Over-temperature protection sampling circuit and switching power supply

Abstract

The utility model discloses an over-temperature protection sampling circuit and a switching power supply, the over-temperature protection sampling circuit comprises N voltage division circuits, each voltage division circuit comprises a voltage division device and a thermistor, one end of each voltage division device is connected together for inputting power supply voltage, and the other end of each voltage division device is connected with the thermistor; the other end of each voltage divider and one end of the corresponding thermistor are connected together to form an output end of the corresponding voltage division circuit and output a corresponding voltage signal, the other ends of the thermistors are connected together to be grounded, and N is a natural number greater than or equal to 2; and the selection circuit comprises N input ends which are used for respectively inputting the voltage signals output by the output ends of the voltage division circuits, and the selection circuit is used for selecting the voltage signal representing the highest temperature of the corresponding thermistor from the voltage signals output by the output ends of the voltage division circuits and outputting the voltage signal through the output ends of the selection circuit. According to the utility model, the shortage of port resources of the single-chip microcomputer can be relieved.

Description

Technical Field

[0001] This utility model relates to the field of switching converters, and in particular to a temperature protection sampling circuit and a switching power supply. Background Technology

[0002] As the application environment in the power supply industry becomes increasingly harsh, in order to ensure product reliability, we need to ensure that each component operates within the allowable temperature range. When the switching power supply contains multiple heat-generating components, in order to achieve over-temperature protection, multiple over-temperature protection sampling circuits containing thermistors need to be introduced. Under normal circumstances, the microcontroller needs multiple ADC sampling ports. In order to meet the requirements of multiple ADC sampling ports, we usually need to select a microcontroller with higher specifications and more ports. However, a microcontroller with higher specifications and more ports will bring higher costs. Utility Model Content

[0003] Therefore, the technical problem to be solved by this utility model is to provide an over-temperature protection sampling circuit and a switching power supply to alleviate the shortage of microcontroller port resources.

[0004] As the first aspect of this utility model, the technical solution of the over-temperature protection sampling circuit is as follows:

[0005] An over-temperature protection sampling circuit, wherein the over-temperature protection sampling circuit includes:

[0006] There are N voltage divider circuits, each including a voltage divider device and a thermistor. One end of each voltage divider device is connected together to input the power supply voltage. The other end of each voltage divider device and one end of the corresponding thermistor are connected together to form the output terminal of the corresponding voltage divider circuit, which outputs the corresponding voltage signal. The other end of each thermistor is connected together to ground. N is a natural number greater than or equal to 2.

[0007] The selection circuit includes N input terminals, which respectively input the voltage signals output by the output terminals of each voltage divider circuit. The selection circuit is used to select the voltage signal that represents the highest temperature of the corresponding thermistor from the voltage signals output by each voltage divider circuit and output it from its output terminal.

[0008] Preferably, each voltage divider device is a resistor.

[0009] Furthermore, the resistance values ​​of all the resistors are equal.

[0010] Furthermore, each of the thermistors is a negative temperature coefficient thermistor.

[0011] Preferably, the selection circuit includes N follower processing circuits, each follower processing circuit including an operational amplifier and a diode. The non-inverting input terminal of each operational amplifier is an input terminal of the selection circuit, the inverting input terminal of each operational amplifier and the anode of the corresponding diode are connected together to form the output terminal of the selection circuit, and the anode of each diode is connected to the output terminal of the corresponding operational amplifier.

[0012] Preferably, each follower processing circuit includes a resistor, one end of which is connected to the inverting input terminal of the corresponding operational amplifier, and the other end of which is connected to the anode of the corresponding diode to form the output terminal of the selection circuit.

[0013] Preferably, each voltage divider is a resistor; the selection circuit includes N follower processing circuits, each follower processing circuit includes an operational amplifier and a diode, the non-inverting input terminal of each operational amplifier is an input terminal of the selection circuit, the inverting input terminal of each operational amplifier and the anode of the corresponding diode are connected together to form the output terminal of the selection circuit, and the anode of each diode is connected to the output terminal of the corresponding operational amplifier.

