JPH08140341A - Micro power supply device using switching element - Google Patents

Abstract

PURPOSE: To provide a micro power supply device, using a switching element, whose high efficiency can be realized even at a MHz-band switching frequency. CONSTITUTION: In a micro power supply device using a switching element, an input voltage Vin from an input DC power supply 1 is switched via an inductor 3, a switched voltage is changed into a direct current by a rectifier diode 6 and a smoothing capacitor 7, and a stabilized output voltage Vout is obtained. A lateral MOSFET 4 is used as the switching element, and it is ON-OFF controlled by a pulse width modulation signal from a PWM control IC.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a small electronic device,
The present invention relates to a micro power supply device using a switching element for supplying a stabilized DC power supply voltage.

[0002]

2. Description of the Related Art Various electronic devices are required to have characteristics such as higher performance, smaller size and lighter weight, and longer operating time. The high integration of devices constituting electronic equipment and the reduction of power loss meet the above-mentioned requirements for characteristics. Similarly, the above-mentioned characteristics are also required for batteries, switching power supplies such as DC / DC converters, and power supplies such as series regulators. Further, in a portable device or the like that uses a battery as a power source, it is a major technical issue to supply a stable power supply voltage to the device and use the energy stored in the battery with high efficiency.

In response to such a demand, a switching power supply is used which obtains an output voltage by high-frequency switching a DC voltage from a DC power supply such as a battery by a chopper circuit and converting this switched voltage into a DC voltage by a rectifying and smoothing circuit. is there. A micro power supply device using such a switching element is effective as a power supply that is small in size and can supply a stable power supply voltage with high efficiency.

Conventionally, a micro-power supply device using a switching element, which should be mounted on an electronic device, is 0.2 to 0.3.
The condition was that the characteristic of (W / cm ³ ) was satisfied. This unit [Wcm ³ ] indicates the power capacity (W) per volume volume (cm ³ ) of the electronic device. In order to satisfy the above conditions, inductors and capacitors that require a large space must be small. Because the voltage,
This is because increasing the frequency of current leads to miniaturization of inductors and capacitors.

In order to be able to use a small inductor and a small capacitor satisfying the above conditions, the switching element requires a switching frequency of about 500 KHz. Conventionally, a vertical MOSFET has been used as a switching element that can achieve such miniaturization and also achieve high efficiency, which is a prerequisite.

However, in recent small electronic devices, especially small electronic devices such as mobile phones, the number is about 15.
The condition is that the characteristic of (W / cm ³ ) is satisfied. In order to be able to use a small inductor or a small capacitor that satisfies this condition, the switching frequency of the switching element needs to be 1 MHz or higher.

However, the vertical type MOSFE is used at a frequency of 1 MHz.
When T is switched, the ON resistance loss is large, so that the characteristic of 15 (W / cm ³ ) cannot be satisfied in the end.

Further, when a MOSFET is used as a switching element, there is a restriction on the voltage of the input DC power source,
When the voltage is V _th + V _ds (V _th : threshold voltage, V _ds : drain-source voltage) or less, the MOSFET cannot be turned on in the linear region, so the current is limited by high on-resistance. However, there is a problem that heat generation becomes large. Therefore, the switching power supply using the MOSFET is practically limited to use only when the voltage of the input DC power supply is sufficiently higher than V _th + V _ds .

As described above, the conventional micro power supply device using the switching element has a problem that it cannot achieve practical efficiency at the switching frequency in the MHz band and cannot be used when the input voltage is low. It was

[0010]

SUMMARY OF THE INVENTION It is a first object of the present invention to provide a micro power supply device using a switching element capable of realizing highly efficient switching operation even at a switching frequency in the MHz band.

A second object of the present invention is to provide a micro power supply device using a switching element which can operate stably and efficiently even when the input voltage is low.

[0012]

The above object can be achieved by a micro power supply device using a switching element as described below. That is, a semiconductor switching device that switches the output of the DC power supply under a switching condition of a switching frequency of 1 (MHz) or more and an ON resistance value of 1 [Ω / mm ² (unit area of one side of the device)] and a switching device using this semiconductor switching device. Based on the output of the rectifying element of the rectifying element for rectifying the output of the DC power source, and a chopper section including an inductance element provided in at least one of the semiconductor switching element and the rectifying element, A micro power supply device using a switching element, comprising: a control section that supplies a switching control signal to a control electrode of the semiconductor switching element of the chopper section.

The above object is achieved by a micro power supply device using a switching element as described below. That is,
Horizontal MO that PWM-switches the output voltage of the DC power supply
SFET, an inductor provided between the DC power supply and the lateral MOSFET, a rectifying element that rectifies the output voltage of the DC power source PWM-switched by the lateral MOSFET, and the lateral MOSFET based on the output of the rectifying element. A control unit for supplying a PWM control signal to the gate electrode and a selection unit for selectively supplying the output voltage of the DC power supply and the output voltage of the rectifying element to the control unit as the power supply voltage of the control unit. A micro power supply device using a switching element provided.

