| BCD Semiconductor Manufacturing Limited Patent applications |
| Patent application number | Title | Published |
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| 20120056551 | HIGH POWER-FACTOR CONTROL CIRCUIT AND METHOD FOR SWITCHED MODE POWER SUPPLY - A switch mode power supply (SMPS) system includes a rectifying circuit for coupling to an AC input voltage and a transformer having a primary winding for coupling to the rectifying circuit and a secondary winding coupled to the primary winding. The system also has a power switch coupled to the primary winding and a control circuit coupled to the power switch. The control circuit is configured to control current flow in the primary winding such that an envelop waveform formed by peak points of current pulses are in phase with the magnitude of the AC input voltage. Moreover, the SMPS system is configured to provide a constant average output current. | 03-08-2012 |
| 20120056548 | CIRCUIT AND METHOD FOR DRIVING LED LAMP WITH A DIMMER - A system for driving an LED (light-emitting diode) lamp includes a dimmer circuit coupled to a line input voltage for varying a magnitude of an input voltage and a transformer having a primary winding, a secondary winding, and one or more auxiliary windings, the primary winding coupled to the dimmer circuit. The system also includes an output rectifying circuit coupled to the secondary winding for providing an output current to the LED lamp and a power switch coupled to the primary winding for controlling a current flow in the primary winding. The system further includes a controller having a comparator and a capacitor for providing a control signal to control the power switch for regulating the output current. The controller coupled to the dimmer circuit for receiving an average input voltage signal from the dimmer circuit, wherein the control signal is characterized by a duty cycle that is determined by a ratio of a charging current to a discharging current of the capacitor, and the ratio is related to the average input voltage signal from the dimmer circuit. | 03-08-2012 |
| 20120025720 | POWER SUPPLY APPARATUS AND METHOD FOR A BACKLIGHT SYSTEM - A power supply system includes a transformer having a primary winding on its primary side for coupling to a power source and one or more secondary windings on its secondary side. A first control circuit is disposed on the primary side of the transformer for controlling a current flow in the primary winding. A second control circuit disposed on the secondary side of the transformer, and the second control circuit is configured to provide a regulated output voltage. In the power supply system, the first control circuit is configured to generate a control signal for controlling the current flow in the primary winding without using a feedback control signal from the secondary side of the transformer. | 02-02-2012 |
| 20110316543 | METHOD AND CIRCUITS FOR SHORT-CIRCUIT PROTECTION OF LED SYSTEMS - An embodiment of the present invention relates to a method for detection of short circuit conditions in an LED array having one or more LED strings, each of which includes one or more LED devices. The method includes determining a minimum voltage that is the lowest of voltages associated with cathode terminals of the one or more LED strings. The method also includes determining if said minimum voltage is between a lower limit voltage and an upper voltage limit. If said minimum voltage is between the lower limit voltage and the upper voltage limit, then a result of a short circuit testing can be considered valid. Here, the short circuit testing includes comparing a sampled voltage associated with a cathode voltage of one of the LED strings with a short-circuit reference voltage. | 12-29-2011 |
| 20110261596 | CONTROL CIRCUIT FOR PRIMARY SIDE CONTROL OF SWITCHING POWER SUPPLY - A switched mode power supply (SMPS) includes a transformer with a primary winding, a secondary winding, an auxiliary winding, and a power switch coupled to the primary winding. During one switching cycle, the auxiliary winding provides a feedback signal which includes a first voltage pulse that is induced after the power switch is turned on and a second voltage pulse that is induced after the power switch is turned off. A control circuit includes a circuit for generating a sampling signal for sampling the second voltage pulse in a switching cycle at a time that is determined based on the first voltage pulse in the same switching cycle. A sample-and-hold circuit is configured for sampling and storing the second voltage pulse in response to the sampling signal. A switching signal generating circuit is configured to generate a switching signal for controlling the power switch based on an output of the sample-and-hold circuit. | 10-27-2011 |
