An EMC-resistant LED driver circuit

Abstract

The utility model mainly relates to the technical field of LED drive circuits. In order to reduce the EMC interference caused by the reverse recovery leakage current in the diode rectification process in the traditional switching power supply LLC backlight driving LED circuit, an anti-EMC interference LED drive circuit is provided. An RC circuit is connected in parallel to the rectifier diode at the secondary end of the transformer to reduce the EMC interference caused by the reverse recovery leakage current of the rectifier diode and improve the working stability of the LED.

Description

Technical Field

[0001] The utility model mainly relates to the technical field of LED drive circuits, in particular to an LED drive circuit that resists EMC interference. Background Art

[0002] With the popularity of LED flat-panel TVs, the market's requirements for their reliability are getting higher and higher. LLC circuits are widely used in switching power supplies for LED TVs due to their superior performance. In the traditional switching power supply LLC backlight driver connection, the rectifier diode in the transformer secondary circuit is directly connected to the drive backlight strip according to the rectifier path. However, due to the high switching frequency of the switching circuit, there is a problem of reverse recovery leakage current of the rectifier diode at the secondary end of the transformer, which is prone to EMC interference, resulting in unstable operation of the LED lamp beads and affecting the use of the LED. Utility Model Content

[0003] Technical problems to be solved by the utility model

[0004] Provided is an EMC interference resistant LED driving circuit, which reduces the EMC interference caused by reverse recovery leakage during the rectification process of a rectifier diode in a switching power supply LLC backlight driving LED circuit.

[0005] The utility model solves the above-mentioned technical problems by adopting the technical solution

[0006] An EMC interference-resistant LED driving circuit comprises: a transformer (T1), wherein the primary end of the transformer (T1) comprises a switch circuit, a drive control circuit and a filter capacitor (C4), and the secondary end of the transformer (T1) comprises a filter capacitor (C3), a rectifier diode (D1), a rectifier diode (D2), a rectifier diode (D3), a rectifier diode (D4), a first RC circuit, a second RC circuit, a third RC circuit, a fourth RC circuit, a resistor (R1), a resistor (R2), a first LED lamp bead and a second LED lamp bead;

[0007] The first RC circuit, the second RC circuit, the third RC circuit, and the fourth RC circuit each include a resistor and a capacitor, and the resistor and the capacitor are connected in series;

[0008] Primary side of transformer (T1): one end of the filter capacitor (C4) is connected to the switch circuit, and the other end is connected to the primary side of the transformer (T1). The drive control circuit is connected to the switch circuit.

[0009] At the secondary end of the transformer (T1): one end of the filter capacitor (C3) is connected to one end of the secondary side of the transformer (T1), and the other end is connected to the cathode of the rectifier diode (D3) and the anode of the rectifier diode (D4); the cathode of the rectifier diode (D4) is connected to the first LED lamp bead through the CS end, and the anode of the rectifier diode (D3) is connected to the first LED lamp bead; the other end of the secondary side of the transformer is connected to the cathode of the rectifier diode (D1) and the anode of the rectifier diode (D2); the cathode of the rectifier diode (D2) is connected to the second LED lamp bead through the CS end, the anode of the rectifier diode (D1) is connected to the second LED lamp bead, the other end of the resistor in the first RC circuit is connected to the anode of the rectifier diode (D1), and the other end of the capacitor is connected to the anode of the rectifier diode (D1). One end of the resistor is connected to the cathode of the rectifier diode (D1); the other end of the resistor in the second RC circuit is connected to the cathode of the rectifier diode (D2), and the other end of the capacitor is connected to the anode of the rectifier diode (D2); the other end of the resistor in the third RC circuit is connected to the anode of the rectifier diode (D3), and the other end of the capacitor is connected to the cathode of the rectifier diode (D3); the other end of the resistor in the fourth RC circuit is connected to the cathode of the rectifier diode (D4), and the other end of the capacitor is connected to the anode of the rectifier diode (D4); one end of the resistor (R2) is connected to the current sampling pin of the LED drive control chip, and the other end is connected to the positive electrodes of the first LED lamp bead and the second LED lamp bead through the resistor (R1), and the other end of the resistor (R1) is grounded.

