Switching power converter with transformer arrangement
A switching power converter includes a transformer having a first primary winding and a second primary winding. The first primary winding is coupled to the positive supply rail. The second primary winding is coupled to the negative supply rail. A switch is connected in between the first primary winding and the second primary winding for switching the transformer. A control circuit is coupled to the switch and the second primary winding to generate a switching signal for switching the switch and regulating the output of the switching power converter. A supplied capacitor is connected to the control circuit to supply the power to the control circuit. The second primary winding has a leakage inductor to store a stored energy when the switch is on. A diode is coupled from the negative supply rail to the supplied capacitor. The stored energy of the leakage inductor is discharged to the supplied capacitor through the diode once the switch is off. The arrangement of the transformer and the switch improves the efficiency and reduces the EMI.
1 . A switching power converter, comprising:
a transformer, transferring the energy from a primary side of the transformer to a secondary side of the transformer, wherein the transformer includes a first primary winding and a second primary winding, wherein the first primary winding and the second primary winding are coupled to a positive supply rail and a negative supply rail respectively;
a switch, connected in between the first primary winding and the second primary winding for switching the transformer;
a control circuit, coupled to the switch and the second primary winding to generate a switching signal for switching the switch and regulating the output of the switching power converter;
a supplied capacitor, connected to the control circuit to supply the power to the control circuit; and
a diode, coupled from the negative supply rail to the supplied capacitor for charging the supplied capacitor.
2 . The switching power converter as claimed in claim 1 , further comprising a current sense device connected from the switch to the second primary winding for generating a current signal in accordance with a switching current of the transformer, wherein the control circuit receives the current signal for generating the switching signal.
3 . The switching power converter as claimed in claim 1 , wherein the second primary winding has a leakage inductor to store a stored energy when the switch is turned on, wherein the stored energy of the leakage inductor is discharged to the supplied capacitor once the switch is turned off.
4 . The switching power converter as claimed in claim 1 , wherein the control circuit further comprising:
a supply terminal, connected to the supplied capacitor and the diode;
a ground terminal, connected to the supplied capacitor for receiving the power, wherein the ground terminal is connected to the second primary winding;
a voltage detection terminal, coupled to the second primary winding for detecting a voltage from the transformer;
a current sense terminal, coupled to the switch for receiving a current signal; and
an output terminal, generating the switching signal to switch the transformer via the switch in accordance with the voltage from the transformer and the current signal.
5 . The switching power converter as claimed in claim 4 , wherein the control circuit further comprising:
a sample-hold circuit, coupled to the voltage detection terminal to detect the voltage from the transformer for generating a sample signal;
an error amplifier, coupled to the sample-hold circuit, wherein the error amplifier receives a reference voltage and the sample signal for generating a feedback signal;
a comparator, coupled to the error amplifier and the current sense terminal to receive the feedback signal and the current signal for generating a reset signal;
an oscillator, generating a periodic pulse signal; and
a flip-flip, coupled to the oscillator, the comparator and the output terminal for generating the switching signal, wherein the periodic pulse signal and the reset signal are used to start and turn off the switching signal respectively.
6 . A switching power converter, comprising:
a transformer, transferring the energy from a primary side of the transformer to a secondary side of the transformer, wherein the transformer includes a first primary winding, a second primary winding and an auxiliary winding, wherein the first primary winding and the second primary winding are coupled to a positive supply rail and a negative supply rail respectively, wherein the auxiliary winding is coupled to the second primary winding;
a switch, connected in between the first primary winding and the second primary winding for switching the transformer;
a control circuit, coupled to the switch and the second primary winding to generate a switching signal for switching the switch and regulating the output of the switching power converter;
a supplied capacitor, connected to the control circuit to supply the power to the control circuit;
a first diode, coupled from the negative supply rail to the supplied capacitor for charging the supplied capacitor; and
a second diode, coupled from the auxiliary winding to the supplied capacitor for charging the supplied capacitor.
7 . The switching power converter as claimed in claim 6 , further comprising a current sense device connected from the switch to the second primary winding for generating a current signal in accordance with a switching current of the transformer, wherein the control circuit receives the current signal for generating the switching signal.
8 . The switching power converter as claimed in claim 6 , wherein the second primary winding has a leakage inductor to store a stored energy when the switch is turned on, wherein the stored energy of the leakage inductor is discharged to the supplied capacitor once the switch is turned off.
9 . The switching power converter as claimed in claim 6 , wherein the control circuit further comprising:
a supply terminal, connected to the supplied capacitor, the first diode and the second diode;
a ground terminal, connected to the supplied capacitor for receiving the power, wherein the ground terminal is coupled to the second primary winding and the auxiliary winding;
a voltage detection terminal, coupled to the second primary winding for detecting a voltage from the transformer;
a current sense terminal, coupled to the switch for receiving a current signal; and
an output terminal, generating the switching signal to switch the transformer via the switch in accordance with the voltage from the transformer and the current signal.
10 . The switching power converter as claimed in claim 9 , wherein the control circuit further comprising:
a sample-hold circuit, coupled to the voltage detection terminal to detect the voltage from the transformer for generating a sample signal;
an error amplifier, coupled to the sample-hold circuit, wherein the error amplifier receives a reference voltage and the sample signal for generating a feedback signal;
a comparator, coupled to the error amplifier and the current sense terminal to receive the feedback signal and the current signal for generating a reset signal;
an oscillator, generating a periodic pulse signal; and
a flip-flip, coupled to the oscillator, the comparator and the output terminal for generating the switching signal, wherein the periodic pulse signal and the reset signal are used to start and turn off the switching signal respectively.
11 . A switching power converter, comprising:
a transformer, having a first primary winding and a second primary winding coupled to a supply rail of the switching power converter;
a switch, connected in between the first primary winding and the second primary winding for switching the transformer;
a control circuit, coupled to the switch and the transformer to generate a switching signal for switching the switch and regulating the output of the switching power converter;
a supplied capacitor, connected to the control circuit; and
a diode, coupled from the transformer to the supplied capacitor for charging the supplied capacitor.
12 . The switching power converter as claimed in claim 11 , further comprising a current sense device coupled to the switch for generating a current signal in accordance with a switching current of the transformer, wherein the control circuit receives the current signal for generating the switching signal.
13 . The switching power converter as claimed in claim 11 , wherein the transformer has a leakage inductor to store a stored energy when the switch is turned on, wherein the stored energy of the leakage inductor is discharged to the supplied capacitor once the switch is turned off.
14 . The switching power converter as claimed in claim 11 , wherein the control circuit further comprising:
a supply terminal, connected to the supplied capacitor and the diode;
a ground terminal, connected to the supplied capacitor and the transformer;
a voltage detection terminal, coupled to the transformer for detecting a voltage from the transformer;
a current sense terminal, coupled to the switch for receiving a current signal; and
an output terminal, generating the switching signal to switch the transformer via the switch in accordance with the voltage from the transformer and the current signal.