Multiplexing amplifier front end applied to high voltage and current signal detection

Abstract

The invention discloses a multiplexing amplifier front end applied to high voltage and current signal detection, and belongs to the technical field of amplifiers. The switch S1 and the switch SN1 for switching are moved behind the R11 / R12 and the R31 / R32, and in the input part of the amplifier core, the S1 and the SN1 are connected in series with the input impedance of the amplifier core instead of being connected in series with the R11 / R12 and the R31 / R32 traditionally. According to the structure, the area of one amplifier core is omitted, multiplexing of current monitoring and voltage monitoring is achieved through switching of the switch, and cost is greatly reduced.

Description

Technical Field

[0001] The present invention relates to a multiplexed amplifier front end applied to high-voltage voltage and current signal detection, and belongs to the technical field of amplifiers. Background Art

[0002] In current shunt monitors and power monitors, it is often necessary to amplify or attenuate the monitored parallel voltage drop and bus power supply voltage signals, and then perform quantization processing by an ADC. Such a front-end amplifier generally needs to amplify the parallel voltage drop of the monitored current and attenuate the bus power supply signal of the monitored voltage. Usually, a programmable gain amplifier (hereinafter simply referred to as PGA) can be used for processing. The PGA can convert the input signal to a specific ADC input range, but the gain that the PGA can change generally uses binary gain, which is not applicable to some application scenarios where the gain has been determined and is not binary. Moreover, with the improvement of the integration degree of integrated circuits, more front-end multiplexing scenarios need to be considered. For example, in a chip integrating a current shunt monitor and a power monitor, the input differential mode range of the parallel voltage drop is -81.92 mV to +81.92 mV, and it needs to be converted to a voltage threshold of -2.048 V to +2.048 V, with a gain of 25; while the bus power supply voltage signal is as high as 36 V, and the signal of 0 to 40.96 V needs to be converted to -2.048 V to +2.048 V, with a gain of only 0.05. In this case, the binary gain PGA is no longer applicable, and generally two amplifiers and two resistor-capacitor feedback networks need to be used for switching.

[0003] As Figure 1 shown, S1 and SN1 are two pairs of high-voltage switches, and S1' and SN1' are two pairs of low-voltage switches. When monitoring the current, S1 / S1' is closed, and SN1 / SN1' is open. R11 = R12 = R, R21 = R22 = 25R. The front-end amplifier amplifies the voltage signal generated by the current flowing through the shunt resistor Rshunt by 25 times, converts the input differential mode range from -81.92 mV to +81.92 mV to a voltage threshold of -2.048 V to +2.048 V, and at the same time transfers the common mode range from 0 to 36 V to an output common mode of 1.25 V for the ADC to perform sampling quantization. When monitoring the bus voltage, S1 / S1' is open, and SN1 / SN1' is closed. R31 = R32 = 20R, R41 = R42 = R. The front-end amplifier transfers the bus voltage threshold from 0 to 36 V to a voltage threshold of 0 to +2.048 V for the ADC to sample and quantize. This structure needs to introduce two pairs of high-voltage switches, and the high-voltage switches are connected in series with R11 / R12 and R31 / R32. The high-voltage switch structure is complex, and the on-resistance will affect the fixed gain of the two front-end amplifiers. The on-resistance is related to the operating voltage and will introduce non-linearity. This structure also needs to configure two front-end amplifier cores, wasting area. Summary of the Invention

[0004] Regarding the problems of non - linearity introduced by the input switch and structural waste of area in the front - end amplifiers of high - voltage current shunt monitors and power monitors, the present invention proposes a multiplexed amplifier front - end applied to the detection of high - voltage voltage and current signals. Its area is greatly reduced and the structure is simple, which can effectively reduce the fixed - gain deviation introduced by the switch resistance.

[0005] The present invention provides a multiplexed amplifier front - end applied to the detection of high - voltage voltage and current signals, which is composed of two pairs of resistor feedback networks R11 / R12 / R21 / R22 and R31 / R32 / R41 / R42, an amplifier core AMP1, and four pairs of switches S1 / S1’ / SN1 / SN1’; where S1 and SN1 are in series with the input impedance of the amplifier core AMP1, the input end of the amplifier core AMP1 is connected to the gate of the MOS transistor, and S1 and SN1 are connected to the resistors R11 / R12 / R31 / R32.

