A voltage conversion circuit

Abstract

The present invention discloses a voltage conversion circuit, which relates to the field of high-voltage voltage monitoring and sampling circuits and solves the problems of low monitoring and sampling voltage accuracy and uncontrollable output current of the monitoring and sampling voltage in existing high-voltage voltage monitoring and sampling circuits. The specific solution includes: a voltage sampling circuit for converting a test voltage inputted at an input end into a monitoring and sampling voltage; the test voltage being greater than the monitoring and sampling voltage; a switch tube voltage adjustment circuit connected to the voltage sampling circuit and for amplifying and outputting the current at the monitoring and sampling voltage; and an output current sampling control circuit connected to the voltage sampling circuit and the switch tube voltage adjustment circuit, for setting a limit sampling current and shutting off the monitoring and sampling voltage when the current corresponding to the monitoring and sampling voltage is greater than or equal to the limit sampling current.

Description

Technical Field

[0001] The present invention relates to the field of high-voltage voltage monitoring and sampling circuits, and in particular to a voltage conversion circuit. Background Art

[0002] In high-voltage DC circuits, accurate online monitoring of voltage changes is necessary to facilitate real-time adjustments by personnel or control systems. However, in applications where voltages exceed 200V, voltage monitoring presents safety risks and is inconvenient for personnel to monitor closely. Currently, high-voltage circuit voltages are typically monitored in real time using high-voltage voltage sampling circuits.

[0003] The existing high-voltage voltage monitoring and sampling circuit is designed based on the voltage division principle of a series resistor network, which has the problems of low monitoring and sampling voltage accuracy and uncontrollable monitoring and sampling voltage output current. Summary of the Invention

[0004] The present invention provides a voltage conversion circuit, which solves the problems of low precision of monitoring sampling voltage and uncontrollable output current of monitoring sampling voltage in the existing high-voltage voltage monitoring sampling circuit.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] In a first aspect, the present invention provides a voltage conversion circuit, comprising an input terminal and an output terminal, and further comprising:

[0007] A voltage sampling circuit, configured to convert a test voltage inputted from an input terminal into a monitoring sampling voltage; the test voltage being greater than the monitoring sampling voltage;

[0008] A switch tube voltage adjustment circuit, connected to the voltage sampling circuit, for amplifying the current of the monitoring sampling voltage and outputting the amplified current;

[0009] The output current sampling control circuit is connected to the voltage sampling circuit and the switch tube voltage adjustment circuit, and is used to set the limit sampling current and turn off the monitoring sampling voltage when the current corresponding to the monitoring sampling voltage is greater than or equal to the limit sampling current.

[0010] In a possible implementation, the switch tube voltage adjustment circuit is an N-channel field effect tube;

[0011] The gate of the field effect tube is connected to the voltage sampling circuit, the drain is connected to the output of the output current sampling control circuit, and the source is one end of the output end.

[0012] In a possible implementation, the voltage conversion circuit further includes a first capacitor connected in parallel between two ends of the input terminal;

[0013] The voltage sampling circuit includes a first resistor, a second resistor and a third resistor;

[0014] One end of the first resistor is connected to one end of the first capacitor, and the other end of the first resistor is connected to one end of the second resistor and the gate of the field effect transistor; the other end of the second resistor is connected to one end of the third resistor; the other end of the third resistor is connected to the other end of the first capacitor; and the other end of the third resistor is the other end of the output end.

[0015] In a possible implementation, the output current sampling control circuit includes a fourth resistor, a fifth resistor, a sixth resistor, a photocoupler, a seventh resistor, and a limiting diode;

[0016] The photoelectric coupler includes a light emitting diode and a phototransistor;

[0017] One end of the fourth resistor is connected to one end of the first resistor connected to the first capacitor, the other end of the fourth resistor is connected to the fifth resistor, one end of the sixth resistor is connected to the connecting line between the fourth resistor and the fifth resistor, the other end of the sixth resistor is connected to the positive electrode of the light-emitting diode, the negative electrode of the light-emitting diode is connected to the negative electrode of the limiting diode, and the positive electrode of the limiting diode is connected to the other end of the fifth resistor; the collector of the phototransistor is connected to the connecting line between the second resistor and the third resistor, the emitter of the phototransistor is connected to one end of the first capacitor connected to the third resistor, and the seventh resistor is connected in series with the collector of the phototransistor.

