A signal transmission system for a DC voltage transformer

Abstract

The present invention discloses a signal transmission system for a DC voltage transformer, comprising: a primary converter and a secondary side; the primary converter includes a voltage-current conversion module, a first LED, a second LED and a first PIN; the secondary side includes a second PIN and a current-voltage conversion module; wherein, the output end of the voltage-current conversion module is connected to the serially-connected first LED and second LED; the light-emitting end of the second LED and the receiving end of the first PIN are connected by a first optical fiber; the first PIN is connected to the input end of the voltage-current conversion module; the light-emitting end of the first LED and the receiving end of the second PIN are connected by a second optical fiber; the lengths of the first optical fiber and the second optical fiber are the same; the second PIN is connected to the current-voltage conversion module; both the first LED and the second LED are identical light-emitting diodes; both the first PIN and the second PIN are identical optoelectronic conversion diodes. The present invention improves the non-linear characteristics of the light-emitting diode and the optoelectronic diode during the conversion process, and realizes the linear optical fiber transmission of the analog signal.

Description

Technical Field

[0001] The present invention relates to the technical field of DC voltage transformers, and particularly to a signal transmission system for a DC voltage transformer. Background Art

[0002] DC voltage transformers are used for metering and protecting DC distribution networks and are one of the important devices in DC distribution networks. A DC voltage transformer based on the principle of resistor-capacitor voltage division outputs a lower voltage signal proportional to the measured DC voltage on the low-voltage side, and after being processed on the ground potential side of the resistor-capacitor voltage divider, it is transmitted to the secondary instrument through a cable. The voltage level of DC distribution networks is usually 10 kV and below. Considering the transmission distance and the overall cost of the machine, cables are the first choice. However, voltage transformers in DC distribution networks are usually installed in DC distribution cabinets. Due to space limitations in the cabinet, there are many installed devices and the busbar layout is complex, resulting in a relatively harsh electromagnetic environment in the cabinet. The output signal cable of the DC voltage transformer is extremely easy to be interfered in this environment, and the DC voltage transformer has weak anti-electromagnetic interference ability when using a cable to transmit analog signals; in addition, the reference ground of the output voltage of the low-voltage arm of the resistor-capacitor voltage divider is the strong electrical ground, which is common with the weak electrical ground of the signal processing circuit. Using a cable to transmit signals makes the weak electrical ground on the secondary instrument side also need to be common with the strong electrical ground on the side of the resistor-capacitor voltage divider, greatly increasing the noise risk and safety risk of the secondary instrument.

[0003] Optical fiber transmission is an ideal way to effectively resist electromagnetic interference and signal isolation and is widely used in electronic transformers with high voltage levels. In electronic transformers with high voltage levels, the output of the sensor is processed in the primary converter to convert into a digital signal and is remotely transmitted using optical fibers, but this method is not suitable for application in distribution network DC voltage transformers. The digital optical fiber transmission method increases the complexity of distribution network DC voltage transformers. The linear characteristics of light-emitting diodes and photoelectric conversion diodes are poor and are not sufficient to meet the performance requirements of transformers, and linear transmission of analog signals cannot be achieved. Summary of the Invention

[0004] The present invention provides a signal transmission system for a DC voltage transformer, which uses two pairs of identical light-emitting diodes LED and photoelectric conversion diodes PIN. One pair is used for optical fiber transmission of analog signals; the other pair is used for feedback output signals, and the negative feedback linearization control strategy of a nonlinear system is utilized to improve the nonlinear characteristics of the light-emitting diode and the photodiode during the conversion process, and linear optical fiber transmission of analog signals is achieved.

[0005] To achieve this, the present invention provides a signal transmission system for a DC voltage transformer, including: a primary converter and a secondary side;

[0006] The primary converter includes a voltage-current conversion module, a first LED, a second LED, and a first PIN. Among them, the output terminal of the voltage-current conversion module is connected to the positive electrode of the first LED; the negative electrode of the first LED is connected to the positive electrode of the second LED; the negative electrode of the second LED is grounded; the light-emitting terminal of the second LED and the receiving end of the first PIN are connected by a first optical fiber; both the positive and negative electrodes of the first PIN are connected to the input terminal of the voltage-current conversion module; the input terminal of the voltage-current conversion module is used as the input terminal of the primary converter; the light-emitting terminal of the second LED is used as the output terminal of the primary converter.

