CN220234484U - Over-temperature protection circuit and switching power supply - Google Patents

Abstract

The utility model discloses an over-temperature protection circuit which comprises a logic circuit, a reference circuit and a plurality of groups of over-temperature control circuits, wherein the reference circuit is connected with the logic circuit; each group of over-temperature control circuits comprises a temperature sampling circuit and an output topology circuit; in each group of over-temperature control circuits, the logic circuit is coupled with the reference circuit and acquires a reference comparison voltage, the logic circuit is also coupled with the temperature sampling circuit and acquires a temperature signal, and the result of the operation processing of the temperature signal and the reference comparison voltage by the logic circuit is output by the output end of the logic circuit; the output end of the logic circuit is coupled with the output topological circuit, and the output result of the output end of the logic circuit is used for controlling the output topological circuit to output the output signal. The utility model also discloses a switching power supply, which adopts the over-temperature protection circuit. The over-temperature control circuits of each group are not mutually interfered, can detect a plurality of objects, and have wide application range.

Description

Over-temperature protection circuit and switching power supply

Technical Field

The present disclosure relates to electronic devices, and particularly to an over-temperature protection circuit and a switching power supply.

Background

In switching power supply design, temperature is a very critical performance indicator, and therefore, temperature protection is also an important protection function in a circuit. High voltage and high current power switching circuits are often integrated in the device, which can result in significant power consumption. Also, as these power consumption increases, the temperature variation of the device may be large. Excessive temperature rise can lead to failure of temperature-sensitive semiconductor devices (such as MOS (metal oxide semiconductor) tubes, diodes, triodes and the like), capacitors and other components, and in severe cases, safety problems can be caused. Therefore, a module having one temperature protection function is indispensable for a switching power supply.

Conventional over-temperature protection circuits may employ temperature sampling devices to sample temperature changes of the chip, such as NTC devices. As shown in fig. 1, the prior art discloses an over-temperature protection circuit, which adopts a temperature-sensitive resistor to sample temperature. When the sampling temperature rises, the resistance value of the temperature-sensitive resistor RT1 is continuously reduced, so that the temperature sampling value (voltage signal value) obtained by the comparator is continuously reduced. Therefore, in this overheat protection circuit, the positive electrode (pin-4) of the chip U1 is set as a comparator reference value, the negative electrode (pin-3) of the chip U1 is set as a real-time sampling value of temperature, and the temperature sampling value and the reference value are calculated by the comparator and outputted to obtain: when the temperature sampling value is detected to be smaller than the reference value (namely, vpin-3< Vpin-4), the output level of the comparator is a constant value (5 VREF, which is also the power supply level VCC of the chip U1); when the temperature sampling value is detected to be normal, the output level of the comparator is a value between intervals [ Vpin-4,5VREF ]. From analysis, the over-temperature protection circuit shown in fig. 1 will only execute the over-temperature protection strategy after the system determines that the comparator output is high (5 VREF). That is, the over-temperature protection circuit only adopts one temperature sampling device, the protection object is single, the number of objects to be protected increases with the increase of the complexity of the application system, and the scheme of the over-temperature protection circuit has a limitation. Moreover, the control mode with single output level cannot form different protection strategies for different protection objects.

Disclosure of Invention

The utility model provides an over-temperature protection circuit and a switching power supply aiming at the defects in the prior art.

In order to solve the technical problems, the utility model discloses an over-temperature protection circuit which comprises a logic circuit, a reference circuit and a plurality of groups of over-temperature control circuits; each group of over-temperature control circuits comprises a temperature sampling circuit for sampling temperature signals in the circuit system and an output topology circuit for outputting output signals, wherein the output signals are used for controlling electrical parameters of the temperature controlled object; the logic circuit is coupled with the reference circuit and acquires a reference comparison voltage; in each group of over-temperature control circuits, the logic circuit is further coupled with the temperature sampling circuit and acquires the temperature signal, and the result of the operation processing of the temperature signal and the reference comparison voltage by the logic circuit is output by the output end of the logic circuit; the output end of the logic circuit is coupled with the output topological circuit, and the output result of the logic circuit is used for controlling the output topological circuit to output the output signal.

Optionally, in each group of the over-temperature control circuits, the temperature sampling circuit includes a temperature sampling device and an input voltage dividing resistor, and the temperature sampling device is connected in series with the input voltage dividing resistor; one end of the series group of the temperature sampling device and the input voltage dividing resistor is grounded, and the other end of the series group of the temperature sampling device and the input voltage dividing resistor is coupled with the reference circuit to acquire set voltage; the reverse input end of the logic circuit is electrically connected to a circuit between the temperature sampling device and the input voltage dividing resistor, and the reverse input end is used for acquiring voltages at two ends of the temperature sampling device; the voltage at two ends of the temperature sampling device represents the temperature signal.

