JPH06191118A - Excess temperature protective device - Google Patents

Abstract

PURPOSE:To provide the device capable of protecting a power supply from over-temp. without increasing the number of signals between the power supply and the load device of a printer. CONSTITUTION:When the load device 2 of a printer becomes abnormal and the output current of a power supply 1 becomes an overcurrent state, the output voltage of the power source 1 drops. As a result, the operation mode of the load device 2 is changed over, for example, to a dividing printing operation mode reducing load of the power supply 1. When the overload state of the load device 2 continues for a long time and the power supply 1 is overheated, a temp. detection means 1a generates output not only to lower the overcurrent detection point of an overcurrent protecting part 13 but also to drop the output of the power supply. Therefore, the operation mode of the power supply 1 is changed over to protect the power supply 1 from an overheated state. Since the output voltage of the power supply 1 is dropped when the power supply 1 becomes an overheated state, it is unnecessary to transmit the output signal of the temp. detection means 1a provided to the power supply 1 to the load device 2 and the number of signals between the power supply 1 and the load device 2 can be reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an overtemperature protection device for protecting an overheated state of a power source due to an overloaded state of the power source for a long time such as heavy duty printing in a printer.

[0002]

2. Description of the Related Art Conventionally, in order to prevent an excessive temperature rise of a power source of a printer during heavy duty printing, the temperature rise of the power source is detected by a thermal, and an output signal of the thermal is transmitted to a processor for controlling the printer, The micro program was used to switch the printer to split printing to protect against overtemperature.

FIG. 4 is a diagram showing the above-mentioned conventional overtemperature protection device. In FIG. 4, 41 is a power source for the printer and 4 is a power source for the printer.
Reference numeral 1a denotes a thermal device which is provided inside the power source 41 and generates an output when the power source is in an over temperature state.
2a is a printer head drive unit, and 42b is a printer 42.
A power supply line for supplying power to the printer 42, and a power supply 41
And the signal line provided between the microprocessor 42b.

In the figure, when heavy duty printing continues for a long time and the temperature of the power supply 41 rises, the thermal 41a provided inside the power supply 41 closes. The output signal of the thermal 41a is transmitted to the microprocessor 42b provided on the printer 42 side via the signal line 44, and the microprocessor 42b switches the printer 42 to the divided printing to reduce the load of the power supply 41.

[0005]

By the way, in the above-described conventional overtemperature protection device, since the fact that the temperature of the power supply 41 has risen is transmitted to the printer 42 side, the thermal 4
It is necessary to transmit the output signal of 1a through the signal line 44, the number of signal lines 44 increases, and the power supply 41,
There is a problem that the number of signal pins of each connector of the printer 42 increases.

The present invention has been made in order to improve the above-mentioned drawbacks of the prior art, and it is possible to protect the power supply from over temperature without increasing the number of signals between the power supply and a load such as a printer. It is an object to provide a temperature protection device.

[0007]

FIG. 1 is a block diagram of the principle of the present invention, in which 1 is a power source of a load device 2, 11 is a power source section,
Reference numeral 1a is a temperature detecting means for generating an output signal when the temperature of the power source section 11 rises, 12 is an overcurrent detecting section for detecting an output current of the power source section 11, and 13 is a power source 1 when the power source 1 is in an overcurrent state. 2 is a load device, and 2a is a control device of the load device 2.

In order to solve the above-mentioned problems, the invention of claim 1 of the present invention is, as shown in FIG. 1, an overcurrent for drooping the output voltage when the output current exceeds a predetermined set value for overcurrent protection. A power source 1 provided with a protection unit 13 and a temperature detecting means 1a for detecting the temperature of the power source;
A load device 2 having a function of switching to an operation mode for reducing the load of the power supply when the output voltage of the power supply 1 droops, and when the power supply 1 overheats, the temperature detecting means 1a
To protect the power supply 1 from overheating by lowering the overcurrent detection point by dropping the output voltage of the power supply 1 and switching the operation mode of the load device 2 to an operation mode that reduces the load on the power supply. It is composed.

