ZERO-VOLTAGE DISCHARGE CIRCUIT DEVICE

Disclosed is a zero-voltage discharge circuit device, in particular, a zero-voltage discharge circuit device configured to discharge a secondary battery while relevant switching elements are kept continuously turned on without being repeatedly turned on and off in a discharge mode of the second battery, so that the discharge circuit can be configured with low withstand voltage switching elements, and is configured to generate a charging current and a discharging current by just selectively turning on the switching elements without changing an operating voltage, thereby reducing power loss in charging and discharging, and simplifying a control operation for the charging and the discharging.

TECHNICAL FIELD

The disclosure relates to a zero-voltage discharge circuit device, and, particularly, a zero-voltage discharge circuit device, which is configured to discharge a secondary battery while relevant switching elements are kept continuously turned on without being repeatedly turned on and off in a discharge mode of the second battery, so that the discharge circuit can be configured with low withstand voltage switching elements, and is configured to generate a charging current and a discharging current by just selectively turning on the switching elements without changing an operating voltage, thereby reducing power loss in charging and discharging, and simplifying a control operation for the charging and the discharging.

BACKGROUND ART

Zero-voltage discharge refers to that a battery operates in a constant current mode (CCM), where current has a constant level, until voltage reaches 0V while the battery is being discharged.

The zero-voltage discharge is necessary for the following reasons: a charger/discharger is classified into a charger/discharger for formation, which is used in the manufacture of a secondary battery product, and a charger/discharger for a cycler, which repeats charging and discharging more times to design and research the products, and it is important to implement a circuit for the zero-voltage discharge to meet the requirements of a user because the charger/discharger for the cycler uses a voltage of 0 to 4.5 V and performs discharge up to a lower voltage.

In a conventional circuit, the zero-voltage discharge was not achieved. The reason is as follows: the load wiring of the charger/discharger is so long (about 6 to 10 m) that a voltage drop (about 0.7 to 1.0 V) occurs when current flows in the load wiring. In addition, a voltage drop also occurs when current flows in semiconductor elements (a diode, a metal oxide semiconductor field effect transistor (MOSFET), etc.) of the circuit. Due to voltage drop components described above, constant current discharge is not maintained in a region where a battery voltage is low. Therefore, the conventional charging/discharging circuit cannot maintain the constant current discharge when the battery voltage is lower than or equal to 2.0 V.

Such a conventional secondary battery charging/discharging circuit used for testing a secondary battery could make the secondary battery be discharged only up to a certain voltage (e.g., up to 20% of a rated voltage) or higher but be not discharged below that voltage. Therefore, there was a problem in that the secondary battery was not sufficiently tested.

To solve this problem of the conventional charging/discharging circuit, Korean Patent No. 10-1197078 (hereinafter referred to as the “related art”) has disclosed a zero voltage discharge circuit with active switching elements, in which only a switching operation is enough to perform discharging without adding separate auxiliary power, thereby making a secondary battery sufficiently discharge a small amount of remaining voltage (20% or below to 0%).

However, the foregoing zero voltage discharge circuit suggested in the related art unavoidably increases the withstand voltage of relevant switching elements due to parasitic resonance because the switching elements repeatedly switch on and off under pulse width modulation (PWM) control during the charging or the discharging, and increases the costs of the circuit because high withstand voltage switching elements are used.

Further, the foregoing zero voltage discharge circuit suggested in the related art has a disadvantage in that control operations for charging and discharging are complicated because all the switching elements connected to the primary and secondary sides of a transformer are required to be selectively controlled to generate a charging current and a discharging current, and the voltage polarity at the secondary side of the transformer is required to be altered according to the charging and the discharging.

DISCLOSURE

Technical Problem

The disclosure is conceived to solve the problems of the related art, and an aspect of the disclosure is to provide a zero-voltage discharge circuit device, which is configured to discharge a secondary battery while relevant switching elements are kept continuously turned on without being repeatedly turned on and off in a discharge mode of the second battery, so that the discharge circuit can be configured with low withstand voltage switching elements, thereby reducing the costs of configuring the charging/discharging circuit.

