An adaptive input switching power supply

Abstract

The present invention discloses an adaptive input switching power supply, which includes a front-end protection rectification unit, a high-voltage switching power supply protection unit, a high-voltage switching power supply unit, a low-voltage switching power supply protection unit, a low-voltage switching power supply shutdown unit, a low-voltage switching power supply unit, and a power output combining unit. For the low-voltage switching power supply part, a combination protection of MOS transistors and thermistors is adopted to achieve short-term overvoltage protection. At the same time, the optocoupler isolation feedback shutdown MOS transistor method is used to achieve long-term overvoltage protection. The triode current limiting protection circuit effectively prevents the MOS transistor from being burned out due to excessive current during the startup of the low-voltage switching power supply. For the high-voltage switching power supply part, a thermistor-varistor composite three-terminal protection is adopted to achieve high-voltage overvoltage protection. The present invention uses two sets of switching power supply systems to work respectively when DC24V or AC220V is input, realizing the same-port adaptive high-efficiency operation and effectively avoiding equipment damage caused by incorrect connection of the power cord.

Description

Technical Field

[0001] The present invention relates to the technical field of switching power supplies, and particularly to an adaptive input switching power supply. Background Art

[0002] Traditional power supplies are powered by DC24V input or AC220V input, and a small number support the input of two power supply sources. At present, most of the power supplies that support the input of two power supply sources adopt a two-port input method, which cannot achieve adaptive input on the same port. When using the two-port input, there is a risk of power supply damage caused by incorrect wiring by users. The design of the power supply with the same port input has the following problems: Since the power supply range of the AC220V power supply is generally AC65V - AC265V, the voltage value after full-wave rectification can reach about 370V, while the power supply range of the DC24V power supply is generally DC9V - DC36V. In this way, under the same port power input, the highest voltage is more than 10 times the lowest voltage. If the same transformer is used for the design of the switching power supply, even if the designed power supply can work, its working efficiency will be very low. Summary of the Invention

[0003] The present invention provides an adaptive input switching power supply, and its purpose is to overcome the defects of the prior art, improve the working efficiency of the adaptive input switching power supply on the same port, and add protection measures to the low-voltage switching power supply part to ensure that the low-voltage switching power supply part is not damaged when the AC220V is input.

[0004] The technical solution of the present invention is as follows:

[0005] An adaptive input switching power supply includes a front-end protection rectification unit, a high-voltage switching power supply protection unit, a high-voltage switching power supply unit, a low-voltage switching power supply protection unit, a low-voltage switching power supply cut-off unit, a low-voltage switching power supply unit, and a power output merging unit.

[0006] The output end of the front-end protection rectification unit is connected to the input end of the high-voltage switching power supply unit through the high-voltage switching power supply protection unit, and the high-voltage switching power supply protection unit is used to achieve overvoltage protection during high-voltage input.

[0007] The output end of the front-end protection rectification unit is connected to the input end of the low-voltage switching power supply unit through the low-voltage switching power supply protection unit, and the low-voltage switching power supply protection unit is used to achieve short-term overvoltage protection of the low-voltage switching power supply unit during high-voltage input.

[0008] The output end of the high-voltage switching power supply unit is connected to the control end of the low-voltage switching power supply cut-off unit; the low-voltage switching power supply cut-off unit is connected to the low-voltage switching power supply protection unit, and is used to cut off the power supply of the low-voltage switching power supply unit during high-voltage input for overvoltage protection.

[0009] The output end of the high-voltage switching power supply unit and the output end of the low-voltage switching power supply are respectively connected to the power output combining unit.

[0010] Further, the low-voltage switching power supply protection unit includes an MOS transistor V7, and the MOS transistor V7 is used to keep the input voltage of the low-voltage switching power supply unit within a certain range.

[0011] Further, the low-voltage switching power supply protection unit includes a thermistor RT2, and the thermistor RT2 is connected to the MOS transistor V7.

[0012] Further, the low-voltage switching power supply protection unit further includes a triode current-limiting protection circuit, and the triode current-limiting protection circuit includes a triode V16 and a plurality of resistors, and is used to prevent the MOS transistor V7 from being burned out due to excessive current when the low-voltage switching power supply unit starts.

