A completely isolated circuit

Abstract

The present invention provides a completely isolated circuit, comprising a first capacitor (C1), a power supply IC (U1), an isolation and energy conversion transformer (T1), a diode (D1), a second capacitor (C2), a third resistor (R5), a fourth resistor (R6), and an optical coupler (U2), wherein the optical coupler (U2) comprises a light emitter (U2-B) and a light receiver (U2-A); the GND end of the power supply IC (U1) is connected to a primary ground GND. The beneficial effects of the present invention are as follows: the energy conversion of the present invention adopts an isolation transformer, and the voltage detection signal of the output part is fed back to the power supply IC through the optical coupler, thereby ensuring complete isolation of the input and output, preventing the risk of electric shock on the other side when one side is connected to high voltage, and ensuring safety when used in multi-purpose composite products for high voltage measurement and low voltage control.

Description

Technical Field

[0001] The present invention relates to the field of electronic circuits, and in particular to a completely isolated circuit. Background Art

[0002] With the development of science and technology, the supply voltage of MCU and other devices is getting lower and lower, but the supply voltage of power supply is still mostly 5V, 12V or higher. To solve this problem, DC TO DC voltage conversion circuits are being used more and more widely, but currently the most commonly used are non-isolated solutions with inductive step-down or solutions that isolate the VIN and VOUT of the transformer, but the ground or other parts are connected. When used in high-voltage measurement or control circuits (such as AC alternating current testing and non-isolated switch control such as thyristors), there is a risk of electric shock, and there are safety issues when used in multi-purpose composite products for high-voltage measurement and low-voltage control; a single constant voltage circuit has no over-current protection function in the use of uncertain loads and is easily damaged.

[0003] With the development of science and technology, the application of power measurement is becoming more and more extensive, and more and more power supplies are equipped with auxiliary power supply interfaces. However, in current products, the power supply and interface of the power module are basically not isolated. In this way, the auxiliary power supply of the power supply is used to power the power module, and the voltage and current of the AC alternating current are measured, which may cause the insulation system to be damaged. Summary of the invention

[0004] The present invention provides a completely isolated circuit, comprising a first capacitor, a power supply IC, an isolation and energy conversion transformer, a diode, a second capacitor, a third resistor, a fourth resistor, and an optical coupler, wherein the optical coupler comprises a light emitter and a light receiver, the GND end of the power supply IC is connected to a primary ground GND; the SW end of the power supply IC is connected to the isolation and energy conversion transformer; the VIN end of the power supply IC is respectively connected to one end of the light receiver, the isolation and energy conversion transformer, the VIN end, and one end of the first capacitor; one end of the first capacitor is respectively connected to the VIN end, the isolation and energy conversion transformer, one end of the light receiver, and the VIN end of the power supply IC, and the other end of the first capacitor is grounded; the FB end of the power supply IC is connected to the other end of the light receiver; the isolation and energy conversion transformer is connected to a secondary ground AGND; one end of the diode is connected to the isolation and energy conversion transformer , the other end of the diode is respectively connected to one end of the second capacitor, the VOUT end, and one end of the third resistor; one end of the second capacitor is respectively connected to the other end of the diode, the VOUT end, and one end of the third resistor, and the other end of the second capacitor is connected to the secondary ground AGND; one end of the third resistor is respectively connected to the other end of the diode, one end of the second capacitor, and the VOUT end, and the other end of the third resistor is connected to one end of the fourth resistor; the other end of the fourth resistor is connected to the secondary ground AGND; one end of the light emitter is connected between the third resistor and the fourth resistor, and the other end of the light emitter is respectively connected to the other end of the fourth resistor and the secondary ground AGND; or, one end of the light emitter is respectively connected to one end of the third resistor, the VOUT end, one end of the second capacitor, and the other end of the diode, and the other end of the light emitter is connected between the third resistor and the fourth resistor.

[0005] As a further improvement of the present invention, the circuit includes a second transistor, the base of the second transistor is connected between the third resistor and the fourth resistor, the emitter of the second transistor is respectively connected to one end of the second capacitor, the other end of the diode, the VOUT end, and one end of the third resistor, the collector of the second transistor is connected to one end of the light emitting device, and the other end of the light emitting device is respectively connected to the other end of the fourth resistor and the secondary ground AGND.

[0006] As a further improvement of the present invention, the circuit includes a voltage reference source IC, wherein the first pin of the voltage reference source IC is respectively connected to the secondary ground AGND and the other end of the fourth resistor, the third pin of the voltage reference source IC is connected between the third resistor and the fourth resistor, the second pin of the voltage reference source IC is connected to the other end of the light emitter, and one end of the light emitter is respectively connected to one end of the third resistor, the VOUT end, one end of the second capacitor, and the other end of the diode.

[0007] As a further improvement of the present invention, the circuit further includes a seventh resistor, one end of the seventh resistor is connected to the other end of the light emitter, and the other end of the seventh resistor is connected to the second pin of the voltage reference source IC.

[0008] As a further improvement of the present invention, the circuit further includes a seventh resistor, one end of the seventh resistor is connected to the other end of the light emitter, and the other end of the seventh resistor is respectively connected to the other end of the fourth resistor and the secondary ground AGND.

