WO2019037437A1

WO2019037437A1 - Current ripple elimination circuit

Info

Publication number: WO2019037437A1
Application number: PCT/CN2018/082431
Authority: WO
Inventors: 庄华龙; 刘羽
Original assignee: 帝奥微电子有限公司
Priority date: 2017-08-25
Filing date: 2018-04-10
Publication date: 2019-02-28
Also published as: CN108575019A; CN108575019B

Abstract

A current ripple elimination circuit, comprising a power transistor, a first resistor, a voltage stabiliser tube, a first capacitor, and a second resistor. A first end of the first resistor is connected to a drain electrode of the power transistor; a cathode of the voltage stabiliser tube is connected to a second end of the first resistor; a first end of the first capacitor is connected to an anode of the voltage stabiliser tube and a gate electrode of the power transistor; and a first end of the second resistor is connected to the gate electrode of the power transistor; the common connection point of the first end of the first resistor and the drain electrode of the power transistor is an input terminal, and the common connection point of a source electrode of the power transistor, a second end of the second resistor, and a second end of the first capacitor is an output terminal.

Description

Current ripple cancellation circuit

Technical field

The invention relates to a current ripple cancellation circuit, in particular to a current ripple cancellation circuit for eliminating current ripple of an LED drive system.

Background technique

In general, LED light sources have the characteristics of low power consumption, light weight, and constant current drive. In the prior art, a constant current output is usually used to drive the LED load, and a high power factor is required. After the rectifier bridge, there is no large electrolytic capacitor, so the low frequency ripple noise caused by the sine wave of the AC grid is transmitted to the output terminal, resulting in The LED light flashes (strobe). For example, if the input source frequency is 50 Hz, the current output by the constant current driving module contains 100 Hz ripple, and the voltage on the filter capacitor also contains 100 Hz ripple. At the same time, the current flowing through the LED load also contains 100 Hz ripple, resulting in a 100 Hz stroboscopic light output from the LED load. Although it is difficult for human eyes to detect such low-frequency strobes, the human eye is exposed to such lighting for a long time, which causes visual nerve fatigue and endangers human health.

Please refer to FIG. 1 and FIG. 2 . FIG. 1 is a schematic structural diagram of a conventional current ripple cancellation circuit and an LED control circuit, and FIG. 2 is an operation waveform of a conventional current ripple cancellation circuit. As shown in FIG. 1, the current current ripple cancel circuit 1 is connected to the storage capacitor C, the constant current control circuit 2, and the LED load 3, wherein the current ripple cancel circuit 1 has a power tube. The waveforms of Figure 2 represent the voltage of node A1, the current of node A2, and the voltage of the power tube gate A3, respectively.

The current ripple elimination circuit 1 of the prior art ensures that the power tube operates in a saturation region, and requires a large external storage capacitor C. As the capacitance of the storage capacitor C increases, its cost increases, and the volume of the capacitor also increases significantly. Large-capacity storage capacitors C may not meet the requirements of new LED luminaires for driving PCB boards. Therefore, how to provide a current ripple cancellation circuit that can suppress ripple and meet the requirements of system cost, efficiency, and versatility is an urgent problem for various industries.

Summary of the invention

In view of the deficiencies of the prior art, it is a primary object of the present invention to provide a current ripple cancellation circuit that suppresses ripple and that satisfies system cost, efficiency, and versatility requirements.

In order to achieve the above and other objects, the present invention provides a current ripple cancellation circuit including a power transistor, a first resistor, a Zener diode, a first capacitor, and a second resistor. The first end of the first resistor is connected to the drain of the power tube; the cathode of the Zener tube is connected to the second end of the first resistor; the first end of the first capacitor is connected to the anode of the Zener tube and the gate of the power tube The first end of the second resistor is connected to the gate of the power tube; and wherein the common end of the first end of the first resistor and the drain of the power tube is an input end, and the source of the power tube The common junction of the second end of the two resistors and the second end of the first capacitor is an output.

In one embodiment, the current ripple cancellation circuit is further coupled to a constant current control circuit, an LED load, and a storage capacitor, wherein the output of the constant current control circuit is coupled to the first end of the storage capacitor to the LED load. At the input end, the input end of the current ripple cancellation circuit is connected to the output end of the LED load, and the output end of the current ripple cancellation circuit is connected to the loop end of the constant current control circuit and the second end of the storage capacitor.

In one embodiment, the constant current control circuit is an LED constant current control circuit having a high power factor.

In an embodiment, the LED load is an LED module that includes one or more LEDs.

Compared with the prior art, since the power tube in the current ripple cancellation circuit of the present invention operates in a saturation region, the gate voltage ripple of the power tube by the first resistor, the first capacitor, the Zener diode, and the second resistor The filtering process is performed to cause the power transistor to reduce the current ripple of its drain, so that under low current conditions, the current ripple is significantly lower than in the prior art. In addition, the current ripple cancellation circuit of the present invention has a simple structure and flexible design, can significantly reduce the system volume and cost, and greatly expand the application field, and fully overcomes the problems in the prior art.

DRAWINGS

FIG. 1 is a schematic structural diagram of a conventional current ripple cancellation circuit and an LED control circuit.

2 is an operation waveform of a conventional current ripple cancel circuit.

FIG. 3 is a schematic structural diagram of a current ripple cancellation circuit and an LED control circuit according to an embodiment of the present invention.

4 is an operation waveform of the current ripple canceling circuit of the present invention.

