Optocoupler simulator

Abstract

The invention relates to the technical field of optical couplers, in particular to an optical coupler simulator which comprises a sending module, an isolation transformer and a receiving module, the sending module is used for receiving input signals, generating high-frequency carrier signals and conducting OOK modulation on the input signals, the isolation transformer is connected between a sending end circuit and a receiving end circuit, and the receiving end circuit is connected with the isolation transformer. Electrical isolation and signal transmission are realized through an insulating medium; according to the optical coupler simulator, a high-frequency carrier wave is generated through the LC oscillator, the OOK (on-off keying) modulation technology is adopted, the transmission rate of the optical coupler simulator can reach 25 Mbps, and the low-speed transmission capacity, ranging from 100 Kbps to 1 Mbps, of a traditional optical coupler is greatly exceeded.

Description

Technical Field

[0001] The present invention relates to the technical field of optical couplers, and more particularly to an optical coupler simulator. Background Art

[0002] In modern electronic systems and communication systems, signal isolation technology plays a vital role in protecting the integrity of circuits and signals. Signal isolation can transmit signals between two electrical systems without conducting current, thereby protecting low-voltage signal equipment in high-voltage and strong interference environments. Optocouplers (optical isolators) are common devices for signal isolation, and are mainly used in industrial automation, power control, medical equipment, communication systems and other occasions with high requirements for isolation protection.

[0003] Traditional optocouplers are usually composed of light-emitting diodes (LEDs) and photosensitive elements (such as phototransistors). The working principle is that the input electrical signal is converted into an optical signal through the LED. After the optical signal passes through a transparent insulating material (such as epoxy resin), it is received by the photosensitive element and then converted into an electrical signal for output. Since the insulating material between the LED and the photosensitive element effectively blocks the DC current, electrical isolation is achieved.

[0004] Although optocouplers are widely used in isolating signal transmission, optocouplers have significant LED aging problems. The luminous efficiency of LEDs will gradually decrease with working time, and its brightness attenuation will directly lead to a weakening of the amplitude of the transmitted signal, affecting the signal quality.

[0005] In addition, the transparent insulating materials (such as epoxy resin) used in traditional optical couplers tend to become cloudy or discolored over a long period of time, which can hinder the transmission of optical signals, attenuate the signals at the receiving end, and affect the overall performance of the isolator.

[0006] With the rapid development of modern electronic devices, the transmission rate requirements for isolators are gradually increasing, but traditional optocouplers are difficult to meet the needs of high-frequency applications with data transmission rates exceeding 1Mbps.

[0007] The electrical isolation of traditional optocouplers mainly relies on the insulation capacity of materials such as epoxy resin, but these materials have limited withstand voltage characteristics and usually cannot provide sufficient isolation voltage. In some high-voltage occasions, such as power systems and industrial control, the isolation voltage capacity of traditional optocouplers is insufficient and cannot effectively protect low-voltage side equipment. In addition, traditional optocouplers have weak adaptability to common-mode transient immunity (CMTI), making it difficult to achieve stable signal isolation in a strong electromagnetic interference environment.

[0008] In addition to traditional optocouplers, there are some alternative isolation methods, such as magnetic coupling isolators and capacitive coupling isolators. Magnetic coupling isolators achieve isolation through magnetic coupling of transformers and have high voltage resistance and anti-interference performance. However, they are usually suitable for low-frequency applications and are not ideal for high-frequency and high-speed data transmission.

[0009] Capacitively coupled isolators use capacitors to transmit high-frequency signals at both ends, but their isolation voltage is usually not high and they are easily affected by electromagnetic interference in high-interference environments.

[0010] With the rapid development of 5G communications, industrial Internet of Things, smart grids and other fields, the application demand for signal isolation devices at higher frequencies, higher data rates, and higher isolation voltages is increasing. However, traditional optocouplers and other existing isolation technologies are difficult to simultaneously meet multiple requirements such as high isolation voltage, low pulse width distortion (PWD), high-speed transmission, and strong anti-interference capabilities. Therefore, the market urgently needs a new type of optical coupling isolation technology to solve the above problems. Summary of the invention

[0011] In view of the deficiencies in the prior art, the purpose of the present invention is to provide an optocoupler simulator that uses electromagnetic coupling to isolate signals, and has the characteristics of high data transmission rate, high isolation voltage and strong anti-electromagnetic interference (EMI) capability.

