JPH0254899A - Fluorescent lamp lighting device for show case - Google Patents

Abstract

PURPOSE:To disappear the fringe and eliminate the flicker of a fluorescent tube by lighting a fluorescent lamp with complex frequency pulses in which a high frequency and a low frequency are mixed. CONSTITUTION:As switching elements Q1 and Q2 connected to each other in series on the output side of a DC power source 1, a high speed transistor or MOSFET is used, forming a switching part. In the elements Q1 and Q2, a high frequency and a low frequency are mixed to their gates or bases, and composite frequency pulses F1, F2 having the opposite poralities are inputted as their driving signals. A fluorescent lamp circuit 3 is connected to output terminals a, a'. A power supply output wave shown by F3 is outputted to the terminals a, a' as complex frequency pulses to light a fluorescent lamp 4. Hence, the fringe caused at the time of lighting with a single frequency is disappeared, and the flicker of the fluorescent lamp 4 is eliminated, so that customers never receive unpleasant feelings.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a lighting device for a fluorescent lamp disposed inside a refrigerator under low temperature conditions, such as a refrigerated showcase.

(b) Prior Art In general, fluorescent lamps used in ATs such as refrigerated showcases use a 50H2 commercial power source as their lighting source, and are lit by an inverter at a single frequency.

(c) Problems to be solved by the invention However, when a fluorescent lamp is lit in a low temperature range and at a single frequency (40 to 80 KHz) using an inverter, a characteristic striped pattern (uneven light emission) occurs. It is confirmed that tens of tons of water is generated. Such a striped pattern is undesirable because it is an eyesore for customers and makes them think that the showcase itself is malfunctioning.

By the way, the following may be considered as the cause of the above-mentioned striped pattern. That is, as shown in Fig. 7, when the fluorescent lamp 4 is turned on at a single frequency (f) of about 40 to 80 to 82, at a certain moment, the current due to the frequency f ■1 is I l- which flows into the pipe from the middle of the heater h.
1 and 1 flowing into the oscillation capacitor C2 through the heater.
It becomes 1-2. At this time, oscillating voltages of fr different single frequencies are stored between C2. This oscillating voltage generates another heater current and tube current. Since the tube current flows at these two similar frequencies, it is conceivable that an interference phenomenon occurs in which a completely new low frequency component (fA=f-fr or fr-f) is generated. Furthermore, it is thought that the luminous efficiency of the tube overlaps at low temperatures. In addition, the power factor of the fluorescent tube itself is 1, but at low temperatures the impedance of the fluorescent tube decreases to several hundred ohms, and since it has load characteristics, the impedance inside the tube always changes depending on the magnitude of the tube current. It's changing. For this reason, it is thought that a large impedance mismatch phenomenon occurs at a certain frequency and within a certain ambient temperature range, and this is thought to cause interference fringes.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a fluorescent lamp ignition device that lights a fluorescent lamp using an inverter at multiple frequencies in order to eliminate the striped pattern.

(d) Means for Solving the Problems The present invention provides a multi-frequency pulse generation circuit that generates multi-frequency pulses that are a mixture of high and low frequencies, and on the other hand, between the power supply terminals obtained by converting the commercial power source to direct current, .

A switching unit is formed by connecting two switching elements in series, a fluorescent lamp circuit is provided at the output end of this switching unit, and an immediate-acting circuit unit for each of the switching elements is provided, and multi-frequency pulses are connected to each non-moving circuit. At the same time, the switching elements are actuated alternately with the multi-frequency pulse drive signal output from each 51i circuit, and the fluorescent lamp is lit with the multi-frequency output pulse obtained from the output terminal of the switching section. It is controlled.

(e) Operation Fluorescent lamps are lit by multi-frequency pulses that are a mixture of high and low frequencies output from the switching section, and do not produce the striped pattern that occurs when lighting with a conventional single frequency.

Therefore, even if fluorescent lights are installed in a low-temperature environment such as in a refrigerated showcase, there will be no flicker caused by the striped pattern.
There is no need to worry about making customers feel insecure.

(I) Implementation Date 1 The present invention will be explained in detail below. Figure 1 is a basic circuit diagram of a fluorescent lamp lighting device using multi-frequency pulses according to the present invention. 1 is a direct current obtained by rectifying a commercial power source; ! ! where Ql and Ql are the direct current type J! A switching element connected in series to the output side of Al, such as a high-speed transistor or MO8 type FET.
is used to constitute the switching section. The switching elements Q1 and Ql have a multi-frequency pulse F1 in which a high frequency and a low frequency are mixed and have mutually opposite polarities at their gates or bases.
, F2 are input as the drive signals. a.

