JPH08214589A - Miniature electric machine - Google Patents

Abstract

PURPOSE: To detect an overload state accurately and protect an inverter circuit which is used in a miniature electric machine as a power supply means for a load from breakdown. CONSTITUTION: A voltage dividing resistor is connected in parallel to a secondary battery which is charged by an inverter circuit 22 and a switching device 74 is connected in series to the voltage dividing resistor. By the on-off control of the switching device 74 with the output voltage of the inverter circuit 22, if the switching device 74 is turned on, a low voltage which is the divided voltage of a terminal voltage can be taken out and, if the switching device 74 is turned off, the terminal voltage can be taken out as it is as a reference voltage. A detected voltage whose magnitude corresponds to a load value is compared with the reference voltage and, if the detected voltage is below the reference voltage, the operation of the inverter circuit 22 is stopped.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a small electric device such as an electric razor, and more particularly to a device using an inverter circuit as a power supply for driving a load.

[0002]

2. Description of the Related Art Conventionally, in this type of electric razor, it is naturally assumed that an operator is present when the razor is used, and protection of an electric circuit is mainly caused by an increase in temperature due to an excessive current during charging. In order to prevent the occurrence of a fire, the method was generally based on a temperature or current fuse.

[0003]

By the way, an ordinary user does not remove hair dust so much that a slight trouble such as a biting of a hair tip causes an overload and causes the motor to stop. There are many. In this case, if the power supply is a battery, the battery is simply discharged, and there is no particular problem if the battery is replaced or charged. However, when the power supply is a commercial power supply using an inverter circuit, a large current continues to flow to the motor for a long time, and there is a possibility that the inverter circuit itself may be damaged.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has a power supply means including an inverter circuit and a power supply means including an inverter circuit, as schematically shown in FIG. A load connected to the supply means and supplied with electric power, a load amount detection means capable of generating a detection voltage whose value decreases as the load increases, and a reference voltage generation means capable of outputting a predetermined reference voltage. And a protection means for comparing the detected voltage with the reference voltage and stopping the oscillation of the inverter circuit when the detected voltage falls below the reference voltage.

Further, while the reference voltage generating means outputs the divided battery voltage as the reference voltage in response to the operation of the inverter circuit, it outputs the battery voltage in response to the stop of the inverter circuit. It is characterized in that it can be output as it is as a reference voltage.

The reference voltage generating means includes a secondary battery 6 charged by an inverter circuit 22 and a voltage dividing resistor 7 connected in parallel with the secondary battery 6, as exemplified in FIG.
5 to 78, a switching element 74 interposed in series with the voltage-dividing resistor and energizing the voltage-dividing resistor from the secondary battery when turned on.
And an auxiliary power supply 53 capable of generating a predetermined voltage for turning on the switching element 74 in response to the operation of the inverter circuit 22.

[0007]

Therefore, the protection means does not work while the small electric equipment is used in a normal state, and the power supply means supplies necessary electric power to the load. Here, when the load increases, a detection voltage of a magnitude corresponding to the load state is generated from the load amount detection means, and the value of the detection voltage is compared with a reference voltage in the protection means.

When it is confirmed that the detected voltage is below the reference voltage, the protection means stops the oscillation of the inverter circuit and limits the output of electric power to the load. At the same time, the value of the reference voltage is increased from the voltage obtained by dividing the battery voltage to the terminal voltage itself, and the stopped state of the inverter circuit is maintained.

[0009]

As described above, according to the present invention, the state of the load is always detected, and when an abnormality in such a state is detected, the oscillation of the inverter circuit is limited and the state is maintained. Damage to the inverter circuit due to overload is prevented.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on an example in which the present invention is applied to an electric shaver capable of driving a motor in parallel with charging.

An electric shaver 1 for carrying out the present invention is shown in FIG.
As shown in FIG. 1, the outer blade 2 is detachably mounted on the upper part of the main body case 3, and the inner blade 4 is slidably disposed inside the outer blade 2. Further, inside the main body case 3, a motor 5 for reciprocatingly driving the inner blade 4, a secondary battery 6 for supplying rotational driving power to the motor 5, a charge control for the secondary battery 6, An electric circuit 7 for performing various controls such as rotation control is housed. On the front of the main body case 3, a first display element 11 for displaying the rotation control state is provided at an upper position on the same line with a push button switch 10 for regulating the timing of energizing the motor 5, and at a lower position. The second display elements 12 for displaying the charge control state are provided separately from each other.

