An input voltage detection device in an electronic load

Abstract

The present invention discloses an input voltage detection device in an electronic load, which is composed of a reference signal, an operational amplifier, a transistor, a resistor and a comparison unit. The reference signal, the transistor and the resistor constitute a constant current source circuit. The reference signal is used to input a predetermined reference voltage to the operational amplifier. The operational amplifier detects the voltage on the resistor and compares it with the reference voltage to control the output drive signal to the transistor, thereby controlling the current flowing through the transistor. The signals to be detected Load+ and Load- are added to the two ends of the transistor and the resistor. The input of the comparison unit is the drive signal of the transistor. By detecting the amplitude of the drive signal, it is determined whether the constant current source circuit works normally, thereby detecting the voltage between the signals to be detected Load+ and Load-. The present invention detects the load input terminal voltage in a disguised manner through the constant current source circuit, and the detection accuracy and anti-interference ability are stronger.

Description

Technical Field

[0001] The present invention relates to the technical field of electronic loads, and in particular to an input voltage detection device in an electronic load. Background Art

[0002] In electronic load applications, it is sometimes necessary to detect a small voltage between the load inputs load+ and load- to determine whether the device under test is connected to the load terminal. The voltage threshold for judgment is usually between tens of mV and hundreds of mV. There are two common approaches: 1. Using an operational amplifier combined with a comparator. Figure 1 As shown in the figure, the operational amplifier processes the signals Load+ and Load- to be detected, scales the voltage difference between the two to an appropriate amplitude, and then sends it to the input of the subsequent comparator. The other input of the comparator is the preset comparison threshold voltage. The output of the comparator is the output state of the voltage detection. 2. It is the way of combining the operational amplifier with the ADC. Figure 2 As shown, the same test signals, Load+ and Load-, are input to an op amp, scaled to an appropriate amplitude, and then fed into an analog-to-digital converter (ADC). The ADC converts the voltage into a digital value and inputs it into a microcontroller. The microcontroller then determines the input voltage. However, both methods require the use of an op amp to scale the input signal to an appropriate amplitude. The voltage between the test signals, Load+ and Load-, typically ranges from several hundred to over a thousand volts. When the rated input voltages of Load+ and Load- are relatively high, this voltage is typically attenuated to an appropriate amplitude, typically within 10V, by using a voltage divider resistor coupled to the op amp. First, the relatively high voltages of the test signals, Load+ and Load-, necessitate a relatively large value for the voltage divider resistor. Large resistor values, coupled with inherent capacitance or parasitic stray capacitance within the circuit, significantly limit the bandwidth of the sampling circuit, resulting in slow response. Second, the proportional attenuation of the voltage divider resistor is also significant. Consequently, the voltage of tens to hundreds of millivolts to be detected is attenuated to a very small value, perhaps only tens of microvolts. The signal amplitude is extremely small, making it difficult for the subsequent voltage comparison circuit to accurately analyze this tiny voltage. Furthermore, inherent circuit noise and even a small amount of external noise can significantly affect the detection of this tiny voltage. Therefore, due to the limitations of system noise and bandwidth, timely and accurate resolution of voltages ranging from tens to hundreds of mV is extremely difficult and unattainable. Summary of the Invention

[0003] The purpose of the present invention is to address the deficiencies of the prior art and provide an input voltage detection device for an electronic load, which detects the load port voltage and converts it into another physical quantity in the form of a circuit for detection, thereby improving detection accuracy and anti-interference ability.

[0004] The present invention discloses an input voltage detection device for an electronic load, comprising a reference signal, an operational amplifier, a transistor, a resistor Rs, and a comparison unit. The reference signal, transistor, and resistor Rs form a constant current source circuit. The reference signal is used to input a predetermined reference voltage Vref into the operational amplifier. The operational amplifier detects the voltage across the resistor and compares it with the reference voltage to control the output drive signal to the transistor, thereby controlling the current flowing through the transistor. When stable, the current I of the constant current source circuit is equal to Vref / Rs. Detection signals Load+ and Load- are applied across the transistor and the resistor. The comparison unit input is the transistor drive signal. By detecting the amplitude of the drive signal, it is determined whether the constant current source circuit is operating normally, thereby detecting the voltage between the detection signals Load+ and Load-.