Optionally, in each group of the over-temperature control circuits, the output topology circuit includes a diode, an output voltage dividing resistor, an output resistor and an output protection resistor; the output voltage dividing resistor is connected with the output resistor in series; one end of a series group of the output voltage dividing resistor and the output resistor is grounded, and the other end of the series group of the output voltage dividing resistor and the output resistor is coupled with the reference circuit to acquire the set voltage; one end of the output protection resistor is electrically connected to a circuit between the output voltage dividing resistor and the output resistor, the other end of the output protection resistor is coupled with the anode of the diode, and the cathode of the diode is coupled with the output end of the logic circuit.

Optionally, the reference circuit includes a first resistor, a second resistor, and a third resistor connected in series; one end of the first resistor is electrically connected with a power supply, and the other end of the first resistor is electrically connected with the second resistor; one end of the second resistor is electrically connected with the first resistor, and the other end of the second resistor is electrically connected with the third resistor; one end of the third resistor is electrically connected with the second resistor, and the other end of the third resistor is grounded.

Optionally, the two ends of the series group of the second resistor and the third resistor are connected with a zener diode in parallel, the cathode of the zener diode is electrically connected to a line between the first resistor and the second resistor, and the anode of the zener diode is electrically connected with the grounding end of the third resistor.

Optionally, the positive input end of the logic circuit is electrically connected to a line between the second resistor and the third resistor, and voltages at two ends of the third resistor are the reference comparison voltages.

Optionally, one end of the series group of the output voltage dividing resistor and the output resistor is electrically connected to a line between the first resistor and the second resistor, and the voltage at two ends of the series group of the second resistor and the third resistor is the set voltage.

Optionally, the output resistor is a variable resistor with an adjustable resistance.

Optionally, the temperature sampling device is a temperature sensitive resistor, a MOSFET tube, a diode or an inductor.

Optionally, when the number of the plurality of groups of the over-temperature control circuits is greater than or equal to two groups, the temperature sampling devices of the different two groups of the over-temperature control circuits are the same.

Optionally, when the number of the plurality of groups of the over-temperature control circuits is greater than or equal to two groups, the temperature sampling devices of the different two groups of the over-temperature control circuits are different.

Optionally, the logic circuit is a comparator or an amplifier.

The utility model also discloses a switching power supply which is a single-topology system and adopts a group of over-temperature protection circuits.

The utility model also discloses a switching power supply which is a parallel topology structure system, adopts a plurality of groups of the over-temperature protection circuits, and the plurality of groups of the over-temperature protection circuits are mutually coupled in parallel

The utility model can multiplex a plurality of groups of over-temperature control circuits on the same chip, and the working states of the protection circuits are relatively independent and mutually decoupled and mutually noninterfere, so that the mutual influence between the circuits can be avoided when a plurality of element objects are protected;

the utility model has the advantages of wide application range, simple output level value setting mode and high reliability.

In the power supply system, the power management chip has an OTP function, so the design of the utility model can form double protection with the OTP function.

Additional aspects and advantages of the utility model will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the utility model.

Drawings

The accompanying drawings, which are included to provide a further understanding of the utility model and are incorporated in and constitute a part of this application, illustrate embodiments of the utility model and together with the description serve to explain the utility model and do not constitute a limitation on the utility model. In the drawings:

FIG. 1 is a prior art over-temperature protection circuit;

fig. 2 is a schematic structural diagram of an over-temperature protection circuit according to a second embodiment of the present utility model;

FIG. 3 is a logic diagram illustrating an over-temperature protection circuit according to a second embodiment of the present utility model;

fig. 4 is a schematic structural diagram of an over-temperature protection circuit according to a third embodiment of the present utility model;

FIG. 5 is a logic diagram illustrating an over-temperature protection circuit according to a third embodiment of the present utility model;

fig. 6 is a schematic diagram of a temperature sampling device in a switching power supply according to a fourth embodiment of the present utility model;

fig. 7 is a schematic diagram of a temperature sampling device in a switching power supply according to a fifth embodiment of the present utility model.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present utility model more clear, the technical solutions of the embodiments of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present utility model. It will be apparent that the described embodiments are some, but not all, embodiments of the utility model. All other embodiments, which can be made by a person skilled in the art without creative efforts, based on the described embodiments of the present utility model fall within the protection scope of the present utility model.

Unless defined otherwise, technical or scientific terms used herein should be given the ordinary meaning as understood by one of ordinary skill in the art to which this utility model belongs. The terms "first," "second," and the like in the description and in the claims, are not used for any order, quantity, or importance, but are used for distinguishing between different elements.

Embodiment one:

the embodiment discloses an over-temperature protection circuit which can perform over-temperature protection and self-recovery of a plurality of temperature sampling devices. The over-temperature control circuit of the present utility model includes a logic circuit, a reference circuit 100, and a plurality of sets of over-temperature control circuits, each set of over-temperature control circuits including a temperature sampling circuit for sampling a temperature signal, and an output topology circuit for outputting an output signal. Each group of over-temperature control circuits is coupled with the logic circuit. The plurality of groups of over-temperature control circuits can be one group, two groups, three groups or other groups according to actual circuit design requirements.

