CN2770273Y - Starting control circuit for inductive fluorescent lamp - Google Patents

Abstract

A starting control circuit for an inductive fluorescent lamp, including a rectification circuit, a clock generation and lamp state sampling circuit, a resistance-capacity filter circuit and a control integrated circuit, the rectification circuit includes a MOSFET for AC/DC conversion; the clock generation and lamp state sampling circuit Send the clock signal to the control integrated circuit to make it generate a standard time base pulse, and send the state voltage of the fluorescent lamp to the control integrated circuit after dividing the voltage, so as to judge whether the lamp is "on" or "not on". state; the resistance-capacitance filter circuit sends the output voltage of the rectifier circuit to the integrated circuit after current limiting and filtering to provide the power supply of the integrated circuit; the control integrated circuit is used for the control of the warm-up time and the "on" and "off" of the MOSFET "control. The utility model enables the preheating time of the filament to be controlled and fully preheated; the inductance current of the ballast is the maximum value during ignition, and the inductance L generates a high induced electromotive force at the moment of current shutdown, which is enough to ignite the lamp tube . Therefore, the utility model can make the fluorescent lamp start reliably.

Description

A start-up control circuit for an inductive fluorescent lamp

technical field

The utility model relates to a starting control circuit of an inductive fluorescent lamp.

Background technique

As shown in Fig. 1, a fluorescent lamp composed of an inductive ballast usually uses a metal sheet to make a starter S, and this type of starter is mechanical in nature. It is widely used because of its low price. But this type of starter has the following disadvantages:

1. The preheating time of the fluorescent filament is not well controlled, so the preheating of the filament is not sufficient, thereby shortening the service life of the lamp tube.

2. Since the "ignition timing" of the starter S is random, not many ignite when the inductance L is at a high current, which makes it difficult for the ignition voltage of the lamp to be able to start the lamp every time. , so the fluorescent lamp with this kind of starter sometimes has to flash several times to ignite the lamp tube.

3. Since the starter S is made of a bimetallic sheet, the bimetallic sheet is prone to fatigue and mechanical damage, so the service life of this starter is not long.

Aiming at the shortcomings of the sheet metal starter, people in the industry have proposed the following improvement methods.

As shown in Figure 2 and Figure 3, a thyristor is used as a starting element. The principle is that when AC is input, the thyristor T as a current switch is first turned on, and then the thyristor is turned off after a period of time. off, so that the light can also be achieved. But the Achilles' heel of this method is: the general thyristor is turned off with "zero current", so when the thyristor is turned off, the current i flowing through the inductor L is almost zero, and the induced electromotive force generated by the inductor L is very small. Small, it is not enough to start the lamp, or the probability of the lamp being ignited is very low.

Utility model content

The purpose of the utility model is to provide a starting control circuit for an inductive fluorescent lamp which can reliably start the fluorescent lamp.

The utility model provides a start-up control circuit for an inductive fluorescent lamp, which is characterized in that it includes a rectifier circuit connected to both ends of the fluorescent tube, a clock generation and lamp state sampling circuit, a resistance-capacitance filter circuit and a control integrated circuit, wherein: The resistance-capacitance filter circuit and the rectification circuit are respectively connected to the control integrated circuit, and the clock generation and lamp state sampling circuits are respectively connected to the rectification circuit, the resistance-capacity filter circuit and the control integrated circuit, and the rectification circuit, including MOSFET, is used as AC/DC conversion; clock generation and lamp state sampling circuit, the clock signal is sent to the control integrated circuit to generate a standard time base pulse, and at the same time, the state voltage of the fluorescent lamp is sent to the control integrated circuit through voltage division, - Judging the two states of "lighting" and "not lighting" of the lamp; the resistance-capacitance filter circuit sends the output voltage of the rectifier circuit to the integrated circuit after current limiting and filtering, so as to provide the power supply of the integrated circuit; The integrated circuit is used as the control of the warm-up time and the "on" and "off" control of the MOSFFT.

In the start-up control circuit of the above-mentioned inductive fluorescent lamp, the clock generating and lamp state sampling circuit is composed of two resistors.

In the start-up control circuit of the above-mentioned inductive fluorescent lamp, the resistance-capacitance filter circuit is composed of a resistor and a resistance-capacitance filter.

Due to the adoption of the above-mentioned technical solution, the preheating time of the fluorescent lamp filament is controlled, so that the filament is effectively and fully preheated: the inductance current of the ballast is at the maximum value when the ignition is ignited, so that at the moment the current is turned off, the inductance L produces a high induced electromotive force, and this high-energy electromotive force is enough to ignite the lamp. Therefore, the utility model can make the fluorescent lamp start reliably.

Description of drawings

Fig. 1 is a schematic diagram of an existing fluorescent lamp composed of an inductance ballast;

Fig. 2 and Fig. 3 are schematic diagrams of other two existing fluorescent lamps composed of magnetic ballasts;

Fig. 4 is a schematic diagram of the start-up control circuit of the inductive fluorescent lamp of the present invention;

Fig. 5 is the voltage waveform figure of point A in the utility model circuit;

Fig. 6 is a view showing the corresponding relationship between the current i and the voltage at point A in the circuit of the present invention.

