JPH0317198B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a discharge lamp lighting device, and sometimes to a discharge lamp lighting circuit including an inverter circuit using switching elements such as transistors.

FIG. 1 shows a conventional discharge lamp lighting circuit (see US Pat. No. 4,170,747). The circuit in the figure includes two sets of transistors 4, 6 and 8, 10 connected in series to a DC power supply 2, and each transistor 4,
Diode 1 connected in parallel with 6, 8, 10
2, 14, 16, 18, an inductor 20, a discharge lamp 22, etc. A series circuit of discharge lamp 22 and inductor 20 is connected between the connection point of transistors 4 and 6 and the connection point of transistors 8 and 10.

In the circuit of FIG. 1, voltages V4 and V8, for example of 50, 60 or 400 Hz, which are inverted to each other, as shown in FIG. 2a, or as shown in FIG. Voltages V4' and V8' having rest periods t are applied, respectively. Also, transistors 6 and 1
For example, high frequency voltages V6 and V10 or V6' and V10' with a variable duty ratio of 20 kHz are applied to transistors 8 and 4 only during the period when transistors 8 and 4 are conductive, respectively. Therefore, for example, when transistor 4 is conductive, transistor 1
0 is turned on and off by high frequency voltage V10 or V10'. When the transistor 10 is on, the DC power supply 2 supplies the transistor 4, the inductor 20, the discharge lamp 22, and the transistor 10.
When the transistor 10 is turned off, current flows from the inductor 20 through the discharge lamp 22, the diode 16, and the transistor 4.
Conversely, when transistor 8 is on, transistor 6 is turned on and off by high frequency voltage V6 or V6'. When transistor 6 is on, direct current 2 flows from transistor 8 to discharge lamp 2.
2. A current flows through the inductor 20 and the transistor 6, and when the transistor 6 is turned off, a current flows from the inductor 20 through the diode 12, the transistor 8, and the discharge lamp 22. Based on the principle described above, the discharge lamp 22 is lit by flowing an alternating current having a frequency corresponding to the on/off states of the transistors 4 and 8. Note that when the transistor 4 (or 8) changes from the on state to the off state, the diode 14 (or 18) connects the inductor 20 - discharge lamp 22 - diode 16 - DC power supply 2 - diode 14 - inductor 20 or inductor 20. -Discharge lamp 22-Transistor 10
- Diode 14 - Inductor 20 (or inductor 20 - Diode 12 - DC power supply 2 - Diode 18 - Discharge lamp 22 - Inductor 20 or Inductor 20 - Transistor 6 - Diode 18 - Discharge lamp 22 - Inductor 20). This protects the transistors. Note that V in FIG. 2a is applied to transistors 4 and 8.
4. When applying a voltage that switches on and off at the same time, such as V8, when transistor 4 turns off, transistor 8 changes from off to on.
A path of inductor 20 - diode 12 - transistor 8 - discharge lamp 22 - inductor 20 is created,
When the transistor 8 is turned off from on, a path of inductor 20 - discharge lamp 22 - diode 16 - transistor 4 - inductor 20 is created, so the diodes 14 and 18 can be omitted. Also, in this circuit, high frequency voltages V6 and V10 or V6' and V1
By varying the duty ratio of 0', that is, the on/off ratio, the current flowing through the discharge lamp 22 is varied to perform dimming or illuminance control.

By the way, in the conventional circuit shown in Figure 1,
As is clear from FIG. 2, the base voltages V4, V8, etc. of transistors 4 and 8 are set to high levels alternately, and the base voltages V6, V10, etc. of transistors 6 and 10 are set to high levels, respectively. The voltage is a voltage that repeats level changes only when the base voltages V8, V4, etc. of are at a high level. However, especially when the discharge lamp serving as a load is a high-pressure discharge lamp, the starting voltage of the high-pressure discharge lamp is high, and a high-voltage pulse is often used as the starting voltage. Therefore, the control circuit (not shown) that controls each transistor 4, 6, 8, 10, etc. may malfunction during startup, and the series-connected transistors 4 and 6 or 8 and 10 may turn on at the same time. be. Such a phenomenon of simultaneous ON occurs when the base voltages applied to transistors 4 and 8 are, for example, V4' and V4' shown in FIG. 2b.
This may occur even when there is a pause period t between each other like 8'. When such a simultaneous ON state occurs, the DC power supply 2 becomes short-circuited, causing a large current to flow through each transistor, causing the transistor to be destroyed.

