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Notification will be sent to this e-mail address. Cancel Save. Product name:. Manufacturer Brand :. During normal operation, each negative edge of output turns off Q 7 of watchdog , for the period set by the IC time constant of capacitor C 6 and the collector current of Q 5. This allows Q 8 to be momentarily turned on, which discharges C 5. Thus, these elements of watchdog circuit function as an edge-triggered monostable. Capacitor C 5 , which functions as a timing capacitor, is then charged by current source Q 6.
Thus, after each negative edge of oscillator output , capacitor C 5 begins to charge up from a discharged state, at a constant rate, as shown by the upwardly-rising portions of waveform Watchdog circuit is configured so that if C 5 is not discharged again within a sufficient time period it will rise above a threshold voltage , thereby causing H bridge to be disabled by tristating its switching transistor s.
Thus, if no more oscillator pulses occur after the negative edge corresponding to time T 1 or if another negative edge does not occur within a sufficient time , then the voltage of C 5 will begin to rise after a short delay after T 1 , causing the voltage sensed by voltage follower Q 14 to exceed the threshold voltage set by the R 1 , R 2 , R 3 combination at time T 3. As will be appreciated, time T 3 is after the time T 2 at which another negative edge of output and the oscillator sync would occur if oscillator were operating normally.
Q 14 and the R 1 , R 2 , R 3 combination therefore help to form a voltage comparator. Exceeding this threshold voltage causes QQ 1 to be turned off and QQ 2 to be turned on, which in turn causes the base of Q 30 to go high, allowing current to flow therethrough to the "timeout" pin of watchdog at T 4 , a short time after T 3. This causes H bridge to be disabled, as described previously, thus the "output off" labeled state of waveform As will be understood by those skilled in the art, the IC time constant of C 5 and current source Q 6 is selected so that C 5 does not reach the turn off voltage of Q 14 before the next negative going edge of oscillator output discharges C 5 again.
The current flowing through the collector of Q 30 is mirrored by the Q 20 , Q 18 combination with sufficient current to overcome the Q 33 current source, thereby also causing the "reset" pin of watchdog to go high. This resets divide by two circuit , as described previously. As will be appreciated, the time between time T 1 and T 2 is a time period corresponding to a normal frequency. As will further be appreciated, watchdog comprises a frequency-to-voltage converter means whereby the voltage corresponding to the period of the oscillator signal and thus inversely related to the oscillator signal frequency will rise above a threshold voltage when the input signal's frequency falls below a corresponding threshold frequency, i.
During power on of watchdog circuit , the "inreg" pin is held high by voltage regulator , turning on Q 24 , which turns on QQ 4 , and prevents current from flowing through Q 19 , so that the voltage across C 4 remains low. When voltage regulator has reached its regulation supply voltage, the "inreg" pin goes low, allowing current to flow through Q 19 and keeping QQ 4 on.
The base current of Q 19 charges up C 4 until Q 29 saturates, removing the current from Q 19 and thus turning off QQ 4. The power on reset outputs QQ 4 collectors are hard-wire OR'd to the "reset" pin and the "timeout" pin. The QQ 4 collectors also provide the "start" pin output signal used to hold oscillator stopped, which can be useful when multiple oscillators are connected together, to cause them to start at the same time. Thus, as will be understood, while inreg is high, watchdog holds the start pin high, which effectively shorts the sync pin of oscillator to ground; holds the timeout signal high, which disables H bridge ; and holds the reset pin high, which resets divide by two circuit As will be understood and as described above, the present invention can be embodied in the form of methods and apparatuses for practicing those methods.
The present invention can also be embodied in the form of computer program code embodied in tangible media, such as floppy diskettes, CD-ROMs, hard drives, or any other computer-readable storage medium, wherein, when the computer program code is loaded into and executed by a computer, the computer becomes an apparatus for practicing the invention.
When implemented on a general-purpose microprocessor, the computer program code segments combine with the microprocessor to provide a unique device that operates analogous to Specific logic circuits. For example, the function of watchdog of circuit of FIG. It will be understood that various changes in the details, materials, and arrangements of the parts which have been described and illustrated above in order to explain the nature of this invention may be made by those skilled in the art without departing from the principle and scope of the invention as recited in the following claims.
All rights reserved. Login Sign up. Search Expert Search Quick Search. DC-AC converter protection. United States Patent A method and apparatus for protecting a DC-AC converter having a transformer. According to one embodiment, an oscillator generates a periodic signal having a frequency. Newlin, Trevor Livingston, GB6. Click for automatic bibliography generation. Download PDF What is claimed is: 1. An apparatus for protecting a DC-AC converter having a transformer, the apparatus comprising: a an oscillator means for generating a periodic signal having a frequency; b a switching means for switching an input voltage across a first winding of the transformer in accordance with the periodic signal; and c a watchdog means for disabling the switching means if the frequency falls below a threshold frequency, the watchdog means comprising: 1 a frequency to voltage converter means for converting the frequency to a voltage; 2 a comparator means for comparing the voltage to a reference voltage corresponding to the threshold frequency; and 3 means for disabling the switching means if the voltage rises above the threshold voltage.
The apparatus of claim 1, wherein means c 1 comprises a timing capacitor, a current source coupled to the timing capacitor for charging the timing capacitor, and discharge means coupled between the periodic signal of the oscillator means and the timing capacitor for discharging the timing capacitor when a transition of the periodic signal is received by the discharge means.
The apparatus of claim 1, wherein means c further comprises 4 means for enabling the switching means if the frequency rises above a second threshold frequency. The apparatus of claim 3, wherein means c 4 comprises means for enabling the switching means if the frequency rises above the second threshold frequency for more than a time out period.
The apparatus of claim 4, wherein the threshold frequency is equal to the second threshold frequency. Zinc has a high specific gravity, high rigidity, and low resonance, so a die-cast zinc panel can reduce distortion caused by vibration. Because components such as the power supply, VFD devices for the display, and the drive mechanism can cause noise in the signal, those components are externally positioned away from the audio signal. After the data from the disc goes through the kHz filter, it is processed by a Burr-Brown advanced segment bit DAC with superior dynamics and resistance to clock jitter.
When the DRZ plays a CD or other source, its display can be turned off to minimize interference from circuits that can otherwise degrade sound quality. The DRZ is truly an audiophile source unit. This power supply gives the DRZ both strength and precision, and its six-sided shielded casing repels noise even during high-load bursts.
To prevent even the smallest vibration, the power supply is wrapped in a die-cast aluminum casing and a copper plated chassis. A key part of the converter is a circuit called a delta-sigma modulator, which takes the binary signal 1s and 0s from the CD and changes them to a steady pulse, called a pulse train. The pulse train contains an average of the change in the amount of energy represented in the sample. A low-pass filter removes all time-domain information and recovers only the average energy of the pulse train that feeds it.
Feb 18, 2, 0 0. MrMatt said:. Nov 17, 3, 1 You might, in a quiet room with an excellent sound system. I have an external DAC on my laptop because the one it came with isn't great. I wouldn't bother for a car, though.
The road noise alone will probably eliminate any difference you'd hear. Apr 5, 11, Not everyone drives a dump truck. Sep 10, 7, 1 Leros said:. Last edited: Oct 20, BTA Senior member. Jun 7, 0 Infinity gear can hardly be considered great, or even good there are worse choices to be had, for sure
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