JPH11262256A - Power unit and electric discharge lamp turning-on device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the power supply efficiency of a power unit by suppressing the power supply loss of the unit to be within the full fluctuating range of the power supply voltage of a DC power source. SOLUTION: A power supply voltage detecting circuit 10 detects the power supply voltage of a DC power source E and outputs a detection output to an electric discharge lamp control circuit 6 and a frequency switching circuit 11. The circuit 11 switches the switching frequency (f) of the switching element of a converter circuit 1 into a frequency f1 or f2 (f2 <f1 ), by outputting a switching signal to a converter driving circuit 9 in accordance with the detection output of the circuit 10. Since the switching frequency (f) is switched in accordance with the detection output, so that the duty of the switching element lies within a range within which the efficiency η of the converter circuit 1 can be maintained at a prescribed value or higher, the efficiency η of the converter circuit 1 can be improved by reducing the power loss of the circuit 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply device having a voltage conversion means for converting a power supply voltage of a DC power supply into a desired DC voltage and supplying the DC voltage to a load means, and a load using such a power supply. The present invention relates to a discharge lamp lighting device for lighting a certain discharge lamp.

[0002]

2. Description of the Related Art FIG. 13 is a block diagram showing an example of a conventional power supply device (discharge lamp lighting device), in which a power supply voltage of a DC power supply E is converted into a desired DC voltage and supplied to a load unit 2. A converter circuit 1 is provided. Also,
The load unit 2 includes a discharge lamp La, an inverter circuit 3 that converts a DC voltage Vdc supplied from the converter circuit 1 into an AC voltage and supplies the AC voltage to the discharge lamp La, and a starting circuit 4 that applies a starting voltage to the discharge lamp La. And The control circuit 5 'detects the DC voltage Vdc and the DC current Idc supplied from the converter circuit 1 to the inverter circuit 3 with the detection resistor Rs,
As the DC voltage output from the converter circuit 1 according to the detection value becomes a desired value, and controls the duty of the switching elements SW _1, comprising the converter circuit 1 (ON duty ratio), the inverter circuit 3 By controlling the oscillating frequency, a series of operation controls from start to lighting of the discharge lamp La are performed.

FIG. 14 shows an example of a specific circuit configuration of the conventional device using a so-called flyback type converter circuit 1 and a full bridge type inverter circuit 3. A power supply capacitor C ₁ and a series circuit of a primary winding of a transformer T and a switching element SW ₁ are connected in parallel between both poles of the DC power supply E. The capacitor C ₁₁ is connected via the diode D ₁ of the rectifier to the secondary winding of the transformer T. Further, a detection resistor Rs is connected between a connection point between the diode D ₁ and the capacitor C ₁₁ and the inverter circuit 3.

[0004] Thus, the output voltage Vdc and the output current Idc of the converter circuit 1 is detected by the resistor Rs so that a predetermined value, the control circuit 5 'is varied the duty of the switching element SW ₁ of the converter circuit 1 It is. That is, if the detection voltage or the detection current increases,
To lower the output of the switching element converter circuit 1 by reducing the duty of the SW _1, the smaller the detected voltage or the detected current, it is to increase the output of the converter circuit 1 by increasing the duty of the switching elements SW _1.

On the other hand, the inverter circuit 3 is a full-bridge type having four switching elements SW _{11 to} SW ₁₄ , and each pair of switching elements SW ₁₁ , SW ₁₂ , SW ₁₃
An inductor L ₁₁ and a series circuit of a capacitor C ₂₁ of the filter between the connection point of the SW ₁₄ is connected, a series circuit of the starting circuit 4 across the capacitor C ₂₁ discharge lamp La is connected. The starting circuit 4 has a capacitor C ₂₁ on the secondary side.
A pulse voltage is applied when the discharge lamp La is started via a pulse transformer PT connected between the discharge lamp La and the discharge lamp La. The discharge lamp La is a discharge lamp such as a xenon metal halide lamp.

FIG. 15 shows another example of the specific circuit configuration of the above-mentioned conventional device using a so-called two-stone (or half-bridge) converter circuit 1 and a full-bridge inverter circuit 3. In this converter circuit 1, a series circuit of a pair of switching elements SW ₁ and SW _{2 and} a series circuit of a pair of capacitors C ₂ and C ₃ are connected in parallel, and a connection point of the switching elements SW ₁ and SW ₂ and a capacitor C ₂ , C
With the primary winding of the transformer T is connected between the _third connection point, through the inductor L ₁ of the filter and the power source capacitor C ₁ and the DC power source E is connected in parallel across the capacitor C ₂ of the low-side , even more secondary windings through the parallel circuit of the diode D ₁ and capacitor C ₁₂ diode D ₃ and diode D ₂ and the capacitor C of the transformer T
₁₁ are connected and configured. Here, the diodes D ₁ to
D ₃ and capacitor C _11, C ₁₂ constitute a double rectification circuit. Note that the configuration of the inverter circuit 3 is the same as that shown in FIG.

