Power factor compensation controller

Details Power factor compensation controller Power factor compensation controller

2000-05-05

2001-02-20

Sterrett, Jeffrey (Department: 2838)

Electricity: power supply or regulation systems

In shunt with source or load

Using choke and switch across source

C323S207000, C363S089000

Reexamination Certificate

active

06191565

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates generally to switching power supplies and, more particularly, the invention relates to a power factor compensation controller for use in switching power supplies.
2. Description of Related Technology
Generally speaking, a switching power supply (SPS) provides a cost effective and energy efficient device for converting energy from a single direct current (DC) supply voltage into one or more DC output voltages that have a greater or lesser magnitude than the supply voltage. Traditionally, a SPS has an integrated control circuit that modulates the duty cycle of a transistor switch, which controls the flow of energy into the primary of a transformer or an input of an inductor to produce one or more desired output voltages that are derived from the secondary of the transformer or the output of the inductor, respectively. As is well known, the energy (i.e., the time integral of power) supplied to the primary of the transformer or the inductor minus efficiency losses equals the energy transferred to the secondary of the transformer or the output of the inductor. Thus, if more energy is needed at an output of the SPS, then the control circuit increases the duty cycle of the transistor switch to provide more energy to the primary of the transformer or the input of the inductor. Conversely, if less energy is needed at the output of the SPS, then the control circuit decreases the duty cycle of the transistor switch.
As is also well known, the inductive components within a SPS may be operated using one of a variety of conventional current conduction modes depending on the particular application for the SPS. For example, a boundary conduction mode (BCM) and a discontinuous conduction mode (DCM) each result in large peak currents and, as a result, BCM and DCM are typically used where small value inductors are desirable and where the SPS has a relatively small load (i.e., low power output). On the other hand, a continuous conduction mode (CCM) control technique requires a relatively large inductance value, which reduces the peak-to-average current ratio within the SPS and which allows a SPS to operate at relatively high power levels (e.g., 300 watts).
The power factor of a SPS can have a significant impact on the efficiency with which energy is conveyed from a source of input power (e.g., a source of alternating current line voltage) to a load that is connected to an output of the SPS. As a result, a variety of conventional techniques for controlling the power factor of a SPS operating in one of the aforementioned current control modes have been developed. For example, control over the power factor of a boost convertor operating in a CCM may be accomplished using an average current mode control (ACMC) method, a charge control method, a peak current mode control (PCMC) method, or a hysteresis control method. While the conventional ACMC, PCMC, hysteresis control, and charge control methods may be used to compensate the power factor of a SPS, these conventional methods typically require relatively complex circuitry and, in some cases, these conventional methods provide a limited compensation range that fails to compensate the power factor of the SPS over the entire range of SPS output loads.
SUMMARY OF THE INVENTION
In accordance with one aspect of the invention, a power factor compensation controller for use in a switching power supply having a switch, an inductor, and upper and lower reference signals that are proportional to an input voltage to the switching power supply includes a multiplier that multiplies an error signal and a signal representative of a current in the switch to produce a multiplier output signal. The power factor compensation controller may further include an adder that adds the multiplier output signal to the lower reference signal to produce an adder output signal and a comparator that compares the adder output signal to the upper reference signal to produce a comparator output signal. The power factor compensation controller may also include a flip-flop that receives the comparator output signal and a clocking signal and a logic gate that receives an output of the flip-flop and the clocking signal to produce a gating signal for controlling the conduction of the switch so that an envelope of peak currents in the switch is substantially in-phase with the input voltage.
In accordance with another aspect of the invention, a power factor compensation controller for use in a switching power supply having a switch, an inductor, and upper and lower reference signals that are proportional to an input voltage to the switching power supply includes a multiplication unit that multiplies an error signal and a signal representative of a current in the switch to produce a multiplier output signal. The power factor compensation controller may further include an error amplification unit that monitors an output of the switching power supply to produce an error signal and a switching driver that receives the multiplier output signal and the upper and lower reference signals and produces a fixed frequency gating signal for controlling the conduction of the switch so that an envelope of peak currents in the switch is substantially in-phase with the input voltage.
The invention itself, together with further objectives and attendant advantages, will best be understood by reference to the following detailed description, taken in conjunction with the accompanying drawings and the appended claims.


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patent: 6069470 (2000-05-01), Feldtkeller

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