FIG. 3 is a block diagram schematically showing the entire electric circuit 7 built in the main body case 3 described above. The secondary battery 6 such as a nickel-cadmium battery which can be charged and discharged a plurality of times and a motor are shown. 5 is a main load, a power supply unit 13 that supplies power to the load, a detection unit 14 that can output detection signals corresponding to various states of the load, and the load is used within a normal operation range. The control unit 15 performs various controls in response to a change in the voltage value of the commercial power supply 20 input to the power supply unit 13 or a change in load, and a power supply unit when the load becomes extremely light or heavy. 13 includes a protection unit 16 that regulates the operation timing and a display unit 17 that performs display corresponding to various states of the load.

The power supply unit 13 uses an inverter circuit 22 which receives a voltage obtained by full-wave rectifying the commercial AC power supply 20 by a rectifying circuit 21, and the input voltage of the inverter circuit 22 is higher than the commercial frequency. It is stepped down to pulse voltage.

The secondary battery 6 can be connected to a circuit for performing various controls at the time of driving the motor via the switch 10. Therefore, the secondary battery 6 functions as a load of the power supply unit 13 when the motor is stopped. In addition, the main power supply 23 is configured together with the output from the power supply unit 13.

The control section 15 includes an output control circuit 24 of the inverter circuit 22 and a rotation control circuit 25 of the motor 5. The output control circuit 24 keeps the voltage supplied to the load substantially constant irrespective of fluctuations in the voltage of the commercial AC power supply 20 or the load.
The control is performed by regulating the oscillation frequency or the oscillation timing of the inverter circuit 22 with the detection signal output from the control circuit 4.

On the other hand, the rotation control circuit 25 constantly detects the rotation speed of the motor 5 and increases / decreases the voltage applied to the motor 5, thereby substantially eliminating the load applied to the motor 5 or the voltage fluctuation of the main power supply 23. It is designed to maintain a constant rotation speed.

The protection section 16 comprises a light load protection circuit 26 and a heavy load protection circuit 27. When the light load is caused by the secondary battery 6 being fully charged or the like, the light load protection circuit 2 is turned on.
6, the load is protected by lowering the output from the power supply unit 13. On the other hand, when the motor 5 is locked and becomes heavy load, the heavy load protection circuit 27 stops the inverter circuit 22. To protect the power supply unit 13.

The display unit 17 includes a charge state display circuit 29 for indicating that the rechargeable battery 6 has been fully charged and has reached a fully charged state, thereby prompting a stop of the charge, and a load increase circuit or a main power supply 23. The rotation control circuit 25
, And a rotation state display circuit 30 for prompting the stop of the motor 5 and the start of charging, and the change and blinking of the emission colors of the display elements 11 and 12 provided on the main body case 3. To make each state distinguishable and displayable.

[0019]

[Power Supply Unit] As shown in FIG. 4, the power supply unit 13 includes a rectifier circuit 21 having a diode bridge 31 and a filter 32, and an inverter circuit 22. After full-wave rectification of the input commercial AC power supply 20 by the rectifier circuit 21, the fuse 3
4 to the inverter circuit 22. The fuse 34 functions as a final protection unit when the protection unit 16 malfunctions, shuts off the power supply to the inverter circuit 22, and forcibly stops the operation of the inverter circuit 22.

The inverter circuit 22 includes a transistor 35
A primary coil 36 and a shock absorbing portion 37 connected to both ends of the primary coil 36 and absorbing a shock voltage generated when the transistor 35 is turned off are provided on the collector side of the primary coil 36, and a feedback portion 40 is provided between the base and the emitter. Is provided. Further, a feedback coil 41, a secondary coil 42, and a tertiary coil 43 are wound on the same iron core as the primary coil 36.

The feedback section 40 connects one end of the feedback coil 41 to the base end of the transistor 35, connects a capacitor 44 between the other end of the feedback coil 41 and the emitter of the transistor 35, and connects the emitter end of the secondary battery 6. Connected to positive side. Further, a feedback coil 41 and a capacitor 44
Is connected to the resistor 45 by the output voltage from the rectifier circuit 21.
The voltage divided at 46 can be applied via the resistor 47.

