JPS6292718A - Identification apparatus of current discontinuation - 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> This invention provides an AC load circuit driven by a commercial power source, and a current breaker such as a current fuse or a temperature fuse connected in series to the AC load circuit to connect a DC power source. In a device that controls the AC load circuit by a control unit serving as a power source,
The present invention relates to a device for determining the current cutoff state of a current breaker.

<Prior art and its drawbacks> For example, in a thermal fixing type copying machine, the temperature of the fuser is detected by a temperature detection element such as a thermistor or thermocouple placed nearby, and the temperature of the fuser is adjusted depending on the state. The temperature of the fixing device is maintained at an optimum temperature by controlling a switching element connected in series with the heater.

In such devices, heaters (halogen lamps,
power may remain supplied to the thin plate heating element). At this time, there is a risk that the fixing device will reach an abnormally high temperature, leading to smoke generation, ignition, etc., so an excessive temperature rise prevention device (temperature fuse, thermal protector) is provided to cut off the power line of this heating element.

However, since the power supply line to the heating element is a commercial power supply line, even if the temperature fuse is blown and the oven state is reached, the control circuit that controls the above temperature control circuit and other controls, which is powered by DC power, will not operate. The condition was difficult to detect. Conventionally, current breakers such as temperature fuses only cut off the power supply to AC load circuits such as heating elements, so it is not possible to directly determine whether the cause of a device stoppage is due to an abnormality in the AC load circuit. I couldn't decide.

<Objective of the Invention> The object of the present invention is to provide an AC load circuit driven by a commercial power source, which also includes a current breaker such as a current fuse or a temperature fuse, and to connect the AC load circuit to a DC power source. An object of the present invention is to provide a current cutoff state determination device that is controlled by a control unit that is capable of determining the current cutoff state of the current breaker. Then, an AC load circuit driven by a commercial power supply, a current breaker such as a current fuse or a temperature fuse connected in series to this AC load circuit, and a primary side connected in parallel to the AC load circuit, and a secondary A first DC power supply circuit outputs DC voltage to the side, a second DC power supply circuit receives commercial power to the primary side and outputs DC voltage to the secondary side, and is driven by this second DC power supply circuit. , said first
and voltage detection means for detecting the output voltage of the DC power supply.

With the above configuration, if some abnormal condition occurs and the current breaker is cut off, current will no longer be supplied to the AC load circuit and AC voltage will not be applied to the primary side of the first DC power supply circuit. It disappears. Therefore, the DC voltage that was being output to the secondary side of the first DC power supply circuit decreases. Even if the current breaker is in the cutoff state, the second
Since the DC power supply circuit outputs a DC voltage to its secondary side, the voltage detection means can detect the secondary output voltage of the first DC power supply circuit. By detecting that the secondary output voltage of the first DC power supply circuit has fallen below a predetermined value, it can be determined that the current breaker is in the cutoff state.

<Embodiment> FIG. 1 shows a circuit of a current cutoff state determining device according to an embodiment of the present invention. In the figure, MSW is a power switch, and by turning it on, commercial power is applied to the input of the DC power supply circuit 2. As a result, the DC power supply circuit 2
consists of a switching regulator and outputs a power supply voltage of 5V and 10V. Note that 2 corresponds to the second DC power supply circuit in the claims.

5 is a control circuit consisting of a microprocessor, which operates with a voltage of 5V output from the DC power supply circuit 2. When the control circuit 5 starts operating, it first outputs a control signal to the driver 7 that drives the relay. When the driver 7 turns on the relay 8, its relay contact PRa (
! : Make PRb conductive.

Reference numeral 3 denotes a heater circuit consisting of a series circuit of a heater 11 and a triac T, which is connected in series with a temperature fuse TF, and commercial power is applied between terminals 1 and N. When the triac T is on, the heater H generates heat, but after reaching a predetermined temperature, the triac is controlled on and off to maintain that temperature. Rt is a thermistor, which is installed near the heater H of the heater circuit 3.

