TWI404336B - Lighting apparatus and driving circuit applied in it - Google Patents

Abstract

A driving circuit including a switching unit and a drive unit is for driving the LED to emit light. The battery current is outputted via the switching unit and the drive unit. When the drive circuit receives current of the power adapter, the switching unit is switched off in response to the current of the power adapter, which stops the battery current to output to the drive unit. The current of the power adapter outputs the constant current to drive the LED via the drive unit, so that the LED would not be damaged or twinkled. The present disclosure also provides a LED lighting apparatus applying the drive circuit.

Description

Light emitting device and driving circuit thereof

The present invention relates to the field of constant current driving, and in particular to a constant current driving circuit and an LED lighting device using the constant current driving circuit.

A Light Emitting Diode (LED) is an illumination source that uses a DC drive. LED lighting devices are equipped with power supply devices that convert city AC power to DC, such as power adapters. Due to the extremely low power consumption of LEDs, batteries or dry batteries can be used as power supply for both emergency lighting and daily lighting. However, the use of LEDs as lighting devices requires constant current to drive LED illumination. When switching from the battery power supply to the power adapter, the user forgets to remove the battery, so that the voltage of the two power supply voltages is superimposed so that the sudden rise of the drive current may exceed its rated current, which may cause the LED to flicker or damage the LED.

In view of this, it is necessary to provide a driving circuit that outputs a constant current.

In addition, it is also necessary to provide an LED lighting device that uses a driving circuit.

a drive circuit for connecting to a battery or a power adapter and receiving both Current. The drive circuit includes a switch unit and a drive unit. The battery current is sequentially output through the switching unit and the driving unit. When the driving circuit switches the current of the receiving power adapter from the receiving battery current, the switching unit receives the current output by the power adapter and disconnects, so that the battery current stops outputting to the driving unit; and the current of the power adapter outputs a constant current through the driving unit.

An LED lighting device includes a battery holder for housing a battery, a power adapter interface, an LED unit, and a driving circuit for driving the LED unit to emit light. The drive circuit includes a switch unit and a drive unit. The battery current is sequentially output to the LED unit via the switching unit and the driving unit. When the driving circuit switches the current of the receiving power adapter from the receiving battery current, the switching unit receives the current output by the power adapter and turns off, so that the battery current is stopped and output to the driving unit. The current output to the LED unit through the drive unit is made constant by the current of the power adapter.

Compared with the prior art, the current received by the switch unit to the power adapter will cut off the battery current, prevent the battery voltage from superimposing with the voltage of the power adapter, and prevent the drive current from suddenly rising, thereby providing a constant current to drive the LED to avoid flashing of the LED. Phenomenon or damage to the LED.

10‧‧‧LED lighting device

20 21 23‧‧‧ battery holder first regulator diode first capacitor

30 31 33‧‧‧Power adapter interface Second regulator diode Second capacitor

40‧‧‧Drive circuit

41‧‧‧Switch unit

43‧‧‧Drive unit

45‧‧‧Split branch access unit

50‧‧‧LED unit

411‧‧‧Switching transistor

431‧‧‧ input

433‧‧‧First voltage output

435 451‧‧‧Second voltage output transistor

27 26 22 29 25 24‧‧‧First access resistor Second access resistor First resistor Second resistor Third resistor Fourth resistor

1 is a block diagram of a preferred embodiment of an LED lighting device.

FIG. 2 is a specific circuit diagram of the LED lighting device shown in FIG. 1.

The invention will be further described in detail below with reference to the accompanying drawings.

Referring to FIG. 1, the LED lighting device 10 includes a battery holder 20 for housing a battery, a power adapter interface 30, an LED unit 50, and a driving circuit 40 for driving the LED unit 50 to emit light. The LED lighting device 10 receives current from a battery or power adapter to drive the LED unit 50 to illuminate. When both the battery (not shown) and the power adapter (not shown) are connected to the LED lighting device 10, the driving circuit 40 automatically selects the power adapter as the power supply for the LED lighting device 10. In this embodiment, the power adapter interface 30 is a USB interface.

