JP2906056B2 - Discharge lamp lighting circuit - Google Patents

Description

The present invention relates to an inverter-type discharge lamp lighting device that operates at a high power factor.

[Conventional technology]

When a high-pressure metal vapor discharge lamp (HID lamp) is lit in a high frequency band of about 10 to 100 kHz, an acoustic resonance phenomenon occurs and the discharge becomes unstable. In order to avoid this, the light may be lit at a higher higher frequency, or conversely, may be lit at a lower frequency. However, in the former case, the implementation is not easy because the frequency lower limit value of the stable discharge differs for each discharge lamp and also varies depending on the discharge state.

An example of the latter is presented in "The Illuminating Engineering Institute of Japan", 1987 "Preprints of the National Convention" (Presentation No. 41). The circuit is the third
As shown in the figure, it includes an AC power supply 10, a voltage doubler rectifier circuit 20, a full-wave bridge type inverter 40, and a lighting circuit 50. Hereinafter, the conventional apparatus of FIG. 3 will be described in more detail.

The voltage of the AC power supply 10 shown in FIG. 3 is boosted by a voltage doubler rectifier circuit 20 including diodes 21 and 22 and rectifying circuit smoothing capacitors 28 and 29. Thus, a DC double voltage having an upper limit of twice the maximum value of the AC power supply 10 voltage is obtained. The full-wave bridge type inverter 40 operates by receiving this DC double voltage. The full-wave bridge type inverter 40 includes switching elements 41, 42, 43, 44 for inverters connected in a full-wave bridge type, and a flywheel diode connected in anti-parallel with each of the switching elements 41, 42, 43, 44 for inverters. Including 45, 46, 47, 48. The lighting circuit 50 is connected to the DC output terminal of the full-wave bridge inverter 40. The lighting circuit 50 includes a discharge lamp 51 and the discharge lamp 51.
And an auxiliary capacitor 52 in parallel with the discharge lamp 51. The lighting circuit 50 is an inductive load circuit including the ballast inductor 59, and the flywheel diodes 45, 46, 47, and 48 cannot be omitted. If you omit this,
When the inverter switching element 41, for example, is turned off, a theoretically infinite overvoltage is generated across the ballast inductor 59. The auxiliary capacitor 52 is for absorbing a high-frequency component current.

The operation will be described by taking as an example a period in which the inverter switching elements 42 and 43 of FIG. 3 are off and 41 and 44 are on. During this period, (28 ・ 29) −41−59−51 (52) −44−
Current flows in the closed circuit of (28 ・ 29). Here, the inverter switching elements 42 and 43 are kept off, and
Is kept in the ON state, and only the remaining inverter switching element 41 is turned off, 59-51 (52) -44-46
Current flows through the closed circuit at -59. When the switching element 45 for the inverter is turned on and off in synchronization with high frequency, the above operation is repeated. The essential point of the inverter operation shown in FIG. 3 is to turn on and off the upper pair of inverter switching elements 41 and 43 at a high frequency cycle and turn on and off the lower pair of inverter switching elements 42 and 44 at a low frequency cycle. In this way, a load current including a low-frequency component and a high-frequency component flows through the ballast inductor 59.
When the high-frequency component is absorbed by the auxiliary capacitor 52,
Only the low frequency component current flows through the discharge lamp 51. Therefore, even if the discharge lamp 51 is a high-pressure metal vapor discharge lamp,
No harmful discharge instability occurs.

The input source of the full-bridge inverter 40 shown in FIG. 3 is a stable voltage source mainly composed of rectifying circuit smoothing capacitors 28 and 29. The DC voltage is applied to the discharge lamp 51 via, for example, inverter switching elements 41 and 44 and further via a ballast inductor 59. Without the ballast inductor 59, because of the constant voltage characteristic or the negative characteristic of the discharge lamp 51,
Stable operation is not possible. If all of the inverter switching elements 41, 42, 43 and 44 are turned on and off at a low frequency cycle, it is necessary to make the ballast inductor 59 large with low frequency specifications, which is not a good idea.

[Problems to be solved by the invention]

The input source of the full-wave bridge type inverter 40 shown in FIG. 3 is a voltage source (a smoothing capacitor 28 for a rectifier circuit) which holds a stable voltage.
・ 29). The voltage must be equal to or higher than the discharge voltage of the discharge lamp 51 (normally equal to or higher than twice). The mechanism for applying the difference to the ballast inductor 59 stabilizes the operation. From a different point of view, a high voltage source is required, which allows for 59 ballast inductors. For this purpose, the voltage doubler rectifier circuit 20 is used, but the burden is heavy, and it cannot be used for the discharge lamp 51 having a higher discharge voltage.

