Storage battery overdischarge protection circuit with low power consumption

Abstract

The utility model relates to the technical field of storage battery overdischarge protection, discloses a low-power-consumption storage battery overdischarge protection circuit, and aims to solve the problems of complex structure and high power consumption of an existing overdischarge protection circuit. According to the scheme, the voltage detection circuit mainly comprises a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor, a sixth resistor, a first transistor, a second transistor, a third transistor and a voltage detection chip, and the first resistor, the second resistor and the third resistor are used for sampling the voltage of the storage battery and inputting the sampled voltage to the voltage detection chip. The first transistor is used for achieving on-off control between the power supply input end of the voltage detection chip and the power supply output end of the storage battery, and the second transistor and the third transistor are used for achieving on-off control between the power supply output end of the storage battery and the load power supply end. The power consumption of the over-discharge protection circuit is reduced, the over-discharge protection effect of the storage battery is improved, and the over-discharge protection circuit is suitable for various storage batteries.

Description

Technical Field

[0001] The present application relates to the technical field of battery over-discharge protection, and in particular to a low-power battery over-discharge protection circuit. Background Art

[0002] Batteries are widely used in electronic devices, especially outdoor electronic devices in remote areas, which generally use solar panels and batteries to power the system. During sunny days, solar panels power the system loads and charge the batteries, while batteries power the system loads at night and on cloudy days. During long periods of rainy weather, the battery cannot be effectively charged, and it is always in a discharging state to power the system loads. The battery voltage continues to decrease, causing over-discharge. Over-discharge can cause irreversible damage to the battery, so it is necessary to provide a protection circuit that can prevent the battery from over-discharging, and when the battery voltage is lower than the specified threshold, the battery power supply to the load is promptly shut down to protect the battery.

[0003] There are many types of protection circuits on the market. The basic method is to detect the battery voltage and cut off the power supply of the battery to the load when the battery voltage is lower than the voltage threshold. However, the circuit structure is complicated, and when the battery cannot be charged for a long time, although the protection circuit cuts off the power supply to the system load, the protection circuit needs to continue to work, and the protection circuit will still consume more battery power, thereby aggravating the over-discharge of the battery. Therefore, a low-power battery over-discharge protection circuit is needed. Utility Model Content

[0004] The present application aims to solve the problems of complex structure and high power consumption of over-discharge protection circuits in the prior art, and proposes a low-power over-discharge protection circuit for a battery.

[0005] The technical solution adopted by this application to solve the above technical problems is:

[0006] A low-power consumption battery over-discharge protection circuit comprises a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor, a sixth resistor, a first transistor, a second transistor, a third transistor and a voltage detection chip, wherein the first resistor, the second resistor and the third resistor are sequentially connected in series between the power supply output terminal of the battery and the earth, the common end of the first resistor and the second resistor is connected to the down-threshold input terminal of the voltage detection chip, the common end of the second resistor and the third resistor is connected to the up-threshold input terminal of the voltage detection chip, the fourth resistor and the fifth resistor are sequentially connected in series between the power supply output terminal of the battery and the earth, the common end of the fourth resistor and the fifth resistor is connected to the control end of the first transistor, the first end of the first transistor is connected to the power supply input terminal of the voltage detection chip, the second end of the first transistor is connected to the power supply output terminal of the battery, the control end of the second transistor is connected to the output terminal of the voltage detection chip, the first end of the second transistor is grounded, the second end of the second transistor is connected to the control end of the third transistor, and is connected to the power supply output terminal of the battery through the sixth resistor, the first end of the third transistor is connected to the power supply output terminal of the battery, and the second end of the third transistor is connected to the load power supply terminal.

[0007] Furthermore, the first transistor is an NPN transistor, the control end of the first transistor is the base of the NPN transistor, the first end of the first transistor is the emitter of the NPN transistor, and the second end of the first transistor is the collector of the NPN transistor.

[0008] Furthermore, the second transistor is an N-type MOS tube, the control end of the second transistor is the gate of the N-type MOS tube, the first end of the second transistor is the source of the N-type MOS tube, and the second end of the second transistor is the drain of the N-type MOS tube.

