MXPA99000583A - Voltage regulator for oscillation - Google Patents

Abstract

A voltage regulator for oscillator includes a device of substantially constant voltage in series with the divider resistors of the polarization network to reduce the current flow and provide a substantially constant voltage drop, and an impedance connected between the first and second residences of the divider resistors and the tank circuit and the base of the amplifier transistor to reduce the load on the tank circuit and to improve the stability, reduce the phase noise, and increase the power output from the amplifier. The use of a silicon PN junction and an NPN transistor provides temperature compensation for hot and cold environments to allow the oscillator to work with a substantially constant feed current.

Description

OSCILLATOR VOLTAGE REGULATOR Field of the Invention This invention relates to a voltage regulator that is particularly suitable for use with a relatively small DC battery voltage to provide a power supply for an oscillator, and has particular application in cellular applications. or portable wireless communication, that is, people search engines, where the depletion of batteries is critical.

BACKGROUND OF THE INVENTION A voltage regulator for oscillator hitherto provided for cellular or portable wireless communication applications used large direct current (DC) batteries such as 3-9 volts. The oscillator had a tank circuit connected to an amplifier, typically an NPN transistor that has a base emitter and collector with a reducing and load resistance connected between the emitter and the ground. Two polarizing network voltage divider resistors were connected between the polarization supply voltage terminal and the ground. There was a direct connection between the junction between the voltage divider resistors and the base of the transistor and the tank circuit. There are two problems when the voltages of the polarization source are reduced from voltages greater than 1.5 volts in the voltage regulator of the prior art before de-storing. 1) a large polarizing current results in waste of power in the polarization resistors and 2) due to the voltage and the currents involved the impedance to ground at the junction between the divider resistors is very low and as a consequence of this they charge the radio frequency voltages (RF) from the tuned circuit, that is, the Q that results in power losses and degraded phase nois abated.

The U.S. Patent No. 4,621, 241 to K discloses an electronic oscillator of the type to which the present voltage regulator can be applied and this description is incorporated herein by reference. The U.S. Patent No. 4,009,454 to Darrow, discloses a circuit for providing a constant amplitude signal generator for DC supply to an oscillator. The U.S. Patent No. 5,001, 373 of Bator et al. describes the use of a Zener diode in a control circuit to prevent the generation of excessive no OBJECTIVES OF THE INVENTION A voltage regulator is described for supplying an oscillator, which is particularly suitable for operating an oscillator with a voltage source or an unregulated 1-1.5 volt DC battery. The voltage regulator circuit of the present invention adds a substantially constant voltage device in the form of a silicon diode with PN junction in series with the polarizing network voltage divider resistors. The voltage across the silicon diode is relatively constant (0.4-0.7 volts) at a very low current and comfortably independent of the voltage of the polarization source and therefore works as a comfortably stable reference to help in establishing the bias voltage base in conjunction with the voltage divider resistors to the supply voltage. Since the voltage across the diode and the voltage across the base of the transistor both change in harmony (both silicon PN junctions) with the temperature, an important compensation is made to keep the collector current more constant with the temperature. An impedance, preferably a resistance, is connected between the junction of the voltage divider resistors and the base of the transistor and the tank circuit. This impedance ra the impedance of the polarizing network to reduce the load on the tuned circuit. Typically the practice of stable polarization does not allow a resistance in this position due to considerations of thermal runaway and voltage drop. However, since the polarization current in a real low-power oscillator is very small, the oscillator is not adversely affected by conventional considerations and this added impedance performs greatly to improve stability, reduce phase no and improve the output power while allowing significant temperature compensation to be carried out as mentioned above.

BRIEF DESCRIPTION OF THE DRAWINGS Details of the invention are described in connection with the accompanying drawings, in which similar parts bear similar reference numerals, and wherein: Figure 1 is an electrical circuit diagram of the voltage regulator for a oscillator that embodies the characteristics of the present invention.

