JPH0667128B2 - Charging circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention is incorporated in a charging circuit, particularly a small electric device such as an electric razor, and can supply a substantially constant charging current regardless of a large fluctuation of a commercial AC voltage. And what to do.

[Conventional technology]

As a conventional charging circuit of this type, as shown in FIG. 5, a voltage drop amount due to a resistor 81 connected in series with a primary coil 80 is detected, and this value is compared with a set voltage by a comparator 82, and the detected voltage is When the voltage exceeds the set voltage, a reverse bias voltage is applied to the base end of the switching element 83 to forcibly turn off the switching element 83 to regulate the current flowing through the primary coil 80 and control the amount of charge to the secondary battery 84. There has been proposed (for example, JP-A-58-103834).

[Problems to be Solved by the Invention] However, in the above configuration, (a) since the detection unit 85 is on the primary high voltage side, a component having high breakdown voltage is required, and as a result, the cost of the entire circuit increases and the shape is increased. However, it is inevitable that the size will increase. (B) The primary side can be detected and appropriate control can be performed on the premise that the primary side and the output side are in direct proportion, and in order to satisfy such a condition, the primary coil 80 and the output coil 86 It is necessary to strictly set the number of windings and the capacitance between windings. (C) Since the AC voltage of about 30 to 50 Hz flowing on the primary side is directly measured, there is a problem in that the comparator 82 requires parts having excellent frequency characteristics.

The present invention has been made in view of the above problems, and provides a charging circuit in which appropriate control of the charging current amount can be easily performed without using any special parts, and the overall size of the device can be reduced. With the goal.

[Means for solving problems]

As shown in FIG. 1, the charging circuit according to the present invention takes out a detection voltage V ₂ proportional to the average value of the charging voltage supplied from the output coil 23 to the secondary battery 16 from the detection voltage generator 33,
The control unit 34 compares the detected voltage V ₂ with the reference voltage V ₁ and controls the inverter circuit 13 corresponding to the detected voltage V ₂ .

The detection voltage generator 33 includes diodes at both ends of the output coil 23.
An integrating circuit consisting of a resistor 43 and a relatively large-capacity capacitor 44 such as an electrolytic capacitor is connected via 42, and
The voltage is divided by 45 and 46 to take out a predetermined detection voltage V ₂ .

Control unit 34 compares the values of the reference voltages V ₁ and the detection voltage V _2, V ₂
While the value of V is lower than V ₁ , a predetermined control voltage is applied to the base end of the switching element 19 of the inverter circuit 13, and V ₂ becomes V ₁
When it exceeds, the base end can be grounded.

[Action]

In the above configuration, as shown in FIG. 2 (b), while the detection voltage V ₂ is substantially equal to the reference voltage V ₁ , the inverter circuit 13
When a driving voltage is applied to the capacitor 25, the current I ₁ is supplied to the capacitor 25 of the feedback unit 22 through the resistors 77 and 26 as in the conventional case, the voltage of the capacitor 25 rises, and the base current flows to the switching element 19. A collector current flows through the coil 20, and the change in the current is fed back to the feedback coil 24 to rapidly turn on the switching element 19. After turning on, feedback coil
The capacitor 25 is charged in the reverse direction by the output voltage from 24, the base current decreases as the charging proceeds, and the charging voltage of the capacitor 25 becomes a reverse bias, and the switching element 19 is rapidly turned off.

When the switching element 19 is turned off, the energy stored in the primary coil 20 is transferred from the output coil 23 to the diode 29.
Is supplied to the secondary battery 16 through. By the way, secondary battery
The apparent terminal voltage when the charging current flows to 16 is the sum of the theoretical voltage value of the secondary battery 16 and the voltage drop value due to the internal resistance.

On the other hand, the output characteristics of the inverter transformer change so that the output power increases as the input power to the transformer increases. However, as a result of keeping the theoretical voltage value of the secondary battery 16 at a substantially constant value, an increase in output power will appear as an increase in charging current exclusively. As a result, when the input side of the transformer becomes a high voltage and the charging current also greatly increases, the voltage drop value due to the internal resistance of the secondary battery 16 also increases due to this increase in the charging current, and the terminal voltage of the secondary battery 16 The output voltage of the coil 23 also increases. This indicates that the output voltage generated in the output coil 23 in the direction of charging the secondary battery 16 changes in accordance with the fluctuation of the charging current with respect to the secondary battery 16.

