JPH08196044A - Charger - Google Patents

Abstract

PURPOSE: To provide a charger with a switching power supply circuit, in which a secondary battery is charged without an influence of ripple, even when the ripple is included in the output of the switching power supply circuit. CONSTITUTION: An AC power voltage is changed into a DC power voltage by a switching power circuit 1. While the output voltage is stabilized to a given level by a constant voltage circuit 2, a secondary battery (E) is charged.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charger for charging a secondary battery such as a lithium battery or a Nick battery.

[0002]

2. Description of the Related Art Conventionally, a secondary battery is charged by, for example, the method shown in FIG. That is, FIG. 22A shows a so-called −ΔV, such as a lithium (Li) ion battery.
Shows a voltage (battery voltage) (V) and a charging current (I) of the secondary battery when charging a secondary battery (which is referred to as a lithium-based battery in this specification) that cannot be detected by FIG. 22B is a battery voltage (V) and a charging current when charging a secondary battery capable of detecting −ΔV (referred to as a nickel-cadmium battery in this specification) such as a Nidd battery. (I) is shown.

FIG. 22 shows a lithium battery.
As shown in (a), first, the battery is charged with a constant current, and after that, the battery voltage reaches a predetermined value (a full-charge voltage or a voltage around it), and then the battery is charged with a constant voltage. Then, when the charging current decreases and almost no current flows, the charging is terminated.

On the other hand, FIG. 2 shows the NiCd battery.
As shown in 2 (b), charging is performed with a constant current.
When a NiCd battery is fully charged, it has a characteristic that the battery voltage that has been rising up to that point decreases by a predetermined value (ΔV). Therefore, by detecting this decrease in battery voltage, that is, -ΔV. Charging is completed.

A DC power supply is required to charge the secondary battery, but the power supply obtained from a certain outlet such as a home is an AC power supply. Therefore, it is necessary to convert the AC power supply into the DC power supply. As a device for performing such conversion, there is, for example, a switching power supply circuit (switching regulator).

FIG. 23 shows an example of the configuration of a conventional switching power supply circuit (charger). AC power is supplied to the two input terminals, one or the other of which is diode D1 or diode D1.
4 cathodes, respectively. Diode D
The anode of No. 1 is connected to the anode of the diode D4, and the connection point is grounded.

The cathode of the diode D1 or D4 is also connected to the anode of the diode D2 or D3, respectively, and the cathode of the diode D2 is connected to the cathode of the diode D3. Therefore, the diodes D1 to D4 form a rectifying circuit 11 that performs so-called bridge rectification.

The connection point between the diodes D2 and D3 is connected to the other end of the capacitor C1 whose one end is grounded and one end of the coil L3. The other end of the coil L3 is connected to the other end of the capacitor C2 whose one end is grounded. Therefore, the capacitors C1 and C2 and the coil L3 are
It constitutes a so-called high-frequency filter.

The connection point between the coil L3 and the capacitor C2 is connected to one end of the primary coil L1 of the transformer 12. The other end of the primary coil L1 is connected to the drain of an FET (N channel MOS FET) 17. In the FET 17, a parasitic diode 17a is formed in the direction in which a current flows from its source to its drain, and its source is grounded.

One end of the secondary coil L2 constituting the transformer 12 is connected to the anode of the diode D6,
The cathode is connected to one end of the capacitor C3. The other end of the capacitor C3 has a secondary coil L2.
Is connected to the other end of. Output terminals are provided at both ends of the capacitor C3.

The detection circuit 14 detects the voltage between the terminals of the capacitor C3, that is, the voltage output from the switching power supply circuit, and outputs the voltage. The time constant circuit 15 gives a predetermined time constant to the output of the detection circuit 14 and outputs it to the control circuit 16. That is, the time constant circuit 15 outputs the output of the detection circuit 14, for example,
The output is delayed by a predetermined time.

The control circuit 16 has the gate of the FET 17
According to the output of the time constant circuit 15, for example, a PWM wave in which the off period (level is at the L level) is changed is applied, whereby the FET 17 is turned on / off.
It is designed to be turned off.

In the switching power supply circuit configured as described above, the input AC current (AC voltage) is
The capacitors C1 and C are rectified by the rectifier circuit 11.
2 and a high frequency filter composed of a coil L3,
It flows through the primary coil L1. When a current flows through the primary coil L1, a current also flows through the secondary coil L2 due to mutual induction, the current is rectified by the diode D6, smoothed by the capacitor C3, and output.

The voltage between the output terminals (the voltage between the terminals of the capacitor C3) is detected by the detection circuit 14, and the time constant circuit 1
5 is supplied to the control circuit 16. In the control circuit 16, the PW in which the off period is changed according to the input voltage
The M wave is supplied to the gate of the FET 17. That is, the control circuit 16 supplies a PWM wave having a longer off period to the gate of the FET 17 as the input voltage is higher.
Therefore, when the voltage between the output terminals is higher than a predetermined voltage, the period in which the FET 17 is off is long, and the period during which no current flows in the primary coil L1 and then the secondary coil L2 is also long. The voltage in between will drop. On the other hand, when the voltage between the output terminals is lower than the predetermined voltage, the period during which the FET 17 is on becomes longer, and
Since the period during which no current flows in the secondary coil L1 and further in the secondary coil L2 becomes short, the voltage between the output terminals rises.

As described above, the input AC voltage (current) is converted into a DC voltage (current) having a predetermined value.

[0016]

By the way, in addition to the switching power supply circuit shown in FIG. 23, for example, instead of the capacitors C1 and C2 and the coil L3, a capacitor having a large capacitance with one end grounded is provided. There are things I did. However, in this case, since the capacitance of the capacitor is large, the diodes D2 and D3 are
The voltage at the connection point with and the current input to the rectifier circuit 11 are as shown in FIG. 24 (a) or FIG. 24 (b), respectively, that is, the voltage waveform and the current waveform are different (voltage and The phase of the current is shifted) and the power factor is deteriorated (however, in this case, the ripple described later is reduced).

On the other hand, in the switching power supply circuit shown in FIG. 23, a capacitor C that constitutes a high frequency filter.
The capacitances of 1 and C2 are usually sufficiently small compared to the capacitances of the above-mentioned capacitors (equal to none of the above-mentioned capacitors), and due to the provision of the time constant circuit 15, diodes D2 and D3 are provided. The voltage at the connection point with and the current input to the rectifier circuit 11 are as shown in FIG.
(B), that is, the voltage waveform and the current waveform can be made similar (the phase shift between the voltage and the current can be reduced), and the power factor can be improved. Can be made.

However, in this case, as shown in FIG. 26, there is a problem that the voltage (current) output from the switching power supply circuit contains ripples.

