JPS6358789A - Dimmer - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a dimming device for discharge lamps, halogen lamps, etc., and particularly relates to a dimming device suitable for dimming discharge lamps such as fluorescent lamps. .

[Prior Art] As a lighting device for a discharge lamp such as a fluorescent lamp, a device using a series inverter in which a pair of power switching transistors (main transistors) are configured into a single-ended push-pull circuit in a so-called half-bridge system is known. There is. Also known is a transformerless lighting device in which a fluorescent lamp as a load is connected to the output end of the series inverter via a current limiting inductor, and a starting capacitor is connected in parallel with the lamp. Furthermore, in such a series inverter, there is an automatic type in which the output ml is detected by a transformer and the main transistors are alternately turned on and off by positive feedback from the secondary winding of the transformer to the base of each main transistor. It is also known that

On the other hand, in a conventional lighting device using a so-called constant current push-pull type inverter, the lamp is dimmed by controlling the phase of the input voltage to the inverter or by intermittent oscillation of the inverter.

[Problems to be Solved by the Invention] By the way, in the transformerless lighting device using the series inverter described above, when there is no load or a high impedance load, the Q of the resonant system increases, so the resonant current increases and the main transistor losses increase. Therefore, when dimming and lighting a lamp in a transformerless lighting device, the conventional methods of phase control and intermittent oscillation described above have the disadvantages of low inverter efficiency and high loss in the main transistor, resulting in low reliability. .

In addition, the method of dimming by linearly changing the oscillation frequency does not have the above problems, but generally the frequency is changed by actively operating a variable impedance element such as a transistor or photocoupler, so the variable impedance element The brightness of the lamp varies due to variations in the brightness of the lamp. especially,
When dimming multiple lights at once, this variation becomes noticeable as uneven brightness, which is inconvenient.

The present invention was made in view of the above-mentioned problems with the conventional type, and an object of the present invention is to provide a dimming method that can be applied to a transformerless type lighting device using a series inverter and causes less stress on switching elements. shall be.

[Means for Solving the Problems] The present invention provides a means for changing the output frequency of the inverter between substantially two frequencies in one lighting mode in which the load of the inverter is equivalently a series circuit with the lamp actance component. It is characterized in that the pulse width i+1II211 is changed in accordance with the setting dimming value.

In one embodiment of the present invention, in the above-mentioned series inverter, the output frequency is periodically switched between 21ifi in a substantially rectangular waveform or trapezoidal waveform in time series, and
The light is dimmed by changing the duty which is the higher frequency of the two values. Furthermore, in this case, switching is performed in synchronization with the frequency of the AC input power source. Also, when switching the output frequency to a trapezoidal waveform, the rise of the frequency is made warmer than the fall.

[Function and Effect 1] In the present invention, since the lamp is equivalently connected in series with the lamp lit at high frequency and has an actance component, changing the output frequency of the inverter changes the lamp current and dims it. Can be done.

Also, even if the load is a series resonant system,
Dimming is performed by changing the inverter's output frequency away from this series common frequency, so the load impedance during dimming is actually higher than during full lighting, reducing load current and reducing stress on the main switching elements. . That is, the light can be adjusted without applying more stress to the main switching element than when the light is full.

In addition, since the output frequency of the inverter is essentially switched between the first frequency for all lights on and the second frequency for dimming, it is difficult to control the dimming of multiple lights at once. However, there is almost no variation in brightness due to differences in lamp current. Furthermore, since it is a binary control, it is possible to use an infrared remote control. In this case, the first and second frequencies are set higher than 38kHz, which is a general carrier frequency of infrared remote controllers, and the lower frequency is set to about 40kHz, for example.
By setting it to kH2, it is possible to prevent the lamp light from interfering with the infrared remote control even during dimming.

In the conventional device that linearly varies the output frequency of the series inverter described above, it is relatively difficult to prevent interference during dimming.

Furthermore, without changing the input/output voltage of the inverter,
Moreover, since the light is dimmed by uninterrupted output, especially when the present invention is applied to an individual light control device, a so-called soft start is possible, which reduces the voltage applied to the discharge lamp for a predetermined period of time after the power is turned on to prevent premature discharge. It is easy to convert. This can be achieved, for example, by starting the device with the frequency switching state similar to the deep dimming state.

Furthermore, when changing the oscillation frequency, that is, the lamp current, by making the change in the oscillation frequency on the side where the lamp current falls more slowly than the change in the oscillation frequency on the side where the lamp current rises, it is possible to prevent the lamp from flickering or turning off. etc. can be prevented.

