A current and frequency sampling circuit for automatic power conversion system

Abstract

The present invention relates to a current and frequency sampling circuit for a power automatic conversion system, which is used to realize the sampling of the current and frequency of the detection load by the power conversion system, and comprises a mutual inductor, a sampling module, a current detection module and a frequency detection module connected in sequence, wherein the frequency detection module is connected to the input capture port of the MCU, and is characterized in that the frequency detection module comprises a voltage comparator unit and a gate circuit unit connected to each other, wherein the input end of the voltage comparator unit is respectively connected to the voltage reference and the current detection module, and the output end is connected to the input capture port of the MCU through the gate circuit unit. Compared with the prior art, the present invention has the advantages of strong anti-interference ability, small frequency output ripple, high sampling accuracy, etc.

Description

Technical Field

[0001] The invention relates to a sampling circuit, in particular to a current and frequency sampling circuit for an automatic power supply conversion system. Background Art

[0002] With the development of the electric power industry, electrical equipment has higher and higher requirements for the continuity and reliability of power supply. Good signal acquisition technology can minimize the misjudgment rate of control system output, while improving the reliability of the system, enabling the controller to detect the status of electrical equipment in real time, and when it deviates from the set normal state, it can reflect and make adjustments in time.

[0003] like Figure 1 As shown, the existing sampling circuit generally connects the current directly to the differential amplifier after passing through the transformer, and the frequency detection generally only passes through a voltage comparator and is directly output to the MCU. This leads to the following problems:

[0004] 1) The current sampling waveform has poor anti-interference ability;

[0005] 2) Prone to oscillation;

[0006] 3) The frequency output ripple is large, which may cause missed detection or over-detection;

[0007] 4) The filtering capability is not strong and the sampling accuracy is easily affected by power supply fluctuations; Summary of the invention

[0008] The purpose of the present invention is to overcome the defects of the prior art and provide a current and frequency sampling circuit for an automatic power conversion system.

[0009] The purpose of the present invention can be achieved by the following technical solutions:

[0010] A current and frequency sampling circuit for an automatic power conversion system is used to implement sampling of the current and frequency of a detection load by the power conversion system. The circuit comprises a mutual inductor, a sampling module, a current detection module and a frequency detection module which are connected in sequence. The frequency detection module is connected to an input capture port of an MCU. The circuit is characterized in that the frequency detection module comprises a voltage comparator unit and a gate circuit unit which are connected to each other. The input end of the voltage comparator unit is respectively connected to a voltage reference and a current detection module, and the output end is connected to the input capture port of the MCU through the gate circuit unit.

[0011] The current detection module includes a first operational amplifier, a first capacitor and a feedback resistor, the output end of the first operational amplifier is connected to the negative input end through the first capacitor and the feedback resistor connected in parallel to each other, and the output end of the first operational amplifier is respectively connected to the ADC port of the MCU and the input end of the voltage comparator unit through the first resistor, the negative input end of the first operational amplifier is connected to the positive electrode of the mutual inductor through the first high-side sampling resistor, and the positive input end is connected to the positive electrode of the mutual inductor through the second high-side sampling resistor.

[0012] The sampling module includes a sampling resistor and a sampling capacitor respectively connected in parallel at both ends of the mutual inductor, the positive input end of the first operational amplifier is connected to the voltage reference through the low-side sampling resistor, the positive electrode of the mutual inductor is connected to the voltage reference through the first pull-up resistor, and the negative electrode of the mutual inductor is connected to the voltage reference through the second pull-up resistor.

[0013] The voltage comparator unit includes a second operational amplifier, a negative input terminal of the second operational amplifier is connected to a voltage reference, a positive input terminal is connected to an output terminal of the first operational amplifier through a second resistor and a first resistor in sequence, and an output terminal of the second operational amplifier is connected to a gate circuit unit.

[0014] The gate circuit unit includes a second capacitor and a gate circuit, one end of the second capacitor is connected to a power supply through a third pull-up resistor, and the other end is grounded, the input end of the gate circuit and the output end of the second operational amplifier are respectively connected between the third pull-up resistor and the second capacitor, and the output end of the gate circuit is connected to the input capture port of the MCU.

