Voltage-equalizing control circuit, source-carrying system and electronic equipment

Abstract

The present application discloses a voltage-equalizing control circuit, a source-load system, and an electronic device. The voltage-equalizing control circuit includes: a power input terminal, a DC-DC module, a voltage sampling unit, and a control unit. The control unit includes an MCU, a DC-DC voltage-equalizing control loop, and a BUCK output control loop. The signal output terminal of the DC-DC voltage-equalizing control loop is respectively connected to the control terminal of the DC-DC module to adjust the output voltage of the DC-DC module according to the DC-DC set voltage value, the given value of the voltage-equalizing bus, and the output voltage of each BUCK module so that the output voltages of each BUCK module are equal; the signal output terminal of the BUCK output control loop is respectively connected to the control terminal of each BUCK module. Voltage-equalizing control of BUCK modules in series can be realized.

Description

Technical Field

[0001] The present application relates to the field of source-carrying systems, and in particular to a voltage-sharing control circuit, a source-carrying system and electronic equipment. Background Art

[0002] In a source-load system, in order to achieve high-power output voltage, multiple buck modules are usually connected in series at the output end to achieve voltage boost.

[0003] The existing three BUCK modules are connected in series to boost the voltage. Figure 7 As shown, in actual applications, the source-load system needs to achieve voltage balancing among the three BUCK modules, that is, the output voltage of each BUCK module is one-third of the total output voltage. If the voltage balancing of the BUCK modules cannot be achieved, the total output voltage may be too high, or the voltage of a certain BUCK module may be too high, which may easily cause the switch tube or capacitor to break down, resulting in power failure.

[0004] A common voltage balancing method is to use BUCK modules with the same hardware materials to achieve voltage balancing. For example, switch tubes, capacitors, inductors, and drive traces of the switch tubes produced by the same manufacturer and the same batch are selected with the same length, and the power traces are the same. However, since it is difficult to achieve complete consistency in parasitic parameters such as the DC impedance of the inductor and the on-resistance of the MOS tube in each BUCK module, or factors such as the switch tube is not synchronized, it is difficult to achieve voltage balancing of the BUCK module. Summary of the invention

[0005] The present application proposes a voltage-sharing control circuit, a source-load system and an electronic device, which can realize voltage-sharing control of BUCK modules connected in series.

[0006] According to the voltage balancing control circuit of the first aspect of the present application, which is used to connect at least two BUCK modules connected in series, it includes: a power input end, which is used to provide a bus voltage; a DC-DC module corresponding to the BUCK module one by one, the power input end is connected to the input end of the DC-DC module, and the output end of the DC-DC module is connected to the input end of the corresponding BUCK module; a voltage sampling unit, the voltage sampling unit includes a total voltage sampling module and a partial voltage sampling module, the total voltage sampling module is used to collect the total output voltage of the series BUCK modules, and the partial voltage sampling module is used to collect the output voltage of each BUCK module; a control unit, the control unit includes an MCU, a DC-DC voltage balancing control loop and a BUCK output control loop; the MCU is connected to the first input end of the DC-DC voltage balancing control loop for inputting a DC-DC set voltage value, and the total voltage sampling module is connected to the second input end of the DC-DC voltage balancing control loop for inputting a DC-DC set voltage value. The second input terminal is used to input a given value of the voltage-equalizing bus, and the given value of the voltage-equalizing bus is one-Nth of the total output voltage, where N is the number of BUCK modules; the voltage-dividing sampling module is connected to the third input terminal of the DC-DC voltage-equalizing control loop to input the output voltage of each BUCK module, and the signal output terminals of the DC-DC voltage-equalizing control loop are respectively connected to the control terminals of the DC-DC modules to adjust the output voltage of the DC-DC modules according to the DC-DC set voltage value, the given value of the voltage-equalizing bus and the output voltage of each BUCK module so that the output voltages of each BUCK module are equal; the MCU is connected to the input terminal of the BUCK output control loop to input the total output voltage set value, and the total voltage sampling module is connected to the feedback terminal of the BUCK output control loop to input the total output voltage feedback value, and the signal output terminals of the BUCK output control loop are respectively connected to the control terminals of each BUCK module.

