WO2015192576A1

WO2015192576A1 - Led drive power start-up circuit and start-up method

Info

Publication number: WO2015192576A1
Application number: PCT/CN2014/089409
Authority: WO
Inventors: 张显伟
Original assignee: 欧普照明股份有限公司
Priority date: 2014-06-19
Filing date: 2014-10-24
Publication date: 2015-12-23
Also published as: CN105282901A; CN105282901B

Abstract

Disclosed are a start-up circuit and start-up method of LED drive power, comprising a drive unit and a power factor correction unit mutually connected; the start-up circuit for the LED drive power source further comprises a time delay unit connected between the drive unit and the power factor correction unit; the power factor correction unit generates a control signal and transmits the control signal to the time delay unit; the time delay unit processes the control signal and generates a start-up signal to the drive unit; and the drive unit starts up after receiving the start-up signal. The technical solution coordinates the start-up timing sequence of the power factor correction unit and the drive unit.

Description

LED driving power source starting circuit and starting method

Technical field

The invention relates to the field of driving power sources, in particular to an LED driving power source starting circuit and a starting method.

Background technique

In the field of LED driving, power factor correction circuits are increasingly used to increase the power factor in LED driving applications. However, after the addition, the driving unit in the LED driving circuit, such as the self-oscillation circuit and the power factor correction circuit, may have a problem of startup timing. The startup time of the self-excited oscillation circuit is usually lower than 100mS; the power factor correction circuit is implemented by means of external resistor-capacitor charging, and there is a problem of delay. Considering the loss, the startup time is usually set at about 500mS. Therefore, at the moment of circuit startup, the power factor correction circuit operates significantly behind the self-oscillating circuit. This will cause the bus voltage to change at a low voltage during the start-up, causing a change in the output current, and the LED light source will flash bright and dark. At the same time, it can also cause the LED to be damaged by the impact of the peak current.

Therefore, there is a need for a new LED drive circuit that can coordinate power factor correction circuits and drive circuits to protect the LEDs at startup.

Summary of the invention

It is an object of the present invention to provide an LED driving power source starting circuit that is activated only after the power factor correction unit is activated.

The invention discloses an LED driving power source starting circuit, comprising a driving unit and a power factor correcting unit; the power factor correcting unit is connected to the driving unit, and the LED driving power source starting circuit further comprises a delay unit connected to the Between the driving unit and the power factor correction unit; the power factor correction unit generates a control signal and sends to the delay unit; the delay unit Processing the control signal and generating a start signal to the driving unit; the driving unit starts after receiving the start signal.

Preferably, the delay unit comprises a diode D1, a resistor R1, a resistor R2 and a capacitor C1. The diode D1 is connected to the power factor correction unit for receiving the control signal; the resistor R2 is connected in parallel with the capacitor C1. An RC circuit is formed; the resistor R1 is connected between the diode D1 and the RC circuit.

Preferably, the power factor correction unit comprises: a capacitor C2, a controller and an auxiliary winding T1; the capacitor C2 is connected to an input end of the controller, and the auxiliary winding T1 is connected to a ZCD end of the controller; The power factor correction unit operates when the capacitor C2 is charged to a startup threshold of the controller.

Preferably, the auxiliary winding T1 generates the control signal.

Preferably, the power correction factor unit further includes a field effect transistor Q1; the FET Q1 is connected to the GD terminal of the controller; and the GD terminal generates the control signal.

Preferably, the control signal is a square wave signal.

Preferably, the activation threshold is 12.5V.

Preferably, the driving unit comprises: a self-oscillating circuit or a constant current type driving circuit.

Preferably, the self-excited oscillation circuit comprises a switch tube Q2; the base of the switch tube Q2 is connected to the delay unit, the collector is connected to an external load, and the emitter is grounded.

The invention also discloses an LED driving power source starting method, comprising: starting a power factor correction unit; the power factor correction unit sends a control signal to a delay unit; the delay unit processes the control signal and sends a start Signaling to the drive unit; activating the drive unit.

After adopting the above technical solution, the starting of the driving unit is limited by the startup of the power factor correction unit, and due to the action of the delay unit, the starting time of the driving unit is delayed, and the large current impact on the LED of the driving unit alone is avoided. .

DRAWINGS

1 is a circuit diagram of a LED driving power source starting circuit in a first embodiment of the present invention;

2 is a circuit diagram of a LED driving power source starting circuit in a second embodiment of the present invention;

3 is a block diagram of a method for starting an LED driving power supply according to the present invention.

detailed description

Advantages of the present invention are further explained below in conjunction with the accompanying drawings and specific embodiments.