The operation of the present invention is as follows. That is, in the present invention, a semiconductor switching element that switches the output of the DC power source under a switching condition of a switching frequency of 1 [MHz] or more and an ON resistance value of 1 [Ω / mm ² (unit area of one side of the element)] or less, preferably, Horizontal MO
Adopt SFET. Such a semiconductor switching element can switch at a frequency of 1 MHz with high efficiency. If the frequency is 1 MHz, 15 (W /
An inductor and a capacitor satisfying the characteristics of ³ cm ³ can be used, and as a result, the power supply device has a capacity of 15 (W / c).
m ³ ) will be satisfied.

Further, in the present invention, a lateral MOSFET
Is normally 30n when an ON signal is applied to the gate.
Within sec, the on-resistance has a value lower than the on-resistance at direct current, and the on-resistance has a quick response characteristic.
Moreover, the lateral MOSFET has a vertical MOSF because of its parasitic capacitance.
Since it is much lower than ET, the switching loss can be suppressed sufficiently low even at the switching frequency in the MHz band.

Therefore, by using the lateral MOSFET as the switching element of the switching power supply, high efficiency can be realized even at the switching frequency in the MHz band.

Further, for the driving means of the control unit for controlling on / off of the switching MOSFET by the pulse width modulation signal, the MOSFET is linear in the input voltage from the DC input power supply and the output voltage supplied to the load. Even if the input voltage from the input DC power supply drops, by selecting the one that has the minimum required voltage for operation or the one with the higher voltage and supplying it as the power supply input,
The MOSFET can be operated in the linear region as much as possible, and stable and high efficiency can be realized.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

First, a lateral MOSFET and a vertical MOSF.
FIG. 1 shows the difference when ET is used as a switching element of a micro power supply device using a switching element.
Also, description will be made with reference to FIGS. Lateral MOS
In the FET, each electrode is formed on the surface side of the substrate, and a current flows in the device surface direction. The device shown in FIG. 2 is an example of a lateral MOSFET. In the vertical MOSFET, one of the main electrodes is formed on the back surface side of the substrate, and a current flows in the element vertical direction. The element shown in FIG.
It is an example of SFET. Horizontal MOSFET and vertical MO
Since the structure of the SFET is known, detailed description thereof will be omitted here.

The first advantage of using the lateral MOSFET as a switching element as in the present invention is as follows.

That is, a lateral MOSFET and a vertical MOS
The FET is different from the FET in the time dependency of the ON resistance for several hundreds nsec after the ON signal is applied to the gate. In the case of the vertical MOSFET, the on-resistance increases in the range of DC (direct current) to several MHz, whereas in the case of the lateral MOSFET, the on-resistance decreases in the same range.

FIG. 1 shows a lateral MOSFET and a vertical MO.
In the SFET, when an ON signal is applied to the gate (specifically, when V _gs rises from 0 V to 4 V (t =
It is a figure which shows the change of ON resistance with respect to the elapsed time t from (0)).

As shown in the figure, horizontal and vertical MOS
The on-resistance of each FET is DC on-resistance (V
The on resistance at _gs = 4V _dc ) is once smaller.

The on-resistance of the vertical MOSFET is
It is higher than the on-resistance (0.2Ω) at DC until about t = 80 nsec, and is about 1Ω on average. On the other hand, the on-resistance of the lateral MOSFET is approximately t = 100.
It is about 0.1Ω, which is lower than the on-resistance (0.5Ω) at DC within the time of nsec. Vertical and horizontal MOSFE
ON resistance of T is 0.1 after t = 100 nsec.
Maintain the Ω state. This difference is because the lateral MOSFET and the vertical MOSFET have different response speeds when an ON signal is applied to the gate.

Therefore, in the operating range of the MHz band, the switching loss is the lateral MO instead of the conventional vertical MOSFET.
By adopting SFET, it is possible to reduce by almost one digit. It should be noted that in practical use, the characteristic may be such that the on-resistance shows a value lower than the on-resistance at DC at the time t = 30 nsec, preferably at the time t = 10 nsec. Specifically, such a lateral MOSFET has a switching frequency of 1 (MHz) or more and an ON resistance value of 1
(Ω / area of gate electrode) The following switching conditions are satisfied.

The second advantage of the lateral MOSFET switching element is as follows. That is, lateral MOS
The input capacitance C _iss , the output capacitance C _oss, and the feedback capacitance C _rss , which are the causes of switching loss in the FET, are the same as those of the vertical MOSFET (the input capacitance C _iss , the output capacitance C
Compared with _oss and feedback capacitance C _rss ), it is smaller by almost one digit.

First, the input capacitance C _iss will be described. That is, in the switching operation of the MOSFET, V
_gs (gate-source voltage) is V _th (threshold voltage)
When switching between a higher voltage and a lower voltage, it is necessary to charge and discharge through the gate. During this charging and discharging,
All the energy stored in the input capacitance is released and becomes part of the switching loss.