In the above-mentioned conventional device, the efficiency η of the converter circuit 1 (= the output of the converter circuit 1) when the power supply voltage of the DC power supply E fluctuates between 0.5 and 1.5 times the rated voltage Vs. FIG. 16 shows the characteristics of (power / input power).
Shown in For example, when the optimum design is performed so that the maximum efficiency is obtained when the power supply voltage is near the rated voltage Vs, as is apparent from FIG.
The efficiency η is as low as 0.5 times s (at low voltage).
Is greatly reduced.

On the other hand, shows the relationship between the converter circuit 1 of the duty of the switching elements SW ₁ (on-duty ratio) (%) and the power supply voltage when the supply voltage varies as described above of the DC power source E in FIG. 17 . As is clear from FIG. 17, only at the time of the low voltage of the power supply voltage duty becomes very large, varying the duty of the switching elements SW _1, comprising the converter circuit 1,
It can be seen that there is a limit to improving the efficiency of the power supply device in a wide range of operating power supply voltage (power supply voltage fluctuation range of the DC power supply E: 0.5 Vs to 1.5 Vs).

[0009]

Generally, the power supply efficiency (= load power / input power) of a power supply device such as the above-mentioned conventional device.
Is considered to greatly depend on the efficiency η of the converter circuit 1. Therefore, when the DC power supply E has a large impedance like a battery or when such a power supply device is used as a discharge lamp lighting device for a vehicle, the power supply of the DC power supply E Voltage fluctuations and fluctuation widths are large, and it is difficult to suppress power loss (input power-load power) in the entire range of the power supply voltage and to improve power supply efficiency. Therefore, there is naturally a limit in reducing the size of these power supply devices and the discharge lamp lighting device while maintaining the performance of the conventional (current), or improving the reliability with the same shape or size as the conventional one.

The present invention has been made in view of the above circumstances, and an object of the present invention is to improve power supply efficiency by suppressing power loss within the entire fluctuation range of the power supply voltage of a DC power supply. A power supply device and a discharge lamp lighting device are provided.

[0011]

According to the first aspect of the present invention, in order to achieve the above object, a DC power supply, a power supply voltage of the DC power supply is utilized by utilizing a voltage conversion operation of a transformer and a switching operation of a switching element. A voltage converting unit that converts the voltage into a predetermined DC voltage and supplies the DC voltage to the load unit; a DC voltage detecting unit that detects a DC voltage supplied from the voltage converting unit to the load unit; Control means for varying the duty of the switching element so that the DC voltage supplied to the load means is at a desired level, power supply voltage detection means for detecting a power supply voltage of the DC power supply, and power supply voltage detection means In accordance with the detection output of the above, so that the duty of the switching element falls within a range in which the conversion efficiency of the voltage conversion means can be maintained at a predetermined value or more. The switching frequency of the switching element is characterized in that a frequency varying means for varying,
The power supply efficiency can be improved by suppressing the power loss within the entire fluctuation range of the power supply voltage of the DC power supply.

According to a second aspect of the present invention, in the first aspect, the duty range of the switching element is set to 15%.
It is characterized by the above and 85% or less, and it is possible to improve the power supply efficiency by suppressing the power supply loss within the entire fluctuation range of the power supply voltage of the DC power supply. According to a third aspect of the present invention, in the first or second aspect, the discharge lamp, an inverter circuit that converts a DC voltage supplied from the voltage converting means into an AC voltage and supplies the AC voltage to the discharge lamp, A discharge lamp lighting device capable of improving power supply efficiency by suppressing power loss within the entire fluctuation range of the power supply voltage of the DC power supply. realizable.

According to a fourth aspect of the present invention, in the first aspect of the present invention, the frequency variable means switches the switching frequency of the switching element in two stages, and is a preferred embodiment of the present invention. According to a fifth aspect of the present invention, in the first or second aspect of the present invention, the frequency variable means switches the switching frequency when a power supply voltage detected by the power supply voltage detection means is 60% or more of a rated voltage of the DC power supply. The power supply efficiency can be improved by suppressing power loss particularly in a range where the power supply voltage is lower than the rated voltage.

