DE102018222554A1 - Device and method for the direction-dependent operation of an electrochemical energy store - Google Patents

Abstract

Device (100) for the direction-dependent operation of an electrochemical energy store (101) with a first semiconductor switch (102) which comprises a first inverse diode (103) and a second semiconductor switch (104) which comprises a second inverse diode (105) and a first measuring device (106) and a second measuring device (107), characterized in that the first semiconductor switch (102) and the second semiconductor switch (104) are connected in series and the first measuring device (106) is set up to measure a first voltage measured value across the first inverse diode (103) and to compare the first voltage measurement value with a first predetermined limit value, the first semiconductor switch (102) being controllable as a function of the comparison of the first voltage measurement value with the first predetermined limit value and the second measuring device (107) being set up to do so and to detect the second voltage value across the second inverse diode (105) to compare the second voltage measurement value with a second predetermined limit value, the second semiconductor switch being controllable as a function of the comparison of the second voltage measurement value with the second predetermined limit value.

Description

State of the art

The invention relates to a device and a method for the direction-dependent operation of an electrochemical energy store, and to a vehicle with such a device.

Battery management systems have isolating switches, such as relays or semiconductor switches, to prevent or disconnect the flow of current. The disconnector is operated as a normal switch and is not sensitive to the current direction. This means that the current can flow in both directions, so that the battery can be charged and discharged at the same time. The semiconductor switches used here are, for example, mosfets which have an intrinsic body diode.

The disadvantage here is that the disconnectors can not be switched depending on the direction, since the power loss in the body diode would be too large.

Battery management systems are also known which have separate connections for charging and discharging. The semiconductor switches are arranged in parallel to one another.

The disadvantage here is that energy recovery via the load is not possible.

It is the object of the invention to overcome these disadvantages.

Disclosure of the invention

The device for operating an electrochemical energy store in a direction-dependent manner has a first semiconductor switch, a second semiconductor switch, a first measuring device and a second measuring device, the first semiconductor switch comprising a first inverse diode and the second semiconductor switch comprising a second inverse diode. According to the invention, the first semiconductor switch and the second semiconductor switch are connected in series. The first measuring device is set up to detect a first voltage value across the first inverse diode and to compare the first voltage measured value with a first predetermined limit value. The first semiconductor switch can be controlled as a function of the comparison of the first voltage measurement value with the first predetermined limit value. The second measuring device is set up to detect a second voltage value across the second inverse diode and to compare the second voltage measured value with a second predetermined limit value. The second semiconductor switch can be controlled as a function of the comparison of the second voltage measurement value with the second predetermined limit value. In other words, the first semiconductor switch and the second semiconductor switch can be switched on or off as a function of the comparison of the voltage measurement value detected in each case via the respective inverse diode with the respectively predetermined limit value.

The advantage here is that the electrochemical energy store can be operated in a direction-dependent manner, it being possible for the individual operating states of the electrochemical energy store to be set, namely charging or discharging.

In a further development, the first semiconductor switch and the second semiconductor switch are each a field effect transistor, in particular a MOSFET.

The advantage here is that the Rdson is low at voltages up to 60V.

In a further embodiment, the first inverse diode and the second inverse diode are each a body diode of the field effect transistors.

In one development, the first semiconductor switch and the second semiconductor switch are each an IGBT.

It is advantageous here that the device is suitable for high voltage classes.

The vehicle according to the invention comprises a device according to the invention for the direction-dependent operation of an electrochemical energy store. The vehicle according to the invention is in particular an electric two-wheeler, for example an electric scooter.

It is advantageous here that the individual operating states of the vehicle, namely charging, discharging or driving, can be set.

The method according to the invention for operating an electrochemical energy store in a direction-dependent manner includes switching on a first semiconductor switch, detecting a second voltage measurement value of a second inverse diode of a second semiconductor switch, comparing the second voltage measurement value of the second inverse diode of the second semiconductor switch with a second predetermined limit value and actuating the second semiconductor switch as a function of the comparison of the second voltage measurement value with the second predetermined limit value. In other words, the electrochemical energy store can be operated depending on the direction, wherein the simultaneous charging of the electrochemical energy store is prevented during the discharge process of the electrochemical energy store and vice versa.