[0009] As a further improvement of the present invention, the circuit also includes a second triode, a voltage reference source IC, an eighth resistor, and a seventh resistor. The second pin of the voltage reference source IC is connected to one end of the eighth resistor; the base of the second triode is connected to the other end of the eighth resistor, the emitter of the second triode is respectively connected to one end of the second capacitor, the other end of the diode, the VOUT end, and one end of the third resistor, the collector of the second triode is connected to one end of the light emitting device, the other end of the light emitting device is connected to one end of the seventh resistor, and the other end of the seventh resistor is respectively connected to the other end of the fourth resistor, the first pin of the voltage reference source IC, and the secondary ground AGND; the first pin of the voltage reference source IC is respectively connected to the secondary ground AGND, the other end of the fourth resistor, and the other end of the seventh resistor, and the third pin of the voltage reference source IC is connected between the third resistor and the fourth resistor.

[0010] As a further improvement of the present invention, the circuit also includes a first transistor and a fifth resistor, the emitter of the first transistor is respectively connected to the other end of the diode, one end of the second capacitor, and one end of the fifth resistor, the base of the first transistor is respectively connected to the other end of the fifth resistor, the emitter of the second transistor, the VOUT end, and one end of the third resistor, the collector of the first transistor is connected to one end of the light emitting device; one end of the fifth resistor is respectively connected to the other end of the diode, one end of the second capacitor, and the emitter of the first transistor; the other end of the fifth resistor is respectively connected to the VOUT end, one end of the third resistor, the base of the first transistor, and the emitter of the second transistor.

[0011] As a further improvement of the present invention, the circuit also includes a sixth resistor, an eighth resistor, and a seventh resistor, one end of the sixth resistor is connected to the base of the first transistor, and the other end of the sixth resistor is respectively connected to the other end of the fifth resistor, the emitter of the second transistor, the VOUT end, and one end of the third resistor; one end of the eighth resistor is connected to the base of the second transistor, and the other end of the eighth resistor is connected between the third resistor and the fourth resistor; one end of the seventh resistor is connected to the other end of the light emitting device, and the other end of the seventh resistor is respectively connected to the other end of the fourth resistor and the secondary ground AGND.

[0012] As a further improvement of the present invention, the circuit also includes a first transistor, a fifth resistor, and a sixth resistor. The emitter of the first transistor is respectively connected to the other end of the diode, one end of the second capacitor, and one end of the fifth resistor. The base of the first transistor is connected to one end of the sixth resistor. The other end of the sixth resistor is respectively connected to the other end of the fifth resistor, the emitter of the second transistor, the VOUT end, and one end of the third resistor. The collector of the first transistor is respectively connected to one end of the light emitting device and the collector of the second transistor; one end of the fifth resistor is respectively connected to the other end of the diode, one end of the second capacitor, and the emitter of the first transistor; the other end of the fifth resistor is respectively connected to the other end of the sixth resistor, the VOUT end, one end of the third resistor, and the emitter of the second transistor.

[0013] As a further improvement of the present invention, the circuit also includes a first resistor, a second resistor, and a thirteenth resistor, one end of the first resistor is connected to the EN end of the power supply IC, and the other end of the first resistor is connected to EN; one end of the second resistor is respectively connected to one end of the first capacitor, the VIN end, the isolation and energy conversion transformer, and the VIN end of the power supply IC, and the other end of the second resistor is connected to one end of the photoreceiver; the other end of the photoreceiver is respectively connected to the FB end of the power supply IC and one end of the thirteenth resistor; one end of the thirteenth resistor is respectively connected to the other end of the photoreceiver and the FB end of the power supply IC, and the other end of the thirteenth resistor is connected to the primary ground GND.

[0014] As a further improvement of the present invention, the circuit also includes a first resistor, a second resistor, a thirteenth resistor, a voltage and current measurement module, a ninth resistor, a tenth resistor, an eleventh resistor, and a twelfth resistor, wherein the VDD end of the voltage and current measurement module is connected to the VOUT end; the GND of the voltage and current measurement module is connected to the secondary ground AGND; the VIN+ end of the voltage and current measurement module is respectively connected to one end of the ninth resistor and one end of the tenth resistor, and the other end of the ninth resistor is connected to A; the VIN- end of the voltage and current measurement module and the IIN- end of the voltage and current measurement module are respectively connected to one end of the eleventh resistor, and the other end of the eleventh resistor is respectively connected to the other end of the tenth resistor and the other end of the twelfth resistor. one end of the light receiver is connected to the FB end of the power supply IC and one end of the thirteenth resistor; one end of the thirteenth resistor is connected to the FB end of the power supply IC and one end of the thirteenth resistor; one end of the first resistor is connected to the EN end of the power supply IC, and the other end of the first resistor is connected to EN; one end of the second resistor is connected to one end of the first capacitor, the VIN end, the isolation and energy conversion transformer, and the VIN end of the power supply IC, and the other end of the second resistor is connected to one end of the light receiver; the other end of the light receiver is connected to the FB end of the power supply IC and one end of the thirteenth resistor; one end of the thirteenth resistor is connected to the other end of the light receiver and the FB end of the power supply IC, and the other end of the thirteenth resistor is connected to the primary ground GND.