Detailed Description of the Invention Referring now to the drawing, a voltage regulator for an oscillator including a resonant, tuned tank circuit, T connected to a signal amplifier A and an output terminal O is shown. A voltage of a supply voltage 10 it has a voltage source terminal VS connected through the primary winding T1 of a coupling transformer X to the collector of the amplifier A. The transformer shown has a second winding T2 connected to the output terminal O. The tank circuit T can be a tank circuit tuned, in series or parallel, and is shown as having a terminal VT of DC voltage tuning input since the oscillator can be a fixed oscillator or a voltage controlled oscillator. The oscillator has capacitors C3 and C4 connected in series, one with the other, between the circuit T and earth, a capacitor C6 connected between terminal 2 and circuit T and a reactance in the form of a capacitor C5 connected between the emitter and between capacitors C3 and C4. The function of these capacitors is described in my U.S. Patent. No. 4,621, 241 mentioned above.

Briefly, in the operation of the oscillator the amplifier overcomes the losses to maintain the oscillations in the tank circuit. The amplifier has an input and an output and the amplifier amplifies a signal in a power output path and provides a feedback signal from its output, feedback signal that is fed back to the input via a part of the tank circuit. The capacitor C5 maintains the phase change of the feedback signal between the input 2 and the feedback output 3 of the amplifier by practically zero degrees. Another suitable oscillator would be the standard Colpitts oscillator, which has no impedance C5 but rather a direct connection instead of C5. A shock coil L is shown connected in series with a CD stabilizing resistor R4 and this series circuit also functions as a feedback phase change impedance. This shock coil L increases efficiency but could be eliminated to reduce costs. A first series circuit is connected between the terminal VS of the supply voltage and ground, which includes a first voltage divider or polarization resistor R1, a second resistor R2 voltage divider or polarization; and a substantially constant voltage device in the form of a silicon diode D1 having a selected resistance that reduces the current flow in the first series circuit while providing a substantially constant voltage across the device. An appropriate device for diode D1 is a conventional, non-linear, computing switching diode having a substantially constant terminal voltage, independent of current. A bypass capacitor CA is shown connected between the terminal VS and earth and a bypass capacitor CB is shown connected through diode D1. These capacitors are optional. An impedance, preferably a resistor, R3 is connected between a junction designated 1 between the voltage divider resistors ppmera and second and a junction designated 2 between the tank circuit T and the base of the amplifier A to increase the RF impedance between earth and the base of the amplifier. Current 11 is drawn through the first voltage divider resistor R1 and branched to provide 12, which flows through R2 and D1 to provide a constant voltage across the terminals of D1 relatively independently of the voltage of VS supply and to supply 13, which flows through the impedance R3 to provide the base bias current of the transistor. The current 14 of the main transistor or collector flows in response to the applied base current 12 to provide the desired amplifier / oscillator action, given by the equation: = 13 + G (I3) = 13 + 14 Circuit constants are usually calculated to provide the so-called amplifier class A or class AB transistor operating conditions by adding the resistor R3 as described to the G gain of the transistor DC current, where G is the gain of the transistor. CD transistor, typically 50 to 150. By adding the resistor R3 as described there is less RF current flow within and less RF power dissipated in the resistors R2 and R1 and this power is directed to the base of the transistor of the resistor. amplifier A. In essence the aggregate impedance R3 raises the RF impedance to ground at junction 2 and directs the RF power so that it is not lost or dissipated in the polarization network of resistors R3, R2 and R1, but rather well applied to the base of the transistor. This reduced load in the tank circuit improves stability and reduces phase noise as well as increases the power output from the amplifying transistor. The silicon diode D1 is a PN junction and the silicon transistor is an NPN junction. The voltage across the base of the transistor and the voltage across the diode Di change in harmony with the temperature to provide temperature compensation for hot and cold environments and allows the oscillator to work with a substantially constant collector current 14. Essentially, as the temperature changes the DC voltage through D1 and the base of the transistor changes by approximately -1.6 millivolts of CD per degree Celsius. To maintain collector current 14, the desired constant DC voltage applied to the base of the transistor at 2 must also change at the rate of -1.6 millivolts per degree centigrade. The DC voltage at 2 is derived as: V2 = VD1 + I2R2 - I3R3, where VD1 changes with temperature at -1.6 millivolts per degree centigrade. At small values of R2 and very small values of 13, V2 = VD1, and changes of the diode with temperature perform regulation / compensation important for the transistor. The circuit described above also provides regulation with changes in the supply voltage. From the relation V2 = VD we observe that since the supply voltage does not appear in this expression that V2 is relatively independent of VS and therefore the base bias voltage becomes largely independent of the supply voltage and VB is substantially regulated with changes in the supply voltage that result in a substantially more constant feed current. In summary, the circuit of the present invention provides a) bias voltage to the oscillator with low supply voltages (1-1.5 V DC batteries), b) temperature compensation for hot and cold environments, c) the previous two while the noise and power performance is improved, and d) reduces the bias current required by the voltage divider resistors. By way of illustration, but without limitation, the values of the circuit components found suitable for the previous circuit are: VS 1-1-5 V CD VD1 0.7 V CD R1 2.2 Kohm R2 2.7 Kohm R3 1.5 Kohm It is understood that the present invention is applicable to other oscillators including but not limited to the Hartley oscillator. Although the present invention has been described with some degree of particularity, it is understood that the present description has been made by way of example and that changes can be made in details of the structure without departing from the spirit of the same.

