Showing posts with label 5. Show all posts
Showing posts with label 5. Show all posts
Sunday, October 5, 2014
5 Volt Regulated PSU Featuring Overvoltage Protection
Notes
The 5 volt regulated power supply for TTL and 74LS series integrated circuits, has to be very precise and tolerant of voltage transients. These ICs are easily damaged by short voltage spikes. A fuse will blow when its current rating is exceeded, but requires several hundred milliseconds to respond. This circuit will react in a few microseconds, triggered when the output voltage exceeds the limit of the zener diode.
This circuit uses the crowbar method, where a thyristor is employed and short circuits the supply, causing the fuse to blow. This will take place in a few microseconds or less, and so offers much greater protection than an ordinary fuse. If the output voltage exceed 5.6Volt, then the zener diode will conduct, switching on the thyristor (all in a few microseconds), the output voltage is therefore reduced to 0 volts and sensitive logic ICs will be saved. The fuse will still take a few hundred milliseconds to blow but this is not important now because the supply to the circuit is already at zero volts and no damage can be done. The dc input to the regulator needs to be a few volts higher than the regulator voltage. In the case of a 5v regulator, I would recommend a transformer with secondary voltage of 8-10volts ac.
The 5 volt regulated power supply for TTL and 74LS series integrated circuits, has to be very precise and tolerant of voltage transients. These ICs are easily damaged by short voltage spikes. A fuse will blow when its current rating is exceeded, but requires several hundred milliseconds to respond. This circuit will react in a few microseconds, triggered when the output voltage exceeds the limit of the zener diode.
This circuit uses the crowbar method, where a thyristor is employed and short circuits the supply, causing the fuse to blow. This will take place in a few microseconds or less, and so offers much greater protection than an ordinary fuse. If the output voltage exceed 5.6Volt, then the zener diode will conduct, switching on the thyristor (all in a few microseconds), the output voltage is therefore reduced to 0 volts and sensitive logic ICs will be saved. The fuse will still take a few hundred milliseconds to blow but this is not important now because the supply to the circuit is already at zero volts and no damage can be done. The dc input to the regulator needs to be a few volts higher than the regulator voltage. In the case of a 5v regulator, I would recommend a transformer with secondary voltage of 8-10volts ac.
Friday, October 3, 2014
5 volt and 12 volt Switching Regulator
Switching regulators is available in different circuit configurations including turnaround time, feed-forward, push-pull, and not iso lated a single terminal or one polarity types. In addition, switching regulators can operate in three modes - down, step-up or reverse polarity.
M 2575 a series developed by National Semiconductor regulators are monolithic IC that provide active functions to step down (again) change the regulator can handle the load A1A, with excellent line and load regulation. These devices are available in fixed output voltages of 3.3V, 5V, 12V, 15V and adjustable output version.
Requiring a minimum number of external components, these regulators are simple to use and include internal frequency compensation and a fixed frequency oscillator. LM 2575 series offers high-performance replacement for popular 3 terminal linear regulators. Substantially reduced the size of the heatsink, and in many cases no heat sink is required. Version sets the output voltage is illustrated in Fig.
The National Semiconductor LM 2577 1577/LM are monolithic integrated circuits that provide all the functions of power and control of step-up (boost), fly backward, forward and converter switching regulators. The device is available in three different output voltage: 12 V, 15 V and adjustable.
M 2575 a series developed by National Semiconductor regulators are monolithic IC that provide active functions to step down (again) change the regulator can handle the load A1A, with excellent line and load regulation. These devices are available in fixed output voltages of 3.3V, 5V, 12V, 15V and adjustable output version.
Requiring a minimum number of external components, these regulators are simple to use and include internal frequency compensation and a fixed frequency oscillator. LM 2575 series offers high-performance replacement for popular 3 terminal linear regulators. Substantially reduced the size of the heatsink, and in many cases no heat sink is required. Version sets the output voltage is illustrated in Fig.
The National Semiconductor LM 2577 1577/LM are monolithic integrated circuits that provide all the functions of power and control of step-up (boost), fly backward, forward and converter switching regulators. The device is available in three different output voltage: 12 V, 15 V and adjustable.
Monday, August 25, 2014
5 Volt Regulated PSU Featuring Overvoltage Protection
Notes
The 5 volt regulated power supply for TTL and 74LS series integrated diagram, has to be very precise and tolerant of voltage transients. These ICs are easily damaged by short voltage spikes. A fuse will blow when its current rating is exceeded, but requires several hundred milliseconds to respond. This schema will react in a few microseconds, triggered when the output voltage exceeds the limit of the zener diode.
This schema uses the crowbar method, where a thyristor is employed and short diagram the supply, causing the fuse to blow. This will take place in a few microseconds or less, and so offers much greater protection than an ordinary fuse. If the output voltage exceed 5.6Volt, then the zener diode will conduct, switching on the thyristor (all in a few microseconds), the output voltage is therefore reduced to 0 volts and sensitive logic ICs will be saved. The fuse will still take a few hundred milliseconds to blow but this is not important now because the supply to the schema is already at zero volts and no damage can be done. The dc input to the regulator needs to be a few volts higher than the regulator voltage. In the case of a 5v regulator, I would recommend a transformer with secondary voltage of 8-10volts ac.
The 5 volt regulated power supply for TTL and 74LS series integrated diagram, has to be very precise and tolerant of voltage transients. These ICs are easily damaged by short voltage spikes. A fuse will blow when its current rating is exceeded, but requires several hundred milliseconds to respond. This schema will react in a few microseconds, triggered when the output voltage exceeds the limit of the zener diode.
This schema uses the crowbar method, where a thyristor is employed and short diagram the supply, causing the fuse to blow. This will take place in a few microseconds or less, and so offers much greater protection than an ordinary fuse. If the output voltage exceed 5.6Volt, then the zener diode will conduct, switching on the thyristor (all in a few microseconds), the output voltage is therefore reduced to 0 volts and sensitive logic ICs will be saved. The fuse will still take a few hundred milliseconds to blow but this is not important now because the supply to the schema is already at zero volts and no damage can be done. The dc input to the regulator needs to be a few volts higher than the regulator voltage. In the case of a 5v regulator, I would recommend a transformer with secondary voltage of 8-10volts ac.
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