A wide voltage switching circuit

Abstract

The present invention provides a wide-voltage switching circuit, which includes a DC input terminal, a DC output terminal, a first voltage control switch, a second voltage control switch, a buck module, a first controllable precision voltage reference source, a second controllable precision voltage reference source, a third controllable precision voltage reference source, a fourth controllable precision voltage reference source, a first voltage dividing circuit, a second voltage dividing circuit, a third voltage dividing circuit, and an overvoltage protection device. By setting the voltage division ratios of the first, second, and third voltage dividing circuits, the magnitudes of the voltages input to the reference terminals of the first, second, third, and fourth controllable precision voltage reference sources are adjusted, so as to control whether conduction occurs from the cathode to the anode, and further control the on / off states of the first voltage control switch and the second voltage control switch, thereby realizing switching between output through the first voltage control switch or the second voltage control switch under different input voltages, and maintaining the adapter to operate within a safe voltage range.

Description

Technical Field

[0001] The present invention relates to the technical field of voltage regulation circuits, and particularly to a wide-voltage switching circuit. Background Art

[0002] An adapter is an interface converter, which generally needs to work within a specific voltage range. The standard operating voltage is generally about 12V, and a certain range of voltage fluctuations is allowed during actual use, such as 9V to 14V. However, if the input voltage is lower than 9V, the adapter will trigger a low-voltage protection mechanism and stop working; if the input voltage exceeds 14V, it may cause unstable operation or even damage to the device due to excessive voltage. Therefore, it is necessary to ensure that the adapter works within a safe voltage range during daily use. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a voltage transmission circuit that can maintain the adapter within a safe voltage range.

[0004] To solve the above technical problem, the present invention provides a wide-voltage switching circuit, including a DC input terminal, a DC output terminal, a first voltage control switch, a second voltage control switch, a step-down module, a first controllable precision voltage reference, a second controllable precision voltage reference, a third controllable precision voltage reference, a fourth controllable precision voltage reference, a first voltage dividing circuit, a second voltage dividing circuit, a third voltage dividing circuit, and an overvoltage protection device; the first voltage control switch is connected in series with the step-down module and then connected between the DC input terminal and the DC output terminal, and the second voltage control switch is connected between the DC input terminal and the DC output terminal; the first voltage dividing circuit, the second voltage dividing circuit, the third voltage dividing circuit, and the overvoltage protection device are each connected in series between the DC input terminal and the ground terminal; the reference terminal of the first controllable precision voltage reference is connected to the voltage dividing point of the first voltage dividing circuit, the anode is grounded, and the cathode is connected to the voltage dividing point of the second voltage dividing circuit. The reference terminal of the second controllable precision voltage reference is connected to the voltage dividing point of the second voltage dividing circuit, the anode is grounded, and the cathode is connected to the control terminal of the first voltage control switch. The reference terminal of the third controllable precision voltage reference is connected to the voltage dividing point of the second voltage dividing circuit, the anode is grounded, and the cathode is connected to the voltage dividing point of the third voltage dividing circuit. The reference terminal of the fourth controllable precision voltage reference is connected to the voltage dividing point of the third voltage dividing circuit, the anode is grounded, and the cathode is connected to the control terminal of the second voltage control switch.

[0005] Further, the breakdown voltage of the overvoltage protection device is 28V.

[0006] Further, the voltage division ratios of the first, second, and third voltage dividing circuits are set as:

[0007] When the input voltage is less than 9V, the voltage after being divided by the first voltage dividing circuit is less than the reference voltage of the first controllable precision voltage stabilizer, the voltage after being divided by the second voltage dividing circuit is less than the reference voltages of the second and third controllable precision voltage stabilizers, and the voltage after being divided by the third voltage dividing circuit is less than the reference voltage of the fourth controllable precision voltage stabilizer;

[0008] When the input voltage is not less than 9V but less than 14V, the voltage after being divided by the first voltage dividing circuit is less than the reference voltage of the first controllable precision voltage stabilizer, the voltage after being divided by the second voltage dividing circuit is less than the reference voltages of the second and third controllable precision voltage stabilizers, while the voltage after being divided by the third voltage dividing circuit is not less than the reference voltage of the fourth controllable precision voltage stabilizer;

[0009] When the input voltage is not less than 14V but less than 28V, the voltage after being divided by the first voltage dividing circuit is less than the reference voltage of the first controllable precision voltage stabilizer, while the voltage after being divided by the second voltage dividing circuit is not less than the reference voltages of the second and third controllable precision voltage stabilizers, and the voltage after being divided by the third voltage dividing circuit is not less than the reference voltage of the fourth controllable precision voltage stabilizer.