| 20110227503 | SYSTEM AND METHOD FOR LED BACKLIGHT DRIVER FOR LCD PANELS - A power supply control system for driving light-emitting diode (LED) loads includes a first power switch for coupling to a voltage source, and a plurality of second power switches, each of which is configured for coupling to one of a corresponding plurality of LED loads. Each of the LED loads can include multiple light-emitting diodes (LEDs) connected in series. The power supply control system also includes an integrated circuit controller that includes a voltage controller configured to control the first power switch to provide an output voltage to each of the LED loads, and a current controller configured for coupling to each of the plurality of second power switches to provide a current through each of the LED loads. The integrated circuit controller is provided in a low-voltage integrated circuit chip, and the first power switch and the plurality of second power switches are high-voltage devices external to the low-voltage integrated circuit chip. | 09-22-2011 |
| 20110148324 | METHODS AND SYSTEMS FOR LED DRIVER HAVING CONSTANT OUTPUT CURRENT - A control circuit for a switched mode power supply includes a transconductance amplifier circuit for receiving a voltage signal related to a current from an input of the power supply and producing a first signal, an analog signal processor coupled to the amplifier circuit for receiving the first signal and a second signal from the input of the power supply and a third signal from an output of the power supply. The analog signal processor is configured to produce a fourth signal as a function of the first, the second, and the third signals. An adder circuit is coupled to the fourth signal and a dimmer control signal, and the adder circuit is configured to output a fifth signal. A comparator circuit is coupled to the adder circuit for providing a control signal to a power transistor that controls current flow in the power supply based on comparison of the fifth signal and a reference signal. | 06-23-2011 |
| 20110122659 | POWER TRANSISTOR DRIVING CIRCUITS AND METHODS FOR SWITCHING MODE POWER SUPPLIES - A power supply controller is provided for providing a drive current to a control terminal of a power transistor in three time intervals. The controller includes control circuits configured to control the drive current in multiple stages. During a first time interval, first drive current includes a current spike for turning on the power transistor in response to a start of the control signal pulse. During a second time interval, a second drive current includes a ramping current substantially proportional to a magnitude of a current through the power transistor. During a third time interval, current flow to the power transistor is at least partially turned off before an end of the control signal pulse. | 05-26-2011 |
| 20110116289 | METHOD AND APPARATUS OF LOW CURRENT STARTUP CIRCUIT FOR SWITCHING MODE POWER SUPPLIES - A startup circuit for a switching-mode power supply (SMPS) includes a first voltage detector configured to trigger the switching-mode power supply from a first operation mode to a second operation mode when an input supply voltage exceeds a first threshold voltage, a current consumption in the first voltage detector in the first operation mode being determined by a reverse leakage current of a diode. A feedback circuit is coupled to the first voltage detector and being capable of maintaining a positive feedback loop. A second voltage detector is coupled to the first voltage detector and the feedback circuit, and is configured to trigger the switching-mode power supply to switch from the second operation mode to the first operation mode when the input supply voltage is below a second threshold voltage. | 05-19-2011 |
| 20110096578 | SYSTEM AND METHOD FOR SYNCHRONOUS RECTIFIER - A synchronous rectification circuit for a power converter includes a power switch coupled to a transformer and an output capacitor and a switching control circuit configured to provide a control signal to the power switch in response to a first state and a second state of the voltage across the power switch. In the switching control circuit, the second state is determined prior to the first state is determined. In an embodiment, the switching control circuit includes a voltage comparing unit configured to act in response to the first and second inputs. The voltage comparing unit is also configured to output a logic signal according to the voltage difference between the sensed voltage drop across the power switch and a reference threshold voltage. A logic processing circuit is coupled to the voltage comparing unit and configured to provide the first state and the second state of the voltage across the power switch. | 04-28-2011 |
| 20110096573 | CONTROL CIRCUITS AND METHODS FOR SWITCHING MODE POWER SUPPLIES - Circuits and method for sensing a system output voltage change and transmitting an electrical signal to an auxiliary winding on the primary side. In an embodiment, a primary side controller detects the electrical signal and turns a power switch on and off to transfer energy from a primary winding to a secondary winding. A secondary side controller generates a voltage pulse at a terminal of the secondary winding when the system output voltage is below a reference voltage. The secondary side controller includes an input terminal connected to a system output, an output terminal connected to a terminal of the secondary winding, and a ground terminal connected to a ground potential of the system output. | 04-28-2011 |
