Flash strobe power supply system and method
First Claim
1. A flash strobe power supply comprising:
- an input filter;
a control circuit coupled to the input filter;
a first and second transistor operatively coupled to the control circuit;
a first and second transformer, each transformer operatively coupled to at least one of the first and second transistors; and
at least two circuits configured to sense an energy state of each transformer, the circuits coupled to the programmable control circuit, the control circuit configured to operate each transistor in response to at least one of the circuits to allow a dead time between cessation of energy in each transformer and an associated transistor turn on via synchronization code in the control circuit, the synchronization code periodically delaying operation of one or the other of the first and second transistors to maintain a 180 degree phase difference in switching cycles of the first and second transistors.
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Accused Products
Abstract
A reliable strobe power supply is disclosed that provides requisite light energy for emergency uses without causing EMI problems. A two phase dual flyback power converter operating in transitional mode is disclosed containing a microcontroller that maintains a 180 degree displacement between the two phases by enabling a small, variable dead time between the cessation of stored energy in the flyback transformers and turn-on of the associated power switching transistor for one or the other phases. The power supply is capable of detecting a fault (neoning) and automatically correcting the condition by incrementing the flash capacitor charge off-time delay. The power supply is also capable of tolerating defective (persistently neoning) strobe tubes that cause an inordinate delay in capacitor charging by turning them off.
24 Citations
16 Claims
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1. A flash strobe power supply comprising:
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an input filter;
a control circuit coupled to the input filter;
a first and second transistor operatively coupled to the control circuit;
a first and second transformer, each transformer operatively coupled to at least one of the first and second transistors; and
at least two circuits configured to sense an energy state of each transformer, the circuits coupled to the programmable control circuit, the control circuit configured to operate each transistor in response to at least one of the circuits to allow a dead time between cessation of energy in each transformer and an associated transistor turn on via synchronization code in the control circuit, the synchronization code periodically delaying operation of one or the other of the first and second transistors to maintain a 180 degree phase difference in switching cycles of the first and second transistors. - View Dependent Claims (2, 3, 4, 5)
at least two isolating circuits coupled to the programmable control circuit, each of the isolating circuits including;
a voltage divider configured to provide a voltage measurement of a flash capacitor and to provide a voltage limiting function for a flash lamp.
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5. The strobe power supply of claim 2 wherein the 180 degree relationship reduces ripple current in the input filter.
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6. A method for operating at least two power converters in at least two phases with transitional conduction mode for a strobe power supply, the method comprising:
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determining which of the power converters has a higher frequency; and
periodically introducing enough dead time to the higher frequency power converter to displace the phases of the at least two power converters by a predetermined amount to maintain a displacement in the at least two phases. - View Dependent Claims (7, 8, 9, 10, 11, 12, 13)
adjusting the at least two phases to a displacement of 180 degrees every fourth cycle of each phase.
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8. The method of claim 6 further comprising:
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measuring a period of a phase according to a time between each turn on of a transistor in at least one of the power converters; and
dividing the measured period by a predetermined number.
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9. The method of claim 6 wherein the phases are two current phases displaced by 180 degrees, the phases being synchronized over every six cycles of the power converters.
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10. The method of claim 6 wherein a programmable control circuit applies a logical function to a combination of turn on commands, the logical function providing for a later command of a measured synchronizing turn on and a normal turn on for a first transistor to be an operative turn on, the synchronizing command enabling synchronization of the turn on of the first transistor with a turn on of a second transistor in an out of phase power converter.
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11. The method of claim 10 wherein the logical function is equivalent to AND-ing.
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12. The method of claim 6 wherein the periodic introduction of dead time is determined via an external interrupt service routine including a first external interrupt occurring at a cessation of secondary current for a first power converter and a second external interrupt occurring at a cessation of secondary current for a second power converter, the first and second external interrupts identifying a cycle to initiate.
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13. The method of claim 12 wherein the first and second external interrupts and a flag variable determine which cycle of the at least two power converters is enabled.
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14. A method for synchronizing phases of a dual power converter in a flash strobe power supply, the method comprising:
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dividing a period of a first phase of the dual power converter and obtaining a predetermined fractional period of time;
waiting for the predetermined fractional period of time;
issuing a turn on command; and
AND-ing the turn on command with a turn on command for a second phase of the dual power converter. - View Dependent Claims (15, 16)
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Specification