阅读说明：本技术 将直流电转换为直流电即dc-dc以得到最大可能效率的具有最大功率点跟踪即mppt的电能转换器单元 (Power converter unit with Maximum Power Point Tracking (MPPT) for converting direct current to direct current (DC-DC) for maximum possible efficiency ) 是由 O·V·林克 徐玮辰 A·L·罗德里格斯·曼萨诺 S·范·德·贾格 于 2020-01-30 设计创作，主要内容包括：本发明涉及用于将直流电转换为直流电即DC-DC的具有最大功率点跟踪的电能转换器单元,所述最大功率点跟踪用于测量在输出和控制器模块处的转换后的功率。(The present invention relates to a power converter unit with maximum power point tracking for measuring the converted power at the output and controller module for converting direct current to direct current, DC-DC.)

1. A power converter unit for converting direct current power to direct current (DC-DC), the power converter unit comprising:

a DC-DC conversion module configured to be connected with an energy harvesting module, such as an RF energy harvesting module, for supplying an electrical input thereto, and to output an electrical output for connection with a load, such as an internet of things sensor module;

a controller module configured to electrically control the DC-DC conversion module and to control electrical parameters of the DC-DC conversion module, wherein the electrical parameters comprise at least an input impedance of the DC-DC conversion module;

a maximum power point tracking module connected with the controller module and configured to output a power point control signal to the controller module to adjust at least one of the electrical parameters,

wherein the maximum power point tracking module comprises a resistor connected in series with the electrical output of the DC-DC conversion module, and provides the power point control signal to the controller module upon a comparison between a first voltage potential sample and a second voltage potential sample across the resistor, wherein the first voltage potential and the second voltage potential are sampled sequentially in time.

2. The power converter unit of claim 1, wherein the power converter unit is configured to subsequently switch the maximum power point tracking module on and off.

3. The power converter unit of claim 1 or 2, wherein the power converter unit is configured to subsequently switch on and off the current to the resistor.

4. The power converter unit of claim 2 or 3, wherein the power converter unit is configured to switch the maximum power point tracking module and the current to the resistor on and off simultaneously.

5. The power converter unit of claim 3 or 4, wherein the maximum power point tracking module further comprises a bypass circuit for bypassing the resistor, and wherein the current to the resistor is disconnected.

6. The power converter unit of any preceding claim, wherein the duty cycle of switching on and off one or more of the currents to the resistor and switching on and off the maximum power point tracking module is at most 50%, preferably 10%, more preferably 5%, most preferably 4%.

7. The power converter unit of any preceding claim, wherein the output current of the DC-DC conversion module is measured by determining the first and second voltage potential samples across the resistor.

8. The power converter unit of any one of the preceding claims, wherein the DC-DC conversion module is a switched capacitor DC-DC converter.

9. The power converter unit of any preceding claim, wherein the resistor is one of an adjustable resistor and a programmable resistor.

10. The power converter unit of any preceding claim, wherein the resistor is part of an output resistance of the DC-DC conversion module.

11. A power converter unit according to any preceding claim in which the controller comprises an oscillator.

12. The power converter unit of any preceding claim, wherein the electrical parameters further comprise one or more of a switching frequency and a voltage gain of a DC-DC conversion module.

13. The power converter unit of any preceding claim, wherein the voltage drop between the first voltage potential and the second voltage potential is amplified by a voltage amplifier.

14. The power converter cell of claim 13, wherein the voltage amplifier is a switched capacitor amplifier.

15. The power converter unit of claim 13 or 14, wherein the maximum power point tracking module further comprises a low pass filter for smoothing at least one of the first voltage potential signal and the second voltage potential signal.

16. The power converter unit of any preceding claim, wherein the maximum power point tracking module further comprises a sample-and-hold comparator for sampling the first voltage potential and the second voltage potential sequentially in time.

17. The power converter unit of any preceding claim, wherein the maximum power point tracking module further comprises a state machine for determining that one or more of the electrical parameters must be changed.

18. The power converter unit of claim 12 or 17, wherein the state machine determines to adjust a bit count of one or both of the controller module and the DC-DC conversion module.

19. A system on chip (SoC) comprising a power converter unit according to any of the preceding claims.

Technical Field

The present invention relates to a power converter unit for converting direct current to direct current (DC-DC) with maximum power point tracking for measuring the converted output power and adjusting the power parameter with a controller module.