[0013] Further, the low-voltage switching power supply turn-off unit includes an optocoupler E2, and the optocoupler E2 is respectively connected to the high-voltage switching power supply unit and the low-voltage switching power supply protection unit, and is used to turn off the MOS transistor V7 when the high-voltage switching power supply unit is working.

[0014] Further, the high-voltage switching power supply protection unit is a thermistor-varistor composite three-terminal protection RT1.

[0015] Further, the front-end protection rectifying unit includes a varistor RV1, a filter network and a rectifier bridge V2. The two ends of the varistor RV1 are respectively connected to the positive and negative ports of the power input, and the two ends of the varistor RV1 are connected to the input end of the rectifier bridge V2 through the filter network.

[0016] Further, the power output combining unit includes a diode V1, a diode V11, a capacitor C1, a capacitor C3 and a resistor R2. After the capacitor C1, the capacitor C3 and the resistor R2 are connected in parallel, one end is connected to the power ground, and the other end is connected to the negative poles of the diode V1 and the diode V11. The positive pole of the diode V1 is connected to the output end of the high-voltage switching power supply unit, and the positive pole of the diode V11 is connected to the output end of the low-voltage switching power supply unit.

[0017] Compared with the prior art, the present invention has the following beneficial effects: (1) A dual-transformer working design is adopted, and two sets of flyback switching power supplies, namely high-voltage and low-voltage ones, are respectively used under different power inputs, improving the working efficiency of the power supply; for the low-voltage switching power supply part, a combination protection of MOS tube and thermistor is used to achieve short-term overvoltage protection of the low-voltage switching power supply under high-voltage input. At the same time, the method of optocoupler isolation feedback to turn off the MOS tube is used to achieve long-term overvoltage protection under high-voltage input, ensuring that the low-voltage switching power supply part is not damaged when the input is AC220V; (2) The triode current-limiting protection circuit of the low-voltage switching power supply protection unit can effectively prevent the MOS tube from being burned out due to excessive current when the low-voltage switching power supply starts, further improving the stability of the switching power supply; (3) The thermistor-varistor composite three-terminal protection of the high-voltage switching power supply protection unit realizes overvoltage protection under high-voltage input; (4) The present invention can be applied to power small-power devices such as instruments and meters, realizing multi-power input adaptability of the devices, and the same-port input can effectively avoid device damage caused by incorrect connection of the power cord. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 is the circuit diagram of the present invention;

[0019] Figure 2 is Figure 1 the enlarged view of Module 4 and Module 5 of DETAILED DESCRIPTION OF THE EMBODIMENTS

[0020] The technical solution of the present invention will be described in detail below with reference to the drawings:

[0021] As Figure 1 shown, an adaptive input switching power supply includes a front-end protection rectification unit 1, a high-voltage switching power supply protection unit 2, a high-voltage switching power supply unit 3, a low-voltage switching power supply protection unit 4, a low-voltage switching power supply turn-off unit 5, a low-voltage switching power supply unit 6, and a power output combining unit 7.

[0022] The output end of the front-end protection rectification unit 1 is connected to the input end of the high-voltage switching power supply unit 3 through the high-voltage switching power supply protection unit 2, and the high-voltage switching power supply protection unit 2 is used to achieve overvoltage protection during high-voltage input. The output end of the front-end protection rectification unit 1 is connected to the input end of the low-voltage switching power supply unit 6 through the low-voltage switching power supply protection unit 4, and the low-voltage switching power supply protection unit 4 is used to achieve short-term overvoltage protection of the low-voltage switching power supply during high-voltage input. The output end of the high-voltage switching power supply unit 3 is connected to the control end of the low-voltage switching power supply cut-off unit 5, and the low-voltage switching power supply cut-off unit 5 is connected to the low-voltage switching power supply protection unit 4, and is used to cut off the power supply of the low-voltage switching power supply unit 6 during high-voltage input for overvoltage protection. The output ends of the high-voltage switching power supply unit 3 and the low-voltage switching power supply unit 6 are respectively connected to the power output merging unit 7.

