JP2000253651A - Power source circuit using dc-dc converter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent price increase of a portable electronic apparatus by making the control input and the control output of an operation control circuit in a portable electronic apparatus not be regulated. SOLUTION: A region surrounded by an alternate long and short dash line in a DC-DC converter is integrated on the same chip as an operation control circuit of a portable electronic apparatus. Only three terminals are needed for outer leading-out terminals from the DC-DC converter, so that the control input terminal and the control output terminal of the operation control circuit 204 are not regulated as compared with the conventional case. A DC-DC converter of exclusive use for a radio detection part 203 is made unnecessary, so that cost reduction is enabled. In order to lower a battery voltage, step-up voltages V1, V2 can be easily formed by changing the number of windings of a first coil 2 and a second coil 16 and capacitances of a first capacitor 4 and a second capacitor 18.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a power supply circuit using a DC-DC converter.

[0002]

2. Description of the Related Art Portable electronic devices (radio, headphone stereo, etc.) use batteries (dry batteries, rechargeable batteries, etc.), but recent portable electronic devices meet market demands for power saving and long life. In addition, the power supply voltage tends to decrease. For example, the power supply voltage has shifted from a 3 volt specification using two batteries to a 1.5 volt specification using one battery. However, a radio, a headphone stereo, and the like are provided with a liquid crystal panel that displays a reception state, a tape running state, and the like by numbers and pictures, and a radio detection unit that tunes to radio reception. The power supply for the liquid crystal panel is 3 volts, and the power supply for the radio detection unit is 9 to 12 volts, which requires a power supply voltage higher than 1.5 volts of a normal power supply for audio signal processing. It is necessary to provide a circuit for boosting the battery voltage of 5 volts.

FIG. 3 is a block diagram showing a power supply circuit used for a conventional radio, headphone stereo or the like.

In FIG. 3, a radio detection unit (101)
Is for extracting an audio signal from a carrier wave of a designated broadcasting station and performing predetermined audio signal processing. The tuning section of the radio detection section (101) requires a higher power supply voltage than the other audio signal processing sections, and the battery voltage of 1.5 volts is directly supplied to the power supply of the normal audio signal processing section. Battery voltage 1.5 volts DC-
A voltage of 9 volts boosted by the DC converter (102) is supplied.

[0005] The doubler circuit (103) doubles the battery voltage. FIG. 4 shows a specific circuit of the doubler circuit (103). The doubler circuit (103) includes four switch circuits SW1 to SW4 and two capacitors C1 and C2. The switch circuits SW1 and SW3 perform the same opening and closing operation, and the switch circuits SW2 and SW4 also perform the same opening and closing operation, and the switch circuits SW1 and SW3 and SW2 and SW4 open and close complementarily. First, when the switch circuits SW1 and SW3 are closed, the upper side of the capacitor C1 becomes the battery voltage V,
The lower side is grounded. Next, switch circuits SW2 and SW4
Is closed, the lower side of the capacitor C1 rises from the ground to the battery voltage V, so that the upper side of the capacitor C1 is
V, and the non-ground side of the capacitor C2 becomes 2V. By controlling the opening and closing of the switch circuits SW1 to SW4 with a clock having a predetermined frequency, a boosted voltage that is twice the battery voltage V can be obtained.

The liquid crystal panel (104) displays the reception state of a radio, a headphone stereo or the like, the tape running state, and the like with numerals and pictures.
Is supplied with a boosted voltage of 3 volts which is twice the battery voltage of 1.5 volts by the doubler circuit (103).

[0007]

However, with respect to the battery voltage of portable electronic devices, further lowering the voltage is being designed, and the battery voltage is less than 1.5 volts (for example, less than 1.5 volts).
9 volts) will be described below.

Since the liquid crystal panel (104) is powered by a 3-volt power supply, two stages of the doubler circuit (103) shown in FIG. 4 are required.
That is, the output of the second stage of the doubler circuit (103) is 3.6 volts. Further, a regulator for adjusting the boosted voltage of 3.6 volts to 3 volts is required. Therefore, when integrating the doubler circuit (103), it is necessary to externally connect four capacitors and one capacitor for stabilizing the voltage adjustment operation of the regulator, occupying a total of seven terminals. become. In particular, when the doubler circuit (103) is integrated with an operation control circuit of a portable electronic device,
There is a problem that the control input and the control output of the operation control circuit are restricted.

