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Claims  |
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What is claimed is:
1. An integrated circuit for use in a switching voltage regulator circuit,
the switching voltage regulator circuit providing a regulated voltage
output at an output terminal, the integrated circuit including internal
drive circuitry, a power switching transistor and control circuitry for
varying the switching duty cycle of the switching transistor, the
integrated circuit having at most five terminals including an input
terminal, an output terminal a ground terminal and first and second
function terminals for connection to discrete external components to
implement the switching voltage regulator circuit, the integrated circuit
comprising:
first means connected to one of the function terminals for accepting a
feedback signal from the output of the switching voltage regulator circuit
and for enabling the integrated circuit to operate in a first mode to
regulate the output of the switching voltage regulator by varying the duty
cycle of the switching transistor as a function of the magnitude of the
feedback signal;
second means connected to the input and output terminals for enabling the
integrated circuit to operate in an isolated flyback mode to regulate the
output of the switching voltage regulator circuit as a function of a
feedback voltage developed across a primary winding of a discrete external
transformer; and
mode select means connected to one of the function terminals and to said
first and second means to disable the first means and to enable the second
means in response to a disable signal applied to that function terminal by
the discrete components.
2. An integrated circuit for use in a switching voltage regulator circuit
providing a regulated output voltage, the integrated circuit having
internal drive circuitry, a power switching transistor and control
circuitry for varying the on and off switching duty cycle of the switching
transistor, and further having an input terminal, an output terminal, a
ground terminal and first and second function terminals for connection to
external components, the integrated circuit comprising:
first means connected to the first function terminal and to the control
circuitry for accepting a first feedback signal indicative of the
regulated output voltage, and for enabling the integrated circuit to
operate in a normal feedback mode to regulate the regulated output voltage
by varying the duty cycle of the switching transistor as a function of the
magnitude of the first feedback signal;
second means connected to the input and output terminals and to the control
circuitry for accepting a second feedback signal between the input and
output terminals indicative of a voltage developed across a winding of an
external transformer, and for enabling the integrated circuit to operate
in a fully isolated flyback mode to regulate the regulated output voltage
as a function of the magnitude of the second feedback signal; and
third means connected to one of the function terminals and to said first
and second means to disable one of the first and second means and to
enable the other in response to a control signal applied to that function
terminal by external components.
3. The integrated circuit of claim 2, wherein said first means includes:
means for producing a first reference signal; and
means for detecting a difference between the first feedback signal and the
first reference signal, and for generating an error signal indicative of
that difference;
and wherein the control circuitry includes:
means for comparing the error signal to a signal indicative of the
magnitude of current conducted by the switching transistor; and
means responsive to said comparing means for turning off the switching
transistor when the current magnitude signal exceeds the error signal.
4. The integrated circuit of claim 2, wherein said second means includes:
means responsive to the second feedback signal for generating an error
signal indicative of a difference between the second feedback signal and a
predetermined threshold signal level;
and wherein the control circuitry includes:
means for comparing the error signal to a signal indicative of the
magnitude of current conducted by the switching transistor, and
means responsive to said comparing means for turning off the switching
transistor when the current magnitude signal exceeds the error signal.
5. The integrated circuit of claim 2, wherein said first means includes:
means for producing a first reference signal; and
means for detecting a difference between the first feedback signal and the
first reference signal, and for generating a first error signal indicative
of that difference;
wherein said second means includes:
means responsive to the second feedback signal for generating a second
error signal indicative of a difference between the second feedback signal
and a predetermined threshold signal level;
and wherein the control circuitry includes:
means for receiving the first and second error signals, for comparing at
any given time one of the first and second error signals to a signal
indicative of the magnitude of current conducted by the switching
transistor; and
means responsive to said comparing means for turning off the switching
transistor when the current magnitude signal exceeds the compared one of
the first and second error signals.
6. The integrated circuit of claim 3, wherein said means for generating an
error signal includes a differential amplifier having a first input for
receiving the feedback signal and a second input for receiving the first
reference signal.