[0010] Further, the reference voltages of the first, second, third, and fourth controllable precision voltage stabilizers are 2.5V.

[0011] Further, the voltage division ratio of the first voltage dividing circuit is set to 10.2:1, the voltage division ratio of the second voltage dividing circuit is set to 4.6:1, and the voltage division ratio of the third voltage dividing circuit is set to 2.6:1.

[0012] Further, the first voltage control switch includes two P-type MOS transistors. Their sources are connected together and then connected to the DC input terminal, their drains are connected together and then connected to the buck module, and their gates are connected together as the control terminal and connected to the cathode of the second controllable precision voltage stabilizer; the second voltage control switch includes a P-type MOS transistor. Its source is connected together and then connected to the DC input terminal, its drain is connected together and then connected to the DC output terminal, and its gate is connected together as the control terminal and connected to the cathode of the fourth controllable precision voltage stabilizer.

[0013] Further, a first anti-backflow diode is connected in series on the branch where the first voltage control switch and the buck module are located, and a second anti-backflow diode is connected in series on the branch where the second voltage control switch is located.

[0014] Further, a surge protection module is connected in series between the DC input terminal and the ground terminal. The surge protection module includes a surge protection resistor and a surge protection capacitor connected in series.

[0015] Further, the buck module includes an NDP2450KC buck chip.

[0016] Further, a contact point between the first voltage control switch and the buck module is connected with an energy storage and filtering capacitor.

[0017] The present invention has the following beneficial effects: Among the four controllable precision voltage regulators, if the reference terminal voltage is less than the reference voltage, the conduction from the cathode to the anode is blocked; if the reference terminal voltage is not less than the reference voltage, the conduction from the cathode to the anode is enabled. Since the reference terminal of the first controllable precision voltage regulator is connected to the voltage dividing point of the first voltage dividing circuit, the reference terminals of the second and third controllable precision voltage regulators are connected to the voltage dividing point of the second voltage dividing circuit, and the reference terminal of the fourth controllable precision voltage regulator is connected to the voltage dividing point of the third voltage dividing circuit, the voltage magnitudes input to the reference terminals of the first, second, third, and fourth controllable precision voltage regulators can be adjusted by setting the voltage division ratios of the first, second, and third voltage dividing circuits, thereby controlling whether the conduction from the cathode to the anode is enabled, and further controlling the on / off states of the first voltage control switch and the second voltage control switch, so as to achieve switching between output through the first voltage control switch or the second voltage control switch under different input voltages.

[0018] Specifically, the voltage division ratios of the first, second, and third voltage dividing circuits are set as follows: when the input voltage is less than 9V, the voltages divided by the first, second, and third voltage dividing circuits are all less than the reference voltage of the controllable precision voltage regulator; when the input voltage is not less than 9V but less than 14V, the voltages divided by the first and second voltage dividing circuits are less than the reference voltage of the controllable precision voltage regulator, while the voltage divided by the third voltage dividing circuit is not less than the reference voltage of the controllable precision voltage regulator; when the input voltage is not less than 14V but less than 28V, the voltage divided by the first voltage dividing circuit is less than the reference voltage of the controllable precision voltage regulator, while the voltage divided by the second voltage dividing circuit is not less than the reference voltage of the controllable precision voltage regulator. Thus:

[0019] When the input voltage is less than 9V, the reference terminal voltage of the first controllable precision voltage regulator is obtained by voltage division of the first voltage dividing circuit, and this voltage is less than the reference voltage, so the conduction from the cathode to the anode of the first controllable precision voltage regulator is blocked, enabling the second voltage dividing circuit to perform normal voltage division. The reference terminal voltage of the second controllable precision voltage regulator is obtained by voltage division of the second voltage dividing circuit, and this voltage is less than the reference voltage, so the conduction from the cathode to the anode of the second controllable precision voltage regulator is blocked. Since the cathode of the second controllable precision voltage regulator is connected to the control terminal of the first voltage control switch, the first voltage control switch is also not turned on when the conduction from the cathode to the anode of the second controllable precision voltage regulator is blocked, and the input voltage cannot be output to the DC output terminal through the first voltage control switch and the buck module.

[0020] Meanwhile, the reference terminal voltage of the third controllable precision voltage stabilizer is obtained by voltage division of the second voltage division circuit. Since this voltage is less than the reference voltage, the cathode-to-anode of the third controllable precision voltage stabilizer is not conducting, enabling the third voltage division circuit to perform normal voltage division. And the reference terminal voltage of the fourth controllable precision voltage stabilizer is obtained by voltage division of the third voltage division circuit. Since this voltage is less than the reference voltage, the cathode-to-anode of the fourth controllable precision voltage stabilizer is not conducting. Since the cathode of the fourth controllable precision voltage stabilizer is connected to the control terminal of the second voltage control switch, the second voltage control switch is also not conducting when the cathode-to-anode of the fourth controllable precision voltage stabilizer is not conducting, and the input voltage cannot be output to the DC output terminal through the second voltage control switch.

