JPS63316643A - Charging circuit - Google Patents

Abstract

PURPOSE:To facilitate the combination of a battery temperature detection method and a battery voltage detection method by making the voltage level of a charging control switching element gate variable through the output of a battery temperature detection sensor circuit. CONSTITUTION:In a battery charger 1, an AC power is rectified to charge a battery B via a thyristor 5. The sensor circuit 10 of a battery pack 2 is supplied with a constant current IS and a voltage drop VS varies by turning ON and OFF of a thermostat Th1. In this manner, an input voltage to the second pin of an IC6 varies and an output from the eighth pin of said IC6 changes in proportion thereto. Said voltage is compared with a battery voltage so that the thyristor 5 is turned OFF. This circuit enables combining a battery temperature detection method with a battery voltage detection method to control them.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a battery charging circuit that controls charging by detecting voltage and temperature rises during charging of a battery to be charged.

(Prior art) As methods for detecting the state of charge of a battery to be charged and controlling charging, there are mainly methods for detecting the temperature of the battery and methods for detecting the battery voltage. Although various detection methods have been proposed, both of them have advantages and disadvantages, and there are points that need improvement.

For example, the battery voltage detection method detects the battery voltage during charging and controls charging.Since charging is cut off at a predetermined voltage just before the battery voltage rise curve reaches its peak, there is no overcharging state and the battery It has the advantage that there is little burden on the battery, and there is little difference in charging time depending on the ambient temperature. If the battery is short-circuited, the charging cut-off voltage will not be reached, so there will be no charging power.

In comparison, the battery temperature detection method controls charging when the temperature of the battery during charging reaches a predetermined temperature, and because charging is cut in the overcharging region where the temperature rise is large, the charging capacity is large and more than one battery is charged. It has advantages such as being able to cut off charging even if the battery is short-circuited, and reducing the burden on the battery because it does not charge a high-temperature battery after overdischarging, but it is easily affected by the ambient temperature, and when placed in a low-temperature atmosphere. Charging with this method had the disadvantage that it took time to reach the operating temperature of the thermoswitch, and the overcharged state continued for a long time.

In terms of actual battery use, the battery voltage detection method is easier to use because it starts charging even an empty battery immediately after over-discharging and the charging time is almost constant, but battery life is prioritized. If so, the battery temperature detection method is more advantageous.

Therefore, it is desired to realize a charging control method that combines the advantages of the two charging control methods described above.

(Objective of the Invention) The present invention detects the temperature of the battery to control charging, and also detects the voltage of the battery in a low-temperature atmosphere to control charging, thereby reducing the burden on the battery due to overcharging. The purpose is to provide a charging circuit that can.

(Structure of the Invention) The present invention includes a series circuit of a charged battery connected to a power source and a switching element, a sensor circuit that detects the temperature of the battery, and an operation signal of the sensor circuit that turns on and off the switching element. A charging circuit comprising a gate control circuit for controlling the charging circuit, wherein the sensor circuit has a series branch of a thermoswitch and a resistor, and the thermoswitch is non-conducting when it is on and conductive when it is off, in parallel with the series branch. It has a bypass path, and the voltage level of the gate control circuit is varied in response to the operation of the sensor circuit.

With this configuration, the control circuit can
Alternatively, the switching element is switched from on to off as the battery temperature rises, and charging control is performed by detecting battery voltage and temperature.

(Embodiment) FIG. 1 shows the configuration of an embodiment of the charging circuit of the present invention. In the figure, 1 is a charger, 2 is a battery pack with a battery to be charged B, and the charger 1 is a step-down transformer T with a primary coil L1 connected to commercial power supply connection terminals 3 and 4, A full-wave rectifier circuit consisting of diodes D1 and D2 connected to both ends of the secondary coil L2 of the step-down transformer T, a positive terminal P of the output of this full-wave rectifier circuit, and a negative terminal connected to the center tap of the step-down transformer T. It has a series circuit of a thyristor (switching element) 5 for charge control connected to PN and a battery to be charged B, and a charge control IC 6, and is connected to the gate 7 of the thyristor 5 to control the thyristor 5 on and off. It is composed of a gate control circuit 8, an LED lighting circuit 9 that lights up to indicate when charging, and the like.

The battery pack 2 also includes a battery B and a thermoswitch Th installed between the plurality of batteries B to detect the temperature of the battery B.
1 and a resistor R1, including a sensor circuit 10 having a series branch circuit. In addition to the series branch, this sensor circuit 10 includes a resistor R1.

