JPH01252166A - Power device - Google Patents

Abstract

PURPOSE:To keep power constant simply at low cost by setting a rated operating point to approximately half the no-load voltage. CONSTITUTION:With a power device, an input from a DC power 1 is stepped down and stabilized by a switching regulator 2 and fed to a lamp 3, and the lamp is lit at a constant power. The switching regulator 2 has a switching transistor(Tr) 21 for turning a current from the DC power 1 ON-OFF and outputting the current, a diode 22 smoothing the output current, an inductor 23, the one-Nth voltage-dividing circuit 24 of a lamp voltage VL, a resistor 25 for detection, a reference voltage source 26, an error amplifier 27 and a PWM control circuit 28. The error amplifier 27 compares the sum of the output voltage VL/N of the voltage-dividing circuit 24 and the inter-terminal voltage rIL of the resistor 26 with the voltage of the reference voltage source 25, and outputs the differential voltage as an error voltage. Accordingly, a lamp power PL is maximized when a no-load voltage V20 is halved, and an inclination is brought to zero, thus approximately preventing the change of a lamp power PL even when the load current and voltage are fluctuated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a switching regulator type power supply device, and particularly to a power supply device suitable for use in lighting a lamp with constant power.

[Prior Art] Conventionally, when configuring a constant power power supply using a switching regulator that stabilizes the output amount (voltage, current, power, etc.) by controlling the output current by pulse width control (PWM control), the load voltage and current are detected, these are input to a multiplier to obtain a voltage proportional to the electric power, and the above-mentioned PWM control is performed based on this voltage. For this reason, the circuit becomes complicated and an expensive multiplier (for example, an IC) must be used, resulting in an inconvenience that the device becomes expensive.

In order to solve the above-mentioned inconvenience, the present inventors first developed a switching element that turns on and off the current supplied from a DC power source to a load, and a peak value (2) of the output current of the switching element. , a peak current detection circuit that detects , and 1a
and a pulse generation circuit that drives the switching element at an on-duty ratio X of p−f(X),
)・We devised and filed an application for a constant power power supply device whose rated output value is the voltage and power at which X becomes the maximum value (Japanese Patent Application No. 131723/1982).

[Problem to be solved by the invention] However, in this prior application device, the load is low.

The discharge lamp (
When a lamp) is connected, constant power property is obtained when the lamp voltage is approximately 1/2 of the secondary open circuit voltage of the output transformer, but the secondary open circuit voltage (starting voltage) is generally 2 times the lamp voltage.
This is disadvantageous in that it requires more than twice the amount and has many restrictions in terms of design. Further, there is a problem in that sufficient constant power characteristics cannot be obtained with respect to input voltage fluctuations.

The present invention has been made in view of the above-mentioned problems, and is particularly characterized by providing a power supply device that exhibits constant power output characteristics regardless of changes in load over time and changes in input voltage. The purpose is to use it in a lamp lighting device to maintain the power supplied to the lamp almost constant regardless of changes in the lamp voltage over time or changes in the power supply voltage, thereby extending the lamp life. do.

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a switching regulator type power supply device in which a voltage obtained by dividing the load voltage to 1/N and a voltage obtained by multiplying the load current by a constant r are applied. A closed loop system is formed so that the voltage obtained is equal to a predetermined reference voltage, and the main switching elements are controlled by PWM.

In one embodiment of the present invention, the rated operating point is set to 1/2 of the load open circuit voltage v2o.

Further, in another aspect of the present invention, the load voltage is reduced to 1/N.
A nonlinear element is used in the voltage dividing circuit that divides the voltage into the voltage, and the voltage division ratio N is nonlinearly increased in the vicinity of the load open state.

Furthermore, in another aspect of the present invention, a lamp lighting circuit including a discharge lamp is connected as a load.

[Function] According to the above configuration, the load voltage is Vo and the load current is I. ,
When the reference voltage is V rcf', the load characteristic is V0/
N+ r I(,, -Vrcf, which is illustrated by the solid line in FIG. 2).

Also, load power P. teeth, p-v. I.

-Vo (NVr, ef -Vo)/Nr, which is illustrated by the broken line in FIG. That is, the load power P0 reaches a maximum when it is V 20/2 (however, the open circuit voltage V2.-NVref'), and the slope becomes zero, so the load voltage V in this vicinity.

Even if the load current IO fluctuates, the load power P0
remains almost unchanged. That is, the load power Po is stabilized.

Furthermore, in this power supply device, the load characteristics are constant even if the input voltage changes, and the load power P0 is stable with respect to the input voltage.

[Effect] As described above, according to the present invention, in particular, the rated operating point is set to approximately 1 of the load open voltage V 20 (=N V rel').
By setting the value to /2, constant power can be achieved with a simple and inexpensive configuration without using a multiplier or the like. Further, according to the present invention, fluctuations in load power due to fluctuations in input voltage are also suppressed, and good constant power to input characteristics can be obtained.

Furthermore, when a lamp lighting device is connected as a load, the constant power effect suppresses ripples in the optical output and reduces flickering. Furthermore, if the rated operating conditions are set appropriately, overpowering will not occur due to changes in the lamp over time or fluctuations in the power supply, so the life of the lamp will be extended. In addition, the ballast (lighting device) itself does not need to have any margin for fluctuations, so it can be designed at low cost.
By using a nonlinear element in the voltage dividing circuit that divides the load voltage to 1/N and nonlinearly increasing the voltage division ratio N near the voltage v20, the load open voltage is partially increased to a higher voltage V2.
゜゛ It can be improved. That is, the rated operating point can be set to approximately V20/2 to make the power constant, and the load open voltage, which is the starting voltage, can be set to v 2o' which is higher than V2O. Therefore, the lamp power can be stabilized without being restricted by the relationship between the open circuit voltage and the lamp voltage.

[Example] The present invention will be described in detail below using the drawings.

FIG. 1 shows the configuration of a power supply device according to an embodiment of the present invention. This device stabilizes the voltage input from a DC power supply 1 using a switching regulator 2 to produce a discharge lamp (lamp).
3, and the lamp 3 is lit with constant power.

The switching regulator 2 has a basic configuration in which the output current is pulse width controlled (PWM control) to keep a predetermined amount of electricity constant, whereas the switching regulator 2 has a basic configuration in which the output current is pulse width controlled (PWM control) to keep a predetermined amount of electricity constant. The feature is that it is set as a function of voltage and current rather than the quantity of electricity. That is, this switching regulator 2 includes a switching transistor 2 that turns on/off the current from the DC power supply 1 and outputs it.
1. A diode 22 and an inductor 23 that smooth the output current of the switching transistor 21, a voltage dividing circuit 24 that divides the lamp voltage VL to 1/N, and a lamp current IL.
A resistor 25 with a resistance value r and a reference voltage source 26 for detecting
, an error in which the sum Vt/N+rlL of the output voltage VL/N of the voltage dividing circuit 24 and the voltage rlL between the terminals of the resistor 25 is compared with the output voltage V rel' of the reference voltage source 2B, and the difference voltage is output as an error voltage. Amplifier 27 and error amplifier 27
The transistor 21 is provided with a PWM control circuit 28 that generates a pulse having a duty ratio corresponding to the output of the transistor 21 to drive the transistor 21.

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

The switching transistor 21 is driven by the pulse output of the PWM circuit 28 to turn on and off the current flowing from the DC power supply 1 to the lamp 3. The inductor 23 controls the lamp 3 while limiting the on-current when the transistor 21 is on.
When the transistor 21 is off, the accumulated electromagnetic energy maintains the current in the closed circuit consisting of the inductor 23, the lamp 3, the diode 22, and the inductor 23. As a result, the transistor 21 and the inductor 2 are connected to the lamp 3.
A current is supplied which is current limited by 3 and smoothed by inductor 23 and diode 22.

The voltage dividing circuit 24 divides the lamp voltage vL of this lamp 3 by 1/N.
The voltage is divided into two and supplied to the non-inverting input terminal of the error amplifier 27.