Background

Existing solutions use a power converter unit with inductance and maximum power point tracking for converting direct current to direct current, which adjusts the power converter input impedance based on input voltage measurements. Disadvantages of power converter units for converting direct current to direct current are the complexity of the design, the size of the footprint of external components (such as inductors, etc.), and the sensitivity to pulsed control signals. A major drawback of maximum power point tracking for adjusting the input impedance of a power converter unit based on input voltage measurements is that the efficiency of the power converter unit is not taken into account during the tracking calculation. Some maximum power point tracking circuits adjust the power converter unit input impedance based on the output voltage measurement, however, this approach depends largely on the amount of capacitance connected at the output of the power converter unit.

Disclosure of Invention

In view of the above disadvantages, it is an object of the present invention to provide an improved power converter unit for converting direct current to direct current based on switched capacitor technology comprising a maximum power point tracking for measuring the converted power at the controller module and the output of the power converter unit.

It is a further object of the invention to provide such a power converter with improved energy efficiency, wherein the energy consumed by the control of the maximum power point tracking is reduced compared to the known power converter unit.

According to a first aspect of the invention, a power converter unit is provided comprising a power detector. The switched capacitor power converter unit for converting direct current into direct current enables large scale integration and very small assembly size of the device. Furthermore, because the power detector included in the present invention measures output current rather than voltage, the power detector allows for the use of high capacitor energy storage.

In an embodiment, the output current of the switched capacitor power converter unit is driven by a resistor that can be programmed, thereby generating a voltage drop of said first and second potential difference across the resistor. Further, the voltage drop across the resistor is amplified by a voltage amplifier and sampled by a sample-and-hold comparator. The sample-and-hold comparator reads the amplified voltage drop and compares the two samples. The sample-and-hold comparator output enters a state machine that is used to decide whether the power converter cell parameters have to be changed to increase the output power. The parameters are varied by a controller module for controlling the switching frequency and voltage gain of the power converter unit.

In energy collection systems such as RF energy collection modules, and PV-based energy collection modules, very low energy levels are captured from energy sources. Therefore, a very efficient power management control is needed to transfer electrical energy from an energy harvesting source to a load (e.g., an internet of things sensor). Known maximum power point trackers typically use a dedicated microcontroller for measuring the maximum power point. These microcontrollers consume a large amount of energy compared to applications of (e.g., RF-based) energy harvesters, which makes these microcontrollers not very efficient and suitable for such applications.

In an embodiment, the power converter unit comprising the DC-DC conversion module, the controller module and the maximum power point tracking module is fully integrated as a system on chip SoC. This enables high power efficiency and sub-microwatt (sub-microwatt) power consumption of the power converter. No additional low power efficient microcontroller is required to measure the maximum power point of the power supply connected to the input of the DC-DC conversion module.

In an embodiment, the power converter unit is configured for subsequently switching on and off the maximum power point tracking module.

In an embodiment, the power converter unit is configured for subsequently switching on and off the current to said resistor.

In an embodiment, the power converter unit is configured for simultaneously switching the maximum power point tracking module and the current to the resistor on and off.

In another embodiment, the power converter unit is configured for power gating of maximum power point tracking module components, such as the maximum power point tracking module itself and preferably also resistors, etc. This is achieved by subsequently disabling and enabling the power point tracking module and/or (but preferably simultaneously) disabling and enabling the current through the resistor to reduce power consumption. Thus, disabling maximum power point tracking may be achieved, for example, by bypassing current to a resistor connected in series with the electrical output of the DC-DC conversion module directly from the output of the DC-DC conversion module to the load. Thus, disabling maximum power point tracking may also be achieved by disabling the maximum power point tracking module itself. Most preferably, simultaneous on and off timing and timing intervals are used to disable both at the same time. Thus, in the most preferred embodiment, the state machine disconnects the maximum power point tracking and shorts/programs the sensor resistor to ensure low power operation.

Preferably, the resistor is one of an adjustable resistor or a programmable resistor. In another example, maximum power point tracking may be disabled by adjusting or programming a resistor with a zero value.

In an example, at least one state machine (preferably a synchronous state machine) is configured for power gating of a maximum power point module. At least one state machine may be included in the maximum power point tracking module or the controller module.

With any embodiment that disables current flow through the resistor for at least a period of time, a discontinuous measurement is obtained. The maximum power point tracking module of any of these aspects or embodiments achieves improved power consumption efficiency compared to known solutions, which are typically based on continuous measurements.

The sub-microwatt power consumption of the electric energy converter unit is realized by utilizing the power gating of the maximum power point tracking module. Power gating ensures that power is not dissipated in the resistor while converting energy.

