JPH0811149B2 - Electric razor motor drive circuit - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a motor drive circuit for an electric razor, which is provided with means for changing the rotation speed of a blade drive motor.

BACKGROUND ART Conventionally, an electric shaver in which the rotation speed of a motor is changed has been provided in order to cope with a person with a strong beard, or particularly in the case of shaving a beard in a hurry. FIG. 5 shows a conventional motor drive circuit for an electric shaver provided with electric shifting means for a motor. This electric razor has a power switch
When SW ₁ is turned on, the battery B is connected to the motor M via the resistor R ₀₁ , and the battery voltage V ₁ is divided by the resistor R ₀₁ and the internal resistance of the motor M, so the voltage applied to the motor M is low. Therefore, the number of rotations of the motor M is suppressed. Switch SW ₂ when dealing with a person with a dark beard or when you want to shave quickly
By turning on the resistor R ₀₁ , both ends of the resistor R ₀₁ are short-circuited and the battery voltage V ₁ is directly applied to the motor M to increase the rotation speed of the motor M.

However, the drawbacks of such a shaver are:
Since the rotation speed of the motor M is used at a lower level than the rated value in the normal state and the rated value is used at the power-up, the outer shape of the motor M becomes larger than the power obtained in the normal state.
Moreover, since the voltage dividing resistor R ₀₁ heats up, power loss increases. Therefore, there is an example in which a diode or the like is used instead of the resistor R ₀₁ , but the result was the same as the case of the resistor R ₀₁ described above.

Therefore, FIG. 6 shows a method considered to solve the above-mentioned drawbacks. In FIG. 6, when the power switch SW ₁ is turned on, the battery voltage V ₁ is directly applied to the motor M because the switch SW ₂ is switched to the terminal a side during normal use. If the user has a strong beard or wants to shave quickly, switch the switch SW ₂ to the terminal b side. This switch SW ₂
By switching at the booster circuit 2 consisting of the switching transistors Q ₁ and transformer T, the battery voltage V ₁ (1.2 to 1.5
V) is directly boosted to 1.5 to 1.8V and applied to the motor M.
Therefore, it is not necessary to make the outer shape of the motor M larger than necessary, and there is no loss because the battery voltage V ₁ is directly used in normal times.

However, in the circuit of FIG. 6, when the switch SW ₂ is switched to the terminal b side, the battery voltage V ₁ is directly boosted.
Large loss and poor efficiency. This inefficiency is especially problematic when the voltage is low, as in the case of a single battery. As this loss, a loss due to a saturation voltage V _CE (sat) between the collector and the emitter of the transistor Q ₁ , a loss due to a transformer coupling, and a loss due to the rectifying diode D ₁ are considered.

[Object of the Invention] The present invention has been made in view of the above points, and an object of the present invention is to provide a motor for an electric razor that can use a small-sized motor and can change the rotation speed of the motor with less loss. It is to provide a driving circuit.

DISCLOSURE OF THE INVENTION (Embodiment 1) FIGS. 1 to 3 are views showing an embodiment of the present invention. In this embodiment, a battery voltage V ₁ is converted into a predetermined voltage, and this converted voltage is converted into a battery. The DC-DC converter 1 to be superimposed on the voltage V ₁ is provided between the battery B and the blade driving motor M, and the motor M is directly connected to the battery B, or the motor M is connected via the DC-DC converter 1. It is provided with a switch SW ₂ for switching whether to connect to the battery B. More specifically, the output voltage V ₂ of the DC-DC converter 1 is added to the battery voltage V ₁ of the battery B, and a ringing choke converter type circuit is used as the DC-DC converter 1. This DC-DC converter 1 includes a pulse transformer T ₁ having a primary winding L ₁ , a secondary winding L ₂ , and a feedback winding L ₃ , a switching transistor Q ₁ , a starting resistor R ₁ , a resistor R ₂ , and a capacitor. An oscillating section consisting of C _1, a rectifying and smoothing section consisting of a rectifying diode D ₁ for rectifying and smoothing the output of the secondary winding L ₂ and a smoothing capacitor C _0, and an oscillating section to prevent the output voltage from exceeding a predetermined voltage. Controlling transistor Q ₂ , diodes D ₂ , D ₃ ,
It is composed of a resistor R ₃ and a controller composed of a capacitor C ₂ . Since the output voltage V ₂ of the DC-DC converter 1 is added to the battery voltage V ₁ , the winding start side of the secondary winding L ₂ and the anode of the battery B are directly connected. Further, the DC-DC converter 1 is adapted to obtain a difference voltage between the predetermined voltage and the battery voltages V ₁ needed to drive the motor M by stepping down the battery voltage V ₁ of the battery B.