| 20110019446 | METHOD AND APPARATUS FOR A SWITCHING MODE POWER SUPPLY - A controller for a switched mode power supply (SMPS) is provided. The SMPS is equipped with a transformer having a primary side winding, a secondary winding, and an auxiliary winding. The controller includes a detection circuit for detecting a transition from a first output load condition to a second output load condition of the SMPS and a control circuit coupled to the detection circuit and being configured to output one or more control signals in response to the detected output load transition. Depending on the embodiment, the one or more control signals include a first control signal for turning on a power switch to cause a current flow in a primary winding of the SMPS and/or one or more second control signals for turning off one or more functional circuit blocks in the controller. | 01-27-2011 |
| 20110019445 | METHOD AND APPARATUS FOR CONTROLLING POWER CONVERTER OUTPUT CHARACTERISTICS - A power converter includes a primary winding for providing a primary current, a secondary winding for providing an output current and an output voltage, and a current sense node for receiving a current sense signal related to the primary current. The power converter also includes a control circuit configured to limit the current sense signal to be lower than or equal to a predetermined reference peak current. Moreover, the power converter includes a first circuit configured to modify the current sense signal using a first signal related to the output voltage to cause an variation in the output current. | 01-27-2011 |
| 20100259952 | SWITCHING MODE POWER SUPPLY CONTROLLER WITH HIGH VOLTAGE STARTUP CIRCUITS - A controller for a switching mode power supply includes two semiconductor chips. The first semiconductor chip has a high-voltage startup transistor coupled to a high-voltage supply input terminal and configured to provide a charging current in a startup phase or protection mode of a switching mode power supply (SMPS) and to provide substantially no current in a normal operation phase of the SMPS. The second semiconductor chip has a control circuit for controlling the switching mode power supply. The second semiconductor chip also has first and second on-chip high-voltage resistors coupled to the high-voltage supply input terminal and the high-voltage startup transistor in the first semiconductor chip. The first and the second on-chip high-voltage resistors are configured to provide a voltage and a current related to a voltage at the high-voltage supply input terminal. | 10-14-2010 |
| 20100246219 | Applying Charge Pump To Realize Frequency Jitter For Switched Mode Power Controller - Method and apparatus for adding jitter to an oscillator for reducing EMI are disclosed An oscillator circuit includes an oscillator configured to generate a first clock having a first frequency and a frequency jitter circuit including a charge pump configured to charge and discharge first and second capacitors repeatedly for obtaining a time-varying voltage having a second frequency. The time-varying voltage is coupled to the oscillator to vary the first frequency within a frequency range. The charge pump includes a first switch for coupling the first capacitor to a voltage source and a second switch for coupling the first capacitor to the second capacitor. A charge transfer between the first and second capacitors is configured to provide the time-varying voltage. | 09-30-2010 |
| 20100244804 | METHOD AND APPARATUS OF LOW CURRENT STARTUP CIRCUIT FOR SWITCHING MODE POWER SUPPLIES - A startup circuit for a switching-mode power supply (SMPS) includes a first voltage detector configured to trigger the switching-mode power supply from a startup mode to a normal operation mode when an input supply voltage exceeds a first threshold voltage, a current consumption in the first voltage detector in the startup mode being determined by a reverse leakage current of a diode. A feedback circuit is coupled to the first voltage detector and being capable of maintaining a positive feedback loop with a current consumption of no more than a microampere. A second voltage detector is coupled to the first voltage detector and the feedback circuit, and is configured to trigger the switching-mode power supply to switch from the normal operation mode to the startup mode when the input supply voltage is below a second threshold voltage. | 09-30-2010 |
