JPH0548546U - Inverter circuit operating status display circuit - Google Patents

Abstract

(57) [Summary] [Purpose] When a load current exceeding the rated value flows to the load 90, the energization amount is reduced and a display corresponding to the load abnormality is displayed. [Configuration] An auxiliary coil 48 and a light emitting diode 44 connected in series are connected in parallel with a load 90. The auxiliary coil 48 is connected so that an output voltage is applied to the light emitting diode 44 in the same phase as the output coil 22, and the light emitting diode 44 is limited to a half cycle in which the load 90 is energized.
A forward drive voltage is applied to.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a circuit that provides a display corresponding to the operating state of an inverter circuit used to charge a secondary battery.

[0002]

[Prior Art]

 Conventionally, as this type of display circuit, there has been proposed, for example, one in which a light-emitting lamp is connected in parallel with the output coil of the inverter circuit so that the operation time of the inverter circuit can be displayed.

[0003]

[Problems to be solved by the device]

 However, the above-mentioned display circuit merely displays whether or not the inverter circuit is operating, and does not provide any appropriate display for a load abnormality. In order to solve this problem, a light emitting diode is used as a light emitting element, and voltage is applied only to the light emitting diode for a half cycle of power supply to the load. It is conceivable to use the fact that the output voltage drops significantly to turn off the light-emitting diode display.

However, the light-emitting diode has a low reverse breakdown voltage, and there is a strong possibility that the light-emitting diode will be destroyed by an overvoltage during a half-cycle period when power is not being supplied to the load. The present invention has been made in view of the above demands and inconveniences, and an object of the present invention is to provide a display circuit capable of appropriately displaying an operation abnormality in an inverter circuit while maintaining a circuit configuration as simple as possible. ..

[0005]

[Means for Solving the Problems]

 In order to achieve the above-mentioned object, in the present invention, as shown in the basic configuration of FIG. 1, the voltage taken out from the output coil 22 of the inverter circuit 52 is half-wave rectified to obtain a secondary battery. A diode 42 capable of supplying to the load 90, an auxiliary coil 48 connected to the output side of the diode 42 to generate a voltage in phase with the output coil 22, and having a threshold value higher than the terminal voltage of the load 90. , A diode 42 and a light emitting diode 44 driven by a voltage obtained by adding output voltages from the auxiliary coil 48 in the same phase.

[0006]

[Action]

 With the configuration described above, when the current value supplied from the inverter circuit 52 to the load 90 is at or below the rated value, the voltage output from the output coil 22 and the auxiliary coil 48 is large, and the light emitting diode 44 Emits light with sufficient brightness to indicate that the inverter circuit 52 is operating normally. In such an operating state, a high reverse voltage is generated in a state close to no load at the phase opposite to the above, but the diode 42 raises the reverse withstand voltage to prevent the light emitting diode 44 from being destroyed. It

By the way, the inverter circuit 52 has poor regulation characteristics, and when a load current exceeding a specified value such as a design value or a rated output value of the inverter coil is taken out, the voltage taken out from the output coil 22 and the auxiliary coil 48 is suddenly increased. Fall to. Therefore, under such an operating condition, the voltage applied to the light emitting diode 44 also falls below the threshold value, and as a result, the light emitting diode 44 is turned off and an abnormality in the charging operation in the inverter circuit 52 is displayed.

[0008]

[Effect of the device]

 As described above, the present invention applies the drive voltage to the light emitting diode 44 in the same phase as the load driving, and compensates for the shortage of the drive voltage by the auxiliary coil 48, while applying the drive voltage to the light emitting diode 44 at the opposite phase to the load driving. Since the voltage for rectifying is blocked by the diode 42 for rectification, the light emitting diode 44 is turned off at the time of overload so that the operation abnormality of the inverter circuit 52 can be properly displayed, and the reverse withstand voltage of the light emitting diode 44 is prevented. Destruction can be prevented.

