Low internal resistance direct current detection circuit and electronic equipment

Abstract

The utility model discloses a low-internal resistance direct current detection circuit and electronic equipment. The circuit comprises a sampling resistor unit, an analog single-pole double-throw switch, a first blocking capacitor, a first voltage amplification unit, a second blocking capacitor, a frequency mixing unit, a second voltage amplification unit, a third blocking capacitor and a control unit. The sampling resistor unit is arranged in a direct current loop to be measured; the analog single-pole double-throw switch is used for converting direct-current voltage at two ends of the sampling resistor into a high-frequency alternating signal; the first voltage amplification unit amplifies the signal and then outputs the signal to the frequency mixing unit through the second blocking capacitor; the mixing unit outputs a low-frequency mixing signal under the action of the mixing control signal; the second voltage amplification unit differentially amplifies the frequency mixing signal and then outputs a third output voltage signal through a third blocking capacitor, and the third output voltage signal is used for determining the magnitude of loop current and controlling gear switching. The circuit is simple in structure, low in cost and suitable for large-range direct current on-line continuous detection.

Description

Technical Field

[0001] This application relates to the field of electronic circuits, specifically to a low internal resistance DC current detection circuit and an electronic device. Background Technology

[0002] In daily operation, the operating current of the device under test often varies widely. To achieve continuous online detection of the device's DC current without affecting its normal operation, the sampling resistor used for measurement must have a very small resistance, as low as hundreds of milliohms, tens of milliohms, or even less. In such cases, the voltage across the sampling resistor can reach the millivolt level when a large current of several amperes flows through it, while the voltage across it may only be at the microvolt level when a small current of microamperes flows through it. Such a small DC voltage places high demands on the subsequent amplification circuit, making it difficult to implement and relatively expensive. Traditional magnetoelectric high-sensitivity ammeters often have a large internal resistance, ranging from hundreds of ohms to typically tens of ohms. In many scenarios, this leads to excessive voltage drop, affecting the normal operation of the circuit. Therefore, such high-resistance ammeters cannot be used in circuits with widely varying currents. Summary of the Invention

[0003] To more clearly describe this application, several signal names mentioned herein are explained:

[0004] The "DC voltage" refers to the voltage signal generated across the sampling resistor unit due to the DC current to be measured flowing through it.

[0005] The "high-frequency alternating signal" refers to the AC signal generated by modulating the DC voltage through an analog single-pole double-throw switch, with its frequency determined by the first control signal.

[0006] The "low-frequency AC signal" refers to an AC signal whose frequency is significantly lower than that of the first control signal, obtained by amplifying and mixing the high-frequency alternating signal, and whose amplitude is related to the magnitude of the DC current to be measured.

[0007] The “first mixing signal” and “second mixing signal” refer to the two mixing results containing low-frequency components output by the mixing unit. They have different phases or polarities and are used for subsequent differential amplification.

[0008] The term "component" refers to the frequency components or amplitude characteristics contained in the signal, particularly the low-frequency components contained in the first and second mixing signals that are proportional to the DC current to be measured.

[0009] To address the aforementioned issues, this application provides a low-internal-resistance DC current detection circuit and electronic device, which can continuously detect DC currents with a wide range of variations in the circuit online, and can reduce technical costs.

[0010] One technical solution adopted in this application is to provide a low internal resistance current detection circuit, which includes:

[0011] The sampling resistor unit has a first sampling resistor that is always placed in the current loop to be detected. One end of this sampling resistor is connected to the current input terminal, and the other end is the current output terminal, which is connected to the ground of the DC detection circuit to convert the DC current to be measured into a DC voltage. Several additional sets of extended sampling resistors are provided, which are switched on and off by an electronic control switch to provide different resistance values. One end of all extended sampling resistors is connected to the current input terminal, and the other end is connected to the input terminal of the electronic control switch. The output terminal of the electronic control switch is grounded, and the control terminal of the electronic control switch is connected to the gear control signal.