Accordingly, a voltage is generated across the resistor 46 simultaneously with the application of the voltage to the inverter circuit 22, and the charging of the capacitor 44 is started by the voltage. Capacitor 4
When the voltage across both ends of the transistor 4 rises and reaches the vicinity of the turn-on voltage of the transistor 35, a current begins to flow in the primary coil 36 connected to the collector end of the transistor 35, and a voltage is generated in the feedback coil 41 due to the increase in the current. .
This voltage rapidly charges the capacitor 44 in the opposite direction through the base-emitter of the transistor 35, and the charging voltage of the capacitor 44 becomes a blocking voltage to rapidly turn off the transistor 35. After the transistor 35 is turned off, the voltage across the resistor 46 is again applied to the capacitor 44 through the resistor 47, and the capacitor 44 is charged in the positive direction, and the above-mentioned on / off operation is repeated.

Here, the energy stored on the primary coil 36 side when turned on is selectively supplied to the load connected to the secondary coil 42 and the tertiary coil 43 by the rectifying diodes 50 and 51 during the off period of the transistor 35. Taken out.

The secondary battery 6 is always connected to the secondary coil 42, and when the switch 10 is turned on to connect the rotation control circuit 25 including the motor 5, the output from the power supply unit 13 and the main power supply 23 are connected. Make up. The switching operation of the switch 10 and the insertion / removal of the power plug 33 enable charging to be performed independently, charging and motor driving to be performed simultaneously in parallel, or motor driving to be performed using a secondary battery alone.

The tertiary coil 43 is the same as the secondary coil 42 described above.
The number of turns is several times larger, so that a voltage higher than that of the secondary coil 42 can be output. Further, the output is smoothed by using the rectifying diode 51 and the large-capacity capacitor 52 to form the auxiliary power supply 53. Therefore, even when the output of the inverter circuit 22 is low because the inverter circuit 22 is being operated but the inverter circuit 22 is sufficiently controlled, the auxiliary power supply 53 can drive and control various circuits. An auxiliary voltage V2 of a necessary and sufficient magnitude can be supplied to the following circuits as a circuit drive voltage or a control signal.

[0026]

[Detection Unit] As shown in FIGS. 4 to 7, the detection unit 14
And four detection circuits 61, 62, 63, and 64, which output detection signals of different values corresponding to the state of the load to be detected.

As shown in FIG. 4, the first detection circuit 61 is connected to both ends of the secondary coil 42 of the main power supply 23 via the diodes 65, and outputs a pulse-like signal output from the secondary coil 42. Is smoothed by a capacitor 66 and the voltage across the capacitor 66 is divided by resistors 67 to 70 to detect a value that changes in response to an increase or decrease in the average value of the pulse voltage output from the power supply unit 13. Signals S1, S2
Is output. Such a signal is used by the output control circuit 24 and the charge state display circuit 29.

Both the second and third detection circuits 62 and 63
A resistor for voltage division is connected in parallel with the main power supply 23, and the secondary battery 6
A detection signal having a voltage value proportional to the change in the terminal voltage V1 of is output. Here, the second detection circuit 62 is used in the rotation state display circuit 30 of the motor 5 as shown in FIG. 7, and therefore, the normally-open switch contact 10a is interposed in series with the voltage dividing resistors 71 to 73. The detection signal S3 is output only when the motor 5 is driven in cooperation with the ON operation of the switch 10.

On the other hand, the third detection circuit 63 can output the detection signal S4 as shown in FIG. 6, and since this signal S4 is mainly used in the light load protection circuit 26, it is turned on by the output V2 from the auxiliary power supply 53. A switching transistor 74 is interposed in series, and while the inverter circuit 22 is stopped, the power supply to the voltage dividing resistors 75 to 78 is stopped to prevent the consumption of the secondary battery 6.

As shown in FIG. 6, the fourth detection circuit 64 forms a rectangular wave signal having a pulse rate corresponding to the rotation speed of the motor 5, thereby increasing or decreasing the rotation speed of the motor 5 and locking the rotation itself. The normally open switch contact 10a, which closes in conjunction with the pressing operation of the switch 10, is interposed on the ground side so that the detection operation is performed only when the motor is driven. I have. The detection signal S5 is used in the rotation control circuit 25 and the heavy load protection circuit 27.

