WO2004084591A1

WO2004084591A1 - Lighting device of discharge lamp

Info

Publication number: WO2004084591A1
Application number: PCT/JP2004/003095
Authority: WO
Inventors: Kengo Kimura
Original assignee: Sanken Electric Co., Ltd.
Priority date: 2003-03-19
Filing date: 2004-03-10
Publication date: 2004-09-30
Also published as: TW200421939A; JP2006185592A; TWI267323B

Abstract

A lighting device of a discharge lamp comprising a circuit (5) for detecting a tube current (IL) flowing through a code cathode ray tube (3), and a light control switching circuit (9) for generating an AC output (VL) continuously from an AC conversion circuit (2) by invalidating a light control signal (VB) being imparted from a light control signal generating circuit (4) to a light control circuit (7) during an interval (TC) when the tube current detecting circuit (5) does not detect the tube current (IL) and driving the light control circuit (7) when the tube current detecting circuit (5) detects the tube current (IL). Since the light control signal (VB) being imparted from the light control signal generating circuit (4) to the light control circuit (7) is invalidated by the light control switching circuit (9) because the tube current (IL) scarcely flow into the cathode ray tube (3) at the time of starting, the AC output (VL) from the AC conversion circuit (2) is fed continuously to the cathode ray tube (3). Consequently, a necessary and sufficient exciting energy is fed quickly to the code cathode ray tube (3) at the time of starting and the cathode ray tube (3) can be lighted in a short time with an arbitrary luminance.

Description

Description Discharge lamp lighting device Technical field

The present invention relates to a discharge lamp lighting device such as a cold cathode fluorescent lamp (CCFL), particularly a dimming control circuit for adjusting the brightness of the discharge lamp, and a discharge lamp that can be arbitrarily controlled in a short time. It belongs to a discharge lamp lighting device capable of lighting with luminance. Background art

A discharge lamp lighting device such as a cold cathode tube used for a backlight or the like of a liquid crystal display device mounted on a liquid crystal television or a notebook personal computer is known. For example, a conventional discharge lamp lighting device shown in FIG. 5, a DC power supply for generating a DC voltage V _IN of ten Porto (1) several hundred Pol Bok-thousand several DC voltage V _IN of the DC power supply (1) a hundred that converts the Pol Bok of the AC voltage V _t AC converter (2), a cold cathode tube as connected discharge tube to the output terminal of the AC converter (2) and (3), a cold cathode tube (3 ) and the dimming signal generating circuit for outputting a dimming signal V _B of (4), a cold cathode tube (3) and the flow tube current I [_ detection for tube current detecting circuit (5), the tube current detection circuitry _A tube current control circuit (6) for outputting a current control signal _VA for controlling the AC voltage _VL of the AC conversion circuit (2) so that the detected current value of (5) becomes a preset current value; optical signal generation circuit (4) of the dimming signal V _B by the tube current control circuit (6) dimming control circuit having a gate means (71) to a current control signal V _a to output continuously or intermittently (7) And the key And a light control circuitry driving circuit for forming a drive signal V _e for driving the AC conversion circuit (2) from the output signal V _D (7) (8).

