JP6233642B2 - Liquid crystal drive device for cooker - Google Patents

Description

  The present invention relates to a cooking device such as an IH rice cooker provided with a liquid crystal display, and more particularly to a liquid crystal driving device in the cooking device.

  Cookers such as IH jar rice cookers and IH cookers used in general homes are equipped with a liquid crystal display unit with low power consumption for displaying the operating state and time of the device in order to improve the convenience of the user. Things are widespread (see, for example, Patent Document 1 and Patent Document 2).

  FIG. 5 is a block diagram showing a power supply driving circuit of a conventional liquid crystal display device described in Patent Document 1. In FIG. As shown in FIG. 5, the power source driving circuit of the liquid crystal display device 402 includes a microcomputer 401, a backup power source unit 403, a power source switching unit 407, a power source generating unit 408, a switching shared unit 409, and a voltage dividing unit 410. And is composed of.

  The backup power supply unit 403 includes a backup battery 404 for the liquid crystal display device 402 and the microcomputer 401, and a diode 405 serving as a backflow prevention unit for preventing the battery 404 from being charged. The power supply circuit 406 is configured to supply a voltage (VDD, approximately 5 V) to the microcomputer 401.

  When the voltage of the power supply circuit 406 is less than a predetermined voltage (for example, 3V), the power supply switching unit 407 determines that a power failure has occurred and performs a switching operation to the backup power supply unit 403. On the other hand, while the power supply circuit 406 is energized, the power supply switching means 407 lowers the voltage (VDD) of the power supply circuit 406 to a voltage equivalent to the voltage of the backup power supply means (about 3V) and supplies the same to the microcomputer 401. The display device 402 is configured to be driven with a desired voltage.

  The power generation means 408 is configured to generate a voltage (VCC) for supplying a voltage from the power supply circuit 406 to other peripheral devices. The switching sharing unit 409 is configured to share the switching circuit of the power switching unit 407 and the power generation unit 408. The voltage dividing means 410 is configured to divide the voltage of the power supply circuit 406 into a desired voltage by a plurality of resistors, and supplies a reference voltage (about approximately) for driving a liquid crystal to a driver (not shown) built in the microcomputer 401. 3V), and the liquid crystal display device 402 is driven.

  In the backup power supply means 403, the negative terminal of the battery 404 is connected to the ground, the positive terminal is connected to the anode terminal of the diode 405, and the cathode terminal of the diode 405 is connected to the output terminal of the power circuit 406.

  In the power supply driving circuit of the conventional liquid crystal display device 402 configured as described above, the voltage (VDD, 5V) is supplied from the power supply circuit 406 when energized. To be supplied. On the other hand, when a power failure occurs, the power from the power supply circuit 406 becomes zero, so that a desired voltage is supplied from the battery 404 to the microcomputer 401. As a result, the liquid crystal display device 402 is driven by supplying a desired voltage to the microcomputer 401 during both energization and power failure.

JP 2001-282207 A JP 2001-350437 A

  However, in the conventional configuration, since the reference voltage for driving the liquid crystal display device 402 is configured by the voltage dividing means 410 composed of a plurality of resistors, the current consumption of the liquid crystal display device varies depending on the display contents. There was a problem that it was not possible to respond sufficiently. In recent years, in order to further improve user convenience, the size of liquid crystal display devices has increased and the amount of information to be displayed has increased, and fluctuations in current consumption of the liquid crystal display devices have become larger in accordance with display contents. Thus, when the fluctuation of the consumption current of the liquid crystal display device is large, the supply power voltage to the liquid crystal display device is lowered, and as a result, there is a problem that the display may be difficult to see.

  In order to cope with such a problem, measures may be taken to reduce the resistance value of the voltage dividing means in order to always supply a sufficient current to the liquid crystal display device for easy display regardless of the display contents. .

  However, in recent years, there is a social demand for electrical products that requires further power saving. As described above, the countermeasure for reducing the resistance value of the voltage dividing means 410 increases the supply current to the liquid crystal display device, but the current consumption of the device always increases regardless of the display content of the liquid crystal display device. This leads to a new problem that power saving cannot be achieved. In addition, such a measure is such that in a device that assists display with a built-in battery, the current consumption in the power supply drive circuit of the liquid crystal display device is constantly increased, which causes a decrease in battery life and an increase in battery size. There are influences and it cannot be said that it is a favorable measure.

  The present invention solves the above-described conventional problems, is inexpensive, consumes less current, and can supply a stable power supply voltage to the liquid crystal display unit regardless of the display content of the liquid crystal display unit which is a liquid crystal display device. It aims at providing the liquid crystal drive device of a cooking appliance.