The advantage here is that the electrochemical energy store can be operated in a direction-dependent manner, it being possible for the individual operating states of the electrochemical energy store to be set, namely charging or discharging.

In a further development, the second voltage measurement value is recorded with the aid of a second measuring device, the second measuring device comprising a comparator.

It is advantageous here that the measuring device can be implemented inexpensively.

In a further embodiment, the control of the first semiconductor switch and the second semiconductor switch takes place as a function of an off switch.

In one development, the first semiconductor switch and the second semiconductor switch are activated as a function of an overcurrent signal.

The advantage here is that when a permissible current is exceeded, both semiconductors are switched off at the same time and an overcurrent protection in the main path can be saved.

Further advantages result from the following description of exemplary embodiments or the dependent patent claims.

Figure list

• 1 eine Vorrichtung zum richtungsabhängigen Betreiben eines elektrochemischen Energiespeichers, und
• 2 ein Verfahren zum richtungsabhängigen Betreiben eines elektrochemischen Energiespeichers.

The present invention is explained below on the basis of preferred embodiments and attached drawings. Show it:

• 1 a device for the directional operation of an electrochemical energy store, and
• 2nd a method for the directional operation of an electrochemical energy store.

1 shows a device 100 for the direction-dependent operation of an electrochemical energy store 101 . The device 100 comprises a first semiconductor switch 102 , a second semiconductor switch 104 , a consumer 108 and a loading unit 109 . The energy storage 101 , the first semiconductor switch 102 , the second semiconductor switch 104 and the consumer 108 are connected in series. The loading unit 109 is parallel to the consumer 108 connected. The first semiconductor switch 102 comprises a first inverse diode 103 . The second semiconductor switch 104 includes a second inverse diode 105 . The first semiconductor switch 102 has a first connection 120 , a second connection 121 and a third port 122 on, with the second connector 121 acts as a control connection. The second semiconductor switch 104 has a fourth connector 123 , a fifth connection 124 and a sixth connector 125 on, the fifth port 124 acts as a control connection.

A cathode of the first inverse diode 103 is with the first connection 120 of the first semiconductor switch 102 and an anode of the first inverse diode 103 is with the third connector 122 of the first semiconductor switch 102 electrically connected. A cathode of the second inverse diode 105 is with the fourth connector 123 of the second semiconductor switch 104 and an anode of the second inverse diode 104 is with the sixth connector 125 of the second semiconductor switch 104 electrically connected.

In other words, the first inverse diode 103 is reverse to the electrochemical energy storage 101 arranged because the cathode of the first inverse diode 103 with the positive pole of the electrochemical energy storage 101 is electrically connected. The second inverse diode 105 is in the forward direction to the electrochemical energy store 101 arranged because the anode of the second inverse diode 105 with the positive pole of the electrochemical energy storage 101 is connected when the first semiconductor switch 102 is switched on.

A first measuring device 106 is with the cathode of the first inverse diode 103 and the anode of the first inverse diode 103 electrically connected. A second measuring device 107 is with the cathode of the second inverse diode 105 and the anode of the second inverse diode 105 electrically connected.

The first measuring device 106 is set up for a voltage drop across the first inverse diode 103 to detect and generate a first signal that is applied to an input of a first OR gate 112 is sent or created. The second measuring device 107 is set up for a voltage drop across the second inverse diode 105 to detect and generate a second signal that is input to a second OR gate 113 is sent or created. The voltage drop across the first inverse diode and the second inverse diode is recorded continuously during operation of the device 100 .

The first OR gate 112 has several inputs and a first output. The first Output is electrical with an input of a first AND gate 114 connected. An output of the first AND gate 114 is with a first driver stage 116 electrically connected. The first driver stage 116 is set up the first semiconductor switch 102 to control or to switch.

