Electric power conversion systems – Current conversion – With means to introduce or eliminate frequency components
Reexamination Certificate
2001-11-20
2002-07-02
Riley, Shawn (Department: 2838)
Electric power conversion systems
Current conversion
With means to introduce or eliminate frequency components
C703S018000, C700S040000
Reexamination Certificate
active
06414858
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to the field of control systems. More specifically, this invention relates to modular power control systems using pulse-width control modulators.
BACKGROUND OF THE INVENTION
FIG. 1
illustrates a conventional switching power module. As illustrated, an alternating (AC) voltage is input into power conversion module
110
, which produces a direct (DC) output voltage, Vo. Output voltage, Vo, is input to feedback compensation control circuit
150
, which monitors the value of output voltage Vo and adjusts the internal parameters of power conversion module
110
to maintain Vo relatively constant. The processing of feedback compensation control circuit
150
is well known in the art and may be implemented in special-purpose circuits, such a Field Programmable Gate Arrays (FPGAs) or Application Specific Integrated Circuits (ASICs).
The use of Application Specific Integrated Circuits to implement the control of power supplies is well known in the art. ASICs can perform the functions of a variety of discrete components on a single Integrated Circuit (IC). This is advantageous as the size of the controller and the overall size of the power supply can be reduced. Also, in large quantity, the cost of an ASIC is significantly less than the cost of discrete components that are required to perform the same functions. Hence, the overall cost and physical size of power supply units is reduced when ASIC technology is employed.
ASICs may be custom-made for the application or may be “off-the-self” components. Custom-made ASICs are expensive and time-consuming to develop. Since the initial development cost for custom-made ASICs may be high, these devices are used in high volume applications. In such cases the development costs can be spread-out over the price of all the units sold. In addition, custom-made ASICs are typically designed to operate with a particular type of component or a component manufactured by a particular manufacturer.
Off-the-shelf ASICs are typically preprogrammed with known functions and interface to external devices, components or other hardware, in order to use them in a designated application. The external components interface the off-the-shelf ASIC to other devices or components. The use of external components, however, is disadvantageous as their use increases the cost and the size of the power supply. It is further disadvantageous when components are changed as the interface and the ASIC may also have to be changed.
One method of creating power supply controllers using off-the-shelf components is to distribute processing among generic component blocks. The generic component blocks can consist of programmable micro-controllers that communicate operational commands to control devices, such as Pulse Width Modulators (PWM), over a data bus. Pulse Width Modulators are routinely included as peripherals in micro-controller based integrated circuits. Timing parameters, such as frequency, i.e., period, on-time, off-time, etc., which are used to control the output voltage level are stored in registers accessible by a micro-controller. Power supply controllers are well known in the art.
FIG. 2
illustrates a conventional modular digital power supply controller
150
comprised of a master unit
200
and at least one slave unit
210
a
,
210
b
. As illustrated, master unit
200
is composed of processor
202
, memory
204
and communication interface
206
. Analog-to-digital (A/D) converter
201
may optionally be included for conversion of analog signals to digital form for processing by processor
201
. Slave units
210
a
,
210
b
are composed of communication interface
222
, PWM generator
218
, registers
212
and micro-controller or DSP
214
. Analog-to-digital (A/D) converter
216
may optionally be included for conversion of analog signals to digital form for processing. PWM generators
218
are routinely included as peripherals in micro-controller integrated circuits. In such cases, timing parameters, e.g., frequency, on-time, off-time, etc., can be are stored in register
212
, These values can be set in register
212
by local micro-controller
214
or remotely by processor
202
over communication link
208
.
Remotely controlled operation of PWM is, however, limited because of bandwidth constraints. In voltage-mode control applications, the control of power module
150
, of
FIG. 1
, by PWM
218
is in the order of few hundred or a few thousand hertz. In this case, the rate of updating the register content is relatively low, hence, the limited bandwidth of micro-controller
202
, such as, 80C51-based micro-controllers, or data bus
208
is sufficient for updating the registers stored, for example, in slave unit
210
a
. On the other hand, in current-mode control applications the PWM output is required to respond within a few hundred nanoseconds. Being bandwidth limited, the earlier described distributed power supply controller cannot respond within such a short time period. Hence, there is in a need in the art to provide a means for high-speed updating of pulse width modulator parameters that does not require expensive high-speed components, control signals or increased bandwidth
SUMMARY OF THE INVENTION
A multi-mode pulse width modulator (PWM) capable of exercising control signals in voltage-controlled, i.e., low-speed, and current-controlled, i.e., high-speed, power supply controllers is presented. The pulse width modulator, responsive to initial or slowly updated control signals can initiate control signals that provide either a slow-speed or high-speed changes. In one aspect of the invention, where the PWM is in communication with a relatively slow processor over a band-limited digital communication link, the PWM can internally generate a high-speed control signal in response to a rapidly changing input signal. In this aspect of the invention, the modular construction of power supply controller provides flexibility and interchangeability without incurring the cost of custom-made integrated circuit development.
REFERENCES:
patent: 5343016 (1994-08-01), Davis et al.
patent: 5481451 (1996-01-01), Kuwahara
patent: 6157093 (2000-12-01), Giannopoulos et al.
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