In order to solve the above-described conventional problems, a liquid crystal driving device for a cooking device according to the present invention drives a liquid crystal display unit that is a liquid crystal display device for displaying information, a DC power supply unit, and the liquid crystal display unit. A liquid crystal driving unit that inputs a plurality of voltages, a voltage dividing unit that a plurality of resistors are connected in series to divide and output the output voltage of the DC power supply unit, and an output voltage of the voltage dividing unit is input to the voltage dividing unit A liquid crystal power supply unit that outputs a voltage equivalent to the output voltage of the unit to the liquid crystal drive unit,
The liquid crystal power supply unit includes a first transistor having a base connected to an input terminal of the liquid crystal power supply unit and an emitter connected to an emitter resistor, a base connected to an emitter of the first transistor, and the first transistor. A second transistor having an emitter connected to the collector of
An emitter of the second transistor is connected to the liquid crystal driving unit, and a collector current of the second transistor is configured to flow without passing through the voltage dividing unit.

  The liquid crystal drive device of the cooking device of the present invention configured as described above can receive a stable voltage supply even if the current consumption changes depending on the display content of the liquid crystal display portion which is a liquid crystal display device. Therefore, a change in display state (appearance) on the liquid crystal display unit due to display contents can be suppressed.

  The liquid crystal driving device of the cooking device of the present invention can suppress the fluctuation that the fluctuation of the current consumption of the liquid crystal display section, which is a liquid crystal display apparatus, gives to the output voltage of the voltage dividing section. Stable voltage supply can be performed, and stable display can be performed without being affected by display contents in the liquid crystal display unit while suppressing power consumption.

The block diagram which shows the structure of the liquid crystal drive device of the cooking appliance of Embodiment 1 which concerns on this invention. The block diagram which shows the liquid crystal drive device of the cooking appliance of Embodiment 2 which concerns on this invention The block diagram which shows the liquid crystal drive device of the cooking appliance of Embodiment 3 which concerns on this invention The block diagram which shows the liquid crystal drive device of the cooking appliance of Embodiment 4 which concerns on this invention The block diagram which shows the liquid crystal display part of the conventional cooking device and its peripheral circuit

A liquid crystal drive device for a cooking device according to a first aspect of the present invention includes a liquid crystal display unit for displaying information, a DC power supply unit, and a liquid crystal drive for inputting a plurality of voltages to drive the liquid crystal display unit. A voltage dividing unit that is connected in series with a plurality of resistors to divide and output the output voltage of the DC power supply unit, and a voltage equivalent to the output voltage of the voltage dividing unit when the output voltage of the voltage dividing unit is input. A liquid crystal power supply unit that outputs to the liquid crystal drive unit,
The liquid crystal power supply unit includes a first transistor having a base connected to an input terminal of the liquid crystal power supply unit and an emitter connected to an emitter resistor, a base connected to an emitter of the first transistor, and the first transistor. A second transistor having an emitter connected to the collector of
An emitter of the second transistor is connected to the liquid crystal driving unit, and a collector current of the second transistor is configured to flow without passing through the voltage dividing unit.

  In the liquid crystal driving device of the cooking device according to the first aspect of the present invention configured as described above, the voltage supplied to the liquid crystal driving unit is set to the voltage of the input terminal of the liquid crystal power supply unit to the base of the first transistor. The difference between the emitter voltage and the base-emitter voltage of the second transistor is added. Accordingly, since the difference between the base-emitter voltage of the first transistor and the base-emitter voltage of the second transistor is small, the voltage is substantially the same as the voltage input from the voltage dividing unit. In addition, the emitter current of the second transistor flowing in the liquid crystal driving unit does not use the voltage dividing unit as a current path, and the fluctuation of the output current of the voltage dividing unit which varies in accordance with the amount of fluctuation of the emitter current of the second transistor is extremely high. It will be small. As a result, in the liquid crystal driving device of the cooking device according to the first aspect, since the necessary voltage can be stably supplied to the liquid crystal driving unit, the liquid crystal display unit can stably display regardless of the display contents. .

  In the liquid crystal drive device for a cooking device according to the second aspect of the present invention, in particular, in the liquid crystal power supply unit according to the first aspect, the first transistor is a PNP transistor and the second transistor is an NPN transistor. In addition, the emitter resistor may be connected between the base and collector of the NPN transistor, and the collector of the NPN transistor may be connected to the high potential side output terminal of the DC power supply unit.

  According to the liquid crystal drive device of the cooking device of the second aspect according to the present invention configured as described above, it is possible to provide a liquid crystal drive device that can supply a stable voltage with low current consumption with an inexpensive component configuration. it can.

In the liquid crystal driving device for a cooking device according to the third aspect of the present invention, in particular, in the liquid crystal power supply unit according to the first aspect, the first transistor is a PNP transistor and the second transistor is an NPN transistor. with some may be configured to connect between the output of the dividing unit of higher potential than the base of the emitter and the PNP transistor of the emitter resistor said PNP transistor.

  According to the liquid crystal drive device of the cooking device of the third aspect according to the present invention configured as described above, a stable voltage can be supplied and the current consumption in the liquid crystal power supply unit can be further reduced. Energy saving can be realized.