[0007] The secondary side includes a second PIN and a current-voltage conversion module. Among them, the light-emitting terminal of the first LED and the receiving end of the second PIN are connected by a second optical fiber; the first optical fiber and the second optical fiber have the same length; both the positive and negative electrodes of the second PIN are connected to the current-voltage conversion module; the receiving end of the second PIN is used as the input terminal of the secondary side; the output terminal of the current-voltage conversion module is used as the output terminal of the secondary side; the first LED and the second LED are both the same light-emitting diodes; the first PIN and the second PIN are both the same optoelectronic conversion diodes.

[0008] Further, the primary converter is specifically configured to: input the input signal into the voltage-current conversion module after low-pass filtering, so that the voltage-current conversion module converts the voltage signal into a first current signal as the driving current of the first LED and the second LED, and drives the first LED and the second LED to emit light.

[0009] Among them, the first optical signal emitted by the first LED is transmitted to the secondary side through the second optical fiber; the second optical signal emitted by the second LED is transmitted to the first PIN through the first optical fiber for optoelectronic conversion, converts the received second optical signal into a second current signal, and feeds back the second current signal to the input terminal of the voltage-current conversion module.

[0010] Further, the voltage-current conversion module specifically includes: a first transconductance amplifier, a plurality of resistor elements, and a plurality of capacitor elements.

[0011] Among them, the positive electrode of the first PIN is connected to the non-inverting input terminal of the first transconductance amplifier and grounded; the negative electrode of the first PIN, the inverting input terminal of the first transconductance amplifier, and one end of a first resistor are connected, and the other end of the first resistor is connected to the input terminal of the voltage-current conversion module; the output terminal of the first transconductance amplifier is used as the output terminal of the voltage-current conversion module.

[0012] The first transconductance amplifier is used to adjust the driving current of the first LED and the second LED, so that the inverting input terminal of the first transconductance amplifier remains at 0V.

[0013] Further, the first transconductance amplifier is used to adjust the driving currents of the first LED and the second LED so that the inverting input terminal of the first transconductance amplifier is maintained at 0V. Specifically:

[0014] When the input voltage at the input terminal of the voltage-current conversion module increases, the voltage at the inverting input terminal of the first transconductance amplifier increases, so that the first current signal output by the first transconductance amplifier increases, and the second optical signal emitted by the second LED is driven to increase;

[0015] When the first PIN receives the increased second optical signal, the output photocurrent of the first PIN increases, and the voltage at the inverting input terminal of the first transconductance amplifier is reduced to 0V, so that the output photocurrent of the first PIN changes linearly with the input voltage.

[0016] Further, the current-voltage conversion module specifically includes: a second transconductance amplifier and a feedback resistor;

[0017] Wherein, one end of the feedback resistor is connected to the inverting input terminal of the second transconductance amplifier and the negative electrode of the second PIN; the positive electrode of the second PIN is connected to the non-inverting input terminal of the second transconductance amplifier and grounded; the other end of the feedback resistor is connected to the output terminal of the second transconductance amplifier, serving as the output terminal of the current-voltage conversion module;

[0018] The output photocurrents of the first PIN and the second PIN are equal; the output photocurrent of the second PIN changes linearly with the input voltage; the second transconductance amplifier is used to convert the output photocurrent of the second PIN into an output voltage through the feedback resistor and output it through the output terminal of the second transconductance amplifier.

[0019] Further, the output terminal and the inverting input terminal of the first transconductance amplifier are connected through a first capacitor.

[0020] Further, the voltage-current conversion module further includes: a triode;

[0021] The output terminal of the first transconductance amplifier is connected to one end of a second resistor, the other end of the second resistor and one end of a third resistor are connected to the gate of the triode; one end of a fourth resistor is connected to the source of the triode; the other end of the third resistor, the other end of the fourth resistor and a first power supply are connected; the drain of the triode is connected to one end of a fifth resistor, the positive electrode of the first LED and the negative electrode of a first diode; the other end of the fifth resistor is connected to a second power supply; the negative electrode of the first LED, the positive electrode of the second LED, the positive electrode of the first diode and the negative electrode of a second diode are connected; the negative electrode of the second LED is connected to the positive electrode of the second diode and grounded.

[0022] Further, the output terminal and the inverting input terminal of the second transconductance amplifier are connected through a second capacitor.

