A low-loss main and standby power supply switching circuit based on double MOS transistors

Abstract

This utility model discloses a low-loss main / standby power switching circuit based on dual MOSFETs, including a main power input terminal VDD1, a standby power input terminal VDD2, a diode D1, MOSFETs Q1, Q2, and Q3, resistors R1, R2, R3, R4, R5, and R6, and an output terminal VOUT. The main power input terminal VDD1 is connected to the anode of diode D1 and the drain (D) of MOSFET Q1. The gate (G) of MOSFET Q1 is connected to one end of resistor R1 and one end of resistor R2, respectively. The other end of resistor R1 is grounded. The other end of resistor R2 is connected to the standby power input terminal VDD2, one end of resistor R3, and the drain (D) of MOSFET Q2, respectively. The other end of resistor R3 is connected to one end of resistor R5 and the gate (G) of MOSFET Q3, respectively. This utility model achieves low loss, improves power supply efficiency, has a simple circuit structure, and is inexpensive.

Description

Technical Field

[0001] This utility model relates to the field of main and backup power switching circuit technology, specifically a low-loss main and backup power switching circuit based on dual MOS transistors. Background Technology

[0002] In many applications involving electrical equipment, primary and backup power supplies are configured to ensure that the equipment can function properly if a single power supply fails. For example, in applications using wireless conferencing units, a primary power supply and a backup power supply are typically configured. Current circuits that configure and switch between primary and backup power supplies generally use MOSFETs and diodes in combination. The primary power supply path uses a MOSFET; when only the primary power supply is connected, the MOSFET is turned on (conducts) to provide current to the load. The backup power supply path uses a diode; when the backup power supply is connected, the MOSFET containing the primary power supply is turned off, and the backup power supply provides current to the load through the diode. When the load is heavy, the output current (load current) is large. Because diodes have a fixed voltage drop when conducting, the larger the load current, the lower the power efficiency (power supply efficiency) of this switching circuit, even if a germanium transistor with a lower voltage drop is used to replace the diode. Assuming the output load current is 1A and the voltage drop is 0.4V, the power consumption is 0.4V × 1A = 0.4W, which means there is a loss of 0.4W, thus reducing the power supply efficiency of the backup power supply. Therefore, a switching circuit with further reduced losses is needed. Utility Model Content

[0003] To address the shortcomings of existing technologies, the purpose of this invention is to provide a low-loss master / standby power switching circuit based on dual MOS transistors, which can solve the problems described in the background art.

[0004] The technical solution to achieve the purpose of this utility model is as follows: a low-loss main / standby power switching circuit based on dual MOSFETs, including a main power input terminal VDD1, a standby power input terminal VDD2, a diode D1, MOSFETs Q1, Q2, and Q3, resistors R1, R2, R3, R4, R5, and R6, and an output terminal VOUT. The main power input terminal VDD1 is used to connect to the main power supply, and the backup power input terminal VDD2 is used to connect to the backup power supply. The main power supply or the backup power supply is used to supply power to the low-loss main / backup power switching circuit. The main power input terminal VDD1 is connected to the positive terminal of diode D1 and the drain terminal of MOSFET Q1. The gate terminal of MOSFET Q1 is connected to one end of resistor R1 and one end of resistor R2. The other end of resistor R1 is grounded. The other end of resistor R2 is connected to the backup power input terminal VDD2, one end of resistor R3, and the drain terminal of MOSFET Q2. The other end of resistor R3 is connected to one end of resistor R5 and the gate terminal of MOSFET Q3. The other end of resistor R5 and the source terminal of MOSFET Q3 are grounded together. The drain terminal of MOSFET Q3 is connected to one end of resistor R6. The other end of resistor R6 is connected to one end of resistor R4 and the gate terminal of MOSFET Q2. The source terminal of MOSFET Q2, the other end of resistor R4, the negative terminal of diode D1, and the source terminal of MOSFET Q1 are connected together and serve as the output terminal VOUT. The output terminal VOUT is used to connect to the load to supply power to the load.

[0005] Furthermore, the rated voltages of the connected main power supply and backup power supply are the same.

[0006] Furthermore, the output terminal VOUT is connected in series with a capacitor C1 and then grounded.

[0007] Furthermore, resistors R1 and R2 form the first voltage divider circuit, which serves the following function: when the main power supply and the backup power supply are connected, the voltage formed by the backup power supply through the backup power supply input terminal VDD2 and then through the first voltage divider circuit is used as the voltage of the gate of MOSFET Q1.