As shown in FIG. 6, the AC conversion circuit (2) includes a rectangular wave voltage generation circuit (21) connected to the DC power supply (1), and a primary winding connected to the rectangular wave voltage generation circuit (21). A leakage transformer (22) including a leakage inductance (22c) formed in series with (22a), and a resonant capacitor (23) connected to the secondary winding (22b) of the leakage transformer (22). ). The leakage transformer (22) and the resonance capacitor (23) form a series resonance circuit (24). Here, the winding of the primary winding (22a) and the secondary winding (22b) of the leakage transformer (22) If the numbers are each NN ₂ [turn], the turns ratio NN, of the leakage transformer (22) is set to about 100. Although not shown in detail, the square wave voltage generation circuit (21) is configured by, for example, connecting a plurality of switching elements in a bridge, and the DC voltage V _IN from the DC power supply (1) is obtained by the switching operation of each switching element. and Suitsuchingu circuit for converting the rectangular wave ac voltage, and output Catelan scan that Suitsuchingu circuit to the primary winding to generate a voltage adjusted rectangular wave AC voltage V _s from the connected and the secondary winding Have. The drive signal V (;) input from the drive circuit (8) causes each switching element constituting the switching circuit to turn on and off at a frequency of about several tens of kHz, thereby providing a DC power supply (1). the DC voltage V _1N inputted into a rectangular wave AC voltage V _s from the. rectangular wave AC voltage V _s output from the rectangular wave voltage generating circuit (21), Li one Quai one Jitoransu (22) and a resonance capacitor The series resonance circuit (24) composed of (23) converts the sine-wave AC voltage V at a high voltage (hundreds of hundreds of volts to hundreds of thousands of volts) and a frequency of about several tens [kHz]. The dimming signal generation circuit (4) has a constant frequency (several tens [Hz] to several [Hz], which is sufficiently lower than the switching frequency (several tens [kHz]) of the AC conversion circuit (2). kHz]) and generates a rectangular pulse signal according to the desired luminance of the cold cathode fluorescent lamp (3). By varying the on-du one tee of No., outputs a dimming signal V _B of the cold cathode triode (3). Thus,-out bets luminance of the cold cathode tube (3) the maximum on-duty 1 0 0 [%] rectangular pulse signal, i.e., outputs a positive voltage level constant dimming signal V _B as shown in FIG. 7 (a).

The tube current detection circuit (5) includes a tube current detection resistor (51) connected in series with the cold cathode tube (3), and an anode terminal having the cold cathode tube (3) and the tube current detection resistor (51). And a smoothing capacitor (53) connected between the force source terminal and the ground terminal of the rectifier diode (52). That is, the tube current detecting circuit (5) is a tube current detecting resistor (51) CCFL tube current I _t flowing through (3) into a voltage corresponding thereto, the tube current detecting resistor (51) by rectifying and smoothing the voltage between the terminals the rectifier diode (52) and a flat smooth capacitor (53) and outputs the DC voltage as a detection voltage V _F. The tube current control circuit (6) includes a reference power supply (61) that generates a reference voltage V _R1 that defines the set value of the tube current flowing through the cold cathode tube (3), and a detection voltage of the tube current detection circuit (5). Outputs an output voltage V _E1 obtained by amplifying the error voltage between V _F and the reference voltage V _K1 of the reference power supply (61). Error and the amplifier (62) that, constant frequency and a triangular wave oscillation circuit (63) .XI for generating a triangular wave voltage V _T (several tens [kHz] C.), the output voltage V _E1 and the triangular wave oscillation circuit of the error amplifier (62) and a on-'generates a current control signal V _a of the rectangular pulse train duty changes P WM (pulse width modulation) comparator (64) by comparing the triangular wave voltage V _T (63). AND signal V of the gate means (71), for example dimming signal current control signal V _A of the generator (4) of the dimming signal V _B and the tube current control circuit (6) of the dimming control circuit (7) It can be composed of an AND gate (71) that outputs _D. That is, the dimming control circuit (7), when a positive voltage level constant dimming signal V _B is input from the dimming signal generating circuit (4) as shown in FIG. 7 (A), the tube current control circuit Since the current control signal _VA from (6) is continuously output, adjustment of the brightness of the cold-cathode tube (3), that is, dimming operation is not performed. On the other hand, as shown in Fig. 8 (A), the frequency (several tens [Hz]) is sufficiently lower than the frequency (about several tens [kHz]) of the current control signal _VA output from the tube current control circuit (6). ] To several [kHz]) and a dimming signal V _B of a rectangular pulse train having a duty ratio corresponding to the desired luminance of the cold-cathode tube (3) is output from the dimming signal generation circuit (4) to the dimming control circuit. when the input to (7), and intermittently outputs a current control signal V _a from the tube current control circuit (6) in a cycle of the dimming signal V _B, performs a dimming operation of the cold cathode tube (3) . Driving circuit (8) is a continuous rectangular wave voltage generation circuit of the AC converter (2) in the logical product signal V _D which are entered (21) from the AND gate one preparative (71) of the dimming control circuit (7) or intermittently to form a drive signal V _e to be driven, and outputs the rectangular wave voltage generating circuit (21). In the configuration shown in FIG. 5, when the dimming signal V _B of the device startup t _t from the dimming signal generating circuit as shown in FIG. 7 (A) (4) of the positive voltage level constant, the dimming control circuit (7 ) Does not perform the dimming operation, and continuously drives the AC conversion circuit (2) from the drive circuit (8) by the current control signal _VA continuously output from the tube current control circuit (6). The drive signal _Vc is output. As a result, the AC voltage _VL is continuously applied from the AC conversion circuit (2) to the cold-cathode tube (3) as shown in FIG. 7 (B), and the time t _{2 as} shown in FIG. 7 (C). When the tube current II starts flowing through the cold-cathode tube (3), the cold-cathode tube (3) starts lighting. Time t ₂ later, since the tube current IL flowing through the cold cathode tube (3) by the tube current control circuit (6) is held substantially constant, the luminance of the cold cathode tube (3) is always the maximum value constant.

