Constant current series-switching regulator

• US 4,146,832 A
• Filed: 07/20/1977
• Issued: 03/27/1979
• Est. Priority Date: 07/21/1976
• Status: Expired due to Term

• Current Assignee: Microtel Limited-Microtel Limitee
• Original Assignee: GTE Lenkurt Electric Canada Ltd (Verizon Communications Inc.)
• Inventors: McConnell, Brian
• Primary Examiner(s): Pellinen, A. D.
• Application Number:
  US05/817,316
• Time in Patent Office: 615 Days
• Field of Search: 323/17, 323/20, 323/DIG. 1, 363/18, 363/19, 363/41, 363/124
• US Class Current: 323/285
• CPC Class Codes: H02M 3/33507 with automatic control of the output voltage or current, e.g. flyback converters H02M3/33561, H02M3/33569 take precedence

Abstract

When connected to a source of unregulated DC power, a series switching regulator delivers a constant output current to a load. A series switch, in response to a control signal, adjusts the flow of input power by switching ON and OFF. The switching operation generates a gated power signal having a variable duty cycle, and the duty cycle depends on the power demands of the load. During the period when the switch is ON, the energy in the gated power signal is stored in the magnetic field of a transformer. During the period when the switch is OFF, the transformer releases the stored energy to capacitive storage devices and to the output load. The capacitive storage devices also supply current to the load when the transformer is storing energy. Feedback signals from voltage and current sensors combine to form a single control signal which adjusts the duty cycle of the switch until the power demands of the load are met.

Claims

1. A series-switching regulator providing a regulated output current from an unregulated DC (direct current) input power source, said regulator comprising:

switching means adapted for connection to an unregulated DC input power source to transfer energy therefrom, said means generating a gated power signal having a variable duty cycle;

transformer means coupled to said switching means and having an input coil with a current I_p and an output coil with a current I_s, said transformer means also having a charging and discharging period, said transformer means receiving energy from said switching means during said charging period and releasing stored energy during said discharging period;

rectification means connected in series with said output coil and permitting current to flow in one direction;

first sensor means coupled to said input coil for providing a first control signal proportional to I_p ;

first capacitive means connected in parallel with said series connected output coil and said rectification means, said capacitive means storing energy from said output coil during said discharging period and releasing energy during said charging period;

a first DC output terminal;

second sensor means having an input and first and second outputs, said input connected to said first DC output terminal and said first output connected to the junction of said first capacitive means and said output coil, said second sensor means producing a second control signal at said second output, said second control signal exhibiting a first binary state when the current through said second sensor means is above a predetermined level, and exhibiting a second binary state when this current is below the same predetermined level;

a second DC output terminal connected to the junction of said first capacitor means and said rectification means;

second capacitive means, connected in parallel with first and second DC output terminals, and providing said second sensor means with a surge of current at the start of the discharge period causing said second sensor means to exhibit said first binary state; and

control feedback means coupled to said switching means for controlling the duty cycle of said gated power signal, and thereby controlling the magnitude of direct current to said first and second DC output terminals, said feedback means comprising;

integrator means responsive to said second control signal and providing a third control signal representative of the average of said second control signal;

added means responsive to said first and third control signals and providing a fourth control signal representative of the voltage sum of said first and third control signals;

voltage sensing means responsive to said gated power signal and providing a fifth control signal indicative of the voltage polarity of said gated power signal;

comparator means having a first and second input and an output, said fifth control signal coupled to the first comparator input, said fourth control signal coupled to the second comparator input, and the comparator output coupled to said switching means, said comparator means generating a sixth control signal at its output for controlling the duty cycle of said gated power signal; and

means coupling said second control signal to said second input of said comparator means.

2. A current regulator as in claim 1 further comprising means for limiting the voltage at said output terminals, said means comprising:

means responsive to the voltage at said first and second DC output terminals for providing a seventh control signal, said signal being a binary signal and of one state when the voltage across said terminals is greater than a predetermined magnitude and of the opposite state when the voltage across said terminals is less than the same predetermined magnitude; and

means coupling said seventh control signal to said second input of said comparator means.

3. A current regulator as in claim 2 wherein said rectification means includes a diode.

4. A current regulator as in claim 3 wherein said first sensor means includes a resistor, and the voltage across said resistor being the first control signal.

5. A current regulator as in claim 4 wherein said means coupling said second control signal to said second input of said comparator means further includes an OR gate having a first and second input and an output, said OR gate output connected to said second input of said comparator means and said OR gate first input connected to said second output of said second sensor means, and said second OR gate input connected to said output voltage responsive means and receiving said seventh control signal.