direct current voltage source

Abstract

The present application relates to a kind of direct current voltage source, by improving overcurrent protection circuit, by triode and overcurrent sampling resistance, overcurrent sampling resistance is connected in series in MOS tube source, current can be obtained in real time, and temperature change resistance change caused by long time high voltage will not occur, can avoid no trigger of recoverable fuse etc., improve overcurrent protection capability.Simultaneously, using output voltage superposition mode, improve the stability of low voltage gear output, reduce the dangerous degree of high voltage capacitor, scalability is higher, when higher voltage is needed, only need to increase rectifier circuit in series can be.And, using MOS tube as regulating tube, structure is small, withstand voltage is high, temperature characteristic is good, improve system output stability.

Description

Technical Field

[0001] This invention relates to the field of metrology, and more specifically to a DC voltage source. Background Technology

[0002] In the metrology system, DC voltage measuring equipment is a crucial part of basic measurements and has a wide range of applications. The metrological calibration of these devices requires DC voltage sources with high stability, wide voltage range, and high accuracy. Currently, most metrology stations and research institutes in China use imported standard sources, especially equipment from Western countries, which occupies a large market share. However, standard source equipment produced by domestic power supply manufacturers is inferior to foreign equipment in terms of stability and accuracy. Furthermore, foreign equipment is more expensive and subject to technological embargoes. Therefore, developing a high-precision, wide-voltage DC voltage source is of great significance.

[0003] The 1000V DC voltage in current DC voltage source designs is generated by rectifying the 850V AC voltage output from the power frequency transformer. This method results in a high-voltage transformer with high cost, poor output voltage filtering stability, and the inability to output different voltage levels. The voltage adjustment circuit uses two transistors to form a Darlington transistor, which can improve the current driving force, but it is not as good as a field-effect transistor in terms of voltage withstand, device life, and stability. The DC voltage source outputs a maximum voltage of 1000V, requiring the design of a protection circuit, but the current design lacks a protection mechanism. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a high-precision, wide-voltage, and cost-effective DC voltage calibration source.

[0005] This invention proposes a DC voltage source, comprising: an adjustable reference voltage source, including a voltage reference chip and a DAC chip; an operational amplifier circuit, with its positive terminal connected to the output of the DAC chip and its negative terminal grounded; a voltage adjustment circuit, which is a MOSFET, with its source grounded, its gate connected to the output terminal of the operational amplifier circuit, and its drain connected to the positive terminal of the output voltage; a protection circuit, including a transistor, with its base connected to the source of the MOSFET, its emitter grounded, and its collector connected to the output terminal of the operational amplifier circuit through a protection resistor; and an output voltage superposition circuit, including a first-stage superposition circuit and a second-stage superposition circuit. The first-stage superposition circuit includes a transformer and multiple parallel first-stage branches disposed on one side of the transformer. Each first-stage branch includes a rectifier bridge, an electrolytic capacitor, a resistor, and a switching switch. The second-stage superposition circuit includes multiple parallel second-stage branches, each second-stage branch including a resistor and a switching switch. The second-stage superposition circuit is also connected in parallel to a feedback resistor, and the first-stage superposition circuit is connected in series with the feedback resistor. The feedback resistor is also connected to the output terminal of the operational amplifier circuit.

[0006] In some embodiments of the present invention, the DAC chip is a 16-bit DAC chip.

[0007] In some embodiments of the present invention, the positive terminal of the operational amplifier circuit is connected to the DAC chip through a first resistor, and the negative terminal is grounded through a second resistor.

[0008] In some embodiments of the present invention, the source of the MOS transistor is grounded through a third resistor.

[0009] In some embodiments of the present invention, the base of the transistor is connected to the source of the MOS transistor through a fourth resistor, the emitter is grounded through a fifth resistor, and a sixth resistor is provided between the collector and the gate of the MOS transistor.

[0010] In some embodiments of the present invention, there are three primary branches, each controlled by a first switch, a second switch, and a third switch, and each primary branch is connected to an AC voltage source.

[0011] In some embodiments of the present invention, the secondary branch has three branches, which are respectively composed of a seventh resistor and a fifth switch, an eighth resistor and a sixth switch, and a ninth resistor and a seventh switch.

[0012] In some embodiments of the present invention, the feedback resistor is connected in the circuit in an on / off manner via a fourth switch.

[0013] In some embodiments of the present invention, the output value of the DC voltage source is adjusted by setting appropriate resistance values ​​for the seventh resistor, the eighth resistor, and the ninth resistor, and by adjusting the on / off state of the first switch to the seventh switch.

[0014] In some embodiments of the present invention, a multimeter is also included, wherein the positive terminal of the multimeter is grounded and the negative terminal is connected to the output terminal of the feedback resistor.

[0015] The DC voltage source of this invention has an improved overcurrent protection circuit, which consists of a transistor and an overcurrent sampling resistor. The overcurrent sampling resistor is connected in series with the source of the MOSFET, which can acquire the current in real time and will not change its resistance due to temperature changes caused by long-term high voltage. This can avoid the failure of resettable fuses to trigger and improve the overcurrent protection capability.

