JPH01258396A - Lighting device for fluorescent lamp - Google Patents

Abstract

PURPOSE:To prevent the electric shock in the no-load state of a fluorescent lamp with an electric circuit by providing an oscillation stopping control circuit which outputs a signal to stop the generation of the control signal to a control signal generating circuit based on the no-load signal detected with a choke in a no-load detecting circuit. CONSTITUTION:A no-load detecting circuit 10 detects the no-load state of a fluorescent lamp 4 such as that the fluorescent lamp 4 is extinguished at the life end or taken off from the socket depending on the current in a choke coil. When the fluorescent lamp is in the no-load state the current in the choke coil is cut off, then no voltage is induced in the secondary winding 12 of the choke coil to make a transistor(TR)Q3 from on-state to off-state. When the TRQ3 is made to off-state a TRQ4 is made to on-state and a voltage is applied to the emitter of the TRQ4 from a DC voltage source E through a resistance R3, and this voltage is inputted to the operation stopping input terminal P2 of an IC in a control signal generating circuit 7 as a command signal to stop the oscillation. The operation of the said circuit 7 is stopped, thus no pulse is applied to an oscillation circuit 6 to stop the oscillation of the said circuit 6. Thereby the electric shock can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a separately excited type fluorescent lamp lighting device for lighting a fluorescent lamp using a high frequency inverter.

[Conventional technology]

The lamp lighting method for fluorescent lamp lighting equipment such as fluorescent lamp stands is generally a commercial frequency lighting method using a ballast, but in recent years, a high frequency inverter lighting method that lights fluorescent lamps at a high frequency of several tens of kilohertz has been introduced. However, compared to commercial frequency lighting systems, it is becoming popular because it has superior overall efficiency, consumes less power, and is easy to reduce weight. An example of a conventional circuit for lighting a fluorescent lamp at high frequency using a separately excitation type oscillation circuit in this inverter lighting type fluorescent lamp lighting device will be described with reference to FIG.

In Figure 2, (1) is a commercial AC power supply, (2) is a power switch, (3) is a voltage doubler rectifier circuit consisting of a bridge of two rectifier diodes D1 and D2 and smoothing capacitors C1 and C2, and (4) is a fluorescent lamp, (5) is a choke coil for limiting lamp current, (6) is a separately excited oscillation circuit, (
7) is a control signal generation circuit that sends an oscillation drive control signal to the oscillation circuit (6) to cause it to oscillate. In addition, (8) is a radio noise prevention circuit that prevents radio noise from being emitted from the lighting circuit to the outside. (9) is an inrush current prevention circuit that prevents overcurrent from entering the lighting circuit when the power switch (2) is turned on. Prevent from flowing.

The control signal generation circuit (7) is driven when a DC power supply voltage E obtained by stepping down and rectifying a commercial AC voltage is applied, and sends a positive pulse signal and a negative pulse signal from the output terminal P1 to the oscillation circuit (6). This is an IC semiconductor component that alternately outputs an oscillation drive control signal. The oscillation circuit (6) is the first MOS-PET
It has a transistor Q1, a second transistor Q1, and a pulse transformer T, and a positive pulse signal from the control signal generation circuit (7) flows through the primary winding N of the pulse transformer T.
The voltage induced in the secondary winding N2 of the pulse transformer T turns on the first transistor Q1, and a negative pulse signal from the control signal generation circuit (7) flows through the primary winding N of the pulse transformer T. , the voltage induced in the secondary winding N3 of the pulse transformer T turns on the second transistor Q2. This first
, the second transistors Q1 and Q2 are alternately turned on and off, causing the oscillation circuit (6) to perform an oscillation operation, and the fluorescent lamp (4) to light up at a high frequency. This lighting is caused by a current I flowing from the first transistor Q to the choke coil (5) and the fluorescent lamp (4) when the first transistor Q1 is turned on, and a current I flowing from the first transistor Q to the choke coil (5) and the fluorescent lamp (4) when the second transistor Q2 is turned on.
4) to choke coil (5), second transistor Q2
This is done with a current I2 flowing through.