Considering the case where such a switching power supply circuit (charger) is used for charging a lithium battery, for example, when charging a lithium battery,
As shown in FIG. 22A, it is necessary to perform constant voltage charging when the state is close to full charge.
Since the voltage is equal to (approximately equal to) the full charge voltage, if the charge voltage includes ripples, a voltage higher or lower than the voltage that should be originally applied is applied to the battery, which is not preferable.

Considering a case where the above switching power supply circuit is used for charging a nickel-based battery, for example, FIG.
As shown in (b), it is necessary to perform constant current charging, but if the charging current includes ripples, the battery voltage fluctuates corresponding to the ripples (see FIG. 22).
(Indicated by a dotted line in (b)), -ΔV will be erroneously detected.

The present invention has been made in view of the above circumstances, and enables a secondary battery to be efficiently charged by using a switching power supply circuit without being affected by ripples. To do.

[0022]

The charger of the present invention is a charger for charging a secondary battery, which is a switching power supply circuit for converting an AC power supply into a DC power supply (for example, the switching power supply circuit shown in FIG. 1). 1 or the switching power supply circuit 21 shown in FIG. 7) and a constant voltage circuit that stabilizes the voltage or current output by the switching power supply circuit to a predetermined constant value (for example, the constant voltage circuit 2 shown in FIG. 1). Alternatively, a constant current circuit (for example, the constant current circuit 31 shown in FIG. 14) is provided, and by the output of the constant voltage circuit or the constant current circuit,
A feature is that the secondary battery is charged.

The charger may further include ripple removing means (for example, ripple filter 41 shown in FIGS. 15 and 17) for removing ripples contained in the output of the switching power supply circuit. Further, a short circuit detection unit (for example, the switch control circuit 51 shown in FIG. 19) for detecting whether or not the secondary battery is short circuited can be further provided.

When at least a constant voltage circuit is provided, the secondary battery can be a lithium type battery. The switching power supply circuit outputs a voltage of a predetermined value Va when the output current is less than the predetermined value Ia, and when the output current is equal to or more than the predetermined value Ia, a voltage that decreases as the current increases. It may have a first current-voltage characteristic to output. Further, the switching power supply circuit can change the first voltage-current characteristic according to the characteristic of the secondary battery.

The switching power supply circuit sets a predetermined value smaller than the predetermined value Ia or Va to Ib or Vb, respectively.
In this case, when the output current is less than the predetermined value Ib, the voltage of the predetermined value Vb is output, and when the output current is the predetermined value Ib or more, the voltage that decreases as the current increases is output. It can further have a second current-voltage characteristic that When a voltage detection unit that detects the voltage of the secondary battery (for example, the Zener diode D11 and the resistors R23 and R24 shown in FIG. 19) is further provided, the switching power supply circuit has a voltage of the secondary battery equal to or higher than a predetermined value. When, or less than a predetermined value, it is possible to output a current and a voltage according to the first or second current-voltage characteristic, respectively.

When at least a constant current circuit is provided, the secondary battery can be a nicad battery.

[0027]

In the charger having the above structure, the switching power supply circuit 1 converts the AC power supply into the DC power supply.
The output is the constant voltage circuit 2 or the constant current circuit 3
It is stabilized to a predetermined constant value by 1 and the secondary battery is charged. Therefore, even if the voltage or current output from the switching power supply circuit 1 contains a ripple, the voltage or current is stabilized to a predetermined constant value, and thus charging can be performed without being affected by the ripple. it can.

[0028]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows the configuration of a first embodiment of a charger according to the present invention. This charger is a switching power supply circuit 1
And a constant voltage circuit 2 of, for example, a series system (amplification system) (amplification system). The switching power supply circuit 1 is configured similarly to the switching power supply circuit of FIG. 23 described above. The output of the switching power supply circuit 1 is
The voltage is supplied to the constant voltage circuit 2, and the constant voltage circuit 2 stabilizes the voltage from the switching power supply circuit 1 to a predetermined constant value and applies the voltage to the secondary battery E. There is.

Here, the secondary battery E is a lithium battery. Further, as the constant voltage circuit for stabilizing the voltage from the switching power supply circuit 1 to a predetermined constant value, for example, a shunt regulator or the like can be used in addition to the series type constant voltage circuit as described above. When the shunt regulator is used, the charging efficiency is slightly deteriorated as compared with the case where a series type constant voltage circuit is used, but it is possible to easily cope with a case where the secondary battery E is short-circuited. .

FIG. 2 shows a detailed configuration example of the charger shown in FIG. In the figure, the same reference numerals are given to the portions corresponding to the case in FIG.

The switching power supply circuit 1 is similar to that shown in FIG.
The switching power supply circuit of FIG. Note that, in FIG. 2, the diodes D1 to D4 forming the rectifier circuit 11 are not shown.

The constant voltage circuit 2 comprises a resistor R1, a transistor (NPN transistor) Tr1 and a Zener diode D5. One end or the other end of the resistor R1 is connected to the collector or base of the transistor Tr1. Further, the base of the transistor Tr1 is also connected to the cathode of the Zener diode D5. The anode of the Zener diode D5 is connected to the output terminal of the output terminal of the charger which is connected to the negative terminal of the secondary battery E and the connection point between the secondary coil L2 of the switching power supply circuit 1 and the capacitor C3. It is connected. The emitter of the transistor Tr1 is + of the secondary battery E.
It is connected to the output terminal that is connected to the terminal.

Diode D6 of switching power supply circuit 1
The connection point between the capacitor C3 and the capacitor C3 is connected to the connection point between the collector of the transistor Tr1 and the resistor R1. Therefore, the voltage output from the switching power supply circuit 1 is the collector and emitter of the transistor Tr1 that constitutes the constant voltage circuit 2. Is applied to the secondary battery E via the.

In the charger configured as described above, the switching power supply circuit 1 first converts the AC power supply into the DC power supply in the same manner as described with reference to FIG.
At this time, the voltage at the connection point between the capacitor C1 and the coil L3 or the current input to the rectifier circuit 11 is the same as that in the case shown in FIG. 25 (a) or FIG. 25 (b). As shown in a) or FIG. 3B, the power factor (power factor of the AC power source input to the switching power supply circuit 1) (AC voltage (current) waveform utilization factor (AC waveform utilization factor)) is improved. Can be made.

By the way, in this case, the voltage appearing across the capacitor C3 includes a ripple as shown in FIG. The voltage including the ripple appears also at the output terminal via the transistor Tr1, but when the voltage between the output terminals becomes lower than a predetermined voltage,
Zener diode D5 cathode and transistor Tr
Since the voltage at the connection point with the base of 1 is always constant, the base-emitter voltage of the transistor Tr1 rises. As a result, the base current of the transistor Tr1 increases, and the collector current thereof also increases. The increase in the collector current means that the collector of the transistor Tr1
This is equivalent to a decrease in the resistance between the emitters, so the voltage across the output terminals will increase.