Further, as shown in FIG. 8 (A), the duty is a frequency sufficiently lower than the frequency of the current control signal _VA of the tube current control circuit (6) and corresponds to the desired luminance of the cold cathode tube (3). The current control signal V _A of the case which is output from the dimming signal V _B the dimming signal generating circuit of a rectangular pulse train (4), the dimming control circuit (7) from the tube current control circuit (6) with a ratio the output signal V _D which is intermittently is output. Thus, the dimming signal drive signal V _G intermittently drive the cycle at AC converter (2) of the V _B are outputted from the drive circuit (8), the AC conversion circuit in the shown Suyo FIG 8 (B) (2) intermittently alternating voltage V _t to the cold cathode tube (3) from is applied. As shown in FIG. 8 (C), a cold cathode tube at time t ₂ (3) to the tube current IL starts flowing cold cathode tube (3) starts lighting, the time t ₂ after the cold-cathode tube ( In 3), the tube current IL continues to flow intermittently. Thus, the repeated blinking period of the cold cathode tube (3) the dimming signal V _B, the desired brightness can be obtained by appropriately adjusting the on-duty of the dimming signal V _B. At the same time, since the tube current IL flowing through the cold-cathode tube (3) is kept substantially constant by the tube current control circuit (6), the brightness of the cold-cathode tube (3) is always constant. A discharge lamp lighting device having a configuration similar to the above-described discharge lamp lighting device is disclosed in, for example, Japanese Patent Application Laid-Open No. 2000-3595999 (page 6, FIG. 6). Problems the invention is trying to solve

In conventional discharge lamp lighting device shown in FIG. 5, when the advance dimming signal V _B to the dimming signal generator circuitry to (4) from the dimming control circuit (7) as shown in FIG. 8 (A) is input AC voltage V _L of the AC converter (2) as shown in the cold cathode tube (3) during the period T _beta the tube current IL is not detected in FIG. 8 (beta) as shown in Figure 8 (C) Is intermittently applied to the cold cathode tube (3). As a result, it is not possible to supply sufficient excitation energy from the AC conversion circuit (2) to the cold-cathode tube (3) to turn on the cold-cathode tube (3) during the dark start period T _B during which no tube current is detected. The time T _B from the start-up of the device t to the start of lighting of the cold-cathode tube (3) 1 to _{2 When} the AC voltage _VL of the AC conversion circuit (2) is continuously applied to the cold-cathode tube (3) There was a drawback that it was longer than the same time T _A in FIG. 7 (B). Therefore, when the cold-cathode tube (3) was left in a cold place without being turned on for a long time, problems such as poor starting occurred.

