Switch Control Circuit Propagation Delay Compensation
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Solution Overview
Problem
Propagation delays in switch control circuits cause errors in load current due to delayed turn-off timings of control switches, leading to increased inductor current beyond set values.
Innovation Solution
A switch control circuit with an integrator that compares integrated sensing voltage and load current setting voltage, using a comparator and off-time controller to adjust the control switch operation, and a gate sensor to initiate integration when the gate terminal is high, thereby compensating for propagation delays by adjusting the integrated signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a comparator is used to compare VCS voltage and ADIM voltage for controlling the control switch, then the load current can be regulated, but propagation delay between the comparator output and gate terminal causes the control switch turn-off timing to be delayed, resulting in increased inductor current exceeding the set value
Solution Approach 1:
The patent applies preliminary action by starting the integration operation at a precisely controlled point in time - when the gate terminal input becomes high. This timing is earlier than traditional methods that wait for voltage equality, allowing the system to preemptively account for the propagation delay. The integrator begins accumulating the sensing voltage signal before the actual switch turn-off event, so that when the integration result matches the reference voltage, the switch has already been turned off by the required amount, compensating for the delay between comparator output and gate terminal response
Solution Approach 2:
The patent uses copying by creating an integrated signal that is a temporal copy or representation of the sensing voltage history. Instead of directly using the instantaneous voltage comparison, the system integrates the sensing voltage over time to create an accumulated signal that copies the past behavior of the current. This integrated signal is then compared against a reference to determine switch timing, effectively creating a time-shifted copy of the current waveform that accounts for propagation delays
2Ease of operation
If the control switch is turned off when VCS voltage equals ADIM voltage, then the control is simple, but propagation delay causes the actual turn-off to occur later, increasing inductor current beyond the desired level
Solution Approach 1:
The patent replaces the direct voltage comparison mechanism with an integration-based control mechanism. Instead of mechanically or electrically comparing instantaneous voltages (VCS = ADIM), the system substitutes this with an integration process where the sensing voltage is accumulated over time and compared against a reference voltage. This substitution transforms the control method from direct instantaneous comparison to temporal accumulation comparison, which inherently accounts for propagation delays and provides more precise current control
Solution Approach 2:
The patent applies parameter changes by transforming the control parameter from instantaneous voltage equality (VCS = ADIM) to integrated voltage equality (∫VCS dt = Vref). This changes the fundamental parameter being controlled from a static voltage level to a time-integrated voltage accumulation. By changing the parameter from instantaneous to cumulative, the system gains the ability to compensate for propagation delays and achieve more accurate current regulation
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution effectively compensates for propagation delays, ensuring accurate load current control by starting integration from a lower point when the gate terminal is high, thus preventing excessive inductor current.
Implementation Method 1
an integrator configured to integrate a sensing voltage (VCS) and a load current setting voltage (ADIM) to generate an integrated signal
Implementation Method 2
a comparator configured to compare the integrated signal and a bias voltage (Bias)
Implementation Method 3
an inductor, a control switch, and a sensing resistance connected in series to an input power source
Data Source
AI summary
A switch control circuit and a switch control method are provided. The switch control circuit includes a load, an inductor, a control switch, and a sensing resistance connected in series to an input power source; an integrator that integrates a sensing voltage and a load current setting voltage to generate an integrated signal; a comparator that compares the integrated signal and a bias voltage; a switch driver that controls the control switch based on an output of the comparator and an output of an off time controller; and a gate sensor that outputs, to the integrator, a gate sensing signal that senses a time when an input of a gate terminal of the control switch becomes a low level. An integration operation is started from a position in which the integrated signal is located lower than the bias voltage, when an input of the gate terminal becomes a high level.