Voltage limiting circuit on high-speed signal line

Abstract

The utility model discloses a voltage limiting circuit on a high-speed signal line, which is connected with a signal line and comprises a positive high voltage limiting unit, a second high voltage limiting unit, a third high voltage limiting unit and a fourth high voltage limiting unit, the negative high voltage limiting unit comprises a second diode D2, the negative electrode of the second diode D2 is connected with the signal line, and the positive electrode of the second diode D2 is grounded; a current limiting unit is arranged on the signal line in series and is used for ensuring that the current passing through the first diode D1 or the second diode D2 is within a set interval; a first diode D1 is connected to a power supply plane to ensure that the signal voltage on a line does not exceed a forward target voltage; a second diode D2 is connected to the ground plane to ensure that the signal voltage on the line does not exceed the reverse target voltage; the input current is limited by arranging the current limiting device, it is ensured that the current does not exceed the positive current tolerable by the diode, and it is ensured that power consumption generated on the voltage-regulator tube does not damage the voltage-regulator tube.

Description

Technical Field

[0001] The utility model relates to the technical field of electronic circuits, and more specifically, to a voltage limiting circuit on a high-speed signal line. Background Art

[0002] For circuits that strictly prohibit high-voltage input, safety protection measures are required to limit the voltage within a certain range on the line. The conventional method is to limit the voltage through a voltage regulator tube, or to cut off the input after the voltage detects the high voltage. However, these two methods are not applicable to high-speed signal lines for the following reasons:

[0003] (1) Zener diode voltage limiting: The junction capacitance of the Zener diode is very large, and the capacitance will affect the transmission of high-speed signals. Therefore, the method of directly using the Zener diode to limit the voltage is not suitable for high-speed signal lines;

[0004] (2) Detecting and controlling high voltage input through semiconductor solutions: This method has a complex circuit and has a certain delay from detection to response control. For internal circuits that need to eliminate transient high voltage, this delay is unacceptable. In addition, in the case of negative voltage input, the control circuit will be more complicated.

[0005] Therefore, how to achieve a method that can limit the voltage on the signal line while preventing the signal transmission in the high-speed signal line from being affected is a problem that needs to be solved at present. Summary of the invention

[0006] In view of the problem that the voltage limiting operation of the signal line is not perfectly compatible with the high-frequency signal high-quality transmission in actual application, the purpose of this application is to propose a voltage limiting circuit on a high-speed signal line. The specific scheme is as follows:

[0007] A voltage limiting circuit on a high-speed signal line, connected to the signal line, comprising:

[0008] A positive high voltage limiting unit, comprising a first diode D1, wherein the anode of the first diode D1 is connected to the signal line, and the cathode is electrically connected to a voltage-stabilizing power supply;

[0009] A negative high voltage limiting unit, comprising a second diode D2, wherein the cathode of the second diode D2 is connected to the signal line and the anode is grounded;

[0010] A current limiting unit is arranged in series on the signal line to ensure that the current passing through the first diode D1 or the second diode D2 is within a set range.

[0011] Through the above technical solution, the positive high-voltage signal on the line is introduced into the voltage-stabilized power supply using the first diode D1, and the negative high-voltage signal on the line is introduced into the grounding point using the second diode D2, so that the voltage on the signal line can be maintained within a set range. By setting a current limiting device, it can be ensured that the current passing through the first diode D1 or the second diode D2 is within the set range, ensuring that the power generated on the voltage regulator meets the specification requirements of the voltage regulator.

[0012] Furthermore, a clamping diode D4 is reversely connected in series with the cathode of the first diode D1.

[0013] Through the above technical solution, if VCC cannot be well stabilized, the clamping diode D4 is used to clamp the voltage at a suitable voltage amplitude.

[0014] Furthermore, the current limiting unit includes at least two current limiting devices, and the connection point between the first diode D1 and the signal line is located between the two current limiting devices.

[0015] Through the above technical solution, it can be well ensured that the current passing through the first diode D1 or the second diode D2 is within the set range, ensuring the stable working state of each diode.

[0016] Furthermore, a transistor is connected on the signal line adjacent to the second diode D2, the collector of the transistor is connected to the signal line, the emitter is grounded via a resistor, and the base is externally connected to a voltage source controlled by a controller.

[0017] Through the above technical solution, the controller is used to control the voltage source to output different voltages, adjust the width of the PN node in the transistor, and then change the parasitic capacitance of the transistor itself, thereby realizing the adjustment of the capacitance size in the voltage limiting circuit without turning on the transistor.

[0018] Furthermore, the control output terminal of the controller is electrically connected to the voltage source, and the signal input terminal is electrically connected to the signal line, and is used to collect the frequency of the signal transmitted in the signal line and output a control signal to control the output of the voltage source.

[0019] Through the above technical solution, the above controller can be used to collect the signal frequency in the signal line, and then the parasitic capacitance value between the PN junctions in the transistor is adjusted according to the collected signal frequency, so that the voltage limiting circuit can finally adapt to the signal frequency in the signal line and reduce the influence of the voltage limiting circuit on the signal transmission in the signal line.