[0009] Furthermore, the third transistor is a P-type MOS tube, the control end of the third transistor is the gate of the P-type MOS tube, the first end of the third transistor is the source of the P-type MOS tube, and the second end of the third transistor is the drain of the P-type MOS tube.

[0010] Furthermore, the model of the voltage detection chip is CN302.

[0011] The beneficial effects of the present application are as follows: the low-power battery over-discharge protection circuit provided by the present application can timely shut down the battery's power supply to the load and the detection circuit to protect the battery when the battery voltage is lower than the specified threshold value. The circuit structure is simple, the circuit consumes small current, and the power consumption is low. It is particularly suitable for occasions with small battery capacity. Through parameter adjustment, it can be widely used in various voltage levels and various types of battery over-discharge protection. In addition, the circuit has the functions of detecting the upper threshold value and the lower threshold value, and the formation of a hysteresis circuit can prevent the problem of repeated on-off of the system load power supply. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 A schematic diagram of a low-power battery over-discharge protection circuit provided in an embodiment of the present application;

[0013] Description of reference numerals:

[0014] VBAT-battery power supply output terminal; VIN-load power supply terminal; R1-first resistor; R2-second resistor; R3-third resistor; R4-fourth resistor; R5-fifth resistor; R6-sixth resistor; Q1-first transistor; Q2-second transistor; Q3-third transistor; U1-voltage detection chip; VCC-power supply input terminal of voltage detection chip; FTH-downward threshold input terminal of voltage detection chip; RTH-upward threshold input terminal of voltage detection chip; LBO#-output terminal of voltage detection chip. DETAILED DESCRIPTION

[0015] In order to enable those skilled in the art to better understand the solution of the present application, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application.

[0016] The technical solution of the embodiment of the present application is applicable to application scenarios where over-discharge protection of the battery is required. Since the over-discharge protection circuit of the current battery basically adopts the method of detecting the battery voltage and cutting off the power supply of the battery to the load when the battery voltage is lower than the voltage threshold. This circuit structure is complex, and the voltage detection circuit needs to work all the time, which consumes a lot of power. In addition, because the battery voltage may fluctuate above and below the voltage threshold under the action of solar energy, the battery voltage may cause the power supply of the battery to the load to be repeatedly turned on and off, and the stability is poor.

[0017] Based on this, the technical solution of the present application is proposed. In an embodiment of the present application, a battery over-discharge protection circuit includes: a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor, a sixth resistor, a first transistor, a second transistor, a third transistor and a voltage detection chip. The first resistor, the second resistor and the third resistor are sequentially connected in series between the power supply output end of the battery and the ground. The common end of the first resistor and the second resistor is connected to the down-threshold input end of the voltage detection chip. The common end of the second resistor and the third resistor is connected to the up-threshold input end of the voltage detection chip. The fourth resistor and the fifth resistor are sequentially connected in series between the power supply output end of the battery and the ground. The common end of the fourth resistor and the fifth resistor is connected to the control end of the first transistor. The first end of the first transistor is connected to the power supply input end of the voltage detection chip, the second end of the first transistor is connected to the power supply output end of the battery, the control end of the second transistor is connected to the output end of the voltage detection chip, the first end of the second transistor is grounded, the second end of the second transistor is connected to the control end of the third transistor, and is connected to the power supply output end of the battery through the sixth resistor. The first end of the third transistor is connected to the power supply output end of the battery, and the second end of the third transistor is connected to the load power supply end.