[0015] The beneficial effects of the present invention are as follows: the energy conversion of the present invention adopts an isolation transformer, and the voltage detection signal of the output part is fed back to the power IC through an optical coupler, thereby ensuring complete isolation of the input and output, preventing the risk of electric shock on the other side when one side is connected to high voltage, and ensuring safety when used in multi-purpose composite products for high voltage measurement and low voltage control. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is a circuit diagram of a first implementation mode of Example 1 of the present invention;

[0017] Figure 2 is a circuit diagram of a second implementation mode of Example 1 of the present invention;

[0018] Figure 3 is a circuit diagram of embodiment 2 of the present invention;

[0019] Figure 4 is a circuit diagram of embodiment 3 of the present invention;

[0020] Figure 5 is a circuit diagram of embodiment 4 of the present invention;

[0021] Figure 6 is a circuit diagram of embodiment 5 of the present invention;

[0022] Figure 7 is a circuit diagram of embodiment 6 of the present invention;

[0023] Figure 8 is a circuit diagram of embodiment 7 of the present invention;

[0024] Fig. 9 is a circuit diagram of embodiment 8 of the present invention;

[0025] Fig.10 is a circuit diagram of embodiment 9 of the present invention;

[0026] Fig.11 This is a circuit diagram of Example 11 of the present invention. DETAILED DESCRIPTION

[0027] The present invention discloses a completely isolated circuit, and the specific implementation is as follows:

[0028] Embodiment 1:

[0029] The completely isolated circuit includes a first capacitor C1, a power supply IC U1, an isolation and energy conversion transformer T1, a diode D1, a second capacitor C2, a third resistor R5, a fourth resistor R6, and an optocoupler U2, wherein the optocoupler U2 includes a light emitter U2-B and a light receiver U2-A; the GND end of the power supply IC U1 is connected to the primary ground GND; the SW end of the power supply IC U1 is connected to the isolation and energy conversion transformer T1; the VIN end of the power supply IC U1 is respectively connected to one end of the light receiver U2-A, the isolation and energy conversion transformer T1, the VIN end, and one end of the first capacitor C1; one end of the first capacitor C1 is respectively connected to the VIN end, the isolation and energy conversion transformer T1, one end of the light receiver U2-A, and the VIN end of the power supply IC U1, and the other end of the first capacitor C1 is grounded; the power supply IC The FB end of U1 is connected to the other end of the light receiver U2-A; the isolation and energy conversion transformer T1 is connected to the secondary ground AGND; one end of the diode D1 is connected to the isolation and energy conversion transformer T1, and the other end of the diode D1 is respectively connected to one end of the second capacitor C2, the VOUT end, and one end of the third resistor R5; one end of the second capacitor C2 is respectively connected to the other end of the diode D1, the VOUT end, and one end of the third resistor R5, and the other end of the second capacitor C2 is connected to the secondary ground AGND; one end of the third resistor R5 is respectively connected to the other end of the diode D1, one end of the second capacitor C2, and the VOUT end, and the other end of the third resistor R5 is connected to one end of the fourth resistor R6; the other end of the fourth resistor R6 is connected to the secondary ground AGND;

[0030] In this embodiment 1, Figure 1As shown, as an implementation mode, one end of the light emitter U2-B is connected between the third resistor R5 and the fourth resistor R6, and the other end of the light emitter U2-B is respectively connected to the other end of the fourth resistor R6 and the secondary ground AGND.

[0031] In this embodiment 1, Figure 2 As shown, as another implementation, one end of the light emitting device U2-B is respectively connected to one end of the third resistor R5, the VOUT end, one end of the second capacitor C2, and the other end of the diode D1, and the other end of the light emitting device U2-B is connected between the third resistor R5 and the fourth resistor R6.

[0032] The main content of the present invention is that the energy conversion adopts the isolation transformer T1, and the voltage detection signal of the output part is fed back to the power IC U1 through the optical coupler U2, thereby ensuring the complete isolation of the input and output.

[0033] Embodiment 2:

[0034] like Figure 3 As shown, on the basis of Example 1, the circuit includes a second transistor Q2, the base of the second transistor Q2 is connected between the third resistor R5 and the fourth resistor R6, the emitter of the second transistor Q2 is respectively connected to one end of the second capacitor C2, the other end of the diode D1, the VOUT end, and one end of the third resistor R5, the collector of the second transistor Q2 is connected to one end of the light emitting device U2-B, and the other end of the light emitting device U2-B is respectively connected to the other end of the fourth resistor R6 and the secondary ground AGND.

[0035] Embodiment 3:

[0036] like Figure 4 As shown, on the basis of Example 1, the circuit includes a voltage reference source IC U3, the first pin of the voltage reference source IC U3 is respectively connected to the secondary ground AGND and one end of the fourth resistor R6, the third pin of the voltage reference source IC U3 is connected between the third resistor R5 and the fourth resistor R6, the second pin of the voltage reference source IC U3 is connected to the other end of the light emitting device U2-B, and one end of the light emitting device U2-B is respectively connected to one end of the third resistor R5, the VOUT end, one end of the second capacitor C2, and the other end of the diode D1.

