JPS6329207B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a thermal pen type recorder that performs recording with a thermal pen, and more particularly to a heating device for a thermal pen that uses a battery as a power source for heating the thermal pen.

Generally, in a battery-powered thermal pen recorder, in order to change the amount of heat generated by the thermal pen, a variable resistor 3 is inserted in series between the battery 1 and the thermal pen 2 as shown in FIG. As shown in the figure, constant voltage circuit 4
is inserted. However, in the circuit shown in FIG. 1, not only the power loss of the variable resistor 3 is large, but also the amount of heat generated by the hot pen decreases when the battery voltage decreases.

Further, in the circuit shown in FIG. 2, even if the battery voltage decreases to some extent, the amount of heat generated by the hot pen does not change, but power loss occurs in the constant voltage circuit 4, which poses a problem in the usage time of the battery.

In view of these points, the present invention is a novel technology that minimizes the power consumption required for heating a thermal pen and supplies a constant amount of power to the thermal pen to maintain a constant amount of heat even when the battery voltage drops to a certain extent. A heating device for a thermal pen is provided.

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

FIG. 3 is a circuit diagram showing an embodiment of the present invention, in which 5 is a thermal pen, 6 is a battery as a heating power source for the thermal pen 5, 7 is a transistor as a switching element, 8 is a voltage power source 9 and a resistor. A reference voltage setting circuit 10 is composed of R ₁ , R ₂ , R ₃ and a variable resistor R ₄ and generates reference voltages Vs and Vk, and 10 is composed of resistors R ₅ , R ₆ and a capacitor C, and is used to turn on and off the switching transistor 7. A charging/discharging circuit that charges and discharges the capacitor C in response; 11 and 12 are comparators that input the charging/discharging voltage V _H at one end and each reference voltage Vs and Vk at the other end; 13 is an inverter 14; NAND
It is a control circuit that controls the switching transistor 7 and is composed of a flip-flop composed of gates 15 and 16. Note that here, the values of the resistors R ₁ , R ₂ , R ₃ , and R ₄ are determined so that the voltage becomes VsVk.

4A to 4E are waveform diagrams of various parts of the circuit of FIG. 3, and the operation of the embodiment will be described below with reference to FIG. 4.

First, when the transistor 7 is turned on, the voltage drop between the collector and emitter of the transistor is very small, so the voltage Vo across the hot pen 5 becomes almost the battery voltage Vc. This voltage Vo charges the capacitor C through the resistor _R5 , and the charging voltage _VH increases according to a time constant determined by the resistors _R5 , _R6 and the capacitor C as shown in FIG. 4A. And the voltage V _H
When the voltage becomes slightly higher than the reference voltage Vs, the output of the comparator 11 becomes "H" level, and the inverter 1
The output a of No. 4 becomes the "L" level as shown in FIG. 4 (b). At this time, the output b of the comparator 12 is at the "H" level as shown in FIG.
Output c of flip-flop composed of 5,16
is inverted from the "L" level to the "H" level and remains at the "H" level. The output c of the flip-flop is applied to the transistor 7 through the resistor R ₇ , so the transistor 7 is turned off and the thermal pen 5
The voltage d at one end of is at the "L" level as shown in FIG. 4(e).

Then, the voltage charged in the capacitor C starts discharging via the resistors R ₅ and R ₆ and the resistor of the hot pen (FIG. 4A). Then, when the voltage _VH becomes slightly lower than the reference voltage Vk, the output a of the inverter 14 remains at the "H" level, but the output b of the comparator 12 changes from the "H" level to the "L" level. Therefore, the output c of the flip-flop becomes "L" level. Therefore, the transistor 7 is turned on again, current flows from the battery 6 to the hot pen 5, and the voltage d returns to the "H" level (FIG. 4(e)).

