Voltage multiplier and driver circuit

• US 4,291,369 A
• Filed: 09/19/1979
• Issued: 09/22/1981
• Est. Priority Date: 09/19/1979
• Status: Expired due to Term

• Current Assignee: Timex Corporation (Tanager Group BV)
• Original Assignee: Timex Corporation (Tanager Group BV)
• Inventors: Hochstrate, Paul E.
• Primary Examiner(s): Shoop, William M.
• Application Number:
  US06/077,258
• Time in Patent Office: 734 Days
• Field of Search: 363/60
• US Class Current: 363/60
• CPC Class Codes: G04G 19/04 Capacitive voltage division or multiplication
• CPC Class Codes: H02M 3/07 using capacitors charged and discharged alternately by semiconductor devices with control electrode , e.g. charge pumps

Abstract

A voltage multiplier and driver circuit for energizing a backlight or lamp device in a timepiece. The circuit includes switching transistors responsive to an alternating signal for alternately disconnecting the lamp (load) while a capacitor is connected across a DC voltage source and for reconnecting the lamp (load) across a series (voltage additive) connection of the DC voltage source and the charged capacitor. The alternating signal frequency and duty cycle are selected to energize the lamp (load) to a predetermined color temperature.

Claims

1. A voltage multiplier and driver circuit energized by a DC supply voltage source comprising:

means for providing an alternating control signal;

first and second switch means connected in series across the DC supply voltage source each being responsive to the alternating control signal for alternately connecting first and second terminals of the DC supply voltage source to the connection between said first and second switch means defining a junction;

a capacitor connected between a first terminal for a load device to be energized and the common junction between said first and second switch means;

third switch means connected between the first terminal of the DC supply voltage source and a second junction between the capacitor and the first terminal for a load device and responsive to said control signal for periodically connecting the first terminal of the DC supply voltage to said second junction; and

fourth switch means connected between the second terminal of the DC supply voltage source and a second terminal for a load device and responsive to said control signal for periodically connecting the second terminal for a load device to the second terminal of the DC supply voltage source;

whereby during each alternate half cycle of the alternating control signal the second and third switch means are rendered conductive to connect the capacitor in parallel circuit relationship across the DC supply voltage source and thereby charge the capacitor to the voltage of the supply voltage source with the first and fourth switch means being maintained off, and during the remaining alternate half cyles of the control signal the first and fourth switch means are rendered conductive with the second and third switch means turned off to thereby connect the DC supply voltage source and the capacitor in its charged state in series circuit aiding relationship across the load device terminals.

2. A voltage multiplier and driver circuit as in claim 1, wherein:

the first switch means is connected between the first terminal of the DC supply voltage source and the second switch means; and

the first terminal is the positive terminal and the second terminal is the negative terminal of the DC supply voltage source.

3. A voltage multiplier and drive circuit as in claim 2, wherein:

the control signal is an alternating square wave signal having a logic "1" and a logic "0" signal portion.

4. A voltage multiplier and drive circuit as in claim 3, wherein:

the first and third switch means are PNP type transistors and the second and fourth switch means are NPN type transistors.

5. A circuit comprising:

a DC supply voltage source having a positive and a negative terminal;

a first, second, third and fourth transistor each having a pair of principal conduction electrodes and a control electrode;

the first transistor having one of its principal conduction electrodes connected to the positive terminal and its other principal conduction electrode connected to one side of a capacitor defining a junction therewith;

the second transistor having one of its principal conduction electrodes connected to the negative terminal and its other principal conduction electrode connected to the junction;

the third transistor has one of its principal conduction electrodes connected to the positive terminal and its other principal conduction electrode connected to the other end of said capacitor defining a first output terminal;

a fourth transistor has one of its principal conduction electrodes connected to the negative terminal and its other principal conduction electrode defining a second output terminal;

means for connecting a load device between said first and second output terminals;

a first resistor connected between the control electrode of the third transistor and the junction;

a second resistor connected between the control electrode of the fourth transistor and the junction; and

means providing a control signal to the control electrodes of the first and second transistors for alternately switching on and off said first and fourth transistors while switching off and on said second and third transistors, and vice versa.

6. A circuit as in claim 5, wherein:

the first and third transistors are of the PNP type;

the second and fourth transistors are of NPN type; and

the control signal alternates between positive and negative voltage values.

7. In combination:

a DC supply voltage source having a first and second terminal;

means providing an alternating control signal;

first, second, third, fourth, fifth and sixth transistors each having a pair of principal conduction electrodes and a control electrode,

the fifth and sixth transistors being of different conductivity types and each have the control electrode thereof coupled to said means providing an alternating control signal;

said fifth transistor having one principal conduction electrode connected to the first terminal of the DC supply voltage source and its other principal conduction electrode connected to a first junction defined by a connection of one end of a third resistor to one end of a fourth resistor, the other end of said third resistor being connected to said second terminal of the DC supply voltage source, and the other end of said fourth resistor being connected to the control electrode of said second transistor,

said sixth transistor having one principal conduction electrode connected to the second terminal of the DC supply voltage source and its other principal conduction electrode connected to a second junction defined by a connection of one end of a fifth resistor to one end of a sixth resistor, the other end of said fifth resistor being connected to said first terminal of the DC supply voltage source, and the other end of said sixth resistor being connected to the control electrode of said first transistor,

said first transistor having one principal conduction electrode connected to the first terminal of the DC supply voltage source and its other principal conduction electrode connected to a third junction defined by the connection of one side of a capacitor and the juncture of a first and second resistor connected in series circuit relationship between the control electrodes of the third and fourth transistors,

said second transistor being of opposite conductivity type from said first transistor and having one principal conduction electrode connected to the second terminal of the DC supply voltage source and its other principal conduction electrode connected to said third junction,

said third transistor having one principal conduction electrode connected to the first terminal of the DC supply voltage source, its other principal conduction electrode connected to the other side of said capacitor to define a first output terminal at the point of interconnection, and its control electrode being connected to one end of said first resistor,

said fourth transistor having one principal conduction electrode connected to the second terminal of the DC supply voltage source, its other principal conduction electrode defining a second output terminal, and its control electrode being connected to one end of said second resistor; and

illumination means connected across said first and second output terminals for emitting light in response to an output voltage developed across said first and second output terminals.

8. The combination as in claim 7, wherein:

the first and second terminals are a positive and a negative voltage terminal respectively of a direct current supply voltage source between approximately 1.5 volts to 5 volts;

the second, fourth and fifth transistors are NPN type transistors;

the first, third and sixth transistors are PNP type transistors;

the control signal is an alternating square wave having a frequency between 200 HZ and 2 KHZ.