CN107219402A - A kind of circuit for quick measurement of DC resistance for power module port - Google Patents

Abstract

The present invention relates to a DC resistance rapid measurement circuit for a power supply module port, comprising a feedback adjustment circuit, a range switching matrix circuit and a voltage and current detection circuit; the input end of the feedback adjustment circuit is connected to a bias voltage, and the output end is connected to the range The input end of the switching matrix circuit is connected, the range switching matrix circuit is used to connect the voltage and current detection circuit and the port of the device under test, the voltage and current detection circuit is also connected to the port of the device under test, the voltage and current detection circuit is connected to an external microcontroller, The bias voltage is controlled by the microprocessor to output DAC1. The present invention is a simple and practical circuit, which is applied to fast DC resistance measurement. The measurement of various resistance-capacitance parallel DC resistances is fast and stable. The measurement time is hardly affected by the resistance and capacitance of the measured object, and the adjustable bias can prevent output. Overvoltage, using a multi-range structure with standard resistors in series, can measure a relatively wide range of DC resistance with high accuracy.

Description

A fast measuring circuit of DC resistance for power module port

technical field

The patent of the present invention relates to a DC resistance rapid measurement circuit for a power module port.

Background technique

The concept of DC resistance widely exists in the field of electronic information. The DC resistance of the power module port is an important parameter reflecting the performance of the power module, including the forward and reverse DC resistance of the input and output ports, and the DC resistance of the S terminal. These parameters are important for judging the performance of the circuit. in accordance with. Due to the presence of large-capacity bypass capacitors and filter capacitors at the input and output ports of the power module, the resistance-capacitance parallel DC resistance becomes an important object for power module measurement. The general methods for measuring DC resistance are constant current measurement method and constant voltage resistance divider method. The constant current method circuit is generally more complicated, and is usually used in a desktop multimeter. It measures the DUT by using a certain constant current, and detects the voltage at both ends to calculate the measurement result. However, due to the large resistance and capacitance of the DUT and Due to the influence of the charging inertia of the current source, it takes a long time for the measurement to reach stability, and the process is slow. In the large-scale production environment, it seriously hinders the improvement of production efficiency. In addition, due to the constant current measurement, the voltage on the measured port is uncontrollable. For devices with low voltage output, overvoltage may be generated during the measurement process to damage the circuit device port. The constant voltage method is measured by resistance voltage division. The circuit is simple and is often used in hand-held multimeters. For the measurement of large resistors and capacitors in parallel, the measurement time is still very long, and the measurement bias voltage is uncontrollable. The DC resistance rapid measurement circuit of the power module port has high innovation and important application value.

Contents of the invention

In order to overcome the above-mentioned problems, the present invention provides a practical circuit for quickly measuring the DC resistance of a power module port. The circuit measures quickly and stably; the measurement efficiency is not affected by the difference of the measured ports, and is suitable for various measured objects; the bias voltage is adjustable, which can prevent the output overvoltage from damaging the low-voltage tested parts; the measuring circuit has multiple ranges, which improves the circuit measurement accuracy. It has the advantages of fast measurement speed, good measurement stability, good measurement accuracy, strong adaptability and anti-interference ability.

The purpose of the present invention is achieved through the following technical solutions: a fast DC resistance measurement circuit for the power module port, including a feedback adjustment circuit, a range switching matrix circuit and a voltage and current detection circuit; the input terminal of the feedback adjustment circuit is connected to A bias voltage, the output terminal is connected to the input terminal of the range switching matrix circuit, the range switching matrix circuit is used to connect the voltage and current detection circuit and the port of the device under test, the voltage and current detection circuit is also connected to the port of the device under test, the voltage and current The detection circuit is connected with an external microcontroller, and the bias voltage is controlled by the microprocessor to output the DAC1.

Further, the feedback regulation circuit includes an integrated operational amplifier U2, capacitor C1, capacitor C2, resistor R1 and resistor R8, the resistor R8 and capacitor C2 form a first-order RC filter circuit, and the microcontroller controls the output of DAC1 to pass through the first-order RC filter circuit. After filtering, it is connected to the non-inverting input terminal of the integrated operational amplifier U2 as a bias voltage, and the output terminal of the integrated operational amplifier U2 is connected to the inverting input terminal of the integrated operational amplifier U2 through a resistor R1, and the capacitor C1 is connected in parallel to the integrated operational amplifier U2. Between the output terminal and the inverting input terminal, one end of the resistor R1 is used to connect the port of the device under test.

Further, the range switching matrix circuit includes resistors R2 to R4, switch module I and switch module II; one end of the resistor R4 is connected to the output end of the integrated operational amplifier U2, and the resistor R4, switch module I and switch module II are connected in series in sequence The switch module II is connected to the port of the device under test; the resistor R2 is connected in parallel to both ends of the switch module I, and the resistor R3 is connected in parallel to both ends of the switch module II.

