Switching power supply circuit with over-temperature protection

Abstract

The utility model discloses a switching power supply circuit with over-temperature protection, comprising a master control IC1 used for outputting a PWM signal; the voltage stabilization output unit is used for obtaining the PWM signal and then carrying out voltage stabilization processing on the voltage; and the over-temperature protection unit is used for detecting the temperature of the master control IC1 and carrying out over-temperature protection. The over-temperature protection unit comprises a resistor NTC, an operational amplifier IC4B and an optical coupler PH1B, the resistor NTC is connected with the input end of the operational amplifier IC4B, the output end of the operational amplifier IC4B is connected with the master control IC1 through the optical coupler PH1B, and the master control IC1 is connected with the operational amplifier IC4B through the voltage stabilization output unit. The switching power supply circuit with over-temperature protection is high in external over-temperature protection precision, simple in circuit and adjustable in over-temperature protection value.

Description

Technical Field

[0001] The utility model relates to the technical field of switching power supplies, in particular to a switching power supply circuit with over-temperature protection. Background Art

[0002] Early switching power supplies lacked protection when power components overheated (due to sudden accidents or abnormalities), or required designers to add external over-temperature protection circuits. These circuits were complex and prone to misjudgment, and their high accuracy made it difficult to meet market demand. Disadvantages: Because switching power supplies lacked external over-temperature protection or had inaccurate over-temperature protection, the power supply housing could easily overheat and exceed the rated value, leading to spontaneous combustion, potentially causing personal injury or, in severe cases, fire. Utility Model Content

[0003] The purpose of the utility model is to provide a switching power supply circuit with over-temperature protection.

[0004] To achieve the above object, the present invention provides the following technical solution: a switching power supply circuit with over-temperature protection, comprising:

[0005] Main control IC1, used to output PWM signal;

[0006] A voltage stabilization output unit, used to stabilize the voltage after acquiring the PWM signal; and

[0007] The over-temperature protection unit is used to detect the temperature of the main control IC1 and perform over-temperature protection.

[0008] The over-temperature protection unit includes a resistor NTC, an operational amplifier IC4B and an optical coupler PH1B. The resistor NTC is connected to the input end of the operational amplifier IC4B, the output end of the operational amplifier IC4B is connected to the main control IC1 through the optical coupler PH1B, and the main control IC1 is connected to the operational amplifier IC4B through the voltage stabilization output unit.

[0009] Furthermore, it also includes a power supply unit for supplying power to the main control IC1 after voltage filtering. The power supply unit includes a rectifier bridge DB1, a capacitor CD1, resistors R1, R2 and an electrolytic capacitor CD2a. The rectifier bridge DB1 and the capacitor CD1 are connected in parallel and then connected to the resistors R1 and R2 connected in series. The other end of the resistor R2 is connected to the main control IC1 through the electrolytic capacitor CD2a.

[0010] Furthermore, the voltage stabilization output unit includes:

[0011] A filter circuit that obtains PWM signals, filters them, and then outputs a DC voltage.

[0012] A feedback loop circuit for stabilizing the DC voltage at a set value; and

[0013] A rectifier and filter circuit is used to rectify and filter DC voltage.

[0014] Furthermore, the filtering circuit includes a switching MOS tube Q1, a transformer T1, a diode D4, and electrolytic capacitors CD4 and CD5. The gate of the switching MOS tube Q1 is connected to the main control IC1, the drain of the switching MOS tube Q1 is connected to the transformer T1, the transformer T1 is connected to the electrolytic capacitors CD4 and CD5 in parallel, the anode of the diode D4 is connected to the transformer T1, and the cathode of the diode D4 is connected to CD4.

[0015] Furthermore, the feedback loop circuit includes resistors R21, R31, R25, R22, R23, R30, a light-emitting diode IC2A, a diode D7, an operational amplifier IC4A, capacitors C15 and C6, one end of the resistor R21 is connected to the anode of the light-emitting diode IC2A, and the cathode of the light-emitting diode IC2A is connected to the output of the operational amplifier IC4A through the diode D7. One end of the resistor R25 is connected between IC2A and D7, and the other end of the resistor R25 is connected to the negative input of the operational amplifier IC4A through the capacitor C6. After C15 is connected in parallel with R31, one end is connected to IC4A, and the other end is connected to the resistor R22. The resistors R22, R23, and R30 are connected in series in sequence. The positive input of the operational amplifier IC4A is connected between the resistors R22 and R31, and the negative input of the operational amplifier IC4A is connected between R23 and R30.