The detection operation in the above-mentioned fourth detection circuit 64 is performed by the cylindrical reflecting plate 8 attached to the rotary shaft of the motor 5.
0 and a photo interrupter 83 including a light emitting diode 81 and a phototransistor 82 that utilize the reflection of light by the reflection plate 80 to generate a signal having a frequency corresponding to the rotation speed of the motor 5. This signal is further input to a filter circuit 84, and selectively sends only an AC signal having a frequency component corresponding to the rotation cycle of the motor 5 to a waveform shaping circuit 85.

The waveform shaping circuit 85 inputs the output signal from the filter circuit 84 to the negative input terminal of the comparator 86, and applies the secondary battery voltage V1 to the positive terminal of the comparator 86.
A reference voltage divided by 7.88 is applied, and a diode 90 connected to the secondary battery 6 side via a resistor 89 is connected to the output terminal, and the rotation of the motor 5 is stopped to input. When the signal disappears, the output side of the comparator 86 opens and the voltage value regulated by the voltage drop of the diode 90 is output, but the motor 5 rotates and the voltage value of the input signal becomes the value of the reference voltage. Each time the voltage exceeds the limit, the both ends of the diode 90 are short-circuited and fall to zero potential, so that the diode 9
From both ends of 0, a rectangular-wave detection signal S5 whose peak value is regulated by the forward voltage of the diode 90 as shown in FIG.

[0033]

[Control Unit] The control unit 15 enables stable load driving during normal use, and comprises an output control circuit 24 shown in FIG. 4 and a rotation control circuit 25 shown in FIG.

The output control circuit 24 includes first and second transistors 93 and 94. The emitter and base terminals of both transistors 93 and 94 are directly connected, and the collector terminal of the first transistor 93 is connected to the resistor 4 of the inverter circuit 22.
Between 5 and 46, the collector end of the second transistor 94 is connected to the base end of the transistor 35 and the output side of the auxiliary power supply 53 via the resistors 95 and 96, respectively.
The detection signal S1 output from the detection circuit 61 is applied. The detection signal S1 is obtained by dividing the voltage between both ends of the capacitor 66 connected to the secondary coil 42 via the diode 65 with a resistor, and corresponds to a change in the voltage value of the commercial AC power supply 20 or a change in the load. It is possible to output a voltage of the specified magnitude.

In the above configuration, for example, the commercial AC power source 2
Assuming that the voltage value of 0 changes in the range of about 100 to 120V, the variable resistor 70 of the first detection circuit 61 is adjusted so that both the transistors 93 and 94 are turned off when the voltage value is 100V and the motor is driven. Then, the voltage value of the detection signal S1 is set in advance.

In this state of use, the resistors 95 and 96 are connected to the base of the transistor 35 of the inverter circuit 22.
, An auxiliary voltage V2 is applied, and this voltage V2
Reduces the discharge time of the capacitor 44 while the transistor 35 is off, and makes the oscillation frequency of the inverter circuit 22 slightly higher than the frequency of the circuit 22 at the highest efficiency.

Here, when the commercial power supply voltage rises or the load becomes lighter, the value of the detection signal S1 rises, the base current starts to flow in the second transistor 94, and the output V2 from the auxiliary power supply 53 is shunted by the transistor 94. The voltage applied to the base end of the transistor 35 is gradually reduced.
Then, the discharge time of the capacitor 44 becomes longer than in the above case, and the oscillation frequency of the inverter circuit 22 decreases. When the value of the detection signal S1 further increases, both ends of the resistor 46 are short-circuited by the first transistor 93 and the inverter circuit 22
The oscillation of is stopped intermittently.

With this operation, control is performed so that the output is constant when the load is constant and the commercial power supply voltage is increased or decreased. When the commercial power supply voltage is constant and the load is increased or decreased, the magnitude of the load is increased or decreased. The inverter circuit 22 is controlled so that the power supply operation can be performed stably during normal load driving.

As shown in FIG. 5, the rotation control circuit 25 converts the detection signal S5 of a rectangular wave having a frequency proportional to the rotation speed output from the fourth detection circuit 64 into a frequency corresponding to the frequency by the DA converter 100. The detection signal is converted into a detection signal having a magnitude, and the detection signal is compared with a reference voltage by the comparator 101. When a deviation occurs between the two, a control signal corresponding to the deviation value is sent to the control circuit 102. The control circuit 102 is interposed in an energizing circuit for the motor 5, and controls a voltage drop in the control circuit 102 by a control signal to increase or decrease the voltage applied to the motor 5, and to reduce a load applied to the motor 5. The rotation speed control is performed in accordance with the magnitude of the output voltage or the increase or decrease of the output voltage of the main power supply 23.

