A full-wave rectifier circuit

Abstract

This invention relates to the field of electronic circuits and discloses a full-wave rectifier circuit, including a first operational amplifier, a second operational amplifier, an optocoupler, a resistor, an inductor, and a detection device. The same-polarity power supply terminals of the first and second operational amplifiers are connected in parallel. The output terminal of the first operational amplifier is connected to one end of an internal LED of the optocoupler, and the other end of the LED is connected to the output terminal of the second operational amplifier. The photodetector of the optocoupler and the inductor are connected in series. The power supply provides power to the first and second operational amplifiers through the resistor. The detection port of the detection device is connected in parallel with the first resistor, and the detection device outputs a full-wave rectified signal. The photodetector of the optocoupler and the inductor are connected in series to a second power supply. This invention's full-wave rectifier circuit is simple, eliminates the need for rectifier diodes, and can accurately control the threshold of the rectifier circuit. It not only achieves effective detection of DC leakage current but also isolates the main circuit from the inductor acting as the coil through the optocoupler.

Description

Technical Field

[0001] This invention relates to a full-wave rectifier circuit, and more particularly to a full-wave rectifier circuit for small-signal processing. Background Technology

[0002] The process of converting alternating positive and negative voltages into unipolar voltages is called rectification. Full-wave rectifier circuits generally refer to two types: one is used in DC power supplies, such as... Figure 1-1 As shown, Figure 1-1 The circuit shown is a full-wave rectifier and filter circuit. It cannot be used directly for mains power rectification. It usually needs to go through the center tap winding of the secondary side of transformer B1 to obtain two sets of voltages U1 and U2 with the same voltage but opposite phase before it can be used. Figure 1-2 It is a bridge rectifier circuit in a full-wave rectifier circuit, also called a full-bridge rectifier circuit. If capacitor C L When not connected, its output waveform is pulsating DC, which is the load R. L The waveform on the screen; capacitor C L After connection, its output waveform is a relatively smooth pulsating DC current.

[0003] Another type of circuit is used in voltage signal processing circuits. The book *Fundamentals of Analog Electronics*, edited by Tong Shibai, published in 1988 (ISBN 7-04-000868-8 / TN•53), shows a full-wave precision rectifier circuit in Figure 9-31 on page 575. This figure is cited here as the basis for this application. Figure 1-3 The rectifier circuit consists of two parts: a half-wave precision rectifier circuit and an inverting summing circuit. This circuit has an inverting input and low input impedance. To address the low input impedance, Figure 9-32 on page 576 of the book shows a full-wave precision rectifier circuit with high input impedance; this figure is cited here as the basis for this application. Figure 1-4 .

[0004] Figure 1-3 and Figure 1-4 The circuit uses two operational amplifiers for full-wave precision rectification. Operational amplifier A1 forms a half-wave precision rectification circuit, and operational amplifier A2 forms a summing circuit. The circuit structure is complex. Diodes are used in the peripheral circuit of operational amplifier A1, and all of them realize full-wave rectification circuits at the signal level.

[0005] In addition, some protection circuits also use similar rectifier circuits used in DC power supplies, such as the DRV411 integrated circuit produced by Texas Instruments. Figures 56 and 57 in the 2013 datasheet of this circuit show this circuit. Figure 56 is referenced here for this application. Figure 1-5As can be seen, diodes D1, D2, D3, and D4 form a protection circuit consistent with the full-wave rectifier circuit. When the compensation coil is overloaded, it does indeed operate in full-wave rectification mode.

[0006] Currently, with the reduction in cost, improvement in efficiency, and enhanced reliability of switching power supplies, DC power supply is becoming a trend. Previously, DC power supply was not widely adopted due to its inability to solve a series of problems, such as long-distance transmission, while AC power supply became the core of industry. At present, DC power supply appears to have lower construction and operating costs, no power factor compensation, and is extremely easy to connect to the grid. Furthermore, underground and submarine power supply is easier to implement, and it is also easier to realize distributed grid-connected solar power generation for individual households, making it likely to become the mainstream in the future. However, leakage protection remains a challenge in DC power supply.

[0007] DC-powered residual current devices (RCDs) differ from AC-powered RCDs. AC RCDs typically operate as follows: the live and neutral wires pass through a high-permeability toroidal core (early models also used iron cores). The live and neutral wires are treated as a parallel line within the RCD. If a leakage current occurs, a difference in current exists between the live and neutral wires, and the current in the parallel line is no longer zero. This current still has the same frequency as the AC current. An induction coil with 1000 to 3000 turns is wound around the toroidal core. This induction coil induces a voltage, essentially a voltage formed across a large-resistance load resistor by a weak induced current. This voltage drives the control unit to quickly disconnect the switch (trip). The leakage current threshold is typically 20–30 mA. The high-permeability toroidal core, the induction coil, and the parallel connection of the live and neutral wires constitute a transformer.

[0008] The circuit of the AC leakage current protector cannot be used to design a leakage current protector for a DC power supply system because DC current cannot be directly transmitted through a transformer, meaning that the DC leakage current cannot be directly detected by a transformer using the above-mentioned technical solution.

[0009] DC residual current devices (RCDs) often employ fluxgate current sensors in conjunction with the control unit to trip the circuit when the leakage current exceeds a threshold. This makes the circuit much more complex, while the market expects the cost to be no higher than that of AC RCDs. Currently, DC RCDs are still more expensive than AC RCDs, and their static power consumption is also far higher.

[0010] The full-wave rectifier circuit in the fluxgate current sensor is also part of the cost. Traditional circuits are complex and have many components. Consequently, under the same component conditions, the static operating current of the circuit is also large.

[0011] Fluxgate current sensors can detect weak direct current. Taking its application in a DC leakage current protector as an example, its working principle is briefly described: A toroidal magnetic core with an air gap is placed in the air gap, containing a detection magnetic core with high permeability that is easily saturated. A detection coil is wound around the detection core. A symmetrical high-frequency signal generated by a local oscillator is applied to the detection coil. In each cycle, the detection core saturates at the top of the positive and negative half-cycles, respectively. The detection coil is part of a phase detector. When DC current passes through the toroidal magnetic core, it generates magnetic flux. This flux passes through the detection core, causing the detection coil to saturate and deflect during the positive and negative half-cycles, respectively. The phase detector outputs the corresponding DC signal. This means that the measurement of a weak magnetic field is based on the nonlinear relationship between the magnetic flux density of the high-permeability magnetic core under the saturation excitation of an alternating magnetic field and the magnetic field strength. This physical phenomenon acts like a "gate" for the measured environment's magnetic field; passing through this "gate," the corresponding magnetic flux is modulated, generating an induced electromotive force. This phenomenon is used to measure the magnetic field generated by an electric current, thereby indirectly achieving the purpose of measuring the current.

[0012] DC residual current devices (RCDs) have their own characteristics. For example, AC RCDs can achieve self-powered operation, generally using capacitor voltage reduction, which is essentially a constant current power supply, similar to Class A power supplies. If DC RCDs use DC bus self-powered operation, the losses are relatively large, and using switching power supplies results in poor reliability and high cost. Moreover, DC power supply buses often have multiple power sources, switching between solar, wind, and battery power. DC self-powered operation is much more difficult than AC self-powered operation. Therefore, the industry mostly adopts centralized power supply for DC RCDs, and their output signals are also collected and processed by an intelligent control center to provide the optimal energy-saving operating mode and achieve intelligent optimal power supply.

