JPS63213860A - Image forming device - Google Patents

Abstract

PURPOSE:To prevent the occurrence of abnormal temperature rise, trouble, or the like by discriminating whether the supply voltage of an external DC power source is correct or not and breaking the power supply in case of connection of an external DC power other than an operation securing voltage. CONSTITUTION:A comparator Q1 detects that the voltage of the external DC power is higher than a preliminarily set value, and the output of the comparator Q1 goes to the high level to turn on a transistor TRQ3 if the voltage of the + (non-inverted) input terminal is higher than a reference voltage ZD1 of the -(inverted) input terminal. then, the base voltage of a TRQ5 is reduced to turn off the TRQ5, and the contact of a relay RL1 is switched to the normally closed side, and the external DC power is not supplied to a control unit. A comparator Q2 detects that the voltage of the external DC power is lower than the set value, and the contact of the relay RL1 is switched to the normally closed side and the external DC power is not supplied to the control unit when the voltage of the - input terminal is lower than the reference voltage. The abnormal temperature rise, trouble, or the like is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an image forming apparatus having a DC power source such as a primary battery and a rechargeable secondary battery.

[Background of the invention]

2. Description of the Related Art Conventionally, image forming apparatuses such as copying machines use AC commercial power, so the power supply is stable.

However, as technology advances, devices are becoming smaller and more power efficient, and small portable devices that can be operated on batteries have also been proposed. In such devices, battery energy is limited, so negative batteries need to be replaced, and secondary batteries need to be recharged, making them uneconomical and difficult to handle. It's a hassle. Therefore, we are equipped with a connector for connecting an external DC power source other than the built-in battery, and a power source switching means for switching between the battery power source inside the device and the external DC power source. It is conceivable that power can be supplied from other sources.

However, there are external DC power supplies with various voltage outputs, and there is a risk that a power supply with a voltage other than the one specified for the device may be connected. The voltage of a car battery is often 1
The voltage is 2V, but some large vehicles have a voltage of 24V. In addition, if the power supply is easier than using a cigarette lighter, there is a risk that a 24V power source may be mistakenly connected to a 12V device, causing abnormal temperature rise or failure.

〔the purpose〕

The present invention has been made in view of the above points, and an object of the present invention is to provide an image forming apparatus capable of preventing deterioration of image quality and occurrence of equipment failure when power is supplied from an external power source. Our goal is to provide the following.

〔Example〕

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 shows the main body configuration of a copying apparatus to which the present invention is applied.

1 is the main body of the copying apparatus, 2 is a built-in primary battery or a rechargeable secondary battery (hereinafter referred to as a battery), and Jl is a connector for connecting an external DC power source.

FIG. 2 shows a schematic configuration of the power supply section. The battery 2 and external power supply connector 11 are connected to a power supply switching unit ul. The power supply switching unit ul supplies power from the built-in battery 2 to the control unit u2 when the external DC power supply is not connected to 11, and when the external DC power supply is connected to Jl,
Power from an external DC power source is supplied to the control unit u2.

The control unit U2 has a built-in microcomputer and performs sequence control of the copying apparatus. For example, the control unit U2 controls the lighting of a fluorescent lamp (not shown) which is a light source for image exposure, a DC motor, and other components necessary for image formation. Controls DC loads such as high voltage power supplies.

FIG. 3 shows a circuit diagram of the power supply switching unit U2.

RLI is a power supply switching relay, and its normally closed terminal is connected to the output of the battery 2, and its normally open terminal is connected to the output of the external DC power supply connector Jl. The drive coil of relay RLI is driven by an external DC power supply, and its 0N10FF control is performed by transistor Q5. Ql is a comparator that detects when the power supply voltage of the external DC power supply is higher than a preset value,
An external DC power supply voltage divided by resistors R3 and R4 is connected to the + (non-inverting) input. zDl is a constant voltage diode for generating a reference voltage, and resistance RIs is a current limiting resistance of ZDI. The reference voltage of ZDI is connected to the − (inverting) input terminal of the comparator Ql, and when the voltage at the input terminal is higher than this reference voltage, the output of the comparator Ql becomes H.
becomes high, and transistor Q3 turns on. Since the collector of the transistor Q3 is connected to the base of the transistor Q5, the base voltage of the transistor Q5 decreases and the transistor Q5 turns OFF4, the contact of the relay RLI becomes normally closed, and the external DC power supply is connected to the control unit U2. will no longer be supplied.

