JPH06113455A - Direct-current power supply - Google Patents

Abstract

PURPOSE:To quickly detect service interruption by presetting a microcomputer, for instance, the interruption of a rectangular wave input is to be service interruption since a rectangular wave input to a microcomputer is interrupted when service interruption is brought about. CONSTITUTION:The secondary output of a transformer 10 is transferred through a full-wave rectification circuit 11, a smoothing capacitor 12 and a stabilized power supply to deliver d.c. voltage (Vcc). A center tap 14 is provided in the secondary winding of the transformer 10, and the voltage taken out from the center tap 14 is inputted to a waveform shaping circuit 18 through a diode 15 and resistors 16, 17 for dividing voltage. The half-wave alternating current output voltage of the diode is shaped into a rectangular wave by the waveform shaping circuit as shown in Fig. 3 and then inputted to a microcomputer 19.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a DC power supply device suitable for being applied to equipment having a built-in microcomputer.

[0002]

2. Description of the Related Art As a DC power supply device of this type, Japanese Patent Application Laid-Open No.
No. 101234 has been described. This conventional example
As shown in FIG. 4, after the secondary side output of the transformer 1 is rectified by the rectifier 2, it is smoothed by the capacitor 3 and the smoothed DC voltage is divided by the resistors 4 and 5 so that the voltage monitoring device (voltage drop detection element ) 6 is taken in. At the time of a power failure, the voltage taken into the voltage monitoring device 6 decreases with time. Therefore, when the voltage drops to a predetermined voltage, it is determined that there is a power failure.

[0003]

In the above-described conventional DC power supply device, since the capacitor 3 is interposed between the voltage monitoring device 6 and the transformer 2, it is taken into the voltage monitoring device 6 after a power failure occurs. There is a problem in that there is a large time lag until the applied voltage actually drops to the predetermined voltage.

[0004]

The DC power supply device of the present invention comprises a transformer for transforming a commercial AC power supply, a rectifier for rectifying the secondary side current of the transformer, and a capacitor for smoothing the output of the rectifier. The DC power supply device has a feature that the transformer is provided with a center tap and the output of the center tap detects a power failure.

[0005]

In the DC power supply device of the present invention, since the voltage is taken out from the center tap of the transformer to judge the power failure, the DC power supply for monitoring the voltage drop through the smoothing capacitor as in the conventional case. Compared to the device, it can detect the voltage change at the time of power failure earlier.

[0006]

EXAMPLES Examples will be described below with reference to the drawings. FIG. 1 is a circuit diagram of a DC power supply device according to an embodiment, and FIGS. 2 and 3 are voltage waveform diagrams at points of and in FIG.

The secondary output of the transformer 10 is output as a direct current voltage (Vcc) through a full wave rectifying circuit 11, a smoothing capacitor 12 and a stabilizing power supply circuit 13. A center tap 14 is provided on the secondary winding of the transformer 10, and the voltage extracted from the center tap 14 is sent to a waveform shaping circuit 18 via a diode 15 and voltage dividing resistors 16 and 17. It has been entered.

As shown in FIG. 2, the half-wave AC output voltage of the diode 15 is shaped into a rectangular wave by the waveform shaping circuit as shown in FIG. 3, and is taken into the microcomputer 19. The microcomputer 19 detects the power failure by monitoring the rectangular wave input voltage. That is, if a power failure occurs at the time point A in FIG. 2, the rectangular wave input to the microcomputer 19 is interrupted after the time point A in FIG. Then, for example, the microcomputer 19 determines that there is a power failure when the input of the rectangular wave is interrupted, and outputs a signal to take measures for the power failure. For example, actions such as returning the operating equipment to the initial state, storing the data in the non-volatile storage element, closing the water supply valve, and starting the emergency power supply are taken.

[0009]

As described above, the DC power supply device of the present invention is
Since the power failure is directly detected by the voltage taken out from the center tap of the transformer, the power failure can be promptly detected.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a DC power supply device according to an embodiment.

FIG. 2 is a voltage waveform diagram of a portion of FIG.

FIG. 3 is a voltage waveform diagram of a portion of FIG.

FIG. 4 is a circuit diagram of a conventional DC power supply device.

[Explanation of symbols]

 10 transformer 14 center tap 18 waveform shaping circuit 19 micro computer

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hiroaki Araki 5-1-1 Koiemotocho, Tokoname City, Aichi Prefecture Inax Co., Ltd.

Claims (1)

[Claims] 1. A DC power supply device comprising a transformer for transforming a commercial AC power supply, a rectifier for rectifying a secondary current of the transformer, and a capacitor for smoothing an output of the rectifier, wherein a center tap is provided on the transformer. A DC power supply device characterized in that a power failure is detected by the output of the center tap.