[0006] Among them, the SN1 is a high - voltage switch. After attenuation, the input voltage of S1 is below 5V. S1’ and SN1’ only need to process signals of 0 - 2.048V and are low - voltage switches; where R11 = R12 = R, R21 = R22 = 25R, R31 = R32 = 20R, R41 = R42 = R; the input common - mode of the amplifier core AMP1 is 36V, the output common - mode is fixed at 2.048V, the control signals of S1 and S1’ are in the same phase, the control signals of S2 and S2’ are also in the same phase, and the control signals of S1 / S1’ and SN1 / SN1’ are opposite; S1 is composed of isolated nmos, and the well of the nmos can withstand voltage. The 5V EN signal is transferred to the high - voltage control signal through a five - transistor OTA with amplitude limiting; SN1, S1’ and SN1’ are composed of low - voltage NMOS switches.

[0007] In the circuit for transferring the 5V EN signal to the high - voltage control signal. When EN is high, the output of the five - transistor OTA is low, but due to the amplitude - limiting effect of the resistor, the lowest voltage that the output can reach is VCMI + 1.2V - IR, protecting the circuit from being burned. The working voltage threshold of the following two - stage inverters is VCMI - 1.2V to VCMI + 1.2V, transferring the 5V control signal to high voltage.

[0008] In an embodiment of the present invention, S1, SN1, S1' and SN1' are all T-type switches. When EN is high, ENB is low, S1 and S2 are closed, S3 is open, and the signal is transmitted from IN to OUT. When EN is low, ENB is high, S1 and S2 are open, S3 is closed, and the intermediate level is set to VCMI / VCMO. VCMI and VCMO are the input common mode and output common mode of the amplifier. By using T-type switches, the isolation degree of the signal can be improved, and a large current can be prevented from occurring when the switch is turned on, burning out the switch.

[0009] In an embodiment of the present invention, when monitoring the working state for current, SN1 and SN1' are closed, S1 and S1' are open. After S1 is open, it is set to the input common mode VCMI of the amplifier. After S1' is open, it is set to the output common mode VCMO of the amplifier. R11 / R12 / R21 / R22 are connected to the amplifier, and the closed-loop gain is 25. The monitored current flows through Rshunt to generate voltage V1, which is amplified and then sent to a 16-bit ADC for sampling and quantization. The range of V1 is -81.92m to +81.92m, and the range of the ADC is -2.048V to +2.048V. Overall, 1 LSB can be 2.5uV, and the current can be accurately monitored.

[0010] In an embodiment of the present invention, when monitoring the working state for voltage, S1 and S1' are closed, SN1 and SN1' are open. After SN1 is open, it is set to the input common mode VCMI of the amplifier. After SN1' is open, it is set to the output common mode VCMO of the amplifier. R31 / R32 / R41 / R42 are connected to the amplifier, and the closed-loop gain is 0.05. The bus voltage is connected to the positive input terminal of the amplifier through R31, and the ground is connected to the negative input terminal of the amplifier through R32. After being scaled down, it is sent to the ADC for sampling and quantization. The ADC is changed to a single-ended 15-bit ADC at this time. The range of the bus voltage is 0 to 40.96V, and the input range for the ADC after being scaled down is 0 to 2.048V. 1 LSB can be 1.25mV.

[0011] The beneficial effects of the present invention are:

[0012] The first is to place the switched switch position in front of the amplifier, avoiding the non-linearity introduced by the on-resistance of the switch, and replacing the switch with a T-type switch. The input common mode and output common mode of the amplifier are used for setting, increasing the off isolation degree of the switch, which helps to reduce signal interference. The second is to creatively save an amplifier. By switching the amplifier, the measurement of voltage and current is realized, saving costs. Description of the Drawings

[0013] To more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the accompanying drawings required for the description of the embodiments. Obviously, the accompanying drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other accompanying drawings can be obtained based on these drawings.

