JPH1098870A - Power source - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power source at a low cost which performs excellent boosted starting characteristics, by utilizing booster capacity of a booster circuit to a maximum limit. SOLUTION: A power source unit 1 comprises an analog switch 17 for switching a booster circuit 13 and a high-voltage load circuit 19 to a connecting state or an interrupting state between an output stage of the circuit 13 and the circuit 19, and a latched circuit 16 for opening a contact of the switch 17 when power source ON is detected by a power source ON detector 14 to switch the circuit 13 to the circuit 19. And, the circuit 16 closes the contact of the switch 17 when counting of a predetermined time is finished by a timer circuit 15 to connect the circuit 19 to the circuit 13. Accordingly, the circuit 13 can boost a power source voltage VDD to a driving voltage VLCD having a predetermined voltage level in the state that it is disconnected from the circuit 19.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply device, and more particularly, to a power supply device provided with a booster circuit for boosting a power supply voltage supplied from a power supply to a predetermined voltage value. And a power supply unit for supplying a load connected to the output stage.

[0002]

2. Description of the Related Art Conventionally, there is provided a booster circuit for boosting a power supply voltage supplied from a power supply to a predetermined voltage value, and a power supply for supplying a voltage boosted by the booster circuit to a load connected to an output stage of the booster circuit. Examples of the device include a power supply unit incorporated in various electronic devices. Such a power supply device (power supply unit) has a circuit configuration in which a load (such as various drive circuits for electronic devices) is always connected to an output stage of a booster circuit.

[0003]

However, such a conventional power supply has the following problems.

That is, as described above, the booster circuit of the power supply device has a circuit configuration in which a load is always connected to the output stage, so that the power supply of the electronic device in which the power supply device (power supply unit) is incorporated. Is supplied, and during a rising period from when the power supply voltage is supplied to the booster circuit to when the power supply voltage is boosted to a predetermined voltage value in the booster circuit, the booster circuit operates in a state where a load is connected to the output stage. Since the power supply voltage had to be boosted to a predetermined voltage value, the booster circuit must have a circuit configuration having a higher boosting capability as compared with the case where no load is connected to the output stage during the rising period. Therefore, there has been a problem that the manufacturing cost of the power supply device is increased.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to provide an inexpensive power supply device which makes full use of the boosting capability of a boosting circuit and can exhibit excellent boosting start-up characteristics.

[0006]

According to a first aspect of the present invention, there is provided a booster circuit for boosting a power supply voltage supplied from a power supply to a predetermined voltage value. A power supply device for supplying the output voltage to a load connected to the output stage of the booster circuit, a disconnection means for connecting or disconnecting between the output stage of the booster circuit and the load, and detecting turning on of the power supply. Disconnection control means for setting the disconnection means to the cutoff state and for setting the connection and disconnection means to the connected state after a predetermined time has elapsed.

According to the present invention, there is provided a booster circuit for boosting a power supply voltage supplied from a power supply to a predetermined voltage value, and the voltage boosted by the booster circuit is connected to an output stage of the booster circuit. A power supply device for supplying power to the load, wherein disconnection means for connecting or disconnecting between an output stage of the booster circuit and the load is provided, and disconnection control means detects the power-on and detects the disconnection. The means is turned off, and after a predetermined time has elapsed, the disconnecting means is turned on.

In this case, as described in claim 2, in the invention according to claim 1, the disconnection control means includes:
The power-on detecting means for detecting the power-on may be provided, and a clock means for measuring the predetermined time when the power-on is detected by the power-on detecting means.

According to the second aspect of the present invention, the disconnection control means sets the disconnection means to the cut-off state when the power-on detection means detects that the power is turned on, and the predetermined time is counted by the timer means. Later, the disconnecting means is brought into the connected state.

According to a third aspect of the present invention, there is provided a booster circuit for boosting a power supply voltage supplied from a power supply to a predetermined voltage value, and a load connected to an output stage of the booster circuit. Disconnecting means for connecting or disconnecting between the output stage of the booster circuit and the load, and disconnecting the disconnecting means until the output voltage level of the booster circuit reaches a predetermined value. Disconnection control means for connecting the disconnection means when the output voltage level reaches the predetermined value.