[0008] Furthermore, resistors R4 and R6 form a second voltage divider circuit, which serves the following function: when the main power supply and the backup power supply are connected, the voltage of the backup power supply acting on the output terminal VOUT after passing through the backup power supply input terminal VDD2, and then the voltage divided by the second voltage divider circuit, becomes the voltage of the gate of MOSFET Q2.

[0009] Furthermore, resistors R3 and R5 form a third voltage divider circuit, which serves the following function: when the main power supply and the backup power supply are connected, the voltage formed by the backup power supply through the backup power supply input terminal VDD2 and then through the third voltage divider circuit is used as the voltage of the gate of MOSFET Q3.

[0010] Furthermore, the resistance of resistor R1 is 10 KΩ, the resistance of resistor R2 is 100 Ω, the resistance of resistor R3 is 22 Ω, the resistance of resistor R4 is 10 KΩ, the resistance of resistor R5 is 10 KΩ, and the resistance of resistor R6 is 10 KΩ.

[0011] Furthermore, the capacitance of capacitor C1 is 22 uF.

[0012] Furthermore, diode D1 is a germanium diode, MOSFET Q3 is an N-type MOSFET, and MOSFETs Q1 and Q2 are both P-type MOSFETs.

[0013] The beneficial effects of this invention are: This invention achieves low power loss and improves power supply efficiency. When using a diode D1 with a voltage drop of 0.4V and a load current of 1A, the power consumption is 0.4W (0.4V × 1A = 0.4W). Now, using a MOSFET, assuming an on-resistance of 10mΩ, the power consumption is changed to 0.01W (0.01Ω × 1²A = 0.01W). Compared to the diode solution, the power supply efficiency is improved by 97.5%, and the smaller the on-resistance of the selected MOSFET, the higher the power supply efficiency.

[0014] This invention also enables seamless switching. By utilizing the body diode of MOSFET Q1 and diode D1 (which uses a germanium diode) to form a dual freewheeling path, the voltage at VOUT drops to a minimum of 4.6V during switching, while the traditional pure MOSFET solution may drop to 4V (1V voltage drop from the body diode). The voltage drop is much smaller, thus enabling seamless switching.

[0015] This invention features a simple structure and controllable cost. It requires only 3 MOSFETs, a few resistors, 1 capacitor, and 1 diode D1, eliminating the need for complex control ICs or high-performance circuits. The circuit structure is simple, inexpensive, and within a controllable range. Attached Figure Description

[0016] Figure 1 This is a circuit diagram of the present invention. Detailed Implementation

[0017] The present invention will be further described below with reference to the accompanying drawings and specific embodiments: like Figure 1 As shown, a low-loss main / standby power switching circuit based on dual MOSFETs includes a main power input terminal VDD1, a standby power input terminal VDD2, a diode D1, MOSFETs Q1, Q2, and Q3, resistors R1, R2, R3, R4, R5, and R6, a capacitor C1, and an output terminal VOUT.

[0018] The main power input terminal VDD1 is used to connect to the main power supply, and the backup power input terminal VDD2 is used to connect to the backup power supply. The main power supply or the backup power supply is used to supply power to the low-loss main / backup power switching circuit.

[0019] The main power supply and the backup power supply connected to it have the same rated voltage, for example, both are 5V.

[0020] It is understandable that the main power supply and backup power supply can be integrated into the low-loss main / backup power supply switching circuit, thus forming a whole with the low-loss main / backup power supply switching circuit. The main power supply and backup power supply can also be external power supplies, which are connected to the main power supply and backup power supply respectively through the main power supply input terminal VDD1 and the backup power supply input terminal VDD2 when needed.

[0021] The main power input terminal VDD1 is connected to the anode of diode D1 and the drain (D) of MOSFET Q1. The gate (G) of MOSFET Q1 is connected to one end of resistor R1 and one end of resistor R2, respectively. The other end of resistor R1 is grounded. The other end of resistor R2 is connected to the backup power input terminal VDD2, one end of resistor R3, and the drain (D) of MOSFET Q2. The other end of resistor R3 is connected to one end of resistor R5 and the gate (G) of MOSFET Q3. The other end of resistor R5 and the source (S) of MOSFET Q3 are grounded together. The drain (D) of MOSFET Q3 is connected to one end of resistor R6. The other end of resistor R6 is connected to one end of resistor R4 and the gate (G) of MOSFET Q2. The source (S) of MOSFET Q2, the other end of resistor R4, the cathode of diode D1, and the source (S) of MOSFET Q1 are connected together and form the output terminal VOUT. The output terminal VOUT is also connected in series with capacitor C1 and then grounded. The output terminal VOUT is used to connect to the load to supply power to it.

