Practical thermosensitive protection circuit
By designing a practical thermal protection circuit including thermal temperature detection and processing circuit, the problem of thermal damage caused by the lack of thermal protection of existing power supplies is solved, and fast and reliable protection actions are achieved, and the reliability of the power supply is improved.
Patent Information
- Application Number
- CN202422133288.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-08-30
- Publication Date
- 2025-06-24
- Estimated Expiration
- 2034-08-30
AI Technical Summary
The lack of thermal protection measures for existing power supplies, which leads to thermal damage and may cause power failure, especially if the AC input voltage is abnormally high or the control logic of the main MCU is inappropriate.
A practical thermal protection circuit is designed, including AC and EMC circuits, input relays and control circuits, thermal temperature detection and processing circuits and main power circuits. Thermal temperature detection and processing circuit detects the temperature of the thermistor through components such as temperature-controlled resistors, comparators and MOS tubes. When the temperature exceeds the set value, the relay short-circuits thermistor to protect it.
It effectively solves the problem of thermal sensitivity failure under abnormal conditions, realizes the rapid and reliable hardware protection operation, and the cost of new circuit devices is low, which further improves the reliability of the power supply.
Smart Images
Figure CN223024086U_ABST
Abstract
Description
Technical Field
[0001] The utility model relates to the technical field of circuits, and particularly relates to a practical thermal protection circuit.
Background Art
[0002] There are basically no thermal protection measures for the power supply in the prior art. Once the thermistor is damaged, it will directly lead to the failure of the power supply. When the AC input voltage is abnormally too high, or the control logic of the main control MCU is improper, such as the relay is not closed in time before the main circuit works, or the relay is disconnected before the main circuit is turned off, it may cause the thermistor to overheat and be damaged, and there is a risk of power supply failure.
Content of the Utility Model
[0003] In order to overcome the above problems, the utility model provides a practical thermal protection circuit that can effectively solve the above problems.
[0004] A technical solution provided by the utility model to solve the above technical problems is: providing a practical thermal protection circuit, including an AC and EMC circuit, an input relay and control circuit, a thermal temperature detection and processing circuit, and a main power circuit. The AC and EMC circuit is connected to the main power circuit, the AC and EMC circuit is connected to the input relay and control circuit, and the thermal temperature detection and processing circuit is connected to the input relay and control circuit; the thermal temperature detection and processing circuit includes a temperature control resistor R0, a resistor R1, a resistor R2, a comparator COMP, a hysteresis resistor R4, a current limiting resistor R3, and a diode D1. The temperature control resistor R0 is connected to the resistor R1, the temperature control resistor R0 is connected to the resistor R2, the resistor R2 is connected to the comparator COMP, the hysteresis resistor R4 is connected to the comparator COMP, the comparator COMP is connected to the current limiting resistor R3, and the current limiting resistor R3 is connected to the diode D1.
[0005] Preferably, the L pole of the AC and EMC circuit is directly connected to the L pole of the main power circuit, and the N pole of the AC and EMC circuit is connected with a thermistor RT.
[0006] Preferably, the input relay and control circuit includes an input relay RELAY. The N pole of the AC and EMC circuit is connected to the contact 1 foot of the input relay RELAY, and the contact 4 foot of the input relay RELAY is connected to the right end of the thermistor RT, and then they are connected together to the N pole of the main power circuit.
[0007] Preferably, the input relay and control circuit includes a current-limiting resistor R7, an MOS transistor Q1, a driving resistor R5, a resistor R6, and an MCU. The second terminal of the control winding of the input relay RELAY is connected to the left end of the current-limiting resistor R7. The right end of the current-limiting resistor R7 is connected to the D pole of the MOS transistor Q1. The G pole of the MOS transistor Q1 is connected to the left end of the driving resistor R5 and the upper end of the resistor R6. The S pole of the MOS transistor Q1 is connected to the lower end of the R6. The right end of the driving resistor R5 is connected to the control pin of the MCU.
[0008] Preferably, the temperature control resistor R0 is close to the pin of the thermistor RT.
[0009] Preferably, the third terminal of the diode D1 is connected to the right end of the driving resistor R5.