On the other hand, the reference voltage source 2 is connected to the inverting input terminal of the error amplifier 27.
5 output voltage (reference voltage) Vrer is supplied.

By the way, since the resistor 26 through which the lamp current IL flows is connected between the negative terminal of the lamp 3 and the reference point a of the reference voltage [25], the negative terminal of the lamp 3, that is, the voltage dividing circuit The reference point S is biased by rll with respect to the reference point a of the reference voltage source 25. That is, with point a as a reference, the voltage VL/N+rlL is applied to the non-inverting input terminal of the error amplifier 27, and the voltage V rcr is applied to the inverting input terminal. However, from the error amplifier 27, Vrer-(VL/N+
An error voltage of rIL) is output. PWM control circuit 2
8 generates a pulse width with a duty ratio corresponding to this error voltage and drives the base of transistor 2[. As a result, the lamp 3 has VL/N+ r I L-Vrel
' A current IL and a voltage VL are supplied, and PL-VL
A lamp power PL of IL-VL (vrer-VL/N)/r is supplied.

This operating characteristic is shown in FIG. In the figure, the solid line indicates the lamp voltage versus lamp current characteristic, and the broken line indicates the lamp voltage versus lamp power characteristic.

Here, the rated operating point of lamp 3 (VLS, ILS
) is the load open circuit voltage V 20 (-V rcr/N )
Therefore, the load short-circuit current 125 (-Vr
It is set to be 1/2 of (ef/r).

As is clear from Fig. 2, the rated operating point when set in this way is the point where the lamp power pts is maximum,
Since the slope is zero, even if the rating of the lamp 3 changes somewhat due to variations, changes over time, etc., the change in the lamp power PLS is slight and is stabilized. Also, VL /N+
Since control is performed so that r I L =Vref', the lamp voltage and lamp current do not depend on the power supply voltage in an ideal state. Therefore, the lamp power is sufficiently stabilized even against power supply voltage fluctuations.

In the device of FIG. 1, a Zener diode 29 is connected to the voltage dividing circuit 24, and the lamp voltage VI.

When the voltage exceeds a predetermined value (the Zener voltage Vz of the Zener diode 29), the voltage division ratio N is increased non-linearly. As a result, the load open circuit voltage is changed from V2O without the zener diode 29 to v as shown in FIG.
It can be increased to 2o'. As a result, the starting voltage (-load open voltage) of the lamp can be set high without impairing constant power performance, and design constraints are resolved and design becomes easier.

[Modifications] Note that the present invention is not limited to the above-described embodiments, and can be implemented with appropriate modifications. For example, in the above embodiment, an example was explained in which the lamp 3 is directly lit with direct current using the DC output of the switching regulator 2, but this DC output is converted into a low frequency signal using a bridge inverter, a pair regulator, another inverter, a high frequency generator, etc. (for example, 50.60 or 400 Hz) or high frequency (for example, 20 to 100 kHz) may be used for alternating current or high frequency lighting.

[Brief explanation of the drawing]

FIG. 1 is a schematic circuit configuration diagram of a power supply device according to an embodiment of the present invention, and FIG. 2 is a diagram showing operating characteristics of the power supply device of FIG. 1. 1: DC power supply, 2: Switching regulator, 3: Lamp, 21 Switching transistor, 24: Voltage dividing circuit, 2
5: Reference voltage source, 26 two lamp current detection resistors, 27:
Error amplifier, 28: PWM control circuit, 29: Zener diode.

Claims (1)

[Claims] 1. A switching element that turns on and off the DC input, and a switching element that controls the sum of the load voltage divided into 1/N and the load current multiplied by r to be constant. A power supply device comprising a pulse width control circuit that controls on/off frequency or duty ratio. 2. The power supply device according to claim 1, wherein a value obtained by dividing the load voltage to 1/N and a value obtained by multiplying the load current by r are set to be substantially equal at a rated operating point. 3. The voltage divider circuit that divides the load voltage to 1/N includes a nonlinear element so that even if the load voltage exceeds twice the rated voltage, the output of the voltage divider circuit does not exceed approximately twice the rated voltage. The power supply device according to claim 2, comprising: