SK289120B6 - Device for measurement of switched current by differential amplifier on common ground - Google Patents

Abstract

Device for measuring the switching current with a differential amplifier on a common ground consists of a switching converter (1), a shaping circuit (2), a voltage divider (3), a differential amplifier (4), a low-frequency filter (5), a block (6) of a voltage output and its own power supply (7). The device is characterized by the fact that the current flowing through the inductance can be determined directly from the voltage drop on the given inductance, which makes it unnecessary to use another measuring element. In addition, the connection includes its own power supply (7), connected to the common ground (GND) of the inverter, which eliminates the need to use a separate auxiliary power supply. The device can also be used for high supply voltage applications.

Description

The field of technology

The subject of the invention is a connection for measuring the switching current with a differential amplifier on a common ground, which is intended primarily for source applications. The invention belongs to the field of measuring technology and power electronics and allows measuring the switching current of the converter directly from the inductance voltage and is suitable for high-voltage applications.

Current state of the art

Current measurement is a necessary part of every switched converter and is almost always implemented using additional elements - measuring resistance, current transformer, Hall sensor or current measuring transistor. Each method of current measurement is based on a different principle and is therefore suitable for a different application, which also results in its properties. In general, these are additional elements that need to be appropriately determined and dimensioned.

The application of the measuring resistance (Dale Li: Current Shunt & Voltage Measurement Reference Design for EV/HEV Automotive Battery Monitoring, In: TI Designs - Precision: Verified Design, TIDUA81, 2015) is associated with precise dimensioning with respect to the power loss and the measurement range with it connected additional electronics.

The application of a current transformer (TI: Three-Phase AC Current Measurement Using Current Transformer Reference Design, In: TI Designs, TIDUBK3A, 2016) is associated with the use of a dimensional element, usable only for measuring alternating currents and additional electronics connected to it.

The application of the Hall sensor (Infineon: Current Sensing Using Linear Hall Sensors, In: Application Note, Sense and Control, 2009) is connected with the use of an element using the Hall effect. The use of this measuring element is limited by its frequency working range.

The application of the current measuring transistor (ON Semiconductor: Current Sensing Power MOSFETs, In: AND8093/D, 2017) is connected with the use of a specific element of the "measuring transistor" and additional electronics connected to it. Another option is to use the resistance of the RDSon MOSFET transistor to measure the current (R. Pajer, M. Milanovič, B. Premzel, M. Rodič: MOS-FET as a Current Sensor in Power Electronics Converters, In: Sensors 2015, 15, 18061-18079 ; doi: 10.3390/s150818061), but in this case it is possible to measure the current flowing only through the transistor and only in its switched state. Another option is to use an additional current-measuring transistor connection to the power transistor (T. Ribarich - International Rectifier: Enhancing switch-mode power performance with RDS(on) current sensing, In: Power Systems Design: Empowering Global Innovation, 2014), but also in in this case, only the current flowing through the transistor can be measured.

The essence of the invention

The connection for measuring the switching current with a differential amplifier on a common ground consists of three parts.

The first part of the system senses the voltage directly on the switched inductance of the device. This voltage is converted into the corresponding shape and value of the measured current by inductance, but in the form of a voltage, in the shaping circuit, the voltage divider and subsequently in the differential amplifier. The time constant of the shaping circuit must be the same as the time constant of the inductance of the converter.

The second part of the system consists of a low-frequency filter that suppresses high-frequency components and a voltage output, in which the level of the output voltage of the connection can be appropriately adjusted by the size of the output resistance according to the needs of other devices (operational amplifiers, converters, etc.).

The last part of the system is its own power supply, which powers the other components of the connection. Thanks to this source, the connection is completely self-sufficient (no other power sources are needed) and at the same time, the connection can also be used in high-voltage applications, where the voltage of the power part exceeds the permissible voltages of the associated electronics.

The connection for measuring the switched current with a differential amplifier on the common ground makes it possible to measure the current flowing through the inductance without an additional current sensor, directly from the voltage on the inductance.

The invention achieves high accuracy and dynamics while preserving all the features of classical current measurement methods and, compared to the original solutions, brings other advantageous features - no additional current sensor (measuring resistance, Hall sensor...) is required and no additional power source is required.

Overview of images on drawings

In fig. 1 shows a block diagram of a circuit for measuring switching current with a common ground differential amplifier.

Examples of implementation of the invention

Connection for measuring the switching current with a differential amplifier on the common ground, according to fig. 1, consists of a switched converter 1, which contains an inductance L together with a series resistance Rl of inductance L, on which the desired voltage is sensed for the shaping circuit 2, which, using the resistance Rt and the capacitor Ct of the shaping circuit 2, creates the desired voltage for the voltage divider 3. In the voltage divider 3, the voltage is adjusted with the help of resistors so that it does not exceed the permitted voltage level for the differential amplifier 4. The output from the differential amplifier 4 is fed to the low-frequency filter 5 and is subsequently converted to a voltage corresponding to the measured inductance current L. Z using the voltage output block 6 of the power supply Vin, the supply voltage Vcc of the electronics is created using its own power supply 7, which is used to power the differential amplifier 4 against the common ground GND of the device.

Industrial applicability

The connection for measuring the switching current with a differential amplifier on the common ground can be used in all applications requiring the measurement of the current flowing through inductance (in converters for drives, electric cars, backup sources, in converters for renewable energy sources, common power sources, etc.).

List of relationship tags

1 2 5 3 4 5 6 7 10 Vin Vcc L Rl Rt 15 Ct - Switched converter - Shaping circuit - Voltage divider - Differential amplifier - Low frequency filter - Voltage output block - Own power supply - Powerful power supply - Supply voltage of the electronics - Inductance - Series resistance of inductance - Resistance of the shaping circuit - Shaping circuit capacitor

GND - Common ground of the device

Claims (1)

PATENT CLAIMS Connection for measuring switched current with a differential amplifier on a common ground, consisting of a switched-mode converter (1), a shaping circuit (2), a voltage divider (3), a differential amplifier (4), 5 a low-frequency filter (5), a block (6) of a voltage output and of its own power source (7), characterized by the fact that the inductance (L) together with the series resistance (Rl) of the inductance (L) of the switching converter (1) are connected by means of signal wires to the forming circuit (2), formed by the resistance (Rt) and capacitor (Ct) of the shaping circuit (2); the output of the shaping circuit (2) is connected to the voltage divider (3), the output of which is connected to the input of the differential amplifier (4); a low-frequency filter (5) is connected to the output of the differential amplifier (4), while the output of the low-frequency filter (5) is connected to the block (6) of the voltage output; the power supply (Vin) is connected to its own power supply (7) by means of power wires; the supply voltage (VCC) of the electronics of the own power supply (7) is connected to the differential amplifier (4) with the help of power wires, and the common ground (GND) is connected with the power wires to the switching converter (1), the voltage divider (3), the differential 15 amplifier (4) and its own power supply (7).