[Explanation of Examples] Hereinafter, the present invention will be explained in detail using the drawings.

FIG. 1 shows an embodiment in which the present invention is applied to a self-help series inverter lighting device whose load is a fluorescent lamp.

The device shown in the figure inputs an AC input from an AC power supply 1 through a filter circuit 2 for surge absorption and noise prevention to a diode bridge DB31 and a smoothing capacitor C.
A rectifier circuit 3 consisting of 31, etc. converts it into a DC smoothed output, which is supplied to an inverter circuit 4 consisting of switching transistors Qla and 01b connected in 5EPP to convert it into a high frequency current, and a fluorescent current connected to an output terminal 5. This is to light up the lamp F. In addition, the dimming level setting circuit 6
The source of the lamp F can be adjusted by operating the dimming level setting variable resistor VR61.

The inverter circuit 4 is a so-called half-bridge type inverter (series inverter), and here a self-excited type is used. Main transistors Q1a and Qlb each have an emitter resistor Rea.

Reb is connected.

The transformer T1 is a saturable feedback current transformer, and has a current detection winding (primary winding) Wll that detects the output current from the connection point 5 between the main transistors Qla and Qlb, and a step winding W11. The first base drive winding (secondary winding) W2a is provided upward.

and a second base drive winding W2b provided separately from these windings Wll and W2a. The first and second base drive windings W2a, W2b connect to the main transistor Q1a via base drive circuits 4a, 4b.

Voltages with mutually opposite phases are supplied to each base of Qlb.

The base drive circuit 4a includes a resistor R for supplying base current from the base drive winding W2a to the main transistor Q1a.
1a, R2a, a diode D1a for drawing out the base current when the main transistor Q1a is turned off, and a transistor Q for varying the oscillation frequency of the inverter circuit 4 according to the signal from the dimming level setting circuit 6.
2a, Q3a, Q4a, etc. The transistor Q2a is a phototransistor, and together with the dimming level setting circuit 60 and the light emitting diode LED1a, the photocoupler P
It constitutes C1a. And photocabra PC1a
When transistor Q2a is on, transistor Q
3a, and then transistor Q4a is turned on and resistor R1
A is shorted. As will become clear in the explanation of the operation described later, the starting frequency of the inverter circuit 4 is determined mainly by the saturation timing of the current transformer T1. In other words, when the resistor R1a is short-circuited, the current flowing in the base drive winding W2a of the transformer T1, that is, the cancellation of the magnetic flux in the core of the transformer T1 is as large as f, and the timing of saturation of the transformer T1 is delayed. Therefore, the starting frequency of the inverter is low. On the other hand, when the transistor Q2a of the photocoupler PC1a is turned off, the series resistance of the resistors R1a and R2a is connected to the base drive winding W2a of the transformer T1, and the current flowing through the winding W2a, that is, the core of the transformer T1. The amount of cancellation of the internal magnetic flux decreases, the core saturation timing becomes earlier, and the oscillation frequency of the inverter increases.

The configuration and operation of the base drive circuit 4b are exactly the same as those of the base drive circuit 4a, so the following description will mainly be based on the base drive circuit 4a.

The output terminal 5 of this inverter circuit 4 is connected to the primary wire W11 of the current transformer T1 and the ballast inductor 14.
1 to the negative side DC output terminal (common terminal) of the rectifier circuit 3
A t1i electric lamp (for example, a fluorescent lamp) F is connected in an alternating current manner between the two. Capacitors C41 and C42 are for DC cut, and capacitor C43 is for starting lamp F. Note that this capacitor C43 and inductor L41 form a series resonant circuit, whose resonant frequency is the lowest oscillation frequency (for example, 40k) during normal operation of the inverter circuit 4.
)-12) Set it lower.

Next, the operation of the apparatus shown in FIG. 1 will be explained.

When the AC power supply 1 is turned on, the AC output is sent to the rectifier circuit 3.
The DC output rectified and smoothed by the smoothing capacitor C31 is supplied to the inverter circuit 4. As a result, a starting circuit (not shown) of the inverter circuit 4 operates to supply base current to the main transistor Q1b on one side.
Transistor Q1b becomes conductive. transistor Q
The current flowing through 1b flows through the current detection winding W11 of the feedback transformer T1, the inductor L41, the filament of the lamp F, the starting capacitor +IC43, etc., and this is positively fed back to the base of the transistor Qlb via the base drive winding W2b. be done. While this transistor Q1b is in a conductive state, the current flowing through the current detection winding ~Vll increases with time, and the magnetic flux density in the core of the saturable transformer T1 increases, and the saturable transformer T1 finally becomes saturated. Then, the induced voltage in the base drive winding W2b becomes zero, and the transistor Q1b is turned off. Therefore, when the current flowing through the current detection winding W11, that is, the magnetomotive force applied to the core of the transformer T1, decreases and becomes smaller than the level that saturates the core, a positive voltage is induced in the base drive winding W2a, and the transistor Q1a Turn on. This on state means that the current detection winding W
11 and the positive feedback through the base drive winding W2a until the transformer T1 is saturated. Thereafter, similarly, transistors Q1a and Qlb are alternately turned on, and inverter circuit 4 continues oscillation.

Immediately after startup, the fluorescent lamp F has not yet reached the dischargeable state, so the starting capacitor C43 connected between the inductor 141 and both filaments of the lamp F is connected to the output terminal 5.
Since the Q of this resonant system is high, the load current becomes larger than that during normal lighting, and a high voltage is generated between the terminals of the capacitor 043. This is applied to lamp F.

On the other hand, in the dimming level setting circuit 6, the voltage induced in the base drive winding W2b of the current transformer T1 is connected to the diode D61. D62 and capacitors C61, C62
, C63, etc., and convert the DC voltage obtained by rectifying and smoothing it into the photocoupler P C1a, P C1b.
It is used as a power source for driving.

This driving power source is slow to rise after VJ due to the resistor R62 and capacitor C63.

For this reason, immediately after startup, for a predetermined period of time until the voltage of the capacitor C63 rises sufficiently, the photocoupler PC1a,
PClb is kept off. Therefore, as described above, the transistor Q4a of the base drive circuit 4a is turned off, and the base drive winding W2a of the transformer T1 and the base of the main transistor Q1a are connected through the series resistance of the resistors R1a and R2a. Therefore, the inverter circuit 4 oscillates at a higher frequency.

As mentioned above, the load-side resonant frequency is set lower than the inverter's lowest oscillation frequency (for example, 40kHz), so the higher the inverter's oscillation frequency is, the further away it is from the resonant frequency, so the load current is reduced.

As a result, the voltage generated between the terminals of the capacitor C43 and applied across the lamp F becomes lower than the discharge starting voltage of the lamp F. Even in this case, a sufficient current is supplied to the filament of the lamp F due to the resonance, and the filament is preheated.

After the power is turned on, after a predetermined period of time has elapsed, the dimming level setting circuit 6
When the terminal voltage of capacitor C63 rises sufficiently,
Every time the transistor Q61 turns on, the photocoupler PC1
a, pClb is turned on. When the transistor Q2a of the photocoupler PC1a is turned on, the transistor Q4a is turned on and the resistor R1a is short-circuited, and the load on the base drive winding W2a of the transformer T1 becomes heavy, which delays the timing of saturation. Therefore, the oscillation frequency of the inverter circuit 4 decreases and approaches the resonant frequency of the load circuit, and the lamp F
The voltage applied to is the upper bound. This causes the lamp to start discharging.

When lamp F starts discharging and becomes low impedance, capacitor C43 is effectively bypassed by the lamp discharge path, the resonance described above is broken, the load current becomes stable, and lamp F returns to a normal lighting state. Become.

Next, the dimming operation in the device shown in FIG. 1 will be explained with reference to the waveform diagram shown in FIG.

The dimming level setting circuit 6 includes a diode D63 connected between the diode bridge DB31 of the rectifier circuit 3 and the smoothing capacitor C31.
Figure a) is the resistor R61 and the variable resistor VR for setting the dimming level.
It is applied to the series circuit with 61. The dotted line in FIG. 2a shows the terminal voltage waveform of the smoothing capacitor C31.

The sliding terminal of the variable resistor VR61 is connected to the base of the transistor Q61, and the photocouplers P Cla and P C1b are turned on only when this voltage is equal to or higher than a predetermined value. Zener diode ZD61 is photocoupler P
CIa.

PClb light emitting diode LED1a, LEDlbl,
: Photocoupler P C1a, P by limiting the flowing current
This is to protect Clb. The oscillation frequency of the inverter circuit 4 is determined by photocoupler p C1a, P C
When lb is on, it switches to a lower frequency f1, and when it is off, it switches to a higher frequency f2 in synchronization with a half cycle of the AC power supply.