[0023] As a preferred solution, the present invention employs two pairs of identical light-emitting diodes LED and photoelectric conversion diodes PIN. Among them, the light-emitting diode LED and the photoelectric conversion diode PIN use optical fibers of the same length for signal transmission; one pair is used for optical fiber transmission of analog signals; the other pair is used for feedback of the output signal of the voltage-current conversion module. The present invention utilizes the negative feedback effect in the primary converter to control the two photoelectric conversion diodes PIN to linearly vary with the input signal; and utilizes the negative feedback linearization control strategy of the nonlinear system to improve the nonlinear characteristics of the light-emitting diode and the photodiode during the conversion process, so as to achieve linear optical fiber transmission of analog signals. Description of the Drawings

[0024] Figure 1 is a schematic structural diagram of an embodiment of a signal transmission system for a DC voltage transformer provided by the present invention;

[0025] Figure 2 is a schematic structural diagram of another embodiment of a signal transmission system for a DC voltage transformer provided by the present invention. Detailed Embodiments

[0026] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0027] Embodiment 1

[0028] Please refer to Figure 1 , a signal transmission system for a DC voltage transformer provided by an embodiment of the present invention, comprising: a primary converter and a secondary side;

[0029] The primary converter includes a voltage-current conversion module, a first LED, a second LED, and a first PIN. Among them, the output terminal of the voltage-current conversion module is connected to the positive electrode of the first LED; the negative electrode of the first LED is connected to the positive electrode of the second LED; the negative electrode of the second LED is grounded; the light-emitting end of the second LED and the receiving end of the first PIN are connected by a first optical fiber; both the positive and negative electrodes of the first PIN are connected to the input terminal of the voltage-current conversion module; the input terminal of the voltage-current conversion module is used as the input terminal of the primary converter; the light-emitting end of the second LED is used as the output terminal of the primary converter.

[0030] The secondary side includes a second PIN and a current-voltage conversion module. Among them, the light-emitting end of the first LED and the receiving end of the second PIN are connected by a second optical fiber; the first optical fiber and the second optical fiber have the same length; both the positive and negative electrodes of the second PIN are connected to the current-voltage conversion module; the receiving end of the second PIN is used as the input terminal of the secondary side; the output terminal of the current-voltage conversion module is used as the output terminal of the secondary side; the first LED and the second LED are both the same light-emitting diodes; the first PIN and the second PIN are both the same optoelectronic conversion diodes.

[0031] In this embodiment, the primary converter is specifically configured to: input the input signal into the voltage-current conversion module after low-pass filtering, so that the voltage-current conversion module converts the voltage signal into a first current signal as the driving current of the first LED and the second LED, and drives the first LED and the second LED to emit light.

[0032] Among them, the first optical signal emitted by the first LED is transmitted to the secondary side through the second optical fiber; the second optical signal emitted by the second LED is transmitted to the first PIN through the first optical fiber for optoelectronic conversion, converts the received second optical signal into a second current signal, and feeds back the second current signal to the input terminal of the voltage-current conversion module.

[0033] In this embodiment, the voltage-current conversion module specifically includes: a first transconductance amplifier, a plurality of resistor elements, and a plurality of capacitor elements.

[0034] Among them, the positive electrode of the first PIN is connected to the non-inverting input terminal of the first transconductance amplifier and is grounded; the negative electrode of the first PIN, the inverting input terminal of the first transconductance amplifier, and one end of a first resistor are connected, and the other end of the first resistor is connected to the input terminal of the voltage-current conversion module; the output terminal of the first transconductance amplifier is used as the output terminal of the voltage-current conversion module.

[0035] The first transconductance amplifier is used to adjust the driving current of the first LED and the second LED, so that the inverting input terminal of the first transconductance amplifier remains at 0V.

[0036] In this embodiment, the first transconductance amplifier is used to adjust the drive currents of the first LED and the second LED so that the inverting input terminal of the first transconductance amplifier remains at 0V. Specifically:

[0037] When the input voltage at the input terminal of the voltage-current conversion module increases, the voltage at the inverting input terminal of the first transconductance amplifier increases, so that the first current signal output by the first transconductance amplifier increases, and the second optical signal emitted by the second LED is driven to increase;

[0038] When the first PIN receives the increased second optical signal, the output photocurrent of the first PIN increases, and the voltage at the inverting input terminal of the first transconductance amplifier is reduced to 0V, so that the output photocurrent of the first PIN changes linearly with the input voltage.