Therefore, an object of the present invention is to provide a discharge lamp lighting device capable of lighting a discharge lamp at an arbitrary luminance in a short time. Disclosure of the invention The discharge lamp lighting device according to the present invention includes a DC power supply (1) and a switching circuit including at least one switching element, and converts a DC power supplied from the DC power supply (1) by a switching operation of the switching circuit into an AC power. An AC conversion circuit (2) that converts power, a discharge tube (3) connected to the output terminal of the AC conversion circuit (2), and a dimming signal output from a dimming signal generation circuit (4) A dimming control circuit (7) for intermittently generating an AC output of the conversion circuit (2) to adjust the luminance of the discharge tube (3). This discharge lamp lighting device consists of a tube current detection circuit (5) that detects the tube current (1) flowing through the discharge tube (3), and a dimming switching circuit (9) connected to the tube current detection circuit (5). The dimming switching circuit (9) is configured to supply the dimming signal (V _B ) effectively from the dimming signal generation circuit (4) to the dimming control circuit (7), and to switch the conduction state to an AC state. An invalid state in which the AC output of the conversion circuit (2) is intermittently generated and the dimming signal (V _B ) supplied from the dimming signal generation circuit (4) to the dimming control circuit (7) is invalidated Switching means (95) for continuously generating the AC output of the AC conversion circuit (2) by switching to the above, starting signal generating means (93) for generating a starting signal when the power is turned on, and starting signal generating means (93). ) Generates a start signal, cancels the switching means (95), and switches when the detected current value of the tube current detection circuit (5) is higher than the reference value. And a state switching means (96) for switching the stage (95) to a permissible state in which the stage (95) is brought into a conductive state, and a dimming switching circuit (9) at startup when almost no tube current () flows in the discharge tube (3). The dimming signal (V _B ) given from the dimming signal generation circuit (4) to the dimming control circuit (7) is invalidated by the AC output (V is continuously discharged from the AC conversion circuit (2). As a result, the necessary and sufficient excitation energy is supplied to the discharge tube (3) quickly at the time of startup, and the discharge tube (3) can be turned on with a desired brightness in a short time. BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a circuit block diagram showing an embodiment of a discharge lamp lighting device according to the present invention. FIG. 2 is an electric circuit diagram showing an internal configuration of each circuit block in FIG.

Fig. 3 is a waveform diagram showing the voltage and current of each part of the circuit of Fig. 1.

FIG. 4 is an electric circuit diagram showing a modified embodiment of FIG.

Fig. 5 is a circuit block diagram showing a conventional discharge lamp lighting device.

Fig. 6 is an electric circuit diagram showing the internal configuration of each circuit block in Fig. 5. Fig. 7 is a waveform diagram showing the voltage and current of each part of the circuit of Fig. 5 when dimming operation is not performed.

FIG. 8 is a waveform diagram showing the voltage and current of each part of the circuit of FIG. 5 when performing the dimming operation.

Hereinafter, an embodiment of a discharge lamp lighting device according to the present invention will be described with reference to FIGS. In FIG. 1 to FIG. 4, substantially the same parts as those shown in FIG. 5 to FIG. 8 are denoted by the same reference numerals, and description thereof will be omitted.

The discharge lamp lighting device of the present embodiment, as shown in FIG. 1, the period T _c dimming (Figure 3) the tube current detecting circuit (5) does not detect the tube current I _t of the cold cathode tube (3) disabled and to generate a continuous manner alternating voltage V _L from the AC conversion circuit (2) by the dimming signal V _B applied to the signal generating circuit (4) or al dimming control circuit (7), the tube current detecting circuit Figure 5 shows that the dimming switching circuit (9) that drives the dimming control circuit (7) when the tube current of the cold cathode tube (3) is detected by (5) is connected to the tube current detection circuit (5). Is different from the conventional discharge lamp lighting device shown in FIG.