Further, an aspect of the disclosure is to provide a zero-voltage discharge circuit device, which is configured to generate a charging current and a discharging current by just selectively turning on switching elements without changing an operating voltage, thereby reducing power loss in charging and discharging, and simplifying a control operation for the charging and the discharging.

Technical Solution

A zero-voltage discharge circuit device according to the disclosure, proposed to solve the foregoing problems, includes a first switching element including a first end connected to an operating voltage applying node corresponding to a node to which an operating voltage is applied by an operating voltage applying unit, and a second end connected to a first node; a second switching element including a first end connected to the operating voltage applying node, and a second end connected to a second node, and being connected in parallel with the first switching element; a third switching element including a first end connected to the first node, and a second end connected to a reference node; a fourth switching element including a first end connected to the second node, and a second end connected to the reference node; a first inductor including a first end connected to the first node, and a second end connected to a third node to which a positive (+) terminal of a secondary battery is connected; a first capacitor including a first end connected to the third node, and a second end connected to the reference node; a second inductor including a second end connected to the second node, and a first end connected to a fourth node to which a negative (-) terminal of a secondary battery is connected; and a second capacitor including a first end connected to the fourth node, and a second end connected to the reference node.

Here, only the first switching element and the fourth switching element are turned on in a charge mode for the secondary battery, and only the second switching element and the third switching element are turned on in a discharge mode for the secondary battery.

Further, the operating voltage applying unit equally applies the operating voltage to the operating voltage applying node in a charge mode and a discharge mode for the secondary battery.

Advantageous Effects

In a zero-voltage discharge circuit device with the foregoing problems and solutions according to the disclosure, a secondary battery is configured to be discharged while relevant switching elements are kept continuously turned on without being repeatedly turned on and off in a discharge mode of the second battery, so that the discharge circuit can be configured with low withstand voltage switching elements, thereby having an advantage of reducing the costs of configuring the charging/discharging circuit.

Further, according to the disclosure, it is configured to generate a charging current and a discharging current by just selectively turning on switching elements without changing an operating voltage, thereby having effects on reducing power loss in charging and discharging, and simplifying a control operation for the charging and the discharging.

BEST MODE

Below, embodiments of a zero-voltage discharge circuit device with the foregoing problems, solutions and effects according to the disclosure will be described with reference to the accompanying drawings.

FIG.1is a configuration diagram of a zero-voltage discharge circuit device according to an embodiment of the disclosure.

As shown inFIG.1, the zero-voltage discharge circuit device according to an embodiment of the disclosure includes an operating voltage applying unit1, and the operating voltage applying unit1generates and applies an operating voltage Vinto an operating voltage applying node Nin. In other words, the operating voltage applying unit1operates to apply the operating voltage Vincorresponding to a positive voltage to the operating voltage applying node Nin.

Further, the zero-voltage discharge circuit device according to an embodiment of the disclosure includes four switching elements, i.e., a first switching element S1, a second switching element S2, a third switching element S3, and a fourth switching element S4; two inductors, i.e., a first inductor L1and a second inductor L2; and two capacitors, i.e., a first capacitor C1and a second capacitor C2in order to perform an operation of charging a secondary battery3and an operation of discharging the secondary battery3

The first switching element S1has a first end connected to the operating voltage applying node Nincorresponding to the node to which the operating voltage applying unit1applies the operating voltage Vin, and a second end connected to a first node N1.

The first switching element S1is made of a metal oxide semiconductor field effect transistor (MOSFET). Specifically, the first switching element S1is disposed with a drain connected to the operating voltage applying node Nin, and a source connected to the first node N1.

A first diode D1is connected to the first switching element S1made of the MOSFET. The first diode D1is connected to prevent the first switching element S1made of the MOSFET from being damaged by high counter electromotive force applied to the drain at the moment when the first switching element S1is turned off from an on state. The first diode D1is disposed with an anode connected to the first node N1, and a cathode connected to the operating voltage applying node Nin.