The invention of claim 2 of the present invention applies the invention of claim 1 to a power source of a printer device 2 having a function of switching to a divided print mode when the output voltage of the power source 1 droops,
When the power supply 1 overheats, the output of the temperature detecting means 1a lowers the overcurrent detection point to drop the output voltage of the power supply 1 and the operation mode of the printer device 2 is switched to the split print mode. It is designed to protect against heat.

[0010]

According to the first aspect of the present invention, the load device 2
Becomes abnormal and the output current of the power supply 1 becomes larger than the overcurrent setting value of the overcurrent protection unit 13, the overcurrent protection unit 13 generates an output and droops the output voltage of the power supply 1. This allows
The operation mode of the load device 2 is switched to an operation mode that reduces the load on the power supply 1.

Further, when the overload state of the load device 2 continues for a long time and the power supply 1 overheats, the temperature detecting means 1a generates an output to lower the overcurrent detection point and droop the output voltage of the power supply. Therefore, the operation mode of the load device 2 is switched to an operation mode that reduces the load on the power supply, and protects the power supply 1 from an overheated state. According to the first aspect of the present invention, when the power supply 1 is overheated, the overcurrent detection point can be lowered and the output voltage of the power supply 1 can be drooped. Therefore, the temperature detection means provided in the power supply 1 The operation mode of the load device 2 can be switched without transmitting the output signal of 1a to the load device 2.

In the invention of claim 2 of the present invention, since the invention of claim 1 is applied to the power supply of the printer device, when the power supply is in an overheated state, the output voltage of the power supply can be drooped. Like the invention of Item 1, the operation mode of the printer device can be switched without transmitting the output signal of the temperature detecting means 1a provided in the power source 1 to the printer device.

[0013]

FIG. 2 is a diagram showing an embodiment of the circuit configuration of a power source 11, 21 is a printer device, 11 is a power source section, and 11a.
Is a thermal that opens the contact when the temperature of the power supply rises, 11b is a PWM control circuit for PWM-controlling the transistor Tr1, 12 is an output current of the power supply unit 11, and an overcurrent is generated by the output of the thermal 11a. An overcurrent detection unit whose detection point is changed, 13 is an overcurrent protection unit, and T
r1 is a transistor, T1 is a transformer, T2 is a current transformer, D1 to D3 are diodes, L1 is a smoothing reactor, C1 is a smoothing capacitor, R1, R
2 is a resistance.

In the figure, the output of the PWM control circuit 11b is connected to the base of the transistor Tr1, and the collector of the transistor Tr1 is connected to the primary side of the transformer T1. Further, a smoothing reactor L1 and a capacitor C1 are connected to the secondary side of the transformer T1 via rectifying diodes D1 and D2, and switching of the transistor Tr1 causes the transformer T1 to be connected to the secondary side of the transformer T1.
The AC voltage generated on the next side is rectified by the diodes D1 and D2, smoothed by the reactor L1 and the capacitor C1, and given to the printer device 21.

A current transformer T2 for detecting the output current of the power supply unit 11 is connected to the secondary side of the transformer T1, and the secondary side of the current transformer T2 is connected to the secondary side.
The series circuit of the contacts of the resistor R1 and the thermal 11a and the series circuit of the diode D3 and the resistor R2 are connected, and the current transformer T2, the resistors R1 and R2, and the thermal 11a form an overcurrent detection unit 12. Furthermore, an overcurrent protection unit 13 is connected to the overcurrent detection unit 12.

Next, the operation of the embodiment shown in FIG. 2 will be described. When the load is normal, the output current of the power supply unit 11 is not in an overcurrent state, and the temperature of the power supply 11 is not rising, PWM
The control circuit 11b generates a PWM signal with a predetermined duty so that the output voltage of the power supply 11 has a predetermined value, and drives the transistor Tr1. This makes the transformer T1
An AC voltage having a predetermined duty is generated on the secondary side of the AC voltage. The AC voltage is rectified by the diodes D1 and D2, smoothed by the reactor L1 and the capacitor C1, and supplied to the printer device 21.

