JPS5826635B2 - Power fluctuation compensation circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention connects a series or parallel circuit of a load such as a discharge lamp L and a thyristor T to an AC power source E through a current limiting element such as an inductance element to form a main circuit. and turn on the thyristor T every half cycle of this AC power supply E.
In the circuit that is turned off and supplies appropriate power to the load, the capacitor C1 of the relaxation oscillation circuit A that controls the thyristor T is charged by the reference voltage source voltage and the fluctuating voltage source voltage, and this fluctuating voltage The present invention relates to a power fluctuation compensation circuit characterized in that the source is set to a portion affected by the load current, and its purpose is to suppress fluctuations in the effective load current due to voltage fluctuations of the AC power supply, An object of the present invention is to provide a power fluctuation compensation circuit that can stably drive a load using a simple circuit.

FIG. 1 shows an example of a conventional phase control type discharge lamp lighting circuit. In the figure, a discharge lamp l receives a voltage via an inductance element serving as a current limiting element and a thyristor T.

The AC power source E is connected to the AC power source E, and the phase of the AC power source E is controlled by a thyristor T, and the discharge lamp l receives power from the above-mentioned phase-controlled power source via an inductance element.

Fig. 2 is a time chart for explaining the operation of the circuit shown in Fig. 1. Fig. 2 a shows the voltage of the AC power supply E, and b shows the lamp currents I, g, and c flowing through the discharge lamp l, which control the conduction of the cyrisk T. The terminal voltage of capacitor c1 installed in relaxation oscillation circuit A is
c1 and d indicate the waveforms of the lamp voltage Vl across the discharge lamp 1, respectively.The operation of the circuit shown in FIG. 1 will be explained below with reference to FIG.

Now, at a certain phase t1 of the voltage VA C of the AC power supply E,
Terminal voltage ■ of capacitor C1, which was being charged by AC power supply E via resistor R1°R2.

1 is Diac D. The breakover voltage of is reached and the thyristor T is triggered.

Therefore, a lamp current I7 flows through the discharge lamp l through an inductance element and a thyristor T, as shown in FIG.
Then thyristor T returns to off.

Furthermore, in the next phase t1, the thyristor T is turned on again, and thereafter the same operation as above is performed to steadily light the discharge lamp I.

By the way, since the above-mentioned circuit of the embodiment shown in FIG. 1 uses only the shaded part of the power supply voltage VAC shown in FIG. This has the advantage that it is possible to use a smaller inductance element than the inductance element L (current-limiting impedance) that would be required if it is not used, and the device can be made more compact. There was a drawback that reducing the size of the current limiting element (current limiting element) worsened the load fluctuation rate.

Figure 3 shows another conventional example, in which a thyristor T is connected in parallel with a discharge lamp l as a load, an oscillating circuit consisting of an inductance element, a capacitor C, and a discharge lamp l, and an inductance element and a capacitor C are in an on state. This system uses a combination of two oscillating circuits consisting of a thyristor T and a thyristor T to light up a discharge lamp L.The operation of the conventional circuit shown in Fig. 3 is explained below with reference to the time chart in Fig. 4. I will explain.

All the discharge lamps l shift to steady lighting, and the power supply ε pressure v in Figure 4 a
The lamp current IA7 as shown in the same figure for Ao is the discharge lamp I.
Assuming that Vc begins to flow, at phase t1 within a half cycle of power supply voltage VAC, the terminal voltage of capacitor C1 of relaxation oscillation circuit A, which has been charged via resistors R1 and R2, becomes
.

1 (e in the same figure) is Diac D.

Breakover voltage ■B. When it reaches , this C diac D.

conducts and the thyristor T is triggered.

At this time, the discharge lamp 1 is short-circuited by the thyristor T, and the thyristor T receives a current 2 as shown in FIG. 4C.

begins to flow. This current (1) is purely a C oscillating current, and is a stronger oscillating current than the current that would flow through the discharge lamp 7 if it were assumed that the thyristor T remained off during the phase t1'ft.

Therefore, the charge on the capacitor C in the main circuit is greater than the amount that would be charged in the above assumption, and the thyristor T is turned off at phase t2 when the current IT is about to go below zero. At this time, capacitor C is charged to a sufficiently high voltage as described above.

Then, the terminal voltage of this capacitor C and the power supply voltage VAC
The above operation is repeated again in the next half cycle.

