JPS62123695A - Electric source device - Google Patents

Abstract

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

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field 1] The present invention relates to a power supply device such as a discharge lamp lighting device that operates switching elements such as transistors at high frequencies to achieve smaller size, lighter weight, and higher power factor.

[Background Art 1] Fig. 4 shows a conventional example in which a discharge lamp lighting device is made smaller and lighter by turning on and off transistors at high frequencies. A completely smoothed DC voltage is generated across the capacitor C7 through the step-down chopper circuit 2 which converts the AC power supply 1 into DC using the rectifier bridge DB and makes the input a high power factor. With this voltage, the high pressure discharge lamp 4 is turned on by the on/off switching operation of the transistor Q2. Choke coil L0
A filter circuit 5 consisting of a capacitor C6 and a capacitor C6 shapes the waveform of the input current. The chopper circuit 2 includes a switching transistor Q3, a diode DI,
The load control circuit 3, which is composed of a coil I, 1, a capacitor C3, resistors R, , R2, etc., and controls the lighting of the discharge lamp 4, which is a load, includes a switching transistor Q2,
It is composed of a diode D2, a fill I-2, a capacitor C2, etc.

Here, in the chopper circuit 2, when the transistor Q is turned on, current flows to the rectifier bridge DB, the fungistor Q, the coil L1, and the capacitor C1.
Current flows into diode D1. This means that when transistor Q1 turns off, the coil L accumulated just before this turns off.
, flows in the same current direction, and the diode D1 is turned on. By repeating this operation and charging the capacitor C1 with high frequency, a DC voltage with less ripple voltage can be obtained. .

Further, the current flowing through the AC power supply 1 is approximately in phase with the power supply voltage waveform, resulting in a high input power factor. The on/off operation of the transistor Q is performed by controlling the on-duty of the transistor Q1 depending on the magnitude of the voltage Vcl across the capacitor CI to keep the voltage Vcl constant. That is, a series circuit of resistors R and R2 is connected across the capacitor C1, the voltage of the resistor R2 is detected, and the detected voltage is sent to the controller 6, which controls the transistor Q as described above. It is controlled by

The load control circuit 3 operates almost the same as the chopper circuit 2 described above, but it is necessary to control the operation of the transistor Q2 depending on the state of the load. Therefore, the load current is detected by a current transformer CT, and the operation is controlled depending on the magnitude of this current. It controls the on-duty of the transistor Q2, performs constant current control, and prevents overcurrent. That is, the load current is detected by the current transformer CT, this detection signal is sent to the control section 7, and the control section 7 controls the transistor Q2. Through the above operation, the input current can be made to have a high power factor and have little distortion, and
Due to the high frequency operation of the transistor Q2, the coil L2% capacitor C2 can be made smaller and lighter.

However, the conventional method has the following drawbacks.

That is, since the transistors Q1 and Q2 were operated under the control of independent individual control units 6 and 7, the control circuit became complicated and the cost increased due to having the two control units 6 and 7. was. Furthermore, when the discharge lamp 4 is used as the load, there is a problem that the stress on the transistor Q2 is large, such as a low impedance state immediately after the discharge lamp 4 is started and a secondary short circuit. - [Objective of the Invention 1] The present invention has been provided in view of two points,
By operating the first switching element on the input side and the second switching element for load control in conjunction with each other depending on the load condition, stress can be reduced and the control circuit simplified. The present invention provides a power supply device for the purpose of achieving high performance.

[Disclosure of the Invention] The present invention detects the state of the load and controls the input three-way transistor Q1 and the load control transistor Q2 in conjunction with each other, thereby providing flexibility against transient changes in the load. This corresponds to the stress on the transistor Q2.

For example, when a high-pressure discharge lamp, which is a load, starts, the lamp voltage immediately after that is as low as 10 to 30V, and the lamp current increases under normal control, so the on-duty of transistor Q2 is narrowed to reduce the lamp current. ing. At this time, the transistor Q also operates to narrow the on-duty, thereby suppressing the power supplied to the capacitor C8 and lowering the voltage of the capacitor C1. In this way, the transistor Q2 on the load side narrows the on-duty and suppresses the current flowing to the discharge lamp 4, and at the same time, the transistor Q1 reduces the on-duty and suppresses the current flowing to the discharge lamp 4.
This means that so-called amplitude control is essentially performed to lower the supply to the discharge lamp 4).

The gist of the present invention is to interlock transistors Q, Q2 to
It is about controlling the time.

