OSCILLATION CIRCUIT

• US 20100007428A1
• Filed: 06/07/2007
• Published: 01/14/2010
• Est. Priority Date: 06/09/2006
• Status: Active Grant

• Current Assignee: THine Electronics, Inc.
• Original Assignee: THine Electronics, Inc.
• Inventors: Nezuka, Tomohiro
• Granted Patent: US 7,940,135 B2
• Time in Patent Office: Days
• US Class Current: 331/36.C
• CPC Class Codes: H03K 4/06 having triangular shape
• CPC Class Codes: H03K 4/501 the starting point of the flyback period being determined by the amplitude of the voltage across the capacitor, e.g. by a comparator

Abstract

This oscillation circuit includes a triangular wave generation circuit that generates a triangular wave signal corresponding to an outputted clock signal, a comparison circuit that generates a clock signal corresponding to a comparison of the triangular wave signal with a first reference voltage and a second reference voltage, a current adjusting circuit that adjusts the value of adjusted current according to the power supply voltage for the comparison circuit, and a reference voltage generation circuit that generates the first reference voltage and the second reference voltage having a voltage differential that corresponds to the value of the adjusted current. The current adjusting circuit increases the adjusted current when the power supply voltage for the comparison circuit rises, and reduces the adjusted current when the power supply voltage drops. The reference voltage generation circuit increases the voltage differential between the first reference voltage and the second reference voltage when the adjusted current increases, and reduces the voltage differential when the adjusted current decreases.

Claims

1. An oscillation circuit for generating a clock signal with a rectangular waveform, comprising:

a triangular wave generation circuit that includes a capacitor, switches the charging or discharging state of the capacitor according to the voltage value of the clock signal, and generates a triangular wave signal;

a comparison circuit that receives the triangular wave signal outputted from the triangular wave generation circuit, receives a first reference voltage and a second reference voltage, and generates the clock signal having a voltage value that corresponds to a comparison of the voltage value of the triangular wave signal with the value of the first reference voltage, and to a comparison of the voltage value of the triangular wave signal with the value of the second reference voltage;

a current adjusting circuit that is connected to a reference current source outputting a reference current, is connected to a power supply for the comparison circuit, and generates an adjusted current in which the value of the reference current has been changed according to the change in voltage of the power supply; and

a reference voltage generation circuit that generates the first reference voltage and the second reference voltage having a voltage differential that corresponds to the value of the adjusted current outputted from the current adjusting circuit,

wherein the current adjusting circuit increases the adjusted current when the voltage of the power supply for the comparison circuit rises, and reduces the adjusted current when the voltage of the power supply drops, and

the reference voltage generation circuit increases the voltage differential between the first reference voltage and the second reference voltage when the adjusted current increases, and reduces the voltage differential between the first reference voltage and the second reference voltage when the adjusted current decreases.

2. The oscillation circuit according to claim 1,

wherein the current adjusting circuit has:

a first current mirror circuit to which the reference current is inputted; and

a second current mirror circuit to which the output current of the first current mirror circuit is inputted and which receives a supply of voltage from the power supply,

and the output current of the second current mirror circuit is outputted as the adjusted current.

3. The oscillation circuit according to claim 1,

wherein the reference voltage generation circuit has:

a third current mirror circuit to which the adjusted current is inputted; and

a voltage division circuit to which the output current of the third current mirror circuit flows,

and the voltage division circuit includes a plurality of resistors connected to each other in series, and generates the first reference voltage and the second reference voltage of which voltage differential is the drop in voltage of at least one of the plurality of resistors.

4. The oscillation circuit according to claim 2,

wherein the reference voltage generation circuit has:

a third current mirror circuit to which the adjusted current is inputted; and

a voltage division circuit to which the output current of the third current mirror circuit flows,

and the voltage division circuit includes a plurality of resistors connected to each other in series, and generates the first reference voltage and the second reference voltage of which voltage differential is the drop in voltage of at least one of the plurality of resistors.

5. The oscillation circuit according to claim 2,

wherein the first current mirror circuit of the current adjusting circuit has:

a first transistor having a first current terminal connected to the reference current source, a second current terminal connected to one potential of the power supply, and a control terminal connected to the first current terminal; and

a second transistor having a control terminal connected to the control terminal of the first transistor, a first current terminal, and a second current terminal connected to one potential of the power supply,

and the second current mirror circuit of the current adjusting circuit has;

a third transistor having a first current terminal connected to the first current terminal of the second transistor, a second current terminal connected to the other potential of the power supply, and a control terminal connected to the first current terminal; and

a fourth transistor having a control terminal connected to the control terminal of the third transistor, a first current terminal, and a second current terminal connected to the other potential of the power supply.

6. The oscillation circuit according to claim 3,

wherein the third current mirror circuit of the reference voltage generation circuit has:

a fifth transistor having a first current terminal connected to the current adjusting circuit, a second current terminal connected to one potential of the power supply, and a control terminal connected to the first current terminal; and

a sixth transistor having a control terminal connected to the control terminal of the fifth transistor, a first current terminal, and a second current terminal connected to one potential of the power supply,

and the voltage division circuit of the reference voltage generation circuit is connected between the first current terminal of the sixth transistor and the other potential of the power supply.

7. The oscillation circuit according to claim 4,

wherein the third current mirror circuit of the reference voltage generation circuit has:

a fifth transistor having a first current terminal connected to the current adjusting circuit, a second current terminal connected to one potential of the power supply, and a control terminal connected to the first current terminal; and

a sixth transistor having a control terminal connected to the control terminal of the fifth transistor, a first current terminal, and a second current terminal connected to one potential of the power supply,

and the voltage division circuit of the reference voltage generation circuit is connected between the first current terminal of the sixth transistor and the other potential of the power supply.