Further, the voltage doubler rectifier circuit 20 shown in FIG. 3 is essentially a low power factor circuit. Since the peak AC power supply 10 current flows only for a short period when the instantaneous value of the AC power supply 10 voltage exceeds the voltage of the rectifying circuit smoothing capacitors 28 and 29, a low power factor type is achieved.

Furthermore, inverter switching elements 41, 42, 43,
When the switch 44 is turned on, a pair of inverter switching elements in series, for example, 41 and 42, may be turned on at the same time.
At this time, an excessive current flows, causing an excessive power loss.

An object of the present invention is to provide a high power factor type discharge lamp lighting device which can use a discharge lamp having a high discharge voltage even under a low voltage AC power supply. Another object of the present invention is to provide an inexpensive lighting device that does not use a smoothing capacitor and a ballast inductor. Still another object of the present invention is to provide a lighting device that does not generate an excessive current and an excessive loss even when a pair of inverter switching elements are turned on simultaneously. Another object is to provide a lighting device which is particularly suitable for high pressure metal vapor discharge lamps.

[Means for solving the problem]

A discharge lamp lighting device according to the present invention includes a full-wave rectifier circuit that performs full-wave rectification on an AC power supply voltage. The rectifying circuit smoothing capacitor connected to the output terminal of the full-wave rectifying circuit is omitted. The term "omitted" in this specification is used not to mean that it may be omitted, but to mean that it must be omitted.

A chopper inductor is provided. A chopper switching element for applying an output voltage of the full-wave rectifier circuit to the chopper inductor in a forward direction and intermittently.
A chopper diode for guiding a forward current flowing through the chopper inductor. A chopper smoothing capacitor connected in parallel with the chopper inductor via the chopper diode is omitted. by this,
A step-up / step-down chopper circuit is configured.

An inverter connected in parallel with the chopper inductor via the chopper diode is provided. The inverter is a full-wave bridge type inverter in which four inverter switching elements are connected in a full-wave bridge type. A half-bridge type inverter in which a pair of inverter switching elements in series is replaced with a pair of arm capacitors must not be used.

A discharge lamp connected to a DC output terminal of the full-wave bridge inverter. The ballast inductor connected in series with the discharge lamp is omitted. An auxiliary capacitor connected in parallel with the discharge lamp is provided.

[Action]

The chopper circuit functions not as a voltage source but as a current source because there is no smoothing capacitor for the chopper.
The current is alternately inverted by the full-wave bridge inverter and supplied to the discharge lamp.

〔Example〕

The embodiment of FIG. 1 according to the present invention will be described. First
The illustrated discharge lamp lighting device includes a full-wave rectifier circuit 20 that performs full-wave rectification on the AC power supply 10 voltage. The full-wave rectifier circuit 20 is formed by connecting four diodes 21, 22, 23, and 24 in a full-wave bridge type. A rectifying circuit smoothing capacitor for connecting the output terminals 20a and 20b of the full-wave rectifying circuit 20 is omitted.

A chopper inductor 31 is provided. A chopper switching element 32 for applying the output voltage of the full-wave rectifier circuit 20 to the chopper inductor 31 in a forward direction and intermittently is provided.
In FIG. 1, the forward direction of the chopper inductor 31 is downward. A chopper diode 33 for guiding a downward forward current flowing through the chopper inductor 31 is provided. The chopper smoothing capacitor connected in parallel with the chopper inductor 31 via the chopper diode 33 is omitted.

An inverter 40 is connected in parallel with the chopper inductor 31 via the chopper diode 33. Inverter 40 has four inverter switching elements 41, 42, 43
・ A full-wave bridge type inverter that connects 44 to a full-wave bridge type.

The discharge lamp 51 is connected to the DC output terminal of the full-wave bridge type inverter 40. An example of the discharge lamp 51 is a high-pressure metal vapor discharge lamp (HID lamp). The ballast inductor connected in series with the discharge lamp 51 is omitted. An auxiliary capacitor 52 connected in parallel with the discharge lamp 51 is provided. The auxiliary capacitor 52 has a small capacity enough to absorb and remove high-frequency components.
Lighting circuit that becomes the load circuit of full-wave bridge type inverter 40
50 is a simple one that includes a discharge lamp 51 and an auxiliary capacitor 52 and does not include a ballast inductor.

