Automatic derating regulation protection circuit for temperature rise of switching power supply

Abstract

The utility model discloses an automatic derating regulation protection circuit for temperature rise of a switching power supply, which belongs to the technical field of LED (light-emitting diode) power supply circuits and specifically comprises a rectification filter circuit, a constant-current control circuit and a temperature detection regulation circuit, the constant-current control circuit converts the rectified direct-current voltage into constant-current direct current for driving an LED lamp bead to work, the temperature detection and regulation circuit detects temperature rise through a thermistor NTC, and outputs high voltage to be superposed to a constant-current reference end of a pin 3 CS of a constant-current control chip U3 in the constant-current control circuit through phase inversion of a three-end adjustable reference voltage chip U2 and a field-effect tube Q2 after temperature rise is detected by the temperature detection and regulation circuit through a thermistor NTC. And the potential of the third pin CS end of the constant-current control chip U3 is increased, so that the constant current output by the whole power supply network is reduced, and the functions of derating output and protecting the circuit are achieved.

Description

Technical Field

[0001] The utility model relates to an LED power supply circuit, in particular to a temperature rise automatic derating regulation protection circuit for a switch power supply for LED power supply. Background Art

[0002] LED lamps have a certain amount of energy conversion loss in the process of converting electrical energy into light energy, causing the product itself to heat up. Long-term lighting, heat accumulation, unreasonable heat dissipation layout, or changes in ambient temperature can easily damage the LED power supply or shorten its service life due to excessive temperature. The product may even explode and cause fire or other serious accidents due to excessive temperature.

[0003] The Chinese utility model patent (CN220139768U) discloses a switching power supply over-temperature automatic output derating protection circuit, which outputs a high level to the derating output proportional adjustment circuit through the over-temperature detection trigger circuit, and the derating output proportional adjustment circuit outputs a high voltage superimposed on the reference end of the constant current control chip in the constant current control circuit, so that the output constant current of the entire power supply network decreases, playing the output derating function. The circuit uses a voltage comparator, a constant voltage power supply chip and a derating output proportional adjustment circuit. The amount of electrical components used is large, and the circuit structure is complex, which needs to be improved. Utility Model Content

[0004] The main purpose of the utility model is to overcome the shortcomings of the above-mentioned background technology, solve the problem of temperature rise of LED lamps or LED power supplies, and reduce the output power of the constant current power supply through a temperature rise detection circuit to control the output power of the LED lamp, so that the temperature of the power devices inside the LED power supply decreases.

[0005] To achieve the above-mentioned purpose, the utility model proposes a switching power supply temperature rise automatic derating regulation protection circuit, including a rectifier and filter circuit, a constant current control circuit, and a temperature detection and regulation circuit. The rectifier and filter circuit provides a DC voltage to the constant current control circuit, and the constant current control circuit converts the rectified DC voltage into a constant current DC power for driving LED lamp beads to work. The temperature detection and regulation circuit detects the temperature rise through a thermistor NTC, passes through a three-terminal adjustable reference voltage chip U2, and is inverted by a field effect tube Q2, and outputs a high voltage to be superimposed on the 3-pin CS constant current reference terminal of the constant current control chip U3 in the constant current control circuit.

[0006] Preferably, the temperature detection and adjustment circuit includes a thermistor NTC, a three-terminal adjustable reference voltage chip U2, a field effect transistor Q2, a resistor R4, a resistor R5, a resistor R6, a resistor R7, a resistor R8 and a resistor R9; the reference end of pin 1 of the three-terminal adjustable reference voltage chip U2 is connected to the common end of the resistor R4 and the resistor R5, the other end of the resistor R4 is connected to the front end of the thermistor NTC, the rear end of the thermistor NTC is connected to the common end of the resistor R6 and the resistor R8, and the common end of the resistor R6 and the resistor R8 is connected to The 6-pin VCC of the constant current control chip U3, the other end of the resistor R5 is grounded, the 2-pin anode of the three-terminal adjustable reference voltage chip U2 is grounded, the 3-pin cathode of the three-terminal adjustable reference voltage chip U2 is connected to the common end of the resistor R6 and the resistor R7, the other end of the resistor R7 is connected to the gate G of the field effect transistor Q2, the source S of the field effect transistor Q2 is grounded, the drain D of the field effect transistor Q2 is connected to the common end of the resistor R8 and the resistor R9, and the other end of the resistor R9 is connected to the 3-pin reference terminal CS of the constant current control chip U3.