According to the present invention, there is provided a booster circuit for boosting the power supply voltage supplied from the power supply to a predetermined voltage value, and the voltage boosted by the booster circuit is connected to the output stage of the booster circuit. In the power supply device for supplying the load, the disconnection means for connecting or disconnecting between the output stage of the booster circuit and the load is provided, the disconnection control means, the output voltage level of the booster circuit to a predetermined value Until the disconnection means is turned off, the disconnection means is turned on when the output voltage level reaches the predetermined value.

As described above, according to the first to third aspects of the present invention, after the power is turned on and the power supply voltage is supplied to the booster circuit, the power supply voltage is boosted to a predetermined voltage value in the booster circuit. In the rising period up to, the power supply voltage can be boosted to a predetermined voltage value in a state where the booster circuit is disconnected from the load, so that a boosting performance equivalent to the conventional one can be obtained with a circuit configuration having a lower boosting ability. Becomes As a result, the manufacturing cost of the power supply device can be reduced.

[0013] Also, as described in claim 4, claim 1 is as follows.
In the invention according to any one of the first to third aspects, the load may be a drive circuit that drives and displays a liquid crystal display panel.

According to the fourth aspect of the present invention,
4. The power supply device according to claim 1, wherein a power supply voltage supplied from a power supply is boosted to a predetermined voltage value by a booster circuit and supplied to a drive circuit for driving a liquid crystal display panel for display. The effect can be obtained.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail with reference to the drawings. In the first to third examples of the embodiment described below, an LCD (Liquid C
A power supply unit (power supply unit) incorporated in a liquid crystal display device that drives and displays a dot matrix liquid crystal panel using a controller / driver LSI will be described.

The above LSI (Large Scale Integrated cir)
cuit) is an LSI that performs various kinds of drive control for displaying alphanumeric characters, kana characters, symbols, etc. on a dot matrix liquid crystal panel, has a three-wire serial interface, and uses a dot matrix based on control signals from an external controller. The liquid crystal panel is driven for display.

This LSI can drive a dot matrix liquid crystal panel capable of displaying a maximum of 12 digits × 4 rows, and can drive a DDRAM (Display Data RAM) and a CGR.
AM (Character Generator RAM), PictRA
M, character attribute RAM, liquid crystal driving circuit, liquid crystal driving quadruple booster circuit, oscillation circuit, and the like are integrated on one chip.

(First Embodiment) FIGS. 1 and 2 are views showing a first embodiment of a power supply unit to which a power supply device of the present invention is applied. First, the configuration will be described.
FIG. 1 is a block diagram of a power supply unit 1 to which the present invention is applied.

In FIG. 1, a power supply unit 1 includes a power supply 1
1, a power switch 12, a booster circuit 13, a power-on detection circuit 14, a timer circuit 15, a latch circuit 16, an analog switch 17, and a capacitor 18. The output stage of the booster circuit 13 is connected via the analog switch 17. It is connected to various drive circuits (high-voltage load circuit 19) for driving the display of the dot matrix liquid crystal panel.

In FIG. 1, a booster circuit 13, a power-on detecting circuit 14, a timer circuit 15, a latch circuit 16,
The high voltage load circuit 19 is built in the LCD controller / driver LSI.

The power supply 11 is composed of a primary battery or a secondary battery, and supplies a power supply voltage VDD to the booster circuit 13 when the power switch 12 is turned on. The power switch 12
A switch for turning on / off the power supply 11 of the liquid crystal display device in which the power supply unit 1 is incorporated.

The booster circuit 13 boosts the power supply voltage VDD supplied from the power supply 11, and drives various drive circuits (high-voltage load circuit 19) connected to the output stage of the booster circuit 13 via the analog switch 17. A driving voltage VLCD having a predetermined voltage level for driving is generated.

The power-on detection circuit 14 includes the power switch 1
2 is an ON operation and a circuit for detecting whether or not the power supply 11 is turned on. When not detected, the detection signal Sou of "Low" is detected.
t is output to the S input terminal of the timer circuit 15 and the latch circuit 16. Further, the power-on detection circuit 14 detects that the power switch 11 is turned on and the power supply 11 is turned on, and detects the detection signal S which becomes "Hi" for a predetermined period.
out is output to the S input terminal of the timer circuit 15 and the latch circuit 16.

