JPH0352252B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention detects voltage, pulse width or
This invention relates to a pulse generation circuit that converts into a period.

Figure 1 shows how to convert a conventional voltage into a pulse width.
This is a circuit diagram of a pulse generation circuit, published in 1973.
It is almost the same as the circuit known in 15378. Reference numeral 1 denotes a power supply that generates a voltage V. A resistor 2 forms a charging circuit together with a capacitor 3. 4 is a discharge transistor connected to both ends of the capacitor 3. Together with the resistor 5 and the Zener diode 6, which is one of the constant voltage elements,
A reference voltage of voltage E is generated. 7 is a comparison circuit that compares the charging voltage of the capacitor 3 with a reference voltage and generates a high or low level. In this circuit, due to fluctuations in the power supply voltage V, the comparison circuit's
It has the characteristic that the pulse width changes.

FIG. 2 is a diagram showing the output waveform of the circuit shown in FIG. 1, and shows the relationship between the power supply voltage V and the pulse width t. The input time to transistor 4, i.e. τ
is also included in the pulse width, but it is a sufficiently small value. When the power supply voltage V is high _V1 , the charging time to the capacitor 3 to the voltage E is fast, and the pulse width t of the output of the comparator circuit 7 is short _t1 ; conversely, when the power supply voltage V is low _V2 At this time, the pulse width t becomes _t2 .

FIG. 3 is a graph showing the relationship among the power supply voltage V, reference voltage E, and pulse width t of the circuit shown in FIG. On the x-axis, x=V/E is plotted on a logarithmic scale. The discharge time τ is extremely small, so it is ignored.
Assuming that the capacitance value of the capacitor 3 is C, and the resistance value of the resistor 2 is R, the value obtained by dividing the pulse width t by the time constant CR at this time is plotted on the y-axis in a logarithmic scale similar to the x-axis. 31 is a characteristic curve of the circuit shown in FIG. 32 is a characteristic with a slope of -2, and when E is a constant value, the relationship between V and t of the straight line 32 is expressed by the following equation (1).

V ² ×t=α (1) α is a constant value.

Now, suppose that there is a resistor with a resistance value γ, and a voltage with a pulse width t and a voltage V is applied to this resistor, the power Pw at this time is given by equation (2).

V ² ×t/γ=Pw (2) If the power Pw is constant, then the equation (2) is the same as the equation (1). That is, the straight line 32 represents the characteristic that the power is constant. Tokuko Showa 53-
15378 was actually aimed at obtaining characteristics close to this straight line 32, but in reality it was similar to the characteristic curve 31.
As can be seen, it is far from the straight line 32 which is the ideal line. The portion that can be approximated parallel to the straight line 32 is in the range of 1.3 to 1.6 in terms of x value from point P to point Q.

The characteristic in which the electric power is constant in this way is hereinafter referred to as the equal-energy characteristic because the applied energy is constant. This iso-energetic property is needed in many ways. For example, in heating elements such as thermal printers that print on thermal paper by energizing the heating element, it is necessary to constantly input a constant amount of energy to obtain a constant density despite fluctuations in the power supply. Thermal printers have also been driven, but there is no suitable driving method. In the early days of manganese batteries, 4 batteries were approximately
6.5V, but if we adjust the temperature of the heating element using the circuit shown in Figure 1, then the x value at point P is 1.6 and the x value at point Q is 1.6.
Since the ratio of 1.3 has equal energy characteristics up to a voltage equal to the ratio of the power supply voltage, the range of equal energy characteristics is up to about 5.3V. In printers such as thermal printers that convert energy applied to a heating element into printing energy, the printing quality deteriorates immediately after starting to use the battery. This is a similar problem in the temperature control of the thermal pen disclosed in Japanese Patent Publication No. 53-15378.

An object of the present invention is to provide a pulse generation circuit that generates a reference signal for supplying constant energy using a power supply whose power supply voltage changes. The present invention provides a pulse generation circuit that has equal energy characteristics over a wide voltage range in equipment used in this application.

The details of the present invention will be described below. FIG. 4 is a circuit diagram of an embodiment of the pulse generating circuit according to the present invention, in which 41 is a battery which is a power source for generating voltage Vd, 42 is a Zener diode which is a type of constant voltage means, and 43 is a Zener diode. Diode zener voltage Vz
44 is an adjustment resistor, 45 is a capacitor, and 46 is a discharge transistor. The Zener diode 42, series resistor 43, adjustment resistor 44, and capacitor 45 form a charging circuit. Together with the discharge transistor 46, it is called a charge/discharge circuit.

47 is a series resistor, and 48 is a Zener diode, which generates a reference voltage E, as shown in FIG. 49 is a voltage comparison circuit that compares the charge level of the capacitor 45 and the reference voltage E. The relationship between output and input is the same as in FIG.

FIG. 5 is a graph comparing the characteristics of the pulse generating circuit according to the present invention with the characteristics of the conventional one. Characteristic curves that are the same as in FIG. 3 are designated by the same numbers. The characteristic of the characteristic curve 31 of the conventional circuit is expressed by the following equation (3).

y=t/C・R=-ln(1-E/v)...(3) ln=natural logarithm C indicates the value of capacitor 3, and R indicates the value of resistor 2. v=V.