The second switching element S2has a first end connected to the operating voltage applying node Nin, and a second end connected to a second node N2, and is connected in parallel with the first switching element S1.

Like the first switching element S1, the second switching element S2is also made of a MOSFET. Specifically, the second switching element S2is disposed with a drain connected to the operating voltage applying node Nin, and a source connected to the second node N2.

A second diode D2is connected to the second switching element S2made of the MOSFET. The second diode D2is connected to prevent the second switching element S2made of the MOSFET from being damaged by high counter electromotive force applied to the drain at the moment when the second switching element S2is turned off from an on state. The second diode D2is disposed with an anode connected to the second node N2, and a cathode connected to the operating voltage applying node Nin.

The third switching element S3has a first end connected to the first node N1, and a second end connected to a reference node Nr. Here, the reference node Nrmay be connected to the ground.

Like the first switching element S1, the third switching element S3is also made of a MOSFET. Specifically, the third switching element S3is disposed with a drain connected to the first node N1, and a source connected to the reference node Nr.

A third diode D3is connected to the third switching element S3made of the MOSFET. The third diode D3is connected to prevent the third switching element S3from being damaged by high counter electromotive force applied to the drain at the moment when the third switching element S3is turned off from an on state. The third diode D3is disposed with an anode connected to the reference node Nr, and a cathode connected to the first node N1.

The fourth switching element S4has a first end connected to the second node N2, and a second end connected to the reference node Nr. Here, the reference node Nrmay be connected to the ground.

Like the first switching element S1, the fourth switching element S4is also made of a MOSFET. Specifically, the fourth switching element S4is disposed with a drain connected to the second node N2, and a source connected to the reference node Nr.

A fourth diode D4is connected to the fourth switching element S4made of the MOSFET. The fourth diode D4is connected to prevent the fourth switching element S4made of the MOSFET from being damaged by high counter electromotive force applied to the drain at the moment when the fourth switching element S4is turned off from an on state. The fourth diode D4is disposed with an anode connected to the reference node Nr, and a cathode connected to the second node N2.

The first inductor L1has a first end connected to the first node N1, and a second end connected to a third node N3to which a positive (+) terminal of the secondary battery3is connected. Specifically, the first inductor L1has the first end connected to the source of the first switching element S1and the drain of the third switching element S3via the first node N1, and the second end connected to the positive (+) terminal of the secondary battery3via the third node N3.

The first inductor L1is made of a current stabilizing coil, and operates so that a charging current and a discharging current can flow stably. In particular, the first inductor L1is directly involved in making the charging current stably flow in the secondary battery3in the charge mode for charging the secondary battery3, as will be described later.

The first capacitor C1has a first end connected to the third node N3, and a second end connected to the reference node Nr. Specifically, the first capacitor C1has the first end connected to the second end of the first inductor L1and the positive (+) terminal of the secondary battery3via the third node N3, and the second end connected to the source of the third switching element S3and the source of the fourth switching element S4via the reference node Nr.

The first capacitor C1operates as a voltage stabilizing capacitor to stabilize a voltage waveform of the secondary battery in the charge and discharge modes for the secondary battery3. In particular, the first capacitor C1is connected in parallel with the secondary battery3in the charge mode for charging the secondary battery3, and is directly involved in stabilizing the voltage waveform of the secondary battery, as will be described later.

The second inductor L2has a second end connected to the second node N2, and a first end connected to a third node N4to which a negative (-) terminal of the secondary battery3is connected. Specifically, the second inductor L2has the second end connected to the source of the second switching element S2and the drain of the fourth switching element S4via the second node N2, and the first end connected to the negative (+) terminal of the secondary battery3via the fourth node N4.

