Micrel, Incorporated

Telcom Semiconductor, Inc.

Stratos Lightware, Inc.

Joseph James Judkins

Peter Chambers

Donald E Alfano

William Andrew Burkland

Douglas Paul Anderson

Quoi V Huynh

Sang Ton Ngo

David J Kunst

Ali Tasdighi

Luis Torres

Steven A Martinez

Chuong Nguyen

Robert James Lewandowski

Thomas A Lindsay

Jerry M Collings

Tom Lindsay

An accelerator circuit is incorporated in a laser diode system for accelerating the turn-on operation of the laser diode independent of the control loop bandwidth of the laser diode system. The accelerator circuit provides a boost current to a compensation capacitor upon laser turn-on which compensation capacitor operates to establish the control loop bandwidth of the laser diode system. The boost current enables the control loop to increase the bias current to the laser diode quickly. When the laser diode reaches the desired operating point, the boost current is terminated and the control loop of the laser diode system resumes normal control of the bias current. In one embodiment, the accelerator circuit includes a timer circuit controlling a current source to implement open loop turn-on control. In another embodiment, the accelerator circuit includes a comparator circuit working in conjunction with an one-shot logic circuit for providing close loop control.

Laser turn-on accelerator independent of bias control loop bandwidth

An automatic power control system provides a control signal that regulates the output power of at least one laser diode. Coarse adjustment of the control signal is provided by a first means, preferably a digital variable resistor, while fine adjustment and compensation is provided by a second means, preferably by a digital-to-analog converter that receives an input signal proportional to a sensed control system parameter. The control system includes an operational amplifier having a first input coupled to sense output power, and a second input coupled to a DAC to provide finer resolution control. Memory can store system parameter or system parameter variations that can be coupled to the DAC and/or variable resistor to enhance system stability over ambient variations.

Automatic control of laser diode current and optical power output

A device for performing numerical value conversion of a digital input value in a first unit to a second, natural unit where the digital input value is a digitized value of a first measurement parameter includes a look-up table storing an array of coefficients for performing the numerical value conversion for multiple measurement parameters. The look-up table is indexed using a first parameter indicative of the first measurement parameter to provide a selected coefficient. The device further includes an arithmetic logic unit (ALU) receiving the digital input value and the selected coefficient and performing the numerical value conversion based on a first equation and the selected coefficient to compute a digital output value. The device also includes a saturation-limit circuit coupled to receive the digital output value from the arithmetic logic unit and provide a predetermined output value when the digital output value exceeds a predetermined maximum value.

Numerical value conversion using a saturation limited arithmetic logic unit supporting variable resolution operands

A device for performing numerical value conversion of a digital input value in a first unit to a second unit being a natural unit includes a look-up table storing an array of coefficients for performing the numerical value conversion. The look-up table is indexed using a first parameter to provide a selected coefficient. An arithmetic logic unit (ALU) is coupled to receive the digital input value and the selected coefficient and perform the numerical value conversion based on a first equation using the selected coefficient to compute a digital output value in the second unit. The first unit can be an arbitrary ADC unit and the second unit is a natural unit of physical measurement, such as volts, amperes, degree Centigrade. Furthermore, the device can be used to perform numerical value conversion from the arbitrary unit to the natural unit having a linear or a non-linear relationship.

Numerical value conversion using a look-up table for coefficient storage

A fan speed control system for controlling the operation and speed of a fan is described. The fan speed control system includes a power control block for supplying an output voltage to the fan. An integrated circuit fan controller causes a resistor divider circuit to operably divide a selected portion of the output voltage. The integrated circuit fan controller comprises a data register which receives values indicative of control or speed operands from a host. A logic state machine translates these values into appropriate logic signals and provides the signals to the resistor divider circuit. A timing reference or an oscillator controls the proper sequencing and timing relationship of the logic state machine. To turn the fan on, the following sequence of steps occurs. The power control block is turned off causing the output voltage not to be supplied to the fan. The logic state machine controls the resistor divider circuit to divide the output voltage to be supplied to the fan. Thereafter, the power control block is enabled to supply the output voltage to the fan. The logic state machine, after an interval, controls the resistor divider circuit to divide up to selected portion of the output voltage to adjust the speed of the fan. To turn the fan off, the power control block is turned off followed by controlling the resistor divider circuit not to be capable of dividing any of the output voltage.