A' is an output terminal, to which the fluorescent lamp circuit 3 is connected. A power supply output wave indicated by F is output as a multi-frequency pulse to the output terminals a and a'. Here, the frequencies fs and f of the high-frequency pulse and low-frequency pulse that constitute the multi-frequency pulse are such that the high frequency is 60 to 100.
KHz, and select one with a low frequency in the range of 3O-50KHz. The fluorescent lamp circuit 3 includes a fluorescent tube 4, a switching capacitor C1, a choke coil CH□, and an oscillation capacitor C2.
, and heater coils 5,5.

Although only one fluorescent lamp 4 is shown in FIG. 1 for explanation purposes, this lighting device is suitable for lighting a plurality of fluorescent lamps 4, and the switching elements QI, Ql, Depending on the situation, it can be lit up to about 500W.

Next, the block diagram of FIG. 2 showing the electric circuit diagram of the entire lighting device will be explained.

Two smoothing circuits 7, 7' and an input voltage detection section 8 are provided from the AC input circuit 6, and one of the smoothing circuits 7 is connected to one FET Fi[!] via a differential amplifier 9. The other smoothing circuit 7' is directly connected to the other FET swelling part 11. The input voltage detection section 8 is connected to a control section 12 that includes an oscillation circuit for generating multi-frequency pulses, a dimming circuit for controlling the dimming of the fluorescent lamp, and a preheating circuit for preheating the heater of the fluorescent lamp. There is.

Further, two control output lines are outputted from this control section 12 to control the respective FETI operating sections 10 and 10'. The switching section 14 is actuated by drive signals from these FET striking sections 10 and 10', and the output is taken out to the output circuit 15.

Further, an overcurrent detection section 16 is provided that detects the current flowing through the switching section 14 and controls the current to flow appropriately.

Therefore, the control unit 12 outputs a multi-frequency pulse that is a mixture of low frequency and high frequency.

Each FET driving section 10, 10' is controlled and driven to alternately switch the switching section 14, and the output circuit 15 outputs a multi-frequency pulse for power supply to the fluorescent lamp, thereby lighting the fluorescent lamp.

Next, a description will be given with reference to FIG. 3, which shows an actual circuit diagram corresponding to the block diagram t1 described above.

The AC input circuit 6 connects a 100V 50/60Hz (7) commercial power source to a diode D1. D2, capacitor C,,C
The voltage is rectified by a voltage doubler rectifier circuit consisting of a choke transformer L2 and a choke transformer L2. C1 to C1 are capacitors, Ll is a coil, and F is a fuse.

Here, trying to improve the power factor with a 1x voltage rectifier circuit, the AC
If you try to insert a choke into the line, it will have no effect unless it has a large capacity choke, but if you insert L2 as shown in this circuit diagram, a single choke transformer with a small capacity will have a power of several to several tens of percent. You can get the effect of improving the rate. Power supply circuit (
The smoothing circuit) 7 is taken out from the commercial power supply to the secondary side via the transformer T2, and the secondary side is connected to the diode D□GjD,
and a voltage doubler rectifier circuit consisting of capacitors C3° and C2, and a constant voltage circuit consisting of Zener diodes ZD1□ and ZDi2. C,2,C,...,C,4 are capacitors, R3,...R4° are resistors, 617 is a shield transformer, and D is a diode. The differential amplifier circuit shown in figure 9 connects the secondary side terminal of a shield transformer 17 to the bases of a pair of transistors Tr, and connects resistors R4, R4, respectively, to the collector side and the emitter side. The configuration is such that a common resistor RS0 is connected. C3,”-”
C,, are capacitors, R4, to R47 are resistors, D,...
, D19 is a diode.

lO is a gate drive, FET protection circuit, which inputs the signal from the differential amplifier 9 via the resistor R1 to the transistor T.
R0°, TR1, and diode D2° provide inductance, and are input as a drive signal to the gate of FET2. Resistor R5s, R, and capacitor C4
, are auxiliary parts for soft-oning FET2.

The series circuit of diode D21 and resistor R92 is an FET.
FET 2 has a function of rapidly dissipating its own capacitance when FET 2 is turned off. Also, a Zener diode ZD1 is connected to the gate of the FET. .