[0021] When the input voltage is not less than 9V but less than 14V, the reference terminal voltage of the first controllable precision voltage stabilizer is obtained by voltage division of the first voltage division circuit. Since this voltage is less than the reference voltage, the cathode-to-anode of the first controllable precision voltage stabilizer is not conducting, enabling the second voltage division circuit to perform normal voltage division. And the reference terminal voltage of the second controllable precision voltage stabilizer is obtained by voltage division of the second voltage division circuit. Since this voltage is less than the reference voltage, the cathode-to-anode of the second controllable precision voltage stabilizer is not conducting. Since the cathode of the second controllable precision voltage stabilizer is connected to the control terminal of the first voltage control switch, the first voltage control switch is also not conducting when the cathode-to-anode of the second controllable precision voltage stabilizer is not conducting, and the input voltage cannot be output to the DC output terminal through the first voltage control switch and the buck module.

[0022] Meanwhile, the reference terminal voltage of the third controllable precision voltage stabilizer is obtained by voltage division of the second voltage division circuit. Since this voltage is less than the reference voltage, the cathode-to-anode of the third controllable precision voltage stabilizer is not conducting, enabling the third voltage division circuit to perform normal voltage division. And the reference terminal voltage of the fourth controllable precision voltage stabilizer is obtained by voltage division of the third voltage division circuit. Since this voltage is not less than the reference voltage, the cathode-to-anode of the fourth controllable precision voltage stabilizer is conducting. Since the cathode of the fourth controllable precision voltage stabilizer is connected to the control terminal of the second voltage control switch, the second voltage control switch is also conducting when the cathode-to-anode of the fourth controllable precision voltage stabilizer is conducting, and the input voltage can be output to the DC output terminal through the second voltage control switch.

[0023] When the input voltage is not less than 14V but less than 28V, the reference terminal voltage of the first controllable precision voltage regulator is obtained by voltage division of the first voltage division circuit. Since this voltage is less than the reference voltage, the cathode-to-anode of the first controllable precision voltage regulator is not conducting, enabling the second voltage division circuit to perform normal voltage division. And the reference terminal voltage of the second controllable precision voltage regulator is obtained by voltage division of the second voltage division circuit. Since this voltage is not less than the reference voltage, the cathode-to-anode of the second controllable precision voltage regulator is conducting. As the cathode of the second controllable precision voltage regulator is connected to the control terminal of the first voltage control switch, when the cathode-to-anode of the second controllable precision voltage regulator is conducting, the first voltage control switch is also conducting, and the input voltage can be output through the first voltage control switch and the buck module. After the input voltage is reduced to 9V - 14V by the buck module, it is output to the DC output terminal.

[0024] Meanwhile, the reference terminal voltage of the third controllable precision voltage regulator is obtained by voltage division of the second voltage division circuit. Since this voltage is not less than the reference voltage, the cathode-to-anode of the third controllable precision voltage regulator is conducting, pulling down the reference terminal voltage of the fourth controllable precision voltage regulator. Since this voltage is less than the reference voltage, the cathode-to-anode of the fourth controllable precision voltage regulator is not conducting. As the cathode of the fourth controllable precision voltage regulator is connected to the control terminal of the second voltage control switch, when the cathode-to-anode of the fourth controllable precision voltage regulator is not conducting, the second voltage control switch is also not conducting, and the input voltage cannot be output to the DC output terminal through the second voltage control switch.

[0025] When the input voltage is not less than 28V, the overvoltage protection device breaks down and conducts, and the input voltage at the DC input terminal is output to the ground terminal through the overvoltage protection device, and cannot be output to the DC output terminal through the first voltage control switch or the second voltage control switch.

[0026] In summary, when the input voltage is less than 9V or not less than 28V, this input voltage cannot be output to the DC output terminal; when the input voltage is not less than 9V but less than 14V, this input voltage is directly output to the DC output terminal through the second voltage control switch; when the input voltage is not less than 14V but less than 28V, this input voltage is output through the first voltage control switch and the buck module. After the input voltage is reduced to 9V - 14V by the buck module, it is output to the DC output terminal. In this way, only a voltage of 9V - 14V is output through this wide voltage switching circuit, enabling the adapter to operate within a safe voltage range. Description of the Drawings

[0027] Figure 1 It is a partial circuit schematic diagram of the voltage control switch part of the wide voltage switching circuit.