In each group of over-temperature control circuits, a logic circuit is coupled with the reference circuit 100 and acquires a reference comparison voltage Vref2, the logic circuit is also coupled with the temperature sampling circuit and acquires a temperature signal, and the logic circuit carries out operation processing on the temperature signal and the reference comparison voltage Vref2 and then outputs the temperature signal and the reference comparison voltage Vref2 through an output end; because the output end of the logic circuit is coupled with the output topological circuit, the output result of the output end of the logic circuit is used for controlling the output of the output topological circuit to the output signal.

In each group of over-temperature control circuits, each group of temperature sampling circuits comprises a temperature sampling device and an input voltage dividing resistor, and the temperature sampling devices are connected in series with the input voltage dividing resistor. One end of a series group of the temperature sampling device and the input voltage dividing resistor is grounded, and the other end of the series group is coupled with the reference circuit 100 to obtain the set voltage Vref1. The reverse input end of the logic circuit is electrically connected to a circuit between the temperature sampling device and the input voltage dividing resistor, and is used for acquiring voltages at two ends of the temperature sampling device, and the voltages at two ends of the temperature sampling device represent temperature signals. The temperature sampling device in this embodiment is a temperature sensitive resistor, and in other embodiments may be a MOSFET, a diode, or an inductor.

In each group of the over-temperature control circuits, the output topology circuit comprises a diode, an output voltage dividing resistor, an output resistor and an output protection resistor. The output voltage dividing resistor is connected in series with the output resistor, one end of the series group of the output voltage dividing resistor and the output resistor is grounded, and the other end of the series group of the output voltage dividing resistor and the output resistor is coupled with the reference circuit 100 to obtain the set voltage Vref1. One end of the output protection resistor is electrically connected to a circuit between the output voltage dividing resistor and the output resistor, the other end of the output protection resistor is coupled with the anode of the diode, and the cathode of the diode is coupled with the output end of the logic circuit. The output resistor of this embodiment is a variable resistor with an adjustable resistance, and the voltage at the common connection end of the output voltage dividing resistor, the output resistor and the output protection resistor is an output voltage. It should be understood that the output topology circuit should also be coupled to a circuit where the temperature controlled object is located, and the output voltage of the output topology circuit controls the electrical parameters of the temperature controlled object by controlling the circuit where the temperature controlled object is located in the switching power supply system, so that multiple or single parameters (i.e., multiple or single parameters are used as the temperature controlled object) of power, current or voltage and the like are adjusted and controlled, thereby realizing temperature protection.

In the reference circuit 100, the reference circuit 100 includes a first resistor R1, a second resistor R2, and a third resistor R3 connected in series. One end of the first resistor R1 is electrically connected with a power supply, and the other end of the first resistor R1 is electrically connected with the second resistor R2; one end of the second resistor R2 is electrically connected with the first resistor R1, and the other end of the second resistor R2 is electrically connected with the third resistor R3; one end of the third resistor R3 is electrically connected with the second resistor R2, and the other end of the third resistor R is grounded. The two ends of the series group of the second resistor R2 and the third resistor R3 are connected with a zener diode D3 in parallel, the cathode of the zener diode D3 is electrically connected to a circuit between the first resistor R1 and the second resistor R2, and the anode of the zener diode D3 is electrically connected with the grounding end of the third resistor R3.

The positive input end of the logic circuit is electrically connected to a line between the second resistor R2 and the third resistor R3, and the voltage at two ends of the third resistor R3 is the reference comparison voltage Vref2. The logic circuit of this embodiment is a comparator, and in other embodiments, the logic circuit may also be an amplifier. In addition, one end of the series group of the output voltage dividing resistor and the output resistor is electrically connected to a line between the first resistor R1 and the second resistor R2, the voltage at two ends of the series group of the second resistor R2 and the third resistor R3 is the set voltage Vref1, and the series group of the output voltage dividing resistor and the output resistor obtains the set voltage Vref1.

Embodiment two:

the embodiment discloses an over-temperature protection circuit, which is based on the over-temperature protection circuit in the first embodiment, and is provided with two groups of over-temperature control circuits, as shown in fig. 2. In addition, the logic circuit adopted in the embodiment is a comparator U1, and temperature sampling devices in the two groups of over-temperature control circuits both adopt temperature-sensitive resistors, but in other embodiments, the temperature sampling devices of each group may be the same or different, and other elements may also be selected. In order to describe two sets of over-temperature control circuits, the present embodiment distinguishes between the first over-temperature control circuit and the second over-temperature control circuit, and uses "first" and "second" to distinguish between names of components included in the two sets of over-temperature control circuits. Correspondingly, the present embodiment also distinguishes between the first output topology 301 and the second output topology 302.

