Automatic zero voltage switching mode controller
View Patent ↗A switching DC to AC power converter includes an automatic zero voltage switching (ZVS) mode controller. The automatic zero voltage switching mode controller may adjust a ZVS dead-time in accordance with a range of load currents being supplied by the power converter that range from quiescent conditions to a predetermined loading level of the power converter. The variable ZVS dead-time may be larger nearer to quiescent conditions, and become progressively smaller as load currents increase. Outside a predetermined range of load currents, the variable ZVS dead-time may be disabled or minimized.
1. An automatic zero voltage switching mode controller comprising:
a first timer operable at a first time interval;
a second timer operable at a second time interval;
a switching control signal output circuit configured to selectively drive a switching stage of a switch mode power converter with zero voltage switching in accordance with one of the first time interval and the second time interval;
a controller coupled with the second timer, where the controller is configured to automatically adjust the second time interval of the second timer to adjust a zero voltage switching dead-time based on a measured parameter indicative of a predetermined range of alternating current flow to a load; and
a counter configured to disable the second timer in response to the measured signal being indicative of a current flow to the load greater than a predetermined amount.
2. The automatic zero voltage switching mode controller of claim 1 , where the controller is further configured to adjust the second time interval of the second timer to be less than the first time interval based on the measured signal being indicative of a current flow to the load greater than a predetermined amount.
3. The automatic zero voltage switching mode controller of claim 1 , where the first time interval of the first timer is a fixed time interval set to maintain a minimum switch dead-time at all times.
4. The automatic zero voltage switching mode controller of claim 3 , where the first timer is configured to automatically adjust the fixed time interval to compensate for changes in temperature of the switching stage.
5. The automatic zero voltage switching mode controller of claim 1 , where the controller is configured to decrease the second time interval in response to the measured parameter being indicative of an increase in the current flow to the load.
6. The automatic zero voltage switching mode controller of claim 5 , where the controller is configured to increase the second time interval in response to the measured parameter being indicative of a decrease in the current flow to the load.
7. The automatic zero voltage switching mode controller of claim 1 , where the automatic zero voltage switching mode controller comprises an integrated circuit that includes the first timer, the second timer, and the switching control signal output circuit.
8. An automatic zero voltage switching mode controller comprising:
an input processing circuit configured to receive a pulse width modulation signal;
a timer circuit configured to selectively impose a zero voltage switching dead time having a variable time period on the pulse width modulation signal; and
a controller configured to receive a measured parameter indicative of a load current of a power converter, the controller coupled with the timer circuit and further configured to dynamically adjust the variable time period to a maximum time period in response to the load current being at quiescent conditions, and the controller further configured to progressively reduce the variable time period in accordance with increased load current,
where the input processing circuit is configured to disable the dynamically adjustable variable time period in response to the load current exceeding a predetermined magnitude.
9. The automatic zero voltage switching mode controller of claim 8 , where the power converter is a half bridge, class D, DC to AC power converter.
10. The automatic zero voltage switching mode controller of claim 8 , where the power converter is a full bridge, class D, DC to AC power converter.
11. The automatic zero voltage switching mode controller of claim 8 , where the controller comprises a peak catch and hold detector configured to catch and hold the measured parameter indicative of the load current.
12. The automatic zero voltage switching mode controller of claim 11 , where the input processing circuit comprises a counter configured to count the pulse width modulation signal, and the peak catch and hold detector comprises a timer capacitor configured to store a charge indicative of a current peak load current, the peak catch and hold detector configured to discharge the timer capacitor when the counter reaches a predetermined count.
13. The automatic zero voltage switching mode controller of claim 8 , where the timer circuit comprises a first timer and a second timer, wherein the first timer is configured to provide a fixed time period representative of a minimum zero voltage switching dead time, and the second timer is configured to provide the variable time period, one of the variable time period and the fixed time period being the zero voltage switching dead time.
14. A method of controlling automatic zero voltage switching, the method comprising:
receiving a pulse width modulation signal;
sensing a measured parameter indicative of a load current of a power converter;
adjusting a variable zero voltage switching dead time in accordance with a magnitude of the load current;
inserting the variable zero voltage switching dead time into the pulse width modulation signal; and
disabling the variable zero voltage switching dead time when the load current exceeds a predetermined magnitude.
15. The method of claim 14 , where inserting the variable zero voltage switching dead time comprises inserting the variable zero voltage switching dead time when the load current is within a predetermined range that includes quiescent operating conditions of the power converter.
16. The method of claim 14 , where adjusting a variable zero voltage switching dead time comprises increasing a time period of the variable zero voltage switching dead time to a maximum time period when the load current is indicative of quiescent conditions of the power converter, and decreasing the variable zero voltage switching dead time when the load current is indicative of increasing load current.
17. The method of claim 14 , where adjusting a variable zero voltage switching dead time comprises replacing the variable zero voltage switching dead time with a minimum zero voltage switching dead time when the load current exceeds a predetermined magnitude.