[0016] The DC voltage source of this invention improves the 1000V voltage by using an output voltage superposition method, which improves the stability of the low voltage output, reduces the danger of high voltage capacitors, and this method has high scalability. When a higher voltage is required, only a rectifier circuit needs to be added in series.

[0017] The DC voltage source of this invention improves the voltage regulation circuit by using a MOSFET as the regulating transistor, which has a small structure, high voltage resistance, and good temperature characteristics, thereby improving the system output stability. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a schematic diagram of the structure of a DC voltage source according to an embodiment of the present invention. Detailed Implementation

[0020] The description of the embodiments in this specification should be taken in conjunction with the accompanying drawings, which should form part of the complete specification. In the drawings, the shape or thickness of the embodiments may be exaggerated and may be indicated in a simplified or convenient manner. Furthermore, parts of the various structures in the drawings will be described separately; it is worth noting that elements not shown in the figures or not described in words are in a form known to those skilled in the art.

[0021] The descriptions of the embodiments herein, including any references to directions and orientations, are for ease of description only and should not be construed as limiting the scope of the invention. The following description of preferred embodiments involves combinations of features, which may exist independently or in combination; the invention is not particularly limited to the preferred embodiments. The scope of the invention is defined by the claims.

[0022] like Figure 1 As shown, the DC voltage source of this embodiment includes: an adjustable reference voltage source, including a voltage reference chip REF and a DAC chip 16-DAC (such as a 16-bit DAC chip); an operational amplifier circuit, the positive terminal of which is connected to the output of the DAC chip 16-DAC through a first resistor R1, and the negative terminal is grounded through a second resistor R2; a voltage adjustment circuit, which is a MOSFET Q1, the source of which is grounded through a third resistor R3, the gate of which is connected to the output terminal of the operational amplifier circuit, and the drain of which is connected to the positive terminal of the output voltage; and a protection circuit, including a transistor Q2, the base of which is connected to the source of the MOSFET Q1 through a fourth resistor R4, the emitter of which is grounded through a fifth resistor R5, and the collector of which is connected to a protection resistor R xThe output of the operational amplifier circuit is connected to a sixth resistor R6 between the collector and the gate of the MOSFET Q1; the output voltage superposition circuit includes a first-stage superposition circuit and a second-stage superposition circuit. The first-stage superposition circuit includes a transformer and multiple parallel first-stage branches located on one side of the transformer. Each first-stage branch includes a rectifier bridge, an electrolytic capacitor, a resistor, and a switching switch. The second-stage superposition circuit includes multiple parallel second-stage branches. Each second-stage branch includes a resistor and a switching switch. The second-stage superposition circuit is also connected in parallel to the feedback resistor R. y Furthermore, the first-stage superposition circuit and the feedback resistor R y Series connection; where the feedback resistor R y It is also connected to the output of the operational amplifier circuit.

[0023] like Figure 1 As shown, in this embodiment, the output voltage superposition circuit has three primary branches, each controlled by a first switch K1, a second switch K2, and a third switch K3, respectively, and each primary branch is connected to an AC voltage source of AC280V. There are three secondary branches, each composed of a seventh resistor R7 and a fifth switch K5, an eighth resistor R8 and a sixth switch K6, and a ninth resistor R9 and a seventh switch K7, respectively. The feedback resistor R... y It is also connected to the circuit via a fourth switch K4. It also includes a multimeter, with its positive terminal grounded and its negative terminal connected to the feedback resistor R. y The output terminal. By setting appropriate resistance values ​​for the seventh resistor R7, the eighth resistor R8, and the ninth resistor R9, and by adjusting the opening and closing of the first switch K1 to the seventh switch K7, the output value of the DC voltage source can be adjusted.

[0024] like Figure 1 As shown, the DC voltage source in this embodiment can be used as a 1000V DC voltage source. The voltage reference chip REF can generate a stable 2.5V DC voltage to provide a reference voltage for the DAC chip 16-DAC. The MCU controls the output of the DAC chip 16-DAC to be adjustable from 0 to 2.5V via SPI communication. The output voltage controls the conduction state of the MOSFET Q1 in the voltage adjustment circuit. The MOSFET Q1 switches to different degrees under different gate voltages, which can realize the adjustment of the voltage output. When a fault such as a short circuit occurs at the output of the operational amplifier circuit, the output current suddenly increases, and the protection resistor R... XAs the voltage increases, transistor Q2 conducts, which divides the gate voltage of MOSFET Q1, reducing the conduction of MOSFET Q1 and thus protecting the circuit. The output voltage superposition circuit can output multiple voltage values ​​up to 1000V. When switch K1 is closed, it outputs a DC voltage of 4-400V. Switches K4, K5, and K6 correspond to the 4V, 40V, and 400V ranges, respectively. That is, when switches K1 and K4 are closed simultaneously, a 4V DC voltage is output; when switches K1 and K5 are closed simultaneously, a 40V DC voltage is output; and when switches K1 and K6 are closed simultaneously, a 400V DC voltage is output. When switches K1, K2, K3, and K7 are closed simultaneously, a 1000V DC voltage can be output.

