Electrical pulse generator uses power transistors and silicon controlled rectifiers for producing a high current pulse having fast rise and fall times. At quiescent conditions, the standby power consumption of the circuit is equal to zero

Woolfson, M. G.

English

NASA Technical Reports Server

October 1966
	 Brief 66-10456 
NASA TECH BRIEF
	
41 
NASA Tech Briefs are issued to summarize specific innovations derived from the U. S. space

program and to encourage their commercial application. Copies are available to the public from

the Clearinghouse for Federal Scientific and Technical Information, Springfield, Virginia 22151.

Pulse Generator Using Transistors and Silicon Controlled Rectifiers

Produces High Current Pulses With Fast Rise and Fall Times 
Input	 Silicon 
Transistor	 Rectifier	 Load 
Steering 
Diode 
Steering 
Diode V Silicon Rectifier 
Switching 
Transistor 
The problem: 
To develop an electrical pulse generator utilizing 
power transistors and silicon controlled rectifiers for 
producing a high current pulse having fast rise and 
fall times. While the power transistor may exhibit 
rapid turn-on and low saturation impedance when 
driven into saturation, its use as a fast switch has 
been severely limited due to its turn-off time and 
storage time effects. Further, the silicon controlled rec-
tifier (SCR), which may be easily turned on, is diffi-
cult to turn off. The two techniques for turning off 
the SCR are to reduce the anode current to a value 
below the holding current, or to drive the anode volt-
age below that of the cathode.
_ Start Pulse 
Steering	 Terminal 
Stop Pulse 
Terminal 
The solution: 
An electrical pulse generator in which power tran-
sistors and silicon controlled rectifiers are used, and 
at quiescent conditions, the standby power consump-
tion of the circuit is equal to zero. 
How it's done: 
The electrical pulse generator contains a storage 
capacitor which upon application of a pulse. to the 
start pulse terminal is discharged into a load through 
an input transistor, the first silicon controlled rectifier, 
and a pair of resistors. Upon application of a pulse 
to the stop pulse terminal, the second silicon controlled 
rectifier is turned on causing the load current to be 
(continued overleaf) 
Now
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diverted through it, and also causing the switching 
transistor to be turned on. When the switching tran-
sistor turns on, the input transistor is turned off. 
Shortly thereafter the first and second silicon con-
trolled rectifiers are turned off and finally the switch-
ing transistor is turned off. The cycle is repeated upon 
application of the next pulse to the start pulse terminal. 
Notes: 
1. In a typical application, the pulse on time (start 
pulse time to stop pulse time) and the circuit 
storage time represent a small fraction of the in-
terpulse period (start pulse time to start pulse 
time). The storage capacitor under these condi-
tions suffers negligible discharge permitting an 
average current to peak current ratio, which 
approaches the duty cycle ratio. In this manner, 
high pulse currents can be generated with high 
circuit efficiency. It should be noted that the 
pulse on time is determined by the turn on char-
acteristics of the circuit elements employed, thus 
resulting in both fast rise and fall times for the 
output pulse.
2. Inquiries concerning this invention may be di-
rected to: 
Technology Utilization Officer 
Manned Spacecraft Center 
Houston, Texas 77058 
Reference: B66-10456 
Patent status: 
Inquiries about obtaining rights for the commercial 
use of this invention may be made to NASA, Code 
GP, Washington, D.C. 20546. 
Source: Martin G. Woolfson 
of Westinghouse Electric Corporation 
under contract to

Manned Spacecraft Center
(MSC-405) 
Brief 66-10456	 Category 01


Pulse generator using transistors and silicon controlled rectifiers produces high current pulses with fast rise and fall times

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