Energy transfer device and energy transfer control semiconductor device

• US 7,778,050 B2
• Filed: 12/02/2008
• Issued: 08/17/2010
• Est. Priority Date: 12/07/2007
• Status: Active Grant

• Current Assignee: Panasonic Semiconductor Solutions Co., Ltd. (Winbond Electronics Corporation)
• Original Assignee: Panasonic Corporation (Panasonic Holdings Corporation)
• Inventors: Yamashita, Tetsuji
• Primary Examiner(s): Berhane; Adolf
• Assistant Examiner(s): PHAM, EMILY P
• Application Number:
  US12/326,179
• Publication Number:
  US 20090147547A1
• Time in Patent Office: 623 Days
• Field of Search: 363/21.12, 363/21.13, 363/21.14, 363/21.15, 363/21.16, 363/21.17, 363/21.18
• US Class Current: 363/21.16
• CPC Class Codes: H02M 1/44 Circuits or arrangements for compensating for electromagnetic interference in converters or inverters
• CPC Class Codes: H02M 3/33507 with automatic control of the output voltage or current, e.g. flyback converters H02M3/33561, H02M3/33569 take precedence

Abstract

The present invention includes a turn-off signal modulating circuit that periodically varies a turn-off timing of a switching element 2 at a preset modulation time after a current detection by a drain current detecting circuit 15, and by modulating the peak of a current flowing through the switching element 2, diffuses switching noise while preventing concentration of an oscillating frequency at a constant frequency even under a constant input voltage and a constant load.

Claims

1. An energy transfer device comprising:

a transformer having a primary winding, a secondary winding, and an auxiliary winding;

a switching element series-connected to the primary winding;

a control circuit that controls a switching operation of the switching element to perform switching control on a first DC voltage to be inputted to the switching element via the primary winding;

an output voltage generating unit that converts an AC voltage generated on the secondary winding by the switching control into a second DC voltage and supplies power to a load; and

an output voltage detecting circuit that detects a variation in the second DC voltage and transfers a feedback signal for the switching control generated in accordance with the variation to the control circuit, wherein

the control circuit includes;

a feedback signal control circuit that determines a level of a current flowing through the switching element based on the feedback signal from the output voltage detecting circuit;

a switching element current detecting circuit that generates a signal that turns off the switching element when the current flowing through the switching element reaches the level value determined by the feedback signal control circuit;

a turn-on detecting circuit that detects, from a voltage of the auxiliary winding, a state of a ringing voltage generated after a secondary current flowing through the secondary winding ceases to flow after the switching element is turned off, and generates a signal for turning on the switching element; and

a current peak modulator that performs modulation so that a peak of the current flowing through the switching element periodically and continuously varies within a current range from a first current value to a second current value.

2. The energy transfer device according to claim 1, wherein

a turn-off signal modulating circuit that performs modulation so that a turn-off signal of the switching element by the switching element current detecting circuit periodically and continuously varies within a time range from a first delay time to a second delay time is provided as the current peak modulator to the control circuit;

and

time modulation is performed by the turn-off signal modulating circuit in order to vary a turn-off timing of the switching element and modulate the current peak.

3. The energy transfer device according to claim 2, wherein

the turn-off signal modulating circuit includes:

a low-frequency oscillator that outputs a triangular wave voltage; and

a V-I converter that converts the triangular wave voltage from the low-frequency oscillator into a current,

the time modulation is determined depending on a magnitude of an output current of the V-I converter, and

a modulation time of the turn-off signal is set based on an amplitude of the triangular wave voltage to the time range from the first delay time to the second delay time while a modulation period is determined depending on a switchover period of the triangular wave voltage.

4. The energy transfer device according to claim 2, wherein

the turn-off signal modulating circuit automatically varies a modulation duration and a modulation period of the turn-off signal according to an output signal from the feedback signal control circuit based on a feedback signal from the output voltage detecting circuit.