[0028] Figure 2 It is a partial circuit schematic diagram of the buck module part of the wide voltage switching circuit. Detailed Implementation Manner

[0029] The present invention will be further described in detail in conjunction with specific embodiments.

[0030] This embodiment provides a wide-voltage switching circuit, as Figure 1 , 2 shown. The wide-voltage switching circuit includes a DC input terminal Vin, a DC output terminal Vout, a first voltage control switch, a second voltage control switch, a buck module DCDC, a first adjustable precision voltage reference U1, a second adjustable precision voltage reference U2, a third adjustable precision voltage reference U3, a fourth adjustable precision voltage reference U4, a first voltage-dividing circuit, a second voltage-dividing circuit, a third voltage-dividing circuit, and an overvoltage protection device D1. Among them, the DC output terminal Vout is used to connect to the power supply terminal of the adapter.

[0031] The first voltage control switch includes a P-type MOS transistor Q1 and a P-type MOS transistor Q2. The gates of these two MOS transistors Q1 and Q2 are connected together as the control terminal of the first voltage control switch. The sources are connected together and then connected to the DC input terminal Vin, and a resistor R7 and a capacitor C1 are connected in series between the source and the gate. The drains are connected together and then connected to the input terminal of the buck module DCDC through the contact VIN14V_28V. The output terminal of the buck module DCDC is connected to the DC output terminal Vout. Then, the first voltage control switch and the buck module DCDC are connected in series between the DC input terminal Vin and the DC output terminal Vout. The second voltage control switch includes a P-type MOS transistor Q3 and a P-type MOS transistor Q4. The gates of these two MOS transistors Q3 and Q4 are connected together as the control terminal of the second voltage control switch. The sources are connected together and then connected to the DC input terminal Vin, and a resistor R8 and a capacitor C2 are connected in series between the source and the gate. The drains are connected together and then connected to the DC output terminal Vout. Then, the second voltage control switch is connected between the DC input terminal Vin and the DC output terminal Vout.

[0032] The first voltage-dividing circuit includes a resistor R1 and a resistor R2 connected in series. The second voltage-dividing circuit includes a resistor R3 and a resistor R4 connected in series. The third voltage-dividing circuit includes a resistor R5 and a resistor R6 connected in series. The first voltage-dividing circuit, the second voltage-dividing circuit, the third voltage-dividing circuit, and the overvoltage protection device D1 are each connected in series between the DC input terminal Vin and the ground terminal.

[0033] The reference terminal R of the first controllable precision voltage regulator U1 is connected to the voltage division point of the first voltage division circuit (i.e., the connection point between resistor R1 and resistor R2), the anode A is grounded, and the cathode K is connected to the voltage division point of the second voltage division circuit (i.e., the connection point between resistor R3 and resistor R4). The reference terminal R of the second controllable precision voltage regulator U2 is connected to the voltage division point of the second voltage division circuit (i.e., the connection point between resistor R3 and resistor R4), the anode A is grounded, and the cathode K is connected to the control terminal of the first voltage control switch (i.e., the gates of MOS transistors Q1 and Q2) via resistor R9. The reference terminal R of the third controllable precision voltage regulator U3 is connected to the voltage division point of the second voltage division circuit (i.e., the connection point between resistor R3 and resistor R4) via connection point 14V_ON / OFF, the anode A is grounded, and the cathode K is connected to the voltage division point of the third voltage division circuit (i.e., the connection point between resistor R5 and resistor R6). The reference terminal R of the fourth controllable precision voltage regulator U4 is connected to the voltage division point of the third voltage division circuit (i.e., the connection point between resistor R5 and resistor R6), the anode A is grounded, and the cathode K is connected to the control terminal of the second voltage control switch (i.e., the gates of MOS transistors Q3 and Q4) via resistor R10.

[0034] In this embodiment, the reference voltages of the first controllable precision voltage regulator U1, the second controllable precision voltage regulator U2, the third controllable precision voltage regulator U3, and the fourth controllable precision voltage regulator U4 are all 2.5V. Then, when the voltage at the reference terminal R of these four controllable precision voltage regulators U1, U2, U3, and U4 is less than 2.5V, the cathode K is not conductive to the anode A, and when the voltage at the reference terminal R is not less than 2.5V, the cathode K is conductive to the anode A.

