Shunt regulator for use with resonant input source

Details Shunt regulator for use with resonant input source Shunt regulator for use with resonant input source

1990-01-10

1991-09-03

Stephan, Steven L.

Electricity: power supply or regulation systems

In shunt with source or load

Using a three or more terminal semiconductive device

323220, G05F 1613

Patent

active

050457705

DESCRIPTION:

BRIEF SUMMARY
FIELD OF INVENTION

The present invention relates to the field of power regulation. More particularly, the invention relates to a regulator useful in apparatus intended to receive electrical power from an external, alternating magnetic field. Most particularly the invention relates to a regulator adapted for substantially total integration on a single VLSI "chip".
Examples of practical devices falling into the above categories would include baggage identification tags, personnel security badges, electronic locks and keys, remote-controlled actuators, and "smart" credit cards.


PRIOR ART

In apparatus adapted to receive power from an external magnetic field, a particular problem has been to compensate for variations in the field intensity at different points in space. This causes the apparatus to receive variable amounts of electrical power.
For such applications, the so-called "shunt" regulator configuration is usually preferred, for the following reasons:
a) The shunt regulator possesses inherent ability to control its input voltage. Regulators such as the "series" type can control only their output, while the input voltage may rise to dangerous levels. The series-type regulators are therefore not desirable when the regulator is to be included with the remainder of the required circuitry, on a single VLSI "chip", as such chips are highly susceptible to damage by over-voltages. The shunt regulator by comparison, operates by imposing an additional load on its power source, sufficient to prevent the input voltage from rising above the intended value.
b) When the power available is only just sufficient to permit operation of the device, it is desirable that the regulator circuit itself should consume a minimum of additional power. Series regulators generally consume significant amounts of power in their own operation, while a shunt regulator may consume almost no power, as the shunt element ("L" in FIG. 1) is essentially turned off.
Several prior-art shunt regulators have been disclosed.
U.S. Pat. No. 4,614,906 discloses the use of a shunt regulator to permit a plurality of loads to be connected across a single, high-voltage supply.
U.S. Pat. No. 4,103,219 discloses a DC supply, rather than a resonant, AC supply. Essentially it follows the known configuration of FIG. 1.
U.S. Pat. No. 3,551,745 discloses the addition of an over-voltage trip to a conventional shunt regulator.
U.S. Pat. No. 3,229,185 discloses an AC supply, although no resonant (it is a conventional transformer). It discloses means of improving the performance of the well-known Zener diode type of shunt regulator.
U.S. Pat. No. 3,141,124 discloses additional loads switched into a (untuned) transformer circuit by Silicon Controlled Rectifier devices. These latter regulators are unsuitable for implementation in VLSI chips.
The principal elements of a shunt regulator, according to prior art, are shown in FIG. 1.
The known shunt regulator consists of a DC power source, S, of uncertain voltage, connected through a resistance R, to output terminals, O, at which there is provided a stabilised voltage. The output voltage is sensed by the amplifier A, and compared to a known reference voltage, V, (developed by a zener diode, band-gap circuit, or the like). The amplifier develops an error voltage, proportional to the difference between the output and reference voltages. This error voltage serves to control the load L (which may take the form of a large transistor, or other power-absorbing device).
It can be seen that the current passing through R will be the sum of that delivered to the load at O, plus that drawn by the controlled load L. The controlling action is provided by adjusting the current through L so as to cause a voltage drop across R. This reduces the incoming voltage S to the desired output voltage, D.
Either the Output or Reference voltages may be attenuated by a resistive voltage divider circuit, before reaching the amplifier A, if desired.
It is apparent from the figure that all parts of the circuit, except the input resistor R, are subje

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