5. The energy transfer device according to claim 4, wherein

the turn-off signal modulating circuit increases the modulation duration and shortens the modulation period as a load condition of the second DC current becomes a lighter load condition according to an output signal from the feedback signal control circuit based on a feedback signal that varies depending on the load condition of the second DC voltage.

6. The energy transfer device according to claim 2, wherein

an input voltage detecting circuit that detects the first DC voltage is provided to the control circuit, and

the turn-off signal modulating circuit automatically varies a modulation duration and a modulation period of the turn-off signal according to an output signal from the input voltage detecting circuit.

7. The energy transfer device according to claim 6, wherein

the turn-off signal modulating circuit increases the modulation duration and shortens the modulation period as the first DC voltage increases according to an output signal from the input voltage detecting circuit which varies depending on the first DC voltage.

8. The energy transfer device according to claim 6, wherein

the turn-off signal modulating circuit causes an operation for automatically varying the modulation duration and the modulation period to be performed when the first DC voltage equals or exceeds a preset constant voltage.

9. The energy transfer device according to claim 2, wherein

a number-of-oscillations counting circuit that counts the number of oscillations due to the switching operation of the switching element is provided to the control circuit;

and

the turn-off signal modulating circuit automatically varies a modulation duration and a modulation period of the turn-off signal according to an output signal from the number-of-oscillations counting circuit.

10. The energy transfer device according to claim 9, wherein

the number-of-oscillations counting circuit includes:

a number-of-oscillations counter that inputs a control electrode signal of the switching element and outputs a high level at a timing when the number of switching operations of the switching element reaches a preset count; and

a D flip-flop that switches an output signal between a low level and a high level at the timing when the preset count is reached, and

the turn-off signal modulating circuit automatically varies the modulation duration and the modulation period according to an output signal from the D flip-flop.

11. The energy transfer device according to claim 10, wherein

the turn-off signal modulating circuit increases the modulation duration and shortens the modulation period as the number-of-oscillations count time quickens according to an output signal from the D flip-flop which is outputted at the timing when the preset count is reached.

12. The energy transfer device according to claim 1, wherein

a feedback signal modulating circuit that modulates an output signal from the feedback signal control circuit which determines the level of a current flowing through the switching element is provided as the current peak modulator to the control circuit, and

the feedback signal control circuit modulates the peak of a current flowing through the switching element so as to periodically and continuously vary within the current range from the first current value to the second current value according to an output signal modulated by the feedback signal modulating circuit.

13. The energy transfer device according to claim 12, wherein

the feedback signal control circuit includes an I-V converter that converts a feedback current into a voltage as a feedback signal from the output voltage detecting circuit, and

a reference voltage of the I-V converter is periodically and continuously varied within a voltage range from a first voltage value to a second voltage value according to an output voltage from the feedback signal modulating circuit in order to modulate the peak of a current flowing through the switching element so as to periodically and continuously vary within the current range from the first current value to the second current value.

14. The energy transfer device according to claim 13, wherein

the feedback signal modulating circuit includes a low-frequency oscillator that outputs a triangular wave, and

the feedback signal control circuit determines the voltage range from the first voltage value to the second voltage value according to an amplitude of a triangular wave voltage from the low-frequency oscillator as the reference voltage of the I-V converter and determines a modulation period according to a switchover period of the triangular wave.

15. The energy transfer device according to claim 14, wherein

the feedback signal control circuit modulates the peak of a current flowing through the switching element so as to periodically and continuously vary within the current range from the first current value to the second current value by periodically and continuously varying an output voltage from the I-V converter within the voltage range from the first voltage value to the second voltage value using the reference voltage of the I-V converter having the voltage range from the first voltage value to the second voltage value determined according to the amplitude of the triangular wave voltage from the low-frequency oscillator and the modulation period.