The second OR gate 113 has multiple inputs and a second output. The second output is electrical with an input of a second AND gate 115 connected. An output of the first AND gate 115 is with a second driver stage 117 electrically connected. The second driver stage 117 is set up the second semiconductor switch 104 to control or to switch.

In addition, the device comprises 100 a first inverter 118 , which detects a switch-off signal as an input signal and on the output side with an input of the first AND gate 114 and the second AND gate 115 is electrically connected. The device 100 includes a second inverter 119 , which detects an overcurrent signal as an input signal and on the output side with a further input of the first AND gate 114 and the second AND gate 115 is electrically connected. The overcurrent signal is from another measuring device 111 generated, the measuring device 111 a voltage drop across another resistor 110 detected.

The first semiconductor switch 102 and the second semiconductor switch 104 are designed, for example, in the form of transistors. They can either be designed as an n-channel or as a p-channel transistor. In one embodiment, the first semiconductor switch 102 and the second semiconductor switch 104 Field effect transistors, especially mosfets. The first inverse diode 103 and the second inverse diode 105 are the body diodes of the mosfets. Alternatively, the first semiconductor switch 102 and the second semiconductor switch 104 be designed as IGBTs.

The electrochemical energy storage 101 includes, for example, Li-ion cells. In one embodiment, the first semiconductor switch 102 and the second semiconductor circuit has a common source connection. In a further exemplary embodiment, the first semiconductor switch has 102 and the second semiconductor switch 104 a common drain connection.

The first semiconductor switch 102 and the second semiconductor switch 104 can also in the negative path of the electrochemical energy storage 101 be arranged.

Depending on the required current carrying capacity or current requirements, several pairs of semiconductor switches can be connected in parallel, with a first semiconductor switch in each case 102 and a second semiconductor switch 101 form a pair of semiconductor switches.

The first measuring device 106 and the second measuring device 107 mainly include analog components. In one embodiment, the first measuring device 106 and the second measuring device 107 only analog components. Due to the analog design, the voltage drop or current flow through the first inverse diode 103 or the second inverse diode 105 quickly recognized because discrete signals can be used directly. A digital structure prevents quick recognition because the signals have to be converted and processed. The first OR gate 112 , the second OR gate 113 , the first AND gate 114 , the second AND gate 115 , the first inverter 118 and the second inverter 119 are designed as analog components.

The directional operation of the electrochemical energy store 101 to start, will either be the first semiconductor switch 102 or the second semiconductor switch 104 switched on with the aid of a switch-on signal which indicates the desired operating state of the electrochemical energy store 101 represents. Becomes the first semiconductor switch 102 turned on in this way, the electrochemical energy storage device 101 be discharged. Will the second semiconductor switch 104 turned on in this way, the electrochemical energy storage device 101 Loading.

How the device works 100 is now explained on the basis of the operating state unloading. The first semiconductor switch 102 is about the driver stage 116 switched on by a switch-on signal or discharge signal at an input of the first OR gate 112 is created. This switch-on signal is sent via the output of the first OR gate 112 to an input of the first AND gate 114 headed. The first AND gate 114 has further inputs, each with a first inverter 118 and a second inverter 119 are electrically connected. There is no switch-off signal at the first inverter 118 another overcurrent signal on the second inverter 119 on, the first semiconductor switch 102 about the first driver stage 116 switched on. By turning on the first semiconductor switch 102 flows with connected load 108 a discharge current via the second inverse diode 104 , the consumer 108 and further resistance 110 . The second measuring device 107 comprises a comparator and detects the voltage drop across the second inverse diode 105 . If the voltage drop exceeds a predetermined limit value, ie the threshold voltage of the second inverse diode 105 , which is approx. 0.7 V, becomes a Signal to an input of the second OR gate 113 headed. This signal is applied to an input of the second AND gate 115 forwarded. The second AND gate 115 has further inputs, each with the first inverter 118 and the second inverter 119 are electrically connected. There is no switch-off signal at the first inverter 118 another overcurrent signal on the second inverter 119 on, so the second semiconductor switch 104 about the second driver stage 117 switched on. The electrical energy storage 101 will be unloaded. In other words, by switching on the first semiconductor switch 102 can only discharge current through the inverse diode 105 flow in the unloading direction. The inverse diode 105 blocks a charging current. A reversal of the current direction from discharge to charging direction is via the measuring device 107 detected and the second semiconductor switch 104 switched off.

