Electrical circuit to detect load current

• US 6,242,938 B1
• Filed: 06/04/1999
• Issued: 06/05/2001
• Est. Priority Date: 09/30/1996
• Status: Expired due to Term

• Current Assignee: Robert Bosch GmbH
• Original Assignee: Robert Bosch GmbH
• Inventors: Kessler, Martin
• Primary Examiner(s): Metjahic, Safet
• Application Number:
  US09/269,590
• Time in Patent Office: 732 Days
• Field of Search: 324/722, 324/522, 324/653, 324/126, 361/160, 388/806, 388/811, 363/132
• US Class Current: 324/765.01
• CPC Class Codes: G01R 19/0092 measuring current only all subgroups of G01R19/00 take precedence
• CPC Class Codes: H02M 1/0009 Devices or circuits for detecting current in a converter
• CPC Class Codes: H02P 7/288 using variable impedance

Abstract

An electric circuit for determining the load current of a clocked load having at least one inductive component and being assigned a free-wheeling circuit has a shunt whose voltage drop is used to determine the current. The shunt is arranged in the free-wheeling circuit to determine the free-wheeling current which is used as a measure for determining the load current (motor current). Furthermore, according to another embodiments the shunt is in series with the load and the free-wheeling circuit is arranged in parallel to the series connection of load and shunt.

Claims

1. An electric circuit arrangement for determining a load current of a clocked load, the clocked load including at least one inductive component, comprising:

a free-wheeling circuit assigned to the clocked load;

a shunt determining a free-wheeling current; and

a determination device for determining the load current according to the following equation;

$I_M=\frac{I_F}{1-D}$

wherein D is a pulse duty factor of a control operation of the clocked load, I_M is the load current and I_F is the free-wheeling current.

2. The electric circuit arrangement according to claim 1, wherein the clocked load is an electric motor.

3. The electric circuit arrangement according to claim 2, wherein the electric motor includes a permanent field d.c. motor.

4. The electric circuit arrangement according to claim 1, wherein a resistance of the shunt is substantially smaller than a further resistance of an ohmic component of the clocked load.

5. The electric circuit arrangement according to claim 1, wherein the pulse duty factor is determined as a function of a quotient of a load voltage.

6. The electric circuit arrangement according to claim 5, wherein the load voltage includes a motor voltage and a power supply voltage.

7. The electric circuit arrangement according to claim 1, wherein the electrical circuit arrangement is dimensioned for enabling the load current to continue to flow at a substantially same level during an operation of the free-wheeling circuit.

8. The electric circuit arrangement according to claim 7, wherein the load current includes a motor current.

9. The electric circuit arrangement according to claim 8, wherein the motor current is determined according to the following equation:

10. An electric circuit arrangement for determining a load current of a clocked load, the clocked load including at least one inductive component, comprising:

a shunt coupled in series with the clocked load;

a free-wheeling circuit assigned to the clocked load, the free-wheeling circuit being coupled in parallel to a series connection of the clocked load and the shunt; and

a determination device for determining the load current according to the following equation;

11. The electric circuit arrangement according to claim 10, wherein the clocked load is an electric motor.

12. The electric circuit arrangement according to claim 11, wherein the electric motor includes a permanent field d.c. motor.

13. The electric circuit arrangement according to claim 10, wherein a resistance of the shunt is substantially smaller than a further resistance of an ohmic component of the clocked load.

14. The electric circuit arrangement according to claim 10, wherein the pulse duty factor is determined as a function of a quotient of a load voltage.

15. The electric circuit arrangement according to claim 14, wherein the load voltage includes a motor voltage and a power supply voltage.

16. The electric circuit arrangement according to claim 10, wherein the electrical circuit arrangement is dimensioned for enabling the load current to continue to flow at a substantially same level during an operation of the free-wheeling circuit.

17. The electric circuit arrangement according to claim 16, wherein the load current includes a motor current.