Further, the switch module I includes a relay K1, a diode D3, a resistor R7, a resistor R11 and a transistor Q2, and the switch module II includes a relay K2, a diode D2, a resistor R6, a resistor R10 and a transistor Q1; the contact of the relay K1 The point is connected in parallel with the resistor R3, and the diode D3 is connected in parallel with both ends of the coil of the relay K1; the collector of the triode Q2 is connected with the anode of the diode D3, the emitter is grounded, the base is connected with one end of the resistor R7, and the other end of the resistor R7 is connected with the IO port connection, one end of the resistor R10 is connected to the IO terminal, and the other end of the resistor R10 is grounded; the contact of the relay K2 is connected in parallel with the resistor R2, and the diode D2 is connected in parallel with both ends of the coil of the relay K1; the collector of the triode Q1 is connected to the diode D2 The positive pole is connected, the emitter is grounded, the base is connected to one end of the resistor R6, the other end of the resistor R6 is connected to the IO port, one end of the resistor R11 is connected to the IO port, and the other end of the resistor R11 is grounded; the cathode of the diode D2 is connected to the diode D3 After the cathode is connected, it is connected to the power supply VCC.

Further, the voltage and current detection circuit includes an ADC U1, a resistor R5 and a resistor R9, the resistor R5 is connected in series with the resistor R9 and grounded, and the reference input terminal of the ADC U1 is connected to the common terminal of the output terminal of the operational amplifier U2 and the resistor R4 connected, the signal acquisition end of ADCU1 is used to connect to the port of the DUT; the common end of the resistor R5 and the resistor R9 is connected to ADC0.

Further, the measurement circuit also includes a diode D1 and a diode D4, the anode of the diode D4 is grounded, the cathode of the diode D4 is connected to the anode of the diode D1, the cathode of the diode D1 is connected to the power supply VCC, the common terminal of the diode D1 and the diode D4 is connected to the operational amplifier The output terminal of U2 is connected.

Due to the adoption of the above technical solutions, the present invention has the following beneficial technical effects:

The present invention is a simple and practical circuit, which is applied to fast DC resistance measurement. The measurement of various resistance-capacitance parallel DC resistances is fast and stable. The measurement time is hardly affected by the resistance and capacitance of the measured object, and the adjustable bias can prevent output. Overvoltage, using a multi-range structure with standard resistors in series, can measure a relatively wide range of DC resistance with high accuracy. The circuit can be combined with a micro control unit for control and data processing, and has good scalability.

Description of drawings

In order to make the purpose, technical solutions and advantages of the present invention clearer, the present invention will be described in further detail below in conjunction with the accompanying drawings, wherein:

Fig. 1 is a schematic block diagram of the fast measurement circuit of the DC resistance of the power module port in the embodiment;

Fig. 2 is the schematic diagram of the fast measurement circuit of the DC resistance of the power module port in the embodiment;

Fig. 3 is the measurement result output stable contrast of fast measurement circuit and other DC resistance measurement modes in the embodiment;

Fig. 4 is the relationship between the typical value of the standard resistance and the measuring range in the embodiment.

detailed description

The preferred embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings; it should be understood that the preferred embodiments are only for illustrating the present invention, rather than limiting the protection scope of the present invention.

The schematic block diagram of the circuit of this embodiment is shown in Figure 1. The microcontroller sets the bias voltage through bus communication, and stably outputs a fixed low bias voltage through the feedback adjustment circuit. After the output terminal of the op amp is stable, the microcontroller The ADC collects the voltage at the output of the operational amplifier, and adjusts the appropriate range according to the detection results. Finally, the DC resistance value is calculated by the internal high-level ADC to detect the standard resistance and the voltage ratio of the measured port.

The schematic diagram of the fast measurement circuit for DC resistance at the port of the power module is shown in Figure 1, a fast measurement circuit for DC resistance at the port of the power module, including a feedback adjustment circuit, a range switching matrix circuit and a voltage and current detection circuit; the feedback adjustment circuit The input terminal is connected with a bias voltage, the output terminal is connected with the input terminal of the range switching matrix circuit, the range switching matrix circuit is used to connect the voltage and current detection circuit and the port of the device under test, and the voltage and current detection circuit is also connected with the port of the device under test, The voltage and current detection circuit is connected with an external microcontroller, and the bias voltage is controlled by the microprocessor to output the DAC1.

