JPH0446531A - Initial drop voltage preventing circuit for lithium battery - Google Patents

Abstract

PURPOSE:To supply a stable voltage to a battery load device M by providing relays for turning ON, OFF connection between a lithium battery and a load device using the battery as a power source in response to the presence, absence of a charging current. CONSTITUTION:A contact S1 of a relay Ry is inserted between a battery E and a device M, and normally ON. When a switch S0 is closed, a charging current flows to a capacitor C through the relay Ry. Thus, while the capacitor C is charged, the contact S1 is turned OFF, and a transient drop voltage of a lithium battery E is not supplied to the device M. When the charging of the capacitor C is ended and hence a protective film in the battery E is vanished, the contact S1 is turned ON, and a stable voltage of the battery E is supplied to the device M.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a power supply circuit for equipment using a lithium battery as a voltage supply source (hereinafter also referred to as battery load equipment), and particularly to a circuit that prevents application of an initial transient drop voltage of a lithium battery to the equipment. Note that in the following figures, the same reference numerals indicate the same or corresponding parts.

[Conventional technology]

The reason why lithium batteries can be stored for a long time is the protective film formed on the lithium negative electrode. When a lithium battery starts discharging, this protective film becomes the internal resistance of the battery, and when the current density exceeds a certain level, the internal resistance of the battery increases. A voltage drop occurs and the terminal voltage of the battery decreases. Furthermore, this protective film has the property of disappearing as the battery discharges. Therefore, immediately after starting discharge, the terminal voltage of the battery becomes lower than the nominal voltage, and approaches the original voltage as the discharge time increases. FIG. 4 shows a configuration example of a power supply circuit of a device (battery load device) using a lithium battery as a voltage supply source. In the figure, E is a lithium battery, SO is a power switch, M is a battery load device, and IC2 is a voltage monitoring circuit that monitors the voltage of the lithium battery E and turns on and off the operation of the device M. In this way, equipment M that uses lithium battery E as a voltage supply source may malfunction due to the transient voltage drop of lithium battery E immediately after the power switch SO is turned on. A circuit IC2 is provided, and after turning on the power switch SO, a RESET signal is given to the device M until the voltage of the battery E is stabilized, and this device M
operation has been stopped.

[Problem to be solved by the invention]

However, when dealing with the initial voltage drop of a lithium battery as shown in Figure 4, the current consumption of the voltage monitoring circuit IC2 itself cannot be ignored, and if the current consumption of the voltage monitoring circuit IC2 is reduced, it will take more time for the voltage to stabilize. There was a drawback that it took a while. Therefore, the object of this invention is to reduce the current consumption of lithium batteries and quickly provide a stable voltage to battery load equipment.
An object of the present invention is to provide an initial drop voltage blocking circuit for a lithium battery that can be supplied to a lithium battery.

[Means for Solving the Problems] In order to solve the above problems, the circuit of the present invention uses a lithium battery (E
A capacitor (such as C) that is charged by a capacitor (such as C), and a relay that is activated by the charging current of this capacitor, and a relay that operates depending on the presence or absence of the charging current, the lithium battery and a load device that uses this lithium battery as a power source ( Let J be equipped with a relay (Ry) that turns off and on the connection (via relay contact S1, etc.) between [Function] A capacitor is provided that is charged when a lithium battery is inserted, and in order to prevent the transient voltage drop of the lithium battery from being transmitted to the battery load equipment, the capacitor is operated by the charging current of the capacitor, and the battery is connected only for the duration of this current. Install a relay or a circuit with the same function as a relay to disconnect the load equipment. That is, the capacitor is charged when a lithium battery is inserted. At this time, the charged battery becomes a discharge current for the battery, and the protective film inside the battery is destroyed by this discharge current. In addition, a relay connected in series with the capacitor or a circuit with the same function as a relay prevents the voltage of the lithium battery from being supplied to the device when charging current is flowing to the capacitor, and also prevents charging. When the battery is finished, that is, when the battery voltage has stabilized, it works to supply battery voltage to the device.

