JPH0241278B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a DC motor, and particularly to a DC motor that efficiently utilizes electric power supplied from a power source.

Conventional configurations and their problems Conventionally, when controlling the speed of a DC motor, for example, a DC power source with a constant output voltage is depressurized and controlled using transistors, etc., and the drive voltage corresponding to the speed of the motor is adjusted. It was supplying the coil.
In such a configuration, the power supplied by the DC power supply is the sum of the effective power consumption in the coil and the collector loss of the transistor. In a normal DC motor, the ratio of effective power consumption to power supplied by the power source (power efficiency) is small, about 10 to 30%. In particular, DC motors with a wide variable speed range and multi-speed switching, and DC motors for take-up with a wide variable range of driving force, have significantly poor efficiency during low speed or low driving force operations.

In order to eliminate such drawbacks, the present applicant has proposed in Japanese Patent Application No. 17375/1989 a power-efficient DC motor using a switching type voltage converter that can extract variable output DC voltage. , using an electronic commutator type (brushless type) DC motor as an example. By the way, in a DC motor with such a configuration, it is necessary to supply voltage and current to the coil through the switching transistor of the voltage converter, and to control the voltage value (or current value) in response to a command signal. be.
Therefore, the on-time ratio of the switching transistor must be variably controlled accurately and accurately in accordance with the command signal. However, in general, the storage time due to the charge accumulated between the base and emitter of the switching transistor is quite large, and the on-time of the switching transistor is considerably longer than the base current pulse width (when the repetition frequency is high Therefore, its influence is large).

The accumulation time varies widely between transistors, and also varies significantly depending on the level of the collector current (relative ratio to the base current). As a result, it is difficult to accurately control the on-time ratio of the switching transistor in response to a command signal, and the speed control accuracy and torque control accuracy of the DC motor are significantly deteriorated. Furthermore, the falling time of the switching transistor was long, and the switching loss was also large. Furthermore, the effects of the accumulation time and fall time become more pronounced as the switching frequency increases, making high frequency switching difficult and requiring larger smoothing inductance elements and capacitors.

Purpose of the Invention The present invention takes such drawbacks into consideration, and improves motor control performance by forcibly discharging the accumulated charge between the base and emitter of the switching transistor to shorten the accumulation time and fall time. The purpose is to improve the

Structure of the Invention In order to achieve the above-mentioned object, the present invention includes a field means, a plurality of coils, and a switching transistor that is inserted between the coil and a DC power source and operates on and off. Voltage conversion means for changing the output voltage in response to a command signal to obtain an output voltage that is proportional or substantially proportional to the on-time ratio of the switching transistor; and distribution means for switching the current path of the coil from the output terminal of the voltage conversion means. , a DC motor comprising current detection means for detecting a current supplied to the coil, wherein the voltage conversion means includes a triangular wave generating means for obtaining a triangular wave signal of a predetermined frequency, and a triangular wave generating means for obtaining a triangular wave signal of a predetermined frequency; A comparator means for comparing and obtaining a duty pulse signal corresponding to the command signal, and an input current that changes in response to the current supplied to the coil detected by the current detection means, and is proportional to the input current. Alternatively, the input current of the first current mirror means is turned on and off by the pulse signal of the comparator means, and the input current of the first current mirror means is turned on and off by the pulse signal of the comparator means. pulsing means for making an output current into a pulse current; first supply means for supplying the pulse current to the base terminal of the switching transistor; and a common connection terminal connected to the emitter side of the switching transistor and the base side thereof. a second current mirror means having an output terminal connected to the output terminal of the second current mirror means, and turning the input current of the second current mirror means off and on in accordance with the pulse signal of the comparator means; a second supply means for supplying a current to discharge the base accumulated charge of the switching transistor; and a smoothing means for smoothing the pulse voltage caused by the on/off operation of the switching transistor using an inductance element, a capacitor, and a diode. It is configured so that it has.

DESCRIPTION OF EMBODIMENTS The present invention will be described below based on illustrated embodiments. FIG. 1 is an electrical circuit diagram representing one embodiment of the present invention. In Figure 1, 1 is a DC power supply, 2
3 is a voltage converter having a switching transistor 11; 3 is a field magnet; 4, 5, and 6 are three-phase coils interlinked with the magnetic flux of magnet 2; 7 is a motor movable part (in this embodiment, magnet 3 is ) is a distributor that switches the current path to the coils 4, 5, and 6 according to the position of the coils 4, 5, and 6, and 8 is a speed detector that detects the speed of the motor movable part.