However, in the conventional circuit shown in FIG. 3, by storing energy in the capacitor C during the on-period of the thyristor T, the power supply voltage Ao is reduced isometrically, and therefore the inductance element and the capacitor C are used as current limiting elements. However, as in the case of the conventional example shown in Fig. 1 mentioned above, the disadvantage is that the load fluctuation rate worsens due to the miniaturization of each element of the current limiting element. there were.

Note that FIG. 4d shows the current supplied from the AC power source E.

This is the waveform of

Further, in the circuit shown in Fig. 3, the operation when the LC vibration itself of the main circuit is used to start the discharge lamp l will be explained in Section 5 below.
This will be explained using the time chart shown in the figure.

The same power supply voltage characteristics as in the case of steady lighting described above. [Figure 5 a
] When a trigger is applied to the thyristor T at phase t1 of It is to be turned off,
At this time, the terminal voltage of capacitor C is V.

is charged as shown in Figure 5.

Next power supply voltage ■Eh. When Cyrisk T is turned on again in phase t1 during the half cycle of , the power supply voltage becomes 1.

and the terminal voltage of capacitor C■. are superimposed, a larger oscillating current flows than in the previous half cycle, and capacitor C is charged to a higher voltage than in the previous half cycle,
At phase t2 of this half cycle, thyristor T is turned off.

On the other hand, the power supply voltage for the discharge lamp L is ■.

and the terminal voltage of capacitor C■.

As mentioned above, the terminal voltage of capacitor C is applied every half cycle.

increases, so this voltage VAc+vc reaches the starting voltage of the discharge lamp l after several cycles, and at that voltage the discharge lamp l starts.
is what starts it.

The above voltage VAo+■o theoretically increases to infinity in a series, but in reality, due to resistance components in the circuit, etc., when it reaches a certain level after several cycles of the power supply voltage ■Ac, it will be balanced at that voltage. do.

In FIG. 5, a is the voltage of the AC power supply E, AC1b is the current flowing through the thyristor T, and C is the terminal voltage of the capacitor C.

, d indicate the waveforms of the terminal voltage (1) of the cyrisk T, respectively.

Therefore, when starting the discharge lamp l in the conventional circuit shown in Fig. 3, the voltage ■Ac+
■o can be balanced at a certain level, but even a slight variation in the phase t, at which thyristor T is turned off, will cause this equilibrium voltage value to fluctuate greatly, and if we consider this variation as well, it will affect the withstand voltage of thyristor T. The problem was that it was extremely disadvantageous.

As mentioned above, in the conventional example shown in Figure 1 and the conventional example shown in Figure 3,
In either case, improving the fluctuation rate was a major issue, and Fig. 6 shows a thyristor T control section used in the conventional example shown in Fig. 1 and the conventional example circuit shown in Fig. 3, which takes into account the improvement of this fluctuation rate. This figure shows another conventional example circuit.
Figure 3: In contrast to the conventional control section (relaxation oscillation circuit A),
A feedback charging control circuit B is newly added to control the charging of the capacitor C1 according to the main circuit current.

In the conventional circuit shown in FIG. 6, the main circuit current is detected by a feedback transformer Tf, and the secondary winding output of this feedback transformer Tf is rectified by a diode D and then connected to a capacitor C2 via a resistor R5. By applying the voltage to the capacitor C2, a current voltage corresponding to the detected current of the main circuit current is applied to the capacitor C2.
Get to both ends.

Thus, the impedance of the transistor Q is changed according to the voltage across the capacitor C2, and the charging time of the capacitor C0 of the relaxation oscillation circuit A is controlled.

That is, in the conventional circuits of FIGS. 1 and 3, the charging time constant of capacitor C0, which is constant regardless of the load condition, is maintained by resistor R3, diode bridge DB, and transistor Q, which are connected in parallel to capacitor C1. It is changed by changing the resistance value of the circuit,
For example, when the main circuit current tries to increase, capacitor C
2 voltage increases, the resistance value of transistor Q decreases, and the charging time constant of capacitor C1 increases, working in the direction of decreasing the main circuit current. When the main circuit current is about to decrease, the operation opposite to the above is performed. On the other hand, as mentioned above, in the conventional example circuit shown in FIG. A feedback transistor and the like for isolation are required, which has the disadvantage of complicating the circuit and making it expensive.

The present invention has been provided in view of the above points, and embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 7 shows an embodiment of the present invention corresponding to the conventional example shown in FIG. This differs from the conventional example shown in FIG. 1 in that the secondary windings are connected in series, and the primary winding of the feedback transformer TF is connected to both ends of the discharge lamp l.