As shown in FIG. 2, the dimming switching circuit (9) includes a Wansho Ttoparusu generator as an activation signal generating means for generating an activation signal V _P of the single pulse when turning on the power switch (not shown) (93), The output terminal is connected to the input terminal of the AND gate (71) of the dimming control circuit (7), and the dimming signal generation circuit (4) is connected to one input terminal. An RS flip-flop as a state holding means having a gate (95), an output terminal connected to the other input terminal of the OR gate (95), and a reset terminal connected to the one-shot pulse generator (93). (94), a comparator (92) as a comparison means for applying an output to the set terminal of the RS flip-flop (94), and a minimum detection value of the tube current IL flowing through the cold-cathode tube (3). And a reference power supply (91) for generating a reference voltage V _K2 . The reference power supply (91), the comparator (92) and the RS flip-flop (94) are connected to a state switching means (96) between the tube current detection circuit (5) and the dimming control circuit (7). Is composed. The state switching means (96) includes a cancel state in which the OR gate (95) is invalidated when the one-shot pulse generator (93) generates a start signal, and a detection current value of the tube current detection circuit (5). When the value is higher than the reference value, the OR gate (95) is switched to the permissible state in which it is turned on. The OR gate (95) is switched between a conductive state and an invalid state. When the OR gate (95) is switched to a conductive state, the RS flip-flop (94) is in an allowable state, and the dimming signal generation circuit ( the dimming signal V _B 4) from the dimming control circuit (7) by effectively supplied intermittently generating an AC output of the ac converter (2). When the OR gate (95) is switched to the invalid state, the RS flip-flop (94) enters the canceling state, and the dimming signal supplied from the dimming signal generation circuit (4) to the dimming control circuit (7). disable optical signal V _B, continuously generates the AC output of the AC converter (2).

Comparator evening (92) generates a non-actuation signal V _E2 of the low voltage (L) level when lower than the reference voltage V _R2 of the detection voltage V _F is a reference power supply (91) of the tube current detecting circuit (5), tube current detection voltage V _F of the detection circuit (5) generates a reference voltage V _R2 or more when a high voltage (H) level activation signal V _E2 of the reference power supply (91). R- S flip-flop (94) is reset (cancel state) when the activation signal V _P is inputted to the reset terminal (R) from Wanshi yacht pulse generator (93) and the output signal of the comparator (92) Since the reset state (cancelled state) is maintained while V _E2 generates a low voltage (L) level inactivation signal, the OR gate (95) is in an invalid state. Further, R - S flip-flop (94) is higher than the reference voltage V _R2 of the detection voltage V _F is the reference power supply of the tube current detecting circuit (5) (91), comparator one motor (92) is set terminal (S ) Is switched to the set state (permissible state) when the high voltage (H) level operation signal _VE2 is generated. Therefore, OR gate Bok (9 5) is rendered conductive, R - S logical sum of the dimming signal V _B of the inverted output signal V _Q and adjusting optical signals generating circuit (4) of the flip-flop (94) The signal _Vc is output.

The reference voltage V _R2 of the reference power supply (91) of the dimming switching circuit (9) is set to a value lower than the reference voltage V _R1 of the reference power supply (61) of the tube current control circuit (6). Further, the AND gate (71) of the dimming control circuit (7), the dimming switch circuit (9) current control signal output from the logic sum signal V _c and the tube current control circuit (6) output from the V outputs a logical product signal V _D and _a. The other configuration is substantially the same as the conventional discharge lamp lighting device shown in FIG.

