CN211831276U

CN211831276U - LED drive circuit with battery under-voltage protection

Info

Publication number: CN211831276U
Application number: CN202020624380.7U
Authority: CN
Inventors: 洪剑华; 戴文礼
Original assignee: Zhangzhou Hetai Electric Lighting Source Tech Co ltd
Current assignee: Zhangzhou Hetai Electric Lighting Source Tech Co ltd
Priority date: 2020-04-23
Filing date: 2020-04-23
Publication date: 2020-10-30
Anticipated expiration: 2030-04-23

Abstract

The utility model discloses a LED drive circuit with battery under-voltage protection, which comprises a PMOS tube, a switch tube, a starting circuit and a holding circuit; the source electrode of the PMOS tube is connected with the positive electrode of the power supply of the LED driving circuit, the drain electrode of the PMOS tube is connected with the LED lamp bank, and the source electrode of the PMOS tube is connected with the grid electrode of the LED lamp bank through a first resistor; the starting circuit is used for generating a pulse signal at the initial power-on stage to control the conduction of the switching tube, so that the PMOS tube is conducted; the holding circuit is used for keeping the PMOS tube in a conducting state when the drain voltage of the PMOS tube is greater than the threshold voltage; and when the drain voltage of the PMOS tube is lower than the voltage threshold value, the PMOS tube is kept in a cut-off state. The utility model discloses a starting circuit and holding circuit that a small amount of discrete device found for LED drive circuit is turn-off when voltage is low excessively, provides low-voltage protection, prevents that the battery from discharging excessively, shortens life, and when LED load short circuit, automatic disconnection drive circuit guarantees the safe in utilization of equipment.

Description

LED drive circuit with battery under-voltage protection

Technical Field

The utility model relates to a LED drive field especially relates to a LED drive circuit with battery under-voltage protection.

Background

In the existing portable LED lighting device, a rechargeable battery such as a lithium battery is often used to supply power, and over-discharge or over-low voltage of the lithium battery can cause the lithium ion battery to completely fail, which affects the service life of the whole LED lighting device.

Therefore, in the prior art, a dedicated low voltage detection chip and/or a short circuit protection circuit are usually used to protect the lithium battery from over-discharge and to disconnect the driving of the LED. However, in the portable LED lighting device product which is sensitive in price and powered by a battery, there is a demand for further cost reduction while the life of the LED lighting device is ensured.

SUMMERY OF THE UTILITY MODEL

The utility model aims at providing a low-cost LED drive circuit with battery under-voltage protection, dedicated low pressure detection chip or short-circuit protection circuit are not carried, can realize the protection of putting excessively the battery.

In order to achieve the above object, the present invention provides an LED driving circuit with under-voltage protection for a battery, which includes a PMOS transistor, a switching transistor, a start circuit and a holding circuit;

the source electrode of the PMOS tube is connected with the positive electrode of the power supply of the LED driving circuit, the drain electrode of the PMOS tube is connected with the positive electrode of the LED lamp bank, the negative electrode of the LED lamp bank is grounded, and the source electrode of the PMOS tube is connected with the grid electrode of the LED lamp bank through a first resistor;

the collector of the switch tube is connected with the grid of the PMOS tube through a second resistor, the emitter of the switch tube is grounded, the base of the switch tube is grounded through a third resistor, and when the switch tube is conducted, the PMOS tube is in a conducting state;

the output of the starting circuit is connected with the base electrode of the switching tube, and the starting circuit is used for generating a pulse signal at the initial power-on stage so as to enable the switching tube to be conducted;

the maintaining circuit is used for feeding back the drain voltage of the PMOS tube to the base electrode of the switch tube, and when the drain voltage of the PMOS tube is greater than the threshold voltage, the switch tube is kept in a conducting state; when the drain voltage of the PMOS tube is lower than the voltage threshold value, the switching tube is in a cut-off state;

the switch tube is an NPN triode.

Further, the starting circuit comprises a capacitor, a first diode, a fourth resistor and a switching tube, wherein the anode of the capacitor is connected with the anode of the power supply of the LED driving circuit, the cathode of the capacitor is grounded through the fourth resistor, and meanwhile, the cathode of the capacitor is connected to the anode of the first diode; the cathode of the first diode is connected with the base electrode of the switching tube;

the emitting electrode of the switch tube is grounded, and the collector electrode of the switch tube is connected with the grid electrode of the PMOS tube.