[0035] In this embodiment, the voltage division ratio of the first voltage division circuit is set to 10.2:1. Specifically, the resistance value of resistor R1 is set to 102 kΩ, and the resistance value of resistor R2 is set to 10 kΩ; the voltage division ratio of the second voltage division circuit is set to 4.6:1. Specifically, the resistance value of resistor R3 is set to 46 kΩ, and the resistance value of resistor R4 is set to 10 kΩ; the voltage division ratio of the third voltage division circuit is set to 2.6:1. Specifically, the resistance value of resistor R5 is set to 26 kΩ, and the resistance value of resistor R6 is set to 10 kΩ. Thus, based on the voltage division ratios of the first voltage division circuit, the second voltage division circuit, and the third voltage division circuit, the voltage magnitude input to the reference terminal R of the first controllable precision voltage regulator U1, the second controllable precision voltage regulator U2, the third controllable precision voltage regulator U3, and the fourth controllable precision voltage regulator U4 can be adjusted, thereby controlling whether the cathode K is conductive to the anode A, and further controlling the on / off of the first voltage control switch and the second voltage control switch, so as to realize switching the output via the first voltage control switch or the second voltage control switch under different input voltages.

[0036] When the input voltage of the DC input terminal Vin is less than 9V, the voltage output after the input voltage is divided by the first voltage dividing circuit is Vin*10 / (102 + 10) < 2.5V. The voltage of the reference terminal R of the first precision voltage regulator U1 is obtained by voltage division of the first voltage dividing circuit, and this voltage is less than 2.5V, that is, less than the reference voltage of the first precision voltage regulator U1. Then, the cathode K to the anode A of the first precision voltage regulator U1 is not conducting, enabling the second voltage dividing circuit to divide the voltage normally. The voltage after the input voltage is divided by the second voltage dividing circuit is Vin*10 / (46 + 10) < 2.5V. The voltage of the reference terminal R of the second precision voltage regulator U2 is obtained by voltage division of the second voltage dividing circuit, and this voltage is less than 2.5V, that is, less than the reference voltage of the second precision voltage regulator U2. Then, the cathode K to the anode A of the second precision voltage regulator U2 is not conducting. Since the cathode K of the second precision voltage regulator U2 is connected to the control terminal of the first voltage control switch, when the cathode K to the anode A of the second precision voltage regulator U2 is not conducting, the control terminal of the first voltage control switch cannot be grounded through the second precision voltage regulator U2. Then, the voltage of the control terminal of the first voltage control switch will not be pulled down, that is, the source voltages of the MOS transistor Q1 and the MOS transistor Q2 of the first voltage control switch are not higher than the gate voltages, causing the first voltage control switch not to conduct, and the input voltage of the DC input terminal Vin cannot be output to the DC output terminal Vout through the first voltage control switch and the buck module DCDC.

[0037] Meanwhile, the voltage of the reference terminal R of the third precision voltage regulator U3 is also obtained by voltage division of the second voltage dividing circuit, and this voltage is less than 2.5V, that is, less than the reference voltage of the third precision voltage regulator U3. Then, the cathode K to the anode A of the third precision voltage regulator U3 is not conducting, enabling the third voltage dividing circuit to divide the voltage normally. The voltage after the input voltage is divided by the third voltage dividing circuit is Vin*10 / (26 + 10) < 2.5V. The voltage of the reference terminal R of the fourth precision voltage regulator U4 is obtained by voltage division of the third voltage dividing circuit, and this voltage is less than 2.5V, that is, less than the reference voltage of the fourth precision voltage regulator U4. Then, the cathode K to the anode A of the fourth precision voltage regulator U4 is not conducting. Since the cathode K of the fourth precision voltage regulator U4 is connected to the control terminal of the second voltage control switch, when the cathode K to the anode A of the fourth precision voltage regulator U4 is not conducting, the control terminal of the second voltage control switch cannot be grounded through the fourth precision voltage regulator U4. Then, the voltage of the control terminal of the second voltage control switch will not be pulled down, that is, the source voltages of the MOS transistor Q3 and the MOS transistor Q4 of the second voltage control switch are not higher than the gate voltages, causing the second voltage control switch not to conduct, and the input voltage cannot be output to the DC output terminal Vout through the second voltage control switch.