The second inductor L2is made of a current stabilizing coil, and operates so that the charging current and the discharging current can flow stably. In particular, the second inductor L2is directly involved in making the discharging current stably flow in the secondary battery3in the discharge mode for discharging the secondary battery3, as will be described later.

The second capacitor C2has a first end connected to the fourth node N4, and a second end connected to the reference node Nr. Specifically, the second capacitor C2has the first end connected to the first end of the second inductor L2and the negative (-) terminal of the secondary battery3via the fourth node N4, and the second end connected to the source of the third switching element S3, the source of the fourth switching element S4, and the second end of the first capacitor C1via the reference node Nr.

The second capacitor C2operates as a voltage stabilizing capacitor to stabilize a voltage waveform of the secondary battery in the charge and discharge modes for the secondary battery3. In particular, the second capacitor C2is connected in parallel with the secondary battery3in the discharge mode for discharging the secondary battery3, and is directly involved in stabilizing the voltage waveform of the secondary battery, as will be described later.

Below, the operations of the zero-voltage discharge circuit device configured as described above according to an embodiment of the disclosure will be described with reference to the circuit diagrams ofFIGS.2and3, and the waveforms ofFIG.4.

The zero-voltage discharge circuit device according to an embodiment of the disclosure further includes a control unit5and a switching signal generation unit7to selectively control the switching of the switching elements S1, S2, S3, and S4so that the operations of charging and discharging the secondary battery3can be performed.

As shown inFIG.5, the control unit5is connected to the switching signal generation unit7so as to output control signals for switching on and off the switching elements S1, S2, S3, and S4. The switching signal generation unit7is connected to each gate of the switching elements S1, S2, S3, and S4to output the switching signals for turning on and off the switching elements S1, S2, S3, and S4ofFIG.1.

Specifically, referring toFIG.4, the control unit5controls the switching signal generation unit7to turn on the first switching element S1and the fourth switching element S4but turn off the second switching element S2and the third switching element S3in the operation of the charge mode Mode1shown inFIG.2, and controls the switching signal generation unit7to turn on the second switching element S2and the third switching element S3but turn off the first switching element S1and the fourth switching element S4in the operation of the discharge mode Mode2shown inFIG.3.

In other words, the zero-voltage discharge circuit device according to an embodiment of the disclosure operates to turn on only the first switching element S1and the fourth switching element S4in the charge mode Mode1for the secondary battery3, and turn on only the second switching element S2and the third switching element S3in the discharge mode Mode2for the secondary battery3.

Referring toFIG.2, the operations in the charge mode Mode1for charging the secondary battery3and the flow of the charging current are as follows.

The switching control signal corresponding to the charge mode Mode1ofFIG.4is output from the control unit5to the switching signal generation unit7ofFIG.5. In other words, in the charge mode Mode1ofFIG.4, the switching signal generation unit7outputs a turning-on signal to the gates of the first switching element S1and the fourth switching element S4, and at the same time outputs a turning-off signal to the second switching element S2and the third switching element S3. Then, the first switching element S1and the fourth switching element S4are turned on, and at the same time the second switching element S2and the third switching element S3are turned off.

As described above, the applying voltage Vingenerated and applied by the operating voltage applying unit1is applied to the operating voltage applying node Ninto which the first ends, i.e., the drains of the first switching element S1and the second switching element S2are connected together.

Then, as shown inFIG.2, the charging current flows in a closed circuit formed by the operating voltage applying node Nin--> the first switching element S1--> the first node N1--> the first inductor L1--> the third node N3--> the positive (+) terminal of the secondary battery3--> the negative (-) terminal of the secondary battery3--> the fourth node N4--> the second inductor L2--> the second node N2--> the fourth switching element S4--> the reference node Nr--> the operating voltage applying unit1.

