Microsemi Corporation

Texas Instruments Corporation

Siliconsystems, Inc.

Microsemi Corp-analog Mixed Signal Group, Ltd.

Chii-Fa Chiou

Yuji Isobe

David K Lacombe

Yuji Yoshida

Yair Darshan

George C Henry

Hwangsoo Choi

A solid state lighting controller arranged for use with a single stage power factor correction switched mode power supply, a light emitting diode (LED) string and a current sense element arranged to sense current through the LED string, the solid state lighting controller constituted of: a current governor in series with the LED string exhibiting a governor differential amplifier and a governor electronically controlled switch responsive to the output of the governor differential amplifier, the current governor arranged to limit current flow through the LED string responsive to a current limit reference; and a feedback circuit exhibiting an error amplifier, the feedback circuit arranged to feedback a signal to the power factor correction switched mode power supply controller whose value is a function of the difference between the current through the LED string sensed by the current sense element and a target current signal.

LED string driver with power factor corrector and current governor

A driver circuit or controller flexibly drives either a half-bridge or a full-bridge switching network in a backlight inverter without modification, redundant circuitry or additional components. The driver circuit includes four outputs to provide four respective driving signals that establish a periodic timing sequence using a zero-voltage switching technique for semiconductor switches in the switching network.

Full-bridge and half-bridge compatible driver timing schedule for direct drive backlight system

A power conversion circuit operates in a discontinuous switching mode over a wide range of loading conditions and varies a coil peak current to maintain efficiency over the wide range of loading conditions. The coil peak current is adjustable based at least in part on a feedback signal generated in response to a load condition.

Boost converter with adaptive coil peak current

A feed-forward correction circuit in a PWM controller adjusts an error signal inversely with respect to a supply voltage for a switching voltage regulator to quickly compensate for changes or transients in the supply voltage. The adjusted error signal is provided to a PWM comparator to control a duty cycle of an output signal. The switching voltage regulator can be a DC-to-DC converter or a DC-to-AC converter, and the output signal is used to generate one or more driving signals to control semiconductor switches in the switching voltage regulator. The feed-forward correction circuit uses an offset compensation technique or a translinear circuit to maintain a substantially inverse product relationship between the supply voltage and the duty cycle of the output signal, thereby reducing overshoots and undershoots in a regulated output voltage of the switching voltage regulator.

Method and apparatus to compensate for supply voltage variations in a PWM-based voltage regulator

A controller for an inverter provides variable gain control in a voltage regulation loop to prevent overshoot in an output voltage of the inverter. A feedback circuit senses the output voltage and provides a voltage feedback signal to the controller. The controller includes a voltage conversion circuit and an error amplifier as part of the voltage regulation loop. A gain control block varies a circuit parameter in the voltage conversion circuit or the error amplifier such that regulation of the output voltage starts at a relatively lower voltage level and increases smoothly to a desired level.

Voltage regulation loop with variable gain control for inverter circuit

A compensation circuit for protecting a lamp from a large transient current. The compensation circuit may include a saw tooth generator configured to generate a saw tooth signal with an amplitude corresponding to a supply voltage of the lamp. A pulse width modulated signal may be generated by a comparator of the compensation circuit based on the saw tooth signal and a DC signal. The duty cycle of the pulse width modulated signal may be used by a controller to control the duration of time that current flows through the lamp. When the supply voltage of the lamp transitions from a low voltage to a high voltage, the amplitude of the saw tooth signal increases. When the amplitude of the saw tooth signal increases, the duty cycle of the pulse width modulated signal decreases thereby causing the controller to decrease the duration of time that current flows through the lamp.

Protecting a cold cathode fluorescent lamp from a large transient current when voltage supply transitions from a low to a high voltage

A transimpedance amplifier uses a pseudo-differential configuration to improve dynamic range and to minimize signal distortion in an optical receiver. The optical receiver includes a photodiode that converts a light signal to an electrical current signal, and the transimpedance amplifier converts the electrical current signal to a pair of differential voltage signals for further processing. The electrical current signal is provided to the transimpedance amplifier by connecting a cathode of the photodiode to a first input amplifier via a DC-blocking capacitor and directly connecting an anode of the photodiode to a second input amplifier. The transimpedance amplifier includes a DC correction circuit that generates a correction current in response to an output of the first input amplifier. The correction current is added to an input of the second input amplifier to adjust a DC offset at an output of the second input amplifier.