In the above configuration, when a power switch (not shown) is turned on at the time (FIG. 3) and the power is turned on, a one-shot pulse start signal V _P from the one-shot pulse generator (93) in the dimming switching circuit (9) is obtained. Is output to the reset terminal (R) of the RS flip-flop (94), and the RS flip-flop (94) is in a reset state, that is, a cancel state. You. At the same time, as shown in FIG. 3 (A), the frequency (several tens [Hz]) is sufficiently lower than the frequency (several tens to several hundreds [kHz]) of the current control signal _VA of the tube current control circuit (6). and a cold cathode tube extent) (output from the desired rectangular pulse train of the dimming signal V _B the dimming signal generating circuit having a duty ratio corresponding to the luminance of 3) (4), the dimming switch circuit (9) in OR gate (95). As shown in Fig. 3 (D), almost no tube current flows through the cold-cathode tube (3) during the dark start period T _e from when the power is turned on until the start of lighting, and the tube current detection circuit (5) low fried than the reference voltage V _R2 of the reference power supply in the detection voltage V _F is the dimming switching circuit (9) (91), the output signal V _E2 of the low voltage (L) level from the comparator (92) is output. Therefore, the output inverted output signal V _Q of the inverted output terminal from a high voltage (H) level in the reset state RS flip opening-up to hold the (cancel state) (94), the input to the OR gate one preparative (95) Is done. As a result, as shown in FIG. 3 (B), the OR gate (95) in the invalid state outputs a logical sum signal V _e having a constant positive voltage level to the AND gate (71) of the dimming control circuit (7). since granted, the dimming signal V _B from the dimming signal generating circuit (4) is disabled, the dimming control circuit (7) does not perform the dimming operation of the cold cathode tube (3). Therefore, the tube current control circuit (6) from the dimming control circuit (7) the AND gate one preparative (71) to the dimming control circuit continuously input the current control signal V _A is as AND signal V _D of (7) output from the drive signal V _s is continuously applied to the rectangular wave voltage generation circuit of the AC converter (2) in the driving circuit (8) (21). As a result, the rectangular wave voltage generation circuit (21) in the AC conversion circuit (2) is continuously driven, and the cold-cathode tube (3) is connected via the series resonance circuit (24) as shown in FIG. High voltage sine wave AC voltage VL is supplied continuously.

At time t _2, the Figure 3 starting tube current I flows as shown in (D) the cold cathode tube (3) starts lit, the detection voltage V _F dimming switching circuit of the tube current detecting circuit (5) When the reference voltage V _R2 of the reference power supply (91) in (9) exceeds the reference voltage V _R2 , a high voltage (H) level output signal V _E2 is output from the comparator (92), and the set terminal of the RS flip-flop (94) (S) is input, and the RS flip-flop (94) is set, that is, allowed. In this case, R - because S flip port Tsu inverted output signal V _Q of the inverted lower the output terminal voltage (L) level-flop (94) is output, OR gate one preparative (95) is switched to a conductive state , and FIG. 3 (B) time 1 ₂ after as shown in the 〇 R gate one Bok (95) from the dimming signal V _B is the logical sum signal of FIG. 3 tone shown in (a) optical signal onset raw circuit (4) is output as V _R, dimming control a circuit (7) Provided to the ND gate (71). Therefore, the AND gate (71) of the current control signal V _A dimming control circuit of the tube current control circuit intermittently in a cycle of the dimming signal V _B of the dimming signal generating circuit (4) (6) (7) It is output as a logical product signal V _D, the AC conversion circuit from the drive circuit (8)

(2) drive signal V _G to the rectangular wave voltage generating circuit (21) in the given intermittently. This ensures that the intermittently driven in a cycle of the rectangular wave voltage generating circuit in the AC converter (2) (21) the dimming signal V _B, Figure 3 via the series resonant circuit (24) (C) sinusoidal alternating voltage of the high pressure is intermittently fed in a cycle of the dimming signal V _B to the cold cathode tube (3) as shown in. Therefore, cold cathode tubes (3) lighting start mode 1 ₂ and later, the tube current IL continues to flow intermittently to the cold cathode tube (3) As shown in FIG. 3 (D), a cold cathode tube (3) dimming operation of the cold cathode tube (3) is carried out but repeating the flashing cycle of the dimming signal V _B. At the same time, the tube current I [_ flowing through the cold cathode tube (3) is kept substantially constant by the tube current control circuit (6), so that the brightness of the cold cathode tube (3) is always constant.