7. The integrated circuit of claim 4, wherein said means for generating the
second feedback error signal includes:
an amplifier having a first input connected to one of the input and output
terminals; and
means connected to a second input of said amplifier and to the other of the
input and output terminals for establishing a threshold voltage, whereby a
voltage differential is established across the inputs of the amplifier
when a voltage difference between the input and output terminals exceeds
the threshold voltage.
8. The integrated circuit of claim 7, wherein said means for establishing a
threshold voltage includes a zener diode.
9. The integrated circuit of claim 8, wherein said zener diode has a zener
breakdown voltage, and wherein said means for establishing a threshold
voltage further includes:
means for establishing a trimming voltage in series with the zener
breakdown voltage such that at least a part of the threshold voltage is
comprised of the sum of the trimming and zener breakdown voltages; and
means connected to said means for establishing a trimming voltage, and to
one of the function terminals, for varying the trimming voltage in
response to a signal at that function terminal, thereby varying the
threshold voltage.
10. The integrated circuit of claim 9, wherein said means for varying the
trimming voltage is connected to the first function terminal.
11. The integrated circuit of claim 10, wherein:
said means for establishing a trimming voltage comprises a resistor; and
wherein
said means for varying the trimming voltage varies a current conducted by
said trimming voltage resistor as a function of a current conducted by the
first function terminal.
12. The integrated circuit of claim 11, wherein the current conducted by
the first function terminal is established at least in part by external
components connected to the first function terminal.
13. The integrated circuit of claim 12, wherein the external components
connected to the first function terminal includes a resistor connected to
ground.
14. The integrated circuit of claim 2, wherein said third means is
connected to the first function terminal.
15. The integrated circuit of claim 14, wherein the control signal is a
current, and wherein said third means includes:
means for sensing the current conducted by the first function terminal; and
means responsive to said sensing means for disabling said first means and
enabling said second means when the current sensed by said sensing means
exceeds a predetermined threshold current.
16. The integrated circuit of claim 2, wherein said third means is
connected to the first function terminal, and wherein the integrated
circuit further comprises:
fourth means connected to the control circuitry and to the second function
terminal for performing at least two of:
(a) frequency compensating the integrated circuit,
(b) limiting the peak current conducted by the switching transistor,
(c) variably limiting the current conducted by the switching transistor as
a function of time, and
(d) shutting down the integrated circuit, whereby the current drawn by the
integrated circuit is reduced.
17. The integrated circuit of claim 16, wherein said fourth means includes:
means for generating a signal indicative of the magnitude of current
conducted by the switching transistor;
means connected to at least one terminal of the integrated circuit for
sensing a feedback signal from the discrete components indicative of the
magnitude of at least one of the regulated output voltage and the voltage
developed across the winding of the external transformer, and for
generating an error signal indicative of the difference between the
feedback signal and a reference signal;
means for comparing the error signal to the current magnitude signal, and
for turning off the switching transistor when the current magnitude signal
exceeds the error signal; and
means for applying the error signal to the second function terminal,
whereby the magnitude of the error signal may be controlled by a network
of one or more external components connected to the second function
terminal.
18. The integrated circuit of claim 17, wherein the network of external
components connected to the second function terminal includes a frequency
compensating capacitor.
19. The integrated circuit of claim 17, wherein the network of external
components connected to the second function terminal includes a frequency
compensation capacitor in series with a resistor.
20. The integrated circuit of claim 17, wherein the network of external
components connected to the second function terminal prevents the error
signal at the second function terminal from exceeding a predetermined
maximum level, thereby limiting to a maximum peak value the magnitude of
current conducted by the switching transistor.
21. The integrated circuit of claim 20, wherein the network of external
components establishes a predetermined maximum voltage at the second
function terminal.