As the operating voltage Vinis applied to the first inductor L1, the first inductor L1allows the charging current to stably flow to the positive (+) terminal of the secondary battery3, and this flow of the charging current enables charging the secondary battery3. Further, as the charging current flows along the second inductor L2and the fourth switching element S4, the negative (-) terminal of the secondary battery3is connected to the reference node Nrto which the second end of the first capacitor C1is connected, and the positive (+) terminal of the secondary battery3and the first end of the first capacitor C1are connected via the third node N3, so that the secondary battery3can be maintained as connected in parallel with the first capacitor C1, thereby charging the secondary battery3while a stable waveform is maintained by the first capacitor C1operating as the voltage stabilizing capacitor.

Meanwhile, as described above, in the charge mode shown inFIG.2, the operating voltage Vinis applied to the operating voltage applying node Nin, and therefore, as shown inFIG.4, the voltage VNinat the operating voltage applying node Ninis +Vinand is continuously maintained at a constant level of +Vinduring the charge mode.

As the first switching element S1is turned on, the voltage applied to the first node N1becomes +Vincorresponding to the operating voltage on the premise that the voltage drop in the first switching element S1is “0”. Further, as the fourth switching element S4is turned on, the voltage applied to the second node N2becomes “0”, i.e., the ground voltage at the reference node Nron the premise that the voltage drop in the fourth switching element S4is “0”. Therefore, voltage between the first node N1and the second node N2, specifically, voltage Vxat the first node N1with respect to the second node N2becomes +Vincorresponding to the operating voltage as shown inFIG.4.

Because the voltage Vxat the first node N1with respect to the second node N2becomes +Vin, the first inductor L1allows the charging current to flow from the positive (+) terminal toward the negative (-) terminal of the secondary battery3, thereby charging the secondary battery3. Of course, the second inductor L2is also helpful in flowing the charging current because the charging current flows along the closed circuit.

Referring toFIG.3, the operations in the discharge mode Mode2for discharging the secondary battery3and the flow of the discharging current are as follows.

The switching control signal corresponding to the discharge mode Mode2ofFIG.4is output from the control unit5to the switching signal generation unit7ofFIG.5. In other words, in the discharge mode Mode2ofFIG.4, the switching signal generation unit7outputs a turning-on signal to the gates of the second switching element S2and the third switching element S3, and at the same time outputs a turning-off signal to the first switching element S1and the fourth switching element S4. Then, the second switching element S2and the third switching element S3are turned on, and at the same time the first switching element S1and the fourth switching element S4are turned off.

As described above, the applying voltage Vingenerated and applied by the operating voltage applying unit1is applied to the operating voltage applying node Ninto which the first ends, i.e., the drains of the first switching element S1and the second switching element S2are connected together.

Then, as shown inFIG.2, the charging current flows in a closed circuit formed by the operating voltage applying node Nin--> the second switching element S2--> the second node N2--> the second inductor L2--> the fourth node(N4) --> the negative (-) terminal of the secondary battery3--> the positive (+) terminal of the secondary battery3--> the third node N3--> the first inductor L1--> the first node N1--> the third switching element S3--> the reference node Nr--> the operating voltage applying unit1. Eventually, current (i.e., the discharging current) flows from the negative (-) terminal to the positive (+) terminal of the secondary battery3, so that the secondary battery3can perform a discharge operation of discharging the charged voltage.

As the operating voltage Vinis applied to the second inductor L2, the second inductor L2allows the discharging current to stably flow to the negative (-) terminal of the secondary battery3, and this flow of the discharging current enables discharging the voltage charged in the charge mode from the secondary battery3. Further, as the discharging current flows along the first inductor L1and the third switching element S3, the positive (+) terminal of the secondary battery3is connected to the reference node Nrto which the second end of the second capacitor C2is connected, and the negative (-) terminal of the secondary battery3and the first end of the second capacitor C2are connected via the fourth node N4, so that the secondary battery3can be maintained as connected in parallel with the second capacitor C2, thereby discharging the secondary battery3while a stable waveform is maintained by the second capacitor C2operating as the voltage stabilizing capacitor.