[0018] Specifically, the embodiment of the present application detects the battery voltage through a voltage detection chip. When the battery voltage is higher than the upward voltage threshold, the connection between the power supply output terminal of the battery and the load power supply terminal is turned on, and the voltage detection chip controls the connection between the power supply output terminal of the battery and the load power supply terminal to achieve normal power supply to the load. When the battery voltage is lower than the downward voltage threshold, the connection between the power supply output terminal of the battery and the power supply input terminal of the voltage detection chip is disconnected. At this time, the connection between the power supply output terminal of the battery and the load power supply terminal is disconnected, thereby achieving over-discharge protection for the battery. The circuit structure of the present application is simple, and during overvoltage protection, the battery no longer supplies power to the voltage detection chip, thereby reducing the power consumption of the overvoltage protection circuit and further improving the effect of overvoltage protection. At the same time, the overvoltage protection circuit provided by the present application has the functions of detecting the upward voltage threshold and the downward voltage threshold, thereby forming a hysteresis circuit to prevent the system load power supply from being repeatedly turned on and off.

[0019] The technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all of the embodiments.

[0020] See also Figure 1The low-power battery over-discharge protection circuit provided in the embodiment of the present application includes: a first resistor R1, a second resistor R2, a third resistor R3, a fourth resistor R4, a fifth resistor R5, a sixth resistor R6, a first transistor Q1, a second transistor Q2, a third transistor Q3 and a voltage detection chip U1, wherein the first resistor R1, the second resistor R2 and the third resistor R3 are sequentially connected in series between the power supply output terminal VBAT of the battery and the ground, the common end of the first resistor R1 and the second resistor R2 is connected to the down-threshold input terminal FTH of the voltage detection chip U1, the common end of the second resistor R2 and the third resistor R3 is connected to the up-threshold input terminal RTH of the voltage detection chip U1, the fourth resistor R4 and the fifth resistor R5 are sequentially connected in series between the power supply output terminal VBAT of the battery A common end of the fourth resistor R4 and the fifth resistor R5 is connected to the control end of the first transistor Q1, a first end of the first transistor Q1 is connected to the power supply input end VCC of the voltage detection chip U1, a second end of the first transistor Q1 is connected to the power supply output end VBAT of the battery, a control end of the second transistor Q2 is connected to the output end LBO# of the voltage detection chip U1, a first end of the second transistor Q2 is grounded, a second end of the second transistor Q2 is connected to the control end of the third transistor Q3, and is connected to the power supply output end VBAT of the battery through the sixth resistor R6, a first end of the third transistor Q3 is connected to the power supply output end VBAT of the battery, and a second end of the third transistor Q3 is connected to the load power supply end VIN.

[0021] See also Figure 1 In the embodiment of the present application, the first transistor Q1 is an NPN transistor, the control end of the first transistor Q1 is the base of the NPN transistor, the first end of the first transistor Q1 is the emitter of the NPN transistor, and the second end of the first transistor Q1 is the collector of the NPN transistor. That is, the base of the first transistor Q1 is connected to the common end of the fourth resistor R4 and the fifth resistor R5, the emitter of the first transistor Q1 is connected to the power supply input end VCC of the voltage detection chip U1, and the collector of the first transistor Q1 is connected to the power supply output end VBAT of the battery.

[0022] See also Figure 1 In the embodiment of the present application, the second transistor Q2 is an N-type MOS tube, the control end of the second transistor Q2 is the gate of the N-type MOS tube, the first end of the second transistor Q2 is the source of the N-type MOS tube, and the second end of the second transistor Q2 is the drain of the N-type MOS tube. That is, the gate of the second transistor Q2 is connected to the output end LBO# of the voltage detection chip U1, the source of the second transistor Q2 is grounded, and the drain of the second transistor Q2 is connected to the control end of the third transistor Q3.

[0023] See also Figure 1In the embodiment of the present application, the third transistor Q3 is a P-type MOS tube, the control end of the third transistor Q3 is the gate of the P-type MOS tube, the first end of the third transistor Q3 is the source of the P-type MOS tube, and the second end of the third transistor Q3 is the drain of the P-type MOS tube. That is, the gate of the third transistor Q3 is connected to the drain of the second transistor Q2, the source of the third transistor Q3 is connected to the power supply output terminal VBAT of the battery, and the drain of the third transistor Q3 is connected to the load power supply terminal VIN.