Detailed ways

As shown in Figure 4, the utility model is a start-up control circuit for an inductive fluorescent lamp, which includes a rectifier circuit 1 connected to both ends of the fluorescent tube, a clock generation and lamp state sampling circuit 2, a resistance-capacitance filter circuit 3 and control integration Circuit 4, wherein: RC filter circuit 3 and rectifier circuit 1 are respectively connected to control integrated circuit 4, and clock generation and light state sampling circuit 2 is connected to rectifier circuit 1, RC filter circuit 3 and control integrated circuit 4 respectively.

The rectifier circuit 1 is used for AC/DC conversion, which is composed of a bridge BR, a MOSFET (Metal Oxide Semiconductor Field Effect Transistor) and a resistor R4, wherein the MOSFET is a current switch.

The clock generation and light state sampling circuit 2 is composed of two resistors R2 and R3. The 100Hz clock signal is sent from point A to the SD terminal of the integrated circuit through R2, so that the integrated circuit can obtain a standard time base pulse; the state voltage of the light The voltage dividing circuit composed of R2 and R3 is also sent to the SD terminal of the integrated circuit after dividing the voltage, so that the two states of the lamp "on" and "not on" can be judged.

The resistance-capacitance filter circuit 3 is composed of a resistor R1 and a resistance-capacitance filter C. The voltage at point A is sent to the VCC terminal of the integrated circuit after current limiting and filtering to provide power for the integrated circuit.

The control integrated circuit 4 has played the control of the warm-up time and the "on" and "off" control of the MOSFFT, and can adopt the chip of the model BL8303 produced by Shanghai Belling Co., Ltd.

Here's how it works:

When the AC input starts, when the output of the integrated circuit is in a high-impedance state, the MOSFET is in a conduction state, and the preheating current I passes through the inductor L→filament→rectifier bridge→MOSFET, and the filament is heated.

As shown in Figure 5, the voltage waveform at point A:

The voltage at point A is about equal to the threshold voltage of MOSFET about 4V. On the one hand, the voltage at point A is used as the power supply of the integrated circuit through the current limiting and filtering of R1C; on the other hand, it is input to the SD terminal through R2 and is internally shaped by the integrated circuit, and then used as the time base signal and phase signal of the internal control circuit. If the preheating time is set to 1 second, the time base pulse with a period of 10ms is used as the frequency division input pulse, and when the counter counts to 1 second, a low level is output from the out terminal of the integrated circuit, so that the MOSFET is turned off.

Furthermore, in order to make the ignition voltage as high as possible, the output of out not only depends on the delay of the frequency divider, but also captures the peak value of the preheating current. When in the preheating state, the current i flowing through the inductor is equal to the current i flowing through the MOSFET. As shown in Figure 6, the waveform correspondence between the current i and the voltage at point A is:

The maximum value of the preheating current i _peak is exactly at the midpoint of the time base signal with a period of 10ms, which is 5ms. If the MOSFET can be turned off suddenly at the maximum value of the preheating current i _peak , the maximum induced electromotive force will be generated in the inductor, and sufficient high-voltage energy will be generated at both ends of the lamp tube, which is enough to ignite the lamp tube.

The above embodiments are only for illustrating the utility model, rather than limiting the utility model, and those skilled in the art can also make various transformations or modifications without departing from the spirit and scope of the utility model , so all equivalent technical solutions should also belong to the category of the present utility model, and should be defined by each claim.

Claims (3)

1. the start-up control circuit of an inductive type fluorescent lamp, it is characterized in that, it comprises rectification circuit, clock generating and lamp state sample circuit, rc filter circuit and the control integrated circuit that is connected the fluorescent tube two ends, wherein: described rc filter circuit links to each other with control integrated circuit respectively with rectification circuit, described clock generating links to each other with rectification circuit, rc filter circuit and control integrated circuit respectively with lamp state sample circuit, again:

Rectification circuit comprises MOSFET, as the AC/DC conversion;

Clock generating and lamp state sample circuit, clock signal is delivered to control integrated circuit, make it the time main pulse of the standard that produces, simultaneously, the of-state voltage of fluorescent lamp is delivered to control integrated circuit after by dividing potential drop, judge that thus lamp " is lighted " and " not lighting " two states;

Rc filter circuit is delivered to integrated circuit with the output voltage of described rectification circuit after through current limliting and filtering, so that the power supply of integrated circuit to be provided;

Control integrated circuit is as the control of the control of warm-up time and MOSFFT " opening " and " pass ".

2. the start-up control circuit of inductive type fluorescent lamp according to claim 1 is characterized in that; Described clock generating and lamp state sample circuit are made up of two resistance (R2, R3).

3. the start-up control circuit of inductive type fluorescent lamp according to claim 1 is characterized in that; Described rc filter circuit is made up of resistance (R1) and capacitance-resistance filter (C).

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