[0012] The simulated single-pole double-throw switch unit has its current input terminal of the sampling resistor connected to the first input terminal of the voltage-controlled simulated single-pole double-throw switch, and its second input terminal grounded; the switch control terminal of the simulated single-pole double-throw switch is connected to the first control signal generated by the control unit.

[0013] The first DC blocking capacitor is connected to one end of the analog single-pole double-throw switch output terminal, and the other end of the first DC blocking capacitor is the first output voltage signal.

[0014] The first voltage amplification unit takes as input a first output voltage signal (i.e., the aforementioned high-frequency alternating signal) after DC is isolated by a first DC blocking capacitor, and outputs an amplified signal; the amplified signal is then isolated by a second DC blocking capacitor to obtain a second output voltage signal.

[0015] The second DC blocking capacitor isolates the DC signal from the amplified signal of the first voltage amplifier unit to obtain the second output voltage signal.

[0016] The mixing unit receives the second output voltage signal and the mixing control signal, and outputs a first mixing output voltage and a second mixing output voltage through mixing. (i.e., the first mixing signal and the second mixing signal).

[0017] The second voltage amplification unit receives the first and second mixing output voltages (i.e., the first mixing signal and the second mixing signal), differentially amplifies them, and obtains a further amplified low-frequency signal. After the DC signal is isolated by the third DC blocking capacitor, the third output voltage signal is output. This voltage is used to determine the current magnitude in the input circuit and to generate the gear control signal.

[0018] The third DC blocking capacitor is used to output a third output voltage signal, which is amplified by the second voltage amplification unit. This voltage is used to measure the current in the input circuit and also to obtain the gear control signal.

[0019] The control unit generates a gear position control signal, a first control signal, and a mixing control signal. The gear position control signal is obtained by measuring the third output voltage signal and performing calculations.

[0020] Preferably, the sampling resistor unit consists of one or more sampling resistors connected in parallel. The parallel connection method involves connecting an electronic control switch and a sampling resistor in series as one group, with multiple groups connected in parallel. The on / off state of the circuit is controlled by a range control signal to measure current with appropriate accuracy. The first group is not always switched on by the electronic control switch to ensure the continuity of the circuit current. At least two groups of sampling resistors are used.

[0021] Preferably, all amplification units are operational amplifiers.

[0022] Preferably, the difference frequency obtained after mixing the mixing control signal and the second output voltage signal is controlled within 8kHz.

[0023] Preferably, the frequencies of both the mixing control signal and the first control signal are several times greater than 8kHz.

[0024] Preferably, the electronic control switch consists of a relay.

[0025] Optionally, the electronic control switch can be composed of one or more MOSFETs connected in parallel to reduce on-resistance and improve performance.

[0026] The technical solutions provided in this application have the following advantages compared with the prior art:

[0027] By converting DC current into a square wave signal for processing, the effects of input offset voltage and other factors in DC amplification are avoided, significantly reducing the requirements for the DC amplification performance of the operational amplifier, substantially reducing material costs, and greatly improving equipment availability. Automatic switching of the appropriate range based on measurement results results in lower internal resistance and a higher measurement range and accuracy. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0029] In the attached image:

[0030] Figure 1 is a schematic diagram of the structure of the first embodiment of the low internal resistance DC current detection circuit provided in this application;

[0031] Figure 2 is a schematic diagram of the first voltage amplification unit structure of the first embodiment of the low internal resistance DC current detection circuit provided in this application;

[0032] Figure 3 is a schematic diagram of the mixing unit structure of the first embodiment of the low internal resistance DC current detection circuit provided in this application;

[0033] Figure 4 is a schematic diagram of the second voltage amplification unit structure of the first embodiment of the low internal resistance DC current detection circuit provided in this application;

[0034] Figure 5 is a schematic diagram of the control unit structure of the first embodiment of the low internal resistance DC current detection circuit provided in this application;

[0035] Figure 6 is a schematic diagram of the first voltage amplification unit structure of the second embodiment of the low internal resistance DC current detection circuit provided in this application;