[0024] In the embodiment of the present application, the characteristics of the voltage detection chip U1 are as follows: when the voltage of the downlink threshold input terminal FTH of the voltage detection chip U1 is lower than the downlink voltage threshold, and when the voltage detection chip U1 is powered off, the output terminal LBO# of the voltage detection chip U1 outputs a low-level signal. When the voltage of the uplink threshold input terminal RTH of the voltage detection chip U1 is higher than the uplink voltage threshold, the output terminal LBO# of the voltage detection chip U1 outputs a high-level signal. In actual applications, the downlink voltage threshold and the uplink voltage threshold of the voltage detection chip U1 can be set as needed.

[0025] In the embodiment of the present application, the model of the voltage detection chip U1 may be CN302. CN302 is a low-power battery voltage detection chip with adjustable hysteresis, which is particularly suitable for voltage detection of single-cell or multi-cell lithium batteries, multi-cell alkaline batteries, nickel-cadmium batteries, nickel-metal hydride batteries and multi-cell lead-acid batteries. Its chip structure is simple and the cost is low.

[0026] In the embodiment of the present application, the first resistor R1, the second resistor R2 and the third resistor R3 are connected in series in sequence to form a battery voltage sampling circuit, the fourth resistor R4, the fifth resistor R5 and the first transistor Q1 form a power supply circuit of the voltage detection chip U1, and the sixth resistor R6, the second transistor Q2 and the third transistor Q3 form a system load power supply switch control circuit.

[0027] The circuit principle of the embodiment of the present application is as follows:

[0028] When the battery continues to supply power to the load, the voltage of the power supply output terminal VBAT will continue to decrease. When the voltage of the downward threshold input terminal FTH of the voltage detection chip U1 is lower than the downward voltage threshold, the output terminal LBO# of the voltage detection chip U1 outputs a low-level signal, so that the second transistor Q2 is turned off, and further the third transistor Q3 is turned off, and the path between the power supply output terminal VBAT of the battery and the load power supply terminal VIN is disconnected, thereby preventing the battery from over-discharging; at the same time, when the voltage of the power supply output terminal VBAT continues to decrease to a certain value, the first transistor Q1 is turned off, and the path between the power supply output terminal VBAT of the battery and the power supply input terminal VCC of the voltage detection chip U1 is disconnected, thereby preventing the voltage detection chip U1 from continuously consuming the power of the battery, further preventing the battery from over-discharging.

[0029] When the battery is charged normally, the voltage of the power supply output terminal VBAT begins to increase. When the voltage of the power supply output terminal VBAT increases to a certain value, the first transistor Q1 is turned on, and the power supply output terminal VBAT of the battery is connected to the power supply input terminal VCC of the voltage detection chip U1, and the voltage detection chip U1 works normally. When the voltage of the power supply output terminal VBAT continues to increase to a certain value, the voltage of the up-threshold input terminal RTH of the voltage detection chip U1 will be higher than the up-voltage threshold. At this time, the output terminal LBO# of the voltage detection chip U1 outputs a high-level signal, so that the second transistor Q2 is turned on, and further the third transistor Q3 is turned on, and the power supply output terminal VBAT of the battery is connected to the load power supply terminal VIN, and the battery resumes supplying power to the system load.

[0030] In practical applications, the battery over-discharge protection voltage point and the power supply recovery voltage point can be set by adjusting the resistance values ​​of the first resistor R1, the second resistor R2 and the third resistor R3. The corresponding relationship is as follows:

[0031] VBAT low =1.211V×(R1+R2+R3) / (R2+R3);

[0032] VBAT hight =1.211V×(R1+R2+R3) / R3;

[0033] When the battery voltage is lower than the over-discharge protection voltage VBAT low When the battery voltage is higher than the recovery power supply voltage VBAT, the circuit disconnects the power supply of the battery and the system load to prevent the battery from further over-discharge. hight When the battery resumes supplying power to the system load.