[0007] Preferably, the constant current control circuit includes a constant current control chip U3, a field effect tube Q1, a diode D5, a diode D6, a diode D7, a resistor R1, a resistor R2, a resistor R3, a resistor RS1, a resistor R10, a resistor R11, a resistor R12, a capacitor C2, a capacitor C3, a capacitor C4, a capacitor C5, a capacitor C6, a capacitor C7 and an inductor T1C;

[0008] The drain electrode D of the field effect tube Q1 is connected to the positive electrode of the diode D6, the source electrode S of the field effect tube Q1 is connected to the common end of the resistor R3 and the resistor RS1, the other end of the resistor R3 is connected to the gate electrode G of the field effect tube Q1, the other end of the resistor RS1 is grounded, and the gate electrode G of the field effect tube Q1 is connected to the 5-pin GATE of the constant current control chip U3 through the resistor R2;

[0009] Pin 1 COMP of the constant current control chip U3 is connected to ground via the capacitor C5, pin 4 GND is connected to ground, pin 5 GATE is connected to the gate G of the field effect transistor Q1, pin 6 VCC is connected to the positive output terminal of the rectifier filter circuit (1), pin 8 is connected to the common end of the resistor R11 and the capacitor C4, the other end of the resistor R11 is connected to the thermistor NTC, and the other end of the capacitor C4 is grounded;

[0010] The common end of the resistor R9, the resistor R10, the resistor R12 and the capacitor C3 is connected to the 3-pin reference terminal CS of the constant current control chip U3, the other end of the resistor R10 is connected to the common end of the resistor R3 and the resistor RS1, the other end of the resistor R12 is connected to the thermistor NTC, and the other end of the capacitor C3 is grounded.

[0011] Preferably, the rear end of the thermistor NTC is connected to the positive electrode of the diode D7, the negative electrode of the diode D7 is connected to the 6-pin VCC of the constant current control chip U3, one end of the capacitor C6 is connected to the negative electrode of the diode D7, the other end of the capacitor C6 is grounded, one end of the capacitor C7 is connected to the positive electrode of the diode D7, and the other end of the capacitor C7 is grounded.

[0012] Preferably, the capacitor C2 is connected in parallel between the DC output positive electrode and the DC output negative electrode.

[0013] The technical solution of the utility model detects the temperature rise through the thermistor NTC, passes through the three-terminal adjustable reference voltage chip U2, and the field effect tube Q2 inversion, and outputs a high voltage to be superimposed on the 3-pin CS constant current reference terminal of the constant current control chip U3 in the constant current control circuit. The thermistor NTC is a negative temperature coefficient thermistor. When the temperature rises, the resistance of the thermistor decreases, the voltage of the 1-pin reference terminal of the three-terminal adjustable reference voltage chip U2 increases, the cathode voltage of the 3-pin of the three-terminal adjustable reference voltage chip U2 decreases in reverse, the field effect tube Q2 inversion, outputs a high voltage to the 3-pin reference terminal CS of the constant current control chip U3, the constant current control chip U3 controls the output corresponding derating value, the temperature rise of the power supply or the body does not exceed the set maximum temperature value, and the switching power supply is guaranteed to work safely and reliably. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] In order to more clearly illustrate the embodiments of the utility model or the technical solutions in the prior art, the drawings required for use in the embodiments or the prior art descriptions are briefly introduced below. Obviously, the drawings described below are only some embodiments of the utility model. For ordinary technicians in this field, other drawings can be obtained according to the structures shown in these drawings without creative work, among which:

[0015] Figure 1 It is a schematic diagram of the circuit principle involved in the embodiment of the utility model;

[0016] Figure 2 It is a schematic diagram of the principle of the temperature detection and regulation circuit involved in the embodiment of the utility model.