IN one embodiment, the first over-temperature control circuit includes a first temperature sampling circuit 201, where the first temperature sampling circuit 201 specifically includes a first input voltage dividing resistor R4 and a first temperature-sensitive resistor RT1, the first input voltage dividing resistor R4 is connected IN series with the first temperature-sensitive resistor RT1, a first forward input terminal in1+ (pin-2) of the comparator U1 is electrically connected between the first input voltage dividing resistor R4 and the first temperature-sensitive resistor RT1, and obtains voltage signals at two ends of the first temperature-sensitive resistor RT1, and the voltage signals at two ends of the first temperature-sensitive resistor RT1 represent temperature signals detected by the first over-temperature control circuit. One end of the first temperature-sensitive resistor RT1 is coupled with the first input voltage dividing resistor R4, and the other end of the first temperature-sensitive resistor RT is grounded. One end of the first input voltage dividing resistor R4 is coupled with the first temperature-sensitive resistor RT1, the other end of the first input voltage dividing resistor R4 is electrically connected to a circuit between the first resistor R1 and the second resistor R2, and a series group formed by connecting the first input voltage dividing resistor R4 and the first temperature-sensitive resistor RT1 in series is used for obtaining the set voltage Vref1. The first inverting input terminal IN1- (pin-3) of the comparator U1 is electrically connected to a line between the second resistor R2 and the third resistor R3 to obtain voltages at two ends of the third resistor R3, i.e. obtain the reference comparison voltage Vref2.

IN one embodiment, the second over-temperature control circuit includes a second temperature sampling circuit 202, where the second temperature sampling circuit 202 specifically includes a second input voltage dividing resistor R5 and a second temperature-sensitive resistor RT2, the second input voltage dividing resistor R5 is connected IN series with the second temperature-sensitive resistor RT2, a second positive input terminal in2+ (pin-8) of the comparator U1 is electrically connected between the second input voltage dividing resistor R5 and the second temperature-sensitive resistor RT2, and obtains voltage signals at two ends of the second temperature-sensitive resistor RT2, and the voltage signals at two ends of the second temperature-sensitive resistor RT2 represent temperature signals detected by the second over-temperature control circuit. One end of the second temperature-sensitive resistor RT2 is coupled with the second input voltage dividing resistor R5, and the other end of the second temperature-sensitive resistor RT is grounded. One end of the second input voltage dividing resistor R5 is coupled with the second temperature-sensitive resistor RT2, the other end of the second input voltage dividing resistor R5 is electrically connected to a circuit between the first resistor R1 and the second resistor R2, and a series group formed by connecting the second input voltage dividing resistor R5 and the second temperature-sensitive resistor RT2 in series is used for obtaining the set voltage Vref1. The second inverting input terminal IN2- (pin-7) of the comparator U1 is electrically connected to a line between the second resistor R2 and the third resistor R3 to obtain voltages at two ends of the third resistor R3, i.e. obtain the reference comparison voltage Vref2.

In one embodiment, as shown in fig. 2, the first output topology 301 includes a first output voltage dividing resistor R8, a first output protection resistor R9, a first output resistor VR1, and a first diode D1. The first output resistor VR1 and the first output voltage dividing resistor R8, one end of the first output protection resistor R9 is electrically connected to a circuit between the first output voltage dividing resistor R8 and the first output resistor VR1, the other end of the first output protection resistor R9 is coupled to the first output end OUT1 (pin-4) of the comparator U1, and a first diode D1 is electrically connected between the first output end OUT1 (pin-4) of the comparator U1 and the first output protection resistor R9. The anode of the first diode D1 is coupled to one end of the ninth resistor, and the cathode is coupled to the first output OUT1 (pin-4) of the comparator U1. In addition, one end of the first output resistor VR1 is electrically connected with the first output voltage dividing resistor R8, and the other end is grounded; one end of the first output voltage dividing resistor R8 is electrically connected to the first output resistor VR1, and the other end is electrically connected between the first resistor R1 and the second resistor R2, so that the series group formed by the first output voltage dividing resistor R8 and the first output resistor VR1 in series obtains the set voltage Vref1 from the reference circuit 100. As shown in the drawing, the voltage at the common connection terminal of the first output voltage dividing resistor R8, the first output protection resistor R9, and the first output resistor VR1 is the first output voltage Vset1.

In one embodiment, as shown in fig. 2, the second output topology 302 includes a second output voltage dividing resistor R6, a second output protection resistor R7, a second output resistor VR2, and a second diode D2. The second output resistor VR2 is connected in series with the second output voltage dividing resistor R6, one end of the second output protection resistor R7 is electrically connected to a line between the second output voltage dividing resistor R6 and the second output resistor VR2, the other end of the second output protection resistor R7 is coupled to the second output end OUT2 (pin-6) of the comparator U1, and a second diode D2 is electrically connected between the second output end OUT2 (pin-6) of the comparator U1 and the second output protection resistor R7. The anode of the second diode D2 is coupled to one end of the second output protection resistor R7, and the cathode is coupled to the second output terminal OUT1 (pin-6) of the comparator U1. In addition, one end of the second output resistor VR2 is electrically connected with the second output voltage dividing resistor R6, and the other end is grounded; one end of the second output voltage dividing resistor R6 is electrically connected to the second output resistor VR2, and the other end is electrically connected between the first resistor R1 and the second resistor R2, so that the series group formed by the second output voltage dividing resistor R6 and the second output resistor VR2 in series obtains the set voltage Vref1 from the reference circuit 100. As shown in fig. 2, the voltage at the common connection terminal of the second output voltage dividing resistor R6, the second output protection resistor R7, and the second output resistor VR2 is the second output voltage Vset2.