  In the liquid crystal drive device for a cooking device according to the fourth aspect of the present invention, in particular, in the liquid crystal power supply unit according to the first aspect, the first transistor is an NPN transistor, and the second transistor is a PNP transistor. In addition, the emitter resistor may be connected between the base and collector of the PNP transistor, and the collector of the PNP transistor may be connected to the low potential side output terminal of the DC power supply unit.

  According to the liquid crystal driving device of the cooking device of the fourth aspect of the present invention configured as described above, a liquid crystal power supply circuit that is configured with inexpensive parts and that consumes less current and has a stable output voltage is provided. Can do.

  In the liquid crystal drive device for a cooking device according to the fifth aspect of the present invention, in particular, the NPN transistor and the PNP transistor according to the second to fourth aspects may be configured in the same package.

  According to the liquid crystal driving device for a cooker of the fifth aspect of the present invention configured as described above, the NPN transistor and the PNP transistor are thermally coupled to each other, so that the element temperatures are always substantially equal. Therefore, fluctuations in the output voltage due to temperature changes in the liquid crystal power supply unit can be reduced.

  Hereinafter, a liquid crystal driving device of a cooking device will be described as an embodiment according to the present invention with reference to the attached drawings. In addition, the liquid crystal driving device of the cooking device of the present invention is not limited to the configuration of the liquid crystal driving device of the cooking device described in the following embodiments, and is equivalent to the technical idea described in the following embodiments. It includes an electric device configured based on the technical idea of.

(Embodiment 1)
FIG. 1 is a block diagram showing a configuration of a liquid crystal driving device that drives and controls a liquid crystal display unit that is a liquid crystal display device in the cooking device according to the first embodiment of the present invention.

  In FIG. 1, a DC power supply unit 2 uses a low-potential side output terminal as a common potential GND (ground potential, hereinafter simply referred to as GND), and outputs a DC voltage VDD to a high potential side output terminal VDD (hereinafter also simply referred to as VDD). . The voltage dividing unit 4 includes a resistor 4a, a resistor 4b, a resistor 4c, and a resistor 4d connected in series. One end on the high potential side of the resistor 4a is connected to the high potential side output terminal VDD of the DC power supply unit 2, and the resistor 4d One end on the low potential side is connected to GND. The voltage divider 4 divides VDD and outputs a reference voltage for driving a liquid crystal display (LCD) 1 that operates with a 1/3 bias and a 1/3 duty. Here, the 1/3 bias is an operation format driven by four voltages (including 0 V) divided into three in the voltage direction in the driving waveform of the liquid crystal display unit 1. The 1/3 duty is an operation format in which one wavelength is divided into three in the time axis direction in the driving waveform of the liquid crystal display unit 1.

  The voltage divider 4 connects the third output voltage VL3 from the connection point between the resistor 4a and the resistor 4b, connects the second output voltage VL2 from the connection point between the resistor 4b and the resistor 4c, and connects the resistor 4c and the resistor 4d. From the point, the first output voltage VL1 is output. A connection point between the resistor 4 a and the resistor 4 b and a connection point between the resistor 4 c and the resistor 4 d are output terminals of the voltage dividing unit 4, and each output terminal is connected to the liquid crystal driving unit 3.

  The liquid crystal power supply unit 5 to which the second output voltage VL2 output from the connection point between the resistor 4b and the resistor 4c is input outputs an equivalent voltage VL2a that is substantially the same as the second output voltage VL2 to the liquid crystal drive unit 3. It is configured as follows. A second transistor 5a composed of an NPN transistor, a first transistor 5b composed of a PNP transistor, and an emitter resistor 5c are provided. The second transistor 5a has a collector connected to VDD, a base connected to a connection point between the emitter of the first transistor 5b and the emitter resistor 5c, and an emitter connected to the collector of the first transistor 5b. The emitter of the second transistor 5 a is the output terminal of the liquid crystal power supply unit 5, is connected to the input terminal of the liquid crystal driving unit 3, and outputs the output voltage VL <b> 2 a to the liquid crystal driving unit 3. The base of the first transistor 5b is connected to a connection point between the resistor 4b and the resistor 4c, which is one of the output terminals of the voltage dividing unit 4. The other end of the emitter resistor 5c is connected to VDD so that forward current can be supplied to the base and emitter of the first transistor 5b. In the first embodiment, since the first transistor 5b is a PNP transistor, the other end of the emitter resistor 5c is connected to the high potential side output terminal VDD of the DC power supply unit 2 that is higher in potential than the base of the first transistor 5b. ing.

  About the liquid crystal drive device in the cooking device of Embodiment 1 comprised as mentioned above, the operation | movement and an effect | action are demonstrated below.

  As described above, the voltage dividing unit 4 outputs the first output voltage VL1 and the third output voltage VL3 as they are to the liquid crystal drive unit 3, but outputs the second output voltage VL2 to the liquid crystal power supply unit 5. .