The timer circuit 15 includes a power-on detection circuit 1
When the detection signal Sout which becomes "Hi" for a predetermined period is inputted from 4, the clocking of a predetermined time is started, and when the clocking of the predetermined time is completed, a clock end signal Tout which becomes "Hi" for a predetermined period is latched. Output to the R input terminal of the circuit 16.

The latch circuit 16 is constituted by an RS flip-flop (Rset Set Flip-Flop). After a detection signal Sout which becomes “Hi” for a predetermined period from the power-on detection circuit 14 is input to the S input terminal, Timer circuit 15
During the period from when the timing end signal Tout, which becomes "Hi" for a predetermined period, is input to the R input terminal, the control signal Lout, which becomes "Hi", is output to the analog switch 17 to control the disconnected state of the analog switch 17. I do.

The analog switch 17 is provided between the output stage of the booster circuit 13 and the high-voltage load circuit 19, and switches the booster circuit 13 and the high-voltage load circuit 19 to a connection state or a cutoff state. This analog switch 17
Open the contact during the period in which the control signal Lout of “Hi” is input from the latch circuit 16, and
And the high voltage load circuit 19 are cut off.

The high-voltage load circuit 19 is various drive circuits for driving the display of the dot matrix liquid crystal panel, and is driven by a drive voltage VLCD boosted to a predetermined voltage level by the booster circuit 13. The above is the configuration of the power supply unit 1 in the present embodiment.

In the power supply unit 1, by connecting an AC adapter instead of the power supply 11, the booster circuit 13 can generate the driving voltage VLCD based on the power supply voltage VDD supplied from the AC adapter. It is possible.

Next, the operation will be described. The operation of power supply unit 1 according to the present embodiment will be described based on a timing chart shown in FIG.

When the power switch 12 is turned on, the power supply 11 supplies the power supply voltage VDD to the booster circuit 13.
At this time, when the value of the power supply voltage VDD supplied to the booster circuit 13 reaches a predetermined value, the power-on detection circuit 14
Is detected, and a detection signal Sout which becomes “Hi” for a predetermined period is supplied to the timer circuit 15 and the latch circuit 16 by the S signal.
Output to the input terminal.

In the latch circuit 16, the power-on detection circuit 1
4, when a detection signal Sout which becomes “Hi” for a predetermined period is input to the S input terminal, a control signal Lout of “Hi” is output to the analog switch 17, the contact of the analog switch 17 is opened, and the booster circuit 13 The high voltage load circuit 19 is disconnected.

On the other hand, the booster circuit 13 boosts the power supply voltage VDD supplied from the power supply 11 to generate a drive voltage VLCD having a predetermined voltage level.

At this time, since the contact of the analog switch 17 is opened and the high-voltage load circuit 19 is disconnected from the booster circuit 13 as described above,
Compared to the case where the drive voltage VLCD is generated with the various drive circuits (high-voltage load circuit 19) connected, the drive voltage VLCD can be generated with a circuit configuration having a lower boosting capability.

In the timer circuit 15, the detection signal Sout which becomes "Hi" for a predetermined period from the power-on detection circuit 14 is output.
Is input, the clocking of a predetermined time starts, and when the clocking of the predetermined time ends, a predetermined period “Hi” is set.
Is output to the R input terminal of the latch circuit 16.

The latch circuit 16 outputs a "Low" control signal Lout to the analog switch 17 when the timer end signal Tout which becomes "Hi" for a predetermined period is input from the timer circuit 15 to the R input terminal. The high-voltage load circuit 19 is connected to the booster circuit 13 by closing the contact 17.

When the contact of the analog switch 17 is closed and the high-voltage load circuit 19 is connected to the boost circuit 13, the drive voltage VLCD having the predetermined voltage level generated in the boost circuit 13 is applied to the high-voltage load circuit 19. Supplied to

In the timing chart shown in FIG. 2, when the value of the control signal Lout output from the latch circuit 16 switches from "Hi" to "Low",
When the contact of the analog switch 17 is closed and the high-voltage load circuit 19 is connected to the boost circuit 13, the value of the driving voltage VLCD generated in the boost circuit 13 decreases. Is connected, and the value of the driving voltage VLCD generated in the booster circuit 13 is calculated by adding the voltage drop to the value of the driving voltage VLCD 'necessary for actually driving various driving circuits. It must be set as an added value.