[0036] Figure 7 is a schematic diagram of the multi-position sampling resistor unit structure of the third embodiment of the low internal resistance DC current detection circuit provided in this application;

[0037] Figure 8 is a schematic diagram of an embodiment of the electronic device provided in this application. The electronic device 300 includes a low-internal-resistance DC current detection circuit 100, which is as described in the above embodiments and will not be repeated here. Detailed Implementation

[0038] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. It is understood that the specific embodiments described herein are only for explaining this application and not for limiting it. Furthermore, it should be noted that, for ease of description, only the parts related to this application are shown in the accompanying drawings, not all structures. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0039] In the following description, specific details such as particular system structures and techniques are set forth for illustrative purposes and not for limitation, in order to provide a thorough understanding of the embodiments of the present invention. However, those skilled in the art will understand that the present invention can be implemented in other embodiments without these specific details. In other instances, detailed descriptions of well-known systems, apparatuses, circuits, and methods are omitted so as not to obscure the description of the present invention with unnecessary detail.

[0040] First Embodiment

[0041] As shown in Figures 1-5, this application provides a low internal resistance DC current detection circuit, comprising:

[0042] An electronic switch can be used to select the resistance value of a sampling resistor, which is set in the current loop to be detected. A voltage-controlled analog single-pole double-throw switch is used. The control terminal of the analog single-pole double-throw switch is connected to the first control signal output by the control signal unit. The first input terminal of the analog switch is connected to the current input terminal of the sampling resistor. The second input terminal of the analog switch is grounded. The output terminal of the analog switch is connected to one end of the first DC blocking capacitor. The other end of the first DC blocking capacitor is connected to the first voltage signal amplification unit. A second voltage signal is output after passing through the second DC blocking capacitor. The second voltage signal enters the mixing module and is mixed with the mixing control signal to obtain the first mixing output voltage and the second mixing output voltage. These two signals enter the second voltage amplification unit for differential amplification. A third voltage signal is output after passing through the third DC blocking capacitor to determine the DC current flowing through the sampling resistor.

[0043] In the first embodiment, the first voltage amplification unit is a single-ended power supply amplifier circuit. The output terminal of the first DC blocking capacitor is connected to the non-inverting input terminal of the operational amplifier. The DC voltage divider at the non-inverting input terminal is fixed at 1 / 2VCC using voltage divider resistors R1 and R2. The inverting input terminal is connected to one end of resistor R3, and the other end of R3 is connected to one end of capacitor C4, with the other end of C4 grounded. A feedback resistor R7 is connected across the output terminal and the inverting input terminal of the operational amplifier.

[0044] In the first embodiment, the mixing unit is a 4-input, 1-output switching mixer. Mixing control signal 1 and mixing control signal 2 are used to control the conduction of channels 1-4 of the analog switch. The second output voltage is processed by the mixing unit to obtain the first mixing output voltage and the second mixing output voltage. The combined level LL of mixing control signal 1 and mixing control signal 2 selects channel 1, the combined level LH ​​selects channel 2, the combined level HL selects channel 3, and the combined level HH selects channel 4. In this embodiment, the first mixing output voltage and the second mixing output voltage are obtained from channel 1 and channel 4, respectively.

[0045] In the first embodiment, the second voltage amplification unit is a differential amplifier circuit powered by a single-ended power supply. The first mixer output voltage and the second mixer output voltage are differentially input and amplified, and the output is passed through a third DC blocking capacitor to obtain a third output voltage.

[0046] Second Embodiment

[0047] In the second embodiment, the first voltage amplification unit adopts an amplifier circuit structure powered by a dual-ended power supply, as shown in Figure 6. The remaining structure is the same as in the first embodiment.