| 20100238689 | METHOD AND APPARATUS FOR CONTROLLING A CONSTANT CURRENT OUTPUT IN A SWITCHING MODE POWER SUPPLY - A controller for providing a constant output current control signal in a switched mode power supply (SMPS) includes a conduction time compensation circuit that is configured to produce a compensated conduction time interval signal that includes compensation for a ringing waveform of a feedback signal. The compensated signal reflects more accurately the actual conductive time of a rectifying diode in a secondary winding of the switched mode power supply. In one embodiment, the compensated conduction time interval signal is used to generate a fixed ratio between the conduction time and the non-conduction time of the rectifying diode. In another embodiment, the controller also provides a constant voltage control signal. | 09-23-2010 |
| 20100164581 | PULSED WIDTH MODULATED CONTROL METHOD AND APPARATUS - A pulse width modulated (PWM) controller has an input terminal for receiving a pulsed input signal having a first duty cycle, a power supply terminal for receiving a power supply voltage. a minimum duty cycle reference voltage signal, and a control circuit for providing a pulse-width-modulated (PWM) output signal having a second duty cycle related to the first duty cycle of the pulsed input signal. The PWM output control signal having a minimum duty cycle that is adjustable in response to a change in the power supply voltage. In an embodiment, the second duty cycle and the first duty cycle are correlated in a substantially linear relationship. In an embodiment, the PWM control circuit also has a triangle wave generation circuit for generating a triangle wave signal configured to oscillate between an upper limit voltage and a lower limit voltage, which are adjustable in response to a change in the power supply voltage. | 07-01-2010 |
| 20100109730 | PWM CONTROL CIRCUIT HAVING ADJUSTABLE MINIMUM DUTY CYCLE - A pulse width modulated (PWM) controller includes a triangle wave generation circuit generating a triangle wave signal to oscillate between an upper limit voltage and a lower limit voltage. The upper limit voltage and the lower limit voltage are adjustable in response to changes in the power supply voltage. A pulse generation circuit is coupled to the triangle wave generation circuit and a minimum duty cycle setting voltage, and is configured to generate a PWM pulse signal with a minimum duty cycle determined by the relative magnitude of the triangle wave signal and the minimum duty cycle reference voltage. In an embodiment, the minimum duty cycle is increased when the power supply voltage is lower than a predetermined reference voltage. | 05-06-2010 |
| 20100091524 | Electronic Power Protection Circuit And Applications Thereof - An electric power protection circuit connected in series to a secondary side circuit of a transformer in a switch mode power supply includes a voltage/current limiting device to get an electric power signal output from the secondary side circuit of the transformer that goes through current and voltage limitation before being output and a constant current/voltage controller to get the electric power signal which has the current and voltage limited by the voltage/current limiting device. The electric power signal further is undergone constant voltage/current control to achieve voltage overshoot protection. | 04-15-2010 |
| 20090279333 | METHOD AND APPARATUS FOR REDUCING STANDBY POWER OF SWITCHING MODE POWER SUPPLIES - An apparatus for coupling a switching mode power supply (SMPS) controller to a rectified line voltage. The apparatus includes a high-voltage startup transistor configured to provide a charging current during a startup phase of the SMPS controller and to provide substantially no current during a normal operation phase of the SMPS controller. A switch coupled to the high-voltage startup transistor. The switch receives a control signal from the SMPS controller, for turning off the switch during the startup phase and turning on the switch during the normal operation phase. A biasing device is connected in series with the switch and maintains the startup transistor in an off state when the SMPS controller is in the normal operation phase. A standby current in the apparatus is substantially lower when the SMPS controller is in the normal operation phase than the charging current in the apparatus when the SMPS is in the startup phase. | 11-12-2009 |
| 20080310191 | METHOD AND SYSTEM FOR PULSE FREQUENCY MODULATED SWITCHING MODE POWER SUPPLIES - A pulse frequency modulation (PFM) controller for controlling a switching mode power supply. The controller includes an output terminal for providing a control signal to turn on and off a current in the power supply to regulate an output of the power supply. A first input terminal receives a feedback signal related to the output of the power supply, the feedback signal exhibiting a ringing waveform when the current in the power supply is turned off. The controller also includes a control circuit configured to provide the control signal in response to the feedback signal. The control signal is adapted to turn on the current in the power supply when the feedback signal is substantially at a valley of the ringing waveform of the feedback signal. In an embodiment, such a PFM controller can reduce turn-on transition loss in a power supply and provides frequency dithering to reduce electromagnetic interference. | 12-18-2008 |