SUMMARY OF THE INVENTION In view of the above-mentioned problems with the conventional type, an object of the present invention is based on the concept of inserting an inductor between transistors connected in series in a discharge lamp lighting device. The purpose is to prevent destruction.

Embodiments of the present invention will be described below with reference to the drawings. FIG. 3 shows a circuit of a discharge lamp lighting device according to an embodiment of the present invention. In the circuit shown in the figure, a series circuit of a transistor 28 and a diode 34 and a series circuit of a transistor 32 and a diode 38 are connected to the DC power supply 24, and one ends of inductors 42 and 44 are connected to the midpoint of each series circuit. A discharge lamp 46 is connected to the other ends of the inductors 42 and 44. Further, a series circuit of the transistor 26 and the diode 36 and a series circuit of the transistor 30 and the diode 40 are connected to the series power supply 24, and the intermediate point of each series circuit is connected to the other end of the inductor 42 and 44, that is, the discharge lamp 46. connected to both ends.

In the circuit of FIG. 3, the same low frequency voltages as the base voltages V4 and V8 or V4' and V8' of transistors 4 and 8 in the circuit of FIG. 1 are applied to the bases of transistors 26 and 30, respectively. Furthermore, the base voltages V6 and V10 of transistors 6 and 10 in the circuit of FIG. 1 are applied to the bases of transistors 28 and 32.
Alternatively, the same variable duty ratio high frequency voltage as V6' and V10' is applied. When the transistor 26 is on, the transistor 32 is turned on and off by the high frequency voltage V10, etc., and when the transistor 32 is on, the DC power supply 24 connects the transistor 26, the discharge lamp 46, and the inductor 4.
When the transistor 32 is turned off, current flows from the inductor 44 through the diode 38, the transistor 26, and the discharge lamp 46. And vice versa,
When the transistor 30 is on, the transistor 28 is turned on and off by a high-frequency voltage, and when the transistor 28 is on, current flows from the DC power supply 24 through the transistor 30, the discharge lamp 46, the inductor 42, and the transistor 28, and the transistor When 28 is turned off, current flows from inductor 42 through diode 34, transistor 30, and discharge lamp 46. In the above manner, the discharge lamp 46
is lit by the flow of an alternating current with a frequency corresponding to the on/off state of the transistors 26 and 30. Diodes 36 and 40 discharge the current in inductors 44 and 42 when transistors 26 and 30 change from an on state to an off state, respectively. To explain the case where the transistor 26 changes from an on state to an off state as an example, a discharge path is formed between the inductor 44 - diode 38 - DC power supply 24 - diode 40 - inductor 44 or the inductor 44 - transistor 32 - diode 40. It is something. but,
As in the conventional case, when a voltage is supplied so that the transistor 30 is turned on at the same time as the transistor 26 is turned off, a discharge path from the inductor 44 to the diode 38 to the transistor 30 is formed. can be omitted.

Incidentally, in the circuit shown in FIG. 3, even if the transistors 26 and 28 are momentarily turned on at the same time, for example, a large current will not flow from the DC power supply 24 through the inductor 42. Short circuit condition and each transistor 26
Otherwise, destruction of 28, etc. is prevented. Similarly,
Even if the transistors 30 and 32 are momentarily turned on simultaneously, the inductor 44 short-circuits the DC power supply 24 and prevents each transistor 30 and 3 from short-circuiting.
2 destruction is prevented.

FIG. 4 shows a circuit of a discharge lamp lighting device according to another embodiment of the present invention. In the circuit shown in the figure, a series circuit of a transistor 50 and a diode 58 and a series circuit of a transistor 56 and a diode 60 are connected in parallel to a DC power supply 48, and one ends of inductors 62 and 64 are connected to the midpoint of each series circuit. , a discharge lamp 66 is connected between the other ends of each of these inductors 62 and 64. Further, transistors 52 and 54 are connected between the other end of each inductor 62 and 64 and the negative voltage terminal of DC power supply 48.
is connected.