51 is a characteristic curve according to the present invention, which is a graph of equation (4).

y=t/C・R=-ln(1-E/Vd-Vz)...(4) As an example, when Vz=E×1.8 (volts), v=
It is graphed as Vd. C is capacitor 4
The value of 5 and R are the values of the adjustment resistor 44, and since the on-time of the discharge transistor is set to be extremely small, it will be ignored. 32, 52 is slope -2
shows a straight line. It can be seen that the range in which the characteristic curve 51 can be approximated to a slope of -2 is extremely wide compared to the characteristic curve 31 of the conventional circuit.
x=7 to 3.8, that is, it can be approximated to a substantially straight line from point J to point K. The closer it is to a straight line with a slope of -2, the
t is close to a characteristic that is inversely proportional to the square of the voltage. When considering the above characteristics in terms of battery voltage, if E=0.9, then Vd=6.3 to 3.4 volts, and the range of equal energy characteristics is significantly expanded compared to conventional circuits. This relationship between voltage and pulse width has a wide range of applications and is extremely useful.

An example of the range of application is temperature control of a thermal head of a thermal printer. In devices such as the thermal head of a thermal printer that drive a large number of heat generating elements at the same time, changes in the number of energized heat generating elements often cause variations in the power supply, which often causes shading. However, by controlling the heating element using the pulse generation circuit according to the present invention, it is possible to always supply constant printing energy.
It is possible to improve printing quality.

Furthermore, by using the pulse generation circuit according to the present invention in equipment using electromagnets or the like, it becomes possible to suppress wasteful power loss and prevent the equipment from generating heat.

FIG. 6 is a circuit diagram of another embodiment according to the present invention, and the same parts as in FIG. 4 are designated by the same numbers. A transistor 61 is used in place of the voltage comparator circuit 49 in FIG. No reference voltage generating means such as a Zener diode is provided, and the voltage between the base and emitter of the transistor (hereinafter abbreviated as Vbe) is used as the reference voltage. 62 is a transistor 61
63 is a capacitor 64 for creating a delay time, 64 is an inverter, 65 is an inverter load resistor, and 66 is a signal transmission resistor.

The pulse generating circuit shown in FIG. 6 is an oscillation circuit having a period approximately inversely proportional to the square of the power supply voltage, and its operating principle is as follows. The power supply 41 is turned on,
When charging of the capacitor 45 starts and reaches Vbe, the transistor 61 turns on and the capacitor 63
, the inverter 64 is turned off with a delay of a minimum time. Therefore, the transistor 46 turns on,
The pulse generating circuit according to the present invention shown in FIG. 6 becomes an oscillator circuit as the capacitor 45 is instantaneously discharged, which also turns off the transistor 46 and begins charging the capacitor.

FIG. 7 is a diagram showing the characteristics of the pulse generating circuit shown in FIG. 6, and shows the output waveform of the inverter 64. 71 is a waveform when the voltage Vd of the power supply 41 is high _V1 , and the period is short _T1 . 72 is a waveform when Vd is low, _V2 , and the period is _T2 , which is long.
The capacitor 63 is provided to ensure the discharge time of the transistor 46, and has little to do with determining the period T. It has almost the same voltage characteristics as the pulse width t of the pulse generation circuit according to the present invention shown in FIG.
It has isoenergetic properties. Another embodiment of the pulse generating circuit according to the invention shown in FIG. 6 can be used as a reference signal source for equipment requiring equal energy characteristics.

FIG. 8 is a diagram showing another example of the charging/discharging circuit of the pulse generating circuit according to the present invention. Components that are the same as those in FIG. 4 are designated by the same numbers. 81 in Figure 8a is
PNP type transistor with resistor 82 and resistor 83
Together with this, they constitute a constant voltage means. Resistor 82
is placed between the base and emitter of the transistor, and the resistor 83 is placed between the base and collector of the transistor.
The resistance value of 3 is R2, and the base-emitter voltage is Vbe.
Then, it is expressed by the following formula.

Vz=(R1+R2)×Vbe/R1 According to the above equation, it is understood that any potential can be generated by appropriately selecting the resistor.

Constant voltage means using transistors basically depends on the temperature characteristics of the transistor's Vbe, so the characteristics do not change depending on the voltage used and are always uniform. It has negative temperature characteristics. For this reason, in a pulse generating circuit using constant voltage means including transistors as a component, the output characteristics thereof tend to be such that the pulse width or period becomes smaller as the ambient temperature rises. By utilizing this feature, thermal printers can be controlled to reduce the applied energy to the thermal head when the ambient temperature is high and increase the applied energy when the ambient temperature is low, and are a control standard that compensates for the power supply voltage. It can be used not only as a signal but also as a reference signal for compensating control for ambient temperature.

