Primary side controlled switching regulator
View Patent ↗A switching regulator includes a transformer having a primary winding and an auxiliary winding connected to the supply rail of the switching regulator. The primary winding is coupled to the positive supply rail. The auxiliary winding is coupled to the negative supply rail. A switch is connected in series with the primary winding and the auxiliary winding for switching the transformer. A control circuit is coupled to the switch and the auxiliary winding to generate a switching signal for switching the switch and regulating the output of the switching regulator. A supplied capacitor is connected to the control circuit to supply the power to the control circuit. The auxiliary winding having a leakage inductor stores 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 connection of the transformer and the switch improves the efficiency and reduces the EMI.
1. A switching regulator, 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 primary winding and an auxiliary winding, wherein the primary winding and the auxiliary winding are coupled to a positive supply rail and a negative supply rail respectively;
a switch, connected in series with the primary winding and the auxiliary winding for switching the transformer;
a control circuit, coupled to the switch and the auxiliary winding to generate a switching signal for switching the switch and regulating the output of the switching regulator;
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;
the control circuit further including:
a voltage detection terminal, coupled to the auxiliary winding for detecting a voltage from the transformer;
a current sense terminal, coupled to the switch for receiving a current signal;
an output terminal, generating the switching signal to switch the transformer via the switch;
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-flop, 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.
2. The switching regulator as claimed in claim 1 , further comprising a current sense device connected from the switch to the auxiliary winding for generating the 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 regulator as claimed in claim 1 , wherein the auxiliary 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 regulator as claimed in claim 1 , wherein the control circuit further comprising:
a supply terminal, connected to the supplied capacitor and the diode; and
a ground terminal, connected to the supplied capacitor for receiving the power, wherein the ground terminal is connected to the auxiliary winding.
5. A switching regulator, 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 primary winding, a first auxiliary winding and a second auxiliary winding, wherein the primary winding and the first auxiliary winding are coupled to a positive supply rail and a negative supply rail respectively, wherein the second auxiliary winding is coupled to the first auxiliary winding;
a switch, connected in series with the primary winding and the first auxiliary winding for switching the transformer;
a control circuit, coupled to the switch and the first auxiliary winding to generate a switching signal for switching the switch and regulating the output of the switching regulator;
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 second auxiliary winding to the supplied capacitor for charging the supplied capacitor;
the control circuit further including:
a voltage detection terminal, coupled to the first auxiliary winding for detecting a voltage from the transformer;
a current sense terminal, coupled to the switch for receiving a current signal;
an output terminal, generating the switching signal to switch the transformer via the switch;
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-flop, 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. The switching regulator as claimed in claim 5 , further comprising a current sense device connected from the switch to the first auxiliary winding for generating the current signal in accordance with a switching current of the transformer, wherein the control circuit receives the current signal for generating the switching signal.
7. The switching regulator as claimed in claim 5 , wherein the first auxiliary 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.
8. The switching regulator as claimed in claim 5 , wherein the control circuit further comprising:
a supply terminal, connected to the supplied capacitor, the first diode and the second diode; and
a ground terminal, connected to the supplied capacitor for receiving the power, wherein the ground terminal is coupled to the first auxiliary winding and the second auxiliary winding.
9. A switching regulator, comprising:
a transformer, having a primary winding and an auxiliary winding, wherein the primary winding is coupled to a positive supply rail;
an inductor, coupled to a negative supply rail and the auxiliary winding;
a switch, connected in series with the primary winding and the inductor for switching the transformer;
a control circuit, coupled to the switch and the auxiliary winding to generate a switching signal for switching the switch and regulating the output of the switching regulator;
a supplied capacitor, connected to the control circuit to supply power to the control circuit;
a first diode, coupled from the inductor to the supplied capacitor for charging the supplied capacitor; and
a second diode, coupled from the transformer to the supplied capacitor for charging the supplied capacitor;
the control circuit further including:
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;
an output terminal, generating the switching signal to switch the transformer via the switch;
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-flop, 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.
10. The switching regulator as claimed in claim 9 , further comprising a current sense device coupled to the switch for generating the current signal in accordance with a switching current of the transformer, wherein the control circuit receives the current signal for generating the switching signal.
11. The switching regulator as claimed in claim 9 , wherein the control circuit further comprising:
a supply terminal, connected to the supplied capacitor, the first diode and the second diode; and
a ground terminal, connected to the supplied capacitor, the inductor and the auxiliary winding.