Signal interface circuit

• US 20080204289A1
• Filed: 02/08/2008
• Published: 08/28/2008
• Est. Priority Date: 02/12/2007
• Status: Active Grant

• Current Assignee: ABB Schweiz AG (ABB Limited)
• Original Assignee: Abb Oy (ABB Limited)
• Inventors: Miettinen, Erkki
• Granted Patent: US 7,652,602 B2
• Time in Patent Office: Days
• US Class Current: 341/141
• CPC Class Codes: H03M 3/43 the quantiser being a single bit one
• CPC Class Codes: H03M 3/474 using time-division multiplexing

Abstract

Interface unit for voltage input signals comprising two or more input channels. The input signals of these two or more input channels are connected alternately by an analog multiplexer to an analog-to-digital converter. The A/D converter comprises an integrated sigma-delta modulator circuit which generates a digitized 1-bit signal representing the input signal voltage level for a control unit irrespective of whether the input channel signal is digital or analog. By means of the invention all input voltage channels are made similar such that the input channels of the interface unit can receive an analog or digital signal irrespective of each other.

Claims

1. An interface unit for voltage input signals, comprising

an analog-digital converter for converting an input signal voltage into a digital output signal for a control unit;

two or more input channels;

an analog multiplexer configured to switch the input signal of said two or more input channels alternately to said analog-digital converter;

each input channel is configurable to receive a digital or analog input signal irrespective of other input channels;

said analog-digital converter comprises an integrated sigma-delta modulator configured to generate a digitized 1-bit signal representing the voltage level of the input signal for the interpretation of the control unit irrespective of whether the signal of the input channel is digital or analog.

2. An interface unit according to claim 1, comprising by galvanic isolation integrated into said sigma-delta modulator circuit between the analog input and the digital output;

an integrated galvanic isolating circuit having at least one control signal input from said control unit and at least one control signal output isolated galvanically from the control signal input, which control signal output provides either directly or indirectly a control signal for the analog multiplexer.

3. An interface unit according to claim 2, wherein said integrated galvanically isolating circuit comprises a DC-DC converter circuit having at least one control signal input from the control unit, and an operating voltage input, as well as at least one control signal output and operating signal output galvanically isolated from the inputs, whereby said control signal output provides directly or indirectly said control signal, and said operating voltage output provides an operating voltage for the analog multiplexer and for the analog side of the sigma-delta modulator circuit.

4. An interface unit according to claim 2, comprising a binary counter configured to generate, clocked by said control signal output, a cyclic binary number sequence to serve as the control signal of the analog multiplexer.

5. An interface unit according to claim 1, comprising digital means for filtering and decimating a digitized 1-bit signal generated by the sigma-delta modulator, so that a multi-bit, digitized, actual current or voltage value is obtained for the control unit.

6. An interface unit according to claim 1, wherein one input channel of the analog multiplexer is connected to a constant voltage for calibration of the interface unit.

7. An electric motor drive comprising an interface unit according to claim 1.

8. An electric motor drive according to claim 7, wherein said control unit comprises a control processor or logic of the electric motor drive.

9. An electric motor drive according to claim 7, wherein the interface unit is positioned on a separate circuit board, which is connected with a serial-communication cable to a motor control board of the motor drive or installed in a board connector on the motor control board of the motor drive, and wherein the control unit is positioned on the motor control board.