[0013] Because DC leakage current protection devices mostly use centralized power supply, there is a need for DC leakage current protection devices with higher isolation, especially the full-wave rectifier circuit in the control section. New solutions are needed to meet the ever-evolving technological requirements. Summary of the Invention

[0014] In view of this, the technical problem to be solved by the present invention is to provide a full-wave rectifier circuit with isolation function, which is simple, does not use diodes for rectification, and can control the threshold of the rectifier circuit more accurately.

[0015] The technical solution of the present invention to solve the above-mentioned technical problems is as follows:

[0016] A full-wave rectifier circuit includes: a first operational amplifier, a second operational amplifier, a first optocoupler, an inductor, resistors, and a detection device. The same-polarity power supply terminals of the first and second operational amplifiers are connected in parallel. The output terminal of the first operational amplifier is connected to one end of an internal light emitter of the first optocoupler, and the other end of the internal light emitter is connected to the output terminal of the second operational amplifier. The light receiver of the first optocoupler and the inductor are connected in series. The resistors are connected to the power supply terminals of the first and second operational amplifiers respectively. A first power supply powers the first and second operational amplifiers through the resistors. The light receiver and the inductor of the first optocoupler are connected in series to the second power supply. The detection port of the detection device is connected in parallel with the resistors, and the detection device is used to output a full-wave rectified signal.

[0017] Preferably, the input terminal of the first operational amplifier is used to connect to the input voltage signal; the input terminal of the second operational amplifier is used to connect to the reference voltage source.

[0018] Preferably, the full-wave rectifier circuit further includes a second optocoupler, which is connected in parallel with the first optocoupler in opposite polarities. The collector of the photodetector in the second optocoupler is connected to the emitter of the photodetector in the first optocoupler, and the emitter of the photodetector in the second optocoupler is connected to the collector of the photodetector in the first optocoupler. The anode of the light emitter in the second optocoupler is connected to the cathode of the light emitter in the first optocoupler, and the cathode of the light emitter in the second optocoupler is connected to the anode of the light emitter in the first optocoupler.

[0019] Preferably, the detection device is a transistor, with the emitter and base of the transistor serving as detection ports. The emitter of the transistor is connected to the first end of the resistor, and the base of the transistor is connected to the second end of the resistor.

[0020] Preferably, the detection device is an operational amplifier, with the inverting input terminal and the power supply terminal of the operational amplifier serving as detection ports. The inverting input terminal of the operational amplifier is connected to the second end of the resistor, and the power supply terminal of the operational amplifier is connected to the first end of the resistor.

[0021] Preferably, the detection device is a comparator, with the inverting input terminal and the power supply terminal of the comparator serving as detection ports. The inverting input terminal of the comparator is connected to the second terminal of the resistor, and the power supply terminal of the comparator is connected to the first terminal of the resistor.

[0022] Preferably, the second power supply is the same as the first power supply, or the second power supply is a different power supply from the first power supply.

[0023] The present invention also provides a full-wave rectifier circuit, comprising: a first operational amplifier, a second operational amplifier, a first optocoupler, an inductor, a constant current source, and a detection device. The same-polarity power supply terminals of the first and second operational amplifiers are connected in parallel. The output terminal of the first operational amplifier is connected to one end of an internal light emitter of the first optocoupler, and the other end of the internal light emitter of the first optocoupler is connected to the output terminal of the second operational amplifier. The light receiver of the first optocoupler and the inductor are connected in series. The constant current source is connected to the power supply terminals of the first and second operational amplifiers respectively. A first power supply supplies power to the first and second operational amplifiers through the constant current source. The light receiver of the first optocoupler and the inductor are connected in series to the second power supply. The detection port of the detection device is connected in parallel with the constant current source, and the detection device is used to output a full-wave rectified signal.

[0024] Preferably, the full-wave rectifier circuit further includes a second optocoupler, which is connected in parallel with the first optocoupler in opposite polarities. The collector of the photodetector in the second optocoupler is connected to the emitter of the photodetector in the first optocoupler, and the emitter of the photodetector in the second optocoupler is connected to the collector of the photodetector in the first optocoupler. The anode of the light emitter in the second optocoupler is connected to the cathode of the light emitter in the first optocoupler, and the cathode of the light emitter in the second optocoupler is connected to the anode of the light emitter in the first optocoupler.

[0025] Preferably, the detection device is a transistor, with the emitter and base of the transistor serving as detection ports. The emitter of the transistor is connected to the first end of the constant current source, and the base of the transistor is connected to the second end of the constant current source.

[0026] Preferably, the detection device is an operational amplifier or comparator, with the inverting input terminal and power supply terminal of the operational amplifier or comparator serving as the detection port. The inverting input terminal of the operational amplifier or comparator is connected to the second terminal of the constant current source, and the power supply terminal of the operational amplifier or comparator is connected to the first terminal of the constant current source.

[0027] Preferably, the current of the constant current source is above the total current, which is the sum of the quiescent operating current of the first operational amplifier, the quiescent operating current of the second operational amplifier, and the leakage current threshold divided by the number of turns of the inductor coil.

[0028] The beneficial effects of the full-wave rectifier circuit of this invention are as follows:

[0029] The full-wave rectifier circuit of this invention is simple and can accurately control the threshold of the rectifier circuit without the need for rectifier diodes. It not only achieves effective detection of DC leakage current, but also isolates the main circuit from the first inductor coil that acts as the coil through optocoupler. Because the isolation capacitor of the optocoupler is less than 1pF, the impact on centralized power supply equipment and intelligent control center is very weak when hundreds of products are working at the same time. Moreover, this invention can also effectively detect high-frequency high-order harmonic leakage current that has potential hazards, and it is low in cost. Attached Figure Description

[0030] Figure 1-1 This is a diagram of an existing full-wave rectifier circuit used in DC power supplies;

[0031] Figure 1-2 This is a diagram of an existing bridge rectifier circuit used in DC power supplies;

[0032] Figure 1-3 The circuit diagram for a full-wave precision rectifier composed of two existing operational amplifiers is shown.

[0033] Figure 1-4 The circuit diagram for a high-input-resistance full-wave precision rectifier circuit composed of two operational amplifiers is shown.

[0034] Figure 1-5 The circuit diagram for the existing protection circuit operating in full-wave rectification mode;

[0035] Figure 2 This is a schematic diagram of the full-wave rectifier circuit according to the first embodiment of the present invention;

[0036] Figure 2-1 This is a schematic diagram of another example of the full-wave rectifier circuit according to the first embodiment of the present invention;

[0037] Figure 2-2 This is a schematic diagram of a second example of the full-wave rectifier circuit according to the first embodiment of the present invention;

[0038] Figure 3 This is a schematic diagram of the full-wave rectifier circuit according to the second embodiment of the present invention;

[0039] Figures 4-1 to 4-7 This is a schematic diagram of the constant current source in the full-wave rectifier circuit of the second embodiment of the present invention;

[0040] Figure 5 This is a schematic diagram of another example of the full-wave rectifier circuit according to the second embodiment of the present invention;

[0041] Figure 6 This is a schematic diagram of the full-wave rectifier circuit according to the third embodiment of the present invention;

[0042] Figure 6-1 Schematic diagram of a constant current source to replace resistor R;

[0043] Figure 7 This is a schematic diagram of the full-wave rectifier circuit according to the fourth embodiment of the present invention;

[0044] Figure 8 This is a schematic diagram of the full-wave rectifier circuit according to the fifth embodiment of the present invention. Detailed Implementation

[0045] To enable those skilled in the art to more easily understand the present invention, the present invention will be described below in conjunction with specific embodiments.