On the other hand, when the voltage between the output terminals rises above a predetermined voltage, contrary to the above case, the transistor Tr
The base-emitter voltage of No. 1 decreases. This allows
Since the base current of the transistor Tr1 decreases, its collector current also decreases. The decrease in the collector current is equivalent to the increase in the resistance between the collector and the emitter of the transistor Tr1. Therefore, the voltage between the output terminals decreases.

As described above, in the constant voltage circuit 2, the voltage output from the switching power supply circuit 1 (the capacitor C3
Voltage between the terminals) is stabilized at a predetermined constant value.

The predetermined constant value is, for example, a value equal to the full charge voltage of the secondary battery E. Therefore, 2
When the full charge voltage of the secondary battery E is 4.2 V, for example,
As shown in FIG. 4, even if the voltage input from the switching power supply circuit 1 to the constant voltage circuit 2 is 4.2 V or more, the constant voltage circuit 2 sets the constant voltage of 4.2 V to the secondary battery E. Will be applied.

Therefore, the secondary battery E, which is a lithium battery, can be charged efficiently and without being affected by ripples. That is, the secondary battery E can be charged efficiently, safely, and completely (sufficiently).

By the way, when the secondary battery E is a lithium battery, as shown in FIG. 5 similar to FIG. 22 (a) described above, first, charging with a constant current is performed, and then with a constant voltage. However, the voltage of the level required at the time of charging with a constant voltage is not required during the period of charging with a constant current.

Therefore, when the secondary battery E is a lithium type battery, a voltage equal to or higher than the full charge voltage is applied to the switching power supply circuit 1 at the time of charging at a constant voltage that does not flow a large current. It is required to output, but it is not required to output such a high charging voltage at the time of charging with a constant current through which a relatively large current flows.

However, according to the switching power supply circuit 1, a constant (almost constant) voltage is output regardless of the magnitude of the output current. Therefore, in this case, FIG.
A loss corresponding to the shaded area will occur.

In order to prevent such a loss, FIG.
As shown in, when the output current is less than the predetermined value Ia, the switching power supply circuit outputs the voltage of the predetermined value Va, and when the output current is the predetermined value Ia or more,
It suffices to have current-voltage characteristics that output a voltage that gradually decreases as the current increases. However, in FIG. 6, the voltage Va is slightly higher than the voltage required for constant voltage charging (in the present embodiment, the full charge voltage is set as described above), and the current Ia is required for constant current charging. The current is smaller than the current.

By determining the current-voltage characteristics as described above according to the characteristics of the secondary battery E, it is possible to reduce or prevent the loss that occurs during constant current charging.

FIG. 7 shows the configuration of the second embodiment of the charger of the present invention. In addition, in the figure, the same reference numerals are given to the portions corresponding to the case in FIG. That is,
This charger has the same configuration as the charger of FIG. 1 except that a switching power supply circuit 21 is provided instead of the switching power supply circuit 1. In this charger,
The above-mentioned loss can be reduced (prevented).

The switching power supply circuit 21 has the current-voltage characteristics shown in FIG. 6, and FIG. 8 shows a detailed configuration example of the switching power supply circuit 21. In the figure, parts corresponding to those in FIG. 2 are designated by the same reference numerals. Further, in the figure, the rectifier circuit 11,
Illustration of the capacitors C1 and C2 and the coil L3 is omitted.

In this switching power supply circuit 21, one end of the resistor R2 is connected to the connection point between the diode D6 and the capacitor C3. The other end of the resistor R2 is connected to one end of the resistor R3, and the other end of the resistor R3 is 2
It is connected to the connection point between the next coil L2 and the capacitor C3. The connection point between the resistors R2 and R3 is connected to the detection circuit 14 and one end of the resistor R4. The other end of the resistor R4 is connected to one end of the capacitor C4, and the other end of the capacitor C4 is connected to a connection point between the secondary coil L2 and the capacitor C3.

The connection point between the resistor R4 and the capacitor C4 is
It is connected to the cathode of the diode D7, and its anode is connected to the other end of the resistor R6 whose one end is connected to the connection point between the secondary coil L2 and the capacitor C3. The other end of the resistor R6 is also connected to one end of the resistor R5, and the other end of the resistor R5 is connected to the collector of the transistor (PNP transistor) Tr2. The emitter of the transistor Tr2 is connected to the connection point between the resistor R2 and the diode D6 and one end of the resistor R7. The other end of the resistor R7 is connected to one end of the resistor R8, and the other end of the resistor R8 is connected to the base of the transistor Tr2.

In the switching power supply circuit 21 configured as described above, when the current flowing through the resistor R7 is small, the potential difference between the emitter and the base of the transistor Tr2 is also small, so that the transistor Tr2 does not turn on. Therefore, in the detection circuit 14, the voltage at the connection point between the resistors R2 and R3, which is a voltage obtained by dividing the voltage appearing across the capacitor C3 by the resistors R2 and R3, that is, the capacitor C
A voltage proportional to the voltage between both ends of 3 is input. Therefore, when the current flowing through the resistor R7 is small, that is, when the charging current is small, the same current and voltage as those of the switching power supply circuit 1 shown in FIG. 2 are output. That is, a constant voltage is output regardless of the output current (however,
In the detection circuit 14, the input voltage is the capacitor C3
Is converted to a voltage between both ends and output to the time constant circuit 15.

On the other hand, when the current flowing through the resistor R7 increases, the potential difference between the emitter and the base of the transistor Tr2 also increases, and the transistor Tr2 turns on. When the transistor Tr2 is turned on, a current flows through the resistor R6 through the emitter and collector of the transistor Tr2 and the resistor R5, and further, the diode D7 and the capacitor C are provided.
Current also flows through 4. As a result, when the capacitor C4 is charged and becomes equal to the voltage at the connection point between the resistors R2 and R3, the voltage at the connection point between the resistors R5 and R6 becomes the diode D7, the resistor R4, and the connection point between the resistors R2 and R3. Is supplied to the detection circuit 14 via. Therefore, a voltage obtained by adding the voltage at the connection point between the resistors R5 and R6 to the voltage at the connection point between the resistors R2 and R3 is applied to the detection circuit 14.

After the transistor Tr2 is turned on, the impedance between the emitter and collector of the transistor Tr2 decreases as the potential difference between the emitter and the base, that is, the current flowing through the resistor R7 increases. The voltage at the connection point of increases as the current flowing through the resistor R7 increases (in this way, at the connection point between the resistors R5 and R6, that is, at the cathode of the diode D7, a voltage corresponding to the current flowing through the resistor R7 is applied. Since it appears, the transistor Tr2,
It can be considered that the resistors R5 to R8 and the diode D7 form a current detection circuit). Therefore,
The relationship between the current flowing through the resistor R7 and the voltage at the connection point between the resistors R5 and R6 is as shown in FIG.

