JPH0217833A - Charger - Google Patents

Abstract

PURPOSE:To prevent malfunction caused by output-drop of a power circuit by keeping the output of a charged current detection section constant. CONSTITUTION:AC power supply (E) is rectified by a diode bridge(DB), converting into AC by an inverter 1, and it is rectified and smoothed by an output section 2 to charge to a secondary battery (B). In the case of completion of charging, when a trickle charge is conducted, an output holding circuit 8 keeping the output of a charged current detection section 3 constant is constituted of a transistor Q2 and resistance R6. During the trickle charge, when output of a non-inversion amplifier 5 increases more than set output in the case of completion of charging, the charged current detection section 3 can't operate normally. However, in this invention, the output-drop of the non-inversion amplifier 5 is controlled by an operation of the output circuit holding circuit 8, and malfunction is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application 1] The present invention relates to a charging device for charging a secondary battery.

[Prior Art 1] The circuit configuration of a conventional charging device is shown in FIG. This charging device converts a rectified output obtained by rectifying an AC power source E by a diode bridge DB into an AC output by an inverter 1, rectifies and smoothes the output of the inverter 1 by an output section 2, and then
It supplies a charging current to the secondary battery B, and includes a charging current detection section 3 that detects the charging current with a charging current detection resistor R0 connected in series with the secondary battery B and feeds and drops the charging current to the control circuit 4. There is. In this embodiment, a passive type is used as the inverter 1, and one large winding #i of the oscillation transformer T1 is used.
The control circuit 4 turns on and off the switching element Q0 connected to the output of the diode Pritsuno DB in series with L,
The resonant circuit between the primary winding L of the oscillation transformer T and the capacitor C1 resonates to obtain an AC output at the secondary winding L2. Note that this charging device uses a MOSFET as the switching element Q0. The control circuit 4 of this inverter 1 includes three large turns #a L of an oscillation transformer T.
The voltage induced in 3 is connected to diode D1 and capacitor C.
It operates using a rectified and smoothed voltage as a power source.

The output section 2 is a diode D that rectifies the alternating current voltage induced in the secondary winding L2 of the oscillation transformer T. 8. D02 and
It consists of a 1,000-square-meter coil L0 and a capacitor C0 that smooth this rectified output. The charging current detection section 3
The voltage across a resistor R0 inserted in series with the next battery B is amplified by a non-inverting amplifier circuit 5 consisting of an operational amplifier OP and a resistor LR2, and the amplified output is output to the control circuit 4 via a photocoupler PC1. , oscillation transformer T, is operated using a voltage induced in the fourth order, i#iL, which is the seven live windings of oscillation transformer T, rectified and smoothed by diode D2 and capacitor C1 as a power source. This charging current detecting section 3 is provided with a trickle charging circuit 9 which uses the output of the charging current detecting section 3 as an output for trickling charging the secondary battery B when charging is completed.

This trickle charging circuit 9 includes a timer circuit 6 in which a charging time is set, a transistor Q2 and a resistor R that increases the amplification factor of the non-inverting amplifier circuit 5 with the output when the timer circuit 6 reaches the charging time. , , R3. The amplification gear switching circuit 10 is
The transistor Q is turned on by the output of the timer circuit 6 when charging is completed, a resistor R6 is connected in parallel to the resistor R4, and the amplification factor of the non-inverting amplifier circuit 5 which is at the time of charging is set as This is to increase the amplification factor of the inverting amplification factor circuit 5.

The operation of the control circuit 4 of the inverter 1 to which the output of the charging current detection g3 is fed back will be described. This control circuit 4 operates to shorten the on period of the switching element Q0 when the charging current increases during charging and the output of the non-inverting amplifier circuit 5 rises. In this way, the switching element Q. By shortening the on-period of the inverter 1, the voltage induced in the secondary winding L2, which is the output of the inverter 1, is lowered, and the charging current of the secondary battery B is lowered. Conversely, when the charging current decreases, the control circuit 4 increases the charging current by lengthening the on period of the switching element Q0.

