JPH04163885A - Power supply device for halogen lamp - Google Patents

Abstract

PURPOSE:To enhance the regulation characteristics by installing a MOS-FET between a DC power supply and the primary coil of an output transformer, turning on and off this MOS-FET with the output of an oscillator. and lighting a halogen lamp with the output from the secondary coil of output transformer. CONSTITUTION:Drains of M0S-FETs 15. 16 are connected with the two ends of the primary coil 17a of an output transformer 17, and the positive side of a DC power supply is connected to the center of the primary coil, and sources of the FETs 15, 16 are connected with the negative side of the DC power supply. The output of an oscillator circuit 10 is fed to the gates of these FETs 15, 16 constituting a push-pull circuit, and rise of signal in the oscillator circuit 10 is delayed through the actions of the gate capacities of FETs and the time constant of transistors 11, 12 and resistances 13, 14, and the FETs 15, 16 are driven. A halogen lamp HL is lighted with the output from the secondary coil 17b of the transformer 17. Thereby the regulation characteristics are enhanced without destroying the FETs with rush current at the time the lamp is lighted up, and the wave height of the output voltage can be lowered.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a power supply device for a halogen lamp.

[Summary of the invention]

A first power supply device for a halogen lamp according to the present invention includes a DC power supply, an oscillator driven by the DC power supply, a MOS-FET whose gate is supplied with the oscillation output of the oscillator to turn it on and off, and a MOS-FET in the primary coil. By having an output transformer to which the output electrode of the FET is connected and the halogen lamp is connected to the secondary coil, there is no risk that the switching element will be destroyed by the rush current when the halogen lamp starts lighting, and the regulation is improved. It has good characteristics and the peak value of the output voltage is low.

A power supply device for a halogen lamp according to a second aspect of the present invention includes a DC power supply, an oscillator driven by the DC power supply, and a pair of MOS-FETs whose gates are supplied with the oscillation output of the oscillator and are turned on and off alternately. By having an output transformer in which a pair of MOS-FET output electrodes are connected to the primary coil and a halogen lamp is connected to the secondary coil, the switching element is not destroyed by the rush current when the halogen lamp starts lighting. The present invention is designed so that there is no risk of damage, has good regulation characteristics, and has a low peak value of the output voltage.

[Conventional technology]

In the world of lighting, there has been a remarkable shift from focusing on brightness to spot lighting with individuality. A halogen lamp is a light source for such spot lighting, and the market for this lamp is rapidly expanding.

Below, with reference to FIG. 4, a conventional example of a power supply device (commonly referred to as an electronic transformer) used for such a halogen lamp, particularly a low voltage halogen lamp, will be explained.

This power supply device is a self-excited half-bridge type electronic transformer that uses a bipolar transistor as a switch notching element.

A 100V commercial AC voltage is rectified by a bridge rectifier circuit BR, and smoothed or noise removed by a series circuit of capacitors C and C2 to obtain a DC voltage (normal temperature or pulsating current), which is then applied to capacitors C1, C2, It is supplied to an oscillation circuit including an output transformer T, output high polar transistors Q, , 02, etc. Thus, the output transistor Q,
, C2 are alternately turned on and off according to the oscillation operation of the oscillation circuit.

The output transformer T has a primary coil a and a secondary coil b, and is configured such that an AC voltage of 10.5 V output to the secondary coil b is applied to the halogen lamp HL.

[Problem to be solved by the invention]

Such conventional power supply devices for halogen lamps have the following drawbacks. The rush current at the start of lighting of a halogen lamp reaches approximately 13 times the steady current. For this reason, when using a hyperpolar transistor as a switching element in a power supply device for a halogen lamp, it is necessary to use a hyperpolar transistor with as large an allowable collector current as possible, and even if a hyperpolar transistor with a somewhat large allowable collector current is used,
Depending on the rush current flowing through the halogen lamp, the transistor could often be destroyed.

In addition, because conventional power supplies are self-excited, they have poor regulation characteristics, as shown in Figure 2, and when the output voltage drops to around 6V, they stop oscillating, as shown in Figure 3B. However, there was a drawback that the peak value of the output voltage rose to nearly 20V.

In view of this, there is no risk that the switching element will be damaged by the rush current when the halogen lamp starts lighting.
Furthermore, the present invention attempts to propose a power supply device for a halogen lamp that has good regulation characteristics and can lower the peak value of the output voltage.

[Means to solve the problem]

A power supply device for a halogen lamp according to a first aspect of the present invention includes a DC power supply (5, 6), an oscillator (10a) driven by the DC power supply (5, 6), and an oscillator (10a) driven by the DC power supply (5, 6).
The oscillation output of the MOS is supplied to the gate and turns on and off.
-FET (15), and an output transformer (17) to which the output electrode of MOS-FET (15) is connected to the primary coil (17a) and to which the halogen lamp HL is connected to the secondary coil (17b). It has the following.

