Method for operating a device for wirelessly transmitting energy in the direction of an electrical consumer by means of inductive coupling, and device

Abstract

The invention relates to a method for operating a device (100) for wirelessly transmitting energy in the direction of an electrical consumer (200) by means of inductive coupling, - wherein the device (100) has: - a rectifier (108) for generating a DC voltage (US) from a network AC voltage (UN), - an inverter (102) which is fed from the DC voltage (US) and is designed to generate a pulse-width-modulated actuation signal (AS), and - a power coil (101) which is actuated by means of the pulse-width-modulated actuation signal (AS) and by means of which a magnetic alternating field can be generated for transmitting the energy during predefined transmission cycles, wherein a transmission cycle corresponds to a respective network half-wave of the network AC voltage (UN), - the method having the following steps for predefined operating conditions: - for a plurality of points in time during a respective network half-wave of the network AC voltage (UN), determining what energy has been transmitted from the device (100) in the direction of the electrical consumer (200) up to the corresponding point in time during the respective network half-wave, - comparing the transmitted energy with a maximum value and - if the transmitted energy is equal to or greater than the maximum value, switching off the pulse-width-modulated actuation signal (AS) for the remaining part of the network half-wave.

Description

[0001] Method for operating a device for wirelessly transmitting energy towards an electrical consumer by means of inductive coupling and device

[0002] DE 102023 108529 A1 discloses a method for operating a kitchen appliance in which, regardless of regulating the electrical power output of the kitchen appliance to a setpoint, the electrical power output of the kitchen appliance is limited to values ​​less than or equal to a maximum value based on an actual power value. The actual power value is determined as a function of an average value of the product of a measured voltage and a measured current over the entire mains half-cycle.

[0003] The invention is based on the objective of providing a method for operating a device for wirelessly transmitting energy towards an electrical consumer by means of inductive coupling and a corresponding device that enables safe operation of the device.

[0004] The method serves to operate a device for the wireless transmission of energy towards an electrical load by means of inductive coupling. The device comprises: a rectifier for generating a DC voltage from a mains AC voltage, an inverter powered by the DC voltage and configured to generate a pulse-width modulated control signal, and a power coil controlled by the pulse-width modulated control signal, by means of which an alternating magnetic field can be generated or is generated for the transmission of energy during predetermined transmission cycles.

[0005] Energy transmission preferably takes place according to the Ki standard of the "Wireless Power Consortium".

[0006] The procedure comprises the following steps for given operating conditions.

[0007] For a large number of points in time, for example 50 to 200 temporally equidistant points in time, during a respective transmission cycle, it is determined which energy has already been transferred from the device towards the electrical consumer up to the corresponding point in time during the respective transmission cycle.

[0008] The transmitted energy determined in this way is then compared with a maximum value. If the transmitted energy is equal to or greater than the maximum value, the pulse-width modulated (PWM) control signal is switched off for the remaining transmission cycle. Otherwise, the PWM control signal continues to be generated depending on a set transmission power.

[0009] In one embodiment, to determine which energy has been transferred from the device towards the electrical consumer up to the corresponding time during the respective transmission cycle, a current into the power coil and a voltage across the power coil are continuously measured, and a product of the measured current and measured voltage up to the corresponding time is integrated.

[0010] One transmission cycle corresponds to one half-cycle of the AC mains voltage. The process comprises the following steps. For a large number of points in time, for example, 50 to 200 equidistantly spaced points in time, during each half-cycle, the energy already transmitted from the device to the electrical load up to that point in time is determined. The transmitted energy thus determined is then compared with the maximum value. If the transmitted energy is equal to or greater than the maximum value, the pulse-width modulated (PWM) control signal is switched off for the remaining half-cycle. Otherwise, the PWM control signal continues to be generated depending on a set transmission power.

[0011] In one embodiment, the specified operating conditions occur when an electrical load of the electrical consumer is changed, and / or when no alternating magnetic field has been generated during a previous transmission cycle, and / or when an electrical power to be delivered by means of the device is changed, and / or when the electrical power to be delivered by means of the device is less than a threshold value, in particular less than 500 watts.

