Systems and methods for reducing input current in photoflash chargers

A method for providing power to a load, the method using a switching regulator that delivers a current to a load, the method comprising:

• building up a current in a primary winding of a transformer during a first portion of a switching cycle;
• releasing current from a secondary winding into the load during a second portion of the cycle;
• and
• following the end of the second portion of the cycle, delaying the onset of the first portion of a next-in-time switching cycle.

A switching regulator that delivers a current to a load, the regulator comprising:

• a transformer comprising:
• a primary winding;
• and
• a secondary winding, wherein current builds up in the primary winding during a first portion of a switching cycle, and current is released from the secondary winding into the load during a second portion of the cycle;
• a switch that closes at the beginning of the first portion of the switching cycle, the switch that is adapted to allow the current to build up in the primary winding when the switch is closed, the switch that opens at the end of the first portion of the switching cycle;
• a latch that is coupled to control operation of the switch and that is responsive to conditions at the load;
• and
• a delay circuit that introduces a delay between the end of the second portion of the switching cycle and the beginning of the first portion of the next switching cycle.

A method for delivering a current to a load, the method comprising:

• building up current in a primary winding during a first portion of a switching cycle, and releasing current from a secondary winding into the load during a second portion of the cycle;
• closing a switch at the beginning of the first portion of a switching cycle, the switch that is adapted to allow the current to build up in the primary winding when the switch is closed, and opening the switch at the end of the first portion of the switching cycle;
• using a latch to control operation of the switch and that is responsive to conditions at the load;
• and
• introducing a delay between the end of the second portion of the cycle and the beginning of the first portion of the next switching cycle.

A switching cycle for operation of a switching regulator to deliver current into a load, the switching regulator comprising a transformer, the transformer comprising a first winding and a second winding, the switching cycle comprising:

• a first portion for building up current in the primary winding;
• a second portion for releasing current from the secondary winding into the load;
• and
• a third portion comprising a voltage-dependent time delay between the completion of the second portion and the onset of a first portion of the next cycle, the voltage-dependent time delay being based at least in part on a voltage in a battery that supplies current to the switching regulator.

A method for providing power to a load, the method using a switching regulator that delivers a current to a load, the method comprising:

• building up a current in a primary winding of a transformer during a first portion of a switching cycle;
• releasing current from a secondary winding into the load during a second portion of the cycle;
• following the end of the second portion of the cycle, delaying the onset of the first portion of a next-in-time switching cycle;
• and
• disabling a delay circuit when an input voltage to the switching regulator is above a first threshold, the delay circuit that controls the delaying such that an average input current that is proportional to the current in the primary winding is substantially independent of variations to the delay.