[0018] In a possible implementation, the output current sampling control circuit further includes a second capacitor, which is connected in parallel across the limiting diode.

[0019] In a possible implementation, the voltage conversion circuit further includes a third capacitor, and the third capacitor is connected in series between two ends of the output end.

[0020] In a possible implementation, the switch tube voltage adjustment circuit includes a plurality of N-channel field effect transistors arranged in parallel.

[0021] In a possible implementation, the field effect transistor is a metal oxide semiconductor field effect transistor.

[0022] The voltage conversion circuit provided by the embodiment of the present invention samples the high-voltage test voltage at the input end through a voltage sampling circuit, and converts the high-voltage test voltage into a low-voltage monitoring sampling voltage according to a set ratio; a sampling current corresponding to the monitoring sampling voltage is amplified by a switch tube voltage adjustment circuit; the monitoring sampling voltage is reduced by an output current sampling control circuit when the sampling current is greater than or equal to a limit sampling current; so that the monitoring sampling voltage output by the voltage conversion circuit of the present invention has higher accuracy and better stability; a larger driving current can still be provided when the internal resistance of the load source externally connected to the input end varies in a large range; and the maximum value of the output current of the monitoring sampling voltage can be limited, and the output of the monitoring sampling voltage can be automatically shut down when the output current is overcurrent.

[0023] The voltage conversion circuit of the present invention is designed to utilize the electrical characteristics of field-effect transistors (FETs) that regulate voltage and amplify current, that the voltage between the drain and source of the FETs follows the voltage between the gate and source, and that the set voltage between the gate and source of the FETs proportionally converts to the input test voltage. Because the electrical characteristics of FETs are very stable within a temperature range of -65°C to 160°C, the voltage conversion circuit of the present invention, which uses FETs as its core, maintains stable input voltage conversion within this temperature range, making the voltage conversion circuit of the present invention suitable for use in high-voltage monitoring and sampling control systems operating over a wide temperature range of -55°C to 125°C.

[0024] The voltage conversion circuit of the present invention can maintain a high sampling accuracy of the input terminal voltage under the conditions of 25° C., -55° C. and +125° C., has a perfect protection function, and is stable and reliable.

[0025] The voltage conversion circuit of the present invention utilizes the isolation control characteristic of the current of the photoelectric coupler. After the output current exceeds the preset limit sampling current, the photoelectric coupler is turned on and the voltage at the end of the third resistor is pulled down through the seventh resistor, so that the voltage of the gate of the field effect transistor is pulled down and the output voltage of the source of the field effect transistor is quickly turned off, thereby protecting the monitor or controller externally connected to the output end from damage and improving the safety and reliability of the circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a structural diagram of an existing high-voltage voltage sampling circuit;

[0027] Figure 2 A schematic diagram of the overall structure of a voltage conversion circuit provided by an embodiment of the present invention;

[0028] Figure 3 A practical application principle diagram of a voltage conversion circuit provided by an embodiment of the present invention.

[0029] Figure numerals: 1. voltage sampling circuit; 2. switch tube voltage adjustment circuit; 3. output current sampling control circuit. DETAILED DESCRIPTION

[0030] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0031] In the following, the terms "first" and "second" are used for descriptive purposes only and are not to be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the embodiments of the present disclosure, unless otherwise specified, "multiple" means two or more. In addition, the use of "based on" or "according to" means openness and inclusiveness, because the process, steps, calculations or other actions "based on" or "according to" one or more of the conditions or values may be based on additional conditions or values beyond the stated in practice.

[0032] Figure 1 Schematic diagram of the structure of an existing high-voltage voltage sampling circuit.

[0033] The existing high voltage sampling circuit is designed based on the voltage division principle of the series network, such as Figure 1 As shown, a filter capacitor C1 is connected in series between the two ends P1 and P2 of the high-voltage input end, and the voltage-dividing resistors R1, R2 and R3 are connected in series in sequence and connected to the two ends of the filter capacitor C1. The two ends of the voltage-dividing resistor R3 are low-voltage output ends P3 and P4, and the monitor or controller is connected to the low-voltage output ends P3 and P4.