When the voltage at the connection point between the resistors R5 and R6 rises, the voltage applied to the detection circuit 14 also rises. Figure 2
As described in Section 3, since the voltage across the capacitor C3 is controlled to decrease as the voltage applied to the detection circuit 14 increases, the current flowing through the resistor R7, that is, the output of the switching power supply circuit 21. As the current increases, the voltage across the capacitor C3, that is, the output voltage of the switching power supply circuit 21, gradually decreases. Therefore, the relationship between the output current and the output voltage of the switching power supply circuit 21 (current-voltage characteristic of the switching power supply circuit 21) is as shown in FIG.

Here, the current-voltage characteristics of the switching power supply circuit 21 shown in FIG. 10 can be changed as shown by the dotted line in the figure by changing the resistance value of the resistor R7 (resistance). The current flowing through R7 and the voltage at the connection point between the resistors R5 and R6 also change as indicated by the dotted line in FIG. 9).

Therefore, for example, the resistor R7 is a variable resistor, and the battery voltage and the charging current at the time of charging the secondary battery E are detected, and according to the detected value,
By changing the resistance value of the variable resistor, the current-voltage characteristic of the switching power supply circuit 21 can be determined according to the characteristic of the secondary battery E, that is, the switching power supply circuit 21.
In addition, the voltage-current characteristics can be changed according to the characteristics of the secondary battery E, which can prevent loss during constant current charging.

When there is no need to improve the power factor, the switching power supply circuit 21 may be configured without the time constant circuit 15, or a high frequency filter composed of capacitors C1 and C2 and a coil L3 (see FIG. 2). ), A capacitor having a large capacity, one end of which is grounded, may be provided and configured.

Next, when the secondary battery E is a lithium type battery, it is charged with a constant current as described above,
Since the secondary battery E is charged at a constant voltage after approaching full charge, it is not necessary to charge via the constant voltage circuit 2 until the secondary battery E approaches full charge. Rather, it is not preferable to charge the secondary battery E via the constant voltage circuit 2 until the secondary battery E is close to being fully charged, because a loss will occur in the elements constituting the constant voltage circuit 2.

Therefore, FIG. 11 shows an example of the structure of the charger (the structure of the third embodiment of the charger of the present invention) designed to prevent such a loss from occurring. In addition,
In the figure, parts corresponding to those in FIG. 7 are designated by the same reference numerals.

In this charger, the switch SW is provided so that the output of the switching power supply circuit 21 can be supplied to the secondary battery E by bypassing the constant voltage circuit 2.
Is provided in parallel with the constant voltage circuit 2, and this switch SW is used when the voltage at the connection point between the resistors R9 and R10, which will be described later, is greater than a predetermined value (greater than or equal to) or less than or equal to a predetermined value. (When less than), they are designed to turn off or on, respectively. Of the output terminals of the charger,
The terminal connected to the + terminal of the secondary battery E is connected to the cathode of the Zener diode D8, and the anode thereof is connected to one end of the resistor R9. The other end of the resistor R9 is connected to one end of the resistor R10, and the resistor R1
The other end of 0 is connected to the output terminal of the secondary battery E, which is connected to the-terminal, and the voltage at the connection point between the resistors R9 and R10 is supplied to the switch SW. .

For example, now, the full charge voltage of the secondary battery E,
That is, when the voltage output from the constant voltage circuit 2 is set to 4.2 V, the current-voltage characteristic (VI
(Characteristic), as shown in FIG. 12, the voltage when the output current is small is set to a value slightly higher than 4.2V. The Zener voltage of the Zener diode D8 is
It should be 4.2V or less.

Here, as shown in FIG. 12, when the battery voltage is somewhat lower than 4.2V, for example, 4.0V or less, the switch SW is turned on, and when the battery voltage is higher than 4.0V. In addition, the Zener voltage of the Zener diode D8 and the resistance values of the resistors R9 and R10 are set so that the switch SW is turned off. That is, when the battery voltage is 4.0 V or lower or higher than 4.0 V, a voltage such that the switch SW is turned on or off appears at the connection point between the resistors R9 and R10.
Zener voltage of Zener diode D8 and resistance R
The resistance values of 9 and R10 are set.

In the charger configured as described above, when the battery voltage is 4.0 V or less, that is, when the secondary battery E is not close to full charge, the switch SW is turned on as described above. . Therefore, in this case, the output of the switching power supply circuit 21 bypasses the constant voltage circuit 2 and becomes 2
It is supplied to the next battery E. Therefore, it is possible to prevent loss in the constant voltage circuit 2.

On the other hand, charging progresses and the battery voltage is 4.0 V.
When it is larger, that is, when the secondary battery E is close to full charge, the switch SW is turned off as described above.
Therefore, in this case, the output of the switching power supply circuit 21 is supplied to the secondary battery E via the constant voltage circuit 2.
Therefore, the secondary battery E can be charged safely and completely.

In the charger of FIG. 11, the switching power supply circuit 21 is replaced by the switching power supply circuit 1 (FIG. 2).
It is also possible to provide by configuring.

Next, FIG. 13 shows a detailed configuration example of the charger shown in FIG. In the figure, the same reference numerals are given to the portions corresponding to those in FIG.

FET (P-channel MOS FET) 22
Corresponds to the switch SW in FIG. 11, and its drain or source is connected to the input terminal or the output terminal of the constant voltage circuit 2, respectively. The gate of the FET 22 is connected to one end of the resistor R13, and the other end of the resistor R13 is connected to a connection point (input terminal of the constant voltage circuit 2) between the switching power supply circuit 21 and the constant voltage circuit 2.
The connection point between the gate of the FET 22 and the resistor R13 is the resistor R
14 is connected to one end, and the other end is connected to the collector of the transistor (NPN transistor) Tr3. The emitter of the transistor Tr3 is connected to one of the output terminals of the charger, which is connected to the negative terminal of the secondary battery E, and the base is connected to the collector of the transistor (NPN transistor) Tr4. ing.

One ends of the resistors R11 and R12 are connected to the connection point between the base of the transistor Tr3 and the collector of the transistor Tr4. The other end of the resistor R11 is
It is connected to the connection point between the switching power supply circuit 21 and the constant voltage circuit 2, and the other end of the resistor R12 is connected to the transistor T.
It is connected to the emitter of r3.

The emitter of the transistor Tr4 is connected to the emitter of the transistor Tr3, and the base thereof is connected to the connection point of the resistors R9 and R10.

In the charger configured as described above, when the secondary battery E is not in a state close to full charge, the Zener diode D8 does not turn on, or even if it turns on, the connection between the resistors R9 and R10 is established. The voltage at the point is the transistor Tr4
Does not reach a voltage at which the transistor Tr4 can be turned on, and therefore the transistor Tr4 is turned off.

When the transistor Tr4 is off, the voltage at the connection point between the resistors R11 and R12 is the voltage obtained by dividing the output voltage of the switching power supply circuit 21 by the resistors R11 and R12 (the output of the switching power supply circuit 21). If the voltage is v, then R12 × v / (R11 + R12)), so the transistor Tr3 turns on and the resistors R13 and R13
A current will flow through 14.