[0023] The front-end protection rectification unit 1 includes a varistor RV1, a filter network, and a rectifier bridge V2. The two ends of the varistor RV1 are connected in parallel with the positive and negative power input ports, and the two ends of the varistor RV1 are connected to the input end of the rectifier bridge V2 through the filter network. Specifically, the filter network includes a capacitor C9, a common-mode inductor T1, and a capacitor C4. The first pin and the fourth pin of the common-mode inductor T1 are connected to the two ends of the capacitor C9, and the second pin and the third pin are connected to the two ends of the capacitor C4. The DC24V or AC220V input is full-wave rectified into direct current through the varistor RV1 clamping protection, the filter network, and the rectifier bridge V2. When the DC24V is input, the rectified DC voltage range is about DC9V~DC36V, and when the AC220V is input, the rectified DC voltage range is about DC90V~DC370V.

[0024] The high-voltage switching power supply protection unit 2 is a thermistor-varistor composite three-terminal protection RT1, and its clamping voltage value is DC400V. When the front-end rectified voltage exceeds 400V, it will be clamped, and the excess voltage part will drop on the three-terminal protection, so that the voltage of the subsequent stage is maintained below 400V, thereby achieving overvoltage protection during high-voltage input.

[0025] The high-voltage switching power supply unit 3 is composed of a switching power supply chip D1, a switching transformer T2, an optocoupler E1, a voltage regulator chip V6, etc. The model of the switching power supply chip D1 is TNY274GN.

[0026] The low-voltage switching power supply protection unit 4 includes a thermistor RT2, a MOS transistor V7, a TVS diode V17, a TVS diode V9, a resistor R11, a resistor R15, a resistor R16, and a capacitor C21. The input end of the low-voltage switching power supply protection unit 4 is connected to the drain of the MOS transistor V7 through the thermistor RT2, and the source of the MOS transistor V7 is connected to the positive electrode of the TVS diode V9; one end of the resistor R16 is connected to the gate of the MOS transistor V7, and the other end is connected to the negative electrode of the TVS diode V9; after the resistor R11 and the resistor R15 are connected in series, one end is connected to the drain of the MOS transistor V7, and the other end is connected to the negative electrode of the TVS diode V9; the negative electrode of the TVS diode V9 is connected to the signal ground through the capacitor C21; the positive electrode of the TVS diode V17 is connected to the signal ground, and the negative electrode is connected to the negative electrode of the TVS diode V9.

[0027] The thermistor RT2 forms overcurrent protection, and the MOS transistor V7, the TVS diode V17, the TVS diode V9, the resistor R11, the resistor R15, the resistor R16, and the capacitor C21 form overvoltage clamping protection, clamping the voltage at DC36V. When the voltage exceeds DC36V, the excess voltage part drops on the source and drain of the MOS transistor V7. The resistor R16 is an anti-self-excitation damping resistor. The thermal power consumption of the MOS transistor V7 is equal to the voltage difference V△ between its source and drain multiplied by the current I, and I is also the primary side current of the low-voltage switching power supply when it works. If the low-voltage switching power supply works, the MOS transistor V7 will heat up, and then cause the thermistor RT2 installed near it to act, dropping the overvoltage on the thermistor and reducing the voltage drop of the MOS transistor V7, thereby protecting the MOS transistor V7 from damage in a short time. This part uses the combination protection of the MOS transistor and the thermistor to achieve the short-time overvoltage protection function of the low-voltage switching power supply when the input voltage is high.

[0028] Further, the low-voltage switching power supply protection unit 4 further includes a triode current limiting protection circuit. The triode current limiting protection circuit includes a triode V16, a resistor R8, a resistor R9, a resistor R10, and a resistor R13. After the resistor R8, the resistor R9, and the resistor R10 are connected in parallel, one end is connected to the positive electrode of the TVS diode V9, and the other end is connected to the emitter of the triode V16 and the input end of the low-voltage switching power supply unit 6. The collector of the triode V16 is connected to the negative electrode of the TVS diode V9. One end of the resistor R13 is connected to the positive electrode of the TVS diode V9, and the other end is connected to the base of the triode V16. The model of the MOS transistor V7 is IRF830PBF, the model of the TVS diode V17 is SMAJ36A, the model of the TVS diode V9 is SMBJ12CA, and the model of the triode V6 is S9013. The triode current limiting protection circuit can effectively prevent the MOS transistor V7 from being burned out due to excessive current when the low-voltage switching power supply starts up, and further improves the stability of the switching power supply.

