BUCK topology short-circuit protection circuit

Abstract

A BUCK topology short-circuit protection circuit is characterized by comprising an output end, the negative electrode of the output end is connected with the drain electrode of an MOS tube Q1 through a transformer T1B, the source electrode of the MOS tube Q1 is grounded, and the grid electrode of the MOS tube Q1 is connected with the control end of a main control unit U1; an analog dimming end of the main control unit U1 is connected with a drain electrode of the field effect transistor Q2, a source electrode of the field effect transistor Q2 is grounded, and the drain electrode of the field effect transistor Q2 is connected with a voltage VCC through a voltage stabilizing diode ZD1 and a resistor R7; the circuit further comprises a transformer T1A, one end of the transformer T1A is connected with the reference end of the reference unit U2 through a diode D2 and a resistor R3 in sequence, the other end of the transformer T1A is grounded, one end of the reference unit U2 is connected with the voltage VCC through a resistor R7, and the other end of the reference unit U2 is grounded.

Description

Technical Field

[0001] The invention relates to the field of LED power supplies, and in particular to a BUCK topology short-circuit protection circuit. Background Art

[0002] The output short-circuit current of the BUCK topology with self-starting control chip and self-BUCK auxiliary winding power supply is smaller than the output current during normal operation. However, the output short-circuit current of the BUCK topology with quick start VCC direct power supply is larger, often 1.5-2 times the normal operating output current, which makes the BUCK transformer easy to saturate, the BUCK freewheeling diode high in temperature and reverse, etc., which makes the BUCK topology output short-circuit and machine explosion prone. Summary of the invention

[0003] In order to solve the above problems, the present technical solution provides a BUCK topology short-circuit protection circuit.

[0004] To achieve the above purpose, the technical solution is as follows:

[0005] A BUCK topology short-circuit protection circuit comprises an output end, wherein the negative electrode of the output end is connected to the drain of a MOS tube Q1 through a transformer T1B, the source of the MOS tube Q1 is grounded, and the gate is connected to the control end of a main control unit U1;

[0006] The analog dimming terminal of the main control unit U1 is connected to the drain of the field effect tube Q2, the source of the field effect tube Q2 is grounded, and the drain is connected to the voltage VCC through the voltage zener diode ZD1 and the resistor R7;

[0007] It also includes a transformer T1A, one end of which is connected to the reference end of the reference unit U2 through a diode D2 and a resistor R3 in sequence, and the other end of the transformer T1A is grounded. One end of the reference unit U2 is connected to the voltage VCC through the resistor R7, and the other end is grounded.

[0008] In some embodiments, a capacitor EC1 and a diode D1 are disposed between the positive and negative electrodes of the output terminal.

[0009] In some embodiments, the source of the MOS transistor Q1 is grounded through a resistor R2.

[0010] In some embodiments, the analog dimming terminal of the main control unit U1 is grounded through a capacitor C3 and is also connected to the field effect transistor Q2 through a resistor R5.

[0011] In some embodiments, the gate of the field effect transistor Q2 is grounded through a resistor R6.

[0012] In some embodiments, the diode D2 is grounded via an electrolytic capacitor EC2.

[0013] In some embodiments, the resistor R3 is grounded via the capacitor C4 and the resistor R8 .

[0014] The beneficial effects of this application are:

[0015] By adopting the protection circuit of the present application, the output short-circuit current of the BUCK topology with VCC direct power supply for quick startup is smaller than the current during normal operation, the BUCK transformer will not be saturated, the temperature of the BUCK freewheeling diode will not be higher, and the problem of the BUCK topology output short-circuit crashing will not occur. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for describing the embodiments are briefly introduced below.

[0017] Figure 1 It is a schematic structural diagram of an embodiment of the present invention. DETAILED DESCRIPTION

[0018] In order to make the technical problems, technical solutions and beneficial effects solved by the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0019] Please refer to Figure 1 As shown, a BUCK topology short-circuit protection circuit is characterized in that it includes an output end, the negative electrode of the output end is connected to the drain of the MOS tube Q1 through the transformer T1B, the source of the MOS tube Q1 is grounded, and the gate is connected to the control end of the main control unit U1;

[0020] The analog dimming terminal of the main control unit U1 is connected to the drain of the field effect tube Q2, the source of the field effect tube Q2 is grounded, and the drain is connected to the voltage VCC through the voltage zener diode ZD1 and the resistor R7;

[0021] It also includes a transformer T1A, one end of which is connected to the reference end of the reference unit U2 through a diode D2 and a resistor R3 in sequence, and the other end of the transformer T1A is grounded. One end of the reference unit U2 is connected to the voltage VCC through the resistor R7, and the other end is grounded.

