LED drive circuit capable of being extinguished in delayed manner after power failure

Abstract

The invention provides an LED drive circuit capable of being extinguished in a delayed mode after power failure. The LED drive circuit comprises a rectifier bridge, a first LED light-emitting lamp set, a first drive chip, a second LED light-emitting lamp set, a second drive chip, an energy storage capacitor and a power supply detection unit. The alternating current output end of the rectifier bridge is connected with the mains supply, and the direct current output end supplies power to the first driving chip and the first LED light-emitting lamp group; one end of the energy storage capacitor is connected to the first LED light-emitting lamp group, and the other end of the energy storage capacitor is connected to the negative electrode of the first LED light-emitting lamp group, so that the energy storage capacitor is charged when the first LED light-emitting lamp group is lightened; the power supply detection unit is used for detecting whether commercial power supplies power or not and outputting a control signal to the second driving chip; when the mains supply is cut off, the second driving chip outputs a driving signal to the switching tube to enable the switching tube to be switched on, and the energy storage capacitor supplies power to the second LED light-emitting lamp set so as to drive the second LED light-emitting lamp set to be turned off after being turned on for a first time.

Description

Technical Field

[0001] The invention relates to an LED driving circuit which delays extinguishing after power failure. Background Art

[0002] The current bulb products on the market use two power supply systems, capacitor charging power supply and LED driving power supply. The circuit is very complex and the cost is high. The product has only one function, which is to delay lighting for 15 seconds after turning off the light. The brightness (50Lm) is lower than the normal state (800Lm). This function is used to ensure that people can safely leave the dark area after turning off the light.

[0003] The disadvantages of the prior art are complex circuits and high costs, especially in small-volume light bulb products, where power supply design is difficult. Summary of the invention

[0004] The main technical problem to be solved by the present invention is to provide an LED driving circuit which delays extinguishing after power failure, and the circuit is simple and the cost is relatively low.

[0005] In order to solve the above technical problems, the present invention provides an LED driving circuit that delays extinguishing after power failure, comprising: a rectifier bridge, a first LED light group, a first driving chip, a second LED light group, a second driving chip, an energy storage capacitor and a power supply detection unit;

[0006] The AC output end of the rectifier bridge is connected to the mains, and the DC output end supplies power to the first driver chip and the first LED light group; one end of the energy storage capacitor is connected to the first LED light group, and the other end is connected to the cathode of the first LED light group, so as to charge the energy storage capacitor when the first LED light group is lit;

[0007] The power supply detection unit is used to detect whether the mains power is supplied, and output a control signal to the second driver chip; when the mains power is disconnected, the second driver chip outputs a drive signal to the switch tube to turn on the switch tube, and the energy storage capacitor supplies power to the second LED light group to drive the second LED light group to light up for a first time and then turn off.

[0008] In a preferred embodiment: the power supply detection unit is an optocoupler and a current limiting resistor, an input end of which is connected between the DC output positive and negative electrodes of the rectifier bridge, and an output end is connected to the second drive chip.

[0009] In a preferred embodiment: the energy storage capacitor is connected to the first LED light group via a diode D2.

[0010] In a preferred embodiment: when the mains power is disconnected, the second driving chip outputs a first PWM driving signal to the switch tube to turn on the switch tube, and the duty cycle of the first PWM driving signal is 100%.

[0011] In a preferred embodiment: within the first time when the second LED light group is lit, if the rectifier bridge is powered on and then off within Ns, the second driver chip outputs a second PWM drive signal to the switch tube to turn on the switch tube, and the duty cycle of the second PWM drive signal is 10%.

[0012] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0013] The present invention provides an LED driving circuit that delays extinguishing after power failure. According to the characteristics of LED lighting driving power supply driving LED lamp beads with constant current, power is taken from the middle of LED lamp beads to charge the capacitor, saving a set of charging power supply system, simplifying the circuit, saving costs, and achieving the same effect. At the same time, a new software program is designed, which can enable consumers to obtain another "sleep function" for free without adding hardware, that is, a 20-30 minute lower light flux (5Lm) longer delay function, which is used to help people fall asleep after turning off the lights. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 4 is a circuit diagram of a preferred embodiment of the present invention. DETAILED DESCRIPTION

[0015] In order to make the technical solutions and features of the present invention clearer, the present invention is further described in detail below in conjunction with the accompanying drawings and specific examples. It should be understood that these examples are only used to illustrate the present invention and are not used to limit the scope of the present invention. After reading the present invention, various equivalent forms of modifications to the present invention by those skilled in the art all fall within the scope defined by the claims attached to this application.

