CN102565501A - Pulse current detection circuit - Google Patents

Abstract

The invention discloses a pulse current detection circuit, which comprises a metal conductor, an RC (resistor-capacitor) integration circuit and a control unit, wherein the metal conductor is used for sampling direct current pulse current; the pulse voltage divider further comprises a freewheeling diode D1, a voltage divider VR1 and a coupling capacitor C1 for transmitting pulse voltage signals; one end of the metal conductor and the anode of the freewheeling diode D1 are grounded, the other end of the metal conductor is connected with the cathode of the freewheeling diode D1 through a coupling capacitor C1, one end of the voltage division potentiometer VR1 is connected with the cathode of the freewheeling diode D1 and the junction between the capacitors C1, a grounding resistor R3 used for releasing residual charges of the coupling capacitor C1 is connected between the other end of the voltage division potentiometer VR1 and the ground in series, and a voltage division output signal of the voltage division potentiometer VR1 is transmitted to the RC integrating circuit.

Description

A pulse current detection circuit

technical field

The invention relates to a pulse current detection circuit, in particular to a detection circuit for DC pulse current used in household appliances such as electromagnetic ovens and power tubes.

Background technique

The single-chip current detection circuit with the typical application of the induction cooker can be basically divided into two categories: 1. The low-frequency AC current is sampled, rectified and filtered by the current transformer and sent to the single-chip computer; 2. The pulse flowing through the power tube is convected by the constantan wire The current sampling is sent to the single-chip microcomputer after the integrated operational amplifier circuit. Among them, the patent application number is 200520121638.7, and the announcement date is March 7, 2007. The circuit content described in the utility model patent titled "A New Type of Electromagnetic Cooker Current Sampling Device" is basically the same as that of the second category, but because it uses The integrated operational amplifier circuit has increased the cost and the complexity of the circuit; the current detection described in the invention patent with the patent application number 200410063503.X and the publication date of February 9, 2005 is "Semiconductor Integrated Circuit Equipment" The circuit adopts a more complicated circuit, and the cost is also high.

If a constantan wire with only tens of milliohms is used for sampling, and then the pulse voltage signal is integrated through RC, when the maximum current reaches 10 amperes, the maximum DC voltage amplitude can only reach the level of several hundred millivolts (mV). For single-chip microcomputers with only 8 or 10-bit AD converters, the current resolution accuracy is too low to effectively identify power changes. Therefore, it is necessary to use an operational amplifier to amplify the DC pulse voltage to identify small changes in power through the single-chip microcomputer. For the mass-produced induction cooker products that are extremely price-sensitive, if an operational amplifier circuit can be saved in the current detection circuit and at the same time meet the requirements of current sampling accuracy, it will be a better solution than the above two current sampling circuits and other existing current detection circuits. The sampling circuit is an economical and practical solution, which will bring huge economic benefits, and it will definitely become the best choice for reducing the cost of the induction cooker circuit. Therefore, how to solve the above problems has become a problem to be solved.

Contents of the invention

The invention provides a pulse current detection circuit with low integration cost, simple circuit structure and higher reliability.

In order to achieve the above object, the present invention adopts the following technical solutions: a pulse current detection circuit, including a metal conductor, the metal conductor is used for sampling the DC pulse current; an RC integration circuit, the RC integration circuit outputs a DC voltage signal to the control unit ; It also includes a freewheeling diode D1, a voltage divider VR1 and a coupling capacitor C1 for transmitting pulse voltage signals; one end of the metal conductor and the anode of the freewheeling diode D1 are all grounded, and the other end of the metal conductor One end is connected to the cathode of the freewheeling diode D1 through a coupling capacitor C1, one end of the voltage divider potentiometer VR1 is connected to the cathode of the freewheeling diode D1 and the contact between the capacitor C1, and the other end of the voltage divider potentiometer VR1 is connected to A grounding resistor R3 for releasing the residual charge of the coupling capacitor C1 is connected in series between the grounds, and the voltage-dividing output signal of the voltage-dividing potentiometer VR1 is transmitted to the RC integrating circuit.

The metal conductor is constantan wire.

The coupling capacitor C1 is a CBB capacitor.

The RC integration circuit is composed of an integration resistor R2 and an integration capacitor C2.

The present invention adopts the above-mentioned circuit structure, wherein the metal conductor is used for sampling the DC pulse current, and the RC integrating circuit outputs a DC voltage signal to the control unit, and simultaneously one end of the metal conductor and the anode of the freewheeling diode D1 are grounded, and the metal conductor The other end of the freewheeling diode D1 is connected to the cathode of the freewheeling diode D1 through a coupling capacitor C1, and one end of the voltage divider potentiometer VR1 is connected to the cathode of the freewheeling diode D1 and the junction between the capacitor C1, and the other end of the voltage divider potentiometer VR1 A grounding resistor R3 for releasing the residual charge of the coupling capacitor C1 is connected in series between one end and the ground, and the voltage-dividing output signal of the voltage-dividing potentiometer VR1 is transmitted to the RC integration circuit. Therefore, the present invention uses a metal conductor to sample the DC pulse current flowing through the power tube, and adopts the principle of a voltage doubling circuit to change the high-frequency DC pulse current into an amplified low-frequency fluctuating DC signal plus a high-pulse carrier voltage signal, and integrates it through RC The circuit integration obtains an amplified stable DC voltage signal, which can be input to the control unit to identify the current operating current. At this time, compared with the primary signal, it not only changes the pulse voltage signal into a stable DC voltage signal, Moreover, compared with the direct integration of the voltage signal on the metal conductor, its amplitude is increased by tens of times. The present invention changes a current sampling circuit with a maximum signal output of only a few hundred millivolts into a current sampling circuit with a voltage output of several volts. , so the present invention has the advantages of low cost, simple circuit structure and high reliability compared with other current detection methods; in addition, the output signal of the present invention can be directly input into the control unit for processing, which greatly provides For convenience, it is very practical.