Overvoltage protection is provided by ZD. However, FET
If external noise enters the gate circuit of FET 2, it may turn on and destroy FET 2. Therefore, −
Regarding the intrusion of abnormal noise that cannot be detected by the membrane element, the critical off-voltage rise rate (d
r/dt) to construct FETs and protection circuits. The sensitivity of the thyristor SCR is adjusted by the gate resistance R.
□ can be done to some extent. C3syC4゜ is a capacitor, D2□
, D2° are diodes.

FET2 is connected in series with the other FET to the power supply terminal, and an output circuit 15 including these two FETs is connected in series with the other FET.
A multi-frequency pulse is extracted from the output terminals + and -. On the other hand, the other power supply circuit 7' converts the secondary side AC output via a transformer T□ into a bridge type rectifier.

A stable DC power source is obtained by a constant voltage circuit consisting of a transistor TR, a resistor R2, and a Zener diode ZD1. C7 to C□ are capacitors, R□ to R2 are resistors,
D, , D are diodes, and ZD2 is a Zener diode.

And the other gate opens, FET protection time lol! A voltage level shift circuit 13 is connected to the front stage of tll. The voltage level shift circuit 13 includes a Zener diode ZD on the emitter side of the transistor TR4.

A reverse bias circuit consisting of a parallel circuit of the transistor TR4 and the capacitor C2 is configured to increase the speed of the transistor TR4. C241C251C2G is a capacitor, R24~R0
is a resistor, and ZD is a Zener diode. The gate drive and FET protection circuit 11 described above is the same as the gate drive and FET protection circuit 11 described above.
It has the same configuration as the ET protection circuit 10, and the gate drive signal to the FET is sent to the voltage level shift circuit 13 via the resistor R1.
Therefore, the signal is inputted to the transistors TR, , TR, and further inputted to the gate of the FET1 via a diode D and an inductance L. In addition, Zener diodes ZD, ZD are provided as overvoltage protection for FET□.
Equipped with a thyristor SCR to prevent surge voltage intrusion from the first gate circuit. R3 is a gate resistance.

Also, a current detection resistor R connected to the source side of the FET
23 and R34 serve as source feedback resistors for soft-on, and capacitor Czs is also an auxiliary component for soft-on.

The series circuit of diode D12 and resistor R1 is connected to the O of FET1.
This is to rapidly dissipate the capacitance it has during FF. C2□ is a capacitor, R3° and R12 are resistors, and D, , D, and 4 are diodes. The gate signal is supplied to each FET described above through the inductance L4.
To explain why it is connected through L, the FET and FET are connected in series between the power supply. Also, because the FET has a very short turn-on time, even if the FET on the opposite side is completely OFF when the FET turns on, its output capacitance of several hundred PF will act as a load. .

Therefore, by inserting inductances (coils) L, L4, the speed near the gate threshold voltage can be slowed down to some extent (
However, when OFF, L3. This is to eliminate the influence of L4 and allow the threshold voltage to pass at high speed.

Therefore, by having such a circuit configuration, the FET
Soft-on and hard-off of FET2 can be realized.

I6 is the overcurrent #limiting circuit and the source side resistance R33 of FET1
, R44 is detected and input to the amplifier IC via the buffer 18, and the change value is used to open the gate,
The voltage is input to the FET protection circuit 11 to lower the gate voltage and limit the current value flowing through the FET□.

R1, ~R23 are resistors, C2, C, are capacitors,
D, ~D1o are diodes.

By the way, 8 is a power supply voltage fluctuation detection circuit with resistors R4 and R9.
The connection potential between the resistors R7 and Ro is compared with the potential at the connection point between the resistors R7 and Ro. C1 to CF are capacitors, and R to R1 are resistors. 19 is a power supply reset circuit, which is a transistor TR.
, generates a power-on signal. Zener diodes ZD, ZD are connected to the collector side of transistor TR2.
, and the base is input to a control circuit to be described later through a Zener diode ZD. R engineering 9. R is resistance. In the control circuit section 12 having the circuit configuration shown in FIG. 4, the terminal C0NT is used for adjusting the frequency of the fundamental wave (high) and can also be used for compensating for voltage fluctuations. It is. This control circuit section 12 is equipped with two types of timer circuits, one for 0.2 seconds and one for 3 to 4 seconds, and the terminal Ct is for a long timer, and is used to adjust the preheating period of 3 to 4 seconds for the fluorescent lamp heater. This is the external terminal of the capacitor C10. The terminal C0NT is a terminal for dimming, and the dimming is performed by adjusting the pause time of the low frequency pulse fL of the multi-frequency pulse, which is a mixture of high frequency and low frequency, output from the output terminals Q and Q. That is, during dimming, the pause time of only the fL section can be adjusted to be longer. Terminal VRL is an output terminal for completing the heater preheating period. 20 is an oscillation frequency adjustment and dimming circuit, in which a diode D7 and an adjustment resistor are connected to the terminal C0NT, and a yA adjustment resistor is connected to the terminal cONTz, and the oscillation frequency is adjusted to yA and dimming by adjusting each resistance. It is supposed to be done.