Here, the DA converter 100 is an integrating circuit using an OP amplifier 103. When the detected digital detection signal S5 is applied to the capacitor 104, the electric charge stored in the capacitor 104 is Diode 10
It flows to the negative feedback capacitor 107 through the pump circuit composed of 5.106. The inflow of such charges is caused by the OP amplifier 1
An analog signal having a voltage value proportional to the pulse rate is obtained on the output side after being integrated via 03.

The comparator 101 is a differential amplifier using an OP amplifier 110. The comparator 101 inputs the signal on the minus side, applies a reference signal on the plus side, and outputs a control signal having a voltage proportional to the difference between the two. Take out. The value of the reference signal can be adjusted by connecting the variable resistor 112 to both ends of the diode 111, and the operating point of the control circuit 102 can be changed.

The control circuit 102 has a first and second transistors 113 and 114 connected in a Darlington connection.
The second transistor 114 is connected to the output side of the
And the second transistor 114
Between the emitter and the collector of the second transistor 114 in a circuit for supplying current to the motor 5, and furthermore, the negative feedback from the collector end of the second transistor 114 to the OP amplifier 110 side of the comparator 101 via the resistor 115.

In such a configuration, the variable resistor 112 of the comparator 101 is adjusted so that the set rotational speed is exhibited when the set load is applied to the motor 5, and the control circuit 102 is adjusted.
Are set to the amplification operation state. Here, when the comparator 101 detects that the rotation speed of the motor 5 is lower than the set speed, the value of the control signal is increased so that the motor terminal voltage required for the set rotation speed is obtained, and the second transistor 114 is turned on. By setting the saturation state, the voltage applied to the motor 5 is increased to correct the rotation speed in the increasing direction. Conversely, when it is detected that the rotation speed has risen above the set value, the value of the control signal is decreased to increase the emitter-collector voltage of the second transistor 114, and the motor application voltage is decreased to decrease the rotation speed automatically. Fix it.

When the capacity of the main power supply 23 is sufficient, the above control is performed relatively stably. However, when the power is supplied only from the secondary battery 6 without using the power supply unit 23 and the battery capacity is reduced, the value of the control signal itself from the comparator 101 is also reduced as much as possible. As a result, the base current that can be supplied to the control circuit 102 decreases,
If the secondary battery 6 still has enough capacity to drive the motor 5, the control circuit 102 turns off and the motor 5
There is a risk that the power supply to the power supply will be forcibly stopped. In the present embodiment, a resistor 116 is connected between the input side of the control circuit 102 and the secondary battery 6, and even after the control from the comparator 101 side becomes ineffective, the control circuit 102 The current is supplied directly from the motor 5 so that the rotatable time of the motor 5 can be extended as much as possible.

[0045]

FIG. 6 is an electric circuit diagram showing the overall configuration of the protection unit 16, which comprises a light load protection circuit 26 and a heavy load protection circuit 27. The light load protection circuit 26 causes the secondary battery 6 to perform quick charging with a 1C current to be in a fully charged state, and when the third detection circuit 63 detects that a light load has occurred, the inverter circuit 22 oscillates. Deterioration due to overcharge of the secondary battery 6 is mainly prevented by regulating the timing to reduce the output and shifting to trickle charge of about 0.1 to 0.2C.

On the other hand, the heavy load protection circuit 27 detects the heavy load by the fourth detection circuit 64 when the motor 5 is locked due to the shavings biting between the outer blade 2 and the inner blade 4 or the like. In this case, the oscillation of the inverter circuit 22 is stopped to prevent the transistor 35 from being damaged.

The light load protection circuit 26 is connected to the negative input terminal of the comparator 120 by the diode 12 of the third detection circuit 63.
While the reference voltage stabilized at 1 is applied, the detection signal S4 output from the third detection circuit 63 is applied to the plus side input end. Furthermore, a capacitor 122 is connected to the output side of the comparator 120, and a resistor 12 is connected across the capacitor 122.
3 and an auxiliary power supply 53, and a base end of the transistor 124 and a Zener diode 125. The transistor 124 has a collector end connected to the base end of the transistor 35 of the inverter circuit 22 via the diode 126, and a resistor 127 connecting the emitter end and the base end.

