CN103368235B - Nickel-metal hydride battery charge-discharge circuit in uninterruptible power supply - Google Patents

Abstract

A nickel-metal hydride battery charge and discharge circuit in an uninterruptible power supply, which includes a charger, a discharge diode and a charge and discharge control circuit, the charge and discharge control circuit includes a single-chip microcomputer, a charging relay and a charging MOS tube, and the charger is connected through the charging relay The normally open contact of the charging relay charges the Ni-MH battery and is connected to the input terminal of the uninterruptible power supply DC boost through the normally closed contact of the charging relay, and its control signal input terminal is connected to the output port of the single-chip microcomputer; the charging MOS tube controls the charging relay control Coil, whose gate is connected to the output port of the single-chip microcomputer; the output voltage of the nickel-metal hydride battery is divided by the first resistor and the second resistor and then connected to the voltage sampling port of the single-chip microcomputer, and the third resistor is connected in series between the negative pole of the nickel-hydrogen battery and the output ground of the charger Between, the output signal is connected to the current sampling port of the microcontroller; the nickel metal hydride battery supplies power to the inverter through the discharge diode. The invention greatly reduces the frequency of charging, thereby prolonging the service life of the nickel-metal hydride battery and reducing the operation and maintenance costs of the uninterruptible power supply.

Description

A Ni-MH battery charging and discharging circuit in an uninterruptible power supply

technical field

The invention relates to a battery charging circuit capable of preventing frequent charging and discharging of nickel-metal hydride batteries inside an uninterruptible power supply, belonging to the technical field of power supplies.

Background technique

Since lead-acid batteries and lithium batteries cannot be discharged at high currents at low temperatures, nickel-metal hydride batteries are generally required for uninterruptible power supplies that work in low-temperature environments. The charging method of Ni-MH batteries is different from that of lead-acid batteries and lithium batteries. It cannot be floated and charged for a long time, and can only be charged by constant current. The current constant current charger of the uninterruptible power supply will stop working after the battery is fully charged. It has been in a low current discharge state, which shortens the charging cycle of the Ni-MH battery and increases the charging frequency, which greatly reduces the service life of the Ni-MH battery and increases the operation and maintenance costs of the uninterruptible power supply.

Contents of the invention

The object of the present invention is to aim at the drawbacks of the prior art, and provide an internal Ni-MH battery charging circuit of the UPS to prolong the service life of the Ni-MH battery and reduce the operation and maintenance costs of the UPS.

Problem described in the present invention is realized with following technical scheme:

A nickel-metal hydride battery charging and discharging circuit in an uninterruptible power supply, comprising a charger, a discharging diode and a charging and discharging control circuit, the charging and discharging control circuit including a single-chip microcomputer, a charging relay, a charging MOS tube and three resistors, the The charger charges the Ni-MH battery through the normally open contact of the charging relay and is connected to the DC boost input terminal of the uninterruptible power supply through the normally closed contact of the charging relay, and its control signal input terminal is connected to the output port of the single-chip microcomputer; the charging MOS The tube controls the charging relay control coil, and its gate is connected to the output port of the single-chip microcomputer; the output voltage of the nickel-metal hydride battery is divided by the first resistor and the second resistor and then connected to the voltage sampling port of the single-chip microcomputer, and the third resistor is connected in series to the negative pole of the nickel-hydrogen battery Between the charger and the output ground, the output signal is connected to the current sampling port of the single-chip microcomputer through the amplifier; the Ni-MH battery supplies power to the DC boost circuit of the uninterruptible power supply through the discharge diode.

The Ni-MH battery charging and discharging circuit in the above-mentioned uninterruptible power supply also includes a discharge relay, a discharge MOS tube and a DC contactor in the composition, and the normally open contact of the discharge relay is connected in series with the control coil of the DC contactor and then connected to the nickel At both ends of the hydrogen battery, the discharge MOS tube controls the control coil of the discharge relay, and its gate is connected to the output port of the single-chip microcomputer; the normally open contact of the DC contactor is also connected to the discharge diode.

The Ni-MH battery charging and discharging circuit in the above-mentioned uninterruptible power supply, the charger includes a rectifier bridge, a switch tube, a transformer, a rectifier diode and a PWM isolation drive circuit, and the switch tube is connected in series with the primary coil of the transformer and then connected to the rectifier bridge The output DC voltage, the input terminal of the PWM isolation drive circuit is connected to the output port of the single chip microcomputer, and the output terminal is connected to the gate of the switch tube; one end of the secondary coil of the transformer is connected to the output ground of the charger, and one end is connected to the charging port through the rectifier diode Common contact of the relay.