[0038] When the input voltage of the DC input terminal Vin is not less than 9V but less than 14V, the voltage after the input voltage is divided by the first voltage dividing circuit is Vin * 10 / (102 + 10) < 2.5V. The voltage of the reference terminal R of the first controllable precision voltage regulator U1 is obtained by dividing the voltage of the first voltage dividing circuit, and this voltage is less than 2.5V, that is, less than the reference voltage of the first controllable precision voltage regulator U1. Then, the cathode K to the anode A of the first controllable precision voltage regulator U1 is not conducting, enabling the second voltage dividing circuit to divide the voltage normally. The voltage after the input voltage is divided by the second voltage dividing circuit is Vin * 10 / (46 + 10) < 2.5V. The voltage of the reference terminal R of the second controllable precision voltage regulator U2 is obtained by dividing the voltage of the second voltage dividing circuit, and this voltage is less than 2.5V, that is, less than the reference voltage of the second controllable precision voltage regulator U2. Then, the cathode K to the anode A of the second controllable precision voltage regulator U2 is not conducting. Since the cathode K of the second controllable precision voltage regulator U2 is connected to the control terminal of the first voltage control switch, when the cathode K to the anode A of the second controllable precision voltage regulator U2 is not conducting, the control terminal of the first voltage control switch cannot be grounded through the second controllable precision voltage regulator U2. Then, the voltage of the control terminal of the first voltage control switch will not be pulled down, that is, the source voltages of the MOS transistor Q1 and the MOS transistor Q2 of the first voltage control switch are not higher than the gate voltages, causing the first voltage control switch not to conduct, and the input voltage of the DC input terminal Vin cannot be output to the DC output terminal Vout through the first voltage control switch and the buck module DCDC.

[0039] Meanwhile, the voltage of the reference terminal R of the third controllable precision voltage regulator U3 is also obtained by dividing the voltage of the second voltage dividing circuit, and this voltage is less than 2.5V, that is, less than the reference voltage of the third controllable precision voltage regulator U3. Then, the cathode K to the anode A of the third controllable precision voltage regulator U3 is not conducting, enabling the third voltage dividing circuit to divide the voltage normally. The voltage after the input voltage is divided by the third voltage dividing circuit is Vin * 10 / (26 + 10) ≥ 2.5V. The voltage of the reference terminal R of the fourth controllable precision voltage regulator U4 is obtained by dividing the voltage of the third voltage dividing circuit, and this voltage is not less than 2.5V, that is, not less than the reference voltage of the fourth controllable precision voltage regulator U4. Then, the cathode K to the anode A of the fourth controllable precision voltage regulator U4 is conducting. Since the cathode K of the fourth controllable precision voltage regulator U4 is connected to the control terminal of the second voltage control switch, when the cathode K to the anode A of the fourth controllable precision voltage regulator U4 is conducting, the control terminal of the second voltage control switch is grounded through the second controllable precision voltage regulator U2. Then, the voltage of the control terminal of the second voltage control switch is pulled down, that is, the source voltages of the MOS transistor Q3 and the MOS transistor Q4 of the second voltage control switch are higher than the gate voltages, causing the second voltage control switch to conduct, and the input voltage of the DC input terminal Vin can be output to the DC output terminal Vout through the second voltage control switch.

[0040] When the input voltage of the DC input terminal Vin is not less than 14V and less than 28V, the voltage after being divided by the first voltage dividing circuit is Vin*10 / (102 + 10) < 2.5V. The reference terminal R voltage of the first precision voltage regulator U1 is obtained by voltage division of the first voltage dividing circuit, and this voltage is less than 2.5V, that is, less than the reference voltage of the first precision voltage regulator U1. Then, the cathode K to the anode A of the first precision voltage regulator U1 is not conducting, enabling the second voltage dividing circuit to divide voltage normally. The voltage after being divided by the second voltage dividing circuit is Vin*10 / (46 + 10) ≥ 2.5V. The reference terminal R voltage of the second precision voltage regulator U2 is obtained by voltage division of the second voltage dividing circuit, and this voltage is not less than 2.5V, that is, not less than the reference voltage of the second precision voltage regulator U2. Then, the cathode K to the anode A of the second precision voltage regulator U2 is conducting. Since the cathode K of the second precision voltage regulator U2 is connected to the control terminal of the first voltage control switch, when the cathode K to the anode A of the second precision voltage regulator U2 is conducting, the control terminal of the first voltage control switch is grounded through the second precision voltage regulator U2. Then, the voltage of the control terminal of the first voltage control switch is pulled down, that is, the source voltage of the MOS transistor Q1 and the MOS transistor Q2 of the first voltage control switch is higher than the gate voltage, enabling the first voltage control switch to conduct. The input voltage of the DC input terminal Vin can be output through the first voltage control switch and the buck module DCDC. The input voltage of the DC input terminal Vin is reduced to 9V - 14V by the buck module DCDC and then output to the DC output terminal Vout.

[0041] In this embodiment, the buck module DCDC includes an NDP2450KC buck chip, which is a synchronous buck converter. It converts the high input voltage into a stable low output voltage through PWM control and synchronous rectification technology. The specific output voltage is sampled by the feedback resistor Rup and the feedback resistor Rdown of the feedback network, and then set after comparison with the internal reference voltage Vref. By adjusting the ratio of the feedback resistor Rup and the feedback resistor Rdown, the output voltage can be accurately set. The formula is as follows:

[0042] Vout = Vref*(1 + Rup / Rdown);

[0043] Among them, the internal reference voltage Vref is set to 1V, the resistance value of the feedback resistor Rup is 115 kΩ, and the resistance value of the feedback resistor Rdown is 10 kΩ. Thus, the specific output voltage Vout after bucking by the buck module DCDC is 12.5V.

[0044] Meanwhile, the voltage of the reference terminal R of the third controllable precision voltage regulator U3 is also obtained by voltage division of the second voltage division circuit. This voltage is not less than 2.5V, that is, not less than the reference voltage of the third controllable precision voltage regulator U3. Then, the cathode K to the anode A of the third controllable precision voltage regulator U3 conducts, grounding the voltage division point of the third voltage division circuit through the third controllable precision voltage regulator U3. Since the reference terminal R of the fourth controllable precision voltage regulator U4 is connected to the voltage division point of the third voltage division circuit, the voltage of the reference terminal R of the fourth controllable precision voltage regulator U4 is pulled down, making this voltage less than the reference voltage of the fourth controllable precision voltage regulator U4. Then, the cathode K to the anode A of the fourth controllable precision voltage regulator U4 does not conduct. Since the cathode K of the fourth controllable precision voltage regulator U4 is connected to the control terminal of the second voltage control switch, when the cathode K to the anode A of the fourth controllable precision voltage regulator U4 does not conduct, the control terminal of the second voltage control switch cannot be grounded through the fourth controllable precision voltage regulator U4. Then, the voltage of the control terminal of the second voltage control switch will not be pulled down, that is, the source voltages of the MOS transistor Q3 and the MOS transistor Q4 of the second voltage control switch are not higher than the gate voltages, making the second voltage control switch also not conduct. The input voltage of the DC input terminal Vin cannot be output to the DC output terminal Vout through the second voltage control switch.

[0045] When the input voltage of the DC input terminal Vin is not less than 28V, the overvoltage protection device D1 breaks down and conducts. The input voltage of the DC input terminal Vin is output to the ground terminal through the overvoltage protection device D1 and will not be output to the DC output terminal Vout through the first voltage control switch or the second voltage control switch.

[0046] In summary, when the input voltage of the DC input terminal Vin is less than 9V or not less than 28V, this input voltage cannot be output to the DC output terminal Vout; when the input voltage of the DC input terminal Vin is not less than 9V but less than 14V, this input voltage is directly output to the DC output terminal Vout through the second voltage control switch; when the input voltage is not less than 14V but less than 28V, this input voltage is output through the first voltage control switch and the buck module DCDC. The input voltage of the DC input terminal Vin is reduced to 9V - 14V by the buck module DCDC and then output to the DC output terminal Vout. In this way, only a voltage of 9V - 14V is output through this wide - voltage switching circuit, enabling the adapter to operate within a safe voltage range.

[0047] In this embodiment, a first anti - reverse - flow diode D2 is connected in series on the branch where the first voltage control switch and the buck module DCDC are located, and a second anti - reverse - flow diode D3 is connected in series on the branch where the second voltage control switch is located. In this way, when switching to output through the first voltage control switch or the second voltage control switch under different input voltages, it prevents the reverse flow of current and protects the safety of the circuit and equipment.

[0048] In this embodiment, a surge protection module is connected in series between the DC input terminal Vin and the ground terminal. The surge protection module includes a surge protection resistor R11 and a surge protection capacitor C3 connected in series. When the circuit is interfered by the outside world and a power surge occurs, it can quickly conduct and shunt, thereby clamping the voltage within a safe range and avoiding damage to other devices in the circuit caused by the surge.

[0049] In this embodiment, energy storage filter capacitors C4, C5, and C6 are connected to the contact point VIN14V_28V between the first voltage control switch and the buck module DCDC, which play a role in smoothing the voltage, storing energy, filtering, reducing electromagnetic interference, and improving the transient response in the wide voltage switching circuit, ensuring the stable operation of the circuit.

[0050] As described above, it is only the implementation mode of the present invention, and the scope of patent protection is not limited thereby. Those skilled in the art make non-substantive changes or substitutions based on the present invention, and still fall within the scope of patent protection.

Claims

1. A wide-voltage switching circuit, characterized in that: It includes a DC input terminal, a DC output terminal, a first voltage control switch, a second voltage control switch, a buck module, a first adjustable precision voltage reference, a second adjustable precision voltage reference, a third adjustable precision voltage reference, a fourth adjustable precision voltage reference, a first voltage dividing circuit, a second voltage dividing circuit, a third voltage dividing circuit and an overvoltage protection device; the first voltage control switch is connected in series with the buck module and then connected between the DC input terminal and the DC output terminal, and the second voltage control switch is connected between the DC input terminal and the DC output terminal; the first voltage dividing circuit, the second voltage dividing circuit, the third voltage dividing circuit and the overvoltage protection device are each connected in series between the DC input terminal and the ground terminal; the reference terminal of the first adjustable precision voltage reference is connected to the voltage dividing point of the first voltage dividing circuit, the anode is grounded, and the cathode is connected to the voltage dividing point of the second voltage dividing circuit. The reference terminal of the second adjustable precision voltage reference is connected to the voltage dividing point of the second voltage dividing circuit, the anode is grounded, and the cathode is connected to the control terminal of the first voltage control switch. The reference terminal of the third adjustable precision voltage reference is connected to the voltage dividing point of the second voltage dividing circuit, the anode is grounded, and the cathode is connected to the voltage dividing point of the third voltage dividing circuit. The reference terminal of the fourth adjustable precision voltage reference is connected to the voltage dividing point of the third voltage dividing circuit, the anode is grounded, and the cathode is connected to the control terminal of the second voltage control switch; the reference voltages of the first adjustable precision voltage reference, the second adjustable precision voltage reference, the third adjustable precision voltage reference and the fourth adjustable precision voltage reference are 2.5V; the voltage division ratio of the first voltage dividing circuit is set to 10.2:1, the voltage division ratio of the second voltage dividing circuit is set to 4.6:1, and the voltage division ratio of the third voltage dividing circuit is set to 2.6:

1.

2. The wide voltage switching circuit according to claim 1, characterized in that The breakdown voltage of the overvoltage protection device is 28V.

3. The wide-voltage switching circuit according to claim 2, characterized in that, The voltage division ratios of the first, second, and third voltage dividing circuits are set as follows: When the input voltage is less than 9V, the voltage divided by the first voltage dividing circuit is less than the reference voltage of the first adjustable precision voltage reference, the voltage divided by the second voltage dividing circuit is less than the reference voltages of the second adjustable precision voltage reference and the third adjustable precision voltage reference, and the voltage divided by the third voltage dividing circuit is less than the reference voltage of the fourth adjustable precision voltage reference; When the input voltage is not less than 9V but less than 14V, the voltage divided by the first voltage dividing circuit is less than the reference voltage of the first adjustable precision voltage reference, the voltage divided by the second voltage dividing circuit is less than the reference voltages of the second adjustable precision voltage reference and the third adjustable precision voltage reference, and the voltage divided by the third voltage dividing circuit is not less than the reference voltage of the fourth adjustable precision voltage reference; When the input voltage is not less than 14V but less than 28V, the voltage divided by the first voltage dividing circuit is less than the reference voltage of the first adjustable precision voltage reference, the voltage divided by the second voltage dividing circuit is not less than the reference voltages of the second adjustable precision voltage reference and the third adjustable precision voltage reference, and the voltage divided by the third voltage dividing circuit is not less than the reference voltage of the fourth adjustable precision voltage reference.

4. The wide voltage switching circuit according to claim 1, wherein: The first voltage control switch includes two P-type MOS transistors. Their sources are connected together and then connected to the DC input terminal. Their drains are connected together and then connected to the buck module. Their gates are connected together as the control terminal and connected to the cathode of the second precision voltage reference source. The second voltage control switch includes a P-type MOS transistor. Its source is connected together and then connected to the DC input terminal. Its drain is connected together and then connected to the DC output terminal. Its gate is connected together as the control terminal and connected to the cathode of the fourth precision voltage reference source.

5. The wide voltage switching circuit according to claim 1, characterized in that, A first anti-backflow diode is connected in series on the branch where the first voltage control switch and the buck module are located, and a second anti-backflow diode is connected in series on the branch where the second voltage control switch is located.

6. The wide voltage switching circuit according to claim 1, characterized in that, A surge protection module is connected in series between the DC input terminal and the ground terminal. The surge protection module includes a surge protection resistor and a surge protection capacitor connected in series.

7. The wide voltage switching circuit according to claim 1, characterized in that, The buck module includes an NDP2450KC buck chip.

8. The wide voltage switching circuit according to claim 1, characterized in that, A storage filter capacitor is connected to the connection point between the first voltage control switch and the buck module.

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