[0012] To achieve the above object, the present invention provides the following technical solutions: An optocoupler simulator, comprising: A sending module, used to receive an input signal and generate a high-frequency carrier signal, and perform OOK modulation on the input signal; An isolation transformer, connected between the transmitting end circuit and the receiving end circuit, and realizing electrical isolation and signal transmission through an insulating medium; The receiving module is used to receive the modulated signal transmitted by the isolation transformer and demodulate it to output a restored signal.

[0013] The present invention is further configured as follows: the sending module includes an LC oscillator and a negative resistance compensation circuit, The negative resistance compensation circuit is composed of a PMOS cross-coupling structure and is used to compensate for the parasitic resistance in the LC oscillator to maintain the stability of high-frequency oscillation.

[0014] The present invention is further configured as follows: the receiving module comprises: Demodulation module (DEMODE), used to demodulate the received OOK modulated signal; Hysteresis comparator (CMP), used to stabilize the output of the demodulated signal; Output buffer (Buffer), used to drive the demodulated signal to output to the load; Low dropout linear regulator (LDO), used to provide regulated power supply; Low frequency oscillator (OSC), used to generate oscillation signal; The mathematical circuit module is used to control the switching of the load capacitor of the receiving module to adjust the slight fluctuation of the oscillation frequency at the center frequency to reduce electromagnetic interference.

[0015] The present invention is further configured as follows: the insulating medium is SiO2, which is used to achieve high voltage electrical isolation.

[0016] Compared with the shortcomings of the prior art, the beneficial effects of the present invention are: The present invention generates a high-frequency carrier through an LC oscillator and adopts OOK (on-off keying) modulation technology, so that the transmission rate of the optical coupler simulator can reach 25Mbps, which greatly exceeds the low-speed transmission capacity of 100Kbps to 1Mbps of the traditional optical coupler; The present invention adopts SiO2 as the isolation medium and provides excellent isolation performance through the material with high dielectric constant, and the isolation voltage can reach 3.75KVrms.

[0017] The electromagnetic coupling and high-frequency oscillator design are adopted to avoid the problems of LED aging and insulation material turbidity of traditional optocouplers, and have a longer service life and more stable performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic diagram of a module of the present invention; Figure 2 It is a partial circuit diagram of the module of the present invention; Figure 3 This is the waveform diagram of OOK modulation. DETAILED DESCRIPTION

[0019] Reference Figures 1 to 3 The embodiments of the present invention are further described.

[0020] An optocoupler simulator comprises a transmitting module TX, an isolation transformer and a receiving module RX.

[0021] The transmitting module TX is used to receive input signals, generate high-frequency carriers, and perform OOK modulation on the input signals. Its core components include an LC oscillator and a negative resistance compensation circuit.

[0022] The LC oscillator is used to generate a 1.5GHz high frequency carrier. Its design principle and component connection relationship are as follows: The inductor Ld and the capacitors (C1, C2, C3) form the resonant circuit of the LC oscillator.

[0023] The two ends of the inductor Ld are connected to the capacitors C1 and C2 respectively to form an oscillation circuit. The other end of the capacitor C1 is connected to the drain of the PMOS transistor MP2 , and the other end of the capacitor C2 is connected to the drain of the PMOS transistor MP3 .

[0024] The negative resistance compensation circuit is composed of a PMOS cross-coupling structure, which is used to compensate for the parasitic resistance in the LC network and ensure the stability of high-frequency oscillation.

[0025] Sources of the PMOS transistors MP2 and MP3 are both connected to the drain of the NMOS transistor MN1 , the source of the NMOS transistor MN1 is grounded, and the gate of the NMOS transistor MN1 is connected to the input signal EN1 .