  The emitter potential of the first transistor 5b is a potential obtained by adding VBE5b (about 0.6V), which is the base-emitter voltage of the first transistor 5b, to the second output voltage VL2, and the emitter potential of the second transistor 5a is the first potential. The base potential of the two transistors 5a, that is, the potential obtained by subtracting VBE5a (about 0.6V), which is the base-emitter voltage of the second transistor 5a, from the emitter potential of the first transistor 5b. Therefore, the emitter potential of the second transistor 5a is the second output voltage VL2 + VBE5b-VBE5a, but the base-emitter voltage VBE5a of the second transistor 5a and the base-emitter voltage VBE5b of the first transistor 5b are both substantially the same. Since the voltage is set to be, for example, about 0.6 V, the base of the first transistor 5b and the emitter of the second transistor 5a can be set to substantially the same potential.

  Next, the influence by the change of the display content of the liquid crystal display part 1 is demonstrated. In the following description, the emitter current of the second transistor 5a is IE5a, the collector current is IC5a, the base current is IB5a, and the current amplification factor is hFE5a. Similarly, the emitter current of the first transistor 5b is IE5b, the collector current is IC5b, the base current is IB5b, and the current amplification factor is hFE5b.

  The current consumption of the liquid crystal display unit 1, that is, the emitter current IEa of the second transistor 5a also changes due to the display change of the liquid crystal display unit 1. The emitter current IE5a of the second transistor 5a is a value obtained by adding the base current IB5a of the second transistor 5a to the collector current IC5a of the second transistor 5a. However, since IB5a is sufficiently smaller than the IC5a, Therefore, it is considered that IE5a≈IC5a. Accordingly, in the second transistor 5a, the relationship between the emitter current fluctuation amount ΔIE5a and the base current fluctuation amount ΔIB5a can be expressed as ΔIE5a = hFE5a × ΔIB5a.

  On the other hand, in the first transistor 5b, the relationship between the emitter current fluctuation amount ΔIE5b and the base current fluctuation amount ΔIB5b can be expressed as ΔIE5b = hFE5b × ΔIB5b as in the case of the second transistor 5a.

  If the current flowing through the emitter resistor 5c is constant, ΔIB5a = −ΔIE5b, so ΔIB5b = −ΔIE5a / hFE5a / hFE5b, and the base current fluctuation amount ΔIB5b can be made extremely small. In the first transistor 5b, even if the current flowing through the emitter resistor 5c changes by ΔIB5a, the emitter current IE5b hardly changes, and therefore the base current IB5b is not affected.

  In addition, although the base-emitter voltage of the transistor has a temperature characteristic of about −2 mV / ° C., the second transistor 5a and the first transistor 5b in the first embodiment are configured by an NPN transistor and a PNP transistor in the same package. By using one, the NPN transistor and the PNP transistor can be thermally coupled. As a result, the influence of the base-emitter voltage on the temperature characteristics can be canceled each other.

  As described above, in the first embodiment, the liquid crystal display unit 1 for displaying information, the DC power supply unit 2, and the liquid crystal driving unit 3 for inputting a plurality of voltages to drive the liquid crystal display unit 1 are provided. The four resistors are connected in series to divide and output the output voltage VDD of the DC power supply unit 2, and the second output voltage VL2 of the voltage dividing unit 4 is input to the second output. And a liquid crystal power supply unit 5 that forms an equivalent output voltage VL2a that is substantially the same as the voltage VL2 and outputs the same to the liquid crystal drive unit 3. The liquid crystal power supply unit 5 includes a first transistor 5b, an emitter resistor 5c provided between the emitter of the first transistor 5b and VDD, and a second transistor 5a. The first transistor 5b has a base connected to the input terminal of the liquid crystal power supply unit 5, and an emitter connected to the emitter resistor 5c and the collector of the first transistor 5b. The base of the second transistor 5a is connected to the emitter of the first transistor 5b, and the emitter is connected to the collector of the first transistor 5b to serve as the output terminal of the liquid crystal power supply unit 5. The liquid crystal power supply unit 5 is configured such that the emitter of the second transistor 5 a is connected to the liquid crystal driving unit 3, and the collector current of the second transistor 5 a flows without passing through the voltage dividing unit 4.

  By using the liquid crystal driving device of the cooker configured as described above, the voltage output to the liquid crystal driving unit 3 is the base-emitter of the first transistor 5b to the second output voltage VL2 input by the liquid crystal power source unit 5. The difference between the base voltage and the base-emitter voltage of the second transistor 5a is added, and the difference between the base-emitter voltages is slight, so that it is substantially the same as the second output voltage VL2 input from the voltage divider 4. Voltage VL2a. In addition, the emitter current of the second transistor 5a flowing through the liquid crystal driving unit 3 does not use the voltage dividing unit 4 as a current path, and the output of the voltage dividing unit 4 varies in accordance with the amount of variation in the emitter current of the second transistor 5a. Current fluctuation is extremely small. Therefore, the liquid crystal power supply unit 5 can stably supply a voltage equivalent to the output voltage of the voltage dividing unit 4 to the liquid crystal driving unit 3 regardless of the display content of the liquid crystal display unit 1. As a result, the liquid crystal display unit 1 can display stably regardless of the display contents.

