Primary-side controlled switching regulator
View Patent ↗A switching regulator includes a switching device to switch a transformer from a primary-side to secondary side. A control circuit generates a switching signal for regulating output of the switching regulator. The control circuit includes a first circuit to generate a first signal and a timing signal by measuring a reflected signal of the transformer. A second circuit produces a second signal by integrating a current signal with the timing signal. The current signal represents a primary-side switching current of the transformer. A first feedback circuit produces a first feedback signal in response to the first signal and the reference signal, in which the reference signal is varied in response to the change of the second signal. Furthermore, a second feedback circuit generates a second feedback signal in response to the second signal. A switching control circuit generates the switching signal in response to the feedback signals.
1. A primary-side controlled switching regulator, comprising:
a transformer, for transferring the energy from a primary-side to a secondary side of the transformer;
a switching device, for switching the transformer;
a control circuit, coupled to the transformer for generating a switching signal to switch the switching device and to regulate the output of the switching regulator;
wherein the control circuit including:
a first circuit, coupled to the transformer for generating a first signal and a timing signal by measuring a reflected signal of the transformer, and wherein the timing signal represents a discharge time of the transformer;
a second circuit and a third circuit producing a second signal by integrating a current signal with the timing signal, and wherein the current signal represents a primary-side switching current of the transformer;
a first error amplifier, having a first reference signal for generating a first feedback signal in response to the first signal; and wherein the first reference signal is increased in response to the increase of the second signal;
a second error amplifier, having a second reference signal for generating a second feedback signal in response to the second signal; and
a switching control circuit, generating the switching signal in response to the first feedback signal and the second feedback signal.
2. The primary-side controlled switching regulator as claimed in claim 1 , wherein the control circuit further comprising:
a supply terminal and a ground terminal, for receiving power;
a detection terminal, for connecting the first circuit to the transformer through a resistor of a divider;
a sense terminal, for connecting the second circuit to a current-sense device for receiving the current signal, and the current-sense device is used for converting the primary-side switching current to the current signal;
an output terminal, for generating the switching signal to switch the transformer via the switching device;
a voltage-compensation terminal, connected to a first-compensation network for the frequency compensation for the first error amplifier;
a current-compensation terminal, connected to a second-compensation network for the frequency compensation for the second error amplifier; and
a programmable terminal, connected a resistor to ground to determine a slope, wherein the slope represents the change of the first reference signal versus the change of the second signal.
3. The primary-side controlled switching regulator as claimed in claim 1 , wherein a time constant of the third circuit is correlated with a switching period of the switching signal.
4. The primary-side controlled switching regulator as claimed in claim 1 , wherein the first circuit comprising:
a threshold voltage, wherein the threshold voltage adds to the reflected signal to produce a level-shift signal;
a plurality of capacitors;
a signal generator, producing sample signals, wherein the sample signals are used for sampling the reflected signal, and hold voltages are respectively generated across the capacitors, and the sample signals are generated in sequence during an enabled period of the timing signal;
a buffer circuit, generating a hold signal from the higher voltage of hold voltages;
a first output capacitor, for generating the first signal in response to the hold signal;
a second signal generator, producing the timing signal, wherein the timing signal is enabled as the switching signal is disabled, and the timing signal is disabled when the level-shift signal is lower than the hold signal.
5. The primary-side controlled switching regulator as claimed in claim 1 , wherein the first circuit multi-sampling the reflected signal to generate the first signal, and the first signal is obtained instantly once the discharge current of the transformer is fallen to zero.
6. The primary-side controlled switching regulator as claimed in claim 1 , wherein the second circuit comprising:
a fourth circuit, generating a fourth signal by sampling the current signal;
a third capacitor, holding the fourth signal;
a second output capacitor, producing a current waveform signal; and
a switch, conducting the fourth signal to the second output capacitor.
7. The primary-side controlled switching regulator as claimed in claim 1 , wherein the third circuit comprising:
a V-to-I converter, generating a charge current in response to the current waveform signal;
a timing capacitor, coupled to the charge current via a first switch to produce an integrated signal in response to the timing signal;
a second switch, connected in parallel with the timing capacitor for discharging the timing capacitor;
a third output capacitor, producing the second signal; and
a third switch, conducting the integrated signal to the third output capacitor.