Further, the holding circuit comprises a voltage stabilizing diode and a fifth resistor, the cathode of the voltage stabilizing diode is connected with the drain electrode of the PMOS tube, and the anode of the voltage stabilizing diode is connected with the base electrode of the switching tube through the fifth resistor.

The power supply circuit further comprises a bipolar multi-position switch, wherein the bipolar multi-position switch is used for simultaneously switching on or switching off the connection between the positive electrode of the power supply and the positive electrode of the capacitor and the connection between the grid electrode of the PMOS tube and the collector electrode of the switching tube; and second resistors with different resistance values are connected between the grid electrode of the PMOS tube and the bipolar multi-position switch, and only one second resistor is gated.

The utility model discloses a following technological effect:

the utility model discloses a starting circuit and holding circuit that a small amount of discrete device found for LED drive circuit is turn-offed when battery output voltage crosses low excessively, thereby provides low-voltage protection, prevents that the battery from excessively discharging, shortens life. And when the LED load is in short circuit, the driving circuit is automatically switched off, so that the PMOS tube is not burnt, and the use safety of the equipment is ensured.

Drawings

Fig. 1 is a circuit diagram of a preferred embodiment of the present invention.

Detailed Description

To further illustrate the embodiments, the present invention provides the accompanying drawings. The accompanying drawings, which are incorporated in and constitute a part of this disclosure, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the embodiments. With these references, one of ordinary skill in the art will appreciate other possible embodiments and advantages of the present invention. Elements in the figures are not drawn to scale and like reference numerals are generally used to indicate like elements.

The present invention will now be further described with reference to the accompanying drawings and detailed description.

As shown in fig. 1, the utility model discloses a LED drive circuit with BATTERY under-voltage protection, including PMOS pipe Q1, triode Q2, starting circuit and holding circuit, the power is provided by BATTERY BATTERY, and the power passes through PMOS pipe Q1 drive LED1 of banks, triode Q2's projecting pole ground connection, and triode Q2's collecting electrode passes through resistance R3 or resistance R4 and PMOS pipe Q1's grid G and connects, and triode Q2's base passes through resistance R2 ground connection. The transistor Q2 is an NPN transistor.

When the transistor Q2 is turned on, a voltage difference is generated across the resistor R6 by the voltage division of the resistor R6 and the resistor R3, or the resistor R6 and the resistor R4, and when the voltage difference is greater than the absolute value of Vgs of the PMOS transistor Q1, the PMOS transistor is turned on. By selecting or adjusting the resistor R3 or R4, the voltage applied to the resistor R6, i.e., the voltage difference between the source S and the gate G of the PMOS transistor Q1, which controls the current output from the PMOS transistor, can be adjusted, so as to adjust the illumination brightness of the LED lamp set.

In this embodiment, a bipolar three-position switch is provided, which functions as both a power switch and a gear switch, and the off state, the first on state or the second on state can be selected by toggling the switch. In an off state, the starting circuit is disconnected, and the collector of the triode Q2 and the grid G of the PMOS tube Q1 are disconnected, so that the PMOS tube is turned off; when the switch is switched to the first conduction state, the starting circuit is connected, and the collector of the triode Q2 is connected with the grid G of the PMOS transistor Q1 through the resistor R3; when the transistor is switched to the second conducting state, the starting circuit is connected, and the collector of the transistor Q2 is connected with the grid G of the PMOS transistor Q1 through the resistor R4.

The starting circuit comprises a capacitor C1, a diode D1 and a resistor R1, wherein the anode of the capacitor C1 is connected with the anode of a power supply of the LED driving circuit, the cathode of the capacitor C1 is grounded through a resistor R1, and the cathode of the capacitor C1 is connected with the anode of the diode D1; the cathode of the first diode D1 is connected to the base of the transistor Q2.