[0012] The device for wirelessly transmitting energy towards an electrical consumer by means of inductive coupling comprises: a rectifier for generating a DC voltage from a mains AC voltage, an inverter supplied by the DC voltage which is configured to generate a pulse-width modulated control signal, a power coil controlled by means of the pulse-width modulated control signal by means of which a magnetic alternating field can be generated for transmitting the energy during predetermined transmission cycles, and a control device which is configured to control the operation of the device in such a way that a method according to one of the preceding claims is carried out.Ki is an interoperability standard for the wireless transmission of electrical power from a wireless power transmission device, hereinafter referred to as a transmitter, to an electrical device, hereinafter referred to as a receiver. Ki is intended, for example, for powering wireless kitchen appliances.

[0013] The Ki standard supports power transfer for a very wide range of possible receiver coil diameters, coil spacings, and load impedances. This also means that the power transfer function P(f) varies considerably, i.e., the resulting power at a given operating frequency can differ significantly. At the same time, the Ki specification requires very short settling times of 60 ms when changing the target power setting, which must be reduced to a response time of 20 ms for very low power levels (low power mode < 50 W).

[0014] The AI ​​standard requires control with an operating frequency and duty cycle optimized for the target power and load impedance, so that on the one hand the fast settling process is supported and on the other hand overshoot is avoided.

[0015] When combining AI transmitters with induction cooktops, the operating frequency between the technologies is preferably synchronized, which may further restrict the selection of a possible operating frequency.

[0016] When an energy transfer begins, the transfer function P(f) is largely unknown. Although indications of the expected transfer function P(f) can be derived from data transmitted by the receiver, significant deviations in the actual transfer function P(f) can occur due to receiver shifts or uncharged buffer capacitors.

[0017] If an initial operating frequency with too low a maximum power output is selected, a timing requirement of the specification cannot be met. If an operating frequency with too high a maximum power output is selected, this can lead to overpowering, especially in one of the first steps after a jump in power demand. In this case, the probability of a deviation is particularly high, as buffer capacitors may be discharged, and the receiver may therefore exhibit an unexpectedly low impedance.

[0018] Since an overpower pulse can damage the receiver, the start frequency and duty cycle must be selected to prevent overpowering. However, this may result in the timing requirement not being met, which can lead to a reset of the receiver.

[0019] According to the invention, a critical operating frequency and a critical duty cycle can be selected initially, since any resulting overpower during a transmission cycle can be detected in time and thus avoided or limited.

[0020] A prerequisite for detecting overpower is that the transmitter's transmitted power is continuously measured during the network half-wave and integrated into a transmitted energy at least at short time intervals.

[0021] The requested target power can be converted into the required energy per transmission cycle or network half-wave and used as a maximum value for limiting. If the calculated maximum value is exceeded during the transmission cycle, the power transmission is immediately terminated, thus protecting the receiver from overvoltage.

[0022] The invention comprises the wireless transmission of electrical energy or power to a consumer in successive transmission cycles, preferably within network half-waves, the continuous determination of the transmitted power during each transmission cycle, the integration of the transmitted power to a transmitted energy, the determination of a (energy) maximum value based on a set target value for the power to be delivered, and finally the termination of the power transmission within the transmission cycle if the measured energy exceeds the maximum value.

[0023] The method according to the invention can, for example, be applied in an initial step after a change in a performance requirement.

[0024] The method according to the invention can, for example, be active at power levels below 500 W, and in particular below 50 W.

[0025] The invention is described in detail below with reference to the drawings. These show:

[0026] Fig. 1 schematically shows a block diagram of a device for wirelessly transmitting energy towards an electrical load by means of inductive coupling; Fig. 2 shows a diagram of the time profiles of a mains AC voltage, a transmitted power and a transmitted energy, each during one half-cycle of the mains AC voltage, if the transmitted energy is equal to or greater than a maximum value; and

[0027] Fig. 3 shows a diagram of the time profiles of the AC mains voltage, the transmitted power and the transmitted energy, each during the AC mains half-cycle, if the transmitted energy is less than a maximum value.

[0028] Fig. 1 shows a device 100 for wirelessly transmitting energy towards an electrical load 200 by means of inductive coupling. The device 100 comprises: a rectifier 108 for generating a DC voltage US from a mains AC voltage U N , an inverter 102 supplied by the DC voltage US, which is configured to generate a pulse width modulated control signal AS, a power coil 101 controlled by means of the pulse width modulated control signal AS, by means of which a magnetic alternating field can be generated for the transmission of energy during predetermined transmission cycles, and a control device 113, which is configured to control the operation of the device 100 in such a way that a procedure described below is carried out for predetermined operating conditions.

