KR960005825Y1 - Printer head and smps overheat protecting device - Google Patents

Abstract

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Description

Print Head and SMPS Thermal Protection

1 is a circuit diagram of a conventional printer head and SMPS thermal protection device

2 is a conventional SMPS block diagram

3 is a circuit diagram of a print head and an SMPS overheat protection device according to the present invention.

* Explanation of symbols for main parts of the drawings

1: Primary side rectifier circuit 2: Converter

3: secondary side rectifier circuit 4a: primary side protection detection circuit

4b: secondary side protection detection circuit 5: switching element

6 control circuit 7 temperature sensing unit

8 comparison unit 9 control unit

P1: Frequency Generator IC1: Photocoupler

IC2: Comparator TH1: Dummyster

R1 to R6: resistors C1 to C4: capacitors

T1: transformer Q1: transistor

D1: bridge diode ZD1: zener diode

SCR1: Thyristor

The present invention relates to an overheat protection device of a printer head and an SMPS, and in particular, a printer head and an SMPS overheat protection device that protect a product from overheating and an overheating of a SMPS using a switching mode power supply (SMPS). It is about.

Most of the commercially available printer heads have a heat sink (heat sink), and the head is the most defective in the printer, and heat sinks using heat sinks do not provide complete heat dissipation. It is the cause of the rise, and even if the head overheating detection device is used, it is not used in combination with the overheat detection circuit of SMPS itself.

That is, most printers do not have an overheat detection circuit built into the head, and a heat sink that reduces heat of the head is attached to the outside to prevent the head from overheating.

Even though there is an overheat detection circuit of some heads, there is an overheat detection circuit in the SMPS itself used in the present invention. Therefore, the SMPS is not used to prevent the damage caused by overheating and the head overheating at the same time.

Here, the heat sink (heat sink) is a device made of a metal that attaches a heat-generating component to heat the heat generated by the component. That is, in the related art, when an AC voltage is applied, as shown in FIG. 1, the AC voltage is converted into a DC voltage through the bridge diode Dl, and is generated as a desired frequency pulse in the pulse generator P1 and switched through the switching transistor Q1. The waveform is transferred to the secondary side through the transformer T1 to make a direct current voltage through the diode D2 and the condenser C3, and the direct current voltage becomes a voltage for driving the print head. When the overheat detection circuit in the head is operated due to excessive use of the print head, current flows to the diode of the port coupler IC1 due to the voltage applied to the photocoupler IC1 connected to the overheat detection, and thus, the primary side of the photo coupler IC1. The thyristor (SCR) is operated so that it does not generate the frequency of the frequency generator (P1) and thus does not operate the SMPS to protect the print head and the SMPS.

Here, the resistor R1 and the capacitor C2 are for noise prevention, and the resistor R2 is for adjusting the amount of current applied to the diode of the photocoupler IC1 and referring to the SMPS block diagram of FIG. To supplement the operation, the AC voltage (110Vac / 220Vac .50 / 60HZ) enters and is made high voltage (about 400VDC) through the primary side rectifier circuit 1 (converts AC voltage to DC voltage). In this case, a frequency designed to several tens of KHZ is applied to the primary winding of the converter 2 (transformer) through the switching element 5 so that the desired voltage is transmitted to the secondary circuit of the converter 2, which is the secondary rectifier circuit (3). After converting AC voltage of tens of KHZ frequency into DC voltage, it comes out as DC output voltage.

In this case, since the output current value changes according to the DC output load, the control circuit 6 is operated in accordance with the changing amount to generate a constant DC output voltage by converting the frequency and width of the primary frequency generator P1.

In addition, a protection circuit 4 is incorporated to protect the equipment and SMPS used from excessive flow of DC output current or high voltage. SMPS is a device that supplies AC voltage to DC voltage and is widely used as a voltage supply for OA equipment such as computer printers and home appliances (TV, etc.) and industrial equipment (PLC NC). However, in the conventional apparatus as described above, the print head may be protected, but the SMPS defect due to the rupture of the SMPS itself may not be protected.

