Bootstrap Control Circuit for Stable DC-DC Capacitor Recharging
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Solution Overview
Problem
Conventional bootstrap controlled voltage converting devices experience output voltage disturbance and extra conduction loss due to energy recycling through an inductor during capacitor recharging, leading to switching losses in DC to DC converting circuits.
Innovation Solution
A bootstrap control circuit with a regulator, capacitor, voltage detector, and charging path controller that isolates the capacitor from the inductor during light load conditions, using a reference voltage to charge the capacitor, thereby avoiding output voltage disturbance and reducing switching losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the bootstrap control circuit provides charging path through the inductor by turning on the lower bridge, then the capacitor can be recharged, but output voltage disturbance occurs due to energy transfer from the inductor
Solution Approach 1:
The patent introduces a diode as an intermediary component between the inductor and the capacitor. This diode acts as a one-way valve for current flow, allowing the capacitor to be recharged through the inductor during normal operation while preventing reverse current flow that would cause output voltage disturbance. The diode effectively mediates the energy transfer process, enabling beneficial charging while blocking harmful reverse energy flow.
2Object-affected harmful factors
If the energy of the inductor is recycled to the input end to avoid excessive output voltage, then output voltage can be controlled, but turn-on loss occurs due to turn on resistance of transistors
Solution Approach 1:
The patent extracts the harmful reverse energy flow from the system by using the diode to block the current path that would otherwise cause output voltage to become excessive. Instead of recycling the energy back to the input end through active transistor switching (which would cause turn-on loss), the diode simply prevents the reverse flow, effectively taking out the problematic energy path while avoiding the losses associated with active switching components.
3Reliability
If the capacitor is continuously connected to the inductor for recharging, then the capacitor can maintain charge, but extra conduction loss occurs due to continuous current flow
Solution Approach 1:
The patent implements periodic action by allowing capacitor recharging only during specific phases of the DC to DC converting circuit operation. The diode enables current flow from the inductor to the capacitor only when the circuit is in a state that supports forward current flow, and blocks it during other phases. This periodic charging approach maintains capacitor charge while avoiding continuous conduction loss that would occur with constant connection.
Data Source
AI summary
A bootstrap control circuit includes a regulator, a capacitor, a voltage detector and a charging path controller. The regulator generates a first voltage. The capacitor is coupled between the regulator and an inductor of the DC to DC converting circuit.The voltage detector detects a voltage difference between two ends of the capacitor to obtain a detection signal. The charging path controller turns on or cuts off a connection path between the capacitor and the inductor of the DC to DC converting circuit, and the charging path controller connects the capacitor to a reference voltage when the connection path of the capacitor and the inductor of the DC to DC converting circuit is cut off.