[0014] Figure 1 is a schematic diagram of the existing front-end amplifier structure;

[0015] Figure 2 is a schematic diagram of the front-end structure of a multiplexing amplifier applied to high-voltage voltage and current signal detection provided by the present invention;

[0016] Figure 3 is a schematic diagram of the high-voltage control signal circuit in the front-end of a multiplexing amplifier applied to high-voltage voltage and current signal detection provided by the present invention;

[0017] Figure 4 is a schematic diagram of the T-switch circuit in the front-end of a multiplexing amplifier applied to high-voltage voltage and current signal detection provided by the present invention;

[0018] Figure 5 is a schematic diagram of the front-end amplifier circuit when monitoring current in the front-end of a multiplexing amplifier applied to high-voltage voltage and current signal detection provided by the present invention;

[0019] Figure 6 is a schematic diagram of the front-end amplifier circuit when monitoring the bus voltage in the front-end of a multiplexing amplifier applied to high-voltage voltage and current signal detection provided by the present invention; Detailed Embodiments

[0020] To make the objectives, technical solutions, and advantages of the present invention clearer, the following will further describe the embodiments of the present invention in detail with reference to the accompanying drawings.

[0021] Embodiment 1:

[0022] This embodiment provides a front-end of a multiplexing amplifier applied to high-voltage voltage and current signal detection. Refer to Figure 2 ,

[0023] A front-end of a multiplexing amplifier applied to high-voltage voltage and current signal detection is composed of two pairs of resistor feedback networks R11 / R12 / R21 / R22 and R31 / R32 / R41 / R42, an amplifier core AMP1, and four pairs of switches S1 / S1' / SN1 / SN1'; where S1 and SN1 are in series with the input impedance of the amplifier core AMP1, the input end of the amplifier core AMP1 is connected to the gate of the MOS transistor, and S1 and SN1 are connected to the resistors R11 / R12 / R31 / R32.

[0024] Among them, the SN1 is a high-voltage switch. After attenuation, the input voltage of S1 is below 5V. S1' and SN1' only need to process signals of 0 to 2.048V and are low-voltage switches. Among them, R11 = R12 = R, R21 = R22 = 25R, R31 = R32 = 20R, R41 = R42 = R; the input common mode of the amplifier core AMP1 is 36V, and the output common mode is fixed at 2.048V. The control signals of S1 and S1' are in the same phase, the control signals of S2 and S2' are also in the same phase, and the control signals of S1 / S1' and SN1 / SN1' are opposite; S1 is composed of isolated nmos. The well of the nmos can withstand voltage, and the 5V EN signal is transferred to the high-voltage control signal through a five-transistor OTA with amplitude limiting; SN1, S1', and SN1' are composed of low-voltage NMOS switches.

[0025] As Figure 3 shown, in the circuit for transferring the 5V EN signal to the high-voltage control signal. When EN is high, the output of the five-transistor OTA is low, but due to the amplitude limiting effect of the resistor, the lowest voltage that the output can reach is VCMI + 1.2V - IR, protecting the circuit from being burned out. The operating voltage threshold of the latter two inverters is VCMI - 1.2V to VCMI + 1.2V, transferring the 5V control signal to high voltage.

[0026] As Figure 4 shown, the S1, SN1, S1', and SN1' are all T-type switches. When EN is high, ENB is low, S1 and S2 are closed, and S3 is open, and the signal is transmitted from IN to OUT. When EN is low, ENB is high, S1 and S2 are open, and S3 is closed, placing the intermediate level at VCMI / VCMO. VCMI and VCMO are the input common mode and output common mode of the amplifier. By using T-type switches, the isolation degree of the signal can be improved, and a large current can be prevented from occurring when the switch conducts, burning out the switch.

[0027] As Figure 5 shown, when monitoring the working state of the current, SN1 and SN1' are closed, S1 and S1' are open. After S1 is open, it is set at the input common mode VCMI of the amplifier, and after S1' is open, it is set at the output common mode VCMO of the amplifier. R11 / R12 / R21 / R22 are connected to the amplifier, and the closed-loop gain is 25. The monitored current flows through Rshunt to generate voltage V1, which is amplified and then sent to a 16-bit ADC for sampling and quantization. The range of V1 is -81.92m to +81.92m, and the range of the ADC is -2.048V to +2.048V. As a whole, 1 LSB can reach 2.5uV, and the current can be accurately monitored.