  The first transistor 5b is a PNP transistor, the second transistor 5a is an NPN transistor, the emitter resistor 5c is connected between the base and collector of the second transistor 5a, and the collector of the second transistor 5a is connected to the DC power supply unit 2. By connecting to the high potential side output terminal VDD, the above operation and effect can be obtained.

  In the liquid crystal driving device according to the first embodiment, the liquid crystal power supply unit 5 connected to the voltage dividing unit 4 has been described as a single circuit configuration with only a circuit for the second output voltage VL2 of the voltage dividing unit 4. The invention is not limited to one circuit. For example, the liquid crystal power supply 5 may be provided for other output voltages (VL1 and / or VL3) of the voltage divider 4, and a desired number of liquid crystal power supplies according to the number of output terminals of the voltage divider 4 The part 5 may be provided. In this way, by providing the liquid crystal power supply unit 5 to the output voltages (VL1, VL2, VL3) of the voltage dividing unit 4, the current supplied to the liquid crystal driving unit 3 does not pass through the voltage dividing unit 4, and the liquid crystal The display unit 1 can display more stably regardless of the display contents.

(Embodiment 2)
Next, a liquid crystal driving device that drives and controls the liquid crystal display unit in the cooking device according to the second embodiment of the present invention will be described with reference to FIG.

  FIG. 2 shows a block diagram of the liquid crystal power supply unit and its surroundings in the cooking device of the second embodiment according to the present invention. In the description of the second embodiment, elements having the same functions as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

  The liquid crystal driving device in the cooking device of the second embodiment differs from the liquid crystal driving device in the cooking device of the first embodiment described above in that the connection position of the emitter resistor 6c in the liquid crystal power supply unit 6 is different. In the first embodiment, one end of the emitter resistor 6c is connected to the emitter of the first transistor 6b, and the other end of the emitter resistor 6c is connected to the connection point between the resistor 4a and the resistor 4b of the voltage dividing unit 4. Different from the configuration. That is, the other end of the emitter resistor 6 c is connected to a terminal that outputs the third output voltage VL <b> 3 of the voltage divider 4. As described above, the emitter resistor 6c is connected at the connection point between the base of the second transistor 6a and the resistors 4a and 4b of the voltage dividing unit 4 so that forward current can be supplied to the base and emitter of the first transistor 6b. It is connected to a certain output terminal.

  About the liquid crystal drive device in the cooking appliance of Embodiment 2 comprised as mentioned above, the operation | movement and an effect | action are demonstrated below.

  First, the influence of the change in the display content of the liquid crystal display unit 1 on the input current of the liquid crystal power supply unit 6 will be described. In the following description, the emitter current of the second transistor 6a is IE5a, the collector current is IC6a, the base current is IB6a, and the current amplification factor is hFE6a. Similarly, the emitter current of the first transistor 6b is IE6b, the collector current is IC6b, the base current is IB6b, and the current amplification factor is hFE6b.

  The current consumption of the liquid crystal display unit 1, that is, the emitter current of the second transistor 6a also changes due to the display change of the liquid crystal display unit 1. The emitter current IE6a of the second transistor 6a is a value obtained by adding the base current IB6a of the second transistor 6a to the collector current IC6a of the second transistor 6a. However, since IB6a is sufficiently smaller than the IC6a, Therefore, it is considered that IE6a≈IC6a. Accordingly, in the second transistor 6a, the relationship between the emitter current fluctuation amount ΔIE6a and the base current fluctuation amount ΔIB6a can be expressed as ΔIE6a = hFE6a × ΔIB6a.

  On the other hand, in the first transistor 6b, the relationship between the emitter current fluctuation amount ΔIE6b and the base current fluctuation amount ΔIB6b can be expressed as ΔIE6b = hFE6b × ΔIB6b as in the case of the second transistor 6a.

  If the current flowing through the emitter resistor 6c is constant, ΔIB6a = −ΔIE6b, so ΔIB6b = −ΔIE6a / hFE6a / hFE6b, and the variation of the base current IB6b with respect to the variation of the emitter current IE6a becomes very small. If the current flowing through the emitter resistor 6c changes by ΔIB6a, the current flowing through the resistor 4a also changes by ΔIB6a. This affects the potential of the third output voltage VL3. However, since ΔIB6a = ΔIE6a / hFE6a, the base current variation ΔIB6a of the second transistor 6a is a very small change and the third output voltage VL3, Since the second output voltage VL2 and the first output voltage VL1 are potentials formed by resistance voltage division, the second output voltage VL2 and the first output voltage VL1 change in the same manner as the potential of the third output voltage VL3 changes. To do. For this reason, the ratios of the first output voltage VL1, the second output voltage VL2, and the third output voltage VL3 do not fluctuate, and the display of the liquid crystal display unit 1 is not affected by unevenness. In this case, since the emitter current IE6b of the first transistor 6b is not changed, the base current IB6b is not affected.