For the Ni-MH battery charge and discharge circuit in the uninterruptible power supply, the charge and discharge control circuit is powered by a DC/DC auxiliary power supply, and the input terminal of the auxiliary power supply is connected to the DC input terminal of the uninterruptible power supply.

In the charging and discharging circuit of the Ni-MH battery in the above-mentioned uninterruptible power supply, the control coils of the charging relay and the discharging relay are all connected in parallel with freewheeling diodes.

The charging and discharging circuit of the Ni-MH battery in the above-mentioned uninterruptible power supply has a fuse connected in series in the discharge circuit of the Ni-MH battery.

The charging and discharging control circuit of the present invention can monitor the voltage of the nickel-metal hydride battery in real time. When the battery is charged, the output terminal of the charger is switched to the DC boost input terminal of the uninterruptible power supply, and the charger provides heat for the uninterruptible power supply. Energy consumption required for backup; when the battery voltage drops due to self-discharge of the Ni-MH battery, the capacity will decrease accordingly, and the single-chip computer program calculates the battery capacity according to the sampling voltage of the Ni-MH battery. %, the charge and discharge control circuit switches the output of the charger to the Ni-MH battery and starts charging the Ni-MH battery. Since the Ni-MH battery does not need to provide thermal backup energy after it is fully charged, the discharge speed of the battery is greatly reduced and the frequency of charging is reduced, thereby prolonging the service life of the Ni-MH battery and reducing the operation and maintenance costs of the UPS. In addition, the invention also has the advantages of simple circuit structure, low cost and high reliability.

Description of drawings

The present invention will be further described below in conjunction with accompanying drawing.

Fig. 1 is the electrical schematic diagram of the present invention.

The list of labels in the figure is: B, Ni-MH battery; U1, single-chip microcomputer; U2, PWM isolation drive; ZQ, rectifier bridge; DC/DC, auxiliary power supply; T, transformer; NB, uninterruptible power supply DC boost; K1, Discharging relay; K2, charging relay; K3, DC contactor; D1, first freewheeling diode; D2, second freewheeling diode; D3, discharging diode; D4, rectifying diode; T1, discharging MOS tube; T2, charging MOS Tube; T3, switch tube; R1 ~ R3, the first resistor to the third resistor; FU, fuse.

Detailed ways

Referring to Fig. 1, the present invention is made up of charger, discharge diode, auxiliary power supply and charge and discharge control circuit. The charger is composed of PWM isolation driver U2, rectifier bridge ZQ, transformer T, rectifier diode D4 and switch tube T3; the charge and discharge control circuit is composed of single-chip microcomputer U1, discharge relay K1, charge relay K2, DC contactor K3, the first freewheeling circuit The diode D1, the second freewheeling diode D2, the discharge diode D3, the discharge MOS transistor T1, the charge MOS transistor T2, the first resistor R1 to the third resistor R3 and the fuse FU are composed, and the auxiliary power supply supplies power for the charge and discharge control circuit.

The circuit works as follows:

The single-chip microcomputer U1 monitors the terminal voltage of the Ni-MH battery B through the voltage divider circuit composed of the first resistor R1 and the second resistor R2, judges whether the Ni-MH battery B needs to be charged, monitors the charging current of the Ni-MH battery B through the third resistor R3, and Controls the output current of the constant current charger. When the Ni-MH battery B is detected to be fully charged, the P1.3 port of the microcontroller U1 gives a low-level signal, which is sent to the gate of the discharge MOS transistor T1, and the discharge MOS transistor T1 is cut off, so that the discharge relay K1 is disconnected , after the discharge relay K1 is disconnected, the DC contactor K3 is disconnected; at the same time, the P1.4 port of the microcontroller U1 also gives a low-level signal, which is sent to the gate of the charging MOS tube T2, and the charging MOS tube T2 cuts off, the normally open contact of the charging relay K2 is disconnected, and the normally closed contact is closed, so that the output terminal of the charger is connected to the input terminal of the DC boost NB of the uninterruptible power supply. At the same time, the control program converts the output voltage of the charger to Stable at the highest charging voltage. At this time, the output voltage of the charger ≥ the terminal voltage of the Ni-MH battery B, that is, the cathode voltage of the discharge diode D3 ≥ its anode voltage, the Ni-MH battery B will not be discharged, and the battery will not be charged. . At this time, the power required by the DC input hot backup is completely provided by the charger.