[0015] After the current path to be detected passes through the current transformer, a voltage is generated across the sampling capacitor and the sampling resistor. The output of this voltage and the voltage reference after passing through the differential amplifier module is connected to the ADC port of the MCU to realize current detection. The output is also connected to the frequency detection module, and after passing through the voltage comparator unit and the gate circuit unit with the voltage reference, it is connected to the input capture port of the MCU to realize frequency detection.

[0016] The negative input terminal of the second operational amplifier is also grounded through a second filtering capacitor.

[0017] The first resistor is grounded via a third capacitor.

[0018] The value of the voltage reference is 1.5V.

[0019] Compared with the prior art, the present invention has the following advantages:

[0020] 1) Strong anti-interference ability: The setting of sampling capacitor and two pull-up resistors improves the stability of the circuit and makes the current waveform output more anti-interference;

[0021] 2) Suppressing self-oscillation: Between the negative input terminal and the output terminal of the first operational amplifier, a first capacitor connected in parallel with the feedback resistor is provided to effectively suppress the generation of self-oscillation of the amplifier;

[0022] 3) Small frequency output waveform ripple: The frequency waveform ripple of the voltage comparator output waveform is extremely small after filtering by the second capacitor and sorting by the gate circuit unit;

[0023] 4) Strong filtering capability: The construction of low-pass filtering enhances the circuit’s ability to resist power supply fluctuations and improves sampling accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 is a circuit diagram of an existing sampling circuit;

[0025] Figure 2 This is a circuit diagram of the sampling circuit of the present invention. DETAILED DESCRIPTION

[0026] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0027] Example

[0028] like Figure 2 As shown, the present invention provides a current and frequency sampling circuit for an automatic power conversion system, which is used for the power conversion system to sample the current and frequency of a detected load, and includes a transformer PT1, a sampling module, a current detection module and a frequency detection module connected in sequence, and the frequency detection module is connected to the input capture port of the MCU.

[0029] The current detection module includes a first operational amplifier U1, a first capacitor C2 and a feedback resistor R7. The output end of the first operational amplifier U1 is connected to the negative input end through the first capacitor C2 and the feedback resistor R7 connected in parallel to each other, and the output end of the first operational amplifier U1 is respectively connected to the ADC port of the MCU and the input end of the voltage comparator unit through the first resistor R8. The negative input end of the first operational amplifier U1 is connected to the positive electrode of the transformer PT1 through the first high-side sampling resistor R2, and the positive input end is connected to the positive electrode of the transformer PT1 through the second high-side sampling resistor R3.

[0030] The sampling module includes a sampling resistor R1 and a sampling capacitor C1 respectively connected in parallel at both ends of the transformer PT1. The positive input end of the first operational amplifier U1 is connected to the voltage reference VREF through the low-side sampling resistor R6. The positive electrode of the transformer PT1 is connected to the voltage reference VREF through the first pull-up resistor R4. The negative electrode of the transformer PT1 is connected to the voltage reference VREF through the second pull-up resistor R5. The value of the voltage reference VREF is 1.5V.

[0031] The frequency detection module includes a voltage comparator unit and a gate circuit unit connected to each other. The voltage comparator unit includes a second operational amplifier U2. The negative input terminal of the second operational amplifier U2 is connected to the voltage reference VREF, the positive input terminal is connected to the first resistor R8 through the second resistor R9, and the output terminal is connected to the gate circuit unit. The gate circuit unit includes a second capacitor C7 and a gate circuit U3. One end of the second capacitor C7 is connected to the power supply VCC through the third pull-up resistor R10, and the other end is grounded. The input end of the gate circuit U3 and the output end of the second operational amplifier U2 are respectively connected between the third pull-up resistor R10 and the second capacitor C7. The output end of the gate circuit U3 is connected to the input capture port of the MCU. The negative input end of the second operational amplifier U2 is grounded through the second filter capacitor C5, and the first resistor R8 and the second resistor R9 are grounded through the third capacitor C4.

[0032] After the current path to be detected passes through the current transformer PT1, a voltage is generated across the sampling capacitor C1 and the sampling resistor R1. The output of the voltage reference VREF after passing through the differential amplifier module is connected to the ADC port of the MCU to realize current detection. The output is also connected to the frequency detection module, and after being sorted out with the voltage reference VREF through the voltage comparator unit and the gate circuit unit, it is connected to the input capture port of the MCU to realize frequency detection.

