Semiconductor apparatus having half-wave rectifier LLC converter
A first series circuit includes a main switch and a resonant switch. A second series circuit includes a primary winding and a resonant capacitor. A transformer includes the primary winding and a secondary winding. A controller controls the main switch and the resonant switch. A rectifier smoothing circuit rectifies and smoothes a voltage in the secondary winding. An output voltage detector detects an output voltage of the rectifier smoothing circuit. The controller controls the main switch based on a first drive signal. The controller turns on the resonant switch during a flyback period when an energy stored in the transformer is released from the secondary winding based on the second drive signal, which causes a resonant current to flow. The controller turns off the resonant switch during an excitation current charging period in which the energy stored in the transformer charges the resonant capacitor after the resonant current stops flowing.
1 . A semiconductor apparatus having a half-wave rectifier LLC converter comprising:
a first series circuit comprising a main switch and a resonant switch, the main switch and the resonant switch being connected in series at terminals of a DC power supply;
a second series circuit comprising a primary winding and a resonant capacitor, the primary winding and the resonant switch being connected in series at terminals of the resonant switch;
a transformer comprising the primary winding and a secondary winding that is electromagnetically coupled with the primary winding with opposite polarity;
a controller that controls the main switch and the resonant switch;
a rectifier smoothing circuit that rectifies and smoothes a voltage in the secondary winding; and
an output voltage detector that detects an output voltage of the rectifier smoothing circuit, wherein
the controller performs operations comprises:
generating a first drive signal;
controlling the main switch based on the first drive signal;
generating a second drive signal;
turning on the resonant switch during a flyback period when an energy stored in the transformer is released from the secondary winding based on the second drive signal, which causes a resonant current to flow; and
turning off the resonant switch during an excitation current charging period in which the energy stored in the transformer charges the resonant capacitor after the resonant current stops flowing.
2 . The semiconductor apparatus according to claim 1 , wherein the controller performs operations further comprising:
generating a third drive signal; and
controlling the resonant switch after the second drive signal based on the third drive signal.
3 . The semiconductor apparatus according to claim 2 , wherein the controller further comprises:
a zero cross detector that outputs a zero cross signal indicating that a zero voltage is detected at which the voltage in an auxiliary winding of the transformer changes from negative to positive or positive to negative voltage; and
a second pulse generator that outputs a second pulse signal to turn on the resonant switch after a predetermined delay time based on the zero cross signal.
4 . The semiconductor apparatus according to claim 3 , wherein the controller further comprises:
an enable signal generator that generates an enable signal based on a feedback voltage detected by the output voltage detector; and
a second pulse delay circuit that delays the third drive signal based on the zero cross signal and the enable signal, wherein
the second pulse delay circuit delays the third drive signal so that a frequency is reduced when a load current decreases.
5 . The semiconductor apparatus according to claim 3 , wherein the controller further comprises;
an enable signal generator that generates an enable signal based on a feedback voltage detected by the output voltage detector; and
a disable signal generator that generates a disable signal based on the second drive signal, and
a second pulse delay circuit that delays the third drive signal based on the zero cross signal, the enable signal and the disable signal, wherein
the second pulse delay circuit delays the third drive signal so that a frequency is reduced when a load current decreases.
6 . The semiconductor apparatus according to claim 2 , wherein the controller comprises:
an excitation current detector that detects an excitation current of the transformer and outputs a first voltage signal proportional to the excitation current; and
an output voltage detector that outputs a second voltage signal proportional to the output voltage, wherein
the controller sets a timing for turning on the second drive signal based on the first voltage signal and a threshold value set based on the second voltage signal,
the controller generates the second drive signal so that an on-width of the second drive signal is at least one-half of a resonant cycle of the resonant current and a turn off timing of the second drive signal is during the excitation current charging period.
7 . The semiconductor apparatus according to claim 2 , wherein
the controller comprises an excitation current detector that detects an excitation current of the transformer and outputs a first voltage signal proportional to the excitation current,
the controller sets a turn-on timing of the second drive signal based on the first voltage signal and a third voltage signal, and generates the second drive signal so that an on-width of the second drive signal is at least one-half of a resonant cycle of the resonant current and a turn off timing of the second drive signal is during the excitation current charging period.
8 . The semiconductor apparatus according to claim 1 , wherein the controller comprises:
an excitation current detector that detects an excitation current of the transformer and outputs a first voltage signal proportional to the excitation current; and
an output voltage detector that outputs a second voltage signal proportional to the output voltage, wherein
the controller sets a timing for turning on the second drive signal based on the first voltage signal and a threshold value set based on the second voltage signal, and
the controller generates the second drive signal so that an on-width of the second drive signal is at least one-half of a resonant cycle of the resonant current and a turn off timing of the second drive signal is during the excitation current charging period.
9 . The semiconductor apparatus according to claim 1 , wherein
the controller comprises an excitation current detector that detects an excitation current of the transformer and outputs a first voltage signal proportional to the excitation current, and
the controller sets a turn-on timing of the second drive signal based on the first voltage signal and a third voltage signal, and generates the second drive signal so that an on-width of the second drive signal is at least one-half of a resonant cycle of the resonant current and a turn off timing of the second drive signal is during the excitation current charging period.