Fan speed control system having an integrated circuit fan controller and a method of using the same

In the preferred embodiment, the outputs of a plurality of analog signal generators are connected to a single wire (the analog bus). Each analog signal generator is addressable by a unique code provided to its respective address input terminals. A host controller selectively addresses only one of the analog signal generators such that an output of only one of the analog signal generators is applied to the analog bus at a time. In this manner, a single wire may be used to transmit a plurality of analog signals to a receiver. In one embodiment, the receiver is a MUX having an output connected to an ADC.

Multidrop analog signal bus

An apparatus for sensing the rotation of a brushless DC fan includes the fan and a sense/driver circuit and a capacitance. The sense/driver circuit is coupled to the fan to receive a sense input signal including a fluctuating electrical effect caused by fan commutation events. The sense/driver circuit processes the sense input signal to generate a sense output signal indicative of fan operation. The sense/driver circuit includes an integrated circuit. The integrated circuit includes a sense input pin, a ground return pin, a driver circuit, an integrated filter portion, a filter pin and a level detecting circuit. The capacitance is coupled to the filter pin to provide a filter with the integrated filter portion. The driver circuit includes a control terminal, a first current handling terminal coupled to the sense input pin and a second current handling terminal coupled to provide a ground return pat. The integrated filter portion includes a filter input coupled to at least one of the first and second current handling terminals of the driver circuit, and a filter output for providing a filter output signal to the level detecting circuit. The level detecting circuit generates the sense output signal from the filter output signal. The filter derives the filter output signal indicative of the fan commutation events responsive to receiving a signal at the sense input pin.

Verification of fan operation

Disclosed herein is a monolithic fan controller circuit which provides the following features: a special start-up routine for the fan; a fan fault detector; a thermal fault detector; an automatic speed controller; a minimum speed controller; a routine for attempting to clear temporary fan faults; and a controllable drive signal frequency. A start-up control circuit provides an initial high duty-cycle kick to the fan in order to initiate the rotation of the fan. A temperature sensor, which may be external or internal to the monolithic fan controller, supplies a signal which is proportional to measured temperature. This signal is used to control the output pulse width of a pulse-width modulator (PWM) or control the frequency of a pulse frequency modulator (PFM). The PWM or PFM output signal regulates the speed of the brushless (or brush) DC fan motor. In a preferred embodiment, the monolithic fan controller has 8 pins.

Monolithic fan controller

A method for controlling the operation of a brushless DC fan for cooling heat generating components of a system is provided. The method includes providing a system temperature signal indicative of a system temperature and providing an intelligent shutdown enable signal. The system temperature signal is compared with a shutdown temperature signal if the intelligent shutdown enable signal has a first value. The shutdown temperature signal is representative of a shutdown temperature value. The fan is operated at a generally temperature proportional speed after comparing the system temperature signal with the shutdown temperature signal if the system temperature as indicated by the system temperature signal is greater than the shutdown temperature value as indicated by the shutdown temperature signal. A shutdown mode is entered by the fan after comparing the system temperature signal with the shutdown temperature signal if the system temperature as indicated by the system temperature signal is less than the shutdown temperature value as indicated by the shutdown temperature signal. The system temperature signal is compared with the shutdown temperature signal after entering the shutdown mode by the fan. Operation of the fan is initiated if the system temperature as indicated by the system temperature signal is greater than the shutdown temperature value as indicated by the shutdown temperature signal and the fan is in the shutdown mode.

Growing community of inventors

Austin, TX, United States of America

Joseph James Judkins