22. The integrated circuit of claim 17, wherein the network of external
components connected to the second function terminal variably controls the
voltage at the second function terminal as a function of time, thereby
variably limiting as a function of time the current conducted by the
switching transistor.
23. The integrated circuit of claim 22, wherein the network of external
components for variably controlling the voltage at the second function
terminal includes:
a resistor connected between a first node and a second node;
a capacitor connected between the second node and the ground terminal; and
means connected between the second node and the second function terminal
for applying at least a portion of a voltage at the second node to the
second function terminal, such that the voltage at the second function
terminal upon application of a voltage at the first node gradually
increases with time to gradually increase the current conducted by the
switching transistor.
24. The integrated circuit of claim 17, the integrated circuit further
having voltage regulator circuitry for providing a regulated voltage to at
least portions of the internal drive circuitry, and wherein said fourth
means further includes:
means for producing second reference signal;
means for comparing the second reference signal to a shutdown control
signal applied to the second function terminal by the external components,
and for generating a shutdown signal when the second reference signal and
the shutdown control signal differ by a predetermined amount; and
means responsive to the shutdown signal for disabling at least the voltage
regulator circuitry, thereby shutting down and reducing the current drawn
by the integrated circuit.
25. The integrated circuit of claim 24, wherein the shutdown control signal
is a voltage, and wherein:
said means for producing a second reference signal includes a diode having
a first forward voltage drop; and wherein
said means for comparing the second reference signal to the shutdown
control signal includes a transistor having a base-emitter circuit
connected between said diode and the second function terminal, the
base-emitter circuit having a second forward voltage drop which differs
from the first forward voltage drop, and said transistor being adapted to
disable the voltage regulator circuitry when the shutdown control signal
voltage at the second function terminal is less than the difference
between the first and second forward voltage drops.
26. An integrated circuit for use in implementing a switching voltage
regulator providing a regulated output voltage, the integrated circuit
having a power switching transistor, circuitry for driving the switching
transistor and control circuitry for varying the on and off switching duty
cycle of the switching transistor, and further having for connection to
external components an input terminal, an output terminal, a ground
terminal and a function terminal, the integrated circuit comprising:
first means connected to the function terminal and to the control circuitry
for accepting a first feedback signal indicative of the regulated output
voltage, and for enabling the integrated circuit to operate in a normal
feedback mode to regulate the regulated output voltage by varying the duty
cycle of the switching transistor as a function of the magnitude of the
first feedback signal;
second means connected to at least one of the terminals and to the control
circuitry for accepting a second feedback signal indicative of a voltage
developed across a winding of an external transformer, and for enabling
the integrated circuit to operate in a fully isolated flyback mode to
regulate the output voltage as a function of the magnitude of the second
feedback signal; and
mode select means connected to the function terminal and to said first and
second means to disable one of the first and second means and to enable
the other in response to a mode select control signal applied to the
function terminal by external components.
27. The integrated circuit of claim 26, wherein said first means includes:
means for producing a first reference signal; and
means for detecting a difference between the first feedback signal and the
first reference signal, and for generating an error signal indicative of
that difference;
and wherein the control circuitry includes:
means for comparing the error signal to a signal indicative of the
magnitude of current conducted by the switching transistor; and
means responsive to said comparing means for turning off the switching
transistor when the current magnitude signal exceeds the error signal.
28. The integrated circuit of claim 26, wherein said second means includes:
means responsive to the second feedback signal for generating an error
signal indicative of a difference between the second feedback signal and a
predetermined threshold signal level;
and wherein the control circuitry includes:
means for comparing the error signal to a signal indicative of the
magnitude of current conducted by the switching transistor; and
means responsive to said comparing means for turning off the switching
transistor when the current magnitude signal exceeds the error signal.