When the AC input of the uninterruptible power supply is abnormal, the output voltage V+ of the charger will drop rapidly. The input of NB is powered by Ni-MH battery B through discharge diode D3, realizing the zero switching function of uninterruptible power supply. At the same time, the P1.3 port of the single-chip microcomputer U1 gives a high-level signal, which is sent to the gate of the discharge MOS transistor T1, and the discharge MOS transistor T1 is turned on, thereby causing the discharge relay K1 to pull in, and the discharge relay K1 to pull in Finally, the DC contactor K3 pulls in, and the discharge diode D3 is short-circuited by the DC contactor K3, ensuring that the discharge diode D3 does not work for a long time and reduces energy loss. During the whole process, Vin+ will not be lower than the battery undervoltage voltage, and the auxiliary power supply works stably and normally.

When the voltage of Ni-MH battery B is detected to be too low, the uninterruptible power supply DC boost NB undervoltage protection will no longer consume battery power. When the AC input returns to normal, the single-chip microcomputer U1 adjusts the output signal of its P1. V+ is connected to the positive pole of Ni-MH battery B, and starts to charge Ni-MH battery B. At this time, the P1.3 port of the single chip microcomputer U1 is at low level, the DC contactor K3 is disconnected, and the charger is charging the battery while providing hot backup DC power for the uninterruptible power supply DC boost NB through the diode D3.

The role of the fuse FU in the circuit is to protect the Ni-MH battery B and the DC circuit; the role of the first freewheeling diode D1 and the second freewheeling diode D2 is to slow down the surge voltage disturbance.

Claims (5)

1. the nickel-metal hydride battery charge-discharge circuit in a uninterrupted power supply, it is characterized in that, described circuit comprises charger, discharge diode (D3) and charge-discharge control circuit, described charge-discharge control circuit comprises single-chip microcomputer (U1), charge relay (K2) and charging metal-oxide-semiconductor (T2), and described charger connects the input of uninterrupted power supply DC boosting (NB) through the normally opened contact of charge relay (K2) to Ni-MH battery (B) charging through the normally-closed contact of charge relay (K2); The drain electrode of described charging metal-oxide-semiconductor (T2) connects the control coil of charge relay (K2), and its grid connects the P1.4 port of single-chip microcomputer (U1), the source ground of charging metal-oxide-semiconductor; The output voltage of Ni-MH battery (B) connects the voltage sample port of single-chip microcomputer (U1) after the first resistance (R1) and the second resistance (R2) dividing potential drop, 3rd resistance (R3) is serially connected in Ni-MH battery (B) negative pole and charger exports between ground, and the output signal of the 3rd resistance (R3) connects the current sample port of single-chip microcomputer (U1); Ni-MH battery (B) is powered to the DC boosting of uninterrupted power supply (NB) through discharge diode (D3);

Electric discharge relay (K1), electric discharge metal-oxide-semiconductor (T1) and D.C. contactor (K3) is also comprised in formation, Ni-MH battery (B) two ends are connected to after the normally opened contact of described electric discharge relay (K1) is connected in series with the control coil of D.C. contactor (K3), the drain electrode of described electric discharge metal-oxide-semiconductor (T1) connects the control coil of electric discharge relay (K1), grid connects the P1.3 port of single-chip microcomputer (U1), electric discharge metal-oxide-semiconductor source ground; The normally opened contact of described D.C. contactor (K3) is attempted by discharge diode (D3).

2. the nickel-metal hydride battery charge-discharge circuit in a kind of uninterrupted power supply according to claim 1, it is characterized in that, described charger comprises rectifier bridge (ZQ), switching tube (T3), transformer (T), rectifier diode (D4) and PWM isolated drive circuit (U2), the direct voltage that rectifier bridge (ZQ) exports is connect after described switching tube (T3) and the primary coil of transformer (T) are connected in series, the input of described PWM isolated drive circuit (U2) connects the P1.2 port of single-chip microcomputer (U1), and it exports the grid of termination switching tube (T3); The secondary coil one termination charger of described transformer (T) exports ground, and one end connects the common of charge relay (K2) through rectifier diode (D4).

3. the nickel-metal hydride battery charge-discharge circuit in a kind of uninterrupted power supply according to claim 2, it is characterized in that, described charge-discharge control circuit is powered by DC/DC accessory power supply, the input of input termination uninterrupted power supply DC boosting (NB) of described accessory power supply.

4. the nickel-metal hydride battery charge-discharge circuit in a kind of uninterrupted power supply according to claim 3, is characterized in that, on the control coil of described charge relay (K2) and electric discharge relay (K1) all and be connected to fly-wheel diode.

5. the nickel-metal hydride battery charge-discharge circuit in a kind of uninterrupted power supply according to claim 4, is characterized in that, is serially connected with fuse (FU) in the discharge loop of Ni-MH battery (B).