A circuit for protection of the operation of power factor correction (PFC) converters from conditions such as input voltage surges that can otherwise cause failure, and to prevent unnecessary down time of the boost converter after a power failure or on startup. The circuit detects the real time rectified input voltage and provides real time comparison of the detected input voltage and the output voltage. The boost function of the PFC is controlled as a function of the output of the comparison circuit so as to quickly inhibit the boost function of the PFC controller thereby disabling boost and protecting the circuit from burning out. The circuit enables the PFC to starts and restart more quickly, even before the output voltage becomes stabilized, since boost is permitted as soon as the output voltage exceeds the real time sampled input voltage. By enabling boost during this period, the circuit eliminates the need to wait at least a few cycle times until the output voltage is higher than the peak of rectified input voltage. In a preferred embodiment, a complementary protection circuit having a voltage clamp is also provided to prevent unnecessary shutdown of the converter.

Real-time voltage detection and protection circuit for PFC boost converters

A power converter circuit (23) and a method for controlling current in a transformer (16). The power converter circuit (23) includes a controller circuit (60), a duty cycle detector circuit (61), a soft start circuit (62), and a switch (63). The switch (63) controls the current in the transformer (16). The controller circuit (60) cooperates with the soft start circuit (62) to alter the duty cycle of the switch (63). During initial start-up, the switch (63) operates at a minimum duty cycle and increases towards a maximum duty cycle to prevent transformer (16) saturation and potential failure of the switch (63). In addition, the duty cycle detector circuit (61) alters the frequency at which the switch (63) turns on and off to reduce the power consumption of the power converter circuit (23).

Power converter circuit and method for controlling

A switch-mode power regulator includes a turn-on controller 52 to limit, during a fixed period of time, the initial current passing through the regulator following turn-on. During this time period the storage elements of the regulator must achieve an acceptable level of stability without excessive current flow. Turn-on controller 52 comprises a divider 72 which clocks zeroes along the length of a shift register 74 which is initially preset to all ones. The outputs of the shift register are coupled to a decoder 76, whose input signals are sequentially steered to its output under the control of a counter 70. The output signal from decoder 76 functions as the power regulator switching signal from turn-on controller 52. Counter 70 cycles many times for each data shift of shift register 74. Thus, turn-on controller 52 generates a train of negative pulses which increase in length monotonically for the duration of the sequence. In one embodiment, the first two data inputs of decoder 76 are grounded, thereby providing a fixed minimum pulse width at the onset of the sequence. In another embodiment, the last two data inputs of decoder 76 are tied to logic supply voltage, thereby preventing cycle skipping.

Turn-on controller for switch-mode regulator

A DC to DC converter for converting an input DC voltage to an output DC voltage. The DC to DC converter may include at least one switch, an inductor coupled to the at least one switch, and a controller capable of providing a control signal. The at least one switch may be responsive to the control signal in a first state to enter an ON state for an ON time interval, the ON time interval based on the input DC voltage and a constant. An electronic device including such a DC to DC converter and related methods are also provided.

Boost converter with enhanced control capabilities of emulating an inductor current

A startup circuit 109 for a power converter 100 including an amplifier circuit 205, a comparator 225, and startup logic 227. The power converter includes an error amplifier 111 that compares an output sense signal with a startup reference signal and that provides a compensation signal. The amplifier circuit charges the startup reference signal to a predetermined reference level based on a second reference signal in response to a start signal. The comparator determines when the compensation signal reaches a predetermined ramp level and asserts a startup complete signal indicative thereof. The startup logic provides the start signal and provides an output enable signal in response to the startup complete signal. The output enable signal enables output switching to initiate normal regulation operation of the output voltage. In one embodiment, the predetermined ramp level is approximately the center voltage of a sawtooth regulation waveform used for PWM modulation.

Startup circuit for a DC-DC converter

A DC/DC voltage converting device is obtained for boosting a DC power supply voltage to provide a higher output voltage, comprising soft start circuit 20 for gradually increasing the turning-on duration of transistor 34 in boosting circuit 30; pulse width control circuit 60 for providing a modulated pulse signal P2 to control the boosted voltage. The device further comprises boosting circuit 30 including an inductor 32, diode 36 and transistor 34. Boosting circuit 30 provides a predetermined boosted voltage higher than the power supply voltage by alternately turning on and off transistor 34. The turning-on duration of transistor 34 is gradually increased during the initial operation period by soft start circuit 20, and is controlled by modulated pulse signal P2 during a stable operation period. The device further comprises gate circuit 40 having diode 46 and transistor 44, and step up circuit 70. Step up circuit 70 turns off transistor 44 during the initial operation period, and turns it on while transistor 34 is off during the stable operation period to allow an efficient current flow from boosting circuit 30 to output terminal 58. Any counter current flow from output terminal 58 to boosting circuit 30 is inhibited during the initial operation period.

Dc/dc voltage converting device

PURPOSE:To prevent reverse flow of power from an output terminal side to a booster side by outputting an output voltage boosted by conducting and interrupting a switching element from the output terminal. CONSTITUTION:A pulse output P3 of an AND circuit 2 is input to the gate of an FET transistor 44 through an inverter 4 and a booster 70. A charged voltage V1 of a capacitor 26 is supplied the non-inverting input of an operational amplifier 72 in the booster 70. A second reference voltage Vvf2 is applied to the inverting input of the amplifier 72. The amplifier 72 produces an output Vs when the voltage V1 is larger than the voltage Vvf2 to open an AND circuit 74. A transistor 44 remains interrupted from when a voltage converter 5 is started to be initialized to when a predetermined time is elapsed after a switch 24 is closed and the voltage V1 exceeds the voltage Vvf2. Accordingly, the reverse flow of the current can be prevented during the initializing period. A desired forward current can flow to a smoothing circuit 50 through a diode 46.

Hibino Kazunori

Papers

Dc/dc voltage converting device

Dc/dc voltage converter