The drive circuit 40 includes a switch unit 41, a drive unit 43, and a shunt branch access unit 45. When the battery supplies power to the LED lighting device 10 through the battery holder 20, the battery current is sequentially output to the LED unit 50 via the switching unit 41 and the driving unit 43. When the power adapter supplies power to the LED lighting device 10, the switching unit 41 receives the current of the power adapter to turn off the switching unit 41 to cut off the current output of the battery to the driving unit 43; the branching branch access unit 45 receives the current of the power adapter to the LED The unit 50 is connected in parallel to the drive circuit 40, and the drive unit 43 receives the current of the power adapter to drive the LED unit 50 to emit light; it ensures that the current on the LED unit 50 is constant.

Referring to FIG. 2, the switching unit 41 includes a switching transistor 411 and a first access resistor 27 connected to the switching transistor 411. In the present embodiment, the switching transistor 411 is a P-channel enhancement type MOS transistor (hereinafter referred to as PMOS transistor Q1), the source thereof is connected to the positive electrode of the battery, the drain is connected to the driving unit 43, and the gate is respectively The first resistor 22 is connected to the power adapter interface 30 and grounded. The first voltage stabilizing diode 21 is also connected in series between the source of the switching transistor 411 and the positive electrode of the battery, and the first capacitor 23 is connected in parallel across the first voltage stabilizing diode 21. When the battery When the power is supplied, the voltage stabilizing circuit composed of the first voltage stabilizing diode 21 and the first capacitor 23 causes the battery to output a stable voltage to the switching unit 41.

The drive unit 43 includes an input 431, a first voltage output 433 (shown as Vout), and a second voltage output 435 (shown as FB). The input terminal 431 receives the current of the battery through the switch unit 41 or receives the current of the power adapter through the power adapter interface 30. In the present embodiment, the voltage of the power adapter is input to the input terminal 431 of the driving unit 43 through the second voltage regulator diode 31, and the cathode of the second voltage regulator diode 31 is grounded through the second capacitor 33. The power adapter is caused to output a stable voltage to the drive unit 43, so that the drive unit 43 outputs a constant current. The first voltage output 433 is coupled to the LED unit 50; the second voltage output 435 is coupled to the shunt branch access unit 45. The second voltage output 435 is also grounded through the second access resistor 26.

The shunt branch access unit 45 includes a transistor 451. The transistor 451 is an N-channel enhancement type MOS transistor (hereinafter referred to as NMOS transistor Q2), and its gate is connected to the gate of the PMOS transistor Q1 through the second resistor 29; the gate is passed through the third resistor 25 Connected to the second voltage output 435; the source is grounded. A fourth resistor 24 is also connected in series between the gate and the source of the NMOS transistor Q2.

When the driving circuit 40 is connected to the power adapter, the switching transistor 411 receives the current of the power adapter to turn off the PMOS transistor Q1 to stop the battery current from being output to the driving unit 43. At the same time, the shunt branch access unit 45 is electrically coupled to the drive circuit 40 in response to the current of the power adapter to form a shunt branch of the drive unit 43; the current of the power adapter is output to the LED unit 50 via the drive unit 43.

Generally speaking, when the battery is used for a period of time, the current outputted by the battery will gradually decrease slightly. When switching to the power supply mode of the power adapter, the voltage output by the power adapter will be greater than the battery voltage, so that the current output by the driving unit 43 increases. The current that is output to the LED unit 50 is not constant. Therefore, the gate of the NMOS transistor Q2 in the shunt branch access unit 45 receives the current of the power adapter through the second resistor 29 to turn on the NMOS transistor Q2; thereby connecting the third resistor 25 and the second access resistor 26 in parallel. The constant current on the LED unit 50 is maintained by the load forming the drive circuit 40.

