05, or C06 is connected to the higher voltage side of the parallel voltage divider, and the negative terminal is connected to the lower voltage side of the parallel resistors. A first positive power supply voltage, e.g., +10V, is output between resistors R01 and R02; a second positive power supply voltage, e.g., +5V, is output between resistors R02 and R03; resistors R03 and R04 are connected to the common power supply terminal COM; a first negative power supply voltage, e.g., -10V, is output between resistors R05 and R06; and a second negative power supply voltage, e.g., -5V, is output between resistors R04 and R05. In this way, the power supply voltage divider circuit can provide different positive and negative intermediate power supply voltages. By setting different numbers of voltage divider resistors and setting the resistance value of each voltage divider resistor, the power supply voltage divider circuit can provide positive and negative intermediate power supply voltages with the required number and required voltage values.

[0043] To prevent voltage from the output signal of the current detection circuit, a voltage regulator can be installed at the output terminal of the current detection circuit. Figure 4 The output protection circuit shown.

[0044] See Figure 4An output protection circuit can be constructed by equipping the first output signal line (outputting the first output signal Vo1) of the operational amplifier UD in the current sensing circuit with protection branches connected to different positive and negative power supply voltages. Each protection branch is connected between the first output signal line of the operational amplifier UD and the corresponding positive and negative power supply voltages, and each protection branch contains a switch and a diode. The diodes are oriented to allow current to flow only from the first output signal line to the corresponding positive power supply voltage, or from the corresponding negative power supply voltage to the second output signal line, and to prevent reverse flow. As an example, Figure 4 The diagram shows a first protection branch connected between the +5V power supply and the first output signal line, containing a switch K1 and a diode D1; a second protection branch connected between the +10V power supply and the first output signal line, containing a switch K2 and a diode D2; a third protection branch connected between the +15V power supply and the first output signal line, containing a switch K3 and a diode D3; a fourth protection branch connected between the -5V power supply and the second output signal line, containing a switch K4 and a diode D4; a fifth protection branch connected between the -10V power supply and the second output signal line, containing a switch K5 and a diode D5; and a sixth protection branch connected between the -15V power supply and the second output signal line, containing a switch K6 and a diode D6.

[0045] Based on the power supply voltage used by the current detection circuit, the switch in the corresponding protection branch is closed, while the switches in the other protection branches are open. When the voltage in the first output signal line momentarily exceeds the corresponding power supply voltage, this protection branch divides the voltage of the first output signal line, suppressing the peak voltage to the corresponding power supply voltage level, thereby protecting the current detection circuit.

[0046] When the current detection circuit has a single-ended output, only the first output signal line (outputting the first output signal Vo1) needs to be equipped with Figure 4 The diagram illustrates a protection circuit. When the current detection circuit has a dual-ended output, both the first and second output signal lines (outputting the second output signal Vo2) can be equipped with... Figure 4 The protection circuit is schematically represented in the diagram.

[0047] The input signal of the current detection circuit in this application is compatible with the single-ended and dual-ended (differential) signal output of the current sensor. Current sensors that meet the characteristics of the current detection circuit can be used directly with this current detection circuit without redesign.

[0048] The current detection circuit of this application has the option of single-ended and double-ended (differential) signal output, which has high compatibility with subsequent signal processing equipment or signal detection equipment, and does not require redesign of subsequent signal processing equipment or signal detection equipment.

[0049] By using adjustable resistors in operational amplifiers UD and UE to form a signal conditioning circuit, the output amplification factor of the current detection circuit in this application is adjustable. After simple debugging, it can be adapted to the amplification requirements of multiple scenarios and can be quickly deployed after simple debugging.

[0050] The current detection circuit of this application can adopt different power supply voltage levels. These different voltage levels, combined with the adjustable resistor in the signal conditioning circuit, can support scenarios requiring different signal levels. By connecting different protection branches to the output of the current detection circuit, circuit protection under various power supply voltage levels can be achieved.

[0051] Analog voltage signals are mainly divided into single-ended and differential types. Using the output signal of operational amplifier UD alone in conjunction with COM results in a single-ended output signal. Using the output signals of operational amplifiers UD and UE simultaneously results in a differential output signal.

[0052] While some embodiments have been described above, these embodiments are given by way of example only and are not intended to limit the scope of this application. The appended claims and their equivalents are intended to cover all modifications, substitutions, and alterations made within the scope and spirit of this application.