[0016] Furthermore, the rectifier and filter circuit includes diodes D3, D5, and capacitor CD2b. The anode of the diode D3 is connected to the transformer T1, the cathode of the diode D3 is connected to the anode of D5, and the cathode of D5 is connected to the main control IC1. One end of the capacitor CD2b is connected between the diodes D3 and D5.

[0017] It can be seen from the above technical solution that the utility model has the following beneficial effects:

[0018] The switching power supply circuit with over-temperature protection has high external over-temperature protection precision, a simple circuit, and an adjustable over-temperature protection value. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is the overall circuit diagram of the utility model. DETAILED DESCRIPTION

[0020] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0021] like Figure 1 As shown, the utility model provides a switching power supply circuit with over-temperature protection, including a main control IC1, a voltage stabilization output unit, an over-temperature protection unit and a power supply unit. The power supply unit includes a rectifier bridge DB1, a capacitor CD1, resistors R1, R2 and an electrolytic capacitor CD2a. The rectifier bridge DB1 and the capacitor CD1 are connected in parallel and then connected to the resistors R1 and R2 connected in series. The other end of the resistor R2 is connected to the main control IC1 through the electrolytic capacitor CD2a.

[0022] When the switching power supply input is connected to AC voltage, it is rectified by rectifier bridge DB1 and then filtered by capacitor CD1, making the voltage across CD1 a DC voltage 1.4 times the input voltage. The electrolytic capacitor CD2a is charged through resistors R1 and R2. When the voltage on electrolytic capacitor CD2a rises to about DC19V, the control main IC1 starts to work, and pin 3 of the main control IC1 starts to output a PWM signal.

[0023] The voltage-stabilized output unit includes a filtering circuit, a feedback loop circuit, and a rectifier filtering circuit. The filtering circuit includes a switching MOS tube Q1, a transformer T1, a diode D4, and electrolytic capacitors CD4 and CD5. The gate of the switching MOS tube Q1 is connected to the main control IC1, the drain of the switching MOS tube Q1 is connected to the transformer T1, the transformer T1 is connected to the electrolytic capacitors CD4 and CD5 in parallel, the anode of the diode D4 is connected to the transformer T1, and the cathode of the diode D4 is connected to CD4.

[0024] The feedback loop circuit includes resistors R21, R31, R25, R22, R23, R30, a light-emitting diode IC2A, a diode D7, an operational amplifier IC4A, and capacitors C15 and C6. One end of the resistor R21 is connected to the anode of the light-emitting diode IC2A, and the cathode of the light-emitting diode IC2A is connected to the output of the operational amplifier IC4A through the diode D7. One end of the resistor R25 is connected between IC2A and D7, and the other end of the resistor R25 is connected to the negative input of the operational amplifier IC4A through the capacitor C6. After C15 is connected in parallel with R31, one end is connected to IC4A, and the other end is connected to the resistor R22. The resistors R22, R23, and R30 are connected in series in sequence. The positive input of the operational amplifier IC4A is connected between the resistors R22 and R31, and the negative input of the operational amplifier IC4A is connected between R23 and R30.

[0025] The rectifier and filter circuit includes diodes D3, D5, and capacitor CD2b. The anode of the diode D3 is connected to the transformer T1, the cathode of the diode D3 is connected to the anode of D5, and the cathode of D5 is connected to the main control IC1. One end of the capacitor CD2b is connected between the diodes D3 and D5.

[0026] When pin 3 of the main control IC1 begins outputting a PWM signal, switching MOSFET Q1 activates. Transformer T1 then transfers energy from the primary side to the secondary side (voltage reduction, current increase) through the proportional relationship between windings P1 and S1. This voltage is then rectified by diode D4 and filtered by electrolytic capacitors CD4 and CD5 before outputting a DC voltage. A feedback loop stabilizes the power supply's output voltage at the set value. Transformer T1's VCC winding generates a coupled voltage, which is rectified by diodes D3 and D5 and filtered by electrolytic capacitors CD2b and CD2a before providing a stable operating voltage for control IC1.

[0027] The overtemperature protection unit includes a resistor NTC, an operational amplifier IC4B and an optical coupler PH1B. The resistor NTC is connected to the input end of the operational amplifier IC4B, the output end of the operational amplifier IC4B is connected to the main control IC1 through the optical coupler PH1B, and the main control IC1 is connected to the operational amplifier IC4B through the voltage stabilizing output unit.