[0022] Among them, resistors R1 and R2 form the first voltage divider circuit, which serves the following function: when both the main power supply and the backup power supply are connected, that is, when both the main power supply and the backup power supply are connected, the voltage formed by the backup power supply through the backup power supply input terminal VDD2 and then through the first voltage divider circuit is used as the voltage of the gate of MOSFET Q1.

[0023] Resistors R4 and R6 form the second voltage divider circuit, which serves the following function: when both the main power supply and the backup power supply are connected, the voltage of the backup power supply acting on the output terminal VOUT after passing through the backup power supply input terminal VDD2 is then divided by the second voltage divider circuit and used as the voltage of the gate of MOSFET Q2.

[0024] Resistors R3 and R5 form the third voltage divider circuit, which serves the following function: when both the main power supply and the backup power supply are connected, the voltage formed by the backup power supply through the backup power supply input terminal VDD2 and then through the third voltage divider circuit is used as the voltage of the gate of MOSFET Q3.

[0025] For example, the resistance of resistor R1 is 10 kΩ, the resistance of resistor R2 is 100 Ω, the resistance of resistor R3 is 22 Ω, the resistance of resistor R4 is 10 kΩ, the resistance of resistor R5 is 10 kΩ, the resistance of resistor R6 is 10 kΩ, and the capacitance of capacitor C1 is 22 uF.

[0026] For example, diode D1 is a germanium diode. MOSFET Q3 is an N-type MOSFET, while MOSFETs Q1 and Q2 are both P-type MOSFETs.

[0027] Working principle: Scenario 1: Connected to main power supply, not connected to backup power supply.

[0028] It is understandable that "not connected to backup power" means that the backup power supply cannot supply power to the low-loss primary / backup power switching circuit through the backup power supply access terminal VDD2. Therefore, it can include the following situations: although the backup power supply access terminal VDD2 is electrically connected to the backup power supply on the physical link, the backup power supply is faulty and cannot supply power to the outside; or, although the backup power supply is normal and can supply power to the outside, the circuit electrically connected to the backup power supply access terminal VDD2 is faulty and cannot transmit power normally; or, other situations, which will not be listed here.

[0029] After the main power supply provides power through the main power input terminal VDD1, it supplies current to the load through diode D1 and MOSFET Q1. At the initial moment when the main power supply starts supplying power, the voltage drop V between the gate (G) and source (S) of MOSFET Q1 is... GS It has not yet exceeded the voltage drop threshold V GSth In other words, the conduction condition has not yet been met. At this time, MOSFET Q1 is not turned on, and the gate of MOSFET Q1 is grounded through resistor R1. The main power supply provides current to the load only through diode D1, and the voltage drop V... GS It also reached the voltage drop threshold V GSth Previously, current was supplied to the load through diode D1. The voltage drop between the main power input terminal VDD1 and the output terminal VOUT is equal to the voltage drop across diode D1.

[0030] As the main power supply continues to supply power, the voltage at the source (S) of MOSFET Q1 will slowly rise until the voltage drops to V. GS Reaching the voltage drop threshold V GSth This causes the MOSFET Q1 to conduct, thus switching the current supply to the load to the MOSFET Q1. At this time, the voltages across the positive and negative terminals of the diode D1 are basically the same, preventing current from passing through the diode D1, and thus the current is not supplied to the load through the diode D1.

[0031] When MOSFET Q1 is turned on, the voltage drop between the main power input terminal VDD1 and the output terminal VOUT is almost zero, meaning there is virtually no voltage drop between them, which can be ignored. Assuming a load current of 1 A and an on-resistance of MOSFET Q1 of 10 mΩ, the voltage drop is 0.01Ω × 1A = 0.01V. This 0.01V voltage drop is negligible compared to a 5V voltage, resulting in extremely low power loss.

[0032] In this situation, since the backup power supply is not connected, the gate and source terminals of MOSFET Q3 are essentially grounded and cannot be turned on. In other words, MOSFET Q3 is in a non-conducting state, and similarly, MOSFET Q2 is also not turned on.

[0033] Scenario 2: Connected to both main power and backup power.

[0034] When a backup power supply is connected, the voltage at the gate (G) of MOSFET Q1, which was originally pulled down to ground (0V) by resistor R1, rises to the first voltage divider V1. This first voltage divider V1 is the voltage applied to the gate (G) of MOSFET Q1 through the first voltage divider circuit. First voltage divider V1 = , The voltage of the backup power supply is used. At this time, the voltage drop V of MOSFET Q1 is... GS When the value is close to 0, MOSFET Q1 is not turned on.

