Inductive contactless power transmitter

• US 20030151930A1
• Filed: 11/28/2002
• Published: 08/14/2003
• Est. Priority Date: 11/30/2001
• Status: Active Grant

• Current Assignee: Friwo Gerätebau GmbH
• Original Assignee: Friwo Gerätebau GmbH
• Inventors: Berghegger, Schroder Ralf gen
• Granted Patent: US 6,912,137 B2
• Time in Patent Office: Days
• US Class Current: 363/21.02
• CPC Class Codes: H02J 50/12 of the resonant type
• CPC Class Codes: H02J 50/80 involving the exchange of data, concerning supply or distribution of electric power, between transmitting devices and receiving devices
• CPC Class Codes: H02M 3/28 using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac

Abstract

The present invention relates to an inductive contactless power transmitter having a primary side including a first inductor (L_P) on the primary side and an oscillator for producing an alternating signal which is supplied to the inductor (L_P) on the primary side, and having a secondary side which includes an inductor on the secondary side that can be coupled to the inductor (L_P) on the primary side, a load (R_L) which is variable in time, and a detection means (42) for determining a power demand of the load on the secondary side, the first oscillator being a voltage-controlled oscillator having a frequency that is adjustable in response to the power demand determined by the detection means (42).

Claims

1. Inductive contactless power transmitter comprising:

a primary side including;

a first inductor (L_P) on the primary side;

a first oscillator for producing an alternating signal which is supplied to said inductor (L_P) on the primary side;

a secondary side including;

an inductor (L_S) on the secondary side which can be coupled to said inductor (L_P) on the primary side;

a load (R_L) which is variable in time or constant; and

a detection mans (42) for determining a power demand of said load on the secondary side,

characterized in that

said first oscillator is a voltage-controlled oscillator (VCO_P) having a frequency which is adjustable in response to the power demand determined by said detection means (42).

2. Power transmitter according to claim 1, characterized in that said primary side includes a disconnector (VCD, 8, 9) for temporarily preventing the alternating signal produced by said oscillator (VCO_P) from being supplied to said inductor (L_P) on the primary side.

3. Power transmitter according to claim 2, characterized in that said disconnector comprises a voltage-controlled duty cycle control unit (VCD) and logic gates (8,99), said duty cycle control unit producing a duty signal (U_T) which controls said logic gates, said duty cycle control unit controlling the duty ratio of said duty signal in dependence upon the power demand determined by said detection means, and said alternating signal being supplied to said logic gates in addition to said duty signal.

4. Power transmitter according to claim 3, characterized in that in the case of a small power demand the primary side is adapted to a slightly changed power demand on the secondary side mainly by increasing or reducing the duty ratio, whereas in the case of a high power demand the primary side is mainly adapted to a slightly changed power demand by increasing or decreasing the frequency of said oscillator.

5. Power transmitter according to claim 4, characterized in that a threshold value is provided for the power demand on the secondary side, the primary side below the threshold value adapting said duty cycle control unit to the power demand on the secondary side by changing the duty ratio, said first oscillator (VCO_P) producing its maximum or minimum frequency, and the primary side above the threshold value being adapted to the power demand on the secondary side by changing the frequency of said first oscillator (VCO_P) between a minimum and the maximum frequency, said duty cycle control unit holding the duty ratio at 100%.

6. Power transmitter according to any one of the above claims, characterized by a photodiode (44) on the secondary side and a photodetector (45) and an analyzing means (46) on the primary side, said photodiode (44) being optically coupled with said photodetector, said detection means (42) controlling said photodiode, and said analyzing means (46) supplying a voltage signal to said first oscillator (VCO_P), said voltage signal depending on the signal supplied by said photodetector.

7. Power transmitter according to claim 6, characterized in that a modulator (43) is further provided on the secondary side and a demodulator (41) on the primary side, said modulator (43) being fed with the output signal of said detection means (42) and said modulator directly driving said photodiode, and the signal supplied by said photodetector being supplied to said demodulator (41) and the output signal thereof being supplied to said analyzing means.

8. Power transmitter according to any one of the above claims, characterized in that a capacitor (C_P) is connected on the primary side in series with said inductor (L_P) on the primary side, the resonant frequency from said inductor (L_P) and capacitor (C_P) on the primary side being equal to the maximum or minimum frequency of said first oscillator (VCO_P).

9. Power transmitter according to any one of claims 1 to 5, characterized in that a short-circuit switch (S_K) which is opened and closed by said detection means (42) in a controlled way is provided on the secondary side in parallel with said inductor (L_S) on the secondary side.

10. Power transmitter according to any one of claims 1 to 5 or 9, characterized in that said inductor on the secondary side is connected via a disconnector switch (S_L) to the load, so that said disconnector switch (S_L) can separate said inductor (L_S) on the secondary side from said load (R_L), said disconnector switch (S_L) being controlled by said detection means (42).

11. Power transmitter according to claim 9 or 10, characterized in that on the primary side a pulse detector (51) is provided for detecting pulses whose duration is short or long in comparison with the period duration of said alternating signal produced by said first oscillator (VCO_P), the output signal of said pulse detector (51) controlling said first oscillator (VCO_P).

12. Power transmitter according to claim 11, characterized in that on the primary side there is further provided a frequency-to-voltage converter (f/v) which has supplied thereto the output signal of said pulse detector (51) and supplies a voltage (U_T) to said first oscillator (VCO_P).

13. Power transmitter according to any one of claims 9 to 12, characterized in that on the secondary side a second voltage-controlled oscillator (VCO_S) is provided which has supplied thereto a control voltage produced by said detection means (42), said second oscillator (VCO_S) controlling said short-circuit switch (S_K) and/or said disconnector switch (S_L), said second oscillator (VCO_S) producing pulses of a pulse duration which is short or long in comparison with the period duration of said alternating signal produced by said first oscillator (VCO_P), and whose frequency is low or high in comparison with that of said alternating signal.

14. Power transmitter according to claim 12, as far as it refers back to claim 3, characterized in that the duty signal of said duty cycle control unit (VDC) is supplied to the frequency-to-voltage converter (f/v) and the frequency-to-voltage converter (f/v) will only change the voltage on the basis of the signal supplied by said pulse detector if said alternating signal of said first oscillator (VCD_P) is supplied to said inductor on the primary side and said frequency-to-voltage converter (f/v) keeps the voltage otherwise constant.