V _gs when the MOSFET is in the on state is V
_{Letting gson} and the switching frequency be f, the magnitude of the loss is approximately proportional to f · C _iss · V _gson ² .

The vertical MOSFET C _iss is 100 to 10
It is 00pF, whereas C _iss of the lateral MOSFET is 1
It is as small as 0 to 100 pF. The difference in C _iss between the vertical MOSFET and the lateral MOSFET is a difference in loss that differs by one digit.

On the other hand, the switching loss due to C _oss and C _rss is the energy released when the charged electric charge is input to the ON signal, so the switching loss has a magnitude of 1 / 2f ( C _rss + C _oss ) · V _gson ² . However, V _gs at the moment of switching is V _gso
And

In this case, C _rss + C _oss is approximately C _iss
Since this is proportional to, the difference in this loss is almost one digit.

As described above, the lateral MOSFET has a sufficient on-resistance response when an ON signal is applied and a small parasitic capacitance, so that the switching loss is sufficient even at a switching frequency in the MHz band. It can be seen that it can be reduced.

The advantages of the lateral MOSFET described above will be confirmed with reference to FIGS. 4, 5 and 6. That is, as shown in FIG. 4, in the relationship between the frequency and the ON resistance loss,
Vertical MOSFETs are horizontal MO up to a frequency of approximately 1MHz
ON resistance loss is smaller than SFET, but frequency 1M
On the contrary, when the frequency exceeds Hz, the lateral MOSFET is a vertical MOS.
ON resistance loss is smaller than that of a FET. The ON resistance loss at a frequency of approximately 1 MHz is 225 mW level.

As shown in FIG. 5, in the relationship between the frequency and the switching loss, as the frequency increases, the switching loss of the vertical MOSFET and the lateral MOS
There is a big difference from the switching loss of the FET. Of course, the switching loss of the lateral MOSFET is
It is smaller than the switching loss of OSFET.

Further, as shown in FIG. 6, the frequency and the FET
In relation to the total loss of the vertical MOSFET, the total loss of the vertical MOSFET is smaller than that of the horizontal MOSFET up to a frequency of 500 kHz, but when the frequency exceeds 500 kHz, the ON resistance loss of the horizontal MOSFET is opposite to that of the vertical MOSFET. Get smaller. The total loss at this frequency of 500 kHz is 250 mW.

Next, a specific embodiment of the micro power supply device using the switching element according to the present invention will be described.

(Embodiment 1) A micro power supply device using a switching element according to Embodiment 1 shown in FIG. 7 is a switching power supply device including a chopper section and a control section. The chopper part here is a concept including a DC power supply, a switching element, an inductor, a transformer, a rectifier circuit, a smoothing circuit, and the like. The control unit is a concept including a feedback circuit, a PWM control circuit, and the like.

The switching power supply device shown in FIG. 7 shows a step-up DC / DC converter which receives the voltage of the input DC power supply 1 as an input and boosts and stabilizes the voltage to obtain a DC output voltage. In FIG. 7, the input DC power supply 1 is, for example, a battery.

In FIG. 7, a stabilizing capacitor 2 for stabilizing the input voltage V _in from the power source 1 is connected in parallel to the input DC power source 1 and a switching element is provided via an inductor 3 as a switching element. Horizontal N-channel MO
An SFET (hereinafter referred to as FET) 4 is connected.
This FET 4 is a pulse width modulation control IC (hereinafter, PWM
It is turned on / off (switched) by a control signal from a control IC 5.

The voltage generated at both ends of the FET 4 by the switching of the FET 4 is rectified and smoothed by the rectifying diode 6 and the smoothing capacitor 7, that is, converted into a direct current, and then the load 8 composed of, for example, a mobile phone or other electronic equipment.
To the output voltage V _out . The output voltage V _out is fed back to the PWM control IC 5 via the variable resistor 9.

The PWM control IC 5 is integrated for the purpose of downsizing a micro power supply device using a switching element and accelerating the operation, and is connected with capacitors 10, 11 and a resistor 12 as external elements.

The operation of the micro power supply device using such a switching element is well known, but it will be briefly described as follows. The FET 4 is switched, that is, turned on / off by a pulse width modulation signal applied to the gate from the pulse width control circuit 5. Where F
While the ET 4 is on, current flows from the input DC power supply 1 to the inductor 3 and energy is stored in the inductor 3. Next, when the FET 4 is turned off, the energy stored in the inductor 3 is released to the load 8 via the diode 6. Due to the smoothing action of the capacitor 7, a DC voltage is always applied to the load 8.

The output voltage V _out applied to the load 8 is fed back to the PWM control IC 5 via the variable resistor 9 and PW
The M control IC 5 changes the waveform (duty ratio) of the PWM modulation signal so that the fed back output voltage V _out becomes constant, that is, the error voltage between the output voltage V _out and the reference voltage is minimized. That is, when the output voltage V _out becomes larger than the reference voltage, the duty ratio of the pulse width modulation signal is made smaller to reduce the energy stored in the inductor 3, and conversely, when the output voltage V _out becomes smaller than the reference voltage, the pulse width becomes smaller. The duty ratio of the modulation signal is increased to increase the energy stored in the inductor 3. In this way, the load 8 is supplied with the output voltage V _{out which} is stabilized and boosted based on the input voltage V _in from the input DC power supply 1. In the above configuration, in order to effectively utilize the above-mentioned two characteristics of the lateral MOSFET used as the switching element, it is desired to drive the gate potential of the FET 4 at about 10's of nanoseconds. Also, load 8
In the case of controlling the FET4 with pulse width, that is, turning on / off with a pulse width modulation signal, the duty ratio of the pulse width modulation signal is 0 for no load and the maximum duty for maximum load. It is necessary to make it a ratio.

FIG. 8 is a concrete circuit diagram of the PWM control IC 5, which can meet the above requirements. This PWM control IC 5 amplifies the pulse width modulation signal generation circuit section 20 and the pulse width modulation signal to FET 4
And a drive circuit section 30 for driving the ON / OFF.

In the pulse width signal generation circuit 20, the output voltage V _out fed back to the feedback input terminal NF is input to the error amplifier 21, and the error voltage with the reference voltage set inside the error amplifier 21 is amplified. It The amplified error voltage is amplitude-limited by the limiter 22 and is one input of the comparator 23. The triangular wave signal generated by the oscillator 24 is applied to the other input of the comparator 23. In addition,
The capacitor 25 is one of the factors that determine the oscillation frequency of the oscillator 24. The comparator 23 is a signal that is high level when the level of the triangular wave signal from the oscillator 24 exceeds the level of the output signal of the limiter 22, and is low level during the other period, that is, the duty ratio changes according to the error voltage. Pulse width modulated signal is generated. The pulse width modulation signal is shaped into a correct rectangular wave by the waveform shaper 26 and becomes the output of the pulse width modulation signal generation circuit 20.

On the other hand, the drive circuit section 30 comprises a plurality of (four in this example) amplifiers 31, 32, 33, 34 arranged in parallel. The input pulse width modulation signal is amplified by these amplifiers 31, 32, 33, 34, and 4
The signals are output from the individual drive output terminals D1, D2, D3, D4. The drive output terminals D1, D2, D3 and D4 are commonly connected to the outside as shown in FIG. 7, and this common connection terminal is connected to the gate of the FET4.

In FIG. 8, VCC is a power supply terminal and is connected to the positive side terminal of the input DC power supply 1 as shown in FIG. Further, AG and PG are ground terminals and are connected to the negative side terminal of the input DC power supply 1. The comparator 27 outputs the output voltage V _out fed back to the feedback input terminal NF and the power supply terminal VCC.
Input voltage applied to the power supply (that is, input DC power supply 1
Input voltage V _in ) is compared and a high level signal is output to the comparison output terminal CMP when V _in <V _{out, and} a low level signal is output when V _in > V _out . It is used in the embodiment. In FIG. 7, the comparison output terminal CMP is not used and therefore not shown.

Since it is necessary to turn on / off the FET 4 at a frequency in the MHz band, the drive circuit unit 3 of the PWM control IC 5
0 requires particularly high-speed response. Therefore, PW
The M control IC5 is a Bi-CMO with excellent high-speed response.
It is desirable to realize with S. In this case, the micro power supply device using the switching element of FIG.
It is configured by using SIC (or Bi-CMOS LSI). Another advantage of the lateral MOSFET is that it is easier to form it together with the PWM control IC 5 on one chip as compared with the vertical MOSFET. This simplification of mounting is advantageous in terms of downsizing of the device and cost reduction.

Next, a specific example of specifications of this embodiment will be shown. FIG. 9 shows the efficiency of the power supply device shown in FIG. 7 = (output power /
Input power) x 100% change as lateral type M as FET4
1 shows a first comparative example using an OSFET and a vertical MOSFET. In this comparative example, the input voltage V _in from the input DC power supply 1 is 3.6.
V, the output voltage V _out supplied to the load 8 is 5 V, and the switching frequency of the FET 4 is from 1 MHz to 11 MHz.
This is the case when changing to MHz.

As shown in FIG. 9, in the switching frequency in the MHz band, the efficiency of Comparative Example 1 begins to decrease when the frequency exceeds 1 MHz, and falls significantly below 80% at several MHz, while in the first embodiment 1 MHz to 11 MHz. The efficiency of 80% or more is realized at the frequency of. Comparing the two, it can be seen that the efficiency of the first embodiment is 13% at 5 MHz and 34% at 10 MHz.

Next, another embodiment of the present invention will be described.
In the following embodiments, the same parts as those in FIG. 7 or parts having the same functions are designated by the same reference numerals, and the description thereof will be omitted or simplified.

(Embodiment 2) FIG. 10 is a circuit diagram of a micro power supply device using a switching element according to the present embodiment, which is a step-up type D capable of supporting a low input voltage.
A C / DC converter is shown. The present embodiment is different from the embodiment of FIG. 7 in that a power supply voltage selection circuit 13 is added.

This power supply voltage selection circuit 13 is a power supply terminal VC of the drive circuit section 30 of the PWM control IC 5 shown in FIG.
As a power supply input for supplying and C, it is a circuit for selecting the higher of the output voltage V _out to the input voltage V _in and load 8 from the input DC power source 1. This power supply voltage selection circuit 13 has a diode 14a whose anode side is connected to the positive side terminal of the input DC power supply 1, and a diode 14b whose anode side is connected to one end of the load 8 and which has diodes 14a, 14
The cathode side of b is connected to the power supply terminal VCC.

According to this embodiment, the input voltage V _in from the input DC power supply 1 is V _th + V _ds (V _th : threshold voltage,
V _ds : drain-source voltage)
Stable and highly efficient operation is possible.

11 (a) and 11 (b), the first embodiment shown in FIG. 7 showing the dependence of the power conversion efficiency on the input voltage, and FIG.
Embodiment 2 shown in FIG. Output power is 1W
(Output voltage V _out = 5V, resistance of load 8 is 20Ω).

As shown in FIGS. 11A and 11B, the second embodiment can operate even when the input voltage V _in, which does not operate in the first embodiment, is less than 3.1V.
V output are possible, the input voltage V _in even 2.3V 80
% Efficiency can be achieved. In the first embodiment, when the voltage is less than 3.1 V, the on-resistance of the FET 4 in the linear region is not low but in the high resistance state close to the saturation region, and the loss due to this makes it impossible to output 5 V. In contrast, in the driver circuit portion 30 of the PWM control IC5 is by the action of the second embodiment in the power supply voltage selection circuit 13, since the higher of the input voltage V _in and the output voltage V _out is supplied as a power supply input, once When the boosting operation is started, the input voltage V _in is V _th
V _out is provided even if + V _ds is not reached. This allows the power supply device to output 5V.

FIG. 12 shows the output dependence of the lower limit of the input voltage V _{in for} the first and second embodiments.
In any of the first and second embodiments, when the input voltage V _in is increased from 0V, the pulse width control signal becomes the input voltage V in.
_It occurs from the time when _in is 1.8V. However, the input voltage V
_The boosting operation is not performed while in does not reach V _th + V _ds . In the first embodiment, the input voltage at the time of starting the boosting operation (V _in <V _out ) is the input voltage = 3.1 V at which the ON resistance of the FET 4 in the linear region is low. On the other hand, in the case of the second embodiment, 5V is supplied to the drive circuit unit 30 before the input voltage reaches 3V.
It is possible to start the boosting operation at a voltage lower by 0.6V. Note that, as shown in FIG. 12, the lower limit of the input voltage at which the boosting operation is possible increases as the output increases. However, regardless of the lower limit value of the input voltage, it can be seen that the second embodiment starts the boosting operation from a voltage lower than the first embodiment by 0.6V. Incidentally, the power supply voltage selection circuit 13 in the above embodiment, is selected as the power input of the drive circuit section 30 the higher of the input voltage V _in and the supply voltage output. However, if both the input voltage V _in and the power supply voltage output have a voltage higher than the minimum required to operate the FET 4 in the linear region, whichever is the drive circuit unit 30?
It may be used as the power input of.

(Third Embodiment) FIG. 13 is a circuit diagram of a micro power supply device using a switching element according to the present embodiment. A step-up DC / DC in which two chopper circuits are cascade-connected in order to increase the step-up ratio. Shows a converter. 1
The chopper circuit in the second stage is composed of an inductor 3a, an FET 4a, a diode 5a and a capacitor 6a, and the chopper circuit in the second stage is composed of an inductor 3b, a FET 4b, a diode 5b and a capacitor 6b. Output voltage V _out
Can be adjusted by the variable resistor 9.

[0059] According to this embodiment, the input voltage V _in from the DC input power source 1 5V, the output voltage V _out 40V, the power output and 1W, FETs 4a by PWM control IC 5,
When the switching frequency of 4b is 5 MHz, 55
% Efficiency was obtained.

(Embodiment 4) FIG. 14 is a circuit diagram of a micro power supply device using a switching element according to the present embodiment, in which resonance operation is partially incorporated. The inductors 3b and 3c form an output transformer. This transformer need not have a coupling coefficient of -1, and the inductors 3a and 3b may be independent of each other. The FET parts 4a, 4b are each composed of a plurality (2 or 3 in the illustrated example).
3) lateral MOSFET.

According to this embodiment, an efficiency of 60% can be obtained under the same conditions as in the third embodiment. In the case of the third embodiment,
When the ON signals of the FET parts 4a and 4b are generated, the charges charged in the capacitors of high voltage outputs C _rss and C _oss are discharged, but this is avoided by incorporating the resonance operation as in the fourth embodiment. Efficiency is improved.

(Fifth Embodiment) FIG. 15 is a circuit diagram of a micro power supply device using a switching element according to the present embodiment, which is an example in which a charge pump circuit 15 having a step-up ratio of 2 is used as a rectifying / smoothing circuit. is there. Charge pump circuit 15
Is a plurality of diodes 15A and a plurality of capacitors 15
It consists of B. In this case, output voltages of 20 V and 40 V are obtained with respect to the input voltage V _in = 5 V from the DC input power supply 1.

(Sixth Embodiment) FIG. 16 is a circuit diagram of a micro power supply device using a switching element according to the present embodiment. A charge pump circuit 16 is also used. The circuit 16 is configured to obtain an output having a boosting ratio of 2 to 5 times. The charge pump circuit 16 includes a plurality of diodes 16A and a plurality of capacitors 16B. According to this embodiment, the output voltage V _out can exceed 100 V at the maximum with respect to the input voltage V _in = 5 V from the DC input power supply 1.

(Embodiment 7) FIG. 17 is a circuit diagram of a micro power supply device using a switching element according to this embodiment, showing a step-down DC / DC converter. As shown in the figure, in the case of this embodiment, the DC input power supply 1 and the load 8
The horizontal PMOSFET 41 and the inductor 3 are connected in series between the line and the line, and the connection of the rectifying diode 42 is changed accordingly. In case of step-down DC / DC converter, FE
Since the PMOSFET is used for T41, the polarity of the pulse width modulation signal is inverted. That is, PW in this case
The M control IC 43 has drive output terminals D1, D2, D shown in FIG.
Inverted output terminals / D1, / D2, / D3, / D
It is configured as 4.

The output voltage V _out can be adjusted by the variable resistor 9 as in the previous embodiments. According to this embodiment, the input voltage V _in from the DC input power source 1 is 5 to 20 V, The output voltage V _out was 6.5 V and the output was 1 W, and an efficiency of 85% was obtained at a switching frequency of 5 MHz.

(Embodiment 8) FIG. 18 is a circuit diagram of a micro power supply device using a switching element according to the present embodiment. It is a step-up / down type DC / D capable of boosting operation and bucking operation.
The C converter is shown. This is the step-up DC / DC converter shown in FIG. 1 and the step-down DC / D shown in FIG.
The C converters are combined as shown in the figure, and the PWM control ICs 5 and 43 are individually provided for these converters.

Here, a step-up converter PWM control IC 5 for turning on / on the step-up NMOSFET 4
Further, the PWM control IC 43 for the step-down converter for controlling ON / ON of the PMOSFET 41 for step-down is provided with the synchronization terminals M and S of the master and the slave respectively, and these terminals M and S are coupled to drive them synchronously. There is. Then, the input voltage V _in from the DC input power source 1 is the output voltage V
When it is lower than _out , NMOSFET 4 is controlled to be turned on and on, and PMOSFET 41 is always turned off to boost DC / D.
It serves as a C converter, the input voltage V _in the output voltage V
When it is higher than _out , the PMOSFET 41 is controlled to be turned on / on, and the NMOSFET 4 is always turned off to step down the DC / D.
Works as a C converter. Further, when the input voltage V _in and the output voltage V _out is To substantially equal, both FET4,41
ON / OFF control. Note that reference numerals 44 and 45
Is a resistor connected to the NF terminals of the ICs 5 and 43.

(Embodiment 9) FIG. 19 is a circuit diagram of a micro power supply device using a switching element according to this embodiment, and shows the functions of the boost converter PWM control IC 5 and the step-down converter PWM control IC 43 of FIG. The integrated PWM control IC 50 is used. This PWM control I
The terminal PWM of C50 means the set of the above drive output terminals D1 to D4, and CMP is the comparator 27 shown in FIG.
, And / CMP is its inverting output terminal. The output of the terminal PWM and the output of the terminal CMP are given to the input of the gate circuit 51, and the output of the gate circuit 51 is N
It is input to the gate of the MOSFET 4. Also, the terminal PW
The output of M and the output of the terminal / CMP are given to the input of the gate circuit 52, and the output of this gate circuit 52 is PMOS FE.
Input to the gate of T41.

The terminal / CMP is provided to always turn on the PMOSFET 41 for step-down during the step-up operation,
The terminal CMP is an NMOSFET for boosting the voltage during the step-down operation.
It is provided in order to always turn off No. 4. That is,
/ CMP is low level, CMP is high level, PM
Since the OSFET 41 is always turned on and the NMOSFET 4 is turned on / off according to the high level and the low level of PWM, the boosting operation is performed. Also, CMP is low level, / CM
When P is at a high level, the NMOSFET 4 is always off and the PMOSFET 41 is turned on / off according to the low level and the high level of PWM, so that the step-down operation is performed.