[0016] refer to Figure 1 , this embodiment provides an LED driving circuit that delays extinguishing after power failure, including: a rectifier bridge, a first LED light group, a first driver chip, a second LED light group, a second driver chip, an energy storage capacitor and a power supply detection unit;

[0017] The AC output end of the rectifier bridge is connected to the mains, and the DC output end supplies power to the first driver chip and the first LED light group; one end of the energy storage capacitor is connected to the first LED light group, and the other end is connected to the cathode of the first LED light group, so as to charge the energy storage capacitor when the first LED light group is lit;

[0018] The power supply detection unit is used to detect whether the mains power is supplied, and output a control signal to the second driver chip; when the mains power is disconnected, the second driver chip outputs a drive signal to the switch tube to turn on the switch tube, and the energy storage capacitor supplies power to the second LED light group to drive the second LED light group to light up for a first time and then turn off.

[0019] In this embodiment, the power supply detection unit is an optocoupler and a current limiting resistor, whose input end is connected between the positive and negative poles of the DC output of the rectifier bridge, and the output end is connected to the second driver chip. The energy storage capacitor is connected to the first LED light group through a diode D2. When the mains power is disconnected, the second driver chip outputs a first PWM drive signal to the switch tube to turn on the switch tube, and the duty cycle of the first PWM drive signal is 100%. Within the first time of lighting the second LED light group, if the rectifier bridge is powered on and then powered off within Ns, the second driver chip outputs a second PWM drive signal to the switch tube to turn on the switch tube, and the duty cycle of the second PWM drive signal is 10%.

[0020] When working, the first driver chip U1 forms a switching power supply to drive LED1~LED5, ensuring that the current of the lamp beads is relatively large when the five lamp beads work normally. Take a tap from one of the lamp beads LED5, use diode D2 to charge the E3 supercapacitor for energy storage, use the working current of the lamp bead to charge, and use the Vf voltage of the lamp bead LED5 to ensure that E3 is not over-voltage when charged. Diode D2 ensures that the current is drawn to charge E3, but the charge will not flow back in the opposite direction, ensuring smooth charging. When E3 is charged to reach the working voltage of the second control chip U2 MCU, MC U starts the control function, and detects the voltage at the bridge stack through the U3 optocoupler. If the voltage at the bridge stack disappears, it means that the light is turned off, and LED1~LED5 is extinguished due to lack of power. MCU immediately controls Q1 to start working 100%, controls LED7~LED8 to light up, and enters the 15S low light flux (50Lm) lighting mode to ensure that the user walks out of the dark area. After 15s, MCU turns off Q1 and the light is completely extinguished. If after entering the 15S low light flux lighting mode, the light control switch is turned on and off again (usually the on and off actions are completed within 2S), the MCU detects that the voltage appears at the bridge stack again and then disappears, and within 2s, the MCU immediately controls Q1 to enter 10% PWM to start working, controls LED7~LED8 to light up, and enters the 20-30 minute lower light flux (5Lm) lighting mode. The user can fall asleep in a dim state, which is especially suitable for taking care of infants and young children to sleep, until the E3 energy is released and the lamp beads LED7~LED8 are not lit.

[0021] The above is only a specific implementation of the present invention, but the design concept of the present invention is not limited to this. Any non-substantial changes to the present invention using this concept shall be deemed as an infringement of the protection scope of the present invention.

Claims

1. An LED driving circuit that delays extinguishing after power failure, characterized in that include: A rectifier bridge, a first LED light group, a first driver chip, a second LED light group, a second driver chip, an energy storage capacitor and a power supply detection unit; The AC output end of the rectifier bridge is connected to the mains, and the DC output end supplies power to the first driver chip and the first LED light group; one end of the energy storage capacitor is connected to the first LED light group, and the other end is connected to the cathode of the first LED light group, so as to charge the energy storage capacitor when the first LED light group is lit; The power supply detection unit is used to detect whether the mains power is supplied and output a control signal to the second driving chip; When the mains power is disconnected, the second driver chip outputs a driving signal to the switch tube to turn on the switch tube, and the energy storage capacitor supplies power to the second LED light group to drive the second LED light group to light up for a first time and then turn off.

2. The LED driving circuit with delayed extinguishing after power failure according to claim 1, characterized in that: The power supply detection unit is an optocoupler and a current limiting resistor, an input end of which is connected between the DC output positive and negative electrodes of the rectifier bridge, and an output end of which is connected to the second drive chip.

3. The LED driving circuit with delayed extinguishing after power failure according to claim 1, characterized in that: The energy storage capacitor is connected to the first LED light group via a diode D2.

4. The LED driving circuit with delayed extinguishing after power failure according to claim 1, characterized in that: When the mains power is disconnected, the second driving chip outputs a first PWM driving signal to the switch tube to turn on the switch tube, and the duty cycle of the first PWM driving signal is 100%.

5. The LED driving circuit with delayed extinguishing after power failure according to claim 1, characterized in that: During the first time when the second LED light group is lit, if the rectifier bridge is powered on and then off within Ns, the second driver chip outputs a second PWM drive signal to the switch tube to turn on the switch tube, and the duty cycle of the second PWM drive signal is 10%.

Images