[0029] Fig. 2 shows a diagram of the time course of a mains AC voltage U. N, a transmitted power P and a transmitted energy E, each during one half-cycle of the AC mains voltage U N , if the transferred energy is equal to or greater than a maximum value E max is.

[0030] According to the invention, for a plurality of (sampling) times during a respective network half-wave, it is determined which energy E has been transferred from the device 100 towards the electrical consumer 200 up to the corresponding time during the respective network half-wave.

[0031] The transferred energy E is then assigned the maximum value E max compared. If, as shown in Fig. 2, the transferred energy E at a time t is equal to or greater than the maximum value E maxIf the power supply is / will be switched off, the pulse-width modulated control signal AS is switched off for the remaining part of the mains half-wave. To determine which energy E has been transferred from the device 100 towards the electrical consumer 200 up to a corresponding time during the respective mains half-wave, a current into the power coil 101 and a voltage across the power coil 101 are continuously measured, and a product of the measured current and measured voltage is integrated up to the corresponding time.

[0032] The specified operating conditions occur, for example, when an electrical load of the electrical consumer 200 is changed, and / or when no alternating magnetic field has been generated during a previous transmission cycle, and / or when an electrical power to be delivered by means of the device 100 is changed, and / or when the electrical power to be delivered by means of the device 100 is less than a threshold value, in particular less than 500 watts.

[0033] Fig. 3 shows a diagram of the time-dependent profiles of the mains AC voltage U. N , the transmitted power P and the transmitted energy E, each during the network half-cycle of the network AC voltage U N , if the transferred energy is less than the maximum value E max As shown in Fig. 3, the transferred energy E is not at any time t A equal to or greater than the maximum value E maxTherefore, the pulse-width modulated control signal AS is not switched off during the mains half-wave. This can correspond to the operating mode of device 100 if the specified operating conditions are not met.

Claims

Patent claims 1. Method for operating a device (100) for wirelessly transmitting energy towards an electrical consumer (200) by means of inductive coupling, wherein the device (100) comprises: a rectifier (108) for generating a direct current voltage (U s ) from a mains alternating voltage (U N ), one from the DC voltage (U s ) fed inverter (102), which is designed to output a pulse width modulated control signal (A s ) to generate, and one using the pulse-width modulated control signal (A s ) controlled power coil (101), by means of which a magnetic alternating field can be generated for the transmission of energy during predetermined transmission cycles, wherein each transmission cycle corresponds to each half-wave of the mains alternating voltage (U N ) corresponds, the procedure for given operating conditions comprises the following steps: for a multitude of times during each half-cycle of the mains AC voltage (U N ) Determine what energy has been transferred from the device (100) towards the electrical consumer (200) up to the corresponding time during the respective network half-wave, Comparing the transferred energy with a maximum value and If the transmitted energy is equal to or greater than the maximum value, the pulse-width modulated control signal (A) is switched off. s ) for the remaining part of the network half-wave.

2. The method according to claim 1, characterized in that To determine which energy has been transferred from the device (100) towards the electrical consumer (200) up to the corresponding time during the respective network half-wave, a current is continuously measured in the power coil (101) and a voltage is measured across the power coil (101), and a product of the measured current and measured voltage up to the corresponding time is integrated.

3. Method according to one of the preceding claims, characterized in that the specified operating conditions occur when: an electrical load of the electrical consumer (200) is changed, and / or no alternating magnetic field has been generated during a previous transmission cycle, and / or an electrical power output by means of the device (100) is changed, and / or the electrical power to be delivered by means of the device (100) is less than a threshold value, in particular less than 500 watts.

4. Device (100) for wirelessly transmitting energy towards an electrical consumer (200) by means of inductive coupling, comprising: a rectifier (108) for generating a direct current voltage (U s ) from a mains alternating voltage (U N ), one from the DC voltage (U s ) fed inverter (102), which is designed to output a pulse width modulated control signal (A s to generate a by means of the pulse width modulated control signal (A s ) controlled power coil (101), by means of which a magnetic alternating field can be generated for the transmission of energy during specified transmission cycles, and a control device (113) which is configured to control the operation of the device (100) such that a method according to one of the preceding claims is carried out.

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