When the printer device 21 becomes abnormal and the output current of the power supply unit 11 detected by the overcurrent detection unit 12 becomes larger than the overcurrent set value of the overcurrent protection unit 13, the overcurrent protection unit 13 produces an output. When the overcurrent protection unit 13 generates an output, the PWM circuit 11b reduces the on-time of the pulse signal given to the base of the transistor Tr1,
The output voltage of the power supply unit 11 is drooped. When the output voltage of the power supply unit 11 droops, the printer device 21 starts divided printing operation.

Here, the input voltage (referred to as an overcurrent detection voltage) of the overcurrent protection unit 13 at which the overcurrent protection unit 13 operates is V
When the temperature is 1, the temperature of the power supply 11 is not raised and the contact of the thermal 11a is closed, the primary current Iocp of the current transformer T2 in which the overcurrent protection unit 13 operates is calculated by the following equation (1). expressed. Iocp = N {R2 (V1 + VF) + R1V1} / R1R2 (1) Note that the resistance values of the resistors R1 and R2 of the overcurrent detection unit 12 in FIG. 2 are R1 and R2, respectively, and the number of turns of the current transformer T2. The ratio is N, and the forward drop voltage of the diode D1 is VF.

Therefore, when the contact of the thermal 11a is closed, when the output current of the power supply 11 reaches the above Iocp, the overcurrent protection unit 13 operates and the output voltage of the power supply 11 drops. Further, if the heavy-duty printing of the printer device 21 continues for a long time and the power supply unit 11 overheats before the thermal provided in the printer head operates, the contact of the thermal 11a opens. The primary-side current I'ocp of the current transformer T2 at which the overcurrent protection unit 13 operates when the contact of the thermal 11a is opened is expressed by the following equation (2).

I′ocp = N · V1 / R2 (2) As apparent from the above equations (1) and (2), the power supply unit 11
When the temperature of the power supply is normal, the overcurrent detection point I'ocp when the temperature is overheated is lower than the overcurrent detection point I'ocp.
Therefore, by appropriately selecting the value of I'ocp, when the power supply unit 11 is overheated, the overcurrent protection unit 13 can be operated and the output of the power supply can be drooped. Here, when the voltage of the power source droops, the printer device 21 switches to the divided printing operation as described above, so the power source unit 1
When 1 is overheated, the printer device 21 can be switched to the divided printing operation to protect the power supply from the overheated state. In addition,
The value of I'ocp needs to be set higher than the maximum current during the division printing operation.

According to the above-described embodiment, when the power supply is overheated, the overcurrent detection point can be lowered and the output voltage of the power supply can be drooped. Therefore, the thermal output signal provided in the power supply can be applied to the printer device. The printer can be switched to divided printing without transmission to a control device such as a microprocessor provided on the 21st side, and protection can be performed when the power source is overheated.

FIG. 3 is a diagram showing another embodiment of the present invention. In FIG. 3, the same parts as those in FIG. 2 are designated by the same reference numerals, 21 is a printer device, 11 is a power source part, 1
Reference numeral 1a is a thermal contact that is opened when the temperature of the power supply rises, 11b is a PWM control circuit for performing PWM control of the transistor Tr1, 12 is an output current of the power supply unit 11, and the output of the thermal 11a causes an overcurrent. An overcurrent detection unit in which the current detection point drops, 13 is an overcurrent protection unit,
Tr2 is a transistor, T3 is a transformer, D11 and D1
2 is a diode, L2 is a smoothing reactor, C2 is a smoothing capacitor, and R11, R12, R13, R14 are resistors.