[0046] First Embodiment

[0047] Please see Figure 2 , Figure 2 This is a schematic diagram of a full-wave rectifier circuit according to a first embodiment of the present invention, used for small signal processing. The full-wave rectifier circuit of this embodiment includes: a first operational amplifier A1, a second operational amplifier A2, a first optocoupler U1, an inductor L, a resistor R, and a detection device Q. The input terminal of the first operational amplifier A1 is connected to the input voltage signal, and the output terminal of the first operational amplifier A1 is connected to one end of the internal light-emitting diode of the first optocoupler U1, which is the cathode of the light-emitting diode. The positive power supply terminal a+ of the first operational amplifier is connected to the positive power supply terminal b+ of the second operational amplifier A2, and the negative power supply terminal a- of the first operational amplifier and the negative power supply terminal b- of the second operational amplifier A2 are connected. This can be simply referred to as: the same-polarity power supply terminals of the first and second operational amplifiers are connected in parallel. The input terminal of the second operational amplifier A2 is connected to a reference voltage source, and the output terminal of the second operational amplifier A2 is connected to the other end of the internal light-emitting diode of the first optocoupler U1, which is the anode of the light-emitting diode. The negative power supply terminal b- of the second operational amplifier A2 is connected to the negative power supply VEE or ground. The first end of the resistor R is used for... The first optocoupler U1 is connected to the power supply VCC. The second end of the resistor R is connected to the positive power supply terminal a+ of the first operational amplifier A1 and the positive power supply terminal b+ of the second operational amplifier A2. The power supply VCC supplies power to the first operational amplifier A1 and the second operational amplifier A2 through the resistor R. The two detection ports of the detection device are connected in parallel across the two ends of the resistor R. In this embodiment, the detection device is a transistor Q, which is a PNP transistor. The emitter and base of the transistor Q serve as detection ports. The emitter of the transistor Q is connected to the first end of the resistor R, and the base of the transistor Q is connected to the second end of the resistor R. The collector of the transistor Q is used to output the full-wave rectified signal after full-wave rectification of the input voltage signal. The photodetector of the first optocoupler U1 and the inductor L are connected in series to the second power supply.

[0048] The working principle of the full-wave rectifier circuit in this embodiment is as follows:

[0049] The first operational amplifier A1, the second operational amplifier A2, and the first optocoupler U1 are referred to as operational amplifier A1, operational amplifier A2, and optocoupler U1 in this embodiment. To facilitate understanding of its working principle, the application of this invention in a DC leakage current protector is used as an example for explanation. The input terminal of operational amplifier A1 is connected to the input voltage signal, specifically to the output terminal of the phase detector that forms the fluxgate in the DC leakage current protector. When the non-inverting input terminal of operational amplifier A2 is connected to a reference voltage source, operational amplifier A2 forms a voltage follower, artificially dividing the single voltage into two voltages. The voltage of the reference voltage source can be any voltage value between the voltage of the positive power supply terminal a+ and the voltage of the negative power supply terminal a-. Commonly, when the negative power supply terminal a- is grounded, i.e., when operating with a single voltage, the reference voltage of the reference voltage source is 2.5V or 1.25V, thus making operational amplifier A2 output a constant DC voltage. If the negative power supply terminal a- is a negative voltage symmetrical to the positive power supply terminal a+, in order to save costs, the non-inverting input terminal of operational amplifier A2 is directly connected to ground, i.e., the reference voltage source is generally 0V, i.e., the same voltage as ground GND. In this case, operational amplifier A2 can be omitted. Figure 2 The anode of optocoupler U1 can be directly grounded. This invention focuses on the single-power-supply scenario and does not focus on the high-cost dual-power-supply method.

[0050] If an inductor L is directly connected between the outputs of operational amplifiers A1 and A2, the current in inductor L can flow bidirectionally. However, this invention connects the inductor L via optocoupler U1, thus eliminating this bidirectional current flow. This is well-suited for DC power supply systems. The principle is briefly described as follows: In DC power supply, regardless of whether the ground is at the intermediate potential, positive, or negative terminal, the leakage current at the user terminal is unidirectional, consistent with the direction of current flow when the appliance is powered. Of course, if other high-voltage power sources inject current into the DC power grid, the current will be reversed, but the protection devices of those high-voltage sources will activate.

[0051] Because leakage current in a DC power grid is unidirectional, the circuit design must ensure that the operational amplifier A1 outputs a low level when leakage current occurs. When the DC leakage current protector experiences leakage, the phase detector of the fluxgate outputs a differential voltage. This differential voltage is amplified by the operational amplifier A1, resulting in a low-level output. Current flows through the LED inside the optocoupler U1 and is injected into the output of the operational amplifier A1. Current is generated in the photodetector inside the optocoupler U1. The ratio of these two currents is the current transfer ratio (CTR) of the optocoupler. CTR is a variable; different currents flowing through the LED will change the CTR. The current generated in the photodetector inside the optocoupler U1 is also the current I in the inductor L. LThe inductor L is a coil with a fixed number of turns. The magnetic flux it produces is opposite to the magnetic flux produced by the parallel DC power supply when leakage occurs. If the gain of the operational amplifier A1 is high enough, the following equation appears after the entire circuit is in closed-loop operation:

[0052] Leakage current = n × I L ……………………Formula (1)

[0053] Wherein, leakage current is the differential current in the parallel line of DC power supply, n is the number of turns of inductor L, and I L Let I be the current in inductor L. This formula is derived from the Ampere-turn balance law, which states that the parallel line of the DC power supply is considered as one turn. The magnetic flux it produces is largely canceled out by the reverse magnetic flux produced by the n turns of inductor L. The remaining magnetic flux is detected by the phase detector circuit of the fluxgate, which outputs a difference voltage proportional to the remaining magnetic flux. This voltage is extremely weak, and after being amplified in open loop by operational amplifier A1, it generates a current I in inductor L. L The product of this current and the number of turns n is the n×I in the above formula. L That is, the current I in the inductor L. L It is always equal to the leakage current divided by the number of turns of the inductor L.

[0054] From the above analysis, it can be seen that I was measured. L This will reveal the magnitude of the leakage current. If you want to improve the efficiency of I... L To improve measurement accuracy, simply increase the open-loop gain of op-amp A1. However, excessively high open-loop gain of op-amp A1 can cause the circuit to self-oscillate, leading to loss of its inherent function. Conversely, by setting a leakage current threshold and dividing it by the number of turns of inductor L, the current I in inductor L can be obtained. L The threshold. If the optocoupler U1 is a linear optocoupler, then its primary current is also a fixed value at this moment. As mentioned earlier, the CTR changes with the different currents flowing through the emitter of a normal optocoupler. However, with the advancement of technology, when the current flowing through the emitter is fixed at a certain value, the consistency of its CTR is also very high, that is, the output current of the receiver is also fixed. Conversely, when the output current of the receiver is set to a threshold, the current flowing through the emitter is also a corresponding fixed value.

[0055] Traditional detection of current I in inductor L L The method involves inserting a low-resistance, high-precision resistor (referred to as a sampling resistor) in series with the inductor L and optocoupler U1. By measuring the voltage across this resistor, the current I in the inductor L can be determined. LIf the current exceeds a certain value, i.e., the voltage across the sampling resistor exceeds a certain value, other circuits will trip the DC leakage current protector's trip switch or relay, cutting off the power supply and protecting the user's safety. Detecting the voltage across the sampling resistor requires an operational amplifier or comparator, as well as a relatively precise rectifier circuit, making the circuit more complex and negating the isolation function of the optocoupler U1.