Therefore, in the present invention, when the output voltage from the output coil 23 is integrated by the capacitor 44 of the detection voltage generating unit 33 to obtain an average value, this average value is the drive voltage of the inverter circuit 13, Since it increases corresponding to the average value of the charging current supplied to the secondary battery 16, this value is set by the resistor 45.
The voltage is divided at 46 and applied as the detection voltage V ₂ to the control unit 34, and compared with the preset reference voltage V ₁ .

While the detection voltage V ₂ is sufficiently lower than the reference voltage V _{1, the} charging current I ₃ is insufficient compared to the reference value. Therefore, when a voltage is applied to the base end of the switching element 19 as shown in FIG. The amount of charging current to the capacitor 25 at I is increased by I _{2 to} increase the oscillation frequency of the inverter circuit 13, and the pulse rate of the current I ₃ supplied from the output coil 23 to the secondary battery 16 is increased to increase the charging current. Increase the average value.

On the contrary, if the value of the detection voltage V ₂ exceeds the reference voltage V ₁ sufficiently, the second
Figure and ground the base terminal of the switching device 19 as (c) temporarily stops the oscillation of the inverter circuit 13 lowers the average value of the charging current I _3, detecting a decrease in response to the charge current I ₃ is compared the voltage V ₂ and the reference voltage V _1, the stop state until the detection voltage V ₂ to sufficiently drop continues. The stop time becomes longer as the input voltage increases, and therefore the average value of the charging current amount supplied to the secondary battery 16 can be regulated to the set value regardless of the magnitude of the drive voltage applied to the inverter circuit 13. is there.

[Embodiment 1] Next, the present invention will be described based on an example in which it is applied to a small electric device such as an electric razor capable of driving a motor in parallel with charging.

As shown in FIG. 3, the commercial AC voltage 10 input through the power plug is a rectifier circuit equipped with a diode bridge.
After full-wave rectification by 11, it is applied to the charging section 12.
The commercial AC voltage 10 to be input corresponds to a change of 100 to 240 V in consideration of the countries using the upper voltage range of 200 to 240 V and the countries using the lower voltage range of 100 to 120 V.

The charging unit 12 includes an inverter circuit 13 that generates a pulse voltage having a frequency higher than that of the commercial AC voltage 10, and the inverter circuit 13
Detects that the load 14 that applies the pulse voltage generated by the output voltage, the output control circuit 15 that increases or decreases the output from the inverter circuit 13 according to the magnitude of the commercial AC voltage 10, and the secondary battery 16 are fully charged. Then, the full charge control circuit 17 that regulates the output of the inverter circuit 13 and the display circuit 18 that displays the charging status
Composed of and.

The inverter circuit 13 includes, on the collector side of a transistor provided as a switching element 19, a primary coil 20 and a shock absorbing portion 21 that is connected to both ends of the primary coil 20 and absorbs a shock voltage generated when the switching element 19 is off. In addition to being interposed, a feedback section 22 is provided between the base and the emitter, and an output coil 23 is wound on the same iron core as the primary coil 20.

The feedback unit 22 connects one end of a feedback coil 24 wound on the same iron core as the primary coil 20 to the base end of the switching element 19, and connects a capacitor 25 between the other end of the feedback coil 24 and the emitter of the switching element 19. . Further, the voltage stabilized by the constant voltage diode 27 is applied to the connection point between the feedback coil 24 and the capacitor 25 via the resistor 26, and the constant voltage diode is connected to the emitter terminal of the switching element 19.
A constant voltage diode 28 having a Zener voltage lower than that of 27 is connected. Therefore, at the same time when the voltage is applied to the inverter circuit 13,
A stabilizing voltage is generated across the constant voltage diode 27, and the capacitor 25 is charged by this voltage. Capacitor 25
When the voltage across the voltage exceeds the turn-on voltage of the switching element 19, the element 19 turns on and a current starts to flow in the primary coil 20, and a voltage is generated in the feedback coil 24 due to the increase in the current. This voltage rapidly charges the capacitor 25 in the opposite direction from the above through the base and emitter of the switching element 19, and the charging voltage of the capacitor 25 becomes a blocking voltage to turn off the switching element 19. Switching element
After 19 is turned off, the voltage across the constant voltage diode 27 is applied to the capacitor 25 through the resistor 26, the capacitor 25 is charged in the positive direction, and the on / off operation is repeated. Here, the energy stored on the primary coil 20 side at the time of on is selectively taken out by the rectifying diode 29 toward the load 14 connected to the output coil 23 during the off period of the switching element 19.