[0028] As Figure 6As shown, in the working state for voltage monitoring, S1 and S1' are closed, SN1 and SN1' are open. After SN1 is open, the input common mode VCMI of the amplifier is set. After SN1' is open, the output common mode VCMO of the amplifier is set. R31 / R32 / R41 / R42 are connected to the amplifier, and the closed-loop gain is 0.05. The bus voltage is connected to the positive input terminal of the amplifier through R31, and the ground is connected to the negative input terminal of the amplifier through R32. After being scaled down, it is sent to the ADC for sampling and quantization. At this time, the ADC is changed to a single-ended 15-bit ADC. The bus voltage range is 0 to 40.96V. After being scaled down, the input range for the ADC is 0 to 2.048V, and 1 LSB can be 1.25mV.

[0029] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A multiplexed amplifier front end for high voltage and current signal detection, characterized in that: The multiplexed amplifier front end includes two pairs of resistor feedback networks R11 / R12 / R21 / R22 and R31 / R32 / R41 / R42, an amplifier core AMP1 and four pairs of switches S1 / S1' / SN1 / SN1'; wherein S1 and SN1 are connected in series with the input impedance of the amplifier core AMP1, the input end of the amplifier core AMP1 is connected to the gate of the MOS tube, and S1 and SN1 are connected to the resistors R11 / R12 / R31 / R32. Among them, SN1 is a high-voltage switch. After attenuation, the input voltage of S1 is below 5V. S1' and SN1' only need to process 0-2.048V signals and are low-voltage switches; wherein R11=R12=R, R21=R22=25R, R31=R32=20R, R41=R42=R; the input common mode of the amplifier core AMP1 is 36V, the output common mode is fixed at 2.048V, the control signals of S1 and S1' are in phase, the control signals of S2 and S2' are also in phase, and the control signals of S1 / S1' and SN1 / SN1' are opposite; S1 is composed of an isolated nmos, the well of the nmos can withstand pressure, and the 5V EN signal is transferred to the high-voltage control signal through a limited five-tube OTA; SN1, S1' and SN1' are composed of low-voltage NMOS switches.

2. The multiplexed amplifier front end for high voltage and current signal detection according to claim 1, characterized in that: The S1, SN1, S1' and SN1' are all T-type switches. When EN is high, ENB is low, S1 and S2 are closed, S3 is open, and the signal is transmitted from IN to OUT; when EN is low, ENB is high, S1 and S2 are open, S3 is closed, and the intermediate level is placed at VCMI / VCMO; VCMI and VCMO are the input common mode and output common mode of the amplifier; by using T-type switches, the isolation of the signal can be improved, and a large current can be prevented from occurring when the switch is turned on, thereby preventing the switch from being burned.

3. The multiplexed amplifier front end for high voltage and current signal detection according to claim 1, characterized in that: When used for current monitoring, SN1 and SN1' are closed, S1 and S1' are disconnected, S1 is disconnected and set to the input common mode VCMI of the amplifier, S1' is disconnected and set to the output common mode VCMO of the amplifier, R11 / R12 / R21 / R22 are connected to the amplifier, and the closed-loop gain is 25; the monitoring current flows through Rshunt to generate voltage V1, which is amplified and sent to the 16-bit ADC for sampling and quantization; the range of V1 is -81.92m~+81.92m, and the range of ADC is -2.048V~+2.048V. The overall LSB can be 2.5uV, which can accurately monitor the current.

4. The multiplexed amplifier front end for high voltage and current signal detection according to claim 1, characterized in that: In the working state for voltage monitoring, S1 and S1' are closed, SN1 and SN1' are disconnected, SN1 is set to the input common mode VCMI of the amplifier after disconnection, and SN1' is set to the output common mode VCMO of the amplifier after disconnection. R31 / R32 / R41 / R42 are connected to the amplifier, and the closed-loop gain is 0.05; the bus voltage is connected to the positive input terminal of the amplifier through R31, and the ground is connected to the negative input terminal of the amplifier through R32, and then sent to the ADC for sampling and quantization after being scaled down; the ADC is changed to a single-ended 15-bit ADC at this time; the bus voltage range is 0-40.96V, and the input range of the ADC after being scaled down is 0-2.048V, which can achieve 1 LSB of 1.25mV.

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