High-speed switching circuit and automotive accessory controller using same

• US 6,876,104 B1
• Filed: 11/27/2001
• Issued: 04/05/2005
• Est. Priority Date: 11/27/2001
• Status: Expired due to Fees

• Current Assignee: Yazaki North America Incorporated (Yazaki Corporation)
• Original Assignee: Yazaki North America Incorporated (Yazaki Corporation)
• Inventors: Guo, Sam Y.
• Primary Examiner(s): DeBeradinis, Robert L.
• Application Number:
  US09/995,033
• Time in Patent Office: 1,225 Days
• Field of Search: 307/125, 307/131, 307/140, 307/9.1, 307/10.1, 307/10.8, 307/412
• US Class Current: 307/140
• CPC Class Codes: G01R 1/203 Resistors used for electric measuring, e.g. decade resistors standards, resistors for comparators, series resistors, shunts resistors in general H01C; microwave or radiowave terminations H01P1/26; coupling devices H01R
• CPC Class Codes: H02H 1/0007 concerning the detecting means in general G01R or other subclasses of G01; reed switches H01H71/2445
• CPC Class Codes: H02H 3/087 for dc applications
• CPC Class Codes: H05K 1/167 incorporating printed resistors
• CPC Class Codes: H05K 2201/09263 Meander
• CPC Class Codes: H05K 2201/09672 Superposed layout, i.e. in different planes parallel traces in one plane H05K2201/09236

Abstract

A high-speed switching circuit with a low or zero inductance shunt resistor is constructed using a trace resistor having parallel overlying trace portions on opposite plane faces of a printed circuit board. The resulting shunt resistor is used in combination with a detector to input data to a microcontroller which controls an automotive load device such as a blower motor. The traces which form the resistor may be extended by horizontal or vertical zig-zag folding or a combination of the two.

Claims

1. A fast response pulse width modulated control circuit comprising:

an electronic switch device having an output circuit and an input circuit, a milliohmic shunt resistor connected in series with the output circuit;

a detector having an input circuit connected across the shunt resistor and an output which changes state according to changes in voltages developed across the shunt resistor;

means connected to the output of the detector to control the switch device to vary the duty cycle thereof;

said shunt resistor comprising a dielectric support with first and second conductive traces printed in overlying parallel relationship on opposite faces thereof and a via through the support and electrically interconnecting the traces at one end thereof such that load current flows in opposite directions through the first and second traces.

2. An automotive accessory control circuit comprising an FET switch and a shunt resistor connected in series between a power supply and a drive motor;

a detector having inputs connected across the shunt resistor and an output which changes state in accordance with voltages developed across the shunt resistor;

a microcontroller having an input connected to receive the output of the detector and being programmed to provide an output which changes state in accordance with a change in state of the detector output; and

a FET driver connected to receive the output of the microcontroller for varying the duty cycle of the FET switch;

wherein said shunt resistor comprises a dielectric support with first and second conductive traces printed in overlying parallel relationship on opposite faces thereof and an electrical connector extending through the support and electrically connecting the traces at one end thereof.

3. A circuit as defined in claim 2 wherein the first and second traces have multiple legs on each of said faces.

4. A circuit as defined in claim 2 wherein shunt resistor comprises third and forth traces electrically continuous with the first and second traces.

5. A circuit as defined in claim 2 wherein the detector is an amplifier.

6. A circuit as defined in claim 2 wherein the detector is a comparator.

7. A control circuit comprising:

a pulse width modulated solid state power switch for connecting a DC power supply to a DC load device;

a shunt resistor connected in series with the switch;

a detector having inputs connected across the resistor for detecting the voltage drop across the resistor and producing an output related thereto;

a control circuit for varying the duty cycle of the switch and having an input connected to receive the output of the detector; and

a circuit board having opposite parallel surfaces;

said shunt resistor comprising first and second overlying traces on said opposite circuit board surfaces and further including a conductive interconnection through said circuit board to connect the traces in series.

8. A circuit as defined in claim 7 wherein the detector is a comparator.

9. A circuit as defined in claim 7 wherein the detector is an electronic amplifier mounted on said circuit board.

10. A circuit as defined in claim 7 wherein the first and second traces have multiple legs on each of said faces.

11. A circuit as defined in claim 7 wherein the shunt resistor comprises third and forth traces electrically continuous with the first and second traces.