It consists of R2, R3, and a smoothing capacitor C, and one terminal S of the sensor circuit is connected to the second pin of IC6 via a resistor R4, and the other terminal is connected to the negative terminal PN. moreover,
This sensor circuit 10 has transistors Q1. It has a bypass path 11 consisting of Q2. The thermoswitch Thj is on (conducting) at normal temperature and turns off (opening) when it reaches a predetermined temperature, and the bypass circuit 11 is non-conductive when the thermoswitch Th1 is on and conductive when it is off, and is latched when it is off. It is configured as follows.

The gate control circuit 8 includes a diode D3 in addition to the IC6.
．． It is composed of resistors R5, R9, and R7, and the gate 7 is connected to the eighth gate of IC6 through the series connection of diode D3 and resistor R5.
connected to the number bin.

Further, from the second pin of the IC6, a sensor circuit terminal S
A constant current Is is configured to flow toward the terminal, and the voltage v8 at the eighth pin is a constant times the voltage v2 at the second pin.

Then, the battery voltage is V, the gate voltage of thyristor 5 is V, the forward voltage of diode D3 is T, and the voltage across resistor R5 is V, then F'
R5 When charging, that is, when thyristor 5 is on, +V +
V (1) There is a relationship of v8>VB+VGT F R5 , and when charging is stopped, that is, when Cyrisk 5 is off, there is a relationship of +V +V (2) v8<VB+vGT F R5 .

Therefore, in both the battery voltage detection method and the battery temperature detection method, charging control becomes possible by reversing the voltage level of v8 during charging and when charging is stopped between the two states. The voltage of v8 is set to be a constant multiple of v2 by resistor voltage division of resistors R6 and R7, and the voltage of v2 is the sum of the voltage drop of resistor R4 and the sensor circuit voltage Vs. Therefore, since a constant current is flowing through the sensor circuit terminal S by the IC 6 as described above, v2 is determined by the value of Vs.

The sensor circuit voltage Vs changes depending on whether the thermoswitch TJ of the sensor circuit 10 is turned on or off. As a result, v2 changes, and in conjunction with this, v8 changes, which turns on and off the thyristor 5 and performs charging control. That is, at normal temperature, the thermoswitch Th
i is on and Vs is large, so v8 is as described in (1) above.
The value satisfies the equation, and the thyristor 5 is on and in a charging state, but when the temperature exceeds a predetermined temperature, the thermoswitch Th1 turns off, and Vs is approximately a small value of the base-emitter voltage of the transistor Q2 in the bypass path 11, as will be described later. Therefore, v8 becomes a value that satisfies the above equation (2), and the thyristor 5 is turned off and charging is stopped. Here, once the bypass path 11 becomes conductive, a latch function is activated, so that even if the battery temperature decreases and the thermoswitch Th1 returns again, the charging stopped state is maintained.

The battery B is preferably resistant to overcharging and exhibits a large temperature rise during overcharging.

Also, the resistor R3 of the sensor circuit 10 is the transistor Q1, Q
This is the second protective resistor.

To explain the charging control operation in more detail below, in the case of normal temperature, from the second pin of IC6 to the sensor circuit terminal S-
(-) of battery B via resistor R1-thermo switch Th1
) terminal flows into the constant current I, and the sensor circuit voltage Vs is I (
The constant voltage becomes J + R3). The resistor R1 is set in advance so that the equation (1) is satisfied at Vs at this time, and the thyristor 5 is in the on state and charging is performed.

When battery B becomes overcharged, the battery temperature rises, and therefore the thermoswitch Th provided adjacent to battery B
The temperature of i also rises, and when the temperature reaches a predetermined temperature, the thermoswitch Th1 turns off (opens), and the sensor circuit current Is flows through the base and emitter of the run risk Q2 (-). ) flows to the terminal. At this time, the transistor Q1 is also turned off to form a bypass path, and the sensor circuit voltage Vs is changed to the transistor Q2 (or Ql
) becomes only the base-emitter voltage, Vs decreases, and therefore, the above-mentioned equation (2) comes to hold, and charging is stopped. Once the transition = 9-star Q1. When Q2 is turned on, the base current of transistor Q2 is supplied by the collector current of transistor Q1, so even if the battery temperature drops and thermoswitch Th1
Even if the battery returns to normal, recharging will not start. To release this latch function, turn off the power or remove battery pack 2 from charger 1, and then remove transistor Q1. All you have to do is turn off Q2 once.