(Embodiment 10) FIG. 20 is a circuit diagram of a micro power supply device using a switching element according to the present embodiment, which is the same as FIG. 19 in a combination of a step-up converter PWM control IC 4 and gate circuits 61 and 62. It realizes a function.

(Embodiment 11) FIG. 21 is a circuit diagram of a micro power supply device using a switching element according to this embodiment, and is the same as FIG. 19 in a combination of a step-down converter PWM control IC 43 and gate circuits 71 and 72. It realizes a function.

(Embodiment 12) FIG. 22 is a circuit diagram of a micro power supply device using a switching element according to the present embodiment, in which D3 and D4 of drive output terminals D1, D2, D3 and D4 are inverted output terminals. By using the step-up / down converter PWM control IC 81 replaced with / D3, / D4, in other words, the gate circuits 51 and 52 of FIG.
It is incorporated in the M control IC 81 to realize the same function as in FIG.

(Embodiment 13) FIG. 23 is a circuit diagram of a micro power supply device using a switching element according to the present embodiment. The FETs 4, 41 and the diodes 6, 42 of FIG. It is an example built in. According to the present embodiment, the number of external parts is only L, C, and R, and the number of parts is greatly reduced, so that the size and weight can be reduced and the cost can be reduced.

(Fourteenth Embodiment) FIG. 24 is a circuit diagram of a micro power supply device using a switching element according to the present embodiment. The inductor 3 and the diode 4 in FIG.
In this example, the positions of 2 are interchanged to form an inverting DC / DC converter. In this case, since the feedback input terminal NF has a negative polarity, it is assumed that the feedback current is detected.

(Fifteenth Embodiment) FIG. 25 is a circuit diagram of a micro-power supply device using a switching element according to the present embodiment, which is a combination of a PWM control IC 90 for an inverting converter and gate circuits 91 and 92, and an inverting DC / DC circuit. It constitutes a converter.

(Sixteenth Embodiment) FIG. 26 is a circuit diagram of a micro power supply device using a switching element according to the present embodiment. The PWM control IC 9 for the inverting converter shown in FIG.
Instead of 0, the boost converter PWM control IC 5 is used as in the embodiment of FIG. 20, and this is combined with the gate circuit 62 to form an inverting DC / DC converter.
Reference numerals 100 and 101 are transistors and resistors incorporated in the feedback circuit.

[0077]

As described above, according to the present invention,
It is possible to provide a micro power supply device using a switching element that achieves high efficiency by sufficiently suppressing switching loss even at a switching frequency in the MHz band.

Further, according to the present invention, there is provided a micro-power supply device using a switching element which realizes stable and high efficiency by operating the MOSFET in the linear region as much as possible even if the input voltage from the input DC power supply is lowered. can do.

[Brief description of drawings]

FIG. 1 is a diagram showing time dependence of on-resistances of a lateral MOSFET and a vertical MOSFET.

FIG. 2 is a sectional view schematically showing a structural example of a lateral MOSFET.

FIG. 3 is a sectional view schematically showing a structural example of a vertical MOSFET.

FIG. 4 is a characteristic diagram of frequency-ON resistance loss in a vertical MOSFET and a lateral MOSFET.

FIG. 5 is a characteristic diagram of frequency-switching loss in a vertical MOSFET and a lateral MOSFET.

FIG. 6 is a characteristic diagram of frequency-total loss in a vertical MOSFET and a lateral MOSFET.

FIG. 7 is a circuit diagram of a micro power supply device using the switching element according to the first embodiment of the present invention.

FIG. 8 is a specific circuit diagram of a PWM control IC used in the present invention.

FIG. 9 is a diagram showing the switching frequency dependence of the power conversion efficiency of the first embodiment and the comparative example.

FIG. 10 is a circuit diagram of a micro power supply device using a switching element according to a second embodiment of the present invention.

FIG. 11 shows the input voltage dependence of power conversion efficiency according to the first embodiment.
And FIG.

FIG. 12 is a diagram showing the output dependence of the lower limit of the input voltage that can be boosted for the first and second embodiments.

FIG. 13 is a circuit diagram of a micro power supply device using a switching element according to a third embodiment of the present invention.

FIG. 14 is a circuit diagram of a micro power supply device using a switching element according to a fourth embodiment of the present invention.

FIG. 15 is a circuit diagram of a micro power supply device using a switching element according to a fifth embodiment of the present invention.

FIG. 16 is a circuit diagram of a micro power supply device using a switching element according to a sixth embodiment of the present invention.

FIG. 17 is a circuit diagram of a micro power supply device using a switching element according to a seventh embodiment of the present invention.

FIG. 18 is a circuit diagram of a micro power supply device using a switching element according to an eighth embodiment of the present invention.