[0020] Compared with the prior art, the beneficial effects of the utility model are as follows:

[0021] By connecting the first diode D1 to the power plane, it is ensured that the signal voltage on the line does not exceed the forward target voltage; by connecting the second diode D2 to the ground plane, it is ensured that the signal voltage on the line does not exceed the reverse target voltage; by setting a current limiting device to limit the input current, it is ensured that the current does not exceed the forward current that the diode can withstand, and the power consumption generated on the Zener diode does not damage the Zener diode. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 is an overall schematic diagram of a voltage limiting circuit (implementation method 1);

[0023] Figure 2 Schematic diagram of the overall voltage limiting circuit (implementation method 2). DETAILED DESCRIPTION

[0024] The present invention will be further described in detail below in conjunction with the embodiments and drawings, but the implementation methods of the present invention are not limited thereto.

[0025] A voltage limiting circuit on a high-speed signal line, such as Figure 1 As shown, it is connected to the signal line and includes a positive high-voltage voltage limiting unit, a negative high-voltage voltage limiting unit and a current limiting unit.

[0026] The positive high voltage limiting unit includes a first diode D1, the positive electrode of the first diode D1 is connected to the signal line, and the negative electrode is electrically connected to a voltage-stabilizing power supply VCC. When working, the first diode D1 is used to introduce the positive high voltage signal on the line into VCC. If VCC cannot be well stabilized, the negative electrode of the first diode D1 is reversely connected in series with a clamping diode D4, that is, a diode is directly reversely connected between the voltage-stabilizing power supply VCC and the ground point to clamp the voltage at a suitable voltage amplitude.

[0027] The negative high voltage limiting unit includes a second diode D2, the cathode of the second diode D2 is connected to the signal line, and the anode is grounded. The second diode D2 can be used to guide the negative high voltage signal on the line to the grounding point.

[0028] The first diode D1 and the clamping diode D4 are connected in series. According to the calculation method of the series capacitance, the overall capacitance of the first diode D1 and the clamping diode D4 is much smaller than that of one of them, which can effectively reduce the influence of the capacitance of the voltage limiting circuit itself on the high-frequency signal.

[0029] Preferably, Figure 2 As shown, a third transistor D3 is connected between the second diode D2 and the signal line, the positive electrode of the third transistor D3 is connected to the signal line, and the negative electrode is connected to the second transistor, thereby further reducing the capacitance value of the voltage limiting circuit and reducing the influence of the voltage limiting circuit on the high-frequency signal in the signal line.

[0030] A current limiting unit is arranged in series on the signal line to ensure that the current passing through the first diode D1 or the second diode D2 is within a set range. The current limiting unit includes at least two current limiting devices. In the embodiment of the present application, the junction point between the first diode D1 and the signal line is located between the two current limiting devices, and the current limiting device is implemented by a current limiting fuse. The above technical solution can well ensure that the current passing through the first diode D1 or the second diode D2 is within a set range, and ensure the stable working state of each diode.

[0031] Furthermore, a transistor is connected adjacent to the second diode D2 on the signal line, preferably an NPN transistor, the collector of the transistor is connected to the signal line, the emitter is grounded after a resistor, the base is externally connected to a voltage source controlled by a controller, and the above-mentioned resistor is implemented by a resistor with a larger resistance value. The above-mentioned controller can be implemented by FPGA, and the signal input end of the above-mentioned controller is electrically connected to the signal line, which is used to collect the signal frequency in the signal line. Based on the above-mentioned signal frequency, a control signal can be output to directly or indirectly control the input voltage of the transistor base, such as through output level control or by controlling the voltage source. The above-mentioned technical solution uses the controller to control the voltage source to output different voltages, adjust the width of the PN node in the transistor, and then change the parasitic capacitance of the transistor itself, thereby realizing the adjustment of the capacitance size in the voltage limiting circuit without turning on the transistor.

[0032] The above is only a preferred embodiment of the present invention. The protection scope of the present invention is not limited to the above embodiments. All technical solutions under the concept of the present invention belong to the protection scope of the present invention. It should be pointed out that for ordinary technicians in this technical field, some improvements and modifications without departing from the principle of the present invention should also be regarded as the protection scope of the present invention.

Claims

1. A voltage limiting circuit on a high-speed signal line, connected to the signal line, characterized in that: include: A positive high voltage limiting unit, comprising a first diode D1, wherein the anode of the first diode D1 is connected to the signal line, and the cathode is electrically connected to a voltage-stabilizing power supply; A negative high voltage limiting unit, comprising a second diode D2, wherein the cathode of the second diode D2 is connected to the signal line and the anode is grounded; A current limiting unit is arranged in series on the signal line to ensure that the current passing through the first diode D1 or the second diode D2 is within a set range.

2. The voltage limiting circuit on the high-speed signal line according to claim 1, characterized in that: A clamping diode D4 is connected in reverse series to the cathode of the first diode D1 .

3. The voltage limiting circuit on the high-speed signal line according to claim 2, characterized in that: The current limiting unit includes at least two current limiting devices, and the connection point between the first diode D1 and the signal line is located between the two current limiting devices.

4. The voltage limiting circuit on the high-speed signal line according to claim 1, characterized in that: A transistor is connected on the signal line adjacent to the second diode D2, the collector of the transistor is connected to the signal line, the emitter is grounded via a resistor, and the base is externally connected to a voltage source controlled by a controller.

5. The voltage limiting circuit on the high-speed signal line according to claim 4, characterized in that: The control output terminal of the controller is electrically connected to the voltage source, and the signal input terminal is electrically connected to the signal line, and is used to collect the frequency of the signal transmitted in the signal line and output a control signal to control the output of the voltage source.

6. The voltage limiting circuit on the high-speed signal line according to claim 3, characterized in that: The current limiting device is implemented by a current limiting fuse.

Images