Pulse width modulation signal generating circuit

• US 5,298,871 A
• Filed: 12/28/1992
• Issued: 03/29/1994
• Est. Priority Date: 12/25/1991
• Status: Expired due to Term

• Current Assignee: Renesas Electronics Corporation
• Original Assignee: NEC Corporation
• Inventors: Shimohara, Kazunari
• Primary Examiner(s): Grimm, Siegfried H.
• Application Number:
  US07/996,900
• Time in Patent Office: 456 Days
• Field of Search: 332/109, 332/110, 332/111, 318/599, 318/684, 318/811
• US Class Current: 332/109
• CPC Class Codes: G06F 1/025 for functions having two-valued amplitude, e.g. Walsh functions
• CPC Class Codes: H02M 7/53873 with digital control
• CPC Class Codes: H03K 7/08 Duration or width modulation ; Duty cycle modulation

Abstract

A microcomputer having a signal generating circuit which generates pulse width modulation signals defined by a carrier wave, and which controls controlled portions according to pulse width modulating signals. The signal generating circuit comprises a carrier wave defining timer which outputs a value varying the same as a waveform providing a carrier wave, a control register which controls the time period of the timer, a reload register which holds a count value, control blocks which generate pulse width modulation signals according to the value of the timer and the count value of the reload register.

Claims

1. A microcomputer having a signal generating circuit provided on a semiconductor substrate for generating pulse width modulation signals defined by a carrier wave, for the purpose of controlling a unit to be controlled in accordance with the pulse width modulation signals, said signal generating circuit comprising:

a carrier wave defining timer for outputting a value that varies the same as a waveform providing said carrier wave;

a control register for controlling a period of said carrier wave defining timer;

a reload register for holding a counting value;

control blocks each for generating said pulse width modulation signals on the basis of a value of said carrier wave defining timer and said count value held in said reload register;

each of said control blocks comprising;

a compare register for ceaselessly comparing the value of said carrier wave defining timer with a comparison value, and outputting a coincidence detecting signal in case of detecting a coincidence between a value of said carrier wave defining timer and said comparison value;

a logical circuit set and reset according to said coincidence detecting signal;

a transfer register for transferring said comparison value to said compare register at a predetermined timing;

a one-shot timer set with said count value held in said reload register in synchronism with said set-reset of said logical circuit;

means for generating said pulse width modulation signal according to an output signal of said one-shot timer and an output signal of said logical circuit.

2. A microcomputer according to claim 1, wherein said carrier wave is a sawtooth modulated carrier wave, and said carrier wave defining timer is an up-timer for outputting a value varying the same as a sawtooth wave defining said carrier wave, and wherein said logical circuit is a reset-set flipflop.

3. A microcomputer according to claim 1, wherein said carrier wave is a chopping modulation carrier wave, said carrier wave defining timer is a down-timer for outputting a value varying the same as a chopping wave defining said carrier wave, and said logical circuit is a toggle flipflop.