[0037] like Figure 5 As shown, Example 4:

[0038] On the basis of Embodiment 3, the circuit further includes a seventh resistor R9, one end of the seventh resistor R9 is connected to the other end of the light emitter U2-B, and the other end of the seventh resistor R9 is connected to the second pin of the voltage reference source IC U3.

[0039] like Figure 6 As shown, Example 5:

[0040] Based on Example 2, the circuit further includes a seventh resistor R9, one end of which is connected to the other end of the light emitter U2-B, and the other end of which is respectively connected to the other end of the fourth resistor R6 and the secondary ground AGND.

[0041] like Figure 7 As shown, Example 6:

[0042] On the basis of Embodiment 1, the circuit further includes a second transistor Q2, a voltage reference source IC U3, an eighth resistor R8, and a seventh resistor R9, and the second pin of the voltage reference source IC U3 is connected to one end of the eighth resistor R8;

[0043] The base of the second transistor Q2 is connected to the other end of the eighth resistor R8, the emitter of the second transistor Q2 is respectively connected to one end of the second capacitor C2, the other end of the diode D1, the VOUT end, and one end of the third resistor R5, the collector of the second transistor Q2 is connected to one end of the light emitter U2-B, the other end of the light emitter U2-B is connected to one end of the seventh resistor R9, and the other end of the seventh resistor R9 is respectively connected to the other end of the fourth resistor R6, the first pin of the voltage reference source IC U3, and the secondary ground AGND;

[0044] The first pin of the voltage reference source IC U3 is respectively connected to the secondary ground AGND, the other end of the fourth resistor R6 and the other end of the seventh resistor R9, and the third pin of the voltage reference source IC U3 is connected between the third resistor R5 and the fourth resistor R6.

[0045] When working, the input voltage is connected to VIN and the primary ground GND, the first capacitor C1 plays a filtering role, the power supply IC U1 is a power supply IC with an integrated power MOSFET or triode, and the circuit startup control signal is added to the enable terminal EN of the power supply IC through the first resistor R1; when the circuit is working, the energy converted by the isolation and energy conversion transformer T1 is rectified by the diode D1 and sent to the second capacitor C2 for filtering, and then VOUT and the secondary ground AGND output a constant voltage; the third resistor R5 and the fourth resistor R6 form a voltage divider sampling circuit for the output voltage, and the sampled voltage signal is sent to the voltage reference source IC U3 for comparison and amplification, and then the second triode Q2 is controlled to turn on, the eighth resistor R8 is a current limiting resistor to prevent excessive current from damaging U3; the seventh resistor R9 plays a current limiting role to prevent the optical coupler U2 from being damaged by excessive current. The internal triode of the optical coupler U2 is turned on after receiving the optical signal, and VIN is added to the switch control feedback pin FB of the power supply IC U1 through the second resistor R2, so that U1 stops working or reduces the output, so as to achieve the purpose of voltage stabilization. The thirteenth resistor R3 is mainly used to ground the FB pin of U1 when the internal transistor of U2 is cut off, so as to prevent interference signals from causing malfunction of the power supply IC U1.

[0046] like Figure 8 As shown, Example 7:

[0047] On the basis of Embodiment 2, the circuit further includes a first transistor Q1 and a fifth resistor R4;

[0048] The emitter of the first transistor Q1 is respectively connected to the other end of the diode D1, one end of the second capacitor C2, and one end of the fifth resistor R4; the base of the first transistor Q1 is respectively connected to the other end of the fifth resistor R4, the emitter of the second transistor Q2, the VOUT end, and one end of the third resistor R5; the collector of the first transistor Q1 is connected to one end of the light emitting device U2-B; one end of the fifth resistor R4 is respectively connected to the other end of the diode D1, one end of the second capacitor C2, and the emitter of the first transistor Q1; the other end of the fifth resistor R4 is respectively connected to the VOUT end, one end of the third resistor R5, the base of the first transistor Q1, and the emitter of the second transistor Q2.

[0049] like Fig. 9 As shown, Example 8:

[0050] On the basis of Example 7, the circuit also includes a sixth resistor R7, an eighth resistor R8, and a seventh resistor R9, one end of the sixth resistor R7 is connected to the base of the first transistor Q1, and the other end of the sixth resistor R7 is respectively connected to the other end of the fifth resistor R4, the emitter of the second transistor Q2, the VOUT end, and one end of the third resistor R5; one end of the eighth resistor R8 is connected to the base of the second transistor Q2, and the other end of the eighth resistor R8 is connected between the third resistor R5 and the fourth resistor R6; one end of the seventh resistor R9 is connected to the other end of the light emitting device U2-B, and the other end of the seventh resistor R9 is respectively connected to the other end of the fourth resistor R6 and the secondary ground AGND.