[0034] In an application example of a 12V lithium iron phosphate battery, the first resistor R1 has a resistance of 910KΩ, the second resistor R2 has a value of 12KΩ, the third resistor R3 has a value of 91KΩ, the fourth resistor R4 has a value of 1MΩ, the fifth resistor R5 has a value of 470KΩ, and the sixth resistor R6 has a value of 470KΩ. At this time, the over-discharge protection voltage VBAT of the battery low 11.9V, restore the supply voltage VBAT hight The voltage of the voltage detection chip U1 is 4V, and the current consumption of the entire protection circuit is about 0.05mA.

[0035] In applications with different voltage levels and battery types, it is only necessary to adjust the resistance values ​​of the first resistor R1, the second resistor R2, and the third resistor R3 according to the specifications of the reference battery to set the battery power supply over-discharge protection voltage and the power supply recovery voltage, and adjust the resistance values ​​of the fourth resistor R4 and the fifth resistor R5 to set the power supply of the voltage detection chip U1 within an appropriate range.

[0036] In summary, the low-power battery over-discharge protection circuit provided by the embodiment of the present application can timely shut down the battery's power supply to the load and the detection circuit to protect the battery when the battery voltage is lower than the specified threshold value. The circuit structure is simple, and during overvoltage protection, the battery no longer supplies power to the voltage detection chip, thereby reducing the power consumption of the overvoltage protection circuit and further improving the effect of overvoltage protection. At the same time, the overvoltage protection circuit provided by the present application has the functions of detecting the upper voltage threshold and the lower voltage threshold, thereby forming a hysteresis circuit to prevent the system load power supply from being repeatedly turned on and off.

[0037] Finally, it should be noted that the above embodiments are only preferred implementations and are not intended to limit the present invention. It should be pointed out that for those skilled in the art, several modifications, equivalent replacements, improvements, etc. can be made without departing from the scope of protection of the present invention and the claims, and all of these should be included in the protection scope of the present invention.

Claims

1. A low-power battery over-discharge protection circuit, characterized in that: The invention comprises a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor, a sixth resistor, a first transistor, a second transistor, a third transistor and a voltage detection chip, wherein the first resistor, the second resistor and the third resistor are connected in series between the power supply output terminal of the battery and the earth in sequence, the common end of the first resistor and the second resistor is connected to the down-threshold input terminal of the voltage detection chip, the common end of the second resistor and the third resistor is connected to the up-threshold input terminal of the voltage detection chip, the fourth resistor and the fifth resistor are connected in series between the power supply output terminal of the battery and the earth in sequence, the common end of the fourth resistor and the fifth resistor is connected to the control end of the first transistor, the first end of the first transistor is connected to the power supply input terminal of the voltage detection chip, the second end of the first transistor is connected to the power supply output terminal of the battery, the control end of the second transistor is connected to the output terminal of the voltage detection chip, the first end of the second transistor is grounded, the second end of the second transistor is connected to the control end of the third transistor, and is connected to the power supply output terminal of the battery through the sixth resistor, the first end of the third transistor is connected to the power supply output terminal of the battery, and the second end of the third transistor is connected to the load power supply terminal.

2. The low power consumption battery over-discharge protection circuit according to claim 1, characterized in that: The first transistor is an NPN transistor, the control end of the first transistor is the base of the NPN transistor, the first end of the first transistor is the emitter of the NPN transistor, and the second end of the first transistor is the collector of the NPN transistor.

3. The low power consumption battery over-discharge protection circuit according to claim 1, characterized in that: The second transistor is an N-type MOS tube, the control end of the second transistor is the gate of the N-type MOS tube, the first end of the second transistor is the source of the N-type MOS tube, and the second end of the second transistor is the drain of the N-type MOS tube.

4. The low power consumption battery over-discharge protection circuit according to claim 1, characterized in that: The third transistor is a P-type MOS tube, the control end of the third transistor is the gate of the P-type MOS tube, the first end of the third transistor is the source of the P-type MOS tube, and the second end of the third transistor is the drain of the P-type MOS tube.

5. The low power consumption battery over-discharge protection circuit according to claim 1, characterized in that: The model of the voltage detection chip is CN302.

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