EP3732935A2

EP3732935A2 - A battery control circuit

Info

Publication number: EP3732935A2
Application number: EP18895367.3A
Authority: EP
Inventors: Mehmet Cahit OZDEMIR; Hakan Suleyman YARDIBI; Halil TURKMEN; Mustafa SEKER
Original assignee: Arcelik AS
Current assignee: Arcelik AS
Priority date: 2017-12-26
Filing date: 2018-10-12
Publication date: 2020-11-04
Also published as: EP3732935A4; WO2019132820A2; TR201721920A2; WO2019132820A3

Abstract

The present invention relates to a battery control circuit (1) comprising a protection unit (2) that is suitable for driving capacitive or inductive loads (L) and that monitors the voltage and current values of the battery packs (B) that provide power supply; at least one power switch (3) that enables the current transferred to the load (L) to be switched by being connected to the output signal of the protection unit (2), and a control unit (4) that enables the protection unit (2) and the power switch (3) to be controlled.

Description

A BATTERY CONTROL CIRCUIT

The present invention relates to a battery control circuit that enables the loads with dominant capacitive or inductive characteristics to be driven by battery packs.

Studies for controlling and decreasing the high current drawn by capacitive or inductive loads with low DC resistances during the start-up are known in the art. In systems energized with the mains or batteries high in-rush currents cause safety risks and the use of safety fuses and protective circuits that enable the circuit to be switched off temporarily or permanently during the high current is known in the art. In battery-powered systems, especially in systems wherein lithium-ion batteries are used, the in-rush currents create a more serious problem. The lithium-ion batteries have a rather narrow safe operational range depending on the temperature, voltage and current values. Accordingly, in battery control circuits, protection circuits are provided, enabling the battery to be protected against high current by cutting the output of the battery in case of high current. When the loads that draw high current during the start-up are powered with batteries, the protection circuit that detects the high current cuts the output of the battery and prevents the load from being driven. Thus, in systems comprising battery control circuits, the in-rush currents have to be decreased or the protection unit has to be modified so as not to switch to the protection mode in case of high current. Furthermore, the battery control circuits are used for controlling the charging and discharging cycles of the battery packs and regulating the voltage differences between the battery packs, and another control circuit that is connected to the battery control circuit, especially a driver circuit is required for driving the load.

In the state of the art International Patent Application No. W003009300, decreasing high in-rush currents in battery-powered systems is disclosed.

In the state of the art International Patent Application No. WO2013064333, an induction heating cooker is disclosed, that has a control unit enabling the in-rush currents to be decreased. In the state of the art International Patent Application No. WO2013064332, an induction heating cooker is disclosed, that has a control unit enabling the in-rush currents to be decreased.

In the state of the art International Patent Application No. W02005096679, a circuit used for decreasing in-rush currents is disclosed.

The aim of the present invention is the realization of a battery control circuit wherein the capacitive and inductive loads are protected against in-rush currents and driven with battery.

The battery control circuit realized in order to attain the aim of the present invention, explicated in the claims comprises a protection that monitors the voltage and current values of the battery packs so as to protect the battery packs, the output of which is grounded via an additional power switch, and a control unit that enables the output signal of the protection unit to be changed by driving the additional power switch with pulse width modulation (PWM) signal. By means of the additional power switch and the PWM signal generated by the control unit, the changed output signal of the protection unit becomes similar to a PWM signal. The voltage of the changed output signal is lower than its original voltage. The internal resistance of the power switch the gate of which is driven by the changed output signal and that enables the current to be transferred to the load changes depending on the frequency or the duty cycle of the PWM signal applied by the control unit. By means of the power switch with changed internal resistance, the amount of current transferred to the load changes. Thereby, the amount of current transferred to the load is controlled depending on the frequency or the duty cycle of the PWM signal applied by the control unit without the need for an additional drive circuit for driving the power switch.