The heavy load protection circuit 27 outputs a rectangular wave detection signal S5 having a frequency proportional to the rotation speed of the motor 5 output from the fourth detection circuit 64 to the converter 130 as shown in FIG. Input and convert digital signals to analog signals.

The conversion unit 130 supplies the base current of the transistor 131 from the detection signal S5 to supply the base current of the transistor 131.
As shown in FIG. 8 (b), by controlling the on / off of the motor 31 and connecting the collector side to the secondary battery 6 and taking out the output, as shown in FIG. To form a rectangular waveform voltage S6 having a pulse rate proportional to.

The output voltage S6 is further supplied to the integrating circuit 13
2 and is integrated and applied to the negative input terminal of the comparator 133 as a detection voltage S7 having a magnitude corresponding to the magnitude of the rotation speed.

The comparator 133 has a third terminal connected to its third terminal.
A detection signal S4 'output from the detection circuit 63 is applied as a reference voltage, and the output terminal is connected to a Zener diode 1
A resistor 1 is added to the base end of the transistor 135 via 34.
Each is connected to an auxiliary power supply 53 via 36.

The collector side of the transistor 135 is connected in parallel with the light load protection circuit 26 through the diode 137. Further, by connecting a normally closed switch contact 10b and a diode 138 in series and a resistor 139 in parallel with the base and the emitter, both ends of the resistor 139 are connected during the period when the power supply to the motor 5 is stopped. The short circuit causes the application of the base voltage to be forcibly stopped, so that the heavy load protection circuit 27 does not malfunction.

Next, the operation of the protection unit 16 will be described in detail with reference to the waveform diagrams shown in FIGS.
In the above configuration, the variable resistor 76 of the third detection circuit 63 is set so that the voltage value of the detection signal S4 is substantially equal to the reference voltage V3 when the secondary battery 6 approaches full charge (time t1).
Is adjusted in advance.

Here, the switch 10 is turned off and the motor 5 is turned off.
When the power plug 33 is turned on at time t0 with the power supply stopped, the rechargeable battery 6 starts charging as a load on the power supply unit 13.

At the beginning of charging, the value of the detection signal S4 is sufficiently smaller than the reference voltage V3, and therefore the capacitor 122
Are short-circuited by the output side of the comparator 120, the transistor 124 keeps off, and the inverter circuit 2
2 continues the normal oscillation controlled by the output control circuit 24.

The charging is further advanced and approaches full charging (at time t).
1), the detection signal S4 instantaneously exceeds the reference voltage in response to the output of the pulse-like voltage from the secondary coil 42, and the output side of the comparator 120 opens in a pulse-like manner to open the auxiliary voltage. V2 is output.

However, the transistor 1 is directly connected to the voltage V2.
Instead of controlling the transistor 24, the voltage is once applied to the capacitor 122 for integration, and when the integrated value exceeds the Zener voltage of the diode 125, the diode 125 is turned on and the base current flows to the transistor 124 only when the integrated value exceeds the Zener voltage.
By turning on 24 and grounding the base end of the transistor 124, the oscillation of the inverter circuit 22 is stopped.

That is, by limiting the output regulation amount of the inverter circuit 22 by the light load protection circuit 26 as much as possible at the start of the control, the charge current amount during such a period is substantially increased, The charging current for the secondary battery 6 is narrowed down with time. Therefore, the output from the inverter circuit 22 at the time of light load is regulated to the necessary minimum, and the deterioration due to the overcharge of the secondary battery 6 is prevented in advance.

Next, when the switch 10 is turned on while the secondary battery 6 is fully charged as described above (time t3),
The motor 5 starts to rotate at a constant speed while the rotation speed is controlled by the rotation control circuit 25.

Although there is no detection signal S5 from the fourth detection circuit 64 at the start of rotation of the motor 5, a signal sufficiently higher than the reference voltage S4 'is applied from the main power supply 23 through the resistor 140 and the diode 141. The reference voltage S4 'is adjusted in advance even after the rotation at the constant speed by adjusting the variable resistor 76 of the third detection circuit 63 so that no load is applied to the inner blade 4. By setting the voltage value so as to be sufficiently smaller than the detection voltage S7, when the rotation speed is sufficiently high and the rotation speed control is effective, the output side of the comparator 133 is always Grounded, the transistor 135 remains off and has no effect on the inverter circuit 22.