[0014] Furthermore, the resistance values ​​of each resistor are equal, and each thermistor is a negative temperature coefficient thermistor; each follower processing circuit includes a resistor, one end of each resistor is connected to the inverting input terminal of the corresponding operational amplifier, and the other end of each resistor is connected together with the anode of the corresponding diode to form the output terminal of the selection circuit.

[0015] As a second aspect of this utility model, the technical solution of the provided switching power supply embodiment is as follows:

[0016] A switching power supply, wherein: it includes the over-temperature protection sampling circuit described in any of the first aspects above.

[0017] Furthermore, the switching power supply is an isolated switching power supply, and the over-temperature protection sampling circuit is located on the same side of the switching power supply.

[0018] The advantages of this utility model compared to the prior art are as follows:

[0019] The over-temperature protection sampling circuit in this embodiment selects the voltage signal that represents the highest temperature of the corresponding thermistor from the voltage signals output by each voltage divider circuit and outputs it from its output terminal. This enables the microcontroller to perform over-temperature protection when any one of the samples is too hot during multi-channel sampling, saving the number of microcontroller ports and reducing the cost of the microcontroller. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of an over-temperature protection circuit according to the present invention.

[0021] Figure 2 For microcontrollers and this utility model Figure 1 A schematic diagram showing the connection of a specific circuit diagram. Detailed Implementation

[0022] To make the above-mentioned objectives, features, and advantages of this utility model more apparent and understandable, the specific embodiments of this utility model will be described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this utility model, not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this application.

[0023] It should be noted that the terms "comprising" and "having" and any variations thereof described in the specification and claims of this application are intended to cover non-exclusive inclusion. For example, including a series of components, unit circuits or control timings is not necessarily limited to those components, unit circuits or control timings that are explicitly listed, but may include components, unit circuits or control timings that are not explicitly listed or that are inherent to these circuits.

[0024] Furthermore, unless otherwise specified, the embodiments and features described in this application may be combined with each other.

[0025] It should be understood that, in the specification and claims, when an element is described as being "connected" to another element, that element may be "directly connected" to that other element or "connected" to that other element through a third element; when a step is described as being connected to another step, that step may be connected directly to that other step or connected to that other step through a third step.

[0026] First Embodiment

[0027] This embodiment provides an over-temperature protection sampling circuit. Figure 1 Please refer to the schematic diagram of an over-temperature protection circuit according to this utility model. Figure 1 The over-temperature protection sampling circuit includes:

[0028] There are N voltage divider circuits, each including a voltage divider device and a thermistor. One end of each voltage divider device is connected together to input the power supply voltage. The other end of each voltage divider device and one end of the corresponding thermistor are connected together to form the output terminal of the corresponding voltage divider circuit, which outputs the corresponding voltage signal. The other end of each thermistor is connected together to ground. N is a natural number greater than or equal to 2.

[0029] The selection circuit includes N input terminals, which are respectively input to the voltage signals output by each voltage divider circuit. The selection circuit is used to select the voltage signal that represents the highest temperature of the corresponding thermistor from the voltage signals output by each voltage divider circuit and output it from its output terminal.

[0030] In this embodiment, the selection output circuit in the over-temperature protection sampling circuit selects the voltage signal that represents the highest temperature of the corresponding thermistor from the voltage signals output by each voltage divider circuit and outputs it from its output terminal. This enables the microcontroller to perform over-temperature protection when any one of the samples is too hot during multi-channel sampling, saving the number of microcontroller ports and reducing the cost of the microcontroller.

[0031] Please continue reading Figure 1 Each voltage divider component is a resistor R1, R2, ..., RN.

[0032] Furthermore, since all resistors have the same resistance value, the circuit parameter design is the simplest.