[0051] like Fig.10 As shown, Example 9:

[0052] On the basis of Example 6, the circuit also includes a first transistor Q1, a fifth resistor R4, and a sixth resistor R7. The emitter of the first transistor Q1 is respectively connected to the other end of the diode D1, one end of the second capacitor C2, and one end of the fifth resistor R4. The base of the first transistor Q1 is connected to one end of the sixth resistor R7. The other end of the sixth resistor R7 is respectively connected to the other end of the fifth resistor R4, the emitter of the second transistor Q2, the VOUT end, and one end of the third resistor R5. The collector of the first transistor Q1 is respectively connected to one end of the light emitting device U2-B and the collector of the second transistor Q2; one end of the fifth resistor R4 is respectively connected to the other end of the diode D1, one end of the second capacitor C2, and the emitter of the first transistor Q1; the other end of the fifth resistor R4 is respectively connected to the other end of the sixth resistor R7, the VOUT end, one end of the third resistor R5, and the emitter of the second transistor Q2.

[0053] When working, the input voltage is connected to VIN and the primary ground GND, the first capacitor C1 plays a filtering role, the power supply IC U1 is a power supply IC with an integrated power MOSFET or transistor inside, and the circuit startup control signal is added to the enable terminal EN of the power supply IC through the first resistor R1; when the circuit is working, the energy converted by the isolation and energy conversion transformer T1 is rectified by the diode D1 and sent to the second capacitor C2 for filtering, and the current is sampled by the fifth resistor R4, and then VOUT and the secondary ground AGND output a constant voltage; the fifth resistor R4 is a current sampling resistor, and the sampled current signal is converted into a voltage signal and sent to the base of the first transistor Q1. When the current reaches the set maximum value and the converted voltage meets the conduction requirement of the first transistor Q1, the first transistor Q1 is turned on, and the internal light emitter U2-B of the optocoupler U2 is powered, so that it sends a light signal to the light receiver U2-A. The internal light receiver U2-A of the optocoupler U2 is turned on after receiving the light signal, and VIN is added to the power supply IC through the second resistor R2 The switch control feedback pin FB of U1 stops U1 from working or reduces the output, achieving the purpose of constant current and overcurrent protection. When the load is small and does not enter the constant current working mode; the third resistor R5 and the fourth resistor R6 form a voltage divider sampling circuit for the output voltage, and the sampled voltage signal is sent to the voltage reference source ICU3 for comparison and amplification, and then the second transistor Q2 is controlled to be turned on. The eighth resistor R8 is a current limiting resistor to prevent excessive current from damaging U3; the seventh resistor R9 plays a current limiting role to prevent the optical coupler U2 from being damaged by excessive current. The internal transistor of the optical coupler U2 is turned on after receiving the optical signal, and VIN is added to the switch control feedback pin FB of the power supply IC U1 through the second resistor R2, so that U1 stops working or reduces the output, achieving the purpose of voltage stabilization. The thirteenth resistor R3 mainly serves to ground the FB pin of U1 when the internal transistor of U2 is cut off, to prevent interference signals from causing the power supply IC U1 to malfunction.

[0054] Embodiment 10:

[0055] On the basis of Embodiment 1 or 2 or 3 or 4 or 5 or 6 or 7 or 8 or 9, the circuit further comprises a first resistor R1, a second resistor R2 and a thirteenth resistor R3, one end of the first resistor R1 is connected to the EN end of the power supply IC U1, the other end of the first resistor R1 is connected to EN, EN is the control end of the operation of the circuit, and can be externally connected to the control output port of an MCU or the like, U1 has a pull-up resistor inside, when a high voltage is connected or not connected, U1 works, and the circuit has a regulated output, when a low level or ground is connected, U1 does not work, and the circuit has no output; one end of the second resistor R2 is respectively connected to one end of the first capacitor C1, the VIN end, the isolation and energy conversion transformer T1, and the VIN end of the power supply ICU1, the other end of the second resistor R2 is connected to one end of the light receiver U2-A; the other end of the light receiver U2-A is respectively connected to the FB end of the power supply IC U1 and one end of the thirteenth resistor R3; one end of the thirteenth resistor R3 is respectively connected to the other end of the light receiver U2-A, the power supply IC The FB end of U1 is connected, and the other end of the thirteenth resistor R3 is connected to the primary ground GND.

[0056] like Fig.11 As shown, Example 11:

[0057] On the basis of Example 6, the circuit further includes a first resistor R1, a second resistor R2, a thirteenth resistor R3, a voltage and current measurement module U4, a ninth resistor R13, a tenth resistor R14, an eleventh resistor R12, and a twelfth resistor R15, wherein the VDD end of the voltage and current measurement module U4 is connected to the VOUT end; the GND of the voltage and current measurement module U4 is connected to the secondary ground AGND; the VIN+ end of the voltage and current measurement module U4 is respectively connected to one end of the ninth resistor R13 and one end of the tenth resistor R14, the VIN+ end of the voltage and current measurement module U4 represents a voltage detection input +, the other end of the ninth resistor R13 is connected to A, A is a point of voltage to be measured, equivalent to the + probe of a multimeter; the VIN- end of the voltage and current measurement module U4 , the IIN- end of the voltage and current measuring module U4 is respectively connected to one end of the eleventh resistor (R12), the VIN- end of the voltage and current measuring module U4 represents the voltage detection input -, the other end of the eleventh resistor R12 is respectively connected to the other end of the tenth resistor R14, the other end of the twelfth resistor R15, and the B_IN end, B_IN is another point of the voltage to be measured, equivalent to the - test lead of the multimeter; the IIN+ end of the voltage and current measuring module U4 is respectively connected to one end of the twelfth resistor R15 and the B_LOAD end, B_LOAD is used in the circuit to test the current, and is connected to the two input ends of the electrical equipment to be tested together with A, which is equivalent to the test lead of the current range of the multimeter; the IIN+ end of the voltage and current measuring module U4 represents the detection input + during current detection.

