Non-contact power supply device

Abstract

To provide a non-contact power feeding device in which a power receiving side can determine a drive synchronization timing of a power feeding side and generate a synchronous signal without using a synchronous coil.SOLUTION: A configuration is made so as to detect a zero-crossing point of a square wave voltage induced on a power receiving coil 2 by a zero-crossing detection circuit 8 to obtain a synchronous signal.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a non-contact power supply device that enables synchronous switching without using a synchronous coil in a synchronous switching method in which the power receiving side performs switching in accordance with the driving timing of the power supply side.

Background Art

[0002] Conventionally, non-contact power supply devices that transmit power without mechanical contact such as electric wires are known. Since there is no mechanical contact, there is an advantage that power can be supplied without the risk of electric shock or short circuit even in water or a dusty place.

[0003] An example of a non-contact power supply device is shown in Non-Patent Document 1 below.

Prior Art Documents

Patent Documents

[0004]

Non-Patent Document 1

[0005] The non-contact power supply device shown in Non-Patent Document 1 above transmits power from the power supply side to the power receiving side by electromagnetic induction. The power transmission principle is the same as that of a transformer, but the iron core is separated between the power supply side and the power receiving side.

[0006] The power supply side is provided with a power supply coupler including an iron core, a power supply coil wound around the iron core, and a magnetic shielding plate, and the power receiving side is provided with a power receiving coupler including an iron core, a power receiving coil wound around the iron core, and a magnetic shielding plate.

[0007] With the power supply coupler and the power receiving coupler opposed to each other without mechanical contact, power is transmitted from the power supply coupler to the power receiving coupler by electromagnetic induction by driving the power supply coil at a high frequency.

[0008] At this time, since there is no mechanical contact between the power supply coupler and the power receiving coupler, the magnetic coupling is very poor, which hinders power transmission. To solve this problem, as shown in FIG. 1 of Non-Patent Document 1, a resonance capacitor is provided in the power receiving coil, and power transmission is realized by reducing the influence of leakage inductance through LC resonance.

[0009] This method has the advantage of having fewer components, but it has disadvantages in terms of output stability. For output load fluctuations and input voltage fluctuations on the power supply side, the fluctuation rate of the output voltage may reach several hundred percent, so it is necessary to provide a wide-range voltage stabilization circuit in the subsequent stage.

[0010] In this stabilization circuit, a DC-DC converter is used to achieve high efficiency, but due to the wide input voltage range, the power loss increases. This power loss is acceptable for small-capacity products, but for large-capacity non-contact power supply devices, the heat dissipation part becomes large and practical miniaturization cannot be achieved. It also causes a decrease in system efficiency.

[0011] To solve such problems, a driving circuit similar to that of the power supply coil is also provided in the power receiving coil, and the power receiving side is driven in synchronization with the switching on the power supply side to obtain an output (hereinafter referred to as the synchronous switching method).

[0012] The circuit diagram of the synchronous switching method is shown in FIG. 2 of the above Non-Patent Document 1. In the non-contact power supply device of the synchronous switching method, the coupler driving part has the same circuit on the power supply side and the power receiving side, and the switching frequencies on the power supply side and the power receiving side are the same.

[0013] By controlling the phase difference between the switching of the power supply coil and the switching of the power receiving coil, the output voltage on the power receiving side can be stabilized.

[0014] To perform this phase control, it is necessary to send a synchronization signal from the power supply side to the power receiving side, and the synchronization signal is sent from the power supply side to the power receiving side using a synchronization coil provided separately from the power supply coil and the power receiving coil for power transmission.

[0015] Also, the power supply control is performed by controlling the phase difference between the square wave voltage applied to the power supply coil and the square wave voltage applied to the power receiving coil within the range of 0° to 90°.

[0016] The control of the phase difference is performed by detecting the driving timing of the power supply coil from the synchronization signal on the power receiving side and changing the switching timing of the driving unit of the power receiving coil.

[0017] The phase difference is determined by feeding back the output voltage of the power receiving circuit. As a result, the output is stabilized against fluctuations in the gap distance between the coils, input fluctuations, and load fluctuations, and the power supply power is controlled.

[0018] Fig. 5 shows an equivalent circuit in which the power receiving coil is regarded as a transformer. In the synchronous switching method, the phase difference between e1 and e2 of the equivalent circuit is controlled within the range of 0° to 90°. The voltage waveform is shown in Fig. 6. By establishing a circuit equation from the equivalent circuit and obtaining the current i2 of the power receiving coil in each section of T1 to T4, the current shown in Fig. 7 is obtained.