When a current flows through the resistors R13 and R14, the voltage at the connection point between the resistors R13 and R14 becomes lower than that when no current flows through it (at this low voltage, the FET 22 is turned on). Is done), F
The ET 22 is turned on, and the output of the switching power supply circuit 21 bypasses the constant voltage circuit 2, that is, is supplied to the secondary battery E via the FET 22.

On the other hand, as the charging progresses and the secondary battery E becomes almost fully charged, the Zener diode D8 turns on and the voltage at the connection point between the resistors R9 and R10 turns on the transistor Tr4. When the voltage reaches a level that can be generated, the transistor Tr4 is turned on.

When the transistor Tr4 is turned on, the resistance R
The voltage at the connection point between 11 and R12 is
Since the voltage becomes substantially equal to the voltage of the emitter of the transistor Tr3, the transistor Tr3 is turned off, and no current flows through the resistors R13 and R14.

When no current flows through the resistors R13 and R14, the output voltage of the switching power supply circuit 21 (this voltage is set to a voltage sufficient to turn off the FET 22) is applied to the gate of the FET 22 by the resistor R13. FET 22 is turned off because it is applied via the. Therefore, the output of the switching power supply circuit 21 is supplied to the secondary battery E via the constant voltage circuit 2.

Next, FIG. 14 shows the configuration of a fourth embodiment of the charger of the present invention. In addition, in the figure, the same reference numerals are given to the portions corresponding to the case in FIG. That is, this charger has the same configuration as the charger of FIG. 1 except that the constant current circuit 31 is provided instead of the constant voltage circuit 2.

The constant current circuit 31 stabilizes the current from the switching power supply circuit 1 to a predetermined constant value and applies it to the secondary battery E.

Here, the secondary battery E'is a nickel-cadmium battery.

In the charger constructed as described above,
The current output from the switching power supply circuit 1 is the same as that shown in FIG.
As shown in 6, the ripple is included. However, this current is stabilized to a predetermined constant value by passing through the constant current circuit 31. Therefore, a constant current is supplied to the secondary battery E '.

Therefore, the secondary battery E ', which is a nickel-cadmium battery, can be charged efficiently and without being affected by ripples. That is, the secondary battery E ′ can be charged efficiently, and erroneous detection of −ΔV can be prevented.

Although not shown in FIG. 14 (the same applies to a charger having a constant current circuit 2 to be described later), the charger detects −ΔV of the secondary battery E ′,
A block that stops charging by the charger when ΔV is detected is provided.

By the way, the ripple contained in the output of the switching power supply circuit 1 is further improved by providing the constant voltage circuit 2 or the constant current circuit 31 and further providing a ripple filter dedicated to the ripple removal to configure the charger. It can be effectively removed.

Therefore, FIG. 15 shows an example of the structure of the charger (the structure of the fifth embodiment of the charger of the present invention) in the case where a ripple filter dedicated to the ripple removal is provided. In addition,
In the figure, the parts corresponding to those in FIG.
The same reference numerals are attached. That is, this charger is configured in the same manner as the charger of FIG. 14 except that the ripple filter 41 and the detection circuit 42 are newly provided.

The ripple filter 41 removes the ripple contained in the output of the switching power supply circuit 1. The detection circuit 42 detects the battery voltage, and when the battery voltage is, for example, a voltage slightly lower than the full charge voltage, that is, when the secondary battery E ′ is in a state where −ΔV is generated. , Outputs a control signal for instructing the constant current circuit 31 and the ripple filter 41 to start the operation, and when the battery voltage is lower than the above voltage, that is, the secondary battery E ′ produces −ΔV. When such a state is not present, a control signal for instructing the constant current circuit 31 and the ripple filter 41 to stop the operation is output.

In the charger configured as described above, the output of the switching power supply circuit 1 is the constant current circuit 31.
The secondary battery E ′ is charged via the ripple filter 41 and is charged.

On the other hand, in the detection circuit 42, the battery voltage is detected, and when it is less than (less than) a voltage slightly lower than the full charge voltage, the constant current circuit 31 and the ripple filter 41 are made to stop the operation. A control signal for instructing is supplied. As a result, the constant current circuit 31 and the ripple filter 41 stop operating, so that the output of the switching power supply circuit 1 is directly processed by the secondary battery E ′ without being processed by the constant current circuit 31 and the ripple filter 41. Supplied.

When the battery voltage is lower than a voltage slightly lower than the full-charge voltage, the secondary battery E'is not in a state of producing -ΔV, and therefore it is necessary to remove the ripple included in the output of the switching power supply circuit 1. In addition, since it is not necessary to stabilize the current output from the switching power supply circuit 1 to a predetermined constant value, the constant current circuit 31 and the ripple filter 41 stop operating, so that an extra charge is generated in the charger. It is possible to prevent power consumption. That is, efficient charging can be performed.

Then, when the charging progresses and the detection circuit 42 detects that the battery voltage becomes a voltage slightly lower than the full charge voltage, the constant current circuit 31 and the ripple filter 41 start operating. A control signal is provided to instruct the device to do so. As a result, the constant current circuit 31 and the ripple filter 41 start operating. Therefore, the ripple of the output of the switching power supply circuit 1 is removed by the ripple filter 41, and the output of the switching power supply circuit 1 is stabilized by the constant current circuit 31. Is supplied to E '.

After charging progresses and the battery voltage becomes a voltage slightly lower than the full-charge voltage, it is necessary to detect −ΔV that occurs thereafter, so that ripples are removed in the secondary battery E ′. By supplying a constant current, it is possible to prevent erroneous detection of -ΔV.

Next, FIG. 16 shows the constant current circuit 3 of FIG.
1, a detailed configuration example of the ripple filter 41 and the detection circuit 42 is shown. The collector of the transistor (NPN transistor) Tr6 is connected to one end of the resistor R17, and the connection point is to the switching power supply circuit 1 (the connection point between the diode D6 of the switching power supply circuit 1 (FIG. 2) and the capacitor C3). It is connected.

The other end of the resistor R17 is connected to one end of the capacitor C5 and the base of the transistor Tr6, and the other end of the capacitor C5 is connected to the cathode of the diode D10. The anode of the diode D10 is one of the output terminals of the charger which is connected to the negative terminal of the secondary battery E ′ (and the switching power supply circuit 1).
It is connected to the connection point between the secondary coil L2 and the capacitor C3 (see FIG. 2).

The emitter of the transistor Tr6 is a resistor R
19 and the other end of the resistor R19 is connected to the base of the transistor (NPN transistor) Tr8. The collector of the transistor Tr8 is connected to the connection point between the base of the transistor Tr6 and the resistor R17, and the emitter thereof is connected to one end of the resistor R20. The other end of the resistor R20 is connected to the connection point between the resistor R19 and the emitter of the transistor Tr6.