For a predetermined time measured by the timer circuit 15, the power supply 11 is turned on, the power supply voltage VDD is supplied to the booster circuit 13, and the high-voltage load circuit 19 is disconnected from the booster circuit 13. A drive voltage VLCD having a predetermined voltage level by boosting the power supply voltage VDD
The time required until is generated is set. The above is the operation of the power supply unit 1 in the present embodiment.

In the present embodiment, the power-on detection circuit 14 is configured to detect that the power supply 11 has been turned on when the value of the power supply voltage VDD supplied to the booster circuit 13 reaches a predetermined value. The present invention is not limited to the above-described contents, and a configuration may be adopted in which it is detected that the power supply 11 is turned on immediately when the power switch 12 is turned on. With such a configuration, from the moment when the power supply voltage VDD is supplied to the booster circuit 13, the booster circuit 13 and the high-voltage load circuit 1
9 can be separated.

As described above, according to the power supply unit 1 of the present embodiment, the booster circuit 13 is provided between the output stage of the booster circuit 13 and the high-voltage load circuit 19 (load).
Switch (switching means) for switching between a connection state and a high-voltage load circuit 19 between the power supply detection circuit 14, the timer circuit 15, and the latch circuit 1
In 6 (disconnection control means), when the power-on is detected by the power-on detection circuit 14 (power-on detection means), and a detection signal Sout which becomes “Hi” for a predetermined period is input to the S input terminal of the latch circuit 16. , "Hi" control signal Lout is output from the latch circuit 16 to the analog switch 17, and the contact of the analog switch 17 is opened to raise the booster circuit 13.
From the high-voltage load circuit 19. In addition, the timer circuit 15 (time measuring means) completes the measurement of a predetermined time, and the timer circuit 15 outputs a timer end signal Tout which becomes "Hi" for a predetermined period.
6, the control signal Lout of "Low" is output from the latch circuit 16 to the analog switch 17, the contact of the analog switch 17 is closed, and the high-voltage load circuit 19 is connected to the booster circuit 13. Let it.

Therefore, after the power supply 11 is turned on and the power supply voltage VDD is supplied to the booster circuit 13, the booster circuit 1
In the rising period until the power supply voltage VDD is boosted to the drive voltage VLCD having the predetermined voltage level in step 3, the booster circuit 13 drives the power supply voltage VDD having the predetermined voltage level in a state of being disconnected from the high voltage load circuit 19. Since the voltage can be boosted to the voltage VLCD, it is possible to obtain the same boosting performance as the conventional one by a circuit configuration having a lower boosting ability.

Further, according to the power supply unit 1 in the present embodiment, in particular, various driving circuits (high-voltage load circuit 19) for driving the display of the dot matrix liquid crystal panel are provided.
The above effect can be obtained when the power supply voltage VDD supplied from the power supply 11 is boosted and supplied to the drive voltage VLCD having a predetermined voltage level by the booster circuit 13. The above is the description of the first example of the embodiment.

(Second Embodiment) Next, a second example of the embodiment will be described with reference to FIGS. In the first example of the above-described embodiment, the booster circuit 13 and the high-voltage load circuit 19 are formed by using hardware resources such as a power-on detection circuit 14, a timer circuit 15, and a latch circuit 16 built in the LCD controller / driver LSI. Although the power supply unit 1 that performs the disconnection control of the power supply unit 1 has been described, in the second example of the embodiment, the disconnection control between the booster circuit 13 and the high-voltage load circuit 19 is performed using software resources provided in the LCD controller / driver LSI. The power supply unit will be described.

First, the configuration will be described. FIG. 3 is a block diagram of the power supply unit 2 to which the present invention is applied. In the figure, the same components as those of the circuit configuration of the power supply unit 1 shown in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted.

In the figure, a power supply unit 2 includes a power supply 1
1, a power supply switch 12, a booster circuit 13, a control unit 21, and an analog switch 17. The output stage of the booster circuit 13 is a driving circuit for driving a dot matrix liquid crystal panel through the analog switch 17. (High voltage load circuit 19).

