Electricity: power supply or regulation systems – In shunt with source or load – Using choke and switch across source
Reexamination Certificate
2002-04-26
2003-11-04
Riley, Shawn (Department: 2838)
Electricity: power supply or regulation systems
In shunt with source or load
Using choke and switch across source
Reexamination Certificate
active
06642695
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a voltage mode boost converter and, more particularly, to a voltage mode boost converter using a period-fixed amplitude-modulated pulse control signal.
2. Description of the Related Art
The voltage required by common semiconductor components or microelectronic devices is mostly between 3.0V and 5.5V, while the voltage source required by some devices may be larger; for example, the voltage for driving an LCD driver, or the voltage for a flash memory, which is mostly between 6V and 7V. Therefore, most industrial manufacturers provide a voltage mode boost converter to convert circuit voltage so that a lower voltage (3.0V-5.5V) can be stepped up (boosted) to a higher voltage (6V-7V) for use.
As shown in
FIG. 1A
, a conventional circuit configuration of a voltage mode boost converter
1
comprises a pulse-width modulation control circuit
11
, a step-up (boost) circuit
12
and a feedback circuit
13
.
As for the voltage mode boost converter
1
, when it converts voltage, it must coordinate with a triangle wave generator (not shown), which is used to generate a triangle wave signal, and the triangle wave signal is input to the pulse-width modulation control circuit
11
to proceed with the pulse-width modulation control. As well known in the art, the pulse-width modulation control circuit
11
is operated in accordance with a clock.
The principle of the pulse-width modulation control is to use the feedback voltage signal V
FB
, which is generated by the feedback circuit
13
, and to use the triangle wave signal to adjust the waveform duty time.
FIG. 1B
is a diagram illustrating how to use the feedback voltage signal V
FB
to adjust the waveform duty time, wherein V
rp
and V
rn
each represents a peak value of the amplitude of the triangle wave signal, and V
FB1
and V
FB2
each represents the feedback voltage signal at different times. As shown in
FIG. 1B
, when the feedback voltage signal V
FB
is at V
FB1
, its corresponding duty time is T
1
, and when the feedback voltage signal V
FB
is at V
FB2
, its corresponding duty time is T
2
. In brief, the above-mentioned pulse-width modulation control circuit
11
, in accordance with the feedback voltage signal V
FB
and the triangle wave signal, can generate a pulse signal with an adjustable duty time, and the pulse signal is a signal that appears at the point O shown in
FIG. 1A
, while the waveform of the signal that appears at the point O is shown in FIG.
1
B.
In addition, as shown in
FIG. 1A
, the step-up circuit
12
of the voltage mode boost converter
1
comprises a MOS device as a switch, an inductor device L for providing an electric charge, a diode device D for rectifying, and a capacitor device C for storing an electric charge. Among these devices, the MOS device, the diode device, and the capacitor device are connected to one another in series, and the inductor device is connected between the MOS device and the diode device in parallel. The signal (i.e., the signal that appears at the point O) output by the pulse-width modulation control circuit
11
is for controlling the gate of the MOS device so that the inductor device L can charge to the capacitor device C.
Also, the feedback circuit
13
comprises a resistor R
1
, a resistor R
2
and a feedback terminal
131
. The resistor R
1
is connected to the resistor R
2
in series, and one end of the feedback terminal
131
is electrically connected between the resistor R
1
and the resistor R
2
, while the other end of the feedback terminal
131
is electrically connected to the pulse-width modulation control circuit
11
. The feedback circuit
13
is used to generate a feedback voltage signal V
FB
to the pulse-width modulation control circuit
11
, and accordingly controls the output of the pulse-width modulation control circuit
11
.
However, as for the voltage mode boost converter
1
, it has a shortcoming that when stepping up (boosting) the voltage, it must rely on a triangle waveform generator to generate a triangle waveform signal; otherwise, the voltage mode boost converter
1
cannot operate smoothly, which means that the triangle waveform generator must keep on operating all the time. In other words, the voltage mode boost converter
1
cannot go into a standby mode.
As shown in
FIG. 2A
, another conventional voltage mode boost converter
2
comprises a pulse-frequency modulation control circuit
21
, a step-up circuit
22
and a feedback circuit
23
. As for the voltage mode boost converter
2
, the circuit configuration and performance of its step-up circuit
22
and feedback circuit
23
are the same as those of the above-mentioned conventional voltage mode boost converter
1
. The difference between the voltage mode boost converters
1
and
2
is that the latter uses a pulse-frequency modulation control circuit
21
to generate control signals. The pulse-frequency modulation control circuit
21
mainly utilizes the amplitude of the feedback voltage signal V
FB
, which is output by the feedback circuit
23
, to adjust the period of the control signal that appears at the point O. As well known in the art, the pulse-frequency modulation control circuit
21
is operated in accordance with a clock. As shown in
FIG. 2B
, the larger the feedback voltage signal V
FB
output by the feedback circuit
23
is, the larger the period of the control signal that appears at the point O will be.
However, as for the voltage mode boost converter
2
, it has a shortcoming that the voltage output by the voltage mode boost converter
2
is affected by the change of amplitude of V
CC
voltage, thereby causing poor quality output voltage.
In view of the shortcomings of the conventional voltage converters, to provide a voltage mode boost converter with a standby mode and good quality output voltage becomes an important task.
SUMMARY OF THE INVENTION
The object of the invention is to provide a voltage mode boost converter, which has a standby mode and the feature of low standby current, and has good quality output voltage.
The feature of the invention is to provide a control signal generating circuit, which uses a feedback voltage signal to generate a step-up control pulse signal that is period-fixed and amplitude-modulated, so that the voltage mode boost converter of the invention can have a standby mode and a low standby current, and also ensure good quality output voltage.
Thus, to achieve the above-mentioned objective, a voltage mode boost converter in accordance with the invention comprises a control signal generating circuit, which is used to generate a step-up control pulse signal that is period-fixed and amplitude-modulated, a step-up circuit, which adjusts the output voltage signal of the step-up circuit according to the step-up control pulse signal generated by the control signal generating circuit, and a feedback circuit, which generates a feedback voltage signal according to the output voltage signal of the step-up circuit. The feedback voltage signal is input into the control signal generating circuit, and the control signal generating circuit generates the step-up control pulse signal according to the feedback voltage signal.
REFERENCES:
patent: 4837495 (1989-06-01), Zansky
patent: 5146398 (1992-09-01), Vila-Masot et al.
Faraday Technology Corp.
Martine & Penilla LLP
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