According to a sixth aspect of the present invention, in the first aspect of the present invention, the frequency varying means switches the switching frequency of the switching element in three or more steps, and is a preferred embodiment of the present invention. According to a seventh aspect of the present invention, in the first aspect of the present invention, the frequency varying means continuously varies a switching frequency of the switching element, and is a desirable embodiment of the present invention.

According to an eighth aspect of the present invention, in the first aspect, the range of the duty of the switching element is set to 45%.
This is a preferred embodiment of the present invention, characterized in that it is not less than 55%. According to a ninth aspect of the present invention, in the third aspect of the present invention, the frequency variable means stops the operation of changing the switching frequency when the discharge lamp is started, and determines the duty range of the switching element. It is possible to eliminate the possibility of insufficient starting power at the time of starting the discharge lamp, to improve the efficiency of the voltage conversion means without hindering the stable lighting of the discharge lamp and instantaneous startup of the luminous flux.

According to a tenth aspect of the present invention, in the third aspect of the present invention, there is provided an inverter control means for controlling the oscillation frequency of the inverter circuit so that the light output of the discharge lamp becomes substantially constant. 2 is a preferred embodiment of the present invention. According to an eleventh aspect of the present invention, in the tenth aspect, the inverter control means reduces the output to the discharge lamp when the detection output of the power supply voltage detection means is equal to or less than a predetermined value. Thus, the stress of the discharge lamp lighting device can be reduced with respect to a load change when the discharge lamp is abnormal or the like, and safety can be improved.

According to a twelfth aspect of the present invention, in the first or second aspect, there is provided a means for switching a turn ratio of the transformer in accordance with a detection output of the power supply voltage detecting means. Thus, the efficiency of the voltage conversion means can be improved. According to a thirteenth aspect, in the third aspect, the rated voltage of the DC power supply is approximately 12 V;
In addition, the discharge lamp is a xenon metal halide lamp, and the frequency varying means reduces the switching frequency of the switching element when the power supply voltage detected by the power supply voltage detection stage is 8 V or more. This is a preferred embodiment of the present invention.

According to a fourteenth aspect, in the third aspect, the rated voltage of the DC power supply is approximately 24 V, and the discharge lamp is a xenon metal halide lamp.
The frequency varying means is characterized in that the switching frequency of the switching element is reduced when the power supply voltage detected by the power supply voltage detection stage is 16 V or more,
2 is a preferred embodiment of the present invention.

[0019]

(Embodiment 1) FIG. 1 shows Embodiment 1 of the present invention.
FIG. 2 shows a specific circuit diagram. The present embodiment is a discharge lamp lighting device in which a load unit 2 of a power supply device has a discharge lamp La, and has a basic configuration of a conventional example, in particular, a discharge lamp having a so-called half-bridge type converter circuit 1 shown in FIG. Since they are common to the electric light lighting device, the common parts are denoted by the same reference numerals and description thereof will be omitted, and only the configuration and operation of the control circuit 5 which is a feature of the present embodiment will be described. The discharge lamp La in the present embodiment is a xenon metal halide lamp as in the conventional example.

As shown in FIGS. 1 and 2, the control circuit 5 in the present embodiment includes a discharge lamp lighting control circuit 6, an inverter drive circuit 7, a voltage / current detection circuit 8, a converter drive circuit 9, a power supply voltage detection circuit 10 And frequency switching circuit 11
It has. The inverter drive circuit 7 turns on and off four switching elements SW _{11 to} SW _{14 included} in the inverter circuit 3 based on a control signal from the discharge lamp lighting control circuit 6. Further, the voltage / current detection circuit 8
Is for detecting a DC voltage Vdc and a DC current Idc supplied from the converter circuit 1 to the inverter circuit 3 by a detection resistor Rs inserted between the converter circuit 1 and the inverter circuit 3. Further, the converter driving circuit 9
Is a pair of switching elements SW included in the converter circuit 1 based on a control signal from the discharge lamp lighting control circuit 6.
₁ and SW ₂ are turned on and off.

The discharge lamp lighting control circuit 6 controls the converter driving circuit 9 so that the output voltage Vdc and the output current Idc of the converter circuit 1 become desired values in accordance with the detection output of the voltage / current detection circuit 8. Controlled switching element SW
The oscillation of the inverter circuit 3 is performed in order to vary the duty of ₁ and to control a series of operations from the start to the lighting of the discharge lamp La (operation of lighting with high output immediately after lighting and then rated lighting). and variably controlling the AC power supplied from the inverter circuit 3 to the discharge lamp La frequency (four switching frequency of the switching elements SW ₁₁ to SW ₁₄₎ variable manner. Although not described in detail, the discharge lamp lighting control circuit 6 also has a function of protecting the circuit when the discharge lamp La is abnormal.