The supplementary description of the full-wave rectifier circuit 20 is provided. Its output end 20a ・ 2
When a rectifying circuit smoothing capacitor (not shown) is connected to 0b, the AC power supply 10 has a low power factor. This is because the AC power supply 10 current does not flow during the period when the AC power supply 10 voltage is lower than the rectifying circuit smoothing capacitor voltage. In the present invention,
In order to increase the power factor, the rectifying circuit smoothing capacitor is omitted.

The chopper inductor 31, the chopper switching element 32, and the chopper diode 33 form a buck-boost type chopper circuit 30. Since there is no chopper smoothing capacitor after the chopper diode 33, the chopper circuit 30 is incomplete in that sense. Hereinafter, this point will be supplemented. During the ON period of the chopper switching element 32, the output voltage of the full-wave rectifier circuit 20 is
The current is applied to the inductor 31 to form a downward forward current in the chopper inductor 31 to store electromagnetic energy. Even if the chopper switching element 32 is turned off, the current of the chopper inductor 31 is still held and functions as a current source.
When a chopper smoothing capacitor is provided at the subsequent stage of the chopper diode 33, the electromagnetic energy of the chopper inductor 31 is absorbed by the chopper smoothing capacitor. In this case, the smoothing capacitor for chopper functions as a voltage source that holds a stable DC voltage. When viewed from the position of the full-wave bridge-type inverter 40 in the subsequent stage, if there is a smoothing capacitor for chopper, it becomes a voltage source, and if there is no smoothing capacitor, it becomes a current source. The current of the voltage source is undefined, and the voltage of the current source is undefined.
An undefined current or undefined. The voltage depends on the load circuit, ie, the full-bridge inverter 40 and the like.

Full-wave bridge type inverter 40 and subsequent lighting circuit 50
Will be described. The feature of this point is that a ballast inductor (an inductor corresponding to 59 in FIG. 3) connected in series with the discharge lamp 51 is omitted. For convenience of explanation, consider a period in which the chopper switching element 32 is off, the inverter switching elements 42 and 43 are off, and the inverter switching elements 41 and 44 are on.
In this case, a chopper inductor that functions as a current source
The forward current of 31 flows through the closed circuit of 31-33-44-51 (52) -41-31. Thereby, the lighting of the discharge lamp 51 is maintained.
The current in this closed circuit is intermittent according to the on / off of the chopper switching element 32. When the high-frequency component current accompanying the interruption is absorbed by the auxiliary capacitor 52, a continuous current that does not include the high-frequency component current flows through the discharge lamp 51. Although the discharge lamp 51 requires a predetermined discharge voltage, the chopper inductor 31 supplies a voltage corresponding thereto.
The voltage of the chopper inductor 31 as a current source is undefined, and its level depends on the discharge lamp 51. On the other hand, the chopper inductor 31 as a current source has an inertial effect of maintaining the same current level. Therefore, a ballast inductor arranged in series with the discharge lamp 51 is unnecessary and can be omitted. Incidentally, if a smoothing capacitor for chopper is attached, a ballast inductor sharing the difference between the capacitor voltage and the discharge voltage is indispensable because it functions as a voltage source.

Change perspective and supplement. Consider the case where there is no chopper smoothing capacitor and there is a ballast inductor. In this case, when the chopper switching element 32 is turned off, a theoretically infinite voltage is generated at both ends of the chopper inductor 31 and the ballast inductor. This is a phenomenon that occurs because the electromagnetic energy stored in the chopper inductor 31 is forcibly emitted to a circuit including the ballast inductor. Next, consider the case where there is no ballast inductor and there is a chopper smoothing capacitor. This is a form in which a voltage line is directly connected to the discharge lamp 51, and either no current flows through the discharge lamp 51 or an excessive current flows. Two cases are assumed, but in either case, it becomes impossible to implement.

The loads of the full-wave bridge type inverter 40 are the discharge lamp 51 and the auxiliary capacitor 52, and the ballast inductor is omitted. Therefore, a voltage source cannot be connected to the input terminal of the full-wave bridge type inverter 40 as described above. By the way, since the full-wave rectifier circuit 20 is also a voltage source, there is a problem whether the output voltage is not applied to the full-wave bridge type inverter 40 via the chopper switching element 32 and the chopper diode 33. This point will be supplemented. When the chopper switching element 32 is on, the voltage of the chopper inductor 31 has a polarity opposite to that of the chopper diode 33, and the chopper diode 33 keeps the off state. When the chopper switching element 32 is turned off, the voltage of the chopper inductor 31 is inverted, and the chopper diode 33 is turned off. The situation is that the former is off and the latter is on. Under these circumstances, when the chopper switching element 32 is turned off, the chopper inductor
The voltage 31 is again inverted, and the chopper diode 33 is turned off. For this reason, the output voltage of the full-wave rectifier circuit 20 is blocked by either the chopper switching element 32 or the chopper diode 33 and is not applied to the full-wave bridge type inverter 40 at the subsequent stage.