In the present embodiment, during start-up when almost no tube current flows through the cold-cathode tube (3), that is, during the black start-up period _Tc , the dimming switching circuit (9) controls the dimming signal from the dimming signal generation circuit (4). since the dimming signal V _B to be applied to the optical control circuits (7) becomes invalid, it is not performed dimming operation of the cold cathode tube (3) by the dimming control circuit (7). As a result, the AC voltage VL of the AC conversion circuit (2) is continuously and rapidly supplied to the cold-cathode tube (3), so that the excitation energy necessary and sufficient for lighting is quickly supplied to the cold-cathode tube (3). Can be supplied. The lighting after the start of the cold cathode tube (3) is, the dimming signal V _B from the dimming signal generating circuit (4) is applied to the dimming control circuit (7), the dimming control circuit (7) by cold Since the dimming operation of the cathode tube (3) is performed, the cold cathode tube

(3) can be turned on with any brightness. Therefore, the cold-cathode tube (3) can be turned on with a desired brightness in a short time. Indeed, if you set the ON duty of the dimming signal generating circuit (4) dimming signal outputted from the V _B into 5 0 [%], the start of lighting the cold-cathode tube (3) from device startup t, The time T _e until time ₂ was reduced to about half of the same time T _{B in} the case of the conventional discharge lamp lighting device shown in FIGS. 5 and 6.

FIG. 4 shows a voltage-to-frequency converter that generates a current control signal _VA with a fixed ON width in which the OFF period of the rectangular pulse train changes according to the level of the error voltage _VE1 output from the error amplifier (62). A modified embodiment using a pulse frequency modulation type tube current control circuit (6) having (65) is shown in the figure. Embodiments of the present invention are not limited to the above embodiments, and various modifications are possible. For example, in the above-described embodiment, the AC conversion circuit (2) is configured by the square wave voltage generation circuit (21) and the series resonance circuit (24) including the leakage transformer (22) and the resonance capacitor (23). A single winding coil is used in place of the leakage transformer (22), and the turns ratio of the output transformer in the rectangular wave voltage generation circuit (21) is set to about 100 to set up the AC conversion circuit (2). You may comprise. Further, a chopper circuit may be provided in place of the rectangular wave voltage generation circuit (21), and a self-excited transistor inverter circuit may be connected to the output side of the chopper circuit to constitute the AC conversion circuit (2). In the above embodiment, the tube current detection circuit (5) is composed of the tube current detection resistor (51), the rectifier diode (52) and the smoothing capacitor (53). A circuit (current-voltage conversion circuit) may be used. Moreover, the tube current detecting circuit in the embodiment (5) of the detected voltage V _F pulse width modulation for outputting a current control signal V _A of the rectangular pulse train is on duty changes according to the level of the (P WM) It was used a tube current control circuit of the type (6), pulse frequency modulation for outputting a rectangular pulse train of a current control signal V _a which changes its frequency in accordance with the level of the detection voltage V _F of the tube current detection circuit (5) (PFM) type tube current control circuit (6) may be used. In the above embodiment, the switching means in the dimming switching circuit (9) is configured by an OR gate (95).-The switching means is configured by using a switching element such as a transistor, a resistor, and the like. S flip-flop (94) is Suitsuchi ring element are turned off by the dimming signal generating circuit (4) for blocking the dimming signal V _B from both a positive voltage level constant signal the dimming control circuit when the reset state granted to (7), R- S flip opening-up (94) regulates the dimming signal V _B from the Suitsuchingu element in the oN state when it is switched to the set state by the dimming signal generating circuit (4) It may be provided to the light control circuit (7). In addition, instead of the one-shot pulse generator (93) in the dimming switching circuit (9), a differentiating circuit composed of a resistor and a capacitor and an inverter are used, and when the power is turned on, the differential circuit outputs the signal via the inverter. The differentiated pulse signal to be applied may be applied to the reset terminal (R) of the RS flip-flop (94). Industrial potential