[0034] In principle, a voltage proportional conversion circuit composed of a series resistor network can achieve proportional sampling and conversion of the high voltage at the input end. However, in practical applications, the existing voltage sampling circuit composed of a series resistor network has the following problems:

[0035] First, when the resistance of the selected resistor network is low, the power consumption of the resistor is large, which seriously affects the reliability of the circuit;

[0036] Second, when the resistance of the selected resistor network is large, the current driving capability of the output voltage is limited, and the equivalent resistance of the output load after being added to the resistor network will cause the accuracy of the sampled output voltage to deteriorate;

[0037] Third, under low temperature conditions, due to the difference in temperature drift of different resistors, the output voltage will drift significantly under high and low temperature conditions, affecting the sampling accuracy. Secondly, the power loss and heat generated by the resistor itself will also cause the output voltage to change with the working time, causing the monitor or controller to misjudge the changes in the input voltage.

[0038] Existing voltage sampling circuits also use operational amplifiers to sample the output voltage. However, since the normal operating voltage of operational amplifiers is relatively low, while the voltage of high-voltage circuits is generally higher than 200V, and since the use of operational amplifiers greatly increases the complexity of the circuit, operational amplifiers are not suitable for use in high-voltage circuits.

[0039] In order to solve the above problem, an embodiment of the present invention provides a voltage conversion circuit.

[0040] Figure 2 A schematic diagram of the overall structure of a voltage conversion circuit provided by an embodiment of the present invention.

[0041] like Figure 2 As shown, the voltage conversion circuit includes an input end and an output end, and also includes a voltage sampling circuit 1, a switch tube voltage adjustment circuit 2 and an output current sampling control circuit 3.

[0042] The voltage sampling circuit 1 is used to convert the test voltage inputted from the input terminal into a monitoring sampling voltage; the test voltage is greater than the monitoring sampling voltage.

[0043] The switch tube voltage adjustment circuit 2 is connected to the voltage sampling circuit 1 and is used to amplify and output the current when monitoring the sampling voltage.

[0044] The output current sampling control circuit 3 is connected to the voltage sampling circuit 1 and the switch tube voltage adjustment circuit 2, and is used to set the limit sampling current and turn off the monitoring sampling voltage when the current corresponding to the monitoring sampling voltage is greater than or equal to the limit sampling current.

[0045] Figure 3 A practical application principle diagram of a voltage conversion circuit provided by an embodiment of the present invention.

[0046] like Figure 2 、 Figure 3 As shown, in one embodiment of the present invention, the switch tube voltage adjustment circuit 2 is an N-channel field effect transistor Q. For example, the field effect transistor Q is a metal oxide semiconductor field effect transistor.

[0047] The gate of the field effect transistor Q is connected to the voltage sampling circuit 1 , the drain is connected to the output of the output current sampling control circuit 3 , and the source is one end of the output terminal.

[0048] Furthermore, the voltage conversion circuit further includes a first capacitor C1, which is connected in parallel between two ends of the input end.

[0049] Specifically, the input terminals include P1 and P2, P1 and P2 are directly connected to a high-voltage power supply terminal, the voltage of the high-voltage power supply terminal exceeds 200V, and the first capacitor C1 is connected in series between P1 and P2.

[0050] The voltage sampling circuit 1 includes a first resistor R4 , a second resistor R5 , and a third resistor R6 .

[0051] Among them, one end of the first resistor R4 is connected to one end of the first capacitor C1, and the other end of the first resistor R4 is connected to one end of the second resistor R5 and the gate of the field effect transistor Q; the other end of the second resistor R5 is connected to one end of the third resistor R6; the other end of the third resistor R6 is connected to the other end of the first capacitor C1; the other end of the third resistor R6 is the other end of the output end.

[0052] Furthermore, the output current sampling control circuit 3 includes a fourth resistor R1 , a fifth resistor R3 , a sixth resistor R2 , a photocoupler IC1 , a seventh resistor R7 , and a limiting diode DZ1 .

[0053] The photocoupler IC1 includes a light emitting diode IC1B and a phototransistor IC1A.