The over-temperature protection mode of the over-temperature protection circuit of this embodiment is as follows:

when the temperature is IN a normal state, the voltage signals at two ends of the first temperature-sensitive resistor RT1 are larger than the reference comparison voltage Vref2 due to the influence of the normal temperature, namely, the second voltage value Vpin-2 obtained by the first positive input end In1+ (pin-2) of the comparator U1 is larger than the third voltage value Vpin-3 obtained by the first negative input end IN1- (pin-3), namely, vpin-2> Vpin-3; at this time, the first output terminal OUT1 (pin-4) of the comparator U1 outputs a high level, and the cathode of the first diode D1 and the first output terminal OUT1 (pin-4) cannot form a path, so the value of the first output voltage Vset1 is the voltage across the first output resistor VR1, that is, the divided voltage obtained from the set voltage Vref1 by the first output resistor VR 1. At this time, the value of the first output voltage Vset1 is:

similarly, the eighth voltage value Vpin-8 obtained at the second positive input terminal IN2+ (pin-8) of the comparator U1 is larger than the seventh voltage value Vpin-7 obtained at the second negative input terminal IN1- (pin-7), namely, vpin-8> Vpin-7; at this time, the second output terminal OUT2 (pin-6) of the comparator U1 outputs a high level, and at this time, the value of the second output voltage Vset2 is:

when the temperature increases continuously, the voltage signal at both ends of the first temperature-sensitive resistor RT1 decreases continuously due to the temperature increase, i.e. the second voltage value Vpin-2 obtained by the first positive input terminal in1+ (pin-2) of the comparator U1 also decreases continuously. When the second voltage value Vpin-2 drops to be smaller than the third voltage value Vpin-3 obtained by the first inverting input terminal IN1- (pin-3), that is, when Vpin-2< Vpin-3, the first output terminal OUT1 (pin-4) of the comparator U1 outputs a low level, and the cathode of the first diode D1 and the first output terminal OUT1 (pin-4) also form a path thereby. At this time, the value of the first output voltage Vset1 is:

similarly, the eighth voltage value Vpin-8 obtained at the second positive input IN2+ (pin-8) of the comparator U1 also continuously decreases. When the eighth voltage value Vpin-8 drops to be smaller than the seventh voltage value Vpin-7 obtained at the second inverting input terminal IN1- (pin-7), that is, when Vpin-8< Vpin-7, the second output terminal OUT2 (pin-6) of the comparator U1 outputs a low level, at this time, the value of the second output voltage Vset2 is:

in summary, compared with the output voltage under normal conditions, after the temperature is continuously increased, the output voltage is gradually reduced along with the temperature increase, so that a plurality of or single parameters of power/current/voltage in the system are reduced, the parameters are used as temperature controlled objects, and after the temperature is controlled to be reduced, the circuit also realizes temperature protection.

Specifically, fig. 3 is a working logic diagram of the over-temperature control circuit according to the present embodiment, and as can be seen from the figure, the over-temperature protection process includes the following steps:

step one: the system is in a steady state of thermal equilibrium with normal temperature. At this time, IN the first over-temperature control circuit, the resistance of the first temperature-sensitive resistor RT1 is kept unchanged, the potential difference across the first temperature-sensitive resistor RT1 is also kept unchanged, the second voltage value Vpin-2 obtained at the first positive input terminal in1+ (pin-2) of the comparator U1 is kept unchanged, and the second voltage value Vpin-2 is kept stable IN a state higher than the third voltage value Vpin-3 (i.e., the set voltage Vref1 of 2.5V). The value of the first output voltage Vset1 is also maintained at a set value position, that is, a divided value of the two ends of the first output resistor VR1 obtained by dividing the set voltage Vref1 by connecting the first output resistor VR1 and the first output dividing resistor R8 in series. As shown by the steady-state curves before the zero time point t0 and after the seventh time point t7 in fig. 3, the power system considers that the first over-temperature control circuit is in the inactive state or enters the thermal equilibrium steady-state at this time. Similarly, in the second over-temperature control circuit, the value of the second output voltage Vset2 of the system in the thermal equilibrium steady state is also kept unchanged and maintained at a set value position. As shown by the steady-state curves before the first time point t1 and after the sixth time point t6 in fig. 3, the power system considers that the second over-temperature control circuit is not operating or enters a thermal equilibrium steady state at this time.

