Digital state controller for a high-voltage generator using the mixed-mode modulation method

• US 7,167,381 B2
• Filed: 01/13/2004
• Issued: 01/23/2007
• Est. Priority Date: 01/16/2003
• Status: Expired due to Fees

• Current Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Original Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Inventors: Hattrup, Christian, Scheel, Thomas
• Primary Examiner(s): Vu; Bao Q.
• Application Number:
  US10/542,132
• Publication Number:
  US 20060050538A1
• Time in Patent Office: 1,106 Days
• Field of Search: 363/17, 363/25, 363/98, 363/132, 363/134
• US Class Current: 363/17
• CPC Class Codes: H02M 1/0012 Control circuits using digital or numerical techniques in DC/DC converters H02M3/157, H02M3/33515; in DC-AC converters H02M7/53873
• CPC Class Codes: H02M 3/3376 with automatic control of output voltage or current
• CPC Class Codes: Y02B 70/10 Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes

Abstract

A description is given of a power supply unit, an X-ray device having a power supply unit, and a method of controlling a power supply unit. In order also to control non-linear control paths, such as of a power supply unit operated with mixed-mode modulation, it is proposed that the control device be designed as a digital control device which calculates at least one correcting variable. The control device processes at least a first actual value U_out, which depends on the output voltage. A time difference value is calculated from two sample values of the first actual value U_out and is multiplied by a first controller coefficient K_out. The value of the first controller coefficient can in this case change as a function of the operating point of the power supply unit.

Claims

1. A power supply unit comprising:

a switching device (18) for converting an intermediate circuit voltage (U_z) into a switched voltage (U_WR);

a resonant circuit (20) that is fed by the switched voltage (U_WR) and has a transformer (T) for supplying an output voltage; and

a control device (30, 32) for setting at least one correcting variable (T_PW), the control device being configured for converting the correcting variable (T_PW) into values of wait time interval (T_W) and active phase time interval (T_P) for actuating the switching device (18) according to a non-linear relationship between T_p, T_W and T_PW for three operating modes of mixed mode modulation, the three operating modes corresponding to low output power, medium output power, and high output power modes,

wherein the control device (30, 32) is configured to process sample values of at least a first actual value (U_out) which depends on the output voltage, and to calculate a time difference value (Δ

U_out) from two sample values,

wherein the time difference value (Δ

U_out) is multiplied by a first controller coefficient (k_out) and the result is used in the calculation of the correcting variable (T_PW), and

wherein the value of the first controller coefficient (k_out) is changeable as a function of the operating point of the power supply unit.

2. A power supply unit as claimed in claim 1, wherein

during the calculation of the correcting variable (T_PW) a second actual value (U_L) is processed, which second actual value depends on the current through the resonant circuit (20),

where a time difference value (Δ

U_L) is calculated from sample values of the second actual value (U_L) and is multiplied by a second controller coefficient (k_L), and

where the value of the second controller coefficient (k_L) is changeable as a function of the operating point of the power supply unit (10).

3. A power supply unit as claimed in claim 1, wherein

the control device (30, 32) processes the intermediate circuit voltage (U_Z) as a third actual value,

where the processing is preferably effected in that a difference value of the intermediate circuit voltage (Δ

U_Z) is multiplied by a controller coefficient (k_Z) and added to other variables, and the result is temporally summed, and

where the controller coefficient (k_Z) is preferably changeable as a function of the operating point of the power supply unit (10).

4. A power supply unit as claimed in claim 1, wherein

the control device (30, 32) has a structure in which

the control deviation, difference values (Δ

U_out, Δ

U_L) from actual values and a coupled-back, time-delayed difference value of the correcting variable (T_PW) are in each case multiplied by controller coefficients (k_l, K_out, k_L, k_E) and added up,

and the result is temporally summed, and

where one, a number, or all of the controller coefficients (k_l, K_out, k_L, k_E) are changeable as a function of the operating point of the power supply unit (10).

5. A power supply unit as claimed in claim 1, wherein

the operating-point-dependent controller coefficient or coefficients (k_out, k_L, k_E, k_l, k_Z) are taken from two-dimensional tables,

where each table contains for each pair of values of a first indexing variable, which depends on the correcting variable (T_PW),

and a second indexing variable, which depends on one or more of the processed actual values (U_L), and

the respective value of the controller coefficient (k_out, K_L, kL, k_l, k_E, k_Z).

6. A power supply unit as claimed in claim 1, wherein

the control device (30, 32) supplies a scalar correcting variable (T_PW),

from which there is calculated a setting for actuating the switching device (18) in order to generate the switched voltage (U_WR).

7. A power supply unit as claimed in claim 1, wherein

with a first operating mode for low output powers, the switching device (18) is actuated by the pulse width being changed at an essentially constant switching frequency that is lower than the resonant frequency at least by a predefined factor,

and in a second operating mode for higher output powers, the switching device (18) is actuated by the switching frequency varying in the region of the resonant frequency.

8. A power supply unit as claimed in claim 1, wherein

the control device (30, 32) comprises at least a first controller unit (34) and a second controller unit (36),

where the first controller unit (34) predefines a first correcting variable in order to regulate at least one actual value (U_out) to a desired value (U_soll),

and the second controller unit (36) predefines a second correcting variable in order to regulate an electrical variable of the resonant circuit (20) to a permissible maximum value,

and where in each case, the lower of the two correcting variables is used for actuation.

9. A power supply unit as claimed in claim 1, wherein

the control device is formed as a digital control device having a central processing unit,

where measured values of at least a first actual value (U_out) are digitized and at least one correcting variable (T_PW) is calculated in order to supply a switched voltage having a timing interval,

where measured values of only some of the timing intervals are processed.

10. An X-ray device having

a power pack (14, 16) for supplying an intermediate circuit voltage (U_Z),

a power supply unit (10) as claimed in claim 1 which is supplied with power by the intermediate circuit voltage (U_Z),

and an X-ray tube (12) which is fed by the output voltage of the power supply unit (10).

11. A method of controlling a power supply unit (10) having a switching device (18) for converting an intermediate circuit voltage (U_Z) into a switched voltage (U_WR), and a resonant circuit (20) that is fed by the switched voltage (U_WR) and has a transformer (T), and possibly a rectifier circuit, for supplying an output voltage, the method comprising:

forming a correcting variable (T_PW) for actuating the switching device, wherein forming includes using a control device (30, 32) for setting at least one correcting variable (T_PW) and converting the correcting variable (T_PW) into values of wait time interval (T_W) and active phase time interval (T_P) for actuating the switching device (18) according to a non-linear relationship between T_P, T_W and T_PW for three operating modes of mixed mode modulation, the three operating modes corresponding to low output power, medium output power, and high output power modes;

calculating a time difference value (Δ

U_out) from sample values of a first actual value (U_out) and multiplying the time difference value by a first controller coefficient (k_out), the multiplication result being used in forming the correcting variable (T_PW), and

where the value of the first controller coefficient (k_out) can change as a function of the operating point of the power supply unit (10).