In the same figure, the boosting circuit 13, the control unit 21, and the high-voltage load circuit 19 include an LCD controller /
It is built into the driver LSI.

The control section 21 controls each section of the power supply unit 2 according to various control programs stored in a ROM (not shown) provided in the control section 21. Specifically, when the power is turned on, the control unit 21 executes a power control process (see FIG. 4) described later, and controls the start / stop of the booster circuit 13 and the connection / disconnection state of the analog switch 17. The above is the configuration of the power supply unit 2 in the present embodiment.

Next, the operation will be described. The power control process executed by the control unit 21 according to the present embodiment will be described with reference to the flowchart shown in FIG.

First, in the control unit 21, the power switch 12
Is turned on and the power is turned on, the booster circuit 13 is stopped, the contact of the analog switch 17 is opened, and the high-voltage load circuit 19 is disconnected from the booster circuit 13 (step S1).

Next, the controller 21 activates the booster circuit 13 (step S2). In response to this start instruction, the booster circuit 13 starts boosting the power supply voltage VDD supplied from the power supply 11 and starts generating the drive voltage VLCD having a predetermined voltage level.

Subsequently, the control section 21 starts measuring a predetermined time. Specifically, the control unit 21 resets the value of a counter provided in the control unit 21 (Step S
3) The value of the counter is incremented (+1) (step S4).

Then, the control section 21 determines whether or not the value of the counter is a predetermined value, that is, whether or not the counting of the predetermined time has ended (step S5), and the counting of the predetermined time has ended. If not, the process returns to step S4. When determining that the clocking of the predetermined time has ended, the control unit 21 closes the contact of the analog switch 17 and connects the booster circuit 13 and the high-voltage load circuit 19 (step S6).

When the contact of the analog switch 17 is closed and the high-voltage load circuit 19 is connected to the boost circuit 13, the drive voltage VLCD having the predetermined voltage level generated in the boost circuit 13 is applied to the high-voltage load circuit 19. Supplied to

The above is the operation procedure of the power supply control process executed in the control section 21 of the present embodiment.

As described above, according to the power supply unit 2 in the present embodiment, the booster circuit 13 is connected between the output stage of the booster circuit 13 and the high-voltage load circuit 19 (load).
Switch (switching means) for switching the connection between the power supply circuit and the high-voltage load circuit 19 to a connected state or a cut-off state is provided, and the control section 21 (switching control means) opens the contact point of the analog switch 17 when detecting the power-on. Let the booster circuit 13
From the high-voltage load circuit 19. The control unit 21
When the counter finishes measuring a predetermined time, the contact of the analog switch 17 is closed to connect the booster circuit 13 to the high-voltage load circuit 19.

Therefore, after the power supply 11 is turned on and the power supply voltage VDD is supplied to the booster circuit 13, the booster circuit 1
In the rising period until the power supply voltage VDD is boosted to the drive voltage VLCD having the predetermined voltage level in step 3, the booster circuit 13 drives the power supply voltage VDD having the predetermined voltage level in a state of being disconnected from the high voltage load circuit 19. Since the voltage can be boosted to the voltage VLCD, it is possible to obtain the same boosting performance as the conventional one by a circuit configuration having a lower boosting ability.

Further, according to the power supply unit 2 in the present embodiment, in particular, various drive circuits (high-voltage load circuit 19) for driving the display of the dot matrix liquid crystal panel are provided.
The above effect can be obtained when the power supply voltage VDD supplied from the power supply 11 is boosted and supplied to the drive voltage VLCD having a predetermined voltage level by the booster circuit 13. The above is the description of the second example of the embodiment.

(Third Embodiment) Next, a third example of the embodiment will be described with reference to FIGS. First, the configuration will be described. FIG. 5 is a block diagram of the power supply unit 3 to which the present invention is applied. In the figure, the same components as those of the circuit configuration of the power supply unit 1 shown in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted.

In the figure, a power supply unit 3 includes a power supply 1
1, a power switch 12, a booster circuit 13, a voltage detection control circuit 31, and an analog switch 17. The output stage of the booster circuit 13 is provided with various types of devices for driving a dot matrix liquid crystal panel through the analog switch 17. It is connected to a drive circuit (high-voltage load circuit 19).