[0007] According to some embodiments of the present application, the DC-DC voltage balancing control loop includes a first subtractor, a first PI error amplifier, a second subtractor and a first PWM modulator, the first subtractor, the first PI error amplifier, the second subtractor and the first PWM modulator all correspond to the BUCK modules one by one, the total voltage sampling module is connected to the first input end of the first subtractor for inputting the given value of the voltage balancing bus, the divided voltage sampling module is connected to the second input end of the first subtractor for inputting the output voltage of the corresponding BUCK module, the output end of the first subtractor is connected to the input end of the first PI error amplifier, the output end of the first PI error amplifier is connected to the first input end of the second subtractor, the MCU is connected to the second input end of the second subtractor for inputting the DC-DC set voltage value, the output end of the second subtractor is connected to the input end of the first PWM modulator, and the output end of the first PWM modulator is connected to the control end of the corresponding DC-DC module for adjusting the output voltage of the DC-DC module so that the output voltages of each BUCK module are equal.

[0008] According to some embodiments of the present application, the DC-DC module is an LLC resonant converter, the first PWM modulator is a voltage controlled oscillator, and the voltage controlled oscillator is connected to a control terminal corresponding to the LLC resonant converter.

[0009] According to some embodiments of the present application, the BUCK output control loop includes a third subtractor, a second PI error amplifier and a second PWM modulator, the MCU is connected to the first input end of the third subtractor for inputting a total output voltage setting value, the total voltage sampling module is connected to the second input end of the third subtractor for inputting a total output voltage feedback value, the output end of the third subtractor is connected to the input end of the second PI error amplifier, the output end of the second PI error amplifier is connected to the input end of the second PWM modulator, and the output end of the second PWM modulator is respectively connected to the control end of each BUCK module.

[0010] According to some embodiments of the present application, a PFC module is further included, wherein an input end of the PFC module is used to connect to an AC input power supply, and an output end of the PFC module is connected to the power input end.

[0011] According to the second aspect of the present application, the source-load system includes a BUCK circuit and the above-mentioned voltage-sharing control circuit, wherein the voltage-sharing control circuit is connected to the BUCK circuit, and the BUCK circuit includes at least two BUCK modules connected in series.

[0012] An electronic device according to an embodiment of the third aspect of the present application includes the above-mentioned voltage equalization control circuit.

[0013] The voltage-sharing control circuit, source-carrying system, and electronic device according to the embodiments of the present application have at least the following beneficial effects:

[0014] In the implementation manner of the present application, a bus voltage is provided through the power input end, and the bus voltage is converted into a voltage by a DC-DC module corresponding to the BUCK module one by one and then input into the corresponding BUCK module as an input voltage. The signal output end of the DC-DC voltage balancing control loop adjusts the output voltage of the DC-DC module according to the DC-DC set voltage value, the given value of the voltage balancing bus and the output voltage of each BUCK module. The input voltage of each BUCK module is changed by adjusting the output voltage of the DC-DC module, thereby achieving the effect of equal output voltage of each BUCK module. At the same time, the BUCK output control loop is adjusted according to the total output voltage set value and the total output voltage feedback value, which can maintain the stability of the total output voltage and realize the synchronization of the MOS tubes in each BUCK module. The present application can realize voltage balancing control of the BUCK modules in series by jointly adjusting the DC-DC voltage balancing control loop and the BUCK output control loop.

[0015] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become apparent from the description below, or will be learned through the practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The present application is further described below with reference to the accompanying drawings and embodiments, wherein:

[0017] Figure 1 Schematic diagram of a DC-DC module in a voltage balancing control circuit in an embodiment of the present application;

[0018] Figure 2 Schematic diagram of a DC-DC voltage balancing control loop in an embodiment of the present application;

[0019] Figure 3 Schematic diagram of a BUCK output control loop in an embodiment of the present application;

[0020] Figure 4 Schematic diagram of a DC-DC module using LLC in an embodiment of the present application;

[0021] Figure 5 Schematic diagram of a DC-DC voltage balancing control loop using LLC in an embodiment of the present application;

[0022] Figure 6 Schematic diagram of a BUCK output control loop using LLC in an embodiment of the present application;

[0023] Figure 7 Schematic diagram of BUCK modules with series boost. DETAILED DESCRIPTION

[0024] The embodiments of the present application are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present application, and cannot be understood as limiting the present application.