The duty cycle of the power gating may vary. For efficient power consumption, the time slots with maximum power tracking enabled are small and the time slots with maximum power tracking disabled are large, preferably with a duty cycle of 10%, more preferably less than 5%. In other words, the ratio between the on-time and the off-time of the maximum power point tracking module, or at least the ratio between the on-time and the off-time of the current flowing through the resistor, is at least 1:2, but more preferably 1:4, 1:8, 1:10, 1:20, or even higher. More preferably, the ratio is dynamic and may change over time.

With this duty cycle, sub-microwatt power consumption during energy conversion is achieved without continuously enabling the maximum power point tracker. The decision on the maximum power point is made during a small time slot, preferably not exceeding 1 second. In a further embodiment, the power converter unit is configured to detect whether no power is delivered to the output of the DC-DC conversion module, e.g. due to a power outage, and to stop the energy conversion. Preferably, this is done by at least one state machine.

Drawings

The present invention will now be described, in a non-limiting manner, with reference to the accompanying drawings, in which like parts are designated by like reference numerals, and in which:

FIG. 1 is a high-level block diagram of the present invention.

Fig. 2 is a block diagram of maximum power point tracking.

Fig. 3 is embodiment 1 of the voltage amplifier.

Fig. 4 is a time chart of a maximum power point tracking operation.

Detailed Description

Fig. 1 depicts a block diagram of a power converter unit for energy harvesting applications comprising a DC-DC conversion module (100), maximum power point tracking (102), sample-and-hold comparator (103), oscillator/controller module (101) and energy harvesting transducer (104).

The DC-DC conversion module (100) converts the energy provided by 104. 104, such as impedance and power, change over time due to weather conditions, line of sight or mobility conditions. Therefore, a control loop is needed to adapt the electrical parameters of the DC-DC conversion module to the electrical parameters of 104.

The impedance of 100 is controlled by a maximum power point tracking and oscillator-controller module (101). In 102, the output current of the DC-DC conversion module is converted to a voltage sampled in a sample-and-hold comparator (103). Further, the two sampled voltages are compared in sequence at 103, and the sample-and-hold comparator outputs a digital signal that is read by a state machine built into 102. The state machine reads the comparator signal and sets the control bits of the DC-DC conversion module 100 and the oscillator/controller module 101.

The control bits are intended to adjust the voltage gain of the DC-DC conversion module 100 and the switching frequency defined by the oscillator/controller module 101 and thereby adjust the electrical parameters of the DC-DC conversion module.

Fig. 2 shows a block diagram of maximum power point tracking 102 including a low pass filter (105), a voltage amplifier (106), a programmable resistor (107), a sample-and-hold comparator (103), and a state machine (109). The DC-DC conversion module output current flows through a resistor 107, the resistor 107 having a first terminal connected to the low pass filter 105 and a second terminal connected to the output. The low pass filter 105 allows to convert the average output current into a DC voltage, which is amplified by the voltage amplifier 106. Subsequently, the sample-and-hold comparator 103 samples the amplified voltage and compares it with a previously sampled voltage. After this comparison, the sample-and-hold comparator 103 outputs a logic signal that is read by the state machine 109 that determines whether to increase or decrease the bit count of the oscillator/controller module and the bit count of the DC-DC conversion module gain.

Fig. 3 illustrates one embodiment of the voltage amplifier 106. The voltage amplifier 106 includes an operational amplifier (110), an input resistor (111), and a feedback resistor (112). The voltage gain of the voltage amplifier 106 is defined by the ratio between the feedback resistor 112 and the input resistor 111.

As a second embodiment, the circuit of fig. 3 may be implemented using a buffer driving input resistor 111. Further, the input resistor 111 and the feedback resistor 112 may be replaced by a switched capacitor network including an input capacitance and a feedback capacitance, and the gain is set by a capacitance ratio.

Fig. 4 shows a time diagram of maximum power point tracking as an example of an embodiment of the algorithm. The control signal 113 changes with a duration T1 called a setup interval (setup interval), and the control signal 113 changes during T2 seconds called a scan interval. The control signal 113 defines a frequency parameter of the DC-DC conversion module (100). Continuously, the control signal 114 is scanned during T3 seconds, referred to as a fine adjustment interval. When the maximum power point is detected at the output of the DC-DC conversion module, the control signals 113 and 114 are considered to be at the optimal values. The duration T4 is the time during which maximum power point tracking is discontinued, referred to as the sleep interval. Generally, the sleep interval T4 is much longer than the active interval, which is the sum of T1, T2, and T3, to reduce the average power consumption for maximum power point tracking and improve system efficiency. The setup interval T1 is constant, on the other hand, the scan interval T2 and the fine adjustment interval T3 may vary with the number of steps required to find the maximum power point of the DC-DC conversion module.