The power supply device for a halogen lamp according to the second aspect of the present invention includes a DC power source (5, 6), an oscillator (10a) driven by the DC power source, and an oscillation output of the oscillator (10a) supplied to the gate. A pair of MOs that alternately turn on and off
S-FET (15), (16) and a pair of MOS-FET (15) in the primary coil (17a)
, (16) are connected, and the secondary coil (17b
) and an output transformer to which a halogen lamp HL is connected.

[Effect]

According to the first halogen lamp power supply device of the present invention, the MOS-FET (15) is connected to the oscillator (10a
) is always turned on and off by the output transformer (1
The AC voltage obtained in the secondary coil (17b) of 7) is applied to the halogen lamp HL.

According to the second power supply device for a halogen lamp of the present invention, the pair of MOS-FETs (15) and (16) are always alternately turned on and off by the oscillator (10a), and the output transformer (17) is turned on and off alternately. The AC voltage obtained at the secondary coil (17b) is applied to the halogen lamp HL.

〔Example〕

Hereinafter, embodiments of the present invention will be described in detail with reference to FIG. FIG. 1A shows the entire circuit of a power supply device (electronic transformer) for a halogen lamp, and FIG. 1B shows an equivalent circuit of the oscillation circuit shown in FIG.

The 100V commercial AC voltage from the input terminals (1) and (2) is supplied to the bridge type rectifier circuit (5) through the surge absorber (3) and noise filter (4) and is rectified, and the rectified output is smoothed or noise-free. Removal capacitor (6
) to smooth or remove noise. However,
A DC voltage (normal temperature or pulsating current) of 100 cm is outputted to both ends of the rectifier circuit (5), with the upper side being positive and the lower side being negative in the figure.

A series circuit of a resistor (7) and a Zener diode (8) serving as a limiter and voltage regulator is connected to both ends of the capacitor (5), so that a DC voltage of IIV is output across the Zener diode (8). done to. A DC voltage holding capacitor (its capacitance value is, for example, 470 μF) is connected to both ends of this Zener diode (8).
) are connected in parallel. Due to the presence of this capacitor (6), even if the DC voltage from the rectifier circuit (5) temporarily decreases or is cut off, the
In c), a DC voltage of 4V or more can be maintained. Therefore, since there is no risk that the oscillator (10a) will stop oscillating, it is possible to adjust the brightness of the halogen lamp by controlling the flow angle of the AC voltage using a dimmer.

(10) is an oscillation circuit, which is constructed by connecting a CMOS inverter IC (for example, μPD4066) with external resistors and capacitors, and includes an oscillator (10a) and a capacitor. It consists of inverters (30) and (31) connected in parallel on the output side. Note that the specific configuration of this oscillation circuit (10) will be described later.

(15) and (16) are N-channel power MOS-FETs as switching elements, and oscillation signals (sine wave or rectangular wave), it is turned on and off alternately.

(17) is the output transformer, its primary coil (17a)
The drains of MOS-FETs (15) and (16) are connected to both ends of the MOS-FET (15) and (16), respectively, and a halogen lamp HL is connected to both ends of the secondary coil (17b) via output terminals (18) and (19). For example, an AC voltage of 10.5V is applied. These MOS-FET(15),
(16) and the transformer (17) constitute a push-pull circuit. Then, one end of the capacitor (6) (
The positive side) is the primary coil (17a) of this transformer (17).
), and the other end (negative side) of the capacitor (6)
is commonly connected to each source of MOS-FET (15) and (16).

Next, an equivalent circuit of the oscillation circuit (10) shown in FIG. 1B,
The resistors (12), (13) and bipolar transistors (11), (I2) connected to the gate sides of the MOS-FETs (15), (16) will be explained.

The oscillation circuit (10) includes six CMOS inverters, and three of the inverters are connected to external elements to form an oscillator (10a), and an inverter (30) is connected to the output side of the oscillator (10). , (31) are connected in parallel, and the remaining inverter (not shown) is not used.

First, the configuration of the oscillator (10a) will be explained.

(23), (26) and (27) are the oscillators (10
There are three inverters that make up a). Input terminal (2
The IIV DC voltage from 1) is applied to the input terminal of the inverter (23) through the resistor (22). A capacitor (2
4) is connected. The output terminal of the inverter (23) is connected to the input terminal of the inverter (26) through a resistor (25). An output terminal of the inverter (26) is connected to an input terminal of the inverter (27). Inverter (2
A resistor (28) is connected between the output terminal of 7) and the input terminal of the inverter (26). A resistor (29) is connected between the output terminal of the inverter (27) and the input terminal of the inverter (23). In addition, resistors (22) and (25
), (28), and (29) are each externally connected resistors, and (24)
is an external capacitor.

In this oscillator (10a), the inverter (26)
, (27) are of course in opposite phase relation to each other. However, Inno \-ta (2
The output of 7) is used as an inverter (30) as a hash sofa.
At the same time, the output of the inverter (26) is supplied to the inverter (31) as a no.lambda.
-output terminals (32) and (30) and (31) respectively.
33) is derived.