Claims

1. A current sensing circuit adapted for use in power conversion device test equipment, characterized by, The current detection circuit includes an input stage and an output stage, wherein the input stage includes a first operational amplifier (UA), a second operational amplifier (UB), and a third operational amplifier (UC), and the output stage includes a fourth operational amplifier (UD). The first operational amplifier (UA) and the second operational amplifier (UB) are two voltage followers configured to process the output signals (V1, V2) from the current sensors of the power conversion device test equipment and then input them into the third operational amplifier (UC). The third operational amplifier (UC) is a differential amplifier configured to convert voltage signals from the first operational amplifier (UA) and the second operational amplifier (UB) into single-ended signals and output them to the fourth operational amplifier (UD). The fourth operational amplifier (UD) is an inverting amplifier with an integrating capacitor, configured to condition and filter the single-ended signal from the third operational amplifier (UC), and the output signal of the fourth operational amplifier (UD) is output as the first output signal (Vo1) of the current sensing circuit.

2. The current sense circuit of claim 1, wherein, The non-inverting input terminal (+INA) of the first operational amplifier (UA) and the non-inverting input terminal (+INB) of the second operational amplifier (UB) are respectively connected to the current sensor to receive the output signals (V1, V2) of the current sensor. The inverting input (-INA) and output (OUTA) of the first operational amplifier (UA) are connected together, and then connected to the inverting input (-INC) of the third operational amplifier (UC) via the first resistor (R1); the inverting input (-INB) and output (OUTB) of the second operational amplifier (UB) are connected together, and then connected to the non-inverting input (+INC) of the third operational amplifier (UC) via the second resistor (R2).

3. The current sense circuit of claim 2, wherein, The inverting input (-INC) of the third operational amplifier (UC) is connected to the output (OUTC) of the third operational amplifier (UC) via the third resistor (R3); the non-inverting input (+INC) of the third operational amplifier (UC) is connected to the common power supply terminal (COM) via the fourth resistor (R4); and the output (OUTC) of the third operational amplifier (UC) is connected to the inverting input (-IND) of the fourth operational amplifier (UD) via the fifth resistor (R5).

4. The current sense circuit of claim 3, wherein, The non-inverting input (+IND) of the fourth operational amplifier (UD) is connected to the common power supply terminal (COM), and the inverting input (-IND) is connected to the output terminal (OUTD) of the fourth operational amplifier (UD) through the integrating capacitor (C4) and the sixth resistor (R6) connected in parallel. The sixth resistor (R6) is an adjustable resistor.

5. The current sense circuit of claim 4, wherein, The resistance value of the sixth resistor (R6) is adjusted based on the required amplification factor of the current detection circuit.

6. The current sense circuit of claim 1, wherein, The output signal line leading from the output terminal (OUTD) of the fourth operational amplifier (UD) is equipped with an output protection circuit, which includes protection branches connected between the output signal line of the fourth operational amplifier (UD) and different positive and negative power supply voltages, and each protection branch is equipped with a switch and a diode.

7. The current sense circuit of any one of claims 1-6, wherein, The output stage also includes a fifth operational amplifier (UE), which is an inverting amplifier configured to invert the output signal from the fourth operational amplifier (UD), and the output signal of the fifth operational amplifier (UE) is output as the second output signal (Vo2) of the current detection circuit.

8. The current sense circuit of claim 7, wherein, The output terminal (OUTD) of the fourth operational amplifier (UD) is connected to the inverting input terminal (-INE) of the fifth operational amplifier (UE) via the seventh resistor (R7). The inverting input terminal (-INE) of the fifth operational amplifier (UE) is connected to the output terminal (OUTE) of the fifth operational amplifier (UE) via the eighth resistor (R8), which is an adjustable resistor.

9. A power conversion device test apparatus, characterized by, include: A current sensor is used to detect the current in a power conversion device; as well as The current detection circuit according to any one of claims 1-8 is connected to the first signal pin (OUT1) and the second signal pin (OUT2) of the current sensor, and is used to process the output signal of the current sensor and output it in a single-ended or differential manner.

10. The power conversion device test equipment of claim 9, wherein, It also includes a power supply voltage divider circuit, which includes multiple voltage divider resistors connected in series between the highest positive and negative power supply voltages, and polarized capacitors connected in parallel with each voltage divider resistor, thereby providing an intermediate power supply voltage different from the highest positive and negative power supply voltages between adjacent voltage divider resistors. The current sensor and current detection circuit use the highest positive and negative power supply voltage or the intermediate power supply voltage provided by the power supply voltage divider circuit as the power supply voltage.

11. The power conversion device test equipment of claim 10, wherein, The power conversion device testing equipment is suitable for testing power electronic converters, frequency converters, tightening gun drivers, or servo drivers.

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