R1□, R engineering 31 Ri 4 is a resistor, D, , D are diodes, C, , , c, are capacitors, and Zn2 is a Zener diode.

In addition to the oscillation and timer functions, the control circuit section 12 has built-in functions such as frequency division, synthesis, and modulation necessary for generation of multi-frequency waves, which are finally output from output terminals Q and Q.

Simultaneous O required for FET engineering, FET, 0N-OFF characteristics
A signal is output that is shaped to satisfy N prevention, time balance, and ensuring that the FET side is turned on first. TR,,TR,is a transistor,Rff,"'
R and 7 are resistors, and C□ is a capacitor. Also, output circuit 1
5, R55-Rsz is the resistance, 04! ~043 is a capacitor, D, , D, is a diode, and L5 is an inductance.

Next, the circuit configuration in the control circuit section 12 will be briefly explained based on FIG.
622 is a preheating control circuit, consisting of resistors R1 to R5, transistors TR, TR2, capacitor C4, diode D1, and Zener diode ZD. 622 is a preheating control circuit that adjusts the preheating period with an external capacitor terminal CT and a preheating period completion circuit. It has an output terminal VRL and a resistor R6.
~R□2, capacitor C,,C,, diode D,,D
, , consists of two operational amplifiers (one is shown as an IC) and three NOT circuits. 23 is an oscillation circuit, which includes an oscillation frequency adjustment terminal C0NT, and resistors R14 to R□5. Capacitors 04 to C0, integrated circuit elements IC, and NOT
It is composed of circuits. The output pulse from the oscillation circuit 23 is input to a frequency dividing circuit 24 consisting of an integrated circuit IC□,
The outputs of the terminals Q0 to Q3 are input to the frequency synthesis circuit 25. Note that the output from the terminal Q0 is also input to a NOR circuit IC, which is an element of the inhibition circuit described later.

Further, the output from the terminal Q is also input to an AND circuit which is one element of the preheating control circuit 22. Frequency synthesis circuit 25
is four AND circuits (one is shown as IC), two N
It is composed of an oT circuit (one is shown as IC4) and a NOR circuit IC. 26 is a frequency dividing circuit connected to the frequency synthesis circuit 25. 27 is a rest time control circuit for dimming equipped with an input terminal C0NT2 for dimming by adjusting the rest time, and includes an integrated circuit IC and resistors R, , R,
, and capacitors C9 to C11. 28 is a prohibition circuit, which consists of two AND circuits (one shown as ±06), two NOR circuits (one shown as IC), a resistor R2°, and a capacitor C7. ~4 seconds)
, prohibits output of multi-frequency pulses.

The output circuit 15 outputs multi-frequency pulses of opposite polarity from output terminals Q and Q. And the three NANDAND circuits are IC
), a resistor R2□, and a capacitor C8.

Next, the operation of the lighting device of the present invention will be explained.

In Fig. 3, a power-on signal (S) is generated by TR□, and the timer circuit in the control circuit section 12 is used as a stable period (tl) of the circuit for about 0.2 seconds as shown in Fig. S. Prohibit output. After that, a small heater current is started flowing at a high frequency, and the frequency is lowered to gradually increase the current, and the light is turned on just before the resonance point fO, during the heater preheating period (t) of 3 to 4 seconds. , sweep lighting is performed using a single frequency, and then switching to frequency-controlled pulses to shift to a stable lighting state (t, ). The pattern is shown in FIG. When the light is on in a stable state, the switching element Q (FET), Q, (FET) shown in Fig.
, ) is a mixture of high frequency (fH) pulses and low frequency (fH) pulses, but when Ql is 10
If p 5eco N L/ then Q2 is 10μ5e
The ON time is balanced so that it turns ON.

Also, the frequency of the low frequency pulse (fL) is 2 in the audio frequency band.
The double frequency is set to the minimum to prevent vibration noise from being generated by the choke coil CH. Further, the frequency of the high frequency (fH) pulse is set to an even multiple of the frequency of the low frequency (fL) part in order to maintain the balance of the ON time of the Q part and Q2.