The feedback regulation circuit includes an integrated operational amplifier U2, capacitor C1, capacitor C2, resistor R1 and resistor R8, the resistor R8 and capacitor C2 form a first-order RC filter circuit, and the microcontroller controls the output of DAC1 to pass through the first-order RC filter As a bias voltage, it is connected to the non-inverting input terminal of the integrated operational amplifier U2, and the output terminal of the integrated operational amplifier U2 is connected to the inverting input terminal of the integrated operational amplifier U2 through a resistor R1, and the capacitor C1 is connected in parallel to the output terminal of the integrated operational amplifier U2 Between and the inverting input end, one end of the resistor R1 is used to connect the port of the device under test.

The range switching matrix circuit includes resistors R2 to R4, a switch module I and a switch module II; one end of the resistor R4 is connected to the output end of the integrated operational amplifier U2, and the resistor R4, the switch module I and the switch module II are sequentially connected in series, The switch module II is connected to the port of the device under test; the resistor R2 is connected in parallel to both ends of the switch module I, and the resistor R3 is connected in parallel to both ends of the switch module II.

The switch module I includes a relay K1, a diode D3, a resistor R7, a resistor R11 and a transistor Q2, and the switch module II includes a relay K2, a diode D2, a resistor R6, a resistor R10 and a transistor Q1; the contacts of the relay K1 and Resistor R3 is connected in parallel, diode D3 is connected in parallel to both ends of the coil of relay K1; the collector of transistor Q2 is connected to the anode of diode D3, the emitter is grounded, the base is connected to one end of resistor R7, and the other end of resistor R7 is connected to the IO port. One end of the resistor R10 is connected to the IO terminal, and the other end of the resistor R10 is grounded; the contact of the relay K2 is connected in parallel to the resistor R2, and the diode D2 is connected in parallel to both ends of the coil of the relay K1; the collector of the triode Q1 is connected to the anode of the diode D2 , the emitter is grounded, the base is connected to one end of the resistor R6, the other end of the resistor R6 is connected to the IO port, one end of the resistor R11 is connected to the IO port, and the other end of the resistor R11 is grounded; the cathode of the diode D2 is connected to the cathode of the diode D3 Then connect the power supply VCC.

The voltage and current detection circuit includes an ADC U1, a resistor R5 and a resistor R9, the resistor R5 is connected in series with the resistor R9 and grounded, the reference input terminal of the ADC U1 is connected to the output terminal of the operational amplifier U2 and the common terminal of the resistor R4, The signal acquisition end of the ADC U1 is used to connect to the port of the DUT; the common end of the resistor R5 and the resistor R9 is connected to the ADC0.

The measurement circuit also includes a diode D1 and a diode D4, the anode of the diode D4 is grounded, the cathode of the diode D4 is connected to the anode of the diode D1, the cathode of the diode D1 is connected to the power supply VCC, and the common end of the diode D1 and the diode D4 is connected to the operational amplifier U2. output connection.

The microcontroller controls the output of DAC1 to pass through the first-order RC filter and connect it to the non-inverting input terminal of the integrated operational amplifier U2 as the measurement bias voltage. The output terminal of the integrated operational amplifier U2 is connected to the inverting input terminal of the operational amplifier through the resistor R1 to form a voltage negative feedback. . The range switching matrix circuit adopts the method of series binning, and the microcontroller controls the IO control port to drive the relay to complete the switching of the resistance measurement range. The microcontroller communicates with the high-bit ADC circuit U1 through the SPI bus to measure the voltage ratio between the standard resistance and the measured port. Diodes D1 and D4 are used to form a clamping circuit for abnormal input voltage protection. The voltage at the output terminal of the integrated operational amplifier U2 is measured through the voltage division of the resistors R5 and R9 through the ADC0, and the measurement range is adjusted in real time to improve the measurement accuracy.

In the present invention, the calculation formula of measured port resistance is:

In the formula: R _x is the resistance value of the tested port, the unit is Ω;

N is the conversion number of ADC circuit U1, no unit;

D is the conversion result read by U1, unitless;

R _ref is the standard resistance value corresponding to the selected range, and the unit is Ω.

In the embodiment, due to the bias voltage measurement used by the measurement circuit, U1 adopts a floating reference voltage, and the reference voltage is proportional to the measured port voltage, so that the number of bits of the ADC can be fully utilized, and the accuracy of the DC resistance measurement can be improved.

The measurement output stability comparison between the fast measurement circuit and other DC resistance measurement methods in the embodiment is shown in Figure 3. The measured port is set to be connected in parallel with a 10kΩ resistor and a 4700uF capacitor, the standard resistance of the fast measurement circuit is 300 ohms, and the other two methods are The bias voltage is measured by the voltage division method of 3V and the constant current method of 100uA. It can be seen that the DC resistance measurement stabilization speed of the DC resistance fast measurement circuit of the power module is very fast, compared with the other two resistance measurement methods, the stabilization time of tens of seconds is greatly reduced, thus improving the measurement efficiency of DC resistance by more than ten times.