[Problems to be Solved by the Invention] In the above lighting device, the fluorescent lamp (4) is attached to a socket (not shown) of the lighting fixture, and the power switch (2)
When the voltage is turned on, a high voltage obtained by voltage double rectification of the 100V commercial AC voltage is applied to the electrodes of the fluorescent lamp (4), and the fluorescent lamp (4) is turned on. In such a lighting device, when the fluorescent lamp (4) is removed from the socket of the lighting equipment for the purpose of replacing the lamp, or when the fluorescent lamp (4) has reached the end of its life and is in an unloaded state, the power switch (2) is turned off. If it is left plugged in, the socket terminals and choke coil (
5), there was a risk of electric shock due to high voltage being generated. Such electric shock accidents often occur at fluorescent light stands, etc., which are easily touched by users.
As a measure to prevent this electric shock, it is necessary to make the lighting equipment have a double insulation structure, but such measures to prevent electric shock are currently impossible to implement because the lighting equipment becomes complicated and costs increase.

The present invention has been made in view of the above problems, and its purpose is to provide a fluorescent lamp lighting device using a high-frequency inverter lighting method that achieves measures to prevent electric shock during no-load conditions at low cost in terms of electrical circuitry. It's about doing.

[Means to solve the problem]

In order to achieve the above object, the present invention includes: a separately excited type oscillation circuit that lights a fluorescent lamp at high frequency through a choke coil that limits the lamp current; a control signal generation circuit that sends an oscillation drive control signal to the oscillation circuit; A no-load detection circuit detects the presence or absence of a current flowing through the choke coil based on a voltage induced in a secondary winding wound around the choke coil, and the control is performed based on the choke no-load detection signal of the no-load detection circuit. The present invention is characterized by comprising an oscillation stop control circuit that outputs a signal generation stop command signal to the signal generation circuit.

[Effect]

When a fluorescent lamp goes out at the end of its lifespan or is removed from the socket, resulting in no load, no current flows to the choke coil, and the no-load detection circuit detects this, and the oscillation stop control circuit activates the control signal generation circuit. The generation of the control signal is stopped, and the oscillation operation of the oscillation circuit is stopped, thereby preventing the generation of high voltage when there is no load.

〔Example〕

An example will be described based on FIG.

The lighting device in Fig. 1 is the lighting device in Fig. 2 with the following two circuits: a no-load detection circuit (10) and an oscillation stop control circuit (11), and is the same as the other one in Fig. 2, or Corresponding parts will be given the same reference numerals and their explanation will be omitted.

The no-load detection circuit (10) detects no-load conditions such as when the fluorescent lamp (4) has reached the end of its life or has been removed from the socket by checking the presence or absence of current flowing through the choke coil (5). This is a circuit in which a capacitor C3 is connected in parallel to a series circuit of a secondary winding (12) wound around a coil (5), a resistor R1, and a rectifier diode D3. When current flows through the choke coil (5), an AC voltage is induced in the secondary winding (12), and this AC voltage is passed through the rectifier diode D.
3, it is rectified to become a DC voltage, and the oscillation stop control circuit (1
1) is output to the input terminal (13).

The oscillation stop control circuit (11) has a third transistor Q3 that turns on when a DC voltage is applied to the input terminal (13) from the no-load detection circuit (10), and when the third transistor Q3 is turned on, the base-emitter is shorted. It has a fourth transistor Q4 which is turned off by being turned off. The DC power supply voltage E of the control signal generation circuit (7) is applied to the collectors of the third and fourth transistors Q3 and Q4 through resistors R2 and R3, respectively, and the collectors of the third and fourth transistors Q3 and Q4 are A malfunction prevention capacitor C4 is connected between the bases, and a signal from the emitter of the fourth transistor Q4 is outputted to the control signal generation circuit (7) as an oscillation stop command signal.

Next, the operation of the above embodiment will be explained.