[0028] When a switching power supply experiences an abnormality due to a fault or improper use, causing certain power components to overheat, the external NTC resistor detects the rising power component temperature. The NTC resistor's resistance decreases linearly with the rising temperature. When the NTC resistor's resistance decreases to approximately 9K, the voltage at IC4B's pin 6 drops to approximately 0.3V, exceeding the voltage at IC4B's pin 5. At this point, the voltage at IC4B's pin 7 transitions from a low level to a high level, reducing the luminous intensity of IC2A and the current flowing through it, which is coupled to PH1B. Simultaneously, the voltage at pin 6 of the main control IC1 increases, causing the PWM output of the main control IC1 to gradually decrease. The power supply's output current decreases, and the temperature of the main power components gradually decreases. If the fault is not corrected, the temperature of the main power components continues to rise. The luminous intensity continues to decrease, the current flowing through it continues to decrease, and the voltage coupled to PH1B continues to increase. When the voltage at pin 6 of the main control IC1 rises to greater than 4.5V, the main control IC1 shuts off the PWM signal output, resulting in no power output and the temperature of the main power components gradually decreasing. When the fault is resolved, the main control IC's PWM signal output returns to normal, and the power supply resumes normal operation. Flexible settings are possible by selecting different NTC temperature change ratios. This overtemperature protection unit offers high accuracy, a simple circuit, an adjustable overtemperature protection temperature, and a low BOM cost.

[0029] Although the embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations may be made to these embodiments without departing from the principles and spirit of the present invention, and the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A switching power supply circuit with over-temperature protection, characterized in that: include: Main control IC1, used to output PWM signal; The voltage stabilization output unit is used to stabilize the voltage after obtaining the PWM signal; as well as Over-temperature protection unit, used to detect the temperature of the main control IC1 and perform over-temperature protection; The over-temperature protection unit includes a resistor NTC, an operational amplifier IC4B and an optical coupler PH1B. The resistor NTC is connected to the input end of the operational amplifier IC4B, the output end of the operational amplifier IC4B is connected to the main control IC1 through the optical coupler PH1B, and the main control IC1 is connected to the operational amplifier IC4B through the voltage stabilization output unit.

2. The switching power supply circuit with over-temperature protection according to claim 1, characterized in that: It also includes a power supply unit for supplying power to the main control IC1 after voltage filtering. The power supply unit includes a rectifier bridge DB1, a capacitor CD1, resistors R1, R2 and an electrolytic capacitor CD2a. The rectifier bridge DB1 and the capacitor CD1 are connected in parallel and then connected to the resistors R1 and R2 connected in series. The other end of the resistor R2 is connected to the main control IC1 through the electrolytic capacitor CD2a.

3. The switching power supply circuit with over-temperature protection according to claim 1, characterized in that: The voltage stabilization output unit includes: A filter circuit used to obtain a PWM signal, filter it, and then output a DC voltage. A feedback loop circuit for stabilizing the DC voltage at a set value; and A rectifier and filter circuit is used to rectify and filter DC voltage.

4. The switching power supply circuit with over-temperature protection according to claim 3, characterized in that: The filter circuit includes a switch MOS tube Q1, a transformer T1, a diode D4, and electrolytic capacitors CD4 and CD5. The gate of the switch MOS tube Q1 is connected to the main control IC1, the drain of the switch MOS tube Q1 is connected to the transformer T1, the transformer T1 is connected to the electrolytic capacitors CD4 and CD5 in parallel, the anode of the diode D4 is connected to the transformer T1, and the cathode of the diode D4 is connected to CD4.

5. The switching power supply circuit with over-temperature protection according to claim 3, characterized in that: The feedback loop circuit includes resistors R21, R31, R25, R22, R23, R30, a light-emitting diode IC2A, a diode D7, an operational amplifier IC4A, and capacitors C15 and C6. One end of the resistor R21 is connected to the anode of the light-emitting diode IC2A, and the cathode of the light-emitting diode IC2A is connected to the output of the operational amplifier IC4A through the diode D7. One end of the resistor R25 is connected between IC2A and D7, and the other end of the resistor R25 is connected to the negative input of the operational amplifier IC4A through the capacitor C6. After C15 is connected in parallel with R31, one end is connected to IC4A, and the other end is connected to the resistor R22. The resistors R22, R23, and R30 are connected in series in sequence. The positive input of the operational amplifier IC4A is connected between the resistors R22 and R31, and the negative input of the operational amplifier IC4A is connected between R23 and R30.

6. The switching power supply circuit with over-temperature protection according to claim 4, characterized in that: The rectifier and filter circuit includes diodes D3, D5, and capacitor CD2b. The anode of the diode D3 is connected to the transformer T1, the cathode of the diode D3 is connected to the anode of D5, and the cathode of D5 is connected to the main control IC1. One end of the capacitor CD2b is connected between the diodes D3 and D5.

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