The operation will be described below. The oscillating unit of this embodiment operates by using the battery voltage V ₁ of the battery B as a power source. When the power is supplied, a base current flows through the switching transistor Q ₁ via the starting resistor R ₁ and the pulse transformer T ₁ Of 1
Collector current flows through the next winding L ₁ . Because of this, the feedback winding
A voltage determined by the winding ratio with the primary winding L ₁ is applied to L ₃ .
A base current flows to the base of the switching transistor Q ₁ via the resistor R ₂ and capacitor C ₁ at this voltage, the switching transistor Q ₁ is reaching saturation. Third
FIG. 6B shows the collector current Ic flowing through the switching transistor Q ₁ at this time. After that, oscillation is repeated such that the switching transistor Q ₁ is rapidly turned off by the transformer action of the pulse transformer T. In this step-down ringing choke converter, the secondary winding L ₂ is reversely wound with the primary winding L _1, and as shown in FIG.
The switching energy in the primary winding L ₁ during the ON period of the transistor Q ₁ is stored, to release this energy as shown in FIG. 1 (c) to the secondary winding L ₂ side (in the drawing I ₀ is the output current ).
The voltage output to the secondary winding L ₂ side is rectified by the rectifier diode D ₁
And smoothing capacitor C _{0 for} rectification and smoothing to obtain voltage V ₂ shown in FIG. Incidentally, FIG. 3A shows the collector-emitter voltage V ₁ of the switching transistor Q ₁ . Then, the control unit makes the voltage obtained by adding the output voltage of the rectifying / smoothing unit to the battery voltage V ₁ of the battery B constant, that is, when the voltage becomes equal to or higher than a predetermined voltage, the transistor Q ₂ is turned on. The switching transistor Q ₁ is controlled to be shorter than the normal conduction period to reduce the energy stored in the primary winding L ₁ and perform feedback so as to keep the output voltage constant. Thus, in this embodiment,
Instead of directly boosting the battery voltage (for example, 1.2V) of the battery B to a predetermined voltage (for example, 1.5V), the battery voltage V ₁ of the battery B is set to a difference voltage (0.3V) between the predetermined voltage and the battery voltage V _1. )
Since the voltage is stepped down to and the voltage is added to the battery voltage V ₁ of the battery B, the current flowing in the switching transistor Q ₁ can be reduced, and therefore the switching transistor Q ₁ and the pulse transformer T ₁ are It can be made small, and it is effective in terms of efficiency and space, and is particularly advantageous for small devices such as electric razors. The battery B may be a primary battery or a secondary battery.

FIG. 2 is a view showing the external appearance of an electric razor having the above-mentioned circuit. This electric razor has a shaving portion at the upper part, and a push button 4 for operating a switch SW ₁ for operating the electric razor on the front surface. With this push button 4
A push button 3 for operating the switch SW ₂ is provided below.

(Embodiment 2) FIG. 4 is a view showing another embodiment of the present invention, in which a secondary battery such as a NiCd battery is used as a power source of the motor M, and a charging circuit for charging the battery B is provided in an electric shaver are those built in the transformer of the charging circuit are also used in the transformer T ₁ of the above DC-DC converter. Therefore, in this embodiment, the switch SW ₅ and the transformer T ₁ that are turned on when charging are used in the charging circuit and when the DC-DC converter 1 is used.
The interlocking switches SW ₃ and SW ₄ for connecting the transformer T ₁ to the respective circuits are provided. The switch SW ₂ is a switch for switching between direct connection of the battery B and the motor M, or connection of the motor M to the battery B via the DC-DC converter 1, as in the above-described embodiment. Also,
The transformer T ₁ is the oscillation transformer of the DC-DC converter 1 described above.
In addition to the windings L _{1 to} L ₃ of T ₁ , it works as an input winding of the charging circuit 4
The secondary winding L ₂ of this embodiment is provided with the secondary winding L _4, and also functions as the output winding of the charging circuit.

To increase the rotation speed of the motor M, set the motor M to DC-
When connecting to the battery B via the DC converter 1, by setting the switches SW _{2 to} SW ₄ to the terminal b side and the switch SW ₄ to the open state, a circuit similar to that of the first embodiment is configured. . Since the circuit configuration of this DC-DC converter 1 is the same as the circuit of the above-described first embodiment,
In the figure, the same circuit parts as those of the circuit of FIG. 1 are designated by the same reference numerals, and detailed description and operation thereof will be omitted.

Next, the charging circuit will be described. In this case, when the switches SW ₃ and SW ₄ are switched to the terminal a side, the switch SW ₅ is closed, and the switch SW ₂ is opened, a charging circuit is formed. This charging circuit operates by using the output obtained by rectifying and smoothing the AC power source E with the diode D ₄ and the capacitor C ₃ , and has a configuration similar to that of the DC-DC converter 1, and the secondary winding of the transformer T ₁ . line L ₂ to 4 winding L _4, the switching transistor Q _3, starting resistor R _4, the resistor R _5, the capacitor
It is composed of C ₄ and switching transistor Q ₁ . still,
The switching transistor Q ₁ is not used as a transistor, but the diode between the base and the collector is used as the rectifying diode of the charging circuit.

Since the operation is substantially the same as the operation of the DC-DC converter 1 described above, only a characteristic part of this charging circuit will be briefly described. The voltage induced in the secondary winding L ₂ by the switching of the switching transistor Q ₃ is applied to the battery B via the diode between the collector and the base of the switching transistor Q ₁ , that is, the voltage rectified by the diode is the battery B. Is applied to.

[Effects of the Invention] As described above, the present invention includes a DC-DC converter that converts a battery voltage into a predetermined voltage and superimposes the converted voltage on the battery voltage between the battery and the motor for driving the blade, and Connect the motor directly to the battery, or connect the motor to a DC
-Since it has a switch that switches whether to connect to the battery via the DC converter, by switching the switch, the motor can be rotated at a normal rotation speed during normal operation.
Also, in the case of a person with a strong beard or when it is necessary to shave quickly, it is possible to superimpose the conversion voltage of the DC-DC converter on the battery voltage and supply it to the motor to increase the rotation speed of the motor.
Moreover, since the converted voltage of the DC-DC converter is superimposed on the battery voltage, the DC-DC converter can create a voltage that is the predetermined voltage required to drive the motor at a higher rotation speed, minus the battery voltage. Therefore, the current flowing through the switching transistor can be reduced, and loss is reduced and heat generation is suppressed compared to when the battery voltage is directly boosted and applied to the motor, and the switching transistor and transformer of the DC-DC converter are suppressed. Since the current flowing through the switch is small, the switching transistor and the transformer can be downsized, and the parts can be downsized and the cost can be reduced.

[Brief description of drawings]

FIG. 1 is a circuit diagram of an embodiment of the present invention, FIG. 2 is an external perspective view of the same as above, FIG. 3 is an operation explanatory diagram of the same as above, and FIG. 4 is a circuit diagram of another embodiment of the present invention. FIG. 5 is a circuit diagram of a conventional example, No. 6
The figure is a circuit diagram of another conventional example. 1 is a DC-DC converter, B is a battery, M is a motor, V ₁ is a battery voltage, and SW ₂ is a switch.

Claims (3)

[Claims] 1. A DC-DC converter for converting a battery voltage into a predetermined voltage and superimposing the converted voltage on the battery voltage is provided between the battery and a motor for driving a blade, and the motor is directly connected to the battery, or Alternatively, a motor drive circuit for an electric razor, comprising a switch for switching whether the motor is connected to a battery via a DC-DC converter. 2. A secondary battery is used as the battery, a charging circuit for charging the battery is provided, and the transformer of the charging circuit is shared with the transformer of the DC-DC converter. A motor drive circuit for an electric razor according to claim 1. 3. A motor drive circuit for an electric shaver according to claim 2, wherein the diode between the base and collector of the switching transistor of the DC-DC converter is used as a rectifying diode of the charging circuit. .