The switching control of the full-wave bridge type inverter 40 will be described. This is an operation mode in which the pair of inverter switching elements 41 and 44 on the opposite side and the remaining pair of inverter switching elements 42 and 43 are alternately turned on and off. This is a normal operation mode of the full-wave bridge type inverter 40. In the conventional device of FIG. 3, only the switching elements 41 and 43 for inverters on the upper side are turned on and off at a high frequency cycle, and the inductor for ballast is used.
Although the size of 59 is reduced, in the case of FIG. 1 there is no ballast inductor intended to reduce the size, so that it is not necessary to use the switching frequency as described above, which is meaningless. Inverter switching elements 41, 42, 43 in FIG.
Reference numeral 44 denotes transistors, each of which is provided with a switching control circuit, but is not shown.

In some cases, a pair of inverter switching elements, for example, 41 and 42 in FIG. 1 are turned on at the same time. In that case, a current flows through the inverter switching elements 41 and 42, and the level thereof matches the current value of the chopper inductor 31 at that time. Therefore, no excessive current and excessive loss occur.

The operation of FIG. 1 will be described again. When an AC power supply 10 voltage of FIG. 1 and V ₁ · sin .omega.t, full-wave rectifier circuit 20
Is given by the following equation.

_{E = V 1 | Sinωt | (} 1) chopper switching element 32 such as a transistor is turned off at time t _2. If the subsequent ON period is sufficiently short, the current i of the chopper inductor 31 via the chopper switching element 32 is given by the following equation.

I _{O in} equation (2) is the chopper inductor at time t ₁
31 is the current (initial value). L is an inductor for chopper
31 inductance.

If the ON period of the equation (2) is T _ON , the following equation is obtained.

(21) of the I _P is the peak current value of the chopper inductor 31, which is formed at turn-off of the chopper switching element 32. During the subsequent off period of the chopper switching element 32, the current i flowing through the chopper inductor 31 is substantially expressed by the following equation.

_{VL in the} equation (3) is the discharge voltage of the discharge lamp 51 and can be regarded as substantially constant voltage because the auxiliary capacitor 52 is attached.

_Assuming that the _OFF period in equation (3) is T _OFF , the following equation is obtained.

In the AC power supply 10, a current i expressed by equation (2) flows during the ON period of the chopper switching element 32. It does not flow during the off period. Therefore, the average current (low-frequency component current excluding harmonic components) i _O of the AC power supply 10 current is expressed by the following equation.

If i _{O in the} equation (4) has the same waveform and the same phase as the AC power supply 10 voltage V ₁ · Sinωt, the power factor becomes maximum. Therefore, the following conditional expression is obtained.

Further, a condition for setting I _O to 0 in the equation (2) or the like is given,
By rearranging equation (41) using the equations after equation (2), the following is obtained.

In FIG. 1, the output terminals 20a and 20b of the full-wave rectifier circuit 20 are shown.
Since the rectifying circuit smoothing capacitor connected to the rectifier circuit is omitted and the input terminal of the chopper circuit 30 is connected to the rectifying circuit smoothing capacitor, the operation is basically of a high power factor type. In particular, if control is performed so as to satisfy Expression (42), the maximum power factor can be obtained. Peak current value I _P of the chopper inductor 31, as substitute from equation (21), the function of the ON period T _ON of chopper switching element 32. Therefore, if the on-duty of the chopper switching element 32 is appropriately changed to satisfy the expression (42), the operation with the maximum power factor is realized.

According to the apparatus shown in FIG. 1, even when a combination of an AC power supply 10 having a low effective value and a discharge lamp 51 having a high discharge voltage is used,
Lighting of 51 becomes possible. Switching element 32 for chopper
The electromagnetic energy accumulated in the chopper inductor 31 during the ON period is supplied to the discharge lamp 51 even when the discharge voltage is high. Also, since there is no ballast inductor,
There is no restriction on the high-frequency switching operation of the inverter switching elements 41, 42, 43, 44 necessary for downsizing. Therefore, a high pressure metal vapor discharge lamp (HID lamp) 51
It is particularly suitable for low frequency lighting.