The invention discloses an LED driving power source starting circuit, which comprises a driving unit and a power factor correcting unit. After the driving unit receives the start signal, it drives the LED to start the illumination. According to the current standard, when the LED power is greater than a certain value (such as 25w), there is a certain requirement on the power factor. Therefore, a power factor correction unit is added to the LED driving power source starting circuit, and is connected to the above driving unit to compensate for the power factor in the LED driving application with a power greater than a certain value. In order to achieve the above mentioned object, the LED driving power source starting circuit further includes a delay unit connected between the driving unit and the power factor correcting unit for coordinating the starting timing between the driving unit and the power factor correcting unit. Specifically, after the power factor correction unit is activated, a control signal is sent to the delay unit connected thereto, and the control signal is sent to start the driving unit; after receiving the control signal, the delay unit will process the control signal. The processing described herein includes, but is not limited to, delaying the transmission of the signal, filtering the control signal, and the like. After the processing is completed, the delay unit generates a start signal and sends the start signal to the driving unit, and according to the start signal, the driving unit responds to start.

From the above startup timing, after the power factor correction unit is started first, the control signal sent by the power factor correction unit is delayed by the delay unit, and the power factor correction unit has been normally started or is about to be normal within the time limit of processing the control signal. After the startup is completed, the drive unit receives the start signal ready to start, so that the start sequence of the drive unit is after the power factor correction unit, that is, the power factor correction unit is not later than the drive unit starts and the peak current surge is avoided.

In a preferred embodiment, the delay unit comprises a diode D1, a resistor R1, a resistor R2 and a capacitor C1, wherein the anode of the diode D1 is connected to the power factor correction unit, more specifically to the signal output of the power factor correction unit. The control signal sent by the power factor correction unit is sent to the diode D1. The resistor R1 is connected to the cathode of the diode D1, and then the resistor R2 is connected in parallel with the capacitor C1 to form an RC circuit, and is connected to the resistor R1 such that the resistor R1 is connected between the diode D1 and the RC circuit. The RC circuit filters the control signal received by the diode D1. The specific working principle is: R1 is used to limit the charging current of C1, and R2 is used to discharge C1. The resistance of R1 determines the magnitude of the charging current; the charging current is large, the delay time is short, and the charging current is small, and the delay time is long. The resistance of R2 determines the magnitude of the discharge current; the discharge current is large, the delay time is long, and the discharge current is small, and the delay time is short. Therefore, it can play a certain delay effect.

Certainly, the selection of the delay unit is not limited to the solution in the foregoing embodiment. For example, the receiving and transmitting timing of the control signal controlled by the single chip connected between the driving unit and the power factor correcting unit can also achieve the above delay effect. .

Optionally or preferably, the power factor correction unit comprises: a capacitor C2, a controller and an auxiliary winding T1. The capacitor C2 is connected to an external power source for receiving power and slowly charging, and is connected to the input terminal Vcc of the controller. Power is forwarded to the controller. In the specific work, after the external AC power supply AC is input, the rectified voltage charges the capacitor C2. Due to the configuration of the capacitor C2, the power factor correction unit will start to work only when the capacitor C2 is charged to the startup threshold of the controller. First, the power factor correction unit has a soft start effect. Similarly, the power factor correction circuit further includes a resistor R2 connected in parallel across the capacitor C2 for limiting the magnitude of the charging current of the capacitor C2 to form another RC circuit for filtering the processed signal, as described above. It can also play a certain delay effect. In one embodiment, the startup threshold is 12.5V. The auxiliary winding T1 is connected to the capacitor C2 through a diode, wherein the diode rectifies the current input to the auxiliary winding T1, and the capacitor C2 is used for energy storage and filtering, and the stored energy can supply power to the controller, and then the auxiliary winding T1 is connected ZCD end of the controller (zero-crossing detection terminal), auxiliary winding T1 to the controller pulse control letter No. The specific use mode can be adjusted according to the actual application.

Referring to Figures 1 and 2, the auxiliary winding T1 has different operating states in both embodiments. 1 is a schematic circuit diagram of an LED driving power source starting circuit in a first embodiment of the present invention. In this embodiment, an auxiliary winding T1 is used for generating a control signal, which passes through an output terminal (A end in FIG. 1). The external output control signal, wherein the output is connected to the ZCD end of the controller and connected to the delay unit. The output control signal is sent to the delay unit and processed by the delay unit. 2 is a schematic circuit diagram of an LED driving power source starting circuit in a second embodiment of the present invention. In this embodiment, the auxiliary winding T1 is an application for supplying power to the controller. In this embodiment, the control signal is controlled by the controller. The PFC chip is generated, and includes a effect transistor Q1 in the power factor correction unit, and one end of the FET Q1 is connected to the GD end (output end) of the controller, and the other end is connected to the current sampling resistor. The control signal is controlled. The output between the GD terminal of the device and the FET Q1 (B terminal in the figure) is sent to the delay unit. The manner in which the control signals are generated in the above two embodiments can be replaced according to actual conditions and can be used.