[0035] Meanwhile, due to the presence of the backup power supply, the voltage at the gate (G) of MOSFET Q3 gradually rises from 0V to the third voltage divider (V3) resulting from the backup power supply voltage after the third voltage divider circuit. This third voltage divider (V3) is the voltage applied to the gate (G) of MOSFET Q3 via the third voltage divider circuit. The third voltage divider (V3) = This causes the voltage drop V of MOSFET Q3 to... GS The pressure rises until it reaches the pressure drop threshold V. GSth This causes MOSFET Q3 to conduct. When MOSFET Q3 is turned on, one end of resistor R6 is effectively grounded via MOSFET Q3. The voltage at the gate (G) of MOSFET Q2, which originally came from resistor R4 to the output terminal VOUT, gradually decreases to the second voltage V2 obtained by the second voltage divider circuit after passing through VOUT. This second voltage V2 is the voltage at the gate of MOSFET Q2 formed by the voltage from the backup power supply after passing through the backup power input terminal VDD2 to the output terminal VOUT, and then further divided by the second voltage divider circuit. The second voltage V2 = V OUT This refers to the voltage at the output terminal VOUT. When the voltage at the gate of MOSFET Q2 drops to a level that causes the voltage drop V... GS Satisfying the voltage drop threshold V GSth When the MOSFET Q2 is turned on, the load current is switched to the backup power supply, that is, the power supply is changed from the main power supply to the backup power supply, thus realizing the switching between main and backup power supply.

[0036] The two scenarios described above are based on practical applications, where the system was originally powered by the main power supply but was later switched to a backup power supply. Other scenarios, such as when neither the main nor backup power supply is connected, are not applicable because no power source is available, and are therefore not the focus of this application. The same applies to other scenarios; therefore, only two scenarios have been listed above.

[0037] This invention employs a collaborative control logic consisting of a first MOS transistor group composed of MOS transistor Q1 and a second MOS transistor group composed of MOS transistors Q2 and Q3. Automatic switching between main and backup power supplies is achieved through a pure resistor voltage divider network, eliminating the need for a comparison or control IC, thereby significantly simplifying circuit design.

[0038] This invention also features a seamless switching and anti-backflow mechanism: During the switching process, diode D1 (using a germanium diode, which can be set to a voltage drop of 0.4V) prioritizes freewheeling to avoid excessive voltage drop caused by relying solely on the body diode (i.e., MOSFET Q1, which has a voltage drop of 1V). When MOSFET Q1 is turned off, it cannot be guaranteed that MOSFETs Q2 and Q3 will be turned on at the same time. If they are not synchronized, it is easy to cause a voltage drop, which may affect the normal operation of the subsequent circuit. Due to the presence of MOSFET Q1, the voltage will not drop too much. Assuming that the voltage drop of MOSFET Q1 is 1V, the VOUT voltage may drop to 4V.

[0039] Therefore, a diode D1 was added to the circuit, and a germanium diode with a low forward voltage drop was selected. Assuming that the voltage drop of diode D1 is 0.4V, the VOUT voltage will drop to 4.6V. When the circuit enters steady state, after the MOSFET Q1 is turned on, the VOUT voltage rises to 5V, which improves the stability and reliability of the circuit.

[0040] Diode D1, MOSFET Q1, and MOSFET Q2 are all reverse-biased by MOSFET Q1, which prevents reverse power flow between the main power supply and the backup power supply.

[0041] This invention achieves low power loss and improves power supply efficiency. When using a diode D1 with a voltage drop of 0.4V and a load current of 1A, the power consumption is 0.4W (0.4V × 1A = 0.4W). Now, using a MOSFET with an on-resistance of 10mΩ, the power consumption is reduced to 0.01W (0.01Ω × 1²A = 0.01W). Compared to the diode solution, the power supply efficiency is improved by 97.5%, and the lower the on-resistance of the selected MOSFET, the higher the power supply efficiency.

[0042] This invention also enables seamless switching. By utilizing the body diode of MOSFET Q1 and diode D1 (which uses a germanium diode) to form a dual freewheeling path, the voltage at VOUT drops to a minimum of 4.6V during switching, while the traditional pure MOSFET solution may drop to 4V (1V voltage drop from the body diode). The voltage drop is much smaller, thus enabling seamless switching.