In an embodiment of the present invention, the control unit controls the in-rush currents drawn by the load during start-up by changing the frequency or the duty cycle of the PWM signal applied. As the frequency of the PWM signal is increased, the voltage of the changed output signal of the protection unit decreases and the internal resistance of the power switch increases. As the internal resistance of the power switch increases, the total resistance of the system (load and the power switch) increases, and since the battery packs provide a constant voltage, the current value that can be transferred to the load decreases. Thus, the capacitive or inductive load with low internal resistance is prevented from being subject to high in-rush currents during the start-up, and the protection unit is prevented from protecting the battery packs and inhibiting the driving of the load.

In another embodiment of the present invention, the control unit controls the power or rate of the load by changing the frequency or the duty cycle of the PWM signal applied. The amount of current that is transferred to the load is controlled by continuing the application of the PWM signal used by the control unit for decreasing the in-rush currents after the load enters the inductive regime, i.e. after the load shows inductive characteristics (inductive impedance). The frequency of the PWM signal (in the frequency range wherein the power switch operates in the saturation mode) and the amount of current that flows to the load are inversely proportional while the duty cycle of the PWM signal and the amount of current that flows to the load are directly proportional, and thus, the power or rate of the load is controlled by changing the frequency value or the duty cycle of the PWM signal. In order to increase the power or rate of the load, the frequency of the PWM signal is decreased or the duty cycle thereof in constant frequency is increased, and in order to decrease the power or rate of the load, the frequency of the PWM signal is increased or the duty cycle thereof in constant frequency is decreased. By controlling both the frequency and the duty cycle of the PWM signal, the resistance applied by the power switch can be controlled precisely. Thus, the need for using an additional drive circuit or a control unit to control the load is eliminated.

In another embodiment of the present invention, the control unit does not drive the additional power switch when the load is to be activated at maximum power or maximum rate. Since the additional power switch is not driven, the output signal of the protection circuit is transferred to the power switch without being changed, and the voltage value of the output signal is high enough to decrease the internal resistance of the power switch to almost zero. Thus, the amount of current transferred to the load is maximized and the load is driven at maximum power or maximum rate.

By means of the battery control circuit of the present invention, the in-rush currents drawn by the load during start-up are controlled, and by decreasing the in-rush currents, the high- loads that require high currents are enabled to be driven with battery packs without the need for the protection unit to shut off the battery pack for providing overcurrent protection. Moreover, the load is controlled without the need for a separate drive circuit or another circuit element that is used to control the power or rate of the load, and by means of the battery control circuit of the present invention, the load is also controlled.

A battery control circuit realized in order to attain the aim of the present invention is illustrated in the attached figure, where:

Figure 1 - is the schematic view of the battery control circuit.

The elements illustrated in the figures are numbered as follows:

1- Battery control circuit

2- Protection unit

3- Power switch

4- Control unit

5- Additional power switch

B- Battery pack

L- Load

The battery control circuit (1) comprises a protection unit (2) that is suitable for driving capacitive or inductive loads (L) and that monitors the voltage and current values of the battery packs (B) that provide power supply; at least one power switch (3) that enables the current transferred to the load (L) to be switched by being connected to the output signal of the protection unit (2), and a control unit (4) that enables the protection unit (2) and the power switch (3) to be controlled. The control unit (4) is triggered by the user or automatically as programmed in advance so as to enable the battery packs (B) to be charged or discharged through the load (L) by means of the protection unit (2). During the discharge through the load (L), the control unit (4) communicates with the protection unit (2) via the communication protocols and enables the current to be transferred to the load (L). The output signal created in the protection unit (2) that is preferably a 9V signal is transmitted to the gate of the power switch (3) connected to the load (L). When the power switch (3) is turned off by means of the output signal, the current is transferred to the load (L) through the battery packs (B). An additional power switch (3) for charging the battery packs (B) can be used on the battery control circuit (1). The load (L) can be capacitive such as a Peltier cooling element or inductive such as an electric motor. The protection unit (2) cuts the output signal if excess current is drawn from the battery packs (B) to the load (L) despite the command of the control unit (4) to feed current to the load (L) and turns the power switch (3) on, and thus, the battery packs (B) are protected by cutting the current flow to the load (L). The power switch (3) can be state of the art switches such as IGBT, MOSFET, BJT, etc. depending on factors such as the purpose of use or the capacity of the load.