[0005] Furthermore, the signal to be detected Load+ is applied to the drain of the transistor, the signal to be detected Load- is applied to one end of the resistor, the other end of the resistor is respectively connected to the inverting input end of the operational amplifier and the source of the transistor, and the reference signal is used to input a predetermined reference voltage to the non-inverting input end of the operational amplifier.

[0006] Furthermore, the rated voltage of the transistor exceeds the voltage between the signals to be detected Load+ and Load-, and the transistor has a minimum on-resistance Rd limit. When the voltage between the signals to be detected Load+ and Load- is higher than I*(Rd+Rs), the constant current source circuit operates normally. When the voltage between the signals to be detected Load+ and Load- is lower than I*(Rd+Rs), the current of the constant current source circuit is always less than Vref / Rs, and the constant current source circuit cannot establish negative feedback. By detecting the amplitude of the drive signal output by the operational amplifier to the transistor through the comparison unit, it can be determined that the constant current source circuit cannot operate normally, thereby detecting that the voltage between the signals to be detected Load+ and Load- is low.

[0007] Furthermore, the comparison unit is a comparator circuit or a clamping diode.

[0008] Furthermore, the detection device is disabled by setting the reference voltage Vref to a negative value.

[0009] The beneficial effects of the technical solution of the present invention include: The present invention discloses an input voltage detection device for an electronic load. This device detects the load port voltage by converting it into another physical quantity in the form of a circuit for detection. This device detects the load input voltage in a disguised manner through a constant current source circuit, resulting in enhanced detection accuracy and anti-interference capabilities. By detecting the amplitude of the transistor drive voltage, the load input voltage is determined, allowing detection of small voltages within a very large voltage input range, with a high response bandwidth. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 This is a circuit diagram for detecting the load input voltage using an operational amplifier combined with a comparator.

[0011] Figure 2 This is a circuit diagram for detecting the load input voltage using an operational amplifier combined with an ADC.

[0012] Figure 3 This is a circuit diagram of the device disclosed in the present invention. DETAILED DESCRIPTION

[0013] The technical solution of the present invention is described in detail below, but the protection scope of the present invention is not limited to the embodiments.

[0014] like Figure 3 As shown, the present invention discloses an input voltage detection device for an electronic load, comprising a reference signal, an operational amplifier U1, a transistor Q1, a resistor Rs, and a comparison unit. The detection signal Load+ is applied to the drain of transistor Q1, and the detection signal Load- is applied to one end of resistor Rs. The other end of resistor Rs is connected to the inverting input of operational amplifier U1 and the source of transistor Q1, respectively. The reference signal is used to input a predetermined reference voltage Vref to the non-inverting input of operational amplifier U1. The operational amplifier U1 detects the voltage across resistor Rs and compares it with the reference voltage Vref to control the output of a drive signal from operational amplifier U1 to transistor Q1, thereby controlling the gate voltage of output transistor Q1 and, in turn, the current flowing through transistor Q1. When stable, the current flowing through transistor Q1 is I = Vref / Rs. The reference signal, transistor Q1, and resistor Rs form a constant current source circuit. The comparison unit receives the drive signal of transistor Q1 as input. By detecting the amplitude of the drive signal, the comparison unit determines whether the constant current source circuit is operating properly, thereby characterizing the voltage between the detection signals Load+ and Load-.