In such a discharge process, the second switching element S2and the third switching element S3, which operate in the discharge mode, are continuously maintained as turned on without being turned on and off while the discharge circuit show inFIG.3operates in the discharge mode. As a result, the zero-voltage discharge circuit device according to the disclosure is configured to discharge the secondary battery3while the second switching element S2and the third switching element S3are kept continuously turned on without being repeatedly turned on and off in the discharge mode of the second battery3, so that the discharge circuit can be configured with low withstand voltage switching elements, thereby reducing the costs of configuring the charging/discharging circuit.

Meanwhile, as described above, in the discharge mode shown inFIG.3, the operating voltage Vinis applied to the operating voltage applying node Ninlike that in the charging mode ofFIG.2, and therefore, as shown inFIG.4, the voltage VNinat the operating voltage applying node Ninis +Vinand is continuously maintained at a constant level of +Vinduring the discharge mode.

In other words, the operating voltage applying unit1applies the same operating voltage Vinto the operating voltage applying node Ninin the charge mode Mode1and the discharge mode Mode2of the secondary battery3. Thus, the zero-voltage discharge circuit device according to the disclosure does not change the operating voltage in the charge mode and the discharge mode. In this way, the operating voltage Vinfor each mode is not varied but constantly applied by the operating voltage applying unit1when the zero-voltage discharge circuit device according to the disclosure switches over between the charge mode and the discharge mode. According to the disclosure, the charge mode and the discharge mode are switched over therebetween by just selectively turning on the switching elements without changing the operating voltage Vin. In otherwords, according to the disclosure, the switching elements are just selectively turned on without changing the operating voltage Vinto generate the charging current and the discharging current, thereby having effects on reducing the power loss in the charging and the discharging, and simplifying a control operation for the charging and the discharging.

As the second switching element S2is turned on, the voltage applied to the second node N2becomes +Vincorresponding to the operating voltage on the premise that the voltage drop in the second switching element S2is “0”. Further, as the third switching element S3is turned on, the voltage applied to the first node N1becomes “0”, i.e., the ground voltage at the reference node Nron the premise that the voltage drop in the third switching element S3is “0”. Therefore, voltage between the first node N1and the second node N2, specifically, voltage Vxat the first node N1with respect to the second node N2becomes -Vincorresponding to the negative operating voltage as shown inFIG.4.

Because the voltage Vxat the first node N1with respect to the second node N2becomes -Vin, the second inductor L2allows the charging current to flow from the negative (-) terminal toward the positive (+) terminal of the secondary battery3, thereby discharging the voltage charged in the charge mode from the secondary battery3. Of course, the first inductor L1is also helpful in flowing the discharging current because the discharging current flows along the closed circuit.

As described above, the discharging current flows in the operating voltage applying unit1, thereby causing the voltage of the secondary battery3to be discharged. Meanwhile, in this discharging process, the voltage of the secondary battery3is not enough to achieve the discharging up to 0 V. To this end, the zero-voltage discharge circuit device according to the disclosure applies the same operating voltage as that for the charge mode to the operating voltage applying node in the discharge mode, and, as a result, the operating voltage is induced in the second inductor L2by turning on the second switching element S2. The operating voltage induced in the second inductor L2serves as auxiliary power in the discharge mode, so that the discharging current of the secondary battery3can be maintained even in a region where the voltage of the secondary battery3is low. Therefore, the secondary battery is sufficiently discharged up to 0 V.

Although a few embodiments of the disclosure have been described above, it will be apparent for a person having ordinary knowledge in the art that these descriptions are for the illustrative purposes only and various changes can be made without departing from the scope of the disclosure. Accordingly, the genuine technical scope of the disclosure should be defined by the appended claims.

Industrial Applicability

A zero-voltage discharge circuit device according to the disclosure is configured to discharge a secondary battery while relevant switching elements are kept continuously turned on without being repeatedly turned on and off in a discharge mode of the second battery, so that the discharge circuit can be configured with low withstand voltage switching elements, thereby having industrial applicability of reducing costs of configuring a charging/discharging circuit.