[0033] Figure 2 For microcontrollers and this utility model Figure 1 Please refer to the schematic diagram of a specific circuit connection. Figure 2 :

[0034] Where N is 3, the power supply voltage is 3V; the resistance values ​​of resistors R1, R2 and R3 are equal, and thermistors RT1, RT2 and RT3 are thermistors with negative temperature coefficients.

[0035] The selection circuit includes three follower processing circuits. Each follower processing circuit includes an operational amplifier (op-amp) and a diode. The non-inverting input of each op-amp serves as an input of the selection circuit. The inverting input of each op-amp and the anode of the corresponding diode are connected together to form the output of the selection circuit. The anode of each diode is connected to the output of the corresponding op-amp. Specifically, the first follower processing circuit includes op-amp U1 and diode D1, the second follower processing circuit includes op-amp U2 and diode D2, and the third follower processing circuit includes op-amp U3 and diode D3.

[0036] Figure 2The working principle of the selection circuit is as follows: The resistance values ​​of each resistor are directly recorded as their corresponding reference numerals. The first voltage signal VRT1 input to the non-inverting input terminal of the first operational amplifier is VRT1 = 3V*RT1 / (R1+RT1), the second voltage signal VRT2 input to the non-inverting input terminal of the second operational amplifier is VRT2 = 3V*RT2 / (R2+RT2), and the third voltage signal VRT3 input to the non-inverting input terminal of the third operational amplifier is VRT3 = 3V*RT3 / (R3+RT3). According to the virtual short principle, the voltage at the non-inverting input terminal of each operational amplifier in the follower processing circuit is equal to the voltage at the inverting input terminal. Therefore, the voltage at the anode of diode D1 is VRT1, the voltage at the anode of diode D2 is VRT2, and the voltage at the anode of diode D3 is VRT3. Since resistor R1... Resistors R2 and R3 have equal resistance values. Thermistors RT1, RT2, and RT3 are negative temperature coefficient thermistors. Assuming the temperature corresponding to thermistor RT1 is the highest, its resistance is the lowest, resulting in the minimum first voltage signal VRT1. Through appropriate parameter design, diodes D2 and D3 can be forward-biased and conducted, while diode D1 is reverse-biased and cut off. Thus, the second voltage signal VRT2 and the third voltage signal VRT3 are pulled down to ground through the corresponding diodes and the grounding loop inside the corresponding operational amplifier. Only the first voltage signal VRT1 is output, thus selecting the voltage signal with the highest temperature corresponding to the thermistor from the voltage signals output from each voltage divider circuit and outputting it from its output terminal.

[0037] The microcontroller only shows the pins closely related to the utility model, which are as follows:

[0038] Tsense pin: This is the over-temperature protection pin, connected to the output of the over-temperature protection sampling circuit. The microcontroller calculates the temperature corresponding to the highest temperature thermistor based on the level signal output by the over-temperature protection sampling circuit, and determines whether over-temperature protection action needs to be performed. If so, the over-temperature protection function is triggered.

[0039] VCC pin: This is the power supply pin, connected to a +3.3V power signal;

[0040] AGND pin: Ground pin, ground signal GND;

[0041] DC_EN pin: Enable pin, connected to the DC power control enable signal. The microcontroller will only work when this pin receives the DC power control enable signal.

[0042] Please continue reading Figure 2 Each follower processing circuit includes a resistor. One end of each resistor is connected to the inverting input of the corresponding operational amplifier, and the other end of each resistor is connected to the anode of the corresponding diode, forming the output of the selection circuit. Specifically, each resistor is... Figure 2The resistors R4, R5, and R6 are used to stabilize the peak voltage.

[0043] Second Embodiment

[0044] This embodiment provides a switching power supply, which includes any one of the over-temperature protection sampling circuits in the first embodiment. Because this switching power supply includes any one of the over-temperature protection sampling circuits in the first embodiment, it can monitor and protect multiple heat-generating components using only one ADC sampling port of the microcontroller. This effectively prevents the switching power supply from failing due to overheating of internal components. This over-temperature protection circuit uses an operational amplifier and diodes to form an AND gate circuit, selecting the path with the highest thermistor temperature and sending it to the microcontroller's ADC sampling port, thus alleviating the strain on microcontroller port resources.