Further, since the DC-DC converter (102) is provided outside the radio detection unit (101), there is a problem that the price of the portable electronic device is increased.

Accordingly, the present invention provides a power supply circuit of a DC-DC converter in which a control input and a control output of an operation control circuit in a portable electronic device are not restricted, and a price increase of the portable electronic device is prevented. The purpose is to.

[0011]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and has a counter electromotive force generated in a first coil by switching a transistor with a clock signal having a predetermined frequency. A first capacitor is charged with a voltage to generate a first boosted voltage, and a back electromotive voltage induced in the second coil and generated in the second coil is charged in the second capacitor to generate a second boosted voltage different from the first boosted voltage. A DC-DC converter that generates a boosted voltage is an integrated circuit, and the first boosted voltage and the second boosted voltage are supplied as power supply voltages for peripheral circuits of the integrated circuit.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be specifically described with reference to the drawings.

FIG. 1 is a block diagram showing a power supply circuit using the DC-DC converter of the present invention.

In FIG. 1, a DC-DC converter (2
01) is for generating and outputting two types of boosted voltages V1 (for example, 3 volts) and V2 (for example, 9 volts) based on the battery voltage (for example, 0.9 volt). The boosted voltage V1 is supplied as a power supply voltage of the liquid crystal panel (202), and the boosted voltage V2 is supplied as a power supply voltage of the radio detector (203).

FIG. 2 is a circuit diagram showing a specific example of the DC-DC converter (201).

In FIG. 2, an NPN transistor (1) is turned on and off by supplying a clock signal of a predetermined frequency to a base. That is, the NPN transistor (1)
Is turned on, energy is stored in the first coil (2), and then, when the NPN transistor (1) is turned off, a back electromotive voltage is generated in the first coil (2), and the back electromotive voltage is a diode (3). Through the first capacitor (4). The higher the number of turns of the first coil (2) or the larger the capacity of the first capacitor (4), the higher the boosting effect. At this time, the terminal voltage of the first capacitor (4) becomes the power supply voltage V1 (3 volts) for the liquid crystal panel (202).

The RC oscillator (5) comprises a Schmitt inverter (6), a resistor (7) and a capacitor (8),
The oscillation clock CK is generated at an oscillation frequency determined by the resistance value of the resistor (7) and the capacitance of the capacitor (8). Note that the oscillation clock CK is a source of the clock signal. The drain-source path of the N-type MOS transistor (9) is connected between the input terminal of the Schmitt inverter (6) constituting the RC oscillator (5) and ground.
One end on the non-ground side of the pull-down resistor (10) is connected to the gate of the N-type MOS transistor (9) via the inverter (11). When a 0.9 volt battery (12) is installed, the inverter (11) outputs "L" and outputs an N-type MO.
The S-transistor (9) is turned off, and the RC oscillator (5) starts the oscillation operation when the input terminal of the Schmitt inverter (6) is released from the control of the N-type MOS transistor (9). Meanwhile, the battery (12) is removed or the battery (12)
Is incorrectly removed, the input of the inverter (11) is grounded via the pull-down resistor (10), so that the inverter (11) outputs "H" and the N-type MOS transistor (9) turns on, and RC The oscillator (5) stops the oscillation operation when the input terminal of the Schmitt inverter (6) is grounded. The threshold voltages of the Schmitt inverter (6), the N-type MOS transistor (9) and the inverter (11) are set low. Therefore, before the oscillation operation of the RC oscillator (5) becomes indefinite with the fall of the power supply voltage,
Since the oscillation operation of the oscillator (5) can be stopped, malfunction of the DC-DC converter can be prevented.

The minus terminal of the comparator (13) is the non-ground side terminal of the first capacitor (4), that is, the liquid crystal panel (202).
+ Terminal is connected to the reference voltage Vre
f. One input terminal of the AND gate (14) is connected to the output of the RC oscillator (5), the other input terminal is connected to the output of the comparator (13), and the output terminal is an NPN transistor via a resistor (15). It is connected to the base of (1). That is, the comparator (13)
The PN transistor (1) is subjected to negative feedback control. More specifically, when the terminal voltage of the first capacitor (4) is lower than the reference voltage Vref, the AND gate (14) is opened according to the "H" output. , NPN transistor (1)
Repeats the switching operation in accordance with the oscillation clock CK. On the other hand, when the terminal voltage of the first capacitor (4) is higher than the reference voltage Vref, the AND gate (14) is closed with the output of "L", and the NPN transistor The switching operation of (1) is stopped. Thus, the terminal voltage of the first capacitor (4) is
It is always kept at Vref irrespective of the side load fluctuation.

First coil (2) and second coil (16)
Has a relationship of primary and secondary coils, the first coil (2)
The windings of the second coil (16) and the second coil (16) are wound so that counter electromotive voltages are generated in opposite directions. That is, when a counter electromotive voltage in the right arrow direction is generated in the first coil (2) as the NPN transistor (1) is turned off, the second coil (16) is induced and the second coil (16) is turned in the left arrow direction. Back electromotive voltage is generated. Further, the number of turns of the second coil (16) is larger than the number of turns of the first coil (2), and the second coil (16) generates a counter electromotive voltage larger than that of the first coil (2). As a result, right and left counter electromotive voltages are generated in the first coil (2) and the second coil (16), respectively, in synchronization with the turning off of the NPN transistor (1). The second coil (1
The back electromotive voltage of 6) is charged in the second capacitor (18) via the diode (17). Zener diode (1
9) is connected in parallel with the second capacitor (18) and clips the terminal voltage of the second capacitor (18) to V2 (9 volts). That is, when the terminal voltage of the second capacitor (18) becomes V2 or more, the second capacitor (18)
Is higher than the cathode potential of the Zener diode (19), a current flows through the resistor (20) and the Zener diode (19), and the second capacitor (1)
The terminal voltage of 8) is held at V2. The number of turns of the second coil (16) is set so that the terminal voltage of the second capacitor (18) does not become lower than V2 due to the on / off control of the NPN transistor (1). This boosted voltage V
2 is the power supply voltage of the tuning part of the radio detection unit (203).

The range of the dashed line of the DC-DC converter in FIG. 2 is integrated on the same chip as the operation control circuit (204) of the portable electronic device. At this time, since only three terminals are required to be externally derived from the DC-DC converter, the control input terminal and the control output terminal of the operation control circuit (204) are not regulated as compared with the related art.

A DC dedicated to the radio detection unit (203)
-Since a DC converter is not required, the cost can be reduced.

Further, in order to reduce the battery voltage, the number of turns of the first coil (2) and the second coil (16) and the capacitance of the first capacitor (4) and the second capacitor (18) are changed. Thus, the boosted voltages V1 and V2 can be easily created. That is, the regulator which is conventionally indispensable to the doubler circuit (103) can be eliminated.

[0023]

According to the present invention, when the DC-DC converter is integrated on the same chip as the operation control circuit of the portable electronic device, only three terminals are required to be externally derived from the DC-DC converter. The control input terminal and the control output terminal of the operation control circuit are not regulated as compared with the related art. Further, since a DC-DC converter dedicated to the radio detection unit is not required, the cost can be reduced. Furthermore, by changing the number of turns of the first coil and the second coil and the capacities of the first capacitor and the second capacitor with respect to the reduction of the battery voltage,
Boosted voltages V1 and V2 can be easily created. That is, the regulator which is conventionally indispensable to the doubler circuit can be eliminated. Such advantages can be obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a power supply circuit using a DC-DC converter of the present invention.

FIG. 2 is a circuit diagram showing one embodiment of the DC-DC converter of the present invention.

FIG. 3 is a block diagram showing a conventional power supply circuit.

FIG. 4 is a circuit diagram showing one embodiment of the doubler circuit of FIG. 3;

[Explanation of symbols]

 (2) First coil (4) First capacitor (16) Second coil (18) Second capacitor (202) Liquid crystal panel (203) Radio detector

Claims (1)

[Claims] 1. A first boosted voltage is generated by charging a first capacitor with a back electromotive voltage generated in a first coil by switching a transistor with a clock signal of a predetermined frequency, and induced from the first coil. DC-DC for generating a second boosted voltage different from the first boosted voltage by charging a back electromotive voltage generated in the second coil to a second capacitor
A converter as an integrated circuit, wherein the first boosted voltage and the second boosted voltage are supplied as power supply voltages for peripheral circuits of the integrated circuit.
Power supply circuit using a C-DC converter.