Symbol Description:

1 prior art current ripple cancellation circuit

2 constant current control circuit

3 LED load

4 current ripple cancellation circuit

A1, A2, A3 nodes

B1, B2 nodes

B3, B4 nodes

C storage capacitor

C1 first capacitor

R1 first resistor

R2 second resistor

M power tube

Z regulator tube

Detailed ways

The embodiments of the present invention are described below by way of specific embodiments, and those skilled in the art can readily appreciate other advantages and advantages of the present invention from the disclosure herein. The invention may also be embodied or applied by other different embodiments.

Please refer to FIG. 3. FIG. 3 is a schematic structural diagram of a current ripple cancellation circuit and an LED control circuit according to an embodiment of the present invention. As shown, the current ripple cancellation circuit 4 of the present invention includes a power transistor M, a first resistor R1, a Zener diode Z, a first capacitor C1, and a second resistor R2. The first end of the first resistor R1 is connected to the drain of the power tube M; the cathode of the Zener diode Z is connected to the second end of the first resistor R1; the first end of the first capacitor C1 is connected to the Zener Z The anode and the gate of the power tube M are connected; and the first end of the second resistor R2 is connected to the gate of the power tube M; and wherein the common end of the first end of the first resistor R1 and the drain of the power tube M is The input terminal B1, and the source of the power tube M, the second end of the second resistor R2 and the second end of the first capacitor C1 are connected to the output terminal B4.

In an embodiment, the power tube M can be, for example, an NMOS tube. The power tube M in the current ripple cancellation circuit 4 of the present invention operates in a saturation region, and the gate voltage ripple of the power tube M is performed by the first resistor R1, the first capacitor C1, the Zener diode Z, and the second resistor R2. The filtering process causes the power transistor M to reduce the current ripple of its drain.

In an embodiment, the current ripple cancellation circuit 4 can also be connected to a constant current control circuit 2, an LED load 3, and a storage capacitor C, wherein the output of the constant current control circuit 2 and the storage capacitor C are The first end is connected to the input end of the LED load 3, the input end B1 of the current ripple canceling circuit 4 is connected to the output end of the LED load 3, and the output end B4 of the current ripple eliminating circuit 4 is connected to the loop end of the constant current control circuit 2 and The second end of the storage capacitor C.

In an embodiment, the constant current control circuit 4 may be an LED constant current control circuit having a high power factor.

In an embodiment, the LED load 3 can be an LED module that includes one or more LEDs.

Please refer to FIG. 4. FIG. 4 is an operation waveform of the current ripple canceling circuit of the present invention. The waveforms of Figure 4 represent the voltage of node B1, the current of node B2, and the voltage of power tube M gate B3, respectively.

Further, the power transistor M operates in a saturation region, and when the gate-source voltage (ie, VGS) of the power transistor M is fixed, its drain current does not vary with the drain-source voltage (ie, VDS). When the LED current ripple cancel circuit 4 operates normally, it can be divided into the following two cases.

In the first case, when the drain-source voltage VDS of the power transistor M is higher than the breakdown voltage BV _Z of the Zener diode Z, the first capacitor C1 is charged through the first resistor R1 and the Zener diode Z, and the charging current value is I ₁ is

In the second case, when the drain-source voltage VDS of the power transistor M is lower than the breakdown voltage BV _{Z of the} Zener diode Z, the first capacitor C1 is discharged through the second resistor R2, and the discharge current value I ₂ is

Adaptively adjusting the gate-source voltage of the power transistor M to an appropriate voltage value by selecting a suitable resistance of the first resistor R1, a resistance of the second resistor R2, and a capacitance of the first capacitor C1. Meet current ripple and start-up time requirements.

Since the current ripple elimination circuit 4 of the present invention adopts an optimization technology, the full output current range has no distortion, and the zero current ripple of the full output current range can be truly realized, especially in a small current condition, the current ripple is more obvious than the prior art. Decrease.

In summary, since the power tube in the current ripple cancellation circuit of the present invention operates in a saturation region, the gate voltage ripple of the power tube is filtered by the first resistor, the first capacitor, the Zener diode, and the second resistor. The process is such that the power transistor reduces the current ripple at its drain, so current ripple is significantly lower than in the prior art under low current conditions. In addition, the current ripple cancellation circuit of the present invention has a simple structure and flexible design, can significantly reduce the system volume and cost, and greatly expand the application field, and fully overcomes the problems in the prior art.

The features and spirits of the present invention will become more apparent to those skilled in the art in the <RTIgt; . Therefore, any modifications and variations of the embodiments described above will be made without departing from the spirit and scope of the invention.

Claims

A current ripple cancellation circuit is characterized in that: the AC charging device control guiding circuit comprises:

Power tube

a first resistor, a first end of the first resistor being connected to a drain of the power tube;

a Zener tube having a cathode connected to the second end of the first resistor;

a first capacitor, a first end of the first capacitor being coupled to an anode of the Zener diode and a gate of the power tube;

a second resistor, the first end of the second resistor is connected to a gate of the power tube;

The common end of the first end of the first resistor and the drain of the power tube is an input end, and the source of the power tube, the second end of the second resistor, and the first capacitor The common contact at the second end is the output.
The current ripple cancellation circuit of claim 1 , wherein the current ripple cancellation circuit is further coupled to a constant current control circuit, an LED load, and a storage capacitor, wherein the constant current control circuit The output end is connected to the input end of the LED load to the first end of the storage capacitor, the input end of the current ripple cancellation circuit is connected to the output end of the LED load, and the current ripple cancellation circuit The output end is connected to the loop end of the constant current control circuit and the second end of the storage capacitor.
The current ripple canceling circuit according to claim 2, wherein the constant current control circuit is an LED constant current control circuit having a high power factor.
The current ripple cancellation circuit of claim 2 wherein said LED load is an LED module comprising one or more LEDs.