[0058] One end of the first resistor R1 is connected to the EN end of the power IC U1, and the other end of the first resistor R1 is connected to EN;

[0059] One end of the second resistor R2 is respectively connected to one end of the first capacitor C1, the VIN end, the isolation and energy conversion transformer T1, and the VIN end of the power IC U1, and the other end of the second resistor R2 is connected to one end of the light receiver U2-A;

[0060] The other end of the light receiver U2-A is connected to the FB end of the power IC U1 and one end of the thirteenth resistor R3 respectively;

[0061] One end of the thirteenth resistor R3 is connected to the other end of the light receiver U2-A and the FB end of the power IC U1 respectively, and the other end of the thirteenth resistor R3 is connected to the primary ground GND.

[0062] A and B-IN are connected to the voltage to be measured, and A and B_LOAD are connected to the load. In this way, the third resistor R5 is connected in series in the load circuit to test the current.

[0063] Fig.11 Module A is the isolated constant voltage circuit part of this patent, and module B is a voltage and current measurement module powered by the isolated constant voltage circuit of this patent.

[0064] The circuit of this embodiment 11 is suitable for a completely isolated electricity meter circuit for measuring and power supply. The energy conversion adopts the isolation and energy conversion transformer T1. The voltage detection signal of the output part is fed back to the power IC U1 through the optical coupler U2, ensuring the complete isolation of the input and output. When working, the input voltage is connected to VIN and the primary ground GND, the first capacitor C1 plays a filtering role, and the power IC U1 is a power IC with an integrated power MOSFET or triode inside; when the circuit is working, the energy converted by the isolation and energy conversion transformer T1 is rectified by the diode D1 and sent to the second capacitor C2 for filtering. The third resistor R5 and the fourth resistor R6 form a voltage divider sampling circuit for the output voltage, and the sampled VOUT voltage signal is sent to the voltage reference source IC U3 for comparison and amplification, and then the second triode Q2 is controlled to be turned on. The eighth resistor R8 is a current limiting resistor to prevent the current from being too large to damage U3; the seventh resistor R9 plays a current limiting role to prevent the optical coupler U2 from being damaged by excessive current. The light receiver U2-A inside the optocoupler U2 is turned on after receiving the light signal, and VIN is added to the switch control feedback pin FB of the power IC U1 through the second resistor R2, so that U1 stops working or reduces the output to achieve the purpose of voltage regulation. The thirteenth resistor R3 mainly serves to ground the FB pin of U1 when the internal transistor of U2 is cut off, to prevent interference signals from causing the power IC U1 to malfunction.

[0065] When measuring electricity, Fig.11 The voltage signal between the two voltage measurement input terminals A and B-IN is attenuated by the ninth resistor R13 and the tenth resistor R14, and then taken out from both ends of the tenth resistor R14 and sent to the voltage comparator VIN+ and VIN- of the U4 module, where VIN- is connected to the internal reference voltage source of the IC; the eleventh resistor R12 has a value equal to the tenth resistor R14, which plays an impedance matching role. The twelfth resistor R15 is a current detection resistor, and B_IN is marked as B_LOAD and A is synchronously connected to the load after passing through the twelfth resistor R15. The current consumed by the load when working is sampled through the twelfth resistor R15 and sent to the current comparator IIN+ and IIN- of U4, where IIN- is connected to the internal reference voltage source of the IC. (For example, when connected to AC, A is connected to L, B_IN is connected to N, and B_LOAD is connected to the point marked as N on the load).

[0066] The beneficial effects of the present invention are as follows: the energy conversion of the present invention adopts an isolation transformer, and the voltage detection signal of the output part is fed back to the power IC through an optical coupler, thereby ensuring complete isolation of the input and output, preventing the risk of electric shock on the other side when one side is connected to high voltage, and ensuring safety when used in multi-purpose composite products for high voltage measurement and low voltage control.

[0067] The above contents are further detailed descriptions of the present invention in combination with specific preferred embodiments, and it cannot be determined that the specific implementation of the present invention is limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, several simple deductions or substitutions can be made without departing from the concept of the present invention, which should be regarded as falling within the protection scope of the present invention.