Pseudo-differential transimpedance amplifier

A transimpedance amplifier selectively activates DC compensation to optimize a signal-to-noise ratio for an optical receiver. The optical receiver includes a photodiode that converts a light signal to an electrical current signal, and the transimpedance amplifier converts the electrical current signal to a pair of differential voltage signals for further processing. The electrical current signal is provided to the transimpedance amplifier by connecting a cathode of the photodiode to a first input amplifier via a DC blocking capacitor and by directly connecting an anode of the photodiode to a second input amplifier. The transimpedance amplifier includes a DC correction circuit that generates a correction current when an output of the first input amplifier exceeds a predefined threshold. The correction current is added to an input of the second input amplifier to adjust a DC offset at an output of the second input amplifier.

Transimpedance amplifier with selective DC compensation

A hard disk drive (HDD) circuit ( ) having feedback provided to an input of an differential amplifier setting the amplifier input impedance close to a flexible printed circuit (FPC) characteristic impedance. A matched source and input impedance produces a generally flat gain frequency response. As the result of flat response and wider gain bandwidth, white noise without high frequency peaking can be obtained. Feedback resistors (R ) provide feedback according to the present invention which is superior in terms of the input referred noise since the feedback attenuates both the input signal from the sensor and the noise from the amplifier. Feedback resistors (R ) may be connected through AC coupling capacitors to compensate the voltage differences between amplifier input and output. The circuit of the present invention provides a method to connect the feedback resistors directly from amplifier outputs to inputs which have a different potential. The advantages of the present invention include matched impedance results and a better system level frequency response, the direct feedback connection eliminates costly on-chip capacitors, and the input impedance can be adjusted by the amount of feedback.

Controlled impedance amplifiers

The present invention achieves technical advantages as an overshoot circuit ( ) for a voltage source/impedance based write coil driver circuit ( ) accurately controlling the current (I )through a coil (L ) that is used to write data to a magnetic medium. The circuit ( ) improves the characteristics of the coil.

Overshoot control for voltage source/impedanced based write coil driver

A cascode H-bridge circuit with particular application to magnetic recording write driver circuits. The present invention avoids the process dependent limitations placed on the head voltage swing in the H-bridge circuits of the prior art. Whereas the circuits of the prior art attempt to increase head voltage swing by minimizing device voltage drops in the current path, the present invention inserts cascode transistors in the current path that have less than a one-volt voltage drop when active, yet allow the circuit to operate under a higher voltage supply with roughly twice the head voltage swing available in the same process in the prior art. By implementing a cascode configuration, the present invention is able to support head voltage swings in excess of the switch breakdown voltage (BV ) without failure of the switches in the &ldquo;off&rdquo; state.

Self-switched cascode write driver

A write driver to operate inductive heads for magnetic recording is disclosed. The inductive recording head is coupled between first and second outputs of a first write driver block. The first and second outputs of the first write driver block are coupled to first and second inputs of a second write driver block, respectively. First and second current sources are coupled to third and fourth inputs of the second write driver block, respectively. A first switching block is coupled to the first current source and to the third input of the second write driver block. A second switching block is coupled to the second current source and to the fourth input of the second write driver block. A first input signal is provided to a first input of the first write driver block and to the first switching block. A second input signal is provided to a second input of the first write driver block and to the second switching block. The second output of the first write driver block, the inductive recording head and the first input of the second write driver block form a first current path when the first input signal is greater than the second input signal. Conversely, the first output of the first write driver block, the inductive recording head and the second input of the second write driver block form a second current path when the second input signal is greater. The first and second input signals may be CMOS or differential ECL signals.

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Lake Forest, CA, United States of America

Chii-Fa Chiou