The load 14 is a secondary battery 16 that is always connected to the output coil 23.
And a motor 31 connected to the output coil 23 via the switch 30. By switching the switch 30, charging can be performed independently, or charging and driving of the motor 31 can be performed in parallel.

The output control circuit 15 compares the reference voltage V ₁ and the voltage generator 32 for driving the circuit, the detection voltage generator 33 for detecting the input voltage, the reference voltage V ₁ and the detection voltage V ₂ , and compares them with each other. The control unit 34 generates a control signal.

The voltage generator 32 outputs a voltage output during a charging period from a quaternary coil 35 wound on the same iron core as the primary coil 20, to a large-capacity capacitor 36, a constant voltage diode 37 and a transistor 3
The voltage is stabilized by 8, and the voltage is further stabilized by the constant voltage diode 39, then divided by the resistors 40 and 41 and applied to the control unit 34 as the reference voltage V ₁ .

The present invention is characterized by the configuration of the detection voltage generator 33. The detection voltage generating unit 33 includes a diode 42 at both ends of the output coil 23.
An integrating circuit consisting of a resistor 43 and a capacitor 44 is connected via, and the voltage across the capacitor 44 is
・ The voltage is divided by 46, and commercial AC voltage 10 is 100 to 2
When it changes within the range of about 40V, the detection voltage V ₂ corresponding to the average value of the charging current amount supplied from the output coil 23 to the secondary battery 16 is taken out in response to the change in the voltage, and the detection voltage V ₂ is extracted. _The control unit 34 controls the output of the inverter circuit 13 corresponding to the vertical fluctuation of ₂ .

The control unit 34 includes two sets of first and second comparators 47 and 48. Both comparators 47, 48 that open collector type is used, the reference voltages V ₁ to the positive input terminal, applying a detection voltage V ₂ to the negative input terminal, the value of V ₂ is sufficiently lower than V ₁ During this period, the output terminals 49 and 50 remain open, but V ₂ is V
_While it is approximately equal to ₁ , it is grounded via a resistor, and when V ₂ exceeds V ₁ sufficiently, output terminals 49 and 50 are directly grounded.

The first comparator 47 connects the output terminal 49 to the connection point between the resistor 26 and the constant voltage diode 27 in the inverter circuit 13, and when the input voltage rises and the detection voltage V ₂ sufficiently exceeds the reference voltage V ₁ ,
The output side of the comparator 47 is turned on and the output terminal 49 is grounded to forcibly stop the oscillation of the inverter circuit 13. When the commercial AC voltage used exceeds the set value, the secondary It prevents an excessive charging current from flowing to the battery 16.

The second comparator 48 has an output terminal 50 through a resistor 51 and a voltage generator.
The switching element 19
Are connected to the base end of each. Therefore, when the detected voltage V ₂ is sufficiently lower than the reference voltage V ₁ , the output terminal 50 of the second comparator 48 is
Is in an open state, the voltage of the voltage generator 32 is applied to the base end of the switching element 19 through the resistors 51 and 52, and the amount of current flowing into the capacitor 25 of the feedback portion 22 during the OFF period of the switching element 19 is increased. Shorten the off period,
The pulse rate of the voltage output from the output coil 23 during charging is increased to prevent the charging current from decreasing when the input voltage is low. When the switch 30 is turned on and the motor 31 is driven, a large current flows through the motor 31 and the amount of current supplied to the detection voltage generator 33 decreases, resulting in a decrease in the detection voltage.
Increase in V ₂ is suppressed, even if high input voltage control unit 34
Performs control at a low voltage, and an excessive current flows through the switching element 19, which may damage the element 19. Therefore, by connecting the output end 50 of the second comparator 48 to the switch 30 via the resistor 53, the voltage output from the voltage generator 32 is divided by the resistors 51 and 53 and applied to the base end of the switching element 19. The voltage value is reduced to suppress the increase in oscillation frequency.