  In addition, although the base-emitter voltage of the transistor has a temperature characteristic of about −2 mV / ° C., by using the second transistor 6a and the first transistor 6b in the second embodiment configured in the same package. The NPN transistor and the PNP transistor can be thermally coupled. As a result, the influence of the base-emitter voltage on the temperature characteristics can be canceled each other.

  As described above, in the second embodiment, the liquid crystal power supply section 6 is provided in place of the liquid crystal power supply section 5 in the first embodiment so that a forward current can be supplied to the base and emitter of the first transistor 6b. In addition, the emitter resistor 6c of the first transistor 6b is connected between the emitter of the first transistor 6b and the output terminal of the voltage dividing unit 4 having a higher potential than the base of the first transistor 6b. As a result, similarly to the first embodiment described above, the fluctuation of the base current of the first transistor 6b with respect to the fluctuation of the collector current of the second transistor 6a becomes very small, and the liquid crystal power supply unit 6 displays the display on the liquid crystal display unit 1. Regardless of the content, an equivalent voltage substantially the same as the output voltage of the voltage divider 4 can be stably supplied to the liquid crystal driver 3. As a result, the liquid crystal display unit 1 in the cooking device of Embodiment 2 can display stably.

  In the liquid crystal driving device according to the second embodiment, the liquid crystal power supply unit 6 connected to the voltage dividing unit 4 has been described as a single circuit configuration with only a circuit for the second output voltage VL2 of the voltage dividing unit 4. The invention is not limited to one circuit. For example, the liquid crystal power supply unit 6 may be provided for another output voltage (VL1) of the voltage dividing unit 4, and a desired number of liquid crystal power supply units 6 are provided according to the number of output terminals of the voltage dividing unit 4. May be. Thus, by providing the liquid crystal power supply unit 6 to the output voltage (VL1, VL2) of the voltage dividing unit 4, the current supplied to the liquid crystal driving unit 3 is configured not to pass through the voltage dividing unit 4, and the liquid crystal display unit 1 enables a more stable display regardless of the display content.

(Embodiment 3)
Next, a liquid crystal driving device that drives and controls the liquid crystal display unit in the cooking device according to the third embodiment of the present invention will be described with reference to FIG.

  FIG. 3 shows a block diagram of the liquid crystal power supply unit and its periphery in the cooking device of the third embodiment according to the present invention. In the description of the third embodiment, elements having the same functions as those in the first and second embodiments are denoted by the same reference numerals, and the description thereof is omitted.

  The liquid crystal driving device in the cooking device of the third embodiment differs from the liquid crystal driving device in the cooking device of the first and second embodiments described above in that the first transistor 7b of the liquid crystal power supply unit 7 is an NPN transistor. The second transistor 7a is a PNP transistor, and the collector of the second transistor 7a is connected to the low potential side output terminal of the DC power supply unit 2, that is, the common potential GND (ground potential).

  The liquid crystal power supply unit 7 in the third embodiment is configured to output to the liquid crystal drive unit 3 an equivalent voltage VL1a that is substantially the same as the first output voltage VL1 at the connection point between the resistors 4c and 4d of the voltage dividing unit 4. Has been. In the second transistor 7a, the collector is connected to GND, the base is connected to the emitter of the first transistor 7b, and the emitter is connected to the collector of the first transistor 7b. The emitter of the second transistor 7a is connected to the liquid crystal drive unit 3 and serves as an output terminal.

  The base of the first transistor 7b is connected to the connection point between the resistor 4c and the resistor 4d of the voltage dividing unit 4. One end of the emitter resistor 7c of the first transistor 7b is connected to the emitter of the first transistor 7b, and the other end of the emitter resistor 7c is connected to the emitter and base of the first transistor 7b so that a forward current flows through the first transistor 7b. It is connected to GND, which is at a lower potential than the base.

  About the liquid crystal drive device in the cooking appliance of Embodiment 3 comprised as mentioned above, the operation | movement and an effect | action are demonstrated below.

  In the third embodiment, the second output voltage VL2 and the third output voltage VL3 at the output end of the voltage dividing unit 4 are output as they are to the liquid crystal drive unit 3, but the first output voltage VL1 is the liquid crystal power supply unit 7 It is connected to the. The emitter potential of the first transistor 7b is a potential obtained by subtracting the base-emitter voltage VBE7b (about 0.6 V) from the base potential (first output voltage VL1) of the first transistor 7b. Further, the emitter potential of the second transistor 7a is obtained by adding VBE7a (about 0.6V), which is the base-emitter voltage of the second transistor 7a, to the base potential of the second transistor 7a, that is, the emitter potential of the first transistor 7b. It is a potential. The emitter potential of the second transistor 7a is the second output voltage VL2-VBE7b + VBE7a, but the base-emitter voltage VBE7b of the first transistor 7b and the base-emitter voltage VBE7a of the second transistor 7a are both substantially the same voltage. For example, since the voltage is set to about 0.6 V, the base of the first transistor 7b and the emitter of the second transistor 7a can be set to substantially the same potential.

