JPS58144234A - Power supply device - Google Patents

Abstract

PURPOSE:To attain continuous power supply for a long period by integrating an output from a detecting means with a prescribed time constant, inputting the integrated output to a means to regulate voltage to be supplied to a load and detecting the temperature of the heating load to control the voltage to be supplied. CONSTITUTION:A voltage regulating transistor (TR) Q1 and a current detecting resistor element RS are connected between an input terminal IN of rectified voltage from a power supply device and an output terminal OUT to detect a load and a current detector U2 is connected to the element RS. Voltage proportional to the load current detected by the detector U2 is inputted to an integration circuit consisting of a capacitor element C6 and a resistor element R0 through a voltage reverse-current preventing diode D3. The time constant of the integration circuit is set up to a value correlated to the time constant of heating/radiation of the load and integrated voltage corresponding to the load current and power supply time is generated in an output point P1 of the circuit. The voltage is inputted to an error amplifier U1 through an amplifier U3 and a reverse-current preventing diode D2 and compared with the partial voltage of the input voltage to control the TR Q1 by the compared output.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a power supply device suitable for use with a circuit or device having a heat generating load such as a high output transistor, a heater, a thermal head of a thermal recording device, etc. In particular, the present invention relates to a power supply device that can control the temperature rise of a heat-generating load within a predetermined range even when the current is continuously energized for a long time.

Conventionally, various overcurrent protection circuits have been used in power supplies to reduce the output voltage when the load current exceeds a set value. FIG. 2 is a connection diagram showing an example of an overcurrent protection circuit. In the drawing, Qi is a voltage regulating transistor, Q! is a current detection transistor, U/ is an error amplifier,
ZD is a Zener diode %R8 is a current detection resistor element,
81 to R indicate resistance elements, IN is an input terminal for input voltage of rectified voltage, and OUT is an output terminal to which a load is connected.

FIG. 1 is a characteristic diagram showing the current-voltage characteristics of the circuit shown in FIG.

In the circuit shown in FIG. 1, the resistance element R8 and the R-type are provided for voltage detection, and their connection point (ha) is provided.

A divided voltage corresponding to the output voltage to the load is detected, and the detected output is connected to one input terminal of the error amplifier U/. It is then compared with the Zener voltage of the Zener diode ZD by a 2wA difference amplifier U/.

When the load current flowing through the current detection resistive element 8 exceeds a set value, the impedance between C and Σ of the current detection transistor Q decreases.

Therefore, the voltage VI of the voltage adjustment transistor Ql is
Since IIC decreases and the c-g voltage VCg increases,
Output voltage is reduced.

This operation prevents overcurrent to the load and voltage adjustment transistor QI. However, in the case of a heat-generating load, even if an overcurrent protection circuit like the one shown in Figure 1 is used, the temperature of the load will decrease. There is no hope of holding back the rise.

The reason for this is, for example, high output transistors.

Heat-generating loads such as heaters or thermal heads of thermal recording devices have a heat storage effect, and it is difficult to control the amount of heat generated by simply controlling the amount of heat determined by the integral of the current and the time it is energized.
This is because it is impossible to control the temperature of the load. In other words, even if the current value is controlled within a predetermined range, the temperature will rise by the amount of heat storage.

Therefore, in the power supply device of Jin's invention, the power supply device equipped with a voltage adjustment means such as a conventional overcurrent protection circuit is improved, and it is designed to function satisfactorily even for heat-generating loads. The object of the present invention is to control the current to the capacitor and also to control the supply voltage according to the temperature rise of the capacitor, thereby enabling continuous current supply for a long period of time.

Therefore, in the power supply device of the present invention.

First, a detection means for detecting load current as a voltage.

An integrator circuit that integrates this detection output with a predetermined time constant is added, and the output of the integrator circuit is given to the voltage adjustment means, so that the supply voltage can be reduced even when the temperature of the exothermic load increases. The idea is to have full control over the

First, a heating element is connected in series with the load, a temperature sensing element such as a thermistor is arranged near the heating element, and a detection means for detecting the impedance of the temperature sensing element is provided. It is characterized in that the detection output is given to the voltage adjustment means to similarly lower the supply voltage in response to the rise in temperature of the load.

First, the first percentage characteristic of the power supply device of the present invention will be explained.

FIG. 3 is a connection diagram showing one embodiment of the power supply device of the present invention. The symbols in the drawings are the same as in FIG. 1, and U is a current detector, U3 is an amplifier, D and ~D are reverse current prevention diodes, Ro is an integral resistance element, and C is an integral capacitance element. Pl indicates the output point of the integrating circuit.

The power supply device shown in FIG.
In addition to reducing the output voltage when it exceeds the set value, the integral value determined by the current value output to the load and its energization time is Detection of the output current, which operates to reduce the output voltage and suppress the heat generation of the load within a predetermined range even when the set value is exceeded, is performed by the current detection resistive element R8 and the current detector U. This is done by k. That is, due to the load current flowing through the current detection resistance element R8, the resistance element R8
A voltage proportional to the load current is generated across the terminal. Therefore, the output voltage of the current detector U is generated in proportion to the load current, and is input to the integrating circuit through the backflow prevention diode D1.

The integrating circuit is composed of a capacitive element C0 and a resistive element R6, and the capacitive element C0 and the resistive element Set the resistance value of R.