FIG. 19 is a circuit diagram of a micro power supply device using a switching element according to a ninth embodiment of the present invention.

FIG. 20 is a circuit diagram of a micro power supply device using a switching element according to a tenth embodiment of the present invention.

FIG. 21 is a circuit diagram of a micro power supply device using a switching element according to an eleventh embodiment of the present invention.

FIG. 22 is a circuit diagram of a micro power supply device using a switching element according to a twelfth embodiment of the present invention.

FIG. 23 is a circuit diagram of a micro power supply device using a switching element according to a thirteenth embodiment of the present invention.

FIG. 24 is a circuit diagram of a micro power supply device using a switching element according to a fourteenth embodiment of the present invention.

FIG. 25 is a circuit diagram of a micro power supply device using a switching element according to a fifteenth embodiment of the present invention.

FIG. 26 is a circuit diagram of a micro power supply device using a switching element according to a sixteenth embodiment of the present invention.

[Explanation of symbols]

1 ... Input DC power supply 2 ... Stabilizing capacitor 3 ... Inductor 4 ... Horizontal NMOS
FET 5 ... PWM control IC 6 ... Rectifier diode 7 ... Smoothing capacitor 8 ... Load 9 ... Variable resistor 13 ... Power supply voltage selection circuit 15 ... Charge pump circuit 16 ... Charge pump circuit 20 ... Pulse width modulation signal generation circuit unit 30 ... Drive Circuit part 41 ... Horizontal PMOSFET 42 ... Rectifying diode 43 ... PWM control IC 50 ... PWM control IC 51 ... Gate circuit 52 ... Gate circuit 61 ... Gate circuit 62 ... Gate circuit 81 ... PWM control IC 82 ... PWM control IC 90 ... PWM control IC 91 ... Gate circuit 92 ... Gate circuit

Claims (8)

[Claims] 1. The switching frequency of the output of the DC power supply is 1
A semiconductor switching element that switches under a switching condition of [MHz] or more and an ON resistance value of 1 [Ω / mm ² (a unit area of one side of the element)] or less, and rectifies the output of the DC power source switched by this semiconductor switching element. A chopper section including a rectifying element, an inductance element provided in at least one of the semiconductor switching element and the rectifying element, and control of the semiconductor switching element of the chopper section based on an output of the rectifying element of the chopper section. A micro power supply device using a switching element, comprising: a control unit that supplies a switching control signal to an electrode. 2. The control section includes a signal generating means for generating the switching control signal, a driving means for amplifying a switching control signal generated by the signal generating means to drive the semiconductor switching element, and a driving means for driving the semiconductor switching element. Selecting means for selecting one of the output voltage of the DC power supply and the output voltage of the rectifying element, which has a voltage more than the minimum necessary for operating the semiconductor switching element in a linear region, as a power supply input to the means; A micro power supply device using the switching element according to claim 1. 3. The control section includes a signal generating means for generating the switching control signal, a driving means for amplifying a switching control signal generated by the signal generating means to drive the semiconductor switching element, and a driving means for driving the semiconductor switching element. 2. The micro power supply device using a switching element according to claim 1, further comprising a selection means for selecting a higher one of the output voltage of the DC power supply and the output voltage of the rectifying element as a power supply input to be supplied to the means. 4. The semiconductor switching element of the chopper section has a characteristic that the on-resistance shows a value lower than the on-resistance at direct current within 30 ns when an on-signal is given as a pulse width modulation signal from the control means. A micro power supply device using the switching element according to claim 1, comprising a MOSFET. 5. The micro power supply device using the switching element according to claim 1, wherein the switching element of the chopper section includes a lateral MOSFET. 6. The chopper section is composed of a plurality of chopper circuits connected in cascade, and each chopper circuit outputs the output of a DC power source at a switching frequency of 1 [MHz] or more and O.
N resistance value 1 [Ω / mm ² (unit area of one side of element)] A semiconductor switching element that switches under the switching conditions described below, and a rectifying element that rectifies the output of the DC power source switched by this semiconductor switching element. The micro power supply device using the switching element according to claim 1, further comprising: an inductance element provided in at least one of the semiconductor switching element and the rectifying element. 7. A lateral MOSFET for PWM switching the output voltage of a DC power supply, an inductor provided between the DC power supply and the lateral MOSFET, and a rectified output voltage of the DC power supply PWM-switched by the lateral MOSFET. And a control unit that supplies a PWM control signal to the gate electrode of the lateral MOSFET based on the output of the rectifying device and a power supply voltage of the control unit, the output voltage of the DC power supply and the output voltage of the rectifying device. A micro power supply device using a switching element, comprising: a selection unit that selectively supplies the control unit. 8. The selection means is a minimum required for operating the semiconductor switching element in a linear region among the output voltage of the DC power supply and the output voltage of the rectifying element as a power supply input to be supplied to the control section. The micro power supply device using the switching element according to claim 7, further comprising means for selecting one having the above voltage.