29. The integrated circuit of claim 26, wherein said first means includes:
means for producing a first reference signal; and
means for detecting a difference between the first feedback signal and the
first reference signal, and for generating a first error signal indicative
of that difference;
wherein said second means includes:
means responsive to the second feedback signal for generating a second
error signal indicative of a difference between the second feedback signal
and a predetermined threshold signal level;
and wherein the control circuitry includes:
means for receiving the first and second error signals, and for comparing
at any given time one of the first and second error signals to a signal
indicative of the magnitude of current conducted by the switching
transistor; and
means responsive to said comparing means for turning off the switching
transistor when the current magnitude signal exceeds the compared one of
the first and second error signals.
30. The integrated circuit of claim 27, wherein said means for generating
an error signal includes a differential amplifier having a first input for
receiving the first feedback signal and a second input for receiving the
first reference signal.
31. The circuit of claim 28, wherein said means for generating the second
feedback error signal includes:
an amplifier having a first input connected to one of the input and output
terminals; and
means connected to a second input of said amplifier and to the other of the
input and output terminals for establishing a threshold voltage, whereby a
voltage differential is established across the inputs of the amplifier
when a voltage difference between the input and output terminals exceeds
the threshold voltage.
32. The circuit of claim 31, wherein said means for establishing a
threshold voltage includes a zener diode.
33. The circuit of claim 32, wherein said zener diode has a zener breakdown
voltage, and wherein said means of establishing a threshold voltage
further includes:
means for establishing a trimming voltage in series with the zener
breakdown voltage such that at least a part of the threshold voltage is
comprised of the sum of the trimming and zener breakdown voltages; and
means connected to said means for establishing a trimming voltage, and to
the function terminal, for varying the trimming voltage in response to a
signal at the function terminal, thereby varying the threshold voltage.
34. The circuit of claim 33 wherein:
said means for establishing a trimming voltage comprises a resistor; and
wherein
said means for varying the trimming voltage varies a current conducted by
said trimming voltage resistor as a function of a current conducted by the
function terminal.
35. The circuit of claim 34, wherein the current conducted by the function
terminal is established at least in part by external components connected
to the function terminal.
36. The circuit of claim 35, wherein the external components connected to
the function terminal include a resistor connected to ground.
37. The circuit of claim 26, wherein said mode select means is connected to
the function terminal.
38. The circuit of claim 37, wherein said mode select means includes:
means for sensing current conducted by the function terminal; and
means responsive to said sensing means for disabling said first means and
enabling said second means when the current sensed by said sensing means
exceeds a predetermined threshold current.
39. The circuit of claim 38, wherein the function terminal is connected to
external components adapted to conduct a current which exceeds the
threshold current.
40. An integrated circuit for use in implementing a switching voltage
regulator providing a regulated output voltage, the integrated circuit
having a power switching transistor, circuitry for driving the switching
transistor and control circuitry for varying the on and off switching duty
cycle of the switching transistor, and further having at most five
terminals for connection to external components consisting of an input
terminal, an output terminal, a ground terminal and first and second
function terminal, the integrated circuit comprising:
first means connected to the first function terminal and to the control
circuitry for accepting a first feedback signal indicative of the
regulated output voltage, and for enabling the integrated circuit to
operate in a normal feedback mode to regulate the regulated output voltage
by varying the duty cycle of the switching transistor as a function of the
magnitude of the first feedback signal;
second means connected to at least one of the input and output terminals
and to the control circuitry for accepting a second feedback signal
indicative of a voltage developed across a winding of an external
transformer, and for enabling the integrated circuit to operate in a fully
isolated flyback mode to regulate the regulated output voltage as a
function of the magnitude of the second feedback signal;
mode select means connected to the first function terminal and to said
first and second means to disable one of the first and second means and to
enable the other in response to a mode select control signal applied to
the first function terminal by external components; and
means connected to the control circuitry and to the second function
terminal for enabling the switching voltage regulator circuit in response
to signals applied to the second function terminal by a network of
external components to be frequency compensated.