In this embodiment, an overcurrent detector 12 for detecting the output current of the power source is provided on the emitter side of the transistor Tr2, and the other structure is the same as that of the embodiment shown in FIG. In FIG. 3, when the contact of the thermal 11a is closed, when the output current of the power supply 11 reaches the overcurrent detection point, the overcurrent protection unit 13 operates and the power supply 11
Output voltage droops.

Further, if heavy-duty printing of the printer continues for a long time and the power supply 11 overheats before the thermal provided in the printer head operates, the thermal 11a
Contact opens. When the contact of the thermal 11a is opened, the overcurrent detection point becomes lower than the overcurrent detection point when the temperature of the power supply is normal, and the output of the power supply droops, as in the embodiment of FIG. Therefore, the printer device 21 is switched to the division printing operation, and the power supply unit 11 can be protected from the overheated state.

In the above embodiment, the thermal 1
When 1a operates, a resistor is inserted in parallel to the overcurrent detection unit to lower the overcurrent detection point and droop the power supply voltage, but the present invention is not limited to the above embodiment. For example, when the thermal 11a operates, the overcurrent detection point may be lowered by any other means such as lowering the overcurrent setting value of the overcurrent protection unit or changing the gain of the overcurrent protection unit. You can

Further, the overheat detecting means of the power source is not limited to thermal, and any other temperature detecting means can be used. Further, in the above embodiment,
In the power source of the printer, an embodiment has been shown in which divided printing is performed when the power source is overheated, but the present invention is not limited to the above-described embodiment, and the power source and the load are separated, and when the power source is overheated,
By switching the load side to the light load operation mode, it can be applied to other devices that protect the power supply from overheating.

[0027]

As is apparent from the above description,
In the present invention, when the power supply becomes overheated, the operation mode of the load device can be switched without transmitting the output signal of the temperature detecting means provided in the power supply to the load device such as a printer. It is possible to protect the power supply from over temperature without increasing the number of signals between load devices such as printers and the number of input / output pins of the connector of the power supply and the load device, and it is possible to downsize the device. Become.

[Brief description of drawings]

FIG. 1 is a principle block diagram of the present invention.

FIG. 2 is a diagram showing an example of the present invention.

FIG. 3 is a diagram showing another embodiment of the present invention.

FIG. 4 is a diagram showing a conventional example.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 power supply 11 power supply part 1a temperature detection means 12 overcurrent detection part 13 overcurrent protection part 2 load device 21 printer device 11a thermal 11b PWM control circuit Tr1, Tr2 transistor T1, T3 transformer T2 current transformer D1, D2, D3, D11 , D12 Diode L1, L2 Reactor C1, C2 Capacitor R1, R2, R11, R12, R13, R14 Resistance

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI Technical display location G05F 1/56 320 H 4237-5H H02H 7/00 A 9177-5G 9/02 Z 9059-5G H02M 3/28 C 8726-5H 9211-2C B41J 3/10 114 D

Claims (2)

[Claims] 1. A power supply comprising an overcurrent protection section for drooping the output voltage to perform overcurrent protection when the output current exceeds a predetermined set value, and a temperature detection means for detecting the temperature of the power supply; When the power supply is overheated, the overcurrent detection point is detected by the output of the temperature detection means when the power supply is overheated and the load device has the function of switching to the operation mode that reduces the load on the power supply when the output voltage of the power supply droops. To lower the output voltage of the power supply,
An overtemperature protection device which protects a power supply from overheating by switching an operation mode of a load device to an operation mode which reduces a load of a power supply. 2. A power supply comprising an overcurrent protection unit for drooping the output voltage to protect the current when the output current exceeds a predetermined set value, and a temperature detection means for detecting the temperature of the power supply; And a printer device having a function of switching to a split print mode when the output voltage of the power supply droops. When the power supply overheats, the output of the temperature detection means lowers the overcurrent detection point, Droop the output voltage of
An overtemperature protection device for a power source in a printer device, which protects the power source from overheating by switching the operation mode of the printer device to a split printing mode.