JPS5851316A - Power supply device - Google Patents

Abstract

PURPOSE:To improve an input power factor by applying the AC component of an impulsive voltage to the voltage control circuit of a constant voltage DC power supply device, and cancelling the peak part of an output current by said AC component. CONSTITUTION:When an output voltage to a load 3 is higher than a reference voltage, an error amplifier 5 outputs a positive error signal and a control circuit 6 lowers the output voltage by decreasing the quantity of fed electricity according to the error signal. When the output voltage is lower than the reference voltage, on the other hand, respective parts operate so that the output voltage is raised. Further, an AC-component superposing circuit 7 superposes an AC component upon the error signal in phase with the error signal, so the error signal varies in the same direction with the raised voltage when the instantaneous value of the AC component is large, or with the lowered output voltage when small, thus decreasing or increasing the input current.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a constant voltage DC power supply device having a high input power factor and suitable for use in a discharge lamp lighting device mainly using an inverter circuit.

Conventionally, as shown in FIG. 1, as a constant voltage DC power supply device, a full-wave rectifier 2 connected to an AC power supply 1 compares the output voltage to a load 6 with a reference voltage of a reference voltage source 4 and outputs the output voltage. An error amplifier 5 that outputs an error signal according to the difference between the voltage and the reference voltage, and a control circuit that is connected to the load side of the full-wave rectifier 2 and controls the amount of current to the load 3 so as to reduce the error signal. 6 and supplies constant voltage direct current to the load 6 is known.

However, since such a power supply device usually includes a smoothing circuit such as a smoothing capacitor on the output side of the full-wave rectifier 2, the waveform of the input current has many harmonic components with high peak values. The power factor was as low as 60% at most.

Also, as disclosed in Japanese Patent Application Laid-open No. 50-98175,
The pulsating voltage waveform on the load side of the full-wave rectifier is compared with the load current waveform to obtain a difference signal, and this difference signal controls the amount of current to the load to forcibly change the load current waveform to the pulsating current waveform. A power supply device that achieves a high input power factor by making the waveform similar is also known.

However, this power supply device does not give any consideration to constant voltage characteristics, and a constant voltage DC power supply with a high input power factor has not yet been realized.

An object of the present invention is to provide a constant voltage DC power supply device with a high input power factor, which is particularly suitable for use in a discharge lamp lighting device using an inverter circuit.

The present invention will be described in detail below using the drawings.

FIG. 6 is a circuit diagram of a power supply device according to an embodiment of the present invention. This power supply device is obtained by adding an AC component superimposing circuit 7 for superimposing an AC component in the pulsating output of the full-wave rectifier 2 onto an error signal in phase with the error signal to the power supply device shown in FIG.

This alternating current component superimposing circuit includes resistors 8 and 9 that divide the pulsating current output and adjust the amount of superimposition, and a capacitor 10 that inputs only the alternating current component in the divided pulsating current voltage to the error amplifier 5.
It consists of In this embodiment, the AC component is added to the signal related to the output voltage to the load 6 and then compared with the reference voltage to obtain an error signal on which the AC component is superimposed. It may be added to the AC component using a device or the like.

In addition, although the capacitor 10 is used as an element for cutting off direct current, an isolation transformer may also be used. Furthermore, a low cutoff filter or a bandpass filter or the like may be used to cut off direct current and reduce each harmonic component at a specific ratio. By superimposing them, the input current may be adjusted to a more suitable waveform.

Next, the operation of this power supply device will be explained. An AC input from an AC power source 1 is rectified by a full-wave rectifier 2, passes through a control circuit 6, becomes DC, and is supplied to a load 3.