It should be understood by those skilled in the art that the above embodiments are only intended to illustrate the invention, and are not intended to limit the invention, as long as it is within the spirit of the invention. Changes and modifications are intended to fall within the scope of the invention.

10‧‧‧LED lighting device

20‧‧‧ battery holder

30‧‧‧Power Adapter Interface

40‧‧‧Drive circuit

41‧‧‧Switch unit

43‧‧‧Drive unit

45‧‧‧Split branch access unit

50‧‧‧LED unit

Claims (8)

A driving circuit for connecting to a battery or a power adapter and respectively receiving currents of the two; the improvement is that the driving circuit comprises a switching unit, a driving unit and a shunt branch access unit; the battery current is sequentially passed through the switching unit and the driving Unit output; when the driving circuit switches the current of the receiving power adapter from the receiving battery current, the switching unit receives the current output by the power adapter and disconnects, so that the battery current stops outputting to the driving unit; the shunt tributary unit responds to the current output of the power adapter Connecting the drive circuit forms a shunt branch of the drive unit, causing the current of the power adapter to output a constant current through the drive unit. The driving circuit of claim 1, wherein the switching unit comprises a switching transistor; the switching transistor is a P-channel enhancement type MOS transistor, the source is connected to the positive electrode of the battery, and the drain is connected to the driving unit. Connecting, the gate is respectively connected to the power adapter interface through the first resistor and grounded; the first voltage regulator diode is also connected in series between the switch transistor source and the battery positive pole, and the first voltage regulator diode is Connect the first capacitor in parallel. The driving circuit of claim 1, wherein the driving unit comprises an input end, a first voltage output end and a second voltage output end, wherein the input end receives the current of the battery through the switch unit or receives the power through the power adapter interface The current of the power adapter, the voltage of the power adapter is input to the input end of the driving unit through the second voltage stabilizing diode, and grounded through the second capacitor in the second voltage regulator diode. The driving circuit of claim 3, wherein the shunt branch The access unit includes a transistor, the transistor is an N-channel enhancement type MOS transistor, and the gate is connected to the gate of the switching transistor through a second resistor; the drain is output through the third resistor and the second voltage The ends are connected; the source is grounded. A light emitting device includes a battery holder for accommodating a battery, a power adapter interface, an LED unit, and a driving circuit for driving the LED unit to emit light, wherein the driving circuit comprises a switching unit, a driving unit, and a shunt branch The battery current is sequentially output to the LED unit via the switch unit and the driving unit; when the driving circuit switches the current of the receiving power adapter from the receiving battery current, the switch unit receives the current output by the power adapter and disconnects, so that the battery current stops. Output to the driving unit; the shunt branch access unit accesses the LED unit to form a shunt branch, so that the current of the power adapter is output to the LED unit through the driving unit and the current is constant. The illuminating device of claim 5, wherein the switching unit comprises a switching transistor; the switching transistor is a P-channel enhanced MOS transistor, the source is connected to the positive electrode of the battery, and the drain is coupled to the driving unit. Connecting, the gate is respectively connected to the power adapter interface through the first resistor and grounded; the first voltage regulator diode is also connected in series between the switch transistor source and the battery positive pole, and the first voltage regulator diode is Connect the first capacitor in parallel. The illuminating device of claim 5, wherein the driving unit comprises an input end, a first voltage output end and a second voltage output end, wherein the input end receives the current of the battery through the switch unit or receives the power through the power adapter interface The current of the power adapter, the voltage of the power adapter is input to the input end of the driving unit through the second voltage stabilizing diode, and grounded through the second capacitor in the second voltage regulator diode. The illuminating device of claim 7, wherein the shunt branch access unit comprises a transistor, the transistor is an N-channel enhanced MOS transistor, and the gate passes through the second resistor and the switch The gate of the transistor is connected; the drain is connected to the second voltage output through a third resistor; the source is grounded.