[0015] The transistor Q1 is selected as a transistor with a rated voltage exceeding the voltages of the signals Load+ and Load- to be detected. At the same time, the transistor Q1 has a minimum on-resistance Rd limit. When the voltage V between the signals Load+ and Load- to be detected is relatively high, that is, when V > I*(Rd + Rs), the constant current source circuit can operate normally, and the drive voltage of the transistor Q1 is approximately 3 to 5V. When the voltage V between the signals Load+ and Load- to be detected is relatively low, that is, when V < I*(Rd + Rs), at this time, limited by the minimum on-resistance Rd of the transistor Q1, the current I of the constant current source circuit is always less than Vref / Rs, and the operational amplifier U1 can never establish a negative feedback stable state. The drive voltage of the transistor Q1 is always in the saturation state. Without other amplitude limiting circuits, this drive voltage will saturate near the positive power supply of the operational amplifier U1. If the power supply of the operational amplifier U1 is ±12V, then the drive voltage of the transistor Q1 is about 10V at this time. When the drive voltage output by the operational amplifier U1 changes significantly, it can reflect the magnitudes of the voltages of the signals Load+ and Load-. When the voltage between the signals Load+ and Load- to be detected becomes small and approaches the minimum on-resistance Rd of the transistor Q1, the drive voltage can be detected and judged by the comparison unit. By detecting the amplitude of the drive voltage of the transistor Q1, the present invention can judge the voltage at the load input terminal, allowing for the detection of tiny voltages within a very large voltage input range and having a high response bandwidth. The reference signal gives the reference voltage Vref according to the voltage amplitude to be detected and the minimum on-resistance Rd of the selected transistor Q1.

[0016] The input of the comparison unit of the present invention is the drive signal of the transistor Q1. By detecting the amplitude of this drive signal, it is judged whether the constant current source circuit is operating normally, thereby characterizing the magnitude of the voltage between Load+ and Load-. This comparison unit can be implemented by a comparator circuit or a clamping diode. It can also disable this detection circuit by setting the reference signal Vref to a negative value. The device disclosed in the present invention converts the detection of the load port voltage into the detection of a physical quantity in another circuit form, and变相 detects the voltage at the load input terminal through the constant current source circuit, with stronger detection accuracy and anti-interference ability.

[0017] As described above, although the present invention has been shown and described with reference to specific preferred embodiments, it should not be construed as a limitation of the present invention itself. Various changes in form and detail can be made without departing from the spirit and scope of the present invention defined by the appended claims.

Claims

1. An input voltage detection device in an electronic load, characterized in that: It is composed of a reference signal, an operational amplifier, a transistor, a resistor Rs and a comparison unit. The reference signal, the transistor and the resistor Rs constitute a constant current source circuit. The signal to be detected Load+ is added to the drain of the transistor, the signal to be detected Load- is added to one end of the resistor, and the other end of the resistor is respectively connected to the inverting input end of the operational amplifier and the source of the transistor. The reference signal is used to input a predetermined reference voltage Vref to the inverting input end of the operational amplifier. The operational amplifier detects the voltage on the resistor and compares it with the reference voltage to control the output drive signal to the transistor, thereby controlling the current flowing through the transistor. When stable, the current I of the constant current source circuit is Vref / Rs. The input of the comparison unit is the drive signal of the transistor. The amplitude of the drive signal output by the operational amplifier to the transistor can be detected by the comparison unit to determine the working state of the constant current source circuit, thereby detecting the voltage between the signals to be detected Load+ and Load-; The rated voltage of the transistor exceeds the voltage between the signals to be detected Load+ and Load-, and the transistor has a minimum on-resistance Rd limit. When the voltage between the signals to be detected Load+ and Load- is higher than I* (Rd+Rs), the constant current source circuit works normally. When the voltage between the signals to be detected Load+ and Load- is lower than I* (Rd+Rs), the current of the constant current source circuit is always less than Vref / Rs, and the constant current source circuit cannot establish negative feedback. By detecting the amplitude of the driving signal output by the operational amplifier to the transistor through the comparison unit, it can be determined that the constant current source circuit cannot work normally, thereby detecting that the voltage between the signals to be detected Load+ and Load- is low.

2. The input voltage detection device in an electronic load according to claim 1, characterized in that: The comparison unit is a comparator circuit or a clamping diode.

3. The input voltage detection device in an electronic load according to claim 1, characterized in that: By setting the reference voltage Vref to a negative value, the detection device is disabled.

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