JPS5845266B2 - Jiyuden Cairo - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a charging circuit, which prevents charging when a battery to be charged is short-circuited, and also stops circuit operation when the charging circuit temperature rises significantly due to use in an abnormal state. The purpose of this invention is to provide a charging circuit that operates safely.

The conventional charging circuit is configured as shown in Fig. 2, and when the battery to be charged (hereinafter simply referred to as the battery) B is in a short-circuit state due to an internal short-circuit state, a connection state of a low resistance load, etc., the charge control circuit S' If the oscillation circuit by transistor Q1 continues to oscillate and charge continues, and the circuit block in which the circuit components shown in Figure 2 are arranged on a single printed circuit board is used in an insulated state, it may become overheated. The drawback was that the plastic case that housed the circuit block was deformed.

Also, even if battery B is not short-circuited, a relatively light load (a load in which the charging control circuit does not work and the discharge current value is about 1/3 to 2/3 of the charging current value when fully charged) Even when the charging circuit block is connected to battery B and charging is continued in an adiabatic state, the charging circuit block becomes overheated and the housing plastic case is deformed.

The present invention has been made in view of this point, and will be explained in detail below with reference to Examples.

In FIG. 1, ■ is an AC power supply, and R2 is a fuse resistor, which burns out and becomes disconnected when an abnormality occurs in the circuit and the input current value exceeds a certain value.

Capacitor C2 and coil L4 constitute a low-pass filter for noise prevention.

Dl is a diode that provides a pulsating DC voltage to the charging circuit, and the control circuit S inside the broken line is for charging control. It detects the voltage between the terminals of battery B, and when it exceeds a certain level, transistor Q3 becomes conductive. , the bias current of transistor Q0 is bypassed to stop the oscillation of the oscillation circuit by transistor Q1, and the charging current of battery B.\ is stopped.

Furthermore, in addition to the charging control function, the transistor Q3 is made conductive to stop charging when battery B is short-circuited or the circuit overheats.

DZ is a constant voltage element that provides a reference voltage.

A diode D9 is connected between the pace emitter of the transistor Q4.
, Dlo are connected to both ends of the resistor R6.

When battery B is short-circuited and the voltage drop across resistor R6 exceeds a certain level, transistor Q4 is turned on.

When transistor Q4 turns on, transistor Q5 turns on and the base voltage of transistor Q2 becomes almost O, so transistor Q2 turns off and transistor Q
3 turns on.

Therefore, when battery B is short-circuited, transistor Q1
The bias current is bypassed to the transistor Q3, and the oscillation of the oscillation circuit by the transistor Q1 is stopped.

Furthermore, when charging is continued in an adiabatic state and the charging circuit block becomes overheated, the forward drop voltage of diodes D3 to D8 decreases, so the voltage across resistor R6 increases and transistors Q4 and Q5 become conductive. As a result, the base potential of transistor Q2 decreases, so transistor Q2 is turned off and transistor Q3 is turned off, as in the case of short circuit described above.
is turned on, and the oscillation circuit formed by the transistor Q1 stops oscillating.

Here, the term "insulated state" refers to a state in which the heat generated from the charging circuit block is difficult to escape to the outside, such as when an electric shaver with a built-in charging circuit is covered with a futon, or in other words, a state in which heat dissipation is poor. If charging continues for a long time in such an adiabatic state, heat will accumulate in the charging circuit block, and the charging circuit block will become overheated.

On the other hand, when the battery is not overheated and the battery is not short-circuited, transistor Q4 is cut off and functions in the same way as control circuit S' in FIG.

Transistor Q, produces a positive feedback effect when transistor Q4 conducts, and transistor Q4. This ensures the continuity of Q5 itself.

Diode D6. D7. Transistor Q from the voltage of D8
The value obtained by subtracting the voltage between the base and emitter of 2 is compared with the voltage of battery B, and the voltage of battery B is low (however, it is not as low as in a short circuit state, usually 0.65 to 1.3μ) when charging is not completed. , and when there is no overheating, transistor Q2 is conductive, transistor Q3 is turned off, transistor Q1 is normally biased, oscillation occurs, and charging is performed.

Diodes D3, D4, D are diode D6,
This is to set the temperature dependence of the end-of-charge voltage to an appropriate value in conjunction with the temperature dependence of D7, D8 and the base-emitter of the transistor Q2, as well as of the constant voltage element DZ.

In addition to detecting short circuit current as described above, the resistor R6 also connects the diodes D6, D7, . The end-of-charge voltage is adjusted by adjusting the forward voltage drop value of D8.

Transistor Q3 performs switching in response to changes in conductivity between the collector and emitter of transistor Q2,
This serves as a bypass for the base bias current of transistor Q1.

The resistors R3 and R provide bias to the transistor Q1, and the capacitor C3 passes an alternating current portion of the base drive current of the transistor Q1 to reduce switching loss of the transistor Q1.

Ll, L2, and L3 are windings of an oscillation transformer wound around the same magnetic core, and are a primary winding, an output winding, and a feedback winding, respectively, and together with the transistor Q1, form a ringing choke type transistor converter.