The basic operation is as described above, but the charging of the capacitor C1 is caused by the terminal voltage of the discharge lamp l, the secondary voltage of the inversely coupled feedback transformer Tf for detection, and the terminal voltage of the AC Zener element ZD. This differs from the conventional example shown in FIG. 1 in that it is performed by VZD.

That is, if the lamp current Il decreases for some reason, the lamp voltage ■l increases in the circuit of FIG.
The phase of the voltage sum of the terminal voltage VZD of the AC Zener element ZD and the secondary voltage 12 of the feedback transformer Tf shown in Figure C advances with respect to the voltage VZD and acts in the direction of advancing the phase t1, and at the same time, the phase t3 Voltage ■ between ~t2
2D and the secondary voltage V7 increases, the charging time of the capacitor C1 is also accelerated, and the phase t is increased by the combination of both.
1 moves further forward, working in the direction of moving the lamp electric current K11 further forward.

Further, when the lamp current I6 increases from the steady state, feedback is performed in the direction of decreasing the lamp current 1 by the opposite effect to the above.

FIG. 8 shows a time chart of the main parts of the circuit according to the embodiment shown in FIG.
1 b is the lamp voltage ■c c is the feedback winding secondary voltage ■1
2 and the terminal voltage ■2D, the composite voltage ■12+■2D,
d is the terminal voltage V of the capacitor C1.

1 is shown respectively. FIG. 9 shows another embodiment circuit of the present invention corresponding to the conventional example shown in FIG.
It has a different configuration from the conventional example shown in Fig. 3 in that the series circuit with 1 is connected in parallel with the discharge lamp l used as a variable voltage source, and the basic operation is the same as that of the conventional example shown in Fig. 3. However, the difference is that the capacitor C1 of the relaxation oscillation circuit A is charged via the resistors R1 and R2, and at the same time is charged via the feedback resistor Rf by the ramp voltage 1.

However, if the lamp current I,5 decreases for some reason, the lamp voltage V,6 will increase, and as a result, the amount of charge charged to the capacitor C8 via the feedback resistor Rf increases, and the thyristor Power supply voltage at which T conducts ■
picture.

The phase t1 of moves forward.

At this time, the instantaneous value of the power supply voltage VAC tends to increase, so the amount of energy stored in the main circuit C increases during the ON period of the thyristor T, which increases the lamp current l for the next half cycle. On the other hand, when the lamp current l increases from the steady state, the phase t1 shifts backward due to the opposite effect to the above, and the lamp current I, l? The feedback is performed in the direction of decreasing the amount.

Note that FIG. 10 shows a time chart of the embodiment in FIG.
In the same figure, a is the terminal voltage of the AC Zener element ZD, ■2D, and b
is the lamp voltage V, 5. c is the terminal voltage of capacitor C1■
.

1 respectively.

As described above, the present invention charges the capacitor of the relaxation oscillation circuit that controls the thyristor T with the reference voltage source voltage and the fluctuating voltage source voltage, and sets this fluctuating voltage source to a portion affected by the load current. Therefore, it is possible to accurately suppress fluctuations in the effective load current caused by voltage fluctuations in the AC power supply and other factors, and it also eliminates the need for a complicated circuit using many expensive elements as in the conventional example. There is no need for any configuration, and the simple configuration simplifies the design, enables a significant reduction in cost, and has the effect of achieving high reliability.

[Brief explanation of drawings]

Figure 1 is a circuit diagram of a conventional example that is the premise of the present invention, Figure 2 is a time chart of the same circuit, Figure 3 is a circuit diagram of another conventional example that is the premise of the present invention, and Figure 4 is the same as the above circuit. Fig. 5 is a time chart at the time of starting the same as above, Fig. 6 is a circuit diagram of the main part of the conventional Cyrisk control section,
FIG. 7 is a circuit diagram of an embodiment of the present invention, FIG. 8 is a time chart of the same as above, FIG. 9 is a circuit diagram of another embodiment of the present invention, and FIG. 10 is a time chart of the same as above. discharge lamp, T
is a thyristor, L is an inductance element, E is an AC power supply, A is a relaxation oscillation circuit, and C1 is a capacitor.

Claims (1)

[Claims] 1 A series or parallel circuit of a load such as a discharge lamp and a thyristor is connected to an AC power source via a current limiting element such as an inductance element to form a main circuit, and the thyristor is connected to the AC power source every half cycle of the AC power source. In a circuit configured to turn on and off to supply appropriate power to the load, the capacitor of the relaxation oscillation circuit that controls the thyristor is charged by the reference voltage source voltage and the fluctuating voltage source voltage, and this variation is A power fluctuation compensation circuit characterized in that a voltage source is set at a portion affected by load current.