[0056] In this implementation, the current I in the inductor L L The current flows from top to bottom because op-amp A2 outputs current, while the output terminal, or output pin, of op-amp A1 receives and sinks current, and this current is equal to I. L Divide by CTR, denoted as I CTR Power supply V CC The supply current flows through resistor R, into the positive power supply terminal b+ of operational amplifier A2, and out from the output terminal of operational amplifier A2. Simultaneously, it flows into the other end of inductor L (the right end), out from the left end of inductor L, and into the output terminal of operational amplifier A1. It then flows out from the negative power supply terminal a- of operational amplifier A1 and back to the power supply V. EE The terminals form a circuit. At this point, the current flowing through resistor R is from top to bottom;

[0057] First, choose a suitable value for the resistor R. When the leakage current reaches a certain specified value, the resulting current I... CTR As an increment, a voltage of 0.6V to 0.7V is generated across the resistor R. At this time, the transistor Q turns on, and the collector of the transistor Q outputs a high level.

[0058] Thus, this invention completes small-signal processing, realizing a special small-signal rectifier circuit and a full-wave rectifier circuit at the signal level. The increment of the current flowing through resistor R after rectification is proportional to the detected leakage current. According to international standards, for DC power supply or DC current, the allowable leakage current threshold for some devices is 6mA, and commonly 30mA; Note: For AC power supply, the allowable leakage current threshold is 30mA.

[0059] In this embodiment, operational amplifiers A1 and A2 are two operational amplifiers inside an LM2904 chip, with a static operating nominal value of 1.5mA and a measured actual value of 1.46mA at a working voltage of 6V. The leakage current protection value is set at 30mA. The optocoupler U1 is a PC817A with a CTR between 80% and 160%. The measured CTR is 100% at a primary current of 1mA. The inductor L has 30 turns (n), and the resistor R is 240Ω. The transistor Q is an S9015. To suppress interference, a 100pF high-frequency ceramic capacitor (0805 package NPO capacitor) is connected in parallel across the base and emitter of transistor Q. A single power supply is used. CC 6V, VEE Grounding. The two op-amps are actually the two op-amps inside the LM2904, and their total operating current is 1.46mA. Since they are powered by resistor R, if the op-amps self-oscillate, a capacitor can be connected in parallel between the positive power supply terminal b+ and the negative power supply terminal b- of op-amp A2. Under the premise of not self-oscillation, the capacitance should be as small as possible, so as not to affect the detection of high-frequency leakage current.

[0060] This circuit implementation uses the above parameters and is applied to a DC leakage current protector. A 1.46mA operational amplifier quiescent current flows through a 240Ω resistor R, resulting in a voltage drop of 0.263V. This voltage is applied to the base and emitter of transistor Q, causing transistor Q to remain off-center. When the leakage current is below 30mA, the current I... L Less than 1mA, I CTR The current, combined with the quiescent current of the operational amplifier, is less than 2.46mA. Flowing through the 240Ω resistor R, the resulting voltage drop is less than 0.59V. At this point, according to the PN junction equation, a weak base current flows through the base of transistor Q. After amplification, this forms a slightly larger current at the collector. This current must be sufficient to trigger the trip switch or relay. Alternatively, the negative power supply V can be applied to the collector of transistor Q. EE A resistor is placed at the terminal to absorb the current appropriately, increasing the reliability of the circuit; when the leakage current is above 30mA, the current I... L Greater than 1mA, I CTR When combined with the quiescent current of the operational amplifier, it exceeds 2.46mA. Flowing through the 240Ω resistor R, the resulting voltage drop is greater than 0.59V. At this point, according to the PN junction equation, a large base current flows through the base of transistor Q. After amplification, an even larger current is formed at the collector. This current is necessary to ensure the trip switch or relay operates, achieving the final goal.

[0061] When using the above parameters, this invention is applicable to DC, but is also compatible with AC applications. Despite the optocoupler's delay being as high as 4µs, it works normally in tests extending from DC to 2.5kHz AC. Leakage current can still be detected under 6kHz AC, but the sensitivity decreases and the phase shifts. The first example tested was used with DC power supply superimposed with AC, and it still worked normally. It should be noted that it only works on one positive half-cycle of AC; it does not work on the negative half-cycle. When leakage occurs, the response is slower, lagging behind by half a cycle of AC.

[0062] When there is no differential current in the parallel circuit, i.e., no leakage current, the current I in the inductor L is... LThe static operating current of the circuit, including the phase detector circuit of the fluxgate, is zero, totaling 4.8mA. The actual power consumption is below 29mW. Even if an operational amplifier and phase detector circuit with a large static operating current are used, the operating current can be easily controlled below 16mA, and the total static power consumption is still below 96mW, or below 0.1W. This is far less than the static power consumption of common high-quality single-phase AC leakage current protection products: 0.23W. Currently, the static power consumption of common high-quality three-phase AC leakage current protection products is 0.40W and above.

[0063] The measured isolation capacitance of optocoupler U1 is 0.57pF. Even if hundreds of products operate simultaneously, the impact on centralized power supply equipment and intelligent control centers is minimal. When lightning surges or electrical fast transient bursts occur in the DC power grid, the impact on the circuit of this invention and connected equipment is extremely negligible due to the optocoupler's isolation capacitance being below 1pF.

[0064] The first embodiment of the present invention uses a full-wave rectifier circuit in a leakage current protector, which not only achieves effective detection of DC leakage current, but also effectively detects high-frequency high-order harmonic leakage current that poses potential hazards, and is low in cost.

[0065] Figure 2-1 Another implementation of Embodiment 1 is shown, with Figure 2 The difference lies in the orientation of the LED in the optocoupler U1 connected between the outputs of operational amplifiers A1 and A2. Specifically, the output of operational amplifier A1 is connected to the anode of the LED, and the output of operational amplifier A2 is connected to the cathode. This achieves the same objective and is another implementation of the principle that "the output of the first operational amplifier A1 is connected to one end of the LED inside the first optocoupler U1, and the output of the second operational amplifier A2 is connected to the other end of the LED inside the first optocoupler U1." Figure 2-1 In the circuit shown, it is designed to ensure that op-amp A1 outputs a high level when leakage current occurs.

[0066] As mentioned earlier, Figure 2 The circuit can only function during one positive half-cycle of the alternating current, and has no effect during the negative half-cycle. When there is a leakage, the response is slow, lagging behind by half a cycle of the alternating current. Figure 2-1 The same problem exists, and Figure 2-2 An improved version of Embodiment 1 is shown, which does not exist. Figure 2 , Figure 2-1 Regarding the issue of only detecting half a cycle of alternating current, Figure 2Alternatively, in the technical solution 2-1, it also includes an optocoupler U2, which is connected in parallel with the optocoupler U1 in opposite polarities as follows: the collector c of the photodetector in optocoupler U2 is connected to the emitter e of the photodetector in optocoupler U1, the emitter e of the photodetector in optocoupler U2 is connected to the collector c of the photodetector in optocoupler U1; the anode of the light emitter in optocoupler U2 is connected to the cathode of the light emitter in optocoupler U1, and the cathode of the light emitter in optocoupler U2 is connected to the anode of the light emitter in optocoupler U1.

[0067] so Figure 2-2 This circuit enables the detection of all positive and negative half-cycles of AC power in any direction of DC. It can function for both the positive and negative half-cycles of AC power. In this case, op-amp A2 can also operate in the inverting amplification mode with op-amp A1. Thus, op-amp A1 and op-amp A2 are equivalent to operating in BTL mode. BTL is an abbreviation for Balanced Transformer Less, which refers to BTL power amplifiers, commonly used in audio power amplifiers. Figure 2-2 The circuit also achieves the invention's objective, and another beneficial effect is its sensitive detection of high-frequency harmonic currents, improving the safety of the leakage current protector. In power supply circuits, due to the widespread use of switching power supplies and various chopper appliances, there are many harmonic components in the power supply current. For example, for 50Hz AC, its 39th harmonic reaches 1950Hz. Traditional leakage current protectors typically have detection coils with over 2000 turns, and household ones typically have 3000 turns. Their distributed capacitance is also large, resulting in significant attenuation of high-frequency harmonics. To prevent false triggering, the circuit filters out high-frequency harmonics. In other words, traditional leakage current protectors have too low sensitivity to high-frequency harmonic leakage currents. We often experience this in our daily lives. When using a laptop power adapter, we often feel a strong electric shock when touching the metal parts of the laptop. This is caused by high-frequency harmonic currents passing through the Y capacitor in the power adapter. Because of the high frequency, it flows more through the skin when passing through the human body, having less impact on the heart. However, over time, it still poses a great danger to the human body. It should be noted that many inferior power adapters or mobile phone chargers, in order to meet the corresponding electromagnetic compatibility standards, have excessively increased the Y capacitor in their internal switching power supply, which greatly increases the high-frequency high-order harmonic leakage current and endangers the user's safety. Figure 2-2 The circuit, which was not tested, can work normally when extended from DC to 4KHz AC.

[0068] Since the voltage drop from the base to the emitter of transistor Q is variable, obeys the PN junction equation, and is related to temperature, reverse saturation current, and the actual base current flowing through it, the circuit will react differently to different leakage currents at different temperatures. The following Example 2 improves this situation.

[0069] Second Embodiment

[0070] Please see Figure 3 , Figure 3 This is a schematic diagram of a full-wave rectifier circuit according to a second embodiment of the present invention. The difference between the full-wave rectifier circuit of this embodiment and the first embodiment is that a constant current source I is used instead of the resistor R in the first embodiment. The first terminal of the constant current source I is connected to the power supply VCC, and the second terminal of the constant current source I is connected to the positive power supply terminal a+ of the first operational amplifier A1 and the positive power supply terminal b+ of the second operational amplifier A2, respectively.

[0071] In this embodiment, the constant current source I can take various forms.

[0072] Please refer to Figure 4-1 , Figure 4-1 This is a schematic diagram of a constant current source implemented using a constant current diode. Pins 1 and 2 correspond to... Figure 3 Pins 1 and 2 of the constant current source I in the circuit. The abbreviation for constant current diode is CRD, which is short for Current Regulative Diode.

[0073] Please refer to Figure 4-2 , Figure 4-2 This is a schematic diagram of a constant current source implemented using a junction field-effect transistor (JFET). Pins 1 and 2 correspond to... Figure 3 Pins 1 and 2 in the diagram. A junction field-effect transistor (JFET) can also be used to implement a constant current source circuit, employing a P-channel design.

[0074] Please refer to Figure 4-3 , Figure 4-3 This is a schematic diagram illustrating the implementation of a constant current source using a junction field-effect transistor (JFET). Adjustment... Figure 4-3 The value of resistor R can be easily changed to alter the constant current value. Its pins 1 and 2 correspond to... Figure 3 Pins 1 and 2 in the diagram. A junction field-effect transistor (JFET) can also be used to implement a constant current source circuit, employing a P-channel design.

[0075] Please refer to Figure 4-4 , Figure 4-4 The schematic diagram shows a classic circuit using two PNP transistors connected as a constant current source. Its output current is approximately:

[0076] …………………………………………Formula (2)

[0077] In the formula, Io is Figure 4-4 The output current is pin 2. UBE is the base-emitter voltage drop of transistor TR202, which is typically around 0.6V for silicon transistors. R201 is the resistance value of resistor R201. This circuit can also be implemented using an NPN transistor.

[0078] When the amplification factor of transistors TR201 and TR202 is large, the value of R202 in the circuit can be larger, thus optimizing the circuit into a two-terminal device for ease of use. For example... Figure 4-5 As shown, its constant current performance is slightly worse than... Figure 4-4 The circuit is [specifically designed / structured]. However, it still meets the requirements for circuit usage.

[0079] Please refer to Figure 4-6 , Figure 4-6 The schematic diagram shows a constant current source constructed using the TL431 precision adjustable reference integrated circuit. A constant current source can be implemented using other precision adjustable reference integrated circuits, such as the TL432. Its output current is approximately:

[0080] …………………………………………Formula (3)

[0081] In the formula, Io is Figure 4-6 The output current of pin 2 is VREF, which is the reference voltage of the precision adjustable reference integrated circuit, typically 2.50V, 2.495V, or 1.25V. R301 is the resistance value of resistor R301.

[0082] Please refer to Figure 4-7 , Figure 4-7 The schematic diagram shows a constant current source constructed using the LM317 voltage regulator integrated circuit. A constant current source can also be implemented using other linear voltage regulator circuits. Its output current is approximately:

[0083] …………………………………………Formula (4)

[0084] In the formula, Io is Figure 4-7 The output current of pin 2 is 1.20V, which is the reference voltage of LM317. Early versions of LM317 were around 1.25V, but later versions were reduced to around 1.20V. R301 is the resistance value of resistor R301.

[0085] It should be noted that when the detection device is a common bipolar transistor, the operating voltage drop of constant current source I must be below 0.6V. Figure 4-1 , Figure 4-2 , Figure 4-3 and Figure 4-4 A constant current source can be used; Figure 4-5 , Figure 4-6 , Figure 4-7 The constant current source has a large voltage drop during operation, so its use in the second embodiment requires the use of more specialized and costly devices, such as... Figure 4-5In such circuits, transistors with extremely high amplification factors, above 300, are required. This ensures that the value of resistor R302 is large enough to maintain constant current performance. However, such high-amplification transistors experience a decrease in thermal stability. Figure 4-6 In the circuit diagram, the TL431 should be selected with a low reference voltage; otherwise, the voltage drop of the entire constant current source will be too large, reducing the overall efficiency. Even if a common 1.25V low reference voltage model of the TL431 is selected, Figure 4-6 The voltage drop of the constant current source circuit is also above 2V. If the TL431 with a reference voltage of 0.866V is selected, it is a special component, which requires customization and significantly increases the cost; while Figure 4-7 In this constant current source circuit, the LM317's minimum operating voltage drop is 2.0V (actual value; the datasheet specifies 2.5V). Adding the 1.20V across resistor R301, the total is 3.20V. Excessive operating voltage drop reduces the overall efficiency of the constant current source. Lowering the voltage drop and reference voltage of the LM317 would require custom-made components, significantly increasing costs. When the sensing device is a field-effect transistor (FET), its high turn-on voltage VGS... Figures 4-1 to 4-7 All of the constant current sources mentioned can be used.

[0086] In this example, the output of operational amplifier A1 is the inflow current and the sink current. This current equals IL divided by the current transfer ratio (CTR) of the optocoupler, denoted as ICTR. For convenience, the constant current value of constant current source I is chosen by assuming I1 is the total current. The total current equals ICTR plus the quiescent operating currents IA1 and IA2 of operational amplifiers A1 and A2, respectively. IL equals the desired leakage current IS divided by the number of turns n of inductor L. Therefore:

[0087] ……………………Formula (5)

[0088] In this embodiment, the operating leakage current IS is set to 23mA, the number of turns of the inductor L is 100, the CTR of the optocoupler U1 is 100%, which is 1, and the operational amplifiers A1 and A2 are TL062. TL062 is a low-power dual operational amplifier with a nominal sum of its static operating currents IA1 and IA2 of 0.2mA, which is measured to be 0.19mA at a 6V operating voltage. The transistor Q is an FMMT591. Therefore, the constant current value of the constant current source I is equal to I1, which should be: I1=(23 / 100)+0.19=0.42(mA). Considering that the leakage current accuracy requirement of the leakage current protector is not high in actual use, generally ±15% is sufficient, which facilitates the selection of the constant current source. Here, the S-701T constant current tube produced by SEMITEC is selected. There are many domestic alternatives of the same model. The nominal constant current value (IP) of this model of constant current transistor is 0.7mA, and the test voltage for the nominal IP value is 10V, which is relatively high. The manufacturer's technical manual specifies another parameter: the turn-on voltage (VK), which refers to the terminal voltage when the operating current rises to 0.8 times the nominal IP value. In fact, below the turn-on voltage, the constant current transistor can still operate at a relatively small current. The measured voltage drop is 0.6V when the current flowing through the S-701T is 0.39mA; and 0.68V when the current flowing through it is 0.42mA. A characteristic of the constant current source is that when the actual operating current is less than its nominal value, the internal transistor used for constant current conduction is essentially saturated, which is suitable for this embodiment.

[0089] The working principle of the full-wave rectifier circuit in this embodiment is as follows:

[0090] The second implementation circuit uses the above parameters and is applied to a DC leakage current protector. The 0.19mA operational amplifier static operating current flows through the constant current source I, and the measured voltage drop is 0.39V. This voltage is applied to the base and emitter of the transistor Q, and the transistor Q does not conduct and is in the cutoff state; at this moment, the leakage current is zero.

[0091] When the leakage current is below 23mA, the ICTR current is less than 0.23mA, and when combined with the quiescent current of the op-amp, it is less than 0.42mA. The voltage drop generated by the constant current source I is less than 0.68V. At this time, according to the PN junction equation, a weak base current flows through the base of transistor Q. After amplification, a slightly larger current is formed at the collector. This current must be ensured to be insufficient to make the trip switch or relay operate. Of course, a resistor can also be set between the collector of transistor Q and the VEE terminal to absorb this current appropriately and increase the reliability of the circuit.

[0092] When the leakage current is above 23mA, the ICTR current is greater than 0.23mA. When combined with the quiescent current of the op-amp, it is greater than 0.42mA. This current flows through the constant current source I, and the resulting voltage drop is greater than 0.68V. At this time, according to the PN junction equation, a large base current flows through the base of transistor Q. After amplification, an even larger current is formed at the collector. This current must ensure that the trip switch or relay operates to achieve the final purpose.

[0093] The second embodiment of the present invention uses a full-wave rectifier circuit in a leakage current protector, which not only achieves effective detection of DC leakage current, but also effectively detects high-frequency high-order harmonic leakage current that poses potential hazards, and is low in cost.

[0094] The second embodiment can also be applied. Figure 2-1 and Figure 2-2 In this embodiment, constant current source I is used instead of the one in the first embodiment. Figure 2-1 The resistance R is obtained. Figure 5 The schematic diagram of the technical solution shown achieves the same purpose of the invention, but uses a constant current source I instead of the one in the first embodiment. Figure 2-2 The resistance R will not be described in detail here, either by drawing or writing.

[0095] Because the voltage drop from the base to the emitter of transistor Q is variable, obeying the PN junction equation, and is related to temperature, reverse saturation current, and the actual base current flowing through it, the circuit will react differently to different leakage currents at different temperatures. For example, in this embodiment, when the leakage current is 23mA, the voltage drop across the constant current source I is 0.68V. If the ambient temperature is low, the voltage drop between the emitter and base of transistor Q is large, and the transistor enters the cutoff region or even turns off completely. When the ambient temperature is as high as 75 degrees Celsius, the voltage drop between the emitter and base of transistor Q is low, and the transistor enters the amplification region or even saturates and conducts. The trip switch or relay in the circuit will operate, resulting in a large ambiguity region, which is unacceptable for a good product. The following embodiment three improves this situation. In embodiment three, the detection device uses an operational amplifier or comparator to eliminate the ambiguity region.

[0096] Third Embodiment

[0097] Please see Figure 6 , Figure 6This is a schematic diagram of the full-wave rectifier circuit according to the third embodiment of the present invention. The difference between this embodiment and the first embodiment is that in this embodiment, the detection device is a third operational amplifier A3. The inverting input terminal and the negative power supply terminal c- of the third operational amplifier A3 serve as the ports of the detection device. The inverting input terminal of the third operational amplifier A3 is connected to the second end of a resistor R. The first end of the resistor R is connected to the negative power supply terminal c- of the third operational amplifier A3 and also to the ground terminal VEE. The second end of the resistor R is connected to the negative power supply terminal a- and the negative power supply terminal b- of operational amplifier A2. In other words, the resistor R used to detect the operating current of operational amplifiers A1 and A2 is replaced with the ground terminal VEE. The detailed connection relationship is as follows:

[0098] The full-wave rectifier circuit of this embodiment includes: a first operational amplifier A1, a second operational amplifier A2, an inductor L, a resistor R, an optocoupler U1, and a detection device, wherein the detection device is a third operational amplifier A3; the first, second, and third operational amplifiers A1, A2, and A3 are hereinafter referred to as operational amplifiers A1, A2, and A3 in this embodiment. The input terminal of operational amplifier A1 is used to connect to the input voltage signal, and the output terminal of operational amplifier A1 is connected to one end of the internal LED of optocoupler U1, which is the anode of the LED. The positive power supply terminal a+ of operational amplifier A1 is connected to the positive power supply terminal b+ of operational amplifier A2, and the negative power supply terminal a- of operational amplifier A1 is connected to the negative power supply terminal b- of operational amplifier A2. The input terminal of operational amplifier A2 is used to connect to the reference voltage source, and the output terminal of operational amplifier A2 is connected to the other end of the internal LED of optocoupler U1, which is the cathode of the LED. The power supply V CC The resistor R is connected to the positive power supply terminal a+ of op-amp A1 and the positive power supply terminal b+ of op-amp A2. The first end of the resistor R is connected to the negative power supply V. EE Alternatively, operational amplifiers A1 and A2 are connected to the negative power supply V through resistor R. EE Alternatively, grounding is used; the two detection ports of the detection device are connected in parallel across the two ends of resistor R. Specifically, the inverting input terminal of operational amplifier A3 is connected to the second end of resistor R, the negative power supply terminal b- of operational amplifier A2 is connected to the second end of resistor R, the power supply terminal of operational amplifier A3 is connected to the second end of resistor R, and the non-inverting input terminal of operational amplifier A3 is connected to the reference voltage V. ref The power supply terminal of op-amp A3 is connected to the power supply V. CC The output of the other power amplifier A3 is used to output the full-wave rectified signal after full-wave rectification of the input voltage signal. The photodetector of the optocoupler U1 and the inductor L are connected in series to the second power supply.

[0099] The op-amp A3 mentioned above can also be replaced with a comparator. The difference between a comparator and an op-amp will be explained in detail here.

[0100] 1. An op-amp can be connected to form a comparator output; a comparator is for comparison.

[0101] 2. The output stage of an operational amplifier generally uses a complementary push-pull circuit. The comparator output is generally an open-collector output, i.e., an OC output, which facilitates level conversion and requires a pull-up resistor. The unipolar output is easy to connect to digital circuits and can easily output TTL levels.

[0102] 3. Comparators lack phase compensation circuitry, resulting in a higher slew rate than comparable operational amplifiers. However, because they lack internal phase compensation, they are prone to self-oscillation when configured as amplifiers. The open-loop gain of a comparator is significantly higher than that of a typical amplifier; therefore, even a small difference between the positive and negative terminals can cause a change in the output.

[0103] 4. The comparator has a fast switching speed, approximately on the order of nanoseconds, while the op-amp's switching speed is generally on the order of microseconds, except for special high-speed op-amps. This characteristic does not affect the present invention.