[0026] The gate of the PMOS transistor MP2 is connected to the drain of the PMOS transistor MP3, and the gate of the PMOS transistor MP3 is connected to the drain of the PMOS transistor MP2, thereby realizing a cross-coupling structure. This cross-coupling structure can provide a negative resistance, thereby offsetting the loss caused by the parasitic resistance of the LC oscillator and maintaining the stability of the oscillation.

[0027] Negative resistance principle: The negative resistance generated by the cross-coupling structure is equivalent to -1 / gm (where gm is the transconductance of the PMOS tube), which can compensate for the parasitic resistance of the oscillator, so that the oscillator remains stable under high frequency conditions.

[0028] The PMOS transistor MP1 is used as a bias transistor to adjust the working state of the negative resistance compensation circuit.

[0029] The source of the PMOS transistor MP3 is connected to VDD, and the drain is connected to a common connection node of the PMOS transistor MP2 and the PMOS transistor MP3 for providing a bias current.

[0030] The gate of the PMOS transistor MP1 is connected to a stable reference voltage Vref to control the bias current of the circuit and ensure the start-up and stability of the LC oscillator.

[0031] The main principle of the oscillator is to use LC resonance. The coil inductance of the transformer is L, and the resonant capacitance is C1=C3=C2=C, so the angular frequency of the resonance is The quality factor of the inductor is ,so ,Right now

[0032] Rs is the series resistance, which indicates the equivalent series resistance of the actual inductor coil, which is usually the energy loss caused by the material resistance of the inductor coil; Rp is the equivalent parallel resistance, which indicates the equivalent parallel loss resistance of the LC oscillator. It reflects the energy loss of the oscillator. If this value is large, it means that the energy loss of the oscillator is small; Q is the quality factor, which indicates the degree of "low loss" of the LC oscillator. The larger the Q value, the smaller the loss of the oscillator and the better the oscillation characteristics. L is the inductance value.

[0033] Due to the existence of Rp, the resonant network will have energy loss, so a negative resistor -Rp and a positive resistor must be connected in parallel to compensate for the energy loss of the resistor. Commonly used negative resistance pairs include PMOS and NMOS negative resistance pairs. In this circuit, we use a PMOS cross-coupling structure to make a negative resistance pair. The structure is simple and the negative resistance is , in order to maintain oscillation, it must be satisfied

[0034] Generally, in order to maintain some design redundancy, Rp is made , which helps to fully offset the influence of the inductor parasitic resistance and maintain the high-frequency oscillation of the circuit.

[0035] At the same time, the receiving module RX has an oscillator of about 10MHz and a small 16-bit digital logic block to switch the size of the capacitor mounted on the receiving end. According to the formula The angular frequency can be obtained , so that the frequency of the oscillator fluctuates at the center frequency, with an approximate fluctuation range of 40MHz. This is mainly to reduce the electromagnetic interference EMI of the circuit under high-frequency working conditions. The receiving module RX then demodulates the high-frequency modulated signal and outputs it to VOUT.

[0036] The transmitting module performs on-off keying OOK modulation on the input signal, that is, the output of the LC oscillator is turned on when the signal is "1", and the output of the oscillator is turned off when the signal is "0". This modulated signal is output through the differential output terminals TX_indp and TX_indn and transmitted to the isolation transformer.

[0037] The isolation transformer is connected between the sending module and the receiving module to achieve electrical isolation through electromagnetic coupling. The transformer uses a high dielectric constant. The material achieves 3.75KVrms high-voltage isolation and improves the ability to resist electromagnetic interference.

[0038] The differential outputs TX_indp and TX_indn of the transmitter are connected to the input of the transformer to realize differential transmission of the modulated signal. This differential transmission method not only enhances the ability to resist common-mode interference, but also ensures the stability of signal transmission.

[0039] The receiving module is used to receive the differential modulation signal transmitted through the isolation transformer and demodulate it into the original input signal. The key components of the receiving module include the demodulation module, hysteresis comparator, output buffer, low frequency oscillator and mathematical circuit module.

