Electricity: power supply or regulation systems – Output level responsive – Using a three or more terminal semiconductive device as the...
Reexamination Certificate
2001-08-27
2002-11-26
Sterrett, Jeffrey (Department: 2838)
Electricity: power supply or regulation systems
Output level responsive
Using a three or more terminal semiconductive device as the...
C323S274000, C323S284000
Reexamination Certificate
active
06486643
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field
The present invention relates generally to H-bridge systems and methods for driving electric loads, and more particularly to high-efficiency H-bridge regulating circuits and methods for driving an electric load such as a thermoelectric cooler (TEC) by using a linear amplifier to drive one end of the load and a switching amplifier to drive the other end of the load.
2. Discussion
In virtually every modern fiber-optic network, there are lasers and TECs. The TECs are required since the laser outputs are highly sensitive to temperature fluctuations. Therefore, at every point in the network where there is a laser beam generating device, such as a laser diode, or where there is a component which has the possibility of undesirable thermal expansion that would adversely impact performance of the network, a thermoelectric cooler is typically employed. For example, in the typical fiber-optic cable system, there may be dozens of laser beams which are all focused together onto a single optical fiber. In addition, a single cable may have several optical fibers running in it. At the locations where these multiple beams come together and are focused into one or several optical fibers in a single cable, there typically is also one or more thermoelectric coolers. These TECs are used to stabilize the temperature of the laser diodes and of other temperature-sensitive components. In addition, the fiber-optic cables may run for a few kilometers, or dozens, hundreds or thousands of kilometers. Because of optical beam attenuation by the fiber, repeater optical amplifiers are used to reamplify the optical beam and send it on its way along the optical fiber cable. Each repeater amplifier includes at least one diode laser as an optical power source and typically utilizes at least one TEC.
In various optical fiber cable installations, there are typically multiple diode lasers which generate the laser beams. To ensure highly stable operation, the each of the laser diodes is rigorously temperature-controlled, typically by a closed-loop controller having a TEC which has a thermistor or other heat-sensing device mounted on it. Some systems rely on sensing the wavelength of the laser beam for sensing and stabilizing the laser diode temperature.
As is well-known, to operate the TECs for the purpose of stabilizing the temperature with any precision requires a power control circuit to regulate the direction and magnitude of the electric current applied across the TEC. The control portion of the overall circuit, not including the power amplifiers to which the TEC is connected, may be very small and draw very little power. But typical maximum power requirements for driving a TEC in applications such as stabilizing the temperature of diode lasers, depending on the size of the TEC, are 1 amp at 2 volts (which equals 2 watts), 2.5 amps at 2.5 volts (which equals 7.5 watts), or 3.5 amps at 3.5 volts (which equals 12.25 watts).
As is well-known, TECs are solid-state heat pumps. They are usually configured as relatively small flat box-like devices and operate when a DC current is passed through the Peltier elements in them. They typically are two-wire devices that have two flat ceramic plates (e.g., top and bottom sides) which serve as the heat sinks, with Peltier elements sandwiched therebetween. Typically, one plate or side is used as the temperature-stabilized side, on which a device, such as a laser diode, is mounted. That side is normally called the cold side, since heat from this side is usually being removed by the TEC. In some cases, like a cold start-up or where the set point is above the ambient temperature, heat may be pumped to this side by the TEC. A TEC transfers heat from one plate or side to the other, using the Peltier effect, with the direction of heat transfer being dependent upon the direction of the current. So, TECs can be used for heating or cooling and the magnitude of the current controls the amount of heat transfer.
Solid-state devices, like thermistors, mounted to one side of the TEC, provide a reliable indication of temperature and/or temperature variation on that side. The other plate or side to which heat is dumped (the heated plate) typically does not need to be controlled—often the heat is simply dumped into the environment. When using thermistors as a temperature feedback device, conventional power control circuits for TEC units can stabilize temperature on the cold side or plate of the TEC to about ±0.0001 degree C. relative stability to a set-point temperature. The relative stability of the temperature required is often ±0.1° C. to ±1° C. for the laser diodes used in fiber optic network applications. In some other cases, such as diode pumped lasers, the temperature stability required may be ±0.01° C. or even ±0.001° C. The size of TECs can be from 1 millimeter (mm) by 2 mm to 90 mm by 90 or more, with the height being from 2 mm to 6 mm or more. The size of the TECs often used in fiber-optic network applications typically varies from about 2 millimeters (mm) by 2 mm up to about 20 mm by 20 mm, with the height of the TECs typically being in the range of 2.5 mm to about 5 mm.
It is common today to use reasonably precise linear amplifiers to operate or drive TECs. Such linear mode TEC controllers are of low efficiency, often 20% to 40% efficient at most. The other 80% to 60% of the power applied to the linear amplifier drivers becomes waste heat which must be dumped to the ambient environment or otherwise removed. When many of these low efficiency TEC controllers are used in a single location, such as within a small enclosure, it is like having many multi-watt light bulbs burning inside that enclosure. This heat load in turn must be removed by appropriate types of heat removal systems, including fans, air-cooled or liquid-cooled heat sinks and/or air conditioning systems. These heat removal systems are an integral part of, and add significantly to the electric utility costs of operating, fiber-optic network equipment. Further, individual hot spots within such TEC-laden controller enclosures are another source of problems. The hot spots occur more often when the TECs are deployed in stacked configurations, since one TEC often transfers its heat to another TEC in the stack. Further, excess heat generally contributes to with long-term temperature stability problems. As is well known, the performance of the power supplies and/or control circuits can degrade due to excess heat over long periods of time, such as three to five or more years, which reduces fiber-optic network stability and/or performance.
Linear mode amplifiers have long been known to have the two major related drawbacks, namely low efficiency and the generation of unwanted heat, which, as noted, can induce long-term stability problems. But, linear mode amplifiers have long been recognized as having their benefits as well, including low cost due to a small number of required components, and very low noise production since they operate linearly.
Another benefit is that linear amplifiers take up less printed circuit board space, because they use a fewer number of components, and because the components used are typically smaller in size. For example, virtually all switch mode amplifiers have at least one big inductor and at least one big filter capacitor, while linear mode amplifiers normally do not. In the switching amplifiers, the filter capacitor is used to attenuate noise spikes generated by the switching actions of the output circuit, which generates large ripple currents in the output inductor. A well-known benefit of switch mode amplifiers is that they have high efficiency, which the linear amplifiers simply do not have since they typically are operated in their linear region.
In the telecommunications industry, network reliability is a very important characteristic which is much sought after. As more and more communications traffic and data flow across fiber-optic networks, the desire for long-term reliability has increased. Two of the main pr
Analog Technologies, Inc.
Cantor & Colburn LLP
Nolan Robert S.
Sterrett Jeffrey
LandOfFree
High-efficiency H-bridge circuit using switched and linear... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with High-efficiency H-bridge circuit using switched and linear..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and High-efficiency H-bridge circuit using switched and linear... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2982569