Description of drawings

The present invention will be described in further detail below in conjunction with the accompanying drawings and specific embodiments.

Fig. 1 is a schematic circuit diagram of the present invention;

Fig. 2 is a circuit schematic diagram of a preferred embodiment of the present invention.

Detailed ways

As shown in Figure 1, a pulse current detection circuit includes a metal conductor 1 and an RC integrating circuit, wherein the metal conductor 1 can use constantan wire or other metal conductors with corresponding resistance and load capacity, and the metal conductor 1 is used for DC For the sampling of pulse current, the RC integrating circuit is composed of integrating resistor R2 and integrating capacitor C2, and the RC integrating circuit outputs a DC voltage signal to the control unit 2, wherein the control unit 2 can be a single-chip microcomputer. In this technical solution, the present invention also includes a freewheeling diode D1, a voltage dividing potentiometer VR1 and a coupling capacitor C1 for transmitting pulse voltage signals, wherein the coupling capacitor C1 is a CBB capacitor with low temperature drift. One end of the metal conductor 1 and the anode of the freewheeling diode D1 are grounded, the other end of the metal conductor 1 is connected to the cathode of the freewheeling diode D1 through a coupling capacitor C1, and one end of the voltage divider VR1 is connected to the freewheeling diode D1. The cathode of the diode D1 is connected to the contact between the capacitor C1. A grounding resistor R3 for releasing the residual charge of the coupling capacitor C1 is connected in series between the other end of the voltage divider potentiometer VR1 and the ground. The divider of the voltage divider potentiometer VR1 The voltage output signal is transmitted to the RC integrating circuit, that is, the voltage dividing potentiometer VR1 transmits the divided voltage output signal to the RC integrating circuit.

As shown in Figure 2, it is an application example of the present invention in an electromagnetic cooker. Its working principle is: the DC pulse current flowing through the power tube IGBT flows into the ground wire after passing through the constantan wire, and a DC pulse voltage signal relative to the ground wire is generated on the constantan wire, and the DC pulse voltage signal is coupled to the current through the coupling capacitor C1 The primary side of the sampling circuit is connected to the cathode of the freewheeling diode D1, and the anode of the freewheeling diode D1 is connected to the ground, so that an amplified low-frequency pulsating DC voltage signal will be generated at the cathode of the freewheeling diode D1. The selected voltage divider potentiometer VR1 is connected, and a grounding resistor R3 is connected in series with the voltage divider potentiometer VR1 to release the residual charge on the coupling capacitor C1. The voltage divider potentiometer VR1 integrates the pulsating DC voltage signal after division through RC After the circuit is integrated, it can become a stable DC voltage signal and can be processed by a single-chip microcomputer. This DC voltage signal has a fixed nonlinear proportional relationship with the current. This nonlinear proportional relationship is related to the capacity of the primary coupling capacitor C1. It is related to the resistance accuracy of the constantan wire, the model of the freewheeling diode D1, the resistance value of the grounding resistor R3, and the integral constant of the RC integrating circuit, but these influencing factors are easily determined by determining the accuracy of these components To reduce its dispersion in mass production, the final output voltage can be controlled within the desired error by using the voltage divider potentiometer VR1.

In short, although the present invention has listed the above-mentioned preferred embodiments, it should be explained that it is obvious that various changes and modifications can be made by those skilled in the art. Therefore, unless such changes and modifications deviate from the scope of the present invention, they should all be included in the protection scope of the present invention.

Claims (4)

1. a pulse current testing circuit comprises metallic conductor (1), and this metallic conductor (1) is used for the sampling of dc pulse current; The RC integrating circuit, this RC integrating circuit output dc voltage signal is given control module (2); It is characterized in that: it comprises that also fly-wheel diode (D1), partial pressure potential device (VR1) and are used to transmit the coupling capacitance (C1) of pulse voltage signal; The anode of one end of described metallic conductor (1) and fly-wheel diode (D1) all is a ground connection; Link to each other through coupling capacitance (C1) between the negative electrode of the other end of this metallic conductor (1) and fly-wheel diode (D1); One end of partial pressure potential device (VR1) is connected with contact between the negative electrode of said fly-wheel diode (D1), electric capacity (C1); Be serially connected with a stake resistance (R3) that is used to discharge the residual charge of coupling capacitance (C1) between the other end of this partial pressure potential device (VR1) and the ground, the dividing potential drop output signal of said partial pressure potential device (VR1) is transferred to said RC integrating circuit.

2. pulse current testing circuit according to claim 1 is characterized in that: said metallic conductor (1) is a constantan wire.

3. pulse current testing circuit according to claim 1 and 2 is characterized in that: said coupling capacitance (C1) is a CBB electric capacity.

4. pulse current testing circuit according to claim 3 is characterized in that: said RC integrating circuit is made up of integrating resistor (R2) and integrating capacitor (C2).

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