[0010] Compared with the prior art, the practical thermal protection circuit of the present utility model adds a thermal protection circuit, which can effectively solve the thermal failure caused by these abnormal conditions, has a rapid hardware protection action, high reliability, and a low cost of the newly added circuit devices, further improving the reliability of the power supply.
Description of the Drawings
[0011] Figure 1 It is the schematic diagram of the practical thermal protection circuit of the present utility model.
Detailed Embodiment
[0012] In order to make the objectives, technical solutions and advantages of the present utility model clearer, the following further describes the present utility model in detail with reference to the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present utility model, and are not used to limit the present utility model.
[0013] It should be noted that all the directional indications (such as up, down, left, right, front, back...) in the embodiments of the present utility model are only relative positions on the specified views, rather than absolute positions.
[0014] In addition, the descriptions such as "first" and "second" in the present utility model are only for descriptive purposes, and cannot be understood as indicating or implying their relative importance or implicitly indicating the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one of such features. In the description of the present utility model, the meaning of "a plurality" is at least two, such as two, three, etc., unless otherwise specifically and clearly defined.
[0015] Please refer to Figure 1, the practical thermal protection circuit of the present utility model includes an AC and EMC circuit, an input relay and control circuit, a thermal temperature detection and processing circuit, and a main power circuit. The AC and EMC circuit is connected to the main power circuit, the AC and EMC circuit is connected to the input relay and control circuit, and the thermal temperature detection and processing circuit is connected to the input relay and control circuit.
[0016] The main power circuit includes a rectifier bridge, a PFC, and a main LLC power circuit part.
[0017] The L pole of the AC and EMC circuit is directly connected to the L pole of the main power circuit, and the N pole of the AC and EMC circuit is connected to a thermistor RT.
[0018] The input relay and control circuit includes an input relay RELAY, a current-limiting resistor R7, a MOS transistor Q1, a driving resistor R5, a resistor R6, and an MCU.
[0019] The N pole of the AC and EMC circuit is simultaneously connected to the contact 1 foot of the input relay RELAY, the contact 4 foot of the input relay RELAY is connected to the right end of the thermistor RT, and then they are connected together to the N pole of the subsequent main power circuit.
[0020] The control winding of the input relay RELAY is powered by VCC. VCC is connected to the 3 foot of the control winding of the input relay RELAY. The 2 foot of the control winding of the input relay RELAY is connected to the left end of the current-limiting resistor R7. The right end of the current-limiting resistor R7 is connected to the D pole of the logic MOS transistor Q1. The G pole of the MOS transistor Q1 is connected to the left end of the driving resistor R5 and the upper end of the resistor R6. The S pole of the MOS transistor Q1 is connected to the lower end of R6, and then they are connected together to GND. The right end of the driving resistor R5 is connected to the control pin of the MCU for receiving the VMCU signal control.
[0021] The thermal temperature detection and processing circuit includes a temperature control resistor R0, a resistor R1, a resistor R2, a comparator COMP, a hysteresis resistor R4, a current-limiting resistor R3, and a diode D1.
[0022] The described thermal temperature detection and processing circuit has VCC connected to the left end of the temperature control resistor R0. The right end of the temperature control resistor R0 is connected to the left end of the resistor R1. The right end of the resistor R1 is connected to GND. The right end of the temperature control resistor R0 is connected to the upper end of the resistor R2. The lower end of the resistor R2 is connected to the positive pole of the comparator COMP. The reference voltage Vref is connected to the negative pole of the comparator COMP. The left end of the hysteresis resistor R4 is connected to the positive pole of the comparator COMP. The right end of the hysteresis resistor R4 is connected to the output terminal of the comparator COMP. The output terminal of the comparator COMP is connected to the left end of the current limiting resistor R3. The right end of the current limiting resistor R3 is connected to pin 1 of the diode D1. Pin 2 of the diode D1 is connected to 3.3V. Pin 3 of the diode D1 is connected to the right end of the driving resistor R5.
[0023] The practical thermal protection circuit of the present utility model mainly adds a hardware detection and protection circuit for the over-temperature of the thermistor itself on the basis of the thermistor in the power supply power loop.