16. The energy transfer device according to claim 12, wherein

the feedback signal modulating circuit includes:

a low-frequency oscillator that outputs a triangular wave; and

a V-I converter that converts a triangular wave voltage from the low-frequency oscillator into a current,

the feedback signal control circuit includes

an I-V converter that converts a feedback current into a voltage as a feedback signal from the output voltage detecting circuit, and

the energy transfer device determines, via the V-I converter, a current range from a first current value to a second current value according to an amplitude of a triangular wave voltage from the low-frequency oscillator as an input current to the I-V converter, determines a modulation period in accordance with a switchover period of the triangular wave voltage, and by periodically and continuously varying the input current to the I-V converter within a current range from a first current value to a second current value according to an output current from the V-I converter, modulates the peak of a current flowing through the switching element so as to periodically and continuously vary within the current range from the first current value to the second current value.

17. The energy transfer device according to claim 12, wherein

the feedback signal control circuit automatically varies a modulation duration and a modulation period of a turn-off signal with respect to the peak of a current flowing through the switching element by controlling a feedback signal from the output voltage detecting circuit using an output signal from the feedback signal modulating circuit.

18. The energy transfer device according to claim 17, wherein

the feedback signal modulating circuit automatically varies the modulation duration and the modulation period with respect to an output signal to the feedback signal control circuit depending on a load condition of the second DC voltage to increase the modulation duration and shorten the modulation period as the load condition becomes on a lighter load condition.

19. The energy transfer device according to claim 12, wherein

an input voltage detecting circuit that detects a magnitude of the first DC voltage is provided to the control circuit,

the feedback signal control circuit automatically varies a modulation duration and a modulation period of a turn-off signal with respect to the peak of a current flowing through the switching element by controlling a feedback signal from the output voltage detecting circuit using an output signal from the feedback signal modulating circuit, and

the feedback signal modulating circuit automatically varies the modulation duration and the modulation period of the output signal to the feedback signal control circuit depending on an output signal from the input voltage detecting circuit.

20. The energy transfer device according to claim 19, wherein

the feedback signal modulating circuit automatically varies the modulation duration and the modulation period of an output signal to the feedback signal control circuit depending on a magnitude of the first DC voltage to increase the modulation duration and shorten the modulation period as the first DC voltage increases.

21. The energy transfer device according to claim 19, wherein

the feedback signal modulating circuit automatically varies the modulation duration and the modulation period of an output signal to the feedback signal control circuit depending on a magnitude of the first DC voltage to perform an operation for automatically varying the modulation duration and the modulation period when the first DC voltage equals or exceeds a preset constant voltage.

22. The energy transfer device according to claim 12, wherein

a number-of-oscillations counting circuit that counts the number of oscillations due to the switching operation of the switching element is provided to the control circuit,

the feedback signal control circuit automatically varies a modulation duration and a modulation period of a turn-off signal with respect to the peak of a current flowing through the switching element by controlling a feedback signal from the output voltage detecting circuit using an output signal from the feedback signal modulating circuit, and

the feedback signal modulating circuit automatically varies the modulation duration and the modulation period of the output signal to the feedback signal control circuit depending on an output signal from the number-of-oscillations counting circuit.

23. The energy transfer device according to claim 22, wherein

the number-of-oscillations counting circuit includes:

a number-of-oscillations counter that counts the number of oscillations of the switching element based on a control electrode signal of the switching element and outputs a high level at a timing when the number of oscillations of the switching element reaches a preset count; and

a D flip-flop that switches an output signal between a low level and a high level at a timing when the output of the number-of-oscillations counter reaches a high level, and

the feedback signal modulating circuit automatically varies the modulation duration and the modulation period of an output signal to the feedback signal control circuit depending on an output signal of the D flip-flop.

24. The energy transfer device according to claim 23, wherein

the feedback signal modulating circuit automatically varies the modulation duration and the modulation period of an output signal to the feedback signal control circuit depending on a switchover time between a low level and a high level of an output signal from the D flip-flop, and increases the modulation duration and shortens the modulation period as the switchover time between the low level and the high level of the output signal from the D flip-flop quickens.

25. An energy transfer control semiconductor device, wherein

the switching element and the control circuit are formed as an integrated circuit on a same semiconductor substrate in the energy transfer device according to claim 1.