Instead, the electrochemical energy store 101 the second semiconductor switch 104 closed. Via the first semiconductor switch 102 and the first inverse diode 103 only one current can flow in the charging direction. As soon as a current flows in the charging direction, this is via the first measuring device 106 recorded and the first driver stage 116 activates the first semiconductor switch 102 .

The electrochemical energy store can operate in the driving mode 101 are both discharged and charged, ie there is recuperation. In this state, both the first semiconductor switch 102 as well as the second semiconductor switch 104 closed.

A switch-off signal is sent to the first inverter 118 or an overcurrent signal to the second inverter 119 applied, both the first semiconductor switch 102 as well as the second semiconductor switch 104 open.

There can be several electrochemical energy stores 101 can be connected in parallel so that efficient operation takes place between the battery packs without equalizing currents.

In another embodiment, only the second measuring device 107 and the further measuring device 111 intended. That means the device 100 has no measuring device that detects the voltage drop across the first inverse diode. This embodiment only allows unloading and prevents charging currents. As a result, a discharge current can always flow and the electrochemical energy store is protected against impermissible charging currents.

2nd shows a process 200 for the direction-dependent operation of an electrochemical energy store. The procedure 200 starts with switching on 210 a first semiconductor switch. The first semiconductor switch is switched on with the aid of a switch-on signal, which represents, for example, a discharge mode or a charging mode. In a subsequent step 220 A voltage drop across a second inverse diode of a second semiconductor switch is detected using a second measuring device.

In a subsequent step 230 the voltage drop is compared to a predetermined limit. The predetermined limit value represents the threshold voltage of the second inverse diode, usually 0.7 V. If the voltage drop is greater than the threshold value, the second measuring device generates a second signal which is sent to an input of a second OR gate. If the voltage drop is less than the threshold value, no second signal is generated and the method is started with the step 220 continued. In one step 230 following step 240 the second OR gate is switched and the second semiconductor switch is controlled or switched on with the aid of a subsequent second driver circuit.

In a first exemplary embodiment, the energy store is discharged. The switch-on signal is applied to one of the inputs of a first OR gate, so that the first semiconductor switch is switched on via a first driver circuit. That means the first semiconductor switch, e.g. B. Mosfet is activated and the current flows through the first semiconductor switch and a second inverse diode, e.g. B. the body diode of the second mosfet, to the consumer. The second measured value device monitors the voltage or the voltage drop across the second inverse diode. As soon as a current flows through the second inverse diode, a voltage drops across the second inverse diode. If the threshold voltage of the second inverse diode is reached, the second semiconductor switch is switched on.

The second semiconductor switch is switched on via the second measuring device and the threshold value of approximately 0.7 V. When switched on, the second semiconductor switch has a contact resistance of approx. 1mΩ, depending on the MOSFET used. As long as a discharge current flows, the voltage drop across the second measuring device is positive, i. H. positive voltage drop from anode to cathode. The measuring device is designed so that a reversal of the current direction, i. H. negative voltage drop from anode to cathode is detected and then the second semiconductor switch is turned off.

In other words, the unloading direction is activated. The first semiconductor switch is switched on permanently. As soon as a discharge current can flow through the second inverse diode, i. H. the voltage drop across the second inverse diode is higher than the threshold value, the second semiconductor switch is enabled via the second measurement value acquisition. When the current direction is reversed from discharging to charging, this is recognized by the second measured value acquisition and the second semiconductor switch is switched off. The discharge direction is still enabled and the second semiconductor switch automatically switches on when the discharge current is reached and off at the charge current.