[0054] Specifically, one end of the fourth resistor R1 is connected to the first capacitor C1 and one end of the first resistor R4, the other end of the fourth resistor R1 is connected to the fifth resistor R3, one end of the sixth resistor R2 is connected to the connecting line between the fourth resistor R1 and the fifth resistor R3, the other end of the sixth resistor R2 is connected to the positive electrode of the light-emitting diode IC1B, the negative electrode of the light-emitting diode IC1B is connected to the negative electrode of the limiting diode DZ1, and the positive electrode of the limiting diode DZ1 is connected to the other end of the fifth resistor R3; the collector of the phototransistor IC1A is connected to the connecting line between the second resistor R5 and the third resistor R6, the emitter of the phototransistor IC1A is connected to one end of the first capacitor C1 connected to the third resistor R6, and the seventh resistor R7 is connected in series to the collector of the phototransistor IC1A.

[0055] Specifically, the output terminals include P3 and P4, and the monitor or controller is connected to the output terminals P3 and P4.

[0056] Furthermore, the output current sampling control circuit 3 further includes a second capacitor C2 , and the second capacitor C2 is connected in parallel across the limiting diode DZ1 .

[0057] The voltage conversion circuit further includes a third capacitor C3 connected in parallel between the two ends of the output end.

[0058] The second capacitor C2 and the third capacitor C3 are both filter capacitors.

[0059] In another embodiment of the present invention, the switch tube voltage adjustment circuit 2 includes a plurality of N-channel field effect transistors Q arranged in parallel.

[0060] In applications where a monitor or controller requires a relatively large input current, a single field effect transistor Q alone cannot provide a sufficiently large current to the monitor or controller.

[0061] In order to output a larger current, multiple field effect transistors Q can be connected in parallel to increase the output current of the source of the field effect transistor Q.

[0062] In the present invention, the high-voltage DC voltage input through the input terminals P1 and P2 absorbs the interference ripple voltage through the first capacitor C1; the input voltage is divided and sampled by a high-precision proportional voltage sampling circuit 1 composed of a first resistor R4, a second resistor R5, and a third resistor R6 connected in series in sequence; because the impedance of the gate and source junctions of the field-effect transistor Q is extremely high, a highly accurate monitoring sampling voltage that follows the real-time changes of the input voltage can be sampled through the second resistor R5 and the third resistor R6 and is provided to the gate and source of the field-effect transistor Q as a reference voltage. The current of the reference voltage is amplified by the field-effect transistor Q, and the monitoring sampling voltage is output through the source of the field-effect transistor Q; the output voltage is buffered and smoothed by the third capacitor C3 and then input into a monitor or controller. The fourth resistor R1 is a buffer resistor. The voltage generated by the current across the fifth resistor R3 causes the sixth resistor R2 to operate by driving the optocoupler IC1. The limiter diode DZ1 is set to the threshold voltage of the limit sampling current. Only when the output current exceeds the limit sampling current does the optocoupler IC1 turn on and pull down the voltage at the end of the third resistor R6 via the seventh resistor R7, thereby lowering the voltage at the gate of the field-effect transistor Q and rapidly reducing the output voltage at the source of the field-effect transistor Q, or directly shutting down the field-effect transistor Q. This protects the switching tube voltage adjustment circuit and any monitor or controller connected to the output terminal from damage, thereby improving the safety and reliability of the circuit.

[0063] The monitoring sampling voltage output by the voltage conversion circuit of the present invention has higher accuracy and better stability; it can still provide a large driving current when the internal resistance of the load source externally connected to the input end varies widely; it can also limit the limit value of the output current and automatically shut down the output of the monitoring sampling voltage when the output current exceeds the set limit value.

[0064] The voltage conversion circuit of the present invention is designed by utilizing the current amplification effect of the field-effect transistor Q, the high impedance of the gate-source junction of the field-effect transistor Q, the voltage between the drain and source of the field-effect transistor Q following the changes in the voltage between the gate and source, and the proportional conversion of the set voltage between the gate and source of the field-effect transistor Q to the input test voltage. Because the electrical characteristics of the field-effect transistor Q are very stable within the temperature range of -65°C to 160°C, the voltage conversion circuit of the present invention, which is based on the field-effect transistor Q, can stably convert the input voltage proportionally within this temperature range. This makes the voltage conversion circuit of the present invention suitable for use in high-voltage DC power supply voltage monitoring and control systems within a wide temperature range of -55°C to 125°C.

[0065] The voltage conversion circuit of the present invention can increase the current driving capability of the monitoring sampling voltage by more than 100 times without affecting the output accuracy of the monitoring sampling voltage; that is, under the conditions of 25°C, -55°C and +125°C, the sampling accuracy of the input voltage can be maintained at a very high accuracy, and the loss is very low when working in the circuit for a long time, which is conducive to ensuring the reliability and stability of the circuit.