The speed detector 8 is composed of, for example, a frequency generator and a period/voltage converter, and when the speed of the motor moving part is slow, its detection voltage Vd is large, and when the speed approaches a predetermined value, Vd responds to the speed. Vd decreases as the speed decreases.

Voltage converter 2 includes switching transistor 1
1, a smoother 12, an oscillator 13, a comparator 14, and a base current supplier 15 (first means)
, a base charge discharger 16 (second means), and a current source 17 for speed-up. The output voltage Vd of the speed detector 8 is input to the comparator 14 of the voltage converter 2, and the output voltage Vd is inputted to the comparator 14 of the voltage converter 2.
is compared with the triangular wave signal Vt of a predetermined frequency (approximately 94.4 KHz), and the transistor 41 is
(output transistor) is turned on and off.

When the transistor 41 is off (when the output voltage Vt of the oscillator 13 is smaller than the speed detector Vd),
The transistor 43 of the base current supply device 15 is turned off, and the current of the constant current source 44 is transferred to the diode 45,
46, transistors 48, 49, resistors 47, 50
Amplification (approx.
40 times) (and the composite current of the output current of the transistor 68 of the current source 17) is output (current sucked) and becomes the base current I ₁ of the switching transistor 11. At this time, the base charge discharger 1
The transistor 51 of No. 6 is also off, and the transistor 55 is off (I ₂ =0).

When the transistor 41 is on (when the output voltage Vt of the oscillator 13 is greater than the speed detection signal Vd), the transistor 43 of the base current supply device 15 is turned on, and its output current becomes zero (I ₁ = 0). .
At this time, the transistor 51 of the base charge discharger 16 is also turned on, and its collector current becomes I ₃ =(v ₁ −V _BE51 −V _D52 )/R ₅₃ (1). Here, v ₁ is the emitter potential of the transistor 41, V _BE51 is the base-emitter forward voltage of the transistor 51 (approximately 0.7 V), V _D52 is the forward voltage of the diode 52 (approximately 0.7 V), and R ₅₃ is the resistor 53. is the value of

The collector current I ₃ of the transistor 51 is input to a second current mirror circuit consisting of a diode 54, a transistor 55, and resistors 56 and 57. The second current mirror circuit connects one end of a resistor 57 to one end of a series circuit of a resistor 56 and a diode 54 (diode-connected transistor), and connects the connection point to the emitter side of the switching transistor 11 with the connection point as a common connection end. Connect the emitter of the transistor 55 to the other end of the resistor 57, and
The base of a transistor 55 is connected to the other end of the series circuit of the switching transistor 6 and the diode 54, and the collector of the transistor 55 is connected to the base side of the switching transistor 11. The collector current I ₃ of the transistor 51 is amplified by the second current mirror circuit and becomes the current I ₂ (the resistance ratio of the resistors 56 and 57 is 5:
1, the emitter area ratio of the diode 54 and the transistor 55 is 1:5, and the current amplification factor is about 5 times), and the switching transistor 11
The charge accumulated between the base and emitter of the device is rapidly discharged. At this time, the current I ₂ becomes small in a short time as the base charge of the switching transistor 11 disappears. Note that the resistors 56 and 57 are used to stabilize the operation of the current mirror, and are not necessarily necessary. Further, the resistance value is selected so that the voltage drop across the resistors 56 and 57 is approximately 0.1V, which is sufficiently smaller than the base-emitter forward potential (0.7 to 7.9V) of the switching transistor 11. .

Therefore, a pulse of the base current _I1 having a pulse width corresponding to the output voltage Vd of the speed detector 8 is supplied to the switching transistor 11 by the base current supply 15.
is supplied to turn on/off the switching transistor 11.

The pulsed current of the base charge discharger 16 complementarily (alternately) with the pulsed current I ₁ of the base current supply 15
I ₃ is input to the second current mirror circuit, and its output current I ₂ momentarily becomes large, discharging the charge accumulated in the base of switching transistor 11 .

