AC-DC converter having saw-tooth wave generating circuit in active filter

Claim 2

An AC-DC converter comprising: a rectifier for rectifying an A.C. input voltage supplied from a commercial power line; an active filter for obtaining higher voltage by boosting up the level of an output voltage from the rectifier; and a DC-DC converter for supplying a stable D.C. output voltage to a load, wherein the active filter comprises: a driving circuit for driving a switching transistor by trigger of a synchronizing pulse signal as synchronized with a switching pulse for driving the DC-DC converter; and a saw-tooth wave generating circuit without a function of self-oscillation, in which a value of the output voltage together with the turn-on of the switching transistor starts rising, in response to a signal which the driving circuit outputs when the synchronizing pulse signal is inputted thereto, and the active filter is characterized in that ON-timing of the switching transistor is determined at the time when it is triggered by the synchronizing pulse signal, and OFF-timing of the switching transistor is determined by comparing a saw-tooth wave voltage outputted from the saw-tooth wave generating circuit with a level voltage as reference to keep the D.C. output voltage constant.

Claim 3

An AC-DC converter comprising: a rectifier for rectifying an A.C. input voltage supplied from a commercial power line; an active filter for obtaining higher voltage by boosting up the level of an output voltage from the rectifier; and a DC-DC converter for supplying a stable D.C. output voltage to a load, wherein the active filter comprises: a driving circuit for driving a switching transistor by trigger of a synchronizing pulse signal as synchronized with a switching pulse for driving the DC-DC converter; and a saw-tooth wave generating circuit without a function of self-oscillation, in which a value of the output voltage together with the turn-on of the switching transistor starts rising, in response to a signal which the driving circuit outputs when a synchronizing pulse signal is inputted thereto. and the active filter is characterized in that ON-timing of the switching transistor is determined at the time when it is triggered by the synchronizing pulse signal, and OFF-timing of the switching transistor is determined by comparing a saw-tooth wave voltage outputted from the saw-tooth wave generating circuit with a level voltage as reference to keep the D.C. output voltage constant, and a value of the level voltage changes in accordance with a difference between a voltage across both terminals of an output capacitor and the reference voltage.

Claim 4

An AC-DC converter comprising: a rectifier for rectifying an A.C. input voltage supplied from a commercial power line; an active filter for obtaining higher voltage by boosting up the level of an output voltage from the rectifier; and a DC-DC converter for supplying a stable D.C. output voltage to a load, wherein the active filter comprises: a driving circuit for driving a switching transistor by trigger of a synchronizing pulse signal as synchronized with a switching pulse for driving the DC-DC converter; and a saw-tooth wave generating circuit without a function of self-oscillation, in which a value of the output voltage together with the turn-on of the switching transistor starts rising, in response to a signal which the driving circuit outputs when a synchronizing pulse signal is inputted thereto. and the active filter is characterized in that ON-timing of the switching transistor is determined at the time when it is triggered by the synchronizing pulse signal, and OFF-timing of the switching transistor is determined by comparing a saw-tooth wave voltage outputted from the saw-tooth wave generating circuit with a level voltage as reference to keep the D.C. output voltage constant, and a value of the level voltage changes in accordance with a difference between a voltage across both terminals of an output capacitor and the reference voltage.

Claim 5

An AC-DC converter comprising: a rectifier for rectifying an A.C. input voltage supplied from a commercial power line; an active filter for obtaining higher voltage by boosting up the level of an output voltage from the rectifier; and a DC-DC converter for supplying a stable D.C. output voltage to a load, wherein the active filter comprises a control circuit including: a saw-tooth wave generating circuit being formed by connecting a resistor and a capacitor in series between electrodes of a constant voltage source in which a low potential side of the electrodes is grounded; a connecting point of the resistor and the capacitor being connected to one of input terminals of a comparator; the other input terminal of the comparator being connected to an output terminal of a voltage error amplifier outputting a level voltage according to a difference between a voltage across both terminals of an output capacitor and a reference voltage; an output terminal of the comparator being connected to a reset input terminal of a flip-flop, a synchronizing pulse signal as synchronized with a switching pulse for driving the DC-DC converter being inputted to a set input terminal of the flip-flop, an output terminal of the flip-flop being connected to a control electrode of the switching transistor; and an inverting output terminal of the flip-flop being connected to a control electrode of another transistor, a main current flow path thereof being connected across the capacitor of the saw-tooth wave generating circuit, and the active filter is characterized in that the switching transistor is turned on by trigger of a synchronizing pulse signal to hold in an ON-state, and OFF-timing of the switching transistor is determined by detecting a difference between a voltage across both terminals of an output capacitor and a reference voltage, causing a value of a level voltage to change by the difference and comparing the saw-tooth wave voltage outputted from the saw-tooth wave generating circuit, the voltage of which is raised by inputting the synchronizing pulse signal, with the level voltage as reference to keep D.C. output voltage constant.