The full-charge control circuit 17 stops the charging of the secondary battery 16 when the secondary battery 16 is fully charged and is in a fully-charged state, and prevents overcharge during IC charging. In this embodiment, a resistor 54 and a diode 55 connected in series at both ends of the secondary battery 16 are connected in parallel to form the reference voltage V ₃ by utilizing the constant voltage action of the diode 55, while the resistor 56
At 57, the voltage V ₄ proportional to the voltage across the secondary battery 16 is taken out and compared with the reference voltage V ₃ . If the generators of both voltages V ₃ and V ₄ are always connected to the secondary battery 16, the secondary battery 16 will be excessively discharged. Therefore, a comparator is used as the switching element 58, the ground side of the diode 55 and the resistor 57 is connected to the output terminal 59 of the comparator 58, and the output voltage of the voltage generator 32 is used as a comparison voltage, whereby an inverter circuit is obtained.
Only when the secondary battery 16 is being charged by the operation of 13 and the control by the full charge control circuit 17 is required, the voltages V ₃ , V ₄
Is applied to the comparator 60.

The comparator 60 has its output terminal 61 connected via a resistor 62 to a voltage generator.
While connected to 32, it is connected to the base end of the transistor 63 via a constant voltage diode 64. The transistor 63 connects the collector end to the base end of the switching element 19 via the low-value resistor 65, and connects the resistor 66 between the base and emitter so that the detection voltage V ₄ is lower than the reference voltage V _3. The output terminal 61 of the comparator 60 is grounded, the transistor 63 maintains the off state, and the inverter circuit 13 performs the normal charging operation, but the detection voltage V ₄ exceeds the reference voltage V ₃ and reaches the full charge state. When this is detected, the output terminal 61 of the comparator 60 is opened and the output voltage from the voltage generator 32 is a constant voltage diode.
The diode 64 is applied to both ends of the resistor 64 and the resistor 66 to make the diode 64 conductive. Then, a base current flows through the transistor 63 to be turned on, the base end of the switching element 19 is grounded, the oscillation of the inverter circuit 13 is stopped, and charging of the secondary battery 16 is stopped to prevent overcharge.

The display circuit 18 has a light emitting diode 67 at both ends of the output coil 23.
And a resistor 68 for limiting the current, a sufficient amount of electric power is taken out from the output coil 23 during the period when the full charge control circuit 17 is not controlled and the light emitting diode is connected.
67 lights up normally, but when the operation period of the full charge control circuit 17 becomes long and the stop period of the inverter circuit 13 becomes long,
The light emitting diode 67 starts blinking and indicates that the battery is fully charged.

[Embodiment 2] FIG. 4 shows a second embodiment of the present invention, which is basically the first embodiment.
The configuration is the same as that of the embodiment, but is different in the following points. That is, in the inverter circuit 13, the switching element 19
The secondary battery 16 is connected to the emitter end of the device to stabilize the potential of the emitter end.

Further, the output from the quaternary coil 35 in the voltage generator 32 is taken out without any particular stabilization process, and is therefore used not for generating a reference voltage but for driving each part.
In this case, the reference voltage V ₁ is taken out from both ends of the diode 69, like the reference voltage V ₃ in the full charge control circuit 17. The secondary battery 16 has a temperature characteristic of about 3 to 4 mV / ° C per cell, but the diode 69 has a forward voltage.
0.6V, the diode 55 is used around 1.5V and with the same temperature characteristics, and the temperature coefficient is adjusted by changing the resistance value of the resistors 70 and 70a to cancel the voltage fluctuation of the secondary battery 16. As a result, the sufficiently stabilized reference voltages V ₁ and V ₃ can be taken out.

By the way, in the charging pressure charging, if charging is performed at a low voltage, there is a possibility that the charging time becomes long or the charging becomes insufficient.
On the other hand, when charging at a high voltage, the charging time is short, but a large current flows at the beginning of charging. Therefore, in the full-charge control circuit 17 in this embodiment, a capacitor 71 is connected to the output terminal 61 of the comparator 60 to form an integrating circuit together with the resistor 62. Therefore, before the full-charge control circuit 17 is controlled, a low voltage is applied. Stable constant voltage charging is performed by the control, and when the control starts, the pulsed ON signal is integrated. In the above-described embodiment, the control that is performed in small steps is delayed every time the detection voltage V ₄ exceeds the reference voltage V _3. By doing so, it is possible to shift to constant voltage charging by a high voltage, and the charging current can be narrowed down in a short time.