On the other hand, the power supply voltage detection circuit 10
Detects the power supply voltage of E and outputs the detected output to the discharge lamp lighting control circuit
6 and the frequency switching circuit 11. Ma
In addition, the frequency switching circuit 11 detects the power supply voltage
Output switching signal to converter drive circuit 9 according to output / output
And the switching element SW included in the converter circuit 1.
₁, SW_TwoThe switching frequency f
₁, F_Two(F_Two<F₁), For example
For example, as shown in FIG.
If the rated voltage is lower than α (≧ 0.6) times,
The switching frequency f₁And the power supply voltage is higher than αVs
The switching frequency f_TwoSwitch to. However
Then, in the present embodiment, as shown in FIG.
The switching of the switching frequency f has hysteresis.
You.

FIG. 3 shows this embodiment having the above-mentioned hysteresis.
Power supply voltage detection circuit 10 and frequency switching circuit 11
3 is a diagram showing a specific circuit configuration of FIG. This power supply voltage detection circuit
10 is a comparator CP, a resistor R₁~ R_Five, Reference power supply
Vr or the like. Inverting input of comparator CP
At the end, a resistor R for dividing the power supply voltage₁, R_TwoConnection point
Connected. Also, the non-inverting input terminal of the comparator CP
Is the resistance R_FiveThe positive electrode of the reference power supply Vr is connected via
With resistance R_Three, R_FourControl power supply Vcc is connected via
And the resistance R_Three, R_FourConnection point of the comparator CP
Is connected to the output end of the
Threshold voltage V₁(= Α₁Vs), V_Two(= Α_TwoVs)
Is set. However, as shown in FIG.
0.6 ≦ α ₁<Α_TwoAnd hence V₁<V_TwoBecomes

[0024] Thus to the detected voltage (power supply voltage) when exceeds the threshold voltage V ₂ of the higher rises the comparator CP
Output along with changes from H level to L level, changes to the value V ₁ of the lower from the value V ₂ towards the threshold voltage is high. Conversely, the output of the detection voltage (power supply voltage) falls below the threshold voltage V ₁ of the lower reduced comparator CP changes from L level to H level, the value of the direction the threshold voltage is lower V changes from ₁ higher in value V ₂ of.

On the other hand, the frequency switching circuit 11 is composed of a switching element Q ₁ consisting of NPN type bipolar transistor and a resistor R _6, power source voltage switching device Q output via a resistor R ₆ of the comparator CP of the detection circuit 10 is input to the _first base, the output of the comparator CP is the switching element Q ₁ is turned on at the H level, the output of the comparator CP is the switching element Q ₁ is turned off when the L-level. This switching element Q
And _first collector is connected to the converter drive circuit 9, when the switching element Q ₁ is frequency f is f ₁ next to the drive signal output from the converter drive circuit 9 when on, the switching element to Q ₁ Off The frequency f of the drive signal output from the converter drive circuit 9 becomes f _2, and the switching frequency f of the switching elements SW ₁ and SW ₂ of the converter circuit 1 according to the level of the power supply voltage.
Are switched to two stages of f ₁ and f ₂ . By providing the switching frequency f with hysteresis, there is an advantage that the stress applied to the circuit element due to chattering or the like at the time of switching the switching frequency f can be reduced.

[0026] Figure 6 shows a power supply voltage in the present embodiment, the duty of the switching elements SW ₁ to the converter circuit 1 is provided, the relationship between the switching frequency f, the curve b is the switching frequency f and f ₁ If
Curve b is a case where the switching frequency f was f _2. As it can be seen from the figure, setting the switching frequency f of the converter circuit 1 so as to use the duty range of the switching elements SW ₁ to 85% or less, the power supply voltage during a low voltage lower than the rated voltage Vs, switching Since it is more appropriate to set the frequency f to the higher value f ₁ , the switching frequency f is set to f ₁ when the power supply voltage is in the range of 0.5 to α times the rated voltage Vs in this embodiment. When the power supply voltage is in the range from α times to 1.5 times the rated voltage Vs, the switching frequency f is switched to f ₂ .

FIG. 5 shows the relationship between the power supply voltage and the efficiency η [%] of the converter circuit 1 when this embodiment is operated as described above, and the curve A shows the switching frequency f as f ₁ . In this case, the curve b changes the switching frequency f to f ₂
Is the case. Here, a field effect transistor (FET) is used for the switching elements SW ₁ and SW ₂ of the converter circuit 1 and the switching frequency f is set to 100.
[KHz] to about 200 [kHz].