Claim 6

An AC-DC converter comprising: a rectifier for rectifying an A.C. input voltage supplied from a commercial power line; an active filter for obtaining higher voltage by boosting up the level of an output voltage from the rectifier; and a DC-DC converter for supplying a stable D.C. output voltage to a load, wherein the active filter comprises a control circuit including: a saw-tooth wave generating circuit being formed by connecting a resistor and a capacitor in series between electrodes of a constant voltage source in which a low potential side of the electrodes is grounded; a connecting point of the resistor and the capacitor being connected to one of input terminals of a comparator; the other input terminal of the comparator being connected to an output terminal of a voltage error amplifier outputting a level voltage according to a difference between a voltage across both terminals of an output capacitor and a reference voltage; an output terminal of the comparator being connected to a reset input terminal of a flip-flop, a synchronizing pulse signal as synchronized with a switching pulse for driving the DC-DC converter being inputted to a set input terminal of the flip-flop, an output terminal of the flip-flop being connected to a control electrode of the switching transistor; and an inverting output terminal of the flip-flop being connected to a control electrode of another transistor, a main current flow path thereof being connected across the capacitor of the saw-tooth wave generating circuit, and the active filter is characterized in that the switching transistor is turned on by trigger of a synchronizing pulse signal to hold in an ON-state, and OFF-timing of the switching transistor is determined by detecting a difference between a voltage across both terminals of an output capacitor and a reference voltage, causing a value of a level voltage to change by the difference and comparing the saw-tooth wave voltage outputted from the saw-tooth wave generating circuit, the voltage of which is raised by inputting the synchronizing pulse signal, with the level voltage as reference to keep D.C. output voltage constant.

Claim 7

An AC-DC converter comprising: a rectifier for rectifying an A.C. input voltage supplied from a commercial power line; an active filter for obtaining higher voltage by boosting up the level of an output voltage from the rectifier; and a DC-DC converter for supplying a stable D.C. output voltage to a load, wherein the active filter comprises: a driving circuit for driving a switching transistor by trigger of a synchronizing pulse signal as synchronized with a switching pulse for driving the DC-DC converter; and a saw-tooth wave generating circuit without a function of self-oscillation, in which a value of the output voltage together with the turn-on of the switching transistor starts rising, in response to a signal which the driving circuit outputs when a synchronizing pulse signal is inputted thereto, and the active filter is characterized in that ON-timing of the switching transistor is determined at the time when it is triggered by the synchronizing pulse signal, OFF-timing of the switching transistor is determined by comparing a saw-tooth wave voltage outputted from the saw-tooth wave generating circuit with a level voltage as reference to keep the D.C. output voltage constant, and an inclination of the saw-tooth wave voltage changes in accordance with a difference between a voltage across both terminals of an output capacitor and a reference voltage.

Claim 8

An AC-DC converter comprising: a rectifier for rectifying an A.C. input voltage supplied from a commercial power line; an active filter for obtaining higher voltage by boosting up the level of an output voltage from the rectifier; and a DC-DC converter for supplying a stable D.C. output voltage to a load, wherein the active filter comprises: a driving circuit for driving a switching transistor by trigger of a synchronizing pulse signal as synchronized with a switching pulse for driving the DC-DC converter; and a saw-tooth wave generating circuit without a function of self-oscillation, in which a value of the output voltage together with the turn-on of the switching transistor starts rising, in response to a signal which the driving circuit outputs when a synchronizing pulse signal is inputted thereto, and the active filter is characterized in that ON-timing of the switching transistor is determined at the time when it is triggered by the synchronizing pulse signal, OFF-timing of the switching transistor is determined by comparing a saw-tooth wave voltage outputted from the saw-tooth wave generating circuit with a level voltage as reference to keep the D.C. output voltage constant, and an inclination of the saw-tooth wave voltage changes in accordance with a difference between a voltage across both terminals of an output capacitor and a reference voltage.