41. The integrated circuit of claim 40, wherein said first means includes:
means for producing a first reference signal; and
means for detecting a difference between the first feedback signal and the
first reference signal, and for generating an error signal indicative of
that difference;
and wherein the control circuitry includes:
means for comparing the error signal to a signal indicative of the
magnitude of current conducted by the switching transistor; and
means responsive to said comparing means for turning off the switching
transistor when the current magnitude signal exceeds the error signal.
42. The integrated circuit of claim 40, wherein said second means includes:
means responsive to the second feedback signal for generating an error
signal indicative of a difference between the second feedback signal and a
predetermined threshold signal level;
and wherein the control circuitry includes:
means for comparing the error signal to a signal indicative of the
magnitude of current conducted by the switching transistor; and
means responsive to said comparing means for turning off the switching
transistor when the current magnitude signal exceeds the error signal.
43. The integrated circuit of claim 40, wherein said first means includes:
means for producing a first reference signal; and
means for detecting a difference between the first feedback signal and the
first reference signal, and for generating a first error signal indicative
of that difference;
wherein said second means includes:
means responsive to the second feedback signal for generating a second
error signal indicative of a difference between the second feedback signal
and a predetermined threshold signal level;
and wherein the control circuitry includes:
means for receiving the first and second error signals, for comparing at
any given time one of the first and second error signals to a signal
indicative of the magnitude of current conducted by the switching
transistor; and
means responsive to said comparing means for turning off the switching
transistor when the current magnitude signal exceeds the compared one of
the first and second error signals.
44. The integrated circuit of claim 40, wherein said means for generating
an error signal includes a differential amplifier having a first input for
receiving the first feedback signal and a second input for receiving the
first reference signal.
45. The circuit of claim 42, wherein said means for generating the second
feedback error signal includes:
an amplifier having a first input connected to one of the input and output
terminals; and
means connected to a second input of said amplifier and to the other of the
input and output terminals for establishing a threshold voltage, whereby a
voltage differential is established across the inputs of the amplifier
when a voltage difference between the input and output terminals exceeds
the threshold voltage.
46. The circuit of claim 45, wherein said means for establishing a
threshold voltage includes a zener diode.
47. The circuit of claim 46, wherein said zener diode has a zener breakdown
voltage, and wherein said means for establishing a threshold voltage
further includes:
means for establishing a trimming voltage in series with the zener
breakdown voltage such that at least a part of the threshold voltage is
comprised of the sum of the trimming and zener breakdown voltages; and
means connected to said means for establishing a trimming voltage, and to
one of the function terminals, for varying the trimming voltage in
response to a signal at that function terminal, thereby varying the
threshold voltage.
48. The circuit of claim 47, wherein said means for varying the trimming
voltage is connected to the first function terminal.
49. The circuit of claim 48, wherein:
said means of establishing a trimming voltage comprises a resistor; and
wherein
said means for varying the trimming voltage varies a current conducted by
said trimming voltage resistor as a function of a current conducted by the
first function terminal.
50. The circuit of claim 49, wherein the current conducted by the first
function terminal is established at least in part by external components
connected to the first function terminal.
51. The circuit of claim 50, wherein the external components connected to
the first function terminal include a resistor connected to ground.
52. The circuit of claim 40, wherein said mode select means is connected to
the first function terminal.
53. The circuit of claim 40, wherein said mode select means includes:
means for sensing current conducted by the first function terminal; and
means responsive to said sensing means for disabling said first means and
enabling said second means when the current sensed by said sensing means
exceeds a predetermined threshold current.
54. The integrated circuit of claim 39, wherein the network of external
components connected to the second function terminal includes a frequency
compensating capacitor.
55. The integrated circuit of claim 40, wherein the network of external
components connected to the second function terminal includes a frequency
compensation capacitor in series with a resistor.
56. An integrated circuit for use in implementing a switching voltage
regulator providing a regulated output voltage, the integrated circuit
having internal drive circuitry, a power switching transistor and control
circuitry for controlling the on and off duty cycle of the switching
transistor to produce a pulsed output, and further having input and ground
terminals for connection to a source of input power, an output terminal
for connection to external components adapted to convert the pulsed output
of the switching transistor into the regulated output voltage, and first
and second multi-function terminals for connection to external components
adapted to apply control signals to the multi-function terminals, the
integrated circuit comprising:
first means responsive to control signals applied to the first
multi-function terminal, said first means including at least two of:
(a) means for controlling the duty cycle of the switching transistor when
the integrated circuit is operating in a normal feedback mode,
(b) means for programming the integrated circuit to operate in one of a
normal feedback mode and a fully-isolated flyback mode, and
(c) means for trimming a flyback voltage developed across a winding of an
external transformer when the integrated circuit operates in a
fully-isolated flyback mode; and
second means responsive to control signals applied to the second
multi-function terminal for performing at least two of:
(a) frequency compensating the integrated circuit,
(b) limiting peak current conducted by the switching transistor,
(c) variably limiting current conducted by the switching transistor as a
function of time, and
(d) shutting down the integrated circuit, whereby current drawn by the
integrated circuit is reduced.
57. The integrated circuit of claim 56, wherein said normal feedback mode
controlling means includes:
means for producing a first reference signal;
means for generating a feedback mode error signal indicative of a
difference between the first reference signal and a feedback signal
applied to the first multi-function terminal indicative of the magnitude
of the regulated output voltage;
means for comparing the feedback mode error signal to a signal indicative
of the magnitude of current conducted by the switching transistor; and
means responsive to said comparing means for turning off the switching
transistor when the current magnitude signal exceeds the error signal,
whereby the duty cycle of the switching transistor is controlled as a
function of the feedback signal.
58. The integrated circuit of claim 56, wherein said programming means
includes:
means for controlling the duty cycle of the switching transistor when the
integrated circuit operates in a fully-isolated flyback mode; and
means connected to the first multi-function terminal for sensing a
mode-select signal at the first multi-function terminal and for
responsively disabling said normal feedback mode controlling means and
enabling said flyback mode controlling means.
59. The integrated circuit of claim 58, wherein said flyback mode
controlling means includes:
means connected to the input and output terminals for receiving a flyback
signal indicative of a voltage developed across the winding of the
external transformer, and for generating a flyback mode error signal
indicative of a difference between the flyback signal and a threshold
signal level;
means for comparing the flyback mode error signal to a signal indicative of
the magnitude of current conducted by the switching transistor; and
means responsive to the output of said comparing means for turning off the
switching transistor when the current magnitude signal exceeds the error
signal, whereby the duty cycle of the switching transistor is controlled
as a function of the flyback signal.
60. The integrated circuit of claim 59, wherein said trimming means
includes:
means connected to the first multi-function terminal for sensing a trimming
control signal; and
means connected to said trimming control signal sensing means and to said
flyback mode error signal generating means for trimming the magnitude of
the threshold signal in response to the trimming control signal, thereby
trimming the flyback voltage.
61. The integrated circuit of claim 56, wherein said second means includes:
means for generating a signal indicative of the magnitude of current
conducted by the switching transistor;
means connected to at least one terminal of the integrated circuit for
sensing a feedback signal indicative of the magnitude of at least one of
the regulated output voltage and the voltage developed across the winding
of the external transformer, and for generating an error signal indicative
of the difference between the feedback signal and a reference signal;
means for comparing the error signal to the current magnitude signal, and
for turning off the switching transistor when the current magnitude signal
exceeds the error signal; and
means for applying the error signal to the second multi-function terminal,
whereby the magnitude of the error signal may be controlled by a network
of one or more external components connected to the second multi-function
terminal.
62. The integrated circuit of claim 61, wherein the network of external
components connected to the second multi-function terminal includes a
frequency compensating capacitor.
63. The integrated circuit of claim 61, wherein the network of external
components connected to the second multi-function terminal includes a
frequency compensation capacitor in series with a resistor.
64. The integrated circuit of claim 61, wherein the network of external
components connected to the second multi-function terminal prevents the
error signal at the second multi-function terminal from exceeding a
predetermined maximum level, thereby limiting to a maximum peak value the
magnitude of current conducted by the switching transistor.
65. The integrated circuit of claim 62, wherein the network of external
components establishes a predetermined maximum voltage at the second
multi-function terminal.
66. The integrated circuit of claim 61, wherein the network of external
components connected to the second multi-function terminal variably
controls the voltage at the second multi-function terminal as a function
of time, thereby variably limiting as a function of time the current
conducted by the switching transistor.
67. The integrated circuit of claim 66, wherein the network of external
components for variably controlling the voltage at the second
multi-function terminal includes:
a resistor connected between a first node and a second node;
a capacitor connected between the second node and the ground terminal; and
means connected between the second node and the second multi-function
terminal for applying at least a portion of a voltage at the second node
to the second multi-function terminal, such that the voltage at the second
multi-function terminal upon application of a voltage at the first node
gradually increases with time to gradually increase the current conducted
by the switching transistor.
68. The integrated circuit of claim 56, the integrated circuit further
having voltage regulator circuitry for providing a regulated voltage to at
least portions of the internal Circuitry, wherein said second means
further includes:
means for producing a second reference signal;
means for comparing the second reference signal to a shutdown control
signal applied to the second multi-function terminal by the external
components, and for generating a shutdown signal when the second reference
signal and the shutdown control signal differ by a predetermined amount;
and
means responsive to the shutdown signal for disabling at least the voltage
regulator circuitry, thereby shutting down and reducing the current drawn
by the integrated circuit.
69. The integrated circuit of claim 68, wherein the shutdown control signal
is a voltage, and wherein:
said means for producing a second reference signal includes a diode having
a first forward voltage drop; and wherein
said comparing means includes a transistor having a base-emitter circuit
connected between said diode and the second multi-function terminal, the
base-emitter circuit having a second forward voltage drop which differs
from the first forward voltage drop, and said transistor being adapted to
disable the voltage regulator circuitry when the shutdown control signal
voltage at the second multi-function terminal is less than the difference
between the first and second forward voltage drops.
70. An integrated circuit for use in implementing a switching voltage
regulator providing a regulated output voltage, the integrated circuit
having internal drive circuitry, a power switching transistor and control
circuitry for controlling the on and off duty cycle of the switching
transistor to produce a pulsed output, and further having input and ground
terminals for connection to a source of input voltage and current, an
output terminal for connection to external components adapted to convert
the pulsed output of the switching transistor into the regulated output
voltage, and first and second multi-function terminals for connection to
external components adapted to apply control signals to the multi-function
terminals, the integrated circuit comprising:
first means responsive to control signals applied to the first
multi-function terminal, said first means including:
(a) means for controlling the duty cycle of the switching transistor when
the integrated circuit operates in a normal feedback mode,
(b) means for programming the integrated circuit to operate in one of a
normal feedback mode and a fully-isolated flyback mode, and
(c) means for trimming a flyback voltage developed across a winding of an
external transformer when the integrated circuit operates in a
fully-isolated flyback mode; and
second means responsive to control signals applied to the second
multi-function terminal for:
(a) frequency compensating the integrated circuit,
(b) limiting peak current conducted by the switching transistor,
(c) variably limiting current conducted by the switching transistor as a
function of time, and
(d) shutting down the integrated circuit, whereby current drawn by the
integrated circuit is reduced.