8. The primary-side controlled switching regulator as claimed in claim 1 , wherein the switching signal has a minimum on-time when the switching signal is enabled, which further ensuring a minimum value of the discharge time for multi-sampling the reflected signal.
9. A switching regulator, comprising:
a transformer, for transferring the energy from a primary-side to a secondary side of the transformer;
a switching device, for switching the transformer;
a control circuit, coupled to the transformer for generating a switching signal to switch the switching device and regulate the output of the switching regulator;
wherein the control circuit including:
a first circuit, coupled to the transformer to generate a first signal and a timing signal by measuring a reflected signal of the transformer, and the timing signal represents a discharge time of the transformer;
a second circuit, producing a second signal by integrating a current signal with the timing signal, and the current signal represents a primary-side switching current of the transformer;
a first feedback circuit, for generating a first feedback signal in response to the first signal;
a second feedback circuit, for generating a second feedback signal in response to the second signal; and
a switching control circuit, generating the switching signal in response to the first feedback signal and the second feedback signal.
10. The switching regulator as claimed in claim 9 , wherein the first feedback circuit further comprising a first reference signal for generating the first feedback signal in response to the first signal and the first reference signal, and the first reference signal is varied in response to the change of the second signal.
11. The switching regulator as claimed in claim 9 , wherein the control circuit further comprising:
a supply terminal and a ground terminal, for receiving power;
a detection terminal, for coupling the first circuit to the transformer;
a sense terminal, for coupling the second circuit to a current-sense device for receiving the current signal, wherein the current-sense device is used for converting the primary-side switching current to the current signal;
an output terminal, for generating the switching signal for switching the transformer via the switching device;
a voltage-compensation terminal, for the frequency compensation of the first feedback circuit; and
a current-compensation terminal, for the frequency compensation of the second feedback circuit.
12. The switching regulator as claimed in claim 9 , wherein the first circuit comprising:
a threshold voltage, wherein the threshold voltage adding the reflected signal for producing a level-shift signal;
a plurality of capacitors;
a signal generator, producing sample signals to sample and to hold the reflected signal to the capacitors, wherein hold voltages are respectively generated across the capacitors, and sample signals are generated in response to the enabling of the timing signal;
a buffer circuit, generating the first signal in accordance with the hold voltages;
a second signal generator, producing the timing signal in response to hold voltages and the level-shift signal, wherein the timing signal is enabled as the switching signal is disabled, and the timing signal is disabled when the level-shift signal is lower than the hold voltages.
13. The switching regulator as claimed in claim 9 , wherein the first circuit multi-sampling the reflected signal to generate the first signal, and the first signal is acquired after the discharge current of the transformer is fallen to zero.
14. The primary-side controlled switching regulator as claimed in claim 9 , wherein the second circuit comprising:
a current generator, generating a charge current by sampling the current signal; and
a capacitor, coupled to the charge current for producing the second signal in response to the timing signal.
15. The switching regulator as claimed in claim 9 , wherein the switching signal has a minimum on-time when the switching signal is enabled, which further ensuring a minimum value of the discharge time for multi-sampling the reflected signal.
16. A switching power converter, comprising:
a transformer, for transferring the energy from a primary-side to a secondary side of the transformer;
a switching device, for switching the transformer;
a control circuit, coupled to the transformer for generating a switching signal to switch the switching device and to regulate the output of the switching regulator;
wherein the control circuit including:
a first circuit, coupled to the transformer for generating a first signal by measuring a reflected signal of the transformer;
a second circuit, producing a second signal in response to a current signal, wherein the current signal represents a primary-side switching current of the transformer;
a first feedback circuit, generating a first feedback signal in response to the first signal;
a second feedback circuit, generating a second feedback signal in response to the second signal; and
a switching control circuit, generating the switching signal in response to the first feedback signal and the second feedback signal.
17. The switching power converter as claimed in claim 16 , wherein the first feedback circuit further including a first reference signal for generating the first feedback signal in response to the first signal, and the first reference signal is varied in response to the change of the second signal.