By lighting the fluorescent lamp with multi-frequency pulses in this manner, the occurrence of striped patterns on the fluorescent tube 4 is eliminated even when the ambient temperature is low (0° C.).

By the way, to explain the case of dimming, when lighting is performed using multi-frequency pulses, the high-frequency pulse f1 (mainly plays the role of heater power supply, and the low-frequency pulse fL mainly plays the role of tube current). Because there is, fH
If the frequency of Q2 is properly set, the heater current is fixed at an appropriate value, and the rest time of only the low frequency (fL) part is adjusted, as shown in FIG.
Stable dimming can be achieved by adjusting the pause time of Q2 to obtain waveform f'. - If you try to dim the light to a certain extent inside the membrane, you need to consider lighting stability and install a special circuit for the heater power supply, but with multi-frequency pulses, you can dim the light more than with a single frequency without a special circuit. can.

Moreover, when the fluorescent tube 4 is replaced, it is immediately turned on again.

The reason is that a moderate amount of heater current always flows in the high frequency section (f+) of a fluorescent tube lit by a multi-frequency pulse, and if the tube is replaced while the tube is lit, the impedance inside the tube increases, causing the capacitor of the fluorescent lamp circuit to Yo, C2,
A resonant current that can be approximately determined by the choke coil CH1 and the heater resistance flows.

That is, the resonance frequency fo is expressed by the following equation.

Therefore, if f+4fo f+ is approximately close to fO, an intermittent current with a peak current of about 2A flows through the heater, and 0.5
Lights up in less than a second.

(G) Effects of the Invention As described above, according to the present invention, a fluorescent lamp is lit with a multi-frequency pulse that is a mixture of high and low frequencies, so that when the fluorescent lamp is lit with a single frequency as in the conventional case, The striped pattern that appears disappears,
Flickering of fluorescent tubes is eliminated, and customers are no longer uncomfortable.

In addition, since lighting is performed using multi-frequency pulses, part of that frequency resonates with the choke coil, which is one circuit component of the fluorescent lamp circuit, causing a peak current to flow to the heater.
Fast time (0
, about 5 seconds).

Two MOS type FETs are used as switching elements that constitute one element of the lighting device, and these are connected in series between DC currents. Each drive circuit that provides a gate signal to each FET has an inductance that delays the gate signal. By providing this, it is possible to prevent the ON operation of a FET with signal power until the other FET is completely OFF, and easily prevent damage caused by simultaneous ON of one FET.

Furthermore, if an abnormal surge voltage from the outside that cannot be protected by the Zener diode used as overvoltage protection for the gate 1- of the FET enters, the thyristor provides a double safety protection device to prevent it from turning on. The device operates without any problems.

[Brief explanation of the drawing]

Fig. 1 is a basic circuit diagram of the lighting device of the present invention that lights a fluorescent lamp with multi-frequency pulses, Fig. 2 is a block diagram of the entire lighting device, and Fig. 3 is a specific electric circuit based on Fig. 2. Figure 4 is a specific circuit diagram of the control circuit in Figure 2, Figure 5 is an output waveform diagram for lighting a fluorescent lamp from power-on to stable lighting, and Figure 6 is a multi-frequency diagram for lighting. Output waveform diagram when adjusting low frequency pulses and dimming,
FIG. 7 is a conventional lighting circuit diagram for lighting at a single frequency. Q□, Q,... switching element, 4... fluorescent tube,
10°11...Switching element drive circuit section, 12.
・Control circuit section. Figure 1

Claims (3)

[Claims] (1) A switching section consisting of two switching elements connected in series between the power supply terminals obtained by converting a commercial power source to DC, a fluorescent lamp circuit connected to the output end of this switching section, and each switching section of the switching section. It includes a drive circuit section that drives and controls the element, and a multi-frequency pulse generation circuit that generates a multi-frequency pulse that is a mixture of high frequency and low frequency, which is a control signal input to each of the drive circuit sections, and outputs from each of the drive circuits. A fluorescent lamp lighting device for a showcase, characterized in that the switching element is actuated by a multi-frequency pulse drive signal, and the fluorescent lamp is lit by a multi-frequency output pulse outputted from its output terminal. (2) The fluorescent lamp lighting device for a showcase according to claim 1, wherein each drive circuit section is provided with an inductance for applying a drive signal to the gate of the switching element with a delay. (3) A fluorescent lamp lighting device for a showcase according to claim 1, wherein each drive circuit section is provided with a thyristor for preventing surge voltage from entering the gate of the switching element.