KR20060091450A - Charge balancing circuit for solar cell and rechargeable lithium battery - Google Patents

Abstract

The present invention relates to a charge control circuit for charging a lithium secondary battery using the output electricity from the solar cell.

The charge control circuit according to the present invention includes a charge control for a solar cell and a lithium secondary battery including a constant current charge (hereinafter referred to as "CC") and a constant voltage charge (hereinafter referred to as "CV") circuit In the circuit, the charge control circuit is connected to a solar cell and a maximum power point tracking controller (hereinafter referred to as 'MPPT') comprising an analog op amp operational amplifier that compares the reference solar cell voltage with the actual solar cell voltage and outputs the result. Maximum Power Point Tracking), and the MPPT controller, CC controller, and CV controller are connected by diode-AND, and the MPPT controller, CC controller, and CV controllers Comparator for AND outputting three output signals and comparing them to a triangular wave, and a gate driver for driving two control signals compared through the comparator with switch S1 and S2 control signals. It is characterized by.

Description

Charge Balancing Circuit For Solar Cell And Rechargeable Lithium Battery}

1 is a schematic diagram of a solar cell-lithium secondary battery charging circuit and a controller according to the present invention.

2 is a flowchart of a controller operation mode according to the present invention.

Figure 3 is a waveform diagram of the battery voltage, current, solar cell voltage when switching the MPPT-CV controller according to the present invention.

Explanation of symbols on the main parts of the drawings

10: load

20 solar cell

30: gate driver

40: MPPT controller

50: CC controller

60: CV controller

The present invention relates to a charge control circuit for a solar cell and a lithium secondary battery, and more particularly, to a charge control circuit for charging a lithium secondary battery using the output electricity from the solar cell.

As the functions of mobile electronic devices are diversified and advanced, the power demand for mobile power sources continues to increase, and accordingly, the need for power systems using free energy sources such as solar power is increasing.

In the conventional commercial mobile devices, the technology used to charge the lithium secondary battery uses an input power source as a commercial AC power source, and converts it into a DC power source, followed by constant current charging (Constant Current) and constant voltage charging (Constant). Voltage (hereinafter referred to as 'CV') technology is a type of continuous operation, that is, CC-CV technology is used.

In order to charge a lithium secondary battery with a solar cell, the constant current circuit and the constant voltage circuit should be configured as described above. The solar cell is a non-linear current source that generates a current proportional to the amount of incident light. Since the operating characteristics are changed in proportion to, a maximum power charging circuit capable of detecting and controlling the state of the solar cell is required.

However, the conventional power system using a solar cell is not equipped with such a maximum power charging circuit for the current source through the solar cell has a problem that the efficiency is lowered in use, for this reason there is a problem that it is not practically used a lot and difficult to commercialize.

An object of the present invention has been proposed to solve the problems in the prior art as described above, comprising a charge control circuit consisting of a maximum power charging circuit, a constant current charging circuit and a constant voltage charging circuit, each of the circuit input conditions And a charging control circuit related to a matching circuit operated according to a battery condition.

According to a preferred embodiment of the present invention for achieving the above object, an embodiment including a constant current charging (hereinafter referred to as 'CC') and a constant voltage charging (hereinafter referred to as 'CV') circuit A charge control circuit for a battery and a lithium secondary battery, the maximum power point tracking controller including an analog op amp operational amplifier connected to a solar cell and comparing a reference solar cell voltage with a solar cell real voltage and outputting the result. (MPPT controller) and a comparator for comparing the output of one of the outputs of the MPPT controller, CC controller, and CV controller and the reference wave, and one control signal output through the comparator with the switch S1 and S2 control signals. Provided is a charge control circuit for a solar cell and a lithium secondary battery, comprising a gate driver.

Preferably, the MPPT controller, the CC controller and the CV controller comprise AC gain amplifier circuits F1 (s) 46, F2 (s) 54, and F3 (s) 64, respectively. They are characterized as PI controllers that have a steady state error of 0 and fast transient response for the input and output response characteristics, respectively.

Also, preferably, when the power Psa coming from the solar cell is smaller than the power Pbat required by the battery, the controller tracks the maximum power from the solar cell and charges the battery, that is, the MPPT controller is operated. Each condition is Vref> Vbat, Iref> Ibat. In this case, the state of the controllers is disabled for the CC controller and the CV controller, and the MPPT controller is enabled for the MPPT controller. The controller is characterized in that the operation.

Also preferably, if the energy that can be extracted from the solar cell is greater than the energy required by the battery, it must enter the battery current-voltage control state, which can be known by first observing the battery current, ie Ibat> Iref. When the controller enters CC-control state, Vref> Vbat, Vsa> Vsa_ref, CV-controller and MPPT-controller are disabled, CC-controller is enabled, and the battery is in constant current control mode. It is characterized by being entered.