[0017] Description of Figure Numbers:

[0018] 1. Rectification and filtering circuit; 2. Constant current control circuit; 3. Temperature detection and adjustment circuit. DETAILED DESCRIPTION

[0019] The present application discloses a switching power supply temperature rise automatic derating regulation protection circuit, such as Figure 1 As shown, the protection circuit includes a rectifier and filter circuit 1, a constant current control circuit 2 and a temperature detection and adjustment circuit 3.

[0020] The rectifier filter circuit 1 provides a DC voltage to the constant current control circuit 2. The rectifier filter circuit 1 includes a fuse resistor F1, a rectifier bridge DB1, a capacitor CX1 and a capacitor CBB1. The two AC input terminals of the rectifier filter circuit 1 are respectively connected to the live wire L and the neutral wire N of the mains, the fuse resistor F1 is connected to the live wire L of the AC input terminal, and the high-voltage filter capacitor CX1 is connected between the two AC input terminals to play a filtering role.

[0021] The two AC input terminals are connected to a rectifier bridge DB1 composed of four diodes, and the unidirectional conductive characteristics of the diodes are used to convert the AC voltage into a DC voltage. The output terminal of the rectifier filter circuit 1 is connected to the capacitor CBB1, which plays a filtering role and bypasses (short-circuits) the AC component. The rectifier filter circuit is a conventional design in this field and will not be described here.

[0022] The constant current control circuit 2 provides the working current to the LED load to drive the LED load to work.

[0023] The constant current control circuit 2 includes a constant current control chip U3, a field effect transistor Q1, a diode D5, a diode D6, a diode D7, a resistor R1, a resistor R2, a resistor R3, a resistor RS1, a resistor R10, a resistor R11, a resistor R12, a capacitor C2, a capacitor C3, a capacitor C4, a capacitor C5, a capacitor C6, a capacitor C7 and an inductor T1C.

[0024] The positive electrode of the output end of the rectifier and filter circuit 1 is connected to the 6-pin VCC of the constant current control chip U3 through the resistor R1, the positive electrode of the diode D5 is connected to the positive electrode of the output end of the rectifier and filter circuit 1, the negative electrode of the diode D5 is connected to the DC output positive electrode (V+), the inductor T1C is connected in series with the diode D6 and then connected in parallel with the diode D5, the same-name end of the inductor T1C is connected to the positive electrode of the diode D5, and the negative electrode of the diode D6 is connected to the negative electrode of the diode D5.

[0025] The drain D of the field effect transistor Q1 is connected to the anode of the diode D6, the source S of the field effect transistor Q1 is connected to the common end of the resistor R3 and the resistor RS1, the other end of the resistor R3 is connected to the gate G of the field effect transistor Q1, the other end of the resistor RS1 is grounded, and the gate G of the field effect transistor Q1 is connected to the 5-pin GATE of the constant current control chip U3 through the resistor R2.

[0026] Pin 1 COMP of the constant current control chip U3 is grounded through capacitor C5, pin 3 reference terminal CS is connected to resistor R9 in the temperature detection and adjustment circuit 3, pin 4 GND is grounded, pin 5 GATE is connected to the gate G of the field effect transistor Q1, pin 6 VCC is connected to the positive output terminal of the rectifier and filter circuit 1, pin 8 DPWM is used for pulse modulation, connected to the common end of resistor R11 and capacitor C4, the other end of resistor R11 is connected to the thermistor NTC, and the other end of capacitor C4 is grounded.

[0027] The common end of resistor R9, resistor R10, resistor R12 and capacitor C3 is connected to the 3-pin reference terminal CS of the constant current control chip U3, the other end of resistor R10 is connected to the common end of resistor R3 and resistor RS1, the other end of resistor R12 is connected to the thermistor NTC, and the other end of capacitor C3 is grounded.

[0028] A capacitor C2 is connected in parallel between the DC output positive electrode (V+) and the DC output negative electrode (V-) to filter out clutter signals.

[0029] The thermistor NTC in the temperature detection and regulation circuit 3 detects the internal temperature rise of the power supply, and the output voltage is superimposed on the 3-pin reference terminal CS of the constant current control chip U3 in the constant current control circuit 2 through the three-terminal adjustable reference voltage chip U2 and the field effect tube Q2.