Claims (8)

1. Novelty of the Invention 1. A voltage regulator for an oscillator that includes a tuned tank circuit, connected to a signal amplifier having an output terminal, which comprises: a supply voltage terminal connected to said amplifier, a first serial circuit connected between said voltage and ground terminal including a first voltage divider resistor, a second voltage divider resistor and a relatively constant voltage device having a resistance selected to reduce the current flow in said first circuit in series and which provides a substantially constant voltage through said device, an impedance connected between a junction between said first and second resistors and a junction between said tank circuit and said amplifier to increase the impedance between said voltage terminal and said amplifier and to reduce the load on the tank circuit to improve the stability, reduce the phase noise and improve the output power from said amplifier, whereby a bias current is drawn through said first resistance and said impedance and a main current from said terminal towards said amplifier makes possible a Relatively constant reference voltage across the device to provide the bias voltage applied to said amplifier, which allows said oscillator to work with substantially constant current with temperature changes and to provide substantially constant feed current to the amplifier for a range of voltages of food.
2. 2. A voltage regulator according to claim 1, wherein a battery of approximately 1-1.5 V DC, unregulated, is connected to said terminal.
3. 3. A voltage regulator according to claim 2, wherein the voltage drop across said device is about 0.7V DC.
4. 4. A voltage regulator according to claim 2, wherein the value of said first resistance is approximately 2.2 Kohms, said second resistance of approximately 2.7 Kohms and said impedance of approximately 1.5 Kohms.
5. 5. A voltage regulator according to claim 1, wherein said device is a silicon diode.
6. 6. A voltage regulator according to claim 1, wherein said signal amplifier is a silicon NPN transistor having a base, emitter and collector, and said device is a PN junction of silicon, said transistor and diode changing both in harmony to provide temperature compensation for hot and cold environments.
7. 7. A voltage regulator for an oscillator that includes a resonant tank circuit, tuned, connected to an NPN silicon transistor having a base, emitter and collector with an inductor and stabilizing resistance connected between said emitter and ground and having an output terminal, said regulator comprising: a supply voltage terminal connected to said manifold, a first series circuit connected between said voltage and ground terminal including a first voltage divider resistor, a second voltage divider resistor and a diode with silicon PN junction to reduce the flow of current in said first circuit in series and providing a substantially constant voltage through said diode, a third resistor connected between a junction between said first and second resistors and a junction between said tank circuit and said base to increase the resistance between said voltage terminal and said base to reduce the charging on the tank circuit to improve stability, reduce phase noise and improve the output power at said output terminal, whereby a bias current is drawn through said first resistance and said third resistance and a main current or from collector from said voltage terminal to said amplifier makes possible a small voltage through said diode with a bias voltage applied to said amplifier, which allows said oscillator to work with substantially constant collector current to provide a substantially constant collector current with temperature changes for a range of supply voltages.
8. 8. A voltage regulator according to claim 7, wherein the voltage across said diode and the voltage across the base of said transistor changes in harmony with the temperature to maintain the current in said collector at a substantially constant level. Excerpt from the Description A voltage regulator for oscillator includes a device of substantially constant voltage in series with the divider resistors of the polarization network to reduce the current flow and provide a substantially constant voltage drop, and a connected impedance between the first and second resistors of the divider resistors and the tank circuit and the base of the amplifier transistor to reduce the load on the tank circuit and to improve the stability, reduce the phase noise, and increase the power output from the amplifier. The use of a silicon PN junction and an NPN transistor provides temperature compensation for hot and cold environments to allow the oscillator to work with a substantially constant feed current.