Filtering and voltage raising circuit for connection between...

Details Filtering and voltage raising circuit for connection between... Filtering and voltage raising circuit for connection between...

2000-06-14

2001-11-13

Tso, Edward H. (Department: 2838)

Electricity: battery or capacitor charging or discharging

One cell or battery charges another

Vehicle battery charging

C320S165000

Reexamination Certificate

active

06316907

ABSTRACT:

TECHNICAL FIELD
The present invention relates to a circuit for connection between the supply terminals of a car radio and a motor-vehicle battery, that provides a filtering and protection function and selectively a voltage raising function.
BACKGROUND OF THE INVENTION
As used herein, the term battery is intended to define the source of direct-current electrical energy of a motor vehicle, comprising recharging and stabilizing circuits in addition to the actual battery. The term car radio relates not only to a radio receiver but also to any electronic apparatus, supplied by the battery, for reproducing sound or for other uses.
As is known when the engine of the motor-vehicle is started, and also during normal operation of the motor vehicle, the direct voltage generated by the battery is subject to interference, such as reductions in level and pulsed positive and negative transients, which may cause malfunctioning or even breakdown of electronic devices connected to the battery. In the case of a car radio, a reduction in level below a minimum permitted voltage may cause the apparatus to switch off, and pulsed transients may cause annoying noises to be emitted by the loud speakers.
It is also known that incorrect connection of the battery (reversal of polarity) can cause serious damage to the apparatus supplied by the battery.
To limit interference, a filter is usually used in the circuit connecting the car radio to the battery. To prevent damage due to accidental reversal of the battery polarity, suitable protection means are used in the connection circuit. A typical connection circuit comprising a filter and a Protection device is shown in FIG.
1
. The circuit, indicated by the reference number
10
in the drawing, is interposed between a battery
11
and a car radio
12
and is normally located physically in the container that houses the car radio. The circuit is constituted by an LC filter and by a power diode. The LC filter in this example is a two-pole, low-pass filter and is formed by an inductor L in series, that is, connected between the positive pole of the battery
11
and a supply terminal of the car radio
12
, and by a capacitor C in parallel with the car radio supply terminals. The diode, indicated Dp, is also connected in parallel with the car radio supply terminals, more precisely, for reverse conduction, that is, with its anode connected to the terminal of the circuit that is to be connected to the negative pole of the battery, so that the diode conducts only when the battery is connected with reversed polarity. A fuse
13
, which intervenes and interrupts the supply in the event of overloading, is normally provided between the positive pole of the battery
12
and the connection circuit
10
.
It is known that, in order to increase the output power of the car radio or of other apparatus supplied by the motor-vehicle battery, it is possible to use a voltage raising circuit as described, for example, in Italian patent application No. MI99A000257 filed by the Applicant herein on Feb. 10th 1999. When necessary, this circuit is connected between the filtering and protection circuit
10
and the supply terminals of the apparatus.
The known filtering and protection circuit
10
of
FIG. 1
has some disadvantages, as a result of which it is not always reliable and effective in use. In particular, if the battery is connected with reversed polarity, the voltage drop in the diode is quite high, for example 2 V, so that, between the supply terminals of the car radio, there will be a negative voltage (−2 V), which may damage the apparatus before the fuse intervenes and interrupts the connection to the battery. Moreover, a negative transient in the battery voltage Vbatt is translated, at the output of the filter, into a voltage Vfil with oscillations of considerable amplitude that are also potentially damaging to the apparatus. For example, as is shown in the graph of
FIG. 3
, relating to an apparatus that absorbs a current of 2A, a transient of the battery voltage Vbatt which starts at 14 V, falls to 0 V and rises again to 18 V before returning to 14 V brings about a ripple of the filter output voltage Vfil, which goes from −0.7 V to 26 V.
SUMMARY OF THE INVENTION
In accordance with the disclosed embodiments of the present invention, a circuit for connection between a car radio and a motor-vehicle battery that contains a filtering and protection circuit that is reliable and effective in all applications is provided.
In accordance with another aspect of the invention, a circuit for connection between a car radio and a motor-vehicle battery that performs filtering and protection functions together with a voltage-raising function is provided.
The circuit includes, in one embodiment, an inductor coupled in series with a supply terminal of an electronic accessory, a capacitor in parallel with the supply terminals of the accessory, and a diode connected in series with the inductor and configured to protect the accessory against reversal of polarity from an electrical energy source, such as a battery.
In accordance with another aspect of the invention, an accessory circuit for motor vehicles is provided, including a source of direct current electrical energy; an electronic accessory; and a circuit coupled to the electrical energy source and the electronic accessory for filtering electrical energy supplied to the electronic accessory and for protecting the electronic accessory from current reversal.
In accordance with another aspect of the foregoing embodiment, the circuit includes an anti-interference filter constituted by an inductor in series with one of the supply terminals of the electronic accessory, a capacitor connected in parallel with the supply terminals of the electronic accessory, and a diode connected in series with an inductor and configured for protection against reversal of the polarity of the battery.
In accordance with yet another aspect of the foregoing embodiment, the circuit may also include an electronic switch coupled between the node of the connection of the inductor to the diode and the other supply terminal on the electronic accessory. Ideally, a circuit for controlling the switching of the electronic switch is provided such that a voltage raising function is provided utilizing the capacitive and inductive components of the anti-interference filter.


REFERENCES:
patent: 4720668 (1988-01-01), Lee et al.
patent: 5110534 (1992-05-01), Yamaguchi
patent: 5514935 (1996-05-01), Oda et al.
patent: 5668466 (1997-09-01), Vinciarelli et al.
patent: 5724237 (1998-03-01), Hunter
patent: 41 24 616 A1 (1993-01-01), None
patent: 44 00 093 A1 (1994-07-01), None
patent: 195 01 985 A1 (1998-02-01), None

Affiliated with

Also associated with

Rating

Filtering and voltage raising circuit for connection between... does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Filtering and voltage raising circuit for connection between..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Filtering and voltage raising circuit for connection between... will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2609197