Similarly, Q2 is a comparator that detects when the power supply voltage of the external DC power supply is lower than a preset setting value, and the external DC power supply voltage divided by the resistor RI + R2 is connected to the - (inverted) input. ing. Also, the above ZD
If the reference voltage by I is connected to the + (non-inverting) input and the voltage at - is lower than this reference voltage, then the comparator Q
The output of the transistor Q2 becomes High 11, and the transistor Q4 is turned on. Since the collector of transistor Q4 is connected to the base of transistor Q5,
The base potential of is lowered, transistor Q5 is turned off, the contact of relay PLI becomes normally closed, and external DC power is no longer supplied to control unit U2.

In the above configuration, when the external DC power source is not connected to Jl, the built-in battery 2 is connected to the control unit U2, and the main body becomes operable. In this example, the rated voltage of the battery 2 is 12V,
This device can operate within the range of 9V to 17V (operation guaranteed voltage).

Next, when the external DC power supply is connected to Jl, a current flows through the voltage regulator diode ZDI through the resistor R6, and in this embodiment, a reference voltage of 5V is generated. This reference voltage is connected to the + (non-inverting) input of comparator Q2, while the comparison voltage obtained by dividing the external DC power supply voltage by resistors R, R2 is connected to the - (inverting) input terminal of comparator Q2. has been done. Here, when the resistance value ratio of the resistors R1 and R2 is 9V or less, the voltage at the - (inverted) input terminal of the comparator Q2 becomes the following, and the output of the comparator Q2 becomes High, turning on the transistor Q4. Since the collector of the transistor Q4 is connected to the base of the transistor Q5, the base potential of the transistor Q5 becomes approximately OV, and the transistor Q5 is turned off.

As a result, relay RLl does not operate, so if the external DC power supply voltage is 9V or less, the power is not supplied to control unit U2. Conversely, if the external DC power supply voltage is 9V or higher, the output of comparator Q2 is Lo.
w, transistor Q4 is OFF, and transistor Q5 is turned off by the external DC power supply via resistor R8.
N, relay RLI operates and supplies external DC power to control unit U2.

Similarly, when an external DC power supply is connected to Jl, a comparison voltage obtained by dividing the external DC power supply voltage by resistors R3 and R4 is connected to the →- (non-inverting) input terminal of the comparator Ql. The above-mentioned reference voltage of 5V is connected to the - (inverting) input terminal of the comparator Ql.

Here, when the external DC power supply voltage across resistor R3 is 17 V or higher, the + (non-inverting) input terminal voltage of comparator Ql is higher than that, and the output of comparator Ql becomes High, turning on transistor Q5. Since the collector of transistor Q5 is connected to the base of transistor Q5, the base potential of transistor Q5 is approximately O,
Transistor Q5 is turned off.

As a result, relay RLI does not operate, so if the external DC power supply voltage is 17V or higher, that power will not be supplied to control unit U2. In addition, if the external DC power supply voltage is 17V or less, the output of the comparator Ql becomes Low, transistor Q3 is OFF, transistor Q5 is turned on by the external DC power supply via resistor R8, and relay PLI is activated to connect the external DC power supply. is supplied to the control unit U2.

〔effect〕

As explained above, by determining whether the power supply voltage of the external DC power supply is appropriate or not, and if it is appropriate, allowing the device to operate with the external DC power supply, the external DC power supply voltage other than the voltage guaranteed for operation of the device can be used. If connected, by reliably cutting off the power supply, you can prevent unstable operation and deterioration of image quality at low voltages, abnormal temperature rises, and malfunctions at high voltages. be.

[Brief explanation of the drawing]

Fig. 1 is a main body configuration diagram of a copying apparatus to which the present invention is applied;
The figure is a schematic configuration diagram of a power supply section according to the present invention, and FIG. 3 is a circuit diagram of a power supply switching unit. In the figure, l is the copying device, 2 is the battery, Jl is the external DC power supply connector, U is the power supply switching unit, U2 is the control unit, RLI is the power supply switching relay, and Q
l-Q2 is a comparator, ZDI is a constant voltage diode,
Q5 is a transistor for driving relay RLI.

Claims (4)

[Claims] (1) A power supply means using a built-in primary battery or a rechargeable secondary battery as a power source; a switching means for switching between supplying power from the power supply means or from an external DC power source; and the external device. An image forming apparatus comprising: a determining means for determining whether a power supply voltage of a DC power supply is appropriate; and a control means for controlling the switching means in accordance with a determined output of the determining means. (2) In claim 1, when the determining means determines that the power supply voltage of the external DC power supply is appropriate, the control means switches the switching to supply power from the external DC power supply. An image forming apparatus characterized by controlling means. (3) The image forming apparatus according to claim 1, wherein the determining means includes a comparing means for comparing the power supply voltage of the external DC power supply with a reference voltage. (4) In claim 3, the image is characterized in that the determining means determines that the power supply voltage is appropriate when the power supply voltage is higher than a first reference voltage and lower than a second reference voltage. Forming device.