Next, the embodiment shown in FIG. 2 will be described. Here, the component code of FIG. 1 is used as it is, and the overlapping description will be omitted as appropriate. Fig. 2 shows a switching element for an inverter.
Thyristors are used as 41, 42, 43 and 44. The switching control circuit is associated with the full-wave rectifier circuit 20 and configured as shown in the figure.

Consider a state where the inverter switching elements 42 and 43 in FIG. 2 are on and 41 and 44 are off. The voltage polarity of the auxiliary capacitor 12 at this time is as illustrated. Under this situation, if the AC power supply 10 voltage reverses to the polarity shown,
Current flows in the closed circuit of 10−21−61−31−32−24−10.
The voltage drop of the diode 61 is applied to the gate of the inverter switching element 41 via the resistor 63, and the inverter switching element 41 is turned off. Then, the charging voltage of the auxiliary capacitor 52 becomes the switching element 41 for the inverter.
Through the inverter switching element 43 in the opposite direction. Therefore, the inverter switching element 43 is turned off. On the other hand, the inverter switching element 44
, The voltage of the auxiliary capacitor 51 is applied to the inverter switching element 44 in the forward direction via the turned-on inverter switching element 42. As a result, the inverter switching element 43 is turned off, so that the current flows from the gate to the cathode of the inverter switching element 44 via the resistor 70, and the inverter switching element 44 is turned off. When the inverter switching element 44 is turned on, the voltage of the auxiliary capacitor 51 is supplied to the inverter switching element 42 via the inverter switching element 44.
, And the inverter switching element 42 is turned off. Thus, the switching is performed such that the inverter switching elements 41 and 44 are on and the inverters 42 and 43 are off. Thereafter, the state returns to the initial state, and the subsequent steps are repeated.
Thus, the full-wave bridge type inverter 40 shown in FIG.
With the current supplied from the AC power supply 10 to the full-wave rectifier circuit 20 as a signal source, the polarity is inverted in synchronization with the frequency of the AC power supply 10. Therefore, there is an advantage that a separately-excited switching control circuit including a timer circuit is not required. Note that the thyristors can be replaced with transistors instead of the inverter switching elements 41 and 42 in FIG.

〔The invention's effect〕

In the present invention, since the input source of the full-wave bridge type inverter is a current source mainly composed of a chopper inductor, a discharge lamp having a high discharge voltage can be used even under a low-voltage AC power supply. . In addition, the operation is of a high power factor type. Furthermore, since no smoothing capacitor and no ballast inductor are used, the cost is low. Moreover, even if a pair of inverter switching elements are turned on at the same time, an excessive current and an excessive loss are not formed. On the other hand, since there is no ballast inductor and the full-wave bridge type inverter can be operated at a low frequency, it is particularly suitable for a high-pressure metal vapor discharge lamp.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a discharge lamp lighting device according to the present invention. FIG. 2 is a similar circuit diagram showing another embodiment. FIG. 3 is a circuit diagram showing a conventional discharge lamp lighting device. 10 AC power supply, 20 full-wave rectifier circuit, 20a / 20b output terminal,
30 ... chopper circuit, 31 ... chopper inductor, 32 ... chopper switching element, 33 ... chopper diode, 40 ... full wave bridge type inverter, 41/42/43/44 ...
Inverter switching element, 51 ... discharge lamp, 52 ... auxiliary capacitor

Claims (2)

(57) [Claims] 1. A smoothing capacitor for a rectifier circuit, comprising: a full-wave rectifier circuit (20) for full-wave rectifying the voltage of an AC power supply (10); A chopper switching element (32) that includes a chopper inductor (31) and applies the output voltage of the full-wave rectifier circuit (20) to the chopper inductor (31) in a forward direction and intermittently. A chopper diode (33) for guiding a forward current flowing through the chopper inductor (31), and a chopper smoother connected in parallel with the chopper inductor (31) via the chopper diode (33). An inverter omitting a capacitor and being connected in parallel with the chopper inductor (31) via the chopper diode (33);
Wherein the inverter (40) is a full-wave bridge type inverter that connects four inverter switching elements (41, 42, 43, 44) in a full-wave bridge type, and the full-wave bridge type inverter (40) A discharge lamp (51) connected to the DC output terminal of the first embodiment, omitting a ballast inductor connected in series with the discharge lamp (51), and providing an auxiliary capacitor (52) connected in parallel with the discharge lamp (51). A discharge lamp lighting device, comprising: 2. An inverter switching element (41, 42, 43) of a full-wave bridge type inverter (40), wherein a current flowing through a full-wave rectifier circuit (20) is used as a signal source.
A discharge lamp lighting device characterized in that switching control is performed so as to be synchronized with the AC power supply (10).