JPS60133698A - Power source - 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 of the Invention] The present invention relates to a power supply device used in electronic equipment such as a copying machine.

[Technical background of the invention and its problems]

As is well known, in recent years, switching type power supplies have become mainstream as power supplies for lighting fluorescent pairs used in copying machines, for example.

FIG. 1 shows a conventional power supply device of this type. The output current of the AC power supply 11 is supplied to the DC' trace circuit 12 . This DC power supply circuit) 12 is a so-called switching regulator, which is first rectified by a rectifier circuit (not shown) and then switched by a switching circuit, and this switching output is rectified to generate stabilized DC power. This DC power is supplied to an inverter circuit 13, where it is converted into high frequency power. This high frequency power is applied to the filament 1 of the fluorescent pair 14.
5. ．． 15□, and the fluorescent pair 14 is turned on.

Incidentally, in the above configuration, the output power of the DC power supply circuit 12 is converted back into high frequency power by the inverter circuit 13 and is supplied to the fluorescent pair 14. For this reason, DC/
The number of AC conversions is large, resulting in poor power efficiency.

Furthermore, the inverter circuit 13 has many parts.

Since the structure is complicated, it is economically disadvantageous.

[Purpose of the invention]

This invention was made based on the above circumstances,
The objective is to provide a power supply device that has good power efficiency, has a small number of parts, has a simple configuration, and is inexpensive.

[Summary of the invention]

This invention provides, for example, a resonant circuit in the secondary winding of a transformer provided at the output end of a switching circuit constituting a DC power supply circuit, and supplies the output power of this resonant circuit as lighting power to a fluorescent lamp via the transformer. It is something to do.

[Embodiments of the invention]

Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

In FIG. 2, the output current of a commercial AC power source 21 is supplied to a rectifier circuit 22 and rectified. The DC power output from this rectifier circuit 22 is supplied to a switching circuit 23. In this switching circuit 23, the supplied DC power is converted into high frequency power of, for example, about 20 kHz via a switching element. This high frequency power is transferred to the transformer 24
A secondary winding 242+2'3 is wound around this transformer 24, and a rectifier circuit 25 is provided in the secondary winding 243 of the transformer 24. In this rectifier circuit 25, the high frequency power is converted into DC power, and this DC power is supplied to a load (not shown), and
The signal is supplied to the feedback circuit 26. This feedback circuit 26 is a so-called pulse width control circuit that generates pulse signals having different duty ratios depending on the DC level, and the generated /4' pulse signal is supplied to the switching circuit 23. The switching circuit 23 is controlled in accordance with this pulse signal to stabilize the DC output.

The above configuration is basically the same as the DC' power supply circuit 12 shown in FIG.

On the other hand, the secondary winding 242 is provided with a fluorescent lamp lighting circuit. That is, the secondary winding 24□ is provided with a series resonant circuit 27 consisting of a coil L and a capacitor C, and this capacitor C has a resistor R and the primary winding 28□ of the transformer 28.
are connected in parallel. This transformer 28 includes secondary windings 28□ and 283 that flow heater current (AT) to the filaments 291 and 292 of the fluorescent lamp 29, respectively, and boost the voltage to the filaments 291 and 292 of the fluorescent lamp 29, respectively.

A secondary winding 284 is provided to supply a discharge voltage to 29□.

The operation of the fluorescent lamp lighting circuit having the above configuration will be explained. A high frequency rectangular wave signal as shown in FIG. 3(a) is normally output to the secondary winding 24□ of the transformer 24. The fundamental frequency of this signal is, for example, f. is set, and coil L1
Similarly, the series resonant circuit 27 consisting of the capacitor C has f. A resonant frequency is set. For this reason, the fluorescent lamp 29
When the load is small, that is, when the fluorescent light 29 is not lit, a high voltage is generated across the capacitor C as shown in FIG. 3(b), and the secondary winding 28 of the transformer 28
4, a high voltage is generated.

Also, at this time, the filament 29□ of the fluorescent lamp 29,
Since a voltage higher than the normal voltage is supplied to 29□,
The firefly C lamp 29 is brought into a discharge state. Fluorescent lamp 2 like this
9 discharges, the fluorescent lamp twinpedance decreases, so the impedance of the primary winding 281 connected in parallel to the capacitor C of the series resonant circuit 27 equally dynamically decreases.

Therefore, the resonance point of the resonant circuit is f. The current regulated by the inductance of the coil L is deviated from the fluorescent lamp 2.
9 and the discharged state is maintained. FIG. 3(c) shows the waveform of the current flowing through the fluorescent lamp 29 at this time.

Note that the load normally connected to the rectifier circuit 25 uses almost constant power, such as a control circuit, and the power flowing into the fluorescent lamp 29 is constant, so voltage fluctuations in the AC power supply 2 The impact of this is extremely small.

According to the above embodiment, the series resonant circuit 27 is provided in the secondary winding 242 of the transformer 24 provided in the switching circuit 23, and the output power of this resonant circuit is transmitted to the fluorescent lamp 29 via the transformer 28 to provide lighting power. It is supplied as. Therefore, since an inverter circuit is not used as in the conventional case, the number of direct/AC conversions is reduced, and the amount of electric power can be improved. Moreover, the number of parts is small and the configuration is 17i.
], LLI: It is possible to make it inexpensive.

1゛ Fortune-telling above ability i! ! 4≦In the case of the river, a series resonant circuit was constructed by the coil ■ and the capacitor C.
It is also possible to connect to the secondary winding 284 of No. 8.

It goes without saying that various other modifications can be made without departing from the gist of the invention.

〔Effect of the invention〕

As described in detail above, according to the present invention, it is possible to provide a power supply device ii that has good power efficiency, has a small number of parts, has a simple configuration, and is inexpensive.

[Brief explanation of the drawing]

Figure 1 is a circuit configuration diagram showing an example of a conventional power supply device;
The figure is a circuit configuration diagram showing one embodiment of the power supply device according to the present invention, FIG. 3 is a waveform diagram shown to explain the operation of FIG. 2, and FIG. 4 is a circuit diagram showing another embodiment of the present invention. FIG. 22... Rectifier circuit, 23... Switching circuit, 2
4.28...Transformer, L...Coil, C...Capacitor, 29...Fluorescent lamp.

Claims (1)

[Claims] A power supply device that lights a discharge tube using high-frequency power, a switching power supply circuit that generates the high-frequency power;
A power supply device comprising a resonant circuit to which the generated high-frequency power is supplied, which has the same resonance frequency as the frequency of the high-frequency power, and which supplies lighting power to the discharge tube.