[0024] The working principle is as follows: When the AC input voltage is ON, due to the high AC voltage and the large PFC bus capacitor, there is a large input current flowing through the thermistor RT after power-on, resulting in the rapid temperature rise of the thermistor RT. The temperature control resistor R0 is a chip resistor close to the pin of the thermistor RT, which converts the temperature change of the thermistor RT into a change in the resistance value of the temperature control resistor R0. R0 has a negative temperature coefficient. As the temperature of RT gradually increases, the resistance value of R0 gradually decreases. After passing through the voltage division circuit, the voltage V1 gradually increases. When the thermistor RT exceeds the set value of X °C, the voltage V1 exceeds the set value Vref, and the logic comparator COMP outputs a high level V2. After current limiting and clamping, it becomes a high level V3, driving the MOS transistor Q1 to conduct. The winding of the input relay RELAY conducts, and the contact closes. At this time, the current flows through the relay contact, and the thermistor RT is short-circuited by the relay contact, so there is no current flowing through the thermistor RT, and the temperature rapidly decreases, achieving the protection purpose.
[0025] When the AC input voltage is OFF, due to the existence of the bus capacitor, within the hold time, the power supply still outputs power outward. When the main power loop disconnects the output, the main control MCU issues a low-level instruction of VMCU. At this time, the thermistor RT is short-circuited by the relay and has a low temperature. The voltage V1 is less than the set value Vref, and the outputs V2 and V3 are at a low level. The MOS transistor Q1 is normally turned off, so the normal turn-off is not affected.
[0026] Compared with the prior art, the practical thermal protection circuit of the present utility model adds a thermal protection circuit, which can effectively solve the thermal failure caused by these abnormal conditions. The hardware protection action is rapid, the reliability is high, the cost of the newly added circuit devices is low, and the reliability of the power supply is further improved.
[0027] The above are only the preferred embodiments of the present utility model, and do not thus limit the patent scope of the present utility model. Any modifications, equivalent substitutions, improvements, etc. made within the concept of the present utility model shall be included within the patent protection scope of the present utility model.
Claims
1. A practical thermal protection circuit, characterized in that: It includes an AC and EMC circuit, an input relay and a control circuit, a thermistor temperature detection and processing circuit and a main power circuit, wherein the AC and EMC circuit is connected to the main power circuit, the AC and EMC circuit is connected to the input relay and the control circuit, and the thermistor temperature detection and processing circuit is connected to the input relay and the control circuit; The thermistor temperature detection and processing circuit includes a temperature control resistor R0, a resistor R1, a resistor R2, a comparator COMP, a hysteresis resistor R4, a current limiting resistor R3 and a diode D1. The temperature control resistor R0 is connected to the resistor R1, the temperature control resistor R0 is connected to the resistor R2, the resistor R2 is connected to the comparator COMP, the hysteresis resistor R4 is connected to the comparator COMP, the comparator COMP is connected to the current limiting resistor R3, and the current limiting resistor R3 is connected to the diode D1.
2. The practical thermal protection circuit according to claim 1, characterized in that: The L pole of the AC and EMC circuit is directly connected to the L pole of the main power circuit, and the N pole of the AC and EMC circuit is connected to a thermistor RT.
3. The practical thermal protection circuit according to claim 2, characterized in that: The input relay and control circuit include an input relay RELAY, the N pole of the AC and EMC circuit is connected to the contact pin 1 of the input relay RELAY, the contact pin 4 of the input relay RELAY is connected to the right end of the thermistor RT, and then connected together to the N pole of the main power circuit.
4. The practical thermal protection circuit according to claim 3, characterized in that: The input relay and control circuit include a current limiting resistor R7, a MOS tube Q1, a driving resistor R5, a resistor R6 and an MCU. Pin 2 of the control winding of the input relay RELAY is connected to the left end of the current limiting resistor R7, the right end of the current limiting resistor R7 is connected to the D pole of the MOS tube Q1, the G pole of the MOS tube Q1 is connected to the left end of the driving resistor R5 and the upper end of the resistor R6, the S pole of the MOS tube Q1 is connected to the lower end of R6, and the right end of the driving resistor R5 is connected to the control pin of the MCU.
5. The practical thermal protection circuit according to claim 2, characterized in that: The temperature control resistor R0 is close to the thermistor RT pin.
6. The practical thermal protection circuit according to claim 4, characterized in that: Pin 3 of the diode D1 is connected to the right end of the driving resistor R5.