As is apparent from FIG. 5, when the power supply voltage is lower than α times the rated voltage Vs, the switching frequency f of the converter circuit 1 is switched to a high value f ₁ and the power supply voltage is reduced to the rated voltage Vs. by the time higher than α times the Vs switching the switching frequency f to a low value f _2, the efficiency η of the converter circuit 1 by reducing the power loss in the converter circuit 1, in particular the supply voltage to improve the efficiency η when low It becomes possible. However, the switching elements SW _1, SW ₂ is capable of the same effect be a bipolar transistor, also, for the switching frequency f, the switching elements SW _1,
Although largely depends on the SW ₂ and the transformer T, the number 1
The same effect can be obtained even when the frequency is set to 00 [Hz] to several tens [MHz]. In the present embodiment, the case where the power supply voltage of the DC power supply E fluctuates in the range of 0.5 to 1.5 times the rated voltage Vs is exemplified, but this can be used as a power supply device and a discharge lamp lighting device. There is no particular limitation as long as it is within the range.

As described above, according to the present embodiment, the converter circuit 1 according to the detection output of the power supply voltage detection circuit 10
The switching frequency f of the switching elements SW ₁ and SW ₂ is switched by the frequency switching circuit 11 so that the duty of the switching element SW _{1 included in} the switching element SW ₁ is within a range capable of maintaining the efficiency η of the converter circuit 1 at a predetermined value or more. Therefore, as described above, the DC power supply E
Even when the power supply voltage fluctuates, the power loss in converter circuit 1 can be reduced, and efficiency η of converter circuit 1 can be improved, particularly, efficiency η when the power supply voltage is low. As a result, the apparatus (particularly, the transformer T, the switching elements SW ₁ ,
(SW ₂ , capacitor C _1, etc.) can be reduced in size and weight, and cost can be reduced. Further, with the same shape and dimensions as those in the related art, temperature rise and stress of circuit components can be suppressed to improve reliability. In addition, it is possible to reduce the loss of the voltage conversion means at the time of low voltage when the power supply voltage is lower than the rated voltage, and to reduce the current flowing through the switching element.
There is an advantage that the temperature rise and stress of circuit components such as W ₁ , SW ₂ and capacitor C ₁ .

[0030] Note that, by controlling the duty of the switching elements SW _1, comprising the converter circuit 1 to enter a range of 85% to 15%, making it possible to improve the efficiency η of the converter circuit 1 as described above Although it is possible, if the duty is controlled so as to fall within the range of 45% or more and 55% or less, the efficiency η of the converter circuit 1 can be further improved. However, in this case, there is a possibility that the usable range of the power supply voltage of the DC power supply E is restricted.

When the discharge lamp La is a xenon metal halide lamp and the rated voltage Vs of the DC power supply E is 12 V as in the present embodiment and the switching frequency f is switched at a power supply voltage of 8 V or more, the converter It is possible to improve the efficiency η of the circuit 1. Further, when the rated voltage Vs of the DC power supply E is 24 V, the same effect can be obtained by switching the switching frequency f when the power supply voltage is 16 V or more. The xenon metal halide lamp has a 35 W
Although there are a plurality of types having different rated outputs, such as and, 70W, etc., the same effect can be obtained in any of the types.

(Embodiment 2) In Embodiment 1, the switching frequency f switched by the frequency switching circuit 11
Although but was two stage f ₁ and f _2, when to switch to a plurality of stages between f ₁ and f ₂ as shown in FIG. 7 (a), the power supply voltage compared to the first embodiment It is possible to improve the efficiency η of the converter circuit 1 within the entire fluctuation range.

If the switching frequency f is continuously varied between f ₁ and f ₂ as shown in FIG. 7B, the switching frequency can be changed more than the multi-stage switching shown in FIG. 7A. The efficiency η of the converter circuit 1 can be improved. In addition,
The circuit configuration for changing the switching frequency f in multiple stages or continuously can be realized by using a conventionally known technique, and therefore detailed description is omitted. Further, in the present embodiment, the case where the power supply voltage of the DC power supply E fluctuates in the range of 0.5 to 1.5 times the rated voltage Vs has been described, but this can be used as a power supply device and a discharge lamp lighting device. There is no particular limitation as long as it is within the range.

[0034] (Embodiment 3) Figure 8 shows a lamp power W _La required several minutes from the start rated output of the xenon metal halide lamp 35W. That is, the discharge lamp La
Is a xenon metal halide lamp, the discharge lamp L
In order to stably light the lamp a and instantaneously start the luminous flux, the rated output (= 35) of the discharge lamp La during the period from the extinguished state to the stable lighting (time t: 0 to t ₁ ).
W) must be supplied with high power W _La than.