In the circuit of FIG. 4, low frequency voltages V4 and V8 shown in FIG. 2a are applied to the bases of transistors 52 and 54, respectively, and high frequency voltages V6 and V10 are applied to the bases of transistors 50 and 56, respectively. Ru. Therefore,
When both transistors 56 and 52 are turned on, current flows from DC power supply 48 through the path: DC power supply 48 - transistor 56 - inductor 64 - discharge lamp 66 - transistor 52 - DC power supply 48 . Transistor 52 on, transistor 56
is off, the inductor 64 - discharge lamp 66
A discharge path of - transistor 52 - diode 60 is formed. When both transistors 50 and 54 are on, current is supplied from DC power supply 48 through the path: DC power supply 48 - transistor 50 - inductor 62 - discharge lamp 66 - transistor 54 - DC power supply 48 . Further, when the transistor 50 is on and the transistor 54 is off, a discharge path of inductor 62 - discharge lamp 66 - transistor 54 - diode 58 is formed. These base voltages cause a circuit including transistor 50, inductor 62, discharge lamp 66, and transistor 54, and transistor 56, inductor 64,
An alternating current is alternately passed through the discharge lamp 66 and the circuit including the transistor 52, and the discharge lamp 66 is turned on. In the circuit of FIG. 4, for example, when transistors 50 and 52 or 56 and 54 are turned on simultaneously, the inductor 62 or 64
This action prevents each transistor etc. from being destroyed. Further, in this embodiment, when the transistor 52 is turned off from on, the transistor 52 is turned off at the same time.
Since the voltage V8 that turns on the transistor 54 is supplied to the transistor 54, the inductor 64
Since a discharge path of - transistor 54 - diode 60 is formed, the diode parallel to transistor 50 can be omitted. For the same reason, the diode parallel to the transistor 56 can also be omitted.

Note that each transistor in each of the above embodiments can be replaced with a switching element such as an SCR or a GTO, and the high frequency voltage and low frequency voltage applied to the base of each transistor can also be replaced. is clear.

Further, the circuit of the present invention detects the current of the discharge lamp and performs constant illuminance illumination by controlling the duty ratio of the high frequency voltages V6, V10 or V6', V10' according to the detected current or manually. It can also be used for night lighting and dimming lighting.

In this way, according to the present invention, one can be added to the conventional circuit.
By simply adding one inductor, short-circuiting of the power supply, destruction of each switching transistor, etc. can be accurately prevented, and the reliability of the discharge lamp lighting device can be improved.

[Brief explanation of the drawing]

FIG. 1 is an electric circuit diagram showing the configuration of a conventional discharge lamp lighting device, FIG. 2 is a waveform diagram for explaining the operation of the discharge lamp lighting device, and FIGS. 3 and 4 are respectively diagrams of the present invention. FIG. 1 is an electric circuit diagram showing the configuration of a discharge lamp lighting device according to an embodiment. 2, 24, 48...DC power supply, 4, 6, 8, 1
0, 26, 28, 30, 32, 50, 52, 5
4, 56...transistor, 12, 14, 16,
18, 34, 36, 38, 40, 58, 60...
Diode, 20, 42, 44, 62, 64...
Inductor, 22, 46, 66...discharge lamp.

Claims (1)

[Claims] 1 A DC power supply having first and second terminals, a first and second inductor, a first switching element connected between one end of the first inductor and a second terminal of the DC power supply, a second a second switching element connected between one end of the inductor and the second terminal of the DC power supply; a third switching element connected between the other end of the first inductor and the first terminal of the DC power supply;
a fourth switching element connected between the other end of the second inductor and the first terminal of the DC power supply; and a fourth switching element connected between the other end of the first inductor and the other end of the second inductor. a discharge lamp connected between the first switching element and the first switching element;
An alternating current is supplied to the discharge lamp by alternately using a circuit including an inductor, a fourth switching element, a second switching element, a second inductor, and a third switching element. Discharge lamp lighting device.