R3 is a resistor, and a voltage obtained by a series circuit of the thermistor Rt and resistor R3 is applied to one side of the comparator 6, and a comparison voltage (r) is applied to the other side. This comparison voltage V" is set in advance so that the output (TS) of the comparator 6 becomes the "I(" level) when the temperature of the heater H reaches a predetermined temperature. The control circuit 5 monitors the state of this signal TS. It discriminates and outputs a control signal to the gate control circuit 9.The gate control circuit 9 controls the gate of the triac T and controls the on/off of the current flowing to the heater H.In this way, the heater circuit 3 is controlled to perform a predetermined control. Maintain temperature.

For example, if the thermistor Rt is damaged and becomes open, the output of the comparator 6 will always be at the "L" level, so the triac T will remain in the on state.

Therefore, the heater H becomes abnormally high temperature and the temperature fuse T
F is broken.

1 is a DC power supply circuit (first DC power supply circuit) (consists of a lance TR, a diode bridge D, and a capacitor C. Unlike the DC power supply circuit 2, this DC power supply circuit 1 has a relatively large power This is a power supply circuit for supplying DC power, and its output voltage does not require much stabilization accuracy.The primary side of the transformer TR is connected in parallel with both ends (terminals 1 and 2) of the heater circuit 3. Therefore, when the temperature fuse TF is cut off, the input voltage of the transformer TR is cut off.By cutting off the input of the DC power supply circuit 1 in this way,
The voltage of the secondary side output voltage V decreases from the rated voltage of 24V as the capacitor C discharges. Comparator 4 divides this voltage ■ by resistors R1 and R2 (V
xR2/(R1+R2)) is input to the child terminal, and the reference voltage IOV is manually input to one terminal. Therefore resistance R1
When the voltage divided by R2 becomes lower than IOV, the output (O8) of the comparator 4 becomes "L" level. The control circuit 5 performs a predetermined display on the display 10 according to the state of the signal O8. For example, it detects that the signal O8 becomes "L" and displays a warning that the temperature fuse is blown.

In addition, when this circuit is applied to a copying machine, the DC power supply circuit 1 can be used as a power source for a large current DC circuit such as a DC motor or a corona generator (high voltage UNISO 1-). In that case, there is no need for a special DC power supply circuit for detecting the cutoff state of the temperature fuse.

FIG. 2 is a flowchart showing the processing procedure of the control circuit 5. When a power supply voltage is applied to the control circuit, first the relay is turned on, and then the state of the signal TS is determined. As mentioned above, this signal is the output signal of the comparator 6 shown in FIG. 1, and if it is at "H" level, it means that the heater circuit has reached a predetermined temperature. If the signal TS is at "L" level, the triac T is turned on. Next, the state of signal O8 is determined. This is the output signal of the comparator 4 as shown in FIG.
A message corresponding to this is displayed and the relay is turned off.

As described above, a DC power supply circuit is provided whose primary side is connected in parallel to the heater circuit, which is an AC load circuit, and which outputs DC voltage to the secondary side, and the control circuit detects a drop in the output voltage of this DC power supply circuit. By this, it can be determined that a current breaker such as a temperature fuse is in a cut-off state.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of a current cutoff state determining device according to an embodiment of the present invention, and FIG. 2 is a flowchart showing the processing procedure of a control circuit in the same device. 1-DC power supply circuit (first DC power supply circuit), 2-DC power supply circuit (second DC power supply circuit), 3-heater circuit, 4-
Comparator, 5-control circuit, TF-temperature fuse.

Claims (1)

[Claims] (1) An AC load circuit driven by a commercial power source, a current breaker such as a current fuse or a thermal fuse connected in series to this AC load circuit, and a primary side connected in parallel to the AC load circuit and a secondary A first DC power supply circuit that outputs DC voltage to the side, a second DC power supply circuit that receives commercial power to the primary side and outputs DC voltage to the secondary side, and is driven by this second DC power supply circuit. and a voltage detection means for detecting an output voltage of the first DC power supply, and a current cutoff state determination device for determining the state of the current breaker based on the detection output of the voltage detection means.