Also preferably, when the battery voltage reaches the full charge voltage (Vbat> Vref), the CC-controller and the MPPT-controller are disabled to enter the CV-controlled state and eventually the CV-controller is enabled. In this case, the state is Iref > Ibat and Vsa > Vsa_ref, and the above state transition is continuously changed according to the states of the battery and the solar cell.

Hereinafter, the charge control circuit according to the present invention will be described in detail with reference to the accompanying drawings.

1 is a schematic diagram of a solar cell-lithium secondary battery charging circuit and a controller according to the present invention.

As shown in the drawing, the new charge control circuit 100 proposed in the present invention comprises 1) a maximum power charging circuit 2) a constant current charging circuit 3) a constant voltage charging circuit, and each charging circuit includes a battery state and an external input condition. It is operated sequentially according to.

Referring to FIG. 1, the power stage includes a synchronous buck converter in order to have high energy conversion efficiency.

The charge control circuit 100 is a circuit for maximizing charging efficiency when charging a capacitor and a lithium secondary battery from a solar cell. The three controllers 40, 50, and 60 have three output values because the output terminals are connected to a reverse diode. Only one output value is selected to be selected. Each of the controllers 40, 50, and 60 is referred to as a maximum power point tracking controller (hereinafter referred to as a 'Maximum Power Point Tracking (MPPT) controller.') And a CC controller ( 50) (battery constant charge current controller, usually reference current is set at 0.5C of battery capacity) and CV-controller 60 (battery constant charge voltage controller, usually full charge voltage is set at 4.2V) It is.

The reference current and full charge voltage were selected from current commercially available lithium ion batteries and polymer-based lithium battery data sheets.

One of the three selected output signals of the controllers 40, 50, and 60 is compared with a triangular wave, which is a reference wave, through the comparator 70 to generate two switch signals S1 and S2, and a gate driver. The switches 22 and 24 are driven through the 30. F1 (s) (46), F2 (s) (54), and F3 (s) (64) are AC gain amplifier circuits, and the steady-state error is zero for the response characteristics of the input and output and fast transient response characteristics are achieved. Branch was selected PI controller.

Reference numeral 20 denotes a solar cell.

Reference numeral 14 denotes a battery (cell), and 11 and 12 denote capacitors. Reference numeral 10 denotes a load.

In addition, reference numerals 33, 52, and 62 denote analog op amp operational amplifiers comparing the reference solar cell voltage and the solar cell voltage, analog op amp operational amplifiers comparing the reference current and the battery current, and comparing the reference voltage and the battery voltage, respectively. Analog op amp operational amplifier.

The analog op amp operational amplifier 44 is connected at one side (non-inverting terminal) to the solar cell 20 and the other side (inverting terminal) to the MPPT reference generator 42, and the gain amplifier circuit 46 is at one side. Is connected to the inverting terminal of the operational amplifier 44 and the other side is connected to the output terminal. The output stage is coupled to the reverse diode 82 to enable if the output of the comparator is negative and to disable it.

In addition, the analog op amp operational amplifier 52 is connected to the negative terminal of the battery 14, one side (inverting terminal) and the other side (non-inverting terminal) is connected to the reference current, the gain amplifier 54 is One side is connected to the inverting terminal of the operational amplifier 54 and the other side is connected to the output terminal. The output stage is coupled to reverse diode 84 to enable if the output of the comparator is negative and disabled if it is positive.

The analog op amp operational amplifier 62 is connected at one side (inverting terminal) to the positive terminal of the battery 14 and the other side (non-inverting terminal) to a reference voltage, and at one side of the gain amplifier circuit 64. It is connected to the inverting terminal of the operational amplifier 62 and the other side is connected to the output terminal. The output stage is coupled to the reverse diode 86 to enable if the output of the comparator is negative and to disable it.

In addition, reference numerals 22 and 24 denote switching elements switched by control signals S1 and S2, respectively, and are connected in series and in parallel between the solar cell 20 and the load 10, respectively, and the gate driver 30 Are adapted to accept a switching signal from the device.

2 is a flowchart of a controller operation mode according to the present invention. Controller configuration and operation principle are as follows.

As shown in FIG. 2, when the operation of the controller is shown through a flowchart, first, when the power Psa input from the solar cell is smaller than the power Pbat required by the battery (ST-2), the controller determines the maximum power in the solar cell. It will track and charge the battery. That is, the MPPT controller 40 is in the operating state, and each condition (Condition) becomes Vref > Vbat and Iref > Ibat. In this case, the state of the controllers is the CC-controller 50 and the CV-controller 60 is disabled (Disable), the MPPT controller 40 is enabled (Enable) and the MPPT controller 40 is operated.