The relationship between the standard resistance selected in the embodiment and the measuring range of the DC resistance is shown in Fig. 4, and the standard resistance is switched in series to form a matrix to avoid short circuit of the resistance. In the embodiment, 3 standard resistors R4, R2 and R3 are used, respectively 3Ω, 297Ω (27Ω and 270Ω in series) and 29.7kΩ (2.7kΩ and 27kΩ in series), and the relays K1 and K2 are used to measure the current. The measuring ranges of DC resistance are 1Ω～150Ω, 100Ω～15kΩ and 10kΩ～1.5MΩ respectively. Each range is set with an over-range range, which avoids the unstable and repeated jumps of the relay during the critical resistance measurement, and improves the measurement stability.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalent technologies, the present invention also intends to include these modifications and variations.

Claims (6)

1. A kind of direct current resistance measurement circuit that is used for power supply module port is characterized in that: comprise feedback adjustment circuit, range switching matrix circuit and voltage and current detection circuit; The input terminal of described feedback adjustment circuit is connected with a bias voltage, output connected to the input end of the range switching matrix circuit, the range switching matrix circuit is used to connect the voltage and current detection circuit and the port of the device under test, the voltage and current detection circuit is also connected to the port of the device under test, and the voltage and current detection circuit is connected to the external micro-controller The device is connected, and the bias voltage is controlled by the microprocessor to output the DAC1. 2. A kind of direct current resistance measuring circuit for power module port according to claim 1, is characterized in that: described feedback adjustment circuit comprises integrated operational amplifier U2, capacitor C1, capacitor C2, resistor R1 and resistor R8, The resistor R8 and the capacitor C2 form a first-order RC filter circuit. The microcontroller controls the output of the DAC1 to pass through the first-order RC filter and then connects it to the non-inverting input terminal of the integrated operational amplifier U2 as a bias voltage, and the output terminal of the integrated operational amplifier U2 passes through The resistor R1 is connected to the inverting input terminal of the integrated operational amplifier U2, the capacitor C1 is connected in parallel between the output terminal of the integrated operational amplifier U2 and the inverting input terminal, and one end of the resistor R1 is used to connect to the port of the device under test. 3. A kind of direct current resistance measuring circuit for power supply module port according to claim 1, is characterized in that: described range switching matrix circuit comprises resistance R2～R4, switch module I and switch module II; One end of R4 is connected to the output end of the integrated operational amplifier U2, the resistor R4, the switch module I and the switch module II are connected in series in sequence, and the switch module II is connected to the port of the device under test; the resistor R2 is connected in parallel to both ends of the switch module I, The resistor R3 is connected in parallel to both ends of the switch module II. 4. a kind of direct current resistance measuring circuit that is used for power module port according to claim 3 is characterized in that: described switch module 1 comprises relay K1, diode D3, resistance R7, resistance R11 and triode Q2, described The switch module II includes a relay K2, a diode D2, a resistor R6, a resistor R10 and a transistor Q1; the contacts of the relay K1 are connected in parallel with the resistor R3, and the diode D3 is connected in parallel with both ends of the coil of the relay K1; the collector of the transistor Q2 is connected with the diode D3 The anode of the resistor R10 is connected to the positive pole, the emitter is grounded, the base is connected to one end of the resistor R7, the other end of the resistor R7 is connected to the IO port, one end of the resistor R10 is connected to the IO end, and the other end of the resistor R10 is grounded; the contact of the relay K2 In parallel with resistor R2, diode D2 is connected in parallel with both ends of the coil of relay K1; the collector of transistor Q1 is connected to the anode of diode D2, the emitter is grounded, the base is connected to one end of resistor R6, and the other end of resistor R6 is connected to IO port , one end of the resistor R11 is connected to the IO port, and the other end of the resistor R11 is grounded; the cathode of the diode D2 is connected to the cathode of the diode D3 and then connected to the power supply VCC. 5. A kind of direct current resistance measuring circuit for power module port according to claim 4, is characterized in that: described voltage and current detection circuit comprises ADC U1, resistance R5 and resistance R9, and described resistance R5 and resistance R9 connected in series and grounded, the reference input end of the ADC U1 is connected to the output end of the operational amplifier U2 and the common end of the resistor R4, and the signal acquisition end of the ADC U1 is used to connect the port of the DUT; the common end of the resistor R5 and the resistor R9 The terminal is connected with ADC0. 6. A kind of direct current resistance measuring circuit for power supply module port according to claim 4, it is characterized in that: measuring circuit also comprises diode D1 and diode D4, and the anode of described diode D4 is grounded, and the cathode of diode D4 and The anode of the diode D1 is connected, the cathode of the diode D1 is connected to the power supply VCC, and the common end of the diode D1 and the diode D4 is connected to the output end of the operational amplifier U2.