Step two: the system temperature is abnormal, and the temperature of the detected object is continuously increased. IN the first over-temperature control circuit, the resistance of the first temperature-sensitive resistor RT1 gradually decreases, so that the potential difference across the first temperature-sensitive resistor RT1 also decreases, so that the second voltage value Vpin-2 obtained by the first positive input terminal in1+ (pin-2) of the comparator U1 gradually decreases. As shown in the falling curve of the second voltage value Vpin-2 between the zero time point t0 and the fourth time point t4 in fig. 3: the temperature of the detected object starts to rise continuously at the zeroth time point t0, the second voltage value Vpin-2 also starts to fall from the zeroth time point t0 and falls to the third voltage value Vpin-3 (namely, the reference comparison voltage Vref2 of 2.5V) at the second time point t 2; between the second time point t2 and the fourth time point t4, the second voltage value Vpin-2 continuously drops below the third voltage value Vpin-3, that is Vpin-2< Vpin-3 (2.5V), and at this time, the first output terminal OUT1 (pin-4) outputs a low level signal; the temperature of the detected object does not continue to rise at the fourth time point t4, so the second voltage value Vpin-2 is reduced to the minimum at the fourth time point t 4. Between the second time point t2 and the fourth time point t4, since the first output terminal OUT1 (pin-4) outputs a low level signal, the value of the first output voltage Vset1 is reduced, and the system performs an over-temperature protection operation, i.e., one or more operations of reducing power and reducing current/voltage parameters. Similarly, in the second over-temperature control circuit, as shown in the falling curve of the eighth voltage value Vpin-8 between the first time point t1 and the third time point t3 in fig. 3: the temperature of the detected object starts to rise continuously at the first time point t1, the eighth voltage value Vpin-8 also starts to fall from the first time point t1 and falls to the seventh voltage value Vpin-7 (namely, the reference comparison voltage Vref2 of 2.5V) at the second time point t 2; between the second time point t2 and the third time point t3, the eighth voltage value Vpin-8 continuously drops below the seventh voltage value Vpin-7, that is Vpin-8< Vpin-7 (2.5V), at this time, the second output terminal OUT2 (pin-6) outputs a low level signal; the temperature of the object to be detected does not continue to rise at the third time point t3, so the eighth voltage value Vpin-8 at the third time point t3 is reduced to the minimum. Between the second time point t2 and the third time point t3, since the second output terminal OUT2 (pin-6) outputs a low level signal, the value of the second output voltage Vset2 is lowered, and the system performs an over-temperature protection operation.

Step three: since the system implements the over-temperature protection strategy, the temperature of the detected object begins to drop. IN the first over-temperature control circuit, the resistance of the first temperature-sensitive resistor RT1 gradually increases, and the potential difference across the first temperature-sensitive resistor RT1 also increases, so that the second voltage value Vpin-2 obtained at the first positive input terminal in1+ (pin-2) of the comparator U1 starts to gradually increase. As shown in the rising curve of the second voltage value Vpin-2 between the fourth time point t4 and the seventh time point t7 in fig. 3: the temperature of the detected object starts to decrease at the fourth time point t4, the second voltage value Vpin-2 also starts to increase from the lowest position, and increases to the third voltage value Vpin-3 (i.e., 2.5V) at the sixth time point t 6; between the sixth time point t6 and the seventh time point t7, the second voltage value Vpin-2 continuously rises to be higher than the third voltage value Vpin-3, that is, vpin-2> Vpin-3 (2.5V), at this time, the first output terminal OUT1 (pin-4) outputs a high level signal; since the temperature of the object to be detected does not decrease any further at the seventh time t7, the second voltage value Vpin-2 returns to the normal state at the seventh time t7, and the second voltage value Vpin-2 remains unchanged as the temperature remains unchanged. Between the sixth time point t6 and the seventh time point t7, although the first output terminal OUT1 (pin-4) outputs the high level signal, the high level does not affect the value of the first output voltage Vset1 due to the presence of the first diode D1, so that the value of the first output voltage Vset1 is restored to the original set value, that is, to the divided value of the first output resistor VR1 obtained by dividing the set voltage Vref1 by the series connection of the first output resistor VR1 and the first output dividing resistor R8, and the system is also exited from the over-temperature protection strategy. Similarly, in the second over-temperature control circuit, as shown in the rising curve of the eighth voltage value Vpin-8 between the third time point t3 and the sixth time point t6 in fig. 3: the temperature of the detected object starts to decrease at the third time point t3, the eighth voltage value Vpin-8 also starts to increase from the lowest position, and increases to the seventh voltage value Vpin-7 at the fifth time point t 5; between the fifth time point t5 and the sixth time point t6, the eighth voltage value Vpin-8 continuously rises to be higher than the seventh voltage value Vpin-7, and at this time, the second output terminal OUT2 (pin-6) outputs a high level signal; since the temperature of the object to be detected does not decrease any further at the sixth time point t6, the eighth voltage value Vpin-8 is raised back to the normal state, and the eighth voltage value Vpin-8 is maintained as the temperature is maintained. Between the fifth time point t5 and the sixth time point t6, the second diode D2 is oriented such that the high level at this time does not affect the value of the second output voltage Vset2, so that the value of the second output voltage Vset2 is restored to the original set value.