The connection point between the resistor R20 and the emitter of the transistor Tr8 is connected to one end of the resistor R18 and the cathode of the Zener diode D9. The cathode of the Zener diode D9 is also connected to one of the output terminals of the charger, which is connected to the + terminal of the secondary battery E ′.

The other end of the resistor R18 is connected to a transistor (NP
N transistor) Tr7 is connected to the base, and its emitter is connected to one of the output terminals of the charger, which is connected to the-terminal of the secondary battery E '.
The collector of the transistor Tr7 is connected to the connection point between the base of the transistor Tr8 and the resistor R19 via the resistor R21.

The base of the transistor Tr7 is connected to the resistor R18 as described above, and is also connected to the collector of the transistor (NPN transistor) Tr5 and the connection point of the capacitor C5 and the diode D10. The emitter of the transistor Tr5 is connected to one of the output terminals of the charger which is connected to the-terminal of the secondary battery E '.

The anode of the Zener diode D9 is connected to one end of the resistor R15, and the other end of the resistor R15 is connected to one end of the resistor R16. The other end of the resistor R16 is connected to the negative terminal of the secondary battery E'of the output terminals of the charger.
It is connected to the terminal that is connected to the terminal and the resistance R1.
The connection point between 5 and R16 is connected to the base of the transistor Tr5.

The transistor Tr6, the resistor R17,
The ripple filter 41 is configured by the capacitor C5, the transistor Tr6, Tr8, and the resistor R1.
The constant current circuit 31 is configured by 7, R19, and R20. In addition, Zener diode D9 and resistor R1
5 and R16 form the detection circuit 42.

The constant current circuit 31, which is configured as described above,
In the ripple filter 41 and the detection circuit 42, the voltage output from the switching power supply circuit 1 is the resistance R17.
Since it is applied to the base of the transistor Tr6 via the transistor Tr6, the transistor Tr6 is turned on, so that the current output from the switching power supply circuit 1 is applied to the transistor Tr6.
2 through the collector, emitter, and resistor R20 of
It is supplied to the next battery E ′.

By the way, when the battery voltage is low (when the battery voltage is slightly lower than the full charge voltage), the Zener diode D9 does not turn on, and no current flows through the resistors R15 and R16. . Therefore, since the transistor Tr5 whose base is connected to the connection point between the resistors R15 and R16 does not turn on, the transistor Tr5 is not turned on.
The voltage of the + terminal of the secondary battery E ′ is applied to the base of 7 through the resistor R18, and the transistor Tr7 is turned on.

When the transistor Tr7 is turned on, the potential of the base of the transistor Tr8 is pulled to the potential of the-terminal of the secondary battery E'through the resistor R21, the collector and the emitter of the transistor Tr7, whereby the transistor Tr8 is turned on. Turn off.

Therefore, the current output from the switching power supply circuit 1 is directly supplied to the secondary battery E'through the collector and the emitter of the transistor Tr6 and the resistor R20.

On the other hand, when the battery voltage becomes high (when the battery voltage becomes slightly lower than the full charge voltage), the Zener diode D9 is turned on, and the resistance R15 and the resistance R
An electric current flows through 16. Therefore, the transistor Tr5 is turned on, and the transistor T5 of the capacitor C5
One end of the one connected to r5 is, through the collector and the emitter, one of the output terminals of the charger, which is connected to the-terminal of the secondary battery E ', that is, the switching power supply circuit 1 ( 2) Secondary coil L2 and capacitor C
3 is connected to the connection point.

As a result, the transistor Tr6 and the resistor R
17, and the capacitor C5 operate as a ripple filter, and the ripple included in the output of the switching power supply circuit 1 is removed.

When the transistor Tr5 is turned on,
A current flows through the resistor R18, the collector and the emitter of the transistor Tr5, and the transistor Tr7 is thereby turned off. Then, since a voltage is applied to the base of the transistor Tr8 via the resistor R19,
The transistor Tr8 is turned on, and the transistors Tr6 and T
The r8, the resistors R17, R19, and R20 operate as a constant current circuit.

That is, when the current flowing through the resistor R20 increases, the current flowing between the collector and the emitter of the transistor Tr8 also increases. This means that the transistor T
Since it is equivalent to the reduction of the collector-emitter impedance of r8, the potential of the base of the transistor Tr6 decreases, and therefore the current flowing between the collector and the emitter thereof, that is, the current flowing through the resistor R20 decreases.

On the other hand, when the current flowing through the resistor R20 decreases, the current flowing between the collector and the emitter of the transistor Tr8 also decreases. This means that the transistor T
Since this is equivalent to the increase in the collector-emitter impedance of r8, the potential of the base of the transistor Tr1 rises, and therefore the current flowing between its collector and emitter, that is, the current flowing through the resistor R20 increases.

As described above, the current flowing through the resistor R20 is stabilized at a predetermined constant value.

In FIG. 16 (FIG. 15), the case where the transistor Tr6 is shared by the constant current circuit 31 and the ripple filter 41 and they are so-called integrated is explained. Ripple filter 4
As shown in FIG. 17, 1 and 1 can be configured separately and independently.

Here, FIG. 18 shows the constant current circuit 31, the ripple filter 41, and the detection circuit 42 shown in FIG.
The detailed configuration example of In the figure, the same reference numerals are given to the portions corresponding to those in FIG. That is, this circuit has the same configuration as the circuit of FIG. 16 except that the transistor Tr9 and the resistor R22 are newly provided.

Transistor (NPN transistor) Tr
The collector of 9 is connected to the emitter of the transistor Tr6 and one end of the resistor R22. The other end of the resistor R22 is connected to the base of the transistor Tr9,
The connection point is connected to the collector of the transistor Tr8. And the emitter of the transistor Tr9 is
It is connected to the connection point between the resistors R19 and R20.

Then, the transistor Tr8 or the resistor R
22 is similar to the transistor Tr6 or the resistor R17, respectively, and therefore, in this case, the constant current circuit 3
1 is a transistor Tr8, Tr9, resistors R19, R2
0, and R22.

Note that the ripple filter 41 or the detection circuit 41 is similar to the case in FIG. 16 in that the transistor Tr6, the resistor R17, and the capacitor C5, or the Zener diode D9, the resistors R15, and R16.
And each is configured.

Therefore, even when the circuit having the configuration shown in FIG. 18 is used, the secondary battery E'can be charged efficiently and erroneous detection of -ΔV can be prevented.

Next, FIG. 19 shows the configuration of a sixth embodiment of the charger of the present invention. The part of the charger after the constant voltage circuit 2 constitutes a switching power supply circuit. In the figure, parts corresponding to those in the switching power supply circuit 21 of FIG. 8 are designated by the same reference numerals. Also, in the charger shown in FIG. 19, as in the case of FIG. 8, the switching power supply circuit may be configured without the time constant circuit 15 or the capacitor C1, when the power factor correction is not necessary. C2 and coil L3
Instead of the high-frequency filter (FIG. 2) consisting of, one end may be grounded and a capacitor having a large capacity may be provided.