[0029] The low-voltage switching power supply shutdown unit 5 includes an optocoupler E2, a resistor R18, a resistor R30, and a capacitor C24. The first and second pins of the optocoupler E2 are connected to both ends of the resistor R18, the third pin is connected to the signal ground, and the fourth pin is connected to the negative electrode of the TVS tube V17. The capacitor C24 and the resistor R30 are in parallel, one parallel end is connected to the second pin of the optocoupler E2, and the other parallel end is connected to the power ground. When the high-voltage switching power supply outputs 5.4V, the optocoupler E2 conducts, the gate voltage of the MOS tube V7 is zero, and the output of the MOS tube is turned off, avoiding the continuous operation of the low-voltage switching power supply unit 6 when the input voltage is AC220V (at this time, the high-voltage switching power supply part has already worked). This unit uses the optocoupler isolation feedback to turn off the MOS tube method to achieve the long-term overvoltage protection function under high-voltage input, ensuring that the low-voltage switching power supply part is not damaged when AC220V is input.

[0030] The low-voltage switching power supply unit 6 consists of a switching power supply chip D2, a switching transformer T3, an optocoupler E3, a voltage regulator chip V19, etc. When the input voltage is DC24V, since the voltage is not within the startup range of the high-voltage switching power supply, the high-voltage switching power supply will not start, and only the low-voltage switching power supply works. The model of the switching power supply chip D2 is UC2845D8TR.

[0031] The power output merging unit 7 includes a diode V1, a diode V11, a capacitor C1, a capacitor C3, and a resistor R2. After the capacitor C1, the capacitor C3, and the resistor R2 are in parallel, one end is connected to the power ground, and the other end is connected to the negative electrodes of the diode V1 and the diode V11. The positive electrode of the diode V1 is connected to the output end of the high-voltage switching power supply unit 3, and the positive electrode of the diode V11 is connected to the output end of the low-voltage switching power supply unit 6. The output voltage value of the high-voltage switching power supply unit 3 is 5.4V, and the output voltage value of the low-voltage switching power supply unit 6 is 5.2V, so the high-voltage switching power supply works preferentially.

[0032] The present invention uses two sets of switching power supply systems to work respectively when DC24V or AC220V is input. When DC24V is input, the low-voltage switching power supply works, and when AC220V is input, the high-voltage switching power supply works, realizing the same-port adaptive high-efficiency operation. In addition, the low-voltage switching power supply part is equipped with protection measures such as short-term overvoltage protection, long-term overvoltage protection, and current limiting protection, ensuring that the low-voltage switching power supply part will not be damaged when AC220V is input.

[0033] The present invention can be applied to the power supply of small-power devices such as instruments and meters, realizing the multi-power input adaptability of the devices, and the same-port input can effectively avoid the device damage caused by the wrong connection of the power cord.

