Linfinity Microelectronics

Cherry Semiconductor Corporation

Other

Semiconductor Components Industries, LLC

Dan Agiman

A control voltage is generated as a function of on-time and off-time of a main regulator loop in response to apparent duty cycle of a voltage regulator circuit. Such control voltage is used in a circuit as to yield a virtual constant frequency of operation. No external compensation is required. This reduces external connections while maintaining stable, accurate, constant frequency operation of a switching voltage regulator circuit.

Virtual frequency-controlled switching voltage regulator

The output terminal of an error amplifier ( ) is coupled to the inverting input of a comparator circuit ( ). Additionally, a clamp circuit is coupled between the output terminal of the error amplifier ( ) and circuitry connected to the non-inverting input of the comparator circuit ( ), to clamp the voltage there between to a predetermined voltage level. This circuit arrangement provides improved controller closed loop response that is adaptive to the power supply ( ) output voltage.

Adaptive loop response in switch-mode power supply controllers

A control circuit for synchronous switching power supplies employing semi-soft switching during turn off and precedent switching during turn on. During turn off, an output voltage is compared to a reference voltage to turn on a synchronous switch after a primary switch is turned off. During turn on, a timing voltage ramp triggers the turn off of the synchronous switch prior to the turn on of the primary switch.

Semi-soft switching and precedent switching in synchronous power supply

A method for sensing motor commutation pulses during motor braking without creating negative voltages, which some junction isolated technologies substantially cannot tolerate. For instance, a commutation pulse sensing circuit containing junction isolated technology may only be able to detect commutation pulses intermittently. An H-bridge motor drive configuration is used to drive and brake a motor. High side clamp diodes are coupled between the motor terminals and a high potential source for high side braking of the motor. As an alternative to high side clamp diodes, any other suitable device may be used, including operating the pair of transistors in the upper portion of the H-bridge in an inverse mode. A commutation pulse sensing circuit is coupled to a terminal of the motor. The use of the high side brake clamp diodes avoids generating negative voltages at the motor terminals.

Elimination of motor negative voltages during motor brake

A pulse detection and conditioning circuit senses and conditions commutation pulses produced by a DC permanent magnet motor to determine motor position. The pulses are sensed using a resistor coupled in series with the motor, so that motor current and the included pulses are continuously sensed, even during motor braking. The serially coupled resistor also provides for sensing and conditioning of pulses of both polarities produced by bi-directional operation of the motor. The pulse detecting and conditioning is performed by circuitry which performs amplitude qualification as well as frequency filtering to effectively detect valid commutation pulses to the exclusion of noise and other unwanted signals. Capacitors coupled to the motor and internal capacitors provide the frequency filtering, while the amplitude qualification is provided by a balanced differential gain stage coupled through an adjustable differential gain stage with adjustable gain to a unity gain comparator. The adjustable gain of the adjustable differential gain stage and a variable reference voltage within the unity gain comparator provide for adjustable amplitude qualification. A differential to single ended converter responsive to the outputs of the unity gain comparator feeds a threshold latch to initiate the generation of a pulse representing each valid motor pulse.

Pulse detection and conditioning circuit

An overcurrent limit circuit in which the output transistor and current sense transistor share a common collector and common base. A reference voltage is compared with a voltage derived from a current sense resistor. The circuit limits the current to the base of the output transistor in response to the reference voltage threshold being reached at the current sense resistor. A Vbe comparator comprised of two transistors may be used with a first bias current to both transistors and a second bias current to one of the two transistors.

Thermally matched current limit circuit

A threshold controlled circuit in which hysteresis precedence is ensured by greatly enhancing the gain of the hysteresis loop with respect to the regulator control loop. The number of gain stages in the hysteresis loop exceeds the number of gain stages in the control loop. In order to ensure hysteresis precedence, the gain of the hysteresis loop times the regulator control shutdown current must exceed the gain of the control loop multiplied by the hysteresis current.

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Irvine, CA, United States of America

Dan Agiman