[0009]

【Example】

 An example in which the present invention is applied to the rechargeable electric toothbrush 10 illustrated in FIGS. 2 and 3 is shown below, but the present invention is not limited to this, and is applied to various small electric devices using an inverter circuit in substantially the same manner. Of course you can.

The electric toothbrush 10 embodying the present invention includes an inverter type charging stand 16 connected to a commercial AC power source 14 via a power plug 12 and a receiving portion 18 provided on the upper surface side of the charging stand 16. On the other hand, the lower end of the toothbrush body 20 is detachably fitted. The charging stand 16 described above is an inverter type charging device and includes a protection circuit 50 and an inverter circuit 52.

The protection circuit 50 prevents the input of a large current by the metal film resistor 54 connected in series to the power supply line to the inverter circuit 52, while preventing the input of the surge voltage by the overvoltage absorption element 56 connected in parallel. To do. Further, after the input voltage is rectified by the rectifier 58, the operation of the inverter circuit 52 at the time of overheating can be forcibly stopped by the temperature fuse 60, and the outflow of noise from the inverter circuit 52 side is prevented by the capacitor 62. I am doing it.

The inverter circuit 52 includes a primary coil 66 on the collector side of the switching transistor 64 and a protective resistor 68 on the emitter side, and an output control section 70 and an output limiting section 80 on the base side. ing.

The output control unit 70 includes a resistor 72, a capacitor 74, and a feedback coil 76 connected in series. The on / off cycle of the switching transistor 64 is, for example, 40 kHz depending on the charge / discharge time constant of the resistor 72 and the capacitor 74. On the other hand, the feedback coil 76 and the capacitor 74 regulate the longest time that the switching transistor 64 is turned on.

That is, when the capacitor 74 is charged through the resistor 72 and the base voltage of the switching transistor 64 exceeds the set value, the collector current starts flowing in the primary coil 66, and the increase in the collector current is caused in the feedback coil 76. A voltage is generated to turn on the transistor 64, and the transistor 64 is turned on rapidly. After the transistor 64 is turned on, the capacitor 74 proceeds to be charged and discharged, and the base current decreases, so that the direction of the voltage output from the feedback coil 76 is reversed, and a reverse bias is applied between the base and emitter of the transistor 64. , The transistor 64 is turned off suddenly.

The capacitor 78 connected in parallel with the primary coil 66 absorbs a shock voltage generated when the transistor 64 is turned off. The protective resistor 68 provided on the emitter side of the transistor 64 regulates the off-timing of the transistor 64 by increasing the emitter potential of the transistor 64 in response to the increase of the collector current, and an excessive current causes an excessive transistor current. It prevents the flow into 64.

The output limiting section 80 has a capacitor 82 connected in parallel with the feedback coil 76 and a zener diode 84 connected in series with the capacitor 82. Here, a diode 86 that allows charging only during the off period of the switching transistor 64 is interposed between the feedback coil 76 and the capacitor 82, while a transistor 64 is provided between the zener diode 84 and the capacitor 82. The diode 88 is interposed in such a direction that it can be turned on by the base voltage during the ON period and the capacitor 82 can be discharged.

Therefore, the charging voltage of the capacitor 82 charged by the feedback coil 76 during the off period of the transistor 64 becomes larger as the load current taken out from the inverter circuit 52 becomes smaller, and this charging voltage is supplied to the zener diode 84. As a result of being added to the base voltage in the direction to turn it on, the Zener diode 84 is turned on at a lower base voltage than during steady charging, and the base current is shunted to shorten the on time of the transistor 64.