  Next, the influence of the change in the display content of the liquid crystal display unit 1 on the input current of the liquid crystal power supply unit 7 will be described.

  In the following description, the emitter current of the first transistor 7b is IE7b, the collector current is IC7b, the base current is IB7b, and the current amplification factor is hFE7b. Similarly, the emitter current of the second transistor 7a is IE7a, the collector current is IC7a, the base current is IB7a, and the current amplification factor is hFE7a.

  The display current of the liquid crystal display unit 1 changes the output current from the liquid crystal power supply unit 7, that is, the emitter current IE7a of the second transistor 7a. The emitter current IE7a of the second transistor 7a is a value obtained by adding the base current IB7a of the second transistor 7a to the collector current IC7a of the second transistor 7a. However, since IB7a is sufficiently smaller than the IC7a, IE7a≈IC7a. Therefore, in the second transistor 7a, the relationship between the emitter current fluctuation amount ΔIE7a and the base current fluctuation amount ΔIB7a can be expressed as ΔIE7a = hFE7a × ΔIB7a.

  On the other hand, in the first transistor 7b, the relationship between the emitter current variation ΔIE7b and the base current variation ΔIB7b can be expressed as ΔIE7b = hFE7b × ΔIB7b, as in the case of the second transistor 7a.

  If the current flowing through the emitter resistor 7c is constant, ΔIB7a = −ΔIE7b, so ΔIB7b = −ΔIE7a / hFE7a / hFE7b, and the base current fluctuation amount ΔIB7b can be made very small. Further, in the first transistor 7b, even if the current flowing through the emitter resistor 7c changes by ΔIB7a, the emitter current IE7b hardly changes, so the base current IB7b is not affected.

  In addition, the voltage between the base and the emitter of the transistor has a temperature characteristic of about −2 mV / ° C. By using the transistor in which the first transistor 7b and the second transistor 7a in the third embodiment are configured in the same package. The NPN transistor and the PNP transistor can be thermally coupled. As a result, the influence of the base-emitter voltage on the temperature characteristics can be canceled each other.

  As described above, in the third embodiment, the liquid crystal power supply unit 7 is provided in place of the liquid crystal power supply unit 5 in the first embodiment, the first transistor 7b is an NPN transistor, and the second transistor 7a is a PNP. The other end of the emitter resistor 7c, one end of which is connected to the emitter of the first transistor 7b, and the collector of the second transistor 7a so that a forward current can be supplied to the base and emitter of the first transistor 7b. This is connected to the low potential side output terminal GND of the DC power supply unit 2 which is at a lower potential than the base of one transistor 7b. Therefore, the fluctuation of the base current IB7b of the first transistor 7b with respect to the fluctuation of the emitter current IE7a of the second transistor 7a is very small, and the liquid crystal power supply section 7 The first output voltage VL1a can be made substantially equal to the first output voltage VL1 of the voltage dividing unit 4 and equivalent. As a result, the liquid crystal display unit 1 in the cooking device of Embodiment 3 can display stably.

  In the liquid crystal drive device according to the third embodiment, the liquid crystal power supply unit 7 connected to the voltage dividing unit 4 has been described as a single circuit configuration with respect to the first output voltage VL1 of the voltage dividing unit 4. The invention is not limited to one circuit. For example, the liquid crystal power supply unit 7 may be provided for other output voltages (VL2 and / or VL3) of the voltage divider 4, and a desired number of liquid crystal power supplies depending on the number of output terminals of the voltage divider 4 The part 7 may be provided. As described above, by providing the liquid crystal power supply unit 7 to the output voltages (VL1, VL2, VL3) of the voltage dividing unit 4, the current supplied to the liquid crystal driving unit 3 is configured not to pass through the voltage dividing unit 4. The display unit 1 can display more stably regardless of the display contents.

(Embodiment 4)
Next, a liquid crystal driving device that drives and controls the liquid crystal display unit in the cooking device according to the fourth embodiment of the present invention will be described with reference to FIG.

  FIG. 4 shows a block diagram of the liquid crystal power supply unit and its surroundings in the cooking device of the fourth embodiment according to the present invention. In the description of the fourth embodiment, elements having the same functions as those in the first to third embodiments are denoted by the same reference numerals, and the description thereof is omitted.

  As shown in FIG. 4, in the liquid crystal drive device in the cooking device of the fourth embodiment, the liquid crystal power supply unit 6 of the liquid crystal drive device in the above-described second embodiment is used as the first liquid crystal power supply unit 6, and the third embodiment. The liquid crystal power supply unit 7 of the liquid crystal driving device is provided as the second liquid crystal power supply unit 7. Therefore, the liquid crystal driving device in the fourth embodiment has the effects described in the liquid crystal driving device in the second embodiment and the liquid crystal driving device in the third embodiment. For this reason, the liquid crystal driving device according to the fourth embodiment stably supplies the liquid crystal driving unit 3 with an equivalent voltage that is substantially the same as the output voltage of the voltage dividing unit 4 regardless of the display content of the liquid crystal display unit 1. Therefore, the liquid crystal display unit 1 can display stably.

  Although the present invention has been described in each embodiment with a certain degree of detail, the disclosure content of these embodiments should be changed in details of the configuration, and the combination and order of elements in each embodiment should be changed. Changes may be made without departing from the scope and spirit of the claimed invention.

  The liquid crystal driving device in the cooking device of the present invention is small in size, low in current consumption, and capable of stably supplying voltage even with power fluctuation required by the liquid crystal display unit according to the display content of the liquid crystal display unit. Since it is an apparatus, it can be applied not only to cookers such as IH jar rice cookers and IH cookers, but also to liquid crystal drive devices for liquid crystal display units such as electronic devices and electric devices used in general households other than cookers.

DESCRIPTION OF SYMBOLS 1 Liquid crystal display part 2 DC power supply part 3 Liquid crystal drive part 4 Voltage dividing part 5 Liquid crystal power supply part 6 Liquid crystal power supply part 7 Liquid crystal power supply part

Claims (6)

A liquid crystal display unit for displaying information, a DC power supply unit, a liquid crystal drive unit for inputting a plurality of voltages to drive the liquid crystal display unit, and a plurality of resistors connected in series to output voltage of the DC power supply unit A voltage dividing unit that outputs the divided voltage, and a liquid crystal power supply unit that receives the output voltage of the voltage dividing unit and outputs a voltage equivalent to the output voltage of the voltage dividing unit to the liquid crystal driving unit,
The liquid crystal power supply unit includes a first transistor having a base connected to an input terminal of the liquid crystal power supply unit and an emitter connected to an emitter resistor, a base connected to an emitter of the first transistor, and the first transistor. A second transistor having an emitter connected to the collector of
The emitter resistor is connected between the base and collector of the second transistor, the collector of the second transistor is connected to the high potential side output terminal of the DC power supply unit,
A liquid crystal driving device for a cooking device, wherein the emitter of the second transistor is connected to the liquid crystal driving unit, and the collector current of the second transistor flows without passing through the voltage dividing unit. A liquid crystal display unit for displaying information, a DC power supply unit, a liquid crystal drive unit for inputting a plurality of voltages to drive the liquid crystal display unit, and a plurality of resistors connected in series to output voltage of the DC power supply unit A voltage dividing unit that outputs the divided voltage, and a liquid crystal power supply unit that receives the output voltage of the voltage dividing unit and outputs a voltage equivalent to the output voltage of the voltage dividing unit to the liquid crystal driving unit,
The liquid crystal power supply unit includes a first transistor having a base connected to an input terminal of the liquid crystal power supply unit and an emitter connected to an emitter resistor, a base connected to an emitter of the first transistor, and the first transistor. A second transistor having an emitter connected to the collector of
Connecting said emitter resistor between the output of the dividing unit of higher potential than the base of the emitter and the first transistor of the first transistor, the high potential side of the collector of the second transistor the DC power supply section Connect to the output end,
A liquid crystal driving device for a cooking device , wherein the emitter of the second transistor is connected to the liquid crystal driving unit, and the collector current of the second transistor flows without passing through the voltage dividing unit. The liquid crystal power source unit, said first transistor is a PNP transistor, cooker liquid crystal driving device of according the second transistor to claim 1 or 2 Ru NPN transistor der. A liquid crystal display unit for displaying information, a DC power supply unit, a liquid crystal drive unit for inputting a plurality of voltages to drive the liquid crystal display unit, and a plurality of resistors connected in series to output voltage of the DC power supply unit A voltage dividing unit that outputs the divided voltage, and a liquid crystal power supply unit that receives the output voltage of the voltage dividing unit and outputs a voltage equivalent to the output voltage of the voltage dividing unit to the liquid crystal driving unit,
The liquid crystal power supply unit includes a first transistor having a base connected to an input terminal of the liquid crystal power supply unit and an emitter connected to an emitter resistor, a base connected to an emitter of the first transistor, and the first transistor. A second transistor having an emitter connected to the collector of
Wherein said emitter resistor second transistor based - connected between the collector and connects the collector of the second transistor to the low potential side output end of the DC power supply unit,
A liquid crystal driving device for a cooking device , wherein the emitter of the second transistor is connected to the liquid crystal driving unit, and the collector current of the second transistor flows without passing through the voltage dividing unit. 5. The liquid crystal driving device for a cooking device according to claim 4, wherein the first transistor is an NPN transistor and the second transistor is a PNP transistor. The liquid crystal driving device for a cooking device according to claim 3 or 5, wherein the NPN transistor and the PNP transistor are configured in the same package.

Images