In a second exemplary embodiment, the energy store is charged. The method for operating an electrochemical energy store for charging in a direction-dependent manner comprises switching on a second semiconductor switch, detecting a first voltage measurement value of a first inverse diode of a first semiconductor switch, comparing the first voltage measurement value of the first inverse diode of the first semiconductor switch with a first predetermined limit value and actuating the first semiconductor switch as a function of the comparison of the first voltage measurement value with the second predetermined limit value.

The switch-on signal or charge signal is applied to one of the inputs of a second OR gate, so that the second semiconductor switch is switched on via the second driver circuit. That means the second Mosfet is activated and the current flows through the second semiconductor switch and the first inverse diode, e.g. B. the body diode of the first mosfet, to the consumer. The first measured value device monitors the voltage or the voltage drop across the first inverse diode. As soon as the voltage drop reaches the threshold voltage of the first inverse diode, a current flows through the first inverse diode and the first semiconductor switch is switched on.

The device can thus switch a current flow depending on the direction. By switching on one of the transistors, the current can only flow in one direction. A current direction is thus specified. The flow in the opposite direction is blocked. A reversal of the current direction can also be detected and prevented.

The method for the direction-dependent operation of an electrochemical energy store for the driving state, i. H. Charging and discharging comprises switching on a first and a second semiconductor switch.

In other words, the invention enables direction-dependent switching of the first semiconductor switch and the second semiconductor switch. For this purpose, the voltage drop across the body diode is recorded and the MOSFET is automatically switched on.

Claims (9)

Device (100) for the direction-dependent operation of an electrochemical energy store (101) with a first semiconductor switch (102) which comprises a first inverse diode (103) and a second semiconductor switch (104) which comprises a second inverse diode (105) and a first measuring device (106) and a second measuring device (107), characterized in that the first semiconductor switch (102) and the second semiconductor switch (104) are connected in series and the first measuring device (106) is set up to measure a first voltage measured value across the first inverse diode (103) and to compare the first voltage measured value with a first predetermined limit value, the first semiconductor switch (102) being controllable as a function of the comparison of the first voltage measured value with the first predetermined limit value, and the second measuring device (107) being set up to un detect second voltage value across the second inverse diode (105) d to compare the second voltage measurement value with a second predetermined limit value, the second semiconductor switch being controllable as a function of the comparison of the second voltage measurement value with the second predetermined limit value. Device (100) after Claim 1 , characterized in that the first semiconductor switch (101) and the second semiconductor switch (102) are each a field effect transistor, in particular a MOSFET. Device (100) after Claim 2 , characterized in that the first inverse diode (103) and the second inverse diode (105) are each a body diode. Device (100) after Claim 1 , characterized in that the first semiconductor switch (102) and the second semiconductor switch (104) are each an IGBT. Vehicle, in particular an electric two-wheeler, with a device for the direction-dependent operation of an electrochemical energy store according to one of the Claims 1 to 4th . Method (200) for operating an electrochemical energy store in a direction-dependent manner, comprising the steps: - switching on (210) a first semiconductor switch, - detecting (220) a second voltage measurement value of a second inverse diode of a second semiconductor switch, Comparing (230) the second voltage measurement value of the second inverse diode of the second semiconductor switch with a second predetermined limit value, and - driving (240) the second semiconductor switch in dependence on the comparison of the second voltage measurement value with the second predetermined limit value. Method (200) according to Claim 6 , characterized in that the second voltage measured value is recorded with the aid of a second measuring device which has a comparator. Method (200) according to one of the Claims 6 or 7 , characterized in that the activation (240) of the first semiconductor switch and the second semiconductor switch takes place as a function of a switch-off signal. Method (200) according to one of the Claims 6 or 7 , characterized in that the control (240) of the first semiconductor switch and the second semiconductor switch is carried out as a function of an overcurrent signal.

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