If the energy that can be extracted from the solar cell is greater than the energy required by the battery, it must enter the battery current-voltage control state, which can be seen by first observing the battery current (ST-4). That is, in step ST-4, if Ibat> Iref, the controller enters the CC-control state and becomes Vref> Vbat and Vsa> Vsa_ref so that the CV-controller 60 and the MPPT-controller 40 are disabled. The CC controller 50 is enabled and the battery enters the constant current control mode.

If the battery voltage reaches the full charge voltage (Vbat> Vref), the CC-controller 50 and the MPPT-controller 40 are disabled to enter the CV-controlled state and eventually the CV-controller 60 Is enabled, and the state at this time is Iref > Ibat and Vsa > Vsa_ref. The above state transition changes continuously according to the state of the battery and the solar cell. This operation is implemented by the analog operational amplifier (OP-Amp) shown in Figure 1, the operation principle is the same as FIG.

Figure 3 is a waveform diagram of the battery voltage, current, solar cell voltage when switching the MPPT-CV controller according to the present invention.

Referring to FIG. 3, an experiment was performed with an actual circuit designed according to the structure of FIG. 1. 3 shows waveforms of the solar cell voltage and the battery voltage-current during charging. When the controller operates in MPPT mode and the battery voltage reaches 4.2 [V], the full charge voltage, the controller switches to CV mode. In CV mode, the voltage of the battery remains constant, but as the charge inside the battery continues to increase, the charge current continues to decrease. At this time, the voltage of the solar cell continues to increase. This is because the operating point of the solar cell is maintained at the maximum power point in the MPPT mode, but in the CV mode, the operating current of the solar cell is decreased from the maximum power point to the right ( That is, since the voltage moves to the open voltage Voc side, the voltage of the solar cell increases.

According to the charge control circuit according to the present invention, the charge control circuit 1) the maximum power charging circuit for operating at the maximum power point of the solar cell 2) constant current charging circuit for constant current charging 3) constant voltage charging circuit for constant voltage charging It is configured to include, these charging circuits are operated in accordance with the external input conditions and the battery condition in order to have the effect of obtaining the maximum power efficiency when trying to charge the lithium secondary battery using a solar cell.

 The present invention has been described above with reference to the accompanying drawings and embodiments, but the present invention is not limited to the specific embodiments, and modifications of the present invention can be easily carried out by those skilled in the art. It is obvious that it belongs to the technical idea of the invention.

Claims (6)

In the charge control circuit for a solar cell and a lithium-based secondary battery comprising a constant current charge controller (CC controller) and a constant voltage charge controller (CV controller), A maximum power point tracking controller (MPPT controller) including an analog op amp operational amplifier connected to the solar cell and comparing the reference solar cell voltage with the solar cell actual voltage and outputting the result; A comparator for comparing an output of one of the outputs of the MPPT controller, the CC controller, and the CV controller with a reference wave; Gate driver for driving one control signal output through the comparator to the switch S1, S2 control signal Charge control circuit for a solar cell and a lithium-based secondary battery, characterized in that consisting of. The method of claim 1, The MPPT controller, the CC controller and the CV controller include a reverse diode, and if the output value of the controller is negative, the output is enabled, and if the output value is positive, the solar cell and the lithium secondary battery are disabled. Charge control circuit. The method of claim 1, The MPPT controller, the CC controller and the CV controller each comprise an AC gain amplifier circuit F1 (s) 46, F2 (s) 54 and F3 (s) 64, each of which is input. A charge control circuit for a solar cell and a lithium-based secondary battery, characterized in that a steady state error is set to zero for a response characteristic of an over output and a PI controller has a fast transient response characteristic. The method according to claim 1 or 2, When the power Psa coming from the solar cell is smaller than the power Pbat required by the battery, each condition is Vref> Vbat, Iref> Ibat, in which case the state of the controllers is the CC-controller and the CV-controller. Charge control circuit for a solar cell and a lithium-based secondary battery, characterized in that disabled, the MPPT controller is enabled (Enable) to operate the MPPT controller. The method according to claim 1 or 2, If the energy that can be extracted from the solar cell is greater than the energy required by the battery, i.e., Ibat> Iref, then the controller goes into CC-controlled state and becomes Vref> Vbat and Vsa> Vsa_ref, so that the CV-controller and MPPT-controller Is disabled and the CC-controller is enabled (Enable), characterized in that the charge control circuit for solar cells and lithium secondary batteries. The method according to claim 1 or 2, When the battery voltage reaches the full charge voltage (Vbat> Vref), the state is Iref> Ibat and Vsa> Vsa_ref, so that the CC-controller and MPPT-controller are disabled and enter the CV-control state. Eventually, the charge control circuit for solar cells and lithium secondary batteries characterized in that the CV-controller is enabled (enabled).

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