[0025] In the description of the present application, it should be understood that the descriptions involving orientation, such as the orientation or positional relationship indicated as up, down, etc., are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0026] In the description of this application, "a plurality" means more than two. If there is a description of "first" or "second", it is only for the purpose of distinguishing technical features, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features or implicitly indicating the order of the indicated technical features.

[0027] In the description of this application, unless otherwise clearly defined, terms such as setting, installing, connecting, etc. should be understood in a broad sense, and technicians in the relevant technical field can reasonably determine the specific meanings of the above terms in this application based on the specific content of the technical solution.

[0028] Reference Figures 1 to 3 As shown, a voltage balancing control circuit is used to connect at least two BUCK modules in series. Figure 7As shown, the embodiment of the present application includes three BUCK modules connected in series, the first BUCK module is composed of a MOS tube Q1, a MOS tube Q2, an inductor L1 and a capacitor C1, the second BUCK module is composed of a MOS tube Q3, a MOS tube Q4, an inductor L2 and a capacitor C2, and the third BUCK module is composed of a MOS tube Q5, a MOS tube Q6, an inductor L3 and a capacitor C3, wherein the MOS tube Q1, the MOS tube Q3, and the MOS tube Q5 share a PWM signal, and the MOS tube Q2, the MOS tube Q4, and the MOS tube Q6 share a PWM signal. The voltage equalization control circuit of the present application includes: a power input end, a DC-DC module, a voltage sampling unit and a control unit. Specifically, the power input terminal is used to provide the bus voltage VBUS; the DC-DC module corresponds to the BUCK module one by one, the power input terminal is respectively connected to the input terminal of the DC-DC module, and the output terminal of the DC-DC module is connected to the input terminal of the corresponding BUCK module. In this embodiment, there are three BUCK modules, so there are also three DC-DC modules, namely the first DC-DC module, the second DC-DC module and the third DC-DC module, which are respectively connected to the three BUCK modules to provide input voltage; the voltage sampling unit includes a total voltage sampling module and a partial voltage sampling module. The total voltage sampling module is used to collect the total output voltage of the series-connected BUCK modules, and the partial voltage sampling module is used to collect the output voltage of each BUCK module. In this embodiment, there are three BUCK modules, and the output voltages of the three BUCK modules are respectively set to V1, V2 and V3, and the total output voltage of the three BUCK modules after being connected in series is set to VO.

[0029] Specifically, in the embodiment of the present application, the control unit includes an MCU, a DC-DC voltage balancing control loop and a BUCK output control loop; the MCU is connected to the first input end of the DC-DC voltage balancing control loop for inputting a DC-DC set voltage value VSET1, and the total voltage sampling module is connected to the second input end of the DC-DC voltage balancing control loop for inputting a given value of the voltage balancing bus, and the given value of the input voltage balancing bus is one-Nth of the total output voltage, where N is the number of BUCK modules, and in this embodiment, N=3, so the given value of the voltage balancing bus is VO / 3; the voltage sampling module is connected to the third input end of the DC-DC voltage balancing control loop for inputting the values ​​of ... The output voltage of the DC-DC voltage balancing control loop is respectively connected to the control end of the DC-DC module for adjusting the output voltage of the DC-DC module according to the DC-DC set voltage value VSET1, the given value VO / 3 of the voltage balancing bus and the output voltage of each BUCK module, so that the output voltages of each BUCK module are equal; the MCU is connected to the input end of the BUCK output control loop for inputting the total output voltage set value VSET2, the total voltage sampling module is connected to the feedback end of the BUCK output control loop for inputting the total output voltage feedback value, and the signal output end of the BUCK output control loop is respectively connected to the control end of each BUCK module.