However, as the load applied to the motor 5 increases, the output voltage V1 from the main power supply 23 decreases, and eventually the rotation control becomes ineffective (time t4), and the rotation of the motor 5 increases as the load further increases. Speed decreases. At the same time, the value of the detection voltage S7 input to the comparator 133 also decreases, and when the rotation of the motor 5 is locked by, for example, biting the bristle tip, the input to the integration circuit 132 is lost (time t7).

At this time, the detected voltage S7 does not immediately disappear, but falls below the value of the reference voltage S4 'at time t9 after a time determined by the discharge time constant of the capacitor 142 and the resistor 143, and the output terminal of the comparator 133 is opened. I do. At the same time, the auxiliary voltage V2 is applied to the base of the transistor 135 via the diode 134, and as shown in FIG.
The transistor 135 is turned on to stop the oscillation of the inverter circuit 22.

When the above-mentioned lock of the motor 5 is temporary and the lock is released immediately at the time t8, from the time of lock until the oscillation of the inverter circuit 22 is stopped, as described above, for example, 0. Since a time difference of about 3 to 1 second is provided in advance, the detection voltage S7 immediately returns to a normal value that is sufficiently higher than the reference voltage S4 ', as shown by the alternate long and short dash line.
The motor 5 continues the normal rotation operation.

In a period in which a large load is applied to the motor 5 but it is not necessary to stop the motor 5, the detection voltage S
Since the value of 7 repeats large fluctuations, it is desirable that the reference voltage S4 'be as low as possible so that the heavy load protection circuit 27 does not accidentally operate. However, once the rotation has stopped, it is necessary to ensure that the heavy load protection circuit 27 continues to operate without turning on and off the switch 10 unnecessarily until the cause of the rotation stop is removed. , The reference voltage S4 'needs to be high to some extent.

In this embodiment, since the output voltage of the main power source 23 is divided as the reference voltage S4 ', the reference voltage S4' is automatically set according to the decrease in the rotation speed.
After the motor stops, it returns to the original value, and satisfies the above contradictory requirements without any troublesome adjustment.

The heavy load condition can be detected not only by directly detecting the rotation itself of the motor 5 but also by detecting the output voltage from the main power supply 23.
In that case, heavy load detection and light load detection can be combined.

[0067]

[Display Unit] As shown in FIG. 7, the display unit 17 operates at the time of charging to display a fully charged state,
A rotation state display circuit 30 that operates when the motor is driven and displays the state of rotation speed control.

The state-of-charge display circuit 29 includes the first detection circuit 6
1 to the first transistor 15
0, the collector end is connected to the base end of the second transistor 151, and the second display element 12 is connected to the collector side of both transistors.
Switching transistor 152 that turns on with 2 inputs
And a main power supply 23 via a normally closed switch contact 10b.

The second display element 12 is a combination of red and green light emitting diodes, and a green light emitting diode 153 is connected in series with the first transistor 150.
Red light emitting diode 15 in series with transistor 151
Connect 4 each.

The rotation state display circuit 30 has a diode 15 of the second detection circuit 62 connected to the positive input terminal of the comparator 155.
6, the reference signal taken from both ends is applied, the detection signal S3 is inputted to the minus side, and the output terminal is connected to the base terminal of the first transistor 157. Furthermore the first
The collector end of the transistor 157 is connected to the second transistor 1
After connecting the green light emitting diode 159 to the first transistor 157 and the red light emitting diode 160 to the second transistor 158, respectively, and then connecting to the main power supply 23 through the normally open switch contact 10a. I have.

The lighting timing of each of the display elements 11 and 12 will be described below with reference to FIGS. In addition,
FIG. 8F shows the lighting time of the second display element 12, and FIG. 8G shows the lighting time of the first display element 11.

In the above configuration, when the inverter circuit 22 is operated with the motor stopped, the auxiliary voltage V2 is output, the transistor 152 is turned on, and the charge state display circuit 2 is turned on.
9 is energized. At the same time, the detection signal S2 is output from the first detection circuit 61. However, when the capacity of the secondary battery 6 decreases as at time t0, the control of the light load protection circuit 26 is not performed, and thus the detection signal Since the value of S2 is large, the first transistor 150 is turned off, the second transistor 151 is turned on, and the red light emitting diode 154 is energized to indicate that charging is being performed.