[0010] Furthermore, the switch circuit comprises a MOS tube (Q1), a MOS tube (Q2), a resistor (R3) and a resistor (R4); the gate of the MOS tube (Q1) is connected to one end of the resistor (R3) and a signal input end of a drive control circuit, the source of the MOS tube (Q1) is connected to a power input end, and the drain of the MOS tube (Q1) is connected to the primary side of a transformer (T1); the gate of the MOS tube (Q2) is connected to one end of the resistor (R4) and the signal input end of the drive control circuit, the drain of the MOS tube (Q2) is connected to the source of the MOS tube (Q1), and the source of the MOS tube (Q2) is connected to a filter capacitor (C4).

[0011] Furthermore, it also includes a capacitor (C1) and a capacitor (C2), wherein the capacitor (C1) is arranged between the anode of the rectifier diode (D1) and the cathode of the rectifier diode (D2), and the capacitor (C2) is arranged between the anode of the rectifier diode (D3) and the cathode of the rectifier diode (D4).

[0012] Beneficial effects of the utility model

[0013] Provided is an EMC-interference-resistant LED driving circuit, in which an RC absorption circuit is connected in parallel to a rectifier diode driving an ELD backlight lamp bead, so as to reduce the EMC interference caused by the reverse recovery leakage current of the rectifier diode and improve the working stability of the LED lamp bead. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 The utility model discloses a circuit structure of an EMC-interference-resistant LED driving circuit. DETAILED DESCRIPTION

[0015] The utility model discloses an anti-EMC interference LED driving circuit, which reduces the EMC interference caused by the reverse recovery leakage current of the rectifier diode by connecting a primary RC circuit in parallel to the rectifier diode at the secondary end of the transformer. Figure 1 As shown, the primary end of the transformer T1 includes a drive control circuit, a switch circuit and a filter capacitor C4. The switch circuit specifically includes a MOS transistor Q1, a MOS transistor Q2, resistors R3 and R4. The gate of the MOS transistor Q1 is connected to one end of the resistor R3 and the signal input end of the drive control circuit, the source of the MOS transistor Q1 is connected to the power input end, the drain of the MOS transistor Q1 is connected to one end of the primary side of the transformer T1, the gate of the MOS transistor Q2 is connected to one end of the resistor R4 and the signal input end of the drive control circuit, the drain of the MOS transistor Q2 is connected to the source of the MOS transistor Q1, the source of the MOS transistor Q2 is connected to the filter capacitor C4, and the other end of the filter capacitor C4 is connected to one end of the primary side of the transformer T1.

[0016] The secondary end of the transformer T1 includes a filter capacitor C3, a rectifier diode D1, a rectifier diode D2, a rectifier diode D3, a rectifier diode D4, a first RC circuit, a second RC circuit, a third RC circuit, a fourth RC circuit, a resistor R1, a resistor R2, a first LED lamp bead and a second LED lamp bead; the first RC circuit, the second RC circuit, the third RC circuit, and the fourth RC circuit each include a resistor and a capacitor, and one end of the resistor is connected to one end of the capacitor; the energy of the primary end of the transformer T1 is transmitted to the secondary end of the transformer T1 through the transformer T1, driving the first LED lamp bead and the second LED lamp bead to emit light.

[0017] One end of the secondary side of the transformer T1 is connected to the filter capacitor C3, the other end of the filter capacitor C3 is connected to the cathode of the rectifier diode D3 and the anode of the rectifier diode D4, the anode of the rectifier diode D3 is connected to the cathode of the diode D5 at the negative end of the first LED lamp bead, the cathode of the rectifier diode D4 is connected to the CS end, the CS end is connected to the anode of the diode D7 at the positive electrode of the first LED lamp bead through the resistor R1, and the capacitor C2 is arranged between the cathode of the rectifier diode D3 and the anode of the rectifier diode D4.

[0018] The other end of the secondary side of the transformer T1 is connected to the cathode of the rectifier diode D1 and the anode of the rectifier diode D2, the anode of the rectifier diode D1 is connected to the cathode of the capacitor D6 at the negative end of the second LED lamp bead, the cathode of the rectifier diode D2 is connected to the CS end, the CS end is connected to the anode of the capacitor D8 at the positive electrode of the second LED lamp bead through the resistor R1, and the capacitor C1 is set between the anode of the rectifier diode D1 and the cathode of the rectifier diode D2.

[0019] The CS terminal is connected to the current sampling pin of the LED driving control chip driving the LED through the resistor R2, and the anode of the diode D7 at the positive pole of the first LED lamp bead, the anode of the diode D8 at the positive pole of the second LED lamp bead, and the other end of the resistor R1 are grounded.