Claims

1. A completely isolated circuit, characterized in that: It includes a first capacitor (C1), a power supply IC (U1), an isolation and energy conversion transformer (T1), a diode (D1), a second capacitor (C2), a third resistor (R5), a fourth resistor (R6), and an optical coupler (U2), wherein the optical coupler (U2) includes a light emitter (U2-B) and a light receiver (U2-A); The GND terminal of the power IC (U1) is connected to the primary ground GND; The SW end of the power IC (U1) is connected to the isolation and energy conversion transformer (T1); the VIN end of the power IC (U1) is respectively connected to one end of the light receiver (U2-A), the isolation and energy conversion transformer (T1), the VIN end, and one end of the first capacitor (C1); One end of the first capacitor (C1) is respectively connected to the VIN end, the isolation and energy conversion transformer (T1), one end of the light receiver (U2-A), and the VIN end of the power IC (U1), and the other end of the first capacitor (C1) is grounded; The FB terminal of the power IC (U1) is connected to the other end of the light receiver (U2-A); The isolation and energy conversion transformer (T1) is connected to the secondary ground AGND; One end of the diode (D1) is connected to the isolation and energy conversion transformer (T1), and the other end of the diode (D1) is respectively connected to one end of the second capacitor (C2), the VOUT end, and one end of the third resistor (R5); One end of the second capacitor (C2) is respectively connected to the other end of the diode (D1), the VOUT end, and one end of the third resistor (R5), and the other end of the second capacitor (C2) is connected to the secondary ground AGND; One end of the third resistor (R5) is respectively connected to the other end of the diode (D1), one end of the second capacitor (C2), and the VOUT end, and the other end of the third resistor (R5) is connected to one end of the fourth resistor (R6); The other end of the fourth resistor (R6) is connected to the secondary ground AGND; One end of the light emitter (U2-B) is connected between the third resistor (R5) and the fourth resistor (R6), and the other end of the light emitter (U2-B) is respectively connected to the other end of the fourth resistor (R6) and the secondary ground AGND; or, one end of the light emitter (U2-B) is respectively connected to one end of the third resistor (R5), the VOUT end, one end of the second capacitor (C2), and the other end of the diode (D1), and the other end of the light emitter (U2-B) is connected between the third resistor (R5) and the fourth resistor (R6); The circuit comprises a second triode (Q2), the base of the second triode (Q2) is connected between the third resistor (R5) and the fourth resistor (R6), the emitter of the second triode (Q2) is respectively connected to one end of the second capacitor (C2), the other end of the diode (D1), the VOUT end, and one end of the third resistor (R5), the collector of the second triode (Q2) is connected to one end of the light emitter (U2-B), and the other end of the light emitter (U2-B) is respectively connected to the other end of the fourth resistor (R6) and the secondary ground AGND; The circuit comprises a voltage reference source IC (U3), wherein the first pin of the voltage reference source IC (U3) is respectively connected to a secondary ground AGND and the other end of the fourth resistor (R6), the third pin of the voltage reference source IC (U3) is connected between the third resistor (R5) and the fourth resistor (R6), the second pin of the voltage reference source IC (U3) is connected to the other end of the light emitter (U2-B), and one end of the light emitter (U2-B) is respectively connected to one end of the third resistor (R5), a VOUT end, one end of the second capacitor (C2), and the other end of the diode (D1).

2. The circuit according to claim 1, characterized in that: The circuit also includes a seventh resistor (R9), one end of the seventh resistor (R9) is connected to the other end of the light emitter (U2-B), and the other end of the seventh resistor (R9) is connected to the second pin of the voltage reference source IC (U3).

3. The circuit according to claim 1, characterized in that: The circuit also includes a seventh resistor (R9), one end of the seventh resistor (R9) is connected to the other end of the light emitter (U2-B), and the other end of the seventh resistor (R9) is respectively connected to the other end of the fourth resistor (R6) and the secondary ground AGND.

4. The circuit according to claim 1, characterized in that: The circuit also includes a second triode (Q2), a voltage reference source IC (U3), an eighth resistor (R8), and a seventh resistor (R9), wherein the second pin of the voltage reference source IC (U3) is connected to one end of the eighth resistor (R8); The base of the second transistor (Q2) is connected to the other end of the eighth resistor (R8), the emitter of the second transistor (Q2) is respectively connected to one end of the second capacitor (C2), the other end of the diode (D1), the VOUT end, and one end of the third resistor (R5), the collector of the second transistor (Q2) is connected to one end of the light emitter (U2-B), the other end of the light emitter (U2-B) is connected to one end of the seventh resistor (R9), and the other end of the seventh resistor (R9) is respectively connected to the other end of the fourth resistor (R6), the first pin of the voltage reference source IC (U3), and the secondary ground AGND; The first pin of the voltage reference source IC (U3) is respectively connected to the secondary ground AGND, the other end of the fourth resistor (R6), and the other end of the seventh resistor (R9), and the third pin of the voltage reference source IC (U3) is connected between the third resistor (R5) and the fourth resistor (R6).