[0033] In this circuit, the first operational amplifier U1, the second operational amplifier U2 and the gate circuit U3 are respectively provided with a first decoupling capacitor C1, a second decoupling capacitor C2 and a third decoupling capacitor C3.

[0034] The circuit of the present invention is mainly used for sampling the current and frequency of the detection load in the power conversion system. The current transformer PT1 can be directly welded to the circuit board. For low-power loads, the current path can directly pass through the current transformer PT1 interface. For high-power loads, a larger current transformer can be connected to the transformer PT1, so that the effect of the current frame is achieved.

[0035] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person familiar with the technical field can easily think of various equivalent modifications or substitutions within the technical scope disclosed by the present invention, and these modifications or substitutions should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention shall be based on the protection scope of the claims.

Claims

1. A current and frequency sampling circuit for an automatic power conversion system, used to implement the sampling of the current and frequency of the detection load by the power conversion system, comprising a transformer (PT1), a sampling module, a current detection module and a frequency detection module connected in sequence, wherein the frequency detection module is connected to an input capture port of an MCU, and characterized in that: The frequency detection module includes a voltage comparator unit and a gate circuit unit connected to each other, the input end of the voltage comparator unit is respectively connected to the voltage reference (VREF) and the current detection module, and the output end is connected to the input capture port of the MCU through the gate circuit unit; The current detection module comprises a first operational amplifier (U1), a first capacitor (C2) and a feedback resistor (R7); the output end of the first operational amplifier (U1) is connected to a negative input end through the first capacitor (C2) and the feedback resistor (R7) connected in parallel to each other, and the output end of the first operational amplifier (U1) is respectively connected to an ADC port of an MCU and an input end of a voltage comparator unit through a first resistor (R8); the negative input end of the first operational amplifier (U1) is connected to a positive electrode of a mutual inductor (PT1) through a first high-side sampling resistor (R2), and the positive input end is connected to the positive electrode of the mutual inductor (PT1) through a second high-side sampling resistor (R3); The sampling module comprises a sampling resistor (R1) and a sampling capacitor (C1) respectively connected in parallel at two ends of a mutual inductor (PT1); the positive input end of the first operational amplifier (U1) is connected to a voltage reference (VREF) via a low-side sampling resistor (R6); the positive electrode of the mutual inductor (PT1) is connected to the voltage reference (VREF) via a first pull-up resistor (R4); and the negative electrode of the mutual inductor (PT1) is connected to the voltage reference (VREF) via a second pull-up resistor (R5); The voltage comparator unit comprises a second operational amplifier (U2), a negative input terminal of the second operational amplifier (U2) is connected to a voltage reference (VREF), a positive input terminal is connected to an output terminal of the first operational amplifier (U1) via a second resistor (R9) and a first resistor (R8) in sequence, and an output terminal of the second operational amplifier (U2) is connected to a gate circuit unit; The gate circuit unit comprises a second capacitor (C7) and a gate circuit (U3); one end of the second capacitor (C7) is connected to a power supply (VCC) via a third pull-up resistor (R10), and the other end is grounded; an input end of the gate circuit (U3) and an output end of a second operational amplifier (U2) are respectively connected between the third pull-up resistor (R10) and the second capacitor (C7); and an output end of the gate circuit (U3) is connected to an input capture port of an MCU; The negative input terminal of the second operational amplifier (U2) is also grounded via a second filter capacitor (C5).

2. The current and frequency sampling circuit for the automatic power conversion system according to claim 1, characterized in that: After the current path to be detected passes through the current transformer (PT1), a voltage is generated across the sampling capacitor (C1) and the sampling resistor (R1). The output of the voltage and the voltage reference (VREF) after passing through the differential amplifier module is connected to the ADC port of the MCU to realize current detection. The output is also connected to the frequency detection module, and after passing through the voltage comparator unit and the gate circuit unit with the voltage reference (VREF), it is connected to the input capture port of the MCU to realize frequency detection.

3. The current and frequency sampling circuit for the automatic power conversion system according to claim 1, characterized in that: The first resistor (R8) is grounded via a third capacitor (C4).

4. The current and frequency sampling circuit for the automatic power conversion system according to claim 1, characterized in that: The value of the voltage reference (VREF) is 1.5V.

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