As a result, a large amount of lamp current flows during the period when the flea generation frequency is fl, and a small amount flows during the period when the flea frequency is f2, and the lamp is lit with a brightness that corresponds to the average value of this lamp current.

In FIG. 2, t)-d shows how the oscillation frequency is switched between fl and f2. b shows the state at full brightness, C shows the state at dimming, and d shows the state at deep dimming. Fl and f2 in the figure correspond to the off and on states of the photocoupler PC1a and PClb, respectively.

FIG. 3 shows a circuit diagram of an individual light control device according to another embodiment of the present invention. This device is a modification of the dimming level setting circuit 6 of the device shown in FIG. 1, and uses an operational amplifier 5A61 to drive the light emitting diodes LED1a and LED lb with a substantially sawtooth wave.

FIG. 4 shows a circuit diagram of dimming [i] according to still another embodiment of the present invention. Figure 4(a) shows a batch dimming ballast that dims multiple lights in stages.When the input terminal of the dimming terminal DIM is in the oven, it is in the full light state, and when the sink power supply is connected to the input terminal, the dimming is dimmed. Becomes a light state. Figure 4(b) is similar to Figure 4(a).
) is a sink power type dimmer for controlling the dimming ballast of 1IIJll.

In the above embodiment, the photocoupler PC1a.

PClb (7) Light emitting diode L E D 1a, L
E D 1b may be driven by the output of the comparator by inputting a rectified output waveform or sawtooth wave and a DC voltage to a comparator. In this case, dimming can also be achieved by varying the DC voltage level.

In addition, in the case of negative dimming, add one signal line to the power line,
The pulse waveform obtained as the output of the above comparator is sent between the common line (COM) with the power supply and the signal line, passed through a noise filter on the ballast side, and the waveform is shaped to drive the light emitting diode EDla and LEDlb. You can do it like this.

As another method of collective dimming, a direct current voltage may be applied to the signal line, and the above-mentioned pulse generation circuit may be provided in the ballast to drive the light emitting diodes E D 1a and L E D 1b.

[Brief explanation of the drawing]

'; Figure 51 is a circuit configuration diagram of a discharge lamp dimmer according to an embodiment of the present invention; Figure 2 is an explanatory diagram showing how the frequency is switched in the apparatus of Figure 1; Figures 3 and 4; 2A and 2B are circuit diagrams of discharge lamp dimming devices according to other embodiments of the present invention, respectively. 1: AC power supply, 3: Rectifier circuit, 4: Inverter, 4a,
4b: Base drive circuit, T1: Feedback transformer, W2a, W2b: Secondary winding, R1a, R2a, R1b, R2b: Resistor, Q
4a, Q4b: Transistor, F: tli lamp, Li2: Ballast inductor, C4
3: Lamp starting capacitor, 6: Dimming level setting circuit.

Claims (1)

[Claims] 1. An inverter that converts input DC voltage to high frequency output;
A lamp that is equivalently connected to the output terminal of the inverter via a reactance component, an oscillation circuit that generates a periodic signal with a duty ratio according to the dimming amount set by the dimming amount setting means, and the output of the inverter. A light control device comprising a frequency switching circuit that varies or switches a frequency between two frequencies, first and second, according to the instantaneous level of the periodic signal. 2. The input DC voltage is obtained by rectifying and smoothing from an AC power source, and the oscillation circuit generates the periodic signal in synchronization with a half cycle of the AC power source. dimmer. 3. The inverter according to claim 1 or 2, wherein the inverter is a so-called series inverter comprising main transistors connected in a single-ended push-pull manner and a drive circuit that alternately turns on and off these main transistors. light device. 4. The inverter is a self-excited series inverter including, as the drive circuit, a saturable current transformer that detects the output current of the inverter and provides positive feedback to each of the main transistors, and the frequency switching circuit includes at least 4. The light control device according to claim 3, wherein the resistance value of the control electrode driving resistor of one main transistor is periodically varied or switched. 5. Claims 1 to 5, wherein the rise when switching the output frequency of the inverter is slower than the fall.
The light control device according to any one of Item 4. 6. Claims 1 to 5, wherein the frequency switching circuit is capable of varying or switching the frequency of the inverter between a frequency at which the lamp is lit at full brightness and a frequency at which the lamp is dimmed at its deepest level. The light control device according to any one of the above.