When the fluorescent lamp (4) lights up normally, when the power switch (2) is turned on, the oscillation circuit (6) starts to oscillate with the pulse signal from the control signal generation circuit (7), and the fluorescent lamp (4) is lit with the lamp current limited by the choke coil (5). At this time, an AC voltage is induced in the secondary winding (12) by the current flowing through the choke coil (5), and the rectified DC voltage is applied to the base of the third transistor Q3 of the oscillation stop control circuit (11). Third transistor Q
3 turns on. Therefore, the fourth transistor Q4 remains off, no oscillation stop command signal is output to the control signal generation circuit (7), and the fluorescent lamp (4) remains lit.

Here, it is assumed that the fluorescent lamp (4) has reached the end of its lifespan and is extinguished, or that the fluorescent lamp (4) is replaced with a new one and removed from the socket of the lighting fixture, resulting in an unloaded state. Then, current no longer flows through the choke coil (5) and the secondary winding (1
2) No voltage is induced in the third transistor Q
3 goes from on to off. When the third transistor Q3 is turned off, the fourth transistor Q4 is turned on, and the voltage from E is sent from the resistor R3 to the emitter of the fourth transistor Q4.
This voltage is input as an oscillation stop command signal to the IC operation stop input terminal P2 of the control signal generation circuit (7), and the control signal generation circuit (7) stops operating and the pulse to the oscillation circuit (6) is stopped. , the oscillation operation of the oscillation circuit (6) also stops. Therefore, there is no risk of high voltage being generated in the terminals of the fluorescent lamp socket, the choke coil (5), etc., and there is no risk of electric shock.

Further, the malfunction prevention capacitor C4 of the oscillation stop control circuit (11) is used for the purpose of preventing malfunction when the power switch (2) is turned on. That is, if this capacitor C4 is not present, the moment the power switch (2) is turned on, the base current flows through the resistor R2 to the fourth transistor Q4, turning on the fourth transistor Q4 and turning on the control signal generating circuit (7). ) may not operate, the oscillation circuit (6) may not oscillate, and the fluorescent lamp (4) may not light up. Therefore, the fourth
Malfunction prevention capacitor C2 is connected to the base of transistor Q4.
When the power switch (2) is turned on, current flows from the resistor R2 to the malfunction prevention capacitor C4, but does not flow to the base of the fourth transistor Q, and therefore, the fourth transistor Q4 is turned on. This prevents the above-mentioned malfunction. The malfunction prevention capacitor C4 is charged for a time constant determined by the resistor R2 from the time when the source switch (2) is turned on, and this charged charge is discharged when the third transistor Q3 is turned on, returning to the original state. return.

〔Effect of the invention〕

According to the present invention, when a fluorescent lamp goes out at the end of its service life, or when the fluorescent lamp is removed from the socket of a lighting fixture due to lamp replacement and becomes in a no-load state, the no-load detection circuit detects this and controls the oscillation stop. Since the circuit stops the operation of the control signal generation circuit of the oscillation circuit and stops the oscillation circuit from oscillating, high voltage will not be generated at the terminals of the fluorescent lamp socket when there is no load, and there is no risk of electric shock. disappears. In addition, since this kind of electric shock prevention is done using an electric circuit, reliability is high, and there is no need for a double insulation structure for lighting equipment, making it possible to reduce the cost of lighting equipment. become.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an embodiment of a fluorescent lamp lighting device according to the present invention. FIG. 2 is a circuit diagram of a conventional fluorescent lamp lighting device. (4)--Fluorescent lamp, (5)--Chilark coil, (6)--Oscillation circuit, (7)--Control signal generation circuit, (10)--No-load detection circuit, (IIL---Oscillation Stop control circuit, (12) - Secondary winding.

Claims (1)

[Claims] (1) A separately excited oscillation circuit that lights a fluorescent lamp at high frequency through a choke coil that limits the lamp current, a control signal generation circuit that sends an oscillation drive control signal to the oscillation circuit, and a control signal generation circuit that is wound around the choke coil. a no-load detection circuit that detects the presence or absence of current flowing through the choke coil using a voltage induced in the secondary winding; and a no-load detection circuit that causes the control signal generation circuit to stop generating a signal based on the choke no-load detection signal of the no-load detection circuit. A fluorescent lamp lighting device comprising an oscillation stop control circuit that outputs a command signal.