[0020] The resistor R9 and the capacitor C9 in the first RC circuit are connected in series and then connected in parallel at both ends of the rectifier diode D1; the resistor R10 and the capacitor C10 in the second RC circuit are connected in series and then connected in parallel at both ends of the rectifier diode D2; the resistor R11 and the capacitor C11 in the third RC circuit are connected in series and then connected in parallel at both ends of the rectifier diode D3; the resistor R12 and the capacitor C12 in the fourth RC circuit are connected in series and then connected in parallel at both ends of the rectifier diode D4, so as to reduce the EMC interference caused by the reverse recovery leakage of the rectifier diodes D1, D2, D3 and D4.

Claims

1. An EMC-resistant LED driving circuit, characterized in that: include: A transformer (T1), wherein the primary end of the transformer (T1) includes a switch circuit, a drive control circuit and a filter capacitor (C4), and the secondary end of the transformer (T1) includes a filter capacitor (C3), a rectifier diode (D1), a rectifier diode (D2), a rectifier diode (D3), a rectifier diode (D4), a first RC circuit, a second RC circuit, a third RC circuit, a fourth RC circuit, a resistor (R1), a resistor (R2), a first LED lamp bead and a second LED lamp bead; The first RC circuit, the second RC circuit, the third RC circuit, and the fourth RC circuit each include a resistor and a capacitor, and the resistor and the capacitor are connected in series; Primary side of transformer (T1): one end of the filter capacitor (C4) is connected to the switch circuit, and the other end is connected to the primary side of the transformer (T1). The drive control circuit is connected to the switch circuit. Secondary end of the transformer (T1): one end of the filter capacitor (C3) is connected to one end of the secondary side of the transformer (T1), and the other end is connected to the cathode of the rectifier diode (D3) and the anode of the rectifier diode (D4), the cathode of the rectifier diode (D4) is connected to the first LED lamp bead through the CS end, and the anode of the rectifier diode (D3) is connected to the first LED lamp bead; the other end of the secondary side of the transformer is connected to the cathode of the rectifier diode (D1) and the anode of the rectifier diode (D2), the cathode of the rectifier diode (D2) is connected to the second LED lamp bead through the CS end, the anode of the rectifier diode (D1) is connected to the second LED lamp bead, the other end of the resistor in the first RC circuit is connected to the anode of the rectifier diode (D1), and the other end of the capacitor is connected to the cathode of the rectifier diode (D1); The other end of the resistor in the second RC circuit is connected to the cathode of the rectifier diode (D2), and the other end of the capacitor is connected to the anode of the rectifier diode (D2); the other end of the resistor in the third RC circuit is connected to the anode of the rectifier diode (D3), and the other end of the capacitor is connected to the cathode of the rectifier diode (D3); the other end of the resistor in the fourth RC circuit is connected to the cathode of the rectifier diode (D4), and the other end of the capacitor is connected to the anode of the rectifier diode (D4); one end of the resistor (R2) is connected to the current sampling pin of the LED drive control chip, and the other end is connected to the positive electrodes of the first LED lamp bead and the second LED lamp bead through the resistor (R1), and the other end of the resistor (R1) is grounded.

2. The EMC-resistant LED driving circuit according to claim 1, characterized in that: The switch circuit comprises a MOS tube (Q1), a MOS tube (Q2), a resistor (R3) and a resistor (R4); the gate of the MOS tube (Q1) is connected to one end of the resistor (R3) and a signal input end of a drive control circuit, the source of the MOS tube (Q1) is connected to a power input end, and the drain of the MOS tube (Q1) is connected to the primary side of a transformer (T1); the gate of the MOS tube (Q2) is connected to one end of the resistor (R4) and the signal input end of the drive control circuit, the drain of the MOS tube (Q2) is connected to the source of the MOS tube (Q1), and the source of the MOS tube (Q2) is connected to a filter capacitor (C4).

3. The EMC-resistant LED driving circuit according to claim 1 or 2, characterized in that: The device also includes a capacitor (C1) and a capacitor (C2), wherein the capacitor (C1) is arranged between the anode of the rectifier diode (D1) and the cathode of the rectifier diode (D2), and the capacitor (C2) is arranged between the anode of the rectifier diode (D3) and the cathode of the rectifier diode (D4).

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