As a result, the actual storage time delay of the switching transistor 11 is significantly reduced, and the fall time is also shortened. That is, the switching transistor 11 is turned on and off at an on-time ratio (duty) that accurately corresponds to the speed detection signal Vd.

Note that the transistors 66, 6 of the current source 17
The collector currents 7 and 68 are connected to the transistor 41 of the comparator 14 and the base current supply 1, respectively.
This signal is supplied to improve the delay caused by the charge accumulated in the base of the transistor 49 of No. 5 and the pulse waveform.

The output voltage Vi caused by turning on and off the switching transistor 11 is smoothed by a smoother 12 consisting of a flywheel diode 61, an inductance element 62, and a capacitor 63, and a DC voltage V _M corresponding to the on-time ratio of the switching transistor 11 is obtained. I am getting . That is, when the switching transistor 11 is turned on, the voltage V _S (12 V) of the DC power supply 1 is output (Vi≒Vs), and current is supplied to the capacitor 63 and the coils 4, 5, and 6 through the inductance element 62. Ru. Further, when the switching transistor 11 is turned off, the flywheel diode 61 becomes conductive and supplies the energy stored in the inductance element 62 to the coils 4, 5, and 6. As a result, diode 6
1. Smoothed by an inductance element 62 and a capacitor 63, the output voltage VM of the voltage converter 2 has a value corresponding to the on-time ratio of the switching transistor 11 (a value corresponding to the speed detection signal Vd).

The output voltage V _M of the voltage converter 2 is the coil 4, 5,
6 and a distributor 7. The distributor 7 includes a position detector 21 that detects the rotational position of the magnet 3.
, selector 22, and drive transistors 23,2
4, 25, and a constant current source 26. The position detector 21 is constituted by, for example, a Hall element and a digital circuit that shapes its output, and changes its output voltage stepwise in accordance with the rotational position of the magnet 3. The output voltage of the position detector 21 is applied to the transistors 27 and 2 of the selector 22.
According to the voltage, the selector 22 distributes the current of the constant current source 26 to the drive transistors 23, 24, 25, and
The current paths to the coils 4, 5, and 6 are switched and controlled by sequentially switching the drive transistors that are turned on as the coils rotate. Therefore, the output voltage of the voltage converter
V _M is supplied to the coils 4, 5, and 6 via the distributor 7, and controls the power supplied to the coils, and therefore the power generated by the motor. As a result, a speed control loop is formed by the speed detector 8, the voltage converter 2, and the coils 4, 5, and 6, and the rotation of the movable part of the motor is controlled at a predetermined speed.

Next, the effect of the base charge discharger 16 will be explained with reference to FIG. Figure 2a shows a triangular wave signal input to the comparator 14 of the voltage converter 2.
It represents Vt (output of oscillator 13) and speed detection voltage Vd (output of speed detector 8). When Vt becomes larger than Vd, transistors 40 and 41 turn on, and the output voltage v ₁ increases (its rise is quite strong). When Vt becomes smaller than Vd, transistors 40 and 41 turn off, but the bases of these transistors It takes some time to discharge the charge, and the falling waveform changes slowly. The collector currents of the transistors 66 and 67 of the current source 17 have the effect of shortening the accumulation time and fall time. Figure 2b shows the waveform of _v1 .

The output v ₁ of the comparator 14 is the transistor 43
If the base-emitter forward voltage of V _BE ≒0.7V is greater than the transistor 43, the transistor 43 is turned on.
The output current I ₁ of the base current supplier 15 changes in a pulsed manner as shown in FIG. 2c.

On the other hand, the output voltage v ₁ of the comparator 14 is the sum of the base-emitter forward voltage of the transistor 51 and the forward voltage of the diode 52 (V _BE +V _D ≈1.4V)
, the current I ₃ of the base charge discharger 16 flows. As shown in Figure 2d, this current _I3 instantaneously reaches a predetermined value when the pulse current _I1 becomes zero (when the switching transistor 11 is turned off), and when _I1 reaches the predetermined value. I ₃ becomes zero before it changes stepwise. That is, I ₃ is operating complementarily (alternately) or substantially complementarily with I ₁ . Current _I3 is passed through the second current mirror circuit (diode 54, transistor 55, resistors 56, 57)
The base charge of the switching transistor 11 is discharged with a predetermined current, and as the base charge disappears, the discharge current _I2 becomes zero (FIG. 2e). As a result, the switching transistor 11
The accumulation time delay and fall time of are becoming significantly smaller.