[0022] In this embodiment, a capacitor EC1 and a diode D1 are provided between the positive and negative electrodes of the output terminal.

[0023] In this embodiment, the source of the MOS transistor Q1 is grounded through a resistor R2.

[0024] In this embodiment, the analog dimming terminal of the main control unit U1 is grounded through a capacitor C3 and is also connected to the field effect transistor Q2 through a resistor R5.

[0025] In this embodiment, the gate of the field effect transistor Q2 is grounded through a resistor R6.

[0026] In this embodiment, the diode D2 is grounded via the electrolytic capacitor EC2.

[0027] In this embodiment, the resistor R3 is grounded via the capacitor C4 and the resistor R8.

[0028] When the LED+, LED_ output ports are short-circuited, the BUCK transformer T1A winding is rectified by D2, and the voltage at the AUX potential after filtering by the EC2 electrolytic capacitor will become smaller. At this time, the voltage at the REF potential divided by the C4 capacitor, R3, and R8 resistors is less than 2.5V, and the U2 TL431 is in a non-conducting state. The voltage at the C potential will not be pulled down. The VCC voltage is divided by the R7 resistor, the ZD1 voltage regulator, and the R6 resistor to make the Q2 field effect tube conduct, so that the voltage of the U1 BUCK chip DIM analog dimming is pulled down to the R5 resistor of the GND ground, and then the current of the BUCK topology to the LED+, LED_ port is controlled to decrease, so that the output current when the LED+, LED_ output port is short-circuited will be very small, the T1 BUCK transformer will not be saturated, the temperature of the D1 BUCK freewheeling diode will not be higher, and the problem of the BUCK topology output short circuit explosion will not occur.

[0029] Similarly, when the LED+ and LED_ output ports output a normal voltage range, the U2 TL431 will be turned on, the Q2 field effect tube will not be turned on, and the voltage of the U1 BUCK chip DIM analog dimming will not be pulled down by the R5 resistor, ensuring that the BUCK topology outputs the current required for normal operation.

[0030] By adopting the circuit of the present application, the output short-circuit current of the BUCK topology with quick start VCC direct power supply is smaller than the current during normal operation, the BUCK transformer will not be saturated, the temperature of the BUCK freewheeling diode will not be higher, and the problem of the BUCK topology output short circuit and machine explosion will not occur, so that the LED power supply of the BUCK topology can be more widely used.

[0031] The above description is only a preferred embodiment of the present application and is not intended to limit the scope of implementation of the present application. Other principles and basic structures that are the same or similar to those of the present application are within the protection scope of the present application.

Claims

1. A BUCK topology short-circuit protection circuit, characterized in that: It includes an output end, the negative electrode of the output end is connected to the drain of the MOS tube Q1 through the transformer T1B, the source of the MOS tube Q1 is grounded, and the gate is connected to the control end of the main control unit U1; The analog dimming terminal of the main control unit U1 is connected to the drain of the field effect tube Q2, the source of the field effect tube Q2 is grounded, and the drain is connected to the voltage VCC through the voltage zener diode ZD1 and the resistor R7; It also includes a transformer T1A, one end of which is connected to the reference end of the reference unit U2 through a diode D2 and a resistor R3 in sequence, and the other end of the transformer T1A is grounded. One end of the reference unit U2 is connected to the voltage VCC through the resistor R7, and the other end is grounded.

2. A BUCK topology short circuit protection circuit according to claim 1, characterized in that: A capacitor EC1 and a diode D1 are provided between the positive and negative electrodes of the output terminal.

3. A BUCK topology short circuit protection circuit according to claim 2, characterized in that: The source of the MOS tube Q1 is grounded through a resistor R2.

4. The BUCK topology short circuit protection circuit according to claim 1, characterized in that: The analog dimming terminal of the main control unit U1 is grounded through a capacitor C3 and is also connected to the field effect transistor Q2 through a resistor R5.

5. A BUCK topology short circuit protection circuit according to claim 4, characterized in that: The gate of the field effect transistor Q2 is grounded through a resistor R6.

6. The BUCK topology short circuit protection circuit according to claim 1, characterized in that: The diode D2 is grounded via the electrolytic capacitor EC2.

7. The BUCK topology short circuit protection circuit according to claim 1, characterized in that: The resistor R3 is grounded via the capacitor C4 and the resistor R8.

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