[0019] In the equivalent circuit, since T1 and T4 are the sections where S1 is ON and S2 is ON, the currents flowing into the respective capacitors (C1, C2) of the power receiving circuit are (1)(2)(6) and (3)(4)(5) shown in Fig. 7. This average value is obtained as the output current.

[0020] Regarding the phase difference (T1), the output power is obtained from the average value of the current flowing into the smoothing capacitor by the following [Equation 1].

[0021]

Equation

[0022] From this equation, it can be seen that the output power can be controlled by changing d, and the maximum output can be obtained when d = 0.5, that is, when the phase difference is 90°.

[0023] Furthermore, it can be seen that higher output power can be obtained when the inductance values of L1 and L2 are small and the coupling coefficient k is close to 1.

Summary of the Invention

Problems to be Solved by the Invention

[0024] However, in the above-described conventional non-contact power feeding device, it is necessary to send a synchronization signal from the power feeding side to the power receiving side. Since the synchronization signal is configured to be sent from the synchronization coil on the power feeding side to the synchronization coil on the power receiving side, a synchronization coil must be provided on the substrates of the power feeding circuit and the power receiving circuit, which hinders miniaturization of the product size.

[0025] Therefore, the present invention provides a non-contact power feeding device that can determine the driving synchronization timing of the power feeding side on the power receiving side and generate a synchronization signal without using a synchronization coil.

Means for Solving the Problems

[0026] This The invention is a non-contact power feeding device that transmits power non-contact from a power feeding coil to a power receiving coil by electromagnetic induction. On the power receiving side, the driving timing of the power feeding coil is detected from a synchronization signal, and when changing the switching timing of the power receiving coil driving circuit for phase control, the synchronization signal is obtained on the power receiving side by using the power receiving coil.

[0027] Furthermore, the present invention is It is characterized in that the driving of the power feeding coil and the power receiving coil is stopped periodically or irregularly, and a synchronization signal is obtained by using the power receiving coil.

[0028] Furthermore, the present invention is It is characterized in that the synchronization signal is obtained on the power receiving side by using the square wave voltage induced in the power receiving coil.

[0029] Furthermore, the present invention is such that the synchronization signal is It is characterized in that it is obtained by detecting the zero-cross point of the voltage induced in the power receiving coil by a zero-cross detection circuit provided on the power receiving side.

[0030] Furthermore, the present invention is It is characterized by generating a sawtooth wave for phase control from a reset signal and a preset signal output based on a synchronization signal.

[0031] Furthermore, the present invention is The generation of a trigger signal with a delayed phase from the synchronization signal is performed using a comparator circuit that compares the sawtooth wave for phase control with an error voltage and outputs a Hi signal at a timing when the phase is delayed with respect to the synchronization signal.

[0032] Furthermore, the present invention is It is characterized by generating a drive signal for the power receiving coil in consideration of the delay in the zero-cross detection timing by the zero-cross detection circuit.

[0033] Furthermore, the present invention is Drive timing of the power receiving coil is It is characterized by being determined in consideration of the error in the clock frequencies on the power supply side and the power receiving side.

[0034] Furthermore, the present invention is It is characterized by controlling so that each switch constituting the power receiving coil drive circuit does not turn on simultaneously.

[0035] Furthermore, the present invention is It is characterized in that it is configured such that the sawtooth wave for phase control rises to the Hi level where the phase difference between the drive signal of the power supply coil and the drive signal of the power receiving coil is 90°.

Advantages of the Invention

[0036] This According to the invention, by controlling the phase difference between the switching of the power supply coil and the switching of the power receiving coil, the output voltage on the power receiving side can be stabilized. Also, since a synchronization signal can be obtained on the power receiving side using the power receiving coil, there is no need to provide a synchronization coil separately from the power receiving coil to obtain the synchronization signal. As a result, since the synchronization coil is not required on the circuit boards of the power supply side and the power receiving side, the size of the device can be reduced.

[0037] Furthermore, this According to the invention, even if there is an error in the clock frequencies on the power supply side and the power receiving side, stable control can be achieved by performing resynchronization periodically or aperiodically.

[0038] Furthermore, this According to the invention, the synchronization signal on the power supply side can be easily obtained on the power receiving side by using a power receiving coil.