FIG. 2 shows the charging characteristics at each temperature (0° C., 20° C., and 40° C.), that is, the relationship between charging time, battery voltage, and battery temperature. In the same figure, the straight line V is v8-(V 10V
10V) battery level, direct GT F R
5 Line TT is the operating temperature of thermoswitch Thi, solid line curve A
When the battery voltage detection method and the battery temperature detection method of the present invention are used together, the broken line curve shows the case where only the conventional battery temperature detection method is used, and points a, b, c, and d indicate the charging cut time points.

As can be seen from the figure, when only the conventional battery voltage detection method is used, the overcharging time becomes long at low temperatures. That is,
The charging voltage tends to be higher at low temperatures. At low temperatures (e.g. 0°C), the battery temperature during overcharging may rise and may not reach or reach the operating temperature of thermoswitch Th1. However, it takes a long time and the overcharge state tends to be prolonged, which tends to increase the stress on the battery.

On the other hand, in the present invention, since charging is also cut by the battery voltage detection method, overcharging at low temperatures is prevented.

In other words, as mentioned above, the voltage of v8 is set at a low temperature (for example, 0
If the voltage is set to almost the charging voltage at 0C), charging will be stopped when v8-VB+v+V+V is reached.

FIG. 3 shows a specific example of the LED lighting circuit 9.

In the charging state, the transistor Q3 at the 6th pin of IC6.
Q4 is in an off state, and current is applied to the LED through resistor R9, causing the LED to light up and display the charging state.

When charging stops, transistor Q3. Q4 is turned on, power is no longer applied to the LED, the LED goes out, and current flows from the second pin of IC6 to transistor Q4 through resistor RIG and diode D4. This current causes the sensor circuit current Is from the second pin
decreases, and thus the sensor circuit voltage Vs decreases, resulting in a decrease in v8. As a result, a hysteresis effect can be applied to v8, and once the charging is stopped, it is maintained.

4 and 5 show the external appearance and internal structure of a charging device equipped with the charging circuit of the present invention.

The charger 1 has a built-in transformer T and a charging circuit module 101, and also has a coupling recess 1 into which the battery pack 2 is inserted.
02, and a contact spring 103 for circuit connection is provided in the four parts 102.

On the other hand, the battery pack 2 is provided with a contact fitting 104 that comes into contact with the contact spring 103 when inserted.

Charging is started by inserting the battery pack 2 into the charger 1, and an LED is displayed during charging. Note that 105 is a power plug.

(Effects of the Invention) As described above, according to the present invention, the voltage level of the gate of the switching element for charge control is varied by the output of the sensor circuit that operates by detecting the battery temperature, and the switching element is turned on.
Since it is designed to perform off control, it is possible to use both the battery temperature detection method and the battery voltage detection method, and therefore,
In particular, overcharging at low temperatures can be prevented and the burden on the battery can be reduced. Furthermore, while the charging time at low temperatures becomes too long when using only the battery temperature detection method, this time can be shortened by using the battery voltage detection method in combination. In addition, since a battery temperature detection method is also used, among multiple batteries,
This has the effect of enabling charging control even if some of the batteries are short-circuited.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram of an embodiment of the charging circuit of the present invention, Fig. 2 is a charging control characteristic diagram, Fig. 3 is a circuit diagram of an LED lighting circuit section, and Fig. 4 is a circuit diagram of an embodiment of the charging circuit of the present invention. An external view of the charging device, and FIG. 5 is a sectional view showing its internal structure. B...Battery, 5...Sirisk (switching element) 16...IC, 7...Gate, 8...Gate control circuit, 10...Sensor circuit, 11...Bypass path, Th1 ...Thermoswitch, R1...Resistance, Ql
, Q2...transistor. Patent applicant Matsushita Electric Works Co., Ltd. Representative Patent attorney Etsushi Koharu
Patent Attorney Long 1) Positive Patent Attorney Yasuo Itaya -14=

Claims (1)

[Claims] 1. A series circuit of a charged battery and a switching element connected to a power source, and a sensor circuit that detects the temperature of the battery;
A charging circuit includes a gate control circuit that controls on and off the switching element according to an operation signal of the sensor circuit, wherein the sensor circuit has a series branch circuit of a thermoswitch and a resistor, and a gate control circuit that is parallel to the series branch circuit. The charging circuit has a bypass path which is non-conductive when the thermoswitch is on and conductive when it is off, and the voltage level of the gate control circuit is varied in response to the operation of the sensor circuit. 2. The charging circuit according to claim 1, wherein the bypass path is connected by two transistors so as to be latched when the thermoswitch is turned off.