JPS63245264A - Power circuit device - Google Patents

Abstract

PURPOSE:To miniaturize a device, by smoothing switching current on the primary side of a converter transformer with a filter circuit. CONSTITUTION:In a power circuit device, the voltage at a commercial power source 11 is converted into DC voltage through a diode bridge circuit 12 and intermittently applied to the primary winding n1 of a converter transformer 15 by switching it with an FET 14 to obtain AC secondary voltage from the secondary winding n2. The secondary voltage is turned into DC voltage through a rectification-smoothing circuit 16. Further, the switching duty of the FET 14 is controlled with a voltage control circuit 17 to make the supply voltage constant to a load 18. On this occasion, a filter 20 is composed of a capacitor Ca and an inductor La to heighten smoothing effect to the switching frequency of the FET 14. A smoothing capacitor of small capacity and small size on the primary side can thus be used.

Description

[Detailed Description of the Invention] [Objective of the Invention] (Industrial Application Field) The present invention is directed to a power supply used in cases where high power and high precision are not required, such as a motor drive power supply for a video tape recorder. Related to circuit devices.

(Prior Art) Generally, a power supply circuit device as shown in FIG. 5 is used as a power supply for a motor of a video tape recorder. In this power supply circuit device, an AC voltage from a commercial power source 11 is full-wave rectified by a diode bridge circuit 12 to convert it into a pulsating voltage, and this pulsating voltage is smoothed by a capacitor 13 to obtain a DC voltage V13. Then, this DC voltage is applied to a converter transformer 1 such as a flyback type by switching drive of the FET 14.
5 is intermittently applied to the primary winding nl, thereby generating an induced current in the secondary winding n2 to obtain an AC secondary voltage.

Further, this secondary voltage is rectified and smoothed by a rectification and smoothing circuit 1B including a diode Dl and a capacitor C1 to obtain a DC voltage. This DC voltage is detected by the voltage control circuit 17 and compared with a reference voltage, and the switching duty of the FET 14 is controlled based on the comparison result, thereby controlling the DC voltage, that is, the voltage supplied to the load 18, to a constant or arbitrary value. Control to value. That is, this power supply circuit device is configured using a so-called switching regulator.

However, in such a configuration, since the commercial power supply 11 is used, the capacitor 13 is connected to the commercial frequency 50.
It is necessary to use a large-capacity device that can smooth the AC voltage of /60/400 [Hz].

In addition, since a commercial type 'ri (-order power supply) generally fluctuates by ±10% to ±20% with respect to the rated voltage, the capacitor 13 should be a capacitor with a withstand voltage that operates stably. must be used. Furthermore, the voltage V13 across the capacitor 13 is accompanied by ripples due to the switching of the FET 14, as shown in FIG.
The primary current 11 supplied from the commercial type ill is shown in Fig. 6 (b
), the positive and negative signals are alternately intermittent. Therefore, the AC-DC conversion efficiency is poor, and the primary winding n1 of the transformer 15
In order to flow the necessary DC current, an effective current approximately twice that amount is required. In this case, a large capacity capacitor is required, especially when a private generator is used. In other words, in the past, it was necessary to use a large-capacity and large-sized smoothing capacitor on the negative side.

(Problems to be Solved by the Invention) As described above, in conventional power supply circuit devices, a smoothing capacitor of large capacity and large size must be used on the negative side, resulting in an increase in the size of the device. - There is a problem in that the effective current on the next side must be nearly twice the required current.

This invention was made to solve the above problem.
- It is an object of the present invention to provide a power supply circuit device which is compact in size as a whole and has excellent power supply voltage conversion efficiency by using a small-sized and small-capacity smoothing capacitor on the next side.

[Structure of the Invention] (Means for Solving the Problems) In order to achieve the above object, a power supply circuit device according to the present invention includes a full-wave rectifier circuit that full-wave rectifies an AC voltage and converts it into a pulsating voltage. , a converter transformer to which a pulsating voltage outputted from the full-wave rectifier circuit is applied to the primary side; a switching means for generating an induced current in the secondary side by intermittent current flowing in the primary side of the converter transformer; A rectifying and smoothing circuit that rectifies and smoothes the induced current generated on the secondary side to generate a DC voltage, and the output voltage of this rectifying and smoothing circuit is compared with a reference voltage, and the pulse width of the switching means is adjusted based on the comparison result. voltage control means for stabilizing the output voltage of the rectifying and smoothing circuit by controlling the output voltage of the rectifying and smoothing circuit; and a filter circuit that performs the following functions.

(Function) The power supply circuit device with the above configuration smoothes the switching current flowing to the primary side of the converter transformer using the filter circuit, so the effective current of the input current is reduced compared to the conventional method that smoothes it at the frequency of the -order power supply. be able to. Further, since the filter circuit only needs to exhibit a smoothing effect only at the switching frequency, the capacitor forming the filter circuit has a small capacity, which contributes to miniaturization of the device.