When the supply voltage to the load 6, that is, the output voltage, is higher than the reference voltage, the error amplifier 5 outputs, for example, a positive error signal,
- In response to this error signal, the control circuit reduces the current flow and lowers the output voltage. When the output voltage is lower than the reference voltage, each part operates to raise the output voltage, contrary to the above. Therefore, this power supply device has a constant voltage characteristic that always outputs a voltage equal to the reference voltage. In addition, in this power supply device, since the alternating current component is superimposed on the error signal in phase with the error signal, when the instantaneous value of the alternating current component is large (Fig. 2 T
I), the error signal fluctuates in the same direction as when the output voltage becomes high, and when the instantaneous value is small (T2 in Figure 2), the error signal fluctuates in the same direction as when the output voltage becomes low, and the input current is Decrease and increase. As a result, the high peak of the input current waveform (FIG. 2a) in the conventional example is suppressed, and a high input power factor of, for example, about 98% is obtained. The input current waveforms (after full-wave rectification) of this power supply are shown in Figure 2 and C.
The input voltage waveform (after full-wave rectification) is shown in Figure 2d. C is b
This is the case when more AC components are superimposed.

As the control circuit 6, for example, a negative feedback direct current constant voltage control circuit such as a step-up circuit or an inverting circuit in a switching regulator or the like may be used.

4 and 5 show specific examples of the control circuit 6 in the power supply device of the present invention. FIG. 4 shows a boost type control circuit, and FIG. 5 shows an inversion type control circuit. In the same figure, 61 is a choke, 62
is a transistor, 65 is a diode, and 64 is a capacitor. Further, the choke 65 and the capacitor 66 form a noise prevention filter.

Next, the operation of the control circuit shown in FIG. 4 will be explained. A pulse width modulation circuit (not shown) that outputs a pulse whose pulse width is controlled by the output of the error amplifier 5 shown in FIG. 6 is connected to the base of the transistor 62. This pulse is output with a pulse width such that, for example, the output of the error amplifier 5 and the duty ratio are directly proportional. Now, when the output voltage to the load 3 in FIG. 6 falls below the reference voltage and the output of the error amplifier 5 rises, the pulse output from the pulse width modulation circuit has a large pulse width (duty ratio). Therefore, when the transistor 62 is turned on, the on time of the transistor 62 becomes longer, the current of the choke 61 increases, and its electromagnetic energy increases. Since the output voltage is smoothed and output, the output voltage increases. When the output voltage increases, the operation is opposite to that described above and the output voltage decreases. In this way the output voltage is always kept constant.

The control circuit shown in FIG. 5 operates in the same manner as the control circuit shown in FIG. 4, except that the signs of voltage and current are reversed, and the output is made constant.

As described above, according to the present invention, by applying the alternating current component of the pulsating voltage to the voltage control circuit of the constant voltage DC power supply and canceling the peak portion of the input current, that is, the output current, with this alternating current component, the input power factor is reduced. It is possible to achieve significant improvements in Further, since this power supply device has a constant average voltage, it is particularly suitable for use in discharge lamps.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram of a conventional power supply device, and Fig. 2 is an input current waveform (, -c
) and input voltage waveform (d), FIG. 3 is a circuit diagram of a power supply device according to an embodiment of the present invention, and FIGS. 4 and 5 show specific examples of the control circuit of the power supply device of FIG. 6. It is a circuit diagram. 1... AC power supply 2... Full wave rectifier 3...
Load 4...Reference voltage source 5...Error amplifier 6...Control circuit 7...AC component superimposition circuit 8
, 9... Resistor 10... Capacitor patent applicant Toshiba Electric Materials Co., Ltd. Representative Patent attorney Tatsuo Ito Tetsuya Ito Figure 2 T, T2

Claims (1)

[Claims] 1. An AC power source, a full-wave rectifier that is connected to the AC power source and outputs a pulsating current, a reference voltage source that generates a reference voltage, and an output voltage to a load and the reference voltage. an error amplifier that compares and outputs an error signal according to the difference between this output voltage and a reference voltage; and an error amplifier that is connected to the load side of the full-wave rectifier and controls the amount of current applied to the load so as to reduce the error signal. A power supply device comprising: a control circuit for controlling; and an exchange superimposition circuit for superimposing an alternating current component in the pulsating output of the full-wave rectifier onto the error signal.