In the same figure, the boosting circuit 13, the voltage detection control circuit 31, and the high voltage load circuit 19 are built in the LCD controller / driver LSI.

The voltage detection control circuit 31 detects the value of the driving voltage VLCD output from the boosting circuit 13, determines whether or not this value has reached a predetermined value, and determines whether the value of the driving voltage VLCD is a predetermined value. If it is less than the value, the detection signal Sou of “Low”
When the value of the driving voltage VLCD reaches a predetermined value, a "Hi" detection signal Sout is output to the analog switch 17 to control the connection / disconnection state of the analog switch 17. The above is the configuration of the power supply unit 3 in the present embodiment.

Next, the operation will be described. The operation of power supply unit 3 in the present embodiment will be described with reference to a timing chart shown in FIG.

When the power switch 12 is turned on, the power supply 11 supplies the power supply voltage VDD to the booster circuit 13.
At this time, the voltage detection control circuit 31 outputs the "Low" detection signal Sout to the analog switch 1 because the value of the drive voltage VLCD output from the booster circuit 13 is less than the predetermined value.
7, the contact of the analog switch 17 is opened to disconnect the high-voltage load circuit 19 from the booster circuit 13.

On the other hand, the booster circuit 13 boosts the power supply voltage VDD supplied from the power supply 11 to generate a drive voltage VLCD having a predetermined voltage level.

At this time, since the contact of the analog switch 17 is opened and the high-voltage load circuit 19 is disconnected from the booster circuit 13 as described above, the booster circuit 13
Compared to the case where the drive voltage VLCD is generated with the various drive circuits (high-voltage load circuit 19) connected, the drive voltage VLCD can be generated with a circuit configuration having a lower boosting capability.

When the value of the driving voltage VLCD generated by the boosting circuit 13 reaches a predetermined value, the voltage detection control circuit 31 outputs a "Hi" detection signal Sout to the analog switch 17, and the contact of the analog switch 17 And the high-voltage load circuit 19 is connected to the booster circuit 13.

When the contact of the analog switch 17 is closed and the high-voltage load circuit 19 is connected to the boost circuit 13, the drive voltage VLCD having the predetermined voltage level generated in the boost circuit 13 is applied to the high-voltage load circuit 19. Supplied to The above is the operation of the power supply unit 1 in the present embodiment.

In the timing chart shown in FIG. 6, the detection signal S output from the voltage detection control
When the value of out changes from “Low” to “Hi”, that is, when the contact of the analog switch 17 is closed and the high-voltage load circuit 19 is connected to the boost circuit 13,
The value of the driving voltage VLCD generated at the time decreases.
This is a voltage drop due to the connection of the high-voltage load circuit 19 to the boost circuit 13 as in the first example of the above-described embodiment, and the value of the drive voltage VLCD generated in the boost circuit 13 is It must be set as a value obtained by adding a voltage drop to the value of the driving voltage VLCD 'necessary for actually driving various driving circuits.

As described above, according to the power supply unit 3 in the present embodiment, the booster circuit 13 is connected between the output stage of the booster circuit 13 and the high-voltage load circuit 19 (load).
An analog switch 17 (switching means) for switching between the connection state and the high-voltage load circuit 19 between a connection state and a cutoff state is provided.
Until the output voltage level of the analog switch 17 reaches a predetermined value, a "Low" detection signal Sout is output to the analog switch 17 and the contact of the analog switch 17 is opened to open the booster circuit 13
From the high-voltage load circuit 19. When the output voltage level reaches a predetermined value, the voltage detection control circuit 31 outputs a "Hi" detection signal Sout to the analog switch 17, closes the contact of the analog switch 17, and applies a high-voltage load to the booster circuit 13. The circuit 19 is connected.

Therefore, after the power supply 11 is turned on and the power supply voltage VDD is supplied to the booster circuit 13, the booster circuit 1
In the rising period until the power supply voltage VDD is boosted to the drive voltage VLCD having the predetermined voltage level in step 3, the booster circuit 13 drives the power supply voltage VDD having the predetermined voltage level in a state of being disconnected from the high voltage load circuit 19. Since the voltage can be boosted to the voltage VLCD, it is possible to obtain the same boosting performance as the conventional one by a circuit configuration having a lower boosting ability.