71. An integrated circuit for use in implementing a switching voltage
regulator providing a regulated output voltage, the integrated circuit
having internal drive circuitry, a power switching transistor and control
circuitry for controlling the on and off duty cycle of the switching
transistor to produce a pulsed output, and further having input and ground
terminals for connection to a source of input voltage and current, an
output terminal for connection to external components adapted to convert
the pulsed output of the switching transistor into the regulated output
voltage, and first and second multi-function terminals for connection to
external components adapted to apply control signals to the multi-function
terminals, the integrated circuit comprising:
first means responsive to control signals applied to the first
multi-function terminal, said first means including:
(a) means for controlling the duty cycle of the switching transistor when
the integrated circuit operates in a normal feedback mode,
(b) means for programming the integrated circuit to operate in one of a
normal feedback mode and a fully-isolated flyback mode, and
(c) means for trimming a flyback voltage developed across a winding of an
external transformer when the integrated circuit operates in a
fully-isolated flyback mode; and
second means responsive to control signals applied to the second
multi-function terminal for:
(a) frequency compensating the integrated circuit,
(b) limiting peak current conducted by the switching transistor, and
(c) variably limiting current conducted by the switching transistor as a
function of time.
72. An integrated circuit for use in implementing a switching voltage
regulator providing a regulated output voltage, the integrated circuit
having internal drive circuitry, a power switching transistor and control
circuitry for controlling the on and off duty cycle of the switching
transistor to produce a pulsed output, and further having input and ground
terminals for connection to a source of input voltage and current, an
output terminal for connection to external components adapted to convert
the pulsed output of the switching transistor into the regulated output
voltage, and first and second multi-function terminals for connection to
external components adapted to apply control signals to the multi-function
terminals, the integrated circuit comprising:
first means responsive to control signals applied to the first
multi-function terminal, said first means including:
(a) means for controlling the duty cycle of the switching transistor when
the integrated circuit operates in a normal feedback mode, and
(b) means for programming the integrated circuit to operate in one of a
normal feedback mode and a fully-isolated flyback mode; and
second means responsive to control signals applied to the second
multi-function terminal for:
(a) frequency compensating the integrated circuit,
(b) limiting peak current conducted by the switching transistor,
(c) variably limiting current conducted by the switching transistor as a
function of time, and
(d) shutting down the integrated circuit, whereby current drawn by the
integrated circuit is reduced.
73. An integrated circuit for use in implementing a switching voltage
regulator providing a regulated output voltage, the integrated circuit
having internal drive circuitry, a power switching transistor and control
circuitry for controlling the on and off duty cycle of the switching
transistor to produce a pulsed output, and further having input and ground
terminals for connection to a source of input voltage and current, an
output terminal for connection to external components adapted to convert
the pulsed output of the switching transistor into the regulated output
voltage, and first and second function terminals for connection to
external components adapted to apply control signals to the function
terminals, the integrated circuit comprising:
first means responsive to a control signal applied to the first function
terminal for controlling the duty cycle of the switching transistor as a
function of the magnitude of the regulated output voltage; and
second means responsive to control signals applied to the second function
terminal for:
(a) frequency compensating the integrated circuit,
(b) limiting current conducted by the switching transistor,
(c) variably limiting current conducted by the switching transistor as a
function of time, and
(d) shutting down the integrated circuit, whereby current drawn by the
integrated circuit is reduced.
74. An integrated circuit for use in implementing a switching voltage
regulator providing a regulated output voltage, the integrated circuit
having internal drive circuitry power switching transistor and control
circuitry for controlling the on and off duty cycle of the switching
transistor to produce a pulsed output, and further having input and ground
terminals for connection to a source of input voltage and current, an
output terminal for connection to external components adapted to convert
the pulsed output of the switching transistor into the regulated output
voltage, and first and second multi-function terminals for connection to
external components adapted to apply control signals to the multi-function
terminals, the integrated circuit comprising:
first means responsive to control signals applied to the first
multi-function terminal, said first means including:
(a) means for controlling the duty cycle of the switching transistor when
the integrated circuit operates in a normal feedback mode, and
(b) means for programming the integrated circuit to operate in one of a
normal feedback mode and a fully-isolated flyback mode;
second means responsive to control signals applied to the second
multi-function terminal for:
(a) frequency compensating the integrated circuit,
(b) | | |