(Embodiment) An embodiment of the present invention will be described below with reference to FIGS. 1 to 4.

FIG. 1 shows a configuration in which the present invention is applied to the power supply device shown in FIG. In FIG. 1, parts that are the same as those in FIG. 5 are indicated by the same symbol -n, and different parts will be explained here.

That is, in this power supply circuit device, capacitors Ca,
The inductor La constitutes a filter 20 that exhibits a smoothing effect on the switching frequency of the FET 14.

According to this configuration, the full-wave rectified voltage of the diode bridge circuit 12 directly becomes the output voltage V20 of the filter 20, as shown in FIG. 2(a). Therefore, the switching current 12 flowing through the primary winding n1 of the converter transformer 15 increases or decreases approximately in proportion to the instantaneous value of the input terminal V20 from the filter 20, as shown in FIG. Since this switching current 12 is smoothed by the capacitor Ca, the primary current i1 from the commercial power supply 11 is
), it flows over the entire range.

Here, the negative side effective current IRMS and the energization time are obtained.

Therefore, if the load current is the same, the device of this embodiment has a smaller effective current than the power supply circuit device of FIG.

Further, since the capacitor Ca does not have a smoothing effect on commercial frequencies like the device shown in FIG. 5, it may have a very small capacitance. For example, if the commercial frequency is 50 [Hz] and the switching frequency is 100 [KHz], 1/200
This means that a capacity of 0 is sufficient. Furthermore, since smoothing of the commercial frequency is performed on the secondary side of the converter transformer 15, it is not affected by fluctuations in the power supply voltage of the commercial power supply 11. for example,
If the power supply voltage fluctuates by ±20%, the circuit will be 33% smaller than the circuit shown in FIG.

Note that the switching current 12 flowing through the primary winding of the converter transformer 15 has an instantaneous value as shown in FIG. It becomes almost proportional to the quantity. In other words, the output voltage V20 of the filter 20
As long as V20 is small, the one-cycle integrated current of the switching current 12 increases linearly from the 0 level, as shown in (b') of the same figure, but as the output voltage V20 of the filter 20 increases, as shown in (C) of the same figure. As shown in , since the integrated current is larger than the load current, it is added to the residual current.

However, in this case as well, the capacitance of the capacitor can be similarly reduced due to the smoothing effect of the filter 20 on the switching frequency.

Therefore, in the power supply circuit device having the above configuration, a small capacitance and small size can be used as the smoothing capacitor on the next side, so that the entire device can be miniaturized.
Since the effective current on the next side can flow over the entire range, the conversion efficiency is extremely high.

In the above embodiment, the capacitor Ca and the inductor La are provided for smoothing the switching current, but the inductor La may be omitted if there is no effect on the outside even if a pulse current is passed as a negative current. . Further, in the above embodiment, a flyback type converter transformer is used, but the same effect can be obtained by using a forward type converter transformer. Further, in the above embodiment, one FET is used as the switch element, but it is needless to say that the switch element is not limited to FET, or that two or more may be used to adopt a double switch system.

[Effects of the Invention] As described above, according to the present invention, by using a small and small capacity smoothing capacitor on the negative side, the entire device is compact and a power supply circuit with excellent power conversion efficiency can be achieved. equipment can be provided.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an embodiment of a power supply circuit device according to the present invention, FIGS. 2 to 4 are waveform diagrams for explaining the operation of the same embodiment, and FIG. 5 is a conventional power supply circuit. A circuit diagram showing the configuration of the device, and FIG. 6 is a waveform diagram for explaining the operation of the conventional circuit. 11... Commercial power supply, 12... Diode bridge circuit, 13... Smoothing capacitor, 14... FET, 1
5... Converter transformer, 16... Rectifier and smoothing circuit, 17... Voltage control circuit, 1B... Load, 20...
·filter. Applicant's agent Patent attorney Takehiko Suzue Figure 1 Figure 5 (a) Figure 6

Claims (1)

[Claims] A full-wave rectifier circuit that full-wave rectifies AC voltage and converts it into pulsating voltage, a converter transformer to which the pulsating voltage output from this full-wave rectifier circuit is applied to the primary side, and A switching means that generates an induced current on the secondary side by intermittent flowing current, a rectifying and smoothing circuit that rectifies and smoothes the induced current generated on the secondary side to generate a DC voltage, and an output voltage of this rectifying and smoothing circuit. voltage control means for stabilizing the output voltage of the rectifying and smoothing circuit by comparing the voltage with a reference voltage and controlling the pulse width of the switching means based on the comparison result; A power supply circuit device comprising a filter circuit interposed between the primary input terminals of the converter transformer and exhibiting a smoothing effect at the switching frequency.