(Example 1) Hereinafter, one example of the present invention will be described with reference to the drawings. FIG. 1 shows a specific embodiment of the present invention. Conventionally, transistors Q1 and Q2 were controlled independently, but in FIG. The on-duty is controlled by changing the voltage and current detection levels, and the on-duty of the transistor Q2 is changed by the current detection level. A resistor R3 for detecting the load current is inserted and connected between the discharge lamp 4 and the ground, and a transistor Q is connected according to the detection level at which this load current is detected.
, , Q2 are controlled simultaneously by a comparator circuit 8.
, pulse width control circuit 16, base drive circuit 17.1
It consists of 8 mag. The comparison circuit 8 consists of two comparators 9, 10, etc., and the pulse 111111111 circuit 1
6, comparators 11, 12, oscillation section 13.7, lip 70, 14. ．． It consists of 15 mag. The base drive circuit 17.38 includes a pulse transformer TI, ]2, and a transistor Q, s.

Q6, etc., and the control voltage Vcc is applied to the transistors Q5, . . . through pulse transformers T, , T2. is applied to the collector of Q. Detection point (e) of resistor R, which detects the voltage of capacitor C3, and resistor R1, which detects the load current.
The detection points (f>) are input to comparators 9 and 10, respectively, and the detection levels of (e) and (f)
, 10, the reference voltage VR input to the other input terminal of
When HFI t V REF2 is exceeded, the output of the comparison circuit 8 is input to the comparators 11 and 12. These comparators 11 and 12 compare the triangular waves of the capacitor CT of the oscillation section 13, and during the period when the voltage of the triangular wave is higher than the output of the comparator circuit 8, the voltage of the triangular wave is higher than that of the output of the comparator circuit 8. Transistors Q,,Q
This is the on time of the transistors Q, , Q2 that drive the transistors Q2 and Q2. In other words, the higher the output of the comparator circuit 8, the shorter the on-time of the transistors Q, Q2, and therefore (e)
, (f), the output of the comparator circuit 8 becomes high, so that the on-time of the transistors Q, . . . , Q2 becomes short.

Next, the overall operation will be explained. When the discharge lamp 4 starts at low impedance, the current flowing through the resistor R3 tends to increase, so the level at point (f) becomes high and the on-time of the transistor Q2 becomes short. At this time, transistor Q
, the on-time becomes shorter in the same way, and the voltage of the capacitor CI also decreases to maintain a predetermined voltage, so the on-time becomes longer as the discharge lamp 4 is lit steadily. Immediately after starting the discharge lamp 4, if the voltage of the capacitor CI is constant, the coil L2
Since the voltage applied to is also high, the choke coil becomes larger,
Although the loss is large, since the transistor Q controls the on-duty in conjunction with the impedance of the load, the voltage applied to the coil L2 is also small, allowing for miniaturization.

As the lamp voltage increases, the voltage across capacitor C1 also increases. During steady lighting, the voltage of the capacitor CI can be kept constant by controlling the on-duty of the transistor Q, even if the power supply fluctuates, for example, in response to the detection level at point (e), and the input current is A good waveform with little distortion can be obtained. The maximum value of the on-duty of the transistors Q, Q2 may be set in the pulse width control circuit 16 (for example, 50% MAX).

By the way, the peak value of the current flowing when the transistor Q2 is turned on is given by the following equation.

((V CI V cz) / L 21 ・T on
However, Vcl represents the voltage of the capacitor C1, Vc2 represents the voltage of the capacitor C2, and Ton represents the on-time of the transistor Q2.

Therefore, when the load has low impedance, c2 is small, so the peak value of the current becomes too large, so To
It is necessary to narrow the on time of n.

However, even if Ton is narrowed, transistor Q2 will turn on again before the energy of coil L2 is completely released during Toff (the off time of transistor Q2).
The current flowing through the coil L2 contains a particularly large amount of DC component. Therefore, by detecting the load current, the transistor Q,
If the on-duty of transistor Q2 is not controlled,
The voltage applied to the coil L2 is not lowered, so the voltage applied to the coil L2
In order to prevent saturation with the DC component at this time, it is necessary to increase the size, and the loss also becomes large. Furthermore, in the transistor Q2, the current during turn-on and turn-off is large due to this DC component, so the switching loss during turn-on and turn-off increases. However, the voltage at point (f) where the load current is detected is input to the comparator circuit 8, and its output is simultaneously connected to the transistors Q, Q2 via the pulse width control circuit 16, base drive circuits 17, 18, etc. Due to this control, even in the case of a secondary short circuit, the voltage applied to the load side of the load control circuit 3 is reduced, and the voltage applied to the transistor Q2 and the coil L2 is low, so that the voltage applied between the collector and emitter of the transistor Q2 is lowered. is lower, switching loss is significantly reduced,
The loss of the coil L will similarly decrease. Of course, the resistor R3 may be connected to the capacitor C2 and the discharge lamp 4.

(Example 2) Fig. 2 shows another example, in which the main circuit is the same as in the above example, but the on-duty of transistors Q, Q2 is adjusted in response to the detection levels at points (e) and (f). The feature is that the control is exactly the same.