Here, it is possible to replace the second current mirror circuit of the base charge discharger 16 with a simple emitter-grounded PNP transistor, but
With such a configuration, the influence of the base accumulation time in the PNP transistor appears, and at the moment the pulse current _I1 changes stepwise to a predetermined value, a current is supplied by the accumulated charge of the replaced PNP transistor (second (Part A in Fig. e) is undesirable because the turning-on time of the switching transistor 11 is delayed and the rising waveform becomes gentle, increasing switching loss.

On the other hand, if it is configured as a second current mirror circuit as shown in the embodiment of FIG. 1, the impedance between the base of the output transistor 55 and the power supply Vs becomes considerably small,
The base charge of 5 is quickly discharged, and the effects of its accumulation are significantly reduced. Furthermore, _{as shown} in FIG. (depending on the waveform), the influence of the charge accumulated in the base of transistor 55 is even smaller.

FIG. 3 is an electrical circuit diagram representing another embodiment of the present invention. In this embodiment, the voltage converter 2 includes a current detector 18, and switches the switching transistor 11 in response to the current Ia supplied to the coil.
By changing the magnitude of the base current I ₁ when the switch is on, the base current loss during low current operation is also reduced. This will be explained below (other configurations and operations are the same as those of the embodiment shown in FIG. 1 described above, and their explanations will be omitted).

A voltage drop R 80 ·Ia proportional to the supplied current Ia is generated across the resistor ₈₀ inserted in series in the current path to the coils 4, 5, and 6 (R ₈₀ is the resistance value of the resistor 80). The voltage drop is converted into a current i ₄ by the transistor 81, the emitter of the constant current source 82, the transistor 83, and the resistor 84.
The forward voltages (approximately 0.7 V) between the bases and emitters of transistors 81 and 83 cancel each other out, and the voltage drop across resistor 80 and the voltage drop across resistor 84 become equal. That is, if the resistance value of the resistor 84 is R ₈₄ , then i ₄ = (R ₈₀ / R ₈₀ ) · Ia ... (2), and the emitter current i ₄ of the transistor 83 responds (proportional) to the current Ia supplied to the coil. and change. Here, if R ₈₄ = 1000・R ₈₀ , i ₄ is Ia
It becomes 1/1000th and is sufficiently small (R ₈₄ is R ₈₀
(preferably set to 100 times or more).

Current i ₄ is combined with current I ₅ of constant current source 85, inverted by a current mirror (transistors 86 and 87), and supplied to base current supplier 15. The first current mirror of the base current supply 15 (diodes 44, 45, transistor 48,
49, resistance 46, 50) is the input current (i ₄ + I ₅ )
is inverted and amplified, and the switching transistor 11
The base current I is ₁ . Now, if the values of the resistors 46 and 50 are R ₄₆ and R ₅₀ (when the transistor 43 is off), I ₁ = (R ₄₆ /R ₅₀ )・(i ₄ +I ₅ )...(3) (diode 44 and 45 and the base-emitter current drop of transistors 48 and 49 cancel each other out). That is, the base current I ₁ of the switching transistor 11 changes in response to the output (i ₄ +I ₅ ) of the current detector 18, and increases when the current Ia supplied to the coil is large, and the current Ia supplied to the coil increases. When it's small, it gets smaller. here,
When R ₄₆ =40·R ₅₀ , I ₁ is 40 times (i ₄ +I ₅ ) (R ₄₆ is preferably set to 10 times or more of R ₅₀ ).

In the embodiment of the present invention shown in FIG. 3, since the base current _I1 of the switching transistor 11 of the voltage converter 2 is changed according to the current Ia supplied to the coil, the base current I1 in the constant speed control state is Current loss is significantly reduced. To explain this, in the motor startup/acceleration stage, the output Vd of the speed detector 8 is large, the on-time ratio of the switching transistor 11 is large, the output voltage _VM of the voltage converter 2 is large, and the coil 4, 5,6
Increase the supply current Ia to. In order to increase the current flowing to the coil, it is necessary to increase the current flowing through the switching transistor when it is on (collector current), and therefore, it is necessary to increase its base current. Now, the current supplied to the coil
Assuming that Ia2A and the current amplification degree _hFE when the switching transistor 11 is on is 25, it is necessary to supply a current of 2A/25=80mA or more as its base current.