【Example】

The present invention will be explained in detail below using FIGS. 1 to 3. FIG. 1 is a conceptual circuit diagram of the present invention, and FIG. 2 shows a circuit in which the relay in FIG. 1 is replaced with a circuit having a similar function. FIG. 3 is a specific embodiment of FIG. 1. In the conceptual circuit diagram of FIG. 1, a series circuit of a relay (coil) Ry and a capacitor C is connected between the negative electrode of the lithium battery E and the load side terminal of the switch SO. Further, the contact Sl of the relay Ry is inserted between the battery E and the device M, and is normally turned on. When switch SO is closed, charging current flows to capacitor C through relay Ry. Therefore, while the capacitor C is being charged, the contact Sl of the relay Ry is turned OFF, and the transient drop voltage of the battery E is not supplied to the device M. When the capacitor C has finished charging and the protective film inside the lithium battery E has disappeared, the relay contact S1 turns ON and the device M
A stable voltage from the lithium battery E is supplied to the lithium battery E. In FIG. 2, a portion corresponding to the relay in FIG. 1 is constructed with a normally ON optical MO3-FET relay PC. Diode D conducts current when capacitor C is discharged. The resistor R1 is a resistor for limiting the charging current of the capacitor C. FIG. 3 shows the circuit of FIG. 1 in a concrete form. In FIG. 3, after the power switch So is turned on, until the charging of the capacitor C is completed, the relay Ry is energized and its contact s1 is OFF, as in FIG. 1, so the transistor Tr remains OFF. , voltage stabilization circuit ICI,
Smoothing capacitors CI, C2, and device M are also not supplied with battery voltage. Next, when the charging of the capacitor C is completed and the +J relay Ry is deenergized and its contact S1 is turned on, the voltage stabilizing circuit IC
I is smoothing capacitor C1, C2 and transistor Tr
At the same time, the device starts operating and starts supplying the constant voltage generated from the lithium battery E to the device M. Here, voltage stabilization circuit IC
I sets the terminal voltage of the battery E to a required voltage, and the transistor Tr and the resistor R2 are components for current boosting and function to assist the circuit IC1.

【Effect of the invention】

According to the present invention, a capacitor C is charged by a lithium battery E turned on via a power switch SO, and a relay is operated by a charging current of the capacitor C, and the relay operates according to the presence or absence of the charging current. Since the lithium battery initial drop voltage blocking circuit is equipped with a relay RY that turns off and on the connection between the lithium battery E and the load device M using the lithium battery E as a power source via the relay contact S1, If the capacitor C has a large capacity, an extremely large current will flow when the capacitor C is charged, so that the protective film can be destroyed more quickly than in the past. Also, relay R
y.The energy used to drive the PC is stored in the capacitor, so it is not wasted and is used to power the device M.
It is effectively used for backup purposes.

[Brief explanation of drawings]

Figure 1 is a conceptual circuit diagram of this invention, Figure 2 is a diagram in which the relay in Figure 1 is replaced with a circuit that functions similarly, and Figure 3 shows a specific embodiment of Figure 1. 4 are conventional circuit diagrams corresponding to FIG. 1. E: Lithium battery, SO: Power switch, Ry: Relay (coil), Sl: Relay contact, PC: Optical MO3FET
Relay, C: Capacitor, M: Equipment, R1, R2: Resistor, Tr: Transistor, CI. C2: Smoothing capacitor, ICI: Voltage stabilization circuit.

Claims (1)

[Scope of Claims] 1) A capacitor that is charged by an inserted lithium battery, and a relay that is activated by the charging current of this capacitor, and which connects the lithium battery and this lithium battery depending on whether or not there is the charging current. An initial drop voltage blocking circuit for a lithium battery, characterized by comprising a relay that turns off and turns on the connection between the load device and the load device using the battery as a power source.