The over-temperature protection circuit of the embodiment forms multi-path temperature protection through a plurality of groups of over-temperature control circuits, the plurality of groups of over-temperature control circuits are multiplexed on the same chip, the working states of the protection circuits are relatively independent and mutually decoupled, mutual interference is avoided, and the mutual influence between the circuits can be avoided when a plurality of element objects are protected. Therefore, the circuit of the embodiment can set different protection thresholds for different protection objects, has strong portability and wide application range.

The design structure of the output topology circuit in this embodiment has a simple setting manner of the output level, high reliability, and a manner of optimizing the output voltage, optimizes the circuit protection logic, and forms a positive correspondence between the first output voltage Vset1 (the second output voltage Vset 2) and one parameter or multiple meals of the power/current/voltage of the system, that is, the lower the first output voltage Vset1 (the second output voltage Vset 2) is, the lower the corresponding power/current/voltage value of the system is, and vice versa. Therefore, the output voltage value can be used for controlling system parameters (parameters such as power/current/voltage) in real time, a plurality of element objects can be protected in a simple and reliable circuit mode in a complex application system, and the device has wide application space. Therefore, the embodiment has the advantages of wide application range, unified protection threshold value, simple output level value setting mode and high reliability.

When the embodiment is applied to a power supply system, the design of the embodiment can form double protection with the power management chip because the power management chip has an OTP function. In addition, the embodiment can be suitable for different protection objects of a single topological structure system, can also be used for the same protection object of a parallel topological structure system, and has simple setting method and high flexibility.

Embodiment III:

the embodiment discloses an over-temperature protection circuit, as shown in fig. 4, and the circuit structure of the over-temperature protection circuit is similar to that of the embodiment, except that the logic circuit of the embodiment adopts an amplifier U2. IN this embodiment, as shown IN the working logic diagram of the over-temperature control circuit of fig. 5, since the comparator U1 rapidly inverts the level and the amplifier U2 slowly amplifies the error, the output level will change with the error value, i.e. the first output voltage Vset1 IN fig. 5 will change slowly with the voltage signal obtained from the first forward input terminal in1+ (pin-2), and the second output voltage Vset2 will change slowly with the voltage signal obtained from the second forward input terminal in2+ (pin-8). The scheme of the embodiment can slowly control the system parameters, and the control force can also gradually increase along with the increase of errors, namely, the control force of over-temperature is also larger along with the increase of errors between the second voltage value Vpin-2 (eighth voltage value Vpin-8) and the reference comparison voltage Vref2 (2.5V), and the lower the level signal of the output voltage is, the larger the over-temperature control force is.

Embodiment four:

the utility model also discloses a switching power supply which is an off-line power supply with a single topological structure, as shown in fig. 6, the embodiment only adopts an over-temperature protection circuit in the second embodiment, and a temperature sampling device in the over-temperature protection circuit can be a temperature sensitive resistor, a MOSFET (metal oxide semiconductor field effect transistor), a diode or an inductor. The topology of this embodiment is a Boost-PFC topology. Since the power management chip itself has the OTP function when in the power system, the design of the over-temperature protection circuit in the second embodiment can also form double protection with the OTP function of the power management chip itself.

Fifth embodiment:

the utility model discloses a switching power supply, which is an off-line power supply with a parallel topological structure, as shown in fig. 7, the embodiment adopts two groups of over-temperature protection circuits in the second embodiment, temperature sampling devices in the two groups of over-temperature protection circuits can be temperature-sensitive resistors, MOSFET (metal-oxide-semiconductor field effect transistors), diodes or inductors, the temperature sampling devices of the two groups of over-temperature protection circuits can be the same or different, and the output results of the two groups of over-temperature protection circuits can jointly act on the same temperature controlled object. In the present embodiment, two sets of the over-temperature protection circuits are connected in parallel with each other: the signal input end of the first group of over-temperature protection circuits is coupled with the signal input end of the second group of over-temperature protection circuits, and the signal output end of the first group of over-temperature protection circuits is coupled with the signal output end of the second group of over-temperature protection circuits. By adopting the design of the embodiment, a plurality of groups of over-temperature protection circuits are connected in parallel to form a plurality of groups of over-temperature protection circuits which are independent relatively, are mutually decoupled and do not interfere with each other, and can avoid the mutual influence among the circuits when protecting a plurality of element objects. The embodiment is used in a system with a parallel topological structure and is used for protecting the technical characteristics of the same protection object, and double protection effects can be formed. Therefore, the circuit of the embodiment not only can multiplex multiple paths of over-temperature protection circuits on the same chip, but also can set independent over-temperature protection circuits aiming at different topological structures, so that the interference among all paths of over-temperature protection circuits is reduced, the working state is independent, the portability is strong, and the application space is wide.