[0066] The voltage conversion circuit of the present invention utilizes the isolation and control characteristics of current by the photocoupler IC1. When the output current exceeds a preset limit sampling current, the photocoupler IC1 turns on and lowers the voltage at the end of the third resistor R6 via the seventh resistor R7, thereby lowering the voltage at the gate of the field-effect transistor Q and rapidly reducing the output voltage at the source of the field-effect transistor Q, causing the field-effect transistor Q to turn off. This protects the field-effect transistor Q and a monitor or controller connected to the output terminal from damage, thereby improving the safety and reliability of the circuit.

[0067] The voltage conversion circuit of the present invention is mainly used in DC high-voltage circuits and systems for real-time monitoring of voltage changes in a power supply bus. It can accurately detect real-time changes in bus voltage, make the voltage value of the monitored sampled voltage proportional to the input voltage change, and amplify the current of the detected reference voltage, so that the value of the sampled output voltage has a more objective load driving capability, thereby improving the accuracy of the monitored sampled voltage output.

[0068] The voltage conversion circuit of the present invention can flexibly set the limit sampling current of the monitored sampling voltage output current and protect the output circuit, so that the circuit can be widely used in military or high-end industrial power supply systems, thereby improving the cost performance of electrical equipment.

[0069] The above are only specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions within the technical scope disclosed by the present invention should be covered by the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A voltage conversion circuit, characterized in that: It includes input and output terminals, as well as: A voltage sampling circuit, configured to convert a test voltage inputted from the input terminal into a monitoring sampling voltage; the test voltage being greater than the monitoring sampling voltage; A switch tube voltage adjustment circuit, connected to the voltage sampling circuit, for amplifying the current of the monitoring sampling voltage and outputting the amplified current; an output current sampling control circuit, connected to the voltage sampling circuit and the switch tube voltage adjustment circuit, for setting a limit sampling current and shutting off the monitoring sampling voltage when the current corresponding to the monitoring sampling voltage is greater than or equal to the limit sampling current; The switch tube voltage adjustment circuit is an N-channel field effect tube; The gate of the field effect tube is connected to the voltage sampling circuit, the drain is connected to the output of the output current sampling control circuit, and the source is one end of the output end; The voltage conversion circuit further includes a first capacitor connected in parallel between the two ends of the input terminal; The voltage sampling circuit includes a first resistor, a second resistor and a third resistor; One end of the first resistor is connected to one end of the first capacitor, and the other end of the first resistor is connected to one end of the second resistor and the gate of the field effect transistor; the other end of the second resistor is connected to one end of the third resistor; the other end of the third resistor is connected to the other end of the first capacitor; the other end of the third resistor is the other end of the output terminal; The output current sampling control circuit includes a fourth resistor, a fifth resistor, a sixth resistor, a photocoupler, a seventh resistor and a limiting diode; The photoelectric coupler includes a light emitting diode and a phototransistor; One end of the fourth resistor is connected to one end of the first capacitor and one end of the first resistor, the other end of the fourth resistor is connected to one end of the fifth resistor, one end of the sixth resistor is connected to the connecting line between the fourth resistor and the fifth resistor, the other end of the sixth resistor is connected to the positive electrode of the light-emitting diode, the negative electrode of the light-emitting diode is connected to the negative electrode of the limiting diode, and the positive electrode of the limiting diode is connected to the other end of the fifth resistor; the collector of the phototransistor is connected to the connecting line between the second resistor and the third resistor, the emitter of the phototransistor is connected to the other end of the first capacitor and the other end of the third resistor, and the seventh resistor is connected in series between the collector of the phototransistor and one end of the third resistor.

2. The voltage conversion circuit according to claim 1, wherein: The output current sampling control circuit further includes a second capacitor connected in parallel across the limiting diode.

3. The voltage conversion circuit according to claim 1, wherein: The voltage conversion circuit further includes a third capacitor, which is connected in series between two ends of the output end.

4. The voltage conversion circuit according to claim 1, wherein: The switch tube voltage adjustment circuit includes a plurality of N-channel field effect tubes arranged in parallel.

5. The voltage conversion circuit according to claim 4, wherein: The field effect transistor is a metal oxide semiconductor field effect transistor.

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