Then, the output terminal (32) is connected to the gate of MOS-FET (15) through the resistor (13). The base of the PNPN convex polar transistor (11) is connected to the output terminal (32), and the emitter is connected to the MOS-
It is connected to the gate of the FET (15), and its collector is connected to the negative side of the rectifier circuit (5). In addition, the output terminal (33) is passed through the resistor (14), and MOS -FET (1
Connect to the gate of 9). Connect the base of the PNPN convex polar transistor (12) to the output terminal (33), connect the emitter to the gate of MOS-FET (16), and connect the collector to the negative side of the rectifier circuit (5). do.

Next, the operation of the parts related to the resistors (11), (12) and transistors (11), (12) of this power supply device will be explained. When the oscillation signal supplied to the base of the transistor (11) rises and the oscillation signal supplied to the transistor (12) falls, the transistor (11)
) is off, the transistor (12) is on, and the resistance value of the resistor (13) and M OS -FET (15
), its input capacitance is charged with a time constant determined by the gate capacitance value of the transistor (12), and the input capacitance is charged with a time constant determined by the collector-emitter resistance value of the transistor (12) and the gate capacitance value of the MOS-FET (16). , a discharge from its gate capacitance takes place.

Furthermore, when the oscillation signal supplied to the base of the transistor (11) falls and the oscillation signal supplied to the transistor (12) rises, the transistor (11) is turned on and the transistor (12) is turned off. (11) Resistance value between collector, emitter and lid and M O
The gate capacitance is discharged with a time constant determined by the value of the gate capacitance of S -F E T (15), and the resistance value of the resistor (14) and the MOS-F E
With the time constant determined by the gate capacitance value of T (16),
Its input capacitance is charged.

In this case, by selecting the resistance values of the resistors (13) and (14) to, for example, about 300Ω, the MOS
-FET The level of the nosh current to the gates of (15) and (16) can be suppressed. Further, by changing the resistance values of the resistors (13) and (14), the charging time constant for the gate capacitance of the MOS-FETs (15) and (16) can be arbitrarily selected. Therefore, due to the charging time constant for the gate capacitance of these MOS-FETs (15) and (16), the rise of the oscillation signal is delayed, and MOS-FET (15
) and (16) are turned on at the same time, and there is no possibility that the drain currents will flow at the same time (vertical currents will flow). Note that the resistance value between the collector and emitter when the transistors (12) and (13) are turned on is much smaller than the resistance value of the resistors (13) and (14), so that MOS - F ET (
The discharge time constant for the gate capacitance in (15) and (16) is:
This is much smaller than the charging time constant.

FIG. 2 shows the regulation characteristics of the power supply device of this embodiment. The regulation characteristics are better than those of the conventional example, and even if the output voltage becomes high, the output current does not drop that much and there is no risk of stopping oscillation.

Further, FIG. 3A shows the instantaneous value of the output voltage of the power supply device of this embodiment, and the peak value of the output voltage can be lowered compared to the conventional example shown in FIG. 3B.

A comparison between the push-pull type power supply device of the embodiment and the conventional half-bridge type power supply device is as shown in the table below.

′ However, Vi is the DC power supply voltage, ■ is its average current,
N is the turns ratio of the transformer (17).

〔Effect of the invention〕

According to the above-described power supply device for a halogen lamp of the present invention, since a MOS-FET is used as a switching element and is of a self-excitation type, there is no risk that the switching element will be damaged by the rush current when the halogen lamp starts lighting.
In addition, the regulation characteristics are good, and the peak value of the output voltage can be lowered.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, FIG. 2 is a characteristic curve diagram showing regulation characteristics of the embodiment and a conventional example,
FIG. 3 is a waveform diagram showing the output voltages of the embodiment and the conventional example, and FIG. 4 is a circuit diagram showing the conventional example. (5) is a rectifier circuit, (8) is a Zener diode, (9
) is the DC voltage holding capacitor, (10) is the oscillation circuit,
(10a) is an oscillator, (11) and (12) are each a bipolar transistor, (13) and (14) are each a resistor,
(15) and (16) are MOS-FETs, (17) is an output transformer, and (18) is a halogen lamp.

Claims (1)

[Claims] 1. A DC power source, an oscillator driven by the DC power source, a MOS-FET whose gate is supplied with the oscillation output of the oscillator to turn it on and off, and an output electrode of the MOS-FET in the primary coil. 1. A power supply device for a halogen lamp, comprising: an output transformer to which a secondary coil is connected, and a halogen lamp is connected to a secondary coil. 2. A DC power source, an oscillator driven by the DC power source, a pair of MOS-FETs whose gates are supplied with the oscillation output of the oscillator and are turned on and off alternately, and an output of the pair of MOS-FETs that is connected to the primary coil. A power supply device for a halogen lamp, comprising an output transformer to which an electrode is connected and a halogen lamp is connected to a secondary coil.