One end of the resistor r5 is connected to the connection point between the resistor R5 and the collector of the transistor Tr2, and the other end is connected to one end of the resistor r6. The other end of the resistor r6 is connected to one end of the resistor R6 which is not connected to the resistor R5. The connection point between the resistors r5 and r6 is connected to the anode of the diode d7.

One end of the resistor r2 is connected to the connection point between the diode D6 and the capacitor C3, and the other end is
It is connected to one end of the resistor r3. The other end of the resistor r3 is
It is connected to the connection point between the secondary coil L2 and the capacitor C3.

The cathode of the diode d7 is connected to the connection point between the resistors r2 and r3. Further, the connection point between the resistors r2 and r3 is also connected to the terminal b of the switch 52.

The switch 52 is connected to the detection circuit 14, and its terminal a is connected to the connection point between the resistors R2 and R3. Further, the switch 52 is controlled by the switch control circuit 51 to select either the terminal a or the terminal b.

The cathode of the Zener diode D11 is
It is connected to the output terminal of the constant voltage circuit 2, and its anode is connected to one end of the resistor R23. Resistance R23
The other end of the resistor R24 is connected to one end of the resistor R24.
The other end of 24 is connected to one end of the resistor r6, which is not connected to the resistor r5. And resistors R23 and R
The voltage at the connection point with 24 is input to the switch control circuit 51. Therefore, the Zener diode D11, the resistors R34, and R24 detect the voltage corresponding to the battery voltage based on the voltage between the output terminals of the charger and supply the voltage to the switch control circuit 51. . The voltage corresponding to the battery voltage may be detected based on a voltage other than the voltage between the output terminals of the charger.

The switch control circuit 51 is adapted to switch the switch 52 to the terminal a or b side in accordance with the voltage input thereto.

In the charger configured as above, when the terminal a is selected by the switch 52, the voltage at the connection point between the resistors R2 and R3 is detected by the detection circuit via the terminal a and the switch 52. 14 are supplied. Therefore, in this case, the switching power supply circuit is equivalent to being configured similarly to the switching power supply circuit 21 of FIG. 8, and from there, the current-voltage characteristics as shown in FIG. The voltage and current will be output according to the characteristics.

In FIG. 19, the resistor R4 and the capacitor C4, which are provided in FIG. 8, are not provided, and the cathode of the diode D7 is directly connected to the connection point of the resistors R2 and R3. But in this case,
Since the voltage is simply applied to the detection circuit 14 without delay in the time until the capacitor C4 is charged, the current-voltage characteristics (a characteristics) are the same in both cases of FIG. 8 and FIG.

Next, considering the case where the terminal b is selected by the switch 52, the resistors R2 and R
A circuit composed of 3, R5, R6, and a diode D7,
The circuit composed of the resistors r2, r3, r5, r6, and the diode d7 has the same (parallel) configuration, and therefore,
In this case, the resistance value of the resistors R2, R3, R5, or R6 and the resistance value of the resistors r2, r3, r5, or r6 are
If they are the same, from the switching power supply circuit,
Similar to the case where the terminal a is selected by the switch 52, the voltage and current according to the a characteristic are output.

However, here, the resistors R2, R3, R5,
Alternatively, the resistance value of R6 and the resistance values of the resistors r2, r3, r5, or r6 are not the same, and the resistance values of the resistors r2 and r3 correspond to the voltages at their connection points. The voltage is set to be higher than the voltage at the connection point between the resistors R2 and R3, which are resistors, and the resistance r
The resistance values of 5 and r6 are also set so that the voltage at the connection point is higher than the voltage at the connection point between the resistors R5 and R6, which are the corresponding resistances.

Therefore, even if the voltage between the terminals of the capacitor C3 is the same voltage, when the terminal b is selected by the switch 52, a higher voltage is generated than when the terminal a is selected. It will be input to the detection circuit 14. In this case, the control circuit 16 controls the FET 17 so as to reduce the voltage between the terminals of the capacitor C3, so that the switching power supply circuit outputs a lower voltage than when the terminal a is selected. Will be.

That is, assuming that the a characteristic is as shown by the solid line in FIG. 20, for example, when the terminal b is selected, the a characteristic shown by the dotted line in FIG. The voltage and current according to the voltage characteristic (hereinafter, appropriately referred to as b characteristic) are output from the switching power supply circuit.

Therefore, in the switching power supply circuit of FIG. 19, when Ia> Ib and Va> Vb, the output current is less than Ia, the voltage Va is output, and the output current is Ia or more. Sometimes, it has a characteristic that it outputs a voltage that decreases as the current increases, and when the current being output is less than Ib, it outputs voltage Vb, and when the current being output is more than Ib, that current is output. It can be said that it further has ab characteristic that outputs a voltage that becomes smaller with an increase in. Then, whether the characteristic of the switching power supply circuit is the a characteristic or the b characteristic can be selected by switching the switch 52.

The curves representing the a and b characteristics can be changed by, for example, the resistance value of the resistor R7, as in the case described with reference to FIG. Further, for example, since the a characteristic is larger in both voltage and current than the b characteristic, it can be said that charging with a large power is performed according to the a characteristic. It can be said that charging is done in).

As described above, the switch 52 is switched by the switch control circuit 51 according to the voltage input thereto. That is, the switch control circuit 51
Controls the switch 52 so as to select the terminal a or b when the voltage input thereto is equal to or higher than the threshold value S or lower than the predetermined threshold value S.

The voltage input to the switch control circuit 51, that is, the voltage at the connection point between the resistors R23 and R24 has a predetermined battery voltage (the secondary battery E fails (for example, the secondary battery E is short-circuited). If it is not, the battery voltage that is considered to exceed by charging will be equal to or higher than a predetermined threshold value. The voltage and the resistance values of the resistors R34 and R24 are set).

Therefore, when the battery voltage is less than the predetermined value (below), the voltage input to the switch control circuit 51 is below the threshold S (below), so that the switch control circuit 51 connects the switch 52 to the terminal. Select b. Therefore,
In this case, from the switch power supply circuit, b shown in FIG.
The voltage and current according to the characteristics are output. That is,
In this case, charging with low power is performed.

When charging progresses and the battery voltage becomes equal to or higher than a predetermined value (or becomes higher), the voltage input to the switch control circuit 51 becomes a voltage equal to or higher than (greater than) the threshold value S. 51 is a switch 52
To select the terminal a. Therefore, in this case, the switch power supply circuit outputs a voltage and a current according to the a characteristic shown in FIG. That is, in this case, high power charging is performed.

