Micro Linear Corporation

Other

National Semiconductor Corporation

James J Locascio

Mehmet Kadri Nalbant

Urs H Mader

Urs Harold Mader

A battery power conversion circuit comprising a cell equalization circuit that ensures that each cell in a multiple battery cell stack is depleted of charge at an equal rate. The stack is coupled to provide current to a primary winding of a transformer. Each of the nodes between cells is coupled to the primary winding of the transformer through a transistor such that an equal number of turns of the primary winding are present between each node. An additional transistor coupled in series with the primary winding controls the current through the primary winding such that a capacitor coupled to a secondary winding of the transformer may be charged by an induced secondary current to a desired voltage level for powering a load. A controller circuit monitors the output voltage level and controls the transistor in series with the primary winding for maintaining the desired load voltage through a feedback loop. When the transistor in series with the primary winding is turned on to allow current to flow through the primary winding, each of the transistors coupled to each of the nodes between battery cells is also turned on by the controller. Only a small current travels through each of the transistors coupled to each of the nodes. Therefore, the voltage across each battery cell is equalized due to the equal number of transformer windings that are present between each of the nodes. This prevents any of the battery cells from being discharged to a voltage level that is lower than any other cell. Because each cell is maintained at a voltage level that is the same as each other cell, the entire battery stack may be discharged to a maximum degree without any one cell becoming depleted first or damaged. Other variations are also disclosed. For example, a single node may serve two battery cells. This results in looser regulation of the voltage to which each cell is discharged, but also results in a simpler and less expensive circuit. Also, the present invention may be used with battery cell stacks having any number of battery cells.

Battery cell equalization circuit

A circuit for supplying power to a fluorescent lamp comprising a buck regulator with a high side drive. A dc battery is coupled to a drain of a first transistor. A source of the first transistor is coupled to an inverter for powering the lamp. A first control signal is coupled to a primary winding of a transformer. A first terminal of a secondary winding of the transformer is coupled to the anode of a diode. The cathode of the diode is coupled to the gate of the first transistor. A second terminal of the secondary winding of the transformer is coupled to the source of first transistor. The first control signal is activated to bias the first transistor through the transformer by charging the gate to a voltage higher than the control voltage due to the transformer turns ratio. A diode is coupled to capture a charge on the gate. A second transistor is coupled to the gate of the first transistor to drain the captured charge to ground, turning off the first transistor when a second control signal is activated. A third transistor is coupled to ground the source of the first transistor when a third control signal is activated. The lamp brightness is regulated by varying a duty cycle of the buck regulator synchronized to the inverter. The first transistor is turned on when two inverter transistors change state. After a time determined by a lamp current feedback signal, the first transistor is turned off and the third transistor is turned on. The third transistor stays on until the inverter transistors change state again, then the first transistor is turned on again.

High side driver technique for miniature cold cathode fluorescent lamp

A circuit for sensing a current in a fluorescent lamp. A control system comprises a buck regulator circuit for supplying a buck current, an inverter circuit for receiving the buck current and for generating a lamp voltage, a circuit for sensing a current in a fluorescent lamp, and a controller for controlling the buck regulator and the inverter. The inverter comprises a Royer-type inverter, a resonant tank, and a transformer. A current flows through a primary winding of the transformer to generate a voltage in a secondary winding of the transformer. The fluorescent lamp is coupled to the secondary winding of the transformer so that the fluorescent lamp is isolated from the remainder of the control system by the transformer. The circuit for sensing the current in the lamp senses a current in the Royer-type inverter which is representative of the current in the lamp. The circuit for sensing the current in the lamp is coupled to the controller for controlling the buck regulator and the inverter.

Primary side lamp current sensing for minature cold cathode fluorescent

A circuit for supplying power to a fluorescent lamp. A control system comprises a buck regulator for supplying a buck current, an inverter circuit for receiving the buck current and for generating a lamp voltage, a circuit for sensing a current in a fluorescent lamp, a circuit for sensing a no lamp condition, and a controller for controlling the buck regulator and the inverter. The circuit for sensing a no lamp condition monitors a voltage level at the inverter transformer. The controller is coupled to the circuit for sensing a no lamp condition. If a no lamp condition is detected, the controller responds by shutting itself down. The controller can be reactivated by toggling an on/off signal to reset a latch.

Lamp out detection for miniature cold cathode fluorescent lamp system

The present invention is for an architecture for an input circuit to a linear circuit having a circuit ground from a linear system having a system ground. The architecture has a linear input signal which is coupled into a current limiting input impedance. The current limiting input impedance is not connected to the system ground. A linear input circuit is coupled to receive the reduced input signal and is coupled to the circuit ground. Accordingly, the analog input to the linear input circuit is a current signal rather than a voltage signal.

Noise reduction technique for PWM controllers

A low dropout voltage regulator with a switched redundant input, which has low dropout voltage before, during, and after a switch to the redundant input. In a preferred embodiment, the inventive voltage regulator includes two transistors that are controlled by the output of an error amplifier, and redundant input voltage sources. A first one of the transistors conducts when a first input voltage is greater than a second input voltage. The other transistor conducts when the second input voltage exceeds the first input voltage. When both input voltages are have substantially equal magnitude, both transistors conduct. In a preferred embodiment, one input voltage is supplied by a battery, and the other is supplied by a storage capacitor charged by the battery. When the battery fails, the storage capacitor will discharge, thus serving as a time-varying redundant voltage source in the event of battery failure.

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San Jose, CA, United States of America

James J Locascio