In this way, the voltage V _H applied to one end of the comparators 11 and 12 charges and discharges between the voltages determined by the reference voltages Vs and Vk at a period determined by the time constants of the resistors R ₅ and R ₆ and the capacitor C. Repeatedly, voltage is applied from the battery 6 to the thermal pen 5 during charging, and application of voltage from the battery 6 to the thermal pen 5 is interrupted during discharging. That is, the voltage Vo at both ends of the thermal pen 5 alternately repeats "H" level and "L" level at a predetermined period.

Here, the variable resistor in the reference voltage setting circuit 8
Try changing the resistance value of _R4 by manipulating _R4 . As shown in FIG. 5, when the reference voltage Vk is Vka, the period when the voltage is "H" level is T _1a and the period when the voltage is "L" level is T _2a (FIG. 5 b).
Change the reference voltage Vk from Vka by changing the resistance value of _R4 .
When set to Vkb, the duty of voltage Vo changes as shown in Fig. 5C, and the period of "H" level is _T1b ,
The “L” level period is T _2b . The power consumption Po in a thermal pen is approximately proportional to T ₁ Vc ² /T ₁ + T ₂ (T ₁ : “H” level period, T ₂ “L” level period), so operate variable resistor R ₄ to By changing the resistance value of ₄ , the power consumption of the thermal pen 5 can be changed.

Next, a case where the battery voltage Vc changes will be explained with reference to FIG. 6.

As shown in Figure 6, the battery voltage Vc changes from Vca to
When the voltage changes to Vcb, the voltage Vo across the thermal pen 5 changes from approximately Vca to Vob. However, the voltage
The period when Vo is at "L" level is the same between T _2a and T _2b , but the period when Vo is at "H" level is from T _1b to T _1a .
is longer. That is, when the battery voltage decreases, the heating time of the thermal pen 5 becomes longer, so that a constant electric power is supplied to the thermal pen 5, and the amount of heat generated by the thermal pen 5 becomes constant.

As mentioned above, the heating device for a thermal pen according to the present invention not only can keep the amount of heat generated by the thermal pen constant even if the battery voltage drops to a certain extent, but also can reduce power consumption as much as possible, thereby significantly extending the usage time of the battery. can be extended to Also, since the configuration does not short-circuit the capacitor of the charging circuit at regular intervals,
Only one switching element is required, and a complicated timer circuit is not required, simplifying the circuit configuration.

Furthermore, since the reference voltage can be changed by a variable resistor in the reference voltage setting circuit, it is possible to make the amount of heat generated by the hot pen variable.

[Brief explanation of the drawing]

1 and 2 are schematic diagrams showing a conventional example of a heating device for a thermal pen, FIG. 3 is a circuit diagram showing an embodiment of a heating device for a thermal pen according to the present invention, and FIGS. Waveform diagrams of each part in the example, Figure 5 is an explanatory diagram of operation when changing the reference voltage Vk, Figure 6 is the battery voltage
FIG. 3 is an explanatory diagram of the operation when Vc changes. Explanation of main drawing numbers, 5... Heat pen, 6... Heating battery, 7... Switching transistor, 8 ...
Reference voltage setting circuit, 10 ... Charge/discharge circuit, 11,
12... Comparator, 13 ... Control circuit.

Claims (1)

[Scope of Claims] 1. A battery as a heating power source for a thermal pen, a switching element connected in series with the thermal pen between terminals of the battery, and a switching element connected in parallel to the thermal pen for turning on/off the switching element. a charging/discharging circuit that performs charging/discharging in response to a first reference voltage and a first reference voltage;
a reference voltage setting circuit that generates a second reference voltage lower than the reference voltage; a first comparator that generates an output when the charging/discharging voltage is greater than the first reference voltage; a second comparator that generates an output when the voltage is smaller than a second reference voltage; and control that turns off the switching element according to the output of the first comparator and turns it on according to the output of the second comparator. A heating device for a thermal pen, characterized by comprising: means. 2. The heating device for a thermal pen according to claim 1, wherein the reference voltage setting circuit includes a variable resistor, and at least one of the first and second reference voltages is made variable.