Pulse-width modulation drive circuit

• US 4,823,056 A
• Filed: 07/02/1986
• Issued: 04/18/1989
• Est. Priority Date: 07/02/1985
• Status: Expired due to Term

• Current Assignee: Pioneer Electronic Corporation (Pioneer Corporation)
• Original Assignee: Pioneer Electronic Corporation (Pioneer Corporation)
• Inventors: Niinuma, Susumi, Kimura, Toshiyuki, Abe, Hiroyuki, Iijima, Takayuki, Watanabe, Yoshihiko, Matsumoto, Isao, Namiki, Akio, Aoyagi, Yoshio, Nomura, Isamu, Kobayashi, Kimito, Haeno, Akira, Nagashita, Tsuneyoshi, Shimokawa, Kazuto
• Primary Examiner(s): Shoop, Jr., William M.
• Assistant Examiner(s): Ip, Paul
• Application Number:
  US06/881,540
• Time in Patent Office: 1,021 Days
• Field of Search: 318/138, 318/254, 318/257, 318/258, 318/259, 318/262, 318/266, 318/267, 318/269, 318/278, 318/280, 318/282, 318/283, 318/286, 318/287, 318/288, 318/289, 318/293, 318/294 , 318/298, 318/299, 318/300, 318/314, 318/316, 318/317, 318/318, 318/326, 318/327, 318/328, 318/331, 318/332, 318/339, 318/340, 318/341, 318/345 R, 318/345 B , 318/345 E, 318/345 F, 318/359, 318/439, 318/599-608, 318/616, 318/617, 318/618, 318/628, 363/41
• US Class Current: 388/829
• CPC Class Codes: H02P 7/29 using pulse modulation
• CPC Class Codes: H03F 2200/33 Bridge form coupled amplifiers; H-form coupled amplifiers
• CPC Class Codes: Y10S 388/91 Operational/differential amplifier
• CPC Class Codes: Y10S 388/915 Sawtooth or ramp waveform generator
• CPC Class Codes: Y10S 388/916 Threshold circuit

Abstract

A pulse-width modulation drive circuit for a load such as a motor, particularly, a motor used in a compact disc player or the like, in which losses in diodes used to absorb reverse EMF are substantially eliminated. For this purpose, the pulse widths of pulse signals used to on-off control drive current flow through the load are controlled so as to eliminate the diode losses. The circuits of the various embodiments of the invention are designed so as to be easily implemented in integrated circuit form.

Claims

1. In a switching drive circuit which has a unidirectional element for absorbing reverse electromotive force across a load and which drives said load by switching current flow through said load on and off in response to a predetermined pulse signal, the improvement wherein said drive circuit comprises:

compensating circuit means receiving said predetermined pulse signal as an input and providing a drive pulse signal for said load, said drive pulse signal having a pulse width larger than a pulse width of said predetermined pulse signal by a predetermined amount, whereby an absorption of energy in said unidirectional element is compensated when said unidirectional element is absorbing said reverse electromotive force.

2. The switching drive circuit according to claim 1, wherein said compensating circuit means comprises means for producing a pulse signal in response to said predetermined pulse signal having a pulse width equivalent to a time interval between generation of said predetermined pulse signal and a point a predetermined time after disappearance of said predetermined pulse signal, the pulse signal thus produced being said drive pulse signal.

3. The switching drive circuit according to claim 1, wherein said compensating circuit means comprises means for producing a second pulse signal in response to said predetermined pulse signal having a given pulse width, and a logical addition circuit which receives the second pulse signal so produced and said predetermined pulse signal as two inputs, a resulting pulse signal produced by said logical addition circuit being said drive pulse signal.

15. The switching circuit according to claim 1, wherein said predetermined amount is determined to compensate for said absorption.

16. The switching circuit according to claim 1, wherein said predetermined amount increases with an increase of said pulse width of said predetermined pulse signal over a range of said increase up to a maximum pulse width of said drive pulse signal.