[0039] Furthermore, this According to the invention, by detecting the zero-crossing point of the voltage induced in the power receiving coil, the phase difference between the synchronization signals on the power supply side and the power receiving side can be obtained.

[0040] Furthermore, this According to the invention, a sawtooth wave for phase control can be generated from a reset signal and a preset signal regardless of the delay in the detection timing of the zero-crossing detection circuit.

[0041] Furthermore, this According to the invention, a trigger signal with a delayed phase can be easily generated from the synchronization signal.

[0042] Furthermore, this According to the invention, appropriate phase control can be achieved without being affected by the delay in the zero-crossing detection timing by the zero-crossing detection circuit.

[0043] Furthermore, this According to the invention, appropriate phase control can be achieved without being affected by the error between the clock frequencies on the power supply side and the power receiving side.

[0044] Furthermore, this According to the invention, since each switch constituting the power receiving coil drive circuit does not turn on simultaneously, a square wave voltage synchronized with the power supply coil can be induced in the power receiving coil.

[0045] Furthermore, this According to the invention, even when the error voltage fluctuates greatly, the crossing point with the sawtooth wave for phase control does not exceed 90°, and stable output power can be obtained even when the load is large.

Brief Description of the Drawings

[0046]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Embodiments for Carrying Out the Invention

[0047] Hereinafter, embodiments of the present invention will be described with reference to FIGS. 1 to 4. The non-contact power supply device A of the present invention shown in FIG. 1 is composed of a separated power supply side and a power receiving side, and transmits power from the power supply side to the power receiving side without mechanical contact therewith. The power supply side is connected to a commercial AC power supply, and the power receiving side supplies an AC output to a load (not shown).

[0048] The power supply side is provided with a power supply coil 1 on the yoke portion of a primary core (not shown) formed in a C shape, for example, and the power receiving side is provided with a power receiving coil 2 on the yoke portion of a secondary core (not shown) also formed in a C shape, for example. By applying a high-frequency alternating current to the power supply coil 1 in a state where the open ends of the primary core and the secondary core face each other without contact, magnetic flux is linked from the primary core to the secondary core, and an AC voltage is induced in the power receiving coil 2.

[0049] On the power supply side, there is a rectifier circuit 3 that rectifies the AC power supplied from a commercial AC power supply, and a power supply side control circuit 5 that controls the power supply coil drive inverter 4. Also, on the power receiving side, there is provided a power receiving side detection circuit that detects, for example, the magnetic force of a magnet 7 and detects that the power supply side and the power receiving side are in an opposing state.

[0050] On the power receiving side, there are provided a zero-cross detection circuit 8 that detects the zero-cross point of the voltage induced in the power receiving coil 2, a synchronization signal generation circuit 9 that outputs the synchronization adjustment signal output by the zero-cross detection circuit 8 as a synchronization signal, and a control circuit 13 that inputs the synchronization signal and the DC voltage output by the smoothing circuit 10 to control the power receiving coil drive inverter 11 and the sine wave output inverter 12.

[0051] Next, the operation of the non-contact power supply device A shown in FIG. 1 will be described. The non-contact power supply device A shown in FIG. 1 uses the square wave voltage induced in the power receiving coil 2 for the power receiving side to obtain a synchronization signal. In this method, the power receiving coil 2 serves as both a power receiving coil and a synchronization coil.

[0052] The phase of the synchronization signal is the same as the phase of the square wave voltage applied to the power supply coil 1. Since the phase of the square wave voltage induced in the power receiving coil 2 is also the same, this phase is acquired.

[0053] The zero-cross detection circuit 8 is used to acquire the phase. The zero-cross detection circuit 8 detects the zero-cross point of the voltage induced in the power receiving coil 2 and outputs it as a synchronization adjustment signal. The synchronization adjustment signal is input to the control circuit 13 as the synchronization signal on the power receiving side by the synchronization signal generation circuit 9.

[0054] When the zero-cross detection circuit 8 outputs a synchronization adjustment signal, the power receiving coil 2 is not driven for power transmission. Therefore, synchronization adjustment is performed once at the start of operation, and thereafter, the power receiving coil 2 is continuously driven for power transmission.

[0055] Since the driving timings on the power supply side and the power receiving side are affected by the clock frequencies used respectively, if the error in the clock frequency is zero, as described above, even if the operation continues using the initially obtained synchronization adjustment signal, it will always be in a synchronized state.

