Energy-supply system for supplying energy to an electrical load from a battery
A motorized window treatment may be configured to adjust a position of a covering material to control the amount of daylight entering a space. The motorized window treatment may include a DC power source for charging an energy storage element, such as a supercapacitor and/or rechargeable battery. The energy storage element may be configured to provide power for the operation of a motor used to adjust the position of the covering material. The energy storage element may discharge when providing power to the motor and may charge such that the current it draws from a battery is at a desired average current level that extends the lifetime of the battery.
1. A motor drive unit for a motorized window treatment, the motor drive unit comprising:
a bus capacitor configured to store a bus voltage;
a motor configured to control movement of a covering material of the motorized window treatment;
a motor drive circuit configured to receive the bus voltage and conduct a motor current through the motor for controlling power delivered to the motor to control movement of the covering material;
a first switching circuit configured to be coupled between the bus capacitor and a first power source that is configured to generate a first power source voltage;
a second power source configured to generate a second power source voltage;
a second switching circuit coupled between the bus capacitor and the second power source; and
a control circuit configured to control the first and second switching circuits,
wherein, prior to controlling the motor drive circuit to conduct the motor current through the motor to control the movement of the covering material, the control circuit is configured to:
when a magnitude of the second power source voltage is greater than a movement capacity threshold, render conductive the second switching circuit to charge the magnitude of the bus voltage to the magnitude of the second power source voltage, and control the motor drive circuit to conduct the motor current from the second power source and through the motor to control the movement of the covering material;
when the magnitude of the second power source voltage is less than the movement capacity threshold, gradually render conductive the first switching circuit to charge the magnitude of the bus voltage to the magnitude of the first power source voltage, and control the motor drive circuit to conduct the motor current from the first power source and through the motor to control the movement of the covering material; and
when movement of the covering material is complete, render non-conductive at least one of the first switching circuit or the second switching circuit that was rendered conductive to control the motor.
2. The motor drive unit of claim 1 , wherein, to gradually render conductive the first switching circuit, the control circuit is configured to generate a pulse width modulated (PWM) gate signal at a gate of the first switching circuit.
3. The motor drive unit of claim 2 , wherein the control circuit is configured to increase an on-time of the PWM gate signal from one period to the next while gradually rendering conductive the first switching circuit.
4. The motor drive unit of claim 2 , wherein the control circuit is configured to generate the PWM gate signal to render conductive the first switching circuit using open-loop control.
5. The motor drive unit of claim 1 , wherein, to gradually render conductive the first switching circuit, the control circuit is configured to pulse width modulate a first switch control signal, wherein the first switch control signal is configured to render the first switching circuit conductive and non-conductive.
6. The motor drive unit of claim 1 , wherein, to gradually render conductive the first switching circuit, the control circuit is configured to decrease an impedance of the first switching circuit from a non-conductive impedance to a conductive impedance.
7. The motor drive unit of claim 6 , wherein the non-conductive impedance of the first switching circuit is greater than the conductive impedance of the first switching circuit.
8. The motor drive unit of claim 1 , wherein the first switching circuit comprises at least one field-effect transistor (FET); and
wherein, to gradually render conductive the first switching circuit, the control circuit is configured to control an impedance of the FET of the first switching circuit in a linear region.
9. The motor drive unit of claim 1 , further comprising:
a filter circuit coupled in series between the first switching circuit and the bus capacitor, the filter circuit configured to filter the motor current conducted through the first power source when the first switching circuit is conductive and the motor drive circuit is controlling the power delivered to the motor.
10. The motor drive unit of claim 9 , wherein the filter circuit comprises an inductor.
11. The motor drive unit of claim 10 , further comprising:
a diode coupled between circuit common and a junction of the first switching circuit and the filter circuit, the diode configured to conduct current through the inductor and the bus capacitor when the first switching circuit is non-conductive while the switching circuit is gradually rendered conductive.
12. The motor drive unit of claim 9 , wherein the filter circuit is configured to filter the motor current to conduct a first power source current through the first power source that has a DC magnitude.
13. The motor drive unit of claim 1 , wherein the motor drive unit is configured such that the first switching circuit and the second switching circuit cannot both be rendered conductive at the same time.
14. The motor drive unit of claim 1 , wherein the first power source comprises one or more alkaline batteries, and the second power source comprises one or more lithium batteries or supercapacitors.
15. The motor drive unit of claim 1 , wherein the first power source comprises one or more replaceable batteries, and the second power source comprises one or more rechargeable batteries or supercapacitors.
16. The motor drive unit of claim 1 , wherein the first power source is characterized by a larger equivalent series resistance than the second power source.
17. The motor drive unit of claim 1 , wherein the first power source comprises a solar energy receiving circuit, an ultrasonic energy receiving circuit, or a radio-frequency (RF) energy receiving circuit.
18. The motor drive unit of claim 1 , wherein the first power source is removably replaceable by a user.
19. The motor drive unit of claim 1 , wherein the movement capacity threshold indicates a storage level sufficient to complete a full movement of the covering material from a fully-lowered position to a fully-raised position.
20. The motor drive unit of claim 1 , wherein the first switching circuit comprises at least one field-effect transistor (FET).
21. The motor drive unit of claim 1 , further comprising:
a power converter circuit configured to charge the second power source from the first power source voltage to produce the second power source voltage across the second power source; and
wherein the control circuit is configured to:
set a charging flag in response to enabling the power converter circuit, and clear the charging flag in response to disabling the power converter circuit.
22. The motor drive unit of claim 21 , wherein the control circuit is configured to:
enable the power converter circuit when the second power source voltage is less than a low-side threshold; and
disable the power converter circuit when the second power source voltage is greater than a high-side threshold, wherein the movement capacity threshold is less than the low-side threshold and the high-side threshold.
23. The motor drive unit of claim 21 , wherein the control circuit is configured to:
wait a delay period after controlling the motor when movement of the covering material is complete before enabling the power converter circuit to charge the second power source from the first power source voltage.
24. The motor drive unit of claim 21 , wherein the control circuit is configured to use a different delay period based on whether the first switching circuit or the second switching circuit was render conductive during the movement of the covering material.
25. The motor drive unit of claim 1 , wherein the control circuit is configured to:
set a lockout flag in response to a reception of a command to move the covering material of the motorized window treatment and a determination that the magnitude of the second power source voltage is less than the movement capacity threshold; and
clear the lockout flag in response to a determination that the magnitude of the second power source voltage is greater than a high-side threshold.
26. The motor drive unit of claim 25 , wherein the control circuit is configured to:
gradually render conductive the first switching circuit to charge the magnitude of the bus voltage to approximately the magnitude of the first power source voltage when the lockout flag is set.
27. The motor drive unit of claim 25 , wherein the control circuit is configured to: gradually render conductive the first switching circuit to charge the magnitude of the bus voltage to approximately the magnitude of the first power source voltage when the lockout flag is set regardless of the magnitude of the second power source voltage.