Systems and methods for limiting DC voltage
Disclosed are exemplary embodiments of systems and methods for limiting DC voltage. In an exemplary embodiment, a DC voltage limiting circuit generally includes a current supply portion configured to receive a voltage input signal and provide a voltage output signal. A protective portion of the circuit is configured to limit or halt, at least temporarily, operation of the current supply portion based on a magnitude of the voltage input signal. A voltage level control portion is configured to limit the voltage output signal to a predetermined voltage level. In some embodiments, the DC voltage limiting circuit is provided in a climate control system controller.
1. A DC voltage limiting circuit comprising:
a current supply portion configured to receive a voltage input signal and provide a voltage output signal;
a protective portion configured to limit or halt, at least temporarily, operation of the current supply portion based on a magnitude of the voltage input signal; and
a voltage level control portion configured to limit the voltage output signal to a predetermined voltage level;
the DC voltage limiting circuit being provided in a climate control system controller;
wherein the current supply portion comprises:
first and second transistors each having an emitter configured to provide current through a switch to provide the output voltage signal, the second transistor having a base in series with a first Zener diode having a cathode facing away from the base;
the first transistor configured to supply current through the switch when the voltage input signal has a voltage less than the Zener voltage of the first Zener diode; and
the second transistor configured to supply current through the switch when the voltage input signal exceeds the Zener voltage of the first Zener diode;
wherein the DC voltage limiting circuit further comprises a second Zener diode connected between a gate of the switch and a source of the switch.
2. The DC voltage limiting circuit of claim 1 , further comprising a third transistor having a base connected with the voltage output through a third Zener diode, wherein the third transistor and the third Zener diode serve as a switch controller that is configured to control operation of the switch.
3. The DC voltage limiting circuit of claim 1 , further comprising a third transistor having a base connected with the voltage output through a third Zener diode having a Zener voltage corresponding to the predetermined voltage level.
4. The DC voltage limiting circuit of claim 3 , wherein the first Zener diode has a Zener voltage of 8.2 volts, the second Zener diode has a Zener voltage of 16 volts, and the third Zener diode has a Zener voltage of 30 volts.
5. The DC voltage limiting circuit of claim 1 , wherein the voltage input signal is provided by a power stealing circuit, and the voltage output signal is for providing power to the controller.
6. The DC voltage limiting circuit of claim 1 , wherein the climate control system controller comprises a thermostat, and/or wherein the predetermined voltage level is thirty (30) volts.
7. The DC voltage limiting circuit of claim 1 , wherein:
the protective portion is configured to limit or halt, at least temporarily, operation of the current supply portion based on a magnitude of the voltage input signal minus capacitor voltage;
the first transistor is configured to supply current through the switch when the voltage input signal minus capacitor voltage has a voltage less than the Zener voltage of the first Zener diode; and
the second transistor is configured to supply current through the switch when the voltage input signal minus capacitor voltage exceeds the Zener voltage of the first Zener diode.
8. A DC voltage limiting circuit comprising:
a current supply portion configured to receive a voltage input signal and provide a voltage output signal;
a protective portion configured to limit or halt, at least temporarily, operation of the current supply portion based on a magnitude of the voltage input signal; and
a voltage level control portion configured to limit the voltage output signal to a predetermined voltage level;
the DC voltage limiting circuit being provided in a climate control system controller;
wherein the current supply portion comprises first and second transistors in a Darlington configuration configured to receive the voltage input signal and connected with the voltage output; and
wherein the protective portion comprises a first Zener diode connected between the voltage input and a base of a third transistor, the protective portion configured to limit the operation of one of the transistors in the Darlington configuration.
9. The DC voltage limiting circuit of claim 8 , wherein the voltage level control portion comprises a fourth transistor having a base connected with the voltage output through a second Zener diode having a Zener voltage corresponding to the predetermined voltage level.
10. The DC voltage limiting circuit of claim 8 , wherein the protective portion is configured to limit or halt, at least temporarily, operation of the current supply portion based on the magnitude of the voltage input signal minus capacitor voltage.
11. A method of limiting DC voltage comprising:
in response to a voltage input signal, supplying current to provide a voltage output signal, the supplying performed by a current supply portion of a DC voltage limiting circuit of a climate control system controller;
limiting operation of the current supply portion based on a magnitude of the voltage input signal, the limiting performed by a protective portion of the DC voltage limiting circuit; and
limiting the voltage output signal to a predetermined voltage maximum level;
wherein the current supply portion comprises:
first and second transistors each having an emitter configured to provide current through a switch to provide the output voltage signal, the second transistor having a base in series with a first Zener diode having a cathode facing away from the base;
the first transistor configured to supply current through the switch when the voltage input signal has a voltage less than the Zener voltage of the first Zener diode; and
the second transistor configured to supply current through the switch when the voltage input signal exceeds the Zener voltage of the first Zener diode;
wherein the DC voltage limiting circuit further comprises a second Zener diode connected between a gate of the switch and a source of the switch.
12. The method of claim 11 , further comprising using the voltage output signal to provide power to the controller.
13. The method of claim 11 , wherein:
the method includes limiting operation of the current supply portion based on the magnitude of the voltage input signal minus capacitor voltage;
the first transistor configured to supply current through the switch when the voltage input signal minus capacitor voltage has a voltage less than the Zener voltage of the first Zener diode; and
the second transistor configured to supply current through the switch when the voltage input signal exceeds the Zener voltage of the first Zener diode.
14. A DC voltage limiting circuit comprising:
first and second transistors configured to receive a voltage input signal, each having an emitter configured to provide current through a switch to provide an output voltage signal, the second transistor having a base in series with a first Zener diode reverse-biased in relation to the voltage input signal;
a second Zener diode having a Zener voltage higher than the Zener voltage of the first Zener diode, the second Zener diode connected between a gate of the switch and a source of the switch and reverse-biased in relation to the gate; and
a third transistor having a base connected with the voltage output through a third Zener diode reverse-biased in relation to the voltage output and having a Zener voltage corresponding to a predetermined voltage level.
15. The DC voltage limiting circuit of claim 14 , wherein:
the first transistor is configured to supply current through the switch when the voltage input signal has a voltage less than the Zener voltage of the first Zener diode; and
the second transistor is configured to supply current through the switch when voltage input signal exceeds the Zener voltage of the first Zener diode.
16. The DC voltage limiting circuit of claim 14 , further comprising a diode in series with the second Zener diode.
17. The DC voltage limiting circuit of claim 14 , wherein the predetermined voltage level is thirty (30) volts.
18. A climate control system controller comprising the DC voltage limiting circuit of claim 14 .
19. The DC voltage limiting circuit of claim 14 , comprised by a thermostat.
20. The DC voltage limiting circuit of claim 14 , wherein:
the first transistor is configured to supply current through the switch when the voltage input signal minus capacitor voltage has a voltage less than the Zener voltage of the first Zener diode; and
the second transistor is configured to supply current through the switch when the voltage input signal minus capacitor voltage exceeds the Zener voltage of the first Zener diode.