[0056] However, in reality, since there are errors in the clock frequencies on the power supply side and the power receiving side, it is conceivable that the driving timings gradually shift and become out of synchronization. Therefore, in order to perform stable control, the driving of the power receiving coil 2 is stopped periodically or irregularly, and during that time, synchronization adjustment is performed again.

[0057] The timing for stopping the driving of the power receiving coil 2 varies depending on the error in the clock frequencies (crystal oscillators) used on the power supply side and the power receiving side. For example, by using crystal oscillators with an error of 50 ppm or less on both the power supply side and the power receiving side, the timing error of the synchronization signal becomes at most 1% with respect to 100 driving signals. Therefore, the driving of the power receiving coil 2 is stopped three times per 100 times, and during that time, the timing error of the synchronization signal is reset to perform stable control.

[0058] Note that the above-described synchronization configuration and the logic of the synchronization signal generation circuit may be realized using an FPGA (Field Programable Gate Array). By using an FPGA, many logic circuits become unnecessary, contributing to miniaturization. In addition, since an FPGA can construct a CPU by synthesizing internal logic circuits, it is not necessary to provide a microcontroller used for clocks and reset signals in the control circuit 13.

[0059] FIG. 2 shows a circuit block diagram of a control circuit 100 in which the synchronization configuration and the logic of the synchronization signal generation circuit are realized by an FPGA 14 and the FPGA 14 is used for clocks and reset signals. As shown in FIG. 2, the control circuit 100 includes, in addition to the FPGA 14, a reference voltage generation circuit 15, an error amplifier 16, a comparator 17, and a sawtooth wave generation circuit 18.

[0060] The synchronization adjustment signal output by the zero-crossing detection circuit 8 shown in FIG. 2 is input to the FPGA 14 that constitutes the control circuit 100. The FPGA 14 generates a synchronization signal from the input synchronization adjustment signal.

[0061] Here, due to the characteristics of the zero-crossing detection circuit 8, a delay of 2.5 μs occurs in the detection timing. Also, since this synchronization signal is generated illogically, the positive and negative of the waveform are reversed compared to the drive signal on the power supply side.

[0062] Since there is a delay of 2.5 μs in the detection timing of the zero-crossing detection circuit 8 in the FPGA 14, instead of directly generating a sawtooth wave for phase control from the generated synchronization signal, the FPGA 14 outputs a reset signal and a preset signal for the sawtooth wave to generate a sawtooth wave for phase control.

[0063] Hereinafter, as an example, the case where the frequency of the synchronization signal is 50 kHz will be described. When the frequency of the synchronization signal is 50 kHz, the period is 20 μs. In the FPGA 14, as shown in FIG. 3, the control counter (FPGA internal counter) operates in accordance with the falling edge of the power reception side synchronization signal.

[0064] Since the power reception side synchronization signal has a delay of 2.5 μs with respect to the power supply side drive signal, the control counter will also be delayed by 2.5 μs accordingly. The reset signal for the sawtooth wave is generated as a pulse with a width of 2 μs 12.2 μs after the timing when the control counter reaches 0 in consideration of this time.

[0065] When the reset signal rises, the sawtooth wave falls, and when the reset signal falls, the sawtooth wave rises. The preset signal is generated 8 μs after the falling edge of the reset signal. By the preset signal, the sawtooth wave rises to the Hi level. The rising timing of the sawtooth wave by the preset signal aims for a delay of 5 μs with respect to the drive signal on the power supply side. This means aiming for the part where the phase is delayed by 90° with respect to the drive signal on the power supply side.

[0066] This 5 μs is the target value, and in actual calculations, it is 4.7 μs. This is because the timing error of the aforementioned synchronization signal is considered to be at most 1%. When there is a 1% timing error, an error of 0.2 μs occurs in a cycle of 20 μs.

[0067] This error difference is added to make it around 5 μs. The change in the operating frequency can be handled by changing the timing of the reset signal and the preset signal considering this error.

[0068] The sawtooth wave for phase control is responsible for generating the drive signal of the power receiving coil 2. By stopping the sawtooth wave for phase control, the drive of the power receiving coil 2 also stops. Therefore, when performing the resynchronization described above, the sawtooth wave for phase control is stopped at the timing described above.