The present invention has been devised to solve these disadvantages and will be described in detail with reference to the accompanying drawings. The present invention circuit includes a primary side rectifier circuit 1, a secondary side rectifier circuit 3, a frequency generator P1, and a conversion 1 ( In the conventional circuit consisting of 2) and primary side and secondary side protection circuits 4a4b and switching elements 5, the outputs of the temperature sensing unit 7 and the temperature sensing unit 7 for sensing the temperature in the SMPS itself are referred to as reference voltages. And a control section 9 which is operated by the output of the comparing section 8 and the comparing section 8 to compare with and controls the operation of the frequency generator. In other words, the present invention has a current limiting resistor (R6), a constant voltage diode (ZD1), a voltage comparator (IC2) and a noise prevention resistor of a dummyster (TH1) and a voltage distribution resistor (R5) comparator (IC2) for sensing the temperature in the SMPS itself. (R3) It comprises a thyristor SCR operated by the capacitor C4 and the output of the comparator IC2.

Referring to the operation state of the configuration device, the operation principle of the general print head overheating circuit is the same as in the prior art.

That is, the AC voltage is converted into DC through the bridge diode D1, and the primary coil of the transformer Tl is connected to one end, and a desired frequency pulse is generated in the pulse generator P1, through the transistor Q1. The signal transmitted to the other end of the transformer Tl and transmitted to the secondary side of the transformer Tl is made into a direct current voltage through the diode D2 capacitor C3, which becomes the voltage for driving the print head.

When the overheat detection circuit in the head is operated due to excessive use of the print head, current flows to the diode of the photocoupler IC1 by the voltage connected from the head overheat detection terminal to the photocoupler IC1. This prevents the SMPS from operating as a result of not generating the frequency of the frequency generator P1, thereby protecting the print head and the SMPS.

Also, to protect the SMPS and the print head caused by the overheating of the SMPS, this paper proposes that when the dummyster TH1 is attached to the part that generates the most heat in the SMPS itself (for example, the transistor transformer heatsink), Accordingly, since the resistance value is increased and the voltage lower than the '+' terminal of the comparator IC2 is induced at the '-' terminal, the '+' voltage is induced at the output terminal of the comparator IC2 to operate the thyristor SCR1.

Therefore, current flows through the diode of the photocoupler IC1 so that the SMPS is shorted down.

Here, the limited current is supplied stably to the '+' terminal of the comparator IC2 through the resistor R6 to supply a stable constant voltage to the comparator IC2.

Also, to prevent noise, a noise preventing resistor R3 and a capacitor C4 are connected to the output terminal of the comparator IC2.

The comparator (IC2) always applies a voltage higher to the '+' terminal than the '-' terminal to induce a 'high' signal at the output terminal and the thyristors are not normally operated, but operate when the signal is applied to the gate. The coupler requires the secondary diode to conduct, but light is emitted from the diode to operate the thyristors on the primary side of the photocoupler.

SMPS has a self-efficiency of about 70%.

For example, if the input of 100 is input, the output of SMPS is 700,000 and 30 is consumed by SMPS itself.

In particular, the heat sink (heatsink built into the transformer transistor SMPS itself) generates the most heat. Dummyster is a kind of electronic component that is a part whose resistance value changes with temperature.

Therefore, this design can prevent the defects of SMPS in advance by attaching heat-sensing parts to the parts that generate the most heat when designing SMPS. Also, since it is connected with the head of the printer, the SMPS and the print head are prevented from overheating at the same time. It has a protective effect.

Claims (1)

In the thermal protection device of the printer head and the SMPS using the photocoupler (IC1), a temperature sensing unit 7 and a temperature sensing unit 7 installed at a portion where the heat in the SMPS itself is generated the most, to sense the temperature in the SMPS itself. Is connected to the cathode end of the photocoupler IC1 connected to the comparator 8 and the head overheat detector to receive the output of the input voltage and is compared with the reference voltage, and is operated by the output of the comparator 8 to operate the photocoupler IC1. And a control unit (9) for controlling the operation of the frequency generator (P1) by controlling the operation of the printer head and the SMPS overheat protection device.