In any of the above embodiments, the control signal is a signal output by the auxiliary winding T1 or the output end of the controller, specifically a square wave signal.

Optionally or preferably, the driving unit comprises a self-oscillating circuit comprising a switching transistor Q2, the base of which is connected to the delay unit, the collector is connected to the external load, and the emitter is grounded. The self-oscillation circuit is an RCC self-oscillation circuit. After receiving the start signal from the delay unit, the switch Q2 is biased to start, thereby changing the start timing of the drive unit and the delay unit. As described above, the self-oscillation circuit can also be provided with a plurality of resistors and capacitors to form an RC circuit, and the magnitude of the charge and discharge current of the capacitor is controlled by the resistor, so that each unit circuit in the LED driving power source startup circuit has a soft start. The function is to avoid the damage of the electronic components caused by the spike current.

In the above embodiment, the selection of the driving unit is not limited to the self-oscillation circuit, and other circuits different from the power factor correction unit startup timing such as the constant current type driving circuit can be used in this embodiment.

Referring to FIG. 3, the present invention also discloses a method for starting an LED driving power source. First, power The factor correction circuit is activated, and then it sends a control signal to a delay unit, and the delay unit performs filtering and delay processing on the control signal, and also has a delay effect. After the processing is completed, the delay unit sends a start signal to the driving unit, and the driving unit starts to work only after the driving unit receives the start signal.

It should be noted that the embodiments of the present invention are preferred embodiments, and are not intended to limit the scope of the present invention. Any one skilled in the art may use the above-disclosed technical contents to change or modify the equivalent embodiments. Any modification or equivalent changes and modifications of the above embodiments in accordance with the technical spirit of the present invention are still within the scope of the technical solutions of the present invention.

Claims

An LED driving power source starting circuit, comprising a driving unit and a power factor correction unit;

The power factor correction unit is connected to the driving unit, and is characterized by:

The LED driving power source starting circuit further includes a delay unit connected between the driving unit and the power factor correction unit;

The power factor correction unit generates a control signal and sends the signal to the time delay unit;

The delay unit processes the control signal and generates a start signal to the driving unit;

The driving unit starts after receiving the start signal.
The LED driving power source starting circuit according to claim 1, wherein:

The delay unit includes a diode D1, a resistor R1, a resistor R2, and a capacitor C1.

The diode D1 is connected to the power factor correction unit for receiving the control signal;

The resistor R2 is connected in parallel with the capacitor C1 to form an RC circuit;

The resistor R1 is connected between the diode D1 and the RC circuit.
The LED driving power source starting circuit according to claim 1, wherein:

The power factor correction unit includes: a capacitor C2, a controller and an auxiliary winding T1;

The capacitor C2 is connected to an input end of the controller, and the auxiliary winding T1 is connected to a ZCD end of the controller;

The power factor correction list when the capacitor C2 is charged to a startup threshold of the controller Yuan work.
The LED driving power source starting circuit according to claim 3, wherein:

The auxiliary winding T1 generates the control signal.
The LED driving power source starting circuit according to claim 3, wherein:

The power correction factor unit further includes a field effect transistor Q1;

The FET Q1 is connected to the GD end of the controller;

The GD terminal generates the control signal.
The LED driving power source starting circuit according to any one of claims 3 to 5, characterized in that:

The control signal is a square wave signal.
The LED driving power source starting circuit according to any one of claims 3 to 5, characterized in that:

The startup threshold is 12.5V.
The LED driving power source starting circuit according to claim 1, wherein:

The driving unit includes a self-excited oscillation circuit or a constant current type driving circuit.
The LED driving power source starting circuit of claim 8 wherein:

The self-excited oscillation circuit includes a switch tube Q2;

The base of the switch tube Q2 is connected to the delay unit, the collector is connected to an external load, and the emitter is grounded.
A method for starting an LED driving power supply, comprising:

Starting a power factor correction unit;

The power factor correction unit sends a control signal to a delay unit;

The delay unit processes the control signal and sends a start signal to the driving unit;

The drive unit is activated.