Output filter ripple circuit

Abstract

The utility model relates to the technical field of LED control circuits, in particular to an output filter ripple circuit, which comprises an AC-DC power supply, a diode D1, a diode D2, a diode D3, a capacitor C1, a capacitor C2, a resistor R1, a resistor R2, an MOS tube Q3 and an LED load, the output end of the AC-DC power supply is connected with the input end of the diode D1, the output end of the diode D1 is connected with the capacitor C1, the diode D2, the resistor R1 and the D pin of the MOS tube Q3, and the output end of the MOS tube Q3 is connected with the LED load. The diode D2 and the resistor R1 are connected between the diode D1 and the MOS tube Q3, the resistor R1 and the resistor R2 are connected between the diode D2, the diode D3 and the MOS tube Q3, a pin S of the MOS tube Q3 is connected with an LED load, a pin G of the MOS tube Q3 is connected with one end of the resistor R2, the other end of the R2 is connected with one end of the capacitor C2, and the capacitor C1 is connected with the other end of the capacitor C2. According to the output ripple filtering circuit, an AC-DC flyback topological circuit does not need to be changed, the ripple part is filtered out, low-ripple voltage and current can be obtained, and the output ripple filtering circuit has the advantages of being simple in circuit, small in output current and low in loss.

Description

Technical Field

[0001] This utility model relates to the field of LED control circuit technology, and in particular to an output ripple filtering circuit. Background Technology

[0002] When the output of an AC-DC flyback circuit is directly connected to an LED, the current ripple is large, resulting in mains flicker, which causes eye strain and limits its application. Therefore, there is an urgent need for an output ripple filtering circuit to solve these problems. Utility Model Content

[0003] The purpose of this invention is to provide an output ripple filtering circuit to solve the technical problems of large current ripple and easy flickering of LED lights in existing AC-DC flyback circuits.

[0004] This utility model discloses an output ripple filtering circuit, comprising an AC-DC power supply, diodes D1, D2, and D3, capacitors C1 and C2, resistors R1 and R2, a MOSFET Q3, and an LED load. The output terminal of the AC-DC power supply is connected to the input terminal of diode D1. The output terminal of diode D1 is connected to capacitor C1, diode D2, resistor R1, and the drain (D) pin of MOSFET Q3. Diode D2 and resistor R1 are connected between diode D1 and MOSFET Q3. Resistors R1 and R2 are connected between diode D2, diode D3, and MOSFET Q3. The source (S) pin of MOSFET Q3 is connected to the LED load. The gate (G) pin of MOSFET Q3 is connected to one end of resistor R2. The other end of resistor R2 is connected to one end of capacitor C2. Capacitor C1 is connected to the other end of capacitor C2.

[0005] Preferably, when a voltage with power frequency ripple passes through the MOSFET, the MOSFET is placed in the amplification range so that the ripple voltage loss is between the MOSFET's drain and source terminals.

[0006] Preferably, the D pin of the MOS transistor Q3 is the input pin, and the S pin is the output pin.

[0007] Compared with the prior art, the beneficial effects of this utility model are as follows:

[0008] This utility model's output ripple filtering circuit connects a MOSFET Q3 in series with the positive terminal of the output power supply. The gate (G) pin is set to a high level, and the gate-source (GS) voltage drop is the turn-on voltage of MOSFET Q3. The output (S) pin is the output pin. When MOSFET Q3 needs to conduct, simply connect the load to the S pin, allowing current to flow to the negative terminal. This generates a gate-source voltage drop across MOSFET Q3, turning it on. Since the load draws most of the voltage from the S pin to the negative terminal of the AC-DC power supply, the gate-source voltage of MOSFET Q3 represents its critical conduction state. MOSFET Q3 is in an amplification state, thus providing a basis for ripple filtering adjustment.

[0009] The output ripple filtering circuit of this utility model does not require changing the AC-DC flyback topology. By adding a ripple filtering circuit to the output, the ripple portion can be filtered out, resulting in low ripple voltage and current. It features simple circuit, small output current, and low loss. It has no impact on the original circuit, no requirements on the output voltage, and low ripple and loss. Attached Figure Description

[0010] The present invention will be further described below with reference to the accompanying drawings and embodiments:

[0011] Figure 1 This is a circuit diagram of an output ripple filtering circuit according to the present invention.

[0012] Figure 2 This is a schematic diagram of the ripple removal process of an output ripple filtering circuit according to this utility model. Detailed Implementation

[0013] This section will describe in detail the specific embodiments of the present utility model. The preferred embodiments of the present utility model are shown in the accompanying drawings. The purpose of the drawings is to supplement the textual description with graphics, so that people can intuitively and vividly understand each technical feature and the overall technical solution of the present utility model, but they should not be construed as limiting the scope of protection of the present utility model.

