Switching circuit for producing an adjustable output characteristic

• US 20050083111A1
• Filed: 03/11/2003
• Published: 04/21/2005
• Est. Priority Date: 03/20/2002
• Status: Active Grant

• Current Assignee: Markus Rademacher
• Original Assignee: Minebea Company Limited (MinebeaMitsumi Inc.)
• Inventors: Rademacher, Markus
• Granted Patent: US 7,161,410 B2
• Time in Patent Office: Days
• US Class Current: 327/540
• CPC Class Codes: G05F 1/613 using semiconductor devices in parallel with the load as final control devices G05F1/461 takes precedence

Abstract

The invention relates to a circuit to generate an output characteristic, having a constant voltage control circuit which receives a voltage supply and generates a constant output voltage; a current reduction section, which receives a control voltage and, depending on this, generates a control current which produces a change in the output voltage; and a limiter section which receives a lower and an upper limit voltage and optionally blocks or activates the current reduction section. The invention also relates to a corresponding method to generate an output characteristic.

Claims

1. A circuit for generating an adjustable output comprising:

a constant voltage control circuit (1) which receives a voltage supply (V_SUPPLY) and generates a constant output voltage (V_OUT);

a current reduction section (2) which receives a control voltage (V_CONTROL) and, generates a control current (I_C) which produces a change in the output voltage (V_OUT); and

a limiter section (3) which receives a lower and an upper limit voltage (V_LIMIT1, V_LIMIT2) and optionally blocks or activates the current reduction section (2).

2. The circuit according to claim 1, wherein the constant voltage control circuit (1) further comprises a programmable reference voltage generator (10) whose output voltage (V_OUT) can be adjusted via a voltage divider (13, 14, 15).

3. The circuit according to claim 2, wherein the voltage divider (13, 14, 15) includes a first ohmic section with two resistors (13, 14) and a second ohmic section with one resistor (15).

4. The circuit according to claim 3, wherein the current reduction section (2) further comprises a resistor (23) which is connected in series to one (13) of the two resistors in the first ohmic section so that the control current (I_C) flows through the one resistor (23) of the current reduction section and through one (13) of the two resistors in the first ohmic section in order to superimpose a voltage (I_C.R1) proportional to the control current (I_C) on the output voltage (V_OUT).

5. The circuit according to claim 1, wherein the current reduction section (2) further comprises a first switching element (22) which optionally activates or blocks the control current (I_C).

6. The circuit according to claim 1, wherein the limiter section (3) comprises a comparator (30, 31) which receives the lower and the upper limit voltage (V_LIMIT1, V_LIMIT2) as well as the control voltage (V_CONTROL), and generates a comparator output signal.

7. The circuit according to claim 6, wherein the limiter section (3) blocks or activates the current reduction section (2) as a function of the comparator output signal.

8. The circuit according to claim 7, wherein the comparator output signal of the limiter section (3) is connected to the first switching element (22) of the current reduction section (2) to activate or block the control current (I_C).

9. The circuit according to claim 8, wherein the comparator output signal is connected to the first switching element (22) via at least one diode (34).

10. The circuit according to claim 8, wherein the first switching element (22) blocks the control current (I_C) when the control voltage (V_CONTROL) is less than the lower limit voltage (V_LIMIT1) or greater than the upper limit voltage (V_LIMIT2).

11. The circuit according to claim 7, wherein the limiter section (3) further comprises a second switching element (32) which receives the comparator output signal and optionally activates the bypass circuit (32, 33).

12. The circuit according to claims 11, wherein the bypass circuit (32, 33) comprises a resistor (33) which is connected in parallel to one (13) of the two resistors in the first ohmic section via the second switching element (32).

13. The circuit according to claim 12, wherein the second switching element (32) activates the bypass circuit (32, 33) when the control voltage (V_CONTROL) is less than the lower limit voltage (V_LIMIT1) or greater than the upper limit voltage (V_LIMIT2).

16. The circuit according to claim 6, wherein the limiter section (3) activates a bypass circuit (32, 33) to generate a voltage drop in the output voltage (V_OUT).

17. The circuit according to claim 8, wherein the first switching element (22) activates the control current (I_C) when the control voltage (V_CONTROL) is substantially between the lower limit voltage (V_LIMIT1) and the upper limit voltage (V_LIMIT2).

18. The circuit according to claims 3 wherein the bypass circuit (32, 33) comprises a resistor (33) which is connected in parallel to one (13) of the two resistors in the first ohmic section via the second switching element (32).

14. A method for generating an output characteristic comprising the following steps:

generating a constant output voltage as a function of a voltage supply and of a reference voltage;

generating a control current depending on a control voltage and changing the output voltage as a function of the control current; and

optionally activating or blocking the control current depending on whether the control voltage lies within or without an interval between a lower and an upper limit voltage.

15. The method of claim 14, wherein the output characteristics is a variable output voltage.