[0030] The temperature detection and adjustment circuit 3 includes a thermistor NTC, a three-terminal adjustable reference voltage chip U2, a field effect transistor Q2, a resistor R4, a resistor R5, a resistor R6, a resistor R7, a resistor R8 and a resistor R9.

[0031] The reference terminal of pin 1 of the three-terminal adjustable reference voltage chip U2 is connected to the common terminal of resistors R4 and R5, the other end of resistor R4 is connected to the front end of the thermistor NTC, the rear end of the thermistor NTC is connected to the common terminal of resistors R6 and R8, the common terminal of resistors R6 and R8 is connected to pin 6 VCC of the constant current control chip U3, the other end of resistor R5 is grounded, the anode of pin 2 is grounded, the cathode of pin 3 is connected to the common terminal of resistors R6 and R7, the other end of resistor R7 is connected to the gate G of the field effect tube Q2, the source S of the field effect tube Q2 is grounded, the drain D of the field effect tube Q2 is connected to the common terminal of resistors R8 and R9, and the other end of resistor R9 is connected to the reference terminal CS of pin 3 of the constant current control chip U3.

[0032] The rear end of the thermistor NTC is connected to the positive electrode of the diode D7, the negative electrode of the diode D7 is connected to the 6-pin VCC of the constant current control chip U3, one end of the capacitor C6 is connected to the negative electrode of the diode D7, the other end of the capacitor C6 is grounded, one end of the capacitor C7 is connected to the positive electrode of the diode D7, and the other end of the capacitor C7 is grounded.

[0033] The thermistor NTC is a negative temperature coefficient thermistor, which has the characteristic that the resistance value gradually decreases as the temperature rises. The thermistor NTC, resistor R4 and resistor R5 form a voltage divider circuit. The resistance value of the thermistor NTC changes due to the influence of temperature, and the corresponding voltage divider of resistor R4 changes, that is, the voltage of the reference terminal of pin 1 of the three-terminal adjustable reference voltage chip U2 changes. If the temperature rises, the voltage of the reference terminal of pin 1 also increases accordingly, and the cathode voltage of pin 3 of the three-terminal adjustable reference voltage chip U2 decreases in the reverse direction. The cathode of pin 3 of the three-terminal adjustable reference voltage chip U2 forms an inverting circuit through resistors R7, resistor R8 and field effect transistor Q2, and inverts the output voltage of the cathode of pin 3 of the three-terminal adjustable reference voltage chip U2. For example, when the temperature rises, a reverse voltage is output, and the rising voltage is output through the inverting of the field effect transistor Q2, and is superimposed on the reference terminal CS of pin 3 of the constant current control chip U3. The CS potential increases, and the constant current control chip U3 controls the output current to decrease.

[0034] The initial parameters of the temperature detection and adjustment circuit 3 are set to the rated output value of the whole machine. Specifically, the temperature of the power supply or the machine body is monitored, and the resistance values ​​of the resistors R4 and R5 are adjusted so that the voltage division value of the resistors R4 and R5 meets the voltage value of the reference terminal 1 of the three-terminal adjustable reference voltage chip U2 (reference value 2.5V), and the maximum temperature value that the power supply or the machine body can withstand is determined; the resistance value of the resistor R9 is then adjusted, and then the output derating value of the constant current control circuit is adjusted. When the resistance value of the resistor R9 is increased, the derating ratio is reduced; when the resistance value of the resistor R9 is reduced, the derating ratio is increased. When the resistance value of the resistor R9 is adjusted to a certain value, the output of the constant current control circuit is correspondingly derated, and the temperature rise inside the power supply or the machine body does not exceed the set maximum temperature value, so as to ensure the safe and reliable operation of the switching power supply.

[0035] The above description is only an optional embodiment of the present invention, and does not limit the patent scope of the present invention. All equivalent structural changes made by using the contents of the present invention specification and drawings under the inventive concept of the present invention, or directly / indirectly applied in other related technical fields are included in the patent protection of the present invention.