Therefore, an integrated voltage corresponding to the load current and its energization time is generated at the output point P of the integrating circuit.

This integrated voltage is amplified by the amplifier U3 and inputted to the II difference amplifier U/ via the backflow prevention diode D.

to the error amplifier U/, in order to simultaneously detect the output voltage to the load, similar to the circuit of FIG. 1 above.

The current detection resistance element R1 and the zero shunt prevention diode D to which the voltage divided by R1 and k is input block reverse current when the output of the amplifier UJ is larger.

The error term @unit U/ is given one of these inputs, that is, the integrated voltage and the detection output of the divided voltage, and the larger of the two is used as the comparison input. A comparison is made with some Zener voltage.

Therefore, in the device shown in Fig. 3, when the integrated output corresponding to the load current and its energization time exceeds the set value, or when the voltage at the dividing point between resistive elements R3 and R1 corresponding to the output current to the load is detected. When the output exceeds the set value, the output voltage to the load is reduced, suppressing heat generation in the load, and
It is maintained at a predetermined temperature.

Note that by inserting another resistance element in series or parallel with the integral capacitance element C, the correlation between heat generation and heat radiation characteristics of the load can be further improved.

Next, the first feature of the power supply device of the present invention will be explained.

FIG. 9 is a connection diagram showing another embodiment of the power supply device of the present invention. The reference numerals in the drawings are the same as those in FIGS. 3 and 3, and RT indicates the thermistor, R& indicates the resistance element, and %pm indicates the connection point between the thermistor RT and the resistance element R.

In the device shown in Fig. 1, the current detection resistor R8 utilizes a wire that generates heat in proportion to the load.

The temperature of this resistance element R8 is detected by a thermistor BT provided near it. That is, when the load generates heat, this resistance element R8 also generates heat in proportion to it, so the resistance value of the thermistor RT decreases.

Therefore, the input voltage of amplifier U3, thermistor R
The voltage at the connection point P between T and resistance element R4 increases. The output of this amplifier U3 is a diode D.

to the error amplifier U/.

The subsequent operations are the same as in the case of the previous diagram IK3.

In this case as well, if a resistance element is inserted in series or parallel with the thermistor RT, the correlation with the heat generation and heat dissipation characteristics of the load is as follows.
Further improvements will be made.

The next FIG. S is a connection diagram showing still another embodiment of the power supply device of the present invention. The symbols in the drawing are the same as those in Fig. ! Indicates a continuation point.

In the device shown in FIG. 5 as well, when the temperature of current detection resistive element R8 increases in proportion to the temperature of the load, the resistance value of thermistor RT decreases.

Therefore, the comparison voltage input to the error amplifier U/, that is, the voltage at the connection point P between thermistor RT and resistance element R1 increases. The subsequent operations are similar to those shown in FIG. 3 and s4.

Note that all of the above embodiments are voltage drop type power supply circuits,
In other words, this is the case of a one-dropper type.

However, even in the case of the switching method, the detection voltage is
A similar implementation can be achieved by inputting to the voltage regulation circuit via an F (voltage-frequency) converter.

As explained in detail above, in the power supply device of the present invention, firstly, an integrating circuit is provided in the conventional voltage regulating means, and the temperature of the exothermic load is detected by the output of this integrating circuit, and the temperature of the exothermic load is adjusted to a predetermined temperature. When this happens, the voltage supplied to the load is reduced.

Further, a heating element is connected in series to the k-th load, a temperature sensing element is provided near the heating element, and an impedance detection means for detecting the impedance of the temperature sensing element is provided. The temperature of the exothermic load is detected by the output, and the voltage supplied to the load is reduced.

Therefore, according to the power supply device of the present invention, not only the current supplied to the exothermic load is controlled, but also the supply voltage is controlled even when the temperature rises. As a result, it has the excellent effect of being able to continuously supply electricity for long periods of time to various heat-generating loads such as high-output transistors, heaters, and thermal heads of thermal recording devices and thermal transfer recording devices. is obtained.

[Brief explanation of the drawing]

Figure 1 is a connection diagram showing an example of an overcurrent protection circuit used in a conventional power supply device, and Figure 1 shows the current of the circuit in Figure 1.
A characteristic diagram showing voltage characteristics, FIG. 3, shows -! of the power supply device of this invention. J! Connection Diagrams Showing Embodiments FIG. Y and FIG. S are connection diagrams showing other embodiments of the power supply device of the present invention. In the drawing, Ql is a voltage adjustment transistor, Q is a current detection transistor, U/ is an error amplifier, υ is a current detector, U3 is an amplifier, ZD is a Zener diode, 8 is a thermistor, and R8 is a current detection resistor element. show. Patent applicant Rico Co., Ltd. −

Claims (1)

[Scope of Claims] L A detection means for detecting load current in terms of voltage, an integrating circuit for integrating a detection output from the detection means with a predetermined time constant, and a voltage adjustment means for adjusting the voltage supplied to the load. Prepare,
A power supply device characterized in that a voltage supplied to a load is controlled by inputting an output of the integration circuit to the voltage adjustment means. A heating element connected in series with a load, a temperature sensing element disposed near the heating element, an impedance detection means for detecting the impedance of the temperature sensing element, and a voltage for adjusting the voltage supplied to the load. A power supply device comprising: an adjusting means, and controlling a voltage supplied to a load by inputting a detection output from the impedance detecting means to the voltage adjusting means.