Therefore, in the present embodiment, the frequency switching circuit 11 is used only during the period from the start of the discharge lamp La to the rated lighting.
Is stopped so that the switching frequency f is not switched, so that a sufficient power W _La is supplied to the discharge lamp La during the period from the extinguishing state to the starting and stable lighting. The operation stop of the frequency switching circuit 11 is controlled by the discharge lamp lighting control circuit 6.

According to the present embodiment, the frequency switching circuit 1 is used only during the period from the start of the discharge lamp La to the rated lighting thereof.
1 is stopped to prevent the switching frequency f from being switched, so that the switching element SW ₁
, The possibility of shortage of rising power at the time of starting the discharge lamp La is eliminated, and the efficiency η of the converter circuit 1 is improved without hindering the stable lighting of the discharge lamp La and instantaneous rise of the light flux. Can be done. The rated output of the discharge lamp La is 35 W of the embodiment.
However, the same effect can be obtained with a discharge lamp La having another rated output.

[0037] (Embodiment 4) This embodiment, limiting the duty of the switching element SW ₁ of the converter circuit 1 is variably controlled through the converter driving circuit 9 by a discharge lamp lighting control circuit 6 at a predetermined upper limit value It is. That is, DC discharge point lighting control circuit 6 according to the supply voltage of the power source E is lowered is performed control to increase the duty of the switching elements SW _1, a predetermined upper limit duty of the switching elements SW _1, as described above When the power supply voltage is reduced, the duty is limited by the upper limit value, and when the power supply voltage is lower than the level corresponding to the upper limit value, the converter circuit 1
, The power supplied to the discharge lamp La also decreases.

Here, the upper limit value of the duty is determined according to FIG.
As shown in (a), fixed regardless of the power supply voltage (for example,
(Upper limit = 85%), or may be varied so as to decrease as the power supply voltage increases as shown in FIG. Note that such variable control of the upper limit value of the duty may be performed in the discharge lamp lighting control circuit 6 according to the detection output of the power supply voltage detection circuit 10.

[0039] By limiting the duty of the switching element SW ₁ of the converter circuit 1 as described above at a predetermined upper limit value, the power supply voltage of power loss of the converter circuit 1 during low such a lower voltage than the rated voltage Vs Can be reduced. Such an effect can be obtained in any case regardless of whether the upper limit value of the duty is fixed or changed. However, particularly when the upper limit value of the duty is changed, the abnormality of the discharge lamp La can be improved. There is an advantage that the stress of the discharge lamp lighting device can be reduced with respect to a load change at the time and the like, and safety can be improved. In the present embodiment, the power supply voltage of the DC power supply E is 0.5 V of the rated voltage Vs.
The case where the value fluctuates in the range of 2 times to 1.5 times is exemplified, but this is not particularly limited as long as it is within a range usable as a power supply device and a discharge lamp lighting device.

(Embodiment 5) FIG. 10 shows the overall configuration of the present embodiment. This embodiment is different from Embodiment 1 in that an intermediate tap 13 is provided in a transformer T 'and the power supply voltage detecting circuit 10 The control circuit 5 is provided with a tap switching circuit 12 for switching the tap of the transformer T ′ according to the detection output. Note that other configurations and operations are the same as those of the first embodiment, and thus common portions are denoted by the same reference numerals and description thereof will be omitted.

As shown in FIG. 11, a switching unit 14 is provided for switching the terminal L of the intermediate tap 13 provided on the primary winding of the transformer T 'and the terminal H at the end of the primary winding to the common terminal C. It is. On the other hand, the tap switching circuit 12 controls the switching unit 14 according to the detection output of the power supply voltage detection circuit 10 when the power supply voltage is equal to or higher than a predetermined voltage set near the rated voltage Vs as shown in FIG. The common terminal C is connected to the terminal H, and when the power supply voltage is lower than the predetermined voltage, the switching unit 14 is controlled to switch the common terminal C from the terminal H to the terminal L so as to boost the voltage of the transformer T ′. This is to increase the ratio (turn ratio).

[0042] In Thus, by the power supply voltage to increase the step-up ratio of the transformer T 'at low such low-voltage region than the rated voltage Vs, the conventional example and implement the duty of the switching elements SW ₁ in the low voltage region It can be varied around 50% compared to the first embodiment. That is, since the duty of the switching elements SW ₁ is most efficient η is increased by around 50% in the converter circuit 1, the switching element SW in the low voltage region of supply voltage as described above
By changing the duty of ₁ around 50%,
The efficiency η of the converter circuit 1 can be improved with a simple configuration in the entire range of fluctuation of the power supply voltage.