18. The switching power converter as claimed in claim 16 , wherein the control circuit further comprising:
a supply terminal and a ground terminal, for receiving power;
a detection terminal, for connecting the first circuit to the transformer through a resistor of a divider;
a sense terminal, for connecting the second circuit to a current-sense device for receiving the current signal, wherein the current-sense device is used for converting the primary-side switching current to the current signal;
an output terminal, for generating the switching signal to switch the transformer via the switching device;
a first-compensation terminal, for the frequency compensation of the first feedback circuit; and
a second-compensation terminal, for the frequency compensation of the second feedback circuit.
19. The switching power converter as claimed in claim 16 , wherein the first circuit comprising:
a plurality of capacitors;
a signal generator, producing sample signals to sample and to hold the reflected signal to the capacitors, wherein hold voltages are respectively generated across the capacitors; and sample signals are generated in response to the enabling of a timing signal;
a buffer circuit, generating the first signal in accordance with the hold voltages;
a second signal generator, producing the timing signal in response to hold voltage, wherein the timing signal is enabled as the switching signal is disabled, and the timing signal is disabled when the reflected signal is significantly lower than the hold signal.
20. The switching power converter as claimed in claim 16 , wherein the first circuit multi-sampling the reflected signal for generating the first signal, and the first signal is acquired once the discharge current of the transformer is fallen to zero.
21. The switching power converter as claimed in claim 16 , wherein the switching signal has a minimum on-time when the switching signal is enabled, which further ensuring a minimum value of the discharge time for multi-sampling the reflected signal.
22. A switching regulator, comprising:
a transformer, for transferring the energy from a primary-side to a secondary side of the transformer;
a switching device, for switching the transformer;
a control circuit, coupled to the transformer for generating a switching signal for switching the switching device and regulating the output of the switching regulator;
wherein the control circuit including:
a first circuit, coupled to the transformer to generate a first signal by measuring a reflected signal of the transformer;
a second circuit, producing a second signal by measuring a current signal, wherein the current signal is correlated to the output current of the switching regulator;
a feedback circuit, including a reference signal for generating a feedback signal in response to the first signal and the reference signal, and the reference signal is varied in response to the second signal; and
a switching control circuit, generating the switching signal in response to the feedback signal.
23. The switching regulator as claimed in claim 22 , wherein the first circuit comprises:
a plurality of capacitors;
a signal generator producing sample signals to sample and to hold the reflected signal to the capacitors, wherein hold voltages are respectively generated across the capacitors, and samples signals are generated in response to the enable of a timing signal;
a buffer circuit, generating the first signal in accordance with the hold voltages;
a second signal generator, producing the timing signal in response to hold voltage, wherein the timing signal is enabled as the switching signal is disabled; the timing signal is disabled when the reflected signal is significant lower than the hold signal.
24. The switching regulator as claimed in claim 22 , wherein the first circuit multi-sampling the reflected signal for generating the first signal, and the first signal is acquired once the discharge current of the transformer is fallen to zero.
25. The switching regulator as claimed in claim 22 , wherein the second circuit comprising:
a current generator, generating a charge current in response to the current signal; and
a capacitor, coupled to the charge current for producing the second signal in response to the timing signal.
26. The switching regulator as claimed in claim 22 , wherein the switching signal has a minimum on-time when the switching signal is enabled, which further ensuring a minimum value of the discharge time for multi-sampling the reflected signal.
27. A switching regulator, comprising:
a transformer, for transferring the energy from a primary-side to a secondary side of the transformer;
a switching device, for switching the transformer;
a control circuit, coupled to the transformer for generating a switching signal to switch the switching device and to regulate the output of the switching regulator;
wherein the control circuit including:
a first circuit, coupled to the transformer for generating a first signal by measuring a reflected signal of the transformer;
a second circuit, producing a second signal by measuring a current signal, wherein the current signal is correlated to the output current of the switching regulator;
a feedback circuit, generating a feedback signal in response to the first signal, and the first signal is varied in response to the second signal; and
a switching control circuit, generating the switching signal in response to the feedback signal.