Voltage transformer and associated operating method

• US 20010019258A1
• Filed: 02/16/2001
• Published: 09/06/2001
• Est. Priority Date: 02/16/2000
• Status: Active Grant

• Current Assignee: Continental Automotive GmbH (Continental AG)
• Original Assignee: Siemens AG
• Inventors: Frohler, Manfred
• Granted Patent: US 6,476,588 B2
• Time in Patent Office: Days
• US Class Current: 323/222
• CPC Class Codes: H02M 1/0022 the disturbance parameters being input voltage fluctuations
• CPC Class Codes: H02M 3/156 with automatic control of output voltage or current, e.g. switching regulators

Abstract

A voltage transformer includes a voltage input and a voltage output. A capacitor is disposed on the output side for providing an output voltage. A controllable switching element controls a current flowing through a coil. A control unit is connected on the output side to the switching element, for controlling switching times of the switching element. The control unit controls the switching times as a function of the input and output voltages. An associated operating method is also provided.

Claims

1. A voltage transformer, comprising:

an input side having a voltage input carrying an input voltage;

an output side having a voltage output carrying an output voltage;

a capacitor disposed on said output side, for providing said output voltage;

a coil having a coil current;

a controllable switching element connected to said coil for controlling current flowing through said coil, said switching element having switching times for setting a voltage ratio; and

a control unit, said control unit having an input side connected to said voltage input and to said voltage output, and said control unit having an output side connected to said switching element for controlling said switching times of said switching element as a function of said input voltage and said output voltage, to set said voltage ratio and to prevent an excessive rise in said coil current.

2. The voltage transformer according to

claim 1

, including a diode connected to said coil in a series circuit, said capacitor connected through said series circuit to said voltage input, said switching element disposed between said coil and said diode, and said switching element alternately conducting said coil current through said capacitor and bridging said capacitor.

3. The voltage transformer according to

claim 1

, wherein said coil and said switching element are connected in a series circuit, said capacitor is connected through said series circuit to said voltage input, and a diode branches off between said switching element and said coil and is connected to ground.

4. The voltage transformer according to

claim 1

, wherein said control unit is a software-controlled microcontroller.

5. The voltage transformer according to

claim 1

, wherein said control unit has a pulse-width modulator for controlling said switching times of said switching element to set said voltage ratio.

6. The voltage transformer according to

claim 1

, wherein said control unit has a pulse-frequency modulator for controlling said switching times of said switching element to set said voltage ratio.

7. The voltage transformer according to

claim 1

, wherein said control unit has a pulse-width modulator and a pulse-frequency modulator, for controlling said switching times of said switching element to set said voltage ratio.

8. The voltage transformer according to

claim 1

, wherein said control unit has a sampling element operating in a time-discrete manner, for measuring at least one of said input voltage and said output voltage.

9. A method for operating the voltage transformer according to

claim 1

, which comprises:

measuring the input voltage and the output voltage;

calculating the switching times of the switching element as a function of the input voltage and the output voltage; and

driving the switching element alternately into conductive and non-conductive states in accordance with the calculated switching times, for achieving a desired voltage ratio of the voltage transformer and to prevent an excessive rise in the coil current.

10. The method according to

claim 9

, which further comprises periodically switching the switching element into the conductive and non-conductive states with a prescribed switching period.

11. The method according to

claim 10

, which further comprises switching the switching element into the conductive state at a start of each switching period for a prescribed initial time interval, to bridge the capacitor.

12. The method according to

claim 11

, which further comprises calculating the initial time interval as a function of a maximum permissible coil current, an inductance of the coil and the input voltage of the voltage transformer.

13. The method according to

claim 11

, which further comprises switching the switching element into the non-conductive state in each switching period after expiration of the initial time interval, at least for a prescribed subsequent time interval, to extinguish the coil current.

14. The method according to

claim 12

, which further comprises switching the switching element into the non-conductive state in each switching period after expiration of the initial time interval, at least for a prescribed subsequent time interval, to extinguish the coil current.

15. The method according to

claim 14

, which further comprises calculating the subsequent time interval as a function of the maximum permissible coil current, the inductance of the coil, the input voltage and the output voltage.

16. The method according to

claim 14

, which further comprises additionally switching the switching element into the non-conductive state in each switching period after expiration of the subsequent time interval, until the end of the switching period, for an additional time interval, to set the desired voltage ratio.

17. The method according to

claim 15

, which further comprises additionally switching the switching element into the non-conductive state in each switching period after expiration of the subsequent time interval, until the end of the switching period, for an additional time interval, to set the desired voltage ratio.

18. The method according to

claim 16

, which further comprises calculating the additional time interval as a function of a capacitance of the capacitor, the maximum permissible coil current, the initial time interval and the subsequent time interval.

19. The method according to

claim 17

, which further comprises calculating the additional time interval as a function of a capacitance of the capacitor, the maximum permissible coil current, the initial time interval and the subsequent time interval.

20. The method according to

claim 9

, which further comprises periodically measuring the input voltage and the output voltage with a prescribed measuring period having a duration substantially greater than a duration of the switching period.

21. A motor vehicle network voltage transformer, comprising:

an input side having a voltage input carrying an input voltage;

an output side having a voltage output carrying an output voltage;

a capacitor disposed on said output side, for providing said output voltage;

a coil having a coil current;

a controllable switching element connected to said coil for controlling current flowing through said coil, said switching element having switching times for setting a voltage ratio; and

a control unit, said control unit having an input side connected to said voltage input and to said voltage output, and said control unit having an output side connected to said switching element for controlling said switching times of said switching element as a function of said input voltage and said output voltage, to set said voltage ratio and to prevent an excessive rise in said coil current.