[0039] In this embodiment, the current-voltage conversion module specifically includes: a second transconductance amplifier and a feedback resistor;

[0040] Wherein, one end of the feedback resistor is connected to the inverting input terminal of the second transconductance amplifier and the negative electrode of the second PIN; the positive electrode of the second PIN is connected to the non-inverting input terminal of the second transconductance amplifier and grounded; the other end of the feedback resistor is connected to the output terminal of the second transconductance amplifier and serves as the output terminal of the current-voltage conversion module;

[0041] The output photocurrents of the first PIN and the second PIN are equal; the output photocurrent of the second PIN changes linearly with the input voltage; the second transconductance amplifier is used to convert the output photocurrent of the second PIN into an output voltage through the feedback resistor and output it through the output terminal of the second transconductance amplifier.

[0042] In this embodiment, the output terminal and the inverting input terminal of the first transconductance amplifier are connected through a first capacitor.

[0043] In this embodiment, the voltage-current conversion module further includes: a triode;

[0044] The output terminal of the first transconductance amplifier is connected to one end of the second resistor. The other end of the second resistor and one end of the third resistor are connected to the gate of the triode. One end of the fourth resistor is connected to the source of the triode. The other end of the third resistor, the other end of the fourth resistor, and the first power supply are connected. The drain of the triode is connected to one end of the fifth resistor, the positive electrode of the first LED, and the negative electrode of the first diode. The other end of the fifth resistor is connected to the second power supply. The negative electrode of the first LED, the positive electrode of the second LED, the positive electrode of the first diode, and the negative electrode of the second diode are connected. The negative electrode of the second LED is connected to the positive electrode of the second diode and grounded.

[0045] In this embodiment, the output terminal and the inverting input terminal of the second transconductance amplifier are connected through a second capacitor.

[0046] For better illustration of this embodiment, please refer to Figure 2 , which is a preferred signal transmission system for a DC voltage transformer, including: a sending side (primary converter) and a receiving side (secondary side);

[0047] The sending side includes: a first transconductance amplifier U1, resistors R1 - R5, a capacitor C1, a triode Q1, light-emitting diodes LED1 and LED2, diodes D1 and D2, and a photoelectric conversion diode PIN2;

[0048] The output terminal of the first transconductance amplifier U1 is connected to one end of the second resistor R2. The other end of the second resistor R2 and one end of the third resistor R3 are connected to the gate of the triode Q1. One end of the fourth resistor R4 is connected to the source of the triode Q1. The other end of the third resistor R3, the other end of the fourth resistor R4, and the high-voltage power supply VCC1 are connected. The drain of the triode Q1 is connected to one end of the fifth resistor R5, the positive electrode of LED1, and the negative electrode of the first diode D1. The other end of the fifth resistor R5 is connected to the low-voltage power supply VDD1. The negative electrode of LED1, the positive electrode of LED2, the positive electrode of the first diode D1, and the negative electrode of the second diode D2 are connected. The negative electrode of LED2 is connected to the positive electrode of the second diode D2 and grounded. The output terminal and the inverting input terminal of the first transconductance amplifier U1 are connected through a first capacitor C1.

[0049] The arrows in the figure indicate the current direction. The photoelectric conversion current I PIN2 output by PIN2 and the current generated by the voltage signal U in on R1 flow into the inverting input terminal of U1 together. U1 adjusts the drive currents of LED1 and LED2 (I F ), thereby adjusting the current I PIN2, so that the inverting input terminal of U1 is maintained at 0V. When the input impedance of the inverting input terminal is very large and approaches infinity, the input current of the inverting input terminal approaches zero. At this time, the following is satisfied:

[0050] I PIN2 = U in / R1; (1)

[0051] When the input voltage U in increases, the voltage at the inverting input terminal of U1 will tend to increase above 0V; at this time, the output of U1 will also increase, causing I F and I PIN2 to increase. The increase in I PIN2 pulls the inverting input terminal of U1 back to 0V again. This process repeats continuously, and finally the inverting input terminal of U1 is 0V. This feedback process makes I PIN2 vary linearly with the input voltage, and the optoelectronic conversion currents of PIN1 and PIN2 are equal, that is, the signal output after fiber optic transmission also varies linearly with the input voltage.