That is, this control circuit 4 has a function of keeping the charging current constant according to the feedback signal from the charging current detection section 3.

Charging is carried out in this manner, and when the charging time set in the timer circuit 6 has elapsed (charging is completed), the transistor Q of the amplification factor switching circuit 10 is turned on, so that the The amplified output of the inverting amplifier circuit 5 increases.

At this time, the charging current is controlled to be small by the control circuit 4 in the same way as when the charging current increases as described above, but in this case, the charging current becomes a line current that does not overcharge the secondary battery B. That's how it is. In other words, the trickle charging circuit 9 controls the amplified output of the non-inverting amplifier circuit 5 to be an output for trickle charging the secondary battery B, so that the secondary battery B is not overcharged when charging is completed. It is.

By the way, the charging current of secondary battery B after this charging is completed is:
In order to prevent deterioration of the secondary battery B, it is necessary to set it as small as possible. However, if this charging current is made too small, the output voltage that can be taken out from the quaternary winding L4 will be lowered, and therefore the charging current detection section 3 will not function normally. Therefore, in this conventional charging device, the amplification factor of the non-inverting amplifier circuit 5 is set ( Resistor R3
~R6) was set. However, operational amplifier OP1
, the photocoupler PC1, and the characteristics of the resistors R1 to R3 change depending on the surrounding environment such as temperature. Therefore, if the characteristics of the operational amplifier OP1 etc. change so that the charging current at the time of completion of charging becomes smaller, the charging current detecting section 3 will not work normally.

[Problem to be Solved by the Invention 1] The present invention has been made in view of the above-mentioned points, and its purpose is to prevent the charging current detection unit from operating normally due to changes in the characteristics of the components at the time of completion of charging. Our goal is to provide a charging device that does not cause any problems.

Means for Solving the Problems 1 In order to achieve the above object, the present invention provides the charging current detecting section with an output holding circuit that keeps the output of the charging current detecting section constant when charging is completed.

(Function) As described above, the present invention provides an output holding circuit in the photoelectric current detecting section that keeps the output of the charging current detecting section constant when charging is completed, so that the output holding circuit can be maintained even if the characteristics of the parts change. The output of the charging current detection section can be kept constant when charging is completed, thereby preventing the output voltage of the power supply circuit from dropping to a voltage at which the charging current detection section will not operate properly when charging is completed. This is what I did.

(Example) FIG. 1 shows an example of the present invention. The basic groove structure of this embodiment is the same as that of the conventional circuit shown in FIG.

Which series circuit is connected to the output of power supply circuit 7 and photocoupler PC1?
This differs from the above-described embodiment in that the output of the non-inverting amplifier circuit 5 is connected to the light-emitting diode LD through the transistor Q2 and applied to the light-emitting diode LD. *9, When charging is complete, the charging device will charge secondary battery B.
An output holding circuit 8 that keeps the output of the charging current detection section 3 constant during trickle charging is composed of the transistor Q2 and the resistor R6. Note that the transistor Q2 operates as an emitter follower, and the resistance value of the resistor R6 is set so that the output of the transistor Q2 is saturated with the output of the non-inverting amplifier circuit 5 when charging is completed. Therefore, when the output voltage of the power supply circuit 7 fluctuates upon completion of charging, the current flowing through the transistor Q2 also fluctuates accordingly. In addition, since the resistor R3 in this embodiment only needs to allow the base current to flow through the transistor Q2,
This is larger than the resistance value of the conventional resistor R2.