R1 and C1 absorb the spike voltage generated in the primary winding L1 during switching of the transistor Q1, and Ro
is a negative feedback resistor for preventing variations in the charging current due to variations in the characteristics of the transistor Q1, especially hFE.

D2 is the output rectifying diode of the converter, and PL indicates the oscillation state of the transistor Q1 to indicate charging (lit), charging completion (off or flickering), and abnormality (battery short circuit or very low resistance load connection) ( (lights off) function.

Now, if battery B is short-circuited, a constant voltage is applied between the terminals of constant voltage element DZ every half cycle of commercial power supply (2).

The voltage is connected to resistor R6, diodes D3, D4, D5
and a resistor R6 with a voltage divided by the base-emitter voltage of transistor Q2 (because battery B is short-circuited, the emitter of transistor Q2 and the cathode of diode D8 are at the same potential).
The value across the terminals of is greater than or equal to the voltage required to cause a forward current to flow through the emitter of transistor Q4 and diode D9I), transistor Q4 becomes conductive and transistor Q5
is also conductive, transistor Q2 is turned off, transistor Q3 is turned on, transistor Q1 is not given the bias necessary for starting, and oscillation does not occur, so battery B is not charged.

Next, the voltage of battery B is 1.1 to 1.2 V (even if the battery is in an over-discharged state, it will be 1.1 to 1.2 V as time elapses in an unloaded state).
1 to 1.2■), battery voltage V8=
The voltage drop across the resistor R6 is reduced by an amount corresponding to 1.1 to 1.2■, and the transistor Q4 can conduct.
Transistor Q5 is also cut off, resulting in the same state as shown in Figure 2, and charging continues until battery voltage 8 reaches the end-of-charge voltage, at which point transistor Q2 is turned off and Q3 is turned on. Since the bias current of transistor Q1 is shunted to transistor Q3, charging stops at least from the next half cycle when the end-of-charge voltage is reached.
Operates as a normal charging circuit.

Next, if battery B is not short-circuited and a light load is connected, charging will continue until the battery voltage reaches the end-of-charge voltage, but the current discharged through the load will depend on the output from the inverter. It will be replenished.

In the embodiment of the present invention shown in FIG.
A diode Dg + is connected between the base of 4 and the resistor R6.
Dlo are connected in series, and when the temperature rises abnormally, the forward voltage drop of the diode D9 and Dlo decreases.

Furthermore, when the temperature rises abnormally, as mentioned above, the voltage drop in the forward direction of the diodes D3 to D8 decreases, causing the resistor R6 to
Since the voltage across the diode D0. increases, when the temperature rises abnormally, the diode D0. D1o forward drop voltage drop and resistance R
As the voltage across the diode D0.6 increases, the voltage between the base and emitter of the transistor Q4 increases. By adding D1o, abnormal temperature rise can be easily detected.

As mentioned above, the present invention provides a circuit in which a plurality of diodes are connected in series in the same direction, and a first and second diode string is connected in series in the same direction. A reference voltage greater than the sum is applied in the forward direction through the current detection resistor, and across the first diode string,
A battery to be charged is connected between the pace emitters of the transistors, and the battery voltage is lower than the voltage across the first diode array, and the voltage difference between the battery voltage and the voltage across the first diode array causes the battery to be charged. In a charging circuit in which the transistor is turned on when a forward current flows between the pace emitters of the transistor, and the charging current is cut off when the transistor is turned off, the voltage across the current detection resistor is set to a predetermined standard. Since the device is provided with a means for shorting both ends of the first diode array when the voltage exceeds the value, when the battery to be charged becomes internally short-circuited or short-circuited due to the connection state of a low resistance load, etc. The voltage drop across the current sensing resistor increases, shorting across the first diode string, turning off the transistor and cutting off the charging current, preventing the device from overheating and improving safety. It has advantages.

In addition, when the ambient temperature rises abnormally, the forward voltage drop across the first and second diode arrays decreases, increasing the voltage drop across the voltage detection resistor and causing a charging problem, similar to the case of a battery short circuit described above. The current is cut off and the same effect as a temperature fuse can be obtained.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of an embodiment of the present invention, and FIG. 2 is a circuit diagram of a conventional example. B is the battery to be charged, D3 to D8 are diodes, Q2+Q5
is a transistor, DZ is a constant voltage element, and R6 is a resistor.

Claims (1)

[Claims] 1. A reference voltage greater than the sum of the 1@ direction voltage drops of each diode is applied to a circuit in which first and second diode strings are connected in series in the same direction, each consisting of a plurality of diodes connected in series in the same direction. A current is applied in the forward direction through a current detection resistor, and a battery to be charged is connected between both ends of the first diode string through the pace emitters of the transistors, and the battery voltage is compared to the voltage across the first diode string. The transistor is turned on when the voltage is low and a forward current flows between the pace emitters of the transistor due to the voltage difference between the battery voltage and the voltage across the first diode string, and charging is performed when the transistor is off. A charging circuit configured to cut off current, characterized in that a means is provided to short-circuit both ends of a first diode string when a voltage across a current detection resistor exceeds a predetermined reference value.