[0052] It can be seen from equation (1) that after feedback stabilization, I PIN2 only depends on the input voltage U in and the value of R1, and has nothing to do with the light output characteristics of LED2. When the light output of LED2 has non-linear characteristics, the first transconductance amplifier U1 adjusts I F to compensate and keep the current in PIN2 constant. Therefore, I PIN2 is proportional to the input voltage U in .

[0053] The LED driving circuit composed of the triode Q1 and resistors such as R2 - R5 helps to maintain the accuracy and bandwidth of the circuit within the entire input voltage range. The diodes D1 and D2 protect LED1 and LED2 to prevent excessive reverse voltage when the LEDs are in the non-emitting state.

[0054] The receiving side includes: a photoelectric conversion diode PIN1, a second transconductance amplifier U2, a second capacitor C2, and a feedback resistor R6;

[0055] Among them, one end of the feedback resistor R6 is connected to the inverting input terminal of the second transconductance amplifier U2 and the negative electrode of PIN1; the positive electrode of PIN1 is connected to the non-inverting input terminal of the second transconductance amplifier U2 and grounded; the other end of the feedback resistor R6 is connected to the output terminal of the second transconductance amplifier U2; the output terminal and the inverting input terminal of the second transconductance amplifier U2 are connected through a second capacitor C2; the second transconductance amplifier U2 is connected to the low-voltage power supply VDD2 and the high-voltage power supply VCC2;

[0056] Since LED1 and LED2 are identical, and PIN1 and PIN2 are identical, LED1 and LED2 are connected in series and driven by the same current, and both operate in the same environment. The two LEDs are connected to PIN through optical fibers of the same length. Therefore, the output photocurrents of PIN2 and PIN1 are equal. Thus, we have:

[0057] I PIN2 = I PIN1 = U in / R1; (2)

[0058] It can be seen that the relationship between the output current of the photodiode PIN1 and the input voltage on the transmitting side is also linear. Therefore, through negative feedback linearization, the output of the photodiode PIN1 is linear and stable. Thus, the linear optical fiber transmission of analog signals is achieved.

[0059] The second transconductance amplifier U2 converts the output current converted by PIN1 into a voltage signal U through the feedback resistor R6 out :

[0060]

[0061] As can be seen from Equation (3), the input voltage on the transmitting side is linearly transmitted to the receiving side through the optical fiber.

[0062] The capacitors C1 and C2 on the feedback branches of U1 and U2 are compensation capacitors, which limit the bandwidth of the circuit within the signal transmission bandwidth to reduce the noise of the circuit and thus improve the stability of the circuit operation.

[0063] Implementing the embodiments of the present invention has the following effects:

[0064] The present invention uses two pairs of identical light-emitting diodes LED and photoelectric conversion diodes PIN. Among them, the light-emitting diodes LED and the photoelectric conversion diodes PIN use optical fibers of the same length for signal transmission; one pair is used for optical fiber transmission of analog signals; the other pair is used for the output signal of the feedback voltage-current conversion module. The present invention utilizes the negative feedback effect in the primary converter to control the two photoelectric conversion diodes PIN to achieve linear variation with the input signal; utilizes the negative feedback linearization control strategy of the nonlinear system to improve the nonlinear characteristics of the light-emitting diode and the photodiode during the conversion process, and realizes the linear optical fiber transmission of analog signals.

Claims

1. A signal transmission system for a DC voltage transformer, characterized in that, Including: A primary converter and a secondary side; The primary converter includes a voltage-current conversion module, a first LED, a second LED, and a first PIN; wherein, the output end of the voltage-current conversion module is connected to the positive electrode of the first LED; the negative electrode of the first LED is connected to the positive electrode of the second LED; the negative electrode of the second LED is grounded; the light-emitting end of the second LED and the receiving end of the first PIN are connected by a first optical fiber; both the positive electrode and the negative electrode of the first PIN are connected to the input end of the voltage-current conversion module; the input end of the voltage-current conversion module is used as the input end of the primary converter; the light-emitting end of the second LED is used as the output end of the primary converter; The secondary side includes a second PIN and a current-voltage conversion module; wherein, the light-emitting end of the first LED and the receiving end of the second PIN are connected by a second optical fiber; the first optical fiber and the second optical fiber have the same length; both the positive electrode and the negative electrode of the second PIN are connected to the current-voltage conversion module; the receiving end of the second PIN is used as the input end of the secondary side; the output end of the current-voltage conversion module is used as the output end of the secondary side; the first LED and the second LED are both the same light-emitting diodes; the first PIN and the second PIN are both the same optoelectronic conversion diodes.