The battery control circuit (1) of the present invention comprises the protection unit (2) the output signal of which is grounded through an additional power switch (5) before entering the power switch (3), and the control unit (4) that enables the additional power switch (5) to be driven with pulse width modulation (PWM) so that the output signal of the protection unit (2) is changed (Figure 1). The output of the protection unit (2) is connected to an additional power switch (5) and the other output of the additional power switch (5) is grounded (other circuit components such as resistances are not shown in Figure 1). The control unit (4) is configured to drive the additional power switch (5) with a pulse width modulation signal (referred to as the PWM signal hereinafter) and to change the output signal of the protection unit (2) when necessary. When the additional power switch (5) is off, the output signal of the protection unit (2) flows to the ground due to the lower resistance, and when the additional power switch (5) is on, the output signal of the protection unit (2) flows to the power switch (3) so as to create a changed output signal. Thus, as the control unit (4) drives the additional power switch (5) with the PWM signal, the output signal of the protection unit (2) simulates the form of the PWM signal, and the power switch (3) that switches the current to the load (L) is enabled to be driven with a signal similar to the PWM signal. Consequently, the power switch (3) is not completely switched off while transferring current to the load (L), creates a resistance against the current flow, and thus, the current drawn by the load (L) is controlled. In an embodiment of the present invention, the control unit (4) controls the in-rush currents that flow to the load (L) during the start-up of the load (L) by changing the frequency of the pulse width modulation signal applied to the additional power switch (5). The control unit (4) can also control the in-rush currents through the additional power switch (5) by changing the duty cycle of the PWM signal. The frequency and the duty cycle of the PWM signal can be changed alternatively or said two variables can be controlled simultaneously. In the embodiments below, only the control of the frequency is disclosed but in all of the embodiments, the same effect can be obtained in a similar manner by decreasing the duty cycle while increasing the frequency or increasing the duty cycle while decreasing the frequency. The voltage of the output signal of the protection unit (2) that is changed so as to have a frequency proportional to the frequency of the PWM signal applied to the additional power switch (5) is sent to the gate of the power switch (3) with a value lower than the output signal received from the protection unit (2), and thus, the on-resistance value of the power switch (3) changes based on the frequency of the PWM signal. As the frequency of the PWM signal applied by the control unit (4) increases, the voltage of the changed output signal of the protection unit (2) decreases and the on-resistance value of the power switch (3) increases. By controlling the resistance on the line through which the current is transferred to the load (L), the in-rush currents drawn by the load (L) at start-up is controlled.

In a version of this embodiment, the control unit (4) enables the in-rush current to be decreased by increasing the frequency of the pulse width modulation signal applied to the additional power switch (5). As disclosed above, by increasing the frequency of the PWM signal applied by the control unit (4), the voltage of the changed output signal of the protection unit (2) is decreased and thereby, the on-resistance value of the power switch (3) is increased. By increasing the frequency of the PWM signal applied by the control unit (4), the resistance value under constant voltage is increased while the amount of current that can be drawn by the load (L) is decreased, and thus, the in-rush currents drawn during the start-up of the load are decreased. Consequently, the protection unit (2) does not cut off the output signal to protect the battery packs (B), and the load (L) can be driven. In another embodiment of the present invention, the control unit (4) controls the power or rate of the load (L) by changing the frequency of the pulse width modulation signal applied to the additional power switch (5). As in the case of in-rush currents during the start-up of the load (L), the current transferred to the load (L), in other words the power or rate of the load (L) can be controlled by changing the frequency or the duty cycle of the PWM signal applied by the control unit (4) after the load (L) enters the inductive regime, in other words reaches the desired inductive impedance value. By means of this embodiment, the need for an additional drive circuit for controlling the power or rate of the load (L) is eliminated.

