JPH01307787A - Heater current control circuit for electrophotographic printer - Google Patents

Abstract

PURPOSE:To suppress a rush current by performing phase angle control for several cycles of a heater current after the device is actuated and then carrying out zero-volt switch control. CONSTITUTION:A control circuit 4 detects the temperature of a heater 8 with a signal from a temperature sensor 3 and outputs a signal to a phase angle control circuit 9 or zero-volt switch circuit 10 according to the temperature. Therefore, when the temperature of the heater 8 is smaller than a set value, a signal 6 is inputted from the control circuit 4 to the phase angle control circuit 9 to supplied only the part of an AC voltage where the phase angle is small. When the temperature of the heater 8 is larger than the set value, a signal 5 is inputted from the control circuit 4 to the zero-volt switch circuit 10 to perform control so that the start and end phase angle of the AC voltage are zero. Consequently, the AC voltage is low in a state wherein a heater resistance value is small and the rush current easily flows, so the rush current can be suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a heater current control circuit for an electrophotographic printer.

[Conventional technology]

Conventionally, the heater current control circuit of an electrophotographic printer has a third
As shown in the figure, a switching element 1 that turns on and off the heater current, a temperature sensor 3 that detects the temperature of the heater 8, and a control circuit 4 that determines the temperature level based on the output signal of the sensor 3. In response to the signal 5 from the control circuit 4, the switching element 1 receives a signal 7 for starting and ending the supply of heater current at zero volts of AC voltage.
It has a zero volt switch circuit 10 that outputs to.

[Problem to be solved by the invention]

The heater current control circuit of the conventional electrophotographic printer described above always starts and ends energization at zero volts from the AC power supply, so if the heater temperature is low and the heater resistance is small, an excessive rush current will flow. There is a drawback.

SUMMARY OF THE INVENTION An object of the present invention is to provide a heater current control circuit for an electrophotographic printer that solves the above problems.

[Means to solve the problem]

To achieve the above object, the present invention provides a heater current control circuit having a switching element that turns on and off a heater current to a fixing unit heater of an electrophotographic printer, in which the switching element is turned on when the heater temperature is below a set value. A phase angle control circuit that controls the drive and controls the heater current only at a low phase angle portion of the AC voltage, and a phase angle control circuit that controls the drive of the switching element when the heater temperature is higher than a set value and controls the heater current when the phase angle of the AC voltage is zero. The present invention includes a zero-volt switch circuit for controlling energization, and a control circuit for controlling operations of the phase angle control circuit and the zero-volt switch circuit.

[Effect]

The heater current control circuit of the electrophotographic printer of the present invention includes:
For several cycles of the heater current when the heater temperature is low, the heater current is passed by the amount of the low phase angle of the AC power supply, and then,
When the heater temperature exceeds a certain set value, energization is started and stopped at zero volts of the AC power supply.

〔Example〕

Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a circuit diagram showing one embodiment of the present invention.

In the figure, reference numeral 1 indicates a switching element for controlling current supply to the heater 8 (in the embodiment, a triac is shown), 2 indicates an AC power supply, and 3 indicates a temperature sensor for measuring the temperature of the heater 8. 9 is a phase angle control circuit that drives and controls the switching element 1 when the heater temperature is below a set value, and controls the heater current only in the low phase angle portion of the AC voltage; 10 is a phase angle control circuit that performs switching when the heater temperature is above the set value; A zero-volt switch circuit drives and controls the element 1 and controls the heater current at a zero phase angle of the AC voltage; 4 is a phase angle control circuit 9 and a zero-volt switch circuit 10 based on the signal from the sensor 3;
This is a control circuit that controls the operation of the

As shown in the figure, the phase control circuit drive signal 6 of the control circuit 4 which inputs the signal from the temperature sensor 3 is input to the phase angle control circuit 9, and the zero volt switch circuit drive signal 5 is input to the phase angle control circuit 9.
is input to the zero-volt switch circuit 10, and the switching element drive signal 7 of the phase angle control circuit 9 and the zero-volt switch circuit 10 is input to the switching element 1, and the heater 8
A current is passed through. The control circuit 4 detects the temperature of the heater based on the signal from the temperature sensor 3, and outputs a signal to the phase angle control circuit 9 or the zero-volt switch circuit 10 according to the detected temperature. 4. Therefore, as shown in FIG. 2, when the heater temperature is lower than the set value A, the control circuit 4 inputs the signal 6 to the phase angle control circuit 9 to energize only the portion of the AC voltage with a low phase angle. Further, when the heater temperature is higher than the set value A, the control circuit 4 inputs the signal 5 to the zero-volt switch circuit 10 to control the AC voltage to start and end at a phase angle of zero degrees.

Therefore, in a state where the heater resistance value is low and inrush current easily flows, only a low value of AC voltage will flow, so that inrush current can be suppressed. In addition, since it turns on and off at zero volts when the temperature rises and there is no risk of inrush current, the influence of noise can also be reduced.

〔Effect of the invention〕

As explained above, the present invention performs phase angle control for several cycles of the heater current after starting the device, and then performs zero-volt switch control, thereby reducing inrush current without problems during device warm-up time and noise. It has the effect of suppressing

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram showing one embodiment of the present invention, and Fig. 2 is a circuit diagram showing an embodiment of the present invention.
FIG. 3 is a diagram showing the relationship between heater temperature and heater current when driven according to the illustrated embodiment, and FIG. 3 is a circuit diagram showing a conventional heater current control circuit. 1... Switching element 2... AC power supply 3...
・Temperature sensor 4...Control circuit 5・
...Zero volt switch circuit drive signal 6...Phase control circuit drive signal 7...Switching element drive signal 8...Heater 9...Phase angle control circuit 10...Zero volt switch circuit patent applicant Niigata NEC Corporation Figure 1 Figure 2

Claims (1)

[Claims] (1) In a heater current control circuit that has a switching element that turns on and off the heater current to the fixing unit heater of an electrophotographic printer, the switching element is driven and controlled when the heater temperature is below a set value, and the phase of the AC voltage is controlled. A phase angle control circuit that controls the heater current only at the lower part of the corner, and a zero-volt circuit that drives and controls the switching element when the heater temperature is higher than a set value and controls the heater current at a zero phase angle of the AC voltage. 1. A heater current control circuit for an electrophotographic printer, comprising a switch circuit and a control circuit for controlling operations of the phase angle control circuit and the zero-volt switch circuit.