Here, if the current supplied to the coil in the constant speed control state is 250 mA (corresponding to the load torque), only 250/25 mA is required as the base current when the switching transistor 11 is turned on. . At this time, if the base current (more than 80mA) required during startup and acceleration is allowed to flow as is, the loss is 80mA - 10mA = 70mA (70mA or more).
(equivalent to mA x 12V = 0.84W).

In this embodiment, the base current _I1 of the switching transistor 11 is increased in response to the current Ia supplied to the coil.
By changing the current, a sufficiently large base current (80 mA or more) is supplied even during startup and acceleration, and the base current is made small during constant speed control. That is, in the start-up/acceleration stage, if Ia = 2A, then i ₄ = 2A/1000 = 2mA, and if I ₅ = 0.1mA, then i ₄ +I ₅ = 2.1mA,
The base current of the switching transistor 11 is I ₁
=40·(i ₄ +I ₅ )=84 mA (switching transistor 11 is sufficiently turned on). Also, Ia
= 250mA (constant speed rotation state) i ₄ = 0.25m
A, and since i ₄ + I ₅ = 0.35 mA, I ₁ = 14 mA
(Since the required base current is 10 mA, the switching transistor 11 operates on and off. Therefore, the base current loss of 84 mA - 14 mA = 70 mA (equivalent to 70 mA x 12 V = 0.84 W) is reduced.

Note that when starting and accelerating the motor from a state where the output voltage V _M of the voltage converter 22 is zero, the initial base current of the switching transistor 11 is a value corresponding to the current I ₅ of the constant current source 85 ( I ₁ = 40・
I ₅ = 4 mA) and switching transistor 1
1 does not turn on completely, but as the output voltage V _M of voltage converter 2 increases, the current to the coil increases.
Ia also increases, the current i ₄ of the current detector 18 increases, the base current I ₁ increases, and the switching transistor 11 comes to perform complete on/off operation. That is, positive feedback occurs transiently, and the output voltage V _M of the voltage converter 2 increases.

In order to operate such positive feedback operation stably and to reduce base current loss, it is desirable to make the following settings.

Even when the current Ia supplied to the coil is zero, a predetermined small base current is supplied to the switching transistor 11 (when turned on).

Current i ₄ from coil current Ia at current detector 18
The conversion gain to A ₁ (A ₁ = R ₈₀ /R ₈₄ in Figure 3),
The transfer gain from i ₄ in the base current supply device 15 to the base current I ₁ of the switching transistor 11 is A ₂ (A ₂ = R ₄₆ /R ₅₀ ), and the current amplification degree of the switching transistor 11 is A ₃ (A ₃ = h _FE ), the total product A ₁ , A ₂ , A ₃ approaches 1.

In reality, since the current amplification degree A ₃ of the switching transistor 11 tends to fluctuate, it is preferable that 0.8≦A ₁ ·A ₂ ·A ₃ ≦10 (4).

(If A ₁ , A ₂ , and A ₃ are too small, the switching transistor 11 will not turn on sufficiently during large current operation, and the maximum value of the output voltage V _M of the voltage converter 2 will become small. If ₁ , A ₂ , and A ₃ are too large, an excessive base current will be supplied to the switching transistor 11, which will increase the base current loss and lengthen the base charge accumulation time and fall time.) Furthermore, in the embodiment shown in Fig. 3, since the base current of the switching transistor changes in conjunction with its collector current, the value of the base excess current is small when a small current is applied (when the collector current is small). As a result, the base accumulated charge also decreases, and the discharge due to the operation of the base charge discharger 16 is completed in a short time. That is, the storage time and fall time of switching transistor 11 are considerably reduced.

