Granted Patent B2

US 8,030,976 · App. 12/691,544 · Granted Oct 4, 2011

Abstract

Claims (40)

1. A triangle wave generating circuit comprising:

a pulse generating circuit configured to generate a plurality of pulse signals with the same period and with phases different from one another; and

a plurality of charge/discharge circuits configured to be supplied respectively with the plurality of pulse signals,

the plurality of charge/discharge circuits each including:

a current supply circuit configured to supply to a capacitor a first current for charging at a predetermined current value or a second current for discharging at a predetermined current value; and

a charge/discharge control circuit configured to switch between the first current and the second current when the pulse signals are supplied thereto and when a voltage across the capacitor reaches a predetermined reference voltage, the first current and the second current supplied from the current supply circuit to the capacitor,

each charge/discharge circuit outputting the voltage across the capacitor as a triangle wave signal;

the plurality of charge/discharge circuits outputting a respective plurality of triangle wave signals having the same period and with phases different from one another.

2. The triangle wave generating circuit of claim 1 , wherein the charge/discharge control circuit includes:

switch circuits in a pair configured to supply the first current and the second current to the capacitor, respectively; and

a switch control circuit configured to turn on or off the switch circuits in the pair in a complementary manner, and wherein

the switch control circuit turns on either one of the switch circuits in the pair when the pulse signals are supplied thereto and turns on the other one of the switch circuits in the pair when the voltage across the capacitor reaches the predetermined reference voltage.

3. The triangle wave generating circuit of claim 1 , wherein the pulse generating circuit includes:

a first edge detecting circuit configured to output a first edge detection signal indicating, as a pulse, timing of a rising edge of a clock signal; and

a second edge detecting circuit configured to output a second edge detection signal indicating, as a pulse, timing of a falling edge of the clock signal, and wherein

the first and second edge detection signals are supplied to the plurality of charge/discharge circuits as the plurality of pulse signals, respectively.

4. The triangle wave generating circuit of claim 2 , wherein the pulse generating circuit includes:

a first edge detecting circuit configured to output a first edge detection signal indicating, as a pulse, timing of a rising edge of a clock signal; and

a second edge detecting circuit configured to output a second edge detection signal indicating, as a pulse, timing of a falling edge of the clock signal, and wherein

the first and second edge detection signals are supplied to the plurality of charge/discharge circuits as the plurality of pulse signals, respectively.

5. The triangle wave generating circuit of claim 1 , wherein the pulse generating circuit includes:

an edge detecting circuit configured to output an edge detection signal indicating, as a pulse, timing of either one of a rising edge and a falling edge of a first clock signal; and

an output selecting circuit configured to sequentially selects any one of the plurality of charge/discharge circuits in each period of the first clock signal, and wherein

the edge detection signal is supplied as the pulse signal to one of the charge/discharge circuits selected by the output selecting circuit.

6. The triangle wave generating circuit of claim 2 , wherein the pulse generating circuit includes:

an edge detecting circuit configured to output an edge detection signal indicating, as a pulse, timing of either one of a rising edge and a falling edge of a first clock signal; and

an output selecting circuit configured to sequentially selects any one of the plurality of charge/discharge circuits in each period of the first clock signal, and wherein

the edge detection signal is supplied as the pulse signal to one of the charge/discharge circuits selected by the output selecting circuit.

7. The triangle wave generating circuit of claim 5 , wherein

the output selecting circuit includes a counter configured to count by the first clock signal, and sequentially selects any one of the plurality of charge/discharge circuits according to a count value of the counter.

8. The triangle wave generating circuit of claim 6 , wherein

the output selecting circuit includes a counter configured to count by the first clock signal, and sequentially selects any one of the plurality of charge/discharge circuits according to a count value of the counter.

9. The triangle wave generating circuit of claim 7 , wherein

the pulse generating circuit further includes a frequency dividing circuit configured to frequency-divide a second clock signal to be output as the first clock signal, wherein

a count number of the counter is set at a value equal to or smaller than the number of the charge/discharge circuits according to a selection signal, and wherein

a frequency division ratio of the frequency dividing circuit is set at a value obtained by dividing by the count number a lowest common multiple of values capable of being set as the count number, according to the selection signal.

10. The triangle wave generating circuit of claim 8 , wherein

the pulse generating circuit further includes a frequency dividing circuit configured to frequency-divide a second clock signal to be output as the first clock signal, wherein

a count number of the counter is set at a value equal to or smaller than the number of the charge/discharge circuits according to a selection signal, and wherein

a frequency division ratio of the frequency dividing circuit is set at a value obtained by dividing by the count number a lowest common multiple of values capable of being set as the count number, according to the selection signal.

Assignments (9)