[0014] like Figure 1 and Figure 2 As shown, this utility model discloses an output ripple filtering circuit, including an AC-DC power supply, diodes D1, D2, and D3, capacitors C1 and C2, resistors R1 and R2, a MOSFET Q3, and an LED load. The output terminal of the AC-DC power supply is connected to the input terminal of diode D1. The output terminal of diode D1 is connected to capacitor C1, diode D2, resistor R1, and the drain (D) pin of MOSFET Q3. Diode D2 and resistor R1 are connected between diode D1 and MOSFET Q3. Resistors R1 and R2 are connected between diodes D2, D3, and MOSFET Q3. The source (S) pin of MOSFET Q3 is connected to the LED load. The gate (G) pin of MOSFET Q3 is connected to one end of resistor R2. The other end of resistor R2 is connected to one end of capacitor C2. Capacitor C1 is connected to the other end of capacitor C2. The drain (D) pin of MOSFET Q3 is the input pin, and the source (S) pin is the output pin.

[0015] The working principle of the output ripple filtering circuit of this utility model is as follows: The AC-DC power supply is rectified by diode D1 and output, then filtered by capacitor C1. A ripple voltage Vpp (e.g., ...) is applied to capacitor C1. Figure 2a) The output of diode D1 is connected in series with MOSFET Q3. The gate (G) pin of MOSFET Q3 is high-level by diodes D2 and D3. Since diodes D2 and D3 each have a voltage drop of 0.7V, the Vdg voltage of MOSFET Q3 is the voltage drop of diodes D2 and D3 minus the voltage drop of capacitor C1. The source (S) pin output of MOSFET Q3 is connected to the LED load.

[0016] A voltage difference Vgs is formed between the gate and source (GS) terminals of MOSFET Q3, causing Q3 to conduct. Vgs is the initial turn-on voltage of MOSFET Q3, determined by its characteristics. The Vgs voltage is filtered by capacitor C2, resulting in a stable voltage. Because Vgs is stable, the output voltage of MOSFET Q3 is also stable (e.g., ...). Figure 2 b is the voltage on the output LED. The ripple voltage Vpp is lost in MOSFET Q3. Figure 2 c) is the Vds of MOSFET Q3.

[0017] The ripple voltage loss is across Vds of MOSFET Q3. Since Vgs is determined by the characteristics of MOSFET Q3, different Vdg settings can filter out voltage ripples Vpp of varying magnitudes. If the ripple is large, diodes need to be connected in series with D2 and D3, and D2, D3, D4, etc., to increase Vdg and thus increase the filtered ripple voltage.

[0018] This utility model's output ripple filtering circuit connects a MOSFET Q3 in series with the positive terminal of the output power supply. The gate (G) pin is set to a high level, and the gate-source (GS) voltage drop is the turn-on voltage of MOSFET Q3. The output (S) pin is the output pin. When MOSFET Q3 needs to conduct, simply connect the load to the S pin, allowing current to flow to the negative terminal. This generates a gate-source voltage drop across MOSFET Q3, turning it on. Since the load draws most of the voltage from the S pin to the negative terminal of the AC-DC power supply, the gate-source voltage of MOSFET Q3 represents its critical conduction state. MOSFET Q3 is in an amplification state, thus providing a basis for ripple filtering adjustment.

[0019] In a preferred embodiment, refer to Figure 1 In this output ripple filtering circuit, when a voltage with power frequency ripple passes through the MOSFET, the MOSFET is placed in the amplification range, so that the ripple voltage loss is between the MOSFET's drain and source channels, resulting in a low-ripple voltage output that drives the LED without flickering.

[0020] The embodiments of the present utility model have been described in detail above with reference to the accompanying drawings. However, the present utility model is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present utility model.

Claims

1. An output ripple filter circuit, characterized by: The application relates to an AC-DC power supply, a diode D1, a diode D2, a diode D3, a capacitor C1, a capacitor C2, a resistor R1, a resistor R2, a MOS tube Q3 and an LED load, wherein the output end of the AC-DC power supply is connected with the input end of the diode D1, the output end of the diode D1 is connected with the capacitor C1, the diode D2, the resistor R1 and the D pin of the MOS tube Q3, the diode D2 and the resistor R1 are connected between the diode D1 and the MOS tube Q3, the resistor R1 and the resistor R2 are connected between the diode D2, the diode D3 and the MOS tube Q3, the S pin of the MOS tube Q3 is connected with the LED load, one end of the resistor R2 is connected with the G pin of the MOS tube Q3, the other end of the resistor R2 is connected with one end of the capacitor C2, and the other end of the capacitor C1 is connected with the capacitor C2. When the voltage with the power frequency ripple is output through the MOS tube, the MOS tube is placed in the amplification interval, the ripple voltage loss is in the DS of the MOS tube, the D pin of the MOS tube Q3 is the input pin, and the S pin is the output pin.

Images