[0048] Third Embodiment

[0049] In the third embodiment, the first sampling resistor is 0.5 ohms, and there are two sets of extended sampling resistors, namely 0.1 ohms and 0.01 ohms, as shown in Figure 7. The remaining structure is the same as in the first embodiment. The control unit outputs gear control signal 1 and gear control signal 2, which are used to switch the 0.01 ohm and 0.1 ohm sampling resistors on and off, respectively. The 0.5 ohm resistor is always on, keeping the device in normal operating condition.

[0050] The above description is merely an embodiment of this application and does not limit the patent scope of this application. Any equivalent structural or procedural transformations made using the content of this application's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of this application.

Claims

1. A low internal resistance DC current detection circuit, characterized in that, The DC current detection circuit includes: a sampling resistor unit, disposed in the DC current loop to be detected, for acquiring DC voltage; a voltage-controlled analog single-pole double-throw switch, for converting DC voltage into a high-frequency alternating signal; a first DC blocking capacitor; a first voltage amplification unit, for amplifying weak voltage signals; a second DC blocking capacitor; a mixing unit, for acquiring low-frequency AC signals; a second voltage amplification unit, for amplifying low-frequency AC signals; a third DC blocking capacitor; and a control unit, for generating a first control signal, a gear control signal, and a mixing control signal.

2. The low internal resistance DC current detection circuit according to claim 1, characterized in that: The control terminal of the analog single-pole double-throw switch is connected to the first control signal output by the control unit. The first input terminal of the switch is connected to the current input terminal of the sampling resistor unit. The second input terminal of the switch is grounded. The output terminal of the switch is connected to one end of the first DC blocking capacitor. The other end of the first DC blocking capacitor obtains the first output voltage signal, which is connected to the first voltage amplification unit.

3. The low internal resistance DC current detection circuit according to claim 1, characterized in that: The sampling resistor unit has a resistance value range of 0.01 ohms to 0.5 ohms, and at least one sampling resistor is always connected, referred to as the first sampling resistor, to maintain the connection of the circuit under test.

4. The low internal resistance DC current detection circuit according to claim 3, characterized in that: The sampling resistor unit uses an electronic control switch to switch gears. The first sampling resistor, which is always connected, has the largest resistance. The extended sampling resistors for each of the other gears are connected in series with an electronic control switch and then in parallel to the first sampling resistor. The electronic control switch is controlled by the gear control signal output by the control unit. The input terminal of the extended sampling resistor is connected to the current input terminal, and the output terminal of the extended sampling resistor is connected to one end of the electronic control switch. The other end of the electronic control switch is grounded, and the control terminal of the electronic control switch is connected to the gear control signal.

5. The low internal resistance DC current detection circuit according to claim 1, characterized in that: The first control signal output by the control unit is a square wave with a 50% duty cycle; the mixing control signal is a square wave with a 50% duty cycle, or two square waves with the same frequency, 50% duty cycle, and a 90° phase difference.

6. The low internal resistance DC current detection circuit according to claim 1, characterized in that: The first voltage amplification unit employs an operational amplifier to amplify the input first output voltage signal into a second output voltage signal, and the second DC blocking capacitor isolates DC.

7. The low internal resistance DC current detection circuit according to claim 6, characterized in that: The second output voltage signal and the mixing control signal enter the mixing unit and output a first mixing signal and a second mixing signal. The main components of the first mixing signal and the second mixing signal are low-frequency signals that are much lower than the frequencies of the first control signal and the mixing control signal.

8. The low internal resistance DC current detection circuit according to claim 7, characterized in that: The first and second mixing signals enter the second voltage amplification unit, which is a differential amplifier circuit used to differentially amplify the first and second mixing signals. After being isolated from DC by the third DC blocking capacitor, the third output voltage signal is output. The third output voltage signal is used to determine the magnitude of the current in the input circuit.

9. The low internal resistance DC current detection circuit according to claim 8, characterized in that: The control unit processes the third output voltage signal, automatically selects the appropriate gear, and outputs the corresponding gear control signal.

10. An electronic device, characterized in that, Includes the low internal resistance DC current detection circuit as described in any one of claims 1-9.

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