Switching voltage regulator circuit

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.

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.

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.

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.

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.

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.

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.

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.

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) limiting peak current conducted by the switching transistor, and
• (c) variably limiting current conducted by the switching transistor as a function of time.

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, the integrated circuit comprising:

• at most five terminals for connection to external components, including input and ground terminals for connection to a source of input power, and 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;
• 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.

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, the integrated circuit comprising:

• at most five terminals for connection to external components, including 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;
• 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 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:
• (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.

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, the integrated circuit comprising:

• at most five terminals for connection to external components, including 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;
• 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 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, and
• (c) variably limiting current conducted by the switching transistor as a function of time.

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, the integrated circuit comprising:

• at most five terminals for connection to external components, including 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;
• 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, 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 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.

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, the integrated circuit comprising:

• at most five terminals for connection to external components, including 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 function terminals for connection to external components adapted to apply control signals to the function terminals;
• first means responsive to control signals 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 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, where current drawn by the integrated circuit is reduced.

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, the integrated circuit comprising:

• at most five terminals for connection to external components, including 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;
• 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 is operating 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 performing at least two of:
• (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.

An integrated circuit capable of implementing a current-mode normal feedback switching voltage regulator and a current-mode fully isolated flyback switching voltage regulator, the integrated circuit having a switching transistor, circuitry for driving the switching transistor, and control circuitry for controlling the on and off duty cycle of the switching transistor to produce a pulsed output, the integrated circuit comprising:

• at most five terminals for connection to external components, including:
• (a) input and ground terminals, connected to the integrated circuitry, for connection to a source of input voltage and current;
• (b) an output terminal, connected to the switching transistor, for connection to external components adapted to convert the pulsed output of the switching transistor into the regulated output voltage;
• (c) a first multi-function terminal responsive to control signals applied by external components connected to the first multi-function terminal for performing at least two functions selected from the group of:
• (1) controlling the duty cycle of the switching transistor when the integrated circuit is operating in a normal feedback mode,
• (2) programming the integrated circuit to operate in one of a normal feedback mode and fully-isolated flyback mode, and
• (3) trimming a flyback voltage developed across a winding of an external transformer when the integrated circuit operates in a fully-isolated flyback mode;
• and
• (d) a second multi-function terminal, responsive to control signals applied by external components connected to the second multi-function terminal, for performing at least two functions selected from the group of:
• (1) frequency compensating the integrated circuit,
• (2) limiting peak current conducted by the switching transistor,
• (3) variably limiting current conducted by the switching transistor as a function of time, and
• (4) shutting down the integrated circuit, whereby current drawn by the integrated circuit is reduced.