Output voltage detection circuit, isolated switching power supply, and semiconductor device
First Claim
1. An output voltage detection circuit incorporated into an isolated switching power supply comprising:
- a transformer having a primary side winding, a secondary side winding, and an auxiliary winding, a switching element connected to the primary side winding, and a control circuit for controlling on/off of the switching element, the output voltage detection circuit generating detection voltage as a detected value of secondary side output voltage based on voltage generated on the auxiliary winding, and feeding back the detection voltage to the control circuit, the output voltage detection circuit, comprising;
a secondary side current detection circuit connected to the auxiliary winding and detecting a period during which current passes through the secondary side winding, a voltage waveform processing circuit connected to the auxiliary winding and processing a waveform of the voltage generated on the auxiliary winding, a hold circuit connected to an output stage of the voltage waveform processing circuit and holding a peak voltage of the voltage having been processed by the voltage waveform processing circuit, a correction circuit connected to an output stage of the hold circuit, and correcting the peak voltage having been held by the hold circuit and generating the detection voltage in the period having been detected by the secondary side current detection circuit, and a reset circuit for resetting, for a fixed period of time after the current starts passing through the secondary side winding, the detection voltage having been generated by the correction circuit.
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Accused Products
Abstract
An output voltage detection circuit is provided for accurately detecting a secondary side output voltage based on a voltage induced to an auxiliary winding in an isolated switching power supply including a transformer having the auxiliary winding. A voltage waveform processing circuit (10-1) processes the waveform of the voltage induced to the auxiliary winding (7-3), a hold circuit (10-2) holds the voltage peak value after the processing, a secondary side current detection circuit (24) detects a period during which current passes through a secondary side winding (7-2), a correction circuit (22) performs correction to decrease the peak voltage which has been held by the hold circuit (10-2) during the period, and the corrected voltage is fed back to a control circuit (9). Meanwhile, are set circuit (23) resets, for a fixed period after the current passes through the secondary side winding (7-2), the peak voltage having been held by the hold circuit (10-2).
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Citations
19 Claims
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1. An output voltage detection circuit incorporated into an isolated switching power supply comprising:
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a transformer having a primary side winding, a secondary side winding, and an auxiliary winding, a switching element connected to the primary side winding, and a control circuit for controlling on/off of the switching element, the output voltage detection circuit generating detection voltage as a detected value of secondary side output voltage based on voltage generated on the auxiliary winding, and feeding back the detection voltage to the control circuit, the output voltage detection circuit, comprising;
a secondary side current detection circuit connected to the auxiliary winding and detecting a period during which current passes through the secondary side winding, a voltage waveform processing circuit connected to the auxiliary winding and processing a waveform of the voltage generated on the auxiliary winding, a hold circuit connected to an output stage of the voltage waveform processing circuit and holding a peak voltage of the voltage having been processed by the voltage waveform processing circuit, a correction circuit connected to an output stage of the hold circuit, and correcting the peak voltage having been held by the hold circuit and generating the detection voltage in the period having been detected by the secondary side current detection circuit, and a reset circuit for resetting, for a fixed period of time after the current starts passing through the secondary side winding, the detection voltage having been generated by the correction circuit. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19)
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Specification