On the other hand, in the toothbrush main body 20, the power supply unit 24 including the output coil 22 forming a part of the inverter circuit 52 of the charging stand 16 described above and the latter half thereof being separated, and the operation of the power supply unit 24. And a display unit 26 for indicating the state to the operator, the toothbrush main body 20 is normally placed on the charging stand 16, and the secondary current of the power supply unit 24 is generated by a minute current sent from the charging stand 16 side in a contactless state. The battery 28 is charged at a low speed for a long time of about 36 hours, and when used, the toothbrush body 20 is taken from the charging stand 16 and the power switch 30 is turned on to supply power from the secondary battery 28 to the motor 32. Then, the rotation of the motor 32 is converted into the vibration of the toothbrush 36 via the transmission mechanism 34.

When the toothbrush body 20 is normally placed on the charging stand 16, the power supply section 24 of the toothbrush body 20 is arranged such that the output coil 22 approaches the arrangement position of the transformer core 40 provided on the charging stand 16 side. By doing so, the charging current can be taken out from the charging stand 16 side in a non-contact state, and a rectifying diode 42 for extracting and picking up a current for a half cycle and an output side of the diode 42 are selected. And a secondary battery 28 that is connected and charged.

The present invention is characterized by the configuration of the display unit 26, which is connected in parallel with the secondary battery 28 and enables a display corresponding to the state of charge by the power supply unit 24. That is, the light emitting diode 44 connected so that the drive current can flow in during the half cycle in which the secondary battery 28 is charged, the resistor 46 for limiting the magnitude of the drive current, and the light emitting diode 44 It is composed of an auxiliary coil 48 for compensating the applied voltage.

While the auxiliary coil 48 has a terminal voltage of the secondary battery 28 of about 1.2 V, the threshold value of the light emitting diode 44 is about 1.8 V, which is higher than that, and thus supplements the shortage. By disposing the output coil 22 close to the output coil 22, it is possible to extract a voltage of, for example, about 1.0 V from the charging stand 16 side within a range where the auxiliary coil 48 alone does not exceed the threshold of the light emitting diode 44. In addition, the winding direction is set so that the voltage is applied to the light emitting diode 44 in the same phase as the output coil 22.

With this configuration, during normal charging operation of the secondary battery 28, the diode 42 interposed in the energizing circuit increases the reverse breakdown voltage of the light emitting diode 44, and the output coil 22 passes through the diode 42. The output voltage of the auxiliary coil 48 compensates for the voltage drop due to the application of the output voltage from the device, and stable light emission is enabled.

On the other hand, because the toothbrush body 20 is not properly installed on the charging stand 16 or the battery is charged while the power switch 30 is on and a large current is taken out, the output voltage from the auxiliary coil 48 drops. If it does, it turns off the light, indicating that normal charging is not performed. It should be noted that such a display is made not only when the power switch 30 is erroneously operated as described above but also when the impedance is lowered as in the case where the load is short-circuited.

[Brief description of drawings]

FIG. 1 is an electric circuit diagram showing a basic configuration of the present invention.

FIG. 2 is a schematic view showing an example in which the present invention is applied to an electric toothbrush.

3 is an electric circuit diagram specifically showing the circuit configuration of FIG.

[Explanation of symbols]

 10 Electric Toothbrush 14 Commercial AC Power Supply 16 Charging Stand 20 Toothbrush Main Body 22 Output Coil 24 Power Supply Section 26 Display Section 28 Secondary Battery 30 Power Switch 32 Motor 42 Rectifying Diode 44 Light Emitting Diode 46 Resistor 48 Auxiliary Coil 52 Inverter Circuit 90 Load

Claims (1)

[Scope of utility model registration request] 1. An output coil (2) of an inverter circuit (52).
Half-wave rectified the voltage extracted from 2) and load (90)
And an auxiliary coil (4) that is connected to the output side of the diode (42) and that generates a voltage in phase with the output coil (22).
8) and a light emitting diode (44) which has a threshold value higher than the terminal voltage of the load (90) and is driven by a voltage obtained by adding output voltages from the diode (42) and the auxiliary coil (48) in the same phase. An operating state display circuit for an inverter circuit, comprising: