JPS6022774Y2 - charger - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to an improvement in a charger that can charge a secondary battery such as a nickel-cadmium battery or a lead-acid battery, and can also be charged with a load connected.

There are various methods for charging secondary batteries, including constant voltage, constant current, and intermediate methods.

Regardless of the method, it is important to closely monitor either or both of the terminal voltage and terminal current of the rechargeable battery and control the power supply accordingly to prevent overcharging or undercharging and to protect the battery. This is essential for preserving useful life.

Further, measuring instruments, communication devices, etc. in which such a secondary battery and a charger are housed in one housing are well known.

In many of these, the main power switch 1 is placed on the side of the circuit 3 used after the battery 2, as shown in FIG.
There are many configurations that do not include a power switch between the entire charger and the battery.

This is because it can be confusing to have a power switch installed in two places, one in the DC circuit and one in the commercial power receiving section, and it is also important to design the charger so that it does not cause overcharging. This is because the second switch may be omitted.

Therefore, in such a configuration, as long as the commercial power source 4 is connected to the battery cord, the battery 2 continues to be charged via the rectifier circuit 5 and the charging control circuit 6, and in this state, the switch 1 is turned off. When the battery is turned on, it enters a state of so-called floating (floating charging) operation, and the utilization circuit 3 becomes operational.

However, on the other hand, a diode 7 for backflow prevention is essential between the battery 2 and the charging control circuit 6, and without it, the diode 7 would be indispensable during discharging, that is, when there is no commercial power supply 4, such as during a power outage or when the battery cord is unplugged. In this case, the current flows backward from the battery 2 to the charging control circuit 6, and the battery is consumed.However, the existence of this check diode 7 causes the following problems.

That is, the forward voltage drop of this diode 7 is approximately 0.6 to 0.8 V in the case of a silicon power diode, but it takes a different value depending on the current, temperature, and individual diode.

Therefore, if you want to correctly set the voltage at which charging of the battery should be stopped (or the voltage that can continue to be applied forever), for example, as shown in Figure 2, it is necessary to divide the output voltage of the charging control circuit using a voltage divider. It is essential to detect and perform feedback control.

Normally, it would be desirable to directly observe the potential of the positive terminal of battery 2 (in this case), but if the top end of the voltage divider circuit (or potentiometer) shown in the diagram is directly connected to the positive terminal of battery 2, it may be difficult to observe the potential during charging. If not, you will inevitably end up with the inconvenient result of the battery draining rapidly.

Therefore, in the example of FIG. 2, the dummy diode 7'
The cutoff voltage is set on the assumption that this and the reverse check diode 7 always give approximately the same potential drop.

However, even in this configuration, the current density differs in the case of large forces due to the size of the junction between both diodes, and the charging current itself also varies depending on the state of charge of the battery.
There is no guarantee that the junction temperature of both diodes will match, and therefore there is a risk that extremely inconsistent control of charging termination (i.e., effective charging termination or applied voltage) may be implemented. is large.

The present invention has been made in order to eliminate the above-mentioned drawbacks, and it is an object of the present invention to provide a charging circuit that accurately monitors the terminal voltage.

That is, in the present invention, when charging (including floating operation) is performed, the current flowing through the non-return diode is detected, and in response to this detection, a voltage dividing circuit for monitoring the charging state is connected to the battery, and the voltage dividing circuit is connected to the battery. By closing the field pack loop using the subsequent voltage comparator, the terminal voltage of the battery can be accurately monitored during charging, but no discharge from the battery to the charger occurs when not charging. This is what I did.

FIG. 3 is a product diagram of a charger according to an embodiment of the present invention.

In the figure, as an example, the battery 2 is a gel-type sealed lead-acid battery of approximately 3AH.

The current flowing through the non-return diode 7 varies over a wide range from about IQmA depending on the discharge state of the battery 2, the ambient temperature, whether a load (utilizing circuit) is connected, etc.

Therefore, the voltage across the diode 7 is the voltage across the transistor 21.
is large enough to supply a base current of

Note that the resistor 23 is for protection against excessive current.

Here, this transistor 21 uses a regular collector as an emitter and an emitter as a collector.

This is because, of the two junctions in general-purpose silicon transistors made using planar technology, the normal base-emitter has a significantly lower transmission voltage, and the base-collector, which is always reverse-biased, has a good withstand voltage. In this case, if the circuit is used normally, not only will the reverse check ability of this circuit part not be effectively produced, but depending on the current battery, this transistor will immediately be destroyed.

Generally, if the nominal voltage of the battery 2 is about 4 to 5V, the transistor 21 is a general-purpose small signal silicon planar junction transistor (for example, a 2N 2222A
) may be used in the normal way.

However, in general, if the nominal battery voltage is 6V or higher, it is dangerous to use it incorrectly.

However, since the principle of operation of bipolar junction transistors is essentially guaranteed regardless of normal or reverse use, the distinction between emitter and collector is not an essential problem in this case.