Claims

1. An adaptive input switching power supply, characterized in that: It includes a front-end protection rectification unit (1), a high-voltage switch power supply protection unit (2), a high-voltage switch power supply unit (3), a low-voltage switch power supply protection unit (4), a low-voltage switch power supply cut-off unit (5), a low-voltage switch power supply unit (6), and a power output merging unit (7); the high-voltage switch power supply unit (3) adopts a flyback switch power supply, and the low-voltage switch power supply unit (6) adopts a flyback switch power supply. By adopting a dual-transformer operation design, two sets of flyback switch power supplies, namely high-voltage and low-voltage, are respectively used for operation under different power inputs. The output end of the front-end protection rectification unit (1) is connected to the input end of the high-voltage switch power supply unit (3) through the high-voltage switch power supply protection unit (2), and the high-voltage switch power supply protection unit (2) is used to achieve overvoltage protection during high-voltage input. The output end of the front-end protection rectification unit (1) is connected to the input end of the low-voltage switch power supply unit (6) through the low-voltage switch power supply protection unit (4), and the low-voltage switch power supply protection unit (4) is used to achieve short-term overvoltage protection of the low-voltage switch power supply unit (6) during high-voltage input. The output end of the high-voltage switch power supply unit (3) is connected to the control end of the low-voltage switch power supply cut-off unit (5); the low-voltage switch power supply cut-off unit (5) is connected to the low-voltage switch power supply protection unit (4) and is used to cut off the power supply of the low-voltage switch power supply unit (6) during high-voltage input for overvoltage protection. The output end of the high-voltage switch power supply unit (3) and the output end of the low-voltage switch power supply are respectively connected to the power output merging unit (7). The low-voltage switch power supply protection unit (4) includes a thermistor RT2, a MOS transistor V7, a TVS diode V17, a TVS diode V9, a resistor R11, a resistor R15, a resistor R16, and a capacitor C21. The input end of the low-voltage switch power supply protection unit (4) is connected to the drain of the MOS transistor V7 through the thermistor RT2, and the source of the MOS transistor V7 is connected to the positive electrode of the TVS diode V9; one end of the resistor R16 is connected to the gate of the MOS transistor V7, and the other end is connected to the negative electrode of the TVS diode V9; the resistor R11 and the resistor R15 are connected in series, one end is connected to the drain of the MOS transistor V7, and the other end is connected to the negative electrode of the TVS diode V9; the negative electrode of the TVS diode V9 is connected to the signal ground through the capacitor C21; the positive electrode of the TVS diode V17 is connected to the signal ground, and the negative electrode is connected to the negative electrode of the TVS diode V9. The low-voltage switching power supply protection unit (4) further includes a triode current-limiting protection circuit, which includes a triode V16, a resistor R8, a resistor R9, a resistor R10, and a resistor R13. One end of the parallel connection of the resistor R8, the resistor R9, and the resistor R10 is connected to the positive electrode of the TVS tube V9, and the other end, that is, the output end of the low-voltage switching power supply protection unit (4), is connected to the emitter of the triode V16 and the input end of the low-voltage switching power supply unit 6. The collector of the triode V16 is connected to the negative electrode of the TVS tube V9, and one end of the resistor R13 is connected to the positive electrode of the TVS tube V9, and the other end is connected to the base of the triode V16. The triode current-limiting protection circuit is used to prevent the MOS tube V7 from being burned out due to excessive current when the low-voltage switching power supply starts up. The low-voltage switching power supply turn-off unit (5) includes an optocoupler E2, a resistor R18, a resistor R30, and a capacitor C24. The first pin and the second pin of the optocoupler E2 are connected to both ends of the resistor R18, the third pin is connected to the signal ground, and the fourth pin is connected to the negative electrode of the TVS tube V17. The capacitor C24 and the resistor R30 are in parallel, one parallel end is connected to the second pin of the optocoupler E2, and the other parallel end is connected to the power ground. When the high-voltage switching power supply VCC5.4V output, which is the output end of the high-voltage switching power supply unit (3) and is connected to the upper end of the first pin of the optocoupler E2 serving as the control end of the low-voltage switching power supply turn-off unit (5), is output, the optocoupler E2 conducts, and the gate voltage of the MOS tube V7 is zero, turning off the MOS tube output, avoiding the continuous operation of the low-voltage switching power supply unit (6) when the input voltage is AC220V, realizing the long-term overvoltage protection function under high-voltage input, and ensuring that the low-voltage switching power supply part is not damaged when AC220V is input.

2. The adaptive input switching power supply according to claim 1, wherein: The high-voltage switching power supply protection unit (2) is a thermistor varistor composite three-terminal protection RT1.

3. The adaptive input switching power supply according to claim 1, characterized in that: The front-end protection rectification unit (1) includes a varistor RV1, a filter network, and a rectifier bridge V2. Both ends of the varistor RV1 are respectively connected to the positive and negative power input ports, and both ends of the varistor RV1 are connected to the input end of the rectifier bridge V2 through the filter network.

4. The adaptive input switching power supply according to any one of claims 1 to 3, characterized in that: The power output merging unit (7) includes a diode V1, a diode V11, a capacitor C1, a capacitor C3, and a resistor R2. One end of the parallel connection of the capacitor C1, the capacitor C3, and the resistor R2 is connected to the power ground, and the other end is connected to the negative electrodes of the diode V1 and the diode V11. The positive electrode of the diode V1 is connected to the output end of the high-voltage switching power supply unit (3), and the positive electrode of the diode V11 is connected to the output end of the low-voltage switching power supply unit (6).

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