On the other hand, Zener diodes have positive temperature characteristics when the generated potential is about 4 V or more, so the potential tends to increase with temperature rise. The output characteristics of a pulse generation circuit using a pulse generator have a tendency for the pulse width or period to increase as the ambient temperature rises. Also, around 4V, there is no temperature dependence, and below that, the temperature characteristics are the opposite. This makes it extremely difficult to handle in terms of circuit design. By using a variable resistor as the resistor 83, it is possible to finely adjust the characteristic curve. Figure 8b
This uses the forward voltage of the diode 85 as a constant voltage means, and the number of diodes 85 is changed to obtain an appropriate Vz. discharge transistor 46
A resistor 86 connected to is a protection resistor that limits the collector current of transistor 46. still,
The constant voltage Vz generated by the transistor 81 changes depending on the temperature, and becomes small at high temperatures and large at low temperatures.The pulse width or period is small at high temperatures and becomes large at low temperatures, so it is suitable for the reference signal of thermal printers, etc. do. In order to increase the temperature dependence, a thermistor or the like may be inserted in series with the adjustment resistor 44. In addition, in the pulse generation circuit of the present invention described above, one end of the capacitor that performs charging, which is the basis for determining the pulse period or pulse width, is grounded, so the range of power supply voltage that can supply constant energy can be extremely wide. . Furthermore, the accuracy of equal energy can be extremely high. The other end of the capacitor is connected between the power supplies to a voltage dividing terminal from a constant voltage means, which is connected in series with a resistor that stabilizes the current flowing through the constant voltage means between the power supplies. Because of the circuit configuration, charging can be performed with high precision in response to fluctuations in power supply voltage, and print density can be made extremely uniform.

As detailed above, the pulse generation circuit according to the present invention is an extremely inexpensive and simple circuit, and
It has the characteristic of having a pulse width or period that is almost inversely proportional to the square of the power supply voltage over a wide voltage range, making it ideal as a reference signal for driving thermal printers, etc., as well as equipment that requires constant temperature control. It is an extremely useful circuit.

Furthermore, by using a constant voltage means that includes transistors as a component in the pulse generation circuit, the pulse width or period changes in a negative manner as the ambient temperature rises, and this feature can be utilized. This makes it possible to control thermal printers by reducing the applied energy to the thermal head when the ambient temperature is high and increasing the applied energy when the ambient temperature is low, and it is not only used as a reference signal for control to compensate for the power supply voltage. Compensation control for ambient temperature is also possible at the same time, and the range of applications is extremely wide.

Furthermore, unlike the case of using Zener diodes, the method using the above transistor allows setting of any voltage, making it possible to finely adjust the voltage-pulse width characteristics, making it suitable for density control in thermal printers, etc. In this regard, it greatly contributes to improving printing quality.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of a conventional pulse generation circuit, where 1 is a power supply, 2 is a resistor, 3 is a capacitor, and 6 is a circuit diagram of a conventional pulse generation circuit.
indicates a Zener diode, and 7 indicates a comparison circuit. FIG. 2 is a diagram showing an output waveform of the conventional pulse generation circuit shown in FIG. 1. Figure 3 shows the first
Power supply voltage V, reference voltage E, pulse width t of the circuit shown in the figure
This is a graph of the relationship between
E is plotted on a logarithmic scale, and t/C and R are plotted on a logarithmic scale on the y-axis. FIG. 4 is a circuit diagram of an embodiment of the pulse generating circuit according to the present invention, in which 41 is a power source, 42 is a zener diode which is a type of constant voltage means, and 44
The adjusting resistor 45 is a capacitor, and 49 is a comparison circuit. FIG. 5 is a diagram showing the characteristics of the pulse generation circuit according to the present invention,
The same scale as in Figure 3 is used. Figure 6 shows
4 is a circuit diagram showing another embodiment of the pulse generation circuit according to the present invention, in which a transistor 61 is used in place of the comparison circuit 49 in FIG. 4, and feedback is provided by an inverter 64 to form an oscillation circuit. Figure 7 shows
FIG. 7 is a diagram showing an output waveform of the circuit shown in FIG. 6;
FIG. 8 is a diagram showing another embodiment of the charging/discharging circuit of the pulse generating circuit according to the present invention, in which a shows an example in which a transistor is used as the constant voltage means, and b shows an example in which a diode is used as the constant voltage means. Each is shown below.

Claims (1)

[Scope of Claims] 1. In a pulse generation circuit that generates a pulse having a period or a pulse width based on the charge/discharge time of a capacitor, the capacitor, a constant voltage means inserted in a charging path of the capacitor, a discharging switching element connected in parallel to the capacitor; and an adjustment resistor having one end connected to the capacitor to enable adjustment of the pulse period or pulse width;
means for turning on and off according to the charge level of the capacitor, and the constant voltage means has at least one
a resistor placed between the base and emitter of the transistor, and a resistor placed between the base and collector of the transistor, and the pulse is generated within a predetermined voltage range to the square of the power supply voltage of the pulse generating circuit. A pulse generation circuit characterized by having a period or pulse width with characteristics that are approximately inversely proportional. 2. The pulse generating circuit according to claim 1, wherein the pulse generating circuit is a part of a component of a drive control section for a heating element for printing of a thermal printer.