[0045] Furthermore, the switching power supply is an isolated switching power supply, and the over-temperature protection sampling circuit is located on the same side of the switching power supply. The reason is that the other ends of each thermistor in the over-temperature protection sampling circuit are connected together for grounding. Therefore, the over-temperature protection sampling circuit can only monitor the heat-generating components on the same side of the switching power supply, such as the heat-generating components on the primary side of the switching power supply or the heat-generating components on the secondary side of the switching power supply.

[0046] The above are merely embodiments of this utility model. It should be particularly noted that the above embodiments should not be regarded as limitations on this utility model. For those skilled in the art, several improvements and modifications can be made without departing from the spirit and scope of this utility model, and these improvements and modifications should also be regarded as protection scope of this utility model.

Claims

1. An over-temperature protection sampling circuit, characterized by, The over-temperature protection sampling circuit comprises: N voltage dividing circuits, each voltage dividing circuit comprising a voltage dividing device and a thermistor, one end of each voltage dividing device being connected together for input of a supply voltage, the other end of each voltage dividing device and one end of a corresponding thermistor being connected together as an output end of the corresponding voltage dividing circuit for output of a corresponding voltage signal, and the other end of each thermistor being connected together for grounding, N being a natural number greater than or equal to 2; a selection circuit comprising N input ends for input of the voltage signals output by the output ends of the voltage dividing circuits, the selection circuit being configured to select and output, from the voltage signals output by the output ends of the voltage dividing circuits, a voltage signal representing the highest temperature of the corresponding thermistor.

2. The over-temperature protection sampling circuit of claim 1, wherein: Each voltage dividing device is a resistor.

3. The over-temperature protection sampling circuit of claim 2, wherein: The resistors have the same resistance.

4. The over-temperature protection sampling circuit of claim 1, wherein: Each thermistor is a negative-temperature-coefficient thermistor.

5. The over-temperature protection sampling circuit of claim 1, wherein: The selection circuit comprises N follow-up processing circuits, each follow-up processing circuit comprising an operational amplifier and a diode, the non-inverting input end of each operational amplifier being an input end of the selection circuit, the inverting input end of each operational amplifier and the anode of a corresponding diode being connected together as an output end of the selection circuit, and the anode of each diode being connected to the output end of the corresponding operational amplifier.

6. The over-temperature protection sampling circuit of claim 5, wherein: Each follow-up processing circuit comprises a resistor, one end of each resistor being connected to the inverting input end of the corresponding operational amplifier, and the other end of each resistor and the anode of the corresponding diode being connected together as the output end of the selection circuit.

7. The over-temperature protection sampling circuit according to claim 1, wherein: Each voltage dividing device is a resistor. The selection circuit comprises N follow-up processing circuits, each follow-up processing circuit comprising an operational amplifier and a diode, the non-inverting input end of each operational amplifier being an input end of the selection circuit, the inverting input end of each operational amplifier and the anode of a corresponding diode being connected together as an output end of the selection circuit, and the anode of each diode being connected to the output end of the corresponding operational amplifier.

8. The over-temperature protection sampling circuit of claim 7, wherein: The resistors have the same resistance, each thermistor is a negative-temperature-coefficient thermistor, and each follow-up processing circuit comprises a resistor, one end of each resistor being connected to the inverting input end of the corresponding operational amplifier, and the other end of each resistor and the anode of the corresponding diode being connected together as the output end of the selection circuit.

9. A switched mode power supply characterized by: The over-temperature protection sampling circuit according to any one of claims 1 to 8.

10. The switching power supply of claim 9, wherein: The switching power supply is an isolated switching power supply, and the over-temperature protection sampling circuit is disposed on the same side of the switching power supply.

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