Switching regulator control

• US 4,316,136 A
• Filed: 05/16/1980
• Issued: 02/16/1982
• Est. Priority Date: 05/18/1979
• Status: Expired due to Term

• Current Assignee: Licentia Patent-Verwaltungs-GmbH
• Original Assignee: Licentia Patent-Verwaltungs-GmbH
• Inventors: Pivit, Erich, Saxarra, Jurgen
• Primary Examiner(s): SHOOP JR, WILLIAM M
• Application Number:
  US06/150,660
• Time in Patent Office: 641 Days
• Field of Search: 323/222, 323/282, 323/286, 323/290, 331/112, 331/146, 363/124
• US Class Current: 323/282
• CPC Class Codes: H02M 3/156 with automatic control of output voltage or current, e.g. switching regulators

Abstract

In a method for controlling a switching regulator composed of a controllable electronic switch and a transformer, in which the electronic switch forms a series path with the transformer primary, the series path is connected in series between a direct voltage source and a load, and the amplitude of the current flowing through the switch constitutes a criterion for controlling the load voltage, which method includes periodically causing the switch to assume one switching state at regular intervals occurring with a predetermined frequency, comparing the value of a comparison voltage corresponding to the load voltage and having a selected nominal value with a second voltage value, and causing the switch to assume its opposite switching state when a predetermined relation exists between the comparison voltage value and the second voltage value, the second voltage value is defined by the sum of the values of a constant reference voltage, a control voltage which varies as a function of the current induced in the transformer secondary by current through the switch subsequent to closing of the switch and while the switch remains closed and a voltage having a sawtooth waveform and varying between an initial value at the start of each regular interval and a final value at the end of each regular interval, the latter voltages being selected so that the sum of the constant voltage value, the value which the control voltage would have at the end of an interval if the switch were closed during the entire interval, and the final value of the sawtooth voltage is greater than the sum of the nominal value of the comparison voltage and the maximum permissible value of a jump in the comparison voltage corresponding to a maximum acceptable interfering voltage jump in the load voltage, and the sum of the constant voltage value, the value of the control voltage at the start of an interval and the initial value of the sawtooth voltage is less than the difference between the nominal value and the maximum permissible jump value of the comparison voltage.

Claims

1. In a method for controlling a switching regulator composed of a controllable electronic switch and a transformer, in which the electronic switch forms a series path with the transformer primary, the series path is connected in series between a direct voltage source and a load, and the amplitude of the current flowing through the switch constitutes a criterion for controlling the load voltage, which method includes periodically causing the switch to assume one switching state at regular intervals occurring with a predetermined frequency, comparing the value of a comparison voltage corresponding to the load voltage and having a selected nominal value with a second voltage value, and causing the switch to assume its opposite switching state when a predetermined relation exists between the comparison voltage value and the second voltage value, the improvement comprising:

providing a constant reference voltage;

providing a control voltage which varies as a function of the current induced in the transformer secondary by current through the switch subsequent to closing of the switch and while the switch remains closed;

providing a time-varying voltage having a sawtooth waveform and varying between an initial value at the start of each regular interval and a final value at the end of each regular interval; and

giving the constant voltage, the control voltage and the time-varying voltage values such that the sum of the constant voltage value, the value which the control voltage would have at the end of an interval if the switch were closed during the entire interval, and the final value of the time-varying voltage is greater than the sum of the nominal value of the comparison voltage and the maximum permissible value of a jump in the comparison voltage corresponding to a maximum acceptable interfering voltage jump in the load voltage, and the sum of the constant voltage value, the value of the control voltage at the start of an interval and the initial value of the time-varying voltage is less than the difference between the nominal value and the maximum permissible jump value of the comparison voltage;

with the second voltage value being defined by the sum of the values of the constant reference voltage, the control voltage and the time-varying voltage.

2. In a switching regulator including a controllable electronic switch defining a current flow path, a direct voltage source, a transformer having primary and secondary windings, and an inductance, with the inductance, the transformer primary winding and the current flow path being connected together in series across the voltage source such that one side of the voltage source is connected to one side of the inductance at a point at the circuit reference potential, the regulator further including a first diode and a load connected together in series across the inductance such that the first diode is poled to conduct current supplied by the source in its forward direction, a capacitor connected across the load, an operational amplifier having a first input connected to receive a voltage corresponding to that across the load, a reference voltage source connected between the point at circuit reference potential and the second input of the operational amplifier, a rectifier forming a series arrangement with the transformer secondary winding, means connecting the series arrangement between one of the second input and output of the operational amplifier and the point at circuit reference potential, means connecting the output of the operational amplifier for controlling the electronic switch, a resistor connected across the series arrangement to provide a control voltage, and a Zener diode and a second diode connected together in series across the transformer secondary winding such that current from that winding flows in the forward direction of the Zener diode and in the reverse direction of the second diode, the improvement comprising a sawtooth voltage generator connected in series with said series arrangement for producing a sawtooth voltage in synchronism with the switching frequency of said regulator.

3. A circuit as defined in claim 2 wherein said switch is caused to assume one switching state at regular intervals occurring with a predetermined frequency and its other switching state when a predetermined relation exists between the value of the voltage applied to the first input of said operational amplifier and the sum of the value of the voltage provided by said reference voltage source, the value of the control voltage and the value of the sawtooth voltage, and said predetermined relation is such that the sum of the reference voltage value, the value which the control voltage would have at the end of an interval if the switch were closed during the entire interval, and the value of the sawtooth voltage at the end of an interval is greater than the sum of the nominal value of the comparison voltage and the maximum permissible value of a jump in the comparison voltage corresponding to a maximum acceptable interfering voltage jump in the load voltage, and the sum of the reference voltage value, the value of the control voltage at the start of an interval and the value of the sawtooth voltage at the beginning of an interval is less than the difference between the nominal value and the maximum permissible jump value of the comparison voltage.