The discharge lamp lighting device of the present invention is a liquid discharge lamp mounted on a liquid crystal television, a notebook PC, or the like. It is suitable for use as a cold cathode tube or the like for a backlight of a crystal display device. In particular, the effect of the present invention is obtained when the dimming signal with a small ON-duty is applied to the dimming control circuit or when the discharge lamp is left in a cool and dark place without being turned on for a long period of time. Appears prominently.

Claims

The scope of the claims

1. A DC power supply, an AC conversion circuit having a switching circuit including at least one switching element, and converting DC power supplied from the DC power supply into AC power by a switching operation of the switching circuit; A discharge tube connected to the output terminal of the conversion circuit; and a dimming signal that is intermittently generated by the dimming signal output from the dimming signal generation circuit to adjust the luminance of the discharge tube by generating the AC output of the AC conversion circuit intermittently. A discharge lamp lighting device having a light control circuit;

A tube current detection circuit for detecting a tube current flowing through the discharge tube;

A dimming switching circuit connected to the tube current detection circuit,

The dimming switching circuit switches to a conductive state in which a dimming signal is effectively supplied from the dimming signal generation circuit to the dimming control circuit to intermittently generate an AC output of the AC conversion circuit. Switching means for switching to an invalid state in which a dimming signal supplied from the dimming signal generation circuit to the dimming control circuit is invalidated and continuously generating an AC output of the AC conversion circuit;

A start signal generating means for generating a start signal at power-on,

A canceling state in which the switching means is disabled when the starting signal generating means generates a starting signal; and a permission state in which the switching means is turned on when the detected current value of the tube current detection circuit is equal to or more than a reference value. A discharge lamp lighting device, comprising: a state switching unit configured to switch between a state and a state.

2. The state switching means generates a non-operation signal when the detected current value of the tube current detection circuit is lower than a reference value, and operates when the detection current value of the tube current detection circuit is equal to or more than the reference value. Comparison means for generating

When the activation signal generating means generates an activation signal, the state becomes a canceling state, and during the period when the comparing means generates the non-operation signal, the state switching means is kept in the canceling state, and the comparing means generates an operation signal. 2. The discharge lamp lighting device according to claim 1, further comprising: a state holding unit that switches the state switching unit to an allowable state.

3. A tube current control circuit that outputs a current control signal for controlling an AC output of the AC conversion circuit and adjusts a detection current value of the tube current detection circuit to a preset current value. The discharge lamp lighting device according to claim 1, further comprising:

4. The dimming signal generation circuit outputs the dimming signal having a frequency sufficiently lower than a switching frequency of the AC conversion circuit and a duty ratio corresponding to a desired luminance of the discharge tube. The discharge lamp lighting device according to any one of claims 1 to 3.

5. The dimming control circuit includes a gate unit that continuously or continually outputs a current control signal of the tube current control circuit according to an output signal of the dimming switching circuit. 2. The discharge lamp lighting device according to item 1.

6. The discharge device according to any one of claims 3 to 5, wherein the tube current control circuit outputs the current control signal that changes an on-duty according to a voltage level of a detection signal of the tube current detection circuit. Lighting device.

7. The discharge lamp lighting according to any one of claims 3 to 5, wherein the tube current control circuit outputs the current control signal that changes a frequency according to a voltage level of a detection signal of the tube current detection circuit. apparatus.