The supply voltage is in a normal state (i.e. the supply voltage is greater than the threshold voltage):

when the power supply is initially powered on, the triode Q2 is conducted when the power supply passes through the capacitor C1 and the diode D1 and the base electrode of the NPN triode Q2 is larger than the conducting voltage of the NPN triode Q2, at the moment, the power supply forms a loop through the resistor R6, the resistor R3 and the triode Q2, a voltage difference is formed between the grid G and the drain D of the PMOS tube Q1 and is larger than the conducting voltage of the PMOS tube Q1, the PMOS tube Q1 is conducted, and the power supply supplies power to the LED1 of the LED lamp group through the PMOS tube Q1.

At this time, the driving voltage output from the drain D of the PMOS transistor Q1 is fed back to the base of the transistor Q2 through the zener diode ZD and the resistor R5, and when the voltage of the drain D of the PMOS transistor Q1 is higher than the sum of the conduction voltage of the zener diode ZD and the conduction voltage of the transistor Q2, the conduction of the transistor Q2 is maintained.

Since the capacitor C1 is in a charged state at the initial power-on, the positive voltage of the capacitor C1 and the positive voltage of the power supply are kept the same, and the negative voltage of the capacitor C1 is decreased, so that the positive voltage of the diode D1 is smaller than the negative voltage, and the diode D1 is in a cut-off state. At this point the start-up circuit completes the triggering operation.

The supply voltage is in a low voltage state (i.e., the supply voltage is less than the threshold voltage):

when the voltage of the drain electrode D of the PMOS tube is lower than the sum of the voltage stabilization value of the voltage stabilization diode ZD and the base electrode conduction voltage of the triode Q2, the voltage acting on the base electrode of the triode Q2 is smaller than the conduction voltage, the triode Q2 is cut off, at the moment, the grid electrode G of the PMOS tube Q1 has no driving current, the voltage difference acting between the source electrode and the grid electrode G of the PMOS tube Q1 is smaller than the conduction voltage of the PMOS tube Q1, the PMOS tube Q1 is cut off, and the LED1 of the LED lamp group is extinguished, so that the low-voltage protection function. The low-voltage protection function is used for performing low-voltage protection on a battery for power supply, preventing the battery from over-discharging and shortening the service life.

Similarly, if the LED lamp group LED1 is short-circuited, so that the voltage of the drain D of the PMOS transistor Q1 is lower than the sum of the regulated voltage value of the zener diode ZD and the base conduction voltage of the transistor Q2, the transistor Q2 is turned off, the PMOS transistor Q1 is turned off, and the LED lamp group LED1 is turned off, thereby achieving the short-circuit protection function.

While the invention has been particularly shown and described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

Claims

1. The utility model provides a LED drive circuit with battery under-voltage protection which characterized in that: the circuit comprises a PMOS tube, a switch tube, a starting circuit and a holding circuit;

the switch tube is an NPN triode.

2. The LED driver circuit with under-voltage battery protection of claim 1, wherein: the starting circuit comprises a capacitor, a first diode and a fourth resistor, wherein the anode of the capacitor is connected with the anode of the power supply of the LED driving circuit, the cathode of the capacitor is grounded through the fourth resistor, and meanwhile, the cathode of the capacitor is connected to the anode of the first diode; the cathode of the first diode is connected with the base electrode of the switching tube;

3. The LED driver circuit with under-voltage battery protection of claim 1, wherein: the holding circuit comprises a voltage stabilizing diode and a fifth resistor, the cathode of the voltage stabilizing diode is connected with the drain electrode of the PMOS tube, and the anode of the voltage stabilizing diode is connected with the base electrode of the switching tube through the fifth resistor.

4. The LED driver circuit with under-voltage battery protection of claim 2, wherein: the bipolar multi-position switch is used for simultaneously switching on or switching off the connection between the positive electrode of the power supply and the positive electrode of the capacitor and the connection between the grid electrode of the PMOS tube and the collector electrode of the switch tube; and second resistors with different resistance values are connected between the grid electrode of the PMOS tube and the bipolar multi-position switch, and only one second resistor is gated.

5. The LED driving circuit with under-voltage battery protection of claim 4, wherein: the bipolar multi-position switch is a bipolar three-position switch and comprises three states, namely a first conduction state, a turn-off state and a second conduction state.