A case will be described in which the characteristics of the operational amplifier OP1, the photocoupler PC1, and the resistors R1 to R1 occur when charging is completed. In the following explanation, a case will be explained in which the charging current detection unit 3 cannot operate normally due to the output of the power supply circuit 7 due to fluctuations in one or both of the resistors R1 to R57) and the operational amplifier OPI.This charging current detection Part 3
A state in which the output voltage of the power supply circuit 7 becomes so low that it cannot operate normally occurs when the output of the non-inverting amplifier circuit 5 increases beyond the set output at the time of completion of charging. However, in this embodiment, since the output holding circuit 8 is provided, the output of the non-inverting amplifier circuit 5 does not increase, and the charging current detecting section 3
The output voltage of the power supply circuit 7 does not drop until the output voltage of the power supply circuit 7 stops operating normally.In other words, when the output of the non-inverting amplifier circuit 5 increases and the output voltage of the power supply circuit 7 decreases, the current flowing through the transistor Q2 decreases, so an increase in the output of the non-inverting amplifier circuit 5 can be suppressed. Therefore, the output voltage of the power supply circuit 7 does not become so small that the charging current detection section 3 cannot operate normally.

Conversely, when the output of the non-inverting amplifier circuit 5 decreases, the output of the power supply circuit 7 increases.
The output of the secondary battery B is increased by the output holding circuit 8, which operates to prevent the charging current from becoming larger than the trickle current that overcharges the secondary battery B. ! By holding the output voltage of the power supply circuit 8 constant at the time of completion of charging with the output holding circuit 8,
Even if the characteristics of the operational amplifier OP or the like vary, the charging current detection section 3 can be operated normally. Therefore, the charging current after charging is completed can be set as small as possible, and the setting range of the charging current for trickle charging tz of 2*electron aB can also be widened.

In addition, as mentioned above, when charging is completed, transistor Q2
Since it is in a saturated state, the output current of the transistor Q2 will fluctuate depending on the fluctuation of the output voltage of the power supply circuit 7, but when the output voltage of the power supply circuit 7 is sufficiently high as during charging, the transistor Since Q2 is designed not to saturate, the current corresponding to the output of the non-inverting amplifier circuit 5 flows to the light emitting diode LD of the photocoupler PC1.
When charging the secondary battery B, it operates in the same manner as the conventional example. In other words, this output holding circuit 8 does not have any adverse effect during charging. Furthermore, even when the characteristics of the Hoshikabura PC1 fluctuate, the output voltage of the power supply circuit 7 can be kept constant to prevent the charging current detection unit 3 from operating normally.

[Effect of the Invention 1] As described above, in the present invention, the charging current detecting section is provided with an output holding circuit that keeps the output of the charging current detecting section constant when charging is completed. The holding circuit can keep the output of the charging current detection section constant when charging is completed, which has the effect of preventing the output voltage of the power supply circuit from dropping to a voltage that would prevent the charging current detection section from operating properly when charging is completed. There are 8

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of an embodiment of the present invention, and FIG. 2 is a circuit diagram of a conventional example. 1 is an inverter, 2 is an output section, 3 is a charging current detection section, 4
is a control circuit, 5 is a non-inverting amplifier circuit, 7 is a power supply circuit, 8 is an output holding circuit, 9 is a trickle charging circuit, B is a secondary battery, Q,
is a switching element, T1 is an oscillation transformer, L is a primary winding, L2 is a secondary winding, L is a quaternary winding, and Ro is a resistor. Agent Patent Attorney Ishi 1) Ai Shichi

Claims (1)

[Claims] (1) An inverter in which the primary winding of an oscillation transformer and a switching element are connected in series to a DC power supply, and the switching element is turned on and off to obtain an AC output to the secondary winding of the oscillation transformer; It is equipped with an output section that charges the secondary battery with a voltage obtained by rectifying and smoothing the AC output, and a power supply circuit that obtains power from the voltage induced in the flyback winding of the oscillation transformer, and a resistor inserted in series with the secondary battery. Consists of a charging current detection section that detects the charging current and amplifies and outputs the voltage across this resistor, turns the switching element on and off, and keeps the charging current constant according to the output of the charging current detection section. The inverter includes a trickle charging circuit that makes the output of the charging current detection section to trickle charge the secondary battery when charging is completed, and an output that keeps the output of the charging current detection section constant when charging is completed. A charging device characterized in that a holding circuit is provided in the charging current detection section.