Claim 9

An AC-DC converter comprising: a rectifier for rectifying an A.C. input voltage supplied from a commercial power line; an active filter for obtaining a higher voltage by boosting up the level of an output voltage from the rectifier; and a DC-DC converter for supplying a stable D.C. output voltage to a load, wherein the active filter comprises a control circuit including: a saw-tooth wave generating circuit being formed by connecting a first resistor and a capacitor between electrodes of a constant voltage source in which a low potential side of the electrodes is grounded and further connecting in series a second resistor and a main current path of a first transistor across the first resistor; an output terminal of a voltage error amplifier that outputs a voltage according to a difference between a voltage across both terminals of an output capacitor and the reference voltage being connected to a control electrode of the first transistor; one of two input terminals of a comparator being connected to a connection point of the first resistor and the capacitor; the other input terminal of the comparator being connected to a reference voltage source outputting a level voltage; an output terminal of the comparator being connected to a reset input terminal of a flip-flop, a synchronizing pulse signal as synchronized with a switching pulse for driving the DC-DC converter being inputted to a set input terminal of the flip-flop; and an inverting output terminal of the flip-flop being connected to a control electrode of a second transistor, a main current flow path thereof being connected parallel to the capacitor of the saw-tooth wave generating circuit, and the active filter is characterized in that a switching transistor is turned on by trigger of the synchronizing pulse signal to hold in an ON-state, an output terminal of the flip-flop being connected to a control electrode of the switching transistor, and OFF-timing of the switching transistor is determined by detecting a difference between a voltage across both terminals of the output capacitor and the reference voltage, causing an inclination of a saw-tooth wave voltage outputted from the saw-tooth wave generating circuit to change by the difference, the voltage of which is raised by inputting the synchronizing pulse signal, and comparing the saw-tooth wave voltage with the level voltage.

Claim 10

An AC-DC converter comprising: a rectifier for rectifying an A.C. input voltage supplied from a commercial power line; an active filter for obtaining a higher voltage by boosting up the level of an output voltage from the rectifier; and a DC-DC converter for supplying a stable D.C. output voltage to a load, wherein the active filter comprises a control circuit including: a saw-tooth wave generating circuit being formed by connecting a first resistor and a capacitor between electrodes of a constant voltage source in which a low potential side of the electrodes is grounded and further connecting in series a second resistor and a main current path of a first transistor across the first resistor; an output terminal of a voltage error amplifier that outputs a voltage according to a difference between a voltage across both terminals of an output capacitor and the reference voltage being connected to a control electrode of the first transistor; one of two input terminals of a comparator being connected to a connection point of the first resistor and the capacitor; the other input terminal of the comparator being connected to a reference voltage source outputting a level voltage; an output terminal of the comparator being connected to a reset input terminal of a flip-flop, a synchronizing pulse signal as synchronized with a switching pulse for driving the DC-DC converter being inputted to a set input terminal of the flip-flop; and an inverting output terminal of the flip-flop being connected to a control electrode of a second transistor, a main current flow path thereof being connected parallel to the capacitor of the saw-tooth wave generating circuit, and the active filter is characterized in that a switching transistor is turned on by trigger of the synchronizing pulse signal to hold in an ON-state, an output terminal of the flip-flop being connected to a control electrode of the switching transistor, and OFF-timing of the switching transistor is determined by detecting a difference between a voltage across both terminals of the output capacitor and the reference voltage, causing an inclination of a saw-tooth wave voltage outputted from the saw-tooth wave generating circuit to change by the difference, the voltage of which is raised by inputting the synchronizing pulse signal, and comparing the saw-tooth wave voltage with the level voltage.