[0025] Furthermore, when switches K1 and K4 are closed, the circuit sampling resistor is at the 4V setting. Due to the virtual short of the op-amp, the negative terminal of the op-amp is grounded, so the voltage at the positive terminal of the op-amp is 0V, and current flows through the feedback resistor R. y The current is determined by the DAC output voltage and resistor R2, and its direction is from left to right as shown in the diagram. Therefore, the feedback resistor R... y The voltage is negative, so it is connected to the negative terminal of the multimeter's voltage range. The positive terminal of the multimeter's voltage range is connected to the circuit ground, so the multimeter outputs a positive voltage.

[0026] The DC voltage source of this invention has the following advantages compared to the prior art:

[0027] (1) The DC voltage calibration source output is adjustable from 0 to 1000V, so a 1000V DC voltage needs to be provided. The DC voltage generated after rectifying the 850V AC voltage output by the transformer is filtered, which requires a high-voltage electrolytic capacitor. However, the use of high-voltage electrolytic capacitors is dangerous, and the filtering effect is poor at different voltage levels. According to the 1000V DC voltage source of this embodiment, the voltage superposition principle is adopted. The power frequency transformer outputs three 280V AC voltages. The three AC voltages are rectified, filtered, and connected in series to generate a 1000V DC voltage. The selection of electrolytic capacitors only needs to meet the 400V DC voltage requirement. When the DC voltage range is 0 to 4V, 4V to 40V, and 40V to 400V, one 280V AC power supply is used. When the DC voltage range is 400V to 1000V, three 280V AC voltages are used to improve the stability of the output DC voltage after rectification and filtering at different voltage levels and reduce the danger of using high-voltage electrolytic capacitors.

[0028] (2) The voltage regulation circuit uses a field-effect transistor, i.e., a MOSFET, as the regulating device. Compared with the Darlington transistor, which is composed of two transistors, it has the advantages of small size, long life, good temperature characteristics, and high voltage resistance, thus improving the stability of the output.

[0029] (3) Add an overcurrent protection circuit, which consists of a protection resistor and a transistor. When the output current is within the rated range, the transistor is cut off and the protection circuit does not work. When a short circuit or other fault occurs at the output, the output current suddenly increases, the voltage of the protection resistor increases, the transistor conducts, and the gate voltage of the MOS transistor in the adjustment circuit is divided, the MOS conduction decreases, and the protection circuit is activated. This protection circuit can be reused and can effectively reduce equipment maintenance.

[0030] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A DC voltage source, characterized in that, include: Adjustable reference voltage source, including voltage reference chip and DAC chip; The operational amplifier circuit has its positive terminal connected to the output of the DAC chip via a first resistor, and its negative terminal grounded via a second resistor. The voltage adjustment circuit is a MOSFET, with its source grounded through a third resistor, its gate connected to the output of the operational amplifier circuit, and its drain connected to the positive output of a first-stage superposition circuit. The protection circuit includes a transistor, with its base connected to the source of the MOS transistor, its emitter grounded, and its collector connected to the output of the operational amplifier circuit through a protection resistor. The output voltage superposition circuit includes a first-stage superposition circuit and a second-stage superposition circuit. The first-stage superposition circuit includes a transformer and multiple parallel first-stage branches disposed on one side of the transformer. Each first-stage branch includes a rectifier bridge, an electrolytic capacitor, a resistor, and a switching switch. The rectified DC output terminals of the multiple first-stage branches are connected in series. The second-stage superposition circuit includes multiple parallel second-stage branches. Each second-stage branch includes a resistor and a switching switch. The second-stage superposition circuit is also connected in parallel to a feedback resistor, and the first-stage superposition circuit is connected in series with the feedback resistor. One end of the feedback resistor is connected to the positive terminal of the operational amplifier circuit, and the other end is connected to the negative output terminal of the first-stage superposition circuit.

2. The DC voltage source according to claim 1, characterized in that, The DAC chip is a 16-bit DAC chip.

3. The DC voltage source according to claim 1, characterized in that, The base of the transistor is connected to the source of the MOS transistor through a fourth resistor, the emitter is grounded through a fifth resistor, and there is a sixth resistor between the collector and the gate of the MOS transistor.

4. The DC voltage source according to any one of claims 1-3, characterized in that, The primary branch consists of three circuits, each controlled by a first switch, a second switch, and a third switch, and each primary branch is connected to an AC voltage source.

5. The DC voltage source according to claim 4, characterized in that, The secondary branch consists of three circuits, each composed of a seventh resistor and a fifth switch, an eighth resistor and a sixth switch, and a ninth resistor and a seventh switch.

6. The DC voltage source according to claim 5, characterized in that, The feedback resistor is connected to the circuit in an on / off manner via a fourth switch.

7. The DC voltage source according to claim 6, characterized in that, The output voltage of the DC voltage source can be adjusted by setting appropriate resistance values ​​for the seventh, eighth, and ninth resistors and by adjusting the on / off states of the first to the seventh switches.

8. The DC voltage source according to claim 6, characterized in that, It also includes a multimeter, the positive terminal of which is grounded and the negative terminal is connected to the end of the feedback resistor that is connected to the first-level superposition circuit.

Images