[0030] In the implementation manner of the present application, a bus voltage VBUS is provided through the power input end, and the bus voltage VBUS is input to the corresponding BUCK module as the input voltage after voltage conversion through a DC-DC module corresponding to the BUCK module one by one. The signal output end of the DC-DC voltage balancing control loop adjusts the output voltage of the DC-DC module according to the DC-DC set voltage value VSET1, the given value VO / 3 of the voltage balancing bus and the output voltage of each BUCK module. The input voltage of each BUCK module is changed by adjusting the output voltage of the DC-DC module, thereby achieving the effect of equal output voltage of each BUCK module. At the same time, the BUCK output control loop is adjusted according to the total output voltage set value and the total output voltage feedback value, which can maintain the stability of the total output voltage and realize the synchronization of the MOS tubes in each BUCK module. The present application can realize voltage balancing control of the BUCK modules in series by jointly adjusting the DC-DC voltage balancing control loop and the BUCK output control loop.

[0031] In the above-mentioned embodiment, the signal output end of the DC-DC voltage balancing control loop adjusts the output voltage of the DC-DC module according to the DC-DC set voltage value VSET1, the given value VO / 3 of the voltage balancing bus and the output voltage of each BUCK module, which means that if the output voltage of the first BUCK module is greater than one-third of the total output voltage, the output voltage of the first DC-DC module is correspondingly reduced, that is, the input voltage of the first BUCK module is reduced; if the output voltage of the second BUCK module is less than one-third of the total output voltage, the output voltage of the second DC-DC module is correspondingly increased, that is, the input voltage of the first BUCK module is increased, and finally, through the action of the voltage balancing ring, the output voltages of the three BUCK modules are all VO / 3.

[0032] In some embodiments of the present application, the DC-DC voltage balancing control loop includes a first subtractor, a first PI error amplifier, a second subtractor and a first PWM modulator. The first subtractor, the first PI error amplifier, the second subtractor and the first PWM modulator all correspond to the BUCK modules one by one. The total voltage sampling module is connected to the first input end of the first subtractor for inputting the given value of the voltage balancing bus. The divided voltage sampling module is connected to the second input end of the first subtractor for inputting the output voltage of the corresponding BUCK module, i.e., V1 / V2 / V3. The output end of the first subtractor is connected to the input end of the first PI error amplifier. The output end of the first PI error amplifier is connected to the first input end of the second subtractor. The MCU is connected to the second input end of the second subtractor for inputting the DC-DC set voltage value. The output end of the second subtractor is connected to the input end of the first PWM modulator. The output end of the first PWM modulator is connected to the control end of the corresponding DC-DC module for adjusting the output voltage of the DC-DC module so that the output voltages of each BUCK module are equal.

[0033] In this embodiment, since there are three DC-DC modules, the DC-DC voltage balancing control loop also includes three groups of DC-DC voltage balancing loops, each of which includes a first subtractor, a first PI error amplifier, a second subtractor and a first PWM modulator. The function of the first subtractor is to subtract the output voltage of the BUCK module from the given value of the voltage balancing bus, and then obtain an error signal through the first PI error amplifier. Then, the DC-DC set voltage value is subtracted from the error signal through the third subtractor, and the first PWM modulator outputs three PWM waves of different frequencies to adjust the output voltages of the three DC-DC modules. In this embodiment, the three first PWM modulators respectively output PWM-DC-DC1, PWM-DC-DC2, and PWM-DC-DC3, and drive their respective DC-DC modules. Through these three groups of voltage balancing loops, the output voltage is balanced.

[0034] In some embodiments of the present application, the BUCK output control loop includes a third subtractor, a second PI error amplifier and a second PWM modulator, the MCU is connected to the first input end of the third subtractor for inputting the total output voltage set value VSET2, the total voltage sampling module is connected to the second input end of the third subtractor for inputting the total output voltage feedback value, the output end of the third subtractor is connected to the input end of the second PI error amplifier, the output end of the second PI error amplifier is connected to the input end of the second PWM modulator, and the output end of the second PWM modulator is respectively connected to the control end of each BUCK module.

[0035] In this embodiment, the function of the third subtractor is to subtract the total output voltage setting value VSET2 from the total output voltage feedback value VO, and after inputting the PI error, the PWM signals PWMA and PWMB of the BUCK modules are output through the second PWM modulator. These two PWM signals drive the six switch tubes of the three BUCK modules. A single voltage output loop is formed to achieve the stability of the total output voltage, and the three BUCK modules are all controlled by PWMA and PWMB, ensuring the synchronization of the MOS tubes.

[0036] In some embodiments of the present application, a PFC (Power Factor Correction) module is further included, wherein an input end of the PFC module is used to connect to an AC input power supply, and an output end of the PFC module is connected to a power input end.

[0037] In this embodiment, the function of the PFC module is to convert the AC input into the bus voltage VBUS. The AC input power source can be the mains or other AC input devices. It should be understood that in addition to the PFC module, other AC to DC power supply modules can also be used.

[0038] In this implementation, the DC-DC module is an LLC resonant converter, the first PWM modulator is a voltage controlled oscillator, and the voltage controlled oscillator is connected to a control terminal of the corresponding LLC resonant converter.

[0039] It should be noted that, in addition to the LLC resonant converter, the DC-DC module may also use other voltage converters such as a phase-shifted full-bridge topology circuit.

[0040] refer to Figures 4 to 6 As shown, the working principle of this application is described in detail below using LLC as an example:

[0041] First, the AC input passes through the PFC module to obtain the bus voltage VBUS, and the bus voltage VBUS passes through three LLC modules. The outputs of the three LLC modules are connected to the inputs of the three BUCK modules respectively.

[0042] VSET-LLC is the LLC setting voltage. The first PWM modulator is a VCO voltage-controlled oscillator. The function of the VCO voltage-controlled oscillator is to output the input voltage into a square wave with a fixed amplitude and a frequency that changes with the input. The VCO controls the LLC open-loop gain by adjusting the frequency. If VSET-LLC is higher, the frequency of the waveform output by the VCO is higher, and the LLC open-loop gain is smaller. Therefore, the VCO controls the LLC output voltage, that is, the input voltage of the BUCK module, by adjusting the LLC open-loop gain.

[0043] The given value of the voltage-equalizing bus is VO / 3, which is 1 / 3 of the total output voltage. The output voltages of the three BUCK modules are subtracted from the voltage-equalizing bus and sent to the first PI error amplifier, and subtracted from VSET-LLC. After the VCO outputs three PWM waves of different frequencies, namely PWM-LLC1, PWM-LLC2, and PWM-LLC3, and drive their respective LLCs. Through these three sets of voltage-equalizing loops, the output voltage is equalized.

[0044] For example, before using the voltage equalization control circuit of the present application, that is, before voltage equalization, the input voltages of the first BUCK module, the second BUCK module, and the third BUCK module are all measured to be 100V, that is, the outputs of LLC1, LLC2, and LLC3 are all 100V. At this time, the output voltages of the first BUCK module, the second BUCK module, and the third BUCK module are measured to be 30V, 50V, and 80V, respectively, and the total output voltage is 150V.

[0045] After adopting the voltage balancing control circuit of the present application, that is, after voltage balancing, since the total output voltage is 150V, the given value of the voltage balancing bus is 50V, and the output of the first BUCK module is less than the given value of the voltage balancing bus. The DC-DC voltage balancing control loop increases the frequency of LLC1, that is, increases the output voltage of LLC1. Similarly, the output of the third BUCK module is greater than the given value of the voltage balancing bus, and the DC-DC voltage balancing control loop reduces the output voltage of LLC1, while the output voltage of LLC2 is equal to the given value of the voltage balancing bus, and therefore remains unchanged. Finally, the output of LLC1 is adjusted to 90V, and the output of LLC3 is adjusted to 110V. It is measured again that the output voltages of the first BUCK module, the second BUCK module, and the third BUCK module are all 50V, and finally the voltage balancing of the outputs of the three BUCK modules is achieved.

[0046] The present application also relates to a source-load system, comprising a BUCK circuit and the voltage-equalizing control circuit of the above embodiment, wherein the voltage-equalizing control circuit is connected to the BUCK circuit, and the BUCK circuit comprises at least two BUCK modules connected in series.

[0047] The present application also relates to an electronic device, comprising the voltage equalization control circuit of the above embodiment.

[0048] The embodiments of the present application are described in detail above in conjunction with the accompanying drawings, but the present application is not limited to the above embodiments, and various changes can be made within the knowledge scope of ordinary technicians in the relevant technical field without departing from the purpose of the present application.

Claims

1. A voltage balancing control circuit, used to connect at least two BUCK modules in series, characterized in that: include: Power input terminal, used to provide bus voltage; A DC-DC module corresponding to each BUCK module, wherein the power input end is connected to the input end of the DC-DC module, and the output end of the DC-DC module is connected to the input end of the corresponding BUCK module; A voltage sampling unit, the voltage sampling unit comprising a total voltage sampling module and a sub-voltage sampling module, the total voltage sampling module is used to collect the total output voltage of the series-connected BUCK modules, and the sub-voltage sampling module is used to collect the output voltage of each BUCK module; A control unit, the control unit comprising an MCU, a DC-DC voltage balancing control loop and a BUCK output control loop; The MCU is connected to the first input end of the DC-DC voltage-sharing control loop for inputting a DC-DC set voltage value, the total voltage sampling module is connected to the second input end of the DC-DC voltage-sharing control loop for inputting a given value of the voltage-sharing bus, the given value of the input voltage-sharing bus is one-Nth of the total output voltage, and N is the number of BUCK modules; the voltage-dividing sampling module is connected to the third input end of the DC-DC voltage-sharing control loop for inputting the output voltage of each BUCK module, the signal output end of the DC-DC voltage-sharing control loop is respectively connected to the control end of the DC-DC module for adjusting the output voltage of the DC-DC module according to the DC-DC set voltage value, the given value of the voltage-sharing bus and the output voltage of each BUCK module so that the output voltages of each BUCK module are equal; the MCU is connected to the input end of the BUCK output control loop for inputting a total output voltage set value, the total voltage sampling module is connected to the feedback end of the BUCK output control loop for inputting a total output voltage feedback value, and the signal output end of the BUCK output control loop is respectively connected to the control end of each BUCK module.

2. The voltage balancing control circuit according to claim 1, characterized in that: The DC-DC voltage balancing control loop includes a first subtractor, a first PI error amplifier, a second subtractor and a first PWM modulator. The first subtractor, the first PI error amplifier, the second subtractor and the first PWM modulator all correspond to the BUCK modules one by one. The total voltage sampling module is connected to the first input end of the first subtractor for inputting the given value of the voltage balancing bus. The divided voltage sampling module is connected to the second input end of the first subtractor for inputting the output voltage of the corresponding BUCK module. The output end of the first subtractor is connected to the input end of the first PI error amplifier. The output end of the first PI error amplifier is connected to the first input end of the second subtractor. The MCU is connected to the second input end of the second subtractor for inputting the DC-DC set voltage value. The output end of the second subtractor is connected to the input end of the first PWM modulator. The output end of the first PWM modulator is connected to the control end of the corresponding DC-DC module for adjusting the output voltage of the DC-DC module so that the output voltages of each BUCK module are equal.

3. The voltage balancing control circuit according to claim 2, characterized in that: The DC-DC module is an LLC resonant converter, the first PWM modulator is a voltage controlled oscillator, and the voltage controlled oscillator is connected to a control terminal corresponding to the LLC resonant converter.

4. The voltage balancing control circuit according to claim 1, characterized in that: The BUCK output control loop includes a third subtractor, a second PI error amplifier and a second PWM modulator. The MCU is connected to a first input terminal of the third subtractor for inputting a total output voltage setting value. The total voltage sampling module is connected to a second input terminal of the third subtractor for inputting a total output voltage feedback value. The output terminal of the third subtractor is connected to an input terminal of the second PI error amplifier. The output terminal of the second PI error amplifier is connected to an input terminal of the second PWM modulator. The output terminal of the second PWM modulator is respectively connected to the control terminal of each BUCK module.

5. The voltage balancing control circuit according to claim 1, characterized in that: It also includes a PFC module, the input end of the PFC module is used to connect to an AC input power supply, and the output end of the PFC module is connected to the power input end.

6. A source-carrying system, characterized in that: It comprises a BUCK circuit and the voltage balancing control circuit according to any one of claims 1 to 5, wherein the voltage balancing control circuit is connected to the BUCK circuit, and the BUCK circuit comprises at least two BUCK modules connected in series.

7. An electronic device, characterized in that: The invention comprises the voltage equalizing control circuit as described in any one of claims 1 to 5.

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