[0069] The generation of the trigger signal is performed by inputting the sawtooth wave for phase control and the error signal (error voltage) shown in FIG. 4 into the comparator 17 shown in FIG. 2. The trigger signal is generated such that the crossing point of the sawtooth wave and the error voltage is the falling edge of the trigger signal, and the falling edge of the sawtooth wave is the rising edge of the trigger signal.

[0070] The trigger signal is input to the FPGA 14, and the upper arm signal and the lower arm signal are generated within the FPGA 14 and output to the power receiving coil drive inverter 11.

[0071] An upper arm signal with a width of 8.8 μs is generated in accordance with the falling edge of the trigger signal, and a lower arm signal with a width of 8.8 μs is generated 10 μs later from the upper arm signal.

[0072] Also, if the falling edge of the trigger signal is within 19 μs from the previous falling edge, it is ignored to prevent the upper arm signal and the lower arm signal from being turned on simultaneously. When changing the operating frequency, these signal timings are adjusted as appropriate.

[0073] As shown in Fig. 3, the sawtooth wave at a phase difference of 90° is raised to the Hi level to limit the maximum output. This prevents the phase difference from exceeding 90°. As a result, when the load is large, the output power cannot be obtained, and the problem of unstable operation can be solved, and stable control can be realized.

[0074] As described above, according to the non-contact power supply device A of the present invention, the synchronization signal of the power supply coil can be obtained on the power receiving side without providing synchronization coils on the power supply side and the power receiving side. As a result, there is no need to provide a synchronization coil on the circuit board, and the non-contact power supply device A can be miniaturized.

[0075] Also, even if there is an error in the clock frequencies of the power supply side and the power receiving side, stable control can be realized by performing synchronization adjustment again regularly or irregularly.

[0076] Furthermore, the phase difference between the driving timing of the power supply coil 1 and the driving timing of the power receiving coil 2 does not exceed 90°, and stable control can be realized.

[0077] Note that the non-contact power supply device of the present invention is not limited to the circuit block configurations shown in Figs. 1 and 2, and includes various configurations modified within the scope not departing from the gist of the present invention.

[0078] Also, as described above, the signal timings shown in Figs. 3 and 4 are appropriately changed according to the change in the operating frequency.

Industrial Applicability

[0079] It can be used for a non-contact power supply device of the synchronous switching method.

Explanation of Reference Numerals

[0080] 1 Power supply coil 2 Power receiving coil 3 Rectifier circuit 4 Power supply coil drive inverter 5 Power supply side control circuit 6 Secondary-side detection circuit 7 Magnet 8 Zero-cross detection circuit 9 Synchronous signal generation circuit 10 Smoothing circuit 11 Power receiving coil drive inverter 12 Sinusoidal wave output inverter 13,100 Control circuit 14 FPGA 15 Reference voltage generation circuit 16 Error amplifier 17 Comparator A Contactless power supply device

Claims

1. A non-contact power supply device including a power supply coil, a power supply side inverter for controlling the voltage applied to the power supply coil to be turned on and off, a power supply side control circuit for driving and controlling the power supply side inverter, a power receiving coil, a power receiving side inverter for controlling the voltage applied to the power receiving coil to be turned on and off, and a power receiving side control circuit for driving and controlling the power receiving side inverter, and transmitting power non-contact from the power supply coil to the power receiving coil by electromagnetic induction, wherein a rising edge and a falling edge of a square wave voltage induced in the power receiving coil are obtained by a square wave voltage applied to the power supply coil, and in a zero-cross detection circuit for detecting zero-cross points of the rising edge and the falling edge of the square wave voltage induced in the power receiving coil, the zero-cross point of the voltage induced in the power receiving coil is used as a synchronization adjustment signal, The non-contact power supply device is characterized in that the power receiving side inverter is driven and controlled so that the on and off timings of the voltage applied to the power receiving coil are synchronized with the on and off timings of the voltage applied to the power supply coil by outputting the synchronization adjustment signal to the power receiving side control circuit.

2. The non-contact power supply device according to claim 1, wherein the synchronization adjustment signal is generated so that the detection timing when the zero-cross timing of the voltage induced in the power receiving coil is detected by the zero-cross detection circuit is delayed by 90°.

3. The non-contact power supply device according to claim 1, wherein synchronization deviation due to an error in the operating clock frequency of the power supply side control circuit and the operating clock frequency of the power receiving side control circuit is corrected by periodically or irregularly stopping the driving of the power receiving coil for synchronization adjustment.

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