Furthermore, the display circuit 18 causes the light emitting diodes 72 and 73 of two colors, such as red and green, to blink for charging display. That is, the emitter end of the first transistor 74 is connected to the positive pole of the secondary battery 16, the base end is connected to the connection point of the capacitor 44 and the resistor 43, and the light emitting diode 72 is interposed at the collector end. At the emitter / collector end of the first transistor 74,
The emitter / base terminal of the second transistor 75 is connected, and the light emitting diode 73 is connected to the collector terminal of the transistor 75.
Further, the cathode sides of both light emitting diodes 72 and 73 are connected to the collector terminal of the third transistor 76, the base terminal of the transistor 76 is connected to the voltage generating section 32, and the base and emitter are connected to the switch 30 to open and close. The switch contact 30a is connected. With such a configuration, when the device is operated when the switch contact 30a is opened, that is, when the motor 31 is stopped, the inverter circuit 13 operates to start charging, and a voltage is output from the voltage generator 32 to cause the transistor
Turn on 76. At this time, the voltage applied from the detection voltage generator 33 to the base terminal of the first transistor 74 is high, so that the transistor 74 remains off. So the secondary battery 16
A base current flows from the positive pole of the second transistor 75 through the base of the second transistor 75, the light emitting diode 72, and the third transistor 76 to turn on the transistor 75 and supply a current to the light emitting diode 73 to turn on the light. .

When the charging of the secondary current 16 becomes dull and approaches a full charge state, the full charge control circuit 17 operates and the oscillating operation of the inverter circuit 13 becomes intermittent. Along with this, the voltage value applied from the detection voltage generator 33 to the base end of the first transistor 74 also gradually decreases, a collector current flows through the first transistor 74, and the light emitting diode 72 starts to light. At the same time, the base-emitter voltage of the second transistor 75 decreases, the base current decreases, the collector current flowing through the light emitting diode 73 also decreases, and the illuminance of the light emitting diode 73 is decreased to indicate that the fully charged state is reached. To do.

When the charging is further advanced, the light emitting diode 73 is completely turned off and only the light emitting diode 72 is turned on to indicate that the charging is completed.

〔The invention's effect〕

As described above, the present invention provides the detection voltage generator on the output coil 23 side.
Since the detection voltage V ₂ corresponding to the average value of the charging current supplied to the secondary battery 16 is provided and the output of the inverter circuit 13 is controlled by the voltage V ₂ , the control unit 34 is provided.
It is possible to easily control the appropriate charging current regardless of the large fluctuation of the commercial AC voltage 10 without requiring special parts considering the withstand voltage or the frequency characteristic, and to reduce the size and weight of the entire circuit. .

Furthermore, by detecting the charging current using the voltage applied to the secondary battery 16, that is, the voltage in the charging direction output from the output coil 23, at the beginning of charging, fluctuations in the ascending direction, such as the charging current, may occur. Even if there is a secondary battery at this point
Since the internal resistance of 16 is still low, the detection voltage V2 and hence the charging current appear lower than the actual value, and therefore, during such a period, the charging is accelerated rather rather and the charging time can be shortened.

On the contrary, at the end of charging, the internal resistance of the secondary battery 16 is high, so if a change in the direction in which the charging current increases is recognized, a voltage higher than the above case is detected, As a result, charging is performed on the safety side, that is, input side control is performed.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing the basic structure of the present invention, and FIG. 2 (a).
3A to 3C are explanatory views showing the operating state of the circuit, FIG. 3 is an electric circuit diagram showing the first embodiment, and FIG. 4 is an electric circuit diagram showing the second embodiment. FIG. 5 is an electric circuit diagram showing a conventional example. 13 ... Inverter circuit, 15 ... Output control circuit, 16 ... Secondary battery, 17 ... Full charge control circuit, 18 ... Display circuit, 19 ... Switching element, 20 ... Primary coil, 22 ... Feedback Section, 23 ... Output coil, 25 ... Capacitor, 33 ... Detection voltage generation section, 34 ... Control section, 47 ... First comparator, 48 ... Second comparator.

Claims (1)

[Claims] 1. A switching element (19) connected in series with a primary coil (20) is regulated to be turned on and off, and when the switching element (19) is turned off, a secondary battery (1) is fed from an output coil (23).
An inverter type charging circuit for supplying a charging current to 6), wherein a diode (42) for selectively extracting a voltage in the charging direction with respect to the secondary battery (16) is provided across the output coil (23). While connecting in series with a capacitor (44) that is charged through the diode (42) and averages the voltage in the charging direction, the voltage across the capacitor (44) is divided to obtain a detection voltage V2, A charging circuit, characterized in that the detection voltage V2 and a predetermined reference voltage V1 are compared by a control section (34) to perform output control of an inverter circuit (13) corresponding to vertical fluctuations of the detection voltage V2.