In a version of this embodiment, the control unit (4) decreases the frequency of the pulse width modulation signal applied to the additional power switch (5) in order to increase the power or rate of the load (L). When the frequency of the PWM signal applied by the control unit (4) is decreased, the voltage of the changed output signal of the protection unit (2) approaches the voltage value of the unchanged output signal, and thus, the on- resistance value, i.e. the internal resistance value of the power switch (3) is decreased. Thus, the load (L) draws more current such that the power or rate thereof increases.

In another version of this embodiment, the control unit (4) increases the frequency of the pulse width modulation signal applied to the additional power switch (5) in order to decrease the power or rate of the load (L). The voltage of the changed output signal of the protection unit (2) is decreased as the frequency of the PWM signal increases and the voltage of the power switch (3) gate driven by said signal decreases. The on-resistance value of the power switch (3) increases as the voltage of the power switch (3) gate decreases, and thereby, a portion of the current to be transferred to the load (L) is converted to heat on the power switch (3). By decreasing the current transferred to the load (L), the power or rate of the load (L) is decreased without the need for an additional drive circuit.

In another embodiment of the present invention, the control unit (4) does not drive the additional power switch (5) when the load (L) is operated at maximum power. During the regime wherein the desired impedance is achieved after the start-up of inductive and capacitive loads (L), the amount of current drawn by the load (L) is very low compared to the in-rush current during the start-up due to the impedance value, and remains below the high current limit level against which the protection unit (2) protects the battery packs (B). In this case, since the control unit (4) does not drive the additional power switch (5) with the PWM signal, the additional power switch (5) remains switched-on and the output signal of the protection unit (2) cannot flow to the ground due to high resistance, and is transferred to the gate of the power switch (3) without being changed. The voltage of the output signal of the protection unit (2) minimizes the on-resistance of the power switch (3), and the total resistance is decreased. Thus, the current drawn by the load (L) is maximized and the load (L) is operated at maximum power and maximum rate.

By means of the battery control circuit (1) of the present invention, the in-rush currents drawn by especially the inductive and the capacitive loads (L) can be controlled and decreased, and thereby, the load (L) is enabled to be driven without the protection unit (2) protecting the battery packs (B). Furthermore, the power and rate of the load (L) can be controlled by means of the battery control circuit (1) of the present invention without the need for another drive circuit, and thus, cost advantage is provided and the electrical losses are minimized by decreasing the amount of circuit components used.

Claims

1- A battery control circuit (1) comprising a protection unit (2) that is suitable for driving capacitive or inductive loads (L) and that monitors the voltage and current values of the battery packs (B) that provide power supply; at least one power switch (3) that enables the current transferred to the load (L) to be switched by being connected to the output signal of the protection unit (2), and a control unit (4) that enables the protection unit (2) and the power switch (3) to be controlled, characterized by the protection unit (2) the output signal of which is grounded through an additional power switch (5) before entering the power switch (3), and the control unit (4) that enables the additional power switch (5) to be driven with pulse width modulation so that the output signal of the protection unit (2) is changed.

2- A battery control circuit (1) as in Claim 1, characterized by the control unit (4) that controls the in-rush currents that flow to the load (L) during the start-up of the load (L) by changing the frequency of the pulse width modulation signal applied to the additional power switch (5).

3- A battery control circuit (1) as in Claim 2, characterized by the control unit (4) that enables the in-rush current to be decreased by increasing the frequency of the pulse width modulation signal applied to the additional power switch (5).

4- A battery control circuit (1) as in any one of the above claims, characterized by the control unit (4) that controls the power or rate of the load (L) by changing the frequency and/or the duty cycle of the pulse width modulation signal applied to the additional power switch (5).

5- A battery control circuit (1) as in Claim 4, characterized by the control unit (4) that decreases the frequency and/or increases the duty cycle of the pulse width modulation signal applied to the additional power switch (5) in order to increase the power or rate of the load (L).

6- A battery control circuit (1) as in Claim 4 or 5, characterized by the control unit (4) that increases the frequency and/or decreases the duty cycle of the pulse width modulation signal applied to the additional power switch (5) in order to decrease the power or rate of the load (L).

7- A battery control circuit (1) as in any one of the above claims, characterized by the control unit (4) that does not drive the additional power switch (5) when the load (L) is operated at maximum power.