5. The circuit according to claim 1, characterized in that: The circuit also includes a first transistor (Q1), a fifth resistor (R4); The emitter of the first triode (Q1) is respectively connected to the other end of the diode (D1), one end of the second capacitor (C2), and one end of the fifth resistor (R4); the base of the first triode (Q1) is respectively connected to the other end of the fifth resistor (R4), the emitter of the second triode (Q2), the VOUT end, and one end of the third resistor (R5); and the collector of the first triode (Q1) is connected to one end of the light emitter (U2-B); One end of the fifth resistor (R4) is respectively connected to the other end of the diode (D1), one end of the second capacitor (C2), and the emitter of the first transistor (Q1); The other end of the fifth resistor (R4) is respectively connected to the VOUT end, one end of the third resistor (R5), the base of the first transistor (Q1), and the emitter of the second transistor (Q2).

6. The circuit according to claim 5, characterized in that: The circuit also includes a sixth resistor (R7), an eighth resistor (R8), and a seventh resistor (R9). One end of the sixth resistor (R7) is connected to the base of the first transistor (Q1), and the other end of the sixth resistor (R7) is respectively connected to the other end of the fifth resistor (R4), the emitter of the second transistor (Q2), the VOUT end, and one end of the third resistor (R5); One end of the eighth resistor (R8) is connected to the base of the second transistor (Q2), and the other end of the eighth resistor (R8) is connected between the third resistor (R5) and the fourth resistor (R6); One end of the seventh resistor (R9) is connected to the other end of the light emitter (U2-B), and the other end of the seventh resistor (R9) is respectively connected to the other end of the fourth resistor (R6) and the secondary ground AGND.

7. The circuit according to claim 4, characterized in that: The circuit also includes a first transistor (Q1), a fifth resistor (R4), and a sixth resistor (R7); The emitter of the first triode (Q1) is respectively connected to the other end of the diode (D1), one end of the second capacitor (C2), and one end of the fifth resistor (R4); the base of the first triode (Q1) is connected to one end of the sixth resistor (R7); the other end of the sixth resistor (R7) is respectively connected to the other end of the fifth resistor (R4), the emitter of the second triode (Q2), the VOUT end, and one end of the third resistor (R5); the collector of the first triode (Q1) is respectively connected to one end of the light emitter (U2-B) and the collector of the second triode (Q2); One end of the fifth resistor (R4) is respectively connected to the other end of the diode (D1), one end of the second capacitor (C2), and the emitter of the first transistor (Q1); The other end of the fifth resistor (R4) is respectively connected to the other end of the sixth resistor (R7), the VOUT end, one end of the third resistor (R5), and the emitter of the second transistor (Q2).

8. The circuit according to any one of claims 1 to 7, characterized in that: The circuit also includes a first resistor (R1), a second resistor (R2), and a thirteenth resistor (R3); One end of the first resistor (R1) is connected to the EN end of the power IC (U1), and the other end of the first resistor (R1) is connected to EN; One end of the second resistor (R2) is respectively connected to one end of the first capacitor (C1), the VIN end, the isolation and energy conversion transformer (T1), and the VIN end of the power supply IC (U1), and the other end of the second resistor (R2) is connected to one end of the light receiver (U2-A); The other end of the light receiver (U2-A) is respectively connected to the FB end of the power IC (U1) and one end of the thirteenth resistor (R3); One end of the thirteenth resistor (R3) is respectively connected to the other end of the light receiver (U2-A) and the FB end of the power IC (U1), and the other end of the thirteenth resistor (R3) is connected to the primary ground GND.

9. The circuit according to claim 4, characterized in that: The circuit also includes a first resistor (R1), a second resistor (R2), a thirteenth resistor (R3), a voltage and current measurement module (U4), a ninth resistor (R13), a tenth resistor (R14), an eleventh resistor (R12), and a twelfth resistor (R15). The VDD terminal of the voltage and current measurement module (U4) is connected to the VOUT terminal; The GND of the voltage and current measurement module (U4) is connected to the secondary ground AGND; The VIN+ end of the voltage and current measurement module (U4) is respectively connected to one end of the ninth resistor (R13) and one end of the tenth resistor (R14), and the other end of the ninth resistor (R13) is connected to A; The VIN-end of the voltage and current measurement module (U4) and the IIN-end of the voltage and current measurement module (U4) are respectively connected to one end of the eleventh resistor (R12), and the other end of the eleventh resistor (R12) is respectively connected to the other end of the tenth resistor (R14), the other end of the twelfth resistor (R15), and the B_IN end; The IIN+ terminal of the voltage and current measurement module (U4) is respectively connected to one end of the twelfth resistor (R15) and the B_LOAD terminal; One end of the first resistor (R1) is connected to the EN end of the power IC (U1), and the other end of the first resistor (R1) is connected to EN; One end of the second resistor (R2) is respectively connected to one end of the first capacitor (C1), the VIN end, the isolation and energy conversion transformer (T1), and the VIN end of the power supply IC (U1), and the other end of the second resistor (R2) is connected to one end of the light receiver (U2-A); The other end of the light receiver (U2-A) is respectively connected to the FB end of the power IC (U1) and one end of the thirteenth resistor (R3); One end of the thirteenth resistor (R3) is respectively connected to the other end of the light receiver (U2-A) and the FB end of the power IC (U1), and the other end of the thirteenth resistor (R3) is connected to the primary ground GND.

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