[0104] Based on the aforementioned differences between comparators and operational amplifiers, the operational amplifier A3 used in this invention is interchangeable with the comparator; that is, operational amplifier A3 in this invention also includes a comparator. The common LM393, similar to a non-adjustable gain operational amplifier, is used as operational amplifier A3 in this invention, thus achieving the same purpose.

[0105] Op-amps A1 and A2 are two op-amps internal to an LM358 chip. Their static operating nominal value is 700uA, but actual measured operating voltage at 5V is 0.65mA. CC 5V, V EE Grounding.

[0106] Optocoupler U1 is a PC817C with a CTR between 200% and 400%. In actual measurements, with a primary current of 0.33mA, the CTR is 226%.

[0107] The two operational amplifiers are powered by resistor R. If the operational amplifiers self-oscillate, a capacitor can be connected in parallel between the positive power supply terminal b+ and the negative power supply terminal b- of operational amplifier A2. The capacitance should be as small as possible without affecting the detection of high-frequency leakage current, provided that self-oscillation is not prevented. The leakage current protection value is set at 6mA. The number of turns n of the inductor L is 8 turns, and the resistor R is 220Ω. Q in the diagram represents operational amplifier A3. An LM393 comparator is selected, using the aforementioned single-supply V. CC Power supply: The reference voltage V is connected to the non-inverting input of the LM393. ref The voltage is 0.216V. Here, a 220K resistor and a 10K resistor are connected in series and then in parallel to a 5V power supply. The 10K resistor is grounded, and the 220K resistor is connected to the 5V power supply. CC The connection point is connected to the non-inverting input of the LM393, and the connection point is a reference voltage of 0.216V to ground, which is actually 0.217V.

[0108] The 0.216V reference voltage is derived from the above formula (2). In this embodiment, the operating leakage current I to be set is... S The current is 6mA, the inductor L has 8 turns, and the quiescent current I of operational amplifiers A1 and A2 is... A1 and I A2 The sum of the nominal values ​​is 0.65mA, so the maximum value of the current I1 flowing through resistor R should be: I1 = [6 / (8 2.27)]+0.65=0.982(mA), the maximum voltage drop across the 220Ω resistor R is U1=I1R=0.982mA×220Ω=0.216V.

[0109] It is important to note that when selecting the A3 op-amp, whether it is an operational amplifier or a comparator, for single-supply operation, a model with an input voltage starting from 0V should be chosen. Generally, if its internal differential stage consists of a PNP transistor or a P-type MOSFET, it is acceptable, such as the LM2904 or LM358. For a detailed introduction to operational amplifiers, please refer to Chinese application number 201110218012.8. Figure 5 , Figure 6 And there is a detailed description in paragraphs

[0036] to

[0039] of the instruction manual.

[0110] The working principle of the full-wave rectifier circuit in this embodiment is as follows:

[0111] If the current I in the inductor L L Ultimately, the current flows from top to bottom and right, so op-amp A1 outputs current, while op-amp A2's output pin receives both incoming and outgoing current. Power supply V CC The supply current flows into the positive supply terminal a+ of operational amplifier A1, flows out from the output terminal of operational amplifier A1, and simultaneously flows into one end of inductor L (the left end), flows out from the right end of inductor L, injects into the output terminal of operational amplifier A2, flows out from the negative supply terminal b- of operational amplifier A2, and returns to the power supply V through resistor R. EE The terminals form a circuit. Power supply V CC and V EE This is equivalent to the positive and negative terminals of a battery. At this point, the current I1 flowing through resistor R is from top to bottom; this invention completes small-signal processing and finally achieves a directional signal output, realizing a special small-signal rectifier circuit.

[0112] First, choose a suitable value for the resistor R. When the leakage current reaches the specified threshold, the resulting current I... CTRThe total current is I1, which is the increment. The voltage generated across resistor R is connected to the inverting input of operational amplifier A3. When the leakage current is within the limit, this voltage is below 0.216V, the non-inverting input of operational amplifier A3 is 0.216V, and operational amplifier A3 outputs a high level, so the trip switch or relay does not operate. When the leakage current exceeds the limit, the voltage generated across resistor R is above 0.216V, the non-inverting input of operational amplifier A3 remains at 0.216V, and the inverting input is relatively high, so operational amplifier A3 outputs a low level, driving the trip switch or relay to operate, causing the leakage current protector to cut off the power supply.

[0113] In this embodiment, replacing the resistor R with a constant current source with an actual operating current of 0.982mA also allows for normal operation. The replacement constant current source can be the one corresponding to the second embodiment. Figure 4-6 To make the constant current source have two terminals, the disclosed portion of the circuitry sacrificed constant current performance. Here, we restore its original form; see [link to original text]. Figure 6-1 To obtain a precise constant current source of 0.982mA and a low voltage drop, the precision adjustable reference integrated circuit selected is the TLV431A with a reference voltage of 1.24V. The upper terminal of resistor R302, which was originally connected to the collector of transistor TR301, is now connected to the power supply V. CC The TR301 uses the S9014, which has an amplification factor of over 300 and a saturation voltage drop of 0.15V. Figure 6-1 In the circuit, the constant current source at terminals 1 and 2 has a turn-on voltage above (1.24V + 0.15V) = 1.39V. The minimum operating voltage of op-amps A1 and A2 (LM358) is 5V, but they can actually operate up to 3.6V. Op-amp A3's minimum operating voltage is 3V, so it is unaffected. Therefore, to ensure the normal operation of the LM358, the power supply V... CC If a voltage of 6.4V or higher is used, and 8V is chosen here, then resistor R302 can be selected from 6.2k to 56kV, and all of them can work normally in actual tests. R301 is a 1.262kV resistor; this value is not standard, and is actually obtained by connecting a 1.3kV resistor in parallel with a 43kV resistor. Meanwhile, the reference voltage V is connected to the non-inverting input of the LM393 comparator via op-amp A3. ref The voltage is adjusted to 1.5V. Here, a 130K resistor and a 30K resistor are connected in series and then in parallel to the 8V power supply. The 30K resistor is grounded, and the 130K resistor is connected to the 8V power supply. CC Above, its connection point is connected to the non-inverting input of the LM393, and its connection point is a 1.5V reference voltage to ground. Actual measurement... Figure 4-1 The constant current source at terminals 1 and 2 of the circuit is 0.983mA, and the turn-on voltage is 1.32V. Replace it with... Figure 2-1In this embodiment, when replacing the resistor R, attention should be paid to the direction of the current. The first end 1 of the constant current source replaces the second end of the resistor R, and the second end 2 of the constant current source replaces the first end of the resistor R. Instead of dogmatically replacing the first end of the resistor R with 1 and the second end of the resistor R with 2, we should replace the second end of the resistor R with 1.

[0114] After power-on, the circuit performs all its functions with extremely low temperature drift and stable performance.

[0115] Fourth embodiment

[0116] Please see Figure 7 , Figure 7 This is a schematic diagram of the full-wave rectifier circuit according to the fourth embodiment of the present invention. The difference between the full-wave rectifier circuit of this embodiment and the first embodiment is that, in this embodiment, the resistor R for detecting the operating current of operational amplifiers A1 and A2 is moved to the ground terminal VEE, and the detection device is changed from a PNP transistor to an NPN transistor; the difference from the third embodiment is that, in this embodiment, the detection device is changed from the third operational amplifier A3 to an NPN transistor.