That is, the comparator 12.717 in FIG.
The block circuit 15 is deleted to simplify the circuit. Control immediately after startup or during a secondary short circuit is almost the same as in the case of FIG. 1, and the detection side at point (f) is prioritized to control on-duty and suppress an increase in current. During steady state (f
) The detection level at point (e) takes priority over the detection level at point (e), and if constant current control from point (f) is canceled, the on-duty is controlled only by the detection level at point (e), and the lamp voltage increases. can prevent overload caused by In other words, even if the lamp voltage increases, the current decreases, so the lamp power hardly increases. Of course, even if power supply fluctuations occur, the voltage of the capacitor C1 is kept constant and the input current waveform is also good. Furthermore, in the control means of this embodiment,
This is more simplified than the case shown in FIG.

Note that although the oscillation section 13 is shared in both Figures 1 and 2, if the load condition is detected and the transistors Q, Q2 are controlled in conjunction, the oscillation frequencies should be the same. There isn't. Further, although the comparators 9 and 10 of the comparison circuit 8 operate as comparators as the name suggests, they may of course operate as amplifiers. This allows for more detailed control.

(Embodiment 3) FIG. 3 shows yet another embodiment, in which the main circuit is different from those shown in FIGS. 1 and 2. In other words, the chimney circuit 2 is similar to that shown in FIG. 1, but the load control circuit 3
are different. The load control circuit 3 is an inverter with a full bridge configuration, and AC power is supplied to the discharge lamp 4. The load control circuit 3 is a Y transistor Q21t
Q 22 y Q 3 v Q diode D21tD
2□, a resistor R1 for current detection, etc. Transistors Q 21 and Q 22 operate at high frequency and the first
This corresponds to transistor Q2 in the figure. Diode D2
1 and D22 correspond to the diode )'D2 in FIG. 1, and the transistor Q2. Or it is a diode that turns on when Q22 turns off and the energy of coil L2 is released. Transistor Q3. Q is turned on and off at low frequencies, and when transistor Q21 is on or off at high frequencies, - means that transistor Q is on, transistor Q3 is off, and when transistor Q22 is on and off, Transistor Q is on and transistor Q4 is off. The control means includes a comparison circuit 8, a pulse width control circuit 16, a low frequency oscillation circuit 19, and each transistor Q21.
Base drive circuits 17a, 17b, 1 B, 20, 21 that drive s Q 22 y Q 3 y Q 4
, Nordate 22.23, etc. Two types of signals are output from the low frequency oscillation circuit 19.
This signal determines whether to operate transistors Q 2+ and Q or transistors Q22 and Q. The operation is the same as in the case of FIG. 2, and the transistors Q, , Q2□Q22 control the on-duty in conjunction with each other.

As described above, the transistors Q, , Q2 are controlled by changing the on-time (oscillation frequency is constant), but it is also possible to change the off-time to reduce the actual on-duty. In this case, the oscillation frequency will change.

[Effect of the Invention 1] As described above, the present invention includes a first switching element that switches a DC voltage and outputs a predetermined voltage to make the input a high power factor, and a switching element that performs a switching operation upon receiving the output of this switching element. A second switching element constituting a load control circuit such as an inverter that generates a high frequency voltage to control the load; Shorter or longer on-time of the second switching element<first. Since the device is equipped with a control means for simultaneously controlling the switching of the second switching element in conjunction with each other, the first switching element and the second switching element are operated in conjunction with each other by one control means. , compared to the conventional system which had two control sections,
It has the effect of significantly reducing the number of parts and providing an inexpensive circuit, and also when the load impedance is low, etc.
The control means detects the load current and controls the on-time of the 1st and 12th switching elements according to the load condition, so that both switching elements control the voltage limit and current limit at the same time. If the current increases, rpJ
1. Switching is controlled in a direction that reduces the on-time of the second switching element, and therefore voltage control and current control to the load is controlled by the first switching element. By suppressing the power supply voltage and supply output to the load, the stress on the second switching element is significantly reduced, improving reliability, reducing loss, and improving operation. This has the effect of improving stability.

[Brief explanation of drawings]

Fig. 1 is a specific circuit diagram of one embodiment of the present invention, Fig. 2 is a main block diagram of another embodiment of the same as above, Fig. 3 is a specific circuit diagram of still another embodiment of the same as above, and Fig. # & 4 is a specific circuit diagram of a conventional example. 3 indicates a load control circuit.

Claims (1)

[Claims] (1) A first switching element that switches the DC voltage and outputs a predetermined voltage to make the input a high power factor, and upon receiving the output of this switching element, generates a high frequency voltage through switching operation to control the load. a second switching element that constitutes a load control circuit such as an inverter;
The load current is detected, and the above-mentioned first,
The first switching element shortens or lengthens the on time of the second switching element.
, and control means for interlocking and simultaneously controlling switching of a second switching element.