For example, when the secondary battery E is short-circuited, it is not preferable to charge it with a large voltage and current, that is, to charge it with a large electric power, considering the influence on the charger. Therefore, as described above, the battery is charged with a small amount of electric power until the battery voltage reaches a predetermined value. If the secondary battery E is not short-circuited, the battery voltage rises due to charging with a small amount of electric power and becomes a predetermined value or more, and thereafter, normal charging (charging with large electric power) (quick charging) is performed. Will be seen.

If the voltage input to the switch control circuit 51 does not exceed the threshold value S even after a lapse of a predetermined time from the start of charging, the control circuit 1
6 is controlled to stop charging. Two
When the secondary battery E is short-circuited, the battery voltage does not exceed the predetermined value even if charging is performed, and therefore the voltage input to the switch control circuit 51 does not exceed the threshold value S. By stopping the charging, it is possible to prevent the charger from being affected. Therefore, it can be said that the switch control circuit 51 has a block that performs switching control of the switch 52 and a block that detects whether or not the secondary battery E is short-circuited.

As described above, when the secondary battery E is charged, first, the secondary battery E is short-circuited by detecting whether the secondary battery E is short-circuited by charging with a small electric power. If it is, the charging is stopped, and if it is not short-circuited, it is charged with a large amount of power.
It is possible to prevent the charger from being adversely affected by the short circuit.

The block for detecting whether or not the secondary battery E (or secondary battery E ') in the switch control circuit 51 is short-circuited can be provided in the other embodiments described above.

Further, in the above, the ripple filter 41 is provided in the charger having the constant current circuit 31, but the ripple filter 41 may be provided in the charger having the constant voltage circuit 2. Is.

Further, in the above, the charger is constituted by the switching power supply circuit and either the constant voltage circuit 2 or the constant current circuit 31, but as shown in FIG. It is also possible to configure the charger by providing both the constant voltage circuit 2 and the constant current circuit 31.

[0137]

As described above, according to the charger of the present invention,
Charging can be performed efficiently without being adversely affected by ripple.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a first embodiment of a charger of the present invention.

FIG. 2 is a diagram showing a detailed configuration example of the charger of FIG.

FIG. 3 is a waveform diagram showing voltage and current input to the charger of FIG.

FIG. 4 is a diagram showing how a constant voltage is output from a constant voltage circuit 2.

FIG. 5 is a diagram for explaining a loss that occurs during charging.

FIG. 6 is a diagram showing a relationship between a charging current and a charging voltage for preventing loss that occurs during charging.

FIG. 7 is a block diagram showing the configuration of a second embodiment of the charger of the present invention.

8 is a diagram showing a detailed configuration example of the switching power supply circuit 21 of FIG.

9 is a diagram showing a relationship between a current flowing through a resistor R7 in the switching power supply circuit 21 of FIG. 8 and a voltage at a connection point between the resistors R5 and R6.

10 is a diagram showing the relationship between current and voltage output from the switching power supply circuit 21 of FIG.

FIG. 11 is a block diagram showing the configuration of a third embodiment of the charger of the present invention.

FIG. 12 is a diagram for explaining a battery voltage for turning on / off a switch SW of FIG. 11.

13 is a diagram showing a detailed configuration example of the charger shown in FIG.

FIG. 14 is a block diagram showing the configuration of a fourth embodiment of the charger according to the present invention.

FIG. 15 is a block diagram showing the configuration of a fifth embodiment of the charger of the present invention.

16 is a diagram showing a detailed configuration example of the charger shown in FIG.

17 is a block diagram showing another configuration example of the circuit including the constant current circuit 31, the ripple filter 41, and the detection circuit 42 of FIG.

FIG. 18 is a diagram showing a detailed configuration example of the circuit of FIG. 17;

FIG. 19 is a block diagram showing the configuration of a sixth embodiment of the charger according to the present invention.

20 is a diagram showing current-voltage characteristics of a switching power supply circuit that constitutes the charger shown in FIG.

FIG. 21 is a block diagram showing the configuration of a seventh embodiment of the charger according to the present invention.

FIG. 22 is a diagram for explaining a method of charging a secondary battery.

FIG. 23 is a diagram showing an example of the configuration of a conventional charger (switching power supply circuit).

FIG. 24 is a waveform diagram showing the voltage and current input to the low power factor charger.

FIG. 25 is a waveform diagram showing voltage and current input to the charger shown in FIG. 23.

FIG. 26 is a voltage (current) output from the charger of FIG.
It is a waveform diagram showing.

[Explanation of symbols] 1 switching power supply circuit 2 constant voltage circuit 11 rectifier circuit 12 transformer 14 detection circuit 15 time constant circuit 16 control circuit 17 FET 21 switching power supply circuit 22 FET 31 constant current circuit 41 ripple filter 42 detection circuit 51 switch control circuit 52 switch

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Yasuyuki Morita 6-735 Kita-Shinagawa, Shinagawa-ku, Tokyo Sony Corporation

Claims (9)

[Claims] 1. A charger for charging a secondary battery, comprising: a switching power supply circuit for converting an AC power supply into a DC power supply; and a voltage or current output by the switching power supply circuit stabilized to a predetermined constant value. A constant voltage circuit or a constant current circuit for charging the secondary battery by the output of the constant voltage circuit or the constant current circuit. 2. The charger according to claim 1, further comprising ripple removing means for removing a ripple included in an output of the switching power supply circuit. 3. The charger according to claim 1, further comprising short-circuit detection means for detecting whether or not the secondary battery is short-circuited. 4. The charger according to claim 1, further comprising at least the constant voltage circuit, wherein the secondary battery is a lithium battery. 5. The switching power supply circuit outputs a voltage of a predetermined value Va when the output current is less than the predetermined value Ia, and outputs a voltage of the current when the output current is equal to or more than the predetermined value Ia. The battery charger according to claim 4, wherein the battery charger has a first current-voltage characteristic that outputs a voltage that decreases with an increase. 6. The charger according to claim 5, wherein the switching power supply circuit changes the first voltage-current characteristic according to the characteristic of the secondary battery. 7. The switching power supply circuit sets a predetermined value smaller than the predetermined value Ia or Va to Ib.
Alternatively, in the case of Vb, when the output current is less than the predetermined value Ib, the voltage of the predetermined value Vb is output, and when the output current is the predetermined value Ib or more, the output current becomes smaller as the current increases. Second current to output voltage −
The charger according to claim 5, further comprising a voltage characteristic. 8. A voltage detection means for detecting the voltage of the secondary battery is further provided, and the switching power supply circuit is configured such that when the voltage of the secondary battery is equal to or higher than a predetermined value or lower than the predetermined value,
The charger according to claim 7, wherein the charger outputs a current and a voltage according to the first or second current-voltage characteristic. 9. The charger according to claim 1, further comprising at least the constant current circuit, wherein the secondary battery is a nicad battery.