4. In a switching drive circuit which includes a first transistor which supplies a load with a drive current for a forward direction in response to a first level of a first pulse signal, and a second transistor which supplies said load with a drive current for a reverse direction in response to a first level of a second pulse signal, said drive circuit driving said load by switching a current through said load on and off in response to said first and second pulse signals, the improvement wherein said drive circuit further comprises:

first switching means controlled by said first pulse signal for shorting said first transistor between its base and emitter in response to a disappearance of said first level of said first pulse signal to thereby discharge an inherent base-emitter capacitance of said first transistor, and second switching means controlled by said second pulse signal for shorting said second transistor between its base and emitter in response to a disappearance of said first level of said second pulse signal to thereby discharge an inherent base-emitter capacitance of said second transistor.

5. A pulse-width-modulation drive circuit which produces a pulse signal with a pulse width which is dependent on a level of a drive signal and which drives a load by switching a current through said load on and off in response to the pulse signal so produced, said drive circuit comprising:

triangular wave generating means for generating two triangular signals having substantially equal peak values and which are opposite to each other in phase, a comparator circuit receiving said two triangular signals of opposite phases as upper and lower reference input signals, respectively, and receiving said drive signal as a comparison input, first gate means for producing first and second pulse signals in response to an output of said comparator circuit, said first and second pulse signals corresponding to two directions in which said load is to be driven, polarity detecting means for determining a polarity of said drive signal with respect to a signal reference level, and second gate means for outputting only one of said first and second pulse signals in response to a result of detection by said polarity detecting means, said drive circuit driving said load in response to an output of said second gate means.

7. The drive circuit according to claim 5, wherein said predetermined time is set to a value approximately twice a delay time of each of said first and second delay means.

6. A pulse-width-modulation drive circuit which produces a pulse signal with a pulse width which is dependent on a level of a drive signal and which drives a load by switching a current through said load on and off in response to the pulse signal so produced, said drive circuit comprising:

a power load drive circuit coupled directly to said load, triangular wave generating means for generating two triangular signals having substantially equal peak values and which are opposite to each other in phase, a comparator circuit receiving said two triangular signals of opposite phases as upper and lower reference inputs, respectively, and receiving said drive signal as a comparison input, first and second gate means for producing first and second pulse signals in response to an output of said comparator circuit, said first and second pulse signals corresponding to two respective directions in which said load is to be driven, and first and second inhibiting means for inhibiting supply of said delayed first and second pulse signals from said first and second delay means to said load drive circuit during a time interval between generation of said first and second pulse signals and a point a predetermined time after disappearance of said first and second pulse signals.

8. In a pulse-width-modulation drive circuit which produces a pulse signal with a pulse width dependent on a level of a drive signal and which drives a load by switching a current through said load on and off in response to the pulse signal so produced, the improvement wherein said drive circuit comprises:

triangular wave generating means for generating two triangular signals which have substantially equal peak values and which are opposite to each other in phase, and a first comparator circuit receiving said triangular signals of opposite phases as upper and lower reference inputs, respectively, and receiving said drive signal as a comparison input, said triangular wave generating means comprising a first constant-current source, a second constant-current source connected in series with said first constant-current source and producing twice the amount of current as that produced by said first constant-current source, charge-storing means connected between a common junction of said first and second constant-current sources and a reference potential point, a second comparator circuit for monitoring an output level of said charge-storing means, control means for selectively activating and deactivating said second constant-current source in response to an output of said second comparator circuit, current value setting means for setting amounts of constant current produced by said first and second constant-current sources, said current value setting means controlling said amounts of constant current of said first and second constant-current sources in accordance with a variation in a supply voltage, and means for providing as a comparison reference level for said second comparator circuit a voltage determined by division of said supply voltage, said two triangular signals of opposite phases being outputting in response to an output signal from said charge-storing means.