Here, when the charging progresses and the light load protection circuit 26 is activated to start the control (time t1), the value of the detection signal S2 is intermittently decreased, the first transistor 150 is turned on and the green color is generated. The light emitting diode 153 starts to light up.
That is, red and green are lit alternately, and as the charging approaches the end, the ratio of the green lighting time gradually increases, and as a result, the emission color changes from red to orange and further at time t.
It changes to green at 2 and indicates that it is fully charged.

Next, when the switch 10 of the main body case 3 is turned on, the rotational driving of the motor 5 is started (at time t).
3). Here, the variable resistor 72 of the second detection circuit 62 is determined in advance.
Is adjusted so that the reference voltage substantially matches the value of the detection signal S3 at time t4 when the control in the rotation control circuit 25 becomes ineffective.

Then, the load is small or the main power supply 23
Is high, the first transistor 157 is turned on and the first display element 11 is lit in green to indicate that normal rotation is being performed.

However, the control becomes ineffective (time t4).
Then, the second transistor 158 starts to turn on, the time during which the red light-emitting diode 160 is lit gradually increases, and changes from green to orange and then to red at time t5 to indicate an abnormality in motor rotation. Further, when the rotation of the motor 5 is about to stop (time t6), the first display element 11 is turned off to indicate that the battery capacity has decreased.

The second display element 1 for displaying the state of charge
When the electric shaver 1 is used, the display of the second display element 12 is covered by the operator's hand by disposing the switch 2 on the main body case 3 at a position below the switch 10. Even if the lighting of the first and second display elements 11 and 12 is switched and displayed, the display is not erroneously recognized.

Further, since the auxiliary power supply 53 for controlling the ON period of the transistor 152 is constructed so as to obtain a stable and sufficiently large output from the first detection circuit 61, the second display element 12 blinks red and green. Even during the period of repeating, the transistor 152 is surely kept in the ON state, and the display element 12 itself is prevented from blinking and flickering.

[Brief description of drawings]

FIG. 1 is a block diagram showing an outline of the present invention.

FIG. 2 is an overall perspective view showing an example in which the present invention is implemented.

FIG. 3 shows a block diagram of an electric circuit according to the present invention.

FIG. 4 is an electric circuit diagram showing a specific configuration of a power supply unit in FIG.

FIG. 5 is an electric circuit diagram showing a specific configuration of a control unit in FIG.

6 is an electric circuit diagram showing a specific configuration of a protection unit in FIG.

FIG. 7 is an electric circuit diagram showing a specific configuration of a display unit in FIG.

FIG. 8 is an explanatory diagram showing an operating state of an electric circuit.

[Explanation of symbols]

 Reference Signs List 4 inner blade 5 motor 6 secondary battery 7 electric circuit 10 switch 13 power supply unit 14 detection unit 15 control unit 16 protection unit 17 display unit 22 inverter circuit 23 main power supply 24 output control circuit 26 light load protection circuit 27 heavy load protection circuit 53 Auxiliary power supply 63 Third detection circuit 64 Fourth detection circuit

Claims (2)

[Claims] 1. A power supply unit including an inverter circuit, a load connected to the power supply unit to which power is supplied, and a load amount detection capable of outputting a detection voltage whose value decreases as the load increases. Means, a reference voltage generating means capable of outputting a predetermined reference voltage, and a protection means for comparing the detected voltage with the reference voltage and stopping the inverter circuit when the detected voltage falls below the reference voltage, The reference voltage generation means enables the battery voltage to be divided and output as a reference voltage in response to the operation of the inverter circuit, and outputs the battery voltage as it is in response to the stoppage of the inverter circuit. A small electric device characterized by being made possible. 2. The above-mentioned reference voltage generating means includes a secondary battery charged by an inverter circuit, a voltage dividing resistor connected in parallel with the secondary battery, and a voltage dividing resistor interposed in series. , A switching element for energizing a voltage dividing resistor from a secondary battery when turned on, and an auxiliary power supply capable of generating a predetermined voltage for turning on the switching element when the inverter circuit is operating. The small electric device according to item 1.