That is, as a result of the current flowing through the check diode 7 being shunted to the transistor 21 and turning it on, the voltage at the upper end of the voltage dividing circuit 25 matches the terminal voltage of the battery 2 to be charged.

By comparing the divided voltage and the reference voltage 27 by the comparison control circuit 29, the accurate charging process of the battery 2 carried out with the stabilized output voltage of the main control circuit 33 from the unregulated voltage 31 can be monitored.No commercial power source is connected. Sometimes, the withstand voltage and leakage current between the diode 7 and the normal base-collector of the transistor 21 are sufficiently good, so that the above-mentioned "reverse check" effect can be fully realized.

Furthermore, even when charging is completed or when the battery 2 is removed intentionally or by accident, or when the protective fuse 37 inserted in series with this battery is blown, the output voltage of the charger remains unchanged. It will not be higher than the value by about 0.7V.

Even in that case, even if the load current is extremely small, the reverse check diode 7 and the normal base-emitter junction of the transistor 21 will realize the same operating state as in the conventional example shown in Figure 2. Only.

FIG. 4 is a block diagram showing a portion of another embodiment of the present invention.

In the figure, the check effect is obtained by only one transistor 41.

That is, in this case, the entire amount of the charging current is used to turn on the transistor 41 without being divided as in the case of FIG.

Such a simplified embodiment is particularly suitable for batteries and loads that do not have much power or capacity, but of course, if a large current transistor of about 10 ampere class or more is used, batteries and loads of the size of the above example can be used. It is quite safe to handle.

In addition, if the battery voltage is less than 4V or 5V, in many cases, the regular base-emitter reverse withstand voltage characteristics will be sufficient to prevent the reverse, especially without using the collector-emitter circuit of the transistor in reverse as described above. It can be effective.

FIG. 5 shows a very specific example of one embodiment of the present invention.

In this case, if Q6 inside the dotted line box does not exist and the three wires that enter there are only connected at one point, then the circuit to the left of here is just a series regulator. , depending on the ZDI voltage (6,19V), it is possible to supply DC power of about 14V (adjustable with RVl) up to the maximum IA (determined by R7).

However, such a state can be equivalently realized if Q6 exists, and a forward current flows between its base and collector (Q6 is used in reverse as described above). Please note that ACIQQ
When there is no V input, all circuits to the left of R7 and C1 are at 0 potential mainly due to the action of R1, so Q
6 completely loses the base current, only the voltage of its collector (original) battery is always applied and nothing else happens, thus achieving the purpose of reverse check mentioned above.

Note that the contents of the box q, indicated by the dotted line, may be replaced with a circuit like the 6th one, and the overall effect is the same as described above, and although this increases the number of parts, it is Since these are more or less expensive, it is practical to reduce the cost of parts.

In any case, adjust RV l in Fig. 5 to set the output voltage to be around 14.0 V under no current or extremely low current (in this case, up to about 10 to 20 mA) load condition. If so, (disconnect S+, remove voltage or F2, and measure and adjust the appropriate resistance as a load) Here, we will use the 12V3AH (nominal) gel type lead acid battery shown as an example, and use the method described above. Thus, a mode of use can be realized in which there is no shortage of charging, and the battery is not damaged due to overcharging even if the power cord is left unplugged.

As has been made clear from the above description, the charger according to the present invention is extremely effective in practical use, since it is possible to accurately set the charge termination voltage filter while ensuring a reverse check effect.

This is particularly noticeable when using a low voltage secondary battery.

[Brief explanation of the drawing]

1 and 2 are block diagrams for explaining a conventional charging circuit, and FIGS. 3 and 4 are block diagrams showing respective embodiments of the present invention. FIG. 5 is a circuit diagram showing an embodiment of the present invention, and FIG. 6 is a circuit diagram showing a partial improvement thereof. The names of the parts are 2: battery to be charged, 7: reverse check diode, 21: transistor, 25: voltage dividing circuit, 27: reference voltage, 29: comparison control circuit, 33: main control circuit.

Claims (2)

[Scope of utility model registration request] (1) In a charger that charges a secondary battery and performs floating operation as necessary, a diode (reverse check diode) 7 is installed between the rechargeable battery 2 and the main control circuit 33 to prevent backflow. A transistor 21 having a forward current passing through the diode, which is a forward current flowing through the diode, is shunted to form a forward current between its base and emitter (base collector). During charging, the collector and emitter of the transistor are turned on by the shunt current, thereby controlling one end of the voltage dividing circuit 25 for monitoring the terminal voltage of the rechargeable battery. It is configured to be connected to the connection point between the diode 7 for preventing backflow and the rechargeable battery 2, so that the terminal voltage of the battery can be correctly observed by the comparator control circuit 29 during charging, while when the battery is not being charged, the 1. A charger characterized in that the charger is configured such that reverse current from the battery to the main control circuit and the voltage divider circuit is blocked. (2) Utility Model Registration In the charger described in Claim No.
The above-mentioned charger is characterized in that it has the function of connecting between the collector and the collector.