9. A triangular wave generator circuit comprising:

a first constant-current source, a second constant-current source connected in series with said first constant-current source and supplying twice the amount of current as said first constant-current source, charge-storing means connected between a common junction of said first and second constant-current sources and a reference potential point, a comparator circuit for monitoring an output level of said charge-storing means, and control means for activating said second constant-current source in response to an output of said comparator circuit, an output signal of said charge-storing means being produced as a triangular signal.

11. The device circuit according to claim 9, wherein said triangular wave generator circuit comprises a constant-current source, a second constant-current source connected in series with said first constant-current source and which supplies twice the amount of current as said first constant-current source, charge-storing means connected between a common junction of said first and second constant-current sources and a reference potential point, a second comparator circuit for monitoring an output level of said charge-storing means, and control means for selectively activating and deactivating said second constant-current source in response to an output of said comparator circuit, a comparison reference level of said second comparator circuit serving as a circuit reference level of said triangular wave generator.

10. In a pulse-width-modulation drive circuit operated from a supply voltage, said drive circuit producing a pulse signal having a pulse width dependent on a signal level of a drive signal and driving a load by switching a current through said load on and off in response to said pulse signal, the improvement wherein said drive circuit comprises:

a triangular wave generator circuit for generating two triangular signals having substantially equal peak values and which are opposite to each other in phase, and a first comparator circuit receiving said two triangular signals of opposite phases as upper and lower reference inputs, respectively, and receiving said drive signal as a comparison input, a circuit reference level of said triangular wave generator circuit and a d.c. bias level of said drive signal being set to values determined by division of said supply voltage.

12. In a pulse-width-modulation drive circuit for use with a motor which includes pulse generating means for generating a pulse signal having a pulse width dependent on a signal level of a drive signal, said motor being driven by switching a current through said motor on and off in response to said pulse signal, the improvement wherein said pulse generating means comprises:

triangular wave generating means for generating two triangular signals which have substantially equal peak values and which are opposite to each other in phase, a first comparator circuit comprising a pair of comparators receiving said triangular signals of opposite phases on their noninverting inputs and said drive signal shifted from a center level of each triangular signal by a predetermined positive level on their inverting inputs, and a second comparator circuit comprising a pair of comparators receiving said triangular signals of opposite phases on their inverting inputs and said drive signal shifted from a center level of each triangular signal by a predetermined negative level on their noninverting inputs, said drive circuit producing said pulse signal in response to outputs of said first and second comparator circuits, and means for setting said predetermined positive and negative levels in accordance with values determined by division of said supply voltage.

13. In a pulse-width modulation drive circuit which includes a first pair of transistors connected in series with a load between a power supply and ground and each of which is actuated to supply said load with a drive current in a forward direction, and a second pair of transistors connected in series with said load between said power supply and ground and each of which is actuated to supply said load with a drive current in a reverse direction, a two of said first and second pairs of transistors which are on a power supply side being npn transistors, and said load being driven by switching a current through said load on and off in response to a pulse signal having a pulse width which is dependent on a signal level of said drive signal, the improvement wherein said pulse-width modulation drive circuit further comprises:

triangular wave generating means for generating two triangular signals which have substantially equal peak values and which are opposite to each other in phase, a comparator circuit receiving said two triangular signals of opposite phases as upper and lower reference inputs, respectively, and said drive signal as a comparison input, means for producing in response to an output from said comparator first and second output pulse signals corresponding to two directions in which said load is to be driven, polarity determining means for determining a polarity of said drive signal with respect to a signal reference level, and first and second unidirectional elements for absorbing reverse electromotive force, one of said unidirectional elements being connected between one terminal of said load and ground and the other being connected between the other terminal of said load and ground, said two of said first and second pairs of transistors which are on said power supply side being driven by said first and second pulse signals, and a two of said first and second pairs of transistors which are on a ground side being driven by a decision output from said polarity determining means.

14. The drive circuit according to claim 13, wherein said first and second unidirectional elements are Schottky diodes.