Claims

1. A switching power supply temperature rise automatic derating regulation protection circuit, comprising a rectifier filter circuit (1), a constant current control circuit (2), and a temperature detection and regulation circuit (3), wherein the rectifier filter circuit (1) provides a DC voltage to the constant current control circuit (2), and the constant current control circuit (2) converts the rectified DC voltage into a constant current DC power for driving LED lamp beads to work, characterized in that: The temperature detection and regulation circuit (3) detects the temperature rise through the thermistor NTC, and outputs a high voltage through a three-terminal adjustable reference voltage chip U2 and a field effect transistor Q2 inversion, and superimposes it on the 3-pin CS constant current reference terminal of the constant current control chip U3 in the constant current control circuit (2).

2. The switching power supply temperature rise automatic derating regulation protection circuit according to claim 1, characterized in that: The temperature detection and adjustment circuit (3) comprises a thermistor NTC, a three-terminal adjustable reference voltage chip U2, a field effect transistor Q2, a resistor R4, a resistor R5, a resistor R6, a resistor R7, a resistor R8 and a resistor R9; the reference end of pin 1 of the three-terminal adjustable reference voltage chip U2 is connected to the common end of the resistor R4 and the resistor R5, the other end of the resistor R4 is connected to the front end of the thermistor NTC, the rear end of the thermistor NTC is connected to the common end of the resistor R6 and the resistor R8, and the common end of the resistor R6 and the resistor R8 is connected to a constant current. The 6-pin VCC of the current control chip U3, the other end of the resistor R5 is grounded, the 2-pin anode of the three-terminal adjustable reference voltage chip U2 is grounded, the 3-pin cathode of the three-terminal adjustable reference voltage chip U2 is connected to the common end of the resistor R6 and the resistor R7, the other end of the resistor R7 is connected to the gate G of the field effect transistor Q2, the source S of the field effect transistor Q2 is grounded, the drain D of the field effect transistor Q2 is connected to the common end of the resistor R8 and the resistor R9, and the other end of the resistor R9 is connected to the 3-pin reference terminal CS of the constant current control chip U3.

3. The switching power supply temperature rise automatic derating regulation protection circuit according to claim 2, characterized in that: The constant current control circuit (2) comprises a constant current control chip U3, a field effect transistor Q1, a diode D5, a diode D6, a diode D7, a resistor R1, a resistor R2, a resistor R3, a resistor RS1, a resistor R10, a resistor R11, a resistor R12, a capacitor C2, a capacitor C3, a capacitor C4, a capacitor C5, a capacitor C6, a capacitor C7 and an inductor T1C; The drain electrode D of the field effect tube Q1 is connected to the positive electrode of the diode D6, the source electrode S of the field effect tube Q1 is connected to the common end of the resistor R3 and the resistor RS1, the other end of the resistor R3 is connected to the gate electrode G of the field effect tube Q1, the other end of the resistor RS1 is grounded, and the gate electrode G of the field effect tube Q1 is connected to the 5-pin GATE of the constant current control chip U3 through the resistor R2; Pin 1 COMP of the constant current control chip U3 is connected to ground via the capacitor C5, pin 4 GND is connected to ground, pin 5 GATE is connected to the gate G of the field effect transistor Q1, pin 6 VCC is connected to the positive output terminal of the rectifier filter circuit (1), pin 8 is connected to the common end of the resistor R11 and the capacitor C4, the other end of the resistor R11 is connected to the thermistor NTC, and the other end of the capacitor C4 is grounded; The common end of the resistor R9, the resistor R10, the resistor R12 and the capacitor C3 is connected to the 3-pin reference terminal CS of the constant current control chip U3, the other end of the resistor R10 is connected to the common end of the resistor R3 and the resistor RS1, the other end of the resistor R12 is connected to the thermistor NTC, and the other end of the capacitor C3 is grounded.

4. The switching power supply temperature rise automatic derating regulation protection circuit according to claim 3, characterized in that: The rear end of the thermistor NTC is connected to the positive electrode of the diode D7, the negative electrode of the diode D7 is connected to the 6-pin VCC of the constant current control chip U3, one end of the capacitor C6 is connected to the negative electrode of the diode D7, the other end of the capacitor C6 is grounded, one end of the capacitor C7 is connected to the positive electrode of the diode D7, and the other end of the capacitor C7 is grounded.

5. The switching power supply temperature rise automatic derating regulation protection circuit according to claim 4, characterized in that: The capacitor C2 is connected in parallel between the DC output positive electrode and the DC output negative electrode.

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