US 12,068,714 B2
Method and circuit assembly for sensorless load detection in stepper motors
Bernhard Dwersteg, Rellingen (DE)
Assigned to Maxim Integrated Products, Inc., Wilmington, MA (US)
Appl. No. 17/289,196
Filed by Maxim Integrated Products, Inc., San Jose, CA (US)
PCT Filed Oct. 29, 2019, PCT No. PCT/DE2019/100933
§ 371(c)(1), (2) Date Apr. 27, 2021,
PCT Pub. No. WO2020/088715, PCT Pub. Date May 7, 2020.
Claims priority of application No. 10 2018 126 954.4 (DE), filed on Oct. 29, 2018.
Prior Publication US 2022/0123673 A1, Apr. 21, 2022
Int. Cl. H02P 8/34 (2006.01)
CPC H02P 8/34 (2013.01) 17 Claims
OG exemplary drawing
 
5. A circuit for detecting a load condition, the circuit comprising:
a bridge circuit that comprises:
a first switch having a first internal resistance;
a second switch having a second internal resistance; and
a coil that operates as at least one of a motor or a generator;
a control circuit coupled to the bridge circuit, the control circuit performing steps comprising:
obtaining an effective PWM coil voltage by causing a first PWM voltage to be applied to the coil in a first direction and causing a second PWM voltage to be applied to the coil in a second direction opposite to the first direction;
in response to the effective PWM coil voltage being zero, determining, between a first voltage at the first internal resistance and a second voltage at the second internal resistance, a difference voltage that, in response to being zero, indicates a current zero-crossing; and
using the difference voltage to generate a current zero-crossing signal;
a difference generator that, in response to receiving a phase angle of a predetermined coil voltage, generates a phase angle difference signal.