[0117] The detailed connection relationships are as follows. The full-wave rectifier circuit in this embodiment includes:

[0118] The system consists of a first operational amplifier A1, a second operational amplifier A2, an inductor L, a resistor R, a first optocoupler U1, and a detection device Q. The input terminal of the first operational amplifier A1 is connected to the input voltage signal, and its output terminal is connected to one end of the internal LED of the first optocoupler U1 (the anode of the LED). The positive power supply terminal a+ of the first operational amplifier is connected to the positive power supply terminal b+ of the second operational amplifier A2, and the negative power supply terminal a- of the first operational amplifier is connected to the negative power supply terminal b- of the second operational amplifier A2. The input terminal of the second operational amplifier A2 is connected to a reference voltage source, and its output terminal is connected to the other end of the internal LED of the first optocoupler U1 (the cathode of the LED). The power supply V... CC The resistor R is connected to the positive power supply terminal a+ of the first operational amplifier A1 and the positive power supply terminal b+ of the second operational amplifier A2. The first end of the resistor R is connected to the negative power supply V. EE Alternatively, the negative power supply terminal b- of the second operational amplifier A2 is connected to the second end of the resistor R, meaning that the first operational amplifier A1 and the second operational amplifier A2 are connected to the negative power supply V through the resistor R. EE Or grounded; In this embodiment, the detection device is a transistor Q, which is an NPN transistor. The emitter and base of transistor Q serve as detection ports. The emitter of transistor Q is connected to the first end of resistor R, and the base of transistor Q is connected to the second end of resistor R. The collector of transistor Q is used to output the full-wave rectified signal after full-wave rectification of the input voltage signal. The photodetector of the first optocoupler U1 and the inductor L are connected in series to the second power supply.

[0119] The fourth embodiment is essentially an equivalent substitution of the first embodiment, replacing the resistor R used to detect the operating current of operational amplifiers A1 and A2 with the negative power supply V. EE Alternatively, it can be connected in series with the operational amplifier (op-amp) and the resistor R can be considered as the power supply resistor, except that it is now connected in series with the negative power supply V instead of in series with the positive power supply. EE In the case of a transistor Q, which is used as a detection device, its polarity should change from PNP to NPN.

[0120] Therefore, the working principle of this embodiment will not be analyzed in detail.

[0121] Fifth embodiment

[0122] Please see Figure 8 , Figure 8 This is a schematic diagram of the full-wave rectifier circuit according to the fifth embodiment of the present invention. The difference between the full-wave rectifier circuit of this embodiment and the third embodiment is that, in this embodiment, the resistor R for detecting the operating current of operational amplifiers A1 and A2 is replaced with the power supply VCC, and the reference voltage connected to the non-inverting input terminal of the third operational amplifier A3 is changed to be based on the power supply VCC.

[0123] The fifth embodiment is essentially an equivalent replacement of the third embodiment. The resistor R that detects the operating current of operational amplifiers A1 and A2 is replaced with the power supply VCC. The resistor R is connected in series with operational amplifiers A1 and A2 and is regarded as the power supply resistor. It is just changed from being connected in series with the negative power supply to being connected in series with the positive power supply. Therefore, the reference voltage Vref connected to the non-inverting input terminal of the third operational amplifier A3, which serves as the detection device, is changed to be based on the power supply VCC.

[0124] Therefore, the working principle of this embodiment will not be analyzed in detail.

Claims

1. A full-wave rectifier circuit, characterized in that, include: The system comprises a first operational amplifier, a second operational amplifier, a first optocoupler, an inductor, resistors, and a detection device. The same-polarity power supply terminals of the first and second operational amplifiers are connected in parallel. The output terminal of the first operational amplifier is connected to one end of an internal LED of the first optocoupler, and the other end of the internal LED is connected to the output terminal of the second operational amplifier. The light receiver of the first optocoupler and the inductor are connected in series. The resistors are connected to the power supply terminals of both the first and second operational amplifiers. A first power supply powers the first and second operational amplifiers through the resistors. The light receiver of the first optocoupler and the inductor are connected in series to a second power supply. The detection port of the detection device is connected in parallel with the resistors, and the detection device is used to output a full-wave rectified signal. The input terminal of the first operational amplifier is used to connect to the input voltage signal; the input terminal of the second operational amplifier is used to connect to the reference voltage source.

2. The full-wave rectifier circuit according to claim 1, characterized in that, It also includes a second optocoupler, which is connected in parallel with the first optocoupler in opposite polarities. The collector of the photoreceiver in the second optocoupler is connected to the emitter of the photoreceiver in the first optocoupler, and the emitter of the photoreceiver in the second optocoupler is connected to the collector of the photoreceiver in the first optocoupler. The anode of the light emitter in the second optocoupler is connected to the cathode of the light emitter in the first optocoupler, and the cathode of the light emitter in the second optocoupler is connected to the anode of the light emitter in the first optocoupler.

3. The full-wave rectifier circuit according to claim 1, characterized in that, The detection device is a transistor, with the emitter and base of the transistor serving as the detection ports. The emitter of the transistor is connected to the first end of the resistor, and the base of the transistor is connected to the second end of the resistor.

4. The full-wave rectifier circuit according to claim 1, characterized in that, The detection device is an operational amplifier. The inverting input terminal and the power supply terminal of the operational amplifier serve as the detection port. The inverting input terminal of the operational amplifier is connected to the second end of the resistor, and the power supply terminal of the operational amplifier is connected to the first end of the resistor.

5. The full-wave rectifier circuit according to claim 1, characterized in that, The second power supply is the same as the first power supply, or the second power supply is a different power supply from the first power supply.

6. A full-wave rectifier circuit, characterized in that, include: The system comprises a first operational amplifier, a second operational amplifier, a first optocoupler, an inductor, a constant current source, and a detection device. The same-polarity power supply terminals of the first and second operational amplifiers are connected in parallel. The output terminal of the first operational amplifier is connected to one end of an internal LED of the first optocoupler, and the other end of the internal LED is connected to the output terminal of the second operational amplifier. The photodetector of the first optocoupler and the inductor are connected in series. The constant current source is connected to the power supply terminals of both the first and second operational amplifiers. A first power supply provides power to both operational amplifiers through the constant current source. The photodetector of the first optocoupler and the inductor are connected in series to a second power supply. The detection port of the detection device is connected in parallel with the constant current source, and the detection device is used to output a full-wave rectified signal. The input terminal of the first operational amplifier is used to connect to the input voltage signal; the input terminal of the second operational amplifier is used to connect to the reference voltage source.

7. The full-wave rectifier circuit according to claim 6, characterized in that, It also includes a second optocoupler, which is connected in parallel with the first optocoupler in opposite polarities. The collector of the photoreceiver in the second optocoupler is connected to the emitter of the photoreceiver in the first optocoupler, and the emitter of the photoreceiver in the second optocoupler is connected to the collector of the photoreceiver in the first optocoupler. The anode of the light emitter in the second optocoupler is connected to the cathode of the light emitter in the first optocoupler, and the cathode of the light emitter in the second optocoupler is connected to the anode of the light emitter in the first optocoupler.

8. The full-wave rectifier circuit according to claim 6, characterized in that, The detection device is a transistor, with the emitter and base of the transistor serving as the detection ports. The emitter of the transistor is connected to the first end of the constant current source, and the base of the transistor is connected to the second end of the constant current source.

9. The full-wave rectifier circuit according to claim 6, characterized in that, The detection device is an operational amplifier or a comparator. The inverting input terminal and the power supply terminal of the operational amplifier or the comparator serve as the detection port. The inverting input terminal of the operational amplifier or the comparator is connected to the second terminal of the constant current source, and the power supply terminal of the operational amplifier or the comparator is connected to the first terminal of the constant current source.

10. The full-wave rectifier circuit according to claim 6, characterized in that, The current of the constant current source is above the total current, which is the sum of the static operating current of the first operational amplifier, the static operating current of the second operational amplifier, and the leakage current threshold divided by the number of turns of the inductor coil.

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