[0043] This invention features a simple structure and controllable cost. It requires only 3 MOSFETs, a few resistors, 1 capacitor, and 1 diode D1, eliminating the need for complex control ICs or high-performance circuits. The circuit structure is simple, inexpensive, and within a controllable range.

[0044] The embodiments disclosed in this specification are merely illustrative of one aspect of the features of this utility model. The protection scope of this utility model is not limited to this embodiment, and any other functionally equivalent embodiments fall within the protection scope of this utility model. Those skilled in the art can make various other corresponding changes and modifications based on the technical solutions and concepts described above, and all such changes and modifications should fall within the protection scope of the claims of this utility model.

Claims

1. A low-loss master / standby power switching circuit based on dual MOS transistors, characterized in that, This includes the main power input terminal VDD1, the backup power input terminal VDD2, diode D1, MOSFETs Q1, Q2, and Q3, resistors R1, R2, R3, R4, R5, and R6, and the output terminal VOUT. The main power input terminal VDD1 is used to connect to the main power supply, and the backup power input terminal VDD2 is used to connect to the backup power supply. The main power supply or the backup power supply is used to supply power to the low-loss main / backup power switching circuit. The main power input terminal VDD1 is connected to the positive terminal of diode D1 and the drain terminal of MOSFET Q1. The gate terminal of MOSFET Q1 is connected to one end of resistor R1 and one end of resistor R2. The other end of resistor R1 is grounded. The other end of resistor R2 is connected to the backup power input terminal VDD2, one end of resistor R3, and the drain terminal of MOSFET Q2. The other end of resistor R3 is connected to one end of resistor R5 and the gate terminal of MOSFET Q3. The other end of resistor R5 and the source terminal of MOSFET Q3 are grounded together. The drain terminal of MOSFET Q3 is connected to one end of resistor R6. The other end of resistor R6 is connected to one end of resistor R4 and the gate terminal of MOSFET Q2. The source terminal of MOSFET Q2, the other end of resistor R4, the negative terminal of diode D1, and the source terminal of MOSFET Q1 are connected together and serve as the output terminal VOUT. The output terminal VOUT is used to connect to the load to supply power to the load.

2. The low-loss master / standby power switching circuit based on dual MOS transistors according to claim 1, characterized in that, The main power supply and the backup power supply connected to it have the same rated voltage.

3. The low-loss master / standby power switching circuit based on dual MOS transistors according to claim 1, characterized in that, The output terminal VOUT is connected in series with a capacitor C1 and then grounded.

4. The low-loss master / standby power switching circuit based on dual MOS transistors according to claim 1, characterized in that, Resistors R1 and R2 form the first voltage divider circuit, which serves the following function: when the main power supply and the backup power supply are connected, the voltage formed by the backup power supply through the backup power supply input terminal VDD2 and then through the first voltage divider circuit is used as the voltage of the gate of MOSFET Q1.

5. The low-loss master / standby power switching circuit based on dual MOS transistors according to claim 4, characterized in that, Resistors R4 and R6 form the second voltage divider circuit, which serves the following function: when the main power supply and the backup power supply are connected, the voltage of the backup power supply acting on the output terminal VOUT after passing through the backup power supply input terminal VDD2, and then the voltage divided by the second voltage divider circuit, becomes the voltage of the gate of MOSFET Q2.

6. The low-loss master / standby power switching circuit based on dual MOS transistors according to claim 5, characterized in that, Resistors R3 and R5 form the third voltage divider circuit, which serves the following function: when the main power supply and the backup power supply are connected, the voltage formed by the backup power supply through the backup power supply input terminal VDD2 and then through the third voltage divider circuit is used as the voltage of the gate of MOSFET Q3.

7. The low-loss master / standby power switching circuit based on dual MOS transistors according to claim 1, characterized in that, The resistance of resistor R1 is 10 kΩ, the resistance of resistor R2 is 100 Ω, the resistance of resistor R3 is 22 Ω, the resistance of resistor R4 is 10 kΩ, the resistance of resistor R5 is 10 kΩ, and the resistance of resistor R6 is 10 kΩ.

8. The low-loss master / standby power switching circuit based on dual MOS transistors according to claim 3, characterized in that, The capacitance of capacitor C1 is 22 uF.

9. The low-loss master / standby power switching circuit based on dual MOS transistors according to claim 1, characterized in that, Diode D1 is a germanium diode, MOSFET Q3 is an N-type MOSFET, and MOSFETs Q1 and Q2 are both P-type MOSFETs.

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