[0040] The demodulation module DEMODE receives the differential signal (RX_indp and RX_indn) from the output end of the transformer and inputs the differential signal to the demodulation module. The demodulation module restores the differential OOK modulated signal to the original digital signal, and the demodulated output signal is sent to the subsequent comparator.

[0041] The differential signal output by the demodulation module DEMODE is sent to the positive and negative input terminals of the hysteresis comparator CMP. The hysteresis comparator has a certain hysteresis characteristic, which can suppress small fluctuations in the signal, avoid signal misjudgment, and make the output signal stable. The differential output of the hysteresis comparator CMP is further amplified to drive the output buffer.

[0042] The output buffer Buffer is located after the hysteresis comparator CMP and is used to provide driving capability to drive the demodulated signal to the external load. The differential signal output by the buffer can effectively resist external interference and ensure the integrity of the output signal.

[0043] The low-dropout linear regulator LDO is used for power regulation of the receiving module to provide a stable DC voltage. The low-dropout linear regulator LDO outputs a stable voltage, allowing the demodulation, comparison and output buffer circuits to work stably without being affected by power supply fluctuations.

[0044] The receiving module includes a low-frequency oscillator OSC with an operating frequency of about 10MHz. The oscillator controls the switching of load capacitors so that the oscillation frequency fluctuates slightly around the center frequency to reduce electromagnetic interference. The oscillator controls the switching of the load capacitors at the receiving end through a mathematical circuit module. Multiple load capacitors (such as CS1 to CSn) are coupled to the oscillator through switches, and different capacitor combinations are switched to achieve fine adjustments to the oscillation frequency.

[0045] The mathematical circuit module controls the switching state of multiple load capacitors through digital logic. The control signal is driven by the low-frequency signal of the oscillator, which switches the capacitor near the center frequency and produces a small range of frequency fluctuations. This frequency fine-tuning design makes the spectrum distribution of the oscillation signal wider, thereby reducing electromagnetic interference (EMI) and enhancing the anti-interference ability of the receiving end.

[0046] The main performance comparison table of this digital isolation optocoupler simulator with traditional optocouplers is as follows:

[0047] This design can achieve data transmission of up to 25Mbps, with pulse width distortion PWD less than 17ns, propagation delay tPHL and tPLH up to 52ns, isolation voltage up to 3.75KVrms, and CMTI as low as ±125KV / us. These performance indicators have significant advantages over traditional optocouplers.

[0048] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Common changes and substitutions made by those skilled in the art within the scope of the technical solution of the present invention should be included in the protection scope of the present invention.

Claims

1. An optocoupler simulator, characterized in that: include: A sending module, used to receive an input signal and generate a high-frequency carrier signal, and perform OOK modulation on the input signal; An isolation transformer, connected between the transmitting end circuit and the receiving end circuit, and realizing electrical isolation and signal transmission through an insulating medium; The receiving module is used to receive the modulated signal transmitted by the isolation transformer and demodulate it to output a restored signal.

2. An optocoupler simulator according to claim 1, characterized in that: The sending module includes an LC oscillator and a negative resistance compensation circuit. The negative resistance compensation circuit is composed of a PMOS cross-coupling structure and is used to compensate for the parasitic resistance in the LC oscillator to maintain the stability of high-frequency oscillation.

3. An optocoupler simulator according to claim 2, characterized in that: The receiving module comprises: Demodulation module (DEMODE), used to demodulate the received OOK modulated signal; Hysteresis comparator (CMP), used to stabilize the output of the demodulated signal; Output buffer (Buffer), used to drive the demodulated signal to output to the load; Low dropout linear regulator (LDO), used to provide regulated power supply; Low frequency oscillator (OSC), used to generate oscillation signal; The mathematical circuit module is used to control the switching of the load capacitor of the receiving module to adjust the slight fluctuation of the oscillation frequency at the center frequency to reduce electromagnetic interference.

4. An optocoupler simulator according to claim 2, characterized in that: The insulating medium is SiO2, which is used to achieve high voltage electrical isolation.

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