In this embodiment, the intermediate tap 13 is provided on the primary winding of the transformer T '. However, an intermediate tap may be provided on the secondary winding to switch the boost ratio on the secondary side. Further, in the present embodiment, the case where the power supply voltage of the DC power supply E fluctuates in the range of 0.5 to 1.5 times the rated voltage Vs has been described, but this can be used as a power supply device and a discharge lamp lighting device. There is no particular limitation as long as it is within the range.

[0044]

According to the first aspect of the present invention, the power supply voltage of the DC power supply is converted into a predetermined DC voltage using a DC power supply, a voltage conversion operation of a transformer, and a switching operation of a switching element, and supplied to a load means. A voltage converter, a DC voltage detector for detecting a DC voltage supplied from the voltage converter to the load, and a DC voltage supplied to the load in accordance with a detection output of the DC voltage detector. Control means for varying the duty of the switching element so as to be at the level of: a power supply voltage detection means for detecting a power supply voltage of the DC power supply; and a duty of the switching element according to a detection output of the power supply voltage detection means. The switching frequency of the switching element is changed so that the conversion efficiency of the voltage conversion means can be maintained at a predetermined value or more. Since a frequency variation means that,
There is an effect that the power loss can be suppressed and the power efficiency can be improved within the entire fluctuation range of the power supply voltage of the DC power supply. In addition, it is possible to reduce the size, weight, and cost of the device while maintaining the same performance as before, and suppress the temperature rise and stress of circuit components and reduce reliability for the same shape and size as before. There is an effect that improvement can be achieved. In addition, it is possible to reduce the loss of the voltage conversion means when the power supply voltage is lower than the rated voltage, so that the current flowing through the switching element can be reduced. Also, there is an effect that reliability can be improved by suppressing stress.

According to the second aspect of the present invention, since the range of the duty of the switching element is set to 15% or more and 85% or less, the power loss is suppressed within the entire fluctuation range of the power supply voltage of the DC power supply, thereby improving the power supply efficiency. There is an effect that it becomes possible. The invention according to claim 3 includes a discharge lamp, an inverter circuit that converts a DC voltage supplied from the voltage conversion means into an AC voltage and supplies the AC voltage to the discharge lamp, and a starting circuit that starts the discharge lamp. With the above load means,
This has the effect of realizing a discharge lamp lighting device capable of suppressing power loss and improving power efficiency within the entire fluctuation range of the DC power supply voltage.

According to a fifth aspect of the present invention, the frequency varying means varies the switching frequency when the power supply voltage detected by the power supply voltage detection means is 60% or more of the rated voltage of the DC power supply. There is an effect that it is possible to suppress power loss in a range where the power supply voltage is lower than the rated voltage and improve power supply efficiency. According to a ninth aspect of the present invention, since the frequency variable means stops the operation of changing the switching frequency when the discharge lamp is started, the shortage of the rising power at the start of the discharge lamp is determined by determining the duty range of the switching element. There is an effect that the efficiency of the voltage conversion means can be improved without hindering the stable lighting of the discharge lamp and instantaneous activation of the luminous flux.

According to an eleventh aspect of the present invention, the inverter control means reduces the output to the discharge lamp when the detection output of the power supply voltage detection means is equal to or less than a predetermined value. Therefore, there is an effect that the stress of the discharge lamp lighting device can be reduced with respect to the load fluctuation at the time of and the safety can be improved. According to the twelfth aspect of the present invention, since means for switching the turns ratio of the transformer according to the detection output of the power supply voltage detecting means is provided, the effect of improving the efficiency of the voltage converting means with a simple configuration can be obtained. is there.

[Brief description of the drawings]

FIG. 1 is an overall block diagram showing a first embodiment.

FIG. 2 is a specific circuit diagram of the above.

FIG. 3 is a specific circuit diagram of a power supply voltage detection circuit and a frequency switching circuit in the above power supply system.

FIGS. 4A and 4B are diagrams showing a relationship between a power supply voltage and a switching frequency in the above power supply system.

FIG. 5 is a diagram showing the relationship between the power supply voltage and the efficiency of the converter circuit in the above power supply system.

FIG. 6 is a diagram showing a relationship between a power supply voltage and a duty of a switching element included in the converter circuit in the above power supply system.

FIGS. 7A and 7B are diagrams illustrating a relationship between a power supply voltage and a switching frequency according to the second embodiment.