Finally, it should be noted that: the above embodiments are only for illustrating the technical solution of the present utility model, and are not limiting; although the utility model has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit of the utility model.

In summary, the foregoing description is only of the preferred embodiments of the present utility model, and all equivalent changes and modifications made in accordance with the claims should be construed to fall within the scope of the utility model.

Claims (14)

1. An over-temperature protection circuit, characterized in that: the device comprises a logic circuit, a reference circuit and a plurality of groups of over-temperature control circuits; each group of over-temperature control circuits comprises a temperature sampling circuit for sampling temperature signals in the circuit system and an output topology circuit for outputting output signals, wherein the output signals are used for controlling electrical parameters of the temperature controlled object; the logic circuit is coupled with the reference circuit and acquires a reference comparison voltage;

in each set of the over-temperature control circuits,

the logic circuit is further coupled with the temperature sampling circuit and acquires the temperature signal, and the result of the operation processing of the temperature signal and the reference comparison voltage by the logic circuit is output by the output end of the logic circuit; the output end of the logic circuit is coupled with the output topological circuit, and the output result of the logic circuit is used for controlling the output topological circuit to output the output signal.

2. The over-temperature protection circuit according to claim 1, wherein in each set of the over-temperature control circuits, the temperature sampling circuit includes a temperature sampling device and an input voltage dividing resistor, the temperature sampling device being connected in series with the input voltage dividing resistor;

one end of the series group of the temperature sampling device and the input voltage dividing resistor is grounded, and the other end of the series group of the temperature sampling device and the input voltage dividing resistor is coupled with the reference circuit to acquire set voltage;

the reverse input end of the logic circuit is electrically connected to a circuit between the temperature sampling device and the input voltage dividing resistor, and the reverse input end is used for acquiring voltages at two ends of the temperature sampling device; the voltage at two ends of the temperature sampling device represents the temperature signal.

3. The over-temperature protection circuit according to claim 2, wherein in each set of the over-temperature control circuits, the output topology circuit includes a diode, an output voltage dividing resistor, an output resistor, and an output protection resistor;

the output voltage dividing resistor is connected with the output resistor in series; one end of a series group of the output voltage dividing resistor and the output resistor is grounded, and the other end of the series group of the output voltage dividing resistor and the output resistor is coupled with the reference circuit to acquire the set voltage;

one end of the output protection resistor is electrically connected to a circuit between the output voltage dividing resistor and the output resistor, the other end of the output protection resistor is coupled with the anode of the diode, and the cathode of the diode is coupled with the output end of the logic circuit.

4. The over-temperature protection circuit of claim 3, wherein the reference circuit comprises a first resistor, a second resistor, and a third resistor connected in series;

one end of the first resistor is electrically connected with a power supply, and the other end of the first resistor is electrically connected with the second resistor;

one end of the second resistor is electrically connected with the first resistor, and the other end of the second resistor is electrically connected with the third resistor;

one end of the third resistor is electrically connected with the second resistor, and the other end of the third resistor is grounded.

5. The over-temperature protection circuit according to claim 4, wherein a zener diode is connected in parallel between two ends of the series group of the second resistor and the third resistor, a cathode of the zener diode is electrically connected to a line between the first resistor and the second resistor, and an anode of the zener diode is electrically connected to a ground terminal of the third resistor.

6. The over-temperature protection circuit of claim 5, wherein a positive input of the logic circuit is electrically connected to a line between the second resistor and the third resistor, and a voltage across the third resistor is the reference comparison voltage.

7. The over-temperature protection circuit according to claim 5, wherein one end of the series group of the output voltage dividing resistor and the output resistor is electrically connected to a line between the first resistor and the second resistor, and a voltage across the series group of the second resistor and the third resistor is the set voltage.

8. The over-temperature protection circuit according to claim 3, wherein the output resistor is a variable resistor with an adjustable resistance.

9. The over-temperature protection circuit of claim 2, wherein the temperature sampling device is a temperature sensitive resistor, a MOSFET tube, a diode, or an inductor.

10. The over-temperature protection circuit according to claim 9, wherein when the number of the plurality of sets of the over-temperature control circuits is greater than or equal to two sets, the temperature sampling devices of the different two sets of the over-temperature control circuits are identical.

11. The over-temperature protection circuit according to claim 9, wherein when the number of the plurality of sets of the over-temperature control circuits is greater than or equal to two sets, the temperature sampling devices of the different two sets of the over-temperature control circuits are different.

12. The over-temperature protection circuit of claim 1, wherein the logic circuit is a comparator or an amplifier.

13. A switching power supply, being a single topology system, characterized in that a set of the over-temperature protection circuits according to any of claims 1-12 is used.

14. A switching power supply, being a parallel topology system, characterized in that several sets of the over-temperature protection circuits according to any of claims 1-12 are employed, which are coupled to each other in parallel.