Further, according to the power supply unit 3 in the present embodiment, in particular, various driving circuits (high-voltage load circuit 19) for driving the display of the dot matrix liquid crystal panel are provided.
The above effect can be obtained when the power supply voltage VDD supplied from the power supply 11 is boosted and supplied to the drive voltage VLCD having a predetermined voltage level by the booster circuit 13.

The present invention has been described with reference to the first to third embodiments.
Although a specific description has been given based on examples, the present invention is not limited to the above-described embodiment, and it is needless to say that the present invention can be appropriately changed without departing from the gist thereof.

For example, in the first to third examples of the above embodiment, a dot matrix liquid crystal panel using an LCD controller / driver LSI as an example of electronic equipment to which the power supply device (power supply unit) of the present invention is applied. Although the liquid crystal display device that drives the display has been described, the electronic apparatus to which the present invention can be applied is not limited to the liquid crystal display device, and uses a power supply voltage supplied from a power supply after boosting the power supply voltage to a predetermined voltage value. Any electronic device may be used.

Further, in the first to third examples of the above-described embodiment, when the power supply 11 is turned on, that is, when the equipment is started, the high-voltage load circuit 19 is separated from the booster circuit 13 during the rising period. However, it is needless to say that the present invention can be similarly applied to a restart from a power saving mode (standby state) or a reset state.

[0075]

According to the first to third aspects of the present invention, after the power is turned on and the power supply voltage is supplied to the booster circuit, the power supply voltage is boosted to a predetermined voltage value in the booster circuit. In the rising period up to, the power supply voltage can be boosted to a predetermined voltage value in a state where the booster circuit is disconnected from the load, so that a boosting performance equivalent to the conventional one can be obtained with a circuit configuration having a lower boosting ability. Becomes As a result, the manufacturing cost of the power supply device can be reduced.

According to the fourth aspect of the present invention, in particular, a power supply device for boosting a power supply voltage supplied from a power supply to a predetermined voltage value and supplying the same to a drive circuit for driving the display of the liquid crystal display panel. In this case, the effects of the inventions described in claims 1 to 3 can be obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram of a power supply unit to which the present invention is applied.

FIG. 2 is a timing chart of each part of the power supply unit shown in FIG.

FIG. 3 is a block diagram of a power supply unit according to a second embodiment.

FIG. 4 is a flowchart of a power control process performed by a control unit shown in FIG. 3;

FIG. 5 is a block diagram of a power supply unit according to a third embodiment.

6 is a timing chart of each part of the power supply unit shown in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Power supply unit 2 Power supply unit 3 Power supply unit 11 Power supply 12 Power switch 13 Boost circuit 14 Power-on detection circuit 15 Timer circuit 16 Latch circuit 17 Analog switch 18 Capacitor 19 High voltage load circuit 21 Control part 31 Voltage detection control circuit

Claims (4)

[Claims] 1. A power supply device comprising a booster circuit for boosting a power supply voltage supplied from a power supply to a predetermined voltage value, and supplying a voltage boosted by the booster circuit to a load connected to an output stage of the booster circuit. Disconnecting means for connecting or disconnecting between the output stage of the booster circuit and the load; detecting disconnection of the disconnecting means by detecting the power-on, and disconnecting the disconnecting means after a predetermined time has elapsed. And a disconnection control means for setting a connection state. 2. The power supply control apparatus according to claim 1, wherein said disconnection control means includes a power-on detecting means for detecting the power-on, and a time-measuring means for measuring said predetermined time when said power-on detecting means detects the power-on. The power supply device according to claim 1, further comprising: 3. A power supply device comprising a booster circuit for boosting a power supply voltage supplied from a power supply to a predetermined voltage value, and supplying a voltage boosted by the booster circuit to a load connected to an output stage of the booster circuit. Disconnecting means for connecting or disconnecting between the output stage of the booster circuit and the load; and disconnecting the disconnecting means until the output voltage level of the booster circuit reaches a predetermined value; And a disconnection control means for setting the disconnection means to a connection state when the predetermined value is reached. 4. The power supply device according to claim 1, wherein said load is a drive circuit for driving a liquid crystal display panel for display.