FIG. 4 shows an electric circuit diagram representing still another embodiment of the present invention. In this embodiment, the current detector 18 and the base charge discharger 1 in the embodiment of FIG.
6, the input pulse current _I3 to the second current mirror circuit of the base charge discharger 16 is changed in conjunction with the current Ia supplied to the coil, and when Ia is large, the switch is made with a large current _I2. When Ia is small, the base charge of the switching transistor 11 is discharged, and when Ia is small, it is discharged with a small current _I2 (the structure and operation of other parts are the same as the embodiment shown in FIG. 1 or 3). , the explanation is omitted.) In each of the above embodiments, a PNP transistor is used as the switching transistor 11, and the output voltage V _M is obtained by stepping down from the positive side with the negative side of the current power supply 1 as a reference. There is. Therefore, voltage converter 2
(oscillator 13, comparator 14, base current supply 15, base voltage converter 16, current source 17, current detector 18) and the main parts of the distributor 7 (constant current source 26, selector 22) It becomes easy to integrate the circuit on a single silicon chip (the ground must be fixed in the integrated circuit, and is usually connected to the negative pole side of the DC power supply 1).

In addition, although the above-mentioned example showed the example which used the three-phase coil, this invention is not limited to such a case, and can generally configure a DC motor having a plurality of coils. Furthermore, the present invention is not limited to an electronic commutator type (brushless type) DC motor, but can also be configured as a brushed DC motor that configures a distributor using a brush commutator. Furthermore, not only a rotary type DC motor but also a linear type DC motor in which the motor movable part moves in a straight line can be configured. Furthermore, the output voltage of the voltage converter may be controlled based not only on speed control but also on other command signals. In addition, various modifications are possible without changing the gist of the present invention.

Effects of the Invention As is clear from the above description, according to the present invention, (a) the base current when the switching transistor of the voltage conversion means is turned on is varied in accordance with the current supplied to the coil; When the current is small, the current loss in the base is small. Furthermore, since the excess current at the base of the switching transistor is reduced, the amount of base nitride charge is reduced, the discharge time thereof can be shortened, and high-speed switching of the switching transistor becomes possible. In addition, (b) when the switching transistor is turned off, the base accumulated charge is forcibly discharged by the second current mirror means, so the discharge time is shortened and the switching transistor changes from on to off. This is done in a short time, and the response delay due to the accumulated charge of the second current mirror means itself is small.
High-speed switching of switching transistors can be achieved. Therefore, it is possible to obtain a DC motor with good power efficiency and control precision of the on-time ratio of the switching transistor. Therefore, if a DC motor for audio and video equipment using a dry battery as a power source is constructed based on the present invention, equipment with low power consumption and long battery life can be realized.

[Brief explanation of drawings]

FIG. 1 is an electric circuit diagram showing one embodiment of the present invention, FIGS. 2 a to e are waveform diagrams for explaining the operation of the embodiment of FIG. 1, and FIGS. FIG. 6 is an electrical circuit diagram showing another embodiment. 1... DC power supply, 2... Voltage converter, 3... Magnet, 4, 5, 6... Coil, 7... Distributor, 8... Speed detector, 11... Switching transistor, 12... smoother, 13... oscillator,
14...Comparator, 15...Base current supply device, 16...Base charge discharger, 17...Current source device, 18...Current detector, 21...Position detector,
22...Selector.

Claims (1)

[Claims] 1. A field means, a plurality of coils, and a switching transistor that is inserted between the coil and a DC power source and that operates on and off is changed in response to a command signal, and the on-time ratio of the switching transistor is changed in response to a command signal. Voltage conversion means for obtaining an output voltage proportional or substantially proportional to the on-time ratio; distribution means for switching a current path from the output terminal of the voltage conversion means to the coil; and current detection means for detecting the current supplied to the coil. The voltage conversion means includes a triangular wave generating means for obtaining a triangular wave signal of a predetermined frequency, and a pulse signal having a duty corresponding to the command signal by comparing the triangular wave signal and the command signal. and a first current mirror that receives an input current that changes in response to the current supplied to the coil detected by the current detection means and outputs a current that is proportional or approximately proportional to the input current. means and
pulsing means for turning the output current of the first current mirror means into a pulse current by turning on and off the input current of the first current mirror means according to the pulse signal of the comparator means;
a first supply means for supplying the pulse current to the base terminal of the switching transistor; and a second current mirror having a common connection terminal connected to the emitter side of the switching transistor and an output terminal connected to the base side. and the input current of the second current mirror means is turned on and off by the pulse signal of the comparator means, thereby discharging the base accumulated charge of the switching transistor from the output terminal of the second current mirror means. A DC motor comprising: a second supply means for supplying current; and a smoothing means for smoothing a pulse voltage generated by the on/off operation of the switching transistor using an inductance element, a capacitor, and a diode.