2. A signal transmission system for a DC voltage transformer according to claim 1, characterized in that, The primary converter is specifically configured to: input the input signal into the voltage-current conversion module after low-pass filtering, so that the voltage-current conversion module converts the voltage signal into a first current signal as the driving current of the first LED and the second LED, and drives the first LED and the second LED to emit light; Wherein, the first optical signal emitted by the first LED is transmitted to the secondary side through the second optical fiber; the second optical signal emitted by the second LED is transmitted to the first PIN through the first optical fiber for optoelectronic conversion, converts the received second optical signal into a second current signal, and feeds back the second current signal to the input end of the voltage-current conversion module.

3. A signal transmission system for a DC voltage transformer according to claim 2, wherein, The voltage-current conversion module specifically includes: a first transconductance amplifier, a plurality of resistor elements, and a plurality of capacitor elements; Wherein, the positive electrode of the first PIN is connected to the non-inverting input end of the first transconductance amplifier and is grounded; the negative electrode of the first PIN, the inverting input end of the first transconductance amplifier, and one end of a first resistor are connected, and the other end of the first resistor is connected to the input end of the voltage-current conversion module; the output end of the first transconductance amplifier is used as the output end of the voltage-current conversion module; The first transconductance amplifier is used to adjust the driving current of the first LED and the second LED, so that the inverting input end of the first transconductance amplifier remains at 0V.

4. A signal transmission system for a DC voltage transformer according to claim 3, characterized in that, The first transconductance amplifier is used to adjust the driving current of the first LED and the second LED, so that the inverting input end of the first transconductance amplifier remains at 0V, specifically: When the input voltage at the input end of the voltage-current conversion module increases, the voltage at the inverting input end of the first transconductance amplifier increases, so that the first current signal output by the first transconductance amplifier increases, and drives the second optical signal emitted by the second LED to increase; When the first PIN receives an increased second optical signal, the output photocurrent of the first PIN increases, and the voltage at the inverting input terminal of the first transconductance amplifier is reduced to 0V, so that the output photocurrent of the first PIN changes linearly with the input voltage.

5. A signal transmission system for a DC voltage transformer according to claim 4, characterized in that, The current-voltage conversion module specifically includes: a second transconductance amplifier and a feedback resistor; Wherein, one end of the feedback resistor is connected to the inverting input terminal of the second transconductance amplifier and the negative electrode of the second PIN; the positive electrode of the second PIN is connected to the non-inverting input terminal of the second transconductance amplifier and is grounded; the other end of the feedback resistor is connected to the output terminal of the second transconductance amplifier and serves as the output terminal of the current-voltage conversion module; The output photocurrents of the first PIN and the second PIN are equal; the output photocurrent of the second PIN changes linearly with the input voltage; the second transconductance amplifier is used to convert the output photocurrent of the second PIN into an output voltage through the feedback resistor and output it through the output terminal of the second transconductance amplifier.

6. The signal transmission system for a DC voltage transformer according to claim 3, wherein, The output terminal and the inverting input terminal of the first transconductance amplifier are connected through a first capacitor.

7. A signal transmission system for a DC voltage transformer according to claim 3, characterized in that, The voltage-current conversion module further includes: a triode; The output terminal of the first transconductance amplifier is connected to one end of a second resistor, the other end of the second resistor and one end of a third resistor are connected to the gate of the triode; one end of a fourth resistor is connected to the source of the triode; the other end of the third resistor, the other end of the fourth resistor and a first power supply are connected; the drain of the triode is connected to one end of a fifth resistor, the positive electrode of a first LED and the negative electrode of a first diode; the other end of the fifth resistor is connected to a second power supply; the negative electrode of the first LED, the positive electrode of a second LED, the positive electrode of the first diode and the negative electrode of a second diode are connected; the negative electrode of the second LED is connected to the positive electrode of the second diode and is grounded.

8. A signal transmission system for a DC voltage transformer according to claim 5, characterized in that, The output terminal and the inverting input terminal of the second transconductance amplifier are connected through a second capacitor.

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