FIG. 8 is an explanatory diagram for explaining the operation of the third embodiment.

FIGS. 9A and 9B are diagrams illustrating a relationship between a power supply voltage and a duty of a switching element included in a converter circuit according to a fourth embodiment.

FIG. 10 is an overall specific circuit diagram showing a fifth embodiment.

FIG. 11 is a main part circuit diagram of the same.

FIG. 12 is an explanatory diagram for explaining the operation of the above.

FIG. 13 is a block diagram of a conventional example.

FIG. 14 is a specific circuit diagram of the above.

FIG. 15 is another specific circuit diagram of the above.

FIG. 16 is a diagram showing the relationship between the power supply voltage and the efficiency of the converter circuit in the above power supply system.

FIG. 17 is a diagram showing a relationship between a power supply voltage and a duty of a switching element included in the converter circuit in the above power supply system.

[Explanation of symbols]

 E DC power supply 1 Converter circuit 2 Load section 3 Inverter circuit 4 Starting circuit 5 Control circuit 6 Discharge lamp lighting control circuit 7 Inverter drive circuit 8 Voltage / current detection circuit 9 Converter drive circuit 10 Power supply voltage detection circuit 11 Frequency switching circuit T Transformer

Continuing on the front page (72) Inventor Akihiro Kishimoto 1048 Kadoma Kadoma, Osaka Pref.Matsushita Electric Works, Ltd.

Claims (14)

[Claims] 1. A DC power supply, a voltage conversion means for converting a power supply voltage of the DC power supply into a predetermined DC voltage by using a voltage conversion operation of a transformer and a switching operation of a switching element, and supplying the DC voltage to a load means; DC voltage detection means for detecting a DC voltage supplied from the conversion means to the load means, and a DC voltage supplied to the load means in accordance with the detection output of the DC voltage detection means, so that the DC voltage is at a desired level Control means for varying the duty of the switching element; power supply voltage detection means for detecting a power supply voltage of the DC power supply; and a duty cycle of the switching element corresponding to a detection output of the power supply voltage detection means. Frequency varying means for varying the switching frequency of the switching element so as to be in a range that can be maintained at or above a predetermined value. A power supply device comprising: 2. The power supply device according to claim 1, wherein the range of the duty of the switching element is 15% or more and 85% or less. 3. The load, comprising: a discharge lamp; an inverter circuit that converts a DC voltage supplied from the voltage conversion means into an AC voltage and supplies the AC voltage to the discharge lamp; and a starting circuit that starts the discharge lamp. The discharge lamp lighting device according to claim 1, further comprising a unit. 4. The power supply device according to claim 1, wherein said frequency varying means switches a switching frequency of said switching element in two stages. 5. The switching device according to claim 1, wherein the frequency changing unit changes a switching frequency when a power supply voltage detected by the power supply voltage detection unit is equal to or more than 60% of a rated voltage of the DC power supply. Or the discharge lamp lighting device according to 2. 6. The power supply device according to claim 1, wherein said frequency varying means switches the switching frequency of said switching element in three or more steps. 7. The power supply device according to claim 1, wherein said frequency varying means continuously varies a switching frequency of said switching element. 8. The power supply device according to claim 1, wherein a range of a duty of the switching element is set to 45% or more and 55% or less. 9. The discharge lamp lighting device according to claim 3, wherein said variable frequency means stops the operation of changing the switching frequency when starting said discharge lamp. 10. The discharge lamp lighting device according to claim 3, further comprising inverter control means for controlling the oscillation frequency of said inverter circuit so that the light output of said discharge lamp becomes substantially constant. 11. The apparatus according to claim 10, wherein said inverter control means reduces the output to said discharge lamp when the detection output of said power supply voltage detection means is equal to or less than a predetermined value.
The discharge lamp lighting device as described in the above. 12. The power supply device according to claim 1, further comprising means for switching a turn ratio of the transformer in accordance with a detection output of the power supply voltage detection means. 13. The rated voltage of the DC power supply is approximately 12 V, and the discharge lamp is a xenon metal halide lamp, and the frequency variable means detects that the power supply voltage detected by the power supply voltage detection stage is 8 V or more. 4. The discharge lamp lighting device according to claim 3, wherein the switching frequency of the switching element is reduced in such a case. 14. The rated voltage of the DC power supply is approximately 24V, and the discharge lamp is